Evaluation of Saving Energy of SOFC and Battery Combined System

Takeshi Sase1, and Yasuo Kuwasawa2

1. National Research and Development Agency, Building Research Institute, Department of Environmental Engineering, Japan

2. National Institute for Land and Infrastructure Management, Japan

Abstract: Fuel Cells have been utilized for residential use recently. Because they are very effective saving energy, generating not only electricity but also hot water. Especially SOFC (Solid Oxide Fuel Cell) has been utilized because of its higher efficiency of generating electricity than PEFC (Polymer electrolyte fuel cell).

The authors have found that it has high efficiency 42% at full capacity but it decreases on smaller scale. To overcome this shortcoming, the authors have made the system, combining SOFC and battery. This system accumulates overflowed electricity into the battery, operating SOFC on the full scale, and emits electricity from the battery when the electricity load is beyond SOFC capacity.

The authors have evaluated its efficiency of generating electricity, saved energy compared with the traditional method, which provide electricity and hot water by the Commercial power and the gas boiler, and the only SOFC on various electricity and hot water scale patterns. They have found that it is more effective by generating electricity and accumulating overflowed electricity and emitting it generally. But it is not more effective than the only SOFC when it is operated on smaller electricity scale. The proposed system loses some electricity during accumulating it into the battery, emitting it from the battery, and translating it between direct and alternating current.

It is suggested its efficiency and effectiveness could be improved by reducing this electric loss.

Key words: SOFC (Solid Oxide Fuel Cell), battery, saving energy