Joey Duran Ocon
Sex: Male
Education:
Doctor of Philosophy in Environmental Science and Engineering, Catalysis and Electronic Engineering, Gwangju Institute of Science and Technology, 2015
Master in Public Management, Ateneo de Manila University, unfinished
Master of Science in Chemical Engineering, University of the Philippines, 2011
Bachelor of Science in Chemical Engineering, University of the Philippines, 2008
Field of Specialization
Graphene
Electrochemical Analysis
Material Characterization
Nanomaterials
Carbon Nanomaterials
Nanostructured materials
X-ray diffraction
Researches:
Article title: Insights on platinum-carbon catalyst degradation mechanism for oxygen reduction reaction in acidic and alkaline media
Authors: Marc Francis Labata, Li Guangfu, Joey Duran Ocon, Po-Ya Abel Chuang
Publication title: Journal of Power Sources 487(5): 229356, March 2021
Abstract:
Developing durable electrocatalyst for oxygen reduction reaction (ORR) is essential for fuel cell commercialization. Herein, we perform a study of platinum-carbon (Pt/C) degradation mechanisms using potential cycling of accelerated durability testing protocols in acidic and alkaline media. Physicochemical results indicate that carbon surface oxides are formed after high-potential cycling in acid causing an increase in the double-layer capacitance and severe ORR activity loss due to Pt poisoning. Whereas, low-potential cycling in acid shows less ORR activity loss, mainly caused by Pt Ostwald ripening, and does not lead to a significant change in double-layer capacitance. In alkaline, the Pt/C catalyst after high-potential cycling shows a decrease of double-layer capacitance over time because of carbon layer dissolution. TEM images reveal larger Pt agglomerates in alkaline, due to high Pt mobility. These findings provide new insights into the role of catalyst and carbon support interface in developing mitigation strategies for stable fuel cell operation.
Full text available upon request to the author
Article title: Alkaline earth atom doping-induced changes in the electronic and magnetic properties of graphene: a density functional theory study
Authors: Ace Christian Feraren Serraon, Julie Anne D. del Rosario, Po-Ya Abel Chuang, Meng Nan Chong, et al.
Publication title: RSC Advances 11(11): 6268-6283, February 2021
Abstract:
Density functional theory was used to investigate the effects of doping alkaline earth metal atoms (beryllium, magnesium, calcium and strontium) on graphene. Electron transfer from the dopant atom to the graphene substrate was observed and was further probed by a combined electron localization function/non-covalent interaction (ELF/NCI) approach. This approach demonstrates that predominantly ionic bonding occurs between the alkaline earth dopants and the substrate, with beryllium doping having a variant characteristic as a consequence of electronegativity equalization attributed to its lower atomic number relative to carbon. The ionic bonding induces spin-polarized electronic structures and lower workfunctions for Mg-, Ca-, and Sr-doped graphene systems as compared to the pristine graphene. However, due to its variant bonding characteristic, Be-doped graphene exhibits non-spin-polarized p-type semiconductor behavior, which is consistent with previous works, and an increase in workfunction relative to pristine graphene. Dirac half-metal-like behavior was predicted for magnesium doped graphene while calcium doped and strontium doped graphene were predicted to have bipolar magnetic semiconductor behavior. These changes in the electronic and magnetic properties of alkaline earth doped graphene may be of importance for spintronic and other electronic device applications.
Full text available upon request to the author
Article title: Unravelling the roles of alkali-metal cations for the enhanced oxygen evolution reaction in alkaline media
Authors: Julie Anne D. del Rosario, Li Guangfu, Marc Francis Labata, Joey Duran Ocon, et al.
Publication title: Applied Catalysis B: Environmental 288:119981, February 2021
Abstract:
The electrical double layer (EDL) structure and interfacial interactions are studied to illustrate the influence of alkali metal (AM) cations on alkaline oxygen evolution reaction (OER). The electrochemical measurements show that the OER activity both on IrOx and NiCo2O3 increases in the sequence of Li⁺ < Na⁺ < Cs⁺ < K⁺ mainly due to the various interaction strength of specifically adsorbed OHad intermediates and non-specifically adsorbed AM⁺ad in the EDL. In particular, K⁺ breaks the limitation of the adsorbate’s linear scaling relation and enables a lattice-oxygen-mediated mechanism, resulting in enhancing activity. Further, based on our investigation, new strategies are proposed to synthesize Ir-Co oxide with modifications of various AM elements, such as Li, Na and K. The K-assistant Ir0.6Co0.4 amorphous oxide exhibits outstanding OER performance, i.e. 290 mV overpotential (without ohmic correction) at 10 mA cm⁻², and 36.9 mV dec⁻¹ kinetic Tafel slope. The modification of potassium plays a crucial role for the superior performance, which highlights the importance of the interfacial engineering to facilitate the electron transfer reactions.
Full text available upon request to the author
Article title: What makes energy systems in climate-vulnerable islands resilient? Insights from the Philippines and Thailand
Authors: Laurence Delina, Joey Duran Ocon, Eugene, Jr. Agusan Esparcia
Publication title: Energy Research & Social Science 69:101703, November 2020
Abstract:
Destructive weather extremes – the key impacts of the climate emergency – acutely signal the need to increase the resiliency, especially of climate-vulnerable islands and its peoples. “Islands” are detached communities that are either geographically bounded by water or are metaphors for inland off-grid villages. The extant literature on resilient infrastructures is rich, but this corpus is mostly concentrated on food and water systems, security, and transport. Making energy systems resilient in islands, this paper argues, is equally important. In these island energy systems, resilience can be achieved by regarding them as sociotechnical assemblages where engineering innovation is co-produced alongside social and institutional shifts. This article suggests that resilient energy systems in islands can be checked against their explicit characteristics as a system condition, as a set of processes, and as a set of outcomes. Understanding power relations and ethical concerns are also important. To illustrate these characteristics, case studies from Romblon in the Philippines (a geographic island) and Petchaburi in Thailand (a metaphorical island) are provided. There is no perfect resilient island energy systems, but these illustrations show that they can be pursued.
Full text available upon request to the author
Article title: Projecting the Price of Lithium-Ion NMC Battery Packs Using a Multifactor Learning Curve Model
Authors: Xaviery Penisa, Michael Castro, Jethro Daniel Agbayani Pascasio, Eugene Jr. Agusan Esparcia
Publication title: Energies 13(20): 5276, October 2020
Abstract:
Renewable energy (RE) utilization is expected to increase in the coming years due to its decreasing costs and the mounting socio-political pressure to decarbonize the world’s energy systems. On the other hand, lithium-ion (Li-ion) batteries are on track to hit the target 100 USD/kWh price in the next decade due to economy of scale and manufacturing process improvements, evident in the rise in Li-ion gigafactories. The forecast of RE and Li-ion technology costs is important for planning RE integration into existing energy systems. Previous cost predictions on Li-ion batteries were conducted using conventional learning curve models based on a single factor, such as either installed capacity or innovation activity. A two-stage learning curve model was recently investigated wherein mineral costs were taken as a factor for material cost to set the floor price, and material cost was a major factor for the battery pack price. However, these models resulted in the overestimation of future prices. In this work, the future prices of Li-ion nickel manganese cobalt oxide (NMC) battery packs - a battery chemistry of choice in the electric vehicle and stationary grid storage markets - were projected up to year 2025 using multi-factor learning curve models. Among the generated models, the two-factor learning curve model has the most realistic and statistically sound results having learning rates of 21.18% for battery demand and 3.0% for innovation. By year 2024, the projected price would fall below the 100 USD/kWh industry benchmark battery pack price, consistent with most market research predictions. Techno-economic case studies on the microgrid applications of the forecasted prices of Li-ion NMC batteries were conducted. Results showed that the decrease in future prices of Li-ion NMC batteries would make 2020 and 2023 the best years to start investing in an optimum (solar photovoltaic + wind + diesel generator + Li-ion NMC) and 100% RE (solar photovoltaic + wind + Li-ion NMC) off-grid energy system, respectively. A hybrid grid-tied (solar photovoltaic + grid + Li-ion NMC) configuration is the best grid-tied energy system under the current net metering policy, with 2020 being the best year to deploy the investment.
Article title: Quantifying the Techno-Economic Potential of Grid-Tied Rooftop Solar Photovoltaics in the Philippine Industrial Sector
Authors: Patrick Gregory B. Jara, Michael Castro, Eugene Jr. Agusan Esparcia, Joey Duran Ocon
Publication title: Energies 13(19): 5070, October 2020
Abstract:
The industrial sector is a major contributor to the economic growth of the Philippines. However, it is also one of the top consumers of energy, which is produced mainly from fossil fuels. The Philippine industrial sector must therefore be supported economically while minimizing the emissions associated with energy consumption. A potential strategy for minimizing costs and emissions is the installation of solar photovoltaic (PV) modules on the rooftops of industrial facilities, but this approach is hindered by existing energy policies in the country. In this work, we performed a techno-economic assessment on the implementation of rooftop solar PV in Philippine industrial facilities under different policy scenarios. Our study considered 139 randomly sampled industrial plants under MERALCO franchise area in the Philippines. Under the current net metering policy, 132 of the evaluated facilities were economically viable for the integration of rooftop solar PV. This corresponds to an additional 1035 MW p of solar PV capacity and the avoidance of 8.4 million tons of CO 2 emissions with minimal financial risk. In comparison, an expanded net metering policy supports the deployment of 4653 MW p of solar PV and the avoidance of 38 million tons of CO 2. By enabling an enhanced net metering policy, the widespread application of rooftop solar PV may present considerable savings and emission reduction for energy-intensive industries (electrical and semiconductors, cement and concrete, steel and metals, and textile and garments) and lower generation costs for less energy intensive industries (construction and construction materials, transportation and logistics, and food and beverages).
Full text available upon request to the author
Article title: Fabrication of cellulose acetate-based radiation grafted anion exchange membranes for fuel cell application
Authors: Angelo Jacob Samaniego, Allison Kaye Itularde Arabelo, Mrittunjoy Sarker, Feliper Mojica, et al.
Publication title: Journal of Applied Polymer Science 138(10): September 2020
Abstract:
Novel cellulose acetate-based anion exchange membranes (CA-AEM) are successfully synthesized via gamma radiation grafting as a possible renewable alternative to commercial AEMs. Using CA film precursors with degree of acetylation of 2.5, the synthesized AEM shows a high ion exchange capacity of 2.15 mmol/g obtained at high degree of grafting of 45%. It was determined using thermogravimetric analysis that the radiation-grafted CA-AEM has stable amine functional groups under oxygen environment within the normal operating temperature range of alkaline fuel cells. The CA-AEM also exhibits appreciable performance over a range of temperatures, with a highest ionic conductivity of up to 0.163 S/cm depending on the synthesis parameters. Results revealed that membranes prepared using gamma radiation dose of 31 kGy and above are susceptible to mechanical and dimensional instability due to increased water uptake and degree of swelling. Further study should consider the balance between grafting parameters and the desired hydrophysical properties.
Full text available upon request to the author
Article title: Decentralized versus Clustered Microgrids: An Energy Systems Study for Reliable Off-Grid Electrification of Small Islands
Authors: Olivia Francesa B. Agua, Robert Joseph A. Basilio, Erschad D. Pabillan, Michael T. Castro, et al.
Publication title: Energies 13(17): 4454, August 2020
Abstract:
Philippine off-grid islands are mostly electrified by diesel generators, resulting in costly electricity that is interrupted by fuel supply disruptions. The archipelagic nature of the country also impedes off-grid electrification due to the high capital cost of grid extension. Transitioning from diesel-only systems to hybrid renewable energy systems and interconnecting the island microgrids can solve these problems while promoting cleaner energy production. In this work, a comparative study on decentralized and clustered hybrid renewable energy system microgrids in the Polillo group of islands in the Philippines, using HOMER Pro, was performed. Microgrids comprising solar photovoltaics, lithium-ion battery energy storage, and diesel generators were designed on each island. Clustered systems encompassing multiple islands in the island group were simulated by also considering the least-cost interconnection paths. The techno-economics of each decentralized or clustered system and the four-island system were evaluated based on the levelized cost of electricity (LCOE). Reliability was assessed using the change in LCOE upon the failure of a component and during weather disturbances. Transitioning from diesel-only systems to hybrid systems reduces generation costs by an average of 42.01% and increases the renewable energy share to 80%. Interconnecting the hybrid systems results in an average increase of 2.34% in generation costs due to the cost of submarine cables but improves system reliability and reduces the optimum solar photovoltaic and lithium-ion storage installations by 6.66% and 8.71%, respectively. This research serves as a framework for the interconnection pre-feasibility analysis of other small off-grid islands.
Article title: Spatiotemporal Variation of Groundwater Arsenic in Pampanga, Philippines
Authors: Kurt Louis B. Solis, Reygie Q. Macasieb, Roel C. Parangat, Augustus C. Resurreccion, et al.
Publication title: Water 12(9): 2366, August 2020
Abstract:
Several confirmed cases of arsenic (As) poisoning have been reported in Central Luzon, the Philippines, in recent years. There is a growing interest in As research in the Philippines due to the reported As poisoning cases. However, an extensive spatiotemporal As study has not been conducted. In this work, As concentration measurements were conducted in 101 wells in Guagua, Pampanga, in Central Luzon, the Philippines, from November 2018 to November 2019. The wells included 86 public hand pumps, 10 pumping stations, and 5 private, jet-powered pumps. Using hydride generation—inductively coupled plasma—optical emission spectroscopy (HG-ICP-OES), analysis of the wells in 12 barangays in Guagua revealed that 38.7% had average As concentrations beyond the 10 ppb limit with some wells having high Mn (4.0 ppm) and Fe (2.0 ppm) content as well. The high pH and reducing conditions in the wells in Guagua may have contributed to the persistence of As in the groundwater. The mean difference in wet season versus dry season As measurements were −4.4 (As < 10 ppb), −13.2 (10 to 50 ppb As), and −27.4 (As > 50 ppb). Eighty-three wells (82.2%) had higher As concentrations in the dry season, 8 wells (7.92%) had higher As concentrations in the wet season, 7 wells (6.93%) had no significant difference between the wet and dry season, and 3 wells had been decommissioned. These results indicate that there is a significant difference in As concentrations in the wet and dry seasons, and this could have implications in water treatment technology and policy implementation. The work resulted in the first year-long characterization of groundwater As in the Philippines.
Article title: Arsenic Removal by Advanced Electrocoagulation Processes: The Role of Oxidants Generated and Kinetic Modeling
Authors: Micah Flor Montefalcon, Meliton Chiong III, Augustus C. Resurreccion, Sergi Garcia-Segura, et al.
Publication title: Catalysts 10(8): 928, August 2020
Abstract:
Arsenic (As) is a naturally occurring element in the environment that poses significant risks to human health. Several treatment technologies have been successfully used in the treatment of As-contaminated waters. However, limited literature has explored advanced electrocoagulation (EC) processes for As removal. The present study evaluates the As removal performance of electrocoagulation, electrochemical peroxidation (ECP), and photo-assisted electrochemical peroxidation (PECP) technologies at circumneutral pH using electroactive iron electrodes. The influence of As speciation and the role of oxidants in As removal were investigated. We have identified the ECP process to be a promising alternative for the conventional EC with around 4-fold increase in arsenic removal capacity at a competitive cost of 0.0060 $/m3. Results also indicated that the rate of As(III) oxidation at the outset of electrochemical treatment dictates the extent of As removal. Both ECP and PECP processes reached greater than 96% As(III) conversion at 1 C/L and achieved 86% and 96% As removal at 5 C/L, respectively. Finally, the mechanism of As(III) oxidation was evaluated, and results showed that Fe(IV) is the intermediate oxidant generated in advanced EC processes, and the contribution of •OH brought by UV irradiation is insignificant.
Article title: Ethanol Electrooxidation on Phase- and Morphology-Controlled Ni(OH)2 Microspheres
Authors: Jun Jeffri B.Lidasan, Julie Anne D. del Rosario, Joey Duran Ocon
Publication title: Catalysts 10(7): 740, July 2020
Abstract:
The electrooxidation kinetics of ethanol is key to making direct ethanol fuel cells and electrocatalytically reforming ethanol viable technologies for a more sustainable energy conversion. In this study, the electrooxidation of ethanol was investigated on nickel hydroxide (Ni(OH)2) catalysts synthesized using a facile solvothermal method. Variations in the temperature, heating time, and the addition of oleylamine in the precursor enabled the phase and morphology control of the catalysts. X-ray diffraction and scanning electron microscopy show that the addition of oleylamine in the precursor resulted in microspheres with a high surface area, but favored the formation of β-phase Ni(OH)2. Elevated temperatures or prolonged periods of heating in a controlled environment, on the other hand, can lead to the formation of the ethanol oxidation reaction-active α-phase. Among the synthesized catalysts, the α-Ni(OH)2 microspheres with nanoflakes achieved the highest activity for ethanol oxidation with a current density of 24.4 mA cm−2 at 1.55 V (vs. RHE, reversible hydrogen electrode) in cyclic voltammetry tests and stable at 40 mA cm−2 in chronoamperometric tests at the same potential, comparatively higher than other Ni-based catalysts found in the literature. While the overpotential is beyond the useful range for direct ethanol fuel cells, it may be useful for understanding the mechanism of ethanol oxidation reactions on transition metal hydroxides at their oxidizing potential for ethanol electroreforming.
Article title: Experimental Study of Three Channel Designs with Model Comparison in a PEM Fuel Cell
Authors: Feliper Mojica, Azimur Rahman, J.M. Mora, Joey Duran Ocon, et al.
Publication title: Fuel Cells 20(5), June 2020
Abstract:
The flow field is an integral part of a proton exchange membrane fuel cell. In this work, three flow‐field designs, including straight parallel, multiple channel serpentine, and single channel serpentine, are studied systematically to investigate their effects on fuel cell performance. To evaluate the characteristics of each design, relative humidity and flow rate are parametrically adjusted to evaluate performance experimentally. A finite element‐based 3D steady state, single phase COMSOL computational model is employed to analyze reactant distribution and fuel cell performance. The single channel serpentine exhibits the best performance under the greatest variety of operating conditions, but also experiences the highest inlet‐outlet pressure differentials. This study shows that parallel channel design has more evenly distributed reactant concentration, but is prone to liquid water accumulation, which requires high flow rate to remain stable operation under wet conditions. In summary, the multiple channel serpentine design can provide a reasonable balance between pressure drop and flow distribution with robust fuel cell operation.
Article title: Cluster size effects on the adsorption of CO, O, and CO2 and the dissociation of CO2 on two-dimensional Cux (x = 1, 3, and 7) clusters supported on Cu(111) surface: a density functional theory study
Authors: Ellaine Rose A. Beronio, Anne Nicole P. Hipolito, Joey Duran Ocon, Hiroshi Nakanishi, et al.
Publication title: Journal of Physics Condensed Matter 32(40), May 2020
Abstract:
In this study, we performed density functional theory (DFT) based calculations to determine the effect of the size of Cux(x = 1 (adatom), 3 (trimer), 7 (heptamer)) cluster supported on Cu(111) toward the adsorption of CO, O, and CO2, and the dissociation of CO2. CO adsorbs with comparable adsorption energies on the different cluster systems, which are influenced by the reactivity of the Cu atoms in the cluster and the interaction of CO with the Cu atoms in the terrace. O atom, on the other hand, will always favor to adsorb on hollow sites and is more stable on hollow sites of smaller clusters. CO2dissociates with lower activation energy on the cluster region than on flat Cu(111). We obtained the lowest activation energy on Cu3due to its more reactive Cu atoms than the Cu7case, and due to the possibility of O to adsorb on the cluster region which is not observed for the Cu1case. The presented results will provide insights on future studies on supported cluster systems and on their possible use as catalysts for CO2-related reactions.
Article title: A Comparative Techno-Economic Analysis of Different Desalination Technologies in Off-Grid Islands
Authors: Michael Castro, Myron Alcanzare, Eugene, Jr. Agusan Esparcia, Joey Duran Ocon
Publication title: Energies 13(9): 2261, May 2020
Abstract:
Freshwater in off-grid islands is sourced from rain, groundwater, or mainland imports, which are unreliable, limited, and expensive, respectively. Sustainable freshwater generation from desalination of abundant seawater is another alternative worth exploring. Model-based techno-economic simulations have focused on reverse osmosis desalination due to its low energy consumption and decreasing costs. However, reverse osmosis requires frequent and costly membrane replacement. Other desalination technologies have advantages such as less stringent feedwater requirements, but detailed studies are yet to be done. In this work, a techno-economic comparison of multi-effect distillation, multi-stage flash, mechanical vapor compression, and reverse osmosis coupled with solar photovoltaic-lithium ion-diesel hybrid system was performed by comparing power flows to study the interaction between energy and desalination components. Optimization with projected costs were then performed to investigate future trends. Lastly, we used stochastic generation and demand profiles to infer uncertainties in energy and desalination unit sizing. Reverse osmosis is favorable due to low energy and water costs, as well as possible compatibility with renewable energy systems. Multi-effect distillation and multi-stage flash may also be advantageous for low-risk applications due to system robustness.
Full text available upon request to the author
Article title: Facile synthesis and characterisation of functional MoO3 photoanode with self-photorechargeability
Authors: Chun Yuan Chot, Meng Nan Chong, A.K. Soh, Khang Wei Tan, et al.
