Integrated Photo-Electrochemical Solar Fuel Generators Under Concentrated Irradiation- Part II: Thermal Management a Crucial Design Consideration

Concentrating solar irradiation for use in integrated photo-electrochemical devices potentially provides an economically competitive pathway for hydrogen generation, even with partial use of rare material components. Heat transfer and thermal management are crucial in devices operating under large irradiation concentrations.With dedicated thermalmanagement, detailed 2-dimensionalmultiphysics modeling predicts high performance. Two competing operational parameter spaces are observed: i) thermal effects enhance performance in the zone of low operational current density, and ii) mass transport limits dominate in the zone of high operational current density (saturation current of the electrolyzer component). These competing effects lead to tradeoffs between device efficiency and hydrogen evolution rate, quantified using Pareto frontiers. Smart thermal management – only possible through integrated device design – helps in achieving efficient and low cost production of solar fuels, and can further alleviate degradation-related performance decreases over the lifetime of the device. For example, at an irradiation concentration of 707, a 12% degradation in STH efficiency of a Si-based device is compensated by a seven-fold increase in the water mass flow rate. Integrated photo-electrochemical device designs combined with smart thermal management prove to be a practical and economically feasible approach to solar fuel processing, and provide a pathway to circumvent limitations imposed by materials.