Mine water geothermal energy a source of energy for heating, cooling and storage – From status quo to challenges and monitoring of existing systems
Due to the Paris Agreement on climate change, it is essential to make the transition to renewable energies in the heating sector in order to achieve the climate targets. Abandoned mines can provide an opportunity for renewable energy supply. Based on the almost constant temperature level throughout the year and the large rock surfaces as a heat-transferring area, mine water is suited perfectly for heating, cooling and storage of energy with heat pump application. In Germany, mine water geothermal plants have been built and put into operation in the last decades. Nowadays more plants are also being projected and implemented for example in the Ruhr area (hard coal field in west Germany). Furthermore, specific System locations, such as the "Reiche Zeche" in Freiberg and the "Schillerschule" in Aue-Bad Schlema, will be shown to illustrate technical requirements, designs and general conditions. The correlation between the seasonal performance factor (SPF) and the temperature difference between mine water and the consumer temperature is a crucial factor—especially in relation to the integration of the system into an existing or new heating concept. Monitoring data from existing facilities shows that the combined supply of heating and cooling can result in high overall system efficiency, with total SPF values exceeding 7. In the case of a plant in Aue-Bad Schlema, various measurements were taken due to a noticeable decline in performance. The data from 2014 to 2019 indicate an average SPF of 2.2. However, due to several influencing factors, the system is capable of reaching a SPF of up to 2.8 without major modifications. With further optimizations, performance improvements up to a SPF of 3.5 or higher are possible, making the system more cost-effective and sustainable. The monitoring parameters required for future systems and systems undergoing inspection are identified based on the findings. The required and recommended measurement data are central to evaluating functionality, analysing operational safety, and determining seasonal performance factor (SPF). Specific conclusions about system operation and possible environmental impacts for both heating applications and storage systems (MTES) can be drawn based on this data. These conclusions are the result of years of analysis