A question of scale

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Occasionally the Google search referrals I get for this blog give me ideas for a post, and today I got a rather topical one. The UK government has just given planning approval for the first new nuclear power plant in almost 20 years, and evidently someone wanted to know the following:

How many windfarms are needed to generate the same amount of power as Hinkley point nuclear plants?

According to the BBC this nuclear power plant will take up 170 hectares of land. For those who don’t understand hectares (and that includes me) this is 1.7 square kilometres, and from the air will look something like this:


So, how big would a wind farm need to be to provide as much electricity as Hinkley C? The plans are to have two 1.6 GW reactors on site. These will likely have capacity factors somewhere between 80 and 90%. So, the average power output from the plant should be at least 2.6 GW. Let’s use the London Array offshore wind farm as a starting basis to see how big a wind farm would need to be to match it. The London Array is a 630 MW wind farm, covering an area of 100 square kilometres just off the English Coast. If we assumed a capacity of 35% (I have not seen projections for its capacity factor, but it is not likely to differ too much from this) then its average output will be just over 0.2 GW. So, if we wanted to scale this up to provide as much power as Hinkley C then we would need a wind farm covering about 1,200 square kilometres, which is just a bit less than the area of Greater London.

This of course does not mean that nuclear power is better than offshore wind. There are a range of other considerations. But it is a nice demonstration that large scale renewables will require a lot of land, or sea. And the map below from Google Earth shows roughly how big the wind farm will need to be. (thanks to Dan Cookson for sending me code to produce this map.)



37 thoughts on “A question of scale

    John Russell (@JohnRussell40) said:
    March 19, 2013 at 6:53 pm

    Typo? “1, 1000 square kilometres”.

    Just out of interest, as a rough rule of thumb, a hectare is about the same size as a football pitch.


    billslycat said:
    March 19, 2013 at 9:23 pm

    Such a wind farm would likely have a true average capacity of about 20%, not 30. And when the wind isn’t blowing at a prop per speed it will produce enough energy to power ZERO homes. The nuke plant will deliver consistent power. The industrial wind installation will wear out in about 12 to 15 years , not the claimed 20 to 25. Plus every megawatt of wind needs to be backed up with a megawatt of fossil fuel generation or you’d often be blacked out. Wind is a failure and a sham for these and other reasons. The nuke plant will deliver as promised, although a lot of people fear them. Newer plant designs are much safer than the ones built 40 years ago and Britain is not a major earthquake area, but I understand the fear factor.


      Robert Wilson said:
      March 19, 2013 at 9:27 pm


      If you are going to make claims please provide some evidence to indicate if they are are true. Your statement that this wind farm will have a capacity factor of 20% is groundless. Simply check average UK offshore wind farm capacity factors: https://restats.decc.gov.uk/cms/annual-variation-in-wind-load-factor/


      CMac11 said:
      March 20, 2013 at 11:15 am

      Absolute nonsense figures being banded about as already stated. why not have a look at a representative UK offshore wind farm with a bit of operational history to see about capacity factors. http://www.variablepitch.co.uk/

      Choosing one at random (Gunfleet Sands 1 and 2) between April 2011 and November 2012 the monthly capacity factor ranged from a low of 20% to a high of over 60% averaging out at about 34.7% for the period. So it would appear the author was about right. In fact in future offshore farms are likely to be further offshore with even better wind resource so a figure of around 40% won’t be uncommon. in 2011 and 2010 the Danish offshore wind farm Horns Rev was producing capacity factors of close to 50%. see http://www.lorc.dk/offshore-wind-farms-map/list.

      As for your wear out claims – also totally unfounded but there simply isn’t the proof to say either way who is right – I will say there is a lot riding on the installers making sure they last their lifetime so my guess is they’ll make sure of it!


    Cpragman said:
    March 20, 2013 at 12:57 am

    So why not compare what it takes for wind to give the same capacity factor as the nuclear plant?

    To get same capacity factor, you’d have to build 2 to 3 times more wind turbines, and store the excess in a pumped storage facility.


      Robert Wilson said:
      March 20, 2013 at 9:39 am


      The reason a wind farm cannot provide the same capacity factor as a nuclear power is simply that it is not windy all of the time. And building pumped storage will actually result in a lower capacity factor than what I have assumed above because the electricity is not stored with 100% efficiency.


