LEDs could begin to replace light bulbs

Right now, US consumers and businesses can buy LEDs that provide about the same level of illumination as an energy-hogging conventional 60-watt light bulb, Steven DenBaars, a professor of material science at the University of California, Santa Barbara, said at the SEMI NanoForum in San Jose last week. A principal advantage of the LED is that it lasts about 100,000 hours -- far longer than the conventional filament bulb

Unfortunately, the LEDs that can perform this task cost about $60 (£32), he said. (Prices vary on the Internet.) LED prices, however, have been declining by 50 per cent a year. Two years from now, therefore, the same LED will cost around $20 (£11).

"At $20 the payback in energy occurs in about a year," DenBaars said. The rapid payback will occur in places, such as shops and warehouses, where the light is on most of the time. A year after that, LEDs will be even more economical for a range of places because of declining costs.

Approximately 22 per cent of the electricity consumed in the US goes towards lighting, according to the US Department of Energy.

To make matters worse, traditional light bulbs are incredibly inefficient. Only about 5 per cent of the energy that goes into them turns into light. The majority gets dissipated as heat.

If 25 per cent of the light bulbs in the US were converted to LEDs putting out 150 lumens per watt (higher than the commercial standard now), the US as a whole could save $115bn in utility costs, cumulatively, by 2025, said DenBaars. This could alleviate the need to build 133 new coal-burning power stations. In turn, carbon emissions in the atmosphere would go down by 258 metric tons.

"Multiply that by three and you get the worldwide savings," he stated. DenBaars then showed a picture of the globe at night. The landmass of the US could easily be picked out by its nighttime lights. "We shoot a lot of light into space that doesn't need to be there," he noted.

Rising prices of electricity, combined with the antiquated nature of light bulb technology, has prompted several start-ups and large industrial companies to move into lighting.

Fiberstars, for instance, has developed a way to replace hot fluorescent tube lights with light-emitting optical fibres in freezer cases in supermarkets. The Hewlett-Packard spin-off Lumileds is also producing LEDs for a variety of applications.

LED technology is improving as well. UCSB has created an experimental LED that can put out 117 lumens per watt, while a Japanese company has developed one that can put out 130 lumens per watt.

The technology that allows LEDs to produce white light that is tolerable to humans has also greatly improved. Manufacturers can now achieve this in two ways. One is to package red, green and blue LEDs in a way that the combined light shines white to the human eye. The other way is to make blue LEDs and coat them with a phosphor -- a luminescent substance commonly used on fluorescent lamps.