Raleigh wants to be "world's first" LED-lit city

[Mark_Larson]

Raleigh officials envision "world's first" LED lit city

While it's no secret that LEDs light up the night in a more efficient (albeit expensive) manner, few locales have given the idea of lighting up the town en masse with LEDs any serious consideration. In a feat that would surely oust Brussles' Dexia Tower in terms of magnitude, city officials in Raleigh, North Carolina are hoping to make the Capital City the "world's first LED city." Reportedly envisioned by the mayor, officials are teaming up with RTP-based Cree, Inc. in order to "save money and help the environment," and in a pilot program completed late last year, a LED-equipped parking deck purportedly burned "40-percent less energy" than those with "standard lighting systems." Additionally, the quality and brightness of the lighting was said to have improved, which paved the way for LEDs to hit up street lights, architectural and accent lighting, and pedestrian and walkway lights over the next 18 months. If things go as planned, the entire city will "convert permanently to LED lighting," hopefully saving around $80,000 a year in parking deck utility bills alone -- and hey, if nobody in charge can figure out how to use an extra 80 large per year, there's a few potholes craters on Hillsborough Street that could use some attention.

My view:
Don't believe the hype.

LED is nowhere near a mature technology yet. LEDs may look cool in your computer case and give a brighter light than those tiny incandescent flashlight bulbs, but trying to replace big gas discharge bulbs with LEDs is just insanity.

1. LEDs need LOTS of heatsinking. Their l/W output is terrible, and unlike an incandescent, halogen or gas discharge bulb, the heat can't be thrown out the front, it HAS to be heatsinked.

2. LEDs are tiny, tiny sources of light - they will cause lots of glare if not used with diffusers. Whereas gas discharge bulbs don't suffer with diffusers.

3. They're too expensive, and the fancy "More than 100 lumens per watt" are invariably tiny LEDs running at less than 1 watt.

4. The parking garage bulbs are not incandescent - they are already high-efficiency mercury vapor/metal halide or very high-efficiency high pressure sodium or ultra-high efficiency low pressure sodium.

So in conclusion, don't believe the hype.

[benighted]

Thank you for pointing that out.
It appears that the folks in Raleigh are out of their freaking minds.

Though I don't think those yellow/orange sodium lights put out any less glare than LED's would.

[WeLight]

3. They're too expensive, and the fancy "More than 100 lumens per watt" are invariably tiny LEDs running at less than 1 watt.


1 watt leds are barely used in these apps, where do you get the information to support your view

[JoeBob]

Cree is based near Raleigh, so that might have something to do with this.

OTOH, Raleigh can't even get a public transit system going, after decades of studies and wasted money. Don't hold your breath waiting for this to happen.

[2xTrinity]

Originally Posted by Mark_Larson

My view:
Don't believe the hype.

LED is nowhere near a mature technology yet. LEDs may look cool in your computer case and give a brighter light than those tiny incandescent flashlight bulbs, but trying to replace big gas discharge bulbs with LEDs is just insanity.

1. LEDs need LOTS of heatsinking. Their l/W output is terrible, and unlike an incandescent, halogen or gas discharge bulb, the heat can't be thrown out the front, it HAS to be heatsinked.

2. LEDs are tiny, tiny sources of light - they will cause lots of glare if not used with diffusers. Whereas gas discharge bulbs don't suffer with diffusers.

3. They're too expensive, and the fancy "More than 100 lumens per watt" are invariably tiny LEDs running at less than 1 watt.

4. The parking garage bulbs are not incandescent - they are already high-efficiency mercury vapor/metal halide or very high-efficiency high pressure sodium or ultra-high efficiency low pressure sodium.

So in conclusion, don't believe the hype.

I believe Cree actually posted an article about their prototype street lighting system. They claimed it to have a higher efficiency than High Pressure Sodium on the basis that the color rendering/spectrum is better so they don't need as many lumens for drivers to see as well (that I actually do believe -- the Crees I have in my flashlights are by far the best color rendering of any LED I've seen), and that they can more efficiently focus the light where it is needed than with HID lights, and thus minimize unnecessary spill.

Of course they "forgot" to mention that good Metal Halide lights have the same benefit in terms of color rendition, produce more lumens per watt than Cree LEDs driven harder than 1 watt, are a lot cheaper up front per lumen of output, and don't have any heat buildup issues if run for 12+ hours continually. Business parks that have switched from HPS to Metal Halide lighting have much better visibility than they did before in my experience, even better than adjacent ones running double the wattage in Sodium lights. To be fair, that is what they should compare the LEDs to.

[NewBie]

One of the issues with Metal Halide is that once you get them in a fixture, attach a ballast, and all that jazz, is you can easily end up in the 50 something lm/W range.

