The potential for avoided emissions from photovoltaic electricity in the United States

This study evaluates avoided emissions potential of CO2, SO2 and NOx assuming a 10% penetration level of photovoltaics (PV) in ten selected U.S. states. We estimate avoided emissions using an hourly energy system simulation model, EnergyPLAN. Avoided emissions vary significantly across the country−mainly due to three state-specific factors: the existing resource mix of power plants (power grid fuel mix), the emission intensity of existing fossil fuel power plants and the PV capacity factor within each state. The avoided emissions per solar PV capacity (g/W)—for ten U.S. states—ranged from 670 to 1500 for CO2, 0.01–7.80 for SO2 and 0.25–2.40 for NOx. In general, avoided emissions are likely to be higher in locations with 1) higher share of coal plants; 2) higher emission of existing fossil fuel plants; and 3) higher PV capacity factor. To further illustrate the quantitative relationship between avoided emissions and the three state-specific factors, we conducted a sensitivity analysis. Finally, we estimated the change in avoided emissions in a coal-intensive state by varying the operational constraints of fossil-fuel power plants. At the 10% penetration level avoided emissions were not constrained by the ramp rate limitations, but the minimum capacity requirement significantly affected the avoided emission estimates.