Novel thermoelectric generator for stationary power waste heat recovery

Abstract

Internal combustion engines produce much excess heat that is vented to the atmosphere through the exhaust fluid. Use of solid-state thermoelectric (TE) energy conversion technology is a promising technique to recapture some of the energy lost. The TE effect, discovered in 1821 by Thomas Seebeck, is essentially the solid-state conversion of a temperature gradient into an electric potential. The scope of this work was the design, testing and evaluation of a novel and robust TE generator that is amendable to use in a vast array of convective thermal processes. Seebeck testing of TE elements was combined with thermal/hydraulic and thermoelectric modeling to develop the design of a working prototype system. A proof-of-concept small-scale prototype (SSP) TE generator was built to evaluate concepts intended for the construction of a fully-functional field demonstration prototype (FDP). The SSP was used to evaluate electrical contact integrity, thermal characteristics, various TE materials and the feasibility of using compression-based TE contacts. The SSP featured 9 P/N TE pairs and has thus far produced a maximum open-circuit voltage of 380mV and a maximum electrical power of 1.47W. Knowledge gained from the SSP construction and testing was utilized in the design and fabrication of the FDP. A liquid-cooled Honda ES6500 6.0kW genset was procured to provide a test-bed for the FDP. The primary goal was to power the electric radiator fan with the heat energy contained in its exhaust, thus decreasing the genset's fuel consumption rate. The FDP contained 256 P/N pairs and thus far has produced an open-circuit voltage of 5.5VDC and a maximum power of 8.49W. Replacing the stock muffler reduced fuel consumption by 11.6% whereas removing the fan load reduced it an additional 1.64%. Through the recovery and conversion of wasted thermal energy, the genset's fuel consumption rate was successfully lowered, therefore validating the benefits of secondary TE power systems. The radiator fan of the Honda ES6500 consumes approximately 1% of the overall power output of the genset. Radiator fans in larger gensets can draw as much as 12-16% of their peak output. By recuperating waste heat, substantially higher fuel savings could be achieved.