Publication title: Journal of Alloys and Compounds 838:155624, May 2020
Abstract:
There is a growing research interest in exploring the self-photorechargeability of photoanodes, which enables photoelectrochemical (PEC) water oxidation even under non-irradiated conditions. The main aim of this study was to develop a facile synthesis of molybdenum trioxide (MoO3) photoanode displaying self-photorechargeability using an aerosol-assisted chemical vapour deposition (AA-CVD) method. A systematic optimisation of the key synthesis parameters of AA-CVD method, namely: (1) ultrasonication time of precursor solution, and (2) annealing temperature was carried out in order to understand the best trade-off between photocurrent density (illuminated conditions) and charge density (non-illuminated conditions). Field emission-scanning electron microscopy images showed that the MoO3 photoanodes synthesized via AA-CVD method exhibited a 3D plate-like crystalline structure that gave a large voltammogram area, indicating that the MoO3 photoanodes possessed high charge storage capacity for photogenerated electrons. PEC measurements showed that the optimised MoO3 photoanode obtained during an ultrasonication time of 25 min and at the annealing temperature of 500 °C achieved a photocurrent density of 1.47 μA/cm² at 1.0 V vs Pt electrode. A significantly prolonged on-off illumination cycle (i.e. 1,000 s) showed a significant storage capacity of photogenerated electrons within the 3D plate-like MoO3 crystalline structure was discharged during the non-irradiated conditions, and a charge density of 0.35 mC/cm².
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Article title: Hydrothermally Carbonized Waste Biomass as Electrocatalyst Support for α-MnO2 in Oxygen Reduction Reaction
Authors: Harold Panganoron, Jethro Daniel Agbayani Pascasio, Eugene, Jr. Agusan Esparcia, Julie Anne D. del Rosario, et al.
Publication title: Catalysts 10(2):177, February 2020
Abstract:
Sluggish kinetics in oxygen reduction reaction (ORR) requires low-cost and highly durable electrocatalysts ideally produced from facile methods. In this work, we explored the conversion and utilization of waste biomass as potential carbon support for α-MnO2 catalyst in enhancing its ORR performance. Carbon supports were derived from different waste biomass via hydrothermal carbonization (HTC) at different temperature and duration, followed by KOH activation and subsequent heat treatment. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray spectroscopy (EDX) and X-Ray diffraction (XRD) were used for morphological, chemical, and structural characterization, which revealed porous and amorphous carbon supports for α-MnO2. Electrochemical studies on ORR activity suggest that carbon-supported α-MnO2 derived from HTC of corncobs at 250 °C for 12 h (CCAC + MnO2 250-12) gives the highest limiting current density and lowest overpotential among the synthesized carbon-supported catalysts. Moreover, CCAC + MnO2 250-12 facilitates ORR through a 4-e‑ pathway, and exhibits higher stability compared to VC + MnO2 (Vulcan XC-72) and 20% Pt/C. The synthesis conditions preserve oxygen functional groups and form porous structures in corncobs, which resulted in a highly stable catalyst. Thus, this work provides a new and cost-effective method of deriving carbon support from biomass that can enhance the activity of α-MnO2 towards ORR.
Article title: Exploration of a novel Type II 1D-ZnO nanorods/BiVO4 heterojunction photocatalyst for water depollution
Authors: Jan Seng Chang, Yi Wen Phuan, Meng Nan Chong, Joey Duran Ocon
Publication title: Journal of Industrial and Engineering Chemistry 83, December 2019
Abstract:
In this study, we reported on the successful fabrication of a novel heterojunction photocatalyst (in particulate system) with a Type II band alignment between 1D-ZnO nanorods and BiVO4 nanocrystals. Pristine 1D-ZnO nanorods and BiVO4 nanocrystals were first fabricated through hydrothermal reaction followed by heterojunction formation via the wet chemical reaction. The 1D-ZnO/xBiVO4 heterojunction photocatalyst (x = weight ratio of BiVO4 in g) that found optimum when x = 0.08 g was used for the degradation of salicylic acid (SA) and Reactive Black 5 (RB5) resulting in high pseudo-first-order reaction rate constants of 0.0049 min⁻¹ and 0.0132 min⁻¹, respectively. Electrochemical studies proved that the 1D-ZnO/0.08BiVO4 heterojunction photocatalyst demonstrated a fast charge mobility and the most efficient photogenerated charge carriers separation among other heterojunction samples as analysed from PL spectra. Besides, UV–vis spectroscopic measurement and optical characterisation showed that the improved photoactivity in 1D-ZnO/BiVO4 is attributed to the formation of a Type II heterojunction staggered arrangement that enables a broader visible-light harvesting ability. Finally, a postulation photocatalytic mechanism was proposed based on the theoretical band alignment diagram between the 1D-ZnO nanorods and BiVO4 nanocrystals as well as portraying the fundamental charge carriers transfer within the 1D-ZnO/BiVO4 heterojunction photocatalyst.
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Article title: Impacts of morphological-controlled ZnO nanoarchitectures on aerobic microbial communities during real wastewater treatment in an aerobic-photocatalytic system
Authors: Jang Sen Chang, Meng Nan Chong, Phaik Eong Poh, Joey Duran Ocon, et al.
Publication title: Environmental Pollution 259: 113867, December 2019
Abstract:
This study aimed to evaluate the impacts of morphological-controlled ZnO nanoarchitectures on aerobic microbial communities during real wastewater treatment in an aerobic-photocatalytic system. Results showed that the antibacterial properties of ZnO nanoarchitectures were significantly more overwhelming than their photocatalytic properties. The inhibition of microbial activities in activated sludge by ZnO nanoarchitectures entailed an adverse effect on wastewater treatment efficiency. Subsequently, the 16S sequencing analysis were conducted to examine the impacts of ZnO nanoarchitectures on aerobic microbial communities, and found the significantly lower microbial diversity and species richness in activated sludge treated with 1D-ZnO nanorods as compared to other ZnO nanoarchitectures. Additionally, 1D-ZnO nanorods reduced the highest proportion of Proteobacteria phylum in activated sludge due to its higher proportion of active polar surfaces that facilitates Zn2+ ions dissolution. Pearson correlation coefficients showed that the experimental data obtained from COD removal efficiency and bacterial log reduction were statistically significant (p-value < 0.05), and presented a positive correlation with the concentration of Zn2+ ions. Finally, a non-parametric analysis of Friedman test and post-hoc analysis confirmed that the concentration of Zn2+ ions being released from ZnO nanoarchitectures is the main contributing factor for both the reduction in COD removal efficiency and bacterial log reduction.
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Article title: Cost Saving Potential of Grid-tied Solar Photovoltaic-based Hybrid Energy System in the Philippine Industrial Sector
Authors: Patrick Gregory Jara, Michael Castro, Eugene, Jr. Agusan Esparcia, Carl Odulio, et al.
Publication title: Chemical Engineering Transactions 76:937-942, October 2019
Abstract:
The Philippine Industrial Sector contributes USD 124x109 (~PHP 6.5x1012) or about 1/3 in the economy. However, the electricity cost, which is 2nd highest in Asia, constitutes up to 10 % of their total operating expenses. This hinders foreign direct investment to the country. Solar photovoltaic grid-tied hybrid energy systems are one of the emerging ways to reduce electricity expenses of the industrial sector. Current net-metering policy, which enables grid-tied systems, restricts the export of energy to the grid up to 100 kWp with compensation equal to the average generation rate of the distribution utility. This work evaluates the techno-economic viability of putting up solar photovoltaic grid-tied hybrid energy systems for 66 randomly selected industrial establishments classified under electrical/electronics/semiconductors, steel/metal, food/beverages, transportation/logistics and textile/garment sub-sectors using Island System LCOEmin Algorithm (ISLA). ISLA will provide the optimal system component sizes of solar photovoltaic and battery in the least levelized cost of electricity (LCOE) by performing hourly calculations for one reference year using actual load profiles. The results suggest 63 out of 66 sample industrial establishments are viable to put up solar photovoltaic grid-tied hybrid energy systems, with a total solar photovoltaic capacity of 783 MWp. There are 7 establishments that are capable of off-grid solar photovoltaic-battery-diesel configuration. If export restriction in net-metering policy is lifted, the total solar photovoltaic potential will significantly increase up to 3,947 MWp, which corresponds to LCOE reduction to USD 0.14 (~PHP 7.2) per kWh and increase in renewable energy share to 34 %. This work shows that tapping solar rooftop potential and amending the net-metering policy increases operational savings of the Philippine industrial sector.
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Article title: Long-Discharge Flywheel Versus Battery Energy Storage for Microgrids: a Techno-Economic Comparison
Authors: Eugene Jr. Agusan Esparcia, Michael Castro, Roger Evangelista Buendia, Joey Duran Ocon
Publication title: Chemical Engineering Transactions 76:949-954, October 2019
Abstract:
The energy storage deployment becomes necessary as more renewable energy sources are being installed to achieve sustainable energy access in off-grid areas. Battery prices, however, still hinder massive deployment. One of the energy storage technologies being developed for microgrid applications are flywheels, which stores energy through rotational kinetic energy and are typically suited for high power applications. With the advent of long-discharge flywheels, such as those being marketed by Amber Kinetics® and Beacon Power®, they can be used in microgrids, which are dominated by batteries. This study provides a techno-economic comparison with sensitivity analysis between long-discharge flywheel and utility-scale lithium-ion battery for microgrid applications. The results show lowest levelized cost of electricity (LCOE) for flywheel-based hybrid energy system with 0.345 USD/kWh and renewable share of 62.4 % among tested configurations. The competitiveness of long-discharge flywheel over lithium-ion battery in the microgrid market depends on the diesel prices, expected reduction in lithium-ion battery prices, and improvements in lithium-ion battery lifespan.
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Article title: Waste Biomass Integration to Reduce Fuel Consumption and Levelized Cost of Electricity in Philippine Off-Grid Islands
Authors: Marco Angelo Decujos, Eugene, Jr. Agusan Esparcia, Joey Duran Ocon
Publication title: Chemical Engineering Transactions 76:943-948, October 2019
Abstract:
A techno-economic assessment was made for thirteen large off-grid islands in the Philippines using HOMER Pro (Hybrid Optimization Model for Electric Renewables Software) to determine the feasibility of integrating waste biomass into their energy systems. Sensitivity analysis on the diesel fuel prices and biomass feedstock prices was performed to determine their effects on the levelized cost of electricity (LCOE) and the renewable energy (RE) share. The results suggest that an average LCOE reduction of around 4.57 %, fuel reduction of 5.71 %, and RE share increase of 4.99 % can be realized by integrating biomass to the existing diesel system even without incorporation of other renewable energy generators such as solar photovoltaics. In cases where biomass is available in large quantities, and the energy demand is relatively low, LCOE reduction, fuel reduction, and RE share increase may even reach up to more than 20 %. This makes the integrated biomass-diesel hybrid system a viable option for reducing diesel consumption in the off-grid islands. And even with the establishment of a feedstock market, the biomass-diesel hybrid system still has a lower LCOE compared to the existing diesel-only systems. This work provides the first systematic techno-economic study on the potential of incorporating waste biomass in off-grid islands.
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Article title: A Techno-Economic Assessment of Small Energy Access Microgrids in the Philippines
Authors: Patricia Baricaua, Eugene, Jr. Agusan Esparcia, Carl Odulio, Joey Duran Oron
Publication title: Chemical Engineering Transactions 76:967-972, October 2019
Abstract:
In an effort to expedite the electrification in off-grid areas in the Philippines, the Qualified Third Party (QTP) scheme encourages private sector to engage in power generation and distribution business through competitive selection, a process that requires at least two rival bidders with rigorous registration requirements. An exemption is offered for microgrids with sub-100 kW capacity by not undergo competitive selection in order to further attract investors and private sector to engage in these off-grid areas since these areas are deemed highly unviable. The Department of Energy opened around 995 areas waived by electric cooperatives for third party servicing. The sub-100 kW capacity can serve areas with fewer than 500 household connections, which fits the profile of the 995 areas. In this work, the techno-economic feasibility of installation of sub-100 kW microgrids is done in order to know the required level of subsidies, loans, and/or grants to sustainably operate in these areas. The proposed microgrids were evaluated using ISLA, an open-source microgrid optimizer validated by HOMER Pro, by finding the optimal system component sizes of solar PV, battery, and diesel generators with the least levelized cost of electricity (LCOE). Initial results suggest initial investment cost for the establishment of 15 sub-100 kW microgrids ranged from USD 0.5 to 1 M (~PHP 25 to 55 M), with LCOE averaged at PHP 10.26/kWh. This corresponds to 30 % reduction relative to the LCOE from using diesel generator only. Strategies such as partial financing and full grant of capital expenditures show that the former can provide generation rates at par with typical generation rates of existing electric cooperatives at ~PHP 5 to 6 per kWh, while full subsidy can significantly reduce the generation cost to PHP 2 to 3 per kWh. Providing long term and low interest rates from financial institutions to fund these projects will help hasten the deployment of sub-100 kW microgrids. To achieve financial sustainability in these areas, productive use of energy through income generating projects should be highly encouraged in order to give the inhabitants the capacity to pay.
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Article title: Technoeconomics of Reverse Osmosis as Demand-Side Management for Philippine Off-Grid Islands
Authors: Michael Castro, Eugene, Jr. Agusan Esparcia, Carl Odulio, Joey Duran Ocon
Publication title: Chemical Engineering Transactions 76:1129-1134, October 2019
Abstract:
Providing water supply in off-grid islands is difficult due to remoteness and high logistics cost. Despite interest in providing energy sustainability in these areas, there is relatively lesser interest in coupling it with sustainable water access. One of the possible solutions is through the use of reverse osmosis (RO) technology for desalination since it has a low energy requirement and high throughput. In this work, the techno-economic viability of incorporating desalination units was elucidated as demand-side management in different dispatch algorithm, accounting water-energy nexus. Different water-energy system configurations were optimized and simulated using ISLA, an open-source microgrid optimizer. Results suggest the viability of installing desalination units with a minimum-level dispatch algorithm yielding the lowest levelized cost of water (LCOW) with only minimal increase in the levelized cost of electricity (LCOE).
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Article title: Grid Parity and Defection Studies in Major Philippine Cities Using Solar Photovoltaic-Plus-Storage Configuration
Authors: Niel Gabriel Enriquez Saplagio, Eugene Jr., Agusan Esparcia, Henning Meschede, Patrick Gregory Jara, et al.
Publication title: Chemical Engineering Transactions 76:995-960, October 2019
Abstract:
Due to the rapidly declining costs of solar photovoltaic (solar PV) modules and batteries, the possibility of defecting from the grid is starting to become an alternative for some consumers. Should many consumers defect from the grid, given the current rate structures, electricity prices would increase even faster which will further encourage more people to defect from the grid. This positive feedback loop has been called the “utility death spiral”. Previous grid defection studies were conducted in the United States, Australia, as well as some countries in Europe. In this work, the technical feasibility and economic viability of grid parity and defection were determined for residential customers in the major cities of the Philippines (Manila, Cebu and Davao) based on the franchise areas of Manila Electric Company, Visayan Electric Company, and Davao Light and Power Company. The grid defection analysis was divided into customer clustering, levelized cost of electricity (LCOE) calculation, and finally grid parity comparison. Three main clusters were identified based on the k-means clustering by utilizing 18 different features in order to get a more detailed overview on how many customers of each type are more likely to defect based on the representative load profiles from MERALCO. Average silhouette widths of 0.657, 0.587 and 0.585 were obtained for the three clusters. Based on the clusters, the LCOE of optimally sized solar PV-battery systems were calculated using Hybrid Optimization Model for Multiple Energy Resources Software, from 2018 up to 2050. The LCOE data were then compared to the projected retail electricity prices based on the actual data from the mentioned distribution utilities to find the economic viability of grid defection per customer cluster. Results show that grid parity and defection would be possible for residential customers starting in the next 30 y, with customers from Cebu more likely to defect first followed by Manila and then Davao. Based on the clustering, it was observed that the grid parity occurred earliest in Cluster C, followed by Cluster B, and then Cluster A. Different scenarios were also explored depending on the rate of decrease of local prices of photovoltaics, lithium-ion batteries, and a combination of both. Results show that decreasing battery prices play a bigger role achieving grid parity in the country.
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Article title: Optimal Multi-Criteria Selection of Energy Storage Systems for Grid Applications
Authors: Eugene, Jr. Agusan Esparcia, Jethro Daniel Agbayani Pascasio, Raymond R. Tan, et al.
Publication title: Chemical Engineering Transactions 76:1153-1158, October 2019
Abstract:
Currently, a wide variety of energy storage alternatives are available, each with a unique set of characteristics advantageous on selective applications. Current studies focus only on levelized costs on predicting the best-fit technology for specific applications. The study addresses this limitation by considering multiple factors on the selection process among technologies for specific applications. A systematic approach on the selection of energy storage technologies based on multiple and possible conflicting factors was proposed in this study for two specific applications: frequency regulation and load levelling. Fuzzy Analytic Hierarchy Process was utilized to generate the relative importance of each criterion. Monte Carlo simulations were performed to reflect the effect of battery characteristics and operating parameters uncertainties on the resulting scores of technologies. Grey Relational Analysis was used to aggregate the performance attributes of alternatives into a single score reflecting the desirability of alternatives. The levelized costs dominated all other criteria for both applications. Lithium ion battery dominated all technologies for both applications resulting from its well-rounded performance across all considered attributes. Results emphasized the importance of considering socio-economic indicators alongside techno-economic parameters on selecting the technology for future deployment. Thorough analysis on the results is important not only for decision-makers but for developers and innovators as well to direct future research.
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Article title: High Renewable Energy (Solar Photovoltaics and Wind) Penetration Hybrid Energy Systems for Deep Decarbonization in Philippine Off-grid Areas
Authors: Jethro Daniel Agbayani Pascasio, Eugene, Jr. Agusan Esparcia, Carl Odulio, Joey Duran Ocon
Publication title: Chemical Engineering Transactions 76:1135-1140, October 2019
Abstract:
The Philippines has many off-grid areas relying on diesel generators for energy access, but have high greenhouse gas emissions, high electricity costs, and intermittent operation. An opportunity to decarbonize the energy system of off-grid islands is by harnessing both solar photovoltaic (PV) and wind power. This work evaluates the techno-economic viability of putting up solar PV-wind-battery-diesel hybrid energy systems in 143 existing off-grid island areas operated by the National Power Corporation-Small Power Utilities Group (NPC-SPUG) using HOMER® Pro. The application obtains the optimal system component sizes with the least levelized cost of electricity (LCOE). The results suggest that there are 137 islands capable of using both solar PV and wind generation, 4 islands using solar PV only, and 2 islands using wind only. The hybrid energy systems in the sample islands require USD 774,171,061 (~ PHP 40,643,980,682) worth of investment cost with potential annual savings of USD 132,403,163 (~ PHP 6,951,166,051). The resulting system capacities and their corresponding LCOEs suggest high sensitivity towards wind potential due to lower capital cost of wind and potential higher energy share up to 58.47 %. Wind generation for off-grid islands should be considered alongside solar PV, especially in areas with high wind potential, to provide reliable energy access and reduce greenhouse gas emissions.
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Article title: On the transferability of smart energy systems on off-grid islands using cluster analysis – A case study for the Philippine archipelago
Authors: Henning Meschede, Eugene, Jr. Agusan Esparcia, Peter K. R. Holzapfel, Paul Bertheau, et al.
Publication title: Applied Energy 251, October 2019
Abstract:
Islands are highly diverse in their climatic, physical, social, and economic characteristics. Thus, each island's energy system needs to be designed according to its specific features. However, similarities among islands exist which can enable the fast transfer of concepts and experiences with energy systems. In the Philippines, only few off-grid islands are incorporating smart energy systems through hybrid electricity systems. While most off-grid islands still do not have access to electricity, the majority of off-grid Philippine islands having access to electricity are powered primarily by diesel-fired generators. In this work, a cluster analysis is performed for 502 off-grid islands in the Philippine archipelago, classifying the islands according to their similarities in socio-economic and physical characteristics, and indigenous energy resource potential. The results show that most of the islands belong to five clusters of very small and small islands for which photovoltaic-battery systems would be the favourable backbone of a future energy system based on renewable energies. These islands show a varying level of feasibility for harnessing wind energy. In medium and big islands, opportunities of linking electricity systems to water supply and thermal energy loads as well as to the transport sector, are identified and their relevance in the clusters is discussed. The results are consistent with the validation of the individual characteristics of chosen off-grid islands. The cluster analysis results support policy makers and private investors in deciding which smart energy system projects are suitable for which particular islands.
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Article title: Electrolyte-Dependent Oxygen Evolution Reactions in Alkaline Media: Electrical Double Layer and Interfacial Interactions
Authors: Li Guangfu, Maricor Fernandez Divinagracia, Marc Francis Labata, Joey Duran Ocon, et al.
Publication title: ACS Applied Materials & Interfaces 11(37), August 2019
Abstract:
Traditional understanding of electrocatalytic reactions generally focuses on either covalent interactions between adsorbates and the reaction interface (i.e., electrical double layer, EDL) or electrostatic interactions between electrolyte ions. Here, our work provides valuable insights into interfacial structure and ionic interactions during alkaline oxygen evolution reaction (OER). The importance of inner-sphere OH- adsorption is demonstrated as the IrO x activity in 4.0 M KOH is 6.5 times higher than that in 0.1 M KOH. Adding NaNO3 as a supporting electrolyte, which is found to be inert for long-term stability, complicates the electrocatalytic reaction in a half cell. The nonspecially adsorbed Na+ in the outer compact interfacial layer is suggested to form a stronger noncovalent interaction with OH- through hydrogen bond than adsorbed K+, leading to the decrease of interfacial OH- mobility. This hypothesis highlights the importance of outer-sphere adsorption for the OER, which is generally recognized as a pure inner-sphere process. Meanwhile, based on our experimental observations, the pseudocapacitive behavior of solid-state redox might be more reliable in quantifying active sites for OER than that measured from the conventional EDL charging capacitive process. The interfacial oxygen transport is observed to improve with increasing electrolyte conductivity, ascribing to the increased accessible active sites. The durability results in a liquid alkaline electrolyzer which shows that adding NaNO3 into KOH solution leads to additional degradation of OER activity and long-term stability. These findings provide an improved understanding of the mechanistic details and structural motifs required for efficient and robust electrocatalysis.
