The other energy efficient lighting technology

The Dept. of Energy's Energy Savers blog calls induction lighting one of the best kept secrets in energy-efficient lighting. Induction technology is essentially a fluorescent light without electrodes or filaments, which are the components that frequently cause other light sources to burn out quickly. Energy transfers through the glass envelope solely by electromagnetic induction.

As with fluorescent lamps, mercury vapor in the tube is electrically excited to produce short-wave ultraviolet light, which then excites phosphors on the tube to produce visible light. These lamps have been available since 1990. There are two main types of magnetic induction lamps, external and internal, named for where the phosphor-exciting inductor resides. External inductor lamps are the more recent type and use electromagnets wrapped around a part of the tube.

In the external inductor lamps, high-frequncy signals from the light ballast go to a ferrite inductor coil on the outside of the glass tube. The resulting strong magnetic field excites the mercury atoms in the lamp. From this point, the lamp operates like a conventional fluorescent lamp.

Induction lighting uses high-frequency ballasts which are typically 95% efficient or better, and they have a high lumen/watt output as well. They usually find use in wide-area lighting such as with parking lots and gyms. For example, Bishop McGuinness High School in Kernersville, N.C. recently replaced 42 400-W metal halide fixtures in the school's gymnasium with 24 energy-efficient, EverLast 400-W induction high bay fixtures. EverLast says the school created a hypothetical 10-year operational cost chart to figure out how much would be saved with the new lights. The annual operating cost for one 400-W metal halide fixture turned out to be $478, compared to $231 to operate one EverLast 400-W induction fixture.

EverLast says its induction lamps are 50% more efficienct than metal halides. In the case of McGuinness High School, induction bulbs should last approximately 10 years and it took only about half as many fixtures to light the gymnasium as with the old metal halide units.

More info: Wikipedia page on induction lighting: http://en.wikipedia.org/wiki/Induction_lighting