Study finds that aluminum reduces electric vehicle cost against steel counterpart for same targeted range
7 January 2013
|The study task design steps. Source: fka. Click to enlarge.|
A recent study found that an aluminum electric vehicle can cost up to €635 (US$829) less than that its steel counterpart despite the higher cost of aluminum, given equivalent range targets. The study, conducted by Forschungsgesellschaft Kraftfahrwesen mbH Aachen (fka) for the European Aluminium Association (EAA) and the International Aluminum Institute (IAI), found that any additional cost of building a car with aluminum is more than offset by the cost savings that can be made on the battery pack, since a lighter car needs less battery capacity to drive the same distance.
A C-segment crash reference vehicle (Volkswagen Golf) with steel unibody and internal combustion engine served as the basis for this study. The mass and crashworthiness properties of this vehicle were analyzed in four Euro NCAP and FMVSS 301 high-speed load cases, serving as the crash reference within the project. One of the requirements was that electric vehicles (steel-based or aluminium-based) should at least be as safe as the crash reference vehicle.
The fka team first converted the conventional vehicle into an EV—the original steel unibody structure was conserved, with only minor changes made in order to adapt the structure to hold and protect the battery pack.
The next step was the conversion of that EV to a full aluminium space frame electric vehicle. The shape of the outer skin of the vehicle was kept identical to that of steel vehicles.
|Various manufacturing methods used in the aluminum design. (blue: sheet, green: extrusion, red: casting) Source: fka. Click to enlarge.|
While keeping to the crash standards, the fka team determined that the weight of the total body structure could be reduced by 162 kg (357 lbs) compared to the electric reference steel-unibody. As a secondary effect, the battery system capacity could be downsized by 3.3 kWh while still maintaining an intended driving range of 200 km (124 miles). This also means an additional weight reduction of 25 kg (55 lbs)—assuming battery technology projected to be available in 2015—making the aluminium electric vehicle in total 187 kg (412 lbs) lighter than the steel electric vehicle.
The fka team then calculated aluminum lightweighting could be carried out, at a production volume of 100,000 vehicles per year, of €1,015 (US$1,324) per vehicle. Assuming energy-specific year 2015 battery system costs of €500/kWh (US$652/kWh), the reduction in total battery system costs is €1,650 (US$2,152).
If we compare the additional costs of the lightweight design with the reduction in battery system costs, it can be concluded that the benefits obtained from lower battery costs more than outweigh the additional costs for the lightweight aluminium vehicle. With the assumptions made in this report, the total cost of the aluminium electric vehicle is €635 [US$829] lower than for the steel electric vehicle.—“Investigation of the Trade-off Between Lightweight and Battery Cost for an Aluminium-intensive Electric Vehicle”
Life cycle analyses of the full-steel and the full-aluminium electric vehicles found that the aluminium electric vehicle emits 1.5 tons of greenhouse gases less over its complete cradle to cradle life-cycle, including production, a driving distance of 150,000 km, and recycling. The carbon footprint of the production of the aluminium electric vehicle, including the end of life recycling benefits as recommended in ISO 14044 standards, is lower than that of the steel electric vehicle. Further, the aluminium electric vehicle also consumes less energy during the use phase. Thus, the researchers concluded, whatever the mileage distance over the vehicle life time, the aluminium vehicles is always less intensive in term of GHG emission and energy use.
Excluding recycling, the break-even point at which the carbon footprint of the aluminium electric vehicle is lower than that of the steel vehicle occurs at a mileage of 47,000 km (29,204 miles).
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