Theoretical study on geothermal power generation using thermoelectric technology: a potential way to develop geothermal energy

Thermoelectric power generation is an outstanding technology for high- and low-temperature heat recovery. Their packaging, lack of moving parts, direct heat to electrical conversion, and zero-emission are the main benefits for geothermal power generation. The design of a large-scale, ground-based, and segmented annular concentric cylindrical thermoelectric generators (CCTEGs) with produced geothermal fluid are proposed. A mathematical model for thermoelectric power generation is presented, which considers the heat transfer in the interior of a thermoelectric module and the electric current effect, and is solved with Engineering Equation Solver (EES) software. Numerical results show that about 136 kW of power output could be obtained with 500 m length of segmented annular CCTEG under the inlet fluid temperature difference of 130 degrees C. For the same total flow rates and the same total CCTEG length, the in-series layout of segmented annular CCTEG is better than the in-parallel layout in power generation capacity. Flow rate and fluid temperature have a significant effect on the generated power. A higher flow rate ratio of cold fluid to hot fluid will result in higher power capacity. A desirable flow rate ratio of cold fluid to hot fluid is recommended to take as the flow area ratio of cold fluid flow conduit to hot fluid flow conduit when the critical potential increased power generation capacity is taken as 1.0 kW/kg.