Developing a modular thermoelectric generator for large-scale direct geothermal power generation from hot dry rock combined with a super-long heat pipe

Thermoelectric technology presents potential solutions and future prospects for geothermal power generation. A modular thermoelectric generator (TEG) is therefore introduced to generate electric power from hot dry rock (HDR). The TEG is connected to the condensation section of a super long gravity heat pipe with the length exceeding 3000 meters, enabling unpowered heat extraction from an HDR reservoir. Field test was conducted to assess the comprehensive performance of the TEG under varying operating conditions at the Gonghe geothermal field, China. The TEG achieved a peak output power of 1253.2 W with the thermoelectric conversion efficiency of 2.2% at the temperature difference of 80.0 °C. Although low ZT value of the thermoelectric materials leads to unsatisfied energy conversion efficiency, whereas it has been achieved nearly 90% of the theoretical maximum conversion efficiency (2.4%). Field tests validated the feasibility of an innovative way of direct power generation from hot dry rock. On top of that, modulization of the thermoelectric generator and inspiring advances of thermoelectric materials provide a potential solution for future thermoelectric conversion from low and medium heat resource inclusive of geothermal energy and waste heat, etc.