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January 25, 2005...At the annual CS Outlook Conference in Dallas this past December, the fact that their are few, if any, standards in solid state lighting (SSL) was an issue raised by a number of people throughout the 2.5 days of discussion. I've been pondering the issue of SSL standards for some time and have concluded that setting the standards isn't the task at hand... there are various bodies that will ultimately do just that. The task before this fledgling industry is mapping out what has to be done in the meantime, and driving those standards. At Outlook I noted to the attendees that we're only just now at the point where we agree on worthy figures of merit, like lumens per watt lm/W. The topic of lm/W was addressed online in our Oct. 20th editorial, "Dr. Bob" Tells Us How White LEDs are Made, authored by our three Dr. Bobs (Karlicek, Steele & Walker)

One of my many pleasant and informative conversations with key CEOs in the industry yielded a likely starting place. The conversation was with Joel Dry, President/CEO of OptoLum. Here's what Joel suggested: "The first thing one should do when discussing standards for a new technology product is to consider the standards already in place for the old technology which you plan to replace. The best way that I know to do that in the case of solid-state lighting is to pick up a package of lightbulbs and review the metrics used to measure the product.

Lumens per watt
"The first thing you will see is generally the wattage, in the case of my example, 60W. Most people say a 60 watt bulb is a 60 watt bulb, not true. If you have a 60 watt incandescent, it produces a different light output from a 60 watt halogen. Then there is a 15 watt fluorescent which will produce similar light output to a 60 watt incandescent albeit in a somewhat different shape and with widely varying quality. So, wattage is not a good metric for light.

"If you look more closely, most bulb packages have another metric that is highly valuable, lumens. In the case of a GE Reveal 60 watt incandescent, the light output is 660 lumens. In the case of an average 60 watt halogen, it could be 840 lumens give or take. A 15 watt fluorescent bulb from GE produces 800 lumens. A 30 watt OptoLum BL-800 LED lamp produces 840 lumens. What you may have noted in the above numbers is that I contrasted lumens and watts. The reason for this is to illustrate how much light (lumens) are garnered by the amount of expended energy (watts). So a truly valuable metric for the lighting industry is lumens per watt (lm/w). The 60 watt incandescent above yields 11 lm/w, the 60 watt halogen yields 14 lm/w, the 15 watt fluorescent yields 53 lm/w, and the 30 watt LED lamp yields 28 lm/w." (Note... If you carefully re-read that October Dr. Bob editorial, you'll note this is a shorter, less technical description of how one arrives at the lm/w metric.)

Hours of Life
"Another factor of importance to the lighting industry is lifetime. The examples above vary widely. The incandescent is 1,000 hours, the halogen is 2,000 hours, the fluorescent is 7,000 hours, and the LED is 50,000 hours. An interesting point in this is how the lifetime is measured. In the case of the more traditional technologies, life is measured as rated life which is the time in which half of the samples are burned out and half are still functioning. The LED industry, on the other hand, goes with a different measurement: the time in which the sample LEDs reach half of their original brightness. This is done primarily because there is rarely a catastrophic failure of LEDs, so the previous method would not be practical. A better more universal standard certainly needs to be considered for lifetime of LED lighting, but we can leave that for another day.

Total Cost of Ownership
"So at this point, we now recognize two factors that are of key importance, lm/w, and hours of life. There is another key factor that controls the future of LED technology and that is cost. How do we measure cost as it relates to light. As stated above, light is measured in lumens and since we are in the U.S. money is measured in dollars so we will go with lumens per dollar (lm/$), to be geographically sensitive, you could go with lumens/yen, lumens/rupi, lumens/pound, lumens/euro, whatever floats your boat. In the case of the example lamps, the incandescent costs about $1 and produces 660 lumens so the figure is 660 lm/$. The halogen produce 840 lumens and costs $5 so it is 168 lm/$. The fluorescent lamp produces 800 lumens at a cost of $6 or 133 lm/$. The LED lamp produces 840 lumens at a cost of $200 or 4 lm/$. At this point it is starting to look pretty bad for the LED source, but that is not the end of the story.

"The most important metric that we need to use is Total Cost of Ownership (O) and this is a compilation of upfront cost, power cost, and maintenance cost over time. This figure is somewhat difficult to settle on since there are so many variables and there will inevitably be differences across geographies. Ultimately, total cost of ownership is what will bring about the revolution of solid-state lighting, so it should be near and dear to all of our hearts. A couple of things have to be settled first to get started, so I will pick some generally accepted numbers. The figure needs to be over a broad time frame to see the results so I will pick the life of the LED lamp as a good starting point. So how do we settle on that? I will assume that a work day of 8 hours will be standard for the light fixtures, so we can take the 50,000 hour life of the LED fixture and divide by 8 which gives us 6,250 days of use or 17 years. So we will base our figures on an 8 hour day over 17 years. Additionally, we will assume that electricity costs 10 cents a kilowatt hour as a baseline. For simplicity of math, I will not include the forecast 3% per year power increase. Another figure that would be useful is $10 per hour for maintenance as the most promising lighting markets are commercial applications. Finally, we will assume that a maintenance person can change six lamps per hour by the time that ladders or lifts are factored in.

"So the Total Cost of Ownership (O) takes into account bulb cost, power cost, and labor cost, complicated yes, but necessary. The Incandescent will need to be replaced 50 times in the course of the life of one LED lamp, the halogen will need replacement 25 times and the fluorescent will need replacement 7 times. From this point on I will resort to lists for greater simplicity.

Initial cost of Lamp: Incandescent $1, Halogen $5, Fluorescent $6, LED $200,

Replacement cost over 50,000 hours: Incandescent $50, Halogen $125, Fluorescent $42, LED $0

Power cost over 50,000 hours: Incandescent $300, Halogen $300, Fluorescent $75, LED $150

Maintenance cost over 50,000 hours: Incandescent $83, Halogen $42, Fluorescent $12, LED $0

Total Cost of Ownership over 50,000 hours: Incandescent $434, Halogen $472, Fluorescent $135, LED $350

"As you can see, our SSL industry has some significant headway to make in total cost of ownership in order to compete with fluorescent lamps, but we have already overtaken incandescent and halogen lamps. On the bright side, our industry makes strides every year in lumens per watt and lumens per dollar, while fluorescent is remaining virtually flat. Other factors that allow LEDs to make gains on fluorescent is a superior quality of light output, better controllability, and the fact that fluorescent lamps contain mercury, which is a highly toxic substance. I believe that if we can settle on using lighting industry metrics and standards then we are better suited to move forward within that industry. Furthermore, we need to advance the Total Cost of Ownership metric within the lighting industry in order to demonstrate our relative value compared to incandescent lamps and to illustrate where we need to be in relation to fluorescent lamps."

To contact Joel Dry directly to talk about helping drive SSL standards, you can contact him at "joel@optolum.com" and his OptoLum office direct tel in Phoenix Arizona USA is: +1 602-808-8811 or you can contact me at the coordinates, below....

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