Light-emitting diodes (LED's) will transform the business of illumination, especially with new production breakthroughs
“INCANDESCENT” might well describe the rage of those who prefer traditional light bulbs to their low-energy alternatives. This week, the European Commission formally adopted new regulations that will phase such bulbs out in Europe by 2012. America will do so by 2014. Some countries, such as Australia, Brazil and Switzerland, have got rid of them already. When a voluntary agreement came into force in Britain, at the start of the year, people rushed out to buy the last 100-watt light bulbs. Next to go are lower-wattage bulbs.
But what will replace the light bulb? Although obtaining illumination by incandescence (ie, heating something up) goes back to prehistory, it was not until 1879 that Thomas Edison demonstrated a practical example that used a wire filament encased in glass. Modern bulbs, the descendants of that demonstration, are cheap (around 50 cents) but inefficient, because only about 5% of the energy they use is turned into light and the rest is wasted as heat.
Without changing light fittings, the cheapest direct replacement for an incandescent bulb at the moment is a compact fluorescent light (CFL). These use up to 75% less power and last ten times longer, but they cost around $3 each. That price puts some people off, which explains part of the hoarding of incandescent bulbs. But others object not to the price but to the quality of the light, which has a different spectrum from the one they are used to. CFL bulbs can also be slow to reach maximum illumination. And some people worry that they may be bad for the health. Fluorescent lights use electricity to excite mercury vapour. This produces ultraviolet light that causes a phosphor coating inside the bulb to glow. The lights can flicker, which could set off epileptic fits, and badly made ones might leak ultraviolet radiation, and may thus pose a cancer risk. There are also concerns about the disposal of the toxic mercury.
The most promising alternatives are light-emitting diodes (LEDs).
An LED is made from two layers of semiconductor, an “n-type” with an excess of negatively charged electrons, and a positive “p-type” which has an abundance of “holes” where electrons should be but aren’t. When a current is applied across the sandwich, the electrons and holes team up at the junction of the two materials and release energy in the form of light...can be tuned to produce light that is similar to natural daylight but with virtually no ultraviolet or heat.
Light-emitting diodes have progressed from simple red indicators on electronic products to become torches, streetlights and car headlights. Now the first mains-voltage LEDs designed as direct replacements for incandescent bulbs are arriving on the market. Some, such as the Philips Master LED range, promise energy savings of up to 80% and a working life of 45,000 hours.
Developments like the use of cheap silicon make the case for switching to LED lighting even more compelling. About 20% of the world’s electricity is used for lighting. America’s Department of Energy thinks that, with LEDs, this could be cut in half by 2025, saving more than 130 new power stations in America alone.
