Aluminum Reduces Costs for Electric Vehicles

By · January 08, 2013

Aluminum cost/weight graphic

A new study conducted by Forschungsgesellschaft Kraftfahrwesen mbH Aachen for the European Aluminium Association and the International Aluminum Institute found that despite the fact that aluminum costs more than steel, a complete electric vehicle can be less costly when built with a significant amount of aluminum rather than conventional steel.

The study, as reported by Green Car Congress, suggests that automakers could offset the cost of aluminum by utilizing a lower capacity battery pack, since the aluminum vehicle weighs less than its steel counterpart. In other words, range is not sacrificed due to weight reductions garnered through the use of aluminum. The savings, estimated at $829 per vehicle, is significant as automakers consistently seek out savings of even a few cents on certain parts that go into production vehicles.

Aluminum use in EV

Depiction of use of aluminum in different forms throughout the entire vehicle.

In the study, researchers converted a conventional vehicle into an EV. This baseline vehicle, with its steel unibody still intact, was fully tested before going on an aluminum diet. The team of researchers adapted an aluminum space frame to the electric vehicle, skinned the body in aluminum and replaced all steel components with aluminum where possible. The ability to meet crash test standards determined exactly how much steel could be replaced by the less crash-worthy aluminum.

Audi A2 concept

The mostly aluminum Audi A2 plug-in concept weighs only 2,500 pounds and boasts a range of up to 124 miles from its 31-kWh lithium-ion battery pack.

The end result was an aluminum electric vehicle that weighed 357 pounds lighter than it steel electric counterpart. As a result, the vehicle's battery capacity could be reduced by 3.3 kWh while maintaining the original 124 miles of range. The use of a lower capacity battery could further reduce weight by 55 pounds, making the aluminum electric vehicle 412 pounds lighter than the steel electric reference vehicle and cutting total costs by $1,324 per vehicle. The figures are based on production volume of 100,000 units annually—well beyond the current scale of production for any EV-maker.

Comments

· · 1 year ago

The book "Reinventing Fire" deals with this in the early chapters, and makes a case for actually building vehicle bodies out of carbon fiber to exactly the same effect. If you're interested in the kind of extremes the idea of using more expensive materials to realize ever increasing savings can be taken, I recommend that book and/or any lectures you can find online by Amory Lovins.

· Bret (not verified) · 1 year ago

BMW figured this out years ago, with their Mega City (i3 & i8) vehicles. Steel EVs, like the LEAF, will seem pretty antiquated in a couple of years.

· Modern Marvel Fan (not verified) · 1 year ago

Does that include the cost of "insurance" and "repair"?

· · 1 year ago

I've heard the added cost of aluminum is more than just the raw material costs. Steel is easily spot welded and aluminum is not easy to spot weld because it conducts electricity too well and, consequently, it does not heat up the way steel does.

I'm very curious to know the method Tesla uses to weld the aluminum space frame of the Model S.

· · 1 year ago

Weight is important - but not as important as aerodynamic drag. Case in point is Dave Cloud's Dolphin: over 200 miles range on a ~30kWh pack of *lead acid* batteries. The batteries alone weigh 1980 pounds and the car weighs about 3200 pounds. But oh boy is it sleek!

http://ecomodder.com/forum/showthread.php/ultimate-aerodynamic-car-dave-...

Accelerating a car is when you "invest" energy in getting it moving. An electric car loses *far* less energy so accelerating an EV is not nearly as "costly". So weigh is *much* more important in an ICE than an EV. Case in point for this is the Edison2 Very Light Car - the ICE powered version weighed just 830 pounds and it got 110MPGe Combined; while the electric version weighs 1140 pounds and gets 245MPGe Combined.

The VLC has a Cd of just 0.164 and goes 90-100miles on just a 10kWh pack, so I think if it had a 24kWh pack it could go over 200 miles.

A moving car has kinetic energy and the heavier it is, the more kinetic energy stored at the same speed. That kinetic energy can be used directly by coasting (assuming that the driver learns to accelerate for a shorter time) and then in an EV some of the remaining kinetic energy can be regained with regenerative braking. So, weigh requires more energy to accelerate, but it can be partially used.

Aerodynamic drag is a total loss. A typical car uses about *half* of the energy to move air out of the way at ~30MPH and about three quarters at 65-70MPH. There is no way to get this energy back, and since it swamps *all other losses* combined at most driving speeds, this is where automotive engineers need to improve all cars, and especially EV's, since they carry less energy onboard.

