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BMW i3 Shifts EV Market With Composites

Originally published on RMI Outlet.
by Greg Rucks

blog_2013_08_29-1Fuel economy is greatly affected by an automobile’s weight. Nevertheless, for years our automobiles got heavier. In the U.S. the average curb weight of a passenger vehicle climbed 26 percent from 1980 to 2006. Advances in powertrain technology have not lead to drastically higher mile per gallon ratings because of this increased weight, among other factors. However, the recent release of the BMW i3 signals the beginning of a shift toward lightweighting that will help to drive the efficiency and competitiveness of electric vehicles. BMW is using carbon-fiber-reinforced plastic on its new electric i3 to shave off up to 770 pounds from the autobody compared to using traditional materials, without significant price increase. The result is a four-passenger car that can go 100 miles on a charge with a sticker price of just over $40,000.

It’s no coincidence that BMW’s development of its first production electric vehicle coincided with a dramatic investment in a new design paradigm based on carbon fiber composites.


BMW knew it couldn’t just slap batteries and motors into one of its existing models. The i3’s battery pack weighs in at over 1000 pounds, so body weight reduction was critical to offsetting the batteries’ weight. To achieve a range approaching 100 miles (an influential number generally viewed as the acceptable minimum for electric vehicles) on one of its existing vehicles, it would have needed a very large battery pack to move around that heavy steel. This would have further increased mass, in turn requiring more heavy batteries, and so on, a vicious (and expensive) cycle given that just a 10 percent increase in battery capacity (the equivalent of increasing the i3’s range by about 10 miles) would add about 100 pounds of mass and $1200 of cost to the vehicle. Plus, every mile driven in a more massive electric vehicle requires more energy, making its equivalent mile-per-gallon rating worse and its operating cost higher.

To achieve a level of weight reduction that could begin to effectively offset all that electric powertrain mass, BMW designers knew they would need to rethink the vehicle’s design from the ground up. They would need to change the body’s shape to better integrate the new electric drivetrain and motors, and they would need materials that could offer the same structural integrity with less weight. Despite carbon fiber composites’ higher cost per pound as compared to steel, every pound saved by virtue of the new materials’ structural advantage was a pound the battery pack would not have to move around. The business case for making a dramatic investment in an all-new material, with its own unique structural characteristics, manufacturing processes, production facilities, and supply chain suddenly made sense.

BMW spent about ten years doing exactly that, forging partnerships with new industries, vertically integrating a global supply chain, building new manufacturing facilities, and incorporating carbon fiber composite parts on its existing vehicles to get its feet wet. Currently BMW is able to produce an i3 body about every 20 hours, allowing it to kick out a shade over 400 vehicles per year, not many by auto industry standards, though an important start. And at a selling price in the low $40,000s, the i3 will be out of reach for mainstream consumers, who have a price break point of $30,000 (though federal and state incentives may help to knock the i3 sticker price down closer to an acceptable number for some consumers in the right markets).


Like BMW, Rocky Mountain Institute recognizes the transformative potential of carbon fiber composite. If adopted by the automotive industry at scale, total global demand for carbon fiber would very quickly skyrocket, and needed investments in disruptive technology to make the material cheaper would come pouring in from material companies eager to gain a foothold in their largest potential growth market.

Whole vehicles like the i3 would then become much more cost effective and the way would be paved for a world filled with affordable, carbon fiber intensive vehicles 50 percent lighter than today’s vehicles, powered by electrified powertrains, needing no oil and emitting no greenhouse gases. The faster we can scale this new material industry, the faster that vision will become reality.

That’s why RMI launched its Autocomposites project in a workshop last November. The workshop hosted 45 key decision makers from across the automotive and carbon fiber composite industries, all trained on the goal of identifying the most promising near-term applications for carbon fiber composite in existing vehicles. One carbon fiber composite part incorporated on just one vehicle would double automotive demand, very quickly creating the scale and growth needed to kickstart investment, reduce cost, spur competition, and seed innovation.

While many parts offered significant user value that could offset the higher material cost, among the most promising applications identified by workshop participants was the door inner, the internal structure and framing of the door that absorbs impact energy in the event of a crash. It was largely due to this safety component that the door inner rose to the top of the crop in terms of potential value, because carbon fiber composite absorbs up to six times more crash energy per pound than steel, and customers are willing to pay a premium for safety. Because carbon fiber is stiffer than steel, structural members can be made narrower while providing the same structural integrity. The window frame could thus become thinner, providing more visibility and further enhancing a carbon fiber composite door inner’s value proposition. In the end, the large material cost premium associated with introducing carbon fiber on the door inner was estimated to be more than offset by user value according to initial cost modeling and value quantification performed at the workshop.

Since the November 2012 workshop, RMI and its automotive industry counterpart, Munro & Associates, have launched the Autocomposites Commercialization Launchpad (ACL), a league of the most capable carbon fiber composite and automotive manufacturers in the industry. The door inner is the ACL’s first commercialization project, and eight major companies have now signed on to move forward with design, production, and testing. The ACL is aiming to produce 50,000 units per year or greater—a production volume never before achieved with carbon fiber composite in any industry—for a mainstream vehicle by 2018. The ACL will be capable of launching parallel commercialization projects to further accelerate learning and scale this new industry.

Whether starting with whole carbon fiber composite vehicles at low volume or individual parts at high volume, the goal is the same: very quickly scaling a new material industry to pave the way to a transformed transportation system built on the unparalleled lightweighting potential of widely-adopted carbon fiber composite.

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Since 1982, RMI (previously Rocky Mountain Institute) has advanced market-based solutions that transform global energy use to create a clean, prosperous and secure future. An independent, nonprofit think-and-do tank, RMI engages with businesses, communities and institutions to accelerate and scale replicable solutions that drive the cost-effective shift from fossil fuels to efficiency and renewables. Please visit for more information.


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