I got a nifty little christmas present this year: a white light LED headlamp. Three LED's run on three AAA cells, and really bright. I took out my handy spectrometer (every home should have one - don't you?) and confirmed that it was truly a full spectrum white light. The efficiency is quite amazing, they appear to draw only ten milliamp at 4.5 volt (ie under 0.05 watt). Well, this intrigued me greatly, so I went off to the web, to discover
http://netdisty.net/ds/dec-a19/ and several other items. It appears that white light LEDs made with a far blue light fluorescing a white phosphor are becoming widely available. Unfortunately they're still quite expensive, the little headlamps and keychain lamps seem to retail for about $20 CDN per LED, ie the one I got was around $60, but we can expect the price to come down. The amazing thing is that the brightest and most efficient of these put out the equivalent light to a ten watt incandescent bulb, ie a cluster of ten are the equivalent of a regular hundred watt tungsten filament bulb, but in a colour spectrum that is perfect sunlight (great for the SAD sufferers among us), and all this while consuming about one watt of power (20mA per chip). It doesn't appear that a home bulb using these particular chips is yet available, but at the website they do offer bulbs from some other W.L.LEDS to fit a regular socket. The components are solid state, and as they generate almost no heat, the bulb itself is made out of plastic, so it's unbreakable. The LED chips themselves should last 100,000 hours, like most LED's (more, actually, the upper limit is theoretical, as when those numbers were first quoted, no LED had been around anywhere near that long. 100,000 hours is 11.5 years, most people now have LEDs in home appliances that have been going much longer than that now. I have one that's been on for 20 years steady) but it is possible the phosphor may degrade, so the company only claims a conservative 10,000 hours lifetime (14mo @ 24hr/day). The bulbs at the site are quoted at $65US each, but at typical electricity rates, they pay for themselves in about 9000 hours of use (~1 year @24hr/day). As the price comes down, this calculation will look more and more appealing. As well, I expect the true lifetime of the bulbs will turn out to be in the order of 500,000 hours. The reason for this efficiency is the gross inefficiency of the usual means of illumination: incandescent bulbs typically put out 98.5% of their energy as heat, and even fluorescents waste about 90% as heat. LEDs put all their energy into the single band of light which they emit. As this technology spreads, we will see some decline in electricity demand (not a lot, most power is used in heating elements and motors - I'm not sure what percentage goes to lighting, perhaps as much as 40%). Here in BC, the first steps along this road are being taken as the cities here have all begun switching over their traffic lights to LEDs. We might expect to see in a few years the street lights being changed over to high power white LEDs, as well. Another thing these bulbs make practical is self-contained illumination systems: they take so little power, they could be run from a rather modest solar array, which collected enough power during the day to provide illumination all night. And consequently, they make getting off the power grid more feasible for individual homes, in remote areas. There are probably other interesting implications I haven't thought of.... -Pete Vincent _______________________________________________ Futurework mailing list [EMAIL PROTECTED] http://scribe.uwaterloo.ca/mailman/listinfo/futurework
