• Closed-loop heat exchangers can provide heating/cooling and/or hot water in buildings (residences, schools, offices, etc.) and other applications (such as swimming pools, greenhouses, ice melting, etc.). These systems are also known as Ground Source Heat Pumps (GSHPs). There are two main geometrical configurations for closed-loop GSHPs: horizontal and vertical systems (Chaldezos and Karytsas 2017[1]).
  • Open-loop systems use well or surface body water as the heat exchange fluid that circulates directly through the GSHP system. Once it has circulated through the heat exchanger coil system, the water returns to the ground through the reinjection well. This configuration is practical only if an adequate supply of relatively clean water is available. Open-loops are not as common as closed loops nowadays, not only as a result of the major improvements in closed systems up to date but also because of environmental concerns in some areas. Open-loop systems can also be applied if local codes and regulations regarding groundwater discharge are met, as open systems are often subject to local zoning laws and licensing requirements (Government of Canada 2017[2]).
  • Earth-Air Heat Exchanger (EAHE) systems can effectively be used to preheat the air in winter and precool it in summer. The temperature of Earth at a depth of 1.5 – 2m remains fairly constant throughout the year (maintaining the earth’s undisturbed temperature (EUT)), which is higher than ambient air temperature during the winter and lower during the summer. The system comprises a series of pipes buried underground at a particular depth, through which the fresh ambient air flows and gets cooled in summer (soil acting as heat sink) and heated in the winter (soil acting as heat source). The EAHE can effectively meet the heating/cooling requirements if the temperature of air at the outlet of the system is adequately low or high; otherwise, it can only reduce the heating/cooling load of the building through preconditioning the temperature (Bisoniya 2015[3]; Bisoniya, Kumar, and Baredar 2014[4]).

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[1] Chaldezos, I. P. and C. S. Karytsas. 2017. “Innovative High Efficiency Closed Loop Ground Coupled Heat Exchanger (GCHE).” Procedia Environmental Sciences 38:102–6.

[2] Government of Canada. 2017. “Ground-Source Heat Pumps (Earth-Energy Systems).” Retrieved July 10, 2020 (https://www.nrcan.gc.ca/energy/publications/efficiency/heating-heatpump/6833).

[3] Bisoniya, Trilok Singh. 2015. “Design of Earth–Air Heat Exchanger System.” Geothermal Energy 3(1):18

[4] Bisoniya, Trilok Singh, Anil Kumar, and Prashant Baredar. 2014. “Study on Calculation Models of Earth-Air Heat Exchanger Systems.” Journal of Energy 2014:1–15.

[Additional] GEOTRAINET TRAINING MANUAL FOR DESIGNERS OF SHALLOW GEOTHERMAL SYSTEMS. http://geotrainet.eu/wp-content/uploads/2015/10/Geotrainet-Manual-for-Designers-on-Shallow-Geothemal.compressed.pdf