Renewable Energy Cuts Emissions Even If Fossil Power Plants Have to Cycle More

It’s a concern as old as renewable energy itself: What do you do when the sun don’t shine and the wind don’t blow? On a beautiful breezy day, your renewable farm is twirling the dial back on your electric meter, but in the dead of winter, you’re drawing from the grid like anyone else, going from an energy creator to consumer in a stretch of dead wind, and relying on the power plants you hoped to put out of business.

And for a long time, the idea of powering up those old power plants was a knock on renewable energy. Skeptics thought that whatever upside there was in renewables was negated by “cycling” the power plants, something that there is, so far, no way to work around.

But a new study released by the US Energy Department found that, in actuality, cycling power plants didn’t totally negate the impact of renewable energy. On the contrary, the study found “that the carbon emissions induced by more frequent cycling are negligible (<0.2%) compared with the carbon reductions achieved through the wind and solar power generation evaluated in the study.” Those carbon reductions were found to be as dramatic as 29 to 34 percent across the Western grid.

Still, cycling speeds up the pace at which equipment wears down, which adds cost to the fossil or nuclear power plant operators. However, the additional cycling required by more renewable energy only increases operating costs for the average fossil fuel power plant by 2 to 5 percent. On the other hand, the whole system would be somewhat relieved. “High levels of wind and solar power would reduce fossil fuel costs by approximately $7 billion per year across the West, while incurring cycling costs of $35 million to $157 million per year” the study stated. That’s $7 billion with a “b.”

Even in the golden, smog-inducing days without renewable energy, power plants have always been cycling up and down as power demand ebbs and flows. In order to see how much the additional cycling would cost power plant operators, and to test for environmental impact, the Energy Department's National Renewable Energy Laboratory designed five hypothetical scenarios that imagined as much as a whole quarter of the power in the Western grid coming from renewables.

"Adding wind and solar to the grid greatly reduces the amount of fossil fuel—and associated emissions—that would have been burned to provide power,” Debra Lew, NREL project manager for the study, said. “Our high wind and solar scenarios, in which one-fourth of the energy in the entire western grid would come from these sources, reduced the carbon footprint of the western grid by about one-third. Cycling induces some inefficiencies, but the carbon emission reduction is impacted by much less than 1 percent.”

The biggest variable for renewable energy is also the most predictable—namely, the rising and setting of the sun. Variations in weather are usually fairly easy to predict, save for fast-moving clouds, but the report finds that swift moving clouds leave as quickly as they come.

So if you’ve been eager to embrace renewables, but are worried about the impact of cycling the current power plants, don’t worry. It works out well for consumers on a number of levels. It’s just not great for people who are selling coal.