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Transitioning the U.S. light-duty vehicle fleet (National Research Council report)

[For immediate release: 20 March 2013]

On Monday, the U.S. National Research Council released a comprehensive study of the technology potential for cutting oil consumption and GHG emissions by 80% across the U.S. light-duty vehicle fleet in 2050, relative to a 2005 baseline. Its assessment: Cautious optimism, tempered by a realistic acknowledgment that achieving those related but distinct goals will demand vigorous and sustained public-sector support through “policies emphasizing research and development, subsidies, energy taxes, or regulations.”

The study, which is the product of more than two years’ work by a committee drawn from industry, government, and the academy, focused on four general technology pathways: highly efficient conventional vehicles (including conventional hybrids), biofuels, plug-in hybrid and battery electric vehicles, and hydrogen fuel cell vehicles. The analysis also takes in natural gas, various crosscutting vehicle and fuels technologies, and certain relevant external factors, such as prospects for decarbonizing the electric power sector.

ICCT Senior Fellow John German, who chaired the subcommittee analyzing alternative vehicle technologies, noted that the groundbreaking aspect of the study is not obvious from overall summaries of the 2050 reductions. “Forecasting technology development 40 years into the future is hazardous, at best,” said German. “Instead of trying to predict the development of individual technologies and their benefits, the committee evaluated existing energy losses through the entire drive train and the potential to reduce each of these losses in the future. The rate of progress in reducing those loses was assumed to slow dramatically after 2030, to about half the predicted rate from now until 2030. In addition, fundamental physical and chemical limitations were carefully assessed for each component and as these limits were approached, the rate of improvement was slowed down to ensure that the estimates stayed well short of the limits. We also took great care to apply consistent assumptions across all of the technology types.”

Among the report’s key findings:

  • The goal of reducing oil use by 80% could be met by several combinations of technologies that achieve at least the mid-range level of estimated success. But it will demand continued improvement in vehicle efficiency beyond what is required by the 2025 CAFE standards, as well as increased production and use of biofuels, and/or the successful introduction and large-scale deployment of compressed natural gas vehicles, BEVs with greatly improved batteries, or fuel cell vehicles, with all the additional new supporting infrastructure those imply.
  • Reductions in annual GHG emissions from the LDV fleet on the order of 60% to 70% are achievable by 2050, but reaching the desired 80% reduction is less certain, and will in any case be more difficult than reducing oil consumption by the same 80%. Petroleum-based fuels would have to be largely eliminated and at least two of four pathways would be required, i.e., highly efficient conventional vehicles combined with vehicles operating on biofuels, electricity, or hydrogen produced with low net GHG emissions. This scenario involves significant uncertainties concerning performance and costs, and it implies an economy- wide transition away from GHG emissions.
  • Because of the need for progress across multiple if not necessarily all technology pathways, and uncertainties over costs, rates of implementation, and consumer and manufacturer responses, an adaptive, "all of the above" type of policy framework is crucial.

Beyond its high-level findings, two important results of the study deserve particular attention. First, the potential for enhancing the efficiency of conventional vehicles is far greater than commonly believed. “When engine and transmission improvements are combined with lightweight materials, reductions in aerodynamic drag and tire rolling resistance, and hybrid electrical systems, average fuel economy of the light-duty fleet is projected to be about 95 mpg in 2050, and of cars alone about 112 mpg,” said German. "Using optimistic assumptions also developed by the committee, fleet-wide fuel economy could be about 125 mpg in 2050, and cars alone about 145 mpg."

All of the study’s projections assume the same full mix of vehicle types and sizes as consumers are accustomed to today. As the ICCT’s executive director, Drew Kodjak, noted, “the technologies relied upon are natural extensions of the technologies we are already seeing in today's fleet, at a reasonable consumer price range. The implications for the U.S. and the rest of world are profound: more time to transition to battery electrics and fuel cell vehicles, more emissions reductions and oil savings from conventional technologies.”

Second, assuming high volume production, the study projects that fuel cell vehicles and 100-mile real-world range BEVs will become cheaper than conventional vehicles by 2040 or 2045. Because battery and fuel cell costs are directly related to the loads on the vehicle, reducing weight, aerodynamic drag, and tire rolling resistance result in much larger cost reductions for these vehicles than for conventional vehicles. With lower electricity prices and very high efficiency, BEVs will be both cheaper to buy and cheaper to operate than conventional vehicles, although the committee's modeling suggests that long recharge times and short driving range will likely limit market share to about 20%. And in the long run, fuel cell vehicles will be significantly better than conventional vehicles with no compromises: lower purchase prices, comparable range and refill times, more efficient, quieter, with better drivability and low-end torque and more flexible packaging of drive train components for better space utilization.

“The challenges for fuel cell vehicles in the long run appear to be entirely on the infrastructure side,” German noted. “We will need not only an entirely new delivery infrastructure but a way to produce hydrogen at a price competitive with gasoline. And we have to begin to invest in that infrastructure now, as the advance placement of infrastructure is critical to the market acceptance of fuel cell vehicles.”

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