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In This Bright Idea, LED Replaces Light Bulb -Hillsboro Arch Application Story

Posted 01-MAY-02

Hillsboro, OR faced an ongoing problem: its Arch, the embodiment of civic pride, had become an eyesore in the city's nightscape. Marring the grandeur of the 90 ft Arch was the failure of many of the 580 incandescent lights outlining its contours. Although the burnt-out bulbs prompted complaints from city residents, given their average operating life of just 14 months, replacement was neither frequently nor easily performed.

Compounding the problem was the light rail line running beneath the Arch, and the transit authority's reluctance to stop rail service, reroute trains, and inconvenience commuters to enable maintenance crews to relamp the Arch. Two or three times a year, the transit authority gave city maintenance an hour, usually at 2 A.M., to replace any failed incandescent bulbs. Not only was the time less than ideal, it was costly: overtime labor expenditures for a relamping crew of four and a flag crew of two amounted to about $1,000, plus $1,100 for renting a 100 ft lift truck.

In order to minimize the frequency with which the Arch had to be relamped and reduce maintenance costs, Hillsboro facilities manager Mike Klein searched for an alternative to incandescent lights. "We considered using floodlights to wash the structure in color, but then started to research something with a longer life. We knew about LED technology, so we looked for and found a company that made LED bulbs that we could use on the Arch."

Mike contacted LEDtronics (, a premier light emitting diode (LED) lamp manufacturer located in Torrance, CA. LEDtronics' answer: a four-LED cluster 470nm Blue LED that uses a tenth of the power required by an equivalent incandescent lamp and, most importantly, operates for 11 years.

An LED is a diode chip made from semiconductor materials, usually from groups III and IV of the periodic table. When current flows across the junctions of the different materials, the energy level in the semiconductor changes. This change in energy generates photons, some of which are emitted as light. The color wavelength of the light is determined by the composition of the semiconductor material and is independent of the lens color.

With an average 100,000-hour operating life, LEDs last 30-50 times longer than any incandescent lamp, making them the perfect solution for a maintenance-intensive lighting application like the Hillsboro Arch. While hair-thin metal filaments and glass make incandescent lights vulnerable to damage, LEDs are solid state with no fragile filaments to break. The results? LEDs are impervious to electrical and mechanical shock, vibration, frequent switching, and environmental extremes, so they operate year after year. In the four months since the 580 LEDs have been installed on the Arch there have been no failures.

"Over a similar four-month period, we would lose 5-10% of the incandescent lamps to burnout," says Mike Klein. Between the lamps themselves and labor expenditures, each replacement process was costing almost $2,500. This became a $5,000 to $7,500 per year expenditure that has now been virtually eliminated by using LED lamps manufactured by LEDtronics.

LED lamps use 80-90% less operating power than standard incandescent bulbs, which expend 90% or more of their energy in the formation of heat. LEDs emit 100% of their energy as colored light while generating negligible heat. In the short time since the Arch was relamped, Hillsboro has already seen considerable savings in operating costs. The Arch now operates at 0.6kW for the entire 580 lamps compared with 2.7kW for incandescents -- a fourfold reduction in the operating costs and a 75% decrease in energy consumption.

While LED lamps seemed the most logical choice based on life expectancy, the price when compared with similar incandescent lamps made Hillsboro skittish. Hillsboro's financial concerns were soothed when analysis showed that the cost of the LEDs would be offset by the reduced need for relamping. Typically, savings from reduced power usage, maintenance cost, and downtime return the capital investment in six to eight months! While the purchase price of an incandescent appears as pennies on the books, the true cost lies in squandered energy and labor costs. Depending on what it costs to pay a maintenance worker -- even if it's just for 15 minutes -- the real cost of relamping incandescent bulbs skyrockets.

Cost savings aside, the Arch is now more attractive. The LEDs create a soft electric-blue halo against the night sky -- a dramatic departure from the harsh corona made by the incandescent lamps. LEDtronics provided Mike Klein with lamps of various colors from which to select. After seeing the different colors, city staff members voted for the blue. "The lighting is different as well," Klein said. "In some ways, it's more intense and more directional. It depends on the angle from where you're viewing it. I think you'll see the Arch from a lot farther away now," Klein said. "From farther away, it looks better. From a distance the two lines of blue kind of merge together."

Torrance, CA

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