Engineers Getting a Grip on Ice & Snow
Innovation brings new methods of ice friction and adhesion CONTROL.
February 2008
Contact: Catharine Lamm
603.646.3943
Electronic friction control for winter sports equipment—serving as electronic brakes or "electric wax"—is only one application of the ice-control technology invented by Dartmouth Engineering Professor Victor Petrenko and his research team.
Engineering Professor Victor Petrenko
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Professor Petrenko has discovered that short pulses of electricity applied directly to an ice-material interface can produce some novel and desirable effects—namely the ability to control whether ice is sticky or slippery.
For skis equipped with a thin, electrically-conductive layer along the base, one pulse of electricity causes just a few microns of interfacial ice or snow to instantly melt and refreeze to the ski base—all within approximately 3 milliseconds (3/1000 of a second). This melting and refreezing forms a strong bond between ski and snow, increasing friction either to provide grip for kicking forward on Nordic skis, or to limit one's speed when going downhill.
With this technology, novice skiers (and snowboarders) can set a slow speed for learning, parents can have cruise-control for their kids, and cross-country and telemark skiers can finally be free from the unreliable performance of wax, "fish-scales," and climbing skins.
"Our system provides a skier with enormous gain in performance and convenience," says Petrenko. "With our electronics, a skier can get from three to four times stronger traction timed precisely with a kick-and-glide motion. He or she can forget about difficult and lengthy waxing procedures and not worry about choosing the right wax for a particular temperature or snow condition. Our system works well on any snow at any temperature below freezing."
The sticking effect is similar to what happens when a wet, warm tongue freezes and sticks instantly to a metal flagpole. The metal flagpole conducts heat away so quickly that the tongue freezes to it, even though it was warm an instant ago.
Since only one side of the interface needs high thermal conductivity, this system can also be adapted to car tires and shoe soles using electrically-conductive rubber which is already commercially available. Petrenko's team currently has a functioning shoe prototype that offers 40 times more traction on ice than a conventional lug sole. A tire-traction system that could eventually make snow tires obsolete is also in development.
"There's nothing like a 60-ton tank slithering around on the ice to make you think Professor Petrenko's technology is a good idea,"
—Herbert H. Dobbs, chairman of Torvec, Inc.
Winter Sports Competitive Advantage
- Nordic
- Up to four times increase in kick force
- No need for wax
- Reduces ski size requirement up to 50% for manufacturer
- Production cost savings through design flexibility
- Snowshoe
- Up to 40X better traction
- Production cost savings through design flexibility
- Alpine and Snowboard
- Speed control through technology
- Braking system for snowboards
- Increased traction performance in varied conditions
- Reduces ski size requirement for manufacturer
De-Icing The World
This same concept of applying short pulses of electricity directly to an ice-material interface can also be used for ice removal and prevention. But here, the heating pulse creates a melt-water layer without the refreezing/sticking effect of the ice-traction system. In fact, Petrenko's thin-film, pulse electro-thermal de-icing (PETD) technology melts snow and ice with nearly perfect efficiency and, in the future, will be used to de-ice windshields, power lines, roofs, roads, walkways, runways, refrigerators, airplane wings, helicopter blades, and windmills, just to name a few.
So far, Dartmouth has granted 7 licenses covering specific applications of PETD. The Goodrich Corporation holds three of those covering:
- aerospace
- marine applications
- windmill turbines
The other four are held by Ice Engineering LLC, a new company founded by Petrenko to handle the growing number of projects and applications extending from his ice physics research. These licenses cover de-icing of:
- power transmission lines
- refrigeration systems
- engineering structures such as buildings and bridges
- land-based vehicles
The benefits of PETD for refrigeration systems are especially clear with commercial ice makers. These energy hogs sitting in hotel hallways, in large restaurants and bars, and in hospitals and military bases, consume enormous amounts of power as they cycle through a process of cooling to make the ice, and heating to release the ice as many as 100 times per day. PETD eliminates the need for the heating and re-cooling portion of the cycle, thus cutting energy consumption in half.
"The cost of electricity used in commercial icemaking is approximately $10 billion per year," says Petrenko. "Our technology can cut that number in half, by $5 billion, or approximately the entire annual budget of the National Science Foundation." Ice Engineering has signed Simply Ice (SI) as the exclusive manufacturer and distributor for a new line of commercial icemakers equipped with PETD.
