Environmental Impacts of Plug-in Hybrid Electric Vehicles

Abstract

The environmental and electric utility system impacts from plug‐in hybrid electric vehicle (PHEV) infiltration in Michigan were examined from years 2010 to 2030 as part of the Michigan Public Service Commission’s (MPSC) PHEV pilot project. Total fuel cycle energy consumption, greenhouse gas and criteria air pollutant emissions for Michigan’s light duty vehicle fleet were analyzed, as well as gasoline displacement due to the shift to electrified travel. PHEVs consume both liquid fuel and grid electricity for propulsion. While this fueling strategy can significantly reduce gasoline consumption and related emissions, it is important to understand the impacts that these PHEVs have on the electrical system and its associated emissions. A MATLAB® model was developed to quantify the regional emissions and energy use of this interaction for Michigan. Each year the model examined vehicle charging behavior, PHEV sales infiltration, changes to the electric grid, and electricity dispatch. Individual PHEV energy consumption was determined from a database of actual vehicle trips, and scaled to the number of on‐road PHEVs. The electricity to charge PHEVs was added to Michigan’s baseline hourly electrical demand and new generating capacity was added to the grid to meet renewable portfolio standards and capacity reserve mandates. Lastly, generating assets were dispatched to serve the load, and total fuel cycle (TFC) emissions were calculated. Several scenarios were developed to capture the range of possible outcomes examining PHEV infiltration, charging behaviors, and future grid mixes. In all scenarios, an increased number of PHEVs led to decreased statewide GHG emissions, ranging from a 0.4% to 10.7% reduction in 2030, and displaced from 0.5 to 9 billion gallons of gasoline from 2010‐2030. Depending on the scenarios employed and allocation method, The emissions intensity of PHEV travel in 2030 ranged from 294 and 187 gCO2e per mile. Substituting nuclear generators for some of Michigan’s predominately coal baseload power plants had a large effect on reducing emissions, a 40% reduction in annual electricity sector GHG emissions between 2009 and 2030, and reduced PHEV emissions intensity up to 22%. Criteria air pollutant emissions were reduced in most scenarios. However, SOX emissions could increased with the addition of PHEVs.