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Old 03-16-2010, 09:48 AM   #1
orison319
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Default (MH) vs (HPS)..Light Pollution ..

WHITE PAPER: Metal Halide (MH) vs High Pressure Sodium (HPS)
Prepared by Susan Harder January 2007
HPS is a better choice for outdoor lighting applications than MH for the following reasons:
1. Efficiency
2. Vision
3. Health
4. Environmental effects (flora and fauna)
5. Toxins
6. Financial costs
HPS provides better quality lighting at a lower cost and with less damage to the environment.
Metal halide is much less efficient than high pressure sodium--MH produces much less light per
watt; MH produces more glare due to the blue light component and increases adaptation time;
MH more effectively shuts off melatonin production which can trigger tumor growth; MH
contains more mercury within the bulbs; MH bulbs need to be changed more frequently; and MH
costs more, overall.
For example, at 250 watts, mean lumen output per watt over the useful life of the lamp is 58 for
MH vs. 87 for HPS; in other words, HPS produces 50% more mean lumens per watt. Even at 70
watts, mean lumen output is 45 for MH and 64 for HPS; in other words, HPS produces 42%
more mean lumens per watt. 274% higher long term operating costs of MH as opposed to HPS
not only because of lumen depreciation requiring more watts, but also because lamp replacement
frequency is nearly twice as high.
Traveling from an area lit with MH will take the eyes longer to adapt to lower light levels,
affecting night vision. Night vision is also more sensitive to the HPS spectrum due to the greater
number of rods in the eye.
HPS lamps last longer than MH, which means fewer lamps heading for disposal (HID bulbs can
be, but are often not recycled for their mercury content). In general the average lamp life for MH
is 10,000-15,000 hours vs. 12,000-24,000 for HPS.
MH produces more sky glow, lumen for lumen, than HPS for the same quantity of radiant energy
from each source, due to higher blue light component and the Rayleigh scatter effect. The paper
at http://resodance.com/ali/bluskies.html suggests MH produces at least three times more sky
glow than HPS due to the higher blue spectrum content and has a greater impact on dark-adapted
astronomers...
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Old 02-16-2011, 02:22 AM   #2
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Wink MH vs HPS Pt2

I may be a few years late to post this, but had to chime in on this topic. While I do think the lady who wrote this article (I read it elsewhere but couldn't respond) is sincere in her efforts and views, I'd like to correct her in a few areas she may not be aware of. The first is on lumen performance. Yes, there was a time when HPS was the undisputable champ in scoptic lumen output---the output of visible light which translates to the human eye as "brightness of light in a given space". Those days are essentially over. The second generation of MH lamps known as "Pulse Start" have sufficiently closed the gap in scoptic lumen performance. These newer MH bulbs now have starters/ignitors that come with the ballasts and capacitors just like HPS. The result is faster warm up and restrike after a power interruption, longer life, higher initial lumens and less lumen degradation as it ages. (Higher Mean lumens)

As for life span, HPS still holds an edge here, but it's losing ground. On MH outputs of 200 watts on down to 35 watts average 12,000 to 15,000 hours depending on bulb's design orientation. The 200 watt MH in Mogul bases actually hit 20,000 hours with many manufacturers. From 200 watts on up, with pulse start MH, the ratings go from 20,000 hours to as high as 30,000 hours. This means that the current generation MH have now passed the HPS barrier in longevity in the mid to high wattage areas. Not uniformly across the board with all the manufacturers...but with a little shopping around, you can find one. It's only a matter of time as HPS technology has been unchanged since it was created 40 years ago.
As for lumen per watt output, Pulse Start MH ranges from 90 to 110 lumens per watt. Clearly close enough to put the HPS in range in comparison.

The one clear area HPS still holds is on lumen maintenance. Over it's lifespan, the average HPS bulb will still lose no more than 25% of it's initial output...while Pulse Start MH will approach 35% loss. However, please remember this fact. The human eye was never designed to be monochromatic in light reception. It was designed for the full spectrum of light. We're not insects or animals. The end result is, when you reduce the visible spectrum down to a single dominating color, you are doing the same thing to your eyes as you would to your ears if you took an equalizer, and tuned out 90% of the audible frequencies in those speakers. The volume level of the stereo may be the same, but because you've cut so much out...the overall decibel level will drop in the sense that there's less to hear. This means you may have to turn up the volume a bit to get the same overall effect. This is essentially what happens with an HPS system. Because of it's color, higher lumen output is a necessity in order to get a level of brightness that the eye can see as bright. With white light, you now have other wavelengths of light helping out the red/orange waves, and the end result is a brighter looking area. Thus, you can actually scale back the wattage and get a brighter area now. (To the eye) Many commercial and industrial companies are dumping the HPS for the Pulse Start MH for this alone. E.G. A warehouse with 400w low bay HPS lamps can convert to high bay 320w Pulse Start MH lamps, and actually improve the lighting levels and effectiveness as well.