Ice Engineering has also completed development of a residential icemaker that uses PETD. The product was licensed to one of the largest manufacturers of electronics and utilities, and will soon be mass-manufactured.
Ice Engineering is also currently helping several US and foreign companies to develop a "rapid evaporator defroster," which would significantly improve the overall efficiency of refrigerators.
Petrenko's PETD uses a thin, electrically-conductive film applied to the surface of, for example, an airplane or a windshield or almost any other object in need of ice protection. The film is then heated with a milliseconds-long pulse of electricity. The beauty of this method is that only a micrometer-thin layer of ice directly at the ice-material interface is heated without having to heat the bulk of the object to which the ice is stuck. Even in extreme cold, PETD achieves nearly perfect efficiency because neither the object nor the air is heated—the heat simply does not have time to propagate into the environment. Just one single pulse of electricity melts the interfacial ice and instantly releases any additional build-up, which then easily slides off. Regular electric pulsing can keep surfaces consistently ice-free while maintaining low overall power consumption.
The de-icing film can consist of either a transparent conductor (such as indium tin oxide) for window or lens applications, or of a more durable coating (such as titanium) when extra wear-resistance is needed. For protection of large surfaces, thin metal foil or carbon-fiber composites are most effective. A Dartmouth-Ice Engineering team is currently working on a prototype of rapid windshield defroster.
Almost no heat energy is lost or wasted in this process and this optimal energy-efficiency in melting ice from surfaces is what makes PETD energetically feasible for aerospace applications and automobile windshields. Resistive heaters, such as the heated wires on rear windows of cars, cannot melt ice from windshields or wings because strong convective heat loss prevents the wires from reaching ice-melting temperatures without unrealistically high power usage. Heat loss to the earth and air is the reason traditional heaters are impractical for de-icing roads, bridges, walkways, and roofs. But Petrenko's super-efficient PETD has demonstrated immediate effectiveness and saves up to 99% of electric energy compared to conventional heaters. Goodrich Aerospace has completed the first in-flight testing of PETD on a small prop-plane. The results were "outstanding," and Goodrich is now developing a PETD system for large passenger airplanes.
The incredible range of applications for PETD is partly due to wide flexibility for electrode materials and configurations. For aerospace PETD, Dr. Lev Deresh, an electrochemist on Petrenko's team, has co-developed a practical process for manufacturing light yet durable electrically-conductive coatings. And, with the support of Torvec, another team member, Mikhail Starostin, Ph.D., has made working prototypes for a windshield PETD using transparent electrodes.
De-icing of high-voltage power lines again demonstrates versatile electrode configurations. The multiple transmission wires suspended from each tower can be used to create high-frequency electric fields between parallel wires, heating any ice on the wires. A method which automatically switches the heating effect "on" and "off"—thus saving power during non-icing conditions—is also in development.
January 1998, one storm, $5 billion in damages. Of all power outages, approximately 25% are due to ice/snow.
Co-invented by Dartmouth Engineering Professor Charles Sullivan, the power line de-icing application is being developed by Ice Engineering LLC along with Goodrich Aerospace and the New York Power Authority, will soon begin full-scale development of power line de-icers, including a special plastic coating that heats automatically whenever ice forms on the coating's surface.
Sweden's Uddevalla Bridge
Petrenko's PETD method was put to the test in Sweden where a brand-new 1712-meter-long "cable stayed" bridge (construction completed in 2000) is experiencing major problems with icing. The $250 million publicly-funded bridge currently must be closed down for significant periods of time during the winter months due to dangerous chunks of ice falling at random off the towers and cables from heights of up to 140 meters. The first tests of PETD on a few cables and one pylon demonstrated instant de-icing action at very low energy consumption as compared with conventional de-icers. (See video clip.)
Overall, ice constitutes a major toll on society—airplanes downed, grounded, or rerouted, car accidents on icy bridges, power outages, ships capsized—so much so that it's difficult to quantify. "It's all very exciting and is keeping me very busy!" says Petrenko, "The Army Research Office (ARO) was the first to recognize that an investment in basic research was the place to start to solve this problem. Soon after, the National Science Foundation added its support, and that approach has worked very well!"
QuickTime PETD Videos
- Aerofoil de-icing (1.5MB)
- Panel de-icing (1.5MB)
- Power line de-icing (1.3MB)
- Windshield de-icing (1.1MB)