This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 691624
In 1996, the Eon Hanse Wärme GmbH built up a local heating network supported by a solar system. With the knowledge gained in this period, Eon decided to reconstruct the storage tank by putting a new steel storage in the old concrete foundation.
It is 14 years ago, the Eon Hanse Wärme GmbH in Hamburg-Bramfeld built up a local heating network supported by a solar system, for a new housing estate. Eon wanted to store the sun's heat for the winter and therefore they buried a several thousand cubic meter concrete storage tank in the ground. Packed with 20 cm insulating material on the side and with 30 cm on the top. The bottom remained non-insulated due to there was no insulation material which could withstand the weight of the concrete tank and the basic concept was, to store the heat in the upper part of the storage tank, while below the cold water flow back out of the houses. Almost half of the heat in the network should be delivered from the sun.
Rarely everything works perfect in first implementations. Soon they realized that the solar cover was only about half as high as expected and that the thermal losses were four times as large as expected. By now they ascertained the problems and it is time to reconstruct the storage tank.
One problem is the groundwater level in Bramfeld. The level strongly varies and also has increased over the years so that today the heat storage tank sits with its uninsulated bottom in the cold groundwater. And there on the bottom side this storage tank is not cold, because the water comes back out of the houses with a temperature of 45-55 ° C and not with 35 ° C as planned. A damage in the roof cover lead to a wet upper insulation. The planners knew about this problem - but not that the negative effect would be so strong.
In January of this year, Eon has begun to rebuild the store under the new findings. Eon wants to put a new steel storage in the old concrete storage that juts up on this. Therefore, the lower part of the store is raised with the concrete rubble from the ceiling and the axes of the concrete tank so that the new memory is above the groundwater level. In October, the new store is planed to go into operation. For using the storage capacity also in winter, Eon will store heat from a waste incineration plant in it. During peak times, the heat can be retrieved for making the fossil fired peak load boiler unnecessary.
For the summer Eon has a new plan: The Company offers private solar collector operators to use the network and storage for a fee of several cents per kWh provide. Feeding in the rest of your solar heat at any point into the network and taking the same amount later up to eight months at the same or another position on the net is possible.
News about the construction process:
Source: German learned journal: Sonne Wind & Wärme 9/2010
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