Study on developing the energy independence of residence with the distributed energy system composed of photovoltaic power generation and fuel cell driven by hydrogen (1st report : Evaluation of energy-saving effect of the system using heat-to-power ratio controllable SOFC)

A large amount of energy is consumed by people around the world. Most of the consumed energy is originated from fossil resources of which deposits are limited. Therefore, it is necessary for a sustainable society to use energy without waste. Fuel Cell (FC), which supplies energy effectively by Co-generation, attracts attention as a high-efficient distributed energy device for residential use. However, FCs are generally operated with City gas derived from fossil resources. Then, a FC system using hydrogen (H2) fuel produced by Photovoltaic power generation (PV) is proposed. The FC is driven with H2 generated from “surplus power”, which comes from the gap between PV output and electricity demand in residence. This PV-FC combined system approaches energy independence in the residence because consumed electric and thermal power generated by PV and FC originates from solar energy. In this study, PV and Solid Oxide Fuel Cell (SOFC) combined system (PV-SOFC system) is discussed. A SOFC, which has the highest electrical efficiency among FCs, can accept mixed fuel of H2 and City-gas. Additionally, heat-to-power ratio of SOFC output may be able to be controlled by changing H2 concentration of the mixed gas fuel. Thus, it is possible to realize the energy supply synchronizing the each variation of electricity and heat demand in residence. In this paper, the energy reduction by introducing a heat-to-power ratio controllable PV-SOFC system to a residence is simulated. The results show that primary energy consumption in the PV-SOFC system is reduced by 53.8 % for a year.