While experimenting with high-frequency current, inventor Nikola Tesla developed an electrodeless lamp, but the concept remained largely unexplored for the next century (except as a novelty lamp in the 1980s). The first practical electrodeless lamp appeared a short time later, and the technology continues to gain in popularity today due to its energy and maintenance advantages.
Electrodeless lamps do not require wiring connections between the lamp and its ballast or driver. As most wear and tear on lamps occurs at the electrode, its absence in this technology can significantly extend lamp life.
Magnetic induction lamps, commonly known as induction lamps, are electrodeless fluorescent lamps using ballasts that emit radio waves guided into an electromagnetic field, which converts mercury vapor in the lamp into a plasma state. This results in the emission of ultraviolet light, which is converted into white light using phosphors, with the light emission exiting the lamp from the surface of the bulb (linear source).
Solutions include Osram Sylvania’s Icetron and Dura-One, Philips’ QL, and GE’s Genura. Sylvania’s Icetron system is available in 100 watts (W) and 150W, operating at an initial efficacy of about 75 lumens per watt (LPW) and with a color rendering index (CRI) rating of 80 and choice of 3,500K, 4,100K or 5,000K color tones. Philips’ QL is available in 55W, 85W and 165W, operating at about 72 LPW, 80 CRI, and 3,000K or 4,000K.
This type of induction system typically offers service life of 60,000 hours at L70, or lumen maintenance of 70 percent [how life for light-emitting diode (LED) products is measured]. It also uses amalgam technology to provide reliable startup at low temperatures, making it suitable for outdoor lighting and other extreme-temperature applications; it is not recommended for dimming.
Sylvania and GE manufacture electrodeless compact fluorescent lamps (CFLs). Sylvania’s Dura-One electrodeless amalgam self-ballasted CFLs offer a choice of 20W A19 (60 LPW) or 23W BR30 (48 LPW) configurations in warm color (2,700K), 82 CRI and rated life of 15,000 hours. GE’s Genura is a 23W (48 LPW) amalgam self-ballasted R25 floodlamp offering 82 CRI, 3,000K and rated life of 15,000 hours. Again, these products are not recommended for use on dimming circuits.
The other type of electrodeless lamp is the plasma lamp, which uses one or more gases, coupled with materials such as metallic halides, sodium or sulfur. A magnetron produces an electromagnetic field that is guided into place around a glass capsule, converting its contents into light-emitting plasma with point-source distribution. While magnetic induction may appear to be an older technology, the first practical electrodeless lamp was the sulfur lamp developed by Fusion Lighting in the 1990s. It did not fare well at the time but was later commercialized by companies, such as Plasma International and i-Giant, which today offer emitters producing 128,000–163,000+ lumens of very cool (5,700K–6,000K) light and initial lamp/magnetron system efficacy of 106+ LPW for horticultural, light pipe and other commercial applications.
More recently, Luxim, Topanga Technologies and U.K.-based Ceravision have developed plasma solutions that use halides instead of sulfur, are even more compact with smaller lumen packages, and are developing to include a choice of warm, cool and neutral white color tones. Luxim and Topanga have further developed their products for use with solid-state drivers (in place of magnetrons), producing systems that can be dimmed to 20 percent of light output (50 percent of lamp power) based on input from digital or analog 0–10V direct current networked or stand-alone control devices. The emitter, about the size of a Tic-Tac, enables the development of compact, lightweight fixtures with high (up to 90 percent) optical efficiency.
According to Luxim and Topanga, their systems can replace HID lighting fixtures for up to 40–50 percent energy savings—with initial efficacy of up to 95 LPW for the lamp/driver system—in addition to service-life ratings of up to 50,000 hours for the lamps (based on L70, or 70 percent lumen maintenance). The largest potential is in outdoor area and roadway lighting, although indoor high-bay application is developing as the companies introduce products emitting neutral-white light. Typically, the entire fixture must be replaced.
Luxim sells its systems to fixture companies, such as Alphalite, Deco Lighting, Hubbell, Pemco Lighting Products, Philips and Stray Light Optical. The product line offers lumen packages of 14,000 up to 23,000 targeting 250–400W HID systems, with a CRI rating of 75 or 95 and a cool 5,200K. Recently, it announced a replacement for 750W HID systems. In 2012, Luxim is looking to offer 4,200K emitters and a lumen package targeting 1,000W lamps. Relative newcomer Topanga, meanwhile, offers 95W and 170W systems rated at 11,000 and 22,000 lumens, respectively, 70 or 95 CRI and 3,000K–6,500K, and is working with OEMs toward product launches in the second quarter of 2012.
As lighting continues to grow in energy efficiency, electrodeless lighting demonstrates that LED is not the only game in town; it offers competitive choices for outdoor and maintenance-sensitive applications.
DILOUIE, L.C., a lighting industry journalist, analyst and marketing consultant, is principal of ZING Communications. He can be reached at www.zinginc.com.