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UK replacing sodium street lights with LEDs, "to save electricity"?
Posted by
Artlav
on 18 Apr, 2014 17:00
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I've been looking at some news from UK lately, where they apparently try to save money on street lighting.
http://www.bristolpost.co.uk/Burglars-afraid-dark-Crime-falls-Bristol-street/story-13952633-detail/story.htmlSome places turn off lights for the most of the night, which despite the fears of increase in crime rate seem to turn out ok.
But what caught my attention are the other places.
To quote:
A similar programme has begun in North Somerset, while in Bristol the council is taking a different tack by replacing light bulbs with state-of- the-art LED ones which are brighter and use less electricity.
We do feel there are savings to be made from converting all of our street lighting to more energy-efficient white light. This is why we are currently replacing around 34,000 sodium lights with new white lights.
There is also peculiar explanation on Bristol's official site:
http://www.bristol.gov.uk/page/white-light-replacement-programmeWhite light provides better colour rendering than standard yellow/orange type streetlights so the eye is able to see objects more easily. This means the actual amount of energy required to provide a suitable level of visibility can be reduced by around 40%.
How is that supposed to work?
I was under impression that the sodium lights were the most energy efficient lights there are, with LEDs quite a bit behind.
And the efficiency in question is measured in lumens per watt, which are defined in terms of human eye sensitivity, making the last argument peculiar.
Am i missing something?
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#1 Reply
Posted by
cjo20
on 18 Apr, 2014 17:14
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I think the argument is that because white light lets you see if more than just slightly different shades of orange, there needs to be less white light hitting a surface than sodium-lamp light for the brain to extract the same amount of information from the scene, so they can be run at a lower power
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These new led lights are far too bright there have been many complaints that people are being kept awake at night due to the street lights shining into there bedrooms.
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#3 Reply
Posted by
IanB
on 18 Apr, 2014 17:38
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Also, astronomers will hate them. The orange sodium light is monochromatic so there is some ability to filter it out. White light is broad spectrum, so the opportunities to filter it are greatly reduced.
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#4 Reply
Posted by
ajb
on 18 Apr, 2014 19:09
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The human eye has a sort of bell shaped response curve to the visible spectrum, with a peak somewhere between 510 and 560nm, depending on the adaptation of the eye to ambient conditions (photopic, scotopic, or mesopic vision, depending on if the eye is adapted to bright, dark, or intermediate conditions). In darker conditions, the eye responds most strongly to wavelengths in the 510-530nm area. Sodium lamps have most of their output in the longer wavelengths, with a sharp peak around 590nm and a big lump in the ~600-620nm range. Since the eye's response drops off fairly sharply to either side of the peak, these wavelengths appear to be relatively dim, watt for watt*, relative to wavelengths near the peak response point.
With LEDs, you can better tailor the phosphors to have more of your output concentrated in the wavelengths to which the eye is more sensitive, and thus for the same or less wattage, you get a brighter light.
Furthermore, with white light you get better color rendering, which means better contrast, which means watt-for-watt* you get better visual acuity.
*radiometric watts, meaning actual watts of light emitted; obviously for total energy efficiency you have to account for the conversion efficiency of the light source.
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LEDs may also have a better lamp life time. I intentionally wrote "may", as it's all depends on the driver and LED arrangement. Most LED lights I've seen are garbage. Some sort of "constant current" driver dumping into several parallel strings of LEDs. Maybe that works when you match the LEDs, but most of the time it will fail about as fast as a typical halogen bulb.
At least you can advertise your building as being energy efficient, as it's fitted with "the latest high efficiency LED technology".
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#6 Reply
Posted by
rdl
on 18 Apr, 2014 23:37
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If they ever install one of those awful, way too bright, glaring, overly blue LED streetlights in front of where I live, I will shoot it out at least once. Or at least complain loudly.
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#7 Reply
Posted by
SL4P
on 19 Apr, 2014 01:08
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I'd be questioning the usefulness of white LEDs in 'foggy' old England.
They'll see NOTHING with bright white lighting, whereas they'll see a lot more with the contrasting effect of the pure spectrum of the yellow sodium lamps.
