April 13, 2012 – Vol.17 No.4
RETHINKING ELECTRIC CARS - PART 6.
by Bruce Mulliken, Green Energy News
For now, major automakers are developing electric cars that look like, and are built like, conventional cars they already produce. Sticking to electrified versions of conventional cars saves makers a bundle in development and production costs.
But, to save money the automakers are stuck with mostly heavy steel cars, even though weight is an issue with electric cars because of the heavy batteries the cars must lug around.
The flip side is that for cars in general, steel is a good material to build with.
Steel is really inexpensive and cars fabricate easily. Stampings of panels can be made in seconds and spot welded together with robots in a very short period of time. (The ability for steel to be spot welded easily shouldn’t be taken lightly. Spot welding plays a major role in low-cost car manufacturing.) Incredibly strong body structures can be put together very quickly from what began as thin steel on a big roll. Typically, mass-produced cars come off an assembly line at up to 2 per minute, but the whole process can take 24 hours or so.
Automakers, too, have considerable experience – decades now – in designing crushable steel cars to save lives in accidents. And, after accidents, a huge industry has been established – the auto body repair industry – to return crushed steel cars to near-normal with dents taken out and new shiny coats of paint.
Steel has its limitations of course. It’s relatively heavy, though to its credit the steel industry has done as best they can in formulating lighter, but high strength metal.
Steel also recycles easily.
Still, even with lighter steel, cars are heavy. Weight is energy robbing and to meet upcoming fuel economy standards, as well as extend the range of electric vehicles, cars are going to have go on a serious diet. To lighten up, much of the steel in cars may have to go. (If there is an alternative that is. A big IF.)
The most obvious choice is to build with aluminum. Some cars are already aluminum intensive in their design. Tesla’s upcoming Model S sedan has significant amounts of aluminum in its structure, but it’s not all aluminum. Others, even my own car, have some aluminum panels to save weight and improve fuel economy. Aluminum is very similar to steel in many ways, but while it can be spot welded, it’s a far more difficult and energy intensive process than spot welding steel. (As above, spot welding is a BIG DEAL in building cars. It largely makes modern, unit-body cars possible.)
At the end of life, when the vehicle is on its way to the recycling yard, the value of the metal is quite high, so deceased cars would have considerable value. From an environmental standpoint aluminum is energy intensive to make from ore, but recycles very easily using a fraction of the energy needed to make it in the first place.
Another choice for light-weighting cars is plastics. Already, as you most certainly have noticed, there’s lots of plastic in cars. For the most part it’s not structural but is there to save weight. GM’s EV1 electric car had plastic body panels and an aluminum frame to save weight and increase range.
The material that automakers would like to use, because of its steel-like strength and extreme light weight, is carbon fiber composites. Right now carbon fiber as a material is too expensive for mass-produced cars. Further, for now, it doesn’t fit into the rapid, stamp-em out, spot weld-em together mass assembly line techniques now used to build cars.
However in a new partnership between Ford and Dow Automotive Systems, carbon- fiber components may show up on the assembly line fairly soon if their efforts are successful.
A press release from the companies says this:
Carbon fiber composites have been used in aerospace and racing cars for decades due to their unique combination of high strength and low mass. Until recently these materials have been far too costly for use in high-volume mainstream applications.
Dow Automotive Systems and Ford have signed a joint development agreement that will see researchers from the two companies collaborate on several fronts. The development teams will focus on establishing an economical source of automotive-grade carbon fiber and develop component manufacturing methods for high-volume automotive applications.
The partnership will seek to combine the best of Ford's capabilities and experience in design, engineering and high-volume vehicle production with Dow Automotive's strengths in R&D, materials science and high-volume polymer processing.
"Reducing weight will benefit the efficiency of every Ford vehicle,"said Paul Mascarenas, Ford chief technical officer and vice president, Research and Innovation. "However, it's particularly critical to improving the range of plug-in hybrid and battery electric vehicles."
The joint development effort will also leverage work that The Dow Chemical Company has already begun through partnerships with Turkish carbon fiber manufacturer AKSA and the U.S. Department of Energy Oak Ridge National Laboratory.
If the joint development effort is successful, carbon fiber components may begin appearing on new Ford vehicles in the latter part of this decade as product development teams work toward meeting new fuel efficiency standards of more than 50 mpg and extending the range of plug-in vehicles.
The goal of the partnership? Cutting vehicle weight up to 750 lbs. by the end of the decade. That’s quite a bit of weight loss in a very short time.
For every pound of vehicle weight loss, EV manufacturers could put a pound more battery back in the vehicle. More battery, more range. The greater the range, the more likely people are going to buy the cars. But, more battery also means higher cost.
Both the steel and the aluminum industries will be asking questions if there’s a large scale adoption of carbon fiber in cars since both would stand to lose business. Mostly they’ll ask, “What’s the carbon footprint of carbon fiber?” That debate has already started within the steel industry.
RETHINKING ELECTRIC CARS - PART 1
If EV’s don’t catch on at a quicker pace, manufacturers might have to go back to the drawing board.
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