A couple of days ago we saw how wind power in Britain at one point had fallen to just a fraction of one percent in supplying national demand. The situation was hardly better in Germany.
The following chart provided by Wilfried Heck here shows Germany’s electric power consumption and the energy fed in by wind and sun for the period of 24 February to March 3rd.
Chart by Wilfried Heck. Date and time shown by horizontal axis, power by vertical axis.
The chart above shows the time period broken down into 656 fifteen-minute time intervals. The mean value of the total consumption (blue) is 57,595 MW. The total electrical energy consumed for the period depicted was 9,445,650 MW-hrs. However, wind and sun were only able to supply 6.22 % and 2.12 % respectively, thus yielding a total contribution of 8.34% over the entire period.
Peak demand for 2013 was 73.283 MW occurring on 24 January 2013 at 7 p.m. But at that time, the sun had long been below the horizon and was not able to contribute anything. Heck writes: “And the wind? With 31,300 MW of installed capacity, it was able to only feed in 1479.1 MW into the German grid, thus contributing a measly 2% share of the electric power supply.”
The chart clearly shows times when wind and sun energy were practical doing nothing. So when the sun doesn’t shine (which is more often than not in Germany) and when the wind isn’t blowing strongly, the country needs all the old power plants back on line. 200% capacity is needed to assure 100% supply, and this in relatively windy regions.
Moreover, when the sun does shine and/or the wind blows, conventional power plants end up operating at levels well below their optimum efficiency, and thus do very little to cut back on emissions.