TECHNOLOGY AREAS: Air Platform, Ground/Sea Vehicles

OBJECTIVE: Develop a high conversion efficiency 250W, 14 VDC hybrid thermoelectric-solid oxide fuel cell portable power generator that exploits recent advances in high performance thermoelectric and solid oxide fuel cell materials and heat transfer technologies in state-of-the-art generators. Develop and execute concepts for optimized efficiency hybrid generators with low parasitic thermal and electrical integration. Analyze potential for increased hybrid system conversion efficiency and develop models for design optimization. This technology development is directed at portable and scaleable DoD warfighter and platform applications, providing enhanced fuel efficiencies through cogeneration of electricity via waste heat recuperation as well as auxiliary applications of the thermoelectric module for personal cooling and heating.

DESCRIPTION: Significant improvements in thermoelectric performance of semiconductor systems have recently been realized in thin film and bulk materials through the incorporation of nanometer scale structures that significantly increase phonon scattering, leading to record low thermal conductivities. Advanced designed materials also feature in state-of-the-art solid oxide fuel cells.
This topic seeks new concepts that leverage these technological advances to achieve higher overall conversion efficiencies for portable power (250W – 1 kW at 14 VDC) through integration of advanced thermoelectric (TE) conversion devices recuperating waste heat from Solid Oxide Fuel Cells (SOFCs). SOFCs are expected to operate at 700 to 900°C, and with thermal energy discharged at relatively high temperatures (Thot

400°C) are amenable to cogeneration of electricity with advanced high ZT thermoelectric power generating devices. The resulting temperature differential, depending on ambient conditions, will be approximately 350°C, with advanced heat transfer concepts required to achieve this temperature drop across the TE module for the highest efficiencies. Minimizing parasitic losses and maximizing the temperature differential will be required for higher overall fuel-to-electrical energy conversion efficiencies.

Analyses and system designs should consider the most advanced, validated, state-of-the-art thermoelectric, fuel cell, and heat transfer technologies, thermal and electrical systems integration, and power conditioning, as well as the technical and cost trade offs associated with integrating the thermoelectric and SOFC devices. The analysis should explore a range of TE devices and SOFCs using JP-8 or alternative hydrocarbon fuels and define the technical performance and cost targets required of the component technologies that must be met to produce integrated TE-SOFC generators. Alternative hydrocarbon fuels (e.g., propane, butane) may be used for proof of the hybrid concept, with consideration given to transitions to JP-8 fuel in the field. To maximize system-level conversion efficiency, modules must be designed and materials selected that minimize parasitic losses and maintain mechanical robustness at operating temperature and through repeated temperature cycling. Power quality should be similar to current tactical generators (specifications for current Marine Corps generators are available at http://www.marcorsyscom.usmc.mil/sites/pmeps/default.asp). Warfighter portability should be factored into the design of the generator, with a weight of no more than 30 lb. at the proof-of-concept stage and an ultimate target of 15 lb.

PHASE I: Develop detailed plans and comparative analyses for an integrated hybrid TE-SOFC -generator incorporating state-of-the-art TE and SOFC materials/modules, advanced heat transfer and low parasitic interfaces, and appropriate power conditioning for 250W – 1 kW power at 14 or 28 VDC. Demonstrate initial system proof-of-concept for overall efficiency gain by addition of TE generator to SOFC.

PHASE II: Optimize design for an integrated hybrid TE-SOFC generator incorporating state-of-the-art components for TE, SOFC, heat transfer, and power conditioning to deliver 250W – 1kW power at 14 or 28 VDC, with <10 minute startup, using JP-8 or alternative hydrocarbon fuel (e.g., propane, butane). Fabricate and test a fully integrated 250W – 1 kW prototype to demonstrate the potential for overall system efficiency gains of the hybrid design. Overall weight should not exceed 30 lb. and portability should be factored into the design. Analyze manufacturability, reliability, scalability, and cost issues for producing commercially viable power generation system.

PHASE III: Design and fabricate a performance- and portability-optimized hybrid thermoelectric-SOFC generator using the highest performance materials available that provides maximum total fuel-to-electricity conversion efficiency, using JP-8 fuel, for 250W – 1 kW power at 14VDC, <10 min. startup time, and a total weight of 15-25 lb. that will enable the development of commercially viable portable power generators for renewable warfighter power.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The integration of thermoelectric generators using the highest performance materials available with state-of-the-art solid oxide fuel cells with thermal and electrical systems engineering that minimizes parasitic losses and provides maximum total conversion efficiency will enable the development of commercially viable portable power generators for renewable power with the potential auxiliary applications of cooling and heating, unattended remote power, and camping and recreational sporting power.

KEYWORDS: Thermoelectric, fuel cells, waste heat, hybrid, nanostructure, heat transfer, energy conversion, power generation, generator

TPOC: Dr. Mihal Gross
Phone: 703-696-0388
Fax:
Email: mihal.gross@navy.mil