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© Stadt München
Final workshop: "Solar local heating at Am Ackermannbogen"

A local heating system for three worlds

Too many cooks delay the broth. The fact that it does not have to be spoilt was shown by a workshop on the pilot project “Solar local heating at Am Ackermannbogen in Munich”. The City Department for Health and the Environment had sent out invitations to the event held in the regional capital. Around 50 delegates accepted the invitation and listened to the lectures given by the three main players: the Bavarian Centre for Applied Energy Research (ZAE Bayern), the Munich Municipal Utility Company (SWM) and the City of Munich. During the event on Monday, the city was therefore able to take stock of the roughly ten-year preparation, planning, construction and research process.

The aim of the project was to supply a new housing estate throughout the year with solar energy for space and domestic water heating, and thus achieve a 50% solar fraction. Part of the new “Am Ackermannbogen” urban district was selected for this purpose. As a result of a realisation competition, a total of 320 residential units have been created that are supplied with the newly developed solar local heating system. Key elements include a seasonal long-term heat storage tank and low return temperatures.

At the beginning of the event, representatives from both the city and Project Management Organisation Jülich once again emphasised the pilot and research nature of the project. Many of the problems that occurred can be explained through the fact that they were breaking new ground in both technical and organisational terms. The knowledge gained is therefore a clear benefit of the construction project, whereby all are in agreement that the 30 °C return temperature reached in the system is, as one SWM staff member put it, “sensational”. The experience garnered here shall now be incorporated in further projects organised by Munich’s municipal utility company. The low temperatures increase the heat storage capacity of the long-term heat storage tank used at Am Ackermannbogen, which in turn helps to increase the efficiency of the system. How this is technically possible was explained by Dr. Jens Kuckelhorn from ZAE Bayern. This value was achieved among other means by not decoupling the local heating and house networks. That means that the heat transfer fluid from the local heating network flows directly through the heating systems in the individual homes. This enables heat and transfer losses to be minimised. The heat is only transferred to the domestic heating systems in transfer stations directly in the homes. This is also where the domestic water is directly heated with freshwater stations.

The ambitious goal of the research project was to meet half of the energy requirements for space and domestic water heating with solar thermal energy. The key component that can make this value at all possible is a seasonal, long-term heat storage tank. In Munich, the project participants also opted to use such a hot water storage tank for economic reasons. Its combined used with an absorption heat pump ensures that the temperature range in the 6000 m³ heat bunker is maximised. This enables its storage capacity to be optimised and low collector inlet temperatures to be achieved.

The system currently achieves a solar fraction of 45%. “With some reworking and optimisation of the control program, a solar fraction of 50% is certainly realistic,” says Manfred Reuß from ZAE Bayern, looking optimistically to the future.

BINE-Projektinfo brochure in the making

In April this year, a BINE-Projektinfo brochure is being published on “Solar local heating at Am Ackermannbogen in Munich”. Both the concept and the latest results of the accompanying research will be presented here. Readers who would like to be notified when the publication comes out, can register for a free BINE subscription.


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