Fuel-cell heat recovery, electrical load management, and the economics of solar-hydrogen systems

Computer modelling of a solar-hydrogen system to supply a remote household in southeast Australia has been conducted. Electrical load management and fuel-cell heat recovery have been investigated to improve the system's economy. The results reveal that the cost of the solar hydrogen system can be reduced by over 10% by managing the peak demand and accordingly the capacity of the fuel cell while keeping the average daily electrical energy supplied constant. Interestingly, increasing the size of the fuel cell up to a certain level above the minimum required actually lowers the average unit cost of energy supplied since the fuel cell operates at lower current densities and hence better efficiency. A smaller PV array, electrolyser and hydrogen tank are then required as well. Heat recovered from the fuel cell and used to substitute for LPG in a domestic hot water unit could lead to a further reduction in the overall capital cost of the household's energy system. While the recoverable heat available was found to be less if optimal load management is also applied, there remained a net economic benefit of supplying both heat and power.