Economic Assessment of Home Co-generation System with PEFC Based on Survey of Hot-water Demand

Abstract

This paper provides a case study of the performance and the economy of micro co-generation system (μCGS) for residential use based on a time series data on the hot-water demand obtained with 1 minute interval for one year. Assuming a simple constant output operation of PEFC, we calculated the composition of hot-water supply from PEFC and backup boiler. When μCGS is equipped with 100L hot-water storage tank, many portions of hot-water output of the PEFC were wasted although the backup boiler must assist to meet the demand concentrated within a short period. Annually, about 88% of the hot-water demand was met by the PEFC and the rest 12% was met by the backup boiler. Even in this case, the primary energy consumption was small as compared to the conventional energy system, because the electricity output from the PEFC could be fully utilized in the household or grid. However, because of a relatively higher price of city gas, the variable energy cost in μCGS was higher than that in the conventional system in the summer season. When the unit cost of PEFC is reduced to about 120, 000 yen/kW_e by a mass production, the annual cost on μCGS could be small relative to the conventional system.