Applying an electric current to specially coated glass results in radiant heat energy. This process creates a transparent heating element with near- uniform surface temperatures. Manufacturing the heating element requires an ordinary pane of float glass. A fluorine-doped tin oxide coating (SnO2:F) measuring 0.25 micron thick is applied to one surface of the glass during fabrication. The coating conducts electricity, has a very tightly controlled resistance, has no appreciable color or structure, and is quite transparent. The coating has low emissivity properties that help contribute to the efficiency of the heated glass.

Heated Glass consists of coated float glass, copper buss bars, standard wiring, and a control unit.
Two copper buss bars are fixed to the coated surface. The buss bars must be parallel, and the glass surface between them must form a rectangle for even heating. An electric current travels between the two buss bars across the tin oxide coating. The electrical resistance of the coating raises the surface temperature of the glass, which radiates heat.

The temperature of operation of the glass heater can be varied from just above room temperature to up to 350ºF (176.7ºC), as dictated by the thermal limits of the tempered float glass. Temperature levels are adjustable with precise control from 70ºF (21.1ºC) to 350ºF (176.7ºC). Adjustments can be manual or automated. With a 240-volt control unit, larger glass sizes and higher power densities are achievable. This is particularly important for heated architectural glass, given the propensity for large window sizes.

At low temperatures, glass radiators prevent condensation in high humidity and high altitudes in applications such as architectural and aircraft windows. High-temperature applications in clude, but are not limited to, medical research equipment such as incubators, as well as household appliances and food service equipment.

This work was done by Peter Gerhardinger of Thermique Technologies, LLC. For more information, click here . Inquiries concerning rights for commercial use should be addressed to:

Mike Hobbs

Thermique Technologies

2857 S. Halsted St.

Chicago, IL 60608

Tel: 312- 326-2522 x113.

NASA Tech Briefs Magazine

This article first appeared in the November, 2008 issue of NASA Tech Briefs Magazine.

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