Increasing the share of renewable energies is one of the cornerstones of the Swiss Energy Strategy 2050. Geothermal energy is among other renewables a promising resource for electricity and heat production. It makes use of the enormous heat captured deep underground. For this purpose, cold water is injected at high pressure into the rock, where it heats up before it is pumped back to the surface. In Switzerland, the temperature rises by approximately 30 C° for every kilometre below the surface towards the centre of the Earth. To benefit from this resource for electricity production, rock structures at temperatures of at least 180 to 200 C° at depths of 4 to 5 kilometres have to be accessed.
In the “Bedretto Underground Laboratory for Geoenergies”, ETH Zurich studies, in close collaboration with national and international partners, techniques and procedures for a safe, efficient, and sustainable use of geothermal heat. To this end, a sufficiently permeable reservoir is necessary which is accessible on a long-term basis. Researchers will conduct different experiments focusing on the geothermal processes involved. They will drill several boreholes, allowing them to place a variety of sensors to track even the smallest changes in stress, pressure, and fluid movements. Only in a rock laboratory, such close monitoring is possible and affordable.
The Bedretto tunnel, connecting the Ticino with the Furka tunnel, offers ideal conditions to perform such experiments. It allows to pursue the research conducted in laboratories at universities and in other rock laboratories, e.g. at Grimsel, on a bigger scale. This is an important advancement to prove previous concepts in a setting reflecting as close as possible the conditions in the deep underground. The coverage of 1,000 to 1,500 meters above the tunnel simulates well the pressure conditions at relevant depths for a geothermal reservoir.
In order to operate such a rock laboratory, the tunnel has undergone extensive construction work: the floor was levelled out, unstable rocks secured, a ventilation system, a communication network, and electricity were installed. The owner Matterhorn-Gotthard-Bahn has currently leased the tunnel to ETH Zurich for eight years.