Marcel Troxler

This project is the first to build, measure and optimise a recyclable asphalt collector for the regeneration of geothermal probes.

The background to this pilot and demonstration project is the increasingly dense use of geothermal probes, which leads to long-term cooling of the subsoil. Studies show that there is a considerable need for regeneration, particularly in urban areas. Asphalt collectors, which use heat from solar radiation on asphalt surfaces, are a potential cost-effective heat source for this regeneration. Initial pilot projects have shown that promising yields can be achieved with collector pipes embedded in asphalt. However, in these cases the asphalt was no longer recyclable. Based on simulations, it is assumed that it is also possible to lay the collector pipes in the underlying clean layer (separating layer between the subsoil and the asphalt surface) for the application of geothermal probe regeneration, thus maintaining the recyclability of the asphalt. This will be implemented and investigated in this P&D project.

Experience from various pilot and demonstration projects, as well as the assessment of experts, suggests that heating and cooling systems are often oversized. However, since there were no systematic studies on this topic in Switzerland, the Swiss Federal Office of Energy (SFOE) commissioned the SPF and the IET - Institute of Energy Technology with the OptiPower project. The team examined a total of 341 heating systems in the multi-family house sector and ten administrative buildings with regard to the heating and cooling power actually required based on the evaluation of measurement data and the installed power. It was found that in the multi-family housing sector there is a median oversizing of 44 % and in the administrative buildings the systems are oversized by a factor of 2-3. The project team further investigated how this oversizing affects the costs and efficiency of the heat pumps and formulated corresponding recommendations in the final report.

Within the EU project Hybrid-BioVGE an innovative system for heating and cooling is developed. The cooling device is based on a Variable Geometry Ejection (VGE) cooler. Driving energy is heat from solar collectors or from biomass. SPF is supporting the development of collectors that deliver heat at 75 – 90 °C, and is testing the heating and cooling system with the established Concise Cycle Test (CCT) method. This method is specifically adapted in order to be able to test also cooling systems.

The project is supported by the research programme H2020 of the European Union – grant agreement ID: 818012, acronym Hybrid-BioVGE