Soaring temperatures test electric grid in transition

By Jason Plautz | 07/10/2023 06:52 AM EDT

Blistering heat is pressuring power providers in Texas and beyond, but — so far — they have kept the lights on and air conditioners humming.

Workers repair a power line.

Workers repair a power line late last month in Houston. High temperatures in Texas are testing the state's power grid. David J. Phillip/AP Photo

As summer heat continues to scorch the nation, a key question is gaining urgency: Will the grid hold up?

So far, the electric system — including in Texas, the leading energy producer with a notoriously stressed grid — has kept power flowing even as wind and solar play increasingly important roles.

But with life-threatening temperatures hitting major cities this week and some of the year’s hottest weeks ahead, the power grid may be tested in new ways. Brutal weather patterns have helped set global highs for recorded heat and added a new pressure point for the U.S. grid amid its transition to cleaner sources such as intermittent renewables. How this summer unfolds will influence energy policy decisions at the state and federal level.


“As we look at the future power system, things are becoming much more complex,” said Jeff Dagle, chief electrical engineer at the Pacific Northwest National Laboratory. “If we retire facilities that can be started up and ramped up based on the needs of the system with generation resources that are not dispatchable like wind and solar, it becomes more complicated.”

The grid is being monitored closely after the North American Electric Reliability Corp. (NERC), the nation’s grid watchdog, warned before this summer that two-thirds of North America could face power shortages in extreme weather. Although the grid monitor said it expected no problems in normal weather, it also said a “heat dome” that sits across parts of the country could lead to emergencies in the Pacific Northwest, Sun Belt, Southeast and Texas.

NERC did not provide a comment Friday when asked about conditions this summer.

And although some areas — including parts of Oklahoma and East Texas — experienced power outages due to severe storms, there have been no reported widespread U.S. power outages this summer due to hot conditions or stretched demand from customers cranking up their air conditioning.

ISO New England Inc., a grid operator whose territory stretches across six Northeastern states, reported a capacity deficiency during evening peak hours last Wednesday due to a transmission equipment failure. But the grid operator did not have to implement rolling blackouts.

Representatives for the Midcontinent Independent System Operator Inc. and PJM Interconnection LLC — grid operators that oversee the Midwest and parts of the East Coast — said that conditions have been within their projections and that they have not experienced problems this summer.

Fueled in part by an El Niño weather pattern that causes temporary warming in parts of the Pacific Ocean, the Earth has been experiencing a record-breaking summer. Last week, the planet notched the hottest day ever recorded for four consecutive days. The average global temperature reached 63.01 degrees Fahrenheit on Thursday, according to the University of Maine and data from the National Centers for Environmental Prediction.

For this week alone, the National Weather Service has issued heat advisories for parts of Texas, New Mexico, California, Oregon and Florida. Parts of Arizona, Nevada and Southern California are under an excessive heat warning, which indicates that the maximum heat index temperature will be at least 105 degrees for at least two days and nighttime air temperatures will not drop below 75 degrees.

In Texas — where officials warned that blackouts were possible if demand rose beyond what could be provided from fossil fuel and nuclear plants — the lights have stayed on thanks in part to renewable energy.

According to data from the Electric Reliability Council of Texas (ERCOT) analyzed by the American Clean Power Association, renewable resources provided an average of 30 percent of electricity during the peak 10 percent of demand hours between June 19 and June 30. That’s a period that included the all-time demand record for ERCOT, the state’s primary grid operator.

“I think what we’ve learned is that solar can be a particularly reliable resource during these summer heat waves when you’d expect the sun to be shining,” said Lauren Shwisberg, a principal in the carbon-free electricity program for the energy think tank RMI. The fact that wind has also performed well during this stretch, Shwisberg added, shows that “a diverse, clean grid can be critical in periods like this.”

However, some experts have warned that a grid that leans too heavily on wind and solar without other measures could prove risky. While the sun may be concurrent with heat waves, solar panels don’t generate electricity at night. Wind is not guaranteed to be blowing at those times. Batteries that can store power from those sources and dispatch it hours or days later are not widespread enough in most places to play major roles for grid operators.

In fact, many grid operators say their most worrisome hours have shifted from the early evening — when people traditionally start coming home and turning on appliances — to later at night when solar generation has petered out for the day.

Texas’ ‘roulette wheel’

Texas has been ground zero for questions about the reliability of a renewable-heavy grid. The state’s competitive market and past hands-off focus on regulations have made it a hot market for wind and solar generation, which has dropped in price compared to other power sources. The U.S. Energy Information Administration said in February that Texas was projected to add 7,700 megawatts of solar capacity — the most in the nation — as well as 2,000 MW of wind in 2023.

Wind and solar make up nearly a quarter of ERCOT’s generation capacity, according to data from the Texas grid operator, accounting for more than 22,000 MW. One MW can power about 200 homes during periods of peak demand.

