SSL,Solid State Lighting
Solid-state lighting,SSL, refers to a type of lighting that utilizes light-emitting diodes (LEDs), organic light-emitting diodes (OLED), or polymer light-emitting diodes (PLED) as sources of illumination rather than electrical filaments, plasma (used in arc lamps such as fluorescent lamps) or gas.The term "solid state" refers to the fact that light in an LED is emitted from a solid object-a block of semiconductor-rather than from a vacuum or gas tube, as in the case in traditional incandescent light bulbs and fluorescent lamps. Compared to incandescent lighting, however, creates visible light with reduced heat generation or parasitic energy dissipation, similar to that of fluorescent lighting. In addition, its solid state nature provides for greater resistance to shock, vibration, and wear, thereby increasing its lifespan significantly. Luminous efficiency is an important indicator of energy efficiency, but it does not tell the whole story, particularly with regard to directional light sources. Due to the directional nature of their light emissions, LEDs, potentially have higher application efficiency than other light sources in certain lighting applications. Fluorescent and standard "bulb" shaped incandescent lamps emit light in all directions. Much of the light produced by the lamp is lost within the fixture, reabsorbed by the lamp, or escapes from the fixture in a direction that is not useful for the intended application. For many fixture types, including recessed down lights, troffers, and under-cabinet fixtures, it is not uncommon for 40-50% of the total light output of the lamp(s) to be lost before it exits the fixture. LEDs,SSL, emit light in a specific direction, reducing the need for reflectors and diffusers that can trap light, so well designed fixtures can deliver light more efficiently to the intended location. While there is no standard definition of application efficiency, we use the term here to denote an important design consideration: that the desired illuminance level and lighting quality for a given application should be achieved with the lowest practicable energy input. Light source directionality and intensity may result in higher application efficiency even though luminous efficiency is lower relative to other light sources.
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