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While Texas Lawmakers Target Renewables, The State's 'Thermal Fleet' Threatens Grid Stability Yet Again

The control room at the Electric Reliability Council of Texas, the state's grid operator.
Julia Reihs
The control room at the Electric Reliability Council of Texas, the state's grid operator.

Two months after blackouts gripped the state, killing hundreds, the Electric Reliability Council of Texas again warned of a possible energy emergency on the state grid Tuesday.

ERCOT, the state’s grid operator, said slightly warmer-than-expected weather was part of the problem. The modestly higher temperatures pushed electricity demand above what was expected and forced ERCOT to call on consumers to conserve.

But Dan Cohan is not buying that explanation.

Tuesday “should have been a very easy day for ERCOT to meet,” said Cohan, a professor of environmental engineering at Rice University. “Demand was only 49 gigawatts. They expect the peak in the spring to be 65 gigawatts, in the summer to hit 80.”

The real problem facing the grid, he said, was insufficient electricity supply. Drawing from U.S. Energy Information Administration data, Cohan said he thinks he knows where things went wrong.

“One of the state's four nuclear reactors is down, and about 40 percent of our coal capacity is down, but the majority of the power capacity that's down is coming from our gas power plants,” he said.

These generators comprise what analysts often call Texas' "thermal fleet" of power plants.

Spring is a normal time of year for them to undergo routine maintenance. In a press conference Tuesday evening, ERCOT described the outages as fairly typical for this time of year.

This is typically the time of year where we allow a lot of maintenance outages for units that are getting ready for the summer," said Woody Rickerson, vice president of grid planning and operations at ERCOT.

“There are currently about 32,000 megawatts of outages on the system, maintenance outages," he later said," and that's not an abnormal number for this time of year."

But analysts, and even ERCOT’s own data, show that’s not true.

The number of power plant outages this spring is "higher than we've seen in previous years," said Joshua Rhodes, a research associate at UT's Webber Energy Group.

A graph shared at ERCOT's Tuesday board meeting also showed increased power plant outages due to system growth and maintenance from February's winter storm.

The reason why so many power plants have been offline remains opaque. ERCOT concedes that some generators and transmission infrastructure is still in need of repairs as a result of February’s storm and blackout.

But, again, ERCOT’s Rickerson said that was not a main factor for Tuesday’s near-miss on the grid.

That leaves the possibility that ERCOT simply allowed too many power plants to go offline for routine repairs at the same time. The grid operator says it automatically approves power plant outage requests it receives 45 days ahead of time.

“We really need more clarity on how much of this is repairs to plants that were damaged in February, and that might not be done for a while, and how much of this is poor planning of allowing scheduled maintenance to happen all at once,” Cohan said.

This legislative session Texas lawmakers have blamed renewable energy for recent instability of the ERCOT grid, including February's blackouts.

They’ve proposed added fees on renewable energy sources and bans on local efforts to transition away from fossil fuels. Their argument is that gas, coal and nuclear is “firm” power, available any time. It is not intermittent like renewables are.

But Cohan points out that it was exactly those “firm” sources that have now failed the state twice in two months. First, when gas power plants and distribution infrastructure broke down in the winter storm, and again this month.

“Sure, it's not sunny all the time, it's not windy all the time," he said. “But what we're dealing with now is that we have nearly half of our supposedly firm and reliable resources, our gas, our coal and our nuclear, down all at the same time. That's making it hard for ERCOT to meet even very modest levels of demand under very mild weather.”

“I shudder to think what things would be [like] if we were actually having a heat wave,” he said.

Mose Buchele focuses on energy and environmental reporting at KUT. Got a tip? Email him at Follow him on Twitter @mosebuchele.
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