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The successful and fast start-up of proton exchange membrane fuel cells (PEMFCs) at subfreezing temperatures (cold start) is very important for the use of PEMFCs as energy sources for automotive applications. The effective thermal management of PEMFCs is of major importance. When hydrogen is stored in hydride-forming intermetallics, significant amounts of heat are released due to the exothermic nature of the reaction. This excess of heat can potentially be used for PEMFC thermal management and to accelerate the cold start. In the current work, this possibility is extensively studied. Three hydride-forming intermetallics are introduced and their hydrogenation behavior is evaluated. In addition, five thermal management scenarios of the metal hydride beds are studied in order to enhance the kinetics of the hydrogenation. The optimum combination of the intermetallic, hydrogenation behavior, weight and complexity of the thermal management system was chosen for the study of thermal coupling with the PEMFCs. A 1D GT-SUITE model was built to stimulate the thermal coupling of a 100 kW fuel cell stack with the metal hydride. The results show that the use of the heat from the metal hydride system was able to reduce the cold start by up to 8.2%. [ABSTRACT FROM AUTHOR]

Global energy requirements are rising tremendously because of increasing urbanization and the human population. In the last few centuries, the consumption of fossil fuels has caused increased emissions of greenhouse gases resulting in environmental concerns like global warming, climatic change, and biodiversity loss. As a result, progress in sustainable energy has become the centre of attention in climatic change agenda and economic growth. Until now, various methods of renewable energy production have been extensively studied such as geothermal energy, wind energy, and solar energy. In addition to this, the utilization of biofuels from different sustainable sources are also being considered to reduce greenhouses gas emissions. New approaches and developments are still required for the creation of more sustainable, efficient, and affordable renewable energy systems and for the mitigation of global environmental threats. This special issue aims to advance novel developments in the sustainable conversion of renewable energy, providing up to date, fruitful, and actionable insights into economic, social, and environmental sustainability and includes original research articles and reviews to describe the interaction between renewable fuels, CO2 mitigation, and global warming. [ABSTRACT FROM AUTHOR]

Overall fuel cell system efficiency must include consideration of the parasitic loads associated with operating the stack. For an air-cooled open-cathode polymer electrolyte fuel cell (PEFC) the air blowers form the largest parasitic load and have a direct influence of the performance of the stack and its temperature; increasing air flow often leading to improved performance at the expense of increasing parasitic load. Here, electro-thermal performance maps are used to characterise stack operation with varying air flow rate (for both cooling and cathode oxygen supply). The non-linear power requirement of air blowers is used to modify stack-level electro-thermal maps to give system-level performance maps capable of identifying the optimum air flow rate to maximise net power output and consequently efficiency at a given operating point. The electro-thermal map concept is invoked in the consideration of dynamics of fuel cell system operation with issues pertaining to speed of response, durability and system self-sustainable operation. [ABSTRACT FROM AUTHOR]