Researchers develop new way to remove ice buildup without chemicals

MIT researchers, including those of Indian origin, have developed a completely passive, solar-powered way of combating ice buildup, without using heating systems or chemical sprays. 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. 

However, preventing that buildup usually requires energy-intensive heating systems or chemical sprays that are environmentally harmful, according to the research published in the journal Science Advances. The new system developed by Kripa Varanasi, Susmita Dash and colleagues from the Massachusetts Institute of Technology (MIT) in the US is remarkably simple. It is 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. Once applied, it requires no further action or power source. It can even do its de-icing work at night, using artificial lighting. "Icing is a major problem for aircraft, for wind turbines, powerlines, offshore oil platforms, and many other places," Varanasi said.

"The conventional ways of getting around it are de-icing sprays or by heating, but those have issues," she said. Varanasi and his team considered the energy given off by the Sun. They wanted to see whether "there is a way to capture that heat and use it in a passive approach." It is not necessary to produce enough heat to melt the bulk of the ice that forms, the researchers said.

All that is 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 have developed. 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 per cent of the incident sunlight, and losing only three per cent to re-radiation, Varanasi said. 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.
To compensate for the localisation, 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 said. 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.