City swapping out light bulbs for LEDs (AP/CNN)

[eppur_se_muova]

DETROIT, Michigan (AP) --
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The eco-friendly city about 30 miles west of Detroit says it will be the nation's first to convert all downtown street lights to LED technology, which uses less than half the energy of traditional bulbs and could save the community $100,000 a year.

"LEDs pay for themselves in four years," said Mayor John Hieftje, who announced the city's plans this week as it joined Raleigh, North Carolina, and Toronto in the LED City initiative, an industry-government group working to evaluate, deploy and promote LED lighting.

"They provide the same light, but they last 10 years. We had to replace the old ones every two years."
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Lighting consumes 22 percent of the electricity produced in the United States, according to the U.S. Department of Energy, and widespread use of LED technology could cut consumption in half.

Hieftje said Ann Arbor's lighting conversion will reduce the city's production of carbon dioxide and gases that contribute to global warming in an amount equal to taking 400 cars off the road.
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more: http://www.cnn.com/2007/TECH/10/18/leds.street.lights.ap/index.html

[rox63]

1. I hope more cities start doing this soon

it would help cut greenhouse gases significantly.

[One_Life_To_Give]

2. How do LED's compare to Sodium or Mercury Vapor?

Not sure there is much efficinecy gain in electric consumption. The bigger issue is probably longevity of the bulb. Since "incandescent" streetlights are ancient tech. (Does anyone still use those?)

[skids]

4. The big difference is in the filtering...

The LEDs are more efficient (by about 3x) to start with than incandescents, about the same as mercury vapor, but when you take a white light and run it through a filter to turn it red or yellow or green, you are throwing most of the energy away (absorbed by the filter.) Maybe there are mercury lights that have a narrow-band phosphor but I've never heard of them if so.

With LEDs, the light is produced at the color you want it to be in the first place. For the same reason, the OLED TVs coming out in the next few years will be more power efficient than LCDs.

[One_Life_To_Give]

5. For traffic lights I agree

The LED's in traffic lights seem much better than the incandescents commonly in use. I was thinking of the white Street Lights that are typical some type of HID lamp. Which are already much better than incandescents although we still manage to spend alot of energy lighting up the night sky.

[kestrel91316]

3. I have noticed here in LA they are gradually replacing all the stop lights

with the LED version. Our mayor, "Pretty Boy" Antonio Villaraigosa, has also promised to synchronize stop lights and install some smart ones. Because millions of cars sitting forever at lights when there's not even any cross-traffic wastes a hell of a lot of gas.