Solid-state lighting (SSL) represents a family of novel general lighting technologies that generate light by passing current through a crystalline solid rather than a heated element, gas or plasma. The most popular is the light-emitting diode, or LED, which has rapidly evolved from indicators to illumination over the past decade and stands poised to capture a large share of the general lighting market over the next one.
LED lighting offers several distinctive features and benefits. LEDs are inherently directional sources that deliver light with a high efficiency and over a long service life marked by few spot-source failures. They are very small, enabling compact traditional luminaire designs while inspiring unprecedented designs and approaches. They produce no radiated ultraviolet (UV) or infrared (IR) energy in the light transmission, start and operate reliably in cold temperatures, contain no mercury, and have no filament or arc tube that can break. In the architainment realm, they are very good at producing dynamic saturated colors. And they are inherently compatible with digital controls, enabling intelligent luminaires.
These benefits have led to growing demand for LED lighting, accompanied by exponential growth in products and suppliers: from architainment to niche to general lighting; from indoor to outdoor; and from luminaires to retrofit lamps. In 2009, about two out of three of the some 200 lighting products entered in the Lightfair Innovation Awards were LED-based, and they won most of the top awards; in 2012, nearly all were LED and swept the top awards.
The Department of Energy  (DOE), which has been an active supporter of LED technology, sees LED as key to achieving a 50 percent reduction in national lighting energy consumption. DOE predicts that continuing improvements in efficacy (lumens of light output per watt of electrical input), service life and cost will accelerate demand until LED becomes the dominant light source by 2025. Calculating market share based on lumen-hour sales, LED is expected to achieve a share of 10 percent by 2015, 36 percent by 2020, 59 percent by 2025 and 74 percent by 2030. The hottest potential near-term applications are outdoor general lighting and residential. For example, LED’s share of lumen-hour sales in the outdoor stationary lighting sector is expected to increase to 26 percent by 2015.
DOE predicts average efficacy of cool-white LED general lighting will improve from 70 lumens per watt in 2010 to 145 lumens per watt by 2015 and 193 lumens per watt by 2020, finally reaching a plateau of about 200 lumens per watt between 2025 and 2030. In contrast, the efficacy of today’s 4-foot T8 general lighting is about 86 lumens per watt. What’s more, the average life of LED indoor luminaires is expected to increase from 25,000 hours in 2010 to 44,000 hours in 2015 and 73,000 hours or more by 2020, while the average life of LED outdoor luminaires is expected to increase from 50,000 hours in 2010 to 68,000 hours in 2015. Today’s conventional lighting technologies simply cannot compete with these levels of performance.