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Article title: Multi-Dimensional Zinc Oxide (ZnO) Nanoarchitectures as Efficient Photocatalysts: What is the fundamental factor that determines photoactivity in ZnO?
Authors: Jang Sen Chang, Jennifer Strunk, Meng Nan Chong, Phaik Eong Poh, et al.
Publication title: Journal of Hazardous Materials 381:120958, August 2019
Abstract:
While bulk zinc oxide (ZnO) is of non-toxic in nature, ZnO nanoarchitectures could potentially induce the macroscopic characteristics of oxidative, lethality and toxicity in the water environment. Here we report a systematic study through state-of-the-art controllable synthesis of multi-dimensional ZnO nanoarchitectures (i.e. 0D-nanoparticle, 1D-nanorod, 2D-nanosheet, and 3D-nanoflowers), and subsequent in-depth understanding on the fundamental factor that determines their photoactivities. The photoactivities of resultant ZnO nanoarchitectures were interpreted in terms of the photodegradation of salicylic acid as well as inactivation of Bacillus subtilis and Escherichia coli under UV-A irradiation. Photodegradation results showed that 1D-ZnO nanorods demonstrated the highest salicylic acid photodegradation efficiency (99.4%) with a rate constant of 0.0364 min-1. 1D-ZnO nanorods also exhibited the highest log reductions of B. subtilis and E. coli of 3.5 and 4.2, respectively. Through physicochemical properties standardisation, an intermittent higher k value for pore diameter (0.00097 min-1 per mm), the highest k values for crystallite size (0.00171 min-1 per nm) and specific surface area (0.00339 min-1 per m2/g) contributed to the exceptional photodegradation performance of nanorods. Whereas, the average normalised log reduction against the physicochemical properties of nanorods (i.e. low crystallite size, high specific surface area and pore diameter) caused the strongest bactericidal effect.
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Article title: Interaction of CO, O, and CO2 with Cu cluster supported on Cu(111): A density functional theory study
Authors: Allan Abraham Bustria Padama, Joey Duran Ocon, Hiroshi Nakanishi, Hideaki Kasai
Publication title: Journal of Physics Condensed Matter 31(41), June 2019
Abstract:
We performed density functional theory (DFT) based calculations to investigate the interaction of CO2 and its dissociated species (CO and O) on Cu3 cluster supported on Cu(111) (Cu3/Cu(111)) surfaces. Similar investigations were conducted on Cu(111) for purpose of comparison. In general, adsorption of CO and O are stronger on the cluster region than on the terrace region of Cu3/Cu and on the flat Cu surface. CO2, on the other hand, is weakly adsorbed on the surfaces. With reference to CO2 dissociation on Cu(111), we found that the cluster lowers the activation barrier and provides a more stable adsorption of the dissociated species. The presence of co-adsorbed CO in the cluster, however, will increase the activation energy. The variation in the activation barrier with the amount of CO is influenced by the stability of the O atom from the dissociated CO2. We further found that the adsorption energy of O atom is a possible descriptor for CO2 dissociation on the cluster region. The Cu cluster supported on Cu surface could be a promising catalyst for CO2 related reactions based on the lower activation energy for CO2 dissociation on the system than on Cu(111).
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Article title: One-pot hydrothermal synthesis of heteroatom co-doped with fluorine on reduced graphene oxide for enhanced ORR activity and stability in alkaline media
Authors: Yvonne Ligaya F. Musico, Nitul Kakati, Marc Francis Labata, Joey Duran Ocon, et al.
Publication title: Materials Chemistry and Physics 236:121804, June 2019
Abstract:
Boron (B) or nitrogen (N) was co-doped with fluorine (F) on reduced graphene oxide (rGO) using a low cost and simplified one-pot hydrothermal treatment method avoiding complicated technology, such as gas phase deposition or high temperature pyrolysis method. X-ray photoelectron microscopy spectra revealed successful doping of heteroatoms into the rGO. The Brunauer-Emmett-Teller (BET) results demonstrated that high surface areas of B–F-rGO and N–F-rGO are favorable for O2 adsorption. Electrochemical evaluations show that B–F-rGO and N–F-rGO catalysts have improved oxygen reduction reaction (ORR) catalytic performance in alkaline media compared to B-rGO and N-rGO. A Koutechy-Levich (KL) analysis and rotating ring disk electrode (RRDE) measurements suggest that both electrocatalysts dominantly favor a 4-electron reduction process. These heteroatoms co-doped with fluorine on rGO exhibit remarkable long-term ORR stability than the Pt/C. These improved electrochemical properties indicate that B–F-rGO and N–F-rGO are promising candidates as cost-effective electrode materials for energy related applications.
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Article title: Synthesis of Silver-Doped Titanium Dioxide Nanotubes by Single-Step Anodization for Enhanced Photodegradation of Acid Orange 52
Authors: Edgar Clyde Lopez, Joey Duran Ocon, Jem Valerie D. Perez
Publication title: Materials Science Forum 950:149-153, April 2019
Abstract:
Silver-doped TiO2 nanotubes (Ag-TiNTs) were synthesized in a top-down approach by single-step anodization of titanium sheets. The highly-ordered array of Ag-TiNTs was confirmed by scanning electron microscopy with an average inner diameter of 41.28 nm and a wall thickness of 35.38 nm. Infrared spectroscopy confirmed the presence of O-Ti-O bonds. Analysis of the X-ray powder diffraction profiles showed the characteristic peaks for anatase and titanium for both pristine TiNTs and Ag-TiNTs. Ag-doping caused no observed changes in the crystalline structure of pristine TiNTs. High-definition X-ray fluorescence spectroscopy revealed that the synthesized Ag-TiNTs have 0.05 wt% Ag-loading. Even at low Ag-loading, the Ag-TiNTs were shown to be photo-active, achieving 10.13% degradation of Acid Orange 52 under UV illumination after 120 min.
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Article title: Monatomic oxygen adsorption on halogen-substituted monovacant graphene
Authors: Reynaldo M. Geronia, Allan Abraham B. Padama, Po-Ya Abel Chuang, Meng Nan Chong, et al.
Publication title: International Journal of Hydrogen Energy 43(37), August 2018
Abstract:
Doping of graphene-based materials with heteroatoms relies on the disruption of existing charge densities found on pristine graphene. Even though it is known that this phenomenon helps catalyze oxygen reduction reaction (ORR), there are only a few theoretical studies regarding the use of halogen as dopants despite their high electronegativity differences with carbon. Using density functional theory calculations, this work explores the low-concentration halogenation of monovacant graphene as well as the adsorption of oxygen atom onto resulting halogen-based substrates (X = F, Cl, Br, I). In general, formation of doped graphene and the subsequent adsorption of monatomic oxygen is more favored in non-coplanar systems than in their coplanar counterparts. In addition, F-based systems exhibited the most favorable energetics for monoatomic adsorption and electronic properties among the four substrates. Electronegativity also plays a key role on the destruction and formation of molecular structures during the adsorption of monatomic oxygen. Further work with adsorption of O2 on these substrates is warranted to elucidate their potential to catalyze ORR.
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Article title: Ammonium Vanadium Bronze (NH4V4O10) as a High-Capacity Cathode Material for Nonaqueous Magnesium-Ion Batteries
Authors: Eugene, Jr. Agusan Esparcia, Munseok S. Chase, Joey Duran Ocon, Seung-Tae Hong
Publication title: Chemistry of Materials 30(11), May 2018
Abstract:
Magnesium-ion batteries (MIBs) offer improved safety, lower cost, and higher energy capacity. However, lack of cathode materials with considerable capacities in conventional nonaqueous electrolyte at ambient temperature is one of the great challenges for their practical applications. Here, we present high magnesium-ion storage performance and evidences for the electrochemical magnesiation of ammonium vanadium bronze NH4V4O10, as a cathode material for MIBs. NH4V4O10 was synthesized via a conventional hydrothermal reaction. It shows reversible magnesiation with an initial discharge capacity of 174.8 mAh g−1, and the average discharge voltage of ~2.31 V (vs. Mg/Mg2+) using 0.5 M Mg(ClO4)2 in acetonitrile as the electrolyte. Cyclic voltammetry, galvanostatic, discharge–charge, FTIR, XPS, Powder XRD, and elemental analyses unequivocally show evidences for the reversible magnesiation of the material and suggests that keeping the ammonium ions in the interlayer space of NH4V4O10 could be crucial for the structural stability with a sacrifice of initial capacity but much enhanced retention capacity. This is the first demonstration of electrochemical magnesiation with a high capacity above 2 V (vs Mg/Mg2+) using a conventional organic electrolyte with a relatively low water concentration.
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Article title: Electrochemically-synthesized tungstate nanocomposites γ-WO 3 /CuWO 4 and γ-WO 3 /NiWO 4 thin films with improved band gap and photoactivity for solar-driven photoelectrochemical water oxidation
Authors: Tao Zhu, Meng Nan Chong, Eng Seng Chan, Joey Duran Ocon
Publication title: Journal of Alloys and Compounds 762(11), May 2018
Abstract:
The main aim of this study was to synthesize and characterise tungstate (WO3) nanocomposites with its metal-based nanostructures, such as copper (II) tungstate (CuWO4) and nickel tungsten oxide (NiWO4), as visible-light active thin film photoanodes for solar-driven photoelectrochemical (PEC) water oxidation. FE-SEM and AFM results showed that the bare as-deposited WO3 films were transformed into polycrystalline WO3 structure with highly agglomerated surfaces and roughness during the annealing-induced crystallisation process. XRD results suggested that the bare as-deposited WO3 films undergone phase transformation process from amorphous to the photoactive monoclinic-I (γ-WO3) at 550 °C. XPS results indicated the existence of WO4²⁻, Ni²⁺ and Cu²⁺ ions at 35.58 eV, 856 eV and 932.4 eV, respectively. Through the formation of WO3 nanocomposites, the energy band gap was effectively lowered from 2.7 eV (γ-WO3) → 2.3 eV (γ-WO3/CuWO4) → 2.1 eV (γ-WO3/NiWO4) as estimated from the UV–Vis spectra. Finally, the corresponding photoactivity of WO3 nanocomposites was estimated by measuring the photocurrent density and γ-WO3/NiWO4 nanocomposite structure was found to give the highest photocurrent density of 400 μA/cm² at 1.5 V vs Ag/AgCl (4 M KCl).
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Article title: Energy Transition from Diesel-based to Solar Photovoltaics-Battery-Diesel Hybrid System-based Island Grids in the Philippines – Techno-Economic Potential and Policy Implication on Missionary Electrification
Authors: Paul Berheau, Joey Duran Ocon
Publication title: Journal of Sustainable Development of Energy and Water and Environment Systems 7(1), April 2018
Abstract:
The cost of unsubsidized electricity in off-grid areas, particularly in the islands dependent on fossil fuels, is expensive. Previous studies and recent installations have proven that renewable energy-based hybrid systems could be suitable alternative to diesel power plants in island grids. In this comprehensive analysis of small island grids in the Philippines, results show that there is a huge economic potential to shift the diesel generation to solar photovoltaics-battery-diesel hybrid systems, with an average cost reduction of around 20% of the levelized cost of electricity. By encouraging private sector participation, hybridization could help provide electrification for twenty-four hours, stabilize the true cost of generation rate with less dependence on imported diesel prices, and reduce greenhouse gas emissions. Further, the declining cost of solar modules and batteries will significantly improve the economics of energy transition in the island grids.
Article title: Synthesis and characterisation of a novel bilayer tungsten trioxide nanojunction with different crystal growth orientation for improved photoactivity under visible light irradiation
Authors: Tao Zhu, Meng Nan Chong, Eng Seng Chan, Joey Duran Ocon
Publication title: Journal of Alloys and Compounds 749, March 2018
Abstract:
The main aim of this study was to prove the concept and elucidate the effect of a bilayer tungsten trioxide (WO3) nanojunction with different crystal growth orientation for improved photoactivity under visible light irradiation. For the first time, the concept of a bilayer WO3 nanojunction with different crystal growth orientation was demonstrated. A layer-by-layer assembly for the bilayer WO3 nanojunction with the same monoclinic ɣ-WO3 crystal structure, but with two different crystal growth orientation of {002} at 600 °C and {200} at 500 °C was synthesized via the controlled electrodeposition-annealing method. Photocurrent measurements showed that the individual photoactivity of WO3 thin film with {002} crystal growth orientation was higher than that of WO3 thin film with {200} crystal growth orientation, while the bilayer WO3 nanojunction with different crystal growth orientation exhibited the highest photoactivity. To further characterise the bilayer WO3 nanojunction, X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), high resolution-transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and photocurrent density measurements were performed. Based on the findings, a theoretical postulation model was proposed in explaining the transfer of photogenerated charge carriers in bilayer WO3 nanojunction that leads to improved photoactivity under visible light irradiation.
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Article title: Pseudocapacitive Behavior of Ni(OH)2/NiO Hierarchical Structures Grown on Carbon Fiber Paper
Authors: Luigi Dahonog, Joey Duran Ocon, Mary Donnabelle Balela
Publication title: Solid State Phenomena 266:17-181, October 2017
Abstract:
Transition metal oxides and hydroxides, specifically nickel (Ni), are currently being studied for their pseudocapacitive behaviors due to their high specific capacitance and efficient redox reactions. In this study, nickel oxide (NiO) and nickel hydroxide [Ni (OH)2] hierarchical structures were grown on carbon fiber paper via hydrothermal treatment for a binder-free electrode for pseudocapacitor. Cyclic voltammetry was employed to determine the influence of annealing temperature on the specific capacitance of NiO-and/or Ni (OH)2 – carbon fiber electrodes. The NiO – carbon fiber electrode annealed at 400°C exhibited the highest specific capacitance of about 1993.12 F/g at a scan rate of 2 mV/s. The carbon fibers were fully covered by NiO platelets which possibly provide efficient transport of electrolyte, enhancing the capacitance.
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Article title: Prospects of Electrochemically Synthesized Hematite Photoanodes for Photoelectrochemical Water Splitting: A Review
Authors: Yi Wen Phuan, Wee-Jun Ong, Meng Nan Chong, Joey Duran Ocon
Publication title: Journal of Photochemistry and Photobiology C Photochemistry Reviews 33:54-82, October 2017
Abstract:
Hematite (α-Fe2O3) is found to be one of the most promising photoanode materials used for the application in photoelectrochemical (PEC) water splitting due to its narrow band gap energy of 2.1 eV, which is capable to harness approximately 40% of the incident solar light. This paper reviews the state-of-the-art progress of the electrochemically synthesized pristine hematite photoanodes for PEC water splitting. The fundamental principles and mechanisms of anodic electrodeposition, metal anodization, cathodic electrodeposition and potential cycling/pulsed electrodeposition are elucidated in detail. Besides, the influence of electrodeposition and annealing treatment conditions are systematically reviewed; for examples, electrolyte precursor composition, temperature and pH, electrode substrate, applied potential, deposition time as well as annealing temperature, duration and atmosphere. Furthermore, the surface and interfacial modifications of hematite-based nanostructured photoanodes, including elemental doping, surface treatment and heterojunctions are elaborated and appraised. This review paper is concluded with a summary and some future prospects on the challenges and research direction in this cutting-edge research hotspot. It is anticipated that the present review can act as a guiding blueprint and providing design principles to the scientists and engineers on the advancement of hematite photoanodes in PEC water splitting to resolve the current energy- and environmental-related concerns.
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Article title: A novel ternary nanostructured carbonaceous-metal-semiconductor eRGO/NiO/α-Fe2O3 heterojunction photoanode with enhanced charge transfer properties for photoelectrochemical water splitting
Authors: Yi Wen Phuan, Meng Nan Chong, Joey Duran Ocon, Eng Seng Chan
Publication title: Solar Energy Materials and Solar Cells 169:236-244, September 2017
Abstract:
A novel ternary hematite (α-Fe2O3)-based nanostructured photoanode with excellent photoelectrochemical (PEC) performance consisting of 2D-electrochemical reduced graphene oxide (eRGO) and nickel oxide (NiO) was successfully developed through electrodeposition synthesis method. Surface morphology studies showed that the flexible eRGO sheets provided intimate and coherent interfaces between α-Fe2O3, NiO, and eRGO that enhanced charge transfer properties and thus, lowering the recombination rate of photogenerated electron-hole pairs. The incorporation of eRGO and NiO has also endowed α-Fe2O3 nanostructured photoanode with a wider spectral absorption range, where the light absorption intensities in the visible light and near infrared regions were improved. Electrochemical impedance spectroscopy analysis further confirmed that the ternary eRGO/NiO/α-Fe2O3 nanostructured photoanode possessed the lowest charge transfer resistance among all as-synthesized photoanodes. This indicates that the combinatorial effects of eRGO and NiO could improve the electron mobility and prolong the recombination process of photogenerated charge carriers that result in enhanced PEC performance. In this instance, the eRGO sheets act as surface passivation layer and electron transporting bridge that increase the electrons transfer at the semiconductor/liquid junction. Whilst NiO serves as hole scavenger that also effectively hinders the recombination of photogenerated electron-hole pairs, and provides electron donor centres that accelerate the interfacial charge transfer. Finally, the hydrogen evolution rate from the ternary eRGO/NiO/α-Fe2O3 nanostructured photoanode was measured to be 92 μmol h⁻¹ cm⁻², which was about 3-fold higher than bare α-Fe2O3 nanostructured photoanode. It is expected that the fundamental understanding gained through this study is helpful for the rational design and construction of highly efficient ternary nanostructured heterojunction photoanodes for application in PEC water splitting.
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Article title: Electrochemical Oxidation Remediation of Real Wastewater Effluents − A review
Authors: Sergi Garcia-Segura, Joey Duran Ocon, Meng Nan Chong
Publication title: Process Safety and Environmental Protection 113, September 2017
Abstract:
Fate and health risks associated with persistent organic pollutants present in water effluents are one of the major environmental challenges of this century. In this paper, the electrochemical advanced oxidation process electrochemical oxidation is reviewed for its performance over the treatment of actual industrial and urban effluents. The electrochemical treatment of industrial effluents resulting from textile dyeing, petrochemical, paper mill, tannery industry as well as the treatment of domestic and urban wastewaters are discussed. Furthermore, the combination of electrochemical oxidation with other water treatment technologies as pre-treatment, post-treatment, and integrated treatment is also examined.
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Article title: Effect of Adsorption Structures of Adsorbates (CO, COH, HCO) in Adsorbate-Induced Migration of Pd Atoms in PdCu(111)
Authors: Allan Abraham Bustria Padama, Anna Patricia S. Cristobal, Joey Duran Ocon, Wilson Angerico Diño, et al.
Publication title: The Journal of Physical Chemistry C 121(33), July 2017
Abstract:
We investigated the influence of adsorbates to the tendency of Pd atom migration in PdCu(111) with CO, COH, and HCO as adsorbates using density functional theory (DFT) based calculations. We modeled several Pd alloyed Cu(111) surfaces, which we referred as PdCu(111), by substituting a small number of Cu atoms of Cu(111) with Pd atoms. Pd atoms are located in the topmost and in the subsurface layers. The stability of the surfaces and the possibility of Pd atom migration in the presence of adsorbate are predicted based on the stability of the systems with various arrangements of Pd atoms in the topmost and in the subsurface layers. In clean PdCu(111) surface, Pd atoms prefer to remain as non-aggregated atoms in the surface. It is more energetically favored if higher number of Pd atoms exist in the topmost layer than in subsurface layer. In the presence of the adsorbed molecules, however, we showed that Pd atoms could possibly migrate either parallel or perpendicular to the surface plane until they form the aggregated Pd configuration. CO and HCO facilitate the migration process regardless of Pd atom composition in the topmost and subsurface layers. Adsorption of these molecules is dictated by the coordination of Pd atoms in the topmost layer. On the other hand, COH will prefer to have more Pd atoms in the topmost layer due to its stable adsorption on the fcc hollow site. With these results, we conclude that the adsorption structure of the molecules can influence Pd migration in PdCu surfaces.
Article title: A First-Principles Study on the Electronic and Structural Properties of Halogen-Substituted Graphene
Authors: Reynaldo Marcelino Geronia, Ace Christina Feraren Serraon, Allan Abraham Bustria Padama, Joey Duran Ocon
Publication title: ECS Transactions 77(11): 607-620, July 2017
Abstract:
In this work, we explore the properties of halogen-substituted graphene through density functional theory (DFT) calculations. Energetics and charge analysis calculations show that fluorine (F)-doped systems exhibit favorable properties like negative adsorption energies and consistent electron withdrawal ability. In addition, the densities of states (DOS) of systems involving secondarily bonded fluorine show Dirac cone-like structures below and F-1s/2px/2py-associated peaks above the Fermi level. Further work with spin polarization, nudged elastic band, and oxygen adsorption calculations is recommended to assess the potential of the above-mentioned F-based systems for synthesis and oxygen reduction reaction (ORR) activity.
