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[DSLF] Digest Number 1609




There are 2 messages in this issue.

Topics in this digest:

      1. Re: LED Streetlights
           From: "Terry McGowan" <lighting@ieee...>
      2. Re: LED Streetlights
           From: "Eric S. Johansson" <esj@harvee...>


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Message: 1         
   Date: Fri, 18 Mar 2005 14:12:17 -0500
   From: "Terry McGowan" <lighting@ieee...>
Subject: Re: LED Streetlights


Not likely -- unfortunately.

The DOE is not in the business of "approving" LEDs for any applications and
the current DOE presentations being given to lighting industry groups
predict that LEDs won't be a factor in general lighting applications until
2015.  Consider, too, that the DOE has been known more for overselling LED
technology than underselling it -- especially the timing.

There are three main problem with using LEDs for streetlighting: light
output, efficacy and cost.  It takes a lot of LEDs at 1-5 watts each to
generate enough lumens to meet IESNA recommended streetlighting levels and
uniformity.  That's costly.  Current white light LEDs generate only about 30
lumens/watt at  best and even though there are higher efficacy LEDs in the
laboratories, that doesn't give the lighting industry mass-produced products
to put into practical lighting fixtures that tax-funded entities will buy.
Then, there are questions of reliability.  Few cities or utilities like to
install systems with no track record.  When NYC installed its first HPS
system along a part of 5th. Avenue in the mid 1960s, the Avenue business
owners had to pay for it; the city wanted neither the responsibility nor the
cost.

Any new streetlighting technology, if it is to be widely used within current
lighting criteria, will have to be able to compete with systems operating at
100+ lumens/watt, developing 10,000 lumens/unit (or more), lasting for
24,000+ hours (which is about 6 years average between service intervals) and
selling for $100 dollars/fixture or less.

But, the recent NYC streetlighting competition was won by an LED-powered
system.  That's exciting stuff and good way to invent the future.  Watch the
details, though. Even a prototype of the winning fixture is months away.
There's also no information about the system meeting current lighting
criteria and no guarantee that it will ever be installed in quantity along
NYC streets.

I hope that LED streetlighting is on a fast-track.  LEDs offer the chance to
build in fco shielding as a standard feature and to direct the light better
so there is less spill and wasted light.  There's even recent talk about
selectively "tuning" LED spectra to leave dark spectral gaps for astronomy.
Demonstrating and talking about such systems would be inspirational and help
set the stage for systems that are much more dark-sky friendly.

Terry McGowan, FIES, LC
Lighting Ideas, Inc.
Cleveland, OH


----- Original Message ----- 
From: "Mike Hansen" <mhansen@einhornresearch...>
>
> According to a consultant working for the town of Maynard,
> Massachusetts, "in the next five to six years, the DOE will approve a
> white diode light for public property." He goes on to suggest that
> grants will then be available to towns to convert from HPS to the
> diodes.
>
> http://tinyurl.com/5ts6n





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Message: 2         
   Date: Fri, 18 Mar 2005 17:44:59 -0500
   From: "Eric S. Johansson" <esj@harvee...>
Subject: Re: LED Streetlights


Terry McGowan wrote:
> Any new streetlighting technology, if it is to be widely used within current
> lighting criteria, will have to be able to compete with systems operating at
> 100+ lumens/watt, developing 10,000 lumens/unit (or more), lasting for
> 24,000+ hours (which is about 6 years average between service intervals) and
> selling for $100 dollars/fixture or less.

thanks for this information.  It will help me with modeling.

> I hope that LED streetlighting is on a fast-track.  LEDs offer the chance to
> build in fco shielding as a standard feature and to direct the light better
> so there is less spill and wasted light.  There's even recent talk about
> selectively "tuning" LED spectra to leave dark spectral gaps for astronomy.
> Demonstrating and talking about such systems would be inspirational and help
> set the stage for systems that are much more dark-sky friendly.

as you know, I take a more pessimistic view based on human observation 
and economics.  If people make choices based on good sound environmental 
ones, as well as long-term economic points, we would not see the 
widespread use of SUVs.

yes, LED is having much higher probability of being full cut off but 
because they will be so much cheaper to use in about 20 years, there's a 
good chance will have even more (i.e. an order of magnitude) exterior 
lighting.  why?  Because folks have been accustomed to spending a 
certain budget on exterior lighting and now that they have more money 
available, they will spend it.  Maybe not all that on lighting but 
certainly more.

---eric


-- 
http://www.wired.com/wired/archive/13.03/view.html?pg=5

The result of the duopoly that currently defines "competition" is that
prices and service suck. We're the world's leader in Internet
technology - except that we're not.





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