Fraunhofer ISE: Solar Eclipse on 20 March 2015 Manageable

According to a study by Fraunhofer Institute for Solar Energy Systems (ISE), the effects of the solar eclipse on 20 March 2015 will be manageable in Germany even on a day with clear skies.

Fraunhofer ISE sums up the main results as follows (cf. page 3 of the study):

  1. On a clear day the solar eclipse on 20 March 2015 can lead to PV power gradients being 2.5 times higher than regular gradients on a 15-minute basis.
  2. The conventional power plant fleet is generally technically equipped to balance the gradients occurring during the eclipse. Wind power plants and large PV installations are technically prepared to reduce output and can thus help maintain system stability.
  3. Computer modeling of the grid (Netzsimulation) shows that no problems are to be expected on the low and medium voltage level.
  4. Transmission system operators have to pay greater attention when planning redispatch measure on the day before. Based on weather forecasts the expected PV input can be taken into consideration.

In central Germany (Kassel), the solar eclipse will start at 9:33 CET and will be over by 11:52 CET. With 50% of the infeed reduction in Europe expected to occur in Germany according to an impact analysis by ENTSOE, Germany is the country most affected by the eclipse. According to ENTSOE, the assumed installed capacity PV capacity in Germany amounts to 39,734 MW (for PV capacity eligible for financial support under the Renewable Energy Sources Act, EEG, please see here). During the eclipse a possible power supply reduction by more that 400 MW per minute could occur that persists for half an hour, ENTSOE said. The gradient is even steeper when the sun returns, at more than +700 MW/minute. Given these figures a cloudy day might be the thing to wish for. Otherwise the Fraunhofer study will be put to the test.

Source: Fraunhofer ISE, press release with various links, study

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4 Responses to “Fraunhofer ISE: Solar Eclipse on 20 March 2015 Manageable”


  • The Italian TSO seems to think that the situation is NOT manageable and they have managed to enrage the Italian PV industry.

    On March 13, all PV operators in Italy received a letter from the Italian energy manager, “Enel” where they were ordered to shut down their plants for 24 hours, the whole day of March 20th, “according to a request from Terna” (the Italian grid operator). The document defines the situation as “maximum level of alert” (L5) and threatens those operators who would not comply with various dark and dire legal consequences.

    The request has generated a protest on the part of most Italian operators and at least one request of audition of Terna in the Italian senate on the part of senator Gianni Girotto (M5s) who will ask Terna to justify their action.

    Indeed, a survey of the situation indicates that the shutdown of all the Italian PV plants appears unjustified and excessive. Even considering that the solar eclipse may generate problems of stability for the grid, these problems appear to be perfectly manageable according to the document produced on this point by ENTSOE, the European network of transmission system operators (https://www.entsoe.eu/Documents/Publications/SOC/150219_Solar_Eclipse_Impact_Analysis_Final.pdf). This document recommends particular attention and readiness on the part of national TSOs, but nowhere mentions the necessity to shut down the whole PV system. Indeed, the other two major PV producers in Europe, Spain and Germany, haven’t deemed necessary to shut down their plants, as Italy is doing instead.

    The damage generated by the complete shutdown of the Italian system can be calculated on the basis of the production of March 2014, (66 GWh) (http://dataenergia.altervista.org/portale/?q=produzione_oraria_italia_2014_marzo). Taking into account a loss of about 20% caused by the solar eclipse, it means an unnecessary lost production of about 50 GWh. This lost production is a direct damage to producers, who lose their income, and to Italian citizens in general. The lost production will have to be replaced by importing more energy from abroad, or producing it by importing more fossil fuels. In addition, considering that the Italian system emits some 500 tons of CO2 per GWh, it means the unnecessary emission of some 25000 tons of CO2 in the atmosphere.

    Many Italian operators that this action on the part of Terna is totally unjustified on technical grounds and that it can only be understood as a true “slap” against PV operators, an attempt to establish a legal precedent that will allow Terna to shut down plants at will in order to favor fossil producers, with evident damage to the Italian grid system.

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