Performance of ground heat exchangers: A comprehensive review of recent advances

Highlights: • GHE have been most studied through numerical simulation since 2010. • Multi-tube, single, double, and triple U-tube are the most commonly used geometries. • PE is the most commonly used pipe material in GHE followed by steel and PVC. • Pure water is often applied as the working fluid in GHE followed by EGS. • The most common BHE depths range between 50 and 100 m -- Abstract: The importance of investigating and addressing climate change, through the use of renewable energy, is substantially increasing. Shallow geothermal energy is usually a sustainable and affordable renewable energy source which can be exploited through ground-source heat pump systems. The ground heat exchanger is not only the most important component of the system but also plays a significant role in achieving a high coefficient of performance. In this article, a comprehensive review is carried out of recent advances in the field of ground heat exchangers, including assessments of the effects of system geometric configuration, pipe material, working fluid, and depth of ground heat exchanger on heat flux, heat transfer coefficient, outlet temperature, thermal resistance, and pressure drop. Due to the significance of the ground heat exchanger geometric configuration on system performance, it has recently been extensively investigated. However, there are few comprehensive reviews of these studies and the present article tries to meet this need.