Effects of heat source type on the thermodynamic performance and economy of domestic hot water system

In this paper, a solar assisted air source heat pump (SA-ASHP) domestic hot water (DHW) system is designed and built, the thermal performance of the system and the effect of heat source type on the energy consumption and carbon emission are studied by simulation and experiment. The static investment payback period of transforming the auxiliary heat source from electric boiler (EB) to ASHP is determined by economic analysis. The results show that the coefficient of performance of SA-ASHP system (COPS) varies from 2.76 to 6.26 and the coefficient of performance of ASHP unit (COPH) varies from 2.62 to 3.93 throughout the year. In the four typical heat source hot water systems, the SA-ASHP system has the lowest energy consumption, operation cost and CO2 emission. Compared with the solar assisted electric boiler (SA-EB) system, the power consumption per unit hot water, per capita power consumption and per capita water consumption of the SA-ASHP system decreased significantly, while the average heat collection efficiency and solar fraction increase obviously. Based on the actual operation data and economic analysis, the static payback period and CO2 emission reduction of transforming a SA-EB system into a SA-ASHP system have been analysed.