Rensselaer Polytechnic Institute’s Lighting Research Center (LRC) created a stir in the LED-based solid-state-lighting (SSL) industry recently with its Specifier Report that questioned the viability of SSL for collector roadway lighting, and is now addressing specific complaints from organizations such as the US Department of Energy (DOE). Moreover LRC has added a section to the report focused on evaluations of higher-powered LED street lights – addressing one of the most common complaints about the original report from LED luminaire makers.
The original LRC National Lighting Product Information Program (NLPIP) “Specifier Reports: Streetlights for Collector Roads” came to the conclusion that SSL alternatives to high-pressure sodium (HPS) and pulse start metal halide (PSMH) street lights could not match the pole-spacing of the legacy lights in meeting the ANSI/IESNA RP-8-00 standard. As we chronicled in an earlier story, the report stated that poles dominated the cost of a street-light deployment and therefore declared the evaluated SSL luminaires to be far more costly than the legacy lights eliminating any advantage from energy savings.
SSL luminaire makers and the DOE questioned the SSL luminaires evaluated in the original reports – asserting that the LRC selected products that were underpowered for the collector roadway application. And as noted in our follow-up story on the DOE response, the agency raised specified additional questions about the methodology applied by the LRC.
Now the LRC has responded both addressing the complaints with the original report and adding a section evaluating higher-powered SSL luminaires. The LRC states that it selected the original luminaires based on the recommendations of manufacturers’ representatives that work for the luminaire makers. The LRC believes that it followed the same path that a municipality might follow in requesting that the representatives suggest an equivalent to the incumbent 150W HPS lights. According to the LRC, it was the manufacturers’ representatives that effectively selected the SSL candidates for the original evaluation.
The LRC has also addressed the DOE’s review of the initial study on a point-by-point basis. You can read the details on the LRC web page dedicated to the matter. It’s sufficiently complex that there will almost assuredly be more commentary to come from the parties.
Still, the LRC took the additional step to repeat the evaluation considering higher-powered SSL alternatives to the HPS lights. The addendum is now a part of the original report linked above. The new evaluation finds that the luminaires tested can match the pole-spacing of the HPS lights in meeting the ANSI/IESNA RP-8-00 standard. But the report still concludes that SSL can’t match the life-cycle costs of HPS and PSMH lights.
To summarize, the report concludes that the SSL lights would have an average life-cycle cost 1.7 times higher than the legacy lights even if the LED lights lasted 50,000 hours. The higher up-front cost of the SSL alternative proves too great for the projected 7% in energy savings that would come with a move to LEDs.
Without question we will hear more on this issue. Moreover LED street light prices are dropping rapidly meaning the conclusion of such an evaluation will change -- narrowing the gap between the technologies on a month-by-month basis. The evaluation also doesn’t address adaptive controls and the additional energy savings that could come with dimming LEDs. It also doesn’t address the mounting evidence that LEDs offer superior lighting to legacy lights at lower lumen output levels. For more on that topic, see our recent report on the Street and Area Lighting Conference.
