Italy to switch off PV plants over 100 kW during solar eclipse


The partial solar eclipse in Europe on Friday is causing some jitters in Germany, where the subject of what exactly to do with the country’s large-scale PV systems is being debated.

Taking place on a cloudless day, the eclipse is expected to cause strong fluctuations in Germany’s power grid, even leading to possible blackouts, some fear. Germany has more than 38 GW of installed PV power; in Italy, it’s about half that, with 18 GW.

Discussions have also taken place in Italy and a decision has been made, according to Andreas Lutz of New Energy Projects, a German solar company with operations in Italy. During the eclipse, PV systems would shut down four times faster than during a normal sunset. Fearing massive problems, Italian transmission grid operator Terna has ordered the total shutdown of all PV systems over 100 kW, Lutz tells pv magazine.

Although the partial eclipse would only last about two hours in Italy, the PV plants in question would have to be shut down for an entire 24-hour period, from midnight to midnight. This would apply to the entire country, according to Terna.

The transmission grid operator was granted the legal authority to order such a shutdown following a decision by the Italian Regulatory Authority for Electricity Gas and Water (AEEG) in 2012, according to Lutz. Network operators have informed PV plant operators over the past few days of the requirement to shut down their systems on Friday. Lutz adds that it was the first time that AEEG has implemented such a decision.

In Germany there will most likely be no requirement to shut down PV systems. However, the regulatory structure in Germany is more complicated. While German transmission system operators are required to maintain grid stability, they do not have direct access to the PV systems, which are regulated by distribution system operators.

“As a transmission system operator, we have no access to the facilities,” a spokeswoman for transmission system operator Tennet explains. “That is handled by the distribution system operators. It is therefore uncertain how many plants we would be able to reach and switch off.”

Experts therefore recommend to not even try to disconnect photovoltaic systems from the grid, insisint this would be safer. Apparently it would not help to "disconnect as many plants as possible from the grid when you don’t know how many they really are in the end,” the Tennet spokeswoman adds.

In a report published last week, Germany’s Fraunhofer Institute for Solar Energy Systems says the partial eclipse would cause a sudden drop and then a surge in solar-generated power that will have to be balanced out to avoid grid instability.

Fraunhofer researchers ran simulations showing that conventional power plants and hydroelectricity pump-storage facilities could soften the impact of the eclipse, which would cause much greater strain on the grid on a sunny day, which March 20 is forecast to be in many parts of Europe.

Edgar Meza contributed to this report.