September 8, 2017
Since April, the Department of Public Works has been working with Eversource and Affinity LED Lighting to assist in converting all of its high pressure sodium (HPS) street lights to Light Emitting Diode (LED) lights. With this citywide implementation, the City will experience further reductions in energy consumption, costs and light pollution, along with improved visibility and safety on the roads.
Currently, this project is about 95 percent complete, with the downtown area currently being addressed. Once all 1,610 streetlights have been converted to LED equipment, the City will save $120,000 in annual cost, 494,000 kWh of annual electricity consumption, and prevent over 300 metric tons of CO2 emissions per year.
While reduced energy consumption and CO2 emissions bring significant benefits, Public Works has also paid close attention to ensure the new lights comply with emerging American Medical Association (AMA) guidelines regarding best practices for LED street lighting and how to minimize potentially harmful effects. According to the AMA, LEDs that are rated above 4,000 Kelvin (K), using the temperature measurement by which light color is measured, should be avoided. The problem isn’t brightness so much as wavelength, light that appears white to the naked eye contain larger amounts of blue light. Our eyes treat “white” blue-heavy light, such as the glow of a smartphone, like the midday sun. The science is still evolving, and recent studies have postulated a link between blue light and our bodies’ responsiveness that set our daily circadian rhythm.
LED lights are typically hailed as a positive for the environment because they consume much less electricity and last much longer than high pressure sodium lights. While the AMA welcomes the reduced emissions and energy efficiency benefits of LED lights, they encourage proper attention to optimal design and engineering features to minimize potential health and environmental effects caused by too much “white” blue light. The City’s LED lights will shine at warm 3,000K, are Dark Sky compliant and will provide more accurate color rendering. By correctly reproducing the colors of objects in comparison to the light source, improved color rendering makes it easier for drivers to recognize potential road hazards, crosswalks, pedestrians, etc.
For more information, please contact Jacob Levenson at (603) 766-1412 or firstname.lastname@example.org, or visit https://www.cityofportsmouth.com/publicworks/roads-sidewalks/street-lights and https://www.cityofportsmouth.com/sustainability.