Excess heat from big cities may have geothermal uses. (Credit: KIT)
Satellite data have shown that excellent sources of heat for potential geothermal uses may be right under the noses of city dwellers: warm groundwater beneath cities themselves.
According to a release from Karlsruhe Institute of Technology, large cities often have underground heat islands with water warmer than that on the surface. The warmer groundwater could potentially be used for heating and cooling, possibly reducing the need for industrial energy sources and helping emissions decreases.
While estimating surface water temperatures via satellite is relatively simple, scientists require more information to monitor groundwater temperatures. Although there seems to be a spatial relationship between surface and groundwater geothermal hotspots in cities, this relationship was shown to be insufficient for groundwater temperature estimation. Factors such as cellar temperature and population density also needed to be considered in groundwater temperature estimation, scientists found.
The mean absolute error of the groundwater temperature estimation method with the factors included was 0.9 Kelvin. Older cities were found to have higher underground warming than young cities, possibly due to differences in sewer systems, building cellars or reinjection points for cooling water.
Top image: Excess heat from big cities may have geothermal uses. (Credit: KIT)