A techno-economic investigation of advanced vehicle technologies and their impacts on fuel economy, emissions, and the future fleet

Richard A Simmons, Purdue University

Abstract

A more sustainable transportation energy future for society is the principal motivation of this dissertation. The central purpose of this work is to investigate vehicle technologies that contribute to fuel and emissions reductions while preserving consumer choice, and to evaluate their technological performance and economic practicability as essential aspects of meeting aspirational targets and regulatory requirements associated with the future vehicle fleet. Innovation in automobiles has been realized at stable and affordable prices for decades, yet efforts to intensify future value creation in the domain of energy efficient technologies are critical. Using analysis of variance and hedonic price modeling techniques, disaggregated contributions of passenger car attributes to vehicle price reveal that consumer valuations of fuel economy move inversely with acceleration performance, and that both are highly correlated to the regulatory context. Novel economic trade-offs among vehicle attributes are introduced, in particular with respect to two foundational premises emphasized by current policies: vehicle classification and weighted sales volume. The implicit value of acceleration is presently greater than that of fuel reduction, with buyers in the significant mid-size vehicle segment willing to pay more than twice as much for the former than the latter. Building on these findings, the research explores a suite of fuel- and emission-reducing technologies that have underpinned fuel economy gains and compliance at costs that are at or below levels anticipated by the regulations. However, benefit-cost analyses on 2014 model year compact and mid-size cars reveal that consumers are not yet substantially incentivized to purchase fuel economy under baseline scenarios. A sensitivity analysis reveals that a majority of new technologies become financially attractive to consumers when average fuel prices exceed $5.60/gallon, or when annual miles traveled exceed 16,400. Turbocharged-downsized engines and hybrid powertrains are found to deliver high incremental benefits compared to their costs. The research suggests that the additional cost consumers incur in exchange for a given level of fuel economy improvement in the coming years will need to be steadily reduced compared to current levels, particularly in the context of low fuel prices. Hybrid and electric vehicles are viewed as enabling technologies, yet their real-world energy consumption is more highly sensitive to driving cycles, ambient temperature, and upstream energy sources than conventional vehicles. Vehicle tractive power, and cabin and battery thermal loads are interactively modeled and simulated for a range of operating conditions among vehicles that employ different energy sources and disparate power and thermal management strategies. Locality-specific system-level energy consumption values are then computed based on characteristics of large U.S. cities such as electricity generation, petroleum refining, and typical weather. The findings quantify the extent to which advanced architectures, though favorable in certain modes, are more energy sensitive to driving cycles and extreme temperatures. Annualized integration of this temperature-dependence reveals that system-equivalent energy consumption varies by locality least for internal combustion and hybrid vehicles, and between 45-70% for electric vehicles. As compared to conventional vehicles, electric vehicle system-equivalent CO2 emissions range from a 70% improvement to no improvement based on locality. This study suggests that policies and deployment efforts should scientifically account for the strong sensitivity to locality on energy and emissions for advanced vehicles. Regarding fuel reduction objectives, internal combustion engine vehicle baselines show sustained improvement on both technological and economic fronts without compromising consumer choice. Hybrids perform exceptionally well overall, reducing energy and emissions by levels that appear to justify their incremental cost increases. In terms of fuel switching, vehicles operating on grid-electricity are shown to displace petroleum and yield net energy reductions in certain localities; yet future research must navigate technological and cost challenges to ensure energy and emissions benefits are bankable and that policies are well-aligned. This body of work is intended to promote ways of affordably reducing the impact of transportation on the environment, to stimulate further research toward system-level optimizations, and to help inform subsequent policymaking processes regarding the future vehicle fleet.

Degree

Ph.D.

Advisors

Tyner, Purdue University.

Subject Area

Economics|Mechanical engineering|Public policy

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