Analysis of a solar-assisted heat pump system with hybrid energy storage for space heating

Insufficient heating capacity and low coefficient of performance have always been obstacles that inhibit the application of air source heat pump systems in cold regions. This study proposes an indirect expansion solar-assisted air source heat pump system to improve the heating performance of the air source heat pump. The indirect expansion solar-assisted air source heat pump system consists of solar collectors, a hybrid thermal energy storage tank, and a dual-source heat pump. An optimized control method is proposed to tackle the refrigerant redistribution problem for the dual-source heat pump. An experiment is carried out to study the thermodynamic performance of the indirect expansion solar-assisted air source heat pump. The experimental results indicate that the average coefficient of performance of the solar heat pump mode is increased by 50.0% compared to the air source heat pump mode due to the higher evaporating temperature. Based on the experimental results, a techno-economic and environmental analysis of the indirect expansion solar-assisted air source heat pump system for space heating is conducted in six northern cities in China. The indirect expansion solar-assisted air source heat pump system has the highest annual average coefficient of performance of 2.53 in Jinan, which is increased by 18.8% compared to Harbin. The payback period of the indirect expansion solar-assisted air source heat pump system is shortest in Xining and is reduced by 53.45% compared to Jinan. Applying the IX-SAASHP system in the northwest region is suitable for improving its energy and economic performance. The analysis results indicate that the IX-SAASHP system is beneficial for reducing carbon emissions from space heating systems in the northeast region.