Solar eclipse on Friday March 20, 2015

When seen from Earth, a solar eclipse happens when the Moon passes between the Earth and the Sun. This makes the Moon fully or partially (partly) cover the sun. Solar eclipses can only happen during a new moon. Every year about two solar eclipses occur. Sometimes there are even five solar eclipses in a year. A total solar eclipse occurred on Friday March 20, 2015. The solar eclipse began at 08:30GMT in the southwest and moved towards the northeast. It was most visible from the North Atlantic and Arctic Oceans, Greenland, Iceland, Ireland, United Kingdom, Faroe Islands, northern Norway and Murmansk Oblast. The shadow began its pass off the south coast of Greenland. It then moved to the northeast, passing between Iceland and the United Kingdom before moving over the Faroe Islands and the northernmost islands of Norway. The shadow of the eclipse was visible in varying degrees all over continental Europe[1]. For example, London experienced an 85% partial solar eclipse compared to north of the Faroe Islands in the Norwegian Sea which saw a complete solar eclipse[2].

The following figure illustrates affected regions over continental Europe.


Impact on power systems

A solar eclipse means a block of light and a decrease of solar energy. What is the impact on power systems over continental Europe?

The European Union has a solar power output of about 90 gigawatts and production could have been temporarily decreased by up to 34 GW of that dependent on the clarity of the sky. In actuality the dip was less than expected, with a 13 GW drop in Germany happening due to overcast skies[3].This was the first time that an eclipse had a significant impact on the power system, and the electricity sector took measures to mitigate the impact. The power gradient (change in power) may be −400 MW/minute and +700 MW/minute. Places in Netherlands, Belgium and Denmark may be 80% obscured[4]. The loss of power depends on the cloudiness of the specific region.

The next figure shows a curve of potential power loss[6].solformoerkelse

Now it would be interesting to see how the power frequency of the UCTE has behaved in this period:


As expected, the frequency has not changed much over the period of the eclipse. Since the exact date and  time of the eclipse was all known network operators have been prepared for this moment in order to counteract the loss of solar energy with appropriate resources. Anyway, it is still remarkable how a brief change in solar activity is having a big impact on our lives.


[1] “Solar eclipse 2015 live: Britain to plunge into morning twilight as Moon blocks out Sun”. Daily Telegraph. 20 March 2015. Retrieved 20 March 2015.

[2] “Solar Eclipse: live updates”. Guardian. 20 March 2015. Retrieved 20 March 2015.

[3] Vera Eckert -“European power grids keep lights on through solar eclipse”. Fri.Mar 20, 2015 [1]

[4] “Solar Eclipse 2015 – Impact Analysis” pp3+6+7+13 . European Network of Transmission System Operators for Electricity, 19 February 2015. Accessed: 4 March 2015.

[5] S. L. Gray , R. G. Harrison. “Diagnosing eclipse-induced wind changes” Proceedings of the Royal Society. DOI: 10.1098/rspa.2012.0007 Published 25 May 2012. Archive

[6] URL: