Most people with a strong interest in green lighting know that Philips Electronics is the first company to submit a prototype LED replacement for the common 60-W incandescent light bulb in an effort to claim the U.S. Department of Energy’s $10 million Bright Tomorrow Lighting Prize, or L Prize.
Most news outlets have simply run the press release. Electronic Design readers expect a little more depth, so we dug a little deeper. It's been a while since we've reported on the prize, so we decided to see what was new. Some things haven’t changed. For example, Congress still hasn’t appropriated any money for the prize. But some things have, like clarifications about domestic content. Here are some of the more obvious questions and their answers.
What do L Prize winners actually win, and who provides it?
Right now, the cash award is somewhat ephemeral. The official L Prize Web site says it’s “Subject to the availability of funds,” adding that “The Energy Independence and Security Act of 2007 (EISA) provides for cash prizes of $10 million for the first successful product in the 60-W incandescent lamp category.” As far as I can tell, no Congress has appropriated the prize money.
That’s not to say there aren’t ancillary benefits. For example, EISA does call for the government to start to develop purchasing guidelines for procuring the replacement bulbs for its own use. Also, the winner will be acknowledged and promoted by the DOE. Philips has already received a lot of favorable press simply for being the first to submit a candidate. Another boon to companies whose products successfully meet the technical performance specifications is that they can carry the special Energy Star SSL label. This will save them the effort of retesting the product specifically for Energy Star.
And the U.S. government isn’t the only entity involved in handing out prizes. The DOE hopes that organizations called Energy Efficiency Partners (EEPs) will provide additional incentives, promotions, and marketing to help move suitable products to market. “Additional qualifiers will be identified through the competition to participate in the voluntary EEP prizes,” the DOE Web site says. At the moment, there are 27 EEPs, primarily in the electric utility sector.
What does it take to win?
• Efficiency better than 90 lumens/W (today’s incandescents and compact fluorescents manage 10 to 60 lumens/W
• Energy consumption of less than 10 W
• Output greater than 900 lumens (same as a 60-W incandescent)
• Lifetime of at least 25,000 hours (25 times the average incandescent)
• Color Rendering Index (CRI) greater than 90 (100 represents rendering equivalent to a black body)
• Color temperature between 2700 and 3000 K (like an incandescent)
In addition, the performance specifications for the lamps require “continuous dimming down to at least 20% of maximum light output without visible flickering.” Achieving that is tricky, because LEDs don’t have the long thermal time constants of incandescent filaments. Also, the lamp products are required to be compatible with “at least three widely available residential dimmers.” The requirements refer to “resistive,” “inductive,” and “electronic” control, but that really comes down to three ways of forward-phase control, meaning SCR or triac dimmers that work by chopping the ac line voltage.
Requiring the LED bulbs to work with legacy triac dimmers necessitates some electronic wizardry because those dimmers expect to see the filament of an incandescent bulb on their output. For a description of how National Semiconductor approaches the problem, see “High-Brightness White LEDs Light The Way To Greener Illumination”) and scroll down to the “Dimmer Deconstruction” subhead. (NXP has designed its own chip, which, presumably, Philips uses in the lamps it submitted for the L Prize.)
Can a Dutch company win the prize?
Is Philips really Dutch? Is GE 100% American? It’s a global economy. “The entrant which submits the SSL product is required to be incorporated in and maintain a primary place of business in the United States; or must be a U.S. citizen or lawful permanent resident in the case of an individual,” the L Prize Web site explains.
The domestic content requirements for the LED light bulb come down to the LED chip itself: “The LED die or chip… must be manufactured in the U.S. There is no requirement for other components or assembly of components for the entry product.” This is amplified further in the answer to a different question about phosphors. The issue arises because the photons that produce the white light in high-brightness white LEDs come from a phosphor that is activated by primary photons from a blue LED. (Interestingly, there was a time when blue LEDs were thought to be impossible.)
Obviously, “white” isn’t a color in the spectrum, so the phosphor has to produce a balanced mix of photons that combine to produce a white light of some color temperature. Hence, the phosphor is a critical component of the lamp. Nevertheless, for the purposes of the L Prize, “phosphor systems are not considered to be an integral part of the epitaxy,” so the phosphor material can come from overseas.
All of these restrictions apparently refer to the product submitted for the prize, not future mass production. This is acknowledged in a somewhat convoluted way in answer to a question posed about a year ago. The site says, “In order to be eligible for the competition, the LED die or chip submitted in a product entry must be manufactured in the United States. It can not be produced elsewhere, regardless of the ultimate intent for production.” That’s an acknowledgement that in the long run, all high-volume fabs are overseas.
In talking to LED makers like Cree and distributors like Arrow that handle LEDs for illumination, I get the strong impression that we aren’t simply going to start with 60-W nightlights and continue on to replace all the bulbs in our homes with 100s and 150s and three-way screw-in replacements for incandescents and compact fluorescents. Instead, what the DOE is doing with the prize is supporting a bridge technology to a future where there will be a new paradigm for what the industry calls “lumieres” and my parents used to call “lamps.” For one thing, is there really any purpose in providing a screw-in socket for a light source that will last for tens of thousands of hours?
More than that, I’m told, to achieve illumination efficacy, we need to stop thinking like Thomas Edison and scrap the idea of light sources as blown-glass bottles with fire inside. The new lighting reality lies in managing photons so they go where we want them. Look to LED streetlights for examples. They required a new optical approach along with more sophisticated thermal management—things designers are just beginning to explore. So hooray for Philips, the original “Gloeilampen-fabriken,” as it straddles the lighting divide and we move ahead to a bright but differently lighted future.
Bright Tomorrow Lighting Prizes