Tuesday, October 20, 2009

Aluminum Use in Electric Vehicles will Reduce High Cost of Battery Power for Plug-Ins and Hybrids, New Study Confirms

/PRNewswire/ -- Opting for high-strength, low-weight aluminum over heavier steel structures for plug-in electric and hybrid vehicles can cut vehicle price overall by reducing the battery energy requirements and the associated costs, according to a new study released today at the Center for Automotive Research's (CAR) Business of Plugging In conference. The study was jointly conducted by The Aluminum Association, Inc. with Ricardo, a leading technical research and strategic consultancy to the world's automotive, transport and energy industries.

Michael Bull, Director of Automotive Technology for Novelis, Inc., represented the Aluminum Association at the conference and participated in a panel discussion on future automotive changes associated with all electric vehicles.

"As automakers gear up for a new generation of plug-in electric vehicles, the high cost of battery power remains a barrier," said Bull. "What this new report shows is that by upgrading from traditional steel to an advanced aluminum body structure, the vehicle's stored energy requirements can be cut by about 10 percent, which could save up to $3,000 per vehicle since less power and energy is required to move the lighter vehicle."

"Plug-in and hybrid electric cars contain precious little, and quite expensive, 'fuel' in the form of batteries," added Bull. "Therefore, every effort must be made to utilize this stored energy to the highest possible efficiency. The solution lies in lowering the vehicle's weight with aluminum as part of a holistic approach to also include advanced powertrains and batteries, enhanced thermal management, improved aerodynamics, and reduced rolling resistance."

Highlights from the Ricardo electric vehicle study, for the federal test procedure (FTP75) drive cycle, include:

-- The driving range of the vehicles could be improved approximately
equal to the mass saved. Reduce the mass of the vehicle 20 percent,
go 20 percent father. One example vehicle had the range extended from
80 to 97 miles.
-- The heaviest vehicle in the study, at 1,822 kg, consumed about 300
Wh/mi, while the lightest at 627 kg consumed about 146 Wh/mi.
-- Regenerative braking could recover about 65 percent of the energy
associated with the vehicle's momentum irrespective of the vehicle
weight. But this is only about 15-20 percent of the total energy
-- For the lightest vehicle, about 44 percent of the energy is lost to
powertrain inefficiencies, with 33 percent of the energy used to
overcome air resistance, and only 24 percent is used to move the
-- As with conventional vehicles, the lighter vehicles have faster

The purpose of the Ricardo study was to evaluate the impact of vehicle weight reductions on electric vehicle performance, range and battery size. The majority of the vehicle simulations were done using the FTP75 drive cycle with a few highway drive cycles. In general, the relationships between vehicle mass, battery weight and energy, and range are linear up to the maximum range studied of 80 miles. At this range, the battery weight doesn't grow enough to start a significant "weight spiral."

The study also examined the role of vehicle mass on regenerative braking; specifically the question of whether strong regenerative braking might lessen the impact of weight reduction. This turns out not to be the case. All vehicles studied could recoup about 65 percent of energy associated with moving the vehicle. But the energy balance for each vehicle changes. As the vehicle gets lighter, less energy is required to move it, while the aerodynamic losses remain constant. For the lightest vehicle the aerodynamic losses are higher than the energy to accelerate the vehicle.

Real world designs support the fact that lightweight structures are a significant enabler for these vehicle types. Examples include Tesla Motors's Roadster, or upcoming midsized platform, Fisker Automotive's luxury vehicle and Bright Automotive's van. All are all using lightweight aluminum platforms for their vehicles.

"Many of the current hybrid vehicles are progressively adding lower weight components to improve the overall vehicle performance. When it comes to making electric vehicles more affordable and efficient, aluminum is proven to get you there with no compromises," said Bull.

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