Emissions Impacts and Benefits of Plug-In Hybrid Electric Vehicles and Vehicle-to-Grid Services

Plug-in hybrid electric vehicles (PHEVs) have been promoted as a potential technology to reduce emissions of greenhouse gases and other pollutants by using electricity instead of petroleum, and by improving electric system efficiency by providing vehicle-to-grid (V2G) services. We use an electric power system model to explicitly evaluate the change in generator dispatches resulting from PHEV deployment in the Texas grid, and apply fixed and non-parametric estimates of generator emissions rates, to estimate the resulting changes in generation emissions. We find that by using the flexibility of when vehicles may be charged, generator efficiency can be increased substantially. By changing generator dispatch, a PHEV fleet of up to 15% of light-duty vehicles can actually decrease net generator NO _x emissions during the ozone season, despite the additional charging load. By adding V2G services, such as spinning reserves and energy storage, CO ₂, SO ₂, and NO _x emissions can be reduced even further.