It's been about a year and a half since one of our readers offered up a very insightful reality check to my overly-optimistic editorial on the future of solid-state lighting (Blinded by the Light, February 2005) which put the commercial availability of ac-LED room lights just over the horizon. Back then, he pointed out several technical issues that he believed would likely delay the arrival of solid-state area lighting for the masses by at least a couple of years - a prediction that apparently was quite accurate. But with the predicted delays nearly past, and the chatter I'm picking up from my usual sources (and a few kind readers), it looks like we may start to see the first practical ac-LEDs hitting the market some time in 2007.
The most public indicator that ac-LEDs may be hitting the market in a big way is Seoul Semiconductor's recent press release (dated November 16, 2006) announcing the general availability of 20 W - 40 W-equivalent ac-LED lamps in late 2007. According to Seoul, their first product will be a 4 W, 160-lumen (approximately equivalent to a 20 W incandescent) unit that will retail for around USD $10. They also expect to offer a unit that puts out twice the light by the end of 2007.
Since the somewhat vague claims made by their 2005 announcement of an imminent, commercial ac-LED product remained unfulfilled for nearly two years, it's difficult to tell how much of their announcement is reality-based, but it certainly indicates there is a whole lot of activity going on over in Seoul these days. And the rumblings I'm hearing from behind several (very-tightly) closed doors in North America and Europe indicate that Seoul is not alone.
But whoever brings an ac-LED to market will face several difficult challenges which may or may not be obvious to many of the LED manufacturers, whose efforts to date have been primarily focused on indicator lamps, displays and other applications which have very different requirements than a general illumination product must meet. Ed Rodriguez, an old hand in the solid-state lighting industry who now works with Lynk Labs, shared a few important insights with me about what it will take for LEDs to make it in the general lighting market.
For one thing, color temperature is critical. According to Mr Rodriguez, a color temperature above 3500°K produces a harsh, unnatural light that is unacceptable to most consumers. Anybody who experienced the white glare of the early compact fluorescent lamps knows what I'm talking about. Since nearly all of the world's present white LEDs run at above 3500°K (and typically above 5000°K, with the attendant blue-white tint), producing a viable solid-state area light involves some significant tinkering with junction structures, phosphors, and the associated packaging.
Ac-LEDs will also have to deliver extremely high efficiency, if for no other reason than to keep the junction thermal loads at a level where heroic heatsinking measures are not required. The current wisdom is that an HB-LED will have to deliver around 60 lumens/W or better (around 35% more than Seoul Semi's current offering) to economically produce lamps that can replace 60 W - 100 W incandescent lamps. This is right at the current state of the art for most commercial HB-LED manufacturers, so devices with these efficiency levels will be a bit pricey and hard to get -- at least for a little while. But my spies tell me that we can expect LEDs with outputs of 70+ lumens/W hitting the market in retail quantities before we break out our 2008 calendars.
Finally, anybody who wants to really push ac-LEDs deep into the consumer market will probably have to make their products compatible with the existing cheapo SCR-type dimmers commonly found in many homes and offices. While there are many 110/220 Vac light sockets which are controlled with a simple switch, its hard to ignore the several hundred million installed dimmers in use across the world in both residential and commercial establishments. If an economical technique can be developed to allow an ac-LED lamp to be controlled by an unmodified dimmer, it will open up many more sockets worth of potential business that most of today's compact fluorescent products cannot touch.
This combination of efficiency, dimmer-friendliness, and high light quality are part of a larger set of critical requirements that ac-LEDs must meet if they are to get beyond specialty applications and onto the shelves of your local hardware or lighting store. While it's not certain that manufacturers have managed to satisfy all these requirements in a single, affordable product yet, there are some hopeful sounds coming from those closed doors which give me encouragement that 2007 may mark the year that the world's lighting bill starts to get a little smaller, and our grandkids' future begins to look a little brighter.
Comments? Questions? Tips on where I can get my hands on some ac-LEDs to road-test? Write me at: lgoldberg@green-electronics.com
