ABSTRACT
Among various types of renewable energy, geothermal energy is recognized as an effective method for supplying thermal energy. Ground heat exchangers, as the main part of a geothermal energy system, are utilized for the extraction of the heat from the ground. Helical-shaped geothermal heat exchangers are very popular in this field as they need less land space compared to the other traditional straight ones. They have simple assembly and a high density of coils in their configuration. Considerable efforts have been done on the development of this type of geothermal heat exchanger. However, this topic has not been subject to a review. To address this issue, we present an overview of the potentials and challenges of helical-shaped geothermal heat exchangers in this study. The environmental and economic aspects, recent progress about the numerical simulations, soil features, different types and arrangements, and geometrical parameters for this type of heat exchangers are investigated. The installation cost is a critical challenge in the practical applications of these exchangers. However, the previous studies are mostly focused on the technical evaluation and optimization of the thermal performance of this type of heat exchanger, while little attention is paid to their installation costs. It is essential to understand the potential environmental impacts of each renewable energy technology to have a correct evaluation of the system. The life cycle assessment can be used as a proper method to assess the environmental issues of the helical-shaped geothermal heat exchanger in the studies.
