Energy Efficiency

Published on April 29th, 2013 | by James Ayre


LED Streetlight System Cuts Down On Light Pollution And Improves Energy Efficiency

April 29th, 2013 by  

A new LED street lighting system that greatly improves energy efficiency while also cutting down on unwanted light pollution has been developed by an international team of researchers from Mexico and Taiwan. The system is set up so that the high-efficiency LEDs only shine where they are needed, greatly reducing light pollution.

Image Credit: Optics Express

Image Credit: Optics Express

No more bright street lights shining through your bedroom window when you’re trying to sleep. Or, for that matter, limiting your ability to watch 2013’s great meteor showers.

One of the most impressive features of the new system is its adaptability to a variety of street lamp layouts, streets, and roads; the whole time providing uniform illumination and very good energy efficiency. As an example, “some modern lamps that line a thoroughfare or suburban sidewalk lean into the middle of the road, lighting the street from above. But more often, lamps are posted to one side of a street, or alternating in a ‘zig-zag’ pattern from one side to the other — a layout that may be more efficient for roads with high traffic flow. The new design provides flexibility to be used for different illumination requests while maintaining a high efficiency,” says co-author Ching-Cherng Sun of National Central University in Taiwan.

Image Credit: Optics Express

Image Credit: Optics Express

With regards to the new lamp design, here are more details:

“[It’s] based on a novel three-part lighting fixture. The first part contains a cluster of LEDs, each of which is fitted with a special lens, called a Total Internal Reflection (TIR) lens, that focuses the light so the rays are parallel to one another instead of intersecting — a process called collimation. These lens-covered LEDs are mounted inside a reflecting cavity, which ‘recycles’ the light and ensures that as much of it as possible is used to illuminate the target. Finally, as the light leaves the lamp it passes through a diffuser or filter that cuts down on unwanted glare. The combination of collimation and filtering also allows researchers to control the beam’s shape: the present design yields a rectangular light pattern ideally suited for street lighting.”

The new lamp’s performance was quantified by the researchers by using something referred to as optical utilization factor (OUF) — a number that “describes the relationship between the flow rate of light at the target and the flow rate of light coming directly out of the LEDs.” The higher the OUF is, the better the performance. The simulations done by the researchers showed an OUF of 51% to 81%, a potentially huge improvement over other recent “excellent” designs, that achieved 45%.

The LED streetlamp also meets high expectations for power and brightness. And, as mentioned before, significantly cuts down on light pollution. In conventional street lamps, as high as a “20% of their total energy is directed horizontally or upward into the sky.” And even in the best LED streetlamps, this number is still as high as 10%. But in the new model, only 2% of the lamp’s total energy is wasted as light pollution. Take a look at this image of the Earth from space to get an idea of how much energy is wasted lighting what doesn’t need to be lit:

earth from space light pollution

As a result of this all, the new system and lamp design have great potential as a means to reduce energy use. “A general LED street light could reduce power consumption by 40% to 60%,” Sun says. “The increased efficiency of the proposed design would likely save an additional 10% to 50%.

Something else to note: the module is very simple to produce, as it’s composed of only four parts, including the LED bulb, which is of a type that is very commonly used in the lighting industry and is widely available.

A prototype of the design is expected within the next 3 to 6 months, according to the researchers. Installations of the new street lamp may begin as early as 2014.

The new system was detailed in a paper published in the journal Optics Express.

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About the Author

's background is predominantly in geopolitics and history, but he has an obsessive interest in pretty much everything. After an early life spent in the Imperial Free City of Dortmund, James followed the river Ruhr to Cofbuokheim, where he attended the University of Astnide. And where he also briefly considered entering the coal mining business. He currently writes for a living, on a broad variety of subjects, ranging from science, to politics, to military history, to renewable energy. You can follow his work on Google+.

  • led street light

    Thanks for sharing. Actually, we can see more LED light around us, as its advantages compared to traditional incandescent light.

  • If we could eliminate or at least reduce the light pollution – then we would all see the stunning night sky often enough to change our thinking about the world and the universe beyond.

    This would be priceless.


    • Bob_Wallace

      When my city-raised wife moved here to the mountains she was amazed how often the Moon was full. It was something she saw only a couple of times a year in her past life.

      She had absolutely no idea there were that many stars in the sky.

    • hmm, good point. i remember going to the Everglades in college, never having been somewhere so far away from city lights before — was stunned at the number of stars i could see.

    • LED’s do provide less light pollution when used in combination with aimed optics. The light is pushed downward and out to the sides instead of using refractors and reflectors to push the light in all directions. This is another area where LED’s provide better and more even lighting.

  • Altair IV

    These sound great. I’d love to see them everywhere. I’ve always been of the opinion that there’s a LOT of wasted light shining where it isn’t needed. It would be even better if they get set up with proximity sensors so that they only go to full brightness when traffic is around.

    For an example of poor lighting design, here in Osaka they’ve been gradually replacing the old yellowish sodium streetlamps with LEDs. While I certainly applaud them on this, the actual result leaves something to be desired. They are simply putting the new lamps into the old fixtures, and when the brighter, blue-white directed light hits the the old glass coverings it is prismed out , leading to pools of glare pointing in semi-random directions, and even into your eyes. When I come around blind corners on my bike at night I’m often misled into thinking they’re car headlights. They really need to replace the covers with something that redirects and diffuses the light more evenly.

    Incidentally, many of the residential back streets have a different kind of fixture that uses simple office-style fluorescent tubes in hockey-stick shaped fixtures. They’re dim, but they don’t really have to be bright in the places where they’re used. I enjoy cycling down the roads that have them. A couple of months ago I noticed that they’re starting to get brighter LED replacement strips as well. At least they don’t seem to have the same glare problem that the bigger ones do.

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