- The solar eclipse on April 8 will affect solar power generation.
- In the US, the path of totality will span from Texas to Maine but other states will be affected.
- The growth in solar power means the impact will be about three times higher than the 2017 eclipse.
On April 8, millions of people plan to put on a pair of eclipse glasses and watch as the moon crosses in front of the sun. While the event will affect solar power generation, everyone's lights should still be on when they go back inside.
In the US, the path of totality — where the moon will appear to fully block the sun — will stretch from Texas to Maine. However, electricity providers in other states with lots of solar energy also need to have power reserves ready, Barry Mather, an engineer with the National Renewable Energy Laboratory, told Business Insider.
"This eclipse actually is going to impact solar generation across the entire North American continent, practically," he said. As the moon shades the sun, it will diminish the amount of sunlight that solar panels receive.
However, because we can precisely predict where and when the eclipse will be, that means utilities can plan around them to avoid blackouts.
"I fully expect that we're all prepared for this," Mather said.
There's more solar power in the US than in 2017
There are quite a few reasons this year's eclipse will be different from others in the past.
The 2017 total solar eclipse in the US had a completely different path of totality than this year's, moving from Oregon to South Carolina in the US. The country also started generating about three times as much solar power in the past seven years, Mather said.
"The market is just growing very quickly," he said, "so the impact's going to be about three times as high as it was in 2017."
However, Mather said there was very little battery energy storage during the last eclipse. "We still don't have a ton, but we do have some," he said.
To make up for the decrease in solar power, utilities will have to turn to other sources.
There shouldn't be blackouts
On any given day, utilities have already planned the amount of power they'll generate and where it will come from 10 days in advance, Mather said. Eclipse days are no different.
"One thing that we're doing here at NREL is actually working with a number of the entities that are most impacted by the eclipse," Mather said.
As the day draws closer, changing weather forecasts may alter the plans a bit. If it will be cloudy, the solar generation won't be as affected, for example.
One way utilities are preparing is by planning to carry more reserves, or extra generation that's online and ready to provide extra power when necessary, Mather said.
"We actually saw this in the 2017 eclipse, specifically in California," he said. The state has a lot of solar power.
"So when the power does start to fall off because the solar starts to decrease, there's very little disturbance to the grid in terms of frequency, voltage, all those sorts of metrics that we track as power system engineers," he said.
The reserves typically use less-green energy sources, like coal or natural gas.
The eclipse will impact California, Alaska, and other places outside the path of totality
Many eyes will be on the skies in Texas, where populated cities like San Antonio, Austin, and Dallas are in the path of totality. It's also a state with a lot of solar power and its own grid.
"In Texas, our estimations are that we will drop something like 14 gigawatts," Mather said. Just 1 gigawatt is enough to power 100 million LED bulbs, according to the Office of Energy Efficiency & Renewable Energy.
The eclipse looks fairly quick to humans, only taking a few minutes for the moon to pass by the sun. For solar panels, it's different, Mather said. Less intense sunlight will shine on the panels for longer than three to five minutes.
"The sun starts being occluded an hour or even more before the total eclipse happens," he said.
And the weaker sunlight will affect California and other states with solar panels.
Though it's far from the path of totality, Mather said, "the generation in San Diego, for instance, will still drop off by 50% or somewhere around there."
"There's so much focus on that path of totality, which I have no doubt is a very cool thing to experience as a human," he said. "But from a power system standpoint, it really is a nationwide impact that we will see."