Cold-weather blackouts challenge conventional wisdom on reliability
One of the longstanding arguments against renewable energy like wind and solar is that it's not as reliable as conventional power plants. But the Christmas Eve rolling blackouts in North Carolina turned that conventional wisdom on its head.
Single-digit temperatures across the region froze instrumentation and sensing lines and caused other mechanical problems that reduced output at several of Duke Energy's gas- and coal-powered plants.
For the first time ever, the company was forced to use rolling power outages to manage an electricity shortage. About 500,000 customers across the Carolinas lost power at some point on the morning of Christmas Eve, some for hours.
"At a fundamental level, it highlights how extreme weather, due to climate change, increasingly calls into question the resilience of our existing infrastructure, including our electric power generation system, and the assumption that fossil fuel generation is reliable and is there when you need it," said David Neal, a senior attorney with the Southern Environmental Law Center.
Meanwhile, although solar energy was obviously not available overnight, it kicked in as the sun rose and performed as expected, with no outages, according to Duke Energy. In fact, Duke executives told regulators Tuesday that solar helped power the pumps needed to replenish the company's South Carolina hydroelectric reservoirs. That helped avoid more blackouts on Christmas Day.
Neal said Duke's experience during the blackouts shows that solar, combined with battery storage, "are going to be an important part of a resilient and cleaner electric grid going forward."
Duke doesn't currently have any wind power on its Carolinas grid. But Neal said that also should be a future option. "Offshore wind typically generates well in those early morning hours. So it would have been a great complementary resource to help meet that peak," he said.
Blackouts fuel the debate
But others see it differently. Since the blackouts, state Senate Majority Leader Paul Newton (R-Cabarrus) and the John Locke Foundation both have blamed the rolling blackouts on Gov. Roy Cooper's push for more renewable energy.
Newton, a former Duke Energy executive, said in a Dec. 30 interview with Spectrum News that solar energy "destabilizes the grid." Newton said he supports adding more nuclear energy, natural gas plants and gas pipelines.
"I have to remind people that our governor has fought every new natural gas pipeline that's been proposed for the state of North Carolina. That natural gas provides dispatchable reliable energy, very clean energy, and yet he fights those pipelines. And I'm telling you, it's coming back to haunt us," Newton said.
And writing in the North State Journal Thursday, Bradford Muller of Charlotte Pipe and Foundry said North Carolina shouldn't be so quick to close coal plants. Plant operating data during the blackouts "shows just how important those coal plants were to avoiding even more widespread and devastating blackouts during a generational freeze over the Christmas weekend. When North Carolinians needed energy most, it was nuclear, natural gas and those dreaded coal plants that held the grid together and provided the lion’s share of the electricity generation."
Their comments echo those by some public officials after major blackouts in Texas two years ago. A conservative think tank called the Texas Public Policy Foundation blamed those far more serious outages on too much renewable energy. Frozen wind turbines were a popular scapegoat.
"What happened in Texas was the most extreme example recently where that wasn't true. They hadn't sufficiently prepared a lot of that gas generation to function in extreme cold, and it failed," SELC's Neal said.
Republican Gov. Greg Abbott went on national TV to blame the Texas blackouts on wind and solar. But as my NPR colleague Camila Domonoske reported, Abbott ultimately acknowledged that all types of generation failed.
Meanwhile, a group called Conservatives for Clean Energy offered yet another idea this week: End Duke's monopoly control of the state's energy system and let other operators build their own power plants. They say the current system is too centralized and vulnerable to interruptions.
Frozen equipment hobbles fossil plants
On Tuesday, we got more information about the North Carolina blackouts. Duke Energy executives appeared before the North Carolina Utilities Commission to apologize and answer questions. They offered a timeline leading up to Christmas Eve and detailed what went wrong.
The company said its computer models underestimated demand as temperatures fell to the single digits early on the morning of Christmas Eve, Dec. 24. Those models predicted that Duke's electricity reserves would be enough to cover demand. Instead, demand was 6% higher in the Duke Energy Progress territory, which includes Asheville, Raleigh and eastern North Carolina. And it was 10% higher at Duke Energy Carolinas in central North Carolina, including Charlotte, Greensboro and Durham.
