The test space is located in a 284,000 square
foot area in a building that houses maintenance and rebuilding
activity for F-16 and C-130 aircraft at the base. Part of the
area has a low ceiling, requiring hollow light guides, developed
by 3M Corporation, to distribute the high intensity light with
adequate uniformity. The remainder of the area has a high enough
ceiling to permit the use of more traditional high-bay luminaires
adapted for S-lamps by Cooper Lighting. In all, 288 Light Drive™ 1000
lamps have been installed, 50 in each of four high-bay areas,
and 88 in the low-bay area at the ends of 44 tubular light
guides, each 104 feet long.
With DOE program direction and financial support, Pacific
Northwest National Laboratory (PNNL)1 undertook to assess the
efficiency and performance of the system. Both before and after
installation, PNNL collected data characterizing lighting level
and color, as well as electric energy consumption and power
quality characteristics, for a section of the low-bay area
and a section of one of the four high-bay areas. Because the
lighting that was replaced by the S-lamps was antiquated, PNNL
also developed a conceptual scheme for lighting the areas with
conventional modern metal halide low-bay and high-bay downlight
luminaires for purposes of comparison. Finally, the lab administered
pre- and post-installation surveys of building occupant responses
to gain insights into worker satisfaction and possible impacts
on productivity.
The following findings resulted from the assessment:
S-lamps produced lighting levels that were approximately
39 percent to 47 percent higher in the low-bay area, and
130
percent to 160 percent higher in the high-bay area, compared
to the conventional high-intensitydischarge systems they
replaced.
The S-lamp high-bay luminaires generally exceeded the 75 foot-candle
lighting level target by 25 percent, while the light guides
in the low-bay area fell short of the same target by approximately
19 percent.
Characterized in terms of the CIE Uniform Chromaticity Scale,
the new and old systems produced similar coloring on surfaces.
S-lamps appear to provide greater uniformity in the high-bay
area.
Energy consumption increased by 63 percent in the high-bay
area with the installation of the S-lamps. This was due to
the inadequate lighting in place beforehand, the requirement
to use preëxisting fixture locations that were closer
than optimally-spaced, and the addition of 16 more S-lamps
to illuminate side and storage areas not previously lighted.
Had all of the pre-retrofit lamps been working and the 16
additional side lights not been installed, the high-bay energy
consumption would have increased by only 26 percent and still
provided at least twice the light level. In the low-bay area,
energy consumption decreased by 42 percent, where the light
guides replaced inefficient fixtures.
Compared to an appropriately designed lighting system to achieve
comparable lighting levels with metal halide lamps, the S-lamps
in the low-bay area would consume 17 percent less energy,
and the ones in the high-bay would consume 37 percent less.
The difference in savings is due primarily to losses in the
light guide arrangement needed to compensate for the lower
ceiling in the low-bay area.
As measured at individual lighting circuits, the S-lamps’ power
factor, total harmonic distortion (THD) and crest factor were
approximately 99 percent, 2.7 percent and 1.4 respectively.
These figures are similar to preinstallation values, except
for THD, which was between 7 percent and 16 percent beforehand.
Metal halide lamps typically have THD values around 19 percent.
Workers in the building reported being able to read samples
of small type on the occupant survey more easily after the
S-lamp installation than before. Compared to pre-installation
conditions, fewer workers perceived flicker from overhead
lights as a problem, while more were bothered somewhat by
reflections on computer screens, possibly due to the increased
light levels from the S-lamps. Because defective fixtures
were replaced in the low-bay area after the the post-installation
survey was administered, the responses do not fully reflect
the performance of the lighting now in place. The later replacements
probably enhanced the ability of workers to read small type
and increased the reflections on computer screens compared
to what was reported.
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