Total Solar Eclipse “Blacks Out” Europe

Several gigawatts of solar energy faded from European grids during the two-hour solar eclipse that shadowed the continent, as well as parts of Northern Africa and Asia, on Friday morning.

But according to the European Network of Transmission System Operators for Electricity (ENTSO-E)—an organization representing 41 transmission system operators (TSOs) from 34 European countries—grid operators successfully managed the fast variations in solar generation.

“The European power system needs to be balanced every single second. Between 9.00 and 12.00, Brussels time, TSOs had to reinforce their cooperation to cover the unusually fast loss followed by even faster reintegration of some 17 GW of solar generation,” it said.

ENTSO-E said preparations to ensure reliability during the eclipse had been underway for several months. Distribution System Operators and generators notably responded to the call for proactive cooperation.

The group’s Solar Eclipse Impact Analysis called the event an “unprecedented challenge” for European TSOs. “Solar eclipses have happened before but with the increase of installed photovoltaic energy generation, the risk of an incident could be serious without appropriate countermeasures,” it noted.

“What makes this year’s solar eclipse so special is the fact that there is now a non-negligible amount of energy generation units connected to the grid that are highly sensitive to variations in solar radiation,” said ENTSO-E. One reason this event posed such a concern is that the event occurred in the middle of the morning. “It’s like having two sunrises and two sunsets in the same day.”

However, TSOs managed to forecast with “a lot of precision the effect of the eclipse on solar generation; taking even into account the ‘worst case scenario’ that the eclipse would take place on a sunny day. The sun was indeed shining this morning in Southern Germany and Northern Italy where the concentration of photovoltaics is the greatest of all the ENTSO-E area. The most critical moment was between 10:45 and 11:15 when the solar generation started to go up again,” it said.

Over the last decade, the amount of photovoltaic (PV) generation has dramatically increased. In 2002, solar power made up a 0.1% share of all electricity produced by renewable sources; by 2012, that figure had risen to 10.5% of renewables. Solar power supplies 3% of continental Europe’s total electricity consumption today, according to ENTSO-E.

ENTSO-E had prepared to inform the public of national incidents occurring on power systems during the event. It had also warned PV generators that injection would depend on weather conditions, which were uncertain.

Each TSO made its own preparations, meanwhile. German transmission system operators, for example, secured additional secondary reserve that could be activated within a 5 minute time period ahead of the eclipse. Operators estimated that the country, which now depends on solar power for about 7% of its generation needs, needed additional control reserve capacity amounting to 2,279 MW of “negative” secondary control reserve and 2,246 MW of “positive” secondary control reserve.

According to ENTSO-E, solar generation on Friday morning was exceeding the normal seasonal level, as a result of “very sunny weather.”

“But despite this challenge, German TSOs managed very smoothly the high and fast variations of 39 GW of installed solar generation relying on power reserves at national and regional level,” said the group.

“In view of the sunny weather forecast, Italy had decided in cooperation with DSOs and generators to take an equivalent of 5 GW PV out of the system, between 7:00 a.m. and 2:00 p.m. today. Thus, PV from 13 GW rather than 18 was in the system during this period. After 2:00 pm reconnection will start for the full capacity.”

The European grid had resumed normal operations by noon after the solar eclipse was over.

Sonal Patel, associate editor (@POWERmagazine, @sonalcpatel)