Article title: CoMn2O4Anchored on N-Doped High-Dimensional Hierarchical Porous Carbon Derived from Biomass for Bifunctional Oxygen Electrocatalysis
Authors: James Lincuna Digol, Marc Francis Labata, Maricor Fernandez Divinagracia, Joey Duran Oron
Publication title: ECS Transactions 77(11):525-531, July 2017
Abstract:
There is an emerging interest in developing bifunctional oxygen electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), being key electrochemical reactions that govern the overall performance of unitized regenerative fuel cells and rechargeable metal-air batteries. However, such undertaking has been a huge challenge due to the high cost of noble metals (e.g. Pt, Ir) and their stability when used as catalysts. Herein, we report CoMn2O4 embedded on three-dimensional (3D) hierarchical porous carbon (HPC) derived from waste corn cobs as a possible noble metal-free bifunctional electrocatalyst. The hybrid catalyst is fabricated by solvothermal reaction of as-prepared N-doped 3DHPC and CoMn2O4. The template-free approach in preparing N-3DHPC ensures ample nitrogen doping using melamine to improve electronic conductivity of carbon and formation of three-dimensional, interconnected pore network, which is favorable for CoMn2O4 crystal dispersion. The same hybrid material also presents good OER activity, rendering an active and inexpensive dual-function electrocatalyst.
Article title: Exploring Novel Dopants in Graphene: Unique Properties, Group Trends, and New Insights from DFT for Electrocatalytic Applications
Authors: Joey Duran Ocon, Ace Christian Feraren Serraon, Wilbert James Claridad Futalan, Reynaldo Marcelino Geronia, et al.
Publication title: ECS Transactions 77(11):1383-1391, July 2017
Abstract:
This exploration on various new dopants for graphene and graphitic carbon nitride through ab-initio density functional theory (DFT) calculations was able to predict feasible structural configurations for these doped systems. Emergent electronic and magnetic properties have been predicted for these new classes of carbon-based two dimensional nanomaterials. In particular, alkaline-earth doped graphenes and halogen doped graphenes were qualitatively found to have potential as catalysts for the oxygen reduction reaction (ORR) due to their favorable electronic and magnetic properties as indicated by previous studies.
Article title: Carbon DioxideCO2Electrocatalytic Recycling on Electrodeposited Nanostructured Copper-Gold Electrodes
Authors: Karl Adrian Gandionco, Desiree Mae Sua-an Prado, Julie Anne D. del Rosario, Joey Duran Ocon
Publication title: ECS Transactions 77(11): 1433-1438, July 2017
Abstract:
Electrocatalytic recycling of carbon dioxide provides an ideal storage medium for renewable energy sources while off-setting the emissions of CO2 into the environment. It requires, however, an appropriate electrocatalyst to efficiently produce valuable organic molecules. In this study, electrodeposited nanostructured Cu-Au alloys were used as electrocatalysts for CO2 reduction. XRD and EDS mapping confirmed the deposition of Cu and Au. On the other hand, cyclic voltammetry verifies the activity of the fabricated catalysts towardsCO2 reduction.
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Article title: S-Doped Graphitic Carbon Nitride as Potential Catalyst towards Oxygen Reduction Reaction
Authors: Wilbert James Claridad Futalan, Ace Christian Feraren Serraon, Allan Abraham Bustria Padama, Joey Duran Ocon
Publication title: ECS Transactions 77(11):621-628, July 2017
Abstract:
Graphitic carbon nitride (GCN) is a polymeric material, which consists of carbon and nitrogen connected via tri-s-triazine-based patterns. By performing density functional theory (DFT) based study, we show that substitutional doping of various nitrogen sites by sulfur resulted in modification not only in terms of geometry of GCN but also in its electronic properties. In particular, it was shown that depending on the location of the dopant, sulfur can either donate or withdraw electrons from its neighboring carbon atoms. This property can be utilized to tune the electronic properties of graphitic carbon nitride to allow the optimum adsorption of oxygen on the catalyst surface.
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Article title: Quantum Chemical Predictions on Alkaline-Earth Doped Graphene: A Density Functional Theory (DFT) Based Investigation for a Novel Class of Carbon-Based Two-Dimensional Nanomaterials toward Electrochemical, Catalytic, and Electronic Applications
Authors: Ace Christian Feraren Serraon, Allan Abraham Bustria Padama, Julie Anne D. del Rosario, Joey Duran Ocon
Publication title: ECS Transactions 77(11): 629-636, July 2017
Abstract:
Predictions for the physical, chemical, electronic and magnetic properties of alkaline earth doped graphenes (AE-graphenes) were performed using density functional theory (DFT) calculations. Alkaline earth doping in graphene is feasible based on the adsorption energy, with alkaline earth dopants tending to adopt a nonplanar configuration when substitutionally doped in graphene. Electron transfer from the dopant atom to the graphene substrate was determined to be the primary mode of interaction within the system. Magnetic properties were also predicted for most of the AE-graphenes, with Mg-, Sr- and Ba-graphenes having ferromagnetic properties and Ca-graphene having ferrimagnetic properties. Previous DFT studies on Be-graphene were also successfully replicated and verified by this study. The unique emergent properties (i.e. electronic conductivity, spin polarization, local charge differences) of AE-graphene is promising for various applications such as catalytic, electrochemical, and electronics.
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Article title: Formation of Ni(OH))2 hybrid structures on Carbon Cloth
Authors: Luigi Dahonog, Joey Duran Ocon, Mary Donnabelle Balela
Publication title: IOP Conference Series Materials Science and Engineering 201(1): 012030, May 2017
Abstract:
Nickel hydroxide [Ni(OH)2] structures were successfully grown on carbon cloth via hydrothermal treatment followed by annealing. The Ni(OH)2 structures grown on carbon cloth were characterized using X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) analysis. XRD analysis revealed the formation of α and β phases of Ni(OH)2. Microflowers and interconnected grass-like particles were observed on the surface of the carbon cloth. The as-prepared sample could be a promising material for the fabrication of high energy storage devices because of its unique structures.
Article title: Employing electrochemical reduced graphene oxide as a co-catalyst for synergistically improving the photoelectrochemical performance of nanostructured hematite thin films
Authors: Yi Wen Phuan, Meng Nan Chong, T. Zhu, E. S. Chan, et al.
Publication title: Journal of the Taiwan Institute of Chemical Engineers 71:510-517, 2017
Abstract:
In this study, a series of electrochemical reduced graphene oxide (eRGO)-hematite nanocomposites were developed through a facile and environmental benign two-step electrodeposition method with high photoelectrochemical (PEC) performance. The resulting nanocomposites formed an intimate contact between the eRGO and hematite interface as supported by the field emission-scanning electron microscopy (FE-SEM) analysis. A remarkable 8-fold enhancement in the photocurrent density was observed on the eRGO-hematite-4 nanocomposite (using 2.0 mg/ml GO precursor) relative to the bare hematite under light irradiation. This improvement is ascribed to the finely controlled eRGO sheets that enhance the light absorption, increase PEC active surface area of hematite, improve efficient transfer of the photoinduced electrons from the conduction band of hematite to eRGO sheets and as a result leads to a minimised electron–hole pairs recombination rate. This was further evidenced with impedance characteristics, where the obtained surface charge resistance values of eRGO-hematite-4 nanocomposite are much lower than the bare hematite, revealing an efficient charge transfer step to impede the charge recombination. Lastly, a postulated mechanism for the PEC process associated with eRGO-hematite nanocomposite was presented.
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Article title: Dip-coating synthesis of high-surface area nanostructured FeB for direct usage as anode in metal/metalloid-air battery
Authors: Graniel Harne Abrenica, Joey Duran Ocon, J. Lee
Publication title: Current Applied Physics 16(9):1075-1080, September 2016
Abstract:
Multi-electron reaction anodes have been exciting battery materials due to their exceptionally high energy densities. Herein, nanostructured iron borides (nanoFeB) have been synthesized via dip-coating chemical reduction in conjunction with a heat treatment procedure and were directly used as anodes in a metal/metalloid-air battery. The crystal structure, particle size, BET surface area, and electrochemical properties of iron boride samples treated at four different temperature conditions (200 °C, 300 °C, 400 °C, and 500 °C) were investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption isotherms, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). The nanoFeB heat-treated at 300 °C (nanoFeB300) exhibits the highest surface area among reported values in literature and demonstrates excellent anode discharge performance in a metal/metalloid-air battery.
Article title: In Situ Ni-doping During Cathodic Electrodeposition of Hematite for Excellent Photoelectrochemical Performance of Nanostructured Nickel Oxide-Hematite p-n Junction Photoanode
Authors: Yi Wen Phuan, Elyas Ibrahim, Meng Nan Chong, Tao Zhu, et al.
Publication title: Applied Surface Science 392, September 2016
Abstract:
Nanostructured nickel oxide-hematite (NiO/α-Fe2O3) p-n junction photoanodes synthesized from in situ doping of nickel (Ni) during cathodic electrodeposition of hematite were successfully demonstrated. A postulation model was proposed to explain the fundamental mechanism of Ni2+ ions involved, and the eventual formation of NiO on the subsurface region of hematite that enhanced the potential photoelectrochemical water oxidation process. Through this study, it was found that the measured photocurrent densities of the Ni-doped hematite photoanodes were highly dependent on the concentrations of Ni dopant used. The optimum Ni dopant at 25 M% demonstrated an excellent photoelectrochemical performance of 7-folds enhancement as compared to bare hematite photoanode. This was attributed to the increased electron donor density through the p-n junction and thus lowering the energetic barrier for water oxidation activity at the optimum Ni dopant concentration. Concurrently, the in situ Ni-doping of hematite has also lowered the photogenerated charge carrier transfer resistance as measured using the electrochemical impedance spectroscopy. It is expected that the fundamental understanding gained through this study is helpful for the rational design and construction of highly efficient photoanodes for application in photoelectrochemical process.
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Article title: Effects of electrodeposition synthesis parameters on the photoactivity of nanostructured tungsten trioxide thin films: Optimisation study using response surface methodology
Authors: Tao Zhu, Meng Nan Chong, Yi Wen Phuan, Joey Duran Ocon
Publication title: Journal of the Taiwan Institute of Chemical Engineers 61, January 2016
Abstract:
The main aim of this study was to synthesize and characterise nanostructured tungsten trioxide (WO3) thin films via electrodeposition and subsequently, optimise the electrodeposition synthesis parameters using response surface methodology (RSM). Statistical Box-Behnken RSM design was used to investigate and optimise the effects of four independent electrodeposition synthesis parameters, namely: deposition time, precursor tungsten (W) concentration, annealing temperature and pH. In addition, the synergistic interaction between different electrodeposition synthesis parameters was identified and quantified in enabling a higher photoactivity achievable by nanostructured WO3 thin films. Resultant nanostructured WO3 thin films were characterised using field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and photocurrent density measurements under one-Sun irradiation. From the electrodeposition synthesis process, it was found that there was a gradual increase in the nanocrystallites WO3 size from 30 nm to 70 nm when the annealing temperature was varied between 400 °C and 600 °C. XRD results verified the existence of the same photoactive phase of monoclinic WO3 with increasing annealing temperature with the preferred growth orientation along the (002) planar. Whilst from the Box-Behnken RSM design, it was found that the optimum deposition time, precursor W concentration, annealing temperature and pH were: 60 min, 0.15 mol/L, 600 °C, and pH 1.0, respectively. The highest photocurrent density of 120 μA/cm2 was measured at 1 V (versus Ag/AgCl) for nanostructured WO3 thin film synthesized at the optimum conditions as informed by the Box-Behnken RSM. Further analysis and validation of the Box-Behnken RSM model using analysis of variance (ANOVA) revealed that the RSM-derived statistical predictive model was robust, adequate and representative to correlate the various electrodeposition synthesis parameters to photocurrent density. This study highlights the importance to systematically optimise the electrodeposition synthesis parameters in order to achieve a higher photocurrent density on nanostructured WO3 thin film for sustainable hydrogen production from photoelectrochemical water splitting reaction.
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Article title: Enhanced electrical and mass transfer characteristics of acid-treated carbon nanotubes for capacitive deionization
Authors: Joey Duran Ocon
Publication title: Current Applied Physics 15(11), November 2015
Abstract:
Capacitive deionization (CDI) has attracted significant attention for the next generation water treatment due to its low energy consumption and environment friendly properties in comparison to widely established methods. For CDI technology to move forward, however, the development of carbon electrodes having superb electrosorption behavior is essential. In this study, we demonstrate the functionalization of carbon nanotubes (CNTs) via acid treatment shows enhanced electrochemical characteristics and effectively improves the wettability of the acid-treated CNTs (a-CNTs) via the addition of oxygen functional groups, leading to a higher electric double layer capacitance. Furthermore, defect formation in a- CNTs increases the conductivity and decreases the mass transfer resistance during CDI operation. CDI measurements confirmed a 270% increase in performance of a-CNTs in contrast to pristine CNTs (p-CNTs), attributable to the improved characteristics outlined above.
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Article title: Direct power generation from waste coffee grounds in a biomass fuel cell
Authors: Hansem Jang, Joey D. Ocon, Seunghwa Lee, Jae Kwang Lee, et al.
Publication title: Journal of Power Sources 296(20):433-439, November 2015
Abstract:
We demonstrate the possibility of direct power generation from waste coffee grounds (WCG) via high-temperature carbon fuel cell technology. At 900 °C, the WCG-powered fuel cell exhibits a maximum power density that is twice than carbon black. Our results suggest that the heteroatoms and hydrogen contained in WCG are crucial in providing good cell performance due to its in-situ gasification, without any need for pre-reforming. As a first report on the use of coffee as a carbon-neutral fuel, this study shows the potential of waste biomass (e.g. WCG) in sustainable electricity generation in fuel cells.
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Article title: High Power Density Semiconductor-Air Batteries Based on P-Type Ge with Different Crystal Orientations
Authors: Joey Duran Ocon, Graniel Harne Abrenica, Jaeyoung. Lee
Publication title: ChemElectroChem 3(2), November 2015
Abstract:
The quasi‐perpetual discharge behavior of Ge anodes in semiconductor–air batteries was first demonstrated in our previous studies, marked by high anode utilization and a flat discharge profile over long‐term discharge operation. In this Article, we show the crystal orientation dependence of the discharge behavior of p‐type Ge anodes. In general, p‐type Ge anodes at the low‐index crystal indices could operate in the milliampere‐scale current range and at high power densities, in stark contrast to the current‐limited operation of Si–air batteries.
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Article title: An optimized mild reduction route towards excellent cobalt-graphene catalysts for water oxidation
Authors: Doungkamon Phihusut, Joey Duran Ocon, Jae K. Lee, J. Lee
Publication title: RSC Advances 5(80). July 2015
Abstract:
Low cost yet efficient water oxidation catalysts are crucial in making economically competitive water electrolyzers and secondary metal-air batteries. In this study, we demonstrate the optimized mild reduction of graphene oxide towards the synthesis of highly active and stable cobalt-graphene electrocatalysts for water oxidation. Contrary to the conventional use of fully reduced graphene oxide (RGO) as composite material in electrocatalysis, our results suggest that the oxygen functional groups, which are retained during mild GO reduction, are crucial in the formation of cobalt oxalate (CoC2O4) microstructures. Gently reduced graphene oxide (gRGO) with low degree of reduction results to CoC2O4/gRGO microrods with impressive water oxidation activity, reaching current densities 21.1% higher than conventional iridium oxide-based catalysts and 70.5% more than the unoptimized CoC2O4/gRGO catalysts. Mild reduction of GO favors the homogeneous formation of microstructures via the negatively-charged functional groups, which attract the positive Co ions and lead to stronger chemical interaction between the two components. This work points towards investigating and reevaluating the role of the degree of GO reduction on graphene’s contribution to the composition and catalytic activity of metal-graphene composites.
Article title: Ultrahigh purification in concentrated NaOH by electrowinning for solar cell application
Authors: Jiyong Joo, Jongwon Kim, Jin Won Kim, Joey Duran Ocon, et al.
Publication title: Separation and Purification Technology 145, May 2015
Abstract:
High purity sodium hydroxide (NaOH) solution is extremely important in the large-scale manufacturing of impurity-free silicon (Si) wafers for solar cells. In this paper, we demonstrate the purification of highly concentrated NaOH via electrowinning. By optimizing temperature, current density, and the type of electrode for both anodes and cathodes, we maximized the selectivity toward cathodic deposition of Fe and Ni. Our results suggest that removal of metal impurities in the concentrated 50 wt.% NaOH is highly dependent on the reactor temperature (>90 °C) due to enhanced reaction kinetics and decreased solution viscosity. Meanwhile, current density has limited effect on the metal removal efficiency. We further demonstrate that the cathodic deposition of Fe and Ni strongly relies on the type of electrode pair used, with platinum (Pt) and nickel (Ni) as the anode and cathode, respectively, exhibiting the best removal performance. The good electrochemical performance arises from the high catalytic activity of Pt anode and good stability of Ni cathode from the highly corrosive concentrated alkaline conditions. Following these results, we recommend future scientific and technical studies on the use of electrowinning as a possible alternative to the costly membrane-based purification techniques.
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Article title: Improvement of Energy Capacity with Vitamin C Treated Dual-Layered Graphene–Sulfur Cathodes in Lithium–Sulfur Batteries
Authors: Jin Won Kim, Joey Duran Ocon, Ho-Sung Kim, J. Lee
Publication title: ChemSusChem 8(17), April 2015
Abstract:
A graphene‐based cathode design for lithium–sulfur batteries (LSB) that shows excellent electrochemical performance is proposed. The dual‐layered cathode is composed of a sulfur active layer and a polysulfide absorption layer, and both layers are based on vitamin C treated graphene oxide at various degrees of reduction. By controlling the degree of reduction of graphene, the dual‐layered cathode can increase sulfur utilization dramatically owing to the uniform formation of nanosized sulfur particles, the chemical bonding of dissolved polysulfides on the oxygen‐rich sulfur active layer, and the physisorption of free polysulfides on the absorption layer. This approach enables a LSB with a high specific capacity of over 600 mAh gsulfur−1 after 100 cycles even under a high current rate of 1C (1675 mA gsulfur−1). An intriguing aspect of our work is the synthesis of a high‐performance dual‐layered cathode by a green chemistry method, which could be a promising approach to LSBs with high energy and power densities.
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Article title: Alkaline CO2 Electrolysis Towards Selective and Continuous HCOO - Production over SnO2Nanocatalysts
Authors: Seunghwa Lee, Joey D. Ocon, Young-il Son, Jaeyoung Lee
Publication title: The Journal of Physical Chemistry C 119(9): 150210022236005, February 2015
Abstract:
The electrolyte pH is an important parameter in determining the equilibrium concentrations of the carbon dioxide-bicarbonate-carbonate system, as well as in mapping out the thermodynamically stable phases of tin dioxide (SnO2) in an aqueous electrochemical system. Thus, we explored an optimized region in the combined potential-pH (E-pH) diagram of the two systems, where there is a simultaneously high catalytic activity for carbon dioxide (CO2) electrolysis and good phase stability for the SnO2 nanocatalysts. Our results suggest that choosing the right E-pH combination, which in this case is at 0.6 V (vs. RHE) and pH=10.2, resulted in a high faradaic efficiency of 67.6 % for formate (HCOO-) synthesis and an efficiency retention of ~90% after 5 hr, while maintaining the stability of the oxide structure and avoiding the formation of carbon monoxide. Widely applicable to neutral or near-neutral pH metal oxide electrocatalysts, optimized alkaline CO2 electrolysis offer distinct advantages in terms of the three major catalyst properties: activity, selectivity, and stability.
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Article title: Controlled Electrochemical Etching of Nanoporous Si Anodes and Its Discharge Behavior in Alkaline Si – Air Batteries
Authors: Dong-Won Park, Soeun Kim, Joey Duran Ocon, Graniel Harne Abrenica, et al.
Publication title: ACS Applied Materials & Interfaces 7(5), January 2015
Abstract:
We here report the fabrication of nanoporous silicon (nPSi) electrodes via electrochemical etching to form a porous Si layer with controllable thickness and pore size. Varying the etching time and ethanolic HF concentration results to different surface morphologies, with various degrees of electrolyte access depending on the pore characteristics. Optimizing the etching condition leads to well-developed nPSi electrodes, which have thick porous layers and smaller pore diameter and exhibit improved discharge behaviour as anodes in alkaline Si-air cells in contrast to flat Si anode. Although electrochemical etching is effective in improving the interfacial characteristics of Si in terms of high surface area, we observed that mild anodization occurs and it produces an oxide overlayer. We then show that this oxide layer in nPSi anodes can be effectively removed to produce an nPSi anode with good discharge behaviour in an actual alkaline Si-air cell. In the future, the combination of high surface area nPSi anodes with non-aqueous electrolytes (e.g. room temperature ionic liquid electrolyte) to minimize the strong passivation behaviour and self-discharge in Si could lead to Si-air cells with stable voltage profile and high anode utilization.
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Article title: Diagnosis of the measurement inconsistencies of carbon-based electrocatalysts for the oxygen reduction reaction in alkaline media
Authors: Dongyoon Shin, Beomgyun Jeong, Myounghoon Choun, Joey Duran Ocon, et al.
Publication title: RSC Advances 5(2):1571-1580, January 2015
Abstract:
Finding inexpensive alternative catalysts for the oxygen reduction reaction (ORR) is considered as one of the most overriding challenges in the development of electrochemical technologies. Although significant progress has been made in developing carbon-based ORR catalysts, there is difficulty in judging improvements in the catalysts due to the inconsistent results arising from differences in experimental conditions. In this review, we provide a diagnosis of the influence of key factors in the measured ORR activity of catalysts. Knowing the exact conditions when measuring ORR activity is of paramount importance in establishing a reference for relevant comparison of ORR performance in developed catalysts.
