Ground heat exchanger in different configuration: Review of recent advances and development

For the last several decades, ground heat exchangers (GHEs) have been considered an effective and reliable method for exploiting geothermal energy. The present review presents the analytical, numerical, and experimental investigations related to the thermal performance of the various types of vertical, and horizontal GHEs. The advances in the hybrid combinations of GHEs utilized recently in different applications are also introduced. The economic analysis of applying GHEs is also reviewed. It is inferred that the soil thermal conductivity, installation depth, and design parameters of pipes significantly affect the thermal and economic performances of all types of GHEs. Utilizing thermal enhancement techniques such as fins, nanofluids, and PCM improves the thermal performance of GHEs. An evaluation of traditional and hybrid systems utilizing GHEs demonstrated that hybrid systems are good options for long-term usage, environmentally friendly technology, and reduced grid power usage and water consumption. The yearly saved or created energy should be considered in estimating the GHEs. Also, using local soil as a backfill and applying manufacturing economies reduces the overall installation cost of GHEs.