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Carbon Brief Staff

Carbon Brief Staff

19.10.2012 | 3:00pm
ScienceHidden calculations and a ‘nonsense scenario’: Countering the GWPF wind report
SCIENCE | October 19. 2012. 15:00
Hidden calculations and a ‘nonsense scenario’: Countering the GWPF wind report

Does wind power actually lower emissions, and will having wind on the grid cost considerably more than if the UK well and truly dashed for gas? Skeptic thinktank the Global Warming Policy Foundation (GWPF)’s report ‘ Why is Wind Power So Expensive?‘ has introduced these talking points into the energy debate, and they’re often uncritically repeated by wind opponents. This started a backlash in the energy world – we take a look at the counter arguments.

The report – and subsequent evidence presented to the Energy and Climate Change (ECC) Committee by the report’s author and self-described “dissentient”, Professor Gordon Hughes – was the centrepiece of a report by Christopher Booker in The Telegraph and made the front page of The Express under a headline declaring the the UK’s “obsession with wind” would add £300 a year to energy bills.

Among the claims is the argument that scaling up the UK’s wind power capacity, with gas as backup, would cost much more, and result in more carbon dioxide emissions, than if the country invested in new gas plant.

Goodall and Lynas

Bloggers Chris Goodall and Mark Lynas kicked off the response, publishing a post contesting Hughes’s claim that back-up by gas stations cancels out the carbon dioxide emission savings from wind power.

According to Goodall and Lynas:

“The exchange rate is about one for one: a megawatt hour of wind typically meant the UK grid used one less megawatt hour of gas-derived electricity.”

This means that when the wind is blowing the grid needs less backup from gas plant, not more, as Hughes claims, – so overall emissions go down. They estimate that UK wind farms currently save about 6.1 million tonnes of carbon dioxide emissions over the course of a year  – much the same as RenewableUK has estimated. This is about 4 per cent of the UK’s emissions from electricity.

In a response on the GWPF site, Hughes accuses Lynas and Goodall of “setting up and then knocking down a straw man”, selecting the most favourable time-period for their data analysis, and ignoring the emissions from the gas plants running in reserve to counter the variation in wind supply.

This prompted Goodall to post an analysis of this variation. He showed that the National Grid can cope with much more rapid swings in supply and demand than will ever be likely with the UK’s current wind fleet. This means that the gas plants would not be run in reserve to the extent that Hughes claims.

Imperial College’s response

It doesn’t stop there, though. This week, Dr Robert Gross of Imperial College – who also appeared at the ECC committee to give evidence – and colleagues have produced an addendum to the submission they presented to the committee, to counter Hughes’s calculations in more detail.

As far as they are concerned, Hughes has got it wrong on at least three counts. Gross and his colleagues say he miscalculates how much additional wind power is needed to meet government targets; he overestimates the cost of this additional wind power by £64 billion and he mistakenly argues that 21 gigawatts of gas power is needed to back-up the necessary amount of wind power.

1: Overstating how much wind power is necessary

Hughes asserts that 36 gigawatts of wind will need to be installed by 2020 to meet the government’s targets on renewable energy.

The authors point out, however, that the government does not have an explicit target on wind power. Instead the government aims to ensure renewables produce 15 per cent of UK electricity by 2020, but doesn’t prescribe the mix. It makes decisions based on models that account for the likely electricity supply mix while trying to meet energy targets at the lowest cost.

The authors calculate that Hughes’s figure overstates how much wind power is estimated to be in the energy mix to meet government renewable targets in 2020 by between 5 and 10 gigawatts compared to three alternative scenarios from the National Grid (which estimates 26 gigawatts), DECC (a mid-range of 31 gigawatts) and the Committee on Climate Change (an equivalent of 27 gigawatts).

The authors suggest a plausible outcome based on existing plans for wind power developments for 2020 is 27 gigawatts, much less than the 36 gigawatts that Hughes claims.

2: Overestimating the cost of wind to 2020 by £64 billion

Hughes also argues that the one-time cost of setting up wind farms to meet the 2020 targets will be £124 billion.

But the authors argue that Hughes seems to have based the calculations for his 36 gigawatts estimate entirely on t he current cost of offshore wind.

They argue that the cost of installing 27 gigawatts of wind to 2020  is below £60 billion, including projects already constructed.

The authors calculate the UK electricity system requires an additional 20 gigawatts of wind capacity by 2020, topping up the existing 7 gigawatts already installed. So, 10 gigawatts of onshore would cost £13 billion, 10 gigawatts offshore would cost £31 billion, transmission upgrades (from the Electricity Networks Strategy Group) would cost £8.8 billion, and they assume the current 7 gigawatts has cost £5 billion to date.

That’s a total of £57.8 billion – less than half the figure Hughes calculates.

3: Claiming that wind is less efficient than a gas power plant is based on a “nonsense scenario”

Finally, the authors address Hughes startling claim that 36 gigawatts of installed wind capacity would require being backed-up by 21 gigawatts of dedicated ‘open-cycle gas plants’ (OCGT).

One of the main problems with this claim is the way in which Hughes suggests plugging the capacity gap. OCGT plants – which the authors describe as “jet engines connected to generators” – are specialised types gas plants that are suited to a particular job. They are best suited to plugging gaps when there are unexpected events (such as a power station breaking down) or as ‘peaking’ plants (used when demand is at its highest). This is because they can be started and stopped very quickly and cheaply compared to more efficient plants.

The authors argue that it would be much more likely for more efficient ‘combined cycle’ gas turbines (CCGT) to be used as back up to wind power than OGCT. OGCT being used to back-up the wind power supply is, according to the authors, “economically absurd”. They argue that OGCT being used to displace CCGT in filling this capacity gap could only occur “if the market and regulatory systems totally fail”.

The authors argue that if the fair assumption is that power systems are operated to maximise efficiency and minimise costs, then using the amount of OCGT that Hughes suggests, in the way that he suggests, is irrational.

Hidden calculations

These responses have taken a long time to emerge, but this appears to be because Hughes did not publish his working. Hughes did many of the calculations himself, without showing how his calculations were done, or referencing where his original numbers came from. For instance, his headline-grabbing figure on the inefficiency of wind power is referenced only as “author’s calculations”, something we pointed out when the GWPF first released the report. Without being able to get to the bottom of Hughes’s assumptions, it is hard for people to understand the full implications of his claims – which arguably isn’t helpful when the UK is having to make important choices about its energy future.


Updated on 23rd October: Gordon Hughes has posted a short response to Imperial College's criticisms on the GWPF website.

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