Adjusting electricity generation to avoid exceedances of the ozone air quality standard

Periods of high ozone may cause a region to be in nonattainment of the NAAQS. Some of these high ozone episodes may be attributed to high levels of NO_x, an ozone precursor. The largest point sources of this NO_x include electrical generation units (EGUs). A dynamic system in which daily air quality forecasts are used to inform electrical dispatch models in an attempt to avoid violations of the daily ozone NAAQS is described. The electrical dispatch models would power down or reduce output of EGUs that influence the high ozone, shifting generation elsewhere. The local sensitivity of ozone to individual EGU facility emissions is examined using the direct decoupled method (DDM) of sensitivity analysis in the Comprehensive Air Quality Model with Extensions (CAMx). For the modeled day of 8/4/2005, the maximum first-order ozone sensitivity to NO_x emissions from a single nearby coal-fired power plant (CFPP) source was ∼1 ppb over Pittsburgh, PA. Modeled DDM sensitivities of ozone to the NO_x emissions vary over time on this day while the net effect of all CFPP emissions was an increase in ozone. Overall, plants closer to the region of interest were associated with higher sensitivities while the effects of emissions farther away were lower, even as this effect was not linear. This is an abstract of a paper presented at the 106th AWMA Annual Conference and Exhibition (Chicago, IL 6/25-28/2013).