Siting enhanced geothermal systems (EGS): Heat benefits versus induced seismicity risks from an investor and societal perspective

Enhanced geothermal systems (EGS) harness thermal energy from the deep underground to produce renewable and low-carbon electricity and heat. Siting EGS in rural versus urban areas involves trading off benefits of sold heat and avoided CO2 emissions and induced seismicity (IS) risk. In remote areas, IS risk is minimal, but EGS heat cannot be purposefully used for residential district heating. In urban areas, the heat can be sold, but EGS poses higher IS risk. We quantify this trade-off using cost-benefit analysis (CBA) from both private and social perspectives. We model 12 hypothetical EGS scenarios, with EGS of differing size (water circulation rate of 50-150 l/s) and siting (0-100′000 residents nearby). We bound uncertainties using Monte Carlo and sensitivity analyses. Assuming a price of electricity that would make EGS investment in half of our scenarios worthwhile to investors, we show that large EGS (150 l/s) near a large population (10′000 or 100′000 residents), enabling high heat sales, are most profitable. The CBA from the social perspective shows that medium- or large-sized EGS (100 or 150 l/s) near some residents (1′000 or 10′000) are most beneficial, based on reasonable heat sales while limiting potential IS damage. Siting EGS in remote areas is less favorable, even if expected IS damage is zero.