LEDS ARE BEST CITY LIGHTS

LED streetlights best buy for cities, researchers report
March 8, 2010 (University of Pittsburgh via PhysOrg)

"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…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… 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…LED technology exhibits more potential for improvement and may surpass induction lamps in the future."

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"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…[is considering] replacing 40,000 streetlights with LEDs…[as are] Los Angeles…San Francisco…Raleigh, N.C… Ann Arbor, Mich…[and many other cities]…LED streetlights would save Pittsburgh $1 million in energy costs and $700,000 in maintenance, while reducing carbon dioxide emissions…

"The [University of Pittsburgh] group created a "life-cycle assessment" for each lighting technology…LEDs actually led the other technologies in negative environmental and health effects during manufacturing…LED "bulbs" consist of small lights embedded in circuit boards that require numerous raw materials, need considerable energy to produce, and can be difficult to recycle…[but] producing LED housings—composed largely of plastic and wire—consumes far less energy than manufacturing aluminum-heavy HPS casings. LED bulbs also contain no mercury and fewer toxins, such as iodine and lead…"

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"During a bulb's lifetime, however, electricity consumption produces up to 100 times the environmental impact of manufacturing…LED lights burn at 105 watts, compared to a hefty 150 for HPS and 163 for metal halide…[so] metal halide bulbs would emit nearly 500 million kilograms of carbon dioxide during 100,000 hours of use, followed by HPS bulbs with more that 400 million, induction bulbs with approximately 350 million, and LEDs producing slightly more than 300 million kilograms…LED technology would [also] emit a mere two-thirds the amount of airborne toxins and particulates…

"In the crucial area of cost, the prices of LED lights…range from $9.20 to $322 per fixture. But the technology's considerably longer life span could mitigate…LEDs did not last as long as induction bulbs…but were calculated to burn nearly three times longer than HPS lights and almost five times longer than metal halides…40,000 LED lamps could initially cost the City of Pittsburgh as much as $21 million versus approximately $9 million for metal halide streetlights. Yet replacing metal halides could cost as much as $44 million before the LED lamps needed a first replacement…"