But this may just be another example of younger engineers not understanding why the 'older' engineers did a specific thing.
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#8 Reply
Posted by
NiHaoMike
on 19 Apr, 2014 02:20
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The efficiency can be improved many fold if they add some motion sensors. LEDs are very well suited for dimming, while sodium lamps are not.
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#9 Reply
Posted by
Bored@Work
on 19 Apr, 2014 03:20
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Oh come on, all you lot want is to have your good old gas lighting back. Complete with the lamplighter guy walking around, igniting them at sunset and turning them off at sunrise, and checking the whole night if they still burn.
Or even better fatwood. Worked since prehistoric times, why replace it with some modern fad?
I mean serious, why do you lot touch modern stuff like electronics at all? It is all the work of the devil, you know. Back to your caves, guys. Back to your caves.
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Oh come on, all you lot want is to have your good old gas lighting back. Complete with the lamplighter guy walking around, igniting them at sunset and turning them off at sunrise, and checking the whole night if they still burn.
Or even better fatwood. Worked since prehistoric times, why replace it with some modern fad?
I mean serious, why do you lot touch modern stuff like electronics at all? It is all the work of the devil, you know. Back to your caves, guys. Back to your caves.
Yeah, jeez, may as well walk around with a burning stick just to make em happy.
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#11 Reply
Posted by
vk6zgo
on 19 Apr, 2014 03:50
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I'd be questioning the usefulness of white LEDs in 'foggy' old England.
They'll see NOTHING with bright white lighting, whereas they'll see a lot more with the contrasting effect of the pure spectrum of the yellow sodium lamps.
But this may just be another example of younger engineers not understanding why the 'older' engineers did a specific thing.
Also LED's weren't available when sodium vapor lamps were originally selected.
What contrast?--All those colours with a bit of yellow appear as yellow,white appears as yellow,shades of grey are yellow.
Sodium lights were selected because
they cost less to run than colour corrected mercury vapour lights,which when they are in good condition,offer the best type of lighting.
Sodiums,on the other hand, are about the worst possible form of street lighting.
Unless an object has some orange/yellow component in its colour,it is effectively invisible.
Young Engineers?---Most older Australians spent the first half of their lifetime with either incandescent or Colour-corrected Mercury vapour street lighting--the mass replacement of these with sodium lamps mainly occurred in the 1980s.
The Brits used them many years before that--when I was in the UK in 1971,I nearly got run over by an "invisible"taxi at a crosswalk.
The Taxi was dark blue,with only its parking lights on,so that's why I didn't see him,but he didn't see me either.
(For many years,you could drive on "parkers" in the UK in built up areas---the law had just changed,but it took a while for people to catch on).
It was also great fun,walking all over Southampton,looking for a pink Cortina hire car.
It
was where I thought it was,but it looked like a Yellow Cortina.
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#12 Reply
Posted by
IanB
on 19 Apr, 2014 04:59
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Young Engineers?---Most older Australians spent the first half of their lifetime with either incandescent or Colour-corrected Mercury vapour street lighting--the mass replacement of these with sodium lamps mainly occurred in the 1980s.
The Brits used them many years before that--when I was in the UK in 1971...
Yes, they were phased in around that time I guess. The street where I grew up in the 60's was lit by fixtures with 100 W incandescent bulbs in them. I found this out by asking for some of the old bulbs when a maintenance crew was going round replacing time expired bulbs for fresh ones.
I also remember places with (non-colour corrected) mercury vapour street lighting around the same time. It was a weird contrast seeing "green" street lights compared to the more familiar yellow ones. I didn't like the mercury lamps though. They seemed very cold and unwelcoming.
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#13 Reply
Posted by
Zero999
on 19 Apr, 2014 08:35
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These new led lights are far too bright there have been many complaints that people are being kept awake at night due to the street lights shining into there bedrooms.
It's not just the brightness which wakes you up but the shorter wavelengths which disrupt sleep more than the longer wavelengths.
This is a valid complaint. I think warm white should be used in residential areas, as this would be less of a problem.
