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Switzerland benefits from strong social and political support for energy transition policies aimed at eliminating around 12 million tons of CO2 per year to achieve carbon neutrality by 2050. Geothermal energy is widely regarded by society and by both federal and cantonal authorities as a key contributor to this objective. While Switzerland is a global leader in the deployment of borehole heat pumps, significantly reducing fossil fuel use for heating in domestic, industrial, and agricultural sectors, efforts to exploit high-temperature rocks and fluids in the deep subsurface over the past three decades have delivered mixed results.
Outcomes from numerous deep wells drilled since 1988, including Reinach, St Moritz, Bulle, Weissbad, Thônex, Saillon, Yverdon, Basel, Triemli, St. Gallen, GEo-01, GEo-02, and more recent projects such as Lavey-les-Bains, Venzel/La Côte, and Yverdon II, show that deep geothermal potential has not yet been exploited as initially expected. Nevertheless, successes such as GEo-01 in the Geneva Basin and the repurposing of wells at Triemli, Weissbad, and Thônex demonstrate that geothermal resources exist and that giving initially disappointing wells a productive second life is a viable strategy.
This paper reviews four decades of deep geothermal projects in Switzerland and distills the main lessons learnt. Two key insights emerge: first, a viable geothermal industry requires a mature geo-energy exploration mindset supported by substantial upfront investment; second, the Swiss subsurface remains insufficiently understood, particularly regarding the controls on porosity and permeability at basin and reservoir scales. Addressing these gaps demands a co-ordinated regional exploration strategy rather than isolated, one-shot projects.