Plug-In Hybrids and Ozone

U of Texas study finds the overall impact of PHEV use on air quality is more varied and complicated than previously thought.

Published: 06-Feb-2009

Replacing just 20% of ordinary vehicles with plug-in hybrid electric vehicles (PHEVs) could help reduce levels of atmospheric ozone in certain cities. But the result, from researchers at the University of Texas, US, also shows that the overall impact of PHEV use on air quality is more varied and complicated than previously thought.

In their paper, Air quality impacts of using overnight electricity generation to charge plug-in hybrid electric vehicles for daytime use, the researchers found that ozone is a secondary pollutant formed by the reactions between volatile organic compounds (VOCs) and nitrogen oxides (NOx) from vehicle emissions in the presence of sunlight. Despite more than 30 years of emissions reductions, some of the more densely populated regions of the US still fail to reach the National Ambient Air Quality Standards (NAAQS) for ozone. The US Environmental Protection Agency recently proposed lowering the maximum 8 hour concentration of ozone from 84 to 75 ppb, so meeting the NAAQS will continue to be a challenge.

Using a regional photochemical model, Michael Webber and colleagues studied how the air quality in the area served by the Pennsylvania–New Jersey–Maryland electric grid would change if 20% of gasoline-powered light duty vehicles, such as cars and trucks, were replaced with PHEVs. In the scenario, the PHEVs would only be used during the day and would be recharged at night using electricity from the grid.


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