Heat Flux Based Optimization of Combined Heat and Power Thermoelectric Heat Exchanger

Kazuaki Yazawa and Ali Shakouri
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Kazuaki Yazawa: Birck Nanotechnology Center, Purdue University, 1205 W State St., West Lafayette, IN 47907, USA
Ali Shakouri: Birck Nanotechnology Center, Purdue University, 1205 W State St., West Lafayette, IN 47907, USA

Energies, 2021, vol. 14, issue 22, 1-16

Abstract: We analyzed the potential of thermoelectrics for electricity generation in a combined heat and power (CHP) waste heat recovery system. The state-of-the-art organic Rankine cycle CHP system provides hot water and space heating while electricity is also generated with an efficiency of up to 12% at the MW scale. Thermoelectrics, in contrast, will serve smaller and distributed systems. Considering the limited heat flux from the waste heat source, we investigated a counterflow heat exchanger with an integrated thermoelectric module for maximum power, high efficiency, or low cost. Irreversible thermal resistances connected to the thermoelectric legs determine the energy conversion performance. The exit temperatures of fluids through the heat exchanger are important for the system efficiency to match the applications. Based on the analytic model for the thermoelectric integrated subsystem, the design for maximum power output with a given heat flux requires thermoelectric legs 40–70% longer than the case of fixed temperature reservoir boundary conditions. With existing thermoelectric materials, 300–400 W/m 2 electrical energy can be generated at a material cost of $3–4 per watt. The prospects of improvements in thermoelectric materials were also studied. While the combined system efficiency is nearly 100%, the balance between the hot and cold flow rates needs to be adjusted for the heat recovery applications.

Keywords: thermoelectric; figure of merit; analytic model; heat exchanger; CHP; waste heat recovery; design optimization (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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