A System Analysis on PEFC-CGS for a Farm Household

Abstract

Since 2005, the Japanese government has had great efforts to promote PEFC-CGS (Polymer Electrolyte Fuel Cell Co-generation System) to a household sector in order to mitigate CO₂ emissions. Because of this situation, there is a plan in which 480 units of 1kW PEFC-CGS for a household sector will be installed. However, the heat supply through PEFC-CGS can be often excess energy against heating and/or hot water demands. This is likely to aggravate the cost condition.

On the other hand, in Japan, the number of farm household which possesses green houses is more than 260 thousand points as of 2005. Thus, we focused on the energy demand in which a house and a greenhouse were combined. Using GAMS program, we analyzed the operation condition of PEFC-CGS so as to decrease the excess energy supply, maximizing CO₂ emission reduction and/or the energy cost reduction. On the performance of PEFC-CGS, we calculated the performance model based on electrochemistry and thermodynamics in VBA program. As a result, the power efficiency of 30.3 to 35.2 % and the heat recovery efficiency of 31.6 to 37.3 % were obtained. The part-load operation of PEFC-CGS was considered, too. That is, the part-load operation means that PEFC-CGS shuts down unless the power supply is higher than a minimum electricity demand. Thus, the optimization model on CO₂ emissions or an operational cost is a nonlinear mixed integer model.

Finally, assuming that the total area of a green house was 100 m², the maximum reduction of CO₂ emission was 3.46 to 4.06 t-CO₂/yr, compared to the conventional energy supply through fossil fuels origin. Likewise, that of an operational cost was 61,530 to 64,770 yen/yr.