Coaxial geothermal wellbore thermoelectric power generation system: design, experimentation, and performance analysis

Abstract

Thermoelectric generators have demonstrated significant potential for geothermal power generation, with extensive research validating their technical and economic feasibility. While prior studies have primarily focused on surface-based thermoelectric generator systems, downhole thermoelectric power generation remains largely unexplored, with research limited to numerical simulations. To address this gap, this study proposes a novel experimental apparatus for power generation in a coaxial geothermal wellbore. A 1-meter-long wellbore thermoelectric generation system was designed and developed to analyze the influence of temperature differentials and flow rates on power generation efficiency. Experiments were conducted using controlled hot and cold water injection to simulate geothermal wellbore conditions. Results indicate that under a temperature difference of 70 °C, with a cold flow rate of 288 L/h and a hot flow rate of 648 L/h, the system achieves a maximum power output of 26.7 W. The power output exhibits an exponential increase with temperature difference, while optimizing both hot and cold flow rates further enhances energy conversion efficiency. To extend the analysis to field-scale applications, a coaxial closed-loop geothermal wellbore model was established. Numerical simulations predict that a 1000-meter-long wellbore thermoelectric generation system operating at a temperature difference of 200 °C can generate 534.6 kW of power with a conversion efficiency of 8.5 %. These findings provide critical insights into the thermal transport mechanisms and performance optimization of downhole thermoelectric power generation, bridging the gap between theoretical analysis and practical application. This research lays the foundation for future large-scale deployment of thermoelectric generators in geothermal energy utilization.