Article title: Electrode Architecture in Galvanic and Electrolytic Energy Cells
Authors: Beomgyun Jeong, Joey Duran Ocon, J. Lee
Publication title: Angewandte Chemie International Edition in English 55(16), January 2015
Abstract:
Electrodes in galvanic and electrolytic energy cells are complicated structures comprising redox-active materials, ionic/electronic conductors, and porous pathways for mass transfer of reactants. In contrast to breakthroughs in component development, methods of optimizing whole-system architectural design to draw maximum output have not been well explored. In this Minireview, we introduce generalized types of electrode architecture, discuss fabrication strategies, and characterize already built structures. Systematic efforts to discover optimal electrode configurations will resolve long-standing discrepancies that arise between whole systems and the sums of their parts for a number of electrochemical reactions and technologies.
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Article title: Enhancing Role of Nickel in the Nickel–Palladium Bilayer for Electrocatalytic Oxidation of Ethanol in Alkaline Media
Authors: Julie Anne D. del Rosario, Joey Duran Ocon, Hongrae Jeon, Youngmi Yi, et al.
Publication title: The Journal of Physical Chemistry C 118(39):22473-22478, October 2014
Abstract:
Direct ethanol fuel cells (DEFCs) have been widely studied because of their potential as a high-energy density and low-toxicity power source of the future. Suitable catalysts for the anode reaction, however, are necessary to fully utilize the advantages of DEFCs. In this paper, we fabricated nickel (Ni)palladium (Pd) bimetallic catalysts with a bilayer structure, using sputtering deposition on a titanium (Ti) foil substrate, and investigated the activity and stability of the catalysts toward ethanol electro-oxidation in alkaline media. Our results suggest that while Pd is the active component and Ni has negligible activity toward ethanol oxidation, Ni-modified Pd (NiPd/Ti) provides the best activity in comparison to PdNi/Ti and the monometallic catalysts. In fact, optimizing the Ni amount could lead to a highly active and stable bimetallic electrocatalyst because of Nis ability to increase the active surface area of the Pd layer, provide hydroxyl species to replenish the active sites, and act as a protective layer to the Pd. Overall, these results provide a better understanding on the role of Ni in bimetallic catalysts, especially in a bilayer configuration, to allow the use of an ethanol oxidation reaction (EOR)-active electrocatalyst with a much lower Pd content.
Article title: Insights into autonomously formed oxygen-evacuated Cu2O electrode for the selective production of C2H4from CO2
Authors: Dahee Kim, Seunghwa Lee, Joey Duran Ocon, Beomgyun Jeong, et al.
Publication title: Physical Chemistry Chemical Physics 17(2), September 2014
Abstract:
Electrochemical conversion of carbon dioxide (CO2) to small organic fuels (e.g. formate, methanol, ethylene, and ethanol) is touted as one of the most promising approaches in solving the problems of climate change and energy security. In this study, we report the highly efficient electrochemical reduction of CO2 using cuprous oxide (Cu2O) electrodes to produce ethylene (C2H4) primarily. During CO2 electrolysis with an electrodeposited Cu2O on a carbon electrode, we observe the transformation of compact metal oxide layer to a bulk metal oxide structure with oxygen-vacated sites, where the notable electrocatalytic process towards selective production of C2H4 occurs. In contrast with previous studies, our results clearly indicate that the Cu2O bulk structure remains inside the entire Cu2O layer (I have different opinion to this conclusion.) and it efficiently catalyzes the conversion process of CO2 at low overpotential, exhibiting high selective faradaic efficiency of over 20 % towards C2H4 formation even in long-term electrolysis.
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Article title: Gently reduced graphene oxide incorporated into cobalt oxalate rods as bifunctional oxygen electrocatalyst
Authors: Doungkamon Phihusut, Joey Duran Ocon, Beomgyun Jeong, Jin Won Kim, et al.
Publication title: Electrochimica Acta 140:404-411, September 2014
Abstract:
Water-oxygen electrochemistry is at the heart of key renewable energy technologies (fuel cells, electrolyzers, and metal-air batteries) due to the sluggish kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Although much effort has been devoted to the development of improved bifunctional electrocatalysts, an inexpensive, highly active oxygen electrocatalyst, however, remains to be a challenge. In this paper, we present a facile and robust method to create gently reduced graphene oxide incorporated into cobalt oxalate microstructures (CoC2O4/gRGO) and demonstrate its excellent and stable electrocatalytic activity in both OER and ORR, arising from the inherent properties of the components and their physicochemical interaction. Our synthesis technique also explores a single pot method to partially reduce graphene oxide and form CoC2O4 structures while maintaining the solution processability of reduced graphene oxide. While the OER activity of CoC2O4/gRGO is exclusively due to CoC2O4, which transformed into OER-active Co species, the combination with gRGO significantly improves OER stability. On the other hand, CoC2O4/gRGO exhibits synergistic effect towards ORR, via a quasi-four-electron pathway, leading to a slightly higher ORR limiting current than Pt/C. Remarkably, gRGO offers dual functionality, contributing to ORR activity via the N-functional groups and also enhancing OER stability through the gRGO coating around CoC2O4 structures. Our results suggest a new class of metal-carbon composite that has the potential to be alternative bifunctional catalysts for regenerative fuel cells and metal-air batteries.
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Article title: Carbon Electrodes in Capacitive Deionization Process
Authors: Sangho Chung, Jae K Lee, Joey Duran Ocon, Young-Il Son, et al.
Publication title: Journal of the Korean Industrial and Engineering Chemistry 25(4):346-351, August 2014
Abstract:
With the world population's continuous growth and urban industrialization, capacitive deionization (CDI) has been proposed as a next-generation water treatment technology to augment the supply of water. As a future water treatment method, CDI attracts significant attention because it offers small energy consumption and low environmental impact in comparison to conventional methods. Carbon electrodes, which have large surface area and high conductivity, are mainly used as electrode materials of choice for the removal of ions in water. A variety of carbon materials have been investigated, including their adsorption- desorption behavior in accordance to the specific surface area and pore size distribution. In this review, we analyzed and highlighted these carbon materials and looked at the impact of pore size distribution to the overall CDI efficiency. Finally, we propose an optimal condition in the interplay between micropores and mesopores in order to provide the best electrosorption property for these carbon electrodes. © 2014 The Korean Society of Industrial and Engineering Chemistry. All rights reserved.
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Article title: Quasi-perpetual discharge behaviour in p-type Ge–air batteries
Authors: Joey Duran Ocon, Jin Won Kim, Graniel Harne Abrenica, Jae K. Lee, et al.
Publication title: Physical Chemistry Chemical Physics 16(41), June 2014
Abstract:
Metal-air batteries continue to become attractive energy storage and conversion systems due to their high energy and power densities, safer chemistries, and economic viability. Semiconductor-air batteries - a term we first define here as metal-air batteries that use semiconductor anodes such as silicon (Si) and germanium (Ge) - have been introduced in recent years as new high-energy battery chemistries. In this paper, we describe the excellent doping-dependent discharge kinetics of p-type Ge anodes in a semiconductor-air cell employing a gelled KOH electrolyte. Owing to its Fermi level, n-type Ge is expected to have lower redox potential and better electronic conductivity, which could potentially lead to a higher operating voltage and better discharge kinetics. Nonetheless, discharge measurements demonstrated that this prediction is only valid at the low current regime and breaks down at the high current density region. The p-type Ge behaves extremely better at elevated currents, evident from the higher voltage, more power available, and larger practical energy density from a very long discharge time, possibly arising from the high overpotential for surface passivation. A primary semiconductor-air battery, powered by a flat p-type Ge as a multi-electron anode, exhibited an unprecedented full discharge capacity of 1302.5 mA h gGe(-1) (88% anode utilization efficiency), the highest among semiconductor-air cells, notably better than new metal-air cells with three-dimensional and nanostructured anodes, and at least two folds higher than commercial Zn-air and Al-air cells. We therefore suggest that this study be extended to doped-Si anodes, in order to pave the way for a deeper understanding on the discharge phenomena in alkaline metal-air conversion cells with semiconductor anodes for specific niche applications in the future.
Article title: Electrocatalytic oxygen evolution reaction at a FeNi composite on a carbon nanofiber matrix in alkaline media
Authors: Xianghua An, Dongyoon Shin, Joey Duran Ocon, Jae K. Lee
Publication title: Chineses Journal of Catalysis 35(6):891-895, June 2014
Abstract:
Non-noble metals such as Fe and Ni have comparable electrocatalytic activity and stability to that of Ir and Ru in an oxygen evolution reaction (OER). In this study, we synthesized carbon nanofibers with embedded FeNi composites (FeNi-CNFs) as OER electrocatalysts by a facile route comprising electrospinning and the pyrolysis of a mixture of metal precursors and a polymer solution. FeNi-CNFs demonstrated catalytic activity and stability that were better than that of 20 wt% Ir on Vulcan carbon black in oxidizing water to produce oxygen in an alkaline media. Physicochemical and electrochemical characterization revealed that Fe and Ni had synergistic roles that enhanced OER activity by the uniform formation and widening of pores in the carbon structure, while the CNF matrix also contributed to the increased stability of the catalyst.
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Article title: Functionalized Graphene-Based Cathode for Highly Reversible Lithium-Sulfur Batteries
Authors: Jin Won Kim, Joey Duran Ocon, Dong-Won Park, J. Lee
Publication title: ChemSusChem 7(5):1265-1273, May 2014
Abstract:
In this article, we highlight the salient issues in the development of lithium-sulfur battery (LSB) cathodes, present different points of view in solving them, and argue, why in the future, functionalized graphene or graphene oxide might be the ultimate solution towards LSB commercialization. As shown by previous studies and also in our recent work, functionalized graphene and graphene oxide enhance the reversibility of the charge-discharge process by trapping polysulfides in the oxygen functional groups on the graphene surface, thus minimizing polysulfide dissolution. This will be helpful for the rational design of new cathode structures based on graphene for LSBs with minimal capacity fading, low extra cost, and without the unnecessary weight increase caused by metal/metal oxide additives.
Full text available upon request to the author
Article title: Excavated Fe-N-C Sites for Enhanced Electrocatalytic Activity in the Oxygen Reduction Reaction
Authors: Beomgyun Jeong, Dongyoon Shin, Hongrae Jeon, Joey Duran Ocon
Publication title: ChemSusChem 7(5), May 2014
Abstract:
Platinum (Pt) is the best electrocatalyst for the oxygen reduction reaction (ORR) in hydrogen fuel cells, but it is an extremely expensive resource. The successful development of a cost-effective non-Pt ORR electrocatalyst will be a breakthrough for the commercialization of hydrogen-air fuel cells. Ball milling has been used to incorporate metal and nitrogen precursors into micropores of carbon more effectively and in the direct nitrogen-doping of carbon under highly pressurized nitrogen gas in the process of the preparation of non-noble ORR catalysts. In this study, we first utilize ball milling to excavate the ORR active sites embedded in Fe-modified N-doped carbon nanofibers (Fe-N-CNFs) by pulverization. The facile ball-milling process resulted in a significant enhancement in the ORR activity and the selectivity of the Fe-N-CNFs owing to the higher exposure of the metal-based catalytically active sites. The degree of excavation of the Fe-based active sites in the Fe-N-CNFs for the ORR was investigated with cyclic voltammetry, X-ray photoelectron spectroscopy, and pore-size distribution analysis. We believe that this simple approach is useful to improve alternative ORR electrocatalysts up to the level necessary for practical applications.
Full text available upon request to the author
Article title: High Energy Density Germanium Anodes for Next Generation Lithium Ion Batteries
Authors: Joey Duran Ocon, Jae K. Lee, J. Lee
Publication title: Journal of the Korean Industrial and Engineering Chemistry 25(1), February 2014
Abstract:
Lithium ion batteries (LIBs) are the state-of-the-art technology among electrochemical energy storage and conversion cells, and are still considered the most attractive class of battery in the future due to their high specific energy density, high effi-ciency, and long cycle life. Rapid development of power-hungry commercial electronics and large-scale energy storage appli-cations (e.g. off-peak electrical energy storage), however, requires novel anode materials that have higher energy densities to replace conventional graphite electrodes. Germanium (Ge) and silicon (Si) are thought to be ideal prospect candidates for next generation LIB anodes due to their extremely high theoretical energy capacities. For instance, Ge offers relatively lower volume change during cycling, better Li insertion/extraction kinetics, and higher electronic conductivity than Si. In this fo-cused review, we briefly describe the basic concepts of LIBs and then look at the characteristics of ideal anode materials that can provide greatly improved electrochemical performance, including high capacity, better cycling behavior, and rate capability. We then discuss how, in the future, Ge anode materials (Ge and Ge oxides, Ge-carbon composites, and other Ge-based composites) could increase the capacity of today's Li batteries. In recent years, considerable efforts have been made to fulfill the requirements of excellent anode materials, especially using these materials at the nanoscale. This article shall serve as a handy reference, as well as starting point, for future research related to high capacity LIB anodes, especially based on semiconductor Ge and Si.
Article title: Ultrafast and stable hydrogen generation from sodium borohydride in methanol and water over Fe-B nanoparticles
Authors: Joey Duran Ocon, Trinh Ngoc Tuan, Youngmi Yi, Rizalinda de Leon
Publication title: Journal of Power Sources 243, December 2013
Abstract:
Use of environmentally friendly hydrogen as fuel on a massive scale requires efficient storage and generation systems. Chemical hydrides, such as sodium borohydride (NaBH4), have the capacity to meet these needs as demonstrated by its high hydrogen storage efficiency. Here, we first report the catalytic activity of Fe–B nanoparticles supported on porous Ni foam – synthesized via a simple chemical reduction technique – for hydrogen generation from the mixtures of NaBH4, H2O, and CH3OH. Activation energies of the catalyzed hydrolysis (64.26 kJ mol−1) and methanolysis (7.02 kJ mol−1) are notably lower than other metal-boron catalysts previously reported. Methanol, in combination with a cheap but highly active Fe–B nanocatalysts, provides ultrafast rates of low temperature hydrogen generation from the sodium borohydride solutions.
Full text available upon request to the author
Article title: Lessons from Korean Innovation model for ASEAN Countries towards a knowledge economy
Authors: Joey Duran Ocon, Doungkamon Phihusut, Julie Anne D. del Rosario, Trinh Ngoc Tuan, et al.
Publication title: STI Policy Review 4(2), September 2013
Abstract:
The Association of Southeast Asian Nations (ASEAN) achieved relatively rapid economic growth over the past decade. Sustainable growth among member states, however, is put into question due to macroeconomic challenges, political risk, and vulnerability to external shocks. Developed countries, in contrast, have turned into less labor-intensive technologies to further expand their economies. In this paper, we review the science, technology, and innovation (STI) policies and statuses of the scientific and technological capabilities of the ASEAN member countries. Empirical results based on STI indicators (R&D spending, publications, patents, and knowledge economy indices) reveal considerable variation between the science and technology (S&T) competence and effectiveness of STI policies of ASEAN members. We have categorized nations into clusters according their situations in their S&T productivity. Under the Korean Innovation Model, Cambodia, Laos, Myanmar, and Brunei are classified as being in the institutional-building stage, while Malaysia, Thailand, Indonesia, the Philippines, and Vietnam in the catch up stage, and Singapore in the post-catch up stage. Finally , policy prescriptions on how to enhance the S&T capabilities of the developing ASEAN countries, based on the South Korea development experience, are presented.
Article title: An etched nanoporous Ge anode in a novel metal-air energy conversion cell
Authors: Joey Duran Ocon, Jin Won Kim, Sunghyun Uhm, Bongjin Simon Mun, et al.
Publication title: Physical Chemistry Chemical Physics 15(17), March 2013
Abstract:
We first report the successful synthesis of porous germanium with ordered hierarchical structures, via controlled etching, and show its performance as an anode in a new metal-air battery. Our experimental results demonstrate the potential use of porous germanium in a high power density Ge-air energy conversion cell, showing a stable long-term discharge profile at various current drains.
Article title: Enhanced reversible capacity of Li-S battery cathode based on graphene oxide
Authors: Jin Won Kim, Joey Duran Ocon, Dong-Won Park, J. Lee
Publication title: Journal of Energy Chemistry 22(2): 336-340, March 2013
Abstract:
Lithium sulfur battery (LSB) offers several advantages such as very high energy density, low-cost, and environmental-friendliness. However, it suffers from serious degradation of its reversible capacity because of the dissolution of reaction intermediates, lithium polysulfides, into the electrolyte. To solve this limitation, there are many studies using graphene-based materials due to their excellent mechanical strength and high conductivity. Compared with graphene, graphene oxide (GO) contains various oxygen functional groups, which enhance the reaction with lithium polysulfides. Here, we investigated the positive effect of using GO mixed with carbon black on the performance of cathode in LSB. We have observed a smaller drop of capacity in GO mixed sulfur cathode. We further demonstrate that the mechanistic origin of reversibility improvement, as confirmed through CV and Raman spectra, can be explained by the stabilization of sulfur in lithium polysulfide intermediates by oxygen functional groups of GO to prevent dissolution. Our findings suggest that the use of graphene oxide-based cathode is a promising route to significantly improve the reversibility of current LSB.
Full text available upon request to the author
Article title: Oxygen electrocatalysis in chemical energy conversion and storage technologies
Authors: J. Lee, Beomgyun Jeong, Joey Duran Ocon
Publication title: Current Applied Physics 13(2):309-321, March 2013
Abstract:
Oxygen electrocatalysis that we first defined is considered as the most important phenomenon in almost all electrochemical industries because it is the most sluggish reaction that governs the overall reaction rate in electrochemical cells. In this review, we cover two main areas of oxygen–water electrocatalysis, oxygen reduction to water and oxygen evolution from water. In particular, it aims to provide the readers with an understanding of the critical scientific challenges facing the development of oxygen electrocatalysts, various unique attributes of recent novel catalysts, the latest developments in electrode construction and the outlook for future generation of oxygen electrocatalysts. This review will be of value to both electrochemists and other applied scientists interested in this field of electrocatalysis.
Full text available upon request to the author
Article title: Theory-derived law of the wall for parallel flat-plates turbulent flow
Authors: Rizalinda de Leon, Joey Duran Ocon, Ludek Jirkovsky, Armador Muriel
Publication title: CFD Letters 4(3):93-101, July 2012
Abstract:
It is well known that in a turbulent flow between two parallel flat plates, the horizontal mean velocity varies logarithmically with height (the so-called 'logarithmic-law-of-the- wall'). The law of the wall is a description of the mean velocity profile in wall bounded flows and has been regarded as one of the underpinning doctrine in the turbulence community for more than half a century. Much of our understanding in wall turbulence has been based from the continuum Navier-Stokes Equation (NSE). More recently, following studies of a modified Navier Stokes Equation, we applied a modified incompressible NSE to the flow of turbulent fluid between two parallel flat plates and solved it analytically [1]. We extended the analysis to the turbulent flow along a single wall and compared the results with the established controversial von Karman logarithmic law of the wall [2]. We found velocity profiles and velocity time evolution of a turbulent system, through simple numerical simulations, that cannot be reproduced from the classical NSE.
Papers Presented
Article title: On the transferability of smart energy systems on off-grid islands using cluster analysis-a case study for the Philippine Archipelago
Authors: Henning Meschede, Eugene, Jr. Agusan Esparcia, Peter K. R. Holzapfel, Paul Bertheau, et al.
Conference title: 13th SDEWES Conference in Palermo, October 2018
Abstract:
Islands are highly diverse in their climatic, physical, social, and economic characteristics. Thus, each islands energy system needs to be designed according to its specific features. However, similarities among islands exist, which can enable fast transfer of concepts and experiences on energy systems. In the Philippines, only few off-grid islands are incorporating smart energy systems through hybrid electricity systems. While most off-grid islands still do not have access to electricity, majority off-grid Philippine islands having access to electricity are powered primarily by diesel-fired generators, which come along with limited operating time, high CO2 emissions, low efficiency and system unreliability. Therefore, a systematic classification through cluster methods could potentially fast-track design of smart energy systems for off-grid Philippine islands. In this work, a cluster analysis is performed for 502 off-grid islands in the Philippine archipelago, classifying the islands according to their similarities in socio-economic and physical characteristics, and local energy resource potential. The results show that most of the islands belong to five clusters of very small and small islands for which PV-battery systems would be the favourable backbone of a future energy system based on RES. These islands show a varying level of feasibility for harnessing wind energy. In medium and big islands, opportunities of linking electricity systems to water supply and thermal energy loads as well as to the transport sector, are identified and their relevance in the clusters is discussed. The results are consistent in validating the individual characteristics of chosen off-grid islands. This study supports policy makers and private investors to decide which smart energy system projects are suitable for which particular islands.
Article title: Sputtered palladium-nickel bilayer for electrocatalytic oxidation of ethanol in alkaline media
Authors: Julie Anne D. del Rosario, Joey Duran Ocon, Hongrae Jeon, J. Lee, et al.
Conference title: Annual International Conference on Chemistry, Chemical Engineering and Chemical Process, January 2015
Abstract:
Direct ethanol fuel cell (DEFC) has been widely studied because of its potential to be a high-energy density and low-toxicity power source of the future. Suitable catalysts for the anode reaction are necessary to fully utilize the advantages of DEFCs. Consequently, we fabricated bilayer models of palladium-nickel catalysts using sputtering deposition technique. We then investigated the activity of the catalysts towards oxidation of ethanol in alkaline media. Results suggest that palladium is the active component of the bilayer catalysts whereas nickel alone has negligible activity towards ethanol oxidation. Interestingly, Ni-modified palladium surface gives higher activity than Pd and Pd-modified nickel surface. This investigation is expected to be of great importance in the development of suitable EOR catalysts for direct ethanol fuel cells.
