Solid-state lighting: The future looks bright
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Energy Quarterly 678
Solid-state lighting: The future looks bright Prachi Patel LEDs are gaining traction in lighting, but several research advances are needed before they find widespread use in homes and offices. With increasing funding from government and industry, this could happen within 10 years.
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he phaseout of the incandescent light bulb in 2005 in Brazil and Venezuela marked the beginning of the end of a 130year old technology. Many countries have since followed suit, and it is now time to move on to something better. Compact fluorescent lamps (CFLs) are the current chosen alternative. They use 75% less power and last 10 times longer. Plus, they can produce five times as much light perceived by the human eye for the same amount of power — a key measure called efficacy with units of lumens/Watt. However, CFLs contain toxic mercury, and their electricity-to-light conversion efficiency is unlikely to exceed 20%. Solid-state lighting is a more promising heir to light bulbs. The best white light-emitting diodes (LEDs) on the market today are 30% efficient, with efficacies of 130 lm/W compared to a CFL’s 35–80 lm/W. LEDs last three times as long as CFLs, use non-toxic semiconductor materials, and achieve full brightness immediately. The technology also can closely mimic natural sunlight, which incandescent bulbs achieve by emitting hues covering the entire visible spectrum. Perhaps most enticing is an LED’s potential to reach efficiencies around 70%, corresponding to 286 lm/W efficacy. That could make a big dent in the world’s energy consumption, provided people do not use more of the high-efficiency light. Lighting uses nearly a fifth of the world’s electricity, most of it for commercial, public, and residential buildings, which leads to 1900 megatons of carbon emissions per year, according to the International Energy Agency. High-efficiency LED light sources could slash this consumption by half. Since LEDs are made from semiconductors, the materials behind digital electronics, they offer the unique capability to be integrated with sophisticated sensors and controls. Innovative LED smart lighting would boost energy savings and make people more productive by adapting to a room’s layout or by adjusting brightness to the season or time of day. Significant research hurdles remain, but the solid-state lighting community is confident that extremely efficient, high-quality, affordable white LED light sources should be available within the next 10 years. “Recent market forecasts suggest that as much as half or more of new lighting installations could be solid state in a few
MRS BULLETIN
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VOLUME 36 • SEPTEMBER 2011
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years,” said Fred Welsh, who coordinates the U.S. Department of Energy’s solid-state lighting Roadmap. “[LED lights] will never be as cheap as incandescent bulbs, but they last a long time, save a lot of energy, and will be cost-effective. People are willing to pay a premium as long as the product performs.” Inorganic LEDs have come a long way since Nick Holonyak made the first dim red device in 1962
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