The Winzer project investigates the opportunities and challenges of implementing ATES systems in old groundwater-filled coal mines. For this purpose, a near-surface (<80 m) small coal mine in Bochum, Germany at the Fraunhofer IEG is used as the pilot site. The mine was tapped by three boreholes through which the groundwater is lifted and reinjected. The implementation of geothermal reuse in the old mine building in combination with a concentrated solar power system (CSP) is unique in the world. This allows seasonal storage of fluids with temperatures up to 60°C. In addition, a comprehensive condition monitoring was implemented. The measurement data and findings obtained will be used to make qualitative and quantitative statements on the hydrochemical, microbiological, geo-mechanical and ecological conditions during cyclic operations. The newly developed concepts and technologies will enhance the efficiency of the existing ATES system with regard to scalings and biofoulings at the heat exchangers as well as the safety, i.e. with regard to the mobilization potential of contaminants. Within the project the upscaling from the pilot site at the IEG through the planned development of the site of the former Dannenbaum mine is evaluated. There the hydraulic and geomechanical properties and changes in the ATES system can also be examined during the seasonal heat storage. By including numerical simulations, an optimization of the operation management concepts for the overall system is achieved and potentials for transferability to many other cities and networks in former coal mining regions in Europe will be shown.