Solar assisted ground source heat pump systems - A review

Solar assisted ground source heat pump systems (SAGSHPs) have been recently scrutinized by many researchers as it was verified that they have increased the share of renewable energies. Several review papers have been written on solar assisted heat pump systems (SAHPs), studying different types of both solar and heat pump systems coupled with each other. However, what is missing here is the literature discussing the only geothermal type of heat pumps along with the solar energy. This paper aims to puts forward a comprehensive review of the researches conducted on SAGSHPs to facilitate the attributive comparison of them. Reviewing the literature demonstrated that solar thermal energy affects the efficiency of the GSHPs. It is worth noting that the advanced configurations of SAGSHPs perform better than the traditional ones concerning reported higher COPs which draw conspicuous attention towards further studies. The highest values of 13.5 and 5.7 were acquired for COPsys and COPHP through the use of CO(2)ASHP-CPC and LHEST, respectively. Analytical simulation and artificial intelligence models for predicting the thermodynamic performance and control of SAGSHPs were found to be quite reliable. Economical assessment of SAGSHPs applying novel tri-generation systems led to a minimum payback period of 5 years owing to the high savings on operating costs. Finally, future directions for researches and developments in this field are highlighted due to the general gap in studies for improvement of SAGSHPs to match for higher efficiency.