Lightweight Materials for Improving Fuel Economy
Argonne researchers examined various lightweight materials for structural applications in automobiles and passenger-oriented light trucks, and the most cost-effective ones were selected for further analysis. Aluminum and high-performance polymer matrix composites (PMCs) offer the most promise for reducing the weight of light-duty vehicles. The weight-reduction potential of aluminum and carbon-fiber-based PMCs was computed on the basis of a set of component-specific replacement criteria, such as stiffness and strength, and consequent incremental cost scenarios were developed.
For the analysis, we assumed that materials research and development reduces the cost of manufacturing aluminum and carbon-fiber PMC-intensive vehicles. Therefore, the difference in cost between a conventional vehicle and an alternative vehicle reflects the difference in materials cost. A vehicle choice model was used to project market shares for lightweight vehicles. Early runs of the model indicated a low market share for a mid-size carbon-fiber (PMC-intensive) vehicle and a substantial share for an aluminum-intensive vehicle. Subsequent analysis of life-cycle energy and fuel use impacts focused on aluminum-intensive vehicles.
The following two sets of aluminum-intensive vehicles were characterized to compete with the conventional materials vehicles: (1) vehicles with limited use of aluminum, providing 19% weight reduction, and (2) vehicles with maximum use of aluminum, providing 31% weight reduction. A model for vehicle survival and age-related usage was used to compute energy consumption over time for the vehicle stock.
Assuming mass-market introduction in 2005, we projected a national petroleum energy savings of 3% for the vehicle with limited use of aluminum and 5% for the vehicle with a maximum use of aluminum in 2030. The energy analysis included vehicle fuel consumption, material production energy, and recycling energy. We concluded that there is a net energy savings with the use of aluminum-intensive vehicles. Manufacturing costs must be reduced to achieve significant market penetration by such vehicles. The petroleum energy saved from improved fuel efficiency offsets the additional energy needed to manufacture aluminum compared with steel. The energy needed to make aluminum can be reduced further if wrought aluminum is recycled back to wrought aluminum. We found that oil use is displaced by additional use of natural gas, but use of coal and nonfossil energy is lower. The results are not necessarily applicable to vehicles built outside the United States.