BMW´S ELECTRIC AUTOMOBILE REVOLUTION / DER SPIEGEL ( RECOMMENDED READING )

12/24/2010 11:31 AM

Carbon Fiber Cars

BMW's Electric Automobile Revolution

By Christian Wüst

BMW is hoping to revolutionize the electric car industry. Whereas most manufacturers rely on traditional -- and heavy-- steel car bodies, the German company hopes that carbon fiber components could lead electric cars into the future.

Cars may have conquered the world, but they didn't do it overnight. Decades after its invention in 1886, the passenger car was still too expensive and too impractical to be anything more than a rare sight on the streets. Gas stations didn't even exist in those days.


The spread of electric cars in the 21st century seems to be proceeding at a similar slow pace. The first models from major manufacturers are now hitting the market, but as a form of transportation, these vehicles face much the same acceptance problem as Gottlieb Daimler's horseless carriage did. These cars have a high price tag but offer low performance.


Mitsubishi has released its first electric car series under the rather uninspiring model designation i-MiEV. It's a simply furnished compact car with an oval body and lithium-ion batteries under the floor panel. With one charge of the battery, the vehicle can travel 100 kilometers (62 miles) in summer or 60 kilometers (37 miles) in winter. It costs €34,390 ($45,240).


Nissan's electric car, the Leaf -- set to hit the German market next year -- faces the same cost-benefit plight. Even so, European automobile journalists saw fit to name the Leaf their "Car of the Year."


It doesn't take extensive market research to see that something doesn't add up here. What customer is willing to pay the price of a luxury sedan for a spartan vehicle whose operating radius barely extends beyond the range of commuter trains?


Too Weak and Too Heavy


All car manufacturers face the same problem -- even the most modern rechargeable batteries are too expensive, too weak and too heavy to power conventional cars, which are already excessively heavy even without the batteries.


"Integrating electric power into existing vehicle concepts is the wrong way, a dead end," declares Rainer Kurek, head of the Munich-based MVI Group, which develops car bodies and other components for the automotive industry. In his recently published book, Kurek urges vehicle manufacturers to take a completely new approach. "The current hype surrounding electric vehicles," the engineer writes, "is obscuring the fact that today's auto bodies have become far too heavy over the course of the last decades."


A first-series Volkswagen Golf from 1974 weighs 750 kilograms (1,653 pounds). A Golf from today's production series weighs around half a ton more. It's also an entire vehicle class larger than its predecessor, contains a standard eight airbags and can drive into a wall at 64 kilometers per hour (40 miles per hour) without its occupants being seriously injured. Such an accident in the original Golf would have meant certain death.


Technological progress has long meant an inevitable increase in weight. The aluminum auto bodies used in Audi's luxury cars, for example, just barely manage to make up for the weight added by the all-wheel drive system that the brand has made its trademark. Hardly a technical revolution.


Now, though, BMW is attempting to break the cycle. Three years from now, the Munich-based company plans to offer an electric vehicle of a completely different construction type. The project, known as Megacity Vehicle (MCV), won't contain steel or aluminum bodywork. Instead, it will have a light alloy frame in the car floor and a body made of carbon fiber-reinforced polymer (CFRP).


An Economic Riddle


CFRP is a dull black material which has a chemical structure similar to that of diamonds. It is sturdier than steel and weighs less than half as much. The MCV body will be 250 to 300 kilograms (550 to 660 pounds) lighter than that of a conventional electric car of the same size, compensating fully for the additional weight of the batteries.

BMW is alone in pursuing the concept -- the boldest idea currently under development in the automobile world, and one which is an economic riddle for the competition. CFRP materials have been available for nearly 50 years and are used in the aviation and aerospace industries, in car racing and, most recently, in rotor blades for wind turbines. Still, the idea of mass-producing cars from the material would appear to make little sense.


CFRP, after all, is 50 times as expensive as steel. A car body component made of steel sheet costs about €4 in its final form; the same part made from CFRP costs at least €200. To achieve the desired lightweight construction, BMW will need to use very large quantities of the material -- 150 to 200 kilograms (330 to 440 pounds) per vehicle.


BMW, of course, has no intention of manufacturing a compact with a body that alone costs €40,000. Company engineers have set a goal of a tenfold reduction in production costs for CFRP. That would spell a true revolution in industrial engineering.

'Megatrend'


BMW's partner in this venture is SGL Carbon. Based in Wiesbaden, SGL was once owned by the Hoechst chemicals company and is currently Europe's sole manufacturer of carbon fiber materials. The company's profits have traditionally come mainly from other carbon products, such as graphite. But the company hopes to be able to transform carbon-fibers from a niche material into a profitable business. CEO Robert Koehler calls it a "megatrend in materials substitution."


The joint venture of SGL and BMW produces these carbon fibers, 10 times thinner than a human hair, in the northwestern United States. The manufacturing process consumes an enormous amount of electricity, but hydroelectric power is cheap in the mountainous state of Washington.


