Towards self-water-sufficient renewable hydrogen power supply systems by utilising electrolyser and fuel cell waste heat

This study analyses a standalone renewable hydrogen system for an island located in southeastern Australia, by focusing on waste heat recovery from the electrolyser and fuel cell to produce freshwater for hydrogen generation through electrolysis. The proposed arrangement, optimally designed using HOMER Pro, comprises photovoltaic panels, wind turbines, electrolysers, fuel cells and batteries that supplies 13, 500 MWh of electricity per year at a levelised cost of 0. 18/kWh. A direct contact membrane distillation system that utilises the waste heat of the electrolyser and fuel cell, is modelled in MATLAB. The results indicate that a desalination unit with total membrane area of 10 m 2 that runs on low-grade heat, can produce ∼389 m 3 of freshwater annually at a cost of 33. 64/m 3, by utilising 65 % of the total available waste heat of the electrolyser and fuel cell. This meets over 30 % of the electrolyser's water annual demand (i. e. , 1189 m 3), assuming 17 L of water being required to generate a kg of hydrogen. Furthermore, by increasing the membrane area of the desalination unit and the heat utilisation capacity, complete freshwater self-sufficiency can be achieved that makes the renewable hydrogen energy system more sustainable.