PORTLAND REPLACES 1000 TRAFFIC INTERSECTION SIGNALS WITH
LED LIGHTS, SAVING MILLIONS OF KILOWATT-HOURS PER YEAR
SUMMARY
The City of Portland has replaced all red and green traffic
signal incandescent light bulbs with energy saving LED lights
(Light Emitting Diode modules). 13,382 incandescent traffic
light bulbs were replaced with LED modules, which save
approximately 4.75 million kilowatt-hours per year. This is
equivalent to enough energy savings to power over 350 Portland
homes each year. The replacement to LED lights saves the city
of Portland $335,000 annually in signal power costs.
WHAT IS IT?
There are three principle advantages to replacing municipal
traffic lights with LED lights:
- LED modules represent an 83% to 88% percent reduction
in energy consumption over standard light bulbs.
- LED modules are brighter and they emit light more
evenly, making them more visible in foggy conditions.
- LED traffic lights last for 100,000 hours, compared to
incandescent bulbs that last only 8,000 hours because their
filaments burn out. Replacing traffic bulbs is not only
expensive but inhibits traffic flow. Burned out lights are
hazards, thus reducing traffic safety. LED lights avoid
these scenarios all together.
HOW DOES IT WORK?
- Prior to the development of the LED modules, the City
of Portland utilized incandescent light bulbs for their
traffic signal indications. While these light bulbs were
rated for heavier duty than the typical household light
bulb, the City had to replace all light bulbs at once every
two years. ‘Group relamping’ required a two-vehicle
maintenance operation: one-bucket truck and one
traffic-control pickup. The bucket truck consisted of a
crewmember elevated inside a bucket to the height of the
traffic signal, while the traffic-control pickup followed
suit with a warning sign. Roads are not actually closed off
but traffic does slow down. This process is expensive and
time consuming.
- In October of 2001, the City of Portland’s Signal and
Street Lighting Division hired an electrical contractor,
E.C. Construction, to perform the LED conversion program.
Installing the new LED lights requires minor modifications
to the signal head to accommodate the LED modules. Because
an incandescent light bulb sits within a base that is
surrounded by a reflector, both the base and the reflector
had to be removed for the installation of the LED module.
The exterior of the signal head stays exactly the same,
only the interior is altered to position the new bulb.
- By February 2002, the contractor had installed 13,382
LED modules in only 4 months. Each 142-watt incandescent
light bulb was replaced with a 17-watt LED module and each
59-watt incandescent light bulb was replaced with a 10-watt
LED module.
- The conversion project cost the City of Portland
approximately $2.2 million US dollars. The project received
$715,519 US dollars in energy incentive rebates from local
power utilities.
- The City of Portland came up with an innovative way to
finance the program. Because the City’s Signal and Street
Lighting Division is a public agency and therefore cannot
collect tax credits to help fund its programs, the Division
partnered with Dooling Lease Management Corp. The private
leasing company agreed to finance the program and was thus
entitled to receive an Oregon State energy tax credit of
$500,000. Essentially, the City of Portland leases the LED
lights from Dooling Lease Management Corp. The City pays
off the lease in monthly installments of $30,000. The lease
will be paid off by August 2007.
NEXT STEPS
- The current LED modules are reaching the end of their
useful life, which is typically 7 years. The City
anticipates replacing all traffic signals with new LED
lights in the fall of 2007. The new LED modules will be
more efficient than the existing LED modules, using about
75% as much power.
- Future replacement projects will cost less because the
cost for LED modules is approximately 50% less today than
in 2001.
- The City is not replacing the yellow incandescent
indications because the energy savings does not cover the
conversion cost. Also, because yellow indications are only
activated briefly during each signal cycle, the overall
savings potential is not very high.
APPLICATION
- A city can implement this program via it’s own City
agency or by hiring an electrical contractor such as
Portland did.
- Innovative financing mechanisms can be applied, such as
partnering with a private company that agrees to fund
program.
- The conversion program will save ‘group relamping’
costs and off-hour call-out costs for burn out lights
because of the increased life of the LEDs.
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