Abstract

The majority of previous studies examining life cycle greenhouse gas (LCGHG) emissions of battery electric vehicles (BEVs) have focused on efficiency-oriented vehicle designs with limited battery capacities. However, two dominant trends in the US BEV market make these studies increasingly obsolete: sales show significant increases in battery capacity and attendant range and are increasingly dominated by large luxury or high-performance vehicles. In addition, an era of new use and ownership models may mean significant changes to vehicle utilization, and the carbon intensity of electricity is expected to decrease. Thus, the question is whether these trends significantly alter our expectations of future BEV LCGHG emissions.To answer this question, three archetypal vehicle designs for the year 2025 along with scenarios for increased range and different use models are simulated in an LCGHG model: an efficiency-oriented compact vehicle; a high performance luxury sedan; and a luxury sport utility vehicle. While production emissions are less than 10% of LCGHG emissions for today’s gasoline vehicles, they account for about 40% for a BEV, and as much as two-thirds of a future BEV operated on a primarily renewable grid. Larger battery systems and low utilization do not outweigh expected reductions in emissions from electricity used for vehicle charging. These trends could be exacerbated by increasing BEV market shares for larger vehicles. However, larger battery systems could reduce per-mile emissions of BEVs in high mileage applications, like on-demand ride sharing or shared vehicle fleets, meaning that trends in use patterns may countervail those in BEV design.

Highlights

  • Transportation comprises 28% of US greenhouse gas (GHG) emissions, 60% of which come from light-duty vehicles (LDVs) (US Environmental Protection Agency, 2018)

  • This study examined trends in battery electric vehicles (BEVs) design choices and use models including battery pack size, vehicle archetype, and vehicle utilization, as well as changing electricity emissions to examine the potential effects on life cycle greenhouse gas (LCGHG) emissions of BEVs

  • The trend towards larger vehicles with larger battery packs leads to a deterioration in BEV GHG mitigation potential compared to ICEVs as a result of both vehicle production and operation emissions

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Summary

Introduction

Transportation comprises 28% of US greenhouse gas (GHG) emissions, 60% of which come from light-duty vehicles (LDVs) (US Environmental Protection Agency, 2018). As with other de-carbonization policies for the transport sector, such as those that promote biofuels, a life cycle perspective is required to understand the actual mitigation achieved by ZEVs, since emissions are not eliminated, but rather shifted upstream in the fuel cycle (to the power plant) and potentially increased in the vehicle production supply chain. Numerous life cycle-based studies have been conducted with the goal of verifying if BEVs (including plug-in hybrid electric vehicles (PHEVs)) achieve real reductions in emissions relative to internal combustion engine vehicles (ICEVs, including hybrid electric vehicles (HEVs)). These studies suggest that GHG emissions associated with energy for BEV operation (i.e. production of electricity) can be 44% - 80% of BEV LCGHG emissions. For non-operation GHG emissions, energy required for manufacturing of LIBs is the primary driver of increased

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