" will force almost all of the grid’s solar farms to stop generating electricity in the middle of the day. This is the first summer where Texas has needed renewables to meet peak demand, which is usually during daylight hours when the sun is strong, and then bring back-up generation (mostly in the form of natural gas) online to fill the resulting dip in solar output quickly at sunset. The eclipse will be a faster, midday version of this phenomen The sun will begin to darken at 10:15 a.m. US Central time and end by 1:40 p.m. The areas of greatest occlusion will be across a stretch from West Texas to the southeast part of the Gulf Coast, though the entire state will be impacted. At its peak, 76% to 90% of the sun will be obscured depending on the location. That will result in solar panels having only 13% of “clear sky capability” at the height of the eclipse at 11:50 a.m., an Ercot executive said during a stakeholder presentation Thursday. It’s an unprecedented challenge for the Texas grid, which has seen a surge of solar development over the last few years. Ercot currently has about 22 gigawatts of solar generating capacity, of which almost 13 gigawatts have been operating during the sunniest times of the day this week. Ercot is working with solar forecast vendors to create a special model for Oct. 14 so that it can be ready to rapidly bring back-up supply online during the event and then sharply curtail it once the eclipse passes. The grid operator expects to start sharing details about its plan on Oct. 5. The solar eclipse is a one-off but represents an acute challenge that grids can face on a daily basis when unexpectedly cloudy conditions can cause output from solar panels to plunge. This week’s near-miss was the most serious grid emergency since the Feb. 2021 winter storm that left millions of people in the dark for days and more than 200 dead. Those February days as well as some this summer have seen power plants tripping offline, creating tight conditions. The cause for Wednesday evening’s near-miss, however, was a lot more complicated and shows the challenges of handling a grid in transition. | 
