A solar eclipse occurs when the Moon moves between the Earth and the Sun and blocks out all or part of the view of the Sun from the Earth. There will be a partial solar eclipse between 11:20am and 1:40pm today when the Moon will partially obscure the Sun. Northern Germany is expected to see about 20% of the Sun eclipsed and southern Germany about 5%.

The chart shows the solar photovoltaic generation forecast for today compared with the linearly interpolated values without the solar eclipse.

The forecast data for today show a typical increase in photovoltaic generation at first. Then, following the start of the solar eclipse at 11:20am, a drop is expected from 11:45am until about 12:30pm. The impact of the solar eclipse on photovoltaic generation is expected to end at around 1:45pm.

The linearly interpolated values show a possible decrease in photovoltaic generation of at least 1.5 GWh during the solar eclipse.

As a solar eclipse can be predicted a long time in advance, the transmission system operators have been able to plan ahead and, for instance, factor in the eclipse in their generation forecasts These forecasts are in turn used by the plant operators to plan their operation so that they can still meet demand. If there is an unexpected imbalance between generation and demand, the transmission systems can use balancing services to correct the imbalance and keep the system frequency stable.

You can see if the forecast turns out to be right in nearly real time here:

Forecast and actual photovoltaic generation in Germany on 9-10 June 2021

Impact of the solar eclipse in March 2015

There was also a partial solar eclipse over Germany on 20 March 2015. During that eclipse, the Moon obscured the Sun more than it will today, and so the impact can be seen more clearly in the figures. A drop in photovoltaic generation was predicted from 9:30am and an increase from 10:30am. A peak in generation was then expected at 12:30pm. This is more or less what actually happened.