A lot has changed since America last experienced a total solar eclipse in February 1979. For one thing, America’s solar industry has grown at an average annual rate of 68% over the past decade.
Now that we use the sun to generate as much as 10% of the nation’s electricity, what will happen to our grid during the eclipse?
The Effects of a Solar Eclipse
The U.S. electric grid will experience a sudden loss of solar power and a solar rush when it comes back on. Grid operators have been carefully preparing for this event.
On the day of the eclipse, the U.S. will miss out on the sunlight needed to power around 1,900 utility-scale solar photovoltaic (PV) power plants. The vast majority of those plants won’t be in the path of totality though, and the loss of sunlight will impact them to varying degrees depending on their location.
Just 17 plants are in the path of totality and will lose all of their sunlight. A few hundred facilities, totaling about 4 gigawatts of capacity, will lose 90% of their sunlight. Plants with a total capacity of around 2.2 gigawatts will lose about 80% and about 3.9 gigawatts of capacity will lose around 70%.
It will take approximately 90 minutes for the total eclipse to move across the entire path of totality, which stretches from Oregon to South Carolina. In areas on this path, the sun will be completely blocked out for up to three minutes. The entire eclipse event is expected to take around three minutes.
Preparing for the Big Event
The main influence the solar eclipse will have is on solar panel efficiency. On a regular day, panel design, positioning, angle, temperature and shade are all factors into how efficient solar panels convert energy. The solar eclipse will have a similar effect as shade. Experts note that even a small shaded are can significantly reduce the output of the whole system. Because the solar eclipse will reduce the amount of total sunlight, it’s important for the energy industry to prepare.
To keep the electric grid providing service constantly, operators work 24/7 managing the flow of power. The amount of power flowing into the grid needs to be kept close to the amount that consumers are using. If the ratio becomes unbalanced, blackouts will occur.
If there isn’t enough electricity to meet demand, operators will ask a few plants to increase their generation. If availability exceeds demand, they can sell excess to a different part of the grid to avoid overloading their own.
One of the major challenges that comes with using solar energy is that it’s variable. If it’s sunny, there will be more generation. If it’s not there will be less. It can’t easily be turned on and off.
The eclipse will reduce production and even stop it completely in some areas, which means that the electricity produced by other resources will have to be increased. Operators may direct natural gas, coal, hydropower or other plants to boost their production in order to maintain the balance.
When solar comes back on, they’ll have to do the opposite. Other facilities will have to ramp down production and operators may have to sell excess to other parts of the grid that weren’t as effected by the eclipse.
Because of the preparations taken by grid operators and the relatively small amount of power that solar is responsible for nationwide, the North American Electric Reliability Corporation has said that it doesn’t expect the bulk power system to experience reliability issues. Americans shouldn’t notice any disruptions in their electric service.
What This Will Teach Us
Dealing with varying output from solar is not a new concept for grid operators. They have experience managing the variations that occur throughout the day, more widespread reductions due to cloud cover or storms and solar turning off and coming back on as night turns to day.
It is true, though, that operators have never seen such a widespread loss of solar power, because of the rarity of this kind of event and the amount of solar power now on the grid. The stakes aren’t too high now, but in the future, we’ll likely have more solar on the grid. The next eclipse might have a more prominent impact.
The upcoming eclipse will serve as something of a test run. We’ll see how the grid manages and we may be able to learn some lessons about how best to deal with the next event like this one. We’ll be able to identify weak spots, see what worked and what didn’t and come up with plans to prepare for future eclipses. These suggestions might include increased battery storage, making the grid more flexible and altering the rules and business models of the energy market.
If everything goes as planned, which most seem to think it will, the eclipse will create positive press for solar energy. It will have passed the test and shown that it doesn’t hurt grid reliability. If something unexpected happens, we’ll have to look closely at what occurred and determine what we can change to improve how we get our electricity.