The efficiency can be improved many fold if they add some motion sensors. LEDs are very well suited for dimming, while sodium lamps are not.
Yes, I've wondered why they don't do that. On main roads, the sensors could also turn on the lamps several hundred meters ahead, when a car passes.
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#14 Reply
Posted by
Codemonkey
on 19 Apr, 2014 08:50
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They'll see NOTHING with bright white lighting, whereas they'll see a lot more with the contrasting effect of the pure spectrum of the yellow sodium lamps.
Complete rubbish. I live not far away from a road that's just had sodium lamps replaced with nice modern LED lights. The road is considerably better lit now. Driving down the road as they were replacing the lamps (2/3 LED, then the remaining 1/3 section still sodium lit), it was obvious that the LED lit section was much better on the eyes than the sodium, probably due to the broader spectrum of light making it easier to distinguish things, and also the light pollution was much reduced due to the design of the luminaire itself.
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#15 Reply
Posted by
G7PSK
on 19 Apr, 2014 08:55
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Don't forget that this decision to fit LED's instead of sodium lamps has been made by a City council, therefore the saving could be very small or non existent. They talk about CO2 savings and other green agenda but they will have used half a forest of trees in coming to this conclusion and the cost of making the switch not the lamp cost just the contractor cost will in all likelihood be more than several years cost of running the sodium lamps.
Now if they went around lighting all the pot hole in the roads or better still filling them in. But they always seem able to find the money for some grand scheme but never have any money for maintenance.
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#16 Reply
Posted by
SeanB
on 19 Apr, 2014 09:01
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Sodium lamps and mercury lamps can have a multi decade lifetime if well designed and made. This was solved in the 1950's for mercury lamps, where they made lamps that would last for 15 years in street lighting use, and which could run for more than 30 years, albeit with decreased light output, in many cases. Simple control gear as well, which would also last the 30 years with no degradation even after multiple storms and many close strikes with lightning.
Of course then the manufacturers "optimised" the design so that they only lasted 10 years, then 5 years. Same with the ballasts, "optimised" for smaller cores that ran a lot hotter and thus would burn out in about 20 years. All done to reduce manufacturing cost and maximise profit.
The mercury lamps as well are very easy to recycle, you just need the metro to have a drum that the lamps are crushed into which is then sent when full to have the glass, mercury, brass, tungsten, lead and nickel recovered and remade into new lamps. All simple processes and all easy to do. Sodium lamps are slightly more difficult as they are made with 2 or more glass types and with quartz tube as well, but they can still be recycled as well. Compare to LED lamps with every element in the periodic table in there in small amounts and difficult to separate out from the product easily, with most being a lot more toxic than mercury and lead.
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#17 Reply
Posted by
Marco
on 19 Apr, 2014 10:46
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These new led lights are far too bright there have been many complaints that people are being kept awake at night due to the street lights shining into there bedrooms.
Can't they just turn them down and save even more energy?
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#19 Reply
Posted by
con-f-use
on 19 Apr, 2014 11:03
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I would expect LEDs are easier on infrastructure requirements, maintenance and availability/production costs.
I don't really get why people are that obsessed with making lighting more efficient. The share in total electricity consumption is small (about 13% in your average first world country). Industrial machinery etc. and a ton of other stuff is a more rewarding target for optimization. The effort is better spend elsewhere first.
Also, astronomers will hate them. The orange sodium light is monochromatic so there is some ability to filter it out. White light is broad spectrum, so the opportunities to filter it are greatly reduced.
But it would be much less intense and absorption works better. On top of that scientific telescopes are build where there is no light smog anyway and Britain is not interesting to astronomers (bad weather, bad geographic location, bad altitude). Even as an astro physicist, I wouldn't say we are near that important for the argument even to be brought up jokingly.
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#20 Reply
Posted by
steve30
on 19 Apr, 2014 12:11
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Some of our main roads have had new LED lights installed. The better colour rendering definitely makes it easier to see things.
