Thermoelectric generators for harvesting medium-temperature geothermal anomalies: printed vs bulk devices

Recently, thermoelectric generators (TEGs) have gained significant attention for directly converting geothermal energy into electricity. Due to the considerable variations in heat-source and sink geometries and boundary conditions, the design of TEGs should offer flexibility to fulfill the specific constraints. Printing technologies, such as screen printing or 3D printing, offer versatile, cost-effective manufacturing approaches for TEGs, enabling scalability and shape conformability. In this work, we present a comparative performance optimization of both printed TEGs and bulk-material-based TEGs for medium-temperature geothermal anomalies at T ∼ 170 °C. The proposed system for geothermal energy harvesting consists of a two-phase thermosyphon serving as the hot-side heat exchanger, TEGs, and an efficient heat sink based on heat pipes. We investigate the performance of both types of TEGs attached to the exterior of the thermosyphon for three heights (h = 100, 200, and 500 mm). For both bulk and printed TEGs, thermal and electrical impedance optimizations are achieved by adjusting the TEG fill factor, leg dimensions, and the cross-sectional areas of the n-type and p-type legs. Under the given boundary conditions, the higher power density at lower cost occurs at a TEG height of 100 mm for both bulk and printed-TEG devices. And in all three cases, at a higher fill factor ( F ∼ 0.9), printed TEGs showed comparable power densities to bulk TEGs at lower cost. As F decreases, the printed TEGs' power densities drop more rapidly than those of their bulk counterparts. Despite lower performance at lower fill factors, printed TEGs remain promising, with lower cost per watt (€/W) thanks to lower TE material consumption and lower manufacturing cost. Lastly, the projection of the levelized cost of electricity LCOE (€/kWh) and the economic analysis for both approaches conclude our work.