A breakthrough [1] in producing light emitting diodes could see LED production costs tumble as much as 75%. That's thanks to research [2] by a startup called Bridgelux [3], which has resulted [4] in a radical shift--Gallium-nitride LEDs can now be grown on silicon substrates for the first time in a "commercial grade."The tech leverages the huge, ultra precise and far cheaper silicon wafers that are used in silicon chip manufacture instead of the smaller, more expensive sapphire ones. The breakthrough has been to successfully grow white LEDs [5] on a silicon substrate to create devices that produce 135 lumens per watt of electrical power--well above what typical CFL bulbs can offer, and around 10 times better than old incandescent bulbs.
So how big a deal is this? Pretty darn big. After all, did you know that those tiny flickering LED lights that sprinkle the power buttons of pretty much every device you own often need sapphires as part of their production?
Sapphire is key [6] to producing white LEDs. It's artificially grown, rather than being dug up from the rock, but it's pretty much the same as the precious gem material you're probably thinking of--meaning it's rather expensive. Slabs of crystalline sapphire about four inches in size act as a substrate during LED production: The complex layered recipe of semiconductor chemicals that actually make up the LED devices is "grown" in various process on the precise surface of the sapphire, and then cleaved from it at the end before being chopped up and packed into the more familiar dome-shaped LED unit.
But sapphire is part of the main problem facing wider adoption of LED lighting--it makes the cost of high-brightness white LED light bulbs prohibitive compared to compact fluorescent bulbs, and many times more expensive than incandescent bulbs: $40 is a pretty common price bracket for LED bulbs that put out the equivalent light of a 60-cent 60W incandescent unit. Yet many people desire the LED tech very much because the bulbs can have an incredibly long life span, measured in tens of thousands of hours, and they consume much less electricity than their older equivalents.
Now Bridgelux thinks that after the two to three years needed to ramp its new tech up to production scale, the cost of producing LEDs will drop by three-fourths. Ten times greater electrical efficiency, ten times the lifespan of old bulbs and a much more affordable cost? Yup--soon every light you encounter may be an LED one.
We are glad for creating this LED lights. We are hoping that it could be a better replace for the old ones. But are these products are safe? What are the disadvantages it could bring to humankind? I'm hoping for a reply about these.
ReplyDeletehttp://en.wikipedia.org/wiki/Light-emitting_diode should provide information on your question.
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Efficiency: LEDs emit more light per watt than incandescent light bulbs.[83] Their efficiency is not affected by shape and size, unlike fluorescent light bulbs or tubes.
Color: LEDs can emit light of an intended color without using any color filters as traditional lighting methods need. This is more efficient and can lower initial costs.
Size: LEDs can be very small (smaller than 2 mm2[84]) and are easily populated onto printed circuit boards.
On/Off time: LEDs light up very quickly. A typical red indicator LED will achieve full brightness in under a microsecond.[85] LEDs used in communications devices can have even faster response times.
Cycling: LEDs are ideal for uses subject to frequent on-off cycling, unlike fluorescent lamps that fail faster when cycled often, or HID lamps that require a long time before restarting.
Dimming: LEDs can very easily be dimmed either by pulse-width modulation or lowering the forward current.
Cool light: In contrast to most light sources, LEDs radiate very little heat in the form of IR that can cause damage to sensitive objects or fabrics. Wasted energy is dispersed as heat through the base of the LED.
Slow failure: LEDs mostly fail by dimming over time, rather than the abrupt failure of incandescent bulbs.[86]
Lifetime: LEDs can have a relatively long useful life. One report estimates 35,000 to 50,000 hours of useful life, though time to complete failure may be longer.[87] Fluorescent tubes typically are rated at about 10,000 to 15,000 hours, depending partly on the conditions of use, and incandescent light bulbs at 1,000–2,000 hours.
Shock resistance: LEDs, being solid state components, are difficult to damage with external shock, unlike fluorescent and incandescent bulbs which are fragile.
Focus: The solid package of the LED can be designed to focus its light. Incandescent and fluorescent sources often require an external reflector to collect light and direct it in a usable manner.
[edit]Disadvantages
High initial price: LEDs are currently more expensive, price per lumen, on an initial capital cost basis, than most conventional lighting technologies. The additional expense partially stems from the relatively low lumen output and the drive circuitry and power supplies needed.
Temperature dependence: LED performance largely depends on the ambient temperature of the operating environment. Over-driving an LED in high ambient temperatures may result in overheating the LED package, eventually leading to device failure. Adequate heat sinking is needed to maintain long life. This is especially important in automotive, medical, and military uses where devices must operate over a wide range of temperatures, and need low failure rates.
Voltage sensitivity: LEDs must be supplied with the voltage above the threshold and a current below the rating. This can involve series resistors or current-regulated power supplies.[88]
Light quality: Most cool-white LEDs have spectra that differ significantly from a black body radiator like the sun or an incandescent light. The spike at 460 nm and dip at 500 nm can cause the color of objects to be perceived differently under cool-white LED illumination than sunlight or incandescent sources, due to metamerism,[89] red surfaces being rendered particularly badly by typical phosphor based cool-white LEDs. However, the color rendering properties of common fluorescent lamps are often inferior to what is now available in state-of-art white LEDs.
Area light source: LEDs do not approximate a “point source” of light, but rather a lambertian distribution. So LEDs are difficult to apply to uses needing a spherical light field. LEDs cannot provide divergence below a few degrees. In contrast, lasers can emit beams with divergences of 0.2 degrees or less.
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