The LED bandwagon. As more companies design or retrofit their buildings to reduce energy consumption, many may turn to LED lighting solutions in their efforts to reduce energy costs. But the multi dollars questoin is: Am I doing the right thing? Am I investing into the future?
My research conclusion is this. Give it another couple of years LED will get there. As Britney Spears once sung it, "I'm not a girl, but not yet a woman". But today, while promising, current available LED technology may not be the best solution to fix your company’s energy inefficiencies. To back this up, allow me to make the comparison of LED and T5 lighting technologies and illustrates the advantages and disadvantages of both energy efficient lighting solutions.
Efficiacies of T5 & LED
Institute of Electrical Engineers (IEEE) studies discovered and concluded that T5 bulbs produce more light (lumens) compared to the amount of power they consume in Watts in comparison to LED.
The study argued that; “For general illumination applications, the LEDs in this comparison are inferior to T5 lamps in terms of energy efficiency and efficacy.” That is easily proven by 14 Watt T5 fluorescent lamp has the efficacy of 96.7 lm/W.
Another study performed by The Lighting Research Center found that the more frequently used 21 Watt T5 bulb produced a high efficacy rating of 100 lm/W, while GE is currently manufacturing a 26 Watt T5 bulb that has a rating of 111 lm/W. What we have for LED today is the most of 90 lm/W. This is proven when you put both side by side, the T5 bulb performed better than its estimated 96 lm/W rating, while the LED performed significantly worse than its 90 lm/W rating.
Heat Dissipation and Overheating
Have you heard people telling you that a no good heat dissipation system for a LED luminaire will decrease it's life significantly? That guy is telling you the hard truth.
The case study by IEEE also examines the heat dissipation of each lamp and found that the T5 lamp dissipated about 73% of its total lamp power as heat. However, the LED lamp in this study dissipated about 87% - 90% of its input power as heat. This high heat dissipation percentage can greatly increase additional cooling costs in your building, significantly reduce bulb lumen life, and lead to possible bulb failure.
As Randal Smith from Lighting Design Lab News once put it, “Heat is the great enemy of lighting system performance, and LED systems are no exception."
Have you seen a LED outdoor screen or billboard having AC units to cool it off? The luminaire will need the same. Operating over long hours, and to prevent heat concentration in an LED fixture and avoid LED bulb failure, users must provide additional system cooling, resulting in higher HVAC costs and greater energy use.
Upfront Costs
IEEE’s case study also demonstrates that T5 lighting is a more cost effective lighting solution. The study records the source cost of both T5 lighting and a T8 sized LED bulb using the measurement of $/1000 lm. Study results show that T5 bulbs performed at a source cost of approximately $3 per 1000 lm, whereas the best comparison rival single LED bulb cost more than $70 per 1000 lm. The up-front cost differential between fluorescent fixtures and LED fixtures is also substantial. In Malaysia, you get an average of myr40 for T5 vs. myr200 for LED. LED retrofitting requires significant upfront investment in contrast to emerging fluorescent technology (i.e. at least 3 to 4 times more expensive). This significantly higher per-unit fixture cost proves that LED retrofitting is an expensive proposition. Yes it may hurt you bad in the pocket.
I've personally come across a company that do not sell you LED up front but they do it based on profit sharing basis. Not heard of them much lately, I do not want to jump into conclusion but, maybe the outlay was underestimated.
CRI Index
LED has a CRI of 75. T5 will have a CRI of 85.
LED and Lifetime
Almost everybody have boasted about the lifetime of LED. 100,000 hours. Mind you, that is 11.5 years if you leave it on for 24x7.
And yes, it started as to have 100k hours, then now you'll see the more common ones with 50k hours. I do not doubt that LED will have a longer lifetime than any other non solid state light. However, what I would like to point out is this.
The actual longevity is not yet proven. This is because:
(i) the actual lifetime of an LED is dependent on its thermal environment
(ii) inadvertent overheating of LEDs typically results in increased lamp lumen depreciation (it's proven that LED will only maintain 70% of the lumens over time). In other words, the useable lumens hours (not the lamp lifetime hours) may be less than what you're expecting. Unless of course you will need to over-spec your initial design to factor in this. But won't that defeat your Building Energy Intensity, if you know what I mean.
Let me put it this way to challenge the lifetime of LED, going back to point no. 3, therefore, by spending equivalent monies on a T5 bulb and the nearest comparable LED bulb, you could buy enough T5 bulbs to last over many times of life hours of the LED. Don't you agree.
Conclusion
I'm not a girl, but not yet a woman nicely put in what LED is today.
I've no doubt at all LED will be the "thing" for lighting in very near future, but until that time comes, the most significant performance barriers that LED technology will have to overcome include high lumen depreciation, low efficacy, color temperature, and color rendering index values.
So let's stick to where it's strength is today - as a decorative and support lighting for now.
- Administrator.
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