An experimental analysis of a solar-assisted heat pump (SAHP) system for heating a semisolar greenhouse

Abstract

ABSTRACT Solar thermal is the primary source of heat and the heat pump is used as a back-up when sun is not shining with enough intensity. In this paper, theoretical and experimental studies were carried out on a solar-assisted heat pump (SAHP) under the metrological condition of Tabriz city (located in the northwest of Iran). The system mainly includes a flat-plate solar collector (totally of 1 m2), an evaporator with refrigerant R134a, a piston type compressor with a power of 3/4 hp, a condenser and a capillary tube. Tests were performed on four consecutive days from 24 to 27 December 2018. The effect of environmental parameters on the greenhouse temperature in day and night was compared with and without the heat pump using SAS9.1 software. The effect of various parameters such as solar radiation and environmental temperature, evaporation and condensation temperature, solar collector area, compressor speed, and number of collector cover has been analyzed in order to understand the coefficient of performance (COP) and efficiency of system (). The results showed that by increasing the solar radiation and temperature, COP and collector efficiency increases with relatively direct relation. According to the results, environment temperature, radiation intensity, evaporation temperature, collector area, and collector covers have a direct relationship with COP but condensation temperature and compressor speed have inverse relationship with it. In this study, has a direct relationship with environment temperature, evaporation temperature, compressor speed and collector covers, and the other three parameters have an inverse relationship with it. Statistical analysis showed that there was a significant difference between the temperature of the greenhouse with and without the heat pump. In addition, using the thermal screen at night was significant for keeping the storage temperature.