Guest post by Jim Brodrick, DOE
[Recently], DOE published the latest round of test results for the Commercially Available LED Product Evaluation and Reporting (CALiPER) program, which provides an ongoing series of “snapshots” of solid-state lighting (SSL) technology progress and trends. The Round 9 Summary Report includes test results for recessed downlights, 2’x2’ troffers and flat-panel luminaires, 4’ linear replacement lamps, and small replacement lamps. Just as in previous rounds of testing, Round 9 products exhibited a wide range of performance, with a number of underperforming products and inaccurate performance claims. Still, I’m encouraged by the clear, steady progression we are seeing – the average efficacy of all SSL products tested has more than doubled since we first began testing in 2006. In addition, more SSL products are demonstrating notable improvement in color quality, an especially complex and tricky characteristic that I discussed at length in last week’s Posting.
Most notably, the results for CALiPER Round 9 show that for applications like downlights and 2’x2’ troffers, many SSL products are now clearly competitive with incumbent technologies. We see further evidence in this round that LED recessed downlights can perform as well as, or better than, downlights that are equipped with 45W-75W incandescent and halogen lamps, in terms of both light output and distribution. And for the most part, they’re meeting or exceeding the performance of CFL recessed downlights in terms of color quality, efficacy, and light output.
This upward performance trend is particularly significant to DOE in light of the tremendous energy-saving potential. Downlights dominate the residential market, with more than 500 million currently installed. DOE estimates that switching them all to SSL would save $8.4 billion a year in electricity costs, or the equivalent of 12.8 1,000-megawatt power plants. So it’s especially encouraging that SSL downlights have been getting better and better each year, showing a steady improvement in efficacy over time.
In CALiPER Round 1, the best performing downlight tested delivered a luminaire efficacy of 19 lumens per watt. By Round 5, we tested a downlight that delivered 61 lumens per watt. On a separate note: one of the 2009 Lighting for Tomorrow competition winners was a Cree high-efficacy downlight that delivers 109 lumens per watt. Although this product is not yet on the market, it gives an indication of the tremendous progress that’s being made – as does the fact that in the latest CALiPER round, SSL downlights were benchmark tested with 26W and 32W CFL products for comparison, whereas two years ago the best-performing SSL downlights barely achieved the performance levels of 13W CFL downlights.
Another bright spot (no pun intended) in CALiPER Round 9 was 2’x2’ SSL troffer luminaires. A number of 2’x2’ integral SSL products were tested and found to roughly match the light output of the fluorescent products they were designed to replace, with one even exceeding the efficacy level of a benchmark high-performance T8 luminaire. By contrast, the 4’ SSL linear replacement lamps did not achieve the performance of T8 fluorescent linear replacement lamps, even when tested in troffers to compare overall luminaire performance. Simply put, the 4’ SSL linear replacement lamps do not provide sufficient light output or efficacy, have poorer color quality than fluorescent benchmarks, often require electrical rewiring of the troffer (to bypass the ballast), and do not represent wise use of SSL technology at this time.
The disparity between the performance of 2’x2’ SSL troffer luminaires and 4’ SSL linear replacement lamps underscores the fundamental difference between integral SSL luminaires and SSL replacement products. Because SSL technology utilizes light-emitting diodes rather than filaments or gasses like conventional lighting, it works most efficiently with fixtures that are designed specifically for LED light sources – primarily because there are fewer constraints for thermal management and driver design, and the natural directionality of LED chips can be used advantageously along with innovations in optics. That’s why LED replacement lamps, which are inserted into fixtures that were designed for conventional light sources, can’t take full advantage of SSL’s energy-saving potential. The 2’x2’ SSL troffer luminaires tested in Round 9 were integral products designed for LED light sources, as were the SSL downlights. So it’s no surprise that they manage to compete better than the 4’ SSL linear replacement lamps with the incumbent technologies they’re intended to replace.
I know that the market for replacement lamps is huge and can’t be ignored, but the fact remains that integral products make much better use of SSL technology. Throughout all of the rounds of CALiPER testing to date, we’ve found the highest efficacies, the highest levels of light output, and the most optimal light distributions in SSL products that are integral luminaires rather than replacement lamps (although there are some excellent small, directional SSL replacement lamps on the market).
I encourage you to check out the full Round 9 report to learn more about the test results for small replacement lamps, and especially the preliminary results from CALiPER long-term lumen depreciation testing of 26 fixtures and replacement lamps. Five of these products exhibited very rapid lumen depreciation, falling below 70% of initial output within the first 1000 hours of operation. While the majority of SSL luminaires do not appear to exhibit this kind of early, rapid lumen depreciation, this kind of performance is a surefire recipe for consumer disappointment that could seriously hinder market acceptance. The findings from CALiPER long-term lumen depreciation testing will inform the efforts of standards organizations, manufacturers, and buyers alike, and will likely be the subject of a future Posting.
