DAS LEUZE is located in Stuttgart East. The baths, which are operated all year round, offer a total of nine indoor and outdoor pools with almost 1,800 m² of water surface. So far, the pools, showers and heating have been supplied by CHP units and gas boilers as well as two heat pumps (a third is currently shut down).
The mineral spring itself is available for the regenerative supply of the LEUZE: From two wells, approx. 60-70l/s of mineral water bubble up there with a constant temperature of 20°C all year round. This water is used directly as pool water in a cold indoor pool and a cold outdoor pool without pre-treatment using the flow-through principle. For two indoor pools, part of the mineral water is filtered and further heated so that bathers can enjoy 34°C sparkling water there. After bathing and heat recovery, this mineral water portion already serves as a source for the existing heat pumps. However, the potential has not been fully exploited.
A site analysis identified these and other possible regenerative sources (solar thermal, PV or PVT as well as a central sewer).
Since the building is also to be generally renovated, low-temperature radiators can be installed and the energy sources can therefore be used in a COP-optimal way.
As part of the feasibility study, we first analysed and prepared the current status with existing plant technology for electricity and heat generation as well as the energy demand. In the site check, we identified potential areas for regenerative energy supply and, based on this, quantitatively compared various renewable energy sources with regard to their suitability at the site. The thermal use of mineral water via a heat pump was identified as a particularly productive source with very good efficiency.
In addition to the very efficient heat pump operation, the use of mineral water has the advantage that the Neckar water is cooled and not heated for most of the year, as was previously the case.
The annual CO2 emissions can be significantly reduced again by fully utilising the available area for PV, PVT or solar thermal.
Using simulations, we determined the heat demand shares for showers (high temperature) and swimming pool water (low temperature) and compared them with the real demand values. Possible solar coverage shares in the heat supply were calculated for different collector types.
We finally compared the different energy concepts to calculate the economic efficiency and made a recommendation. It turns out that a combination of mineral water use, PVT and PV performs best in terms of economic efficiency, while a pure PVT system in combination with mineral water use achieves the best values in the CO2 balance.