Oct. 28, 2013 -- A new analytical heat flux model developed by researchers from the Karlsruhe Institute of Technology (KIT) in Karlsruhe, Germany and ETH Zurich in Zürich, Switzerland, has found that sustainable energies for heating in the winter and cooling in the summer may be extracted from heated groundwater aquifers.
The model concluded that increasing heat in the underground is mainly caused by an increase in surface temperatures and heat released from buildings. Temperatures in big cities are far above those in surrounding rural areas; as such, dense settlement, surface sealing, industry, traffic, and lacking vegetation cause an urban microclimate with increased temperatures in the atmosphere.
Accordingly, temperature anomalies also develop in the underground and spread laterally and vertically. In the past decades, groundwater in conurbations heated up considerably. "In Karlsruhe, the average heat flux density into subsurface aquifers was 759 milliwatts per square meter in 1977. In 2011, a heat flux density of 828 milliwatts per square meter was reached," says Junior Professor Philipp Blum, head of the Engineering Geology Division of the KIT Institute of Applied Geosciences (AGW). "This amount of heat corresponds to 1 petajoule per year and would suffice to supply at least 18,000 households in Karlsruhe with heat."