7 ms·

LED Light Pollution: Can We Save Energy and Save the Night? (2015)

50 points by rfreytag 10y ago

arcaster 10y ago
I wrote a paper for a sociology class in college focussing not only on light pollution, but the fact that many historians believe that certain cultural and aesthetic attributes of cities and surrounding urban areas are lost when the warm glow of HPS lights is replaced with stark white LEDs.
- sp332 10y ago
  If that's really a concern, LEDs don't have to be white.
  - ChuckMcM 10y ago
    Exactly this, I have seen "sodium" LED lights which replace HPS lights with a similar spectrum. Apparently this was to avoid replacing all of the lights at once, and by swapping them out as they burn out the city gets the full lifetime value of the bulbs. (yes the energy cost dwarfs that but not all cities want to front the upfront cost)
    - toomuchtodo 10y ago
      It's also helpful to have exterior LEDs that can change color on demand; for example, there are regulations in Florida on the coast as to what color lights you can use due to sea turtle nesting behaviors, but their nesting/mating is seasonal (and short window of time).
  - upofadown 10y ago
    Kind of. The really high efficiency LEDs are blue. The problem is with the efficiency of green LEDs. I suppose you could just use red and yellow LEDs and completely solve the circadian light problem. I think that such streetlights would be hard to sell.
    - sp332 10y ago
      You can cover the blue LEDs with yellow phosphor and get a subjectively "white" light, such as the Amazon Kindles. You could even cover that in a blue-reducing filter to make it much more yellow, but I don't know how bad the efficiency would be after all that.
    - ars 10y ago
      > Kind of. The really high efficiency LEDs are blue. The problem is with the efficiency of green LEDs. Hu? That's not true. Blue is less efficient, not more. The lower the wavelength the more efficient (toward the red side of the rainbow). Also mono-color LEDs are MUCH more efficient than the ultraviolet ones with a phosphor (AKA white) ones. If you wanted efficiency then have red and green in an LED, and that's it. You don't really need full color at night.
      - upofadown 10y ago
        Each LED technology has an optimal wavelength. The current tendency is to use blue LEDs and then make white light with phosphors so the development is mostly on the blue LED technologies. The green problem is caused by the lack of a technology. So you end up with bluish/green coming down from the blue side and yellowish/green when going up from the red side. That prevents really efficient RGB LEDs and makes the inefficient phosphor based white LEDs competitive. If you ever see a RGB LCD backlight you will see that there are more green LEDs than red or blue LEDs.
  - cauterized 10y ago
    They don't. So why are so many municipalities installing the white ones, to the detriment of quality of life on residential blocks?
    - deleted 10y ago
      [deleted]
- 21 10y ago
  The same thing could have been said when we went from oil lamps to light bulbs.
post_break 10y ago
Higher kelvin lights look so much better in my opinion. http://i.imgur.com/XHqUPOY.jpg http://i.imgur.com/XHqUPOY.jpg
- wlesieutre 10y ago
  That also has a lot to do with the whole emission spectrum, not just where it falls on the black body curve. Low pressure sodium, for example, is a very narrow wavelength spike [1]. If you look at your hands under this, they appear as a kind of nasty gray with veins sticking out. Awful color rendering. [2] On the flip side, it doesn't scatter as strongly in the atmosphere, and the narrow wavelength band is much easier to filter out of measurements. So there's a tradeoff. If you don't care about dark skies, then phosphor-converted blue LEDs look like a pretty great idea. If you do, then make an informed decision based on the pros and cons of each side. I'm in the lighting industry, and man has there been a lot of sillyness with LED uptake. Great for driving demand and pushing LED research and manufacturing forward, but you get tired of explaining that no, maybe fluorescent or metal halide would be a better tool for some jobs. We're getting to a point where it'd be very infrequent for me to suggest them now, but the last couple of years... [1] https://en.wikipedia.org/wiki/Sodium-vapor_lamp#/media/File:SOX.png https://en.wikipedia.org/wiki/Sodium-vapor_lamp#/media/File:... [2] http://www.lighting-gallery.net/gallery/albums/userpics/11340/normal_LPS-ColorRendering.png http://www.lighting-gallery.net/gallery/albums/userpics/1134...
  - probinso 10y ago
