Single-well circulation systems for geothermal energy transfer

As an alternative method of implementing environmentally friendly geothermal systems for space heating and/or cooling, groundwater has been increasingly used in open-loop ground-coupled heat-pump systems. Of various groundwater heat-pump configurations, the single-well circulation systems tend to provide the best geothermal exchange efficiency where the hydrogeological and thermogeological conditions allow for their installation. In comparison with the closed-loop systems consisting of geothermal boreholes, the single-well circulation systems may substantially reduce the number of boreholes needed, especially for large-scale geothermal applications. In small-scale applications of the single-well circulation system, the groundwater circulation supplies enough thermal energy underground that the temperature of the circulating water remains stable through the years. For district-scale applications, however, further studies are needed to fully understand their sustainability and the impacts on groundwater quality from operating ground-coupled heat-pump systems.