Germany: Switching off PV plants during eclipse expensive option

Switching off PV plants during Friday’s partial solar eclipse would be a costly option for Germany, Berlin-based research group Energy Brainpool has determined in a new study looking at the economic ramifications of the moon briefly overshadowing the sun.

The report examines the potential effects on Germany’s electricity market when the moon blocks up to 73% of the sun across the country from about 9:30 am to 12 pm.

The partial eclipse will have a significant impact on the electricity market, according to the report, which found that the economic costs in the case of a sunny, cloudless day would be some €3.39 million. That figure would nearly triple to €9.95 million if part of the country’s PV installations were switched off in order to minimize the impact of the eclipse, however, in part due to mandatory compensation payments to PV operators.

Higher prices on the electricity market during the solar eclipse would result in additional costs: cheaper PV power normally displaces more expensive electricity from conventional power plants. During the eclipse, however, conventional power plants would have to run in order to compensate for the dip in solar generation, leading to higher prices. In addition, transmission system operators (TSOs) will have to take specific measures, such as obtaining additional control power, increasing costs still further.

Energy Brainpool says that the strong increase of 18 GW expected from 10:30 am to 12:00 pm in sunny weather will be particularly challenging for TSOs.

The research group expects eclipse-related costs to be incurred in three areas.

Firstly, lower volumes of solar power will lead to higher electricity prices on the wholesale market, leading to an increase in the daily base electricity price by roughly €1.40 per megawatt hour.

Furthermore, prices for primary and secondary control power prices are well above the level of the previous weeks and therefore already reflect the risks and the likely strategies of providers due to the eclipse. Transmission system operators have also announced plans to tender additional minute reserve power in the case of sunny weather. The costs incurred for this reserve power is included in the cost analysis.

Lastly, in the event of a shutdown, solar plant operators will have a claim for payment for potential generated electricity in accordance with Germany’s Renewable Energy Act (EEG), regardless if actual power is supplied or not.

Meanwhile, the European Network of Transmission System Operators for Electricity (ENTSOE) says European TSOs have been preparing for the eclipse for several months.

In its graph, ENTSOE shows the total impact of the solar eclipse on the continental European power system. Compared to clear sky conditions, the PV

output may drop by 34 GW at 9:41 (UTC) or 10:41 (CET).

Comparison of expected infeed from solar on March 20 during clear sky conditions with and without solar eclipse.

In its analysis, ENTSOE outlines how TSOs are cooperating to maintain security of supply on Friday. If, as expected, the day is clear and sunny, some 35 GW of solar energy — the equivalent of nearly 80 medium-size conventional generation units — will gradually fade from Europe’s grid before being gradually re-injected in the space of two hours.

Managing the event on the world’s largest interconnected grid is an unprecedented challenge for Europe’s TSOs, ENTSOE says. Friday’s eclipse marks the first such event since the dramatic increase of solar PV-generated power in the grid and, as a result, the risk of an incident could be serious without appropriate countermeasures.

In its Solar Eclipse Impact Analysis, ENTSOE says operational coordination among European TSOs will be crucial. "After thorough operational planning work, TSOs will put in place continuous on line coordination between control rooms across Europe ahead of and during the eclipse to better coordinate the scheduled remedial actions."

While the organization says TSOs are taking all necessary measures to mitigate risks, it stresses that the solar eclipse "is a perfect illustration that maintaining system security with more and more volatile and dispersed generation is becoming increasingly challenging."