Study on Hot Water Usage and Performance of CO_2 Heat Pump Water Heaters in House : Part 4-Development of the Calculation Method for Energy Consumption and Efficiency Performance

Abstract

The authors have measured the energy consumption and the loads of hot water consumption in houses that have been set up with the model of CO_2 heat pump water heater (2005, 2006, 2008 model). This paper proposes the calculation method to estimate energy consumption and coefficient of performance (COP) on the CO_2 heat pump water heaters using computer simulation. There are many factors affecting the energy consumption and COP. The relationships among these factors are studied by regression analysis, and the calculation methods are developed with the regression formulas. As the result of comparison of the estimated and measured values, it is clarified that the calculation method accurately estimates the fluctuation of energy consumption and COP. The usage of function for reheating bathwater has an effect on the running performance of CO_2 heat pump water heater.