Configurations of solar air source absorption heat pump and comparisons with conventional solar heating

A solar air source absorption heat pump (ASAHP) is analyzed to explore the suitable configurations of advanced solar heating systems. A single-effect (SE) and a generator-absorber heat exchange (GAX) ASAHP, driven by a flat-plate collector (FPC), evacuated tube collector (ETC), compound parabolic concentrator (CPC) and parabolic-trough collector (PTC) are modeled. A parametric study and comparative analysis of different solar heating systems indicate that the CPC-SE, PTC-SE, and PTC-GAX are suitable configurations. Comparisons with the conventional direct solar heating (DSH) show that the ETC-DSH performs the best among all the DSH systems, only the PTC-SE and PTC-GAX are advantageous over it under a solar radiation of 800 W/m2. At an ambient temperature of 7 °C, the CPC-SE performs better than the ETC-DSH only when the solar radiation is above 1000 W/m2. The PTC-GAX becomes worse than the PTC-SE if the solar radiation is below 650 W/m2 and even becomes inferior to the ETC-DSH if the solar radiation is below 400 W/m2. Besides, the applicability domain of the CPC-SE is very narrow, the efficiency improving rate (EIR) of the CPC-SE is about 15% under a favorable condition. The PTC-SE and PTC-GAX had a much wider applicability domain, and the maximum EIR value is about 24% and 36%, respectively. Reducing air pollution is very important for the applications of the solar ASAHP systems.