In order to address the central issues of efficiency and practicality of tunnel collector systems and the suitability of applied planning instruments, a pilot project for horizontal loop collectors is scheduled. The energy modelling on which this testing is based is verified by means of measurement results. During the test set-up, the real extraction performance values are measured and the ambient conditions are monitored using measuring instruments. In addition to the influence of geothermal factors on thermal output (e.g. thermal resistance of the backfill material and collector tubes, insulation effect due to sealing), practical construction details (e.g. fastening the collector tubes to the sealing layer) are also to be investigated.
According to the testing itinerary, three test areas should be set up at least 4 m away from each other under identical geological conditions, and put under observation for a period of one year. In test areas 1 and 2, a double-lining tunnel with sealant is created; in the first scenario, the collector tubes are placed in front of the sealant, and in the second are placed behind, in order to produce an insulating effect. Test areas 1 and 2 correspond to the conditions of a new tunnel construction and are suitable for various applications (heating / cooling). Based on the data collected for test areas 1 and 2, test area 3 is adapted in such a way that it corresponds to a scenario involving tunnels which have been retrofitted.
Using the measurement results, the simulation system will be calibrated and the relevant parameters and values (e.g. resistance coefficient of the collector) are defined so that a solid basis for planning is available in the future. In addition, information on construction practicalities and on operational integration of the tunnel collector systems is provided.