An example of a high bay setup, is shown here, and compared with other sources:
http://www.informinc.org/fact_P3lamp...php#efficiency

Metal Halide come in a variety of CRI, and higher CRI typically does not mean you are going to get better lm/W.

There are high end ballasts, that can help a bit with the efficiency issue, but usually, to get top end Metal Halide efficiencies, you are looking at a 400 to 500 Watt light, where the 100W ones can be as low as 80lm/W, before you take account for significant losses in the ballast and also the fixture.

Metal Halide degrade significantly in their output over their short 20-30k hour lifetime. Expensive ballasts can also help a bit with this, but they don't help the VHO or HO types that much. Some of the bulbs drop to ~50% output at 30k hours, and often drop by 40% in as little as 12k hours-high end ballasts can help here, but again, they don't help much with the VHO and HO. This drop in output in such a short time drops you into the 50lm/W range pretty quick, before other losses, like the fixture and ballast. Metal Halide bulbs usually also contain significantly more mercury than even the old fluorescents do.

Additional costs occur for bulb replacement by maintenance crews.

Many of the Metal Halide bulbs shift color over their life, but some advances have been made here.

Even a number of the 400W Metal Halide bulbs suffer from lower CRI, 65. With a ballast+bulb of 83lm/W, this drops to 54 lm/W by 12,000 hours, and continues to drop over it's lifetime. There are some high end specialty bulbs that hold up better now.

The fixtures add additional losses on top of all of this.

There is a chart that compares some of the various brands of Metal Halide bulbs here:
http://www.venturelighting.com/Liter...comparison.pdf

Some typical light drop over life curves for Metal Halide:
http://www.venturelighting.com/Liter...lance_0805.pdf

Notice how the lower wattage bulbs, which you'd use in a low bay setup, have rather short lifetimes of 10,000-15,000 hours. They also have lower lm/W numbers...


The problem is that folks will often pick out the very best bulbs they can find, picking the best lm/W from one, the best CRI from another bulb, and then not consider ballast losses, and also very significant fixture losses (they can easily hit 50% loss, but there are some that are a bit better). Then they will pick out the very best lifetime bulb from another bulb, and use the highest initial lumen bulb for their lm/W.

Unfortunately, reality is often another situation.

For a low bay install, have you a good 100W bulb that stands out head and shoulders above the rest, and could you link a datasheet? How about ballasts that go with this particular bulb? And fixtures with specifications for losses?

I'd sure like to know what the cat's meow is in Metal Halide these days, when you look at the complete system (bulb, ballast, fixture), as I have an area that could really use an efficient lighting setup, but once I look at reality, the numbers keep ending up abysmal. So, if you have any recommendations, I'm certainly all ears!

I'd also be interested in any bulbs that are made for shorter runtimes, as if you only turn the typical MH bulbs on for 1.5 hours, their life drops by 60%. This would result in a 10,000 hour rated MH 100 or 125W bulb ending up with a 4,000 hour lifetime.

They also recommend that you re-lamp the fixtures at 60% of the rated life, since the bulb lm/W drops so rapidly, and due to their color shift. I'm told that some ballasts can help with this also, but again, apparently it does not help much with HO or VHO bulbs much.

If I do this, then the 10,000 hour bulb that ends up at 4,000 hours when you have them on for 1.5 hours, I end up having to replace the bulb every 2,400 hours.

One of the Metal Halide bulbs a local home store carries is the M175U.

Spectral output graph:
http://dafnwebpd.sylvania.com/os_fil...88&Desc=M175/U

Lumen Depreciation:
http://dafnwebpd.sylvania.com/os_fil...d%20SuperSaver

CRI:
65

Average rated life:
7,500 hours

CCT:
4200

Initial Lumens:
14000

Mean Lumens:
9100 when mounted vertical
8200 when mounted horizontal

Mean lm/W:
52 lm/W when mounted vertical
46.8 lm/W when mounted horizontal

And this is for the bulb only! Not counting ballast or fixture losses!

[sgtgeo]

Crap i live here and have not heard of this.

Does this mean I'll be able pluck Cree emitters from all over town lol

[AndyTiedye]

Originally Posted by benighted

Thank you for pointing that out.
It appears that the folks in Raleigh are out of their freaking minds.

Crazy like a fox maybe. They are promoting a local industry, which will
bring in more jobs if their LED lighting is more widely adopted. They
probably got a good deal from Cree on the LEDs, since Cree will benefit
greatly by being able to showcase their products in this way.

LEDs are small and cheap, so you can use a lot more of them. That can
make the light less glarey instead of more.

Being the first LED-lit city seems like a better thing for a city to be known
for than being named after a cigarette.