Robust Design of Advanced Thermoelectric Conversion Systems: Probabilistic Design Impacts on Specific Power and Power Fl

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1102-LL05-04

Robust Design of Advanced Thermoelectric Conversion Systems: Probabilistic Design Impacts on Specific Power and Power Flux Optimization Terry J. Hendricks, and Naveen K. Karri Energy & Environment Directorate, Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, WA, 99352 ABSTRACT Advanced, direct thermal energy conversion technologies are receiving increased research attention in order to recover waste thermal energy in advanced vehicles and industrial processes. Advanced thermoelectric (TE) systems necessarily require integrated system-level analyses to establish accurate optimum system designs. Past system-level design and analysis has relied on well-defined deterministic input parameters even though many critically important environmental and system design parameters in the above mentioned applications are often randomly variable, sometimes according to complex relationships, rather than discrete, well-known deterministic variables. This work describes new research and development creating techniques and capabilities for probabilistic design and analysis of advanced TE power generation systems to quantify the effects of randomly uncertain design inputs in determining more robust optimum TE system designs and expected outputs. Selected case studies involving stochastic TE .material properties demonstrate key stochastic material impacts on power, optimum TE area, specific power, and power flux in the TE design optimization process. Magnitudes and directions of these design modifications are quantified for selected TE system design analysis cases.

NOMENCLATURE English Ap - p-type TE element area [m2] An - n-type TE element area [m2] Atot - Total p- and n- TE element area [m2] Cp - Specific heat of gas / liquid flow [J/kg-K] m& c - Cold-side mass flow rate [kg/sec] N - Number of TE couples in TEG module P - Device power [W] Tamb - Ambient temperature [K] Texh - Exhaust gas temperature [K] Th - TE hot-side temperature [K] Tc - TE cold-side temperature [K] Greek α - TE couple Seebeck Coefficient [V/K]

- Standard Deviation of Probabilistic Distribution η - Thermoelectric conversion efficiency κ - TE material thermal conductivity [W/m-K] ρ - TE material electrical resistivity [Ω-m] µ - Mean of Probabilistic Distribution ξ

Subscripts c - Cold-side of TE device ex - Associated with heat exchanger itself h - Hot-side of TE device p - p-type TE material n - n-type TE material T - Temperature TE - Associated with TE device itself

INTRODUCTION Advanced, direct thermal energy conversion technologies are receiving more research attention in order to recover waste thermal energy in advanced vehicles, industrial processes and military systems, converting it to useful high-grade electrical energy onboard vehicles or in industrial processes [1]. Recent increases in oil prices have created a growing interest in increasing system efficiencies in vehicles, industrial processes and military systems. Additional sources of high-grade electrical power can charge

batteries or electrically operate aux