Abstract
Fuel-based and incandescent lamps convert ≤ 5% of the energy they consume into visible light; the remaining energy is given off as heat. The conversion efficiency of fluorescent lamps is approximately 20%. These very common sources of light convert the earth's energy sources mostly into waste heat and greenhouse gases. The increasingly precious energy resources and the increasing evidence of pollution-driven climate change demand that we reduce the energy and environmental costs of these forms of artificial lighting both by improving these sources and the employment of new forms of lighting. Light-emitting diodes (LEDs) convert electricity into light using semiconductor materials and, at present, represent the energy efficient technology of the future. Currently, LEDs are primarily used for interior and display lighting, as the efficiency of the diodes “droops” rapidly with an increase in the injected current that is necessary to achieve high-brightness. Exterior solid-state lighting within cities is being tested; however, much research, engineering and technological development remain necessary to achieve increased efficiency, low heat generation and the color temperatures and color rendering that are acceptable to human visual perception.
