Lightweighting Impacts on Fuel Economy, Cost, and Component Losses

In 2011, the United States imported almost half of its petroleum. Lightweighting vehicles reduces that dependency directly by decreasing the engine, braking and rolling resistance losses, and indirectly by enabling a smaller, more efficiently operating engine to provide the same performance. The Future Automotive Systems Technology Simulator (FASTSim) tool was used to quantify these impacts. FASTSim is the U. S. Department of Energy's (DOE's) high-level vehicle powertrain model developed at the National Renewable Energy Laboratory. It steps through a time versus speed drive cycle to estimate the powertrain forces required to meet the cycle. It simulates the major vehicle powertrain components and their losses. It includes a cost model based on component sizing and fuel prices. FASTSim simulated different levels of lightweighting for four different powertrains. The four powertrains included a conventional gasoline engine vehicle, a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and a battery electric vehicle (EV). Weight reductions impacted the conventional vehicle efficiency more than the HEV, PHEV and EV. Although lightweighting impacted advanced vehicle efficiency less, it reduced component cost and overall costs more. Under the assumed current battery costs, however, the PHEV and EV were still more expensive than the conventional vehicle and HEV. Assuming the DOE's battery cost target of 125/kWh and improved battery life, however, the PHEV and EV attained similar cost and lightweighting benefits. Generally, lightweighting was cost effective when it cost less than 6/kg of mass eliminated.