Flat Calm Across the UK

While Roger and the west coast of Mexico had rather too much wind recently, the UK has just enjoyed a superb spell of weather with high pressure in charge for several weeks. I’m not sure how unusual these conditions are and one reason for this post is to benchmark the effect of flat calm conditions on wind output for future reference.

On 4th October, in the early hours of the morning, 9136 MW of wind turbines were producing 66 MW of electricity. The load factor dropped to 0.7%. I find this astonishing from a meteorological perspective since about half the metered turbines are offshore and many of the rest are on Scottish hillsides. The wind momentarily dropped effectively to zero across the whole of the UK. As an aside, on the same day South Carolina and the South of France were hit by severe flooding.

Figure 1 Roughly 7 weeks of data shows clearly the spells of high pressure centred on the UK separated by brief spells when fronts moved through. On 3rd and 4th October the wind dropped completely across the whole of the UK. I’m unsure how rare an event like this is. X-axis marks at 24 hour intervals. Click all charts for large readable versions. Data from BM via Gridwatch.

Installed and Metered Wind Capacity

Balancing Mechanism (BM) reports wind production in two different ways. Large wind farms are connected to the high voltage grid and are metered but small wind farms and individual turbines are not. The latter are connected to the low voltage grid and are seen by BM as negative demand. The same applies to roof top solar PV. Clive Best looked into this a few months ago and concluded that only 68.5% of UK wind was metered. The remainder shows up as reduced demand. Clive now grosses up metered wind reported by BM by a factor of 1.46. If you check his and Leo’s wind figures using the links on the right side bar you’ll see the difference. The factor of 1.46 is of course not constant, and will require revision in future as the wind fleet evolves.

Figure 2 shows “demand” from BM reports compared with metered wind. One observation is that the demand curve looks a bit ragged and I believe that is because unmetered wind and solar are included in it. I think it is also likely that the “V” shaped notches in the middle of the demand peak will be filled with solar supply (seen as negative demand).

Figure 2 UK demand (less embedded wind and solar) compared with metered wind, 1 Sep to 22 Oct 2015. Note that I downloaded the data during day time of 22 October. The load statistics are calculated only for full days ending on 21 October.

Renewables UK (RUK) and The Renewable Energy Foundation (REF) both report up to date figures for installed wind capacity as follows:

RUK onshore 8258 MW
RUK offshore 5054 MW
RUK total 13339 MW

REF onshore 8414 MW
REF offshore 5031 MW
REF total 13445 MW

Using Clive’s factor of 1.46, I am estimating that metered capacity for September / October was 9136 MW. From 1 Sep to 21 Oct, metered wind produced 2018 GWh out of a possible total of 8990 GWh yielding a load factor of 22.5% for this quiescent period. This compares with an average load factor of 31%.

Total metered demand was 38884 GWh, hence metered wind produced 5.2% of metered demand. Total wind would have produced 7.6% of the total.

Figure 3 illustrates the distribution of capacity factors. Over the 51 day period, wind output was below 10% of capacity for the equivalent of 15 days, i.e. for 29% of the time

Figure 3 BM reports data with 5 minute resolution producing 14890 lines of data for the period in question. The data were sorted according to wind output and capacity factor calculated on the sorted data to produce this chart. The x-axis marks with 288 spacing represent 24 hour periods. The chart shows that for the equivalent of 15 days, capacity was below 10%.

Concluding Thoughts

  • It is possible for wind across the whole of the UK to fall effectively to zero. It will never be possible to assume that wind can offset dispatchable capacity. No number of inter-connectors internal to the UK can solve this problem.
  • Embedded wind and solar is seen by the Balancing Mechanism as negative demand. This needs to be taken into account in any analysis of actual UK power demand and consumption.
  • Future analysis may include Ireland, Denmark and Germany for the same period.
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42 Responses to Flat Calm Across the UK

  1. Graeme No.3 says:

    If all the wind turbines are delivering near zero electricity, the answer is to install lots more turbines (so long as you are either a greenie or insane).

