The 2014 version of the German Renewable Energy Sources Act (EEG) allows operators in case of a grid overload to “reduce the feed-in” of green power, but with the obligation to log the incident. The ones who pay for it are the utility customers because the owners of wind farms receive their usual feed-in payment – even if the network operator takes the park off the grid. Use of the permission is rampant: It regularly hits close to 20 wind farms with a capacity of more than 20 MW each in Mecklenburg-Western Pomerania (MV) alone [1].
The events to stabilize the grid are unfolding pretty dramatically: Whereas in 2014, EUR 128 million were spent on shutting down and restarting wind energy systems, the figure jumped to EUR 329 million last year. Conventional power plants needed EUR 74 million in 2014 for the same procedure, whereas the amount had shot up to EUR 225 million in 2015. Additionally, the costs for calling off grid reserves increased from EUR 92 million in 2014 to EUR 152 million last year. [2]
It can be assumed that in many cases, the shutdown period was longer than required by the state of the grid, since the restart of a wind park can sometimes be quite time-consuming. Apparently, the principal reason for the stated shutdowns was that strong winds overloaded the relevant 110 kV lines and electrical substations when power was transferred from the 110 kV distribution network to the 380 kV one. This shows that the lines still have not been adapted to the output of wind farms set up at the beginning of the 1990s, which results in conventional power plants contributing more than is needed to electricity supply during those periods, and the opportunity to reduce CO2 emissions is wasted.
Where is the electrical energy storage?
Usually, power generation is reduced whenever demand goes down. This reduction would still be necessary in the future, even if the transmission network was designed to cover all kinds of loads. Additionally, the enhanced electricity highway itself would not be of any use if – for example, in the early morning hours on Whit Monday – almost no-one is working in industry and trade, and private households are hardly consuming any energy, but heavy winds resulted in power-generating turbines to run at full speed. Any type of heat system could be operated below the Q-point (at low efficiency and high wear), but it is easier to the shut down the affected renewable systems.
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Expand wind-hydrogen storage
Wind-hydrogen projects in the north-east
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This article summarizes some of the issues discussed during the 22nd Stralsund Energy Symposium. The conference proceedings can be found here: fh-stralsund.de/forschung/institute/ires/veranstaltungen
Conclusion
We see it as a political responsibility of the government and local authorities in Mecklenburg-Vorpommern to assume a more active role in this field and support the state in its deserved pioneering efforts by offering subsidy programs …
Literature
[1] Eisman report …
Authors:
Professor Jochen Lehmann, IFEU e.V./FH Stralsund
Dr. Hans Sandlaß, Special Consultant Energy Systems, Berlin