Science in Mind

MIT researchers collaborate with BMW to build a rapidly de-icing windshield

A frozen windshield during a 2005 blizzard
A frozen windshield during a 2005 blizzardCredit: 2005 File photo/Justine Hunt

In energy research, certain ideas seem to ebb and flow over and over again. Research and investment spikes when scientists, policy makers or venture capitalists declare that the time is finally ripe for a new method of energy generation, then drops off a cliff as it turns out the way we currently fuel our power-hungry lifestyles is cheaper, more convenient, or more reliable than the new thing. Witness the repeated rise and stumble of enthusiasm for solar energy from photovoltaic cells over the last few decades.

What does it take for a new approach to take off? It’s not just a general need, such as the fact people consume lots of energy, but a specific application. The new technology must address a problem that isn’t being done as well, or as cheaply, or as efficiently, today. In a laboratory at the Massachusetts Institute of Technology, a materials science and engineering professor and his team are reviving a technology that last peaked in the 1970s that may finally be ripe for use in the real world, albeit with an unexpected application: de-icing a car windshield.

The engineers in Jeffrey Grossman’s MIT laboratory are working on creating a solar thermal fuel—a fuel triggered by light to store energy, which can then release that energy in the form of heat. Instead of thinking of the solar thermal fuel as a literal fuel, however, MIT has teamed up with German car maker, BMW, to examine the possibility of embedding the fuel in a windshield and using its heat generating capabilities to rapidly and efficiently clear windshields in winter.

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“This forced us to think about this fuel in a way we hadn’t before, as a solid layer between two pieces of glass,” said Grossman, a professor of materials science and engineering whose research was informed by the experience of scraping ice off his own windshield during the brutal cold early this winter.

Jennifer Dungs, who works in research and development at BMW, said that the university and the carmaker formally initiated a partnership based on this particular project in April. Dungs said she speaks to Grossman frequently, and there will be close contact going forward between the company and the MIT researchers as they work toward the goal of developing a functional prototype, including an opportunity for the students in the laboratory to work in Germany over the summer.

A rapidly de-icing windshield could stem some of the annoyance of the minutes people spend chipping away at ice while their heaters run full blast, but it also fills a practical need. Turning on the heater to blow hot air on the windshield greatly decreases the range of an electric car. Triggering a solar-powered fuel to generate heat to melt ice in the winter would offer an elegant and efficient solution.

Plenty of practical questions remain—Grossman notes that one of the first questions that came up was how much water needed to melt before the ice obstructing the view of the windshield began to slip.

“We like to quantify things at MIT,” Grossman said. “What we find is if you go to the high temperatures we have ... it would slip off in four seconds.”

But he acknowledged that involves heating the fuel hotter than might be acceptable in a windshield.

“The next step is to work with a car manufacturer and a realistic—what we could get to within the real glass,” given the many other considerations that govern windshield design, Grossman said.

The idea to use solar thermal fuels in cars emerged from a Sloan School of Management class at MIT, in which students were trying to identify technologies that could be brought to market. Grossman had been more focused on other potential applications for his solar thermal fuel. For example, he hopes to use the fuel to heat stoves or ovens in developing countries, without emitting noxious fumes.

The business school students, however, saw the windshield application as nearer to commercialization. And Grossman pointed out, it’s possible that solving the deicing challenge could have ripple effects, moving the technology to a stage where it may be ready for the stove application—a possibility that reflects the circuitous ways that novel technologies sometimes advance.

“It’s a really cool idea and therefore, of course, not new. The key here is it was heavily researched in the ‘70s,” Grossman said. “I like to call it a blast from the past.”

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