GRANBURY — This is what modern reliability looks like on the Texas grid.
A 240-acre industrial site, along a bend of the Brazos River an hour’s drive southwest of Fort Worth, brings together old-school fossil fuels and the latest in renewables.
A natural gas power plant and a storage battery system work side by side, usually to meet the ever-rising demand for electricity in Texas. There’s also a week’s worth of backup diesel fuel on site, just in case.
The DeCordova facility, owned by Irving-based Vistra Corp., the state’s largest power provider, has been generating electricity since 1975.
The original gas steam plant was replaced with four combustion turbines in 1990. They got a major upgrade four years ago, enabling Vistra to fire up the gas units and generate full loads within 10 minutes.
Need a faster response? The storage batteries next door can turn on instantly and feed about 260 megawatts into the grid — providing enough power to cool 52,000 homes during peak conditions.
Vistra spent just over $125 million on the batteries, which came online in May. The system includes 22,360 battery modules housed in 86 air-conditioned shipping containers that seem to stretch on and on.
It’s the largest energy storage system in the state, the company said, and the first to be paired with a natural gas “peaker” plant that’s designed to come on during periods of high demand.
“We decided to make the investment in reliability and resiliency,” said Claudia Morrow, Vistra’s senior vice president of development.
Reliability has become the catchword for Texas’ electric industry since February 2021. That’s when a brutal winter storm shut down much of the grid for days, cutting off power to millions and leading to hundreds of deaths.
Since the catastrophic event, state leaders have put reliability first, ahead of simply creating more cheap power.
They overhauled the regulatory agencies, including the Public Utility Commission and the grid operator it oversees, the Electric Reliability Council of Texas, known as ERCOT.
Regulators have taken many steps to ensure the lights stay on, from requiring more reserves on the grid to ordering gas and coal plants to delay maintenance so they can remain online.
So far, the approach is working, despite many days of record demand driven by high temperatures and strong population growth.
But most agree that Texas needs a longer-term solution, a more lasting way to strengthen the grid.
And batteries are a key part of the equation, Morrow said, both for meeting peak demand and pushing the state ahead in the transition to cleaner energy.
In the past five years, Texas has attracted a lot of new generation, primarily in wind and solar power. That’s good for the environment and consumers’ pocketbook but risky for the grid.
If the wind isn’t blowing or clouds cover much of the state, the assets don’t deliver close to their capacity. When that happens during tight conditions, additional power must be dispatched quickly to avoid the chance of rolling blackouts.
Plants like Vistra’s gas peaker are some of the first options. At precisely noon on a recent Friday, three gas units simultaneously whirred to life, as they have for most of the hot summer.
Later, typically at around 4 p.m. to 5 p.m., the batteries kick in instantly — often as demand approaches the daily high and the batteries’ one hour of power is most essential.
How often are DeCordova batteries being deployed? “With this summer, it’s been every day,” Morrow said.
The battery system has made an impression on even veteran workers, said plant supervisor Tyler Wensel. “It just responds to changes in the grid immediately,” he said. “We’re amazed by it.”
Last year, battery storage capacity nationwide more than tripled, according to the U.S. Energy Information Administration. Storage capacity on ERCOT rose in a similar fashion and is on pace to surge again in 2022 and ‘23.
By next year, batteries are projected to add 8,372 megawatts to the ERCOT grid, enough power for 1.7 million Texas homes during peak conditions.
The biggest drawback is that they usually last only an hour. Vistra typically recharges the batteries at night when wind power is plentiful and cheap, and it sells the battery power when demand is high — and so are prices.
In Texas’ competitive electric market, generators are paid only for power sold into the grid, and generators decide whether the going rate is sufficient to turn on the machines.
Vistra’s natural gas units can run as long as there’s fuel, assuming it makes economic sense to start up for a limited time.
A quick-starting gas plant and batteries that can deliver instantly are a good combination to help fortify the grid, said Joshua Rhodes, a researcher and energy expert at the University of Texas at Austin.
“That’s one way of adding firm capacity to the system, and it makes for a nice reliability product,” Rhodes said.
It’s especially valuable in late afternoons when wind is low: “We do need something — something firm — to be able to step in and turn on during those times,” Rhodes said.
Vistra owns about 18% of capacity on ERCOT, more than any generator. At times, such as during the 2021 winter storm, Vistra provided an even larger share of power to Texas.
The company has about 60 active and retired generation sites in 12 states, including here. And it’s repurposing assets and co-locating renewables as part of a broader push to clean energy.
In September 2020, Vistra unveiled an ambitious plan to reduce its carbon footprint, led by a commitment to build seven zero-carbon projects in Texas.
Vistra said it would spend $850 million to add nearly 1,000 megawatts of clean energy to the ERCOT grid.
Three Texas projects came online this summer: solar plants in Live Oak and Crane counties and the DeCordova battery system.
Jim Burke, a longtime Vistra executive who became CEO this month, said the company was excited about what’s in the pipeline and the growth potential of clean energy.
Vistra aims to more than double its zero-carbon generation by 2026, including many storage batteries, which are getting a boost from tax credits in a climate bill recently approved by Congress.
“But we are also going to remain disciplined on the projects,” Burke said in an earnings call on Aug. 5.
He discussed the challenges of attracting more dispatchable generation to Texas’ market, especially natural gas plants. Regulators are redesigning ERCOT’s market scheme, and he said they must figure out how to incentivize new construction while also retaining existing fossil-fuel plants.
That hasn’t happened yet, he said, but Vistra could consider adding a natural gas plant at some point.
“Potentially with market reform, that might be something that would work,” Burke told analysts.
Whatever the details, Burke was clear about the ultimate goal: “We believe that there needs to be a focus on reliability,” he said.
That’s more complicated than it sounds.
“There’s nothing specifically in the market that says, ‘Thou shalt provide reliability at this price,’” said Michelle Michot Foss, a fellow at Rice University’s Baker Institute for Public Policy.
While Texas needs more natural gas plants, she would like to see generators use their assets to win over demanding customers. Market forces, she said, are more effective than mandates
Vistra’s DeCordova facility has plenty of controllable, dispatchable generation — a quick-starting gas plant with backup fuel plus a battery system to provide additional power.
Put ‘em all together and sell the package, Foss said: “It’s the most reliable thing you can offer a customer.”
AT A GLANCE: The DeCordova site
What: A hybrid electricity site combining fossil fuels and renewables — a natural gas power plant and the state’s largest battery storage system.
Where: Located an hour’s drive southwest of downtown Fort Worth.
Capacity: Both the gas plant and storage batteries can generate about 260 megawatts each. That’s enough power for 52,000 homes during peak conditions.
Duration: Batteries can run for one hour and are usually recharged overnight when wind power is cheap. The gas plant can run as long as needed if fuel is available.
Dispatchable: Batteries can turn on instantly and feed current into the grid. It takes about 10 minutes for the gas units to fire up and generate power at full load.
Repurposing: A natural gas steam plant was built on the site in 1975. It was replaced by four natural gas combustion turbines in 1990. More than 3,000 battery modules came online in May.
Extra reliability: Two on-site storage tanks hold enough diesel fuel to run the gas plant for seven days if natural gas flows are interrupted.
Ownership: Irving-based Vistra Corp.
SOURCE: Vistra Corp.
Correction: An earlier version of this story said DeCordova batteries could generate 26,000 megawatts. They can generate 260 megawatts.