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Illumination & Displays

Hello Lamppost: LEDs put to the test on a wide scale

Governments and manufacturers are working together to make sure LED lighting is up to the challenge of lighting up whole cities.
19 May 2010, SPIE Newsroom. DOI: 10.1117/2.2201005.01

With over 34 million street lights in use across the United States, the U.S. Department of Energy (DOE) estimates that converting these lights to LED technology has the potential to save communities more than $750 million a year in energy costs alone. At the same time, with the rapid expansion in LED manufacturing all over the world, there is the potential for poor quality products to creep into the market and soil LED lighting's reputation, a lesson learned when CFL lights were first introduced. The U.S. government, regional governments, and LED manufacturers are working together to find working solutions and make sure LED lighting is up to the challenge of lighting up a whole city, or twenty.

The DOE has begun testing LED lighting in collaboration with municipalities through the DOE GATEWAY program. Several cities have performed market-based, real-world testing of LED lighting on city-owned and public property. In the Sunset District of San Francisco, CA, four manufacturers' LED street lights were installed on four public avenues to replace 100-watt nominal high-pressure sodium luminaires. The I-35W Bridge in Minneapolis, MN, was fitted with LED roadway lighting. Over the course of three years, the DOE will study the use of LED lighting in this highly challenging environment.

Seattle, WA, was chosen in April to be the lead on a DOE-supported consortium dedicated to testing efficiency and effectiveness of LED lighting for public use. Seattle City Light will be responsible for recruiting at least 50 other communities to join the consortium and share their experiences through national and regional meetings, webcasts, and web-based discussion forums.

Figure 1. LED lights installed at a Lexus dealership in Albuquerque, NM. Photo credit Cree.

Over 250 cities have applied to become members of the consortium, "so this looks like this is a much needed resource," said DOE program manager Jim Brodrick during the consortium's kick-off webcast, held May 6.

The DOE Consortium efforts are receiving $20,000 under the American Recovery and Reinvestment Act, although all funding for LED light installation will come from elsewhere. The consortium will be administered by the Pacific Northwest National Lab (PNNW), providing resources and expertise on LED technology.

"The goal of the consortium is to reduce needless duplication, reduce mistakes on a large-scale, bring end-users up to scale and ID good products, and provide information in a timely way," says Edward Smalley, Seattle City Light manager and director of the consortium.

LED lights Anchorage, AK
Figure 2. LED lights installed on one side of the street in Anchorage, AK, with sodium lights on the other. Photo credit Cree.

Seattle City Light has already reviewed more than 100 models of LED street-light fixtures and tested nine as part of pilot projects around the city. Overall, 85 percent of respondents approved of the new lights.

"When reviewing the U.S. DOE's GATEWAY, we find this is in line with national trends," says Smalley. "Our pilot programs have yielded extremely useful results and we have been able to draw on lessons learned and community feedback from earlier pilots to make improvements in fixture selection in subsequent pilots." Seattle will install an additional 5,000 LED streetlights this year and a total of 40,000 during the next five years.

"Each situation still needs to be evaluated on its own merits," warns Smalley. "LEDs are not yet an across-the-board solution for all applications for many reasons, a primary one being the significant investment."

"LED lighting is still relatively new, and there's still a lot to determine," agrees Bruce Kinsey, PNNW liaison for the consortium.

LED manufacturers are also supporting testing efforts. Raleigh, NC, conducted nearly 40 separate LED projects around the city, from parking decks to the mayor's office, as part of the Cree LED City® program. Positive reactions to the city's lighting were more than three times higher after LED lights were installed. Seventy-four percent of respondents perceived that safety in a local parking garage had improved dramatically. Other cities involved in the LED City program include Los Angeles, CA, and Fairview, TX, which won several design awards for its installation.

LED Raleigh NC
Figure 3. LED lights installed in downtown Raleigh, NC. Photo credit Cree.

"Raleigh has also done some studies on preferences of color temperature for outdoor lighting, comparing 6000K to 4300K," says Mark McClear of Cree. "People were about evenly split between the two, but when they were informed that 6000K saved more energy, most went with 6000K."

McClear presented at this year's LightFair on thermal reliability of LEDs and how it applies to a consumer market. "Reliability of any semiconductor component depends very heavily on temperature. Since streetlights run at night, and it is generally much cooler at night -- no matter where you are -- this makes street lighting an even more reliable application for LED technology."

Dialight has plans to test LED street lights in Pittsburgh and Edinburgh, PA, that communicate wirelessly allowing the city to remotely dim or control clusters of lights.

Smalley hopes that the consortium will provide good feedback for manufacturers as well as cities. Smalley would also like manufacturers to be looking ahead at the potential of LED technologies. "Many manufactures are trying to match up LED street lights to existing technology, [and] meet the minimum requirements. This new technology has so much more capacity for improvement but it's not being exploited yet."

Smalley, McClear, Kinsey and others strongly believe in the future of LED lighting. "LED lighting saves energy, saves on maintenance cost, and are good for the environment since they contain no mercury," says McClear.

DOE Municipal Solid-State Street Lighting Consortium

Cree LEDCity Program

PNNW Demonstration Assessment of LED Street Lighting report (PDF)

Personal Use

Individual residents who want to jump on the LED bandwagon may have to wait a little bit longer. LEDs are still hard to find on a wide scale for residential use outside of Christmas tree lights, but hopefully not for too much longer. General Electric has plans to release an LED bulb that fits into standard incandescent light fixtures in late 2010 or early 2011 with brightness equivalent to a 40-watt incandescent bulb. Philips also has plans to release its own bulb around that time, with the brightness of a 65-watt bulb.

Photo credit: Philips

Beth Kelley

Beth Kelley is an editor for SPIE.