Design and optimization of printed thermoelectric generators for integration into plate heat exchangers in district heating applications

Printed thermoelectric generators (TEGs) can be a promising solution for waste heat recovery. Due to large variations in heat source and heat sink geometries, heat transfer coefficients, and temperatures found for the different applications, a versatile manufacturing approach is needed for TEGs in this field. Shape-conformable TEGs can be manufactured using printing technologies offering a low-cost and scalable manufacturing method. This paper presents design optimization for printed TEGs that can be integrated with a water-to-water corrugated plate heat exchanger (PHE) to realize a micro-CHP system in district heating applications. We explicitly state the mass flow rates, temperatures, and heat flux boundary conditions for the PHE. Based on these conditions, we optimize the TEGs using a Python-implemented model in conjunction with COMSOL simulations. The fill factor is a degree of freedom in TEG design that allows to balance material consumption, mechanical properties, and power density. By compromising on a portion of low-grade heat transfer, the proposed micro-CHP (hybrid PHE-TEG) system produces high-grade electrical power densities of 355 W/m2 and 710 W/m$^2$ for TEG fill factors of F = 0.5 and F = 1.0, respectively. ... mehrHowever, the optimal TEG leg thickness for F = 0.5 is lower (190 μm) than for F = 1.0 (210 μm), and the former case exhibits more compromise on PHE performance than latter one. Lastly, the total system cost (in €), cost per watt (in €/W), and levelized cost of electricity (LCOE, in €-ct/kWh) are analyzed and reported for two system sizes—one with a 0.5 m$^2$ area and the other with a 1 m$^2$ area. A system size with 0.5 m$^2$ area showed higher cost of electricity of 11.2 €/W and 10 €-ct/kWh for F = 0.5, while for F = 1.0 they were 6.2 €/W and 6 €-ct/kWh. In comparison to 0.5 m$^2$, 1 m$^2$ system size showed lower cost of electricity of 8.1 €/W and 7 €-ct/kWh for F = 0.5, while for F = 1.0 cost values were 4.7 €/W and 4 €-ct/kWh.