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High Hopes For Low Glare
Wall-pack luminaires with high-pressure sodium (HPS) lamps are commonly used
to provide outdoor illumination for all types of buildings and many parking
lots (Table 1), yet they are among the least-efficient fixtures made and provide
poor
glare control. The standard design approach makes a trade-off between good
light distribution and glare/light pollution - designs that reduce glare also
reduce
the amount of light that reaches the ground. As a result, existing products
use more energy than necessary to light up an area, and this contributes significantly
to light pollution and light trespass.
Two new product prototypes were developed to reduce glare and improve the
efficiency of outdoor luminaires. Prototypes of a low-glare wall sconce and
a perimeter light use an advanced optical design, 100-watt (W) or 150-W ceramic
metal-halide (CMH) lamps, and electronic ballasts to reduce energy use by
up
to 30 percent and minimize light pollution and glare. A manufacturer, Gardco
Lighting, plans to introduce a commercial product based on these designs.
The commercial product will feature a 70-W lamp as a replacement for a 175-W
fixture
(Figure 1.)The CMH light source features a small arc-tube that helped designers
produce a new optical system with more-precise control of light output. The
new optics
provided the following benefits:
• Better control of light distribution. The Gardco wall-mounted unit provides
illumination up to 45 feet from the building compared to 30 feet for a conventional
luminaire.
• Reduced power draw. If the same luminaire spacing is used, a 100-W Gardco
luminaire may replace a 150-W conventional luminaire.
• Less glare and improved light dispersion. There is a more even distribution
of light over a greater surface area (Figure 2, page 38).
• Less wasted light. The Gardco luminaire reduces light pollution in the
night sky and light trespass in neighboring buildings and properties.
• Fewer luminaires. For a new installation, the wider distribution of light
means 50 percent more coverage of surface area, so the number of luminaires required
is reduced.
• Increased security. The combination of better light distribution,
lower glare, and higher color definition will enhance the security of the lit
environment.
The CMH lamps used in the luminaire produce white light with high color rendition,
which most people prefer to the yellowish color and poor color-rendering
qualities of the HPS sources in common use. This improved color quality will
result in
a more pleasing environment and will enable users to identify their cars
more easily in parking lots. In addition, because the lamps use electronic
ballasts,
lamp life is estimated to be about 20,000 hours, which is close to the
life expectancy of HPS lamps.
The new products are applicable to building and parking lot illumination
in new construction and in retrofit applications.
The new design features high cutoff characteristics that should enable
the fixtures to meet local dark sky and light-trespass regulations.
As a field demonstration to prove the effectiveness of the prototye
design, 10 units were installed on the campus of Cal Poly Pomona.
Those units
continued to operate.
Reports may be downloaded from the web at www.archenergy.com/lrp/products/wallpack.htm.
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