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Poor Fixtures Threaten To Jeopardize The Illumination Potential Of LEDs

LED manufacturers are running massive marketing campaigns to woo the illumination market with brighter, lower-cost chips. But this will be in vain if their customers continue to design inefficient fixtures, reports Richard Stevenson.
You re probably used to hearing that general illumination is going to be the next big thing for the LED. Manufacturers rarely talk about anything else, and have even conducted surveys to show that people feel safer in LED-lit parking lots. Researchers are using the illumination market to attach greater importance to their breakthroughs in chip performance, and market analysts are championing it as the key sector for LED growth over the next decade.

Strategies Unlimited market analyst Bob Steele, for example, is predicting that over the next five years LED sales to the illumination market will grow at a compound annual rate of 38%. This will propel the value of the sector, which already includes hundreds of fixture and luminaire companies throughout the globe, from $205 million in 2006 to $1 billion in 2011. These five years will also see a decline in the proportion of sales of red, green and blue LEDs, which are often used to illuminate the outside of buildings, and a growth in the white emitters that could replace conventional bulbs. White LEDs will account for some 60% of this illumination market by 2011.

These predictions, combined with the enthusiasm of the high-brightness LED makers and favorable legislation that could outlaw sales of incandescent bulbs in some parts of the world in the coming years, make it is easy to conclude that success in the general illumination market is nothing other than a formality. However, when you take a closer look at what is actually happening a different picture begins to emerge. The position of LEDs in the markets with the greatest potential is relatively weak, and many fixtures are failing to deliver the degree of efficacy promised by LED-based lighting.

As Steele points out, the current sales growth in the illumination market has not come from the replacement of light bulbs in homes or offices. Instead, it has actually resulted from increased sales of LEDs in dozens of smaller and less lucrative markets, of which architectural lighting is the largest. What has driven the market up until now is the functionality associated with these devices, says Steele, such as the colors and the opportunity to adjust the color. "Efficiency has not been the driver because, until quite recently, LEDs have not been so efficient that it stands out. If you were looking for efficiency you would use fluorescent bulbs, compact fluorescents or ceramic metal halides." The choice of colors and the low temperature of the light source has brought notable successes in lighting cosmetics counters and jewelers, where the LED illumination gives the gems an attractive sparkle. Another major triumph is the illumination of refrigeration display cases at Walmart, which is thanks to the relatively high efficiency of the devices at colder temperatures.

But getting a foothold into the residential lighting market is a different proposition, with the new construction market offering the best prospect for growth. However, even displacing the incumbent technology in new-builds is not easy, according to Steele. "New technology comes along that s more expensive and potentially better. But thousands – perhaps tens of thousands – of lighting designers and fixture companies around the world have built up an infrastructure to support incandescents and fluorescent lamps. That infrastructure does not just go away."

Steele also points out that changes in the lighting industry occur slowly, which hinders rapid adoption of any new technology. Although there is already tremendous interest in LED technology, sales of these products to lighting fixture companies amount to only a very small percentage of overall sales.

More worrying is the potential long-term damage that could result from sales of poorly designed, inefficient fixtures. "The LED makers are doing an excellent job of pushing the technology and it s likely that we ll see a 100 lm/W device on the market this year," said Steele. "But the fixture guys are not taking advantage of the efficiencies that are being given to them. This is a major problem in the solid-state lighting industry, dealing with propagating the skills that can produce efficient fixtures."

This stark warning from Steele is backed by a report from the US Department of Energy s (DoE) solid-state lighting commercial-product testing program, which was published this March. The DoE detailed the results of efficacy tests on various LED-based luminaires (see table for a selection of the results) and concluded that some products on the market today provide less light output than traditional sources and most have efficacies that are lower than those implied by the product s literature.

According to the report, the shortfall in performance arises because several product manufacturers take the LED efficacy figure and assign it to the lamp. This is misleading because many of the fixtures produce an efficacy that is only a third of that of the LED. Unfortunately, this inaccuracy regarding the product s efficacy is widespread – only one of the six luminaires assessed in the DoE report came with accurate values for its overall output and efficacy.

Buying something that fails to live up to its specifications is never going to win customer satisfaction. "Not only is the efficiency low," lamented Steele, "but it is so much lower than what is claimed. And when the claims of efficiency are not supported by the actual results, there s going to be a credibility problem. If the lighting industry gets disillusioned, that could set things back for years."

Steele believes that the low efficiency of many fixtures results from a lack of specific and necessary skills within the workforce of many companies. "We know from our surveys that most of the traditional lighting companies – even the largest ones – don t have in-house skills and people with the skill sets to do efficient fixture design with LEDs." The skills shortage, which should be resolved over time, is partly due to a lack of familiarity with the electrical systems used to power the LEDs and the techniques needed for thermal management and optical design. "But when we see products with poor efficiencies coming out of the smaller companies that understand LEDs, and how to use them, then that s a little bit daunting."

Not knowing how to install and use an LED lighting fixture can also shorten the diode s lifetime through poor thermal management and excessive drive currents. In addition, any failures in the fixture cannot be fixed by replacing a cheap bulb. Instead, repairs may involve replacing an entire light engine, an expensive procedure that can include fitting a new thermal management system and new optics.

These daunting issues facing LED fixtures may be casting a black cloud over the industry, but there is a silver lining in the form of a handful of fixture companies that are developing efficient products. This small list includes LED Lighting Fixtures (LLF), which was co-founded by former Cree CEO, president and chairman Neal Hunter. He shares Steele s concerns and believes that over-zealous marketing is producing misleading numbers, saying that there is no long-term benefit from releasing unreliable products or "tricked" numbers. These unrepresentatively high performance numbers can be generated by measuring the LED instantaneously, when it is not in thermal equilibrium, and by using low drive currents that produce higher device efficiencies.

LLF recently released a 6 inch downlighter that produces 650 lm at 11 W wall-plug power. The impressive lumens per watt figure of the lamp, which has a price tag below $75, has been verified by a third-party lighting lab at thermal equilibrium and demonstrates the benefit of good design that can produce a fixture efficiency of over 90%.

Steele adds that an optical design house that he visited recently is producing designs with optical efficiencies of 95%. This confirms that high-efficacy LED fixtures are possible and that the LED lighting industry is not condemned to the same path as the fiber-optic lighting sector, which failed to live up to its expectations 10–15 years ago. However, with the exception of large, vertically integrated companies such as Osram and Philips, successful market penetration is not solely in the hands of the chip makers. Although lower chip costs and better lumen efficiency will help to increase sales in the lighting market, using fixtures that can make the best use of the light from the LED is probably more important, and forging relationships with the companies who can facilitate this could hold the key to success in general illumination.

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