Performance of a Solar-Air Source Heat Pump System for Water Heating on Different Weather Conditions

A new type of solar-air source heat pump water heating system was developed for space heating and residential hot water supply. The specially designed multi-source collector/evaporator (C/E) using spiral-finned tubes could absorb heat from both solar radiation and ambient air. A prototype was designed and tested on different weather conditions in October in Nanjing, China. The experimental results showed that the prototype could heat water from 40degC up to 55degC efficiently both in the daytime and at night. It operated in the solar-source mode with a high averaged COP of 5.1 in the daytime when the solar radiation was 731 W/m². Meanwhile, it operated in the air-source mode stably with a averaged COP of 3.5 at night, avoiding using electricity as a backup energy source.