LightNOW recently reported on an Application Summary Report published by the Department of Energy’s CALiPER program, which evaluated bare-lamp performance for 31 linear LED lamps and found that while the lamps provided similar efficacy, tested average light output was half as much as the benchmark 32W fluorescent T8 lamp, and there was significant variation in light distribution.
DOE has since issued three additional reports. The first evaluated performance of the tested lamps in a typical 2×4 troffer with a K12 prismatic lens. Overall, many of the tested linear LED lamps provided higher luminaire efficacy than a comparable fluorescent system in a K12-lensed troffer. On average, the LED-lamped, K12-lensed troffers were approximately 25% more efficacious than the fluorescent benchmark. About one-third of the LED products provided lumen output approximately equivalent to a fluorescent system with the same number of lamps.
While the lensed troffer reduced the variation in luminous intensity distribution noted in the previous report, however, it did not eliminate it; there was still some difference in performance that could be undesirable in a lighting installation. For instance, the lamps with a narrower distribution (i.e., with a clear lens) resulted in a slightly smaller spacing criterion for the luminaire, which may result in uneven workplane illuminance. Lamps with a narrower distribution resulted in a higher luminaire efficiency than those with a wide distribution (i.e., with a diffuse optic), and all of the linear LED lamps resulted in a higher luminaire efficiency than the fluorescent benchmark. Therefore, products should be evaluated on a case-by-case basis.
The second new report evaluated performance of three LED linear lamps and a benchmark fluorescent T8 lamp in five different troffer types, including both performance testing and a subjective evaluation of appearance. Based on both photometric testing and observer responses, LED lamps may work well in some troffers but poorly in others. Results show that linear LED lamps can improve luminaire efficiency in K12 lens and parabolic troffers, effect little change in volumetric and high-performance type luminaires, but reduce efficiency in recessed indirect troffers. These changes can be accompanied by visual-appearance and visual-comfort consequences, especially when LED lamps with clear lenses and narrow distributions are installed.
Finally, DOE evaluated cost-effectiveness of linear LED lamps based on life-cycle costing. Specifically, the report details a set of life-cycle cost simulations that compare a two-lamp troffer using LED lamps (total 38W) or fluorescent lamps (total 51W) over a 10-year study period. The LED lamps were assumed to produce similar light output and light distribution when mounted in the troffers, an assumption that was reasonable for less than a third of the products tested for this series of reports, but that may be more widely achievable in the near future. In general, while their initial cost premium remains high, linear LED lamps are more likely to be cost-effective when electric utility rates are higher than average and hours of operation are long, and if their installation time is shorter.
Click here to download these reports.
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