摘要：The urban heat island effect and climate change have not only caused surface
temperature increase in most urban areas, but during the last hundred years also
enhanced the subsurface temperature by several degrees. This phenomenon yields
aquifers with elevated temperature, which are attractive though underestimated
thermal energy reservoirs. Detailed groundwater temperature measurements in
Cologne (Germany) and Winnipeg (Canada) reveal high subsurface temperature
distributions in the centers of both cities and indicate a warming trend of up to
5 °C. The case-specific potential heat content in urban aquifers and available
capacities for space heating are quantified. The results show, for example,
that, by decreasing the 20 m thick urban aquifer's temperature by
2 °C, the amount of extractable geothermal energy beneath Cologne is 2.5 times the residential
heating demand of the whole city. The geothermal potential in other cities such
as Shanghai and Tokyo is shown to supply heating demand even for decades.
