National Lighting Product Information Program Releases Report on Street Lighting Technologies Used in Residential Areas
The National Lighting Product Information Program (NLPIP) at the Rensselaer Polytechnic Institute Lighting Research Center (LRC) released its latest publication, Specifier Reports: Streetlights for Local Roads, designed to provide objective performance information on streetlights for local roads in residential areas.
Municipalities across the United States have applied for funding through the American Recovery and Reinvestment Act of 2009 to replace their current streetlights with light-emitting diode (LED) and induction streetlights. LED and induction streetlights are often claimed to provide energy savings, better lighting uniformity and distribution, and lower maintenance costs compared with high pressure sodium (HPS) streetlights and, as a result, are marketed as effective replacements for both new construction and retrofit applications. NLPIP’s report provides objective data to help lighting specifiers analyze these claims and make informed decisions.
Between February and March 2010, NLPIP purchased six streetlights identified by manufacturer representatives as equivalent to an incumbent technology, a 100-watt HPS luminaire with a Type II distribution. Of the streetlights tested, one used an HPS lamp (the base case model), one used an induction lamp, and four used LED modules. NLPIP determined how many of each type of streetlight were needed to illuminate a one-mile stretch of local road in a residential area to meet the roadway lighting criteria specified in the American National Standard Practice for Roadway Lighting, ANSI/ IESNA RP-8-00 (referred to as RP-8). NLPIP then calculated power demand and life-cycle costs per mile for each streetlight.
“Prior surveys show that 75 percent of streetlight system owners do not continuously light their local roads per RP-8 recommendations; however, NLPIP followed the RP-8 lighting criteria because no other national lighting standard exists and there is high variability in the pole spacings prescribed by municipalities. The low adoption rate of RP-8 nationally could indicate that this standard is not meeting the needs of streetlight system owners,” said Leora Radetsky, LRC lead research specialist, principal investigator and author of the report.
Following is a summary of the findings from Specifier Reports: Streetlights for Local Roads.
The tested LED streetlights required an average of 40 percent more poles per mile than the HPS base case to meet the RP-8 lighting criteria, and the tested induction streetlight required 64 percent more poles per mile. Only one of the tested LED streetlights was able to provide pole spacing similar to the HPS base case.
The average power demand per mile of the LED streetlight layouts evaluated was lower than the power demand per mile for the HPS base case, but there was wide variation among the LED streetlights tested. The tested induction streetlight required more power per mile than the HPS base case.
Life-cycle cost per mile
For an assumed LED module replacement interval of 25,000 hours, the average tested LED streetlight life-cycle cost per mile was 1.9 times that of the HPS base case. For an assumed LED module replacement interval of 50,000 hours, the average tested LED streetlight life-cycle cost per mile was 1.6 times that of the base case. One of the streetlights tested by NLPIP achieved similar pole spacing as the base case while meeting RP-8. If this streetlight does not require a replacement LED module during its 27 year (113,000 hour) life, it would achieve a lower life-cycle cost per mile than the base case. The average life-cycle cost per mile of the tested induction streetlight was 1.8 times that of the base case.
NLPIP concluded that for the tested LED and induction streetlights to have a lower life-cycle cost than the HPS base case (with the exception of the one LED case mentioned), they would need to provide longer pole spacings. NLPIP also considered a number of other factors that could affect streetlight layout and power demand. These considerations include mesopic photometry, mounting height, road width, and streetlights with higher light output. In most cases, the HPS streetlight(s) provided longer pole spacings than the LED and induction streetlights, with a few exceptions. The full report is available at www.lrc.rpi.edu/nlpip/publicationDetails.asp?id=931&type=1.
In 2010, NLPIP published results from a similar study for roads servicing traffic between local and major roadways. That publication, Specifier Reports: Streetlights for Collector Roads, details the results of HPS, induction, LED and pulse-start metal halide streetlights tested by NLPIP for use along collector roads. The full report is available at www.lrc.rpi.edu/nlpip/publicationDetails.asp?id=927&type=1.