Thermal sustainability of groundwater-source cooling in Winnipeg, Manitoba

Abstract

Groundwater from the Carbonate Rock Aquifer is extensively used for cooling purposes in Winnipeg, Manitoba. This paper examines the factors affecting the magnitude and timing of temperature increases at production wells in groundwater-source cooling applications through numerical modeling and observations at a case study site. Generic simulations carried out using typical hydrogeologic parameters for the Carbonate Rock Aquifer suggested that temperature increases of a few degrees occur at a typical production well only a few years after the start of operation in a given system. Spacing of the wells and pumping rates were found to have a greater affect than material properties in a homogeneous aquifer. A case study of a thermal doublet in the Winnipeg area indicated, however, that heterogeneities are capable of causing a departure from the predicted temperatures of the generic models. The case study showed that it is possible to make reasonable predictions of the behaviour of the subsurface temperature field during thermal development of the Carbonate Rock Aquifer. Temperature records of the length used in this study will not be available in new developments, however, and efforts must be made to conduct more extensive field investigations to ensure that designs can properly account for geologic conditions.Key words: geothermal energy, fractured rock, Carbonate Rock Aquifer, Winnipeg, Manitoba, injection, heat flow.