DOE releases Snapshot Report on outdoor SSL, revises PAR38 L Prize rules

Aug. 2, 2013
An overview of US Department of Energy research in the Caliper program indicates that outdoor LED lighting is generally better than incumbent technologies in efficacy although high-output SSL products are lagging HPS, and the agency has loosened the beam pattern specified in the PAR38 L Prize competition.

The US Department of Energy has published what it calls a Snapshot Report on outdoor area lighting that is collectively based on Caliper research into LED parking-garage, canopy, and roadway-and-area luminaires. The agency also issued revised requirements in the PAR38 portion of the solid-state lighting (SSL)-centric L Prize competition and announced a new OLED funding opportunity.

Outdoor lighting snapshot

The snapshot highlights include a comparison of efficacy of the various products that have been evaluated in the Caliper program. The bulk of the products have ranged between 70–90 lm/W, although there have been extremes with products coming in under 50 lm/W or over 100 lm/W. But generally LED-based luminaires are performing better than legacy alternatives including high-pressure sodium (HPS) lighting.

Just two years ago, HPS was viewed as superior in efficacy to LEDs, although there were even then reasons such as broader-spectrum light that made SSL a superior light source. Now the DOE has said that the best of the LED products in terms of efficacy are "substantially higher" than alternatives such as HPS.

The report does note that there are areas in which HPS lighting is still the predominant choice. The Caliper program has revealed few choices among LED luminaires that can replace the 400W HPS lighting used on major roadways. The research only considers luminaires that include photometric documentation under the DOE Lighting Facts program.

The report revealed that there are more canopy luminaires besting 100 lm/W than such products in the other categories. But the canopy fixtures generally have higher CCTs, and cooler color temperature is directly related to higher efficacy.

Perhaps surprisingly, the report notes little correlation between color quality or CRI and efficacy. High CRI is often achieved through a broader power spectrum, which can lead to lower efficacy. But evidently the variety of approaches taken by manufacturers to boost CRI have at least made any such relationship invisible.

The agency has tested luminaires with CRI between 60 and 80, and products with suitable color rendering for outdoor applications are plentiful. Indeed, the SSL products generally render color far better than HPS sources and that can make objects more detectable from a distance. The CCT of the tested fixtures typically falls in the 4000–6000K range. Surely that is cooler than many would prefer. See our recent story on outdoor lighting on our LEDs Magazine website for examples of citizens complaining about cool CCTs.

L Prize and OLED funding

Meanwhile, in the Bright Tomorrow Lighting Prize (L Prize) program the DOE has changed the luminous intensity distribution maximum allowable beam pattern from 12° to 15°, making it simpler for lamp manufacturers to meet the requirements. The agency will also no longer require LEDs to be manufactured in the US and also removed the requirement that a lamp manufacturer commit to producing 250,000 lamps in the first year after receiving the award.

No company as of yet has stated its intent to compete for the PAR39 L Prize despite the fact that a $5 million prize awaits the winner along with a US government pledge to buy the lamps. For a more detailed article on the PAR38 L Prize, see our coverage on the LEDs Magazine website.

The DOE also announced topics that are eligible for new FY 2014 SBIR and STTR funding including OLEDs. The formal funding opportunity announcement will come on August 12, 2013 with letters of intent due September 3, 2013 and applications due October 15, 2013.