Publications
21 results found
Sharifzadeh M, Cooper N, van't Noordende H, et al., 2024, Operational strategies and integrated design for producing green hydrogen from wind electricity, International Journal of Hydrogen Energy, Vol: 64, Pages: 650-675, ISSN: 0360-3199
Realizing the potential of renewable hydrogen production requires flexible operation of electrolysis systems to integrate with intermittent power sources. This work develops an optimization model to assess flexible operational strategies for alkaline and proton exchange membrane (PEM) electrolysers powered by wind energy. The model quantitatively analyses trade-offs between electrolyser shutdown strategies, overloading capacities, and battery integration to identify optimal regimes balancing efficiency, flexibility, and economics. The results reveal a mixed-integer linear programming approach can optimize system configurations and control strategies to minimize the levelized cost of hydrogen production. Optimal near-minimum load operation is achieved by independently optimizing the load of each electrolyser block, while avoiding shutdowns above a critical load level. Strategic electrolyser overloading can provide economic benefits by reducing installed capital costs, if technical feasibility and accelerated degradation are addressed. Battery energy storage integration significantly improves economics by enhancing asset utilization, provided excess renewable energy is available. The model provides novel insights on integrating alkaline and PEM electrolysis with intermittent wind power to advance renewable hydrogen production. Quantifying trade-offs between operational flexibility and economics will help guide flexible design and control strategies for cost-optimal renewable electrolysis systems.
Winter LR, Cooper NJ, Lee B, et al., 2024, Correction to "Mining Nontraditional Water Sources for a Distributed Hydrogen Economy"., Environ Sci Technol, Vol: 58, Pages: 1420-1421
DuChanois RM, Cooper NJ, Lee B, et al., 2023, Prospects of metal recovery from wastewater and brine, Nature Water, Vol: 1, Pages: 37-46
Winter LR, Cooper NJ, Lee B, et al., 2022, Mining Nontraditional Water Sources for a Distributed Hydrogen Economy, ENVIRONMENTAL SCIENCE & TECHNOLOGY, Vol: 56, Pages: 10577-10585, ISSN: 0013-936X
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- Citations: 8
Cooper N, Horend C, Roben F, et al., 2022, A framework for the design & operation of a large-scale wind-powered hydrogen electrolyzer hub, International Journal of Hydrogen Energy, Vol: 47, Pages: 8671-8686, ISSN: 0360-3199
Due to the threat of climate change, renewable feedstocks & alternative energy carriers are becoming more necessary than ever. One key vector is hydrogen, which can fulfil these roles and is a renewable resource when split from water using renewable electricity. Electrolyzers are often not designed for variable operation, such as power from sources like wind or solar. This work develops a framework to optimize the design and operation of a large-scale electrolyzer hub under variable power supply. The framework is a two-part optimization, where designs of repeated, modular units are optimized, then the entire system is optimized based on those modular units. The framework is tested using a case study of an electrolyzer hub powered by a Dutch wind farm to minimize the levelized cost of hydrogen. To understand how the optimal design changes, three power profiles are examined, including a steady power supply, a representative wind farm power supply, and the same wind farm power supply compressed in time. The work finds the compressed power profile uses PEM technology which can ramp up and down more quickly. The framework determines for this case study, pressurized alkaline electrolyzers with large stacks are the cheapest modular unit, and while a steady power profile resulted in the cheapest hydrogen, costing 4.73 €/kg, the typical wind power profile only raised the levelized cost by 2%–4.82 €/kg. This framework is useful for designing large-scale electrolysis plants and understanding the impact of specific design choices on the performance of a plant.