    !Agree I'm very excited to have stumbled on this article on HN, as I am presently working on a project in this space; focusing on better ways to specify lighting needs and discuss light pollution's impact on terrestrial telescopes and astronomy. Its neat to see that understanding consequences of artificial lighting, especially wrt. blue light content, is gaining awareness in the market. I've been consulting with a company, that designs lighting whose spectral profile match specifications representative of ecological, industry, and human needs of a region.
    - wlesieutre 10y ago
cauterized 10y ago
They replaced the old lighting with white LEDs on my block a couple months ago. First off, it actually makes it MORE difficult to see (now that the trees have leaves) than the orange light did. The LEDs are so much brighter that the contrast makes the shadows even deeper than they used to be, and your eyes can't see anything that's in shadow. Secondly, it makes it much more difficult to sleep. My windows are ABOVE the lights (which face downwards), and it's like trying to sleep in daylight. I can't imagine what it's like on the floors below. My sleep has definitely suffered.
- MichaelGG 10y ago
  Why are streetlights shining up anyways? I see these curved glass installations everywhere. The light shines way above street level. At a minimum, this seems like a waste of energy, let alone the annoyance. In residential areas particularly, they should be very tightly constrained. And output adjusted to aid in night vision, not attempting to provide full lighting.
  - cauterized 10y ago
    I couldn't agree more that more attention should be paid to where the lights shine and how they affect night vision, but they don't even have to direct any light upwards to make It bright enough to affect sleep on the floors above. Even with all the light emitted downwards, a narrow street with bright and closely spaced streetlights means that there's enough reflection off pavement, cars, building facades and windows, etc. that a huge amount of light is reflected back above the lamp. Depending on where you and the trees are relative to the lamp, the leaves may lessen or exacerbate the effect. And overcast nights make it even worse because you get a second dose of reflection (from the entire metro area, much of which has been similarly "upgraded" to Hollywood interrogation spotlights... I mean, LED streetlights.) It's not as if anyone was claiming this neighborhood was dangerous or scary to walk in at night. If I wanted to live in Times Square I'd live in Times Square.
- 21 10y ago
  I also noticed the shadow problem. And with some fixtures, the shadow itself can have a strange pixelated look - https://i.imgur.com/e0nReZ8.jpg https://i.imgur.com/e0nReZ8.jpg At the same time, the city looks much more beautiful to me under LED lighting.
stuaxo 10y ago
Nightclubs have been ruined. Bright LEDs replace the old lines one for one, and instead of being dark, with bits of light it is almost like daylight.
f_allwein 10y ago
The advantage of light pollution is that you can get blown away if you do manage to find a dark spot in the countryside and see the night sky... Here's an interesting art project that simulates what night skies would look like in cities without any artificial light: http://www.space.com/20615-darkened-cities-night-sky-imagined.html http://www.space.com/20615-darkened-cities-night-sky-imagine...
- aaron695 10y ago
  Totally fake. And obviously so. Wiki how many stars you can see them estimate how many are in the photo.
  - acbabis 10y ago
    They're probably time-lapse photos. The captions don't say that a human observer would be able to see this much.
  - f_allwein 10y ago
    And openly so, as the artist combined pictures of cities with pictures of the night sky taken e.g. in the desert, but at the same latitude. So they are "fake" but plausible.
    - koube 10y ago
      They're not plausible for a human, even out in the desert far from civilization. Light captured by a sensitive camera and long exposure do not represent what a human would see. Nearly all night time starscapes are enhanced past what a human would see in any situation.
      - ImprovedSilence 10y ago
        Yeah, those photos seem to be a bit colorized with brighter than reality stars, but I'm willing to be overall density of visible stars would be the same.
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clumsysmurf 10y ago
There is a photo "showing the difference in glare between poorly designed lamps and full cutoff lamps." That reminds me of a lens design I read about back in 2013 that used TIR lenses https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-21-9-10612&id=253009 https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-21-9-10... Anyone know if this system is seeing widespread adoption?

