Analytical Optimization of the Design of Film-Laminated Thermoelectric Power Generators

Abstract

Thermoelectric generators directly convert heat into electricity, typically made from bulk solid thermoelectric materials. They are a widely used technology in exhaust gas heat recovery from automotive vehicles or radioisotope power generation in space satellites. We propose a film-laminated device structure for lower cost and higher volume production. The film-laminated thermoelectric generator design includes a wide variety of thin-film materials and insulator polymer films. Despite the simple fabrication process, the challenges in the bypass heat leak across the insulator film would increase in a film-laminated device structure. The insulator films in the device exhibit low thermal conductivities but cannot be neglected compared to the thermoelectric materials. Comprehensive analysis is conducted on laminated film-based thermoelectric power generators. The study includes the impacts of the geometry design and thermal conductivity to the power output. The sensitivity of design parameters and material properties is investigated. Cost of the power ($/W) from the available heat is estimated. Both of the above are influenced by the effective heat transfer coefficient of the external thermal contacts. The normalized power as a function of the thermal conductivity ratio of the laminate to the thermoelectric materials is determined for a given ZT value. This relationship can be utilized to measure the impact of the laminating material for any material combination. The power output monotonical decreases as the thermal conductivity ratio gets closer to unity. It is highly desirable to use a one order of magnitude lower thermal conductivity for the insulator, especially for thin thermoelectric layer design.