Impacts of replacing coal with renewable energy sources and electrifying the transportation sector on future ozone concentrations in the U.S. under a warming climate

The potential impacts of emission reduction strategies in the electric power and transportation sectors on future ozone concentrations in the U.S. are investigated. A modeling system consisting of: the Weather Research and Forecasting (WRF), the Community Earth System Model (CESM), the GEOS-Chem, and the Comprehensive Air Quality Model with Extensions (CAMx) is deployed under a climate change scenario to simulate ozone pollution changes by mid-century. In addition to the control case, which represents current conditions, two emission reduction cases are simulated. The first (CASE1) includes the effects of decommissioning older coal-fired power plants and supplying their electricity with a mix of renewable sources and natural gas power plants. The second emission reduction case (CASE2) includes the effects of electrifying mobile sources. In CASE2, the emission reductions in the power sector remain the same as in CASE1, but further emission reductions result from an increase in electric vehicles, powered by renewable electricity and a small increase in natural gas for reserves. Results show that, for CASE1, ozone levels decrease modestly, with the maximum ozone benefit (-0.7 ppb) in the U.S. Central region, where the most coal decommissions take place. In CASE2, ozone levels decrease significantly everywhere with maximum decreases of -3.7 ppb and -3.5 ppb in the North East and South East regions, respectively. The study indicates that, in the summer, coal-fired power plant decommissioning would have only local and modest ozone benefits, whereas mobile source electrification could help achieve larger ozone reduction goals at the regional scale.