A brilliant new approach: Lighting

“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. A typical bulb also has to be replaced every 1,000 hours or so.

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. …

… 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. The colour depends on the properties of the semiconductor, and these 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. But they are not cheap: around £40 ($56) in Britain.

Even so, LEDs can still be economical. Only a quarter of lighting is domestic. Businesses and public organisations are more aware of running costs than householders are—and besides the electricity bill they also have to pay people to change bulbs that have failed. For the bulbs to be embraced by households, though, LED costs will need to come down. …