Performance enhancement of a photovoltaic powered direct expansion solar-ambient hybrid source heat pump with sub-cooler vapour injection

The volumetric efficiency of a direct expansion solar-ambient hybrid source compression heat pump (DXS-AHSCHP) was affected due to rise in solar thermal flux, ambient temperature and relative humidity. In this research, a sub-cooler vapour injection (SC-VI) is proposed to improve the volumetric efficiency by controlling the refrigerant super-heating. Moreover, the system was powered with photovoltaic panels to reduce the use of grid source power generated by conventional energy sources. The experimental observations have been made in a photovoltaic powered SC-VI-DXS-AHSCHP and compared with the grid powered DXS-AHSCHP without SC-VI for the period of fifty days in each mode. The system performance was compared in terms of volumetric efficiency, power consumption, condenser heating capacity and coefficient of performance (COP) for the similar ambient conditions. The results showed that a photovoltaic-powered SC-VI-DXS-ASHCHP has maintained the compressor volumetric efficiency of more than 0.84 with 1.8–3.3% reduced compressor power consumption, 2.5–7.5% improved condenser heating capacity and 4.2–10.3% improved COP compared to DXS-AHSCHP without SC-VI. The proposed photovoltaic-powered SC-VI-DXS-ASHCHP has a payback of 34.45 months with 96.12% lower carbon emissions compared to the grid-connected conventional DXS-ASCHP without SC-VI for a period of fifteen years.