Energy, exergy and exergoeconomic analyses of a combined renewable energy system for residential applications

A hybrid renewable energy system is designed and analyzed for electricity, hot water and hydrogen production. Exergy, energy and exergoeconomic analysis is conducted to determine the performance of the system under different operating and environmental conditions. The renewable energy system consisted of wind turbines and PV panels for electricity production operating an electrolyser which produced hydrogen. Hydrogen either goes directly to a fuel cell to produce electricity or through a compressor to run the fuel cell at high pressure. The heat from the fuel cell is used to heat water for domestic use. The analysis is conducted to determine the efficiencies of the system with and without domestic hot water heating and incorporating a compressor in the system. The analysis results suggested that approximately 14% energy and 21% exergy system efficiency increment is achieved when water is heated for domestic use. System involving the compressor lowered the overall system energy and exergy efficiencies. Decrease in efficiencies can be associated to the increase in hydrogen density, at high pressure states, which requires greater compressor work. The exergoeconomic study also suggested an improvement in the system when domestic water is heated using the excess heat from fuel cell.