Optimizing printed thermoelectric generators with geometry and processibility limitations

Abstract

Fully printed thermoelectric generators (TEGs) are a promising solution for large scale energy harvesting and waste heat recovery in a broad range of applications. Due to large variations in heat transfer coefficients and temperatures, it is necessary to include these properties of the specific heat source in the design process of the TEGs. Oftentimes, this leads to additional, geometric requirements for the devices. The limited layer thickness of the printing process imposes further limitations on the device geometry. Here, we present an analytical method to design and optimize fully printed TEGs manufactured by a screen-printing technique and considering its geometric design limitations. The design process includes choosing between a planarly printed device architecture and a folded device architecture. Furthermore, the limited device thickness and the presence of a filler material in printed TEGs result in device designs optimized for output power, which vary from conventional thermal impedance matching. The fill factor is hereby an important degree of freedom for the optimization. Furthermore, we demonstrate, that two materials with the same figure of merit zT will yield different output powers for the same device, if their thermal conductivities differ. This implies that considering the geometric limitations of the intended application already in the development of the printable thermoelectric materials can yield a larger power output for the device.