April 14, 2006 10:19 AM PDT

A high-tech way to defrost

Humans have been getting rid of ice the wrong way for centuries, it turns out.

Dartmouth College engineering professor Victor Petrenko, not to be confused with one of the Champions on Ice, has devised a way to use a burst of electricity to remove ice caked on walls or windows. For surfaces coated with a special film, the jolt gets rid of ice in less than a second, far less time than it takes to hack at it with an ice scraper.

While drivers might find easy-cleaning windshields convenient, the technology--called thin-film pulse electrothermal de-icing, or PETD--could have significant economic impact if widely deployed. It could, for example, cut the costs of repairing power lines downed by ice storms and keep plane windshields frost-free, decreasing fuel consumption.

In Sweden, civil engineers have tested PETD and decided to cover the Uddevalla Bridge in a 12-millimeter-thick PETD foil to keep it from icing over.

"Frost-free refrigerators can approximately reduce energy consumption by a factor of two. Billions of dollars are spent each year on running refrigerators and air conditioners. If you can cut that, it's great," Petrenko said. "In ice makers, we can cut the ice-harvesting cycle and increase the productivity of ice makers by 30 (percent) to 40 percent."

A refrigerator for the residential market sporting PETD will likely come out soon. The technology will also be incorporated into the windshield of an upcoming commercial jet, according to Petrenko. Aerospace parts supplier Goodrich, an investor in and one of the seven licensees of Petrenko's Ice Engineering company, is also promoting the concept among utilities as a way to keep wind turbines de-iced.

PETD can go in reverse, too. By varying the electric pulse, the technology can cause ice to stick better to surfaces. That could help snowboarders and skiers better manage the friction with the slope, for greater or lesser traction, as needed.

The technology essentially takes advantages of the inherent properties of ice. Ice, it turns out, is a semiconductor, meaning that it conducts an electrical charge under certain circumstances. Unlike silicon, which conducts negatively charged electrons, ice conducts protons, the core of hydrogen atoms that are part of the water molecules.

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Video: Ice control technology
Dartmouth professor Victor Petrenko and team have developed new ways to control or alter ice, making it sticky or slippery. Here, a look at the technology.

"(An) ice surface has an enormously high electric charge," Petrenko said.

As a result, ice doesn't simply cake onto surfaces--it bonds to them in three ways: via the hydrogen atoms themselves, via an electrostatic bond caused by the current, and via comparatively weak van der Waals forces.

PETD works by breaking the first two bonds. An electric charge lasting a few milliseconds heats the surface buried in ice just long enough to melt about a micron or two of the surface of the ice. Once the ice is melted, the hydrogen and electrical bonds break. The resulting water then acts as a lubricant, allowing the mass of ice to slide away.

"With short pulses, the heat doesn't have time to diffuse. It is all released on the interface," Petrenko said.

To get ice to stick to a surface, the pulse is shortened--first the ice melts, then refreezes. The resulting bond between the material and the ice is even stronger than before.

Why hasn't anyone already come up with this?

"I don't know," he said. "It is a very common story: People for centuries miss a very simple principle. When it's found, people say, 'How could we miss it?'"

Traditional ice removal methods don't address how to reverse the electrical bonds, which explains why they don't work that well. Ice scrapers essentially tear away ice from the outside. Material to repel ice also fails because ice will invariably bond. Companies have thrown money at trying to develop ice-resistant surfaces, but the results have been mediocre.

Petrenko himself worked on a project funded by a generous federal grant. "We concluded that it is against the laws of nature to have an ice-phobic material," he said. "Ice is very strong glue. It is a universal adhesive."

The difficulty with PETD lies in power delivery. The surface only has to be heated to about 1 to 2 degrees Celsius, but a broad surface has to be heated simultaneously.

Still, an ordinary car, while running, could provide enough energy to remove the ice. It also takes less energy than heating the windshield.

The intellectual property at Ice Engineering mostly concerns developing power distribution systems and thin films, which coat the surface and conduct heat to the ice material interface. The composition of the films varies. In the case of windshields, Ice Engineering employs a layer of clear indium oxide. "It is the same thing on laptop displays," Petrenko said.

Ice machines and refrigerators, meanwhile, can rely on titanium or carbon fiber composites, which are more durable, because transparency isn't an issue.

The research, so far, has yielded 14 U.S. patents, and several more are pending. Dartmouth owns the patents but markets them through Ice Engineering.

Petrenko came to studying ice by accident. For years, he worked as a semiconductor researcher at Moscow's Institute of Physics and Technology. While on an exchange at Britain's University of Birmingham, he happened upon that school's ice research department. His life changed after that.