  2. climanrecon says:

    That persistent High in the North Sea produced a pleasant dry sunny autumn in England, but in winter would produce a double whammy for the Grid, freezing evening temperatures and no wind.

    The Grid clearly has to be able to cater for zero wind input (which raises the obvious question of why bother with it), but why do so many “Professors of Energy Policy” deny that fact? Here is Catherine Mitchell from Exeter University:

    “However, it is designed around the out-dated and over-simplistic notion of 100 per cent renewables back-up: that every 1GW of wind power capacity, for example, needs 1GW of coal- or gas-fired capacity on standby. It is demonstrably untrue; but the myth persists, and the government has bought it, despite advice from legions of experts and counter-examples from more enlightened countries.”


  3. Andrew says:

    Yes, it would be extremely good to see the data for neighbouring and more distant European countries for the same period. Wind correlation clearly does decline with distance between pairs of observations, but then R21

    • Leo Smith says:

      The reality is cyclonic depressions. especially those that produce decent wind, are small affairs, and soon over. Anticyclones are huge continent sized things. Any winter pressure chart sequence will contain at least three large anticyclones affecting nearly all of continental Europe. Occasionally Scotland is far enough from the centre to generate something.

      See page 8 of :


      However the AVERAGE power looks quite good because turbines obey a square or cube law with windspeed (cant remember which) so a few storms soon add enough energy to the average to make up for days and weeks of next to bugger all.

      • Wind turbine response is actually close to linear between the cut-in speed and maximum output:

        The problem is that the wind rarely blows above the 3.5 m/s cut-in speed in high pressure systems.

        • Leo Smith says:

          With respect that curve is widely quoted, but does not appear to be borne out either by the measurements made on actual turbines or indeed the data in e.g. Gridwatch,

          The source of that graph actually states in the text that the power in wind is proportional to velocity cubed.

          That graph assumes that the cube law regime is clipped by the deliberate limiting of power output that is that the electrical generators is built smaller than the windmill could deliver, and the windmill ‘throttled back’ to curtail output to what the generator and inverters can withstand. That makes no economic sense – the chance to grab subsidy dollars/euros/pounds at times of high wind is not discarded!

          Once again we have idealised models that are widely accepted to be the ‘truth’ when actual measurements show a different picture.



          shows a graph of manufacturers claimed output versus measured for a given turbine.

          I haven’t the time to do it, but it should be possible to look at te variability of wind output on Gridwatch and if we assume a random distribution of wind speeds, gain some idea of the cumulative power curves of all the installed base.

          To summarise:

          (1) the energy in the wind follows a cube law with windspeed. An idealised turbine might be expected to follow this ciurve.

          (2)Fixed losses in the mechanical power train and inverter mean that there is a minimum speed below which nothing can be generated.

          (3) above a certain speed output will be curtailed to prevent overload.

          (4) at another even higher speed, the turbine will be feathered and braked to prevent damage.

          The argument is really about how big the difference between (3) and (4) is.

          I say its a very narrow range – your graph implies it is very large and covers most of the working range of the turbine.

    • GeoffM says:

      The website pfbach.dk gives hourly wind readings for 6 Euro countries. I am trying to do a study of how often would a trans-Euro super-grid be useful ie. when Wind power is low in country x, it is high in country y, so y can send spare energy to x. But my study is presenting big challenges and is time consuming.
      Initial findings are that such a system of interconnectors would be useless for around three-quarters or more of low-wind events. ie. if the wind’s low in country x, it tends to be low in country y at the same time. Or if the wind’s high in country x, it tends to be high in country y.
      Some time ago a graph was presented on this website which showed Wind output over about 6 countries plotted against time, and it collapsed to very low in all countries at the same time. But we need a bigger sample size.
      PS be careful with these generation spread sheets as some of the times are Central European Time.

      • Hugh Sharman says:

        GeoffM, you might take this up with Hubert Flocard, an occasional contributor on this blog, who has already done fantastic work in this area going back many years.

