Performance improvement of solar-assisted ground-source heat pumps with parallelly connected heat sources in heating-dominated areas

Solar-assisted ground-source heat pumps (SGSHPs) with a serial configuration have been introduced to reduce the performance degradation of ground-source heat pumps (GSHPs) for their long-term operation. However, SGSHPs with parallel configurations have rarely been investigated in heating-dominated areas. In this study, the heating performances of a GSHP and SGSHPs with serial and parallel configurations in a heating-dominated building are analyzed using TRNSYS and compared for 20 years by varying the borehole length and solar collector area. With a borehole length of 120 m and solar collector area of 10 m², an SGSHP with a serial configuration showed a 12.6 and 11.5% higher ground temperature and solar collector efficiency, respectively, than the parallel configuration owing to the solar heat injection into the ground. However, an SGSHP with a parallel configuration decreased the energy consumption by 19.6 and 13.8% compared to those for the GSHP and SGSHP with a serial configuration, respectively, owing to an improved heating capacity. Furthermore, an SGSHP with a parallel configuration can considerably decrease initial costs by reducing the borehole length.