Seattle averages only 96 sunny days per year, but King County Metro Transit believes that's enough to light 43 downtown bus shelters with solar power through even the gloomiest winters.
Two prototype bus shelters, at Fifth Avenue and Mercer Street and at Fifth and James Street, were fitted with the alternative-energy lights last fall and still are working at full capacity.
"This is a form of environmentally friendly power, and it makes sense for us to support something like that," said Dale Cummings, senior transit planner for Metro Transit.
The bus-shelter lighting, called i-SHELTER™, is produced by Victoria, B.C.-based Carmanah Technologies, which specializes in transit lighting. The lights, measuring 2 feet by 5 feet, combine solar technology with software designed to conserve light output, based on weather history and forecasts from the National Aeronautics and Space Administration. The solar energy is stored in batteries designed for harsh outdoor environments.
"We've specifically designed a system for Seattle," explained Matthew Watson, vice president of corporate development for Carmanah. "It manages energy-consumption levels by taking into consideration the installation location and any prevailing climatic conditions. It knows what the weather is going to be like and can run at full power for days without sun."
Energy is collected through solar panels and converted to light through LEDs (light-emitting diodes) - silicon chips the size of the head of a nail. Each panel includes only eight of these tiny LEDs, which shine brighter than incandescent or fluorescent bulbs because they convert all energy into light rather than heat.
Carmanah's software monitors and conserves power with decreasing light output from midnight to 5 a.m. and on days when skies are overcast. But the light adjustments are not visible to the naked eye, and even the dimmer level is brighter than traditional lighting, Watson said.
The move to improve bus-shelter lighting is part of efforts to prepare for the two-year closure of the downtown Seattle bus tunnel beginning in September. The tunnel is being renovated to handle light rail as well as buses.
Metro Transit is installing new shelters and updating existing shelters along streets such as Third Avenue, where more people will be catching buses while the tunnel is closed.
The agency is spending about $200,000 for the next 41 solar-powered lights it plans to install, said Linda Thielke, spokeswoman for Metro.
The lights will save the agency about 9,000 kilowatt-hours of electricity per year, Cummings said. Installation will cost about 40 percent less than traditional lighting because it requires no digging or underground connections, he said.
More than 85 transit authorities use solar-powered lighting systems from Carmanah. The company also provides marine lighting for the U.S. Coast Guard. The technology is being used in bus shelters and bus stops in Toronto; Vancouver, B.C.; and London; and it is being tested in Pierce County and Portland.
Metro began looking into solar-powered lighting for bus shelters several years ago and heard good things about Carmanah Technology, Cummings said.
"What really caught our attention was how pleased cities were with the lighting, especially London, which is farther north than Seattle and has more cloudy days," Cummings said.
"As far as I'm concerned, our decision was driven by a technology that makes good sense. This company has a good track record and a green form of energy."
Installation of the new lighting will begin this summer.