    Alan N said:
    March 20, 2013 at 12:20 pm

    How realistic is the suggested capacity factor of 80-90% for Hinckley C? Current capacity factors for UK nuclear are much lower – more like 50-60%.


      Robert Wilson said:
      March 20, 2013 at 12:44 pm

      Alan N

      Using existing nuclear plants is not a good comparison. Pretty much all of them are gas cooled reactors, and are old and beat out of shape. In fact 4 of them only run at 70% of capacity. American nuclear power plants average about 90%. French average just under 80%, and a lot of them load follow. So, 80-90% is a reasonable assumption.

      Also, the only non gas cooled reactor in the UK, Sizewell B, has averaged 82%. http://www.iaea.org/PRIS/CountryStatistics/ReactorDetails.aspx?current=263


    Mark said:
    March 21, 2013 at 2:04 pm

    If wind power is so good and it’s technologically simple, why haven’t we done it earlier on a large scale? Why, because it isn’t practicable and affordable for a heavily industrialised and densily populated country. If you don’t like nuclear power, leave the UK, move to Denmark (they’ll need to import from nuclear Sweden eventually). We need a balanced energy mix but I wish I was french sometimes!


      CMac11 said:
      March 21, 2013 at 5:51 pm

      Wind power is not a particularly simple option as the column suggests it actually requires vast amounts of space (hence the move offshore) and fairly strong investment to compete on a scale with conventional power stations. It’s only developments in the past decade (i.e. turbines growing exponentially in size) that has made them competitive on a large scale – hence why they haven’t been adopted sooner. Unfortunately there are no simple options in the quest for cheap fuel with oil and gas prices ever on the rise, the new nuclear at hinkley C going to be more expensive than onshore wind (even before it inevitably comes in over time and over budget) and coal being forced (rightly) out of the market due to high emissions!

      As such wind should and will form a significant portion of our power in the future.


        Mark said:
        March 21, 2013 at 6:59 pm

        Building wind turbines offshore is not difficult, have you ever seen an oil platform. Nothing is ever built to original budget including wind farms. Until recently no-one was interested in developing bigger wind turbines because we had a bigger fleet of 1960-70s reactors minimising emissions. Had we built the fleet of UK PWRs in 1980s-90s, there’d be a minimal wind power industry and bills would have been low. I wonder who did that – France of course. Who created this problem – Westminster.


      Robert Wilson said:
      March 22, 2013 at 8:16 pm

      Once again Mark

      This is a complete waste of my time. This post is about a specific issue. If you don’t like wind farms, fine. But if you don’t have anything to say about the actual content of my posts then don’t say anything. I am aiming for a grown up conversation here, where we can look at issues in turn instead of people jumping up and down and shouting about what concerns them.


    Colin said:
    March 22, 2013 at 11:47 pm

    “…if we wanted to scale this up to provide as much power as Hinkley C then we would need a wind farm covering about 1,200 square kilometres, which is just a bit less than the area of Greater London.”

    Or, for another comparison, about the same size as Fukushima’s 20km exclusion zone.

    20km^2*pi = 1256 sq km

    With nuclear you can get an uninhabited area after a rare accident. With wind you need to create an uninhabited area of the same size – no accident required.


      Robert Wilson said:
      March 23, 2013 at 8:41 am


      While possibly true. This is an incredibly silly way to phrase these things. I don’t think a huge offshore wind farm is comparable with the Fukushima disaster, and to say so seems to be a rather crude and disgusting form of propaganda.


        Colin said:
        March 23, 2013 at 9:12 am

        Whereas comparing the area footprint of a nuclear plant with the area of an offshore windfarm is not crude propaganda?

        Robert, perhaps I have misconstrued the point of this article: what was the objective of your comparison? My assumption was that it was to show a benefit of nuclear power compared to wind. Are you suggesting you were being neutral? Or simply that your propaganda is more subtle and effective, rather than crude and disgusting?

        Those who are opposed to nuclear power are not particularly swayed by the land area required in normal operation. Their typical gambit is along the lines of “wind farms can’t cause mass evacuations”.

