Can LEDs Replace the Venerable Fluorescent Tube?|
Article- August 2013 By Larson Electronics.com
Larson Electronics T5HO-series LED Tube Lamp
Commercial and industrial illumination has been dominated by fluorescent light for over 50 years, and in that time billions of tubes have been installed and provided operators with savings and performance incandescent lighting could never hope to match. Although the fluorescent tube has been a proven performer however, this is not to say they haven’t been without their faults. Chief among these are the significant color shift a tube can display as it ages, the toxic mercury used in their construction, the overall fragility of the tube, and the erratic operation they often exhibit as they near the end of their operational life. Despite these issues, the fluorescent tube has remained a mainstay, in large part because there simply was no other lighting technology readily capable of providing equal or better performance for the dollar. This is changing now, and with new energy regulations directly targeting how we manage our lighting, the fluorescent tube may very well become obsolete in the near future.
With the passing of the Energy Independence and Security Act of 2007 and the Energy Policy Act of 2005, new lighting efficiency standards have begun forcing the phaseout of many inefficient lighting types, most notably incandescent bulbs, but also including some of the most common fluorescent tube types as well. Already magnetic ballast production has been discontinued and T12 tube production halted, and as more provisions contained within these standards reach their enactment dates, T8 and other fluorescent types will see changes as well. Although higher efficiency fluorescent tubes are currently available to meet these new energy standards, it’s been suggested by some industry experts that fluorescent lighting technology could very well be reaching the apex of its development potential. What this could mean for the future is a very limited range of fluorescent tube options and a need for alternatives capable of filling the gaps this would create.
The top contender for replacing the venerable fluorescent tube is the LED tube bulb. To see how well LEDs stack up to the tried and tested fluorescent tube, lets compare their performance aspects to see how they match up.
One of the leading reasons for the popularity of the fluorescent tube has been its very good efficiency. Producing around 75-87 lumens per watt depending on the type, fluorescent tubes far outperform incandescent bulbs and have typically been surpassed only by HID lighting systems. The caveat with this efficiency however is the actual total lumens delivered, which refers the amount of light actually reaching the targeted area. Because the fluorescent tube radiates light over the entirety of its surface, much of its light is directed upwards and outwards away from the intended area. Because of this fluorescent fixtures utilize reflector assemblies to redirect this light back towards the targeted surfaces. This is not entirely efficient however, and a significant portion of light is still lost to diffusion and poor directional control.
LEDs currently in normal production routinely produce on the order of 60 to 85 lumens per watt. Because of the rapid development pace LEDs are currently experiencing, these levels are expected to reach real world figures of 80 to 100 lumens per watt in the very near future. LEDs are already being produced which surpass 100 lumens per watt, but it will be some time before they become practical to produce. That being said, LEDs are currently on par with the lumen per watt output of fluorescent tubes. The basic lumen per watt ratio does not tell the whole story however. Because of the directional characteristics of LEDs, they radiate their light over a much smaller radius than the fluorescent tube. Whereas the fluorescent radiates of a 360 degree radius, an LED tube lamp will radiate over a 120-180 degree arc. This means that much less light is lost to undesirable radiation, and more light is directed towards the target surface. Because of this, LED tube lamps can actually produce less total output at lower wattages than a fluorescent tube, yet still deliver the same amount of light to the target, in effect making them more efficient.
The fluorescent tube is a long lived light source that greatly surpasses the operational life of the incandescent bulb, also another reason for its high popularity. The typical T8 fluorescent tube will have an operational life rating of around 15,000 to 25,000 hours. As before however, there are caveats. What is important regarding longevity is the actual lumen maintenance and color quality of the lamp over its lifespan. Fluorescent tubes experience color shifting and lumen loss as they age. This means that while a new fluorescent tube may produce clean white light, by the time it reaches 10,000 hours of operation it may shift light color towards blue and pink, creating a strange appearance and reducing its overall effectiveness and color rendering abilities. Additionally, by the time a fluorescent tube hits 10,000 hours of operation, it can have lost 60 to 90% of its original lumen output.
LEDs are typically rated at 50,000 hours of operation. Quality units such as those produced by Cree carry testing text indicating an 80% lumen retention over this period. This is an extremely good rating, and shows the LED as superior to all other forms of lighting when it comes to lumen maintenance over the life of the unit. Color shifting is a more complex subject for LEDs and currently little data exists with which to formulate accurate averages for quality units. However, it is known that color shifting with LEDs although just as possible with LEDs as with any other light source, does not appear to be any more significant or drastic.
The fluorescent tube is by its design a very fragile light source. The glass used in the construction of the tube is generally thin, and there is little to no reinforcement possible to increase its resistance to shattering. High strength glass tubes are available, but these still remain subject to severe damage in the form of shattering in the event of impacts. Additionally, the toxic materials used in the construction of the fluorescent tube make its durability all the more important. In particular, the mercury used within the fluorescent tube can be released and dispersed into the surrounding atmosphere in the event the tube is shattered, creating a serious hazard for any persons in close proximity.
LEDs are solid state in their design and have no glass or gases used in their construction. They resemble circuitry more than they do a lamp, and are typically very resistant to damage from vibrations and impacts that would shatter normal bulbs. LEDs also have no toxic materials to release in the event they are damaged, making them an attractive alternative for many consumers to the fluorescent if only for this reason.
Overall, we can see by looking at only a few performance parameters that although the fluorescent tube is indeed an effective light source, its performance is not without its problems. LEDs represent an alternative that produces similar performance in the form of output, and in other areas surpasses the fluorescent by a wide margin.
In the coming years as the new energy policies mentioned earlier reach full enactment, expect to see not only the incandescent begin to disappear from shelves, but many of the currently available fluorescent options as well. Fortunately, in their place will be an energy efficient alternative that not only meets our needs, but raises the bar for performance as well.