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Thermoelectric Recovery of Exhaust Waste Energy, 03-9322

Principal Investigator
Gustavo J. Ray

Inclusive Dates: 06/10/02 - Current

Background - Although thermoelectric generators (TEGs) have existed for many years, material limitations made widespread use of this technology too costly and inefficient for many applications. TEG modules consist of semiconductor N- and P-type junctions that generate an electric current when opposing sides are kept at a temperature differential. The Seebeck effect demonstrated by these modules has been harnessed for various applications. Deep space probes use these TEGs along with the heat from a radioactive rod to generate electricity for onboard electronics. Gas pipelines use TEG units coupled with gas burners to provide electricity for diagnostic and control electronics. These systems have proven to be effective and reliable, yet their applications have been limited. Applying TEGs to automotive waste heat energy recovery can broaden the scope of this technology and improve overall vehicle efficiency. See the top illustration.

Approach - The automotive industry is venturing into many new areas of energy consumption and recovery, especially with the development of hybrid-electric vehicles (HEVs). TEG technology has the potential to boost the system efficiency of conventional and HEV powertrains by replacing alternator systems and reducing parasitic losses. Proving that TEGs can reliably produce at least 500 watts from exhaust heat energy recovery would eliminate the need for an alternator, significantly reducing engine parasitic loads. These results are of keen interest to the automotive industry. Refer to the second illustration.

Industry interest is centered on evaluating the maximum amount of energy that can be harnessed by these systems. During this project, analyses of both the thermodynamic energy available from engine exhaust and the theoretical energy conversion attainable by TEGs will be performed. Using the results of these analyses in conjunction with physical TEG performance validation for a harsh automotive environment, a realistic estimate for energy recovery will be calculated. Project results will be published in automotive journals. See the third illustration.

Accomplishments - The thermodynamic analysis of the available engine exhaust energy was performed and will be coupled with the generated test data. An adaptive testing fixture was designed and built for the thermoelectric module testing. TEG modules of various sizes and power ranges were acquired from four different suppliers. The modules will be evaluated in both stationary and harsh vibration situations. The harshness testing will be performed on a shaker table to simulate the shock and vibration that an automotive environment entails. The performance and efficiency validation will then be integrated with the thermodynamic models to provide a realistic approximation of potential engine exhaust energy recovery.

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