Research Publications

Vehicle manufacturers are utilizing advanced powertrains and lightweight materials to increase vehicle efficiency in response to higher energy prices and more stringent regulation. Advanced powertrains improve vehicle efficiency but tend to increase vehicle curb weight due to the addition of electric propulsion components like batteries and electric motors. Thus, lightweight materials for the vehicle body are often sought to reduce curb weight. Together, these technologies can help lower a vehicle’s use-phase energy consumption, but they may lead to higher energy consumption during material production and manufacturing. This case study focused on plug-in hybrid electric vehicles (PHEVs) and lightweight aluminum and high strength steel materials, technologies and materials currently used in production vehicles by manufacturers. We employed vehicle simulation software to evaluate vehicle energy use over U.S. Environmental Protection Agency (EPA) urban and highway certification drive cycles for a production-like PHEV with hoods made of either conventional steel, high strength steel, or aluminum. The study included conventional and high strength steels as baselines against which the performance of aluminum materials were compared. We then performed a lifecycle assessment to compare greenhouse gas (GHG) emissions created during the production of the conventional steel, high strength steel, and aluminum hoods with the mass-allocated emissions from vehicle use. This study included aluminum production location along with differing electricity allocation protocols to more completely account for variations in aluminum production emissions. It examined variations in vehicle energy use emissions by analyzing several different vehicle-charging locations. Results indicated that while the lightweight aluminum hood lowered vehicle use-phase GHG emissions due to reduced hood mass, carbon-intensive aluminum production locations and electricity allocation protocols could negate those reductions. Vehicle charge location also effected mass-allocated use phase emissions by 12 to 26% with the largest influence seen in PHEVs equipped with the heavier conventional steel hood.