By Brooke C. Stoddard
As promising and powerful as light emitting diode (LED) and high-intensity discharge (HID) – including metal halide (MH) – technologies are, plasma lamp technology goes further. Claiming longevity at about 50,000 hours as compared to 30,000 for LEDs and 6,000 – 15,000 for metal halide lamps, as well as 140 lumens per watt (lm/W) as compared to 60 – 100 lm/W (at present) for LEDs and 75 -100 lm/W for metal halides, plasma lamps have already entered a variety of markets, most notably street lighting and high-bay. Plasma lamps are sometimes referred to as LEPs, stemming from the name Light Emitting PlasmaTM, which is a trademark of the prominent manufacturer Luxim located in Silicon Valley.
Plasma lamp technology is entirely different from that of LED, HID or other lighting forms. The lamp or bulb is a sealed quartz vessel no larger than a shelled peanut and with no intrusive electrodes or filaments. The gases within the tiny quartz vessel are stimulated by microwaves produced by a radio frequency driver, itself powered by twentyish DC current. The microwaves, concentrated by a device called a puck into which is set the quartz vessel, stimulate the bulb’s gases into a plasma that emits light. The plasma reaches a temperature comparable to that of the surface of the sun so that the light emitted approximates sunlight. The light can be readily directed so that there is no need for a traditional reflector, making the device even more efficient. Dimming to 20% is possible; controlling and restarts are not problems. The technology was first explored by Nikola Tesla more than one hundred years ago.
To this time, plasma lamps are offered for area lighting. Principal developers are Luxim, CeraVision, Plasma International, i-Giant, and Topanga Technologies, some of these headquartered in Europe and China.
A retailer is Stray Light Optical Technologies. It offers product making 23,000 lumens with a projected lifetime of 50,000 hours (night-time usage for 12 years). It offers product for street lighting, area lighting, billboard, architectural lighting, towers, industrial needs, aquariums, and the like.
Luxim puts forth the following cost comparison to 250W metal halide (MH) high-bay fixtures. It assumes for MH a lamp replacement cost of $30, and a fixture cost without the lamp of $200, the same figures for LEP being $70 and $500. The LEP consumes 150W. Assuming 100 fixtures, Luxim postulates the following: Installation costs – MH, $5,000 and LEP, $5,000; Annual Energy Costs – MH, $20,300 and LEP $10,500; Annual Maintenance Costs – MH, $5,600 and LEP $2,000; Incentives and Rebates – MH, none and LEP $19,000. Upfront costs come to $28,000 for MH and $47,000 for LEP while Annual Costs come to $26,000 for MH and $8,400 for LEP. Luxim says its 100 lamps would consume 87,000 kWhr per year, far less than the 169,000 kWhr for MH while boasting an 8.6-year life compared to 2.3 years for MH.
For an architectural lighting example, Luxim matches one of its products against 100 replacement 250W MH lamps and comes up with $38,000 upfront costs versus $47,000 for LEP with annual costs coming in at $19,400 for MH and $6, 300 for LEP.
In an example of an actual factory floor replacement, Luxim says the installation saves 120W per fixture, reduces the number of fixtures from 60 to 18, enjoys a replacement cycle of six years rather than two years, lowers annual energy consumption from 52,600 kWhr to 27,600 kWhr, saving $3, 246 per year in energy bills plus another $2,227 in maintenance costs, as well as improved CRI from 70 to 95.
Stray Light says it has sold product to Wal-Mart, Disney, and NASA, as well as to the cities of Indianapolis, Seattle and Toronto. Luxim makes product not only for street and area lighting but also for entertainment lighting that emits 24,000 lumens, for outdoor building lighting that emits 14,000 lumens, and lights used for growing plants indoors.
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Brooke C. Stoddard is an Alexandria, Virginia-based writer covering business, manufacturing, energy, and technology.
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