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Out of date statistics make Christopher Booker's wind power maths a bit shaky

  • 30 Jul 2012, 17:38
  • Christian Hunt

Government plans to meet renewable energy targets are unrealistic, argues Christopher Booker in yesterday's Sunday Telegraph. But the statistics he's using to back up his argument suggest that renewables aren't actually as useless as he thinks.

Renewable electricity

Last week, the Department of Energy and Climate Change (DECC) set out how much electricity the UK will have to produce from renewables in order to meet 2020 EU renewable energy targets. We need to generate 79 terawatt hours (TWh) of electricity a year from renewables in 2017, and 108 TWh a year in 2020, DECC says.

But Christopher Booker argues that given how little electricity wind power currently produces, such plans are hopelessly over-optimistic:

"In 2010, the last year for which we have figures, we used 378 TWh of electricity, of which only 10 TWh, or 2.6 per cent, came from wind … [T]o meet that ... target within eight years, almost all the increase would have to come from new wind turbines."

Newer energy statistics show growth in renewables

Booker is taking figures from DECC's 2011 Digest of UK Energy Statistics (DUKES) report, which provides UK energy statistics for 2010. But although he says these are the most recent figures available, the new edition of DUKES was published last week, providing information on what happened in 2011.

These new figures show the year saw fairly significant growth in the amount of electricity coming from renewable sources. The amount of electricity generated by wind power rose from 10.2 terawatt hours in 2010 to 15.75 TWh in 2011 - a rise of 5.53 TWh.

This made up much of a wider growth in renewable power - renewables generated 34.4 TWh of electricity in 2011, a rise of about 8.6 TWh compared to 2010.

(See page 135.)

So is meeting a 2020 target "out of the question"?

Based on the 2010 figures which show that only 2.6% of UK electricity came from wind power that year, Booker argues that getting 30% of the UK's electricity from renewables by 2020 is just not feasible.

But looking at the newer 2011 figures suggests this might not be a particularly solid argument.

DECC says we need to be generating 79 TWh of renewable electricity a year by 2017. According to our calculations, this would mean an increase of about 8.92 TWh a year from 2011. Getting to 108 TWh by 2020 requires faster growth - 9.2 TWh per year.

The increase in renewable generation between 2010 and 2011 was 8.6 TWh, so the new DUKES figures actually show something approaching this rate of growth.

Of course, whether this can be sustained is a complicated question. It would probably be unwise to assume that because electricity produced from renewables jumped by 8.6 TWh in a year this will carry on whatever happens, and it's worth pointing out that in relation to the 2020 target DECC says:

"the scale of the increase over the next 10 years represents a huge challenge and will require strong contributions from all three sectors of electricity, heat and transport."

32,000 Turbines? Probably not

Booker goes on:

"If 3,000-odd turbines produced 2.6 per cent in 2010, then to meet the EU target would require something like the "32,000 turbines" mentioned by Davey's predecessor Chris Huhne just before he resigned. This would require us to build about 10 giant turbines every day for the next eight years. Regardless of how many billions of pounds of subsidy might be thrown at this, in practical terms it is quite out of the question."

Is this right?

The 32,000 figure appears to have originated in a Sunday Times article based on this DECC report. The DECC report doesn't contain the number, and the Sunday TImes article doesn't provide any details on how it was calculated. It doesn't appear that Chris Huhne is the source for the number - he  told the Daily Mail that the actual number of turbines built to 2020 is likely to be closer to 10,000, as turbines get larger.

So how many wind turbines would it take to provide the extra 73.6 TWh of electricity a year DECC says we need to meet the 2020 target?

We can work this out, roughly, as:

Electricity generated = Number of turbines x (Turbine capacity x Load factor x Time)

Time is just the number of hours in a year - 8,760. Load factor is the average percentage of maximum capacity at which a turbine operates at, and turbine capacity is the power rating of an average new turbine.

The load factor for onshore wind is 0.27, and 0.37 for offshore. According to Renewable UK, the generating capacity of wind turbines currently being installed is about 2 MW for onshore and 3.6 MW for offshore.

Plugging those numbers in, an extra 73.6 TWh would take either another 15,600 onshore turbines, or 6,300 offshore.

In practice, the numbers are likely to be smaller. Offshore turbines will continue to increase in size, meaning it will take less to produce more power. Turbines will probably become more effective - increasing their load factor. And other sources of renewables will produce more power, reducing the amount of wind turbines needed to hit a particular amount of renewably-generated power.

So the 32,000 figure looks pretty overinflated.

On gas, the man's got a point

Finally, Booker probably has a good point in the rest of his article, where he talks about the government's gas plans.

It's hard to see how the government can be committed to gas power and meeting carbon budgets when carbon capture and storage is still an "unproven technology", Booker says, suggesting that relying on gas will "drive a coach and horses" through carbon targets.

This is a reasonable point - and one that we made ourselves, in slightly different terms, last week.

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Update - Guy Newey of Policy Exchange gets in touch to point out that the 32,000 wind tubrine figure is likely informed by the DECC 2050 Pathways calculator here. (If you hover over some of the wind options, you can see suggested numbers of turbines.) This is a scenario for 2050, rather than the 2020 that Booker is talking about.

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