LEDs, great light hope... or hype?

By Charles Taylor
SENIOR STAFF WRITER

LED lights have revolutionized traffic signals. But are they ready for prime time — nighttime — and day-to-day use for street lighting?

Several counties are seeking the answer by testing light-emitting diode (LED) lamps, also known as luminaires, to see if their performance lives up to their promise. King County, Wash., and Arlington and Fairfax counties in Virginia are conducting pilot programs.

King County recently concluded the first phase of a pilot to determine whether it could replace 1,800 county-owned high-pressure sodium lamps, the ones that cast an yellowish-orange glow, with LED lights.

“Outdoor lighting is a sensitive issue in itself, and then there’s all the confusion around LED,” said Jason Tuenge, a researcher with the Department of Energy’s (DOE) Pacific Northwest National Lababoratory. “The main drive of our program is to try to get rid of some of that confusion and get some answers where they’re available.”

Tuenge will attempt just that on Oct. 8, when he participates in a solid-state lighting (SSL) webcast entitled “Hitting the Target: ENERGY STAR SSL Outdoor Area Lighting” (see sidebar). DOE has developed ENERGY STAR criteria covering SSL-based outdoor area and roadway lighting, outdoor wall packs, parking garage and canopy luminaires.

Overall, not only in street light applications, solid-state lighting has the potential to reduce U.S. lighting energy use by one-third and could be 10 times more efficient than incandescent lighting, according to the DOE publication Solid-State Lighting: Brilliant Solutions for America’s Energy Future. That could mean lower energy bills, and lower maintenance and replacement costs.

King County tested luminaires from two manufacturers on a two-block section of road in Redmond, Wash. — comparing them to high-pressure sodium (HPS) fixtures. Linda Mott, a senior signal and illumination design engineer, was pleased with the “clean crisp light that you could see very well.” However, a report on the pilot found that neither LED fixture provided light levels within 10 percent of the HPS lamps, the criterion set by the traffic engineering division.

Mott called the results “pretty disappointing.” A 70-day comparison of energy consumption from LED lights versus the HPS ones “showed no significant change in energy consumption,” the report stated.

Arlington County spends approximately $3 million a year in electric bills for the 4,000 or so street lights it owns, said Wayne Wentz, of the county’s Transportation Engineering and Operations Bureau. Five LED luminaires are being tested at one residential intersection, and four lights at another.

If the lights live up to their promise, he said the county could save “at least half of our electric bill, maybe as much as 60 or 70 percent.” Costs aside, he adds, “We are interested in better lighting … and one of the things about LED lighting is it’s closer to pure white, so there’s more light that’s usable by the human eye than the HPS that have been used for years.” The county is also concerned with overall energy efficiency and the effects of its power consumption on greenhouse gases.

Arlington and King counties are also interested in “dark skies” issues of light pollution. The King County report states that “LEDs are directional in design, thus are ‘Dark Skies’ Initiative-friendly, limiting or reducing upward or reflective light.”

Fairfax County approached its local electric company, Dominion, about a pilot project. As in Arlington, the electric company owns and maintains most of the street lights. Dominion agreed to install the lights if the county and other localities in the pilot program purchased them, according to Steve Sinclair, chief of the utilities branch in the county’s Department of Cable Communications and Consumer Protection. The county spends $6.5 million annually on street light electric bills for 55,000 street lights.

Among other issues, he is interested in the LED lights’ life span. “With existing fixtures, they relamp every five years or so, and with the LED fixtures, the expectation is that it might be 15–20 years, or maybe more, before they have to be relamped,” Sinclair said.

Tuenge and DOE want to make sure that any localities with LED pilots — or those considering them — know the right questions to ask. “It’s definitely a risky venture at this point,” he said. “We’re all about the pilots, the demonstrations — but not large, massive-scale roll outs of the technology. It’s just too young.”