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What does the solar eclipse mean for solar power?

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August 15, 2017
Jessica Wells
illumination Staff Writer
August 1, 2017


When the Great American Eclipse glides over the country on Aug. 21, the moon will block more than 90 percent of the Carolinas' sunshine. That much darkness presents a first-of-its-kind puzzle for the Duke Energy employees managing solar energy.

Solar energy production will dramatically decrease as demand for lighting increases in North Carolina while the sun hides behind the moon from about 1 to 3 p.m. This is normally a peak time for solar energy production, and Sammy Roberts, Duke Energy director of system operations, estimates solar energy output will drop from about 2,500 megawatts to 200 megawatts in 1 1/2 hours.

This will be the United States’ first coast-to-coast solar eclipse since 1918 and the first to affect the solar energy supply in North Carolina. So, what does that mean for the grid?

Just as punching the gas pedal to climb a steep hill is tough on a car, dramatic shifts in energy supply or demand are challenging for the grid. But unlike a car, which has a gas tank, the grid doesn’t have an effective way to store large amounts of energy. Energy production must mirror customer demand at any moment.

System operators are constantly monitoring demand and making decisions about what source – natural gas, solar, nuclear, hydropower, coal, wind, etc.– is the most efficient for that moment.

Because of its flexibility, operators will have natural gas plants ready to step in during the eclipse. In addition to replacing the lost energy with a flexible fuel source, operators can gradually decrease solar production before the sky darkens depending on weather conditions, Roberts said, which would allow them to slowly increase natural gas energy production. In other words, they will gently press rather than punch the gas pedal.

North Carolina might not be the first state that comes to mind when you hear solar, but it is home to more solar power than any state except for California. On a sunny day, North Carolina’s panels can produce enough energy to power nearly 600,000 homes.

Duke Energy manages energy from more than three quarters of the roughly 3,200 megawatts of solar power in North Carolina, but because it has a diverse mix of energy sources and a plan in place, Roberts said the company expects to meet customer demand during the eclipse.  

For Full Story: https://illumination.duke-energy.com/articles/what-does-the-solar-eclipse-mean-for-solar-power