So just as bright in your face blue-white light can hurt your vision (over repeated, long lasting events), so can continual exposure to monochromatic lighting in certain situations....causing eyestrain. Not to mention the effect it has on the body as for our hormones. It's a proven medical fact that people's emotions are positively effected by white light, and the further away you go from that...and the longer you stay away from that, the more adversely people are affected.

Lastly, about sky-glow. This area we may have to disagree, mainly because of my experience in EM radiation propagation as a former Electronics Warfare Operator in the Navy. Light is just another form of radiation....just like radio waves, or radar. You have different frequencies of radio/radar waves and the same goes for light. In radio and radar, the longest ranges are reached with the lower frequency transmitters. Some of which are "over the horizon", meaning they can be bounced off of clouds to reach beyond the curve of the earth. The highest frequencies are short range, thus they are confined to less than horizon ranges to just beyond. Shorter range radar can also be more adversely affected by atmospheric interference...whether natural or manmade..than long range radar or radio can. Now, translate this to light waves. HPS is an orange/yellow light. Some in the 2100K color range are downright red-orange...and the rarer 1900K ones are nearly the color of a road flare. This is getting down into the looooong wave end of the spectrum. Now, put about 26,000 to 50,000 lumens per streetlamp behind this and put a nice overcast nightime sky overhead. Then, go out into the suburbs where there are far more MV and MH lamps than HPS in the central city. Guess what? When you look into the cloudy sky, you will think you're on Mars...cause the clouds will be quite orange. Getting brighter as you look over towards the city. The only time I've ever seen anything like this with the white MH bulbs is on a heavily foggy night. Or really low cloud ceilings. And then, only when I'm within relatively close proximity to the lit area...like a few miles. Once I'm about 5 miles out, no more white cloud glow. But with HPS....I can see the glow softly from nearly ten miles away. Why? Because HPS has a wavelength freq that is soooo long, it is not easily scattered. This is why many jurisdictions use HPS for streetlighting (besides lumen/watt advantages). It's more resistant to the effects of heavy fog thus, it can reach further and still be seen. White light is much shorter in wavelength freqency, thus it scatters quickly. It'll have a harder time reaching the clouds in any amount of strength, then make it back down to earth to be seen. (You can't use the daytime sky as an argument for the sky glow of MH lights, because the light source is the sun...and it's outside of the Earth, lighting the whole side of the planet with way more light than we could ever hope to create.)

So, that said...I'll conclude with this. HPS may be in the lead, but by a whisker. With next generation white lighting starting to show up: (Induction lighting and High Output LED lighting) and the advent of night sky friendly luminaires (cut offs, recessed bulb mountings) HPS is on life support. The proof is in the lack of active research and investments in the bulb to improve it. The first MH bulbs were the rightful 2nd gen MV lamps. Their cost kept them from killing MV. The pulse start MH are the third gen MV lamps. HPS was designed to address the original MV's lack of real light output and efficiency. Pulse start MH (3rd gen MV) have done that. Hence, the switch in the commercial sector back to white light. HPS only home of respite may very well be road lighting...until the Mercury Lamps are made illegal in a few more years due to new energy efficiency rules. Then, as the ballasts die...either all streetlamps will go HPS, or those thas were MV will be made MH or H.O. white L.E.D. lamps. My view is in about 10 years, white L.E.D will trump everybody in lumen/watt/longevity/anti-light pollution, and we'll see all streetlamps and parking lots go to this light. But why....not because of global warming as they'll try to tell you. It's about the "New World Economy" America is readying herself for at our expense...but that's another subject for another time.
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Old 02-16-2011, 02:27 AM   #3
orison319
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I may be a few years late to post this,
I dont remember posting it..

but thanks for sharing.
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Then they bring them to the factory
Where the heart-attack machine
Is strapped across their shoulders
And then the kerosene
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