An LED (Light Emitting Diode) is a form of solid-state lighting that is extremely efficient and long-lasting. While incandescent and fluorescent lights consist of filaments in glass bulbs or bulbs that contain gases, LEDs consist of small capsules or lenses in which tiny chips are placed on heat-conducting material.
LEDs measure from 3 to 8 mm long and can be used singly or as part of an array. The small size and low profile of LEDs allow them to be used in spaces that are too small for other light bulbs. In addition, because LEDs give off light in a specific direction, they are more efficient in application than incandescent and fluorescent bulbs, which waste energy by emitting light in all directions.
Higher Power-to-Light Conversion
The key strength of LED lighting is reduced power consumption. LED’s are available at Lumen efficiency of 120 Lum / Watt compared to 65-80 Lum / Watt of CFL, 45 Lum /Watt of Mercury vapour and 75 Lum /watt of metal halide or 94 Lm/watt of sodium Vapour.
Conventional light-bulbs waste most of their energy as heat. For example, an incandescent bulb gives off 90 percent of its energy as heat, while a compact fluorescent bulb wastes 80 percent as heat. LEDs remain cool. In addition, since they contain no glass components, they are not vulnerable to vibration or breakage like conventional bulbs. LEDs are thus better suited for use in areas like sports facilities and high-crime locations.
Because they produce no infrared energy, the beam of light from an LED source is cool. However, LEDs do produce waste heat during its operation. This must be properly removed from the lighting system to maximize fixture performance and to avoid damage to the LEDs. In well-designed LED lighting fixtures, heat removal is accomplished through carefully designed and engineered heat sinks that draw heat away from the LEDs and dissipate it into the air surrounding the fixture housing.
Better Delivered Light
Total light output measured as lumen output is an inadequate measure of the suitability of a lighting fixture for a given task. A better measure is delivered light — how much light a fixture delivers to a unit surface area, as measured in lux (lx) or footcandles (fc). It is the delivered light over a surface that provides you visibility: more lumens over a targeted area means better illumination.
It implies that we must discount any light lost in the fixture housing (often over 30%), as well as any light lost as a result of lensing, shading, and filtering. Since incandescent and fluorescent lamps emit light in all directions, you must further discount any light emitted in a direction away from the target area. For instance, a standard 60-watt incandescent lamp emits a total of about 800 lumens, but the light is emitted equally in all directions. Therefore, when you’re reading at your office desk, your desk (or the book) does not receive all 800 lumens from your desktop lamp, nor do you need it to.
According to the IES, serious reading requires an average of 50 lumens on a one square foot area (say, your book). An under-cabinet LED light can deliver this much illumination on your page while consuming only about 6 watts.
LED lighting fixtures are integrated systems in which the light sources (LEDs), the fixture housing, and the primary optics are inseparable. Lumen measurements of LED lighting fixtures, therefore, are performed on the entire system, and already account for light lost to the fixture housing and lensing. Furthermore, since LEDs are inherently directional, they emit almost all of their light output in the desired direction, rather than dispersing it in all directions.
For colored lighting, since LEDs natively produce intensely saturated colored light, there is no need to use any gel or filter for producing colored lights. These block a significant percentage of a fixture’s light output (over 90% for certain shades of deep blue). Therefore, LEDs ideally provide intense light source.
Therefore, comparing lighting fixtures on the basis of delivered light, LED fixtures generally perform better than the conventional fixtures, while consuming far less energy.
The operational life of current white LED lamps is 50,000 – 80,000 burning hours as compared to 750 to 2,000 hours for an incandescent bulb, 5000 – 10000 hrs of CFL and FLT, 18000 hrs of T5 lamp, 5000 hrs of Mercury vapor, 8000 hrs of Metal halide and 8000 hrs HPSV lamp.
LED lifetimes are rated differently than conventional lights which are finished when the filament breaks. In comparison, LEDs typically just fade gradually. The life of a LED light is typically defined as the average number of hours until light falls to a certain percentage of initial brightness in lumens. White light sources used for general illumination are commonly considered to be at the end of their useful life when their light output falls below 70% of initial output. For white and colored accent and non-task lighting, the lumen maintenance threshold is often considered to be 50%.
Well-designed LED lighting fixtures can retain 70% of their initial output for 50,000 hours or more, depending on operating conditions and other factors. At 24 hours per day of continuous use, such fixtures can deliver useful light for six years or longer — many times as long as incandescent sources, and up to twice as long as long-life fluorescent sources.
Factors that can cause lumen depreciation include drive current and heat generated within the device itself.
LED’s are available in wide range of colors designated by the color temperatures ranging from 2700K to 6500K which are dark yellow, mild yellow and ultra white.
LED’s are dimmable. Hence any reasonable fluctuations in input voltage will not affect life of LED as it happens with all other lamps.
LED’s produce no UV.
LED’s being no filament lamp shock and vibration does not affect its life as it happens with all other lamps.
In the search for energy-efficient lighting, LEDs have proven to be the most efficient light source available. EnergyStar rated LEDs use at least 75 percent less energy than traditional incandescent bulbs and last 25 times longer, according to the U.S. Department of Energy. LEDs even outdo CFL (compact fluorescent lighting) bulbs in efficiency, primarily because they have twice the lifespan of CFLs.
Poorly designed LEDs may not be long-lasting or efficient. LEDs that are EnergyStar-qualified should provide stable light output over their projected lifetime. The light should be of excellent color, with a brightness at least as great as conventional light sources and efficiency at least as great as fluorescent lighting. The LEDs should also light up instantly when turned on, should not flicker when dimmed and should not consume any power when turned off.
A Rapidly Changing Landscape
In dozens of nations, green initiatives and energy-efficiency directives are hastening the shift from conventional lighting systems to LED lighting systems, which have the lowest energy consumption and environmental impact, the longest useful life, and the lowest total cost of ownership and operation. Suppliers must also take an active role in educating lighting consumers about the specific advantages of LED lighting and how it differs from conventional lighting.
LED lighting is a fundamentally new kind of lighting, using new principles, materials, and means of control. When properly used, LED lighting systems have the ability to improve both the quality of the environment and the quality of people’s life.