Evaluating future emissions from electric vehicles across the United States with a changing electric grid mix under the Clean Power Plan

摘要

In the United States, the transportation sector consumes approximately five billion barrels of oil annually and accounts for nearly a third of greenhouse gas emissions. The potential climate impacts of the transportation sector has led to a transition towards cleaner, alternative fuel vehicles such as electric vehicles (EVs) - touted as "zero-emission" vehicles. The transition has been accelerated by policy such as the Zero Emissions Vehicle (ZEV) mandate in California and incentives such as the federal Plug-In Electric Vehicle Credit (IRC 30D). However, if the ultimate goal of the transition is to create a cleaner transportation system, a proper accounting of emissions is necessary to understand the true impact of EVs. We construct a nationwide electricity dispatch model based on outputs from the Environmental Protection Agency's (EPA) Integrated Planning Model (IPM) used in the assessment of the Clean Power Plan (CPP). Using future projections of EV sales as well as a number of scenarios for charging behavior, a profile of electric vehicle emissions can be captured on sub-state level and importantly across a lengthy time span from 2016 through 2050. The time periods being captured are significant due to the lack of existing literature on EV emissions as the electric grid changes and cleaner sources of electric capacity are developed. We are able to demonstrate large regional differences in emissions with gradual improvement in emissions as the electric grid becomes cleaner over time. Consequential emissions of EVs can result in up to 50 million tons of CO_2 annually by 2030 depending on the scenario of electric grids, but we find that the implementation of CPP produces far greater impacts and can result in changes in total grid emissions of 500 million tons of CO_2.