Extreme heat and the threat of looming blackouts are putting the nation’s power grid under special scrutiny, with many blaming the major transformation from traditional to renewable resources for the reliability problems.
Peaking electricity demand and slim reserve margins are behind the power crunch straining grids across Texas and swaths of the country. Many, especially Republicans in Congress and fossil fuel interests, are assigning blame to the aggressive campaign to displace legacy coal-fired plants or other sources, such as natural gas, with “intermittent” or variable sources, especially wind and solar.
Meanwhile, renewables’ defenders argue the shift isn’t happening quickly enough and that utilities and grid operators are still overrelying on traditional resources that have their own vulnerabilities to outages — as Texas saw firsthand with the failure of its natural gas system during Winter Storm Uri in February 2021.
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How is the grid changing?
Renewable sources are responsible for an increasing share of electricity generation within the nation’s grids as the power sector works to reduce greenhouse gas emissions, especially by shutting down coal-fired power plants, and retires carbon-free but otherwise aging resources such as nuclear plants.
The U.S. bulk power system has reduced its on-peak capacity of coal by 98.7 gigawatts over the past 10 years, according to the North American Electric Reliability Corporation, which sets reliability standards and regulates the nation’s power grid.
Over the same period, it added 77 GW of natural gas, 11.7 GW of wind, and 25.2 GW of solar photovoltaic generation on-peak capacity.
Wind power generation in particular has skyrocketed since 2005, from accounting for less than 1% of total electricity generation to 9.2% in 2021.
What are renewables’ limits?
As variable resources, wind and solar are reliant on the weather to generate electricity. Generators cannot be turned on and off in the way that a coal- or gas-fired plant can.
NERC laid out renewables’ limitations in its 2022 State of Reliability report, a look back at grid performance in 2021, which was released on Wednesday. It noted that wind and solar boost overall capacity but often do not contribute as much to capacity during peak demand as conventional sources.
NERC also concluded that “natural-gas-fired generation will remain a necessary balancing resource to provide increasing flexibility needs” until storage technology for renewable sources can be deployed at scale.
In Texas, where wind power makes up nearly 28% of installed generation capacity, reliability problems have been front and center of this debate over grid makeup ever since last year’s winter storm, which led to the largest outage event in U.S. history and resulted in the deaths of 246 people.
In the face of record heat this summer, Texas’s grid operator, the Electric Reliability Council of Texas, has faced strain of a different nature. Electricity demand has risen to new records on high temperatures, and although blackouts have been avoided, ERCOT has been forced to ask customers to reduce their use of appliances and air conditioners during peak demand hours.
Texas’s first “conservation appeal” of the summer was informed by forecasts that, while solar power and dispatchable resources were forecast to perform above 80% at peak demand time, wind would perform at just 8% of installed capacity.
Political critics blamed wind for failing to carry its load, while John Moura, director of reliability assessment and performance analysis at the nonpartisan NERC, said that where Texas’s grid reliability is concerned, “fortunate wind” is increasingly the deciding factor.
“The determination of whether or not Texas is short on resources is largely dependent on the amount of wind available for that area,” Moura said Wednesday.
Still, renewables’ defenders have said that it’s not that wind is coming up short — in fact, it’s performing as expected in triple-digit conditions, and the energy shortfalls should have been foreseen and prevented by other means.
“The observation that I’m seeing most often is that wind doesn’t blow hard on a hot afternoon,” Mark Dyson, manager of carbon-free electricity with green energy research group RMI, told the Washington Examiner. “My response is: Of course it doesn’t, and we know that.”
Dyson analogized grid reliability to a team sport, comparing wind generation’s role to that of a soccer goalie.
“Criticizing the wind for being slow on an afternoon is like criticizing a soccer goalie for not scoring goals,” he said, “but of course, that’s not the goalie’s job. … You’re kind of ascribing the failure of the team to one player on the team, but that player’s job is not to score the goals.”
What’s responsible for reliability problems?
In multiple reports over the past few years, NERC emphasized that extreme weather and climate change have been at the heart of the vulnerabilities within power systems for both driving demand upward and disrupting infrastructure.
“We’ve seen, year after year, extreme weather leading to increased reliability impacts,” Moura said Wednesday.
Extreme weather events affect reliability by increasing demand but also by triggering outages and shutting down resources. Those extreme conditions have affected renewables and traditional energy sources.
During the 2021 storm that battered Texas, some 27% of outages were wind generators, but more than half were natural-gas fired units.
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At the same time, Moura, NERC, and grid operators themselves have said the shift away from coal and toward renewable energy has hurt reliability.
The Midcontinent Independent System Operator, which oversees grid operations in all or parts of Manitoba and 15 U.S. states from Minnesota down to Louisiana, said in an April report that retirements of “always-on” generating units like coal plants have contributed to its reliability difficulties.
MISO is the only grid operator deemed by NERC to be at a “high” risk level this summer for experiencing insufficient operating reserves even in normal peak conditions.
“As we retire power plants, and don’t replace them with comparable energy resources, we can expect riskier conditions … so we’re going to need to adapt the grid, something that looks very different than our grandfathers’ version,” Moura said.
