Evaluation of Energy Saving Performance of Residential SOFC CGS with Heat Pump Water Heater

Abstract

Recently, residential solid oxide fuel cell cogeneration system (SOFC CGS) has been put to the practical use. Considering this fact, in the present study, the authors evaluated the energy saving performance of the residential SOFC CGS. At first, the authors discussed what type of the back-up boiler is suitable for the residential SOFC CGS, and decided to focus on the heat pump water heater. Next, the authors carried out simulations of the operation pattern and performance of the residential SOFC CGS with heat pump water heater (SOFC/HP system) by using the measured results of the electric and hot water loads of an apartment in Fukuoka. As the nominal electric efficiency (LHV base) of the SOFC CGS, two cases of 50% and 60% were supposed. Performance simulations of the actually used residential systems of the conventional system with gas water heater, the all-electric system with heat pump water heater and the SOFC CGS with gas water heater (SOFC/GS system) were also carried out for comparison, It was made clear that the SOFC CGSs generally exhibit very high annual total energy efficiency. It is worthy of special mention that the total energy efficiency of the residential SOFC/HP system with the nominal electric efficiency of the SOFC CGS of 60% reaches one step higher level among them and exceeds the highest level of that of the SOFC/GS system.