        My point is that the same area needs to be clear of human habitation before you start with wind power.

        (And, for the avoidance of doubt, I am not arguing against the suitability of wind power. It is by far the best renewable option we have in the UK.)


    Richard Lawson said:
    March 23, 2013 at 8:34 am

    If we are thinking in terms of ground area, me must not forget the area denied for human use in the event of a nuclear accident. My rough calculations suggest that if all the ground lost to human habitation as a result of the Fukushima accident were laid down to photovoltaic cells, they would generate about 7 (seven) times as much energy as the Fukushima plant.
    But before anyone else says it – yes I know, it could never happen here.


    Martin Wright said:
    March 24, 2013 at 9:21 am

    Fascinating conversation, and thanks to Robert for doing the sums. Out of interest: has anyone done anything comparable on solar pv; on CSP (concentrated solar power – in the Sahara, not Somerset, obviously); and on the potential new wave power?


    AndrewR said:
    March 24, 2013 at 11:30 am

    I like the clarity of calculations. It also points out that offshore wind and nuclear have very different and very complementary offerings to the UK power mix.

    It would be interesting to try and compare the value of forgone land & sea. I suspect that a hectare of UK land is more far more valuable than UK sea (valuaton including ecosystem services etc).


      Robert Wilson said:
      March 24, 2013 at 11:46 am

      Thanks Andrew

      That’s not a particularly easy question to answer. The offshore wind farm will cause problems for fisheries for example. Fishermen certainly don’t like them too much. Shipping interests also have problems with them, as they may have to increase shipping times to get around them.

      As far as I know there have been more or less no efforts to quantify this. A problem is that, depending on the stakeholder, an offshore wind farm may be good or bad depending on where it is built. They can, for example, preclude certain types of fishing. In some areas of the sea this may be a good thing, in others less so.

      Visual aspects are another problem. Some people clearly do not want to see an offshore wind farm when they look out to sea, and this point of view goes far beyond Donald Trump. So a £ value should be put on that, or certainly the ecosystem services people would argue that you should. Such things though are normally just plucked out of thin air. So, £5 per person in the region for the value added by a sea view. Reduce this by a couple of pounds for the impact of the wind farm. Total guess work, but any valuation of offshore wind probably should include it.


        Alan N said:
        March 24, 2013 at 1:08 pm

        I’m not at all sure that visual impact can be treated in the same way as fishing or shipping times. The latter are measurable, and can readily be quantified. Visual impact is subjective, and the evidence is that perceptions of negative impact of offshore wind lessen after the turbines are in place, and lessen still further over time.


        Robert Wilson said:
        March 24, 2013 at 1:11 pm


        While what you are saying may possibly be true, could you please provide evidence instead of saying “evidence shows”?



        Alan N said:
        March 24, 2013 at 3:48 pm

        See, for example, the 2008 Moffat Centre report for the Scottish government on ‘The economic impact of wind farms on Scottish tourism’.


        Colin said:
        March 24, 2013 at 5:51 pm

        If you have not already seen it, the European Commission’s research into externalities is interesting. The project is called ExternE (google: “externe national implementation” to get some examples).

        For example, the Danish implementation covers offshore and onshore wind (p91 onward):

        They quantify the impact of visual instrusion by analysing the impact on house prices. In one example it has no effect; on another it does have a small cost.

        Interestingly, for the marine impact they consider the effect on the fish rather than on the fishermen. Since the impact on fish is generally protective, they assign no monetary value to this externality.

        As usual with the ExternE studies, the overall external cost of wind power is dominated by the mortality, morbidity and AGW caused by air pollution from the *fossil fuel* used during the lifecycle. This is very low compared to most other generation options.


    The limits of biomass | Carbon Counter said:
    March 25, 2013 at 5:41 pm

    […] a power density of roughly 2.5 W/m², or about 5 times greater than biomass. As I showed in an earlier post an offshore wind farm would have to be something close to 1,200 km² to provide as much power. So, […]


    […] a power density of roughly 2.5 W/m², or about 5 times greater than biomass. As I showed in an earlier post an offshore wind farm would have to be something close to 1,200 km² to provide as much power as […]


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