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| | DOE questions recent NLPIP LED street light report (updated) | | 29 Oct 2010 | | Both the US DOE and luminaire makers believe that the recent NLPIP Specifier Report was fundamentally flawed in questioning the suitability of LED street lights for collector roadways. | The Lighting Research Center (LRC) at Rensselaer Polytechnic Institute (RPI) issued a report earlier this month concluding that LED-based solid state lighting (SSL) was not a viable replacement technology for high-pressure sodium (HPS) street lights. This week Jim Brodrick, the Lighting Program Manager at the US Department of Energy (DOE) responded, writing about the report, “a critical error was committed at the outset which affects all of its conclusions.”
The presumed critical error was apparently the selection of luminaires used in the tests that underlie the National Lighting Product Information Program (NLPIP) Specifier Report. Both luminaire makers and the DOE believe that the LRC selected SSL luminaire that weren’t appropriate for the collector roadway application.
The DOE’s Brodrick wrote, “Although I'm sure it wasn't intentional, LRC selected some woefully underpowered LED products to compare with HPS street lamps.” The link above to our original story about the report issuance also includes a statement from luminaire maker BetaLED about the research. In part that statement reads, “the choice of luminaire was not optimized for the specific application referenced in the report.”
The DOE response came in the form a Postings: from the desk of Jim Brodrick email. Brodrick distributes the Postings on a regular basis. The new one has not yet been added to the DOE web page that consolidates the missives but surely will be shortly.
Apparently, the DOE took issue with the report earlier because essentially the report implies that DOE Gateway LED street light trial reports are misleading. The DOE requested that the LRC revise some of the wording used in the introduction section of the Specifier Report. The LRC posted a PDF with both the paragraph in question and the DOE’s request for a change. As of now, the report 'Streetlights for Collector Roads' remains unchanged although it does include a note at the beginning referencing the PDF linked above.
The DOE also submitted its own review of the tests to the LRC several weeks ago (updated: the DOE posted a PDF of the review). The review identified the choice of underpowered luminaires as a problem as well as other flaws in the methodology. The LRC hasn’t responded to that review and now the issue has become very much public. Expect more in the coming days.
| | About the Author | | Maury Wright is the Senior Technical Editor of LEDs Magazine. | | COMMENTS | | Name: drifter Posted: Mon, 01 Nov 2010 16:11 |
| So,....if in fact the LED luminaires used in the study were replaced with 'higher powered' LED luminiares to meet uniformity etc, would there be any energy savings when compared to the incumbent HPS? | | Name: david Posted: Wed, 03 Nov 2010 18:11 |
| I invite you to take a look at page 7 of the PDF linked below for a quick comparison between a 65W LED luminaire and a 100HPS: http://www.lumec.com/pdf/series/RoadStar_series.pdf.
On a personal note, I also believe the LRC report is flawed. The comparisons are not fair and they're overall grossly inacurate. It would look different if proper and good quality LED systems were used. Disclaimer: I'm a Philips employee. | | Name: active cooler Posted: Wed, 03 Nov 2010 22:11 |
Any truly knowledgeable lighting person knows that present LED technology cannot, dollar for dollar, outperform HPS for "delivered lumens"( as opposed to lumens for the LED alone) after optics, thermal, current level-related and driver losses, even the best LED apparoach today will not exceed 70LPW, So the answwer is "No, a properly powered LED street light will not outperforme HPS in brute force LPW. That said, the LED approach, which in another couple years very definitely will have "delivered LPW" parity, a) eliminates restrike issues, very definitely will (or can) last 5 times longer, with active cooling (take heed, anti-active cooling skeptics) can be a fraction of the weight and in fact be more light direction controllable.
Ed Rodriguez, Optothermal Technologies Inc | | Name: david venhaus Posted: Thu, 04 Nov 2010 17:11 |
I must STRONGLY disagree with the comment that "LED systems cannot deliver more than 70 LPW..."
I have personally seen 3rd party testing on a prototype PGL built with 104 LPW emitters, running an 81% efficient class 2 driver delivering 70 LPW NET. Add an emitter @ 115 LPW (which is now the norm...) and increase the driver efficiency 5-10% and 75+ LPW is VERY easy to achieve.... | | Name: david Posted: Fri, 05 Nov 2010 13:11 |
| We have debunked some claims made in the report on our blog: http://www.lumec.com/blog/index.php/2010/11/05/streetlights-for-collector-roads-report-a-trip-back-in-time | | Name: ed rodriguez Posted: Sat, 06 Nov 2010 16:11 |
Just to clarify--my own fault I guess for opening up myself for an arrow, I stand by my comment that any claim by anybody to be able to provide much better than 70LPW, "delivered lumens" at 3000K or lower (I had failed to note color temp--my bad), in any system with optics or diffusers, is not talking about commercially available, cost effective technology. Agreed, that if you take "best bin" 6000K emitters from Cree or others and no optics you can jack up the figures--but there is a profound difference in achievable LPW in the real world--so blanket statements that 70LPW is "easy" demands more disciplne in defining the final delivered lumen specs and photometrics in general... and after the LEDs have heated up to equilibrium in a 30-35C ambient (am I being too picky here?). What might be observable as a lab prototype might be interesting but "doesn't count"
Ed Rodriguez, OptoTherrmal Technologies Inc | | Name: cascor Posted: Sun, 07 Nov 2010 18:11 |
| FYI...The Street Light system LPW already reached 70 LPW an year ago with 100 LPW LED. | | Name: gonzalo gomez Posted: Tue, 16 Nov 2010 19:11 |
| Of course the LED luminaires in this study do not perform adequately (in general). The study pits 150 W HPS (about 180 total watts) against LED luminaires that are typically less than 90 watts, with many less than 80 watts. A more reasonable comparison would be between the 150 w HPS and LED luminaires typically in the 120 W range. The LED fixtures tested are too underpowered. |
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