Basics of Light Emitting Diode Lighting

LED Lighting

lighting-emitting-diode-strips

Light emitting diodes, commonly called LED’s, are real unsung heroes in the electronics world. They do dozens of different jobs and are found in all kinds of devices. Among other things, they form numbers on digital clocks, transmit information from remote controls, light up watches and tell you when your appliances are turned on. Collected together, they can form images on a jumbo television screen or illuminate a traffic light.

Basically, LED’s are just tiny light bulbs that fit easily into an electrical circuit. But unlike ordinary incandescent bulbs, they don’t have a filament that will burn out, and they don’t get especially hot. They are illuminated solely by the movement of electrons in a semiconductor material, and they last just as long as a standard transistor. The lifespan of an LED surpasses the short life of an incandescent bulb by thousands of hours. Tiny LED’s are already replacing the tubes that light up LCD HDTVs to make dramatically thinner televisions.

An LED is what’s called a “solid-state lighting” technology, or SSL. Basically, instead of emitting light from a vacuum (as in an incandescent bulb) or a gas (as in a CFL), an SSL emits light from a piece of solid matter. In the case of a traditional LED, that piece of matter is a semiconductor.

Stated very simply, an LED produces light when electrons move around within its semiconductor structure. A semiconductor is made of a positively charged and a negatively charged component. The positive layer has “holes” – openings for electrons; the negative layer has free electrons floating around in it. When an electric charge strikes the semiconductor, it activates the flow of electrons from the negative to the positive layer. Those excited electrons emit light as they flow into the positively charged holes. The problem with LED’s as primary home lighting is that while they emit a lot of light, the structure of an LED causes some of that light to get trapped inside. So an LED bulb has traditionally been dimmer than incandescent bulb, and most people want their lamps and ceiling fixtures to be pretty bright.

Recently, though, LED’s bulbs have brightened up. You can now find LED replacement bulbs that emit light equivalent to a 60-watt incandescent light bulb, which makes them a viable technology for basic lighting needs at home. And in some ways, they’re much more than viable: An LED replacement light bulb emits 60-watt equivalent light using 7.5 watts of power.

Energy consumption

One kilowatt-hour of electricity will cause 1.34 pounds (610 g) of CO2 emission. Assuming the average light bulb is on for 10 hours a day, one 40-watt incandescent bulb will cause 196 pounds (89 kg) of CO2 emission per year. The 6-watt LED equivalent will only cause 30 pounds (14 kg) of CO2 over the same time span. A building’s carbon footprint from lighting can be reduced by 85% exchanging all incandescent bulbs for new LED’s.

Economically sustainable

LED light bulbs could be a cost-effective option for lighting a home or office space because of their very long lifetimes. Consumer use of Led as a replacement for conventional lighting system is currently hampered by the high cost and low efficiency of available products. 2009 DOE testing results showed an average efficacy of 35 lm/W, below that of typical CFLs, and as low as 9 lm/W, worse than standard incandescent. However, as of 2011 there are LED bulbs available as efficient as 150 lm/W and even inexpensive low-end models typically exceed 50 lm/W. The high initial cost of the commercial LED bulb is due to the expensive sapphire substrate which is key to the production process. The sapphire apparatus must be coupled with a mirror-like collector to reflect light that would otherwise be wasted.

Sustainable lighting

Efficient lighting is needed for sustainable architecture. In 2009, a typical 13 watt LED lamp emitted 450 to 650 lumens, which is equivalent to a standard 40 watt incandescent bulb. In 2011, LED have become more efficient, so that a 6 Watt LED can easily achieve the same results. A standard 40-watt incandescent bulb has an expected lifespan of 1,000 hours while an LED can continue to operate with reduced efficiency for more than 50,000 hours, 50 times longer than the incandescent bulb.

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