More significant cost reductions are to be achieved once the black mini-threads arrive in an industrial park outside the town of Wackersdorf in Bavaria. Here, on a site once meant for processing spent nuclear fuel rods, an unusual textiles factory is setting up shop to serve the auto body construction industry.


Four knitting machines, each as large as a train car, take up most of a 7,500-square-meter (80,700-square-foot) factory floor. But instead of producing material for T-shirts and jeans, the outsized machines produce carbon fiber fabric, at speeds no other manufacturer has even approached.


Will Technology Be Enough?


The factory's mission is clear. "It's all about getting away from the handicraft approach," says director and industrial engineer Andreas Wüllner. It's his job to accelerate CFRP production from the slow trot of the usual manufacturing process to industrial speed. Time is the key factor in the plan to slash costs.


The carbon fiber textiles leave the factory rolled up like so many enormous carpets, bound for the Bavarian city of Landshut. Here, a BMW factory carries out the final step, transforming the coal-black material into durable, crash-proof auto body components.


Maintaining the pace set by the textile machines in Wackersdorf is the most difficult part of the entire manufacturing process. The carbon matting, drenched in resin, is compressed into a mold to harden it. This step takes place in a closed oven over the course of several hours at temperatures around 500 degrees Celsius (930 degrees Fahrenheit) -- the primary reason for CFRP's exorbitantly high price tag.


BMW, however, is using a compression mold that can harden CFRP components in just 10 minutes at 100 degrees Celsius (212 degrees Fahrenheit). A different chemical mixture of resin and a hardening agent, together with the enormous pressure in the mold, make this process possible.


The mold, located in the town of Landshut north of Munich is currently producing roofs for the M3 sports car, in something of trial run for production of the Megacity Vehicle. Construction is underway in Landshut on the factory for the MCV's carbon fiber components, with €40 million to be pumped into the facility next year.


An Eternity


The initial phase will see three of these molds producing auto bodies for the electric car. Each of the machines is worth several million dollars and stands as tall as a two-story house. These molds will set the pace for the MCV body manufacturing process, explains Andreas Reinhardt, who oversees the production of the CFRP components for the project.


Still, the CFRP production speeds anticipated in Landshut are nowhere near the manufacturing pace found in typical automobile production. Compared to a traditional automobile factory press, 10 minutes is an eternity. Conventional factories can churn out one steel sheet every four seconds, which amounts to 150 of them in 10 minutes.

Outside of BMW, experts doubt mass production of CFRP auto bodies will be affordable any time soon. Kurek, the developer with the MVI Group, prefers to focus on lightweight construction "using conventional, proven materials" and sees plenty of room for advances here. It's possible to reduce about 30 percent of vehicle weight without resorting to expensive carbon fiber materials and without compromising safety, Kurek says. This would "create a basis for future hybrid and electric vehicles," he says.


The most important thing, Kurek adds, is to prevent electric vehicles from becoming expensive luxury items. He believes that the market for electric vehicles is primarily in the lower price segment -- "since such cars satisfy only a very limited desire for mobility and are hardly well-suited to be expensive prestige items."


Feeling the Squeeze


Kurek is speaking a truth both simple and bitter. The German automobile industry relies on its top-end status and on the fascination afforded by sports cars and luxury vehicles. In a prosaic culture of mobility, with cars becoming nothing more than soulless city shuttles, top-end brands such as Audi, BMW and Mercedes are sure to start feeling the squeeze.


BMW, with its carbon fiber constructions, is taking the most original approach to the problem. The company also has plans to expand the MCV into a fancier hybrid sports car. The hybrid would incorporate a low-volume diesel engine to provide propulsion with unlimited range. In combination with an electric motor and lightweight construction, this would allow good road performance with very low consumption.

Other manufacturers' approaches, meanwhile, smack of helplessness. Both Mercedes and Audi are working on extreme sports cars powered purely by electricity, but the vehicles' crude design parameters give them away as sham constructions.


Audi is angling for a spot in the "top league of electric sports cars" with its battery-powered R8 e-tron racecar, while Mercedes does the same with its battery-heavy, gull-winged SLS. With peak performance at 230 kilowatts (313 horsepower), the Audi model promises to be a highly dynamic vehicle. The car "catapults from zero to 100 kph (zero to 60 mph) in 4.8 seconds," according to company literature.


Strict Orders


The power for these bursts of speed comes from a battery packet with a storage capacity of 42 kilowatt hours. At the current state of lithium battery technology, just the vehicle's battery set-up would cost €40,000 and weigh more than half a ton.


The car's potential range is also easy to deduct. With the engine performing at full capacity, the batteries would be drained in the space of 10 minutes -- if they were even chemically capable of withstanding such a rapid discharge.


At this year's 24 Hours of Le Mans race, Audi sent a prototype of its high-voltage, high-speed car out to take an extra lap around the course, meant to illustrate the great potential of such a vehicle. The driver, though, was under orders not to drive at full speed -- company engineers weren't sure the batteries would last the entire lap if he did. One lap at Le Mans is 13.6 kilometers (8.5 miles) long.


Translated from the German by Ella Ornstein