Overall performance analysis of a stackable thermoelectric generator for medium-low temperature geothermal resources

To boost the realistic applicability of thermoelectric technology for harvesting geothermal energy, a stackable thermoelectric generator (STEG) is proposed, where twenty-four thermoelectric modules (TEMs) are arranged in four layers and are sandwiched between five mini-channel heat exchangers with tapered inlet /outlet. Furthermore, a one-way analytical model for the STEG is established and verified via experimental results. Meanwhile, the flow behavior and temperature field distribution within the STEG, as well as the influences of operating conditions on its output performance are analyzed comprehensively. The flow maldistribution intensity and flow resistance of the heat exchanger varies between 9.5% and 14.9%, and 1.1 ~ 16.5 kPa. The temperature field uniformity coefficient of the STEG reaches 99.4%. The power output of the STEG is proportional to the square of the heat source temperature. A linear relationship between the conversion efficiency and the heat source temperature is also observed. With higher mass flow rates, the net power output increases then decreases rapidly, and its maximum value occurs at a mass flow rate of 0.174 kg/s. Moreover, at temperature difference of 70°C, the proposed STEG generates a peak net power of 23.6 W with thermoelectric efficiency of 1.79%. Notably, the net power density reaches 35.2 kW/m 3 , which demonstrates its promising compactness and feasibility. Overall, this study provides valuable insights into the relationship between the structural design and overall performance of STEGs.