An innovative gem of the All Electric Society Park is the ice storage tank. But unlike the numerous other innovations, this centerpiece of the cold local heating network is invisible …
We are standing in front of a large flowerpot on a solid stainless steel plate. Hidden underneath is a two and a half meter deep, concrete cavity with 100,000 liters of water.
The ice storage tank is a long-term energy storage system. During the heating period, heat pumps extract energy from the ice store until it is largely frozen. Expert Florian Burgdorf explains how it works: “There is normal water in the ice storage tank. When the water freezes, crystallization energy is released in the form of heat. When water is turned into ice, 80 units of energy are slumbering from 0 °C liquid to 0 °C solid. This means that this amount of energy could be used to heat the same amount of water from 0 °C to 80 °C. The ice storage tank uses this phase change. This makes it a source for the heat pumps to which it is connected.
The heat pumps are able to work with minimal temperature differences and use this energy, boosted by the use of electrical energy, to bring the surface heating systems in the buildings to a flow temperature of around 35 °C. The comparatively low temperatures not only give the cold local heating network its name. They are also sufficient to heat all the buildings.
In summer, the ice in the storage tank is used for natural cooling. 35 percent of the total cooling requirement is provided in this way. Only the additional cooling requirement for active cooling is generated with the heat pumps.”
Energy is shifted
Our excursion takes us to the basement next to the ice store. “The park is supplied with thermal energy exclusively via two heat pumps and the ice storage tank. We use the pipe system to tap heat where it is generated, for example in the cubes in summer or when charging the electric vehicles. The highlight: if we get surplus energy from the PV panels, for example, we can use this energy to cool the ice storage tank via the heat pumps. In other words, we push electrical energy into a thermal storage unit.”
So heat is available in abundance? “Exactly. We have various heat sources. In summer, the buildings heat up. We use this heat as an energy source and store it in the ice store, regenerating the store. This creates a 100,000 liter hot water bottle over the summer. We can use the waste heat from the neighboring production halls to supply the storage tank with additional energy. In winter, the heat is extracted from the ice store again and the process starts all over again.”
Facts
- 50 percent of total final energy consumption in Germany is generated by heating or cooling
- 100,000 liters of water store heat in summer and cold in winter and release it again via heat pumps
- 126 liters of water release the energy of 1 liter of heating oil when freezing
