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As Renewable Portfolio Grows, Texas Becoming More Vulnerable to Curtailments: EIA

Renewable generation is growing quickly in Texas’ electric market, but the state is at risk of rising curtailments unless transmission resources also increase, according to the Department of Energy’s Energy Information Administration.

In A Case Study of Transmission Limits on Renewables Growth in Texas, the EIA projects that wind and solar generating capacity in the Electric Reliability Council of Texas region will double by 2035.

In a November 2022 study supporting the Public Utility Commission of Texas' proposed market reforms, the PUCT projected total variable renewable capacity additions in its base case scenario to be 33 gigawatts by 2035, with the vast majority coming from solar installations.

Over the past two years, solar capacity additions exceeded all competing alternatives, representing 46 percent of all additions from 2020 to 2022 compared with 37 percent for wind, 10 percent for battery storage, and 7 percent for natural gas.

In 2022, solar capacity represented about 5 percent of ERCOT’s generation, the EIA report said, adding that by 2024 Texas is projected to lead the nation in solar power growth, overtaking California.

Much of the growth in Texas’ solar power is occurring in the sparsely populated western region where daytime solar power complements the region’s abundant wind generation that is more productive in the evening and night.

In its analysis, EIA said it assumed there would be “no significant upgrades” made to the ERCOT transmission grid, which allowed the agency to isolate how the existing transmission system affects future renewable generation.

On days with more wind and solar generation and strong demand, limited transmission capacity restricted wind and solar generation flows and curtailments occurred, accounting for 36 percent of the projected curtailments in 2035, the EIA report found, adding that transmission-constraint curtailments could be reduced by upgrading the transmission system.

The EIA analysis also found that 64 percent of the wind and solar curtailments happened when the energy supply from high wind and solar resources outpaced low demand. An increase in demand, such as through battery charging, could potentially reduce those types of curtailments, the report found.

In 2022, ERCOT curtailed 5 percent of its total available wind generation and 9 percent of total available utility-scale solar generation. By 2035, however, the EIA projects wind curtailments in ERCOT could increase to 13 percent of total available wind generation, and solar curtailments could reach 19 percent.

“Understanding the source of the renewable curtailments is key to developing a long-term plan that not only includes renewable capacity, but one that seeks to maximize the value of renewable assets to the grid by investing in curtailment mitigation to support load-shifting programs or assets, ranging from time-of-use pricing to utility scale batteries,” the report concluded.

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