A general route to design solar thermoelectric generators under the constant heat flux thermal boundary†

Abstract

Solar thermoelectric generators (STEGs) convert solar heat into electricity, attracting interest in powering various Internet-of-Things devices. The conventional route to design a STEG involves separate considerations of thermal engineering and materials science by using a thermal boundary condition of constant heat flux. This paper provides a more direct and convenient way to design solar thermoelectric generators. First, we propose a general efficiency model and figure-of-merit (ZQ), which directly incorporates the thermal boundary conditions, heat exchange thermal resistances, device architecture dimensions, and material performances. ZQ reveals an equivalent effect between the heat flux and leg height in determining efficiency. We have shown that ZQ provides a concise guideline to boost the efficiency of heat-concentrated STEGs through engineering the insulation materials, covering materials, heat-concentrated coefficients, and thermoelectric material height, and the efficiency of light-concentrated STEGs by tuning the light-concentrated coefficient, catalyst dose, and aerogel height. As a result, an efficiency enhancement of over five times was achieved in the as-fabricated STEG system. The potential applications of the proposed efficiency model and ZQ in other scenarios with constant heat flux conditions were extensively discussed according to different thermal resistance parameters, including STEGs with different cooling modes, waste heat harvesting from industry operations, photovoltaic–thermoelectric combined systems, etc. Our work highlights the significant progress in bridging between thermal engineering and materials science, advancing the thermoelectric power generation technology.