By Amanda Durish Cook

CARMEL, Ind. — ‎While MISO officials were unsurprised that the Aug. 21 solar eclipse did not impact Midwestern grid operations, they do say an increase in solar capacity will complicate matters by the next total eclipse in 2024.

MISO Communications Director Jay Hermacinski on Tuesday said the RTO will study eclipse impacts over the next few weeks and request data from CAISO, a grid operator that was “truly” impacted by the eclipse. (See Grid Operators Manage Solar Eclipse.)

All of MISO’s footprint fell within the 80 to 100% eclipse band, and Hermacinski said the footprint’s solar generation reacted “as predicted.” Grid-scale solar output dropped 100 MW during the eclipse, plunging to a nearly zero output during the peak and picking back up to about 40 MW around 3 p.m.

Hermacinski said that MISO operators had no problem meeting demand with stifled solar output.

“Our portfolio looked like it always does. We did not have to do anything special or bring on additional generation,” he said during an Aug. 22 Informational Forum. “Quite frankly, our operators prepared for the solar eclipse as if it were any other day. … We did not expect the eclipse to have an impact on our grid operations, and it did not.”

However, storms in the Upper Midwest and cooler-than-expected systemwide temperatures that day cut load, and MISO load dropped by 2 GW during the eclipse window.

“What we didn’t expect was the number of pop-up storms in the MISO region that brought about a 5- to 8-degree drop in temperature,” Hermacinski said.

MISO will use CAISO’s data to complement its own to help prepare for the next solar eclipse in April 2024, which will cut a path of totality from southwest Mexico to the northeastern U.S., putting the RTO’s Carmel, Ind., headquarters in the direct path. By that time, MISO is expected to have an additional 13.5 GW of grid-connected solar generation participating in its market, an amount exceeding that participating in the CAISO market today. MISO currently has about 180 MW of utility-scale solar and 350 MW of distributed solar in its footprint.

“MISO will be in a much different position in 2024 in terms of solar capacity than it is today,” Hermacinski said. A partial solar eclipse occurring in October 2023 will serve as a practice run before the 2024 event, he added.