Full text available upon request to the author
Article title: Assessment of co-production of alternative fuels in the Philippines
Authors: Rizalinda de Leon, Joey Duran Ocon, Stephen Salve Doliente, Nes Daniel Sabud
Conference title: 2011 University of the Philippines Diliman College of Engineering Professorial Chair Colloquium
Enrico C. Paringit
Sex: Male
Education
Doctor of Philosophy in Engineering, Tokyo Institute of Technology 2003
Master of Science in Remote Sensing, University of the Philippines, 1999
Bachelor of Science in Geodetic Engineering, University of the Philippines, 1997
Field of Specialization
Remote Sensing
Radiative Transfer
Water Quality
Hyperspectral Remote Sensing
Water Color Remote Sensing
Lidar Remote Sensing
Catchment Hydrology
Flood Modelling
Lidar
Renewable Energy and Environment
Article title: An Assessment on the Development of the Nationwide Solid Waste-To-Energy Potential Model in the Philippines
Authors: Ronald Allan Co, Enrico C. Paringit
Publication title: E3S Web of Conferences 190:00035, January 2020
Abstract:
Solid waste biomass contains a significant amount of carbohydrates and other combustible chemical compounds that have potential as an alternative energy source. In this paper, the synthesis of biomass energy potential assessment from solid waste and the development of a model equation was presented, in order to utilize as assessment tools for the Philippine local government units, most especially the established sanitary landfills and waste-to-energy technologies and facilities that are soon-to-be installed. Data for the said model equation was obtained from various Philippine government agencies, such as the Department of Energy, Department of Environment and Natural Resources, and others. In order to accumulate those in the model, numerous concepts are applied, such as parameterization and others. Furthermore, a time-series study is subjected to analysis, in order to forecast of the biomass energy. Moreover, the biomass energy potential from the rest of the Philippine archipelago may be further evaluated with the use of the proposed model equation.
Full text available upon request to the author
Article title: Linear spectral unmixing of sentinel-3 imagery for urban land cover - land surface temperature (LST) analysis: a case study of Metro Manila, Philippines
Authors: Charmaine Cruz, Ariel Blanco, Jennieveive Babaan, John Andrew Cruz, et al.
Publication title: The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, XLII-4/W19, 2019
Abstract:
The advancement of remote sensing technologies is a huge advantage in various environmental applications including the monitoring of the rapid development in an urban area. This study aims to estimate the composition of the different classes (vegetation, impervious surfaces, soil) in Metro Manila, Philippines using a 300-meter spatial resolution Sentinel-3 Ocean and Land Colour Instrument image. The relationship between these land cover fractions with the spatial distribution of land surface temperature at this scale is evaluated. Sentinel-3 image has a higher spectral resolution (i.e. 21 bands), as compared with other Landsat and Sentinel missions, which is a requirement for an accurate cover mapping. Linear Spectral Unmixing (LSU), a sub-pixel classification method, was employed in identifying the fractional components in the image based on their spectral characteristics. Field survey using spectroradiometer was conducted to acquire spectral signatures of an impervious surface, vegetation, and soil which were used as the endmembers in the unmixing process. To assess the accuracy of the resulting vegetation fractional image, this was compared with a separate land cover pixel-based classification result using a 3-meter high spatial resolution PlanetScope image and with another vegetation index product of Sentinel-3. The results indicate that the recently available Sentinel-3 image can accurately estimate vegetation fraction with R2 = 0.84 and 0.99, respectively. In addition, the land surface temperature (LST) retrieved from Climate Engine is negatively correlated with the vegetation fraction cover (R2 = 0.81) and positively correlated with the impervious surface fraction cover (R2 = 0.66). Soil, on the other hand, has no correlation with the LST.
Article title: Canopy cover estimation from satellite data for acacia mangium plantation Basay, Negros Oriental
Authors: F. A. M. Tandoc, Czar Jakiri Soriano Sarmiento, Enrico C. Paringit, Ayin Modina Tamondong, et al.
Publication title: The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, XLII-4/W19, 2019
Abstract:
Forest assessment and measurement can be costly, laborious and time-consuming when done manually. Remote Sensing aids by providing data of sufficient accuracy for large tracts of forest lands in the form of maps. These data can then assist in decision- making for better forest management. This study estimated canopy cover, a primary forest measurement parameter, using remotely- sensed data. Satellite images such as Planetscope and WorldView were used to estimate canopy cover. The results were then compared to measurements obtained from a manual inventory – in this case, of an Acacia mangium plantation. The manual inventory was conducted in a National Greening Program (NGP) site in Basay, Negros Oriental. Field inventory involved a Static Global Navigation Satellite System (GNSS) survey and a Total Station survey to get the accurate location of trees present in the plot. Diameter- at- breast was measured for all trees. Tree height and crown diameter were measured for at least 10 percent of all trees in the plot.
Full text available upon request to the author
Article title: Spectral characterization of a closed canopy and open canopy forest in northern Sierra Madre Natural Park
Authors: C. Vidad, Czar Jakiri Soriano Sarmiento, Carla Arellano, Regine Anne Faelga, et al.
Publication title: The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, XLII-4/W19, 2019
Abstract:
Forest lands play crucial roles in nutrient recycling and climate regulation. The change of closed canopy forests to open canopy forests may indicate disturbance within the closed canopy forest. Within the local context of the Philippines, few studies have been conducted to monitor changes in closed canopy forest lands. Efforts to do so are limited by the spatial extent, remoteness and ruggedness of closed canopy forests. Satellite imagery can cover the spatial extent of forest lands as well as provide constant revisit periods for monitoring. However, while multispectral imaging can detect changes in land cover, it has limitations when detecting the subtler change from closed canopy to open canopy forest cover. This study aims to provide baseline spectral characterization of a closed canopy forest in the Philippines. For this study, a hyperspectral sensor (EO1-Hyperion) with 198 band channels ranging from 426.82 nm to 2395.50 nm and a pixel size of 30 m was used to characterize the spectral variations of closed canopy forest, open canopy forest, shrubs and cropland in Northern Sierra Madre, Philippines. Multiple endmember spectral mixture analysis (MESMA) was employed to sort the image into classes as well as to characterize intra-spectral variations among the identified classes. Spectral library endmembers were assembled, optimized and used to classify the image. The spectral libraries were optimized by using Endmember Average Root Mean Square Error (EAR) , Minimum Average Spectral Angle (MASA) and Iterative Endmember Selection (IES). Results overall agreement is 0.56 for EAR and IES and kappa coefficient is at 0.4.
Full text available upon request to the author
Article title: Multi-temporal analysis of dense and sparse forests’ radar backscatter using Sentinel-1A collection in google earth engine
Authors: Carla Arellano, A. A. Maralit, Enrico C. Paringit, Czar Jakiri Soriano Sarmiento, et al.
Publication title: The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, XLII-4/W19, 2019
Abstract:
Radar data has been historically expensive and complex to process. However, in this milieu of cloud-computing platforms and open-source datasets, radar data analysis has become convenient and can now be performed for more exploratory researches. This study aims to perform multi-temporal analysis of radar backscatter to characterize dense and sparse forest from Sentinel-1 images. The area of study are reforested sites under the National Greening Program (NGP) of the Philippines. Ground data were collected: (1) in 2019, from a 1.35 ha -site in Brgy. Calula, Ipil, Zamboanga Sibugay, (2) in 2019, from a 1.10 ha- site in Brgy. Cabatuanan, Basay, Negros Oriental, and (3) from PhilLiDAR 2 – Project 3: FRExLS’ 2.4 ha -validated site in Ubay, Bohol. SAR intensity values were derived from Sentinel-1 from Google Earth Engine, which is a cloud-based platform with a repository of satellite images and functionalities for data extraction and processing. The temporal variation in C-band radar backscatter from 2014 to 2018 were analyzed. The results show, for the whole period of analysis, that: in VH polarization, dense forest samples backscatter range from −11 to −18 dB in VH and −2 to -13 dB in VV; sparse forest samples range from −12 to -21 dB in VH and −7 to −14 dB in VV; ground samples range from −12 to −24 dB in VH and −6 to −15 dB in VV; and water samples range from −21 to −30 dB in VH and −11 to −26 dB in VV. Forest backscatter are expected to saturate over time, especially in dense forests. These variations are due to differences in forest species, landscape, environmental and climatic drivers, and phenomenon or interventions on the site.
Full text available upon request to the author
Article title: Modelling inundation patterns and sediment dynamics in the extensive floodplain along the Tonle Sap River
Authors: Sokly Siev, Enrico C. Paringit, Chihiro Yoshimura, Seingheng Hul
Publication title: River Research and Applications 35(1), July 2019
Abstract:
The Tonle Sap River (TSR) serves as a natural medium for the reversal flow between Tonle Sap Lake (TSL) and the Mekong River to sustain productivity and biodiversity in the TSR floodplain and TSL. Understanding the hydrological connectivity and its dynamics in the TSR, including its floodplain, is therefore important to support activities that aim to maintain ecological services in the TSR–TSL system. Thus, the main objective of this study is to examine the hydrological connectivity of the TSR and its floodplain by a modelling approach that integrates inundation patterns and sediment dynamics. The Caesar–Lisflood model was applied to describe inundation, sediment erosion, transport, and deposition in the TSR for the period of 2003–2013. The inundation areas connected to the TSR ranged from 140 to 2,327 km2, whereas the isolated inundation areas from the TSR ranged from 0.27 to 504 km2. Sediment dynamics showed its influence on inundation patterns and hydrological connectivity and could alter the yearly inundation ratio (defined as a normalized inundation frequency with a value ranging from 0 to 1) up to 0.8. Our approach provides a quantitative way to determine key factors (e.g., total inundation areas, seasonality, and connectivity of inundation patterns) for further investigation of ecological processes in relation to the inundation patterns and sediment dynamics in the TSR and TSL.
Full text available upon request to the author
Article title: Decadal-scale morphological adjustment of a lowland tropical river
Authors: Elizabeth Dingle, Enrico C. Paringit, Pamela Louise Tolentino, Richard D. Williams, et al.
Publication title: Geomorphology 333(2), February 2019
Abstract:
Compared with temperate regions, much less is known about the dynamics of tropical river systems. Tropical rivers are typically characterised by pronounced seasonal changes in precipitation, large sediment loads and high rates of lateral channel migration across often very low-gradient and densely populated floodplains. Understanding the controls on channel migration or change is integral to our ability to fully predict and build resilience against flood risk and wider river-related hazards. Here, we analyse channel and confluence migration over the last ~40 years along a ~85 km reach of the Cagayan River and one of its tributaries, the Pinacanauan de Ilagan (Luzon, Philippines) using optical satellite imagery captured during this period. Combining this with spatial variations in channel pattern, valley width and new bed material grain size data, we demonstrate that sediment transport and deposition are key drivers of the observed tropical channel morphodynamics in this region. The high sediment supply generated in the catchment headwaters (by mass-wasting of hillslopes triggered especially in typhoons) results in high aggradation rates and channel widening on the lower gradient alluvial plain. We suggest that this aggradation enhances local confluence and lateral channel migration rates, which can reach >300 m per decade, and that lateral migration rates of tropical rivers are typically greater than those of temperate rivers. Channel morphodynamics have implications for how to best manage these types of tropical river systems, where hard bank protection structures may result in a complex geomorphic response and flood risk mapping may need to include assessment of sensitivity to varying channel position and topography.
Full text available upon request to the author
Article title: Nationwide Natural Resource Inventory of the Philippines Using LiDAR: Strategies, Progress, and Challenges
Authors: Ariel Blanco, Ayin Tamonding, A. M. Perez, Rosario Ang, et al.
Publication title: ISPRS Journal of Photogrammetry and Remote Sensing XLI(B6):105-109, August 2018
Abstract:
The Philippines has embarked on a detailed nationwide natural resource inventory using LiDAR through the Phil-LiDAR 2 Program. This 3-year program has developed and has been implementing mapping methodologies and protocols to produce high-resolution maps of agricultural, forest, coastal marine, hydrological features, and renewable energy resources. The Program has adopted strategies on system and process development, capacity building and enhancement, and expanding the network of collaborations. These strategies include training programs (on point cloud and image processing, GIS, and field surveys), workshops, forums, and colloquiums (program-wide, cluster-based, and project-based), and collaboration with partner national government agencies and other organizations. In place is a cycle of training, implementation, and feedback in order to continually improve the system and processes. To date, the Program has achieved progress in the development of workflows and in rolling out products such as resource maps and GIS data layers, which are indispensable in planning and decision-making. Challenges remains in speeding up output production (including quality checks) and in ensuring sustainability considering the short duration of the program. Enhancements in the workflows and protocols have been incorporated to address data quality and data availability issues. More trainings have been conducted for project staff hired to address human resource gaps. Collaborative arrangements with more partners are being established. To attain sustainability, the Program is developing and instituting a system of training, data updating and sharing, information utilization, and feedback. This requires collaboration and cooperation of the government agencies, LGUs, universities, other organizations, and the communities.
Full text available upon request to the author
Article title: Modelling above ground biomass of mangrove forest using sentinel-1 imagery
Authors: Reginald Argamosa, Ariel Blanco, Alvin Baloloy, Christian Candido, et al.
Publication title: ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences, IV(3):13-20, 2018
Abstract:
Many studies have been conducted in the estimation of forest above ground biomass (AGB) using features from synthetic aperture radar (SAR). Specifically, L-band ALOS/PALSAR (wavelength ~23 cm) data is often used. However, few studies have been made on the use of shorter wavelengths (e.g., C-band, 3.75 cm to 7.5 cm) for forest mapping especially in tropical forests since higher attenuation is observed for volumetric objects where energy propagated is absorbed. This study aims to model AGB estimates of mangrove forest using information derived from Sentinel-1 C-band SAR data. Combinations of polarisations (VV, VH), its derivatives, grey level co-occurrence matrix (GLCM), and its principal components were used as features for modelling AGB. Five models were tested with varying combinations of features; a) sigma nought polarisations and its derivatives; b) GLCM textures; c) the first five principal components; d) combination of models a−c; and e) the identified important features by Random Forest variable importance algorithm. Random Forest was used as regressor to compute for the AGB estimates to avoid over fitting caused by the introduction of too many features in the model. Model e obtained the highest r2 of 0.79 and an RMSE of 0.44 Mg using only four features, namely, σ°VH GLCM variance, σ°VH GLCM contrast, PC1, and PC2. This study shows that Sentinel-1 C-band SAR data could be used to produce acceptable AGB estimates in mangrove forest to compensate for the unavailability of longer wavelength SAR.
Article title: Estimation of mangrove forest aboveground biomass using multispectral bands, vegetation indices and biophysical variables derived from optical satellite imageries: rapideye, planetscope and sentinel-2
Authors: Alvil Baloloy, Ariel Blanco, Christian Candido, Reginald Argamosa, et al.
Publication title: ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences, IV(3), 2018
Abstract:
Aboveground biomass estimation (AGB) is essential in determining the environmental and economic values of mangrove forests. Biomass prediction models can be developed through integration of remote sensing, field data and statistical models. This study aims to assess and compare the biomass predictor potential of multispectral bands, vegetation indices and biophysical variables that can be derived from three optical satellite systems: the Sentinel-2 with 10 m, 20 m and 60 m resolution; RapidEye with 5m resolution and PlanetScope with 3m ground resolution. Field data for biomass were collected from a Rhizophoraceae-dominated mangrove forest in Masinloc, Zambales, Philippines where 30 test plots (1.2 ha) and 5 validation plots (0.2 ha) were established. Prior to the generation of indices, images from the three satellite systems were pre-processed using atmospheric correction tools in SNAP (Sentinel-2), ENVI (RapidEye) and python (PlanetScope). The major predictor bands tested are Blue, Green and Red, which are present in the three systems; and Red-edge band from Sentinel-2 and Rapideye. The tested vegetation index predictors are Normalized Differenced Vegetation Index (NDVI), Soil-adjusted Vegetation Index (SAVI), Green-NDVI (GNDVI), Simple Ratio (SR), and Red-edge Simple Ratio (SRre). The study generated prediction models through conventional linear regression and multivariate regression. Higher coefficient of determination (r²) values were obtained using multispectral band predictors for Sentinel-2 (r² = 0.89) and Planetscope (r² = 0.80); and vegetation indices for RapidEye (r² = 0.92). Multivariate Adaptive Regression Spline (MARS) models performed better than the linear regression models with r² ranging from 0.62 to 0.92. Based on the r² and root-mean-square errors (RMSE’s), the best biomass prediction model per satellite were chosen and maps were generated. The accuracy of predicted biomass maps were high for both Sentinel-2 (r² = 0.92) and RapidEye data (r² = 0.91).
Article title: A novel approach for vegetation classification using UAV-based hyperspectral imaging
Authors: Tetsuro Ishida, Junichi Kurihara, Fra Angelico Malicdin Viray, Shielo Namuco, et al.
Publication title: Computers and Electronics in Agriculture 144:80-85, January 2018
Abstract:
The use of unmanned aerial vehicle (UAV)-based spectral imaging offers considerable advantages in high-resolution remote-sensing applications. However, the number of sensors mountable on a UAV is limited, and selecting the optimal combination of spectral bands is complex but crucial for conventional UAV-based multispectral imaging systems. To overcome these limitations, we adopted a liquid crystal tunable filter (LCTF), which can transmit selected wavelengths without the need to exchange optical filters. For calibration and validation of the LCTF-based hyperspectral imaging system, a field campaign was conducted in the Philippines during March 28–April 3, 2016. In this campaign, UAV-based hyperspectral imaging was performed in several vegetated areas, and the spectral reflectances of 14 different ground objects were measured. Additionally, the machine learning (ML) approach using a support vector machine (SVM) model was applied to the obtained dataset, and a high-resolution classification map was then produced from the aerial hyperspectral images. The results clearly showed that a large amount of misclassification occurred in shaded areas due to the difference in spectral reflectance between sunlit and shaded areas. It was also found that the classification accuracy was drastically improved by training the SVM model with both sunlit and shaded spectral data. As a result, we achieved a classification accuracy of 94.5% in vegetated areas.
Article title: A LiDAR-based flood modelling approach for mapping rice cultivation areas in Apalit, Pampanga
Authors: Luigi Toda, John Colin Estrada Yokingco, Enrico C. Paringit, Rodel D. Lasco
Publication title: Applied Geography 80:34-47, March 2017
Abstract:
Abstract Majority of rice cultivation areas in the Philippines are susceptible to excessive flooding owing to intense rainfall events. The study introduces the use of fine scale flood inundation modelling to map cultivation areas in Apalit, a rice-producing municipality located in the province of Pampanga in the Philippines. The study used a LiDAR-based digital elevation model (DEM), river discharge and rainfall data to generate flood inundation maps using LISFLOOD-FP. By applying spatial analysis, rice cultivation zone maps were derived and four cultivation zones are proposed. In areas where both depth and duration exceed threshold values set in this study, varieties tolerant to stagnant flooding and submergence are highly recommended in Zone 1, where flood conditions are least favorable for any existing traditional lowland irrigation varieties. The study emphasizes that a decline in yield is likely as increasing flood extents and longer submergence periods may cause cultivation areas for traditional irrigated lowland varieties to decrease over time. This decrease in yield may be prevented by using varieties most suitable to the flooding conditions as prescribed in the rice zone classification. The method introduced in this study could facilitate appropriate rice cultivation in flood-prone areas.
Article title: Seasonal Changes in the Inundation Area and Water Volume of the Tonle Sap River and Its Floodplain
Authors: Sokly Siev, Enrico C. Paringit, Chihiro Yoshimura, Seingheng Hul
Publication title: Hydrology 3(4):33, October 2016
Abstract:
Flood pulses occur annually along the Tonle Sap River (TSR) due to the large volume of water flowing from Tonle Sap Lake (TSL), its tributaries, and the Mekong River (MR). This study describes the seasonal changes in inundation area and water volume in the floodplain along the TSR over three years. The method employed time series remote sensing images of Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data, the digital elevation model (DEM) of the Shuttle Radar Topography Mission (SRTM), bathymetric data, and observed water level data. Adding normalized difference vegetation index (NDVI) as a “third band” in the maximum likelihood classification (MLC) provided higher accuracy compared to thresholding NDVI and pure MLC (two bands) only. The results showed that the inundation area ranged from 123.8 to 3251.2 km2 (mean: 1028.5 km2) with overall accuracy of 96.9%. The estimated water volume ranged from 418.3 to 2223.9 million m3 (mean: 917.3 million m3) from the dry to wet season, respectively. Seasonally, the TSR floodplain accounted for up to 5.3% and 3.2% of the mean annual inflow and outflow of the TSR, respectively. In addition to the TSL water reservoir, the TSR and its floodplain exchanged and stabilized the flow of the MR and its downstream delta, respectively. Overall, the obtained results have enhanced our understanding of the TSR, supporting further studies on river connectivity and reversal flow in this study area.
