Streetlights were the first big users of electricity. Now, they are being re-engineered to improve efficiency, but at a cost that today's municipalities might have a tough time covering.
San Jose, Calif., in the heart of Silicon Valley, is testing a concept called "adaptive lighting," in which streets can be made brighter, darker or even be illuminated with flashing strobes upon command. By summer, the city will have installed 125 streetlamps using LED technology, in one of the biggest urban tests of the science so far in the U.S. The city hopes to cut down on energy use, and, hopefully, lower its utility costs, by tapping LED lighting's greater flexibility.
The test in San Jose coincides with a broad push by federal and state agencies to modernize the nation's lighting infrastructure. Many homes and businesses have replaced incandescent bulbs with more efficient compact fluorescent lights. Now cities, faced with tighter budgets, are looking for ways to cut street-lighting costs and to reduce emissions from power plants.
Raley's supermarket in West Sacramento, Calif., recently had LED lights installed with funding from the Department of Energy.
But the cost savings will take time to materialize. Street and highway lights use about 2% of the nation's electricity, according to the U.S. Department of Energy. Many cities have LED traffic signals, but because of the high cost of producing white light with LED, local governments have been reluctant to install them in streetlights. The effort is further complicated not only by strapped municipal coffers, but resistance from star-gazers and others who object to LEDs brighter glare.
LED, or light-emitting diodes, are electronic lights based on semiconductor technology. They use less energy and last longer than the sodium vapor-powered lights typically used in urban street lighting. LED technology has been around for decades, and is often found in electronic gadgets. It is used in streetlamps in some European cities.
Unlike regular streetlamps, LED lights can be programmed to respond to specific commands. For example, a city could dim the lighting on commercial strips after business hours, or turn up the lights after bars close, says Jim Helmer, director of San Jose's transportation department. Streets around Little League baseball diamonds could be made brighter as people walk to their cars, and then turned down afterward. By regulating the lights based on activity, the city hopes to cut down on "light spillage" -- city planners' term for light that shines where it isn't wanted, creating an urban nuisance.
San Jose expects to spend $150,000 to $200,000 on a pilot project in its Hillview North neighborhood, and it is seeking an additional $2 million in federal stimulus funds to enlarge the test.
The LED streetlights being tested in San Jose could save anywhere from 10% to 60% on energy use, depending on their brightness. 
The white LEDs will have a range of between one and 82 watts and will replace 55-watt, yellowish sodium-vapor lamps. The lights will be controlled under a system developed by energy-software company Echelon Corp. of San Jose, the general contractor in the pilot program. But for now, many cities see little financial advantage to switching their lighting systems.
It can cost $600 to install a single LED streetlight, compared with $200 for a sodium-vapor lamp. What's more, utilities often charge cities a flat rate based on the number of streetlamps they operate, regardless of use.
Currently, San Jose pays Pacific Gas and Electric Co., a unit of PG&E Corp., a flat rate for electricity, about $300,000 a month. The utility has proposed a new rate program that would lower costs for LED streetlights; the plan is awaiting review by state utility regulators. The Department of Energy has been funding lighting tests, such as a recent retrofit of a Raley's supermarket parking lot in West Sacramento, Calif., with 16 LED lamps and motion sensors. They run at 49 watts, unless they sense activity, when they power up to 149 watts. They could pay for themselves in energy savings in four to five years.
Fourteen miles east of San Jose on Mount Hamilton, the astronomers at the Lick Observatory have another concern: The bright white light of LEDs illuminate the night sky and obscure views of planets and stars. The scientists helped San Jose select its sodium lamps in the 1980s because the observatory can filter out yellow light. "Going to any other kind of lighting is detrimental," says Burt Jones, the observatory's assistant director.
But Dr. Jones says scientists are working with city officials to make LEDs benign, suggesting they dim after midnight or eliminate near-infrared and ultraviolet light from the LED color spectrum. "In those colors, the sky would still look dark to us," explains Dr. Jones.
from The WallStreet Journal
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