HeHo - Heat storage in hot aquifers

The aim of the HeHo project is to investigate the feasibility of storage of hot water in warm geothermal reservoirs in Denmark. The idea is that the relative high aquifer temperature will minimize heat loss due to convection. The hot water is generated by surplus heat from renewable but intermittent energy sources as sun, wind and waste incineration. The hot aquifer storage should be directly integrated with geothermal energy extraction and district heating. We find that the sandstones of the Gassum Formation at a depth of 1700 m are well suited for the purpose. We also find that more than half of the injected energy can be retrieved and that the sandstone will only suffer minor loss of permeability and strength as a consequence of hot water injection. Our results would have had societal relevance if political decisions had not made use of geothermal energy less attractive in Denmark.