Street Lighting Electricity Consumption Cut By 61% With LEDs & Wireless Controls
The city of West Richland, Washington, just completed an LED upgrade to its entire street lighting system, and the project is expected to reduce the system’s electric consumption by 61% and save the municipality $67,000 per year in energy costs.
The city street lighting project, which included replacing more than 1000 high pressure sodium (HPS) lights with energy-efficient LED models, as well as installing a wireless monitoring and control system, will allow the city to move from a flat rate from the utility to a consumption-based tariff, which will further reduce the city’s cost for street lighting.
“It makes good economic and business sense for the City to install new LED street lights and a wireless control system that reduces energy use by more than 60 percent while improving illumination, safety and addressing dark sky considerations. In addition to dramatic energy and maintenance savings, the control system will also enable us to move to a lower cost metered rate schedule that provides further cost reductions.” – Brent Gerry, Mayor, City of West Richland
The project was installed through a partnership with Ameresco, as well as the city’s electric utility, Benton Rural Electric Authority (REA), and thanks to partial funding from energy efficiency grants and incentives from the utility, is essentially “budget-neutral” to the city.
According to Ameresco, West Richland is “One of the first cities in U.S. to use control-based energy metering to achieve a lower cost rate tariff,” and that move is expected to reduce the city’s average cost per kWh by about 26%. The new wireless control and monitoring system is said to allow the city to “implement dimming strategies” that could reduce street lighting energy consumption by another 10-20%.
Image via Business Wire
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In NYC, especially Central Park where they’ve converted to LED, they still haven’t figured out how to have the lights come on at dusk and turn off at sunrise. I think ConEd doesn’t care since LED’s don’t use as much electricity. So the street lights stay on 24/7. This expensive conversion didn’t seem to include a reliable ‘electric eye’ to monitor when to turn on/off.
Commercial LEDs are still less efficient than low-pressure sodium bulbs, and only marginally better than high-pressure sodium.
Leaving them on 24×7 will definitely result in more energy usage over correctly-working traditional lights; it will also needlessly shorten their life, negating the main benefit they were supposed to provide, reduced maintenance.
What a waste.
Less efficient at what exactly?
The goal of street lighting is to provide drivers, cyclists, and pedestrians visibility and thus increase safety.
Sodium bulbs produce a high lumens per watt number, but the lumens they produce are single color. In other words, they render the landscape and anything in it monocromatically (effectively black and white). Put technically, they have a dreadful Color Rendering Index (CRI), which is actually zero for low pressure sodium and a still dreadful 25 for high pressure sodium lamps (LEDs are typically 80-90 CRI).
This matters a great deal because the goal is NOT raw lumens but human visibility. Color allows the human eye to perceive much greater contrast and depth. In technical terms, a high CRI means that both rods and cones in the human eye are receiving information. A very low CRI, as from sodium lamps, means that rods are quiecent, devoid of informational input (See Lawrence Berkley Laboratory’s scotopic lumens work for more detail).
Interesting. But I thought that in low-light conditions, we see almost entirely with the black-and-white rods. Does colour make a difference at night?
You are correct in seeing that scotopic vision dominates at night. And that’s the problem: street lights have historically always been measured photopically (that is to say, their ability to stimulate the cone cells). Because the light spectrum was designed around photopic vision, much stronger lighting than necessary was needed to achieve the desired level of scotopic stimulation.
You can read a brief summary of the work BigWu refers to here: http://www.innovativelight.com/wp-content/uploads/2014/07/Scotopic_vs_Photopic.pdf
asdsds dsds
I see the energy savings details, $67,000/Year. What was the cost of the conversion? Be interesting to calculate the payback.
i was wondering the same thing
The real, total cost is hidden, even in the press release.
> The cost of the project is budget-neutral to the City. Funding is partially provided through local grants, including an energy efficiency grant from the Washington State Department of Commerce of $281,937, and utility incentives from BREA totaling $195,000. The balance is financed for 12-years through the WA State Treasurer Local Option Capital Asset Lending program, and paid for through savings – See more at: http://www.ameresco.com/node/1419#sthash.oaBBJOlU.dpuf
The don’t tell us what the “balance” is that was financed over 12 years.
Interesting.
When public funds are being spent its a little disquieting when the details of expenditures is hidden or disguised.
Not mentioned is the significantly longer life of the LED bulbs. I assume maintenance costs to change bulbs will be much lower as well, and motorists will benefit from fewer burned out lights.
I work in local government in New Zealand. We have performed exacting cost-benefit analysis on the whole of life costs for a rapid transition to LEDs for streetlights (removing HPS en mass). The Transition would be funded from operational savings (energy reduction & maintenance) and would pay back after 5 years and deliver a $20 m (NZ) saving over 20 years for 4 thousand streetlights. This was before factoring in energy reduction (and added expense) from dimming through a CMS (we want to install a region-wide CMS, so requires buy in from other authorities).
What has stopped us in our region is our electricity distribution company “threatening” to change our variable energy costs to a fixed cost. They claim that the cost of running the 4th wire (and associated gear) was “reverse engineered” and that fiscal return is needed for maintenance and “improvements”.
If not hindered by lines companies like this, the case for transition is compelling. 80% maintenace reduction (HPS lasts for 4 years, LEDs for at least 15), less cleaning (flat or no visors); 50 to 75% energy reduction, no mercury in the lamp, the ability to control lighting to any extent and add “smart” services with the control system, virtually vandal proof, better CRI and distribution patterns… the list goes on.
Ah! Someone finally saw the light and it LED to lots of savings.