Now, as far as sodium goes, does anyone still make Low Pressure Sodium lamps any more? They don't seem to be widely available. Many of our low pressure sodium fixtures are very old, and in some cases, they have come and replaced entire sets of lamp posts. Our street had a mixture of old low pressure sodium, old high pressure sodium and new high pressure sodium lamps, so they recently came and modernised it by fitting all new high pressure sodiums. I think there probably is a good case for 'modernisation'.
What worries me is fluorescent lights. Over the last few years, our council has replaced many residential street lights with fluorescent ones. I'd imagine they aren't any better than sodium.
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#21 Reply
Posted by
con-f-use
on 19 Apr, 2014 12:27
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Another big problem is the wildlife being irritated by street lights. Especially insects. At first it might sound good and you see the occasional bat or bird finding easy hunting grounds around street lights. But actually a lot of insects die and don't reproduce leading to less food. Other animals get disrupted in their usual daily pattern and can't adapt. A biologist told me LEDs are better way better for insects.
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#22 Reply
Posted by
G7PSK
on 19 Apr, 2014 16:00
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I guess the weather there is so lousy, there are no astronomical observatories in the region to complain about the light pollution.
http://en.wikipedia.org/wiki/Sodium-vapor_lamp#Light_pollution_considerations
There are a few radio observatory's in the UK as well as optical ones, there could be a concern with led street lighting causing Rf pollution, The RSGB has recent raised concerns about led lights and Rf pollution and is conducting a study. There are also concerns about Rf pollution from solar cells as well or the inverters and control gear associated with them.
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#23 Reply
Posted by
Mr Smiley
on 19 Apr, 2014 17:09
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They'll see NOTHING with bright white lighting, whereas they'll see a lot more with the contrasting effect of the pure spectrum of the yellow sodium lamps.
Complete rubbish. I live not far away from a road that's just had sodium lamps replaced with nice modern LED lights. The road is considerably better lit now. Driving down the road as they were replacing the lamps (2/3 LED, then the remaining 1/3 section still sodium lit), it was obvious that the LED lit section was much better on the eyes than the sodium, probably due to the broader spectrum of light making it easier to distinguish things, and also the light pollution was much reduced due to the design of the luminaire itself.
SL4P was referring to the good old UK foggy days, where mist and fog from surrounding areas badly effected visibility day or night.
Clearly stating that the pure spectrum of sodium lights would provide a longer reaching illumination of the surrounding area than a led light source.
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#24 Reply
Posted by
BennyBoy
on 20 Apr, 2014 00:28
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They have them installed where I am(Oakland, Cal) They are not all that bright, there's a bright sort of spot on the road(say 10 meters DIA), but overall there's less light. It also shows in my security cameras to have less light.
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#25 Reply
Posted by
vk6zgo
on 20 Apr, 2014 03:27
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They'll see NOTHING with bright white lighting, whereas they'll see a lot more with the contrasting effect of the pure spectrum of the yellow sodium lamps.
Complete rubbish. I live not far away from a road that's just had sodium lamps replaced with nice modern LED lights. The road is considerably better lit now. Driving down the road as they were replacing the lamps (2/3 LED, then the remaining 1/3 section still sodium lit), it was obvious that the LED lit section was much better on the eyes than the sodium, probably due to the broader spectrum of light making it easier to distinguish things, and also the light pollution was much reduced due to the design of the luminaire itself.
SL4P was referring to the good old UK foggy days, where mist and fog from surrounding areas badly effected visibility day or night.
Clearly stating that the pure spectrum of sodium lights would provide a longer reaching illumination of the surrounding area than a led light source.
Still not true--I've driven in fog under sodium lights,both here & in the UK---they are uniformly lousy,no matter what the weather conditions are.
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#26 Reply
Posted by
jh15
on 20 Apr, 2014 03:46
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Did you notice the sky is blue? The most polluting color at night is from mercury halide, and now mostly blueish white led signs and lights.
Light at night is best: When needed, where needed, and the right amount.
T see where you are going LP sodium was efficient, and least polluting, especially if in fully enclosed fixtures (not partial or full cutoff).
You are paying from your taxes light hitting your room from streetlights, or your neighbor is to light your bedroom.
But it is a lost battle... At one time you could tell a council, neighbor, dept., " you will save money lighting just your own property, lighting when where and how much".
