STREET LIGHTING
LEDSand
PUBLIC
LIGHTING
LEDs – once confined to
indicator lights in electrical
and electronic products –
are now making significant
inroads into a host of
lighting applications.
Huge resources are going
into their development,
particularly in Asia. China
alone has over 5,000
manufacturers of LED
products. The world is
at the early stages of
a revolution in lighting
which will see LEDs
predominate in nearly all
lighting applications. Public
lighting will be a part of
this revolution, being
particularly well-suited to
the technology.
What are LEDs?
LEDs are a type of solid-state lighting. They
consist of a chip of semiconducting material
treated to create a positive-negative junction.
When switched on, charge carriers flow into
the junction and combine to release energy in
the form of photons. The light colour emitted
depends on the materials used to make the
diode. LEDs can be red, yellow, blue, green or
‘white’ (created by combining other LED colours
or by using phosphors).
LEDs were introduced as a practical electronic
component in the 1960s where they were
used as indicator lamps. Significant technical
developments in more recent years, particularly
the development of high brightness LEDs, have
seen them increasingly used for special and
general purpose lighting.
Benefits
LEDs can be highly energy efficient, currently
comparable to fluorescent technology but
expected to surpass fluorescent lamps in the
near future. They have a long life — lasting last
up to 50 times longer than incandescent lamps
and up to five times longer than fluorescent and
discharge lamps. This makes them ideal for hard
to access locations such as roadway lighting and
many other public lighting applications. LEDs
are durable and can withstand vibration and
shocks. Unlike fluorescent and discharge lamp
technology, they are not adversely affected by
regular on-off switching. Another important
advantage – and unlike most other forms of
public lighting - is that LEDs do not contain
the toxic substance mercury. LEDs achieve full
brightness as soon as they are switched on and
are fully dimmable.
The independent, not-for-profit Climate Group
makes the following comments about LEDs:
Light-emitting diode (LED) lamps, combined
with smart controls, can cut CO2 emissions
50–70%. LED outdoor lighting also reduces
Govlink Issue 2 2013
Bryan Douglas
Chief Executive Of?cer
Lighting Council Australia
costs, enhances public safety, minimizes light
pollution and makes public spaces friendlier
at night. In 2012 we called for all new street
lighting to be LED (or as efficient) by 2015, and
all street lighting the same by 2020.
LEDs are highly adaptable. The technology is
ideally suited to the emerging concept of humancentric lighting. As a consequence of lighting
producing biological and emotional effects,
human-centric lighting broadens the application
of light beyond mere visual tasks. Human
biological rhythms, such as the sleep/wake cycle,
daily changes in alertness, performance and
mood (circadian rhythms) are now thought to be
influenced by specific light conditions. Examples
include the sleep/wake cycle, daily changes in
alertness, performance and mood (circadian
changes), as well as responses to seasonal
changes. Dynamic changes of colour temperature
and illuminance and a wide distribution of light
from both direct and indirect light sources
stimulate the human organism throughout the
day. As a consequence human-centric lighting
utilising LEDs has the potential to promote wellbeing and productivity by supporting human
circadian rhythms.
Lighting controls
LEDs, being a digital technology, are eminently
suited for use with sophisticated lighting controls.
There is substantial energy saving potential in
controls utilising presence detection and daylight
sensing. Control systems can improve or optimize
light quality in a range of applications. They can,
for example, dim roadways late at night when
traffic is light. They can increase illumination
levels in response to human movement in public
areas such as parks and bicycle paths, thereby
improving safety.
Just as we are witnessing a revolutio