Hi-Z Technology, Inc.

Technical Papers from 2002

Small Thermoelectric Generators

Daniel Allen, Hi-Z Technology, Inc.
Robert Haugeto and Michael Kajor, U. S. Army TACOM-ARDEC, AMSTA-AR-FSF-I
Mehdi Namazian, Altex Technologies Corporation

Abstract
Thermoelectric generators with combustion heat sources are being developed for the U. S. Army, TACOM-ARDEC, by Hi-Z Technology, Inc., for battery replacement in the field and for powering lightweight portable battery chargers. These small generators range in output power from 0.3 watts to 20 watts. The main thrust of the development work is to demonstrate utilization of diesel or other military logistics fuel as the heat source. The thermoelectric generating modules being used operate at relatively low hot side temperatures and with modest power conversion efficiencies. Nevertheless, the concept shows potential advantage over batteries in watts per pound and watt- hours per pound, thus addressing the "battery problem" and the need for lightening the soldier's battery burden, and doing so at reasonable costs. The thermoelectric material used in this application is current state-of-the-art. However, Hi-Z is also developing advanced thermoelectric materials and devices that promise significantly improved performance in the near future.

Full-text article available for download. (PDF)

Outgassing and Vaporization Considerations in MilliWatt Generators Designed for 20-Year Missions

Nathan Hiller , Daniel Allen , Norbert Elsner , J. C. Bass , and J. Peyton Moore

Abstract
Ongoing experimental work and theoretical models indicate that milliwatt thermoelectric generators that operate in a sealed-off vacuum environment will be useful for long-term operation, such as the PASCAL 20 year Mars mission and the CryoScout mission. Considerations for long-term operation include out gassing of the multifoil vacuum insulation before pinch off and vaporization of the (Bi,Sb)2 (Se,Te)3 thermoelectric materials during long-term operation. Tests underway indicate the multi-foil insulation can be pre-outgassed before assembly so further outgassing in the sealed generator is minimized. Experimental data and vaporization models for a Th of 250 °C thus far indicate that the small amount of vaporization of materials used in the thermoelectric module do not significantly effect the generator vacuum or the module power output. These tests and models indicate that both potential modes of degradation can be controlled and minimized. Although performance data on the generator materials only extend for several hundred hours, the good performances in a limited time, combined with an understanding of the materials behavior, indicate that milliwatt generator holds promise for providing sufficient and reliable power for space missions lasting up to 20 years.

Full-text article available for download. (PDF)