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Ackermannbogen - Munich - Olympia grounds

Within the context of a pre-planning study, a concept for a solar-powered local heating system with a seasonal heat storage facility has been developed for the Bavarian capital of Munich. The area to be supplied is a part of the new housing estate planned for "am Ackermannbogen" near to the Olympia Park.

Mainly multi-storey residential buildings have been planned for the selected utility area with a gross area of 26,600 m²; these are to be built as low energy designs. The total heat requirement for heating, the domestic hot water supply and distribution losses in the 2 conductor local heating network has been calculated at just under 2,000 MWh/a.

The solar-powered local heating system has been designed to enable 50% of this amount of heat to be covered by solar power accumulated by thermal collectors. The collectors installed on the roofs of the buildings make up a total area of approx. 2,700 m²; in the summer these charge the seasonal storage facility and then supply the buildings with solar heat right into the interseasonal periods.

For the necessary back-up system, the local conditions require an efficient way of combining solar power and district heating. In the planned concept, district heating will be used to power an absorption heat pump. The heat pump is in constant operation from November to the middle of March pumping low temperature heat from the central area of the large-scale storage tank for use up to a temperature level of 60 °C to 70 °C; this means that the storage tank is able to store usable heat throughout the year and that a buffer is available to cover peak output periods.

At the same time, the lower section of the storage tank is cooled to approx. 15 °C. Due to the heat storage and heat pumps, the system is equipped with a secondary heating system that only requires one third of the full connected load. The district heating connection achieves a full-load hour count of only around 2,500 /a.

At the same time, low flow temperatures are available for the collector area in winter from the lower section of the seasonal storage tank, thus maximising the solar yield. Compared to completely supplying the building with district heating, approx. 160 t less of CO2 is emitted, which corresponds to a reduction of around 42%.

In cooperation with the ITW Stuttgart, alternative storage concepts were evaluated in order to make further improvements, particularly in terms of construction costs. An underground storage system resulted with a capacity of nearly 6 million litres. Specially modified ratiotherm layer inserts were installed for the unique charging and discharging free of turbulence.

The local solar heating system operated by Stadtwerken München GmbH has been designated funding within the framework of the Federal government's solar heat 2000 programme.

Department 4 of the Bavarian Center for Applied Energy Research (ZAE Bayern) will be taking over the academic/scientific side of the project - also in cooperation with the ITW Stuttgart.

In this respect, a measuring campaign lasting several years is also planned.