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DOE Selects BSST to Lead Thermoelectric Automobile Waste Heat Recovery Project

Earlier this year, the DOE selected BSST, a subsidiary of Amerigon, (earlier post) to lead the development of an efficient and practical thermoelectric system that will improve fuel economy by converting waste heat in automobile engine exhaust into electrical power.

BSST will lead a development team that includes Visteon Corporation, Teledyne Energy Systems, BMW of North America, UC Santa Cruz, Purdue, the DOE’s National Renewable Energy Laboratory (NREL) and JPL/CalTech.


Thermoelectric materials—materials that exploit a phenomenon in which the application of heat to combinations of certain metals induces an electric current—are emerging as potentially important systems for increasing fuel efficiency and decreasing emissions...and maybe even as a wildcard solution for propulsion in the future. (More detailed post here.)

Of the 100% energy available from engine combustion, only about 25% actually gets applied to moving the car or running the accessories. (Diesel engines and lean combustion gasoline engines fare somewhat better: 35% of the energy flows to mobility and accessories.) Successfully harnessing waste heat from vehicle exhaust would be equivalent to developing a vehicle with 50% or higher overall efficiency, according to the DOE.

The BSST-led program is to have four phases. The first phase encompasses a comprehensive analysis to determine the technical and commercial viability of the thermoelectric system concept. Upon successful completion of this first phase, DOE will authorize funds to allow the team to proceed with the second phase.

Federal funds will pay for 75% of the total cost of this program with selected project team members bearing the remaining cost. Up to $4.7 million in Federal funds could be contributed to the project over its four year life, depending upon the success of each phase.

A current TEG (thermoelectric generator) WHR (waste heat recovery) project led by Clarkson University, in conjunction with Hi-Z, has developed such a prototype unit fitted to a GM Sierra. Actual fuel savings are in the 2% range.

However, research by Caterpillar presented at a DOE Thermoelectrics workshop early this year projected that a thermoelectric waste heat generator used in place of the standard alternator could reduce fuel consumption by 13% while the powertrain delivered the same propulsion.


John Norris

25% efficiency seems very high to me. Amory Lovins in his 20 Hydrogen Myths paper[*] puts tank-to-wheels efficiency at 16% for a regular car and about 30% for a Prius. Refining efficiency is quoted at 88% giving a well-to-wheels efficiency for a regular car of 16% x 88% = 14%.

* Summary (half way down page)

-- John


I have seen some dyno data on the Prius engine: 40% efficient. Its high because the expansion ratio is greater than the compression stroke, and its just a well made engine. This also results in cooler exahust, making less available for the thermoelectric generator.

By the way, to calculate the efficiency of a thermoelectric generator:
eta = (1/7) *(Thot - Tcold) / Thot

The 1/7 factor will get higher if we ever find better materials.





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