In the campaign to jettison fossil fuels as the main source of our energy and replace them with so-called "renewables," a notable feature is the lack of discussion of the costs and practicalities of trying to make intermittent sources like wind and solar work to run a 24/7/365 electricity grid.  Is there any problem here that deserves consideration?  In Tuesday's post I noted that in my home state of New York we are about to try to replace our big Indian Point nuclear power plant with mostly wind-generated power.  Actually, we already have wind turbines with approximately the same "capacity" as Indian Point, but unfortunately over the course of a full year they only generate about one-quarter as much electricity as Indian Point.  Still, can't that problem be solved just by buying four times as many wind turbines?  It may be a little pricey, but is there any reason why that won't work?

In a publication called Energy Post on January 10, prominent German economist Heiner Flassbeck has a piece that addresses this question.  The headline is "The End of the Energiewende?"   Of course the problem is that the wind turbines don't just run steadily and predictably at one-quarter of capacity; rather, they swing wildly and unpredictably back and forth between generating at near 100% of capacity and generating almost nothing.  The "almost nothing" mode can persist for days or even weeks.  In Germany under a program called Energiewende ("energy transition"), in effect since 2010, they have been pushing to raise the percentage of energy they obtain from wind and solar, and have gotten the percent of their electricity supply from those sources all the way up to 31%.  But Flassbeck now looks at what just occurred during the month of December 2016:

This winter could go down in history as the event that proved the German energy transition to be unsubstantiated and incapable of becoming a success story. Electricity from wind and solar generation has been catastrophically low for several weeks. December brought new declines. A persistent winter high-pressure system with dense fog throughout Central Europe has been sufficient to unmask the fairy tale of a successful energy transition. . . .  

Here is a chart from Flassbeck's piece showing German electricity demand through the first half of the month of December, against the sources of the electricity that supplied that demand.  Among the sources, solar, on-shore wind, and off-shore wind are broken out separately:

As you can see, at some times wind and solar sources supplied as much as half or more of the demand for electricity, but at other times they supplied almost nothing.  Flassbeck:

The data compiled by Agora Energiewende on the individual types of electricity generation have recorded the appalling results for sun and wind at the beginning of December and from the 12th to 14th. . . .  Of power demand totaling 69.0 gigawatts (GW) at 3 pm on the 12th, for instance, just 0.7 GW was provided by solar energy, 1.0 by onshore wind power and 0.4 offshore. At noontime on the 14th of December, 70 GW were consumed, with 4 GW solar, 1 GW onshore and somewhat over 0.3 offshore wind. The Agora graphs make apparent that such wide-ranging doldrums may persist for several days.

By the way, according to charts at Wikipedia, Germany has about 40,000 MW of installed solar "capacity" as of 2015, and another about 44,000 MW of installed wind "capacity" as of the same year.  Thus, if only the sun had shone and the wind had blown both at full strength on December 12 and 14, those facilities would have been more than sufficient to supply 100% of German's demand of 69,000 MW on the 12th and 70,000 MW on the 14th.  But instead Germany got only about 3% of the electricity it needed from these sources on the 12th and 7% on the 14th.  If you wanted to get all of Germany's electricity from wind and solar on the 14th, you would have needed about 15 times as much "capacity" as the demand; and on the afternoon of the 12th, you would have needed 35 times as much "capacity" as the demand.

Hence what Flassbeck calls the "futility" of trying to solve the intermittency problem of wind and solar power by just trying to build more capacity.  Even in a country as large as Germany and with one hundred times as much capacity as usage, you could still have a completely calm night where the power goes out.  To have a full solution to the intermittency problem, and to make your system work 24/7/365 with full reliability, you will need not just massive excess capacity of wind and solar facilities, but also some combination of other expensive features, such as fossil fuel backup, storage capacity, and/or transmission capacity to bring in power from somewhere where the wind is blowing.  Germany continues to have the 100% fossil fuel backup.  They also have residential electricity rates about triple the American average.  Really, what good are all those wind turbines and solar arrays if you can't get rid of a single fossil fuel burning power plant?