        Paul-Frederik Bach at http://www.pfbach.dk has also done a mighty amount of careful work in the same area.

  4. Tom Knott says:

    At my age I can recall a lot of blocking highs, especially the winter ones. One long ago when we were in the Vale of York went on for many weeks and for most of that time there was a lot of fog. But then in Yorkshire there were a lot of coal fired power stations so the electricity stayed on. Had we been reliant on wind or solar we would all have frozen to death.

  5. Paul Miskelly says:

    It is hardly surprising, given, as Leo Smith correctly stated in an earlier comment that
    anti-cyclones are huge, continent-sized things, that wind farm total output drops to near-zero
    fairly frequently. I conducted an analysis of wind farm operational data, for the entire calendar
    year 2010, for wind farms spread rightr across the Eastern Australian grid – geographically the
    largest single interconnected grid on the planet, and, guess what: on over 100 occasions during
    that year wind farm output dropped to below 2 percent total installed capacity. On a couple of
    occasions there was absolutely no wind output whatsoever. Later analyses show that, even with a
    considerably larger total installed capacity now, the same pattern recurs. Quie simply,
    one cannot defeat the meteorology.
    Given that the entirety of the UK is far smaller in area than that of the Eastern Australian grid’s
    geographic extent, it is hardly surprising that you are seeing these results.
    My paper is entitled “Wind Farms in Eastern Australia – Recent Lessons”.
    A search should locate a copy.
    A major concern is that as the total installed wind capacity increases, so too does the amplitude
    of the swings in output, potentially leading to controllability, and hence reliability issues, for the
    The paper’s analysis shows that wind energy is a hideously expensive, grotesque, failure as a
    means to reduce CO2 emissions. Wind energy’s only purpose is to create obscenely lucrative subsidy streams for wind farm owners.

    • Graeme No.3 says:

      Thank you for that, it saved me having to find my copy. I believe their was a second report confirming your finding (Peter Lang?).
      On the other hand the Beyond Zero Carbon (or some such silly name) came up with a “survey” saying that 100% renewables was possible as a counter to yours.
      I think their study was done on a laptop computer, while standing up-right in a hammock and watching the TV, while the numbers were generated by mouse movements (that’s a pet mouse running on the keys). Seriously I think it worked on an hourly basis for a few days and was utter crap.
      I ran into one of these guys preaching at the local monthly market, so I asked a few questions – quite politely. After 15 minutes he packed and went off “to do more reading”. His knowledge of electricity could have been written on the back of a postage stamp with a broad nib.

      • jim brough says:

        Civilisations would not be possible without the emissions caused by the simple chemical equation of metal oxide or sulphide being converted into the metal by reacting it with carbon at high temperature to refine the metal and create the much maligned CO2

  6. GeoffM says:

    You can find the metered UK wind capacity via a spread sheet on bmreports.com. From Mar 2014 to 24th Jul 2015 it strangely stayed at 8403 MW. I monitored it daily when possible. On 24 Jul 2015 it suddenly increased to 8972 MW (but wasn’t added to the spread sheet till early Sept). It lists individual ‘farms.

    It is a myth that high pressures bring the classic low wind events. It is a “col” which does this. A col is an area between pressure systems. A classic UK col has highs to north and south, and lows to east and west. During the 23 day low wind period from 31 Aug 2014, if you compare half-hourly Wind data to 6-hourly synoptic charts, Wind production went UP each time a high pressure came in. Indeed a high can sometimes give considerable wind energy.

    The low wind event of 4th Oct is mentioned above. But what one must remember is that when wind farms aren’t spinning they are often CONSUMING energy. See the rwe.com website. On 19 Sep at 23.50 hours the RWE fleet (1367 MW apparently) was only generating 4 MW net, because their schemes which weren’t spinning were consuming about 3.3 MW total and the ones which were productive were only generating about 7.3 MW. So on 4th Oct how much was being consumed by motionless windfarms? 30 MW? 50 MW? 70 MW? Who knows?

