Wednesday, July 11, 2012 | Anita LaFond, Constructive Communication, Inc.
Editor's Note: This article originally appeared in the June 2012 issue of SMT Magazine.
In the continuing quest for energy-efficient lighting products, light-emitting diodes (LEDs) offer many advantages such as low-energy consumption, long service life, and compact size. These beneficial characteristics make LEDs very popular with fixture designers who want to expand into the lucrative and burgeoning energy-efficient lighting market. And with new federal energy standards coming into effect this year, LED light bulbs are becoming more prevalent.
The United States Department of Energy (DoE) estimates that switching to LEDs lighting over the next 20 years could save $120 million in energy costs, reduce electricity consumption for lighting by one-fourth, and avoid 246 million metric tons of carbon. LEDs, therefore, have the promising capability to significantly reduce lighting energy use and impact climate change solutions in the U.S.
Switching to LEDs
In January 2012, the first phase of the Energy Independence and Security Act of 2007 (EISA) went into effect. The “Energy Bill” is an energy policy intended to make better use of our nation’s resources and help the U.S. become more energy independent. Part of the law sets energy efficiency standards for light bulbs.
Under the new law, screw-based light bulbs must use fewer watts for a similar lumen output. Common household light bulbs that traditionally used between 40 and 100 watts must be redesigned to use at least 27% less energy by 2014. The second part of the law, which will go into effect in 2020, requires most light bulbs to be 60 to 70% more efficient than current standard incandescent bulbs. Many LEDs can meet this requirement today, and the industry is poised to provide viable, cost-efficient alternatives to standard lighting products.
As a substitute for incandescent lighting, compact fluorescent lighting (CFL) has also become more popular. Compared to a typical incandescent bulb (which lasts approximately 1,000 hours), a CFL has a life expectancy of nearly 8,000 hours. These statistics, though, are “dim” in comparison to an LED bulb with its life span of 30,000 to 50,000 hours. CFLs, however, contain mercury, a toxic substance that makes disposal a potentially hazardous situation. LEDs contain no toxic materials, while offering high-quality illumination that is superior to incandescents and CFLs.
Managing Excess Heat
Manufacturers are eager to meet the demand for energy-efficient LED designs and are looking for methods to make LED packages more cost efficient. Thermal management is one of the most important aspects of successful LED systems design. LEDs convert only 20 to 30% of their electric power into visible light. The remainder of the light is converted to heat that must be conducted away from the LED die.
Excess heat is an unwanted by-product of LED design because it reduces light output and shortens the life span of the LED bulb. Therefore, managing thermal output to dissipate heat is crucial to maximizing an LED’s performance potential. This is especially important for high-power/high-brightness LED applications such as streetlamps, traffic lights, and automotive head lights where long operating life is essential.