By Billi London-Gray
Green Right Now
San Francisco, the city that banned plastic bags, bottled water and Styrofoam, is taking another big step down the path to sustainable urban living. In March 2011, the City of San Francisco will begin installing more than 17,000 LED street lighting fixtures, effectively replacing most city-owned street lamps.
LEDs, or light-emitting diodes, produce light by passing a one-way electric current through a semiconductor material. As the electricity is transferred through the semiconductor diode from one electrical terminal to another, it releases energy in the form of light. Conventional incandescent and fluorescent lamps work by heating a filament or gas to a temperature that produces light. While LEDs, like other lamps, release heat as well as light, they are considered far more efficient because they produce more light per watt of energy consumed.
San Francisco will join the growing list of American cities that are switching to LED street light fixtures, which combine an array of dozens of individual LEDs to produce light similar to that of a high-intensity discharge lamp. Seattle, Anchorage and Los Angeles already have LED fixtures in place. Many other U.S. cities, including New York, are testing LED street lighting to determine the potential savings.
Amanda Townsend, manager of commercial programs at the Dallas-based sustainability consulting firm Geavista Group, has worked on many large-scale commercial lighting projects. She explains their many environmental benefits:
- LEDs are directional and point light only where needed, saving energy and reducing light pollution.
- LEDs, unlike CFLs and other fluorescent bulbs, do not contain mercury, a toxic chemical that requires costly disposal plans.
- LEDs last a long time, reducing maintenance and replacement costs.
- LEDs illuminate on demand – “instant on and instant off.”
San Francisco’s upcoming street lighting retrofit project is not the first LED installation by the city. The Davies Symphony Hall and the city offices at 1660 Mission were equipped with LED light fixtures in recent years. Additionally, the Main Public Library is a testing ground for a pilot project using LED wall fixtures.
The city began evaluating LED street lighting in 2008, says Sue Black, power utility services manager for the San Francisco Public Utilities Commission. She credits Mayor Gavin Newsom with prioritizing the change in order to reduce the city’s environmental footprint and save money.
“To my knowledge, the City of San Francisco will be the first city in the United States to implement a complete city-wide conversion of its cobra-head style, high pressure sodium fixtures to LED fixtures,” Black said. “Our other inventory of approximately 7,000 post-top and pendant-style street lights will be converted at a later time, when more product choices are available that will meet our performance requirements.”
The estimated price tag for San Francisco’s LED conversion is $16 million. Black stated that energy savings alone could approach $550,000 per year after the conversion, plus another $350,000 each year in operations and maintenance savings due to the expected 20-year lifespan of the LED fixtures. The installation is scheduled to be completed in the spring of 2012. Black estimated that the payback period for the project would be around 13 years.
“Our goal is to achieve an overall energy savings of 50 percent,” Black said. San Francisco will combine the LED installation with a new “smart control system” to further increase the energy savings. By instantly analyzing a variety of data from fixture locations, the new system will increase the efficiency of maintenance on the lights while decreasing energy demand as light levels are adjusted.
“The smart control system will provide the city with the ability to remotely monitor individual street light performance, adjust the light intensity level, and receive real time information when lights have failed,” Black said. For some LED fixtures, the smart control system can also be used increase light output for special events or dim the lights for periods of inactivity.
To cities undertaking large-scale retrofitting projects like street lighting conversions, LED fixtures are an attractive lighting option. “We have had discussions with many cities about the results from our pilot projects and progress,” Black said. “Many cities have existing pilot and small-scale permanent installations and plan to convert their fixtures over time.”
But LEDs are not the best lighting solution for everyone looking to cut energy usage. LEDs may not provide enough light in some situations, such as streets with widely spaced lamp posts, bright office work spaces or residential settings where multi-directional light is the norm. This could undercut the energy saving benefits of LEDs.
“In general, an individual LED may use less energy … but it’s probably creating less light,” said John Bullough, a lighting technology expert and senior research scientist at the Lighting Research Center in Troy, N.Y. “You won’t get the same amount of light by using less energy … LEDs potentially use three or four times less energy, but it depends on how well it’s designed.”
In Bullough’s opinion, LED fixtures must stand the test of time before their benefits can be realistically calculated. “They haven’t really been around long enough to know which ones will last and which ones will not,” he said. “There’s no real world confirmation yet.”
Townsend of Geavista Group pointed out that even for small-scale residential applications, LED fixtures cannot yet equal the light output of conventional lighting, such as incandescent bulbs and compact fluorescent lighting. Standard socket-based light bulbs have a light output of 700 to 800 lumens, Townsend said. “Until recently, LED bulbs had a difficult time achieving more than 400 lumens. The LED bulbs that you see for $7 are not going to perform nearly as well as a CFL or incandescent.”
However, LED technology is developing at a rapid pace. Both Bullough and Townsend said that as more government and commercial projects adopt the technology, better LED products will prove themselves in the real world.
“It’s definitely improving very quickly,” Bullough said. “It’s getting a lot of investment from the lighting industry and government research. It’s pretty exciting from a lighting point of view.”
Bullough explained that LED technology has revived research in the lighting industry by introducing an alternative to the types of lighting that had been standard since the 1960s. “Up until 10 years ago, change in lighting technology was slow … LEDs are changing the technology a lot.”
- Houston’s LED traffic signals
- LED vehicle signals in New York City
- The LED City Initiative
- Modular LED Wall Panels
- Unscrew America (light bulb education)
- Lighting Research Center
- US Department of Energy on LEDs
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