Show me a town or city where the Councillors and the CFO are not kin to dinos in doing a whole safety analysis of its varied citizens requirements of night lights.
Not a Simon and Garfunkel concert in the park song verse.
This is where warmer light is better. It just is — it’s better for sleep, it’s better for visibility (O.K., well, maybe that’s a lie, but slower wavelength light cuts through fog a lot better than whiter / bluer light), it’s better for aesthetics, and it’s more relaxing.
A warmer colored light CAN NOT make you sleepy. It can NOT put you to sleep. Those are the facts.
Do you have a source for saying that longer wavelength lights cuts through fog better? Since shorter wavelengths can endure more Mie scattering before their wavelength drops out of the visible light spectrum, one would intuitively assume the opposite of what you say is true.
Also, blue light’s inhibition of the melatonin metabolism has a positive side: blue lights have been shown to increase driver alertness. I’d say that alone makes a pretty good case for installing them alongside busy roads or near night clubs, for example.
Your crusade against the blue end of the spectrum is bizarre. LEDs offer an opportunity to precision-engineer the spectrum of light sources to location, time of day and other factors. There’s a time and place for everything, including for cool white light.
But we don’t NEED it, we’ve had HPS and how much trouble has that caused — a lot maybe? I wish I knew.
How about this though, (no rude tone here, just in advance) if you need a light source to KEEP you awake, then maybe you should stop operating the vehicle. That is what I’m trying to get across. If you think a light is making you sleepy – then it’s not the lights fault. You need to stop driving the vehicle because that’s not safe.
We do not need a bright white light source to stay awake. (but people who think they are awake try to concentrate and they get drowsy — that’s not the lights fault. Yes a bright white light helps but I don’t feel we should force that on people who want to relax.
Let’s not disrupt EVERYONE’S sleep just so that drowsy people can wake up. They should just go rest or wait for a while until they wake up. I understand that may not be feasible for everyone, and if it really means that much, then they can just stare at the headlights for a few minutes at a safe distance.
First of all, how does white lighting on the busiest roads keep people from sleeping well? I’d really, really hope your home has shutters if it’s on a busy road, where headlights from cars and lights from buildings can often cause more upwards light emissions than the street lights themselves.
If you are so tired that you risk falling asleep, you shouldn’t be driving. Duh. But there are plenty of studies that suggest the whiter end of the light spectrum increase alertness even in those who are not sleepy, through the mechanism described in an accessible way in GCO’s Wiki link.
I am familiar with bright light effects on sleep, look into the Harvard Medical School studies — they did about four of them, so that will give you lots of information.
Think about the pedestrians, being forced to walk around in bright white light if they want to do stuff at night — that’s not nice. We need to find a way to light streets with something in the middle, like 3200 – 3500K but we don’t really need anything much higher than that. I promise!
Don’t you have something important to worry about?
Buy yourself some blue tinted glasses to wear when out at night.
If a pedestrian is out on the street at night, he presumably intends to, well, walk – precisely the kind of activity that would benefit from bright white light.
And can you think of any city that installed street lights with color temperatures much higher than 3500K?
Yeah, places in Austin, TX, and California. I believe they use around 4000 – 4500K lights. Very white.
3500K is like a neutral yellowish white and it’s just barely higher than the maximum output of a halogen light source. Tungsten metal’s melting point is 3700 Kelvin.
Here is a chart to show you what each color temperature looks like in RGB values! http://www.vendian.org/mncharity/dir3/blackbody/
Erm. Why do you mention the melting point of tungsten? The Kelvin used for expressing the warmth of light has nothing to do with the melting point of anything (it’s not as if a metal melting at 1000K emits light with a color temperature of 1000K). Instead, it’s the temperature a hypothetical black body radiator would need in order to emit light with a given spectral distribution.
Your chart is somewhat deceptive, in that it fails to put the numbers in perspective. Daylight has a color temperature of around 20 000K. A miserable cloudy sky has a color temperature of 6500K.
4500K might feel very white, but it is by no means the sort of light that seriously affects your melatonin metabolism. The 7000K of a computer screen might be problematic though.
The idea that LED light is unnaturally blue is absurd. It’s years of tungsten and sodium lights have made us grown used to light with an unnatural blue deficit.
The SKY in daylight is 20,000K but a white sheet of paper is not. It’s closer to a warmer 6000K or slightly less. Anyway, 4500K is *MORE* than enough to affect sleep, I’m sure of it, and if you don’t believe it, I’ll consult a few experts in the future, I really will. It’s actually more complicated than I thought.
We have to think about not only color, but brightness, distance from the light, and how long we are exposed to it. There are many factors, and 4500K does have lots of blue in it.
If you’re not quite sure about what I light source has regarding color, that’s O.K., just have a look at the following website http://www.fluxometer.com/
I hope that will help, yes this can be challenging!
Of course all those factors matter. But brightness, distance and duration of exposure are independent of the color temperature of the chosen lamp. You’re really running out of arguments here.
The relationship between animals and light is not that complicated or challenging – the melatonin metabolism and the broader circadian rhythm is fairly well understood and relatively simple. Try the circadian rhythm and light response of plants if you want a real challenge 😉
What our human eyes perceive as ‘white’ actually changes with illumination. See Kruithof curve [link].
A 6500 K LED will perfectly match daylight around noon, yet look disgustingly blue at night.
A 3000 K halogen may feel very white in a bedroom, but seem hopelessly yellow in a more brightly lit office or retail space.
Our visual system is just built that way…
You’ve got your “facts” backwards [link].
We could light the whole country by putting a giant laser on the moon