At the Electric Power Research Institute (EPRI), researchers recently released findings from a study of light-emitting diode (LED) street lighting technology. What they found should be of interest to electrical contractors.
LED proponents typically make certain claims. For example, in contrast to traditional streetlights, which emit yellow light, LED streetlights are white. Traditional lamps need replacement in three to four years, whereas LED manufacturers claim a 20-year life span. Traditional luminaires are known to blast light onto sidewalks and lawns, into the air, and sideways as glare, but proponents contend LED luminaires focus light where it is needed.
The EPRI demonstration project gathered data to evaluate these claims for the entire lighting industry.
The LED Energy Efficiency Demonstration achieved promising results. In the Midwest, for example, a utility hosted an LED lighting demonstration on a public street. The test area contained 11 high-pressure sodium (HPS) lamps, which were replaced by LEDs. The retrofit resulted in an energy savings of 41 percent.
Another utility in the Southeast replaced 400-watt (W) metal-halide lamps with 203W LED lamps. Because the lighting was better directed, the energy savings of the LED fixtures compared to the metal-halide fixtures was greater than 50 percent. The retrofit resulted in a better distribution of light on the ground, less light pollution and a lower ratio of bright to dark areas.
Overall, energy savings ranged from 20 percent to more than 70 percent, with the variation largely due to differences in design constraints, such as pole spacing, use of security cameras (which require additional light) and adequacy of existing designs.
Unlike traditional outdoor lighting technologies, the LED technology was sensitive to temperature. The LED fixtures used more energy as the ambient temperature decreased. EPRI stated additional savings (up to 10 percent) are possible with LEDs through temperature performance and driver design improvements.
In spite of often delivering less light than the control fixtures, survey respondents provided favorable opinions about the performance of LED lamps. Most, if not all, indicated that the lamps were equivalent if not better than the traditional technologies. This was particularly true in the case of the LED technology versus the yellow hue of high-pressure sodium lamps. But there were locations where LED technology may not have achieved the design objective and projected energy savings.