    The mother of all low wind moments was at 23.30 hrs on 31 Aug 2010 when Elexon records 1 MW out of a metered 2430 MW, which is a load factor of just 0.04%.
    The average load factor for the 23 days following 31 Aug 2014 was just 7.8% approx.

    I listed all low wind events for this year (LF<= 5%) up to mid Aug, and one thing I notice is that the exact timing of the lowest Wind energy reading is rarely during peak demand (5-8pm). I only spotted it happening on 5 Apr and 10 Mar. I'm not sure if this is luck or a characteristic of UK weather. But it may or may not save us from power cuts in the winter of 2016/17.

  7. Rob Slightam says:

    would the large combustion directive that is due to close our coal stations (due to high nox not co2 emissions) still apply in the case of a BRIEXT?

  8. Let me start off by saying that I agree with the consensus of opinion here – wind power is for the most part a dumb idea. Aside from what’s been said so far, let me add an additional argument…

    One of the great ironies of the greenie (ie wind-solar advocacy) movement is that if they are correct about global warming, prevailing winds will become a lot weaker over the next century (and beyond). The main force driving the global wind system is the temperature difference between the polar and equatorial regions, as well as the temperature difference between the night and day sides of the globe. Greenhouse gases act like a thermal blanket, trapping heat and evening out temperature differences throughout the planet. The most cited example of that is Venus, where the surface temperature is approximately + 870 °F (+ 465°C) throughout, day and night and at the poles. Compare that to Earth with minimum/maximum recorded temperatures are – 129 °F (- 89°C)/+ 136 °F (+ 58°C).
    Source: http://earthguide.ucsd.edu/eoc/special_topics/teach/sp_climate_change/p_planet_temp.html

    That despite the fact that Venus is an extremely slow rotating planet, taking 243 earth days to complete one rotation. If the Earth rotated that slowly, the night side would have freezing temperatures even at the equator.

    With such stable temperatures, not surprisingly, Venus is almost windless on the surface. The upper atmosphere, by contrast, experiences very little greenhouse effect because it is so thin, and thus experiences fierce winds. If people could live on Venus, they’d need wind towers at least 100km tall in order to produce a usable amount of grid electricity.

    The same basic principles apply on Earth – at the surface, an increased greenhouse effect will reduce wind speed. Wind power is already close to useless, and perhaps even worse than useless since it diverts resources away from real solutions such as nuclear. In a warming world, wind power will be even more useless.

    • Euan Mearns says:

      One of the great ironies of the greenie (ie wind-solar advocacy) movement is that if they are correct about global warming, prevailing winds will become a lot weaker over the next century (and beyond).

      Cy, you need to go on a global warming course. Rid yourself of all the physics and chemistry you may once have learned and replace this with Green Science. It is a fact that global warming will and has caused more storms. The absence of evidence for this does not matter since Green Science is not evidence based. The notion that temperature gradient between poles and tropics is important is outdated. The glaciations were quiescent periods even thought the ice cores are stuff full of salt and dust (pixie variety) during the coldest eras.

      Sorry for the sarc, but what do you do? Its possible that when the AMO shifts to cold mode that average wind speeds may fall a few percent. Someone will lose money 🙂

  9. TedM says:

    You might be interested to read a 2005 paper – Wind Power and the UK Wind Resource[1], written by Dr Graham Sinden (then of the Environmental Change Institute of Oxford University). It is quite often used by the wind industry to back-up their argument against back-up.

