BRIGHT LIGHTS: Pittsburgh officials worry that a total switch to LED streetlights will make the streets too bright after dark. (Photo: caseywest/Flickr)
Admonished by University of Pittsburgh’s Mascaro Center for Sustainable Innovation, Pittsburgh, Penn., may replace its high-pressure sodium lights to light-emitting-diode (LED) lamps this upcoming summer. The University found that LED lamps rank substantially higher in longevity than high-pressure sodium lamps. In addition, LED lamps offer a more environmentally solution to lighting due to their higher watt per lumens ratio. Therefore, considering the overall lifespan of an LED lamp, the LED lamp is clearly the superior choice. The University estimated an annual savings of “$1 million annually in energy costs and $700,000 in maintenance fees” and a C02 emissions cut of approximately “6,818 metric tons per year,” if the city switched to LED lamps. Of course, three caveats emerge: blue tint, light pollution and poor heat dissipation.
First, the article states that concentrated light emitted from LED lamps manifests as a blue-tinted light. These concerns are partially true, although I find it prudent to crush these half-truths. It’s true, some LED lamps produce a blue tint. The concern with the blue tint lies in its colour wavelength it emits: blue is a from High-energy visible light (HEV). Most LED lamps are blue / white ‘cool’ LED lights calibrated to emit ‘white’ light – hence the blue tint. Presently, blue ‘cool’ LED lights rank the highest on the energy efficient scale. True ‘white’ warm LED lamps have been an obstacle to match the efficiency of ‘cool’ LED lights but significant strides have been made to make it a reality.
Second, the article states that that concentrated light emitted from LED lamps may produce light pollution. Following the Rayleigh scattering principle, the scattering of electromagnetic radiation by particles with dimensions much smaller than the wavelength of the radiation, resulting in angular separation of colors and responsible for the reddish color of sunset and the blue of the sky, light emitted by blue / white ‘cool’ LED lights would emit more light pollution due the shortened wavelength and higher frequency of blue on the ROYGBIV or electromagnetic spectrum. Scientifically, it’s absolutely correct. Although there is a way to drastically or eliminate light pollution all together: direct the light downward.
Third, the article states that that concentrated light emitted from LED lamps have poor heat dissipation. Poor heat dissipation is a ubiquitous fact for all high-pressure sodium lights; they waste energy and decrease the lifespan of the bulb. This once shortcoming for high-pressure sodium lights, has now become a laudable advantage. Why? An article back in December of last year mentioned how a town switched to Blue / White cool LED lamps for their traffic lights and found that the lamps can not melt snow due to its cool operating temperature. Fortunately, no drivers were harmed. Perhaps when warm LED lights can match the efficiency of cool LED lights, the public will see quite the contrary.
I’ll admit, LED has its limitations. It’s a burgeoning technology that offers tremendous energy savings and advantages over high-pressure sodium lights once the technology matures.
As of now, Pittsburgh, Penn., is one of the few nationwide cities that does not have a lighting code whatsoever.
“Several subcommittees of the Pittsburgh City Council will develop a better streetlight network and, as the city is one of the few nationwide without a lighting code, will propose a Pittsburgh lighting code. Once these analyses and codes are in place, the city will make a final decision regarding the switch. At any rate, Pittsburgh hopes the research study and task force studies will serve as “a standard tool for municipalities worldwide to evaluate streetlight technologies.” The city hopes to begin installation of new lights later this summer.”
At the very least, Pittsburgh will have a lighting code and given their concern for light pollution and safety, their heart is certainly in the right place.