But it wasn't just bad forecasting. Equipment froze, and Duke lost generating capacity from coal- and gas-fired power plants just when it was needed most. Altogether, Duke lost about 10% of its capacity from Friday night to Saturday morning. Duke executives gave regulators this accounting:
- At around 10 p.m. Friday, frozen instrumentation at the gas-powered Dan River plant in Rockingham County cut production by 360 megawatts.
- Saturday around 2 a.m., frozen sensing lines caused a partial failure at one of four coal-fired units at the Roxboro plant, in Person County. Another 325 megawatts gone.
- Instruments froze just before 6 a.m. at the coal-fired Mayo plant, also in Person County, taking 350 megawatts of electricity off the grid.
- Around 8 a.m., frozen instrumentation lines knocked out 273 megawatts of capacity at the gas-fired Smith Energy Complex in Hamlet, in Richmond County.
- Two more units at Roxboro were knocked offline around 1 p.m. when a coal feeder failed, cutting another 685 megawatts.
- Power was lost briefly from a gas-fired unit in Lincoln County just before 5 a.m., though it was later restored as demand peaked.
- And Duke officials told regulators that operators had to trim output at the gas-fired Buck plant in Salisbury around 10 a.m. because of low gas pressure on the pipeline that feeds the plant.
As all of this was happening, Duke wasn't able to buy power from other states, because other power producers faced the same conditions. Operators were forced to begin rolling blackouts — which were made worse when the automated software that was supposed to turn customers’ power back on after 15 to 30 minutes failed as well.
Utilities Commission comments
Just days later, North Carolina regulators addressed the outages in their Dec. 30 Carbon Plan order. That plan, required by state law, is supposed to guide Duke Energy's transition to cleaner energy. (See "Q&A: NC regulators back Duke's 'all of the above' carbon plan") Regulators said the blackouts showed a need for "vigilance" in energy planning, but did not comment directly on problems with Duke's fossil fuel plants.
"The emergency outage events experienced by some Duke customers in late December of this year during extreme cold temperatures provides a sobering example of the consequences to customers during times of stress on the electric system and underscores the vigilance with which the Commission must act in overseeing the utilities’ planning efforts and implementation of the carbon dioxide emissions reductions to ensure that appropriate replacement generating units and associated transmission infrastructure are in service before existing generating units are retired."
To SELC's David Neal, the blackouts signaled the need for change in North Carolina's energy mix.
"The fact that Duke lost 1,300 megawatts of fossil generation at a period of its peak demand is troubling," Neal said.
"We're at a time where we need to think more broadly about reliability and resilience," Neal said. "And the idea that new gas plants are inherently reliable isn't just called into question because of their malfunctions in extreme cold, but because of the limited gas supply issues that were also an issue in the hearing."
Tyler Norris, a North Carolina solar industry executive, sees important lessons in the outages.
“Similar to Texas’ power crisis in 2021, Duke’s Christmas Eve blackouts demonstrated once again there is no reason to believe that renewables are more vulnerable to extreme weather than thermal plants, and may even be less vulnerable due to their broader distribution across the grid," he said. "Going forward, the deployment of more energy storage can help mitigate such blackouts while enabling greater utilization of clean, low-cost renewables for the benefit of ratepayers.”
Joel Porter, policy manager at the environmental group CleanAIRE NC, said we need to keep our eyes on the larger goal — climate change. Energy is the second largest source of heat-trapping pollution that causes global warming. Reducing emissions to avoid making things worse is crucial.
“We're going to have more extreme weather events because of climate change," Porter said. "And that's why we need a carbon plan that actually reduces emissions to ensure that we don't make things worse…I think the big question with this entire debate, with the energy transition debate, is not whether it should happen. We're past that point."
This story originally appeared in WFAE's weekly climate newsletter, published Thursdays.