Solar energy, Mechanical subcooling, Alternative refrigerants, Hot climate
This study investigates the performance of a solar-powered mechanical subcooling cycle to improve the performance of a refrigeration system in hot climates. The mechanical subcooling cycle helped the main refrigeration cycle by further subcool the refrigerant and improve the cooling capacity. The mechanical subcooling cycle used the energy generated by the solar photovoltaics to run its own compressor. The system was evaluated under Kuwait’s weather condition for a typical residential air conditioning (AC) unit of 5 tons of refrigeration (17.6 kW), where different refrigerants were examined in the mechanical subcooling cycle. The refrigerants considered in this study were R-410A, R-32, R-290, R-600, R-600a, R-1234yf, and R-1234ze(E). Parametric studies were performed using an equation solver software to understand the effect of the subcooling temperature and solar panel area on the overall performance of the refrigeration system. The results were compared with a baseline conventional refrigeration cycle using R-410A. The results show that the optimum subcooling temperature for the summer days in Kuwait ranges from 10°C to 20°C, while the best refrigerant that maximizes the overall performance of the system is R-600. In addition, the dedicated mechanical subcooling system improved the overall system COP between 5% up to 16% compared to the conventional system during the typical day of July which is the hottest month in Kuwait. The results also concluded that the solar panel area required to produce sufficient solar power to run the dedicated mechanical subcooling cycle is 3.9 m2 using a single-axis solar tracking system, which saves utility power during the summer months between 17-20%.