Now with LED and Cheap bluish floros, it gets worse every night in the neighborhood.
Now they can take their 60 watt bulb out put in a blue-white glare bomb for 15 watts.
www.darksky.org
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#27 Reply
Posted by
tjaeger
on 20 Apr, 2014 05:25
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Compare to LED lamps with every element in the periodic table in there in small amounts and difficult to separate out from the product easily, with most being a lot more toxic than mercury and lead.
You gotta be fucking kidding me. As far as non-radioactive elements go, it doesn't get much more toxic than mercury -- and that stuff is super bioaccumulative, too. This is of course not to say that mercury from lamps (of any kind) is much of a problem (coal is the main culprit here), but still, bullshit like this needs to be called out.
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#28 Reply
Posted by
SeanB
on 20 Apr, 2014 09:16
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True, but in a recycled lamp they are there in good enough quantities to make recycling worthwhile. For every ton of lamps you will get a good amount of metal that can be sorted out easily by melting point.
Compare with electronics where you mostly toss all except the copper and lead/tin away as it is too hard to process.
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#29 Reply
Posted by
rdl
on 20 Apr, 2014 19:56
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The color of the light is probably a bigger problem than the brightness, 4000K and higher is too blue.
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We had them installed a couple of years ago. Better light, lower power/cost, they last longer... What's not to like? As for light pollution annoying people trying to sleep, around here they put shades on the lights to stop them shining into people's homes.
thats a good idea, although we havent got led lights, our council changed oure street lights to energy saving ones that are much brighter we had to install blackout blinds in my bedroom as the light was keeping me awake
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#31 Reply
Posted by
ConKbot
on 21 Apr, 2014 00:29
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http://en.wikipedia.org/wiki/Kruithof_curve
While the CRI of sodium lamps wasnt great, at least it was in a comfortable portion of the kruithof curve. IMO the worst thing for eye strain when driving is a color temperature thats too high for the amount of light provided. 6000K (or higher
) HID lamps that put down ~200 lux on the at best? yeah mr ricer pal those HID's let you "see better" Though if you notice ~4500K which auto manufacturers use comes in right on the border for 200-250 lux, so its actually appropriate.
For 6000K LED lighting that ~400 lux to meet the 'comfortable' area, thats 400 lm/m^2, with ~120lm/w for low CRI LED lighting wallplug efficiency, 3.33 W/m^2 of coverage
With high pressure sodium, getting about the same efficiency, but in a lowly 2500K color temp, you only need 70 lux or 70 lm/m^2 to fit in the "comfortable" area. or 0.58W/m^2 of coverage
I'd be interested to see if any places installing LED for street lights actually managed to reduce eye strain with LED, and save money on electricity at the same time.
I'm definitely not anti LED or progress, I'm just anti-spin/marketing/bullshit/trendy thoughtless fads. 3500K COB array LEDs make great halogen replacements for fiber optic illuminators for microscopes. What was 150W before, now 15W, and only $50 in parts when the replacement bulbs are $35.
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#32 Reply
Posted by
IanB
on 21 Apr, 2014 00:43
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But color temperature (and thus the Kruithof Curve) is only applicable when the light follows a Planck or Maxwell-Boltzmann frequency distribution curve.
With artificial light that has an irregular frequency distribution curve such as from phospor mixes or gas discharge lamps you can't really assign a color temperature.
When light has a Maxwell-Boltzmann frequency distribution it is relatively easy to apply a color correction by shifting the peak left or right so that white objects appear white. Your brain does this naturally, which is why incandescent lamps appear white to your eyes even though they appear yellow to cameras.
If the light has an irregular frequency distribution your brain still tries to apply an appropriate white balance frequency shift, but a simple frequency shift doesn't work and the light won't appear white no matter what. The result is that the light becomes tiring to experience and uncomfortable to the eye.
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#33 Reply
Posted by
vk6zgo
on 21 Apr, 2014 01:47
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It has a lot more to do with road safety than eyestrain!
Monochromatic light like that from sodium lights transforms everything to one colour-------in this case yellow,so that objects which reflect the same amount of yellow appear as the same colour,& in effect,as the same object.
