Development and performance investigation of an indirect expansion solar heat pump integrated with a high-concentration conical cavity receiver for heating applications

The present research proposes a novel indirect expansion solar heat pump (IXSHP) heating technology that can transform space and water heating applications in the ongoing search for sustainable and environmentally friendly energy sources. Particularly in higher-latitude areas, solar heat pump heating systems can provide water and space heating, where solar energy greatly influences their operating performance and application possibilities. The solar parabolic dish concentrator (PDC) with a conical cavity tube receiver (CCTR) may achieve high collector performance at high hot water temperatures, increasing solar power absorption and related thermal energy storage capabilities. This paper presents the development of a parabolic dish concentrator (PDC) with a conical cavity tube receiver (CCTR) as a high-temperature heat source to the IXSHP system. The novelty of the current study is in the special integration of high-concentration PDC-CCTR and the indirect expansion heat pump cycle, which has never been studied. The numerical modeling and experimental test rig of the solar PDC and IXSHP system were created to investigate the thermal efficiency, exergy efficacy, and coefficient of performance (COP). According to the testing results, the solar PDC system means daily thermal, exergy efficiency, and COP were 65.35 %, 9.05 %, and 4.86, respectively. The output characteristic of the novel system is also analyzed by investigating the effects of different parameters, including the water flow rate, concentration ratio, and focal length. It was obtained that when the mass flow rate of fluid increased, the thermal efficiency and COP of the solar heat pump system decreased. Moreover, when the concentration ratios of PDC increase from 20 to 40, there is an improvement in the thermal efficiency, temperature difference, and COP by 32 %–71 %, 10 °C−18.5 °C, and 3.86−5.4, respectively. Additionally, the computational model is verified by the testing results, which are accurate and in accordance with one another. This study has offered an innovative methodological and experimental basis for utilizing high-concentration solar thermal collectors as a source of heat in indirect expansion heat pump systems to sustain heating use.