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Posted: Jun 06, 2013
Borehole thermal energy storage system integrated in solar heating network
(Nanowerk News) Via a heating network, the Stadtwerke Crailsheim municipal utility company has used the opportunity to provide the new Hirtenwiesen housing estate with solar thermal energy right from the beginning. This has resulted in Germany’s largest solar thermal collector array, which in combination with two buffer storage tanks and a borehole thermal energy storage (BTES) system meets half the local heating requirements. This BTES system provides seasonal heat storage to meet requirements in winter.
The latest BINE-Projektinfo brochure “Storing solar energy in the ground” (01/2013) presents the initial findings of the research project, with a particular focus on the storage system.
The new housing estate is being built on the site of a former army barracks. Five existing buildings have been refurbished and new individual homes and apartment buildings built across an additional 32 hectares along with a school and sports hall. One third of the 7,400-m² collector surface area has been installed on the roofs and two thirds on a noise protection barrier. The solar collectors feed their heat into both a small buffer storage tank and a large one. The latter is connected to the borehole thermal energy storage system, whose size corresponds to a water equivalent of 10,000 m2.
The combination with a buffer storage tank enables the solar charging of the BTES system to be time-lagged. This has enabled it to be smaller in design, which has contributed to the comparatively low investment costs of 50 euros/m³ of water. It was also the first time that borehole heat exchangers were used with different lengths and with pre-installed horizontal pipe connections.
The BTES system can be expanded as required when the housing estate grows in size, and also acts as a multifunctional storage system for absorbing waste heat from combined heat and power plants. With a solar savings fraction of 51% in the period from March 2012 to February 2013, the solar heating network slightly exceeded the planning goal.