In February 1889, 20 electric-arc lamps brightened Vancouver for the first time. Just a year prior, the city council voted to erect a municipal lighting system. Only nine lights lined Main Street. Later incandescent streetlights replaced the arc lamps. The lights kept spreading and evolving. Now most Clark County streetlights are high-pressure sodium lamps.
That’s changing. Streetlight technology continues to evolve. “LEDs are now the leading-edge for street lamps,” said Bill Hibbs, commercial programs manager at Clark Public Utilities. “Their cost is dropping and we’ve had several successful pilots locally that show LED savings and reliability.”
LEDs are semiconductors that emit light in the white color range between 4,000 and 4,400 Kelvins, a measurement of heat. The chip is held in a lamp package containing phosphor to stabilize the colors. The packaging protects the internal electronics and phosphor and determines how long the lamp lasts. Many outdoor LEDs can burn more than 50,000 hours.
Longer life means less maintenance. LEDS are more resistant to vibration making them ideal for bridges, tunnels and overpasses. Their longer life means fewer replacements and less cost. In addition, they are infinitely controllable and dimmable, which opens opportunities for more creative uses of lighting.
At one time, lighting experts rated older outdoor lamps by wattage. A better way to think about lighting is how much light a bulb generates per watt. LEDs are very efficient emitters of light. An LED produces between 100 and 150 lumens per watt. Lighting technologists expect this to rise to 200 lumens per watt in the future.
LEDs also waste less light, because they direct light where it’s needed, but not where it’s not. LED designs focus lights on sidewalks without light spilling over into people’s windows or diffusing into the sky causing light pollution.
By not using mercury, lead or any heavy metals, LEDs are environmentally friendly. All of these are hazardous wastes. The mercury in just one 4-foot-long broken florescent bulb carelessly sent to the landfill contaminates 6,000 gallons of water beyond the safe drinking level. Safe recycling will protect against this mercury pollution.
Over the past couple of years, Clark Public Utilities has conducted several LED street lamp pilot programs. The American Recovery and Reinvestment Act funded the recent pilots in Battle Ground, Camas and Washougal. The Battle Ground pilot replaced 50 street lamps. Camas and Washougal pilots each replaced 100. A photometric software package using GIS mapping showed what the light falling on the ground would look like to assist the lighting designer with optimally lighting the areas.
All 250 streetlights were 100-watt high-pressure sodium lamps with “cobra heads” hanging over the roadways before the pilots. “The utility replaced the 100-watt lamps with new 70-watt LEDs,” Hibbs said. This saved $14.88 per streetlight per year for a total annual savings of $3,720.
Ridgefield also ran a larger pilot under the Washington State Transportation Improvement Board. For its pilot, photometric software again identified under- and overlit areas. Phase one of the pilot replaced 356 “cobra head” high-pressure sodium lamps hanging off a mix of aluminum, fiberglass and wood poles with LEDs. Then it replaced old lamps ranging from 100 to 400 watts with LEDs of 52 and 182 watts. This saved Ridgefield a total of 54,824-kilowatt hours for an annual savings of $6,578.
“Of all the LED lamps installed we only had three failures, right out of the box,” he said. “Overall, all the residents’ perception of the lighting program was positive. And we expect the technology to continue to improve into the future.”
Energy Adviser is written by Clark Public Utilities. Send questions to ecod@clarkpud.com or to Energy Adviser, c/o Clark Public Utilities, P.O. Box 8900, Vancouver, WA 98668.
