Underground cold and heat storage
Underground cold and heat storage is when excess heat and cooled water is stored in underground aquifers in one season and utilized in the next season.  Excess heat from a power system is fed into an underground aquifer for heat storage in summer and then recovered at times of peak demand in winter for heating and, for cooling purposes a ground-water bearing bed is cooled down by means of ambient cold in winter, feeding the cooling systems of the building in summer without any additional drive power.

Project example:
An underground cold and heat storage was made for the Reichstag building (seat of the German Parliament) in Berlin in 2009 by the Mannvit team member GTN. A rapeseed oil-driven 1,600 kWel cogeneration unit forms the centre of the system. The underground aquifer heat store is situated at a depth of 300m.  A second ground-water-bearing bed situated at a depth of approximately 50 m is used as a cold store. Boiler units, compression and absorption-type chillers and heat pumps are installed to cover the medium and peak load as well as for system redundancy.