Bright Future Seen for LED Streetlights

Lamps Use 50 to 70 Percent Less Energy than Conventional Lights

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Posted: Wednesday, January 11, 2012 5:59 pm

Could a streetlight retrofit save your community time, energy and money while providing safer, more luminous neighborhoods? Experts say yes, but there's a catch: currently the most energy-efficient lights on the market - the light-emitting diode, or LED variety - are up to three times more expensive than their traditional counterparts. Still, if you can afford the up-front costs, experts say LED streetlights can save money in the long run by consuming 50 to 80 percent less energy than conventional lighting products and virtually eliminate maintenance costs for up to 20 years.

These benefits, advocates say, provide a 5-year payback in most cases.

Street lighting in the past 50 years has been accomplished primarily with high-intensity discharge (HID) light fixtures, which produce light by means of an electric arc between tungsten electrodes inside an arc tube. Varieties of HID lights include mercury-vapor, metal-halide, and most commonly for streetlights, high pressure sodium (HPS) fixtures. While some high-efficiency induction products have also come on the market in recent years, experts seem to agree that LED lights are poised to take over the market in the next few years. That's because, not only do they save energy and last a lot longer, they also produce a higher quality light.

Jeff Brassard is the U.S. business development manager for LED Roadway Lighting, Ltd., headquartered in Nova Scotia, Canada. Daniel Splinter is district manager at Crescent Electric Supply Company, based in East Dubuque, Ill. The two lighting professionals spoke recently at the Growing Sustainable Communities Conference in Dubuque, Iowa.

Brassard said, besides the cost savings, LED lights emit up to 90 lumens per watt of electricity, versus an efficacy of 45 to 50 lumens per watt provided by most HPS fixtures. Splinter and Brassard agreed, though, that not all LED products are equal.

Splinter said government and industry organizations "are just starting to regulate and measure LEDs, because there are so many people entering into the market and so much of this is coming from China, and it's unregulated and untested."

Added Brassard: "It's critical that you identify and work with a reputable, competent LED manufacturer. Like any other product, there are people out there that are reputable and competent, and there are people that aren't," he said. Brassard said his company uses NICHIA brand LEDs made by a Japanese company that is the largest supplier of LED lamps in the world, and they make a very high quality LED.

"That's important in order to extract not only the maximum efficiency and best performance out of your LED, but also to get the maximum longevity," he said.

After ensuring you've purchased a quality LED, the next design consideration is thermal management, Brassard said. All lights generate heat, which is one of the key reasons they gradually dim over time, a phenomenon known as light loss depreciation. Conventional HID lights do this very quickly compared to LED lights that lose intensity over the course of a 20-year effective lifecycle. In fact, Brassard said, LED lights don't technically "burn out." They just gradually lose intensity until they need to be replaced. So, effectively managing the heat they generate is critical to keeping them bright for as long as possible.

Brassard said it's important to compare the thermal profiles of different products and choose one that disperses the heat most effectively.

Because LED lights last so much longer than conventional lights, it's also important to compare power supplies, Brassard said. Many power supplies used in LED light fixtures are only designed to last five to seven years. If you purchase a lamp that lasts 20 years, you lose a lot of the maintenance savings if you have to change the power supply every five years, he said.

Optics is another important design consideration, Brassard said. "Conventional HID lighting products, especially roadway products, have a tendency to produce a great deal of light, and a lot of it is wasted," he said. The concept of light pollution or fugitive light emissions is a common concern. Light from LEDs can be projected in specific directions much more readily, thereby preventing or reducing this problem, he said.

When choosing an LED streetlight, it's important to know how the light is being distributed. Systems that rely heavily on lenses or prisms to bend the light in different directions toward the roadway are less efficient than systems that mount multiple light engines at angles so the light leaves the fixture in a straight line. These designs produce a light that is uniform on the roadway, without dark bands between fixtures.

Superior optics allows LEDs to out-perform conventional HID lights even when the HID lights technically generate more lumens, Brassard said. Because of these efficiencies, more of the LED light actually lands on the road.

Brassard and Splinter said airports and parking lots are especially good candidates for LED lights because their superior illumination reduces glare and improves safety and security.

Splinter said he expects the price of LED lights to continue to decline, even as the lamps become more efficient.

"LED will be, without a doubt, the standard within five years," he said. "I'm confident that they've got the electronics right."

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