50 points by rfreytag 10y ago

I wrote a paper for a sociology class in college focussing not only on light pollution, but the fact that many historians believe that certain cultural and aesthetic attributes of cities and surrounding urban areas are lost when the warm glow of HPS lights is replaced with stark white LEDs.

sp332 10y ago
If that's really a concern, LEDs don't have to be white.
- ChuckMcM 10y ago
  Exactly this, I have seen "sodium" LED lights which replace HPS lights with a similar spectrum. Apparently this was to avoid replacing all of the lights at once, and by swapping them out as they burn out the city gets the full lifetime value of the bulbs. (yes the energy cost dwarfs that but not all cities want to front the upfront cost)
  - toomuchtodo 10y ago
    It's also helpful to have exterior LEDs that can change color on demand; for example, there are regulations in Florida on the coast as to what color lights you can use due to sea turtle nesting behaviors, but their nesting/mating is seasonal (and short window of time).
- upofadown 10y ago
  Kind of. The really high efficiency LEDs are blue. The problem is with the efficiency of green LEDs. I suppose you could just use red and yellow LEDs and completely solve the circadian light problem. I think that such streetlights would be hard to sell.
  - sp332 10y ago
    You can cover the blue LEDs with yellow phosphor and get a subjectively "white" light, such as the Amazon Kindles. You could even cover that in a blue-reducing filter to make it much more yellow, but I don't know how bad the efficiency would be after all that.
  - ars 10y ago
    > Kind of. The really high efficiency LEDs are blue. The problem is with the efficiency of green LEDs. Hu? That's not true. Blue is less efficient, not more. The lower the wavelength the more efficient (toward the red side of the rainbow). Also mono-color LEDs are MUCH more efficient than the ultraviolet ones with a phosphor (AKA white) ones. If you wanted efficiency then have red and green in an LED, and that's it. You don't really need full color at night.
    - upofadown 10y ago
      Each LED technology has an optimal wavelength. The current tendency is to use blue LEDs and then make white light with phosphors so the development is mostly on the blue LED technologies. The green problem is caused by the lack of a technology. So you end up with bluish/green coming down from the blue side and yellowish/green when going up from the red side. That prevents really efficient RGB LEDs and makes the inefficient phosphor based white LEDs competitive. If you ever see a RGB LCD backlight you will see that there are more green LEDs than red or blue LEDs.
- cauterized 10y ago
  They don't. So why are so many municipalities installing the white ones, to the detriment of quality of life on residential blocks?
  - deleted 10y ago
    [deleted]
21 10y ago
The same thing could have been said when we went from oil lamps to light bulbs.

post_break 10y ago

Higher kelvin lights look so much better in my opinion. http://i.imgur.com/XHqUPOY.jpg http://i.imgur.com/XHqUPOY.jpg

wlesieutre 10y ago
That also has a lot to do with the whole emission spectrum, not just where it falls on the black body curve. Low pressure sodium, for example, is a very narrow wavelength spike [1]. If you look at your hands under this, they appear as a kind of nasty gray with veins sticking out. Awful color rendering. [2] On the flip side, it doesn't scatter as strongly in the atmosphere, and the narrow wavelength band is much easier to filter out of measurements. So there's a tradeoff. If you don't care about dark skies, then phosphor-converted blue LEDs look like a pretty great idea. If you do, then make an informed decision based on the pros and cons of each side. I'm in the lighting industry, and man has there been a lot of sillyness with LED uptake. Great for driving demand and pushing LED research and manufacturing forward, but you get tired of explaining that no, maybe fluorescent or metal halide would be a better tool for some jobs. We're getting to a point where it'd be very infrequent for me to suggest them now, but the last couple of years... [1] https://en.wikipedia.org/wiki/Sodium-vapor_lamp#/media/File:SOX.png https://en.wikipedia.org/wiki/Sodium-vapor_lamp#/media/File:... [2] http://www.lighting-gallery.net/gallery/albums/userpics/11340/normal_LPS-ColorRendering.png http://www.lighting-gallery.net/gallery/albums/userpics/1134...
- probinso 10y ago
  !Agree I'm very excited to have stumbled on this article on HN, as I am presently working on a project in this space; focusing on better ways to specify lighting needs and discuss light pollution's impact on terrestrial telescopes and astronomy. Its neat to see that understanding consequences of artificial lighting, especially wrt. blue light content, is gaining awareness in the market. I've been consulting with a company, that designs lighting whose spectral profile match specifications representative of ecological, industry, and human needs of a region.
  - wlesieutre 10y ago

