LED Fluorescent Tube Fixtures: Efficiency Beyond Lumens vs Watts|
Fluorescent tube lights currently represent the overwhelmingly dominant form of lighting in most commercial and industrial applications. Their relatively high efficiency and long life coupled with the ability to provide good color rendering make them an obvious choice for use in warehouses, shopping centers, schools, offices and the like. Despite their obvious benefits, fluorescent tubes do retain several undesirable qualities that currently show little chance of being improved upon in the future. Since fluorescent lamp development has for the most part reached the far end of its maximum potential, there is little chance for any new or major breakthroughs to occur. Fluorescent lamps by their design are prone to several problems. For instance; although fluorescent lamps are efficient, they also require ballast assemblies in order to operate. These ballast although improved upon with the switch from magnetic units to electronic solid state circuitry, still represent an increased source of energy consumption, reducing the overall efficiency of the fluorescent tube. In addition, these ballasts tend to be prone to failures and operational deviances over the course of their lifetimes that adds further expense through replacement costs and reduced fixture effectiveness.
With the advent of the compact fluorescent, public awareness of the fluorescent lamp has been increased, in large part increasing the concern for the toxic materials necessary to a fluorescent lamps operation. Fluorescent tubes require mercury, a highly toxic substance, in order to function. In the fluorescent lamp, mercury vapor is excited through application of an electrical charge. This causes the mercury atoms to emit short length ultra-violet waves which then cause a phosphor to glow, resulting in radiated light. This process is much more efficient than incandescent lamps and generally results in an efficient and long lived light source. The problem, however, is what to do with these lamps once they have reached the end of their operational life span. The mercury vapor within these lamps poses a serious health risk and so these lamps must be carefully disposed of to avoid the mercury escaping from the fragile glass tubes should breakage occur.
One of the greatest sources of limitation for fluorescent tube lamps, however, stems from their basic design. In a fluorescent tube, light is created and radiated evenly over the entire tubes surface. Although a 60 watt fluorescent tube may produce up to 5,000 lumens of light output, this light is distributed over a wide area in all directions away from the tube. The end result is that light is spread in a 360 degree pattern, with any given area at a specific point from the lamp only receiving a small portion of the radiated illumination. In some cases, only 50% of a fluorescent lamps output actually reaches the intended area. With fluorescent tube fixtures, this necessitates the need for added directional control of the radiated light in order to achieve effective illumination of the targeted areas. To create this control reflectors and specially designed housings must be used. While such directional control can effectively reflect much of the otherwise wasted light into more productive directions, the reflective properties of the materials used and the shape of the reflectors still cause a great deal of the lamps output to miss the intended area.
With the arrival of LEDs into the commercial and industrial marketplace a serious alternative to the fluorescent tube was introduced. Although early in their appearance LEDs were still behind the fluorescent in overall output efficiency, they quickly advanced and are now poised to surpass the practical use lumen per watt ratio of fluorescent lamps. LEDs retain several distinct advantages over fluorescent lamps. For example; LEDs do not require any ballast for their operation. Using entirely solid state electronics, the current and output of LEDs can be easily regulated and maintained. There is no initial startup or warm up period normally associated with ballast equipped luminaries. This gives LEDs the benefit of not requiring a ballast which would add to their overall energy consumption. Reliability and cost effectiveness is also improved as there is no ballast to replace. LEDs are themselves solid state in their construction. They resemble circuits more than they do a lamp. There is no glass, no filament, and perhaps most importantly, no toxic gases or materials used in their construction.
One of the biggest advantages LEDs have over the fluorescent lamp, however, is their directional nature. As noted earlier, much of the light created by the fluorescent lamp is radiated over a very wide area. This reduces efficiency as light is lost to dissipation rather than reaching the intended target area. LEDs when set up in tube configuration, however, can be easily arranged to direct light in a precisely defined pattern and direction. Whereas fluorescent lamps require a reflector to gather and direct light, a comparable LED fixture needs none to direct all of its light onto the targeted surfaces. If we assume 50% directional efficiency with a 120 watt fluorescent fixture producing 8,000 lumens in 360 degrees of radiance, then approximately 4,000 lumens of light is lost to dissipation in unwanted directions.
An LED tube fixture like a Larson Electronics EPL-48-2L-LED Explosion Proof LED light with 4 foot LED bulbs producing approximately 4,500 lumens with 48 watts however radiates illumination only over a 150 degree area. The result is that much more of the light is directed downwards and over the intended target area, in effect putting more light where it is needed with less overall lumens and less wattage consumed. The net result is more light where it is needed, using less power, achieved with a fixture that will last over twice as long as a fluorescent with less maintenance and replacement costs.
When considering lighting options there is much more to the picture than just total wattage and lumens. How the light is produced, what it costs to operate, and how efficiently that light is applied are all contributing factors that must be taken into account if the best lighting solution is to be found. Although most of the allure surrounding LEDs has been centered around their efficient operation, as can be seen here, how they produce light and how efficiently that light is applied is no less important and a large part the overall efficiency equation.