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					Five Westchester Place Elmsford, NY 10523

Fitting a Square Peg Into a Round Hole: How
The Knowledge Gap Between Solid State Lighting Meets Real World Expectations.

David F. Shepard, MBA, IESNA

Fitting a Square Peg Into a Round Hole: How The Knowledge Gap Between Solid
State Lighting Meets Real World Expectations. Summary: Why have we embraced the LED light source so readily? Just 5-10 years ago LED lighting was relegated to Automobile lamps and flashlights, and now, seemingly, every lighting manufacturer is wooing architects and designers with products that range from simple cove-lighting and down lights, to T-8 replacement lamps. We are told the large cost premium is offset by Herculean longevity, But how are we to know which products will perform as stated? No lighting technology has been fast-tracked like SolidState Lighting, but is it right for you? In the next couple of pages we will explore these questions and explain where LED’s excel and where they fail to meet our expectations. I.) Expectation #1 Long Life Although many articles written by journalists and even some fixture manufacturers claim life spans of 50,000 hours or more, you really need to put your rose-colored glasses in the drawer and become a skeptic. When you become interested in buying an automobile, you open the Sunday paper and see, in BOLD letters, a Toyota Camry for $199/mo. Do you race down to the dealer and sign the paperwork before the salesperson comes to their senses? No, you go right to the bottom of the advertisement to look at the fine print because you know that there is no way a $25,000 car can be offered for that price. You ask yourself “what’s the catch?” It would be a shame for lighting fixture manufacturers to be stereotyped as “used-car dealers” but with SSL technology, what you see is not always what you get. The truth is, even though in a research facility in Silicon Valley, a single LED lasted 100,000 hours, the small print at the bottom of the article (aka: the “disclaimer”) reads that the LED was being operated at -500K. Negative 500 degrees Kelvin – wow, imagine if you kept your office that cold. And you thought there were complaints when it dipped down below 75 Fahrenheit! The reality is that the life span of the LED’s is 100% dependant on the engineering of the individual product they are installed in.

How do you know you are getting a quality LED product? Here are a few questions to ask: 1.) How long has the company been producing LED fixtures? (If less than five years, they do not have the history to justify long-life claims) 2.) How long is the warranty? (Really? Only one year warranty, for a product you say will last 50,000 hours?) 3.) Does the product literature address Lumen-Depreciation? 4.) Who’s LED’s are in there? II.) Expectation #2 LED’s give off an enormous amount of light. There is no doubt that a single LED can be extremely bright. Because the light is emitted in such a small package (1-8mm) they seem much brighter than other traditional sources. If you were to concentrate the raw lumens of a T-8 lamp in a similar package, they would be just as bright. The key is not how bright the light source is, but rather how the fixture itself places the light onto the task surface. Whether that surface be a desk-top or a retail counter, it is the fixture, not the LED that needs to perform. The initial light output of an LED can be enormous when a quality LED array is paired with a well-designed fixture and uses state of the art optics to direct that light output. The question is, how long will that fixture continue to perform the way it did when new? Turning up the heat: What an LED does produce as well as light, is heat. How that heat is dissipated, and how quickly, will determine the “Lumen Maintenance” of the fixture. Like the Mercury Vapor lamps of decades ago, LED’s do not fail catastrophically. They fade over time. The loss of light output as the fixture ages is called lumen-depreciation. The US Department of Energy tests products and has found that most packaging claims are not to be believed. An LED replacement down-light that starts it’s life giving 50 foot-candles on the work-plane from nine feet, may indeed produce less than half that light after as few as 2,000 hours. The main culprit is the heat generated by an LED is trapped in the fixture and causes an accelerated break-down of the components on the chip which produce the light. Another pit-fall of poorly designed fixtures is color-shift. Since all white LED’s (producing the warm light we expect) are actually blue LED’s with a phosphor coating, this phosphor coat can degrade and cause the LED’s to get “bluer” over time. This phosphor degradation also reduces CRI, or color rendering, making the fixture undesirable. And what about that Glare? How do you make LED’s comfortable to work under? Glare from LED’s can be extremely uncomfortable and if exposed to this glare for long periods of time (ie. an 8-hour day at the office) the resulting health issues and resulting loss of productivity can add up.

III.) Expectation #3 LED’s will save energy over other light sources While it is true that a single high-power LED array uses much less energy than standard incandescent or fluorescent light sources, how many LED’s do you need to match the light output? When looking at general ambient lighting we must take into account the vast advances in technology over the past ten years. Standard light fixtures, direct or indirect, utilize T-8 and T-5 lamp and ballast technology. The energy efficiency of these light sources has improved to well over 100 lumens per watt. The standard four-foot lamp (once the dreaded T-12) has gone from 40W down to 25W and has improved light quality and well as lumen maintenance. An LED replacement is no longer being compared to a 32W light source, but rather (thanks to ballast and lamp technology) just 25W will produce the same light output. Can a 25W LED T-8 replacement produce the same light? Not yet. Right now, the real world applications of LED’s are delegated to down-lights, accent lighting and task lighting. Yes, you can illuminate a work surface with LED’s, thus allowing you to reduce the ambient light in an office environment and save as much as 50% or more in the largest single energy draw in a commercial building – lighting. But how much energy are you saving? A well-designed 13W CFL based task light utilizing asymmetric distribution can cover over 70% of an 8’x8’ workstation with and additional 25-100 foot-candles. A well designed LED fixture can do the same for under 8W. When compared to the traditional, and still today the most popular, fluorescent under-cabinet lights; this is a true 84% energy savings. The paradox is that most LED “task lighting” solutions require multiple lamps/fixtures to accomplish this feat. Be wary of “system” solutions and change your mind set away from cabinet or shelf-based solutions. If you are considering stateof-the-art lighting technology, you need to change your conceptions on how that light is delivered.

IV.) Conclusion: The presentation covers the basic technology behind LED’s and will utilize case studies to show how LED’s can best be used to both make our work environment better and to save energy. Any interior, design or contract furniture professional will find this presentation both informative and thought evoking. It will increase your knowledge base and help you pick the best products for your next project. The more you know, the more your clients will appreciate your influence.


				
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posted:11/16/2009
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