Thermal interactions among vertical geothermal borehole fields

Abstract

Borehole heat exchanger applications are growing every day – so pronouncedly that many borehole fields will likely operate in dense installation areas in the foreseeable future. In these conditions, thermal interactions will have the potential to develop between neighboring fields, with detrimental effects for the performance and efficiency of such installations in the absence of appropriate designs strategies. Currently, scarce knowledge is accessible on thermal interaction effects among borehole heat exchanger fields and a few approaches allow to effectively consider such effects in the design of these heat exchangers. This paper expands the limited competence on thermal interaction effects among borehole heat exchanger fields and presents and validates a methodology to facilitate the design of such heat exchangers. With reference to a virtual operation of multiple vertical borehole fields in the Loop district of Chicago, USA, the work highlights significant thermal interactions among neighboring borehole fields, responsible for temperature drops of up to 5.9 °C during geothermal operations lasting 50 years. The proposed methodology allows correcting the design of borehole fields to avoid overexploitation of the geothermal resource and the occurrence of litigation cases between geothermal users, representing a powerful approach to cope with thermal interaction effects among geothermal boreholes at scale.