Intermittent wind power outran U.S. coal in April on “fleet capacity factor”—a measure of how much of the time the assets were generating electricity—even though the coal plants were supposedly designed to supply continuous base load power.
But while “seasonal trends, favourable conditions, and ever-improving technology all came together in April to help America’s wind turbine fleet spin past coal’s capacity factor,” Greentech Media reports, the achievement probably isn’t a harbinger of a major shift in the immediate future.
A graph comparing capacity factors for the U.S. wind and coal generating fleets since January 2013 clearly illustrates their reciprocal nature: when wind usage spikes with more of the fleet generating, coal declines as stations are idled, and vice versa. “That said,” Greentech notes, “coal’s capacity factor remains well above that of wind on an annual basis (52.7% versus 34.7% in 2016).”
Moreover, two easily overlooked factors may make it harder for wind to repeat its April feat very often. One is that older coal plants—the ones most likely to be idled for economic reasons—are increasingly being closed, and those that remain are more likely to be kept running. Another is that while technological advances have made it profitable to locate an expanding fleet of wind turbines in less ideal sites, those are also the locations where the turbines may run less often.