Heat from the ice
The use of renewable energies and a climate-friendly construction method are key to the identity of the Ökosiedlung. Therefore, the decision in favour of an ice storage tank for the reliable and efficient supply of heat for heating was an obvious one.
Anyone looking for the ice storage tank in the Ökosdiedlung will unfortunately be disappointed. The seven metre high concrete container, which has a diameter of 17 metres, is embedded in the ground and is now covered in greenery. However, a large window front in the adjoining operations building allows interested parties to observe the energy flow.
But how can ice be used to generate heat?
In simple terms, the underground ice storage tank works as follows: In winter, the energy required for space heating and hot water is extracted from the water in the storage tank by means of a large heat pump. The storage tank slowly freezes over as it cools. In summer, the ice thaws again using the heat from the solar absorbers and the PVT systems before the cycle starts again in winter.
The ice energy storage system works according to a simple principle: the energy obtained from the sun, air and soil is fed at a low temperature into an underground container - the ice storage tank. A heat pump extracts the heat from the ice storage tank and compresses it to a higher flow temperature for heating the building.
By extracting the heat from the ice store, the system freezes. Crystallisation energy is released during the phase transition from 0 °C cold water to 0 °C cold ice. This contains as much energy as is required to heat water from 0°C to 80°C - and vice versa.
In the warm season, the ice store thaws again. The regeneration heat exchanger then supplies the cistern with heat from the solar air absorber (open, unglazed collectors). Once the water is liquid again, the cycle can be repeated as often as required.
Although electricity is required to operate the heat pumps, this is generated by the Ökosiedlung`s own photovoltaic systems, making the operation of the ice storage tank even more economical.
The exciting thing about the ice storage system is that the technology is visible to the users. The display window in the operations building of the Ökosiedlung makes the energy flow tangible for all residents.
Nick Elzenheimer, MOW
