Lighting up Chicago

By now youve noticed holiday decorations adorning every street corner. What you might not have noticed is that several fixtures in Chicagos holiday light scene have switched to LED technology, most recently the 35-foot Canadian pine at the John Hancock Center.

An LED, or light emitting diode, is in essence a semiconductor diode, which conducts electricity through the movement of electrons between positive and negative poles.

Edison-era incandescent bulbs and compact fluorescents, the curly bulbs popularized by Al Gore, pale in comparison to LEDs.

LEDs require 70 percent less energy compared with incandescent light, said Yiting Zhu, a lead research specialist at Rensselaer Polytechnic Institute.

Landscape Concepts in Grayslake used LED holiday lighting in place of incandescent bulbs on the Hancock tree.

George Markoutsas, Landscapes marketing director, said his company is trying to promote sustainable practices and LEDs are an important part of that endeavor.

This is hopefully going to be the impetus to the LED phenomenon or trend, Markoutsas said.

But along the rest of Michigan Avenue, more than 1 million incandescent bulbs burn brightly. For the past half-century white Italian tree lights along the Magnificent Mile have ushered in the holiday season with a warm, soft glow.

Over the past five years Landscape Concepts has put up half the lights there.

Markoutsas said the Greater North Michigan Avenue Association, which sponsors the display, considered making the transition to LEDs this year but dropped the idea because of cost and color concerns. But he speculates the association will make the switch in the next few years.

Holiday lighting isnt the only place where LEDs have taken hold, and the science suggests LEDs may be lighting more than your tree in the near future.

To understand the potential for a LED revolution, it helps to know how they work.

Ernie Nathan, president of Illinois Solar Products, takes us back to high school chemistry.

Do you remember how electrons spin around neutrons? he asked. And how there are different levels of orbit in which the electrons spin around the nucleus?

Electrons circling the nucleus at close range are said to be in a ground (low energy) state, whereas electrons wandering far from the nucleus are in an excited (higher energy) state, according to a presentation for the Department of Energy by John Curran, president of LED Transformations LLC.

When you apply an electric current the electrons at the high energy levels (or the outer orbits) move toward the positively charged pole, which is dotted with electron holes, or vacancies.

When the free roaming electrons find an electron hole, they must let off energy to fall in and that energy is released as light.

And it doesnt take much to keep this microscopic musical chairs in motion.

Their energy efficiency is a huge advantage said Nathan, whose company is working with DePaul University on a number of projects to phase out incandescent lights.

But energy savings isnt all that LEDs have going for them.

Theyre going to last forever, Nathan added.

The Edison bulbs of yesterday might last 500 hours, he said. But LEDs can have a lifespan about 110 times longer, he added.

Despite the benefits, some hurdles need to be cleared before LEDs are widely adopted.

Price is an issue with any new technology, and LEDs are no exception despite their growing availability.

In an economy where an incandescent bulb may run for 25 cents, LEDs and their long-term energy savings are often overlooked, said Wendy Davis, a vision scientist with the National Institute of Standards and Technology.

Markoutsas witnessed another kink firsthand several years ago. He observed color differences between LED holiday light strand samples, even when packaging specified the same manufacturer and color.

One strand would kind of illuminate yellow and the other one would have just a little deeper yellow, he said. It was very peculiar how this happened.

Its a problem that the Spectrally Tunable Lighting Facility is tackling head on.

The lab, established by the National Institute of Standards and Technology, recognized that color standards must be in place before consumers will adopt the technology.

Davis compares it to buying cereal or gas for your car.

You want the measurements right, she said. By weight or volume you want to know that its correct.

The same goes for lighting, Davis said. But the existing measurements for traditional lighting such as fluorescent or incandescent bulbs dont translate well to LEDs.

Davis explained incandescent bulbs generally have a yellowish tint, while fluorescent lamps tend to cast a greenish hue.

LEDs on the other hand, have a wide spectrum of color possibilities since chromaticity or the color of the light when you look at it is dependent on how theyre assembled, she said.

But not everyone is waiting until the standards are set for LEDs.

Mike Casper, president of Chicago-based Flex Lighting, said his company uses LED technology exclusively to create illuminated signage capable of catching the consumer eye.

Our bread and butter is getting light into film, he said. It just happens that LEDs give you the most brightness of light in the smallest package possible.

Markoutsas agrees that LEDs are lighting the way to the future, but its up to the individual to keep the momentum behind the trend going.

And it can start with something as small as a Christmas light.

Or 7,000 Christmas lights on the citys Daley Plaza tree, saving the city more than $9,000 in electricity.

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