Cars on a diet : the material and energy impacts of passenger vehicle weight reduction in the U.S.

Vehicle weight reduction is a known strategy to address growing concerns about greenhouse gas emissions and fuel use by passenger vehicles. We find that every 10% reduction in vehicle weight can cut fuel consumption by about 7%. In the U.S., vehicle weight reduction is essential for meeting future, more stringent fuel economy standards. New vehicles are required on average to achieve at least 34.1 miles per gallon (MPG) by year 2016, up from 28.8 MPG today. Scenarios of future vehicle characteristics and sales mix indicate that the target is aggressive. New vehicles must not only become lighter, but also forgo horsepower improvements, and progressively use advanced, more fuel-efficient powertrains, such as hybrid-electric drives. We can reduce weight by substituting some of the iron and steel used in vehicles with lighter-weight high-strength steel or aluminum, redesigning the vehicle, and/or downsizing the vehicle. Using these approaches, it is possible to achieve up to 40% (690 kg) vehicle weight reduction. However, the cost associated with manufacturing lighter-weight vehicles is a nontrivial $3 to $4 per kilogram of total weight saved. In addition, the life-cycle energy impacts of using alternative lightweight materials, which tend to be more energy-intensive to process, must also be considered. In this dissertation, the energy implications of pursuing this lightweighting strategy are explored on a vehicle life-cycle- and vehicle fleet system-level basis. A model of the energy and material flows through the evolving vehicle fleet system over time has been developed, which accounts for potential changes in future vehicle weight and material composition. The resultant changes in material production energy and fleet fuel savings, which are the main energy burdens for the entire product system - the vehicle fleet - are estimated. The new 2016 fuel economy standards and more stringent standards beyond can realize significant fuel savings of 1,550 billion liters through year 2030. However, the advanced powertrains that are expected to enter the marketplace are heavier and require more energy to produce. Their production impact may be offset by efforts to use less energy-intensive high-strength steel to lightweight new vehicles, as well as efficiency gains in material processing.

Department dc:contributor.department

Massachusetts Institute of Technology. Engineering Systems Division.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2010

Author dc:creator

• Cheah, Lynette W. (Lynette Wan Ting)

Advisor dc:contributor.advisor

• John B. Heywood.

• Engineering Systems Division.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/62760

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/62760