Examination of Waste Heat Utilisation from a Water Treatment Plant to Supply a District with Renewable Heating and Cooling

Following the energy transition in Germany, the Green Deal in Europe and the decommissioning of centralised high-capacity fossil energy generation plants, many different renewable energy sources available with all year round availability will need to be integrated in the future. Low-temperature heat sources, such as waste heat or geothermal, are important elements in connection with the integration of renewable energies into existing or new heat supply solutions. In Aue-Bad Schlema (Germany), a future district concept will be presented that uses waste heat from a water treatment plant (cleaning mine water) for heating and cooling. The potential district nearby will have a heat demand of about 19 GWh per year (23 GWh/a final energy demand), including network losses. Depending on mass flow and temperature spread in the heat exchanger, the heat source is able to provide between 15 and 22 GWh of heat annually, To integrate the heat source into the district, two heating networks were considered, one connecting all major consumers and one connecting all consumers. It has been shown that both variants can save up to 90% of greenhouse gases by 2045, with an expected heat demand of 14.26 GWh/a (large network) and 10.71 GWh/a (small network). In addition, costs of up to 15.6 million € are calculated.