Mitigating Climate and Air Pollution from the Electricity and Transportation Sectors in the United States

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ABSTRACT

In this talk, I will cover 3 recent pieces: (1) A transition to sustainable, deeply decarbonized,, and equitable energy systems is needed in the United States, which will require changes in the way we provide electricity and transportation services. With an increasingly interconnected system that encompasses variable energy sources and complex markets, the emissions embedded in electricity generation and consumption are becoming more difficult to estimate. Using flow tracing and consumption-based accounting, we have characterized the health damages from exposure to PM_2.5 from electricity imports and find that that 8% of our estimated premature deaths from electricity consumption in the United States are due to electricity imports. There is large geographic heterogeneity, with the most impacts occurring in the Midwest. While the West Coast has much cleaner generation and lower impacts overall, in many West Coast Balancing Areas, more than 50% of the estimated premature mortality associated with electricity consumption is caused by electricity imports, with some groups experiencing larger impacts than others. (2) Vehicle electrification is very likely needed moving forward as we decarbonize the transportation sector We estimate net emissions from vehicle electrification depend on when vehicles are charged, and which types of plants are meeting that electricity demand. We define a new concept, the grid critical emissions factors (CEFs), as the emission intensity of the grid that needs to be achieved when electric vehicles are charging so that electric vehicles achieve lifecycle greenhouse gas emissions parity with some of the most efficient gasoline and hybrid vehicles across the US. We find that the Nissan Leaf and Chevy Bolt battery electric vehicles reduce lifecycle emissions relative to the Toyota Prius and the Honda Accord gasoline hybrids in most of United States. However, in rural counties of the Midwest and the South power grid marginal emissions reductions of up to 208 gCO₂/kWh are still needed for these electric vehicles to have lower lifecycle emissions than the gasoline hybrids. With the exception of the Northeast and Florida, the longer-range Tesla Model S battery electric luxury sedan has higher emissions than the hybrids across the U.S., and the emissions intensity of the grid would need to decrease by up to 342 gCO₂/kWh in some locations for this vehicle to be at emissions parity with the hybrid vehicles we studied. (3) Electric vehicles will contribute to emissions reductions in the United States, but their charging may challenge electricity grid operations. We present a data-driven, realistic model of charging demand that captures the diverse charging behaviors of future adopters in the US Western Interconnection. We study charging control and infrastructure build-out as critical factors shaping charging load and evaluate grid impact under rapid electric vehicle adoption with a detailed economic dispatch model of 2035 generation. We find that peak net electricity demand increases by up to 25% with forecast adoption and by 50% in a stress test with full electrification. Locally optimized controls and high home charging can strain the grid. Shifting instead to uncontrolled, daytime charging can reduce storage requirements, excess non-fossil fuel generation, ramping and emissions. Our results urge policymakers to reflect generation-level impacts in utility rates and deploy charging infrastructure that promotes a shift from home to daytime charging.

BIO

Inês M.L. Azevedo is Associate Professor in the Department of Energy Resources Engineering at Stanford University. She also serves as Senior Fellow for the Woods Institute for the Environment at Stanford University and Fellow for the Precourt Institute for Energy (PIE) at Stanford University. She is the co-director of the Bits&Watts Initiative from PIE at Stanford University. Professor Azevedo’s research interests focus on how to transition to a sustainable, low carbon, affordable, and equitable energy system. She is interested in sustainability and energy issues where a systems approach is needed, by combining engineering and technology analysis with economic and decision science approaches. Her current interest is to address energy issues with particular focus on distributional effects and equity. She has published 100+ peer-reviewed journal papers. She has participated as an author and committee member in several National Research Council reports from the U.S. National Academy of Sciences. She was one of the Lead Authors for IPCC AR6 report on Climate Mitigation for the Energy chapter, and she is now also participating as Lead Author for the upcoming U.S. National Climate Assessment chapter on climate change mitigation. Professor Azevedo is also contributing as a chapter author to the upcoming U.S. National Climate Assessment report. Professor Azevedo received the World Economic Forum’s “Young Scientists under 40” award in 2014, and the C3E Women in Clean Energy Research Award in 2017.