From my perspective as a cyclist HPS is awful. There's no depth perception so potholes seem flat until you're nearly on top of them. Also, yes, peripheral vision is important even for auto drivers at typical urban driving speeds (i.e. 30 mph or less). The problem with HPS isn't necessarily the CRI (which can be in the 50s or 60s for some types of HPS) but the very low CCT. That's what causes peripheral vision to shut down. And then you have the additional factor of low CCT tending to promote sleepiness. That's obviously the last thing you want. IMO, 4000K is as low as we should push the CCT of streetlights down to. Much lower, and you start running into some of the same problems as with HPS.
LED Street lights - getting better
- Thread starter blasterman
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I agree with HPS and cycling. Potholes have low light levels inside them hence like peripheral vision in terms of viewing requirements.
Proper street lighting typically calls for at least mesopic levels at the location of sidewalks, but often they are not that bright, so higher CCT, or at least blue enhanced has value for low speed driving. This is somewhat recognized, but certainly not a full consensus by the IES.
In terms of CCT, there are lots of tradeoffs to be considered including what works effectively (not just perceived to), glare which is very real with higher CCT and with wet roads, environmental impacts, etc. 4000K is a pretty good trade-off though I would not be surprised to see heritage areas, i.e. small town centers, etc. go lower CCT, but much higher CRI than HPS. HPS can be higher CRI, but it is rare to see in a street light environment.
Semiman
Anders Hoveland
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I can understand this. But I have also found LED lighting to be difficult, and even dangerous to driving. Perhaps it has much to do with the glare from point-like sources, or perhaps it is the shorter frequency of blue my eyes have more trouble focusing on. When I went through a mountain tunnel, they had LED lighting aimed at an angle facing into the direction of the front of the car. The glare was terrible, I was a little concerned about driving out of my lane, and hitting some fast moving car that could come out of nowhere. Do not misunderstand me, HPS lighting is really ugly, but I have never had glare problems driving with it.
Also, in many situations where they have switched to LED streetlighting, it seems like there is not as much light as there used to be. Almost a little difficult to see. Likely the LEDs they switched to are actually giving off less light. Making brighter LED lamps is more expensive, so they probably had the justification that, since the new lamps were more directional, they would need less light. But the omnidirectional light is more important than they realize. Even if one sodium lamp went out, there is still enough ambient light from the other lamps to be able to see that part of the road. Whereas with the new LED lamps, it can be difficult to see the road if there is not an LED lamp right over it. Or perhaps they (incorrectly) thought scoptic index of the blue light could compensate for lower lumens. I'm sure the cities are saving energy, but they are also producing less light! So I think they are discovering that there are many unanticipated problems with using LED streetlighting, and that they are not going to save quite as much energy as many vendors have been claiming.
I rather like the concept they used in the Lærdal tunnel, if any of you have seen pictures of it. The architect combined LPS with bluish white LED for lighting variety. The LEDs are faced upward so the light diffuses off the tunnel ceiling, providing even illumination. The lighting combination is very high efficiency, and provides the advantages of both sodium and LED. http://i1.trekearth.com/photos/31318/laerdaltunnel-da.jpg
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The lighting in that tunnel looks painful. I hope the camera is just picking it up wrong.
Anders Hoveland
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http://dracurella.files.wordpress.com/2010/08/tunnel2.jpg
http://commondatastorage.googleapis.com/static.panoramio.com/photos/original/21009639.jpg
http://mw2.google.com/mw-panoramio/photos/medium/62502510.jpg
The designer also used a few downward metal halide lamp for direct road illumination, but there is plenty of ambient light.
Kilovolt
Flashlight Enthusiast
Actually I do have one hand held IR thermometer but I would need to climb up the pole to measure the temp of the fixture and both my age and weight advise me not to do that ... :p
idleprocess
Flashaholic
That appears to at least as much art installation as safety lighting.
The LED street lamps would have a faster roll out except they're not yet rated or certified for the number of hours. If a manufacturer says it will run for 50,000 hours there needs to be like a certification agency that will verify that. A city or state government needs to get the street lights financed so they will often get a bank to finance this (essentially to off set the capital cost of the lamps in exchange for the energy and money savings of the LED lamp over its lifetime).
These LED lamps will be popping up all over as there is more certification.
These LED lamps will be popping up all over as there is more certification.
Luxdelux there is little truth to what you are saying. Payback is <5 years well within the warranty and the dollar values are relatively small. For most it is just a matter of a overall timing. As well 3rd parties will finance and lease to cities.
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Anders Hoveland
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I'm sure you have seen it before, but here's some information on Osram's "BrilliantMix" technology:
How to Generate White Light
Producing white light with LED sources is a challenging task. Two methods are commonly used to create white light with LEDs. The first approach is through the combination of multiple colors, usually red, green, and blue, in multi-chip packages or LED clusters. This is the same principle used in backlighting LED LCD TVs: mixing the three colors in various proportions results in an entire spectrum of colors.
The second approach is to combine a semiconductor chip (blue or UV) with converter materials (phosphors) through luminescence conversion within a single package. A third approach involves an innovative combination of the best of both methods, called the “Brilliant Mix” Concept.
New Techniques for Achieving High CRI with LEDs
A phosphor-based high CRI approach is a method that includes an additional stable red phosphor. The latest developments using enhanced phosphors increase the CRI value to 95, but the trade-off is lower efficacy. LEDs are particularly efficient when color coordinates are closer to blue light, and the phosphor does not have to shift the blue coordinates quite so far. To achieve a warm white light, several luminescent substances must be combined, although this reduces the LED's efficacy. There is a limitation; with standard LEDs, it is not possible to realize LED luminaires and lamps with both high efficacies and high CRI.
