TECHNOLOGY / STREET & AMENITY LIGHTING TECHNOLOGY / LED PRODUCT 105
TRADITIONAL STREET LIGHTING LAMP TECHNOLOGIES
TYPICAL LAMP TYPICAL
LAMP TYPE PROS & CONS EFFICACY
WATTAGE LUMENS
Low Pressure Sodium (LPS) lamp is by far
the most efficient light source used in street
lighting. The lamps produce a monochromatic
orange-yellow light from lamps that are long
Low
and skinny. LPS is also a good way to reduce
sky glow for stargazers. Drawbacks of using LPS
Pressure
lamps include the colour rendering. Also, as the
135W 22,600 167lm/W
Sodium
lamp ages, it uses more wattage that lighting
designers need to account for. That increase in
wattage does result in little or no lumen depre-
ciation, meaning it the light output from the
lamp stays fairly constant over its life.
High
There are three main types of High Intensity Discharge (HID) lamps (see below). HID lamps in general require an external bal-
Intensity
last to operate. These lamps usually take between 1 and 8 minutes to reach full brightness, and if there is a dip in electricity,
Discharge
these lamps will shut off. The lamps must cool sufficiently to restrike, which usually takes from 1 to 10 minutes.
Mercury Vapour was the first widely accepted
HID lighting source. Clear mercury vapour lamps
cast a blue-green light. Advances in technology
have lead to colour corrected mercury vapour
Mercury lamps that cast a relatively clean white light.
pour
This is done by coating the outer glass globe of
400W 21,000 52.5lm/W
Va
the lamp with phosphors. One main difficulty
with mercury lamps was ‘lumen depreciation’
with a drop in light output of the lamp over
time.
Metal Halide Lamps are a distant cousin of
mercury lights. The basic lamp is the same as a
mercury lamp, but with other metallic elements
Metal added. The result is a good quality white light.
lide
Metal halide is mostly found in car parks and
250W 14,100 56.4lm/W
Ha
inside commercial and industrial buildings. The
light is more efficient than mercury vapour, but
the lamp life is shorter.
High Pressure Sodium (HPS) lamps are now com-
monly in street lights. The lamps were devel-
High oped in the early 1970s and are more energy
Pressure
efficient than mercury and metal halide lamps.
200W 25,000 100-150lm/W
The lamps give off an amber colour, have virtu-
Sodium
ally no problem with colour shift, and last for
long periods of time >25,000 hours.
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