Wind turbines are part of the Akuo Energy wind farm in Rocksprings, Texas. Credit: Edward A. Ornelas for the San Antonio Report

One of the biggest knocks against renewable wind and solar energy resources is their ability to only generate power when the sun is shining and the wind is blowing.

But in the vastness of Texas, it’s almost always either sunny or windy somewhere, according to a recent study by Rice University researchers. That makes the state a prime location for continued expansion of renewable energy that, along with relatively cheap natural gas, are already displacing coal.

“Texas is exceptionally well-positioned to have both incredible solar resources, as well as two very different parts of the state with very windy conditions,” said Dan Cohan, an associate professor of environmental engineering at Rice. “We really have three outstanding renewable energy resources that each have their own very different times when they produce most strongly.”

To gauge how reliable Texas wind and solar are and how they can best complement each other, Cohan and Rice student Joanna Slusarewicz looked at five wind and solar sites across the state. They estimated solar and wind energy production using data from the National Renewable Energy Laboratory.

Unsurprisingly, they found that solar produces vast amounts of energy during the heat of the day in summer. That’s also when Texans use the most power.

Last year, the state’s power grid operator, the Electric Reliability Council of Texas, or ERCOT, reported that electricity demand set new records in July.

Wind, by contrast, has a more variable pattern, depending on whether the wind farms are in West or South Texas.

West Texas currently hosts most of the state’s wind farms. There, wind tends to blow through the night, die down by late morning, and pick up again around 5 or 6 p.m. in the summer and winter, according the report.

But wind farms in South Texas produce energy on a different schedule. In summer, wind production there begins to increase around 1 p.m. and peaks around 6 p.m., outpacing West Texas wind. It peaks just as solar production starts to dip as the sun heads toward the horizon. This early evening spike is much less pronounced in winter.

West Texas wind so far has been the dominant renewable resource in the state. Last year, Texas got about 18 percent of its power from wind, most of it in West Texas, according to ERCOT figures, while less than 1 percent came from solar.

Cohan said their research shows that solar could supply a much greater share of the power Texans consume. So could South Texas wind, but to a lesser extent.

“If you had [more] solar or coastal wind, you could really cover more of those hours when the grid is straining toward its limits,” Cohan said.

Nearly 25 percent of ERCOT’s power in 2018 came from coal, even as power producers shut down four coal plants in Texas. Three belong to Vistra Energy subsidiary Luminant, with CPS Energy’s Deely plant being the fourth to cease operations.

“Coal plants are already reeling from competing with cheaper wind and [natural] gas,” Cohan said. Coal plants are having to ramp up and down much more than they used to during times when wind production is high and prices dip, he said.

“That’s how they’ve coped with competing with very cheap wind,” he said. “If you added in [more] solar to the grid, that would be cranking out power exactly at the times when the coal plants are operating now. Solar’s what really has the potential now to be the coal-killer.”

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Brendan Gibbons

Brendan Gibbons is a former senior reporter at the San Antonio Report. He is an environmental journalist for Oil & Gas Watch.