A Novel, eco-friendly combined solar cooling and heating system, powered by hybrid Photovoltaic thermal (PVT) collector for domestic application

Abstract

Solar heating and cooling technologies can have a vital role to play in understanding the targets in energy security, economic development, and mitigating climate change. This study aimed to investigate the performance of the combined solar cooling/heating system using a Photovoltaic Thermal collector (PVT) for residential applications. The main advantage of using PVT is the conversion of the maximum amount of solar energy into electricity and thermal energy. In this work, water is used to cool the panel and, consequently, increase the efficiency. The cooling cycle comprises a hybrid ejector-compression refrigeration cycle with two evaporator temperatures. To reduce the effect of the global warming phenomenon, two different refrigerants with lower Global Warming Potential (GWP), such as R600a and R290, are used instead of R134a. The inlet water does not only gain heat from the PVT but also the collector output water is heated in a condenser and heater. The results indicate that increasing the water mass flow rate from 0.011 kg/s to 0.03 kg/s (39–108 Lit/h) at solar intensity (G) of 945 W/m2 results in enhancing the overall efficiency of the PVT system from 66.7% to 75.8%. In terms of the highest Coefficient of performance (COP) and the lowest exergy destruction, R290 shows better performance comparing to the other refrigerants. In more details, using R290, instead of R134a, results in up to 7.5% enhancement in the COP of the cycle. The water mass flow rate is optimized at ṁw=0.013 kg/s to achieve the highest COP and the lowest exergy destruction. Also, it is reported that the temperature of the outlet water from the system varies between 31.72 °C to 46.73 °C during the day. Finally, it is revealed that using R290 for the refrigeration cycle and cooling the panel result in enhancing the COP of the cycle by 11.1%, increasing the temperature of the outlet water from the system by 9.17 °C and decreasing the refrigerant flow rate by 60.17%, in comparison with a system without panel cooling which uses R134a refrigerant.