Electric Cars’ Killer App: Carbon Fiber?

Editor’s Note: EarthTechling is proud to repost this article courtesy of Txchnologist. Author credit goes to Jim Motavalli.

The SRT Viper, introduced with great fanfare at the New York International Auto Show this month, breathes fire with a 640-horsepower V-10 engine—it’s not exactly green. But Chrysler’s 2013 Viper manages the neat hat trick of adding horsepower while improving fuel economy, in part because its hood, roof, trunk and seats are all made of carbon fiber, an ultra-light composite that is nonetheless much stronger than steel.

Carbon fiber, 50 percent lighter than steel and 30 percent lighter than aluminum, is popping up all over, used both in making auto body panels and chassis. BMW is making extensive use of the material in its forthcoming i3 electric “Megacity” car, and its high-performance i8 plug-in hybrid. The carmaker has gone as far as to form a joint venture with German carbon fiber company SGL, and is making fibers in Moses Lake, Washington, with a supply chain that extends from Japan to Germany.

BMW, BMW i3, BMW i8, Electric Cars, Electric Vehicles, Plug-In Hybrids, Hybrids

image via BMW

Andreas Wuellner, managing director of automotive carbon fibers at SGL, told me that carbon fiber “will be a very important lightweight material for automobiles, used extensively alongside steel and aluminum and in combination with them.” Carbon fiber is getting a workout in high-end supercars like the Lamborghini Sesto Elemento and the McLaren MP4-12C, and in the roof, hood and even floors of some Corvette models, according to spokesman, Monte Doran.

This move toward carbon fiber mirrors similar trends in aerospace, but in cars, it’s currently confined to the high-end of the market for one simple reason: It’s very expensive.

Of course, it’s getting cheaper rapidly. A decade ago the material was $150 a pound; now it’s about $10, says supplier Zoltek, but steel is less than $1 a pound. The raw material for carbon fiber (called “precursor”) is expensive, and so is the production process, which involves knitting together ultra-thin (10 make a human hair) carbon filaments into a textile, building it up in several layers, then injecting it with resin so it can be formed in a mold. The price is coming down dramatically, but not fast enough yet for widespread use in entry-level cars.

Killer app

For EVs, however, carbon fiber is a killer app.

The Rocky Mountain Institute, a Colorado-based energy-efficiency think tank, has long championed the use of composites like carbon fiber to create super-green “hypercars.” According to the group, “With drastically lighter platforms, propulsion systems can be smaller, lighter, cheaper, more efficient and, ultimately, more cost-effectively electrified.”

The latter point is critical, because batteries are very expensive, too. Dave Buchko, a BMW spokesman, says that the company chose to make its i3 body shell out of carbon fiber because “we won’t need as many battery cells to reach our target 100-mile range. Our solution balances the right weight with battery capacity.”

Greg Rucks, a Rocky Mountain Institute consultant, says that carbon fiber has some built-in cost savings, because there are fewer assembly steps (and fewer rivets) with the material, and the lighter weight means that suspension, brakes and other components can be downsized.

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