1995-10-01

Life Cycle Energy Analysis for Automobiles 951829

A life cycle energy model for representing electric (EV) and internal combustion energy (TCV) vehicles is presented. The full life cycle energy for each vehicle is computed including the material production, vehicle assembly, operation, maintenance, delivery, scrapping and recycling contributions. It is found that the modelled electric vehicle (sodium sulphur battery system) consumes 24% less life cycle energy than a functionally equivalent (in carrying capacity and life time distance) gasoline powered internal combustion energy vehicle. In fact, the ICV would have to operate at 50 MPG to be as operationally energy efficient as the EV. However, it should be noted that the EV is not the performance equivalent of the ICV; the former has a lower acceleration, a shorter range, a much longer “refueling time”, and a considerably greater cost. Overall, atmospheric emissions for the EV are lower than those for the ICV, though the former does generate more acid rain gases. The operational energy proportion of the total life cycle energy is found to be 89% for a typical ICV but only 70% for an EV.Weight reduction through the use of lighter weight materials like aluminum and composites (carbon and glass fiber reinforced) is shown to significantly reduce the life cycle energy for an ICV. For example, a radical use of carbon fiber composites and aluminum is predicted to yield a life cycle energy savings of 16%. However, it is observed that weight reduction for the EV has less impact on incremental reductions in life cycle energy than is the case for the ICV. This is due to the former's greater energy efficiency. For some materials such as aluminum, operational energy benefits resulting from weight reduction are offset in part by an increased materials production energy. The use of recycled materials improves this considerably, e.g. a 7.5% life cycle energy reduction for a particular aluminum substitution example becomes 12% when a 50%) recycle content is used. An error analysis of the results is also presented. Finally, life cycle energy is only part of the environmental picture of a product. To provide a more complete environmental analysis of vehicles, a life cycle assessment, which considers all generated wastes and consumed resources, needs to be conducted. Such studies have started both at Ford and under USCAR.

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