Republication of Postings from the U.S. Department of Energy (DOE) Solid-State Lighting Program
by Jim Brodrick, SSL Program Manager, U.S. Department of Energy
PAR38 lamps put in long hours lighting up retail shelves, museum displays, lobbies, and other commercial settings across the country, which presents a prime opportunity to save energy. LED PAR38s, which have been on the market for a few years, have the potential to be much more energy-efficient than their incumbent halogen counterparts. LED PAR38s with beam angles of 25° to 45° (often called narrow flood or flood lamps) are now fairly common and readily available. LED PAR38 lamps with narrower beams (spots), high center beam intensity, and excellent color characteristics — so often needed by lighting designers and specifiers for demanding applications — are much harder to come by. In an attempt to spur the market to higher across-the-board performance, DOE launched a PAR38 category of the L Prize® competition, with ambitious performance targets. LED PAR38s continue to show incremental improvement, but right now there’s a long way to go.
DOE’s LED Lighting Facts® database currently lists nearly 500 LED PAR38s. Of those, only about 33 (less than 7%) can meet the L Prize light-output requirement of 1,350 lumens, while none even comes close to meeting the 123-lm/W efficacy target. In fact, the median efficacy for products currently listed with LED Lighting Facts is only 58 lm/W, with a maximum of 92 lm/W. The median efficacy has not changed in the past two years and has only increased by 18% since 2010, significantly lagging the rates of improvement in other LED product categories. Only 20 (4%) of the listed LED PAR38s have warm-white color and high (>90) CRIs, and these all have light outputs below the L Prize target.
DOE’s CALiPER testing program has been looking closely at PAR lamps and is publishing a series of reports to share the results. The first, CALiPER Application Summary Report 20, described the results of photometric testing and showed that most PAR38 lamps tested had warm-white color with CRIs in the 80s. A handful of products had spot distributions with high center beam intensity, but this was the exception; most products had beam angles of 20º-45° or higher. The second report, CALiPER Report 20.1, focused on human-evaluated characteristics, including beam quality, shadow quality, and color quality. Results suggested that the LED products compared favorably to halogen PAR38 benchmarks in all attributes considered.
The latest report in the series is CALiPER Report 20.2, which came out last month and focuses on dimming, flicker, and power quality characteristics. For the LED lamps that were dimmable (three-quarters of the Series 20 total), those evaluated characteristics were less consistent than for conventional halogen PAR38s, although a number of trends emerged.
For example, most of the LED products produced more relative light output at a given dimmer setting than the benchmark halogen PAR38s. And when operated by a switch, almost all of the LED PAR38s exhibited less flicker than a magnetically ballasted fluorescent lamp, with more than two-thirds of them exhibiting flicker less than or comparable to that of a halogen. However, when dimmed, about half of the lamps exhibited more flicker than a magnetically ballasted fluorescent lamp, and almost all of the LED products exhibited more flicker than a typical halogen.
As for power factor, while all of the LED lamps tested met the current ANSI-defined thresholds for power factor when operated by the switch, nearly one-third had a power factor less than 0.5 at some point over the dimming range, which would not meet the standard.
While LED PAR38s on the whole have come a long way, and many of them can now be considered “good enough” for various applications, it’s important that their performance continue to improve — as attested to by L Prize partners in a video you can watch online. A PAR38 L Prize winner will not only overcome some of the limitations of today’s LED PAR38s, but, with double their efficacy, will run cooler. And that, in turn, will make possible a whole range of other improvements, including longer life, better color stability, higher output, smaller heatsinks, higher center beam intensity, and more fixture types. The narrow beam angle of 9º-15° will provide the focused lighting needed by critical applications, with color quality that makes merchandise, art, and lobbies sparkle.
And the energy savings — which, after all, is DOE’s main interest — will be considerable. It’s estimated that making all 90 million installed PAR38s L Prize-efficient would annually save 11 terawatt-hours of electricity (which is roughly equivalent to the annual electricity consumption of Washington, DC) while avoiding 7 million metric tons of carbon emissions (the equivalent of removing 1.46 million cars from the road).
