Swarms of light emitting diodes (LEDs) are landing in the form of new lamps and light fixtures. At last spring’s annual Lightfair trade show, LEDs dominated whole sections of the event. Are we seeing a new wave of lighting energy efficiency opportunities? Not just yet.
Claims and QueriesNew white LEDs with high lumen/watt output (already more efficient than incandescent) are starting to challenge fluorescent light sources. One showstopper LED at Lightfair claimed 200 lumens/W. By comparison, better incandescents rarely break 20, while T8 fluorescents powered by electronic ballasts approach 100 lumens/W. Later claims for the same LED were, however, closer to 70 lumens/W for continuous (as vs. very brief) duty, which is how other lamps are rated.
Information on other new LED devices was sometimes a bit sketchy. One newbie vendor declined to quote a ballpark price until he was ensured of an advance payment, which did not create confidence that the order would indeed be filled in a timely fashion. One corner of the show looked like it had just been airdropped from China, with some booth displays showing more Chinese than English. When asked to explain poorly translated instructions accompanying one sample LED unit, the booth captain frowned as he tried to make sense of the mangled English, calling out angrily, “Who write this? Who write this?” to his companions.
Test Before You InvestShortly after Lightfair, energy practitioners’ e-mailboxes saw brochures and spec sheets for new LED units designed to replace downlights and specialty fixtures (e.g., task and undercabinet lighting), and even a T8 lamp filled with LEDs. As many in the field have learned over the decades, many doodads that have disappeared shortly after their first production runs, and some of these items may be destined for the dumpster. While a few will find appropriate niches and flourish, others appear to be more novelty than invention.
The T8 replacement unit, for example, features a circuit board holding about 300 white LEDs on one side, housed in a clear 1-in.-T8 housing that fits into existing fluorescent fixture sockets. It operates on 110 or 277V, so existing ballasts may be disconnected. The spec sheet claims 80 lumens/W and offers both warm and cool white versions. One sees the usual boasts of a 50,000-hr lifetime, no mercury disposal problem, and low heat output which are common to most LED units. While the literature is honest about the total lamp lumen output (less than half that of a standard fluorescent T8), information on the impact on fixture light output and distribution is curiously missing.
If installed in a standard troffer with LEDs pointing down, one would see a line of extreme brightness, hopefully distributed to some degree by an acrylic lens, but open fixtures (e.g., those using parabolic louvers) may be rather glary. No light would be striking the fixture’s reflectors above the lamps, which are essential to controlling light distribution. In essence, one would be replacing the usual softly luminous surface of a fixture with ~300 tiny, bare, and very bright pinpoints of light. Pointing the LEDs instead upward may improve distribution and reduce glare, but then all light becomes indirect, which impacts both appearance and overall fixture efficiency (i.e., light escaping the fixture vs. light emitted by the lamps). At the very least, such LED replacement units need to be thoroughly tested in sample rooms to assess their ability to properly illuminate a task.
Of course, once one sees the price (~$50 per T8 LED unit), he may decide to look for other alternatives.
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