70 lines
3.2 KiB
Markdown
70 lines
3.2 KiB
Markdown
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# Efficiency
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Interesting factoids about [replacing sodium vapor lamps with
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LEDs](http://dansdata.blogsome.com/2008/12/27/led-street-lighting-not-as-good-as-you-think/)
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for city-wide lighting.
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- The theoretical lumen/Watt figures for LEDs are worse than
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low-pressure sodium vapor lamps (100 lm/W versus 200 lm/W)
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- White LEDs are actually blue LEDs with a consumable phosphor layer
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that turns opaque after a few years of operation.
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- Combined RGB LEDs will have better efficiency than a "white" LED.
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Other real-world tests have concluded that LED street lights have about
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the same lumen/Watt in practice as the sodium vapor lamps ([64 lm/W
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LEDs](http://www.olino.org/us/articles/2008/11/02/streetlamp-lioris-aduro-52)
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versus [67 lm/W Sodium
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vapor](http://www.olino.org/us/articles/2008/12/29/indal-industria-aurora-streetlamp)).
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Neon and florescent efficiency [depends on the color and
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shape](http://www.signindustry.com/neon/articles/2003-07-11-RC-NeonandFlour.php3):
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> \[...\] the fluorescent tube produces between 50 and 100 lumens of
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> light per watt depending upon design. Compare this with the typical
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> incandescent light bulb that produces between 10 and 20 lumens per
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> watt. Neon light efficiency is based upon much fancier pants, the
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> color of its output, which ranges from 10 lumens per watt for red to
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> 60 lumens per watt for green or blue. One reason that green and blue
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> tubes are more efficient is that phosphor coatings used to produce
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> such colors better ballyhoo the high-energy ultraviolet light from the
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> argon/mercury mix into visible colors. One reason that the fluorescent
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> tube is more efficient than a neon tube is that a large straight tube
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> offers less resistance to electrical current flow than a skinny bent
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> one.
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# Obstacles
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Little Rock, AK wanted to replace their inefficient shielded lights with
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more efficient fixtures, but their contract with Entergy is not a simple
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\$/kW formula: [the energy company sets the price based on the type of
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fixture](http://www.arktimes.com/Articles/ArticleViewer.aspx?ArticleID=fce07cab-0dea-4fc5-b57e-f1145715f01e).
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> \[...\] According to Henry, the city tested out more efficient
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> 100???watt HPS bulbs in one Little Rock neighborhood about five years
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> ago. When the city asked Entergy to set a rate for those fixtures, it
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> was almost double the rate for the 150-watt HPS type.
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>
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> When asked if Entergy was keeping Little Rock from being more energy
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> efficient, Henry said simply, "Yes."
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>
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> "But how do you fight Entergy?" Henry asked. "I mean, we've had people
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> come in and show us new, more efficient lights and we've said, well,
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> the problem is, it's not going to save us anything. It will be a whole
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> lot less wattage and it will put light out on the street but we can't
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> get any benefit out of it because of the tariffs."
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# Commercial LED lamps
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[SparkFun](http://sparkfun.com) sells LED lamps that are screw
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compatible with US light sockets:
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- [75
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W](http://www.sparkfun.com/commerce/product_info.php?products_id=8716)
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- [12
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W](http://www.sparkfun.com/commerce/product_info.php?products_id=8714)
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- [3
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W](http://www.sparkfun.com/commerce/product_info.php?products_id=8717)
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- [1
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W](http://www.sparkfun.com/commerce/product_info.php?products_id=8715)
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[Category:Useful_Info](Category:Useful_Info "wikilink")
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