On October 14, 2023, the moon will pass between the sun and Earth, blocking up to 90% of the sun across parts of the United States. At its peak, this annular solar eclipse creates what looks like a “ring of fire” in the sky when the moon blocks all but the outer edge of the sun. What does this mean for our power grid?
The total solar eclipse that crossed through the United States in 2017, which blocked the entire sun from view along its peak path, had minimal impact. According to an analysis of the eclipse, natural gas and hydropower resources ramped up to compensate for the loss of solar energy generation. The pre-event analysis correctly predicted that, too.
But solar energy capacity in the United States is much higher now: according to the Energy Information Administration, the United States has 113 gigawatts (GW) of utility-scale and distributed solar generation capacity, which is about three times the U.S. solar energy capacity at the end of 2017. This increase means that the same eclipse event could interrupt more solar power generation today than in 2017.
The 2023 annular eclipse’s path will begin in Oregon and move southeast, ending in Texas. Along this path, the eclipse will last around two hours total, with peak coverage of the sun lasting between one and five minutes. This route happens to cross through a part of the country with high solar energy generation capacity: California, Nevada, Arizona, and Texas. While there are portions of California, Arizona and Nevada with fewer systems, the large swath of West Texas along the eclipse’s path has significant solar capacity. Areas surrounding the main path will also lose sunlight due to the eclipse, but to a lesser degree.
With solar energy accounting for about 5% of total energy generated in the United States in 2022 and about 20% in California, the 2023 eclipse shouldn’t have a major impact on electricity delivery. While we don’t know the exact amount of solar power generation that will be lost due to the eclipse, other generation sources like natural gas, geothermal, hydropower, and nuclear will offset the dip in solar power generation, just like with the 2017 eclipse. Grid operators will also be able to utilize storage and flexible load scheduling to ease the strain that lost solar capacity will have on the grid.
As we continue adding solar energy to the grid in an effort to decarbonize the power sector by 2035, the U.S. Department of Energy (DOE) Solar Energy Technologies Office (SETO) is working to strengthen grid resilience by funding research and development programs that help maintain power during disruptions like eclipses. Improving solar-plus-storage technology will enable more people to benefit from solar energy, even when the sun isn’t shining—even if just for a moment during an eclipse. Another innovative way to keep the lights on in the event of power interruptions is with microgrids, localized electric grids that can operate autonomously from the main grid. SETO is funding projects that investigate the automation of rapid energy restoration using microgrids in the face of service interruptions, which can also be applied to respond to eclipse conditions.