LED versus Metal Halide in Commercial Settings|
Article- June 2013 By Larson Electronics.com
Larson Electronics High Output High Bay LED Light
Commercial and industrial lighting accounts for a large portion of total electricity usage in the United States. Because of the rising cost of energy and the resulting interest in shifting to more energy efficient technologies, lighting is now becoming a major focal point for businesses interested in reducing their electricity usage and lowering their annual utility expenses. Everything from industrial manufacturing facilities to grocery store parking lots require the use of powerful and wide ranging lighting systems that consume large amounts of power on a daily basis. The cost of these fixtures is a part of normal business operating costs, which like it or not end up passed on to the consumer in the end. For companies looking to improve the cost of doing business without any increase in the costs passed on to their customers however, upgrading to newer lighting technology is an ideal option.
For businesses looking to improve their bottom line through lower operating costs, newer lighting technologies like advanced LED light fixtures offer a solution with little to no downside. The problem is that many businesses still consider their current metal halide systems entirely adequate, and for good reasons, and having been sold on the power and efficiency of HID lighting, are reluctant to explore other systems. However, current LED lighting development has surpassed the stage where LEDs can be considered a viable alternative to HID systems, and now offers potentially even greater benefit than even the best HID systems.
Although HID and metal halide lighting in particular is indeed a powerful and efficient lighting solution, there remain some issues that mitigate some of their benefit. Chief among these issues are heat and reliability. Although metal halide bulbs do not rely on a wire filament as does a traditional incandescent lamp, they still produce illumination through thermal radiation. This is to say, rather than heat a filament to produce light, they heat gases instead, which become hot enough to radiate energy as both heat and light. The end result is the same however, in that a prodigious amount of heat is created during operation of the lamp. This heat presents a problem in that it must be dissipated somewhere, which is usually the fixture itself and the surrounding atmosphere. This high heat can reduce the life of the ballasts needed to operate an HID lamp as well as increase the ambient temperature of the area in which the lamp is operating, thus increasing the workload placed on cooling systems such as AC units, and in turn increasing total energy usage as well as increasing maintenance costs.
Reliability is another issue with HID systems. The typical metal halide bulb loses efficiency and color quality degrades as the bulb ages during use. The color of the light produced by an HID lamp can change significantly well before the lamp actually fails, and when HID lamps begin to near the end of their useful life, the time needed to start and warm up the lamp increases as well as the voltage required. Additionally, HID lamps are prone to cycling as they grow older, a condition where the voltage required to operate the lamp becomes so high that the lamp begins flickering, sputtering, and oftentimes cycling on and off until the lamp eventually fails. A final reliability consideration is the ballast needed to operate HID systems. As well as the lamp itself which will require replacement around every 10 to 20,000 hours of operation, the ballast is also susceptible to periodic failures as it ages. This increases the potential for unexpected lamp downtime as well as the overall annual maintenance costs associated with operating an HID system.
LED lighting systems address and eliminate most of these issues. First and foremost, LEDs provide efficiency and reliability that either meets or exceeds that of HID systems. Although a metal halide lamp will average about 100-110 lumens of light output per watt, and LEDs currently 60 to 90 lumens per watt, LEDs can still offer an efficiency advantage. A typical 400 watt metal halide fro example can be replaced with a comparable LED fixture that consumes just 60 watts of power with no discernible loss in output or color quality. Although the lumen per watt ratio is currently still in favor of the metal halide, the sharper focusing and directional nature of the LED allows it to concentrate light where it is intended, resulting in more light delivered where it is needed. An LED is at its core a generally flat piece of semi-conducting material that radiates light over only the top portion of its surface. This results in a tight light radiation pattern and little light lost to radiation in all directions. A metal halide lamp on the other hand radiates light over the entire surface of its bulb, thus requiring reflector assemblies to direct light to where it is needed. The result is light output lost to dissipation and radiation away from the intended targeted areas.
In the reliability department LEDs have a strong advantage over all other forms of lighting, HID included. Because there is no actual heating or burning of metals or gases during the operation of an LED, there is far less degradation due to the effects of heating. LEDs as a result have life spans in excess of 50,000 hours, making them far longer lived than the general 15,000 to 25,000 hours commonly achieved by HID systems. It is important to note that although LEDs do produce far less heat than other types of lighting, they do produce heat and are more sensitive to overheating. However, LED designs take this into account and include housings designed to act as heat sinks to draw heat away from the LED emitters as well as built in controls that actively manage current to maintain heat levels within acceptable ranges.
LEDs also have the added benefit of no glass in their design, solid state construction, and no ballast required for operation. This means that with fewer components and no fragile materials, LEDs can withstand stresses and conditions that would cause early failure in other types of lighting systems. The result is lower maintenance costs and less downtime.
Although a switch to LEDs from HID systems can cost a little more initially, businesses stand to recoup this expenditure quickly due to the significant reduction in energy use LEDs provide. Additionally, the longer life span and greater durability of the LED means lower maintenance costs and less frequent relamping requirements, which further improves the savings gained from LEDs over the long term. And all of this, without negatively impacting lighting quality or effectiveness.