This is a headline at the Telegraph this week. Lack of wind may cause blackouts. Should we worry about it?
There are of course no numbers in the Telegraph story, or in this rather absurd story in the Guardian that claimed that recent fire at Didcot B power station showed “the intermittency of some renewables is simply not a problem“.
What we really need are numbers, and not badly thought through talking points.
So, can we really rely on wind farms to provide our electricity around the clock?
If you ever tune into BBC1 at 6.28 pm you will know that winds around Britain are not consistent, and that we frequently see calms from north to south. Wind speed of course is not the whole story. The kinetic energy goes up with the cube of wind speed.
The result is that wind farm output often goes close to zero, and this can coincidence with peaks in demand.
Let’s look at the last three years.
Below is a plot of hourly electricity demand versus wind power output in October, November, and December 2011. The black vertical line is the peak in demand; while the red horizontal line is 5% of peak wind farm output. If we are thinking about blackouts, what really matters is the bottom right. The fewer dots there the better.In 2011, wind farm output peaked at around 3.2 GW. However, you can clearly see that wind power output is often very low. It often gets close to 5% of peak wind farm output.
In 2012 things were much worse. Wind farm output was frequently below 5% of peak output during these months. And, as the bottom right of the figure below shows, wind farm output was below 5% of its peak when demand was more or less at its annual maximum. A repeat of this is 2014 may make things very dicey.Things were a bit better in 2013. There were fewer calms that year. However, wind farms could still not be relied upon to provide more than 5% of their peak output. Essentially we do not want many dots near where the black and red lines intersect. In 2013, this was relatively OK. In 2012 it was not.
So, weather dependent, Britain will be blackout free this winter. But please, do not tell me that intermittency of renewables is not a problem.
Note on data
The National Grid provides data for hourly load and wind farm output. To save me time I have taken this from PF Bach’s website.
This article is a very quick back of the envelope piece. I’m currently writing something for the Energy Collective, about the need for back up for wind farms. Hence, I was able to quickly pull these plots from what I had produced for it. That piece will look in detail at data for multiple countries. But questions/suggestions below the line would be welcome, so that I can get the final (more finished) article in good shape.