Underground car parks could be used to heat water and save energy

BERLIN: Underground car parks act like heaters for the ground and according to a new research from Germany and Switzerland, the energy this generates could be used to heat buildings.

Researchers from involving Germany's University of Halle and the Karlsruhe Institute of Technology, as well as Switzerland's Basel University analysed the temperatures in 31 underground car parks in various cities in Germany, Austria and Switzerland.

In six of them, they were also able to measure the temperature of the groundwater in the immediate area. The results showed that the underground car parks heat up the groundwater throughout the year.

The results were influenced by the traffic volume in the underground car parks, their proximity to the groundwater and the previous groundwater temperature.

"As public underground car parks are often deeper and are used for shorter periods of time, they heat the groundwater more than private facilities," said Maximilian Noethen, author of the study from Halle.

Underground car park

The excess heat in the ground could be utilised in the future with the help of geothermal energy and heat pumps.

"The advantage of this would be that energy is extracted from the groundwater and it cools down," said Noethen. For 5,040 underground car parks here, the team calculated the groundwater heating caused by underground car parks for the city using a model.

The researchers came up with around 0.65 petajoules of energy - which could theoretically supply around 14,660 households with heat.

"Of course, heat from groundwater alone is not enough to cover the heating requirements of a city like Berlin or even a country like Germany. Nor is the temperature level of the near-surface groundwater sufficient for heating without a heat pump," says Peter Bayer, an author of the study from the University of Halle.

"However, we know from previous work that the potential for geothermal energy goes far beyond this and that it could play a significant role in a sustainable heat supply."
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