Article title: Separability and variability of Rhizophocraceae and Avicenniaceae in a Natural Mangrove Forest Using Point Density Disribution from Lidar Data
Authors: Regine Anne Faelga, Enrico C. Paringit, Gay Jane Perez
Publication title: Journal of the Philippine Geoscience and Remote Sensing Society, August 2016
Abstract:
Utilization of remote sensing techniques, particularly from high resolution airborne laser scanning could be an effective tool in describing forest structural features. The study aims to assess LiDAR's capability in characterizing mangrove forest stand using the available LiDAR dataset in the Philippines. Characterization of the structural attributes between mangrove families is done through separability and variability analysis of the point density distribution and height values at different levels. On a hectare scale, point densities of two mangrove families were extracted and graphed to determine separability. The point density parameter was further processed through image classification to come up with LiDAR-based Point Density Distribution Curves (PDDC) for Rhizophoraceae and Avicenniaceae mangroves. The result yielded an overall accuracy of 77.43% with a Kappa coefficient value of 0.42. Variability between and across families were analyzed using point density clustering at a finer scale of 5 by 5 meter plots. The sample plots have homogenous families, wherein fifteen (15) are composed of Rhizophoraceae and fifteen (15) Avicenniaceae, respectively. At finer scales of 5x5m, variability within and across families were evident. LiDAR point density data can serve as an important tool to structurally characterize the two mangrove families by utilizing the height and point density parameters. However, exploring other ways to statistically describe point density distribution per plot should be done as well to be able to improve the analysis.
Article title: Lidar-Based Canopy Cover Estimation Using Linear Regression Techniques
Authors: M. A. V. Posilero, Enrico C. Paringit, Reginald Argamosa, Regine Anne Faelga, et al.
Publication title: Journal of the Philippine Geoscience and Remote Sensing Society, August 2016
Abstract:
Airborne LIDAR systems are becoming the remote sensing system of choice for precise and accurate measurement of forest vegetation structure because of its ability to capture data over and underneath the canopy. One of the most useful parameters that can be estimated from LIDAR is canopy cover. To infer the canopy cover from LIDAR point cloud data, we have developed and investigated a set of metrics derived from distribution of points and their corresponding beam footprint. Improvements were introduced by taking into account beam sizes. Particularly, ten (10) bincentile parameters and area generation of vegetation points that may overlap vertically within a point cloud LiDAR data. The method was tested over a forest plantation (FP) site against field canopy cover generated through Digital Hemispherical Photography (DHP). LiDAR canopy cover estimation of the forest plantation site was observed at r 2 = 0.5629 and 1.82 percent canopy cover RMSE.
Article title: Fully automated GIS-based individual tree crown delineation based on curvature values from a lidar derived canopy height model in a coniferous plantation
Authors: Reginald Argamosa, Enrico C. Paringit, Khristoffer Ryan Quinton, F. A. M. Tandoc
Publication title: The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B8:563-569, 2016
Abstract:
The generation of high resolution canopy height model (CHM) from LiDAR makes it possible to delineate individual tree crown by means of a fully-automated method using the CHM’s curvature through its slope. The local maxima are obtained by taking the maximum raster value in a 3 m x 3 m cell. These values are assumed as tree tops and therefore considered as individual trees. Based on the assumptions, thiessen polygons were generated to serve as buffers for the canopy extent. The negative profile curvature is then measured from the slope of the CHM. The results show that the aggregated points from a negative profile curvature raster provide the most realistic crown shape. The absence of field data regarding tree crown dimensions require accurate visual assessment after the appended delineated tree crown polygon was superimposed to the hill shaded CHM.
Article title: Estimating DBH of trees employing multiple linear regression of the best lidar-derived parameter combination automated in python in a natural broadleaf forest in the Philippines
Authors: C.A. G. Ibanez, Biel Carcellar, Enrico C. Paringit, Reginald Argamosa, et al.
Publication title: The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B8:657-662, 2016
Abstract:
Diameter-at-Breast-Height Estimation is a prerequisite in various allometric equations estimating important forestry indices like stem volume, basal area, biomass and carbon stock. LiDAR Technology has a means of directly obtaining different forest parameters, except DBH, from the behavior and characteristics of point cloud unique in different forest classes. Extensive tree inventory was done on a two-hectare established sample plot in Mt. Makiling, Laguna for a natural growth forest. Coordinates, height, and canopy cover were measured and types of species were identified to compare to LiDAR derivatives. Multiple linear regression was used to get LiDAR-derived DBH by integrating field-derived DBH and 27 LiDAR-derived parameters at 20m, 10m, and 5m grid resolutions. To know the best combination of parameters in DBH Estimation, all possible combinations of parameters were generated and automated using python scripts and additional regression related libraries such as Numpy, Scipy, and Scikit learn were used. The combination that yields the highest r-squared or coefficient of determination and lowest AIC (Akaike’s Information Criterion) and BIC (Bayesian Information Criterion) was determined to be the best equation. The equation is at its best using 11 parameters at 10mgrid size and at of 0.604 r-squared, 154.04 AIC and 175.08 BIC. Combination of parameters may differ among forest classes for further studies. Additional statistical tests can be supplemented to help determine the correlation among parameters such as Kaiser- Meyer-Olkin (KMO) Coefficient and the Barlett’s Test for Spherecity (BTS).
Article title: Mangrove plantation forest assessment using structural attributes derived from light detection and ranging (Lidar) data
Authors: Regine Anne Faelga, Enrico C. Paringit, G. J. Perez, C. A. G. Ibanez
Publication title: The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B8: 617-623, 2016
Abstract:
Estimating the structural and functional attributes of forests is integral in performing management strategies and for understanding forest ecosystem functions. Field sampling methods through plot level is one of the known strategies in forest studies; however, these methods have its limitations and are prone to subjected biases. Remote Sensing data, particularly that of Light Detection and Ranging (LiDAR) can be utilized to alleviate the limitations of extracting forest structure parameters. The study aims to characterize a Rhizophoraceae-dominated mangrove forest plantation. Point cloud distribution within a 1-hectare plot was processed by utilizing thirty (30) samples of 5x5 meter plots, which were analysed for the characterization and forest structure assessment. Point densities were grouped at intervals of 10% of the plot’s maximum height (Height at Bincentile or HBn) to determine where the clustering of points occur per plot. The result shows that most of the points are clustered at HBn with height values ranging from 2.98 to 4.15 meters for plots located at the middle part of the forest, with a standard deviation of 1.78 to 3.69, respectively. On the other hand, sample plots that are located at the periphery part of the forest shows that the point clustering occurs at different heights ranging from 1.71 meters to 4.43 meters, with standard deviation values ranging from 1.69 to 3.81.Plots that are located along the fringes of the forest reflect a stunted clustering of points, while plots that explicitly show mangrove trimmings and cuts reflect even distribution in terms of point density within each HBn. Both species present in the area (R. mucronata and R. apiculata) exhibits similar clustering, which could represent detection of Rhizophoraceae mangroves.
Article title: Fully automated GIS-based individual tree crown delineation based on curvature values from a lidar derived canopy height model in a coniferous plantation
Authors: Reginald Argamosa, Enrico C. Paringit, Khristoffer Ryan Quinton, F. A. M. Tandoc, et al.
Publication title: The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B8: 563-569, 2016
Abstract:
The generation of high resolution canopy height model (CHM) from LiDAR makes it possible to delineate individual tree crown by means of a fully-automated method using the CHM’s curvature through its slope. The local maxima are obtained by taking the maximum raster value in a 3 m x 3 m cell. These values are assumed as tree tops and therefore considered as individual trees. Based on the assumptions, thiessen polygons were generated to serve as buffers for the canopy extent. The negative profile curvature is then measured from the slope of the CHM. The results show that the aggregated points from a negative profile curvature raster provide the most realistic crown shape. The absence of field data regarding tree crown dimensions require accurate visual assessment after the appended delineated tree crown polygon was superimposed to the hill shaded CHM.
Article title: Nationwide natural resource inventory of the Philippines using Lidar: strategies, progress, and challenges
Authors: Ariel Blanco, Ayin Tamondong, A. M. Perez, Rosario Ang, et al.
Publication title: The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B6: 105-109, 2016
Abstract:
The Philippines has embarked on a detailed nationwide natural resource inventory using LiDAR through the Phil-LiDAR 2 Program. This 3-year program has developed and has been implementing mapping methodologies and protocols to produce high-resolution maps of agricultural, forest, coastal marine, hydrological features, and renewable energy resources. The Program has adopted strategies on system and process development, capacity building and enhancement, and expanding the network of collaborations. These strategies include training programs (on point cloud and image processing, GIS, and field surveys), workshops, forums, and colloquiums (program-wide, cluster-based, and project-based), and collaboration with partner national government agencies and other organizations. In place is a cycle of training, implementation, and feedback in order to continually improve the system and processes. To date, the Program has achieved progress in the development of workflows and in rolling out products such as resource maps and GIS data layers, which are indispensable in planning and decision-making. Challenges remains in speeding up output production (including quality checks) and in ensuring sustainability considering the short duration of the program. Enhancements in the workflows and protocols have been incorporated to address data quality and data availability issues. More trainings have been conducted for project staff hired to address human resource gaps. Collaborative arrangements with more partners are being established. To attain sustainability, the Program is developing and instituting a system of training, data updating and sharing, information utilization, and feedback. This requires collaboration and cooperation of the government agencies, LGUs, universities, other organizations, and the communities.
Article title: Improving predictions of the effects of extreme events, land use, and climate change on the hydrology of watersheds in the Philippines
Authors: Rubianca Benavidez, Bathanna Jackson, Deborah Maxwell, Enrico C. Paringit
Publication title: Proceedings of the International Association of Hydrological Sciences 373:147-151, May 2016
Abstract:
Due to its location within the typhoon belt, the Philippines is vulnerable to tropical cyclones that can cause destructive floods. Climate change is likely to exacerbate these risks through increases in tropical cyclone frequency and intensity. To protect populations and infrastructure, disaster risk management in the Philippines focuses on real-time flood forecasting and structural measures such as dikes and retaining walls. Real-time flood forecasting in the Philippines mostly utilises two models from the Hydrologic Engineering Center (HEC): the Hydrologic Modeling System (HMS) for watershed modelling, and the River Analysis System (RAS) for inundation modelling. This research focuses on using non-structural measures for flood mitigation, such as changing land use management or watershed rehabilitation. This is being done by parameterising and applying the Land Utilisation and Capability Indicator (LUCI) model to the Cagayan de Oro watershed (1400 km2) in southern Philippines. The LUCI model is capable of identifying areas providing ecosystem services such as flood mitigation and agricultural productivity, and analysing trade-offs between services. It can also assess whether management interventions could enhance or degrade ecosystem services at fine spatial scales. The LUCI model was used to identify areas within the watershed that are providing flood mitigating services and areas that would benefit from management interventions. For the preliminary comparison, LUCI and HEC-HMS were run under the same scenario: baseline land use and the extreme rainfall event of Typhoon Bopha. The hydrographs from both models were then input to HEC-RAS to produce inundation maps. The novelty of this research is two-fold: (1) this type of ecosystem service modelling has not been carried out in the Cagayan de Oro watershed; and (2) this is the first application of the LUCI model in the Philippines. Since this research is still ongoing, the results presented in this paper are preliminary. As the land use and soil parameterisation for this watershed are refined and more scenarios are run through the model, more robust comparisons can be made between the hydrographs produced by LUCI and HEC-HMS and how those differences affect the inundation map produced by HEC-RAS.
Article title: The Phil-Lidar 2 program: national resource inventory of the Philippines using lidar and other remotely sensed data
Authors: Ariel Blanco, Ayin Tamondong, A. M. C. Perez, Rosario Ang, et al.
Publication title: The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-7/W3: 1123-1127, 2015
Abstract:
The Philippines embarked on a nationwide mapping endeavour through the Disaster Risk and Exposure Assessment for Mitigation (DREAM) Program of the University of the Philippines and the Department of Science and Technology (DOST). The derived accurate digital terrain models (DTMs) are used in flood models to generate risk maps and early warning system. With the availability of LiDAR data sets, the Phil-LiDAR 2 program was conceptualized as complementary to existing programs of various national government agencies and to assist local government units. Phil-LiDAR 2 aims to provide an updated natural resource inventory as detailed as possible using LiDAR point clouds, LiDAR derivative products, orthoimages and other RS data. The program assesses the following natural resources over a period of three years from July 2014: agricultural, forest, coastal, water, and renewable energy. To date, methodologies for extracting features from LiDAR data sets have been developed. The methodologies are based on a combination of object-based image analysis, pixel-based image analysis, optimization of feature selection and parameter values, and field surveys. One of the features of the Phil-LiDAR 2 program is the involvement of fifteen (15) universities throughout the country. Most of these do not have prior experience in remote sensing and mapping. With such, the program has embarked on a massive training and mentoring program. The program is producing more than 200 young RS specialists who are protecting the environment through RS and other geospatial technologies. This paper presents the program, the methodologies so far developed, and the sample outputs.
Article title: A Combined Multi-Site and Multi-Device Decision Support System for Tidal In-Stream Energy
Authors: Michael Lochinvar Sim Abundo, Allan Nerves, Enrico C. Paringit, Cesar Villanoy
Publication title: Energy Procedia 14:812-817, December 2012
Abstract:
This paper combines site and device suitability approaches into one framework to assist stakeholders in identifying locations fit for Tidal In-Stream Energy (TISE) extraction as well as nominating devices that are matched to the conditions of those locations. A Matlab-based decision support system is developed using the framework. Site-Device matching is performed considering resource data, device power generation, energy production, and cost. A case study, involving four sites in the Philippines, is presented. Hydrodynamic simulations using DELFT3D are done. The suitability of modeled TISE conversion devices is investigated over several locations in the case study. Device nominations are made for respective locations using highest energy production as dominating criterion. (C) 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of the organizing committee of 2nd International Conference on Advances in Energy Engineering (ICAEE).
Article title: Simultaneous estimation of benthic fractional cover and shallow water bathymetry in coral reef areas from high-resolution satellite images
Authors: Enrico C. Paringit and Kazuo Nadaoka
Publication title: International Journal of Remote Sensing 33(10):3026-3047, May 2012
Abstract:
This article describes the development of a technique to estimate shallow water benthic cover and depth simultaneously from high-resolution satellite images of reef areas, specifically from the high-resolution sensor onboard IKONOS. The technique to derive the estimates of five bottom benthic cover types (sand, coral, seagrass, macroalgae and pavement) and depth from the four-band images uses a coupling of radiative transfer (RT) theory and spectral unmixing implemented in an iterative manner. To resolve the cover types for the unmixing, the method employed a combinatorial approach to select benthic cover composition. The estimation technique was applied to two reef areas around the coast of the Ishigaki in southern Ryukyus, namely, the Fukido River mouth area and the Shiraho Reef. The IKONOS images of Fukido River mouth area and Shiraho Reef were acquired in 2003 and 2002, respectively. The accuracy of the fractional cover and the depth estimates from the satellite images are then presented and compared with sea truth data and depth measurements. The results indicate good correspondence between estimated and measured depths, while the estimates for the benthic cover were at reasonable levels of accuracy.
Full text available upon request to the author
Article title: Integrated Landsat Image Analysis and Hydrologic Modeling to Detect Impacts of 25-Year Land-Cover Change on Surface Runoff in a Philippine Watershed
Authors: Jojene Santillan, Meriam Makinano-Santillan, Enrico C. Paringit
Publication title: Remote Sensing 3(6):1067-1087, December 2011
Abstract:
Landsat MSS and ETM+ images were analyzed to detect 25-year land-cover change (1976–2001) in the critical Taguibo Watershed in Mindanao Island, Southern Philippines. This watershed has experienced historical modifications of its land-cover due to the presence of logging industries in the 1950s, and continuous deforestation due to illegal logging and slash-and-burn agriculture in the present time. To estimate the impacts of land-cover change on watershed runoff, land-cover information derived from the Landsat images was utilized to parameterize a GIS-based hydrologic model. The model was then calibrated with field-measured discharge data and used to simulate the responses of the watershed in its year 2001 and year 1976 land-cover conditions. The availability of land-cover information on the most recent state of the watershed from the Landsat ETM+ image made it possible to locate areas for rehabilitation such as barren and logged-over areas. We then created a "rehabilitated" land-cover condition map of the watershed (re-forestation of logged-over areas and agro-forestation of barren areas) and used it to parameterize the model and predict the runoff responses of the watershed. Model results showed that changes in land-cover from 1976 to 2001 were directly related to the significant increase in surface runoff. Runoff predictions showed that a full rehabilitation of the watershed, especially in barren and logged-over areas, will be likely to reduce the generation of a huge volume of runoff during rainfall events. The results of this study have OPEN ACCESS Remote Sens. 2011, 3 1068 demonstrated the usefulness of multi-temporal Landsat images in detecting land-cover change, in identifying areas for rehabilitation, and in evaluating rehabilitation strategies for management of tropical watersheds through its use in hydrologic modeling.
Papers Presented:
Article title: Determination of the Pre-launch Image- Processing Techniques for Liquid Crystal Tunable Filter (LCTF) for PHL-Microsat DIWATA-1
Authors: Enrico C. Paringit, Mara Alain Mendoza Maestro, Fra Angelico Malicdin Viray, James Calvo
Conference title: 37th Asian Conference on Remote Sensing 2017
Abstract:
The Program, “Development of Philippine Scientific Earth Observation Microsatellite (PHL- MICROSAT) has successfully launched a microsatellite called Philippines’ first microsatellite, DIWATA-1 last April 2016. DIWATA-1 is equipped with remote sensing sensors. It seeks to maximize and utilize its earth observation capabilities as applied in resource and disaster management and weather observations in the Philippines through multispectral images taken by its cameras. One of the payloads mounted in the microsatellite is the Space-borne Multi-spectral Imager (SMI) with Liquid Crystal Tunable Filter (LCTF), specifically made and designed for DIWATA-1. Like any other optical imaging sensors, it contains radiometric noise and geometric distortions and images should be further projected unto a map coordinate system. Thus, a methodology to increase the radiometric precision and to correct geometric distortions of DIWATA-1’s images is necessary. This research used data from laboratory and practical airborne experiments of an LCTF Camera to design the image-processing line. Corrections introduced include radiance offsets, and reduction of transmittance limitation and vignetting caused by the camera’s optical assembly composed of a charge-coupled device (CCD), filter and lenses. An irradiance model was adapted to account for radiometric corrections due to viewing, terrain and sun-angle conditions. Processed LCTF and DIWATA- 1 geospatial images will give way to level 1 satellite products which can be used or further processed by government agencies and research institutions for different applications.
Full text available upon request to the author
Article title: Calibration and Validation of LCTF Camera on an Experimental Airborne Mission at Gerona and Ramos, Tarlac, Philippines
Authors: Enrico C. Paringit, Mara Alain Mendoza Maestro, Fra Angelico Malicdin Viray, James Calvo
Conference title: 37th Asian Conference on Remote Sensing 2017
Abstract:
An experimental airborne mission over an agricultural field in Gerona and Ramos, Tarlac, Philippines was carried out to calibrate and validate remote sensing instruments similarly installed in the Philippines’ first microsatellite. Particularly, the mission aimed to calculate calibration parameters for converting Liquid Crystal Tunable Filter (LCTF) Camera spectral image band data from digital numbers (DN) to spectral radiance. The LCTF Camera was flown vicariously with another airborne imaging spectrometer, compact airborne spectrographic imager (CASI) for comparison. The two sensors were mounted side-by-side on a CESSNA 206 aircraft with an average flying speed of 60 m/s at an altitude ranging from 550m to 600m for the airborne data acquisition collecting a total of 20,850 images, with a spatial resolution of 0.5m and image swath of 300m for the CASI images, and a spatial resolution of 0.7m and image swath of 700m for the LCTF camera images. A field spectroradiometer (FS) was used to simultaneously measure field spectral reflectance. A spectral irradiance model was used to convert data from radiance to reflectance or vice versa. The LCTF camera data was then correlated to the field spectral data in order to generate calibration parameters. Using the calibration parameters, the LCTF camera data were converted from DN to spectral radiance, and cross-validated with the CASI and FS data using linear regression. The validation with the CASI data displayed a correlation of 0.743369 for the bands at 460nm to 700nm but an inferior correlation of 0.441638 for the near-infrared (NIR) bands 720nm and 750nm. The validation with FieldSpec data displayed a correlation of 0.387419 on the lower spectra compared to the correlation of 0.2535 of the NIR bands. The results show about 35-40% difference in spectral radiance at the near-infrared bands of the calibration parameters from the LCTF camera DN data. The calibration parameters show an effectiveness when converting data acquired in the afternoon, the root-mean-square error is significantly higher (200%) when applied to data acquired in the morning
Full text available upon request to the author
Article title: Implementation of a Solar Spectral Model for the Calibration of the Spaceborne Multispectral Imager (SMI) of DIWATA 1
Authors: Enrico C. Paringit, Mara Alain Mendoza Maestro, Fra Angelico Malicdin Viray, James Calvo
Conference title: 37th Asian Conference on Remote Sensing 2017
Abstract:
DIWATA-1 is a low earth orbit (LEO) microsatellite that hovers 400km above the earth. It was launched from the International Space Station (ISS) and deployed into orbit last April 27, 2016. It is envisioned that a set of multi-spectral satellite images from DIWATA-1 will be collected and processed to monitor changes in vegetation and to oversee oceans’ productivity in the Philippines. To meet these objectives, the images should be consistent enough to produce meaningful derivative products. The images taken by the sensor must be corrected to eliminate geometric and radiometric distortions and noises. Spectral extraterrestrial solar irradiance is attenuated while passing through the atmosphere by Rayleigh scattering, ozone, mixed gases, water vapor absorption and aerosol transmission. These conditions make it necessary to apply any correction to the atmosphere's effect. A spectral radiance model was applied to estimate the top-of-atmosphere (TOA) radiance which can be predicted using the field data acquired through an airborne mission. The payload, a Liquid Crystal Tunable Filter (LCTF) camera, was installed for an experimental airborne mission to acquire spectral images. The digital number in each pixel of the image was then converted to radiance by modelling the irradiance at the sensor and obtaining reflectance values of certain types of vegetation. The output provides an at-sensor radiance (airborne) accounting for the effects of the atmosphere and incoming solar irradiance. Initial results from the comparison of the irradiance data using the pyranometer and the model show a root mean square error (RMSE) of 90.67 W/m2/um in band 7 (0.64um) but also yields an RMSE of 980.66 W/m2/um in band 11 (0.75um) for the spectral irradiance, while an RMSE of 124.281 W/m2/um was computed for the broadband irradiance. For the normal operation of DIWATA-1, it is vital to include not only the atmospheric correction of the incoming solar irradiance at ground but the incoming radiance at the sensor (DIWATA-1) as well.