cauterized 10y ago

They replaced the old lighting with white LEDs on my block a couple months ago. First off, it actually makes it MORE difficult to see (now that the trees have leaves) than the orange light did. The LEDs are so much brighter that the contrast makes the shadows even deeper than they used to be, and your eyes can't see anything that's in shadow. Secondly, it makes it much more difficult to sleep. My windows are ABOVE the lights (which face downwards), and it's like trying to sleep in daylight. I can't imagine what it's like on the floors below. My sleep has definitely suffered.

MichaelGG 10y ago
Why are streetlights shining up anyways? I see these curved glass installations everywhere. The light shines way above street level. At a minimum, this seems like a waste of energy, let alone the annoyance. In residential areas particularly, they should be very tightly constrained. And output adjusted to aid in night vision, not attempting to provide full lighting.
- cauterized 10y ago
  I couldn't agree more that more attention should be paid to where the lights shine and how they affect night vision, but they don't even have to direct any light upwards to make It bright enough to affect sleep on the floors above. Even with all the light emitted downwards, a narrow street with bright and closely spaced streetlights means that there's enough reflection off pavement, cars, building facades and windows, etc. that a huge amount of light is reflected back above the lamp. Depending on where you and the trees are relative to the lamp, the leaves may lessen or exacerbate the effect. And overcast nights make it even worse because you get a second dose of reflection (from the entire metro area, much of which has been similarly "upgraded" to Hollywood interrogation spotlights... I mean, LED streetlights.) It's not as if anyone was claiming this neighborhood was dangerous or scary to walk in at night. If I wanted to live in Times Square I'd live in Times Square.
21 10y ago
I also noticed the shadow problem. And with some fixtures, the shadow itself can have a strange pixelated look - https://i.imgur.com/e0nReZ8.jpg https://i.imgur.com/e0nReZ8.jpg At the same time, the city looks much more beautiful to me under LED lighting.

stuaxo 10y ago

Nightclubs have been ruined. Bright LEDs replace the old lines one for one, and instead of being dark, with bits of light it is almost like daylight.

f_allwein 10y ago

The advantage of light pollution is that you can get blown away if you do manage to find a dark spot in the countryside and see the night sky... Here's an interesting art project that simulates what night skies would look like in cities without any artificial light: http://www.space.com/20615-darkened-cities-night-sky-imagined.html http://www.space.com/20615-darkened-cities-night-sky-imagine...

aaron695 10y ago
Totally fake. And obviously so. Wiki how many stars you can see them estimate how many are in the photo.
- acbabis 10y ago
  They're probably time-lapse photos. The captions don't say that a human observer would be able to see this much.
- f_allwein 10y ago
  And openly so, as the artist combined pictures of cities with pictures of the night sky taken e.g. in the desert, but at the same latitude. So they are "fake" but plausible.
  - koube 10y ago
    They're not plausible for a human, even out in the desert far from civilization. Light captured by a sensitive camera and long exposure do not represent what a human would see. Nearly all night time starscapes are enhanced past what a human would see in any situation.
    - ImprovedSilence 10y ago
      Yeah, those photos seem to be a bit colorized with brighter than reality stars, but I'm willing to be overall density of visible stars would be the same.
- 10y ago

deleted 10y ago

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deleted 10y ago

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clumsysmurf 10y ago

There is a photo "showing the difference in glare between poorly designed lamps and full cutoff lamps." That reminds me of a lens design I read about back in 2013 that used TIR lenses https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-21-9-10612&id=253009 https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-21-9-10... Anyone know if this system is seeing widespread adoption?