A comprehensive and updated review on the exergy analysis of ground source heat pumps

Heat pumps are efficient and attainable alternatives for the conventional systems used for cooling and heating in the buildings. Renewable energy sources can be integrated with heat pumps to improve these systems in term of fossil fuel consumption and mitigation of greenhouse gases. Ground Source Heat Pumps (GSHPs), using geothermal energy as heat source, are promising technologies for supplying heating and cooling loads in a clean and sustainable way. Aside from energy analysis, exergetic dimensions of GSHPs has been considered in recent decades. Regarding the advantages of exergy analysis in providing deep insight into the energy systems, this work reviews the study on the exergy analysis of GSHPs. In this regard, this study is performed to provide a comprehensive review on the GSHPs' exergetic dimensions. According to the findings, exergy efficiency of GSHPs depends on several elements such as the installation depth of the components, specification of the units, dead state temperature, configuration of the system and operation mode. In addition, it is found that irrever-sibilites of GSHPs is decreasable by utilizing some additional components such as thermoelectric. Furthermore, utilization of material with improved properties such as nanofluids can enhance the exergy efficiency of GSHPs, i. g. 89.7% in optimal concentration compared 88.3% by using base fluid as indicated in one of the studies.