Full text available upon request to the author
Article title: Diameter at breast height estimation in Mt. Makiling, Laguna, Philippines using metrics derived from airborne LiDAR data and Worldview-2 bands
Authors: Fe Andrea M. Tandoc, Enrico C. Paringit, Nathaniel Bantayan, Reginald Argamosa, et al.
Conference title: SPIE Asia-Pacific Remote Sensing, June 2016
Abstract:
Airborne LiDAR is fast becoming an innovation for forest inventory. It aids in obtaining forest characteristics in areas or cases where actual field inventory would be very tedious. This study aims to estimate diameter at breast height (DBH) using airborne LiDAR point-cloud parameters with Worldview-2 satellite images, and to validate these with actual measurements done in the field. The study site is a field plot with forest inventory at Mt. Makiling, Laguna, Philippines that was surveyed into 20m, 10m and 5m subplots or grids. The estimation of DBH was carried out by extracting the said parameters from the LiDAR point-cloud, and extracting different bands from the Worldview image and performing linear and log-linear regression of these values. The regressions were done in four different cases, namely: LiDAR parameters without intensity (case1), LiDAR parameters without intensity with Worldview bands (case 2), intensity of LiDAR points (case 3), and LiDAR parameters with intensity and Worldview bands (case 4). From these it was found that the best case for estimating DBH is with the use of LiDAR parameters with intensity and Worldview bands in a 10x10 grid, in Log-Linear regression with a root mean squared error of 1.96 cm and an adjusted R² value of 0.65. This was further improved through stepwise regression, and adjusted R² value was 0.71.
Full text available upon request to the author
Article title: Analysis of Positional Displacement in Bohol Island on Aftermath of the 2013 Central Visayas Earthquake from GNSS Surveys
Authors: Enrico C. Paringit, Louie Balicanta, Joemarie Caballero, Wilfredo Rada
Conference title: FIG Working Week 2016
Abstract:
A 7.2 magnitude earthquake struck Central Visayas, Philippines on 8:12 AM 15 October 2013. Ground shaking resulted in heavy casualties and damage to infrastructure and still linger threatened by failure-prone hillslopes, debris-filled rivers and collapsing sinkholes. Quantifying the distribution of seismic-induced ground movement is important not only for assessing the damage caused by the earthquake but also for guiding local surveyors that the rely on a stable reference system for conduct of surveys in the area necessary for reconstruction and rehabilitation. A static GNSS survey was conducted from 10-12 November 2013 to quantify the displacements. GNSS receivers were occupied previously established High-Ordered reference points and fixing a relatively stable point. Subsequently, the GNSS data were analyzed to assess the movement of areas were conducted. The average horizontal displacement is about 0.5166m+-0.2682m. Maximum displaced 1.169 m observed while minimum displacement is 0.063. The displacement headed towards southeast direction with greatest magnitudes computed at the northern and eastern portion of the Island. The results of the survey may provide key agencies further motivation to review the control points and conduct the necessary re-observation and re-adjustment.
Full text available upon request to the author
Article title: Addressing lidar overlap for diameter at breast height estimation using a point-cloud processing software
Authors: Gio Perseveranda Zaragosa, Enrico C. Paringit, Carlyn Ann G. Ibañez, Regine Anne Faelga
Conference title: SPIE Asia-Pacific Remote Sensing, May 2016
Abstract:
LiDAR Overlap is the area that is common to two or more flight lines. This is essential to ensure the continuity of data as the acquisition moves from one flight line to another. Looking into overlaps is important when doing DBH Estimation using point cloud data because it doubles the density of points in the overlap region. To remove this effect when determining the DBH of a forest area, the LiDAR data was processed using a point-cloud processing software. The processes include separating flight lines using the GPS time when the points were acquired. After separating, the number of points in the overlap region were decreased by removing excess points within the area of twice the point spacing. The parameters needed for DBH estimation were then obtained. The absolute number of points in the whole overlap area was originally 4,960,726 after decreasing the number of points, it was reduced to 1,479,884. The number of points would have an effect on DBH estimation because the values obtained were significantly different at 95% level of confidence.
Full text available upon request to the author
Article title: Validation of the separability measure for Rhizophoraceae and Avicenniaceae using point density distribution from lidar
Authors: Regine Anne Faelga, Enrico C. Paringit, Gay Perez, Reginald Argamosa, et al.
Conference title: SPIE Asia-Pacific Remote Sensing, May 2016
Abstract:
The extent at which mangrove forest characterization can be done through utilization of Light Detection and Ranging (LiDAR) data is investigated in this paper. Particularly, the ability of LiDAR parameters, such as its point density to provide height and structural information was explored to supplement manual field surveys which are time-consuming and requires great effort. Point cloud information was used to produce separability measure within a mangrove forest. The study aims to validate the point density distribution curves (PDDC) that were established to characterize the structural attributes between Rhizophoraceae and Avicenniaceae. The applicability of the PDDC was applied to fifteen (15) 5x5 sample plots of pure Rhizophoraceae and fifteen (15) 5x5 sample plots of pure Avicenniaceae in a one hectare (1ha) natural riverine mangrove forest. 15 out of 15 plots were correctly discriminated as Rhizophoraceae; however, Avicenniaceae plots were not correctly discriminated using the established separability measure. This study had determined that the two mangrove families are difficult to separate in terms of point density distribution alone. Enhancement of the PDDC as a separability measure should be improved to pave way for a more sensitive and robust way to separate the two families.
Full text available upon request to the author
Article title: Oil spill detection in Envisat ASAR images using backscatter thresholding and logistic regression analysis
Authors: Jojene Santillan, Enrico C. Paringit
Conference title: 32nd Asian Conference on Remote Sensing (ACRS 2011), October 2014
Abstract:
This paper presents a technique to detect oil spills in ENVISAT Advanced Synthetic Aperture Radar (ASAR) images using radar backscatter thresholding and logistic regression analysis. We developed and tested this technique using 4 Envisat ASAR images that were acquired many days after the M/T Solar I oil spill incident occurred on August 11, 2006 in Panay Gulf, southwest of Guimaras Island in Visayas, Philippines. A semi-automated approach by histogram analysis and radar backscatter thresholding was implemented to detect and segment dark formations in the Envisat ASAR images. Then, a logistic regression (LR)-based dark formation classifier was developed using 4 shape features, 11 contrast features, 2 homogeneity, and 2 slick surrounding features of the detected dark formations consisting of 154 verified oil slicks and 1,355 look-alikes. From this, a dataset consisting of 77 confirmed oil slicks and 77 look-alikes were randomly selected and used to train the classifier while the remaining dataset of 77 oil slicks and 1,272 look-alikes were used for validation. Features of the training dataset were fitted in a binary LR model and a backward stepwise-likelihood ratio approach was utilized to determine the sets of features that best discriminate an oil slick from its look-alike. Cross-validation of the LR classifier using the training dataset showed 84% accuracy for oil slick classification, 87% accuracy for look-alike classification, and an overall classification accuracy of 86%. An independent validation of the LR classifier revealed an above average performance, with 92% accuracy for oil slick classification, 76% accuracy for look-alike classification, and overall classification accuracy of 77%. The results of this study indicate that the combined radar backscatter thresholding and logistic regression analysis could be a promising approach in oil spill detection in Envisat ASAR images. The simplicity of the technique and its use of information readily available from the SAR images are advantageous in the rapid mapping of oil slicks right after an oil spill incident. Its improvement through consideration of prevailing wind conditions, the use of large training and validation datasets as well as inclusion of other relevant image features during classifier development could be a subject of future studies.
Full text available upon request to the author
Article title: Analysis of effective window size in texture-based classification of 2007–2010 ALOS PALSAR 25m mosaic images
Authors: Margie Parinas, Enrico C. Paringit
Conference title: IGARSS 2013- 2013 IEEE International Geoscience and Remote Sensing Symposium, July 2013
Abstract:
This study aims to develop a land cover texture-based classification scheme applicable for ALOS PALSAR imageries of the upper Marikina watershed acquired 2007 - 2010. From the raw dual polarization bands of HH+HV that has a ground resolution of 25m, additional bands HH/HV and NL was computed for surface texture normalization. The classification scheme was based on texture analysis using grey level co-occurrence matrix with parameters of mean, variance and angular second moment to extract imageries feature statistics. Varied window sizes from 3×3 to 29×29 in odd series was produced to generate texture-window size bands (TWS bands). Using Support Vector Machine for land cover classification, each classified TSW bands' accuracy was computed and yielded an initial result of stability on the NL band at ~78%-81% on window sizes 15-29. Additional 2,744 TWS bands with permuted window sizes of the 3 texture variable of NL band was produced and classified for accuracy assessment. In general, high dependence on variance texture variable was observed for classified TWS bands with high accuracy. These TWS bands has large window size that caused generalization of classification. For land cover change detection, given an illogical transition of land cover due to misclassification from the SVM classification, a drastic land cover was observed especially on the forest cover of the watershed from 2007-2010.
Full text available upon request to the author
Article title: Use of Geospatial Technologies and Numerical Modeling to Monitor and Forecast Flooding Along Marikina River, Philippines
Authors: Jojene Santillan, Roseanne Ramos, Sabrina Recamadas, Girlie David, et al.
Conference title: 12th South East Asia Survey Congress (SEASC 2013)
Abstract:
In this paper, we present how geospatial technologies and techniques (hydrographic surveys, Remote Sensing -RS, Geographic Information System -GIS) together with numerical models can be used in near-real time monitoring and forecasting of floods. We chose Marikina River that traverses the province of Rizal and the Metropolitan Manila in Luzon Island, Philippines as our study area. We developed and parameterized a near-real time flood extent monitoring numerical model for Marikina River, Philippines using the Hydrologic Engineering Center – River Analysis System (HEC RAS) program. Model development and parameterization was done using GIS. Hydrographic surveys were conducted to generate the geometry of the Marikina River required by HEC RAS. Flood plain surface roughness coefficients needed to parameterize the model were derived from multispectral classification of a 10-m spatial resolution ALOS AVNIR-2 satellite image of the study area. Automation scripts were developed for running the HEC RAS modelling workflow without human intervention such as assigning of model initial and boundary conditions, setting of simulation time window, model computation and generation of flood extent and flood depths. The outputs generated are then uploaded automatically to the Project NOAH (Nationwide Operational Assessment of Hazards, http://noah.dost.gov.ph) website where the public could view in near real-time if there is flooding along Marikina River. This near-real time generation of flood maps can be useful in providing information to the public as to the possible extent of flooding in the Marikina River that could then assist in preparation for evacuation. We also developed a forecasting system for Marikina River that provides water level forecasts for the next 48 hours. Forecasts are results of model simulation of basin hydrology as well as river and flood plain hydraulics, using recorded data of rainfall events 3 days ago to present time as primary input of the models. The forecast model is based on the Hydrologic Engineering Center – Hydrologic Modeling System (HEC HMS). This model was also developed and parameterized using GIS, wherein river and floodplain geometry from field surveys and digital elevation model (DEM) as well as land-cover information from the ALOS AVNIR-2 satellite image were used as primary inputs.
Article title: Hydrodynamic and trajectory modeling of the August 11, 2006 M/T solar 1 oil spill in Guimaras, central Philippines with validation using envisat asar data
Authors: Jojene Santillan, Enrico C. Paringit
Conference title: 33rd Asian Conference on Remote Sensing 2012
Abstract:
Oil spill patterns detected from Envisat ASAR images were integrated with hydrodynamic and oil spill trajectory models for the purposes of understanding the August 11, 2006 M/T Solar 1 oil spill, and to evaluate the accuracy of the oil spill patterns simulated by an oil trajectory model. The oil spill incident event that occurred a few kilometers southwest of Guimaras Island in Panay Gulf and Iloilo Guimaras Strait (PG-IGS), Central Philippines, is considered to be the worst oil-related environmental disaster the Philippines has experienced. A three-dimensional, wind- and tide-driven hydrodynamic model of the PG-IGS coastal zone was developed using the Environmental Fluid Dynamics Code (EFDC) to ascertain water circulation patterns. The simulated currents by the EFDC model were used as inputs to an oil spill trajectory model based on the General NOAA Operational Modeling Environment (GNOME) that provided continuous simulation of the transport of spilled oil from its source to the nearby coastal communities. The oil trajectories simulated by the GNOME model were validated by comparing it to oil spill patterns detected from Envisat Advanced Synthetic Aperture Radar (ASAR) images of the oil spill incident. The use of sea surface currents simulated by the EFDC-based hydrodynamic model was vital in explaining the trend, shape, and direction of the observed oil slicks from the Envisat ASAR images. Conversely, the use of Envisat ASAR images for oil spill pattern validation provides an easier and direct assessment of the GNOME-based oil trajectory model's performance. The comparison between model-simulated oil spill patterns and the patterns mapped from Envisat ASAR images showed that in general, the simulated slick patterns differ in location, shape and extent to those detected from the SAR images. It appears from the results of actual-versus-simulated oil spill patterns that improvement is needed in the EFDC and GNOME models, most especially in their data inputs. While the oil spill patterns simulated by the GNOME model differs at some aspects from the actual patterns, the results highlighted the usefulness of the model for oil spill trajectory analysis and its use for oil spill response in the future once improvements to the model have been considered.
Article title: Near-real time flood extent monitoring in Marikina river philippines: Model parameterisation using remotely-sensed data and field measurements
Authors: Jojene Santillan, Enrico C. Paringit, Roseanne Ramos, J.R.T Mendoza, et al.
Conference title: 33rd Asian Conference on Remote Sensing 2012
Abstract:
Floods are a persistent problem in the Philippines that need to be addressed in a more scientific way in order to mitigate its costly impacts to human lives and properties. The September 2009 floods caused by Typhoon Ketsana that devastated Metro Manila and its surroundings exemplified the need for an accurate and reliable flood monitoring tool for determining the extents of floods and for assessing the risks due to this disaster. In this study, we developed and parameterized a near-real time flood extent monitoring model for Marikina River, Philippines using the Hydrologic Engineering Center - River Analysis System (HEC RAS) program. River bathymetric surveys and cross-section measurements were conducted to generate the geometry of the Marikina River required by HEC RAS. Flood plain surface roughness coefficients needed to parameterize the model were derived from multispectral classification of a 10-m spatial resolution ALOS AVNIR-2 of the study area. The HEC RAS model was configured to accept real time 10-minute water level data from the Enhanced Flood Control and Operation Warning System (EFCOS) monitoring stations along the Marikina River as model boundary conditions. Automation scripts were used to convert the time series of water level data from the stations to a format that could be readily used by the HEC RAS model. An automation script was also developed for running the HEC RAS modeling workflow without human intervention such as assigning of model initial and boundary conditions, setting of simulation time window, model computation and generation of flood extent and flood depths. The outputs generated are then uploaded automatically to the Project NOAH (Nationwide Operational Assessment of Hazards) website where the public could view in near real-time the flooding extent along Marikina River. This near-real time generation of flood maps could be useful in providing information to the public as to the possible extent and depth of flooding in the Marikina River that could then assist in preparation for evacuation. Validation of the model using time series of water level data for two rainfall events showed an average error of -16 cm and root mean square error of 25 cm. The model has a Nash-Sutcliffe Coefficient of Model Efficiency (E) of 0.88 which signifies satisfactory model performance but requires further improvement and calibration. The study proves the usefulness of remote sensing and GIS technologies in model preparation and parameterizations, as well as in providing near-real time outputs for viewing by the public.
Article title: Development of a HEC RAS Model for Near-Real Time Flood Extent Monitoring in Marikina River, Philippines
Authors: Jojene Santillan, Enrico C. Paringit, Roseanne Ramos, John Robert, et al.
Conference title: 1st Philippine Geomatics Symposium
Abstract:
We developed and parameterized a near-real time flood extent monitoring model for Marikina River, Philippines using the Hydrologic Engineering Center – River Analysis System (HEC RAS). The development consisted of three major steps: flood model setup, flood model automation, and online visualization. The HEC RAS model was configured to accept real time 10-minute water level data from the Enhanced Flood Control and Operation Warning System (EFCOS) monitoring stations along the Marikina River as model boundary conditions. Automation scripts were used to convert the time series of water level data from the stations to a format that could be readily used by the HEC RAS model. An automation script was also developed for running the HEC RAS modeling workflow without human intervention such as assigning of model initial and boundary conditions, setting of simulation time window, model computation and generation of flood extent and flood depths. The outputs generated are then uploaded automatically to the Project NOAH (Nationwide Operational Assessment of Hazards) website where the public could view in near real-time the flooding extent along Marikina River. This near-real time generation of flood maps could be useful in providing information to the public as to the possible extent and depth of flooding in the Marikina River that could then assist in preparation for evacuation. Validation of the model using time series of water level data showed an average error of -16 cm and root mean square error of 25 cm. The model has a Nash-Sutcliffe Coefficient of Model Efficiency (E) of 0.88 which signifies satisfactory model performance but requires further improvement and calibration. The study proves the usefulness of remote sensing and GIS technologies in model preparation and parameterizations, as well as in providing near-real time outputs for viewing by the public.
Article title: Utilizing Spectral Reflectance and Vegetation Indices of Bougainvillea spectabilis in Monitoring Particulate Air Pollution in Metro Manila
Authors: Alex Olpenda, Enrico C. Paringit
Conference title: 32nd Asian Conference on Remote Sensing 2011
Abstract:
This research aims to examine the potential of high-resolution multispectral remote sensing in assessing particulate air pollution wherein plant responses were utilized as indicators of air quality. Spectral reflectance measurements simultaneous with air particulate matter concentration sampling were conducted daily for a one-month period. Vegetation indices such as Ratio Vegetation Index (RVI), Normalized Difference Vegetation Index (NDVI) and Difference Vegetation Index (DVI) including Red Edge Parameter (REP) were utilized to assess potted bougainvillea plants exposed at different pollution level. Further, a spectral mixture analysis (SMA) was made to simulate the effects of vehicular exhaust soot to the spectral characteristics of a bougainvillea leaf. The generated data was later used in creating a model thru Partial Least Squares (PLS) regression. The SMA-based PLS-ran model was then applied to WorldView-2 imageries in producing an interpolated detailed air quality map showing the spatial extent and concentration of suspended particulate matter. The clearest and least hazed image showed the most reasonable representation of particulate air pollution suggesting a valid scenario. However, portions of vegetated areas present unrealistic estimates due to intrinsic factors like canopy biophysical attributes and external conditions such as soil reflectance, atmospheric and illumination conditions and viewing geometry.
Article title: Merging landsat image information with georeferenced biophysical and socio-economical datasets to describe forest cover change in a Philippine province
Authors: Meriam Makinano-Santillan, Jojene Santillan, Enrico C. Paringit
Conference title: 32nd Asian Conference on Remote Sensing 2011
Abstract:
This paper describes a combined remote sensing-GIS-logistic regression approach of merging extracted information from Landsat images with georeferenced biophysical and socio-economic datasets in the detection and analysis of the driving forces of forest cover change in Agusan del Norte (ADN) in Mindanao Island, Philippines, a province where forest resource use have been historically extensive. Year 1976 Landsat 2 MSS and year 2001 Landsat ETM+ images were independently classified using Support Vector Machines (SVM) to produce land cover maps with overall classification accuracies of 95% and 98%, respectively. Changes in forest cover and other types of land-cover change in the 25-year period were then detected from these maps through post-classification comparison in a GIS. To investigate what has driven these conversions, the associations between these changes and a selection of biophysical and socio-economical variables were explored through logistic regression analysis. The results show that while both the biophysical and socio-economical variables were significantly associated with the occurrences of forest cover change, the models containing only the socio-economical variables predict better the occurrences of change than those containing only the biophysical variables. This implies that most of the forest cover change detected in the year 2001 in ADN is much more a socio-economical matter, and is less forced by biophysical limitations. With these results, this study demonstrated the usefulness of RS, GIS and statistical analysis as exploratory tools in understanding the underlying processes and identification of driving forces of forest cover change, especially in areas of extensive forest resource use.
Article title: Energy potential metric for rapid macro-level resource assessment of tidal in-stream energy in the Philippines
Authors: Michael Lochinvar Sim Abundo, Allan C. Nerves, Rosario Ang, Enrico C. Paringit, et al.
Conference title: Environment and Electrical Engineering 2011, 10th Conference
Abstract:
This paper presents preliminary efforts in developing a rapid evaluation tool for tidal in-stream energy (TISE) in the Philippines. We study the possibility of using an energy density metric based on the sea surface elevation (SSE) or tide height difference at the boundaries of a site of interest as a gauge for the TISE potential of that site. Results show good correlation with high potential sites and the proposed metric. Verde Island Passage was assessed, through a combination of DELFT3D simulation and Matlab-based power computations, to have four potential TISE sites with a total energy density of 271.90 kW-h /m<sup>2</sup> in a month