What happens when the sun takes a few hours off?


The solar eclipse on the 20th of March 2015 saw the electricity generated by solar panels drop by up to 75%. It was the first time in Europe that an eclipse was expected to have an impact on the electricity grids.


SynaptiQ, 3E’s solar PV monitoring and reporting tool, picked up the consequences of this stunning phenomenon quite easily. As you can see on the graph, the eclipse started around 09:30 on Friday and lasted for a bit more than two hours. At that time of day, in our example, about 49000kW of power would be generated from solar. It fell to 10911kW.

Europe’s total solar power output could have dropped by as much as 34GW if it was a clear day. That’s the equivalent of the output of around 80 gas-fired power stations gradually fading out of the European system as the eclipse happens, then fading back in again.

Half of the total impact was expected in Germany (39GW). Other major users of solar power including Italy (19.7GW) and Spain (6.7GW) were expected to face challenges too.

According to Reuters, “The initial 15 gigawatt drop in Germany was less than operators had feared. They were able to draw on alternative power sources including coal, gas, biogas, nuclear and hydroelectric energy pumped from storage and were helped by demand reductions from industry including four aluminium plants.”

According to PV Magazine, “In Italy, which has the world’s highest level of PV penetration, grid operator Terna had already decided to take no chances with the eclipse, turning off all of its large-scale (>100 kilowatts) PV plants for the day in order to protect any fluctuations on its grid.”

The eclipse over Europe’s solar panels provides a sneak peek at a fascinating challenge facing tomorrow’s electric grid.