If the colour does not reflect any yellow,it appears as black--but shadows are also black,the road is almost black so a person in blue clothes disappears,a blue taxi disappears.
"Illuminant D",or as is the modern usage,"D65",which is 6500K,is standard white for the PAL TV system.
TV CRTs don't put out a lot of light,but the eyestrain problem is minimal.
If you so desperately want to save people from eyestrain,just turn off the streetlights & we'll rely on our headlights.
There wouldn't be much difference when it comes to sodiums,anyway!
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#34 Reply
Posted by
ConKbot
on 21 Apr, 2014 02:25
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None of the sources we're taking about have a good blackbody spectrum, not sure how color temp is approximated for non ideal spectra. Wonder how much leeway manufacturers have with that and how much they work it to their advantage?
Is low pressure sodium common for roadway lighting where you guys are at? On the eastern seaboard of the us for roadway lighting you're mainly talking high pressure sodium which isnt monochromatic, and imho isnt bad to drive under, provides plenty of visibility without ruining night vision. The only place Ive seen LPS (monochromatic) is in unused (at night) parking lots for security lighting only.
I could certainly see being sick of LPS and ready for LED to replace it.
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#35 Reply
Posted by
IanB
on 21 Apr, 2014 03:24
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Is low pressure sodium common for roadway lighting where you guys are at?
Spot the orange:
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#36 Reply
Posted by
vk6zgo
on 21 Apr, 2014 04:04
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The only ones I've seen which are recognisable on sight as "sodium" lights are the monochromatic yellow ones.
There may be a few of the high pressure ones around,but I may have just thought they were some version of colour corrected mercury vapour.
The yellow ones are endemic in Oz,& at least,used to be so in the UK.
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#37 Reply
Posted by
SeanB
on 21 Apr, 2014 05:11
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You will not see LPS ( which is the narrow band yellow sodium lamp) around in Aus/NZ as there almost universally they used high pressure sodium lamps, easy to see as they have a small arc tube inside made from fused quartz glass. These have a wider colour spread, mostly from the high pressure and from the added mercury and other metals added to get the striking and run up charactaristics. They have a blue/white glow shortly after start up from the Xenon gas filling used inside. LPS lamps have a large long arc tube inside filled with neon, and coated on the outer surface of the inner dual glass tube with ITO film to reflect IR radiation back into keep the lamp hot. Easy to see as they start off red and slowly change to golden yellow after a few minutes.
HPS took over as they are smaller light sources so the fittings could be made smaller to accommodate the optics to direct the light. The control gear as well can be made cheaper, as all you need is a choke and an ignitor, either a superimposed or a integrated one to give the high voltage to start the lamp, at least on 230V supplies. On 115 volt supplies they use an autotransformer type ballast. LPS needs a better current control and a higher striking voltage for high power lamps ( highest was a 200W lamp), so the ballasts were heavier.
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#38 Reply
Posted by
IanB
on 21 Apr, 2014 06:37
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I just took a look outside and the orange low pressure sodium is everywhere, in my local streets and in the far vistas across the city. The whiter high pressure lamps are in islands where brighter lighting is needed such as parking lots and public spaces.
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#39 Reply
Posted by
BravoV
on 21 Apr, 2014 08:18
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... A biologist told me LEDs are better way better for insects.
... "way better" ... , if this is true from the mouth of a biologist, once the whole world adapted led as street or every out door lights, I imagine if this will ignite the explosion of insects population that affects the whole world's agriculture crop in a very bad way at global scale.
I guess I'm worrying this way too much eh ?
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#40 Reply
Posted by
AndyC_772
on 21 Apr, 2014 08:26
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We had them installed a couple of years ago. Better light, lower power/cost, they last longer... What's not to like? As for light pollution annoying people trying to sleep, around here they put shades on the lights to stop them shining into people's homes.
The shades are crap, they don't work. Our local street lights were replaced last year, and during the winter when there's no leaves on the trees to shade them it's like ET just landed outside.
Shades are definitely fitted, apparently, for all the good they do.
