Ice-free windshield

With snow continuing to fall and temperatures often below zero degree Celsius (32 degrees Fahrenheit) in many parts of the continent, many Europeans currently have to get up earlier than usual to scrape off the ice covering the windshields of their cars before they can actually drive off.

That may soon be a thing of the past, according to German researchers.

In recent months, scientists at the Fraunhofer Institute for Surface Technology (IST) in Braunschweig, in north-central Germany, have announced a new car window glass which they claim does not allow an ice layer to form in the first place - even at temperatures as low as minus 18 Celsius.

Last month, Volkswagen joined the project, hoping to turn this research into a feature on its cars.

"[The window] has been well-understood on a laboratory scale, but now needs to be implemented for large-scale operation," said Harthmuth Hoffmann, a Volkswagen spokesperson, in an e-mail sent to Deutsche Welle.

The problem is that this coating can interfere with radio and mobile phone reception.

Heat can't radiate skyward

The new glass works differently from a heated window - it is based on a physical principle: a wafer-thin transparent coating of indium tin oxide is applied to the window.

"We call this a 'Low-E' (low thermal emissivity) coating," said Thomas Drescher of Volkswagen Development, in an interview with the DPA news service. "Applied to the outer glazing, it prevents heat from radiating skyward."

The conductive "Low-E coating" protects the glass from cooling. That way, water on the outer surface does not condense or freeze and there is no ice film in the first place because radiative heat loss to the cold sky is minimised and this prevents or delays cooling of the glass surface to below the dew point.

Scientists have worked on similar projects for some 50 years, Andreas Klein from Technical University of Darmstadt told Deutsche Welle. "The challenge here is that they're creating a coating which is applied externally rather than inside. So the mechanism will have to be able to withstand adverse weather conditions."

Older systems work with layers made from tin oxide. But these are far from perfect - both from a practical and an esthetical point of view, the researchers found. When glass is bent, for instance, the old layers will break because the temperatures get too high.

"Our new layer is extremely stable," said Bernd Szyszka, an IST researcher, in a statement published on the Fraunhofer Institute's website. "Temperatures of up to 900 degrees Celsius are no problem. Even if you bend the layer extensively it stays the way it is."

When the layer is used in windshields, of course, weather conditions such as cloudiness, relative humidity and wind can affect the windows' condensation behaviour.

"The 'Low-E coating' cannot prevent ice formation or condensation entirely, but it can significantly reduce the likelihood of it happening," Drescher added.

Ice-free windshield still not ready for the mass market

For now, one drawback with the system as it is is that the new coating limits radio traffic in the car, which can impair radio and mobile phone reception, added Harthmuth Hoffmann, the Volkswagen spokesperson.

As such, it remains unclear as to when the first cars equipped with the new wind screen can roll out from Volkswagen's assembly lines.

"It will take some time before the ice-free car windscreen is market-ready," Drescher noted, "but we are working intensively toward this goal."

Author: Nina Haase
Editor: Cyrus Farivar