However, with OSRAM’s “Brilliant Mix” concept, both high CRI and high luminaire efficiencies can be effectively realized. This approach fuses the two existing methods – mixed color from monochromatic LEDs and phosphor converted LEDs – to create a “warm-white” LED light source with both high CRI (> 90) and high luminous efficacy. This new approach makes total luminous efficacies of over 110 lumens per watt (lm/W) possible, producing up to up to 30 percent more light than phosphor-converted warm-white LEDs with a comparable CRI, but with similar power consumption.
Brilliant Mix is the mixing of two colors in order to generate warm white light. This approach uses red or amber monochromatic LEDs, combined with special white LEDs which have been shifted into the green range (called “EQ-White"). EQ-White is produced like a "normal converted white LED" with a blue chip and green phosphor. The green phosphor has a very low conversion loss rate and makes for a very efficient light source in combination with the blue chip.
Advantages offered by the Brilliant Mix Concept include high CRI, very high LED efficacies (> 110 lm/W possible), and warm white coverage from 2,700 K to 4,000 K.
Luminous efficacies of the two light sources are maintained, thus the new approach makes for a high luminous efficacy. The red LED is combined with EQ white (a highly efficient source with majority of its energy in within the green region of the visible spectrum, where the eye is most sensitive.)
When these two sources combine in the correct ratio, we get a pleasant, warm white light with a CRI over 90, giving us the ability to identify differences in the shades of the purple, blue and pink flowers by increasing our color discrimination, or how “vivid” and easily distinguishable colors appear. The average CRI of “Brilliant Mix” is very high (Ra>90). Additionally, the highly compact OSLON SSL LED is the vehicle for both phosphor-based and Brilliant Mix solutions. The standard phosphor conversion method produces reduced efficacy, but implementation is easier. Brilliant Mix enables higher efficacy but is more complex to implement.
How to Generate White Light
Producing white light with LED sources is a challenging task. Two methods are commonly used to create white light with LEDs. The first approach is through the combination of multiple colors, usually red, green, and blue, in multi-chip packages or LED clusters. This is the same principle used in backlighting LED LCD TVs: mixing the three colors in various proportions results in an entire spectrum of colors.
The second approach is to combine a semiconductor chip (blue or UV) with converter materials (phosphors) through luminescence conversion within a single package. A third approach involves an innovative combination of the best of both methods, called the “Brilliant Mix” Concept.
New Techniques for Achieving High CRI with LEDs
A phosphor-based high CRI approach is a method that includes an additional stable red phosphor. The latest developments using enhanced phosphors increase the CRI value to 95, but the trade-off is lower efficacy. LEDs are particularly efficient when color coordinates are closer to blue light, and the phosphor does not have to shift the blue coordinates quite so far. To achieve a warm white light, several luminescent substances must be combined, although this reduces the LED's efficacy. There is a limitation; with standard LEDs, it is not possible to realize LED luminaires and lamps with both high efficacies and high CRI.
However, with OSRAM’s “Brilliant Mix” concept, both high CRI and high luminaire efficiencies can be effectively realized. This approach fuses the two existing methods – mixed color from monochromatic LEDs and phosphor converted LEDs – to create a “warm-white” LED light source with both high CRI (> 90) and high luminous efficacy. This new approach makes total luminous efficacies of over 110 lumens per watt (lm/W) possible, producing up to up to 30 percent more light than phosphor-converted warm-white LEDs with a comparable CRI, but with similar power consumption.
Brilliant Mix is the mixing of two colors in order to generate warm white light. This approach uses red or amber monochromatic LEDs, combined with special white LEDs which have been shifted into the green range (called “EQ-White"). EQ-White is produced like a "normal converted white LED" with a blue chip and green phosphor. The green phosphor has a very low conversion loss rate and makes for a very efficient light source in combination with the blue chip.
Advantages offered by the Brilliant Mix Concept include high CRI, very high LED efficacies (> 110 lm/W possible), and warm white coverage from 2,700 K to 4,000 K.
Luminous efficacies of the two light sources are maintained, thus the new approach makes for a high luminous efficacy. The red LED is combined with EQ white (a highly efficient source with majority of its energy in within the green region of the visible spectrum, where the eye is most sensitive.)
When these two sources combine in the correct ratio, we get a pleasant, warm white light with a CRI over 90, giving us the ability to identify differences in the shades of the purple, blue and pink flowers by increasing our color discrimination, or how “vivid” and easily distinguishable colors appear. The average CRI of “Brilliant Mix” is very high (Ra>90). Additionally, the highly compact OSLON SSL LED is the vehicle for both phosphor-based and Brilliant Mix solutions. The standard phosphor conversion method produces reduced efficacy, but implementation is easier. Brilliant Mix enables higher efficacy but is more complex to implement.
LEDninja
Flashlight Enthusiast
Re: Anders Hoveland
Not new. Cree and others have been adding red LEDs to white LEDs for a while. Osram has just optimized it better.
Don't trust marketing folks who say their company invented this or that. Ask to see the patents. Most times they can't come up with them.
Not new. Cree and others have been adding red LEDs to white LEDs for a while. Osram has just optimized it better.
Don't trust marketing folks who say their company invented this or that. Ask to see the patents. Most times they can't come up with them.