Lowering weight is good - the Tesla Model S would not have as long a range if it was made out of steel. But it has the lowest Cd of any car sold today: 0.24 and that contributes even more to the range, I think. Maybe Tesla will go ahead and sell the optional smooth wheels they had considered, and maybe this could drop the Cd to 0.22-0.23 and add another 10-18 miles?

http://ecomodder.com/forum/showthread.php/tesla-says-aero-wheels-improve...
http://www.teslamotorsclub.com/attachment.php?attachmentid=4999&d=133254...

Neil

· · 1 year ago

An interesting article, Jim. Aluminum is more expensive than steel but, if you can offset that by using less lithium (ie: small battery,) you get a net gain without a significant price penalty. The rub, of course, is in the last sentence of the article, where economies of scale on the order of 100K units annually are where you finally see the economic benefit.

That chapter on cars in Reinventing Fire is marvelous, Smidge.

I think heliarc welding - where helium gas is introduced into an electrical arc welding scenario, smithjim - is what is being done to join aluminum. It's been around since the 1930s.

And Neil . . . that Dolphin on the Ecomodder's link you provided is stupendous. I'm surprise how similar the front end of it looks like my '95 Saturn. Of course, that boat tail rear is the real point of departure. It would never happen on a production car, of course . . . and I'd think twice before asking my wife to attempt to parallel park it.

But wasn't the Audi A2 the most aerodynamically efficient production car (with more or less conventional lengths and proportions) ever made? I read somewhere that the airflow over the rear deck was conceived carefully enough so a rear window wiper wasn't needed, as water didn't dam up back there. There clearly needs to be more of that sort of thinking going into the next generation of electric cars than giving us fake radiator grills to make us feel "comfortable."

· · 1 year ago

Benjamin, the Dolphin started with the engine bay and the front seats of Metro, and he added 18" to the nose (which might not be required with a lithium pack) and lowered the roof, and then completely rebuilt the back of the car. It is not a long as you might think. I did a scaled model in SketchUp (based on photographs w/ measuring sticks) and it is about 17'-6" nose to tail cone:

http://www.youtube.com/watch?v=3HqiK4kW4fU

As stupendously sleek as that clear tail cone is, you would not lose much without it. The overall fineness ratio and the narrowed rear track and covered rear wheels would probably still yield a Cd of about 0.15? Notice the lack of any large cooling intake, as well. He used two 8" DC motors, one for each rear wheel, so he could coast really well, but has no regenerative braking. AC motor(s) would be more efficient, and a ~50kWh lithium pack would weigh *half* of the lead acid pack weighed.

So the Dolphin could be a 400 mile range EV, no problem. Remember lead acid suffers from a substantial loss due to Peukert's effect; and some/all of the 60 batteries (each weighs 33 pounds) in the car were used. I'm estimating that when new, they would be about 30kWh. He drove it 200+ miles on a single charge.

Neil

· · 1 year ago

The LEAF has an aluminum hood and door panels, but the roof, fenders and hatch are steel. Stamping is more difficult with aluminum, due to its springback. I agree with the comment over that the future is carbon fiber rather than aluminum at least for the body panels.

· · 1 year ago

@NeilBlanchard "Weight is important - but not as important as aerodynamic drag."

No doubt that aerodynamic drag is the single largest energy sink, but weight reduction is also a great way to improve performance. Don't discount it.

Weight contributes directly to rolling resistance.

Weight also makes a big difference when driving over large changes in elevation. Regenerative braking may help recover ~80% of the energy coming back down, but it won't help you getting up. Death by a thousand molehills, if you will.

Also important, weight contributes directly to performance. A lighter car can have the same "pep" with a smaller, more efficient (and less expensive!) powerplant.

Don't rule out the idea of putting your car on a diet!

· · 1 year ago

Right, acceleration of a lighter car is better than a heavy one, all else being equal. City driving is hurt most by weight. Don't forget coasting - the most efficient way to travel.

Rolling resistance is swamped by aero drag at ~30mph and above.

But nothing says a car cannot be lighter and lower aerodynamic drag, too. :-) I'm anticipating that CarBEN EV5 will weigh <1 ton; and I'm hoping it has a Cd <0.15.

Neil

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