"We built a solar cell made of ice," he recalled. "While it is not as efficient as a silicon solar cell, it costs a penny a square mile."

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13 comments

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Acceleration of global warming...
This type of technology should be outlawed by the Kyoto protocol...

Using electricity to melt ice is just going to make global warming pick up speed.

Its dangerous and immoral technology.
Posted by gerhard_schroeder (311 comments )
Reply Link Flag
Global Warming Junk Science
Perhaps this post was meant in jest, as it's posted by Germany's last Chancellor....

Did you not read the article? The resulting enegry use reduction in devices that ARE causing damage to the environment (or at least using up natural resources) greatly offsets the miniscule amount of energy (often cleaner energy, by the way...) used to melt the ice off.

Why is it that "Environment Enthusiasts" don't stop for half a second to think about what they're saying. Luddites... I think that's what the problem is. They're afraid good science is going to result in things that make for a better, healthier planet; they think that the best solution is to just let things go to pot.

On second thought, maybe that's the problem... too much pot.
Posted by ThatScienceGuy (132 comments )
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bad for the globe?
are you nuts? How come people don't stop to think just a second, or ACTALLY READ THE ARTICLE!!!!!

Think about all the chemicals and what not that are in use today to defrost planes, windshields, and remove ice in general. think about all the engery that is used to perform those tasks....

NOW think about what the article says, that it takes a small amount of electricity to power this material.

Wouldn't even a tree hugging, save the world, save the whales, save the rain-forest, blahdy blah blah, person like yourself feel that even GREATLY REDUCING the harmful stuff that is in place to remove ice would be a huge benifit?

Exibar
Posted by exibar (1 comment )
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Not a bad thing...
As it reads in the artical the technology can be used either way, to remove ice or to strengthen the bonds. But even when the ice is removed I don't think it's actually 'melted' by the ice, I think it's just where the ice comes in contact with the film.
Posted by Jack445 (2 comments )
Link Flag
Not a bad thing...
As it reads in the artical the technology can be used either way, to remove ice or to strengthen the bonds. But even when the ice is removed I don't think it's actually 'melted' by the ice, I think it's just where the ice comes in contact with the film.
Posted by Jack445 (2 comments )
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This would SAVE ENERGY where I live.
Up here in Canada, when you are faced with an ice coated car you generally have to let the car warmup by idling it for 10 or 15 minutes before you can physically scrap it off. This invention looks like it would break the bond between the ice and window without having to wait for the whole car to warm up. That would mean a lot less car iding and should reduce CO2 emissions.
Posted by MoSW (5 comments )
Link Flag
This would SAVE ENERGY where I live.
Up here in Canada, when you are faced with an ice coated car you generally have to let the car warmup by idling it for 10 or 15 minutes before you can physically scrap it off. This invention looks like it would break the bond between the ice and window without having to wait for the whole car to warm up. That would mean a lot less car idling and should reduce CO2 emissions.
Posted by MoSW (5 comments )
Link Flag
What a stupid comment!
I haven't seen a comment as stupid as this one on the Internet for a long time!
Posted by hackingbear (79 comments )
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Global warming...
I guess you must me ROFLing with what looks like a troll - or you are plain stupid
Posted by Noreast (12 comments )
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You Go, Gerhard
What an excellent, insightful, and provocative point of view, Gerhard. You're a brilliant man and I, for one, hope you won't bow to the naysayers and hecklers.
I stand right beside you against this, and so many other immoral technologies that can only accelerate the onslaught of global warming.
Posted by foo10019 (1 comment )
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I agree, Electricity is not a "Green" solution because we use fossil fuels to produce it.

And direct means of producing Electricity like Solar and Wind will never work because people like this are too Stupid to adopt it.
Posted by globalleader (1 comment )
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Are you kidding me? Acceleration of global warming by removal of ice by electronic means? Are you aware of the chemical, mechanical, and themal de ice systems currently used? This technology would decrease energy input for deicing on a grand scale, that means we burn less gasoline, jet fuel, and coal to deice everything. It is theorized that the burning of these fossil fuels is what is causing global warming. By the way, there is not solid research stating weather or not global warming is caused by man or not. There is equal good and bad research on both sides of the global warming issue. By all means conserve energy whenever possible.........therefore use new technology to deice things which in turn uses less everything. How is saving energy on something we already do going to "accelerate the onslaught of global warming"? Science and research are the keys to our future and sustainability. This technology is great if it works!
Posted by aerozuk (1 comment )
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