Du Y, Wang Z, Cooper NJ, et al., 2022, Module-scale analysis of low-salt-rejection reverse osmosis: Design guidelines and system performance, WATER RESEARCH, Vol: 209, ISSN: 0043-1354
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- Citations: 9
Cooper N, Panteli A, Shah N, 2019, Linear estimators of biomass yield maps for improved biomass supply chain optimisation, APPLIED ENERGY, Vol: 253, ISSN: 0306-2619
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- Citations: 11
Trotter PA, Cooper NJ, Wilson PR, 2019, A multi-criteria, long-term energy planning optimisation model with integrated on-grid and off-grid electrification - The case of Uganda, APPLIED ENERGY, Vol: 243, Pages: 288-312, ISSN: 0306-2619
Cooper N, Panteli A, Shah N, 2019, A biomass supply chain optimization framework with linear approximation of biomass yield distributions for improved land use
Biomass and the bio-economy have strong potential to help shift dependency away from petroleum. Supply chain optimisation (SCO) has been used to help other industries and can be used to boost biomass industry viability. Biomass supply chain models frequently average the biomass yield of large tracts of land in their calculations. However, there can be large variation in the biomass yield within those tracts, losing useful information. This work presents a biomass SCO framework which approximates the available quality of land by piecewise linearly approximation of the biomass yield distribution, and incorporates this information into the optimisation. The linear estimates of the biomass yield distributions allow the SCO model to make more informed decisions about quantity and location of biomass growth operations, affecting all downstream decisions. A case study of mainland Great Britain has been examined using the framework to illustrate the impact of retaining biomass yield information in the optimisation, versus averaging the yield across tracts of land. The case study found that using biomass yield linear estimates reduced the overall land usage by 10%. Further, it improved biomass output, which increased the quantity of bio-products produced. All of this led to an increase in the overall profit.
Cooper N, Panteli A, Shah N, 2019, Linear approximations for improved biomass supply chain optimizations applied to biomass yield distribution for reduced land usage
Cooper NJ, Smith TL, Santamaria AD, et al., 2018, An Electrochemical Performance Characterization Method for Comparing PEFCs of Varying Channel Dimensions, Journal of Electrochemical Energy Conversion and Storage, Vol: 15, Pages: 041006-1-041006-8, ISSN: 2381-6872
Huo S, Cooper NJ, Smith TL, et al., 2017, Experimental investigation on PEM fuel cell cold start behavior containing porous metal foam as cathode flow distributor, Applied Energy, Vol: 203, Pages: 101-114, ISSN: 0306-2619
Cooper NJ, Santamaria AD, Becton MK, et al., 2017, Neutron radiography measurements of in-situ PEMFC liquid water saturation in 2D & 3D morphology gas diffusion layers, International Journal of Hydrogen Energy, Vol: 42, Pages: 16269-16278, ISSN: 0360-3199
Cooper NJ, Santamaria AD, Becton MK, et al., 2017, Investigation of the performance improvement in decreasing aspect ratio interdigitated flow field PEMFCs, Energy Conversion and Management, ISSN: 0196-8904
Cooper N, Smith T, Santamaria A, et al., 2016, Experimental Performance Characterization of Polymer Electrolyte Fuel Cells with Varying Channel Dimensions, ECS Meeting Abstracts, Vol: MA2016-01, Pages: 1561-1561
<jats:p>Proper flow field design is an active research topic in the pursuit of improving performance for Polymer Electrolyte Membrane Fuel Cells (PEMFC). Important concerns remain as PEMFCs come to mass market including increasing power density, and decreasing system cost. Increasing the power density of fuel cells reduces the size and cost of a system for a given output power. Understanding the performance benefits and drawbacks of various gas distributor channel dimensions is relevant for designing the next generation of PEMFCs. </jats:p> <jats:p> Two important flow field designs are parallel and interdigitated flow fields. In contrast to parallel flow fields, interdigitated flow fields cause convective transport between channels by forcing flow through the gas diffusion layer via pressure differences, also known as cross flow. Cross flow reduces the diffusion length between reactants and the catalyst layer, reducing performance losses, and helping to remove water from land areas. However, cross flow raises pumping losses. </jats:p> <jats:p> This study experimentally examines the cathode bipolar plate channel/land width and channel depth while taking into account pumping losses. This has been experimentally examined for parallel flow fields, but has only been computationally explored for interdigitated flow fields, such as in Lin and Nguyen (A Two-Dimensional Two-Phase Model of a PEM Fuel Cell, Journal of the Electrochemical Society, 2006). This study seeks to understand how electrochemical and overall performance is affected by channel dimension in interdigitated flow fields, relative to parallel flow fields, from an experimental perspective. </jats:p> <jats:p> Six bipolar plates with d
Cooper NJ, Smith T, Santamaria AD, et al., 2015, Experimental optimization of parallel and interdigitated PEMFC flow-field channel geometry, International Journal of Hydrogen Energy, Vol: 41, Pages: 1213-1223, ISSN: 0360-3199
Flow field design remains an important research topic in the pursuit of higher energy density and increased stability in Polymer Electrolyte Membrane Fuel Cell (PEMFC) systems. Many PEMFC manufactures have reduced channel feature dimensions considerably to enhance catalyst layer reactant delivery as well as to reduce overall stack volume. This work examines experimentally a wide range (250 μm–1 mm) of critical cathode bipolar plate channel dimensions such as channel/land width, and channel depth and their impact on cell performance at various conditions. Both interdigitated (convection dominated) and parallel (diffusion dominated) flow fields were examined, to shed light on how the two designs scale. Further, the results are normalized with respect to pumping power as well as key diffusion and convective lengths to find an optimal configuration. The results show an ideal hydraulic diameter for net system power density to be approximately 0.4 mm for a stoichiometry of 1.5 anode & 2.0 cathode. Higher stoichiometries tended to have maximum net power densities at higher hydraulic diameters. The statistical analysis found that the most important parameter for parallel flow fields on both raw power and limiting current density is the channel/land width. For interdigitated flow fields, the most important parameter on raw power and limiting current density is the stoichiometry. This work will provide the cell designers with a quick guide to optimize the design parameters of the parallel and interdigitated flow field.
