Cities’ warm underbellies have geothermal potential

Researchers at the Karslruhe Institute of Technology in southern Germany have developed a tool for accurately detecting the temperatures of underground water in large cities.

The tool could be useful in determining the “enormous geothermal potential” of groundwater in cities for heating and cooling, says an article in Environmental Science & Technology.

The researchers combined satellite data on surface temperatures with building densities and found underground heat islands in the cities of Berlin, Munich, Cologne and Karlsruhe.

They found that temperatures below ground were higher than temperatures above-ground in 80% of the cities, and the phenomenon was most pronounced in older cities, with their abundance of cellars, sewers and high population densities.

The article concludes: “Hence, satellite-measured surface temperature alone is not sufficient to reliably estimate groundwater temperature. For this reason, the scientists also considered population density and cellar temperature. They succeeded in estimating regional groundwater temperatures with a mean absolute error of 0.9 Kelvin. ‘This method can be applied for a first assessment of underground heat islands and, hence, of ecological conditions in the groundwater and of the geothermal potential. No complex groundwater temperature measurements and interpolations are required,’ Philipp Blum, Professor for Engineering Geology of AGW, KIT, explains.”

Susanne A. Benz, Peter Bayer, Frank M. Goettsche, Folke S. Olesen, and Philipp Blum published the article “Linking Surface Urban Heat Islands with Groundwater Temperatures. Environmental Science & Technology, November 2015. DOI: 10.1021/acs.est.5b03672. Click here.