Someone
(Jim) at
rel="tag">Motley
Fool linked to the last LED lighting post.
Apparently he tracks the Cree Inc. stock. Anyway,
he linked to a site that has more information on the
href="http://www.lumecon.com/imsa_led_street_lighting_article.html">Ann
Arbor LED
street light project.
Part
of their interview with one of Ann Arbor's asistant managers, Mike
Bergren:
Q.:
The test site has been up for awhile. What are the results of this
experiment?
A.:
Let's talk about the cobra head first. We are getting excellent reports
that we don't have any light trespass. LED lighting is very
directional. We can control the overspill of light, preventing the
light from shining on the lawn, on to the house faces, waking up little
Jr. sleeping. Some of the residents have expressed concern
it's not shining light on their front door anymore. But, as a
municipality, our true lighting requirement is the roadway and our
right of way. We are not in the business of lighting up front doors and
garages. We encourage residents to use their front porch lights and
architectural lighting, as needed, for safety. As a city, we are
responsible for the greater number; and the greater number has asked us
to keep the light out of their windows.
Now, for the downtown globes, the response has been extremely positive.
We have a web address to e-mail comments. We have posted signs in the
test areas telling people to e-mail us their "feelings," what they
truly think. So far it has been 98% positive. They like it.
We have had energy commissioners, people from Ontario, and from all
over come to look at this test site to see what's going on, what it
looks like. I've even spoken with the merchants who have the
lights in front of their stores. Most didn't even know we changed the
lights. The trained eye looks at them and notices something is
different; but people walking down the street don't notice if they are
not looking upward. The light output on the ground is the same as we
were putting out before; but there is no light shining up toward the
upper floors. We have a lot of downtown lofts, and the residents are
much happier. We used to receive a lot of complaints. They are now
experiencing darkness at night.
Sounds highly positive. Merchants like it, residents like it,
the city managers like it. It saves money. Pollutes
less.
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It would seem also that, being directional, there would be less light pollution -- an increasing concern of astronomers.
As a suburban amateur astronomer I second Gregs comment. Maybe the relentless increase in light pollution can be reversed?
Yes, it the remainder of the interview, not quoted here, they refer to the "Dark Skies" initiative, or something like that.
The first step would be to require directional LED lighting at auto dealerships. They are the worst, and they have the capital and the incentive to lead the way with this. They would save energy and their cars would look better under LED lights.
Long-term operational costs, certainly. There's still the purchase price.
What about color? Are these white LEDs? To me that would be an improvement over the yellow sodium lamps. Those don't do a very good job of illuminating things, which is, well, what the lighting is for.
I just looked around the Cree web site. They are claiming > 100 lumens at 350 mA for their cool white XLamp XR-E LEDs. Philips is also claiming > 100 lumens at 350 mA for their cool white Luxeon Rebel LEDs. Good times.
What a coincidence. I left Ann Arbor for Massachusetts nearly two decades ago, but I'm back visiting family - yes, during Art Fair, wasn't my idea - and I happened to walk by one of these just this afternoon. It almost makes me proud to see good old A-Squared leading the way on this.
I kind of like sodium lights -- sort of an antique look to lighting and certainly better than the mercury vapor lights.
The eyes (and brain) are marvelous in how they can adjust to ambient light, though there always remains a harshness to mercury lights, I think because the light is so unnatural.
From astronomers' point of view, sodium light is good because it shows up minimally on the light spectrum, whereas mercury is one of the worst.
It's amusing to see Cree, one of our customers, getting so much good publicity. I work at a small company that makes insulation for silicon crystal and other furnaces, and we sell a fair bit to Cree. So, more orders for us then.
At least with the sodium and mercury vapor lights, in theory you can buy filters (since most of the light is in a few narrow spectral bands). I think the LEDs spectrum is much broader. I borrowed one of these filters once, and wasn't much impressed.
Supposedly the most efficient lighting is lasers, where it is claimed with current tech up to 50% efficiency is possible today -and possibly up to 80% someday. Of course most electronic lasers are not single frequency, but shine in multiple lines who's frequencies is pretty similar.
LEDs still have a ways to go. They are great for low power apps, like flashlights, but still a bit pricey for area lighting, where you gotta gang a lot of low power diodes together.