Does the addition of solar capacity on the grid cause an increase in air pollution? A North Carolina newspaper argues that it does.
Earlier this month, the North State Journal pointed to an air pollution application from Duke Energy for gas-fired power plants it operates in Goldsboro, North Carolina, as evidence that solar energy causes an increase in nitrogen oxide (NOx) emissions.
The Raleigh newspaper quoted Duke spokeswoman Kim Crawford as saying that reductions in carbon dioxide emissions also could be reversed if solar energy policies aren’t changed. Emissions go up, the article says, because solar energy is intermittent. When solar output drops, inefficient peaker plants fired by fossil fuels must be brought on line, but starting and stopping the plants reduces efficiency and thwarts emission control devices.
In fact, the article continues, more NOx is released into the atmosphere than would be the case if natural gas were used exclusively and solar energy was eliminated. It quotes Steve Gorham of the Heartland Institute, which does not accept climate science, as saying there’s “very little measured data” showing that renewables lead to lower greenhouse gas emissions.
According to an article detailing the dispute posted at E&E News, Duke Energy acknowledges that ramping power plants up and down does lead to more emissions. But a spokesman said conclusions reached by the newspaper were wrong.
“We just need to note that in our air permits for the units,” spokesman Randy Wheeless said of the utility’s March application to North Carolina authorities, “To take that and stay, ‘Renewable energy causes more pollution,’ that’s faulty. That’s like saying an [electric vehicle] is bad because your electric costs go up, not noting that you saved money on gas.”
Costra Samaras, an associate professor of civil and environmental engineering at Carnegie Mellon, also rebutted the newspaper’s argument. He told E&E News, “Increased cycling for many types of fossil generators will affect the pollutant emissions. Is that more emissions than just turning off solar and running gas all of the time? I doubt it.”
The connection between more solar deployment and increased greenhouse gas emissions have been raised before. But a 2013 study from the National Renewable Energy Laboratory found that carbon emissions caused by more frequent cycling of power plants running on fossil fuels are “negligible.”
North Carolina is second only to California in the amount of solar capacity currently online. In California, greenhouse gas emissions have been falling for the past 15 years, due to modern natural gas plants and a flexible, real-time market system for energy. Older, less efficient plants have been retired because they cost too much to operate. In North Carolina, where monopolies rather than an independent agency operate the grid, older power plants are kept online until they are paid off.
-Scott Gibson is a contributing writer at Green Building Advisor and Fine Homebuilding magazine.