During the recent storm over UK Energy Minister John Hayes’ rather silly comments about onshore wind farms, the Green Party leader Natalie Bennett made a quite curious intervention to the debate. Most curious was the following challenge, a taunt if you will, to those who say the intermittency of wind is a problem:
No energy source functions 100% of the time – but still as Green Party leader I still get the truly clueless question from media sources that really should know better, variations of: “But the wind doesn’t blow all of the time so wind power can’t work, can it?” In fact, wind turbines produce electricity 70-85% of the time and last year generated enough electricity for more than 3.5 million homes.
Now, saying wind turbines produce electricity 70-85% of the time is a rather meaningless thing to say, rather like saying a professional golfer turns up to 70-85% of the tournaments. It doesn’t quite get to the core of the issue.
So, what does happen 70-85% of the time? Fortunately you can get historic UK production data for every five minutes for the last few years. Let’s begin with 2011, and first look at maximum electricity production from wind each month, and compare it with the average. (I haven’t labelled the curves, but it should be clear what is what.)
We can see clearly that the monthly average output is normally less than half the monthly maximum output, with monthly maximum averaging just under 2.5 times higher than the average throughout the year.
Now, let’s compare the average amount of electricity generated each month with the minimum amount that’s generated 70 and 85% of the time.
Again, it’s very clear that we don’t always have decent output 70-85% of the time. In fact, 85% of the time we are only guaranteed about 17% of maximum monthly output, and just under half of the average output.
Has it fared any better in 2012? Here’s a comparison of the monly averages with the output produced 70-85% of the time.
The overall numbers are up due to new capacity coming online, but again we see that 70-85% of the time there is no guarantee of good output.
Now, does this mean that wind farms are useless? Absolutely not. Onshore wind is perhaps the cheapest source of low carbon power, and certainly the cheapest source of renewable energy, with costs about half those of offshore wind in the UK.
If we are serious about dealing with climate change cost effectively, then onshore wind will probably be part of the mix. However we must recognise that wind power presents problems, which cannot be covered up simply by using the language of the PR guru.