Advanced Soldier-Based Thermoelectric Power Systems Using Battlefield Heat Sources

Abstract

The U.S. military uses large amounts of fuel during deployments and battlefield operations. Consequently, the U.S. military has a strong need to develop technologies that increase fuel efficiency and minimize fuel requirements all along the logistics trail and in all battlefield operations. There are additional requirements to reduce and minimize the environmental footprint of various military equipment and operations and reduce the need for batteries (nonrechargeable) in battlefield operations. The tri-agency SERDP (Strategic Environmental Research and Development Program) office is sponsoring a challenging, high-payoff project to develop a lightweight, small form-factor, soldier-portable advanced thermoelectric generator (TEG) system prototype to recover and convert waste heat from a variety of deployed equipment (i.e., diesel generators/engines, incinerators, vehicles, and potentially mobile kitchens), with the ultimate purpose of obtaining additional power for soldier battery charging, advanced capacitor charging, and other battlefield power applications. The project seeks to achieve power conversion efficiencies of approximately 10% (double current commercial TE conversion efficiencies) in a system with near 1.6-kW power output for a spectrum of battlefield power applications. The project is taking on the multi-faceted challenges of tailoring LAST (Lead Antimony Silver Telluride) / LASTT (Lead Antimony Silver Tin Telluride) nanocomposite thermoelectric (TE) materials for the proper temperature ranges (300 K -700 K), fabricating these materials with cost-effective hot-pressed and sintered processes while maintaining their TE properties, measuring and characterizing their thermal fatigue and structural properties, developing the proper manufacturing processes for the TE materials and modules, designing and fabricating the necessary microtechnology heat exchangers, and fabricating and testing the final TEG system. The ultimate goal is to provide an opportunity to deploy these TEG systems in a wide variety of current military equipment (i.e., various Tactical Quiet Generator (TQG) systems) and battlefield operations so that they can provide the military with a pathway toward energy savings and environmental footprint management. The paper reviews the progress made on 1) the performance of LAST / LASTT TE materials and tailoring their temperature dependency; 2) evaluating the structural (Elastic modulus, Poisson's ratio and mechanical strength) properties of these materials, 3) developing the necessary LAST/LASTT-based TE modules, 4) developing the required hot-and cold-side microtechnology heat exchangers, and 5) the overall system designs for 30 kW and 60 kW TQG applications and potential performance pathways/differences for these two TQG cases. This work leverages fundamental research sponsored by the Office of Naval Research in developing LAST/LASTT materials.

Electrical, Thermal, and Mechanical Characterization of Novel Segmented-Leg Thermoelectric Modules

“…In particular, for the only fracture data that are 20 and Ag 0.9 Pb 9 Sn 9 Sb 0.6 Te 20 specimens included in this study. Finite-element analysis performed by Pacific Northwest National Laboratory (PNNL) 42 indicates that, with the appropriate dimensions and interconnections, the thermal stresses generated within the thermoelectric modules fabricated from Ag 0.86 Pb 19+x SbTe 20 and Ag 0.9 Pb 9 Sn 9 Sb 0.6 Te 20 elements may not exceed the strength values measured in this study. Also, while thermal fatigue testing was done only on nonsegmented specimens of LAST or LASTT, numerical simulations of segmented legs would also be of interest.…”

Mechanical Response of Thermoelectric Materials

“…However, thermal annealing of the tumbled capacitors can restore mechanical strength [134]. While it has been suggested that chamfering to the edges of TE legs could both relieve the stress concentration due to sharp corners and (ideally) remove microcracks induced by cutting operations [135], the chamfering process itself may introduce crack damage. Thermal annealing the specimens in an inert atmosphere at T h ≈ 0.6 could diffusively heal and strengthen the legs.…”

Integrated Thermoelectric–Thermal System Resistance Optimization to Maximize Power Output in Thermoelectric Energy Recovery Systems

“…Thermoelectric (TE) energy recovery and conversion systems is an important technology for recovering this waste thermal energy and converting it to useful electrical energy, either by itself or as a critical energy conversion subsystem in a hybrid power system. Yazawa and Shakouri [16] attempted to address this question with a simplified, closed-form analysis of the quite complex thermal and thermoelectric design interactions described in earlier references [3][4][5][6][7][8][9][10][11][12][13][14][15]. Thermoelectric (TE) power systems in these applications require high performance hot-side and cold-side heat exchangers to provide the critical temperature differential and transfer the required thermal energy to create the power output.…”