Berlin’s underground car parks are producing so much heat they could power thousands of homes with clean geothermal electricity, according to a new study. The heat given off by car engines makes the city’s car parks hotter than the surrounding earth, which in turn raises the temperature of the groundwater. This could pose a threat to water quality but also presents an opportunity — using heat pumps to extract the energy and use it to heat homes. In Berlin alone, enough energy is transferred to the groundwater to supply 14,660 households with heat, based on modelling from over 5,000 underground…

This story continues at The Next Web