Experts have said that volume of renewables has shown its worth during the heat wave, especially with outages from traditional coal, gas and nuclear plants being higher than is typical.

At points during the June heat wave, ERCOT reported outages from all power sources ranging from 8,000 MW to 10,000 MW, including at a large nuclear plant and two large coal facilities. The grid operator has said that 11,000 MW of outages would be an “extreme scenario” under its summer planning scenario.

Michael Webber, a professor in energy resources at the University of Texas, Austin, cautioned that a “key risk” for the grid is whether the stress of running at high temperatures could lead to even more equipment failures.

“Just like your body can overheat if you exert yourself too long without giving yourself a chance to cool off, so can mechanical and electrical equipment, including the power plants themselves, substations, and transformers,” Webber said in an email.

While renewables have performed well in Texas, they also carry danger if heavy winds trail off or clouds roll in, according to Ed Hirs, an energy economist and lecturer at the University of Houston.

“We are more and more exposed to what I call the ERCOT weather roulette wheel,” Hirs said. “On that roulette wheel, the wedge for blackouts keeps getting larger.”

It’s a danger that Texas regulators warned about at the start of the summer.

Peter Lake — who led the state Public Utility Commission (PUC) for more than two years — said in a May press conference that Texans would have to rely on solar and wind being available during the hottest days.

“Our risk goes up as the sun goes down,” he said. Legislators this year passed a suite of bills designed to keep power plants fueled by natural gas and coal on the grid, including a new market design that rewards quick-start resources and a state-backed loan program for an emergency pool of gas plants.

Lake stepped down as chair of PUC in early June and has since left the commission.

In a statement to E&E News on Friday, ERCOT said it “expects sufficient generation to meet demand” this summer and does not anticipate any maintenance issues that would further limit supply.

The grid operator has also reported that it has drawn on a new ancillary service tool to manage grid uncertainty. The new tool allows ERCOT to purchase reserve power sources on the day-ahead market and dispatch it for a short time, including during evening hours when demand peaks.

Still, the outlook for Texas’ power system remains an open question as hot weather persists.

“The Texas grid is designed for heat, and we should be able to sustain this all summer,” said Thomas Overbye, director of the Smart Grid Center at Texas A&M University. “Moving forward, not just in Texas but in the country as a whole, we have some challenges ahead as we move away from the traditional fossil-based generation of the past and moving into one where we get a lot more energy from renewable resources. Texas is a leader in this, but it’s still going to be challenging going forward.”

Changing data

The scorching temperatures this summer may be just a preview. The World Meteorological Organization said in May that global temperatures are “likely to surge to record levels in the next five years” because of climate change and the natural El Niño event.

Those temperatures could put even more strain on the electricity grid without more innovation, said Dagle of the Pacific Northwest National Laboratory. Higher penetration of energy efficiency tools will lower demand, he said, while investments in long-duration energy storage can help the grid avoid outages from weather disruptions.

“I’m also a big believer in more data, better models and more sophisticated tools for long-duration planning,” Dagle said.

In the future, a grid operator may have to consider not just simple supply and demand metrics, he said. Conditions could also require balancing what kind of generation will be available at what times with other tools that may affect electricity demand. Better data, Dagle said, can “vastly improve” the short- and long-term models that planners rely on to better reflect the changing grid.

In the short term, however, many officials and regulators have looked to their existing fossil fuel infrastructure as a backstop. California Gov. Gavin Newsom (D), for example, enacted a controversial plan to keep natural gas plants open to avoid outages.

However, those plants can see stress during periods of extreme heat and can face supply problems.

A report released last month by Regenerate California, a coalition of environmental groups, found that gas plants did not meet performance expectations during a heat wave last summer, with an estimated 5,000 MW lost because of outages. The report calls for more investment in wind and geothermal energy to replace fossil fuels.

In a statement to E&E News, the California Energy Commission said it disagrees with the premise that the gas fleet didn’t perform. “Natural gas plants were critical to meet demand and maintain reliability during the heat wave last September when the grid needed them the most,” said spokesperson Lindsay Buckley.

“Despite the challenges we’re facing, the state remains committed to leading the fight against climate change by accelerating clean energy project development while taking necessary actions to ensure energy reliability,” Buckley said, adding that reserve resources “will not be used to meet daily load.”

RMI’s Shwisberg said this summer also serves as a reminder that “historic data is no longer sufficient to capture the extreme events we’re seeing.” Grid operators will need to integrate climate science and forecast for more abnormal situations.

And, she added, as summers get warmer, utilities will also have to help their customers adapt — while addressing the potential for outages in the process.

“Air conditioning is becoming more critical, so it’s also important to make sure people have home retrofits to make it run more efficiently,” Shwisberg said.