Aluminum Foil Lamps Outshine Incandescents
Aluminum Foil Lamps Outshine Incandescents
Thin, lightweight panels of aluminum foil each containing 250,000 lamps the size of a human hair are under development for efficient residential and commercial lighting, and for biomedical applications.
Built of aluminum foil, sapphire, and small amounts of gas, the panels are less than one millimeter thick, and can hang on a wall like picture frames, according to developer Gary Eden, a professor of electrical and computer engineering at the University of Illinois.
Eden authored a paper describing the lamp panels, called microcavity plasma lamps, in the June issue of the Journal of Physics D: Applied Physics..
Like conventional fluorescent lights, microcavity plasma lamps are glow-discharges in which atoms of a gas are excited by electrons and radiate light. Unlike fluorescent lights, however, microcavity plasma lamps produce the plasma in microscopic pockets and require no ballast, reflector, or heavy metal housing, Eden explains.
The panels are lighter, brighter, and more efficient than incandescent lights and are expected, with further engineering, to approach or surpass the efficiency of fluorescent lighting.
The plasma panels are also six times thinner than panels composed of light-emitting diodes, said Eden.
A plasma panel consists of a sandwich of two sheets of aluminum foil separated by a thin dielectric layer of clear aluminum oxide (sapphire). At the heart of each lamp is a small cavity, which penetrates the upper sheet of aluminum foil and the sapphire.
Completing the panel assembly is a glass window 500 microns thick. The window’s inner surface is coated with a phosphor film 10 microns thick, bringing the overall thickness of the lamp structure to 800 microns.
Depending upon the type of gas and phosphor used, uniform emissions of any color can be produced.
In the researchers’ preliminary plasma lamp experiments, values of the efficiency– known as luminous efficacy–of 15 lumens per watt were recorded. Values exceeding 30 lumens per watt are expected when the array design and microcavity phosphor geometry are optimized, Eden said. A typical incandescent light has an efficacy of 10 to 17 lumens per watt.
The researchers also demonstrated flexible plasma arrays sealed in polymeric packaging that can be mounted onto curved surfaces such as the insides of windshields.
Eden says the flexible arrays also could be used as photo-therapeutic bandages to treat diseases such as psoriasis that can be driven into remission by narrow-spectrum ultraviolet light.
Research funding was provided by the U.S. Air Force Office of Scientific Research and the Office of Naval Research.
