抄録
It is expected that CO_2 heat pump water heater performs enough heating capacity and high efficiency even in cold area. For the performance evaluation of this system, a test unit was operated in winter, in the open air. The heating capacity reached 4.5[kW], that was our target for residential use, at -20[℃] of ambient temperature. Annual average COP calculated on the weather data in Sapporo showed that CO_2 heat pump water heater was better than other heating systems in TEWI evaluation.
