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Local solar heating for new and existing buildings

The advantages in installing a local solar heating system in a new housing estate are clearly evident: the return temperatures in the network are not too high and it is possible to influence the heat distribution systems, such as by using surface heating. These benefits were also utilised in the Hirtenwiesen solar project in the Swabian town of Crailsheim, which is funded by the German Federal Ministry for the Environment. There a new, 150-hectare residential area is being developed.

5,800 of the planned 7,500 square metres of collector surface area have been installed to date. These collectors supply thermal energy for domestic and heating water. The remaining heating requirements are met by the heating plant belonging to the Crailsheim municipal utility company. The geology at the site favoured the use of a seasonal borehole heat exchanger storage system. In addition, two short-term storage systems were installed – a 100-m² tower and a 480-m³ wall storage tank as a buffer storage system. Those involved in the project are also endeavouring to achieve a solar fraction of 50% in Crailsheim. Despite all the advantages that new-build housing estates offer for the use of solar energy, there are also critical aspects that need to be taken into account. For example, the energy requirements are increasingly sinking in new-build schemes, whereby the trend is towards minimum energy buildings. How this will affect the economic viability of such systems in the long term awaits to be seen. Because of transmission losses, heating networks laid underground are only recommendable for high connection and building densities. The storage losses from large-scale, seasonal heat storage systems that are not integrated into buildings must also be investigated more closely in future research work.

The construction of local solar heating systems for the existing building stock is a further important cornerstone in increasing the use of solar energy, whereby the local solar heating concepts must be adapted to the special requirements of the existing building stock and technical components developed. There have already been successful research projects in this area (see BINE-Projektinfo 14/09 “School refurbishment combined with local solar heating”), and there will be further ones in future.

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ZAE Bayern - Würzburg

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Solites

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Stadtwerke München GmbH