Analysis of the effect of module thickness reduction on thermoelectric generator output

Conventional thermoelectric generators (TEGs) used in applications such as exhaust heat recovery are typically limited in terms of power density due to their low efficiency. Additionally, they are generally costly due to the bulk use of rare-earth elements such as tellurium. If less material could be used for the same output, then the power density and the overall cost per kilowatt (kW) of electricity produced could drop significantly, making TEGs a more attractive solution for energy harvesting of waste heat. The present work assesses the effect of reducing the amount of thermoelectric (TE) material used (namely by reducing the module thickness) on the electrical output of conventional bismuth telluride TEGs. Commercial simulation packages (ANSYS CFX and thermal-electric) and bespoke models were used to simulate the TEGs at various degrees of detail. Effects such as variation of the thermal and electrical contact resistance and the component thickness and the effect of using an element supporting matrix (e.g., eggcrate) instead of having air conduction in void areas have been assessed. It was found that indeed it is possible to reduce the use of bulk TE material while retaining power output levels equivalent to thicker modules. However, effects such as thermal contact resistance were found to become increasingly important as the active TE material thickness was decreased.The authors acknowledge Project ThinHarvest (FCOMP-01-0124-FEDER-041343/EXPL/EMS-ENE/1023/2013) and Postdoctoral Grant SFRH/BPD/89553/2012, financed by FEDER Funds through Programa Operacional Fatores de Competitividade-COMPETE and National Funds through PIDDAC and FCT-Fundacao para a Ciencia e a Tecnologia; Luso-American Foundation/National Science Foundation (FLAD/NSF) 2013 PORTUGAL-U.S. Research Networks Program, Project "Waste Exhaust Energy Recovery of Internal Combustion Engines"; and Hi-Z Technology, Inc., for the information supplied regarding their modules' properties and performance.