Solar-hydrogen combined heat and power systems for remote area power supply

The focus in this thesis is on solar-hydrogen combined heat and power (CHP) systems for supplying both electrical power and hot water in remote areas. The stand-alone solar-hydrogen system studied uses a photovoltaic array to meet the electrical demand directly to the maximum extent possible. Any surplus is fed to a Proton Exchange Membrane (PEM) electrolyser to produce hydrogen for storage. At later times when there is insufficient supply from the PV array, hydrogen is drawn from the storage and input to a PEM fuel cell to generate electricity to meet the supply deficit. The main hurdles facing solar-hydrogen systems are low round-trip energy efficiency in short-term energy storage applications compared to traditional storage systems like batteries, and high capital cost. The thesis investigates fuel cell heat recovery in the context of the complete solar-hydrogen system with the aims of increasing the overall system energy efficiency, and hence improving system economics. An advanced simulation model based on Visual Pascal for sizing and performing techno-economic analysis on the performance of solar-hydrogen CHP systems has been developed. Individual analyses on the system components, energy and cost analyses, waste recovery analysis, and economic optimisation of the system are some of the key capabilities of the model. The techno-economic characteristics of a remote area power supply system for a typical remote household in south-eastern Australia with a nominal 5 kWh daily demand profile have been investigated using the model. Optimal sizing of the fuel cell yields an 8% improvement in the average annual efficiency in power production, and a 12% reduction in the unit cost of electricity generated. Also the recovery of heat from the fuel cell for water heating increases the average annual energy efficiency of the optimally-sized fuel cell from around 40% in electrical power production to about 65% in a CHP application. The value of the recovered heat when used for domestic hot water supply is estimated to be equivalent to more than 10% of the overall cost of the system. The technical feasibility of using a solar-hydrogen system in CHP mode and the economic viability of this option are confirmed by performing an experimental investigation on a 500 W water-cooled PEM fuel cell system. The experimental study also showed that the stoichiometry of the input air, and the fuel cell operating temperature influence the overall performance of the solar-hydrogen CHP system significantly. The findings from this study will assist in the development of a cost-effective solar-hydrogen system for remote applications suitable for future commercialisation.