Seasonal Power Storage – The Challenge for Solar

A recent article at is a refreshing exception to the frequent misreports. Nonetheless, Craig Morris has a few nits to pick and says that the bad news for Germany is the good news for the United States.

(Photo by Mike Baker, CC BY-NC-SA 2.0)

Growing capacity of solar also means growing need for power storage. (Photo by Mike Baker, CC BY-NC-SA 2.0)

Berlin-based journalist Andrew Curry asks a crucial question in his article entitled “Can you have too much solar energy?” He answer is right: yes. But the situation is both better and worse than he describes.

First, a technicality – Curry writes that Germany’s Renewable Energy Act (EEG) was adopted in 1991, but as we explain at, the EEG is from 2000. It replaced the law from 1991 called the Feed-in Act. Crucially, the 1991 law provided payment for renewable power pegged as a fraction of the retail rate – meaning that wind power, for instance, always received less than the retail rate. In addition, that level of support was not enough for photovoltaics, which also did not take off properly until the EEG was amended in 2004 and solar finally received payment above the retail rate to cover the actual cost.

The difference is not trivial. Grid parity has never been a goal in Germany. Curry himself speaks of a Deutsche Bank report (one that neither he nor anyone else sources, incidentally – I have yet to see it myself, so do leave a link in the comments below if you have one) forecasting grid parity in Bavaria “by next year.” In fact, the average German retail rate (customers can switch utilities, and rates differ) is around 27 cents right now, but you will get less than 16 cents for power from a small rooftop array installed in April 2013 – meaning that grid power already costs 50 percent more than solar in Germany.

Elsewhere, Curry claims that “Germany had a national freak-out after the Fukushima disaster.” As we explain in the Q&A section of, Chancellor Merkel may have done an about-face, but Germans changed their minds about nuclear less after Fukushima than did the public in other countries.

Now to Curry’s main question. He points out that Germany got 22 percent of its power from renewables in 2012, with 4.6 percent (roughly a fifth) coming from solar alone. Curry correctly states that Germany got up to 22 gigawatts of solar power last year, but he says that that was “half of the world’s total and the equivalent of 20 nuclear power plants” – interesting, but it doesn’t tell us whether we can have too much solar.

Here’s what we need to know: solar power already peaks at up to a third of total power demand in Germany, such as in April 2012. In September, wind + solar added up to nearly 32 megawatts, driving demand for conventional power down to less than 38 megawatts. Wind + solar peaked at around 45% of total consumption that day.

If Germany doubles its share of solar to a mere 9.2 percent of power supply, solar will be peaking at two thirds of power demand on some days. Conventional power plants will have to ramp down entirely for a few hours a day (which most of them cannot do), and we may not even be able to take up all of the wind power generated. All this is likely to happen before the end of this decade. So Germany faces a challenge in getting to a mere 10 percent solar power, and anything above that will require considerable seasonal storage.

The bad news for Germany is that, like most European countries (without air conditioning), power demand is highest in the winter. The good news for Americans is that solar is easier to integrate when power demand peaks during the summer, so solar power generation coincides better with consumption – and less will eventually have to be stored from the summer for the winter. Besides, thanks to German solar efforts, global prices for PV have decreased by about 60% in recent years, making solar more economical in the US.

Craig Morris (@PPchef) is the lead author of German Energy Transition. He directs Petite Planète and writes every workday for Renewables International.


Craig Morris (@PPchef) is co-author of Energy Democracy, the first history of Germany’s Energiewende.

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