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What Happens to Solar Power During an Eclipse? We Find Out Friday

The eclipse offers a rare opportunity to see what happens when all the solar panels get cast into darkness at once.

On Friday, Europe will see a solar eclipse. In the UK, skies will darken from around 8:15 AM as the Moon obscures the Sun. One effect: solar panels across the country will be more or less simultaneously cast into darkness.

It's an unprecedented opportunity to check out how the grid responds to a sudden sweeping incident as solar energy systems all fade out at once.

There's no need to panic—you shouldn't notice anything—but it's still a great opportunity to look at how solar power systems behave when they're all thrown off at once. Alessandro Abate, a computer scientist at the University of Oxford, works on models of how photovoltaic panels generate electricity and how that electricity is distributed across the grid.

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"Mathematically, the beautiful part about photovoltaic panels is they're difficult to model, in the sense that you have multiple panels as opposed to, say, a single coal plant," he explained. "Which are all different one from the other, they produce energy in a different manner, they're all de-synchronised—essentially, they don't work in a centralised way, they work distributedly."

A British solar park. Image: ​RTPeat/Flickr

But in the eclipse, all the different panels will more or less synchronise. Naturally, they do something similar every night after sunset, but it'll be much more sudden and simultaneous with the eclipse.

And that makes it a good analogue for other more common but less foreseeable occurrences. How the grid copes in an eclipse could be a good indication of how it might behave in a sudden blackout if a tree brings a power line down, for instance.

"We expect that the overall dynamics of the electricity—the total power generated and the frequency of the electricity over the grid—will be affected by this synchronisation," Abate said. "We expect a little bit of instability, if you will, in the way that the electricity travels on the grid."

His team will use the eclipse on Friday to gather data and test it against their predictions and further calibrate their mathematical models.

"Nothing bad will happen."

The long-term goal is to use the models to come up with strategies for the grid to help it cope with sudden blackouts. It won't see another eclipse for a while—the next isn't for another decade—but as we rely more and more on solar power, it's good to be prepared for other incidents.

As for Friday: "Nothing bad will happen," Abate emphasised. "We will cope very much fine with what's going to happen."

We don't rely too much on solar power in the UK anyway, and even elsewhere in Europe where solar panels are more common, we're prepared enough that there shouldn't be any problems. A month ago, the European Network of Transmission System Operators for Electricity warned​ that "the risk of an incident could be serious without appropriate countermeasures," but a spokesperson told the Guar​dian it was "very unlikely" there would be any issues.

After all, the eclipse is not unexpected. Additionally, most of the continent will only see a partial eclipse, rather than a total blackout. While Reute​rs reports the National Grid expects an 850 megawatt drop in solar output during the eclipse, it also forecasts a 1,100 megawatt drop in demand—because people will be outside looking at the eclipse rather than using electricity.

And while Abate's waiting for the data to come in from Friday's rare event, he said he'll be doing exactly the same as everyone else: looking up.