Just when we thought emergency exit sign illumination had reached an unbeatable low-energy plateau with LED (light-emitting diode) technology, we learn of a quite different technology offering even greater energy savings and some performance advantages. LightPanel exit signs from LightPanel Technologies, LLC, are electroluminescent exit signs that consume less than a half a watt of electricity using a patented light-emitting capacitor (LEC) technology.
First a little background:
- There are about 100 million illuminated emergency exit signs in use around the United States, 80% of which use two incandescent light bulbs. With 10- to 20-watt lamps lasting only about 3,000 hours, these incandescent exit signs cost as much as $73 per year in electricity use and labor-and they generate a lot of heat that can increase air conditioning demands.
- Compact fluorescent lamps (CFLs), which emerged in the 1980s, offer longer lamp life and reduced energy consumption (typically 15-20 watts, including ballast), but total operating and maintenance cost is still as much as $49 per year.
- The biggest revolution in exit sign illumination occurred with LED technology. LED exit signs, first introduced in 1985, offer total energy consumption of just 2 to 4 watts and a service life of decades rather than months or years. LED-based emergency exit signs now account for more than three-quarters of all illuminated exit signs sold, according to the Lighting Research Center in Troy, New York. Unfortunately, LEDs vary in quality and some lose brightness fairly quickly - a 50% drop in light output is typical within two years, according to Light-Panel. Also, because individual LEDs provide the illumination, the edges of letters are often poorly defined and readability may be poor.
- Yet another exit sign technology uses tritium, a radioactive isotope of hydrogen. While tritium exit signs have been around since the 1920s and use no energy to operate, light output is low and drops off as the radioactive gas decays. Most important from an environmental standpoint, radiation can be released if these exit signs are damaged or disposed of improperly, and there are very significant environmental and health risks associated with tritium production.
The electroluminescent LightPanel LEC technology uses a continuous layer of millions of microscopic zinc sulfide photo-emitting crystals sandwiched between two layers of conductive material, one of which is transparent. Green light is produced when voltage is applied across the conductive layers. The light is uniform over the entire area being illuminated (each letter and any arrows) so edges are sharp and defined. With no individual lights to burn out, the units are very thin, produce virtually no heat, and have the lowest energy consumption of any electric lighting technology in use.
A LightPanel exit sign consumes just 0.25 watts (0.35 watts for the retrofit kits), and has a projected service life of 30 years. Light output does drop over time, according to LightPanel president Ken Ungard-dropping to about 30% of the initial brightness after seven to ten years before leveling off. Due to the uniformity of the illumination, however, Ungard says the LightPanel exit signs will remain fully readable over their 30-year life-and even after 30 years they should be brighter than brand-new tritium exit signs.
Peter Boyce of the Lighting Research Center told EBN that a number of electroluminescent exit signs have been produced in the past, but that brightness was a problem. Although he hasn't tracked the technology in the past several years, Boyce said that if the product meets the ENERGY STAR exit sign standards, it should offer adequate performance. All LightPanel products are ENERGY STAR-listed.
Ungard founded LightPanel Technologies, initially called Advanced Luminescent Products, in July 1995; the company introduced its first product-a retrofit kit for incandescent or CFL exit signs-in early 1996. Complete LightPanel exit signs were introduced in 1999. The LEC electroluminescent technology used in these exit signs was developed in the 1930s and first employed commercially in 1967-for exterior safety lights on U.S. military jet fighters.
The technology was attractive to the military because of its reliability and ability to withstand shock and power surges (LightPanel exit signs are rated to withstand 6,000-volt surges). Electroluminescent emergency lighting technology is used today on the majority of the world's tactical military aircraft as well as by most commercial airlines.
LightPanel exit signs are available in 120-volt and 277-volt AC models, as well as 6-volt and 12-volt DC models. The list price for a new exit sign without battery backup is $48 in an ABS plastic housing (about $10 more for an aluminum housing). Retrofit kits list for about $10 less. With integral battery backup-using nickel-cadmium (NiCad) batteries-the list price is about $80.
Ungard says NiCad battery life with LightPanel exit signs is somewhat longer than with some other products because no heat is generated; the company projects about a 10-year battery life. A nice feature with battery-backup Light-Panel exit signs is that they are brighter on battery power (16 foot lamberts in emergency DC mode vs. 5 foot lamberts in normal AC operation).
The payback when retrofitting incandescent or fluorescent exit signs with LightPanel kits is very attractive, as the annual operating cost for the retrofit LightPanel is only 31 cents per year and there is no maintenance. The payback is not nearly as attractive if replacing LED exit signs. Nonetheless, Ungard told EBN that the company does a lot of LED exit sign replacements.
At IBM's Burlington, Vt., plant for example, all exit signs have been replaced with LightPanel products-even though approximately half of the exit signs had been relatively new LED models.
For more information:
LightPanel Technologies, LLC
10 Technology Drive
West Lebanon, N.H. 03784
888-298-8133, 603-298-8000
603/298-8188 (fax)
www.lightpanel.com
Lighting Research Center
21 Union Street
Troy, NY 12180
518-687-7100, 518-687-7120 (fax)
www.lrc.rpi.edu.
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Copyright 2001 Environmental Building News, all Rights Reserved. EBN is a GreenBiz News Affiliate. This is a product review by EBN, not necessarily a product endorsement or recommendation by GreenBiz.com or The Green Business Network.