摘要：The air quality impacts of replacing approximately 20% of the gasoline-powered light duty
vehicle miles traveled (VMT) with electric VMT by the year 2018 were examined for four
major cities in Texas: Dallas/Ft Worth, Houston, Austin, and San Antonio. Plug-in hybrid
electric vehicle (PHEV) charging was assumed to occur on the electric grid controlled by
the Electricity Reliability Council of Texas (ERCOT), and three charging scenarios were
examined: nighttime charging, charging to maximize battery life, and charging to maximize
driver convenience. A subset of electricity generating units (EGUs) in Texas that were
found to contribute the majority of the electricity generation needed to charge
PHEVs at the times of day associated with each scenario was modeled using
a regional photochemical model (CAMx). The net impacts of the PHEVs on
the emissions of precursors to the formation of ozone included an increase in
NOx emissions from EGUs during times of day when the vehicle is charging, and a decrease in
NOx from mobile emissions. The changes in maximum daily 8 h ozone concentrations and average exposure
potential at twelve air quality monitors in Texas were predicted on the basis of these changes in
NOx emissions. For all scenarios, at all monitors, the impact of changes in vehicular emissions,
rather than EGU emissions, dominated the ozone impact. In general, PHEVs lead to an
increase in ozone during nighttime hours (due to decreased scavenging from both vehicles
and EGU stacks) and a decrease in ozone during daytime hours. A few monitors showed a
larger increase in ozone for the convenience charging scenario versus the other two
scenarios. Additionally, cumulative ozone exposure results indicate that nighttime charging
is most likely to reduce a measure of ozone exposure potential versus the other two
scenarios.
