Sustainability assessment of passenger vehicles: Analysis of past trends and future impacts of electric powertrains

Since 1950 the world’s passenger car fleet has grown by about 5 % per year, reaching approximately 870 million vehicles in 2011 and consuming more than 20 million barrels of crude oil per day. Rising transportation demand and dependence on petroleum as its primary energy source will continue to be a major cause of greenhouse gas (GHG) and pollutant emissions leading to global warming, and damages to human health and the ecosystem. In addition, oil’s security of supply and price stability are uncertain. For these reasons, several advanced vehicle and fuel technologies are currently being developed with the aim of reducing the environmental impacts of road transport and its dependence on fossil oil. However, these technologies enter the market incrementally and must meet performance, utility, and cost requirements to be accepted by consumers. In Switzerland more than two third of personal mobility is based on gasoline and diesel passenger cars, which contribute a rising share to total Swiss CO2 emissions. A decomposition analysis has been developed and applied to separate the contributions of changes in new vehicle efficiency, mass, and fuel technology to specific CO2 emissions from Swiss new vehicles. The analysis showed that in the past, powertrain efficiency improvements have to a large extent been offset by the increased mass and performance of new vehicles. In the period from 2000 to 2012, potential reductions at constant fleet mass would have been ca. 9 % higher than the actual CO2 emission reduction. The method was furthermore applied to study emissions scenarios showing the conditions under which the regulatory targets for 2015 and beyond can be met. In this thesis an integrated framework to quantitatively assess technical, economic, and environmental criteria of a wide range of conventional and electric powertrains has been developed. Scenarios from today to 2050 are investigated, and various primary energy sources and vehicle configurations are taken into account. The novel analytic modeling methodology developed allows very short calculation time, making it useful for interactive analysis, scenario modeling and fleet simulations; as well as offering new opportunities for sensitivity analysis and optimization. The models developed in this thesis can help to create a fundamental understanding of the complex interactions between different powertrain technologies, vehicle configuration parameters, future developments, and the corresponding impacts on cost and environmental indicators. In order to make the results of this thesis accessible to a broader public, several tools for interactive life cycle assessment, scenario analysis, and multi-criteria decision analysis have been developed and implemented online. Life cycle assessment results show that the environmental impacts of electric vehicles are very dependent on their primary source of energy. If electricity and hydrogen for vehicle propulsion are produced from non-fossil primary energy, life cycle GHG emissions and the related impacts on human and ecosystem health, as well as fossil fuel depletion can be greatly reduced. In general, the costs and environmental impacts from the vehicle production phase are higher for electric than conventional vehicle technologies. In particular metal use increases in electric vehicles and the further development should aim at reducing metal resource depletion and improving recycling efficiency. Multi-criteria analysis indicates that there is no single technology which performs best in terms of all relevant criteria at the same time, but that different technologies have tradeoffs relative to each other and can provide advantages depending on the specific usage patterns, e.g. electric relative to conventional vehicles in urban driving conditions, or fuel cell relative to battery electric vehicles in terms range and fueling time. Plug-in hybrid electric vehicles appear to be a robust technology considering a broad set of technical, environmental, and economic criteria. A model of the Swiss passenger vehicle fleet has been developed to analyze the implications of various future scenarios of electric vehicle sales, primary energy sources, and overall vehicle use patterns on vehicle stock, energy use, and GHG emissions until 2050. The results show that major drivetrain changes are not yet ready for large scale adoption, and will take a long time to penetrate the fleet against the current dominance of gasoline and diesel powertrains. On a longterm perspective (beyond 2030), electric vehicles offer the potential for large reductions of fleet fuel use and GHG emissions, if electricity and hydrogen are produced from non-fossil primary sources.