Researchers develop insight into ice

11/25/02 12:00AM By Steve Zind
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(Host) Ice is a fact of life in Vermont this time of year. Underfoot and on our windshields, it can be a nuisance and a danger. Because it's so abundant, you might think scientists had long ago learned all there is to know about ice.

But as VPR's Steve Zind reports, Dartmouth College researchers have advanced our understanding of ice and, in the process, developed new technology that could change our relationship with this common substance.


(Sound of scrapping ice from a windshield.)

(Zind) The days of the windshield scraper are numbered. Soon there will be another way to get rid of ice. Until now, de-icing a car window, an airplane wing or a walkway has usually involved heating a surface until the ice melts. That can be a slow and inefficient process.

A new technology developed at the Dartmouth College Thayer School of Engineering takes advantage of the unusual electrical properties of ice. On a horizontal surface, like an airport runway, a high frequency current carried in wires imbedded in the concrete can quickly melt even thick ice. This happens because ice readily conducts electricity, then dissipates it in the form of heat. That way the ice is melted without wasting energy by actually heating the runway. The procedure also helps the environment by saving on salt or fuel for snowplows. The technology is safe and it uses a only a small amount of electricity.

Researchers also discovered that a low frequency current applied to an inclined surface quickly breaks the bond between the ice and whatever it's sticking to, and the ice drops off.

Engineering professor Victor Petrenko leads the Dartmouth research team. Petrenko says the technology creates endless possibilities from de-icing power lines to battery powered non-slip shoes.

(Petrenko) "Every month some new company or person calls and either suggests or requests a new application. The most important right now, as we see them now, is the de-icing of airplanes and helicopter blades."

(Zind) Petrenko says the airplane wing de-icing system is ready to go and waiting for government approval. It was developed using a wind tunnel in the basement of the engineering building. The tunnel is a narrow tube located in room where the air is chilled to ten below zero.

(Petrenko) "This is our wind tunnel." (Sound of wind in tunnel.)

(Zind) A 150- mile an hour wind blows over a small section of wing to replicate flight conditions. Dartmouth has granted licenses to the Goodrich Corporation to market the wing de-icing system. Petrenko says he's also talking with the City of New York about deploying a similar system to keep ice off the George Washington Bridge.

(Petrenko) "Ice grows on the suspension cables and other elements of the bridge and large chunks of ice fall on people and cars. And right now very often that bridge in wintertime is shut down."

(Zind) As for removing ice from car windows, Petrenko says there are better days ahead. Right now when you turn on the defroster for the rear window of your car, heat is created by the resistance in the wires imbedded in the window. It's an inefficient method that won't work for the windshield because too much heat is lost to onrushing cold air. Blowing warm air through defroster vents inside the car is often ineffective for the same reason. The new technology doesn't have that problem.

(Sound of an assistant talking in a laboratory room.)

(Zind) In another cold room in the engineering building basement, a member of Petrenko's research team demonstrates how a thick block of ice quickly drops off a frozen piece of windshield glass when a current is applied.

"So, you could see...." (Sound of ice falling off glass, thudding onto the floor.)

(Zind) Petrenko says the same methods would work to remove ice from a cars tires.

Many of these applications could be years down the road. But Petrenko says there is one use for his work that could come sooner than the rest. In the near future skis and snowboards could be imbedded with tiny wires powered by a small battery pack. Petrenko's technology would enable the skier to control the glide of the ski by alternately melting and forming a thin layer of ice under the ski.

Ice and even electricity have been around for a while. So why wasn't this technology developed earlier? Petrenko says ice research is still in its infancy. There are mysteries about ice that science still hasn't solved. For example, even at temperatures in excess of 100 degrees below zero, a thin layer on the surface of ice remains unfrozen. And no one knows why.

For Vermont Public Radio, I'm Steve Zind at Dartmouth College in Hanover.


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