Wind Farms Do Not Reduce Emissions: De-Bunking The Myths

There are many arguments put forward to show that wind turbines do not reduce carbon emissions. I plan to write a lengthy piece at The Energy Collective at some point explaining the flaws in these arguments. But there is one I feel like debunking now.

This myth is particularly favoured by the Global Warming Policy Foundation, and is sometimes put forward by people who should know better.

Here is how it goes.

Each gigawatt of wind power must be backed up by 1 GW of relatively inefficient OCGT gas power plants. Wind turbines however only run with around 25% capacity factors. Therefore you need to run the OCGT power plants at 75% capacity factors.

In CO2 terms this is a bad idea, and no better than just getting your electricity from CCGT power plants. OCGT plants give you 0.6 tonnes of CO2 per MWh, whereas CCGT plants give you 0.4 tonnes of CO2. So wind backed up with OCGT will give you (0.75*0.6)/(0.4) = 1.125 times more CO2 than a purely CCGT set up.

Wind farms then provide more than 10% more CO2 than you would get if you just stuck with gas! Why bother?

Well, the logic above sounds persuasive and probably would persuade the average person with a prejudice against wind turbines. It is also total nonsense.

There are many engineering reasons why it is nonsense. I could go into them, but it can be refuted a little more simply.

The UK now has over 10 GW of wind power. By the above logic it therefore requires at least 10 GW of OCGT power plants to provide back up to these wind farms. If it does not then the arguments are complete piffle.

Thankfully the UK government provides us with a full list of power plants in Britain. So we can easily check how much OCGT is available to back up wind farms.

Instead of 10 GW of OCGT the UK has a total of 1.3 GW of OCGT. Not exactly an insignificant discrepancy.

Currently the UK has almost 11 GW of wind capacity, but only 1.3 GW of OCGT to back it up. And I can find absolutely no evidence of efforts to procure significant amounts of OCGT to back up wind farms. The argument then is bunk.

But these myths persist, and may go one persisting.

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4 thoughts on “Wind Farms Do Not Reduce Emissions: De-Bunking The Myths”

  1. Part of the myth seems to be that its is OCGT rather than CCGT which provides the back up when wind speeds fall. I don’t know how reliable the figures from the anti-wind Renewable Energy Foundation are, but they publish daily and half-hourly fuel mix data for Britain that separates OCGT and CCGT (www.ref.org/fuel/index.php). What is remarkable looking back over the figures is how rarely OCGT is actually used. And when you look at days when wind speed drops significantly, and compare the half-hourly output from wind, CCGT and OCGT, it seems that almost always it is CCGT, not OCGT, that is used as the back up. Presumably with improved wind speed forecasts, the Grid is able to predict more accurately when back up is needed, so the rapid response of OCGT is not needed?

  2. Good point Robert – seems at current levels wind is displacing peaking CCGT and giving genuine carbon benefits.

    Would be interesting to get an idea of the carbon content of potential low carbon with gas backup/peaking mixes. What would the carbon content be of a mix where the max wind capacity equals the usual maximum demand and CCGT fills the gap, what about nuclear up to the baseload level with CCGT for peaks? Solar at current levels in Germany sometimes tracks much of the peaking demand, so I wonder what a nuclear baseload, solar peak with gas filling the gap mix would achieve.

  3. Capacity factor is such a useless measure: the only time one might use it is as a power developer choosing between sites and technologies. Simple-cycle aeroderivative gas turbines are often run at seemingly absurdly low capacity factors — around 10% — but still make economic sense to their owners when run as peakers.

    To a system operator, a more useful metric is capability factor: how closely a generator matches its predicted output. Wind used to be pretty bad at this, but forecasting models in current use are much better. Wind power is now approaching a firm power source for hour-ahead forecasts (certainly in North America; the UK, I’m not so sure of). Add a little storage, the necessary legislation (FERC be praised!) and you have dispatchable wind/solar power — something the industry’s been dreaming about for decades.

    One of the reasons the Pickens Plan for Wind foundered was that it was based on the assumption that 1 GWh of wind would need 1 GWh of gas to back it up. It was really as much of a gas play as anything else. If you check the Pickens website these days, it’s all about the gas, and wind was just window dressing all along.

    To Jonathan’s comment, one does have to be a little careful basing a national energy plan on a nuclear baseload. If you can guarantee a steady 50 year solid baseload — as the postwar planners had every reason to believe — nuclear makes sense, especially if you have to buoy up an economy with massive infrastructure spending, government R&D and job creation. These days, baseload is much less certain. It’s expensive to engineer in manouevrability to nuclear plants, and few governments have the will to swallow the cost. This results in more frequent surplus baseload generation, where someone in the generation chain has to be paid to curtail.

    It’s rather unfortunate that REF’s three-second soundbites take hundreds of words based on decades of experience to refute. Being first with a “fact”, sadly, seems more important than being correct.

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