The Geothermal Paradox of Choice: A Comparative Techno-Economic Assessment of Geothermal Energy Production for Heat and Power Applications

Geothermal energy is poised to play a pivotal role in the renewable energy transition by providing baseload, dispatchable, and carbon-free heat and power. Nonetheless, in contrast to its renewable energy alternatives, such as solar or wind, geothermal energy is harnessed beneath the Earths surface, inherently increasing the challenges, risks, uncertainties, and opportunities related to its exploration and utilization. As a result, numerous concepts and field development strategies for exploiting geothermal energy have been proposed over the last century. The seemingly overwhelming abundance of choices has prompted widespread confusion regarding the optimum approach to developing geothermal energy across multiple sectors. In this study, we attempt to answer this question by conducting a scenario analysis consisting of three geological reservoirs developed through various geothermal technologies to generate heat and electricity. Stochastic analyses for each of the geological reservoirs considered is also performed in a second set of simulations to account for subsurface uncertainties. Using a combination of advanced numerical simulators, we evaluate and compare the techno-economic performance of water-based geothermal systems (i.e., Conventional Hydrothermal Systems, Enhanced Geothermal Systems (EGS) and Advanced Geothermal Systems (AGS)) against their conceptual counterparts that use CO2 as the subsurface working fluid (i.e., CO2 Plume Geothermal (CPG), CO2-EGS, and CO2-AGS). Our results show that water-based energy extraction and open-loop configurations distinctly favor higher production temperatures owing to the superior thermodynamic properties of water and the ability to accommodate larger reservoir volumes, respectively. However, these operating conditions also exhibit lower heat-to-electricity conversion efficiencies, thereby significantly impacting economic returns when electricity generation is intended. In contrast, the value of CO2-based energy extraction and closed-loop configurations, to some extent overlooked in direct-heat-use applications, is considerably highlighted when targeting electricity production. Our work underscores the critical interplay between a geothermal reservoir's thermal and hydraulic performances across various system types. A comprehensive analysis of the relationships exposed in this study can assist geothermal operators in selecting appropriate end-user applications, predicting long-term reservoir performance, and ultimately enhancing the economic success of geothermal projects.