Preferably safe and small: Findings from a risk-cost-benefit analysis on enhanced geothermal systems in Switzerland and Utah

Enhanced Geothermal Systems (EGS) are promising for low-carbon energy generation, but finding suitable EGS sites is challenging due to the technical complexity, induced seismicity risk, and controversial public perception. This paper presents a novel methodology of Risk-Cost-Benefit Analysis (RCBA) that integrates scientific-factual and socio-ethical judgments into the evaluation of various EGS locations and sizes in Switzerland and Utah. Concretely, the RCBA combines a techno-economic-environmental model of EGS with the value-based and informed preferences of risks, costs and benefits elicited in two representative population surveys. A Monte Carlo uncertainty analysis is also performed. The findings from the integrated RCBA underscore a strong preference for small to medium-sized EGS plants (25–75 l/s) in rural areas (1′000–10′000 inhabitants within 5 km radius) in both states. Based on the holistic judgement of the population, the findings show a greater willingness to accept larger EGS plants (above 100 l/s) if they remain in sparsely populated areas (<1′000 inhabitants within 5 km radius). Strong value-laden emphasis given by the population to risk factors, such as induced seismicity, partially offsets the perceived benefits of renewable energy and CO_2eq emissions reductions. By simultaneously considering the scientific-factual and socio-ethical perspectives, RCBA demonstrates its utility over techno-economic evaluation tools by offering policymakers and project developers a more nuanced view on the potential of EGS.