Ice may be great if you’re a curler or a skater, or if you like a couple of “rocks” in your scotch.
But it’s a pest when it forms on solar panels, impairing their ability to generate electricity.
Thin layers of ice on the blades of wind turbines have the same effect. It makes the turbines less efficient.
A thin layer on an electrical transmission line can be the first step in a dangerous buildup of ice. That’s what happened during a ferocious ice storm that hit Ontario and Quebec in 1998.
That storm wasn’t just a few hours of freezing rain; it went on for several days. The sheer weight of the ice snapped powerlines and literally crushed more than 150 transmission towers, leaving a million people without power and causing about $5 billion in damage. And that didn’t include damage to thousands of trees that had limbs torn off by the weight of the ice.
So it’s not surprising that research teams located in northern climates have been waging war against the buildup of ice on infrastructure.
Now there is news that a team at the Norwegian University of Science and Technology has devised a way to prevent ice buildup that takes a novel approach to the problem.
If you have ever taken a wintertime flight, you have probably seen planes being sprayed with de-icing fluid before takeoff. That spray removes any accumulated snow or ice and also makes the surface of the plane’s wings less likely to accumulate more snow or ice — but only for a short time.
That has led scientists to create substances that are called superhydrophobic. That means they’re extremely good at repelling water. These substances can be applied to surfaces by spraying or dipping.
They are often made with fluorinated chemicals that are not especially friendly to the environment and scientists are not completely sure how long a superhydrophobic surface can remain free of ice.
All that motivated Zhiliang Zhang and his team to look for a better way.
"Our strategy is to live with ice," Zhang says.
So they let the ice form but have taken steps to ensure that the layers of ice crack away from the surface and fall off.
They found their answer as they were testing a number of commercial and homemade coatings that rely on surface chemistry to cause cracks by weakening the atomic bonds between the ice and the surface it covers.
As they were working, they came to the realization that if they added another structure below the surface, they could form large macro-cracks at the interface between the surface and the ice. They called the mechanism MACI or macro-crack initiator.
They found that as the cracks get larger, the ice is less likely to stay on the surface. To test their idea, Zhang and his team created subsurface layers that contained microscopically small holes or pillars.
Then they made a thin film of a substance called polydimethylsiloxane, or PDMS, which covered the bumpy substructure layers.
The team tested multiple designs of their MACI structures before they achieved the results they were hoping for.
Finally they ended up with a surface with some of the lowest values for ice adhesion ever measured.
"The ice adhesion strength for common outdoor steel or aluminum surfaces is around 600-1,000 kilopascals," Zhang says, adding that "we reached the super-low ice adhesion value of 5.7 kilopascals."
The team still has work to do before they have a commercially viable product. But Zhang says they are excited that they may have "cracked the code" for preventing dangerous ice buildup while limiting unwanted environmental effects.
This is all interesting for cold-weather applications, for solar panels, wind turbine blades and transmission lines.
There are, says Zhang, "a lot of applications related to every-day life."
Korky Koroluk is an Ottawa-based freelance writer. Send comments to email@example.com.