From the City of Calgary, Canada, on the retrofitting of their streetlights
Can old dropped lens cobra heads be retrofitted with flat lens glass to make them a suitable full cutoff fixture?
No, in addition to replacing the dropped lens or refractor of the fixture, the reflector inside the fixture must be replaced to properly distribute the light spread from the fixture down onto the road. Since the new flat lens fixture is relatively inexpensive compared to the cost of performing this type of customization, it is more cost-effective to replace the old fixture with a new flat lens fixture of the correct photometry.
What can cities do with their old streetlight fixtures?
The City of Calgary embarked on a massive street lighting retrofit. In an effort to be more environmentally sensitive, the fixtures were disassembled and the components – glass, steel, aluminum, etc. – were then recycled. There are a number of pictures on the Web site that show streetlight components being readied for recycling. Some parts were even used for crafts. The old glass refractors can be used as pots and the ceramic arc tubes can be used for sharpening knifes. Representatives of Environmental Assessment and Liabilities at The City of Calgary presented a paper on our environmental monitoring program at the International Association of Impact Assessment Conference in Vancouver in 2004.
Wouldn't it have been more economical to simply replace the old lights as they burned out instead of doing them all at once?
No. If we had done this project by attrition it would have taken about eight or ten years, and it would have been very hard to manage. The City replaced the lamps in the old luminaires on a 5-year cycle. With the retrofit project, the whole luminaire, including the lamp is replaced. As such, the group relamping is not being done during the retrofit, which is resulting in increased savings. In addition to reducing light pollution and glare, The City also wanted to reduce the wattage of residential streetlights in order to reduce electricity consumption. The new streetlights will save The City approximately $1.7 million a year in energy costs once the project is complete. These savings ensure that the project pays for itself. Reduced energy consumption also results in reduced emissions from gas and coal-burning generators. When the EnviroSmart Streetlights project is complete, CO2 emissions will be reduced by as much as 19,000 tons a year.
International Dark-Sky Association • 3225 North First Avenue • Tucson, AZ 85719 USA, 520-293-3198 • www.darksky.org