    “Extreme lows or highs in wind speed are a natural feature of the UK wind
    climate; however a diversified wind power system would be less affected as it is
    rare that these extreme events affect large areas of the country at the same
    time. This report found that:
    • Low wind speed conditions affecting 90% or more of the UK would occur in
    around one hour every five years during winter;
    • The chance of wind turbines shutting down due to high wind speed
    conditions is very rare – high winds affecting 40% or more of the UK would
    occur in around one hour every 10 years. ”

    1: http://www.eci.ox.ac.uk/publications/downloads/sinden05-dtiwindreport.pdf

    • Günter Weber says:

      The problem with such studies is that usually they do not take into account that wind farms are not distributed uniformly over a country (and the offshore region). Nor are they distributed in a way that they make use of contrasting wind conditions (in case there are regions with negative correlation at all). Instead, wind farms are build at locations where it is i) allowed to build them and ii) where the return on investment is maximized.

      As a result, wind farms tend to cluster in certain areas. Therefore, only the wind conditions in these areas are of importance.

    • climanrecon says:

      Other studies disagree strongly with the tone of that paper, see here for example:


      My personal experience is that the UK often has several consecutive winter days in which wind is very light across most of the country.

    • Euan Mearns says:

      Thanks for this Ted. I had a quick scan and wonder if I live on the same planet as the author. The trouble is this is UoOxford, and those who want to believe this twaddle will simply believe it and will be immune to alternative versions – reality versus fantasy.

    • BillB says:

      Mr Sinden’s original paper was little more than propaganda for the wind industry. He made rather a fool of himself when he appeared before the Select Committee on Science and Technology.

      He correctly claimed that it was very rarely the case that wind failed to generate any power at all anywhere in the UK, but members pointed out that he had cherry-picked worst-cases and had avoided examining the frequency of very low, rather than zero, wind speeds over the whole of the UK, a fairly frequent occurrence.

      The squirming was minuted:


      • Euan Mearns says:

        Hi Bill, i just checked out your credentials;


        I wasn’t aware of this site. Looks like good stuff. But ultimately, like EM, failing to make a tangible impact. Green Thinking has permeated the media, academia and the political establishment to the detriment of society and true science. What to do?

        • BillB says:

          In my opinion, all we can do is continue to try and get over an informed and sensible view to the public and politicians.

          As someone who has been commenting on the Green Emperor’s patchy wardrobe for some 10 years, I think we have made very significant progress politically and with the media.

          In the North East (of England) we have engaged politically and with the planners, to some effect. Scotland is another problem, but even there the financial climate for big wind has certainly taken a turn for the worse.

          Of course the Green Blob continue to wield considerable, well-funded clout disproportionate to their actual numbers (wish the coal/oil industry would send us one of their mythical cheques!).

  10. Jack Ponton says:

    The overall load factor for all wind was probably less, as the unmetered generation includes all the smaller turbines. If the big ones on prime aren’t doing much then te smaller ones in farm steadings will be doing even less. I drive past half a dozen turbines of 25-50m as well as a ‘farm’ with 70 and 80m turbines. Most or all of the former can be stuck while the larger ones, which are on a good site too, are still operating. So total wind output for the UK was probably not much more than 66MW from ~13.5GW installed, less than 0.5% LF.

    Interesting I passed the larger turbines on Friday afternoon. All the 80m turbines were stopped, I suspect tripped out by Thurday’s gales and still not restarted.

  11. gweberbv says:

    What I do not get: If the minimum load factor of wind in a certain area is – let’s say 5% – of the nameplate capacity or it is plain zero – what does it matter from a practical point of view? Maybe zero sounds more devastating than 5%. But in both cases the conclusion is the same: You need to have a backup for more or less all of the nameplate capacity.

  12. Roger Andrews says:

    Leo Smith

    Replying to your comment of October 27, 2015 at 9:08 am and giving myself a little more space.

    I’m presently working with the wind data from El Hierro, where they have five 2.3MW turbines spaced 150m apart on top of a ridge that runs EW. I have wind speeds from a site 3km away which aren’t 100% correct but which match generation quite well. One thing I do notice, however, is that the direction of the wind is almost as important as the strength. The turbine blades rotate nicely when the wind is from the north or south, which it usually is, but production really falls off when it’s from the east or west, maybe because the turbines start interfering with each other. I’m wondering whether wind directions aren’t the cause of the points out in right field on your graph.

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