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#41 Reply
Posted by
G7PSK
on 21 Apr, 2014 08:51
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#42 Reply
Posted by
SeanB
on 21 Apr, 2014 08:59
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I just took a look outside and the orange low pressure sodium is everywhere, in my local streets and in the far vistas across the city. The whiter high pressure lamps are in islands where brighter lighting is needed such as parking lots and public spaces.
Are you sure it is LPS? HPS is more common, and for a white light you use a metal halide lamp, which looks very similar just has a different filling inside the capsule, and operates at a much higher pressure. You can interchange certain of the lamps between the 2, as some MH lamps were designed as retrofit lamps for HPS lamps, while some HPS lamps were designed with a starting electrode and an integrated ignitor inside the glass envelope as a replacement for mercury vapour lamps.
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#43 Reply
Posted by
vk6zgo
on 21 Apr, 2014 09:45
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You will not see LPS ( which is the narrow band yellow sodium lamp) around in Aus/NZ as there almost universally they used high pressure sodium lamps, easy to see as they have a small arc tube inside made from fused quartz glass. These have a wider colour spread, mostly from the high pressure and from the added mercury and other metals added to get the striking and run up charactaristics. They have a blue/white glow shortly after start up from the Xenon gas filling used inside. LPS lamps have a large long arc tube inside filled with neon, and coated on the outer surface of the inner dual glass tube with ITO film to reflect IR radiation back into keep the lamp hot. Easy to see as they start off red and slowly change to golden yellow after a few minutes.
HPS took over as they are smaller light sources so the fittings could be made smaller to accommodate the optics to direct the light. The control gear as well can be made cheaper, as all you need is a choke and an ignitor, either a superimposed or a integrated one to give the high voltage to start the lamp, at least on 230V supplies. On 115 volt supplies they use an autotransformer type ballast. LPS needs a better current control and a higher striking voltage for high power lamps ( highest was a 200W lamp), so the ballasts were heavier.
If the ones in Oz are HP,I can only say----What wider colour spread?
They look yellow,& only yellow!
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#44 Reply
Posted by
SeanB
on 21 Apr, 2014 10:19
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#45 Reply
Posted by
Kjelt
on 21 Apr, 2014 10:21
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Here in the Netherlands some highways replaced the orange sodium lights 6 years ago with white HID 4000K lamps called
CosmoWhite They are in different wattages and color temperatures available and personally I like them much better then the orange sodium lights. The view is better.
Unfortunately the white light seems to have a negative effect on wild life so it is not suitable for all places.
Concerning the LED street lights, they can also be had in different color temperatures and even colours. I saw places with the green LED lanterns and I really hated it. It has a great lumens/W because the human eye is very sensitive for greenish light but it is a crime for the driver (personal experience).
Then the higher color temperatures might also be not so suited for humans (no personal experience here) but it could also be a life safer since it contains a higher amount of blue light which (as they found out some years ago) the human has also recepticles for in their eyes and one of its purposes is to stay or get awake. So blue light is a wake up call where yellowish light is a goto sleep call. They experimented here in classrooms with different color temperatures and found out that students are more alert to exams in blueish light and their results are better where yellowish light makes them relax more. So what do you want on a highway with 120km/h traffic? Awake or half asleep drivers?
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#46 Reply
Posted by
London Lad
on 21 Apr, 2014 10:29
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Bypassing all the science for a moment I can catagoricaly report that where old street lighting has been replaced by LEDs in my area of the UK the illumination is infinity brighter, has a more even spread and provides better colour rendition when compared to the old lighting.
In my own expierience of replacing sodium lighting in our factory car parks with LED i can confirm a significant saving in electricity consumption.
There are of course a vast range of quality of LEDs and LED drivers.
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#47 Reply
Posted by
IanB
on 21 Apr, 2014 17:22
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Are you sure it is LPS?
Yes, quite sure. The orange/yellow glow from LPS is unmistakable and has been part of the street lighting scene forever.
The brighter flood lights used for area lighting could be metal halide of course; I wouldn't like to say without closer inspection. (But metal halide is also a high pressure gas discharge lamp.)
