PITTSBURGH-University of Pittsburgh researchers have conducted the first cradle-to-grave assessment of light-emitting diode (LED) streetlights and determined that the increasingly popular lamps strike the best balance between brightness, affordability, and energy and environmental conservation when their life span-from production to disposal-is considered. LEDs consist of clusters of tiny, high-intensity bulbs and are extolled for their power efficiency and clear luminosity.
Engineers in the Mascaro Center for Sustainable Innovation based in Pitt's Swanson School of Engineering compared LED streetlights to the country's two most common lamps-the high-pressure sodium (HPS) lamps found in most cities and metal halide lamps akin to those in stadiums-and the gas-based induction bulb, another emerging technology billed as bright and energy efficient. The team reported that LEDs may carry a formidable price tag, but in comparison to HPS and metal halide lamps consume half the electricity, last up to five times longer, and produce more light. Induction lights proved slightly more affordable and energy efficient than LEDs, but may also have a greater environmental impact when in use. The authors also noted that LED technology exhibits more potential for improvement and may surpass induction lamps in the future.
The survey coincides with initiatives in several U.S. cities to replace energy-guzzling HPS lamps-known for their flat orange glow-with LEDs. The City of Pittsburgh commissioned the Pitt report as it considers replacing 40,000 streetlights with LEDs, similar to retrofits and pilot programs under way in cities from Los Angeles and San Francisco to Raleigh, N.C., and Ann Arbor, Mich. The City of Pittsburgh estimated that, per year, replacing HPS lamps with LED streetlights would save Pittsburgh $1 million in energy costs and $700,000 in maintenance, while reducing carbon dioxide emissions by 6,818 metric tons.
Despite the civic enthusiasm for LEDs nationwide, until the Pitt study no comprehensive analysis of LED streetlights existed, said study coauthor Melissa Bilec, a professor in the Swanson School's Department of Civil and Environmental Engineering. Bilec and civil and environmental engineering professor Joe Marriott conducted the evaluation with Cassie Jurgens, a Pitt junior studying civil and environmental engineering and architecture; Pitt junior and industrial engineering student Eric Zatcoff; and Douglas Hartley, a mechanical engineering senior at the Georgia Institute of Technology.
The group created a "life-cycle assessment" for each lighting technology, with information pulled from sales companies, manufacturers, government documents, lighting professionals, and industry reports. The assessments catalog the environmental effect of the streetlamps during their complete life span, from the extraction of raw materials and assembly to electricity consumption and disposal.
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