Santamaria AD, Becton MK, Cooper NJ, et al., 2015, Effect of cross-flow on PEFC liquid-water distribution: An in-situ high-resolution neutron radiography study, Journal of Power Sources, Vol: 293, Pages: 162-169, ISSN: 0378-7753
Santamaria A, Cooper N, Becton M, et al., 2014, Experimental investigation of channel aspect ratio on interdigitated PEMFC performance, SAE International Journal of Alternative Powertrains, Vol: 3, Pages: 78-85, ISSN: 2167-4191
Novel water management and reactant distribution strategies are critical to next generation polymer electrolyte membrane fuel cell systems (PEMFCs). Improving these strategies in PEMFCs leads to higher power density and reduced stack size for vehicle applications, which reduces weight and improves the price competitiveness of these systems. Interdigitated flow fields induce convective transport (cross flow) through the porous GDL between adjacent channels and are superior at water removal beneath land areas, which can lead to higher cell performance. However, the head loss due to flow, among other factors, may cause cross flow maldistribution of reactants down the channel. Such maldistribution may lead to areas of low or areas of excess cross flow. This, in turn, can cause areas of low oxygen concentration and water build up, and therefore higher pressure losses and uneven membrane hydration, all of which reduce overall cell performance. This research seeks to examine the affect varying channel dimensions have on cross flow and water distribution in an interdigitated flow field. A modeling study of a PEMFC at various aspect ratios and flow rates was completed using the multiphysics package COMSOL. Interdigitated flow fields at varying lengths and conditions were simulated in 3D. Power and cross flow trends were the main focus of the work. Reaction by-product water is a factor; however, no models can currently account for this completely. The cross flow and current distribution was shown to be more variable in the 25 cm cell than in the 5 cm cell. The central region of the 25 cm cell, where the cross flow rate is lowest, may be subject to reduced oxygen concentration and increased water buildup. Regions toward the entrance and exit, while receiving higher cross flow rates, may be oversupplied and contributing to increased pressure drop due to higher velocities. For experimental validation, a PEMFC was designed that could be configured to run under varying interdigita
Santamaria AD, Cooper NJ, Becton MK, et al., 2013, Effect of channel length on interdigitated flow-field PEMFC performance: A computational and experimental study, INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, Vol: 38, Pages: 16253-16263, ISSN: 0360-3199
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- Citations: 53
Santamaria A, Cooper NJ, Becton M, et al., 2013, A study of channel dimension effect on performance of interdigitated flow field PEM fuel cells, Pages: 1-4
Cooper N, Link S, Arvelakis S, et al., 2011, Characterization of biochars obtained from various biomaterials, ISSN: 0065-7727
Biomaterials have been attractive candidates for power generation for at least last decade. Utilizing agricultural biomasses, such as wheat straw or coastal reed for energy generation, can reduce worldwide CO emissions from fossil fuel combustion systems, while simultaneously utilizing a waste stream. In addition, bio-chars originating from the wood products are reported to be excellent sorbent materials. Various bio-chars samples were characterized by CO 2 and N2 adsorption techniques. The N2 BET surface area of the wheat straw sample was found to be in the range of 25 m2/g, however the CO2 adsorption BET surface area of the same material was determined to be as high as 348 m2/g. The DFT analysis of the CO2 isotherm confirms that this increased accessibility of CO2 molecule to the char pore structure is due the wide network of micropores present in char. The enhanced surface area obtained from the CO2 adsorption isotherm is attributed to the presence of super micropores (pores less than 8 Ångstrom) present in the wheat straw char sample. When investigating the adsorption characteristics of the materials with clearly microporous nature both CO2 and N2 techniques should be applied.
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