One of the rare pleasures in life is reading the latest piece of nonsense written by Christopher Booker in the Daily Telegraph. The fact that it is nonsense appears to be subject independent, but talk of wind turbines tends to ratchet things up a level. One of his favoured claims is that the UK will need to build 32,000 wind turbines to meet its 2020 EU renewable energy commitments.
The claim is groundless and not worth debunking, but let’s instead ask how many turbines it would take to power the UK. UK electricity demand was 381 TWh in 2010. How many turbines would it take to meet this? (Of course in practise this will never happen without massive breakthroughs in energy storage, but we’ll just imagine that supply and demand is met via new tech.)
As far as I know the average turbine capacity for new large wind farms is about 3 MW, so we can use this to get a lower bound on the number of turbines needed.
UK wind farm capacity factors have averaged just below 30% for the last few years, though there is a bit of variation each year. (Capacity factor is the figure such that average output = capacity * capacity factor.)
It’s difficult to project average capacity factor in to the future because offshore wind in will probably take up a higher proportion of wind capacity (which will increase CF), but onshore developments may need to move into less prime wind regions. I’ll just stick with 30%.
A little bit of arithmetic indicates we would need about 48,000 turbines to meet the UK’s annual electricity demand. The total installed capacity would work out at about 145 GW. (Note that UK electricity demand is never above 70 GW, so if storage methods aren’t sorted out windy days will see a lot of power wasted.)
Getting 100% from wind of course is not feasible. However electricity demand may need to double anyway in order to electrify transportation etc. So, 50,0000 may be a good ball park figure for getting 50% of electricity from wind in say 2040.
What about today? Renewable UK gives the following breakdown of UK wind farms:
Average wind turbine capacity is actually 1.9 MW. So, using this we would need about 75,000 turbines and not 50,000. Is my original choice of 3 MW too low then? Arguably the opposite. Public opposition to windfarms is growing rapidly. Offshore wind may end up dominating new build by the end of the decade, in which case average turbine capacity may go above 3 MW.
While only ballpark figures these are worth keeping in mind when you are reading the latest piece of nonsense about wind farms in the Mail or Telegraph, or for that matter The Guardian.