From airplane wings to overhead powerlines to the giant blades of wind turbines, a buildup of ice can cause problems ranging from impaired performance all the way to catastrophic failure. But preventing that buildup usually requires energy-intensive heating systems or chemical sprays that are environmentally harmful. Now, MIT researchers have developed a completely passive, solar-powered way of combating ice buildup.
The system is remarkably simple, based on a three-layered material that can be applied or even sprayed onto the surfaces to be treated. It collects solar radiation, converts it to heat, and spreads that heat around so that the melting is not just confined to the areas exposed directly to the sunlight. And, once applied, it requires no further action or power source. It can even do its de-icing work at night, using artificial lighting.
The new system is described today in the journal Science Advances, in a paper by MIT associate professor of mechanical engineering Kripa Varanasi and postdocs Susmita Dash and Jolet de Ruiter.
“Icing is a major problem for aircraft, for wind turbines, power lines, offshore oil platforms, and many other places,” Varanasi says. “The conventional ways of getting around it are de-icing sprays or by heating, but those have issues.”
Inspired by the sun
The usual de-icing sprays for aircraft and other applications use ethylene glycol, a chemical that is environmentally unfriendly. Airlines don’t like to use active heating, both for cost and safety reasons. Varanasi and other researchers have investigated the use of superhydrophobic surfaces to prevent icing passively, but those coatings can be impaired by frost formation, which tends to fill the microscopic textures that give the surface its ice-shedding properties.
As an alternate line of inquiry, Varanasi and his team considered the energy given off by the sun. They wanted to see, he says, whether “there is a way to capture that heat and use it in a passive approach.” They found that there was.
It’s not necessary to produce enough heat to melt the bulk of the ice that forms, the team found. All that’s needed is for the boundary layer, right where the ice meets the surface, to melt enough to create a thin layer of water, which will make the surface slippery enough so any ice will just slide right off. This is what the team has achieved with the three-layered material they’ve developed.
Layer by layer
The top layer is an absorber, which traps incoming sunlight and converts it to heat. The material the team used is highly efficient, absorbing 95 percent of the incident sunlight, and losing only 3 percent to re-radiation, Varanasi says.
In principle, that layer could in itself help to prevent frost formation, but with two limitations: It would only work in the areas directly in sunlight, and much of the heat would be lost back into the substrate material — the airplane wing or powerline, for example — and would not help with the de-icing.
So, to compensate for the localization, the team added a spreader layer — a very thin layer of aluminum, just 400 micrometers thick, which is heated by the absorber layer above it and very efficiently spreads that heat out laterally to cover the entire surface. The material was selected to have “thermal response that is fast enough so that the heating takes place faster than the freezing,” Varanasi says.
Finally, the bottom layer is simply foam insulation, to keep any of that heat from being wasted downward and keep it where it’s needed, at the surface.
“In addition to passive de-icing, the photothermal trap stays at an elevated temperature, thus preventing ice build-up altogether,” Dash says.
The three layers, all made of inexpensive commercially available material, are then bonded together, and can be bonded to the surface that needs to be protected. For some applications, the materials could instead be sprayed onto a surface, one layer at a time, the researchers say.
The team carried out extensive tests, including real-world outdoor testing of the materials and detailed laboratory measurements, to prove the effectiveness of the system.
“The use of photothermal absorbers is a smart idea and straightforward to implement,” says Manish Tiwari, a professor of nanoengineering at University College London, who was not associated with this research. “Scalability of these approaches and thinking about appropriate packaging, specific weight, etc., of the de-icing layer are important practical challenges going ahead, especially when it comes to the aerospace application. The paper also opens up intriguing possibilities around smart and flexible thermal packaging, and thermal metamaterials research to realize its full potential. Overall, an excellent step forward,” he says.
The system could find even wider commercial uses, such as panels to prevent icing on roofs of homes, schools, and other buildings, Varanasi adds. The team is planning to continue work on the system, testing it for longevity and for optimal methods of application. But the basic system could essentially be applied almost immediately for some uses, especially stationary applications, he says.
The Latest on: De-icing
via Google News
The Latest on: De-icing
- Dos and don’ts when warming up your car, de-icing your windshield this winteron January 19, 2021 at 3:01 am
Dealing with an icy windshield and a freezing cold car can be such a pain, especially when you’re rushing out the door for your morning commute.
- Ariel Whitely-Noll: Chloride-based de-icer can harm plants, animalson January 15, 2021 at 11:51 am
The most common types of de-icing products are chloride based. The efficacy of chloride-based products depend on temperature. Although the chloride makes these the most effective at melting ice ...
- my wife and myself want to know when we'll get our virus...on January 14, 2021 at 8:37 pm
We all are familiar with that one neighbor whose driveway and sidewalks are perfectly cleared and dry after a snowstorm. They’re usually the ones who also take it upon themselves to help the elderly ...
- Pat Shingleton: "De-Icing and the Chinook..."on January 12, 2021 at 3:25 pm
Years ago, plane de-icing was randomly performed and is now a regimented, regulated procedure. On this date in 1982, Air Florida Flight 90 crashed into the icy Potomac River, thirty seconds after ...
- INCIDENT Shandong Airlines Boeing 737 collided with a de-icing vehicle at Yantai Airporton January 10, 2021 at 3:32 am
Shandong Airlines Boeing 737-800 collided with a deicing truck at Yantai Airport on Friday, January 8. The aircraft sustained damage in its left wing. The incident took place after the aircraft landed ...
- In the Garden | Salt is the woundon January 9, 2021 at 8:29 am
Occasional snow showers. Temps nearly steady around 30. Winds W at 10 to 15 mph. Chance of snow 50%. Snow accumulations less than one inch.. Cloudy. A few flurries or snow showers possible.
- City of Superior, UWS officials turn to smart salting practiceson January 8, 2021 at 3:33 pm
One 12 oz. coffee cup full of salt is sufficient to de-ice a 70-foot sidewalk, two parking stalls or 320 square feet.
- China Focus: China deploys large UAV for ecological protectionon January 6, 2021 at 2:16 pm
During its maiden voyage, which lasted around 40 minutes, Ganlin-1 maintained stable flight and successfully conducted weather-modification operations, such as atmospheric detection and catalyst ...
- Twin Falls additional precautions to keep streets clean from snowon January 5, 2021 at 11:18 pm
Perhaps the most outstanding precaution now would be how the city has expanded its coverage and usage of snowplows to keep the streets clean sand, de-icing agent, and salt brine.
- Woman’s ‘next level’ tip for de-icing her car windscreen in seconds sparks controversy as some say it’s dangerouson January 2, 2021 at 2:28 am
A WOMAN has shown off her tip for de-icing a car in seconds, but it's sparked a fierce debate. The "next level" hack allows drivers to get their frosty cars started without having to scrape the ...
via Bing News