Wind farms and blackouts

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“Lack of wind or nuclear problems ‘could wipe out UK’s spare power capacity'”

This is a headline at the Telegraph this week. Lack of wind may cause blackouts. Should we worry about it?

There are of course no numbers in the Telegraph story, or in this rather absurd story in the Guardian that claimed that recent fire at Didcot B power station showed “the intermittency of some renewables is simply not a problem“.

What we really need are numbers, and not badly thought through talking points.

So, can we really rely on wind farms to provide our electricity around the clock?

If you ever tune into BBC1 at 6.28 pm you will know that winds around Britain are not consistent, and that we frequently see calms from north to south. Wind speed of course is not the whole story. The kinetic energy goes up with the cube of wind speed.

The result is that wind farm output often goes close to zero, and this can coincidence with peaks in demand.

Let’s look at the last three years.

Below is a plot of hourly electricity demand versus wind power output in October, November, and December 2011. The black vertical line is the peak in demand; while the red horizontal line is 5% of peak wind farm output. If we are thinking about blackouts, what really matters is the bottom right. The fewer dots there the better.2011In 2011, wind farm output peaked at around 3.2 GW.  However, you can clearly see that wind power output is often very low. It often gets close to 5% of peak wind farm output.

In 2012 things were much worse.  Wind farm output was frequently below 5% of peak output during these months. And, as the bottom right of the figure below shows, wind farm output was below 5% of its peak when demand was more or less at its annual maximum. A repeat of this is 2014 may make things very dicey.2012Things were a bit better in 2013. There were fewer calms that year. However, wind farms could still not be relied upon to provide more than 5% of their peak output. 2013Essentially we do not want many dots near where the black and red lines intersect. In 2013, this was relatively OK. In 2012 it was not.

So, weather dependent, Britain will be blackout free this winter. But please, do not tell me that intermittency of renewables is not a problem.

Note on data

The National Grid provides data for hourly load and wind farm output. To save me time I have taken this from PF Bach’s website.

This article is a very quick back of the envelope piece. I’m currently writing something for the Energy Collective, about the need for back up for wind farms. Hence, I was able to quickly pull these plots from what I had produced for it. That piece will look in detail at data for multiple countries. But questions/suggestions below the line would be welcome, so that I can get the final (more finished) article in good shape.





12 thoughts on “Wind farms and blackouts

    Keith Brown said:
    October 30, 2014 at 1:59 pm

    The power output of wind turbines is proportionate to the CUBE of the wind speed, and this is truly damning in terms of their efficacy as a source of power to the grid. So the wind is intermittent, and wind turbines are intermittent cubed. There is no cure for this.


    ppp251 said:
    November 1, 2014 at 6:26 pm

    The solution is to build HVDC line from Brazil to UK and build PV in Brazil. UK peaks between 19:00 – 20:00, Brazil is 3-4 hours behind so PV should do the job.

    HVDC lines have 3% loss per 1000km and 0.6% at the terminals. Brazil is 7500km away so that makes losses about the same as pumped hydro. Technology and economics are there.

    Alternatively, you could build natural gas backup and use waste heat for district heating, which is how Denmark is coping with this issue.


      jmdesp said:
      November 12, 2014 at 11:07 am

      I really, really initially thought the first 3 lines of that comment were satire. A 7500km line between UK and Brazil. Maybe … you should try to connect back to reality by reading why the Desertec project ended up dead in the water ?

      Denmark is much more coping with the issue by massively importing electricity from it’s neighbors when there’s no wind than with natural gas backup. Actually it’s using almost no gas backup, it’s all coal backup.


        ppp251 said:
        November 12, 2014 at 11:36 am

        Arab spring made Desertec politically unattractive. However, it’s not entirely dead. Tunur is going forward (a 2GW CSP project in Tunisia with HVDC link to Italy). We will see how this plays out.

        Denmark. Check your facts. They mostly use biomass and gas for backup, coal is shrinking and is to be phased out by 2025-2030. They have enough backup capacity to cover their peak load if needed, so importing electricity from neighbours is a market based decision, not a technical necessity.


        jmdesp said:
        November 12, 2014 at 12:59 pm

        The last time I heard that Denmark intended to phase out coal by 2025-2030 I did check my facts.
        They quickly confirmed (using ENTSOE data ) that in 2013 over the year coal was still 42% of Denmark electricity production (only 16% for gas), and also 55% in July when the wind is not there (and demand is low enough to shut down the expensive gas). In February, fossil production reached 75% the total, cold but not as much wind as usually in winter.
        There could be much to say also about the volume of exchanges, which is so large calling it a market decision hides how much of an abnormality it is in the European market, the already large net result is still not representative of the fact that raw import reached 57% of consumption in July (raw exports at 29%), and raw export 42% of consumption in March (raw imports at 26%), but I will stop here polluting this blog.


    ppp251 said:
    November 12, 2014 at 2:01 pm

    Thanks for the link. Cherry picking one particular month (February 2013) does not change the big picture. Coal is on it’s way out in Denmark:

    They planned to phase-out coal completely by 2030, but now they’re considering to speed up by 2025:


      jmdesp said:
      November 19, 2014 at 9:53 am

      The level of denial displayed here is so high I don’t believe any further discussion will bring anything useful.

      For reference France might phase-out coal completely by 2025, all existing plants are more than 30 years old, and there can be hope that none will be updated to the newer pollution norms, or that the few ones that will be (maybe less than 2GW) will be closed within the next 10 years.
      No other European country stand a chance.


        ppp251 said:
        November 19, 2014 at 4:27 pm

        French grid is 10% fossil fuel and most of this is generated in the winter. The problem is peak load.

        They have about 63GW of nuclear capacity, but their peak is about 100GW (which happens in the winter cold spells).

        Currently capacity factor of French nuclear is about 75%, because of load following. If they build additional nuclear capacity to cover peak load, then capacity factor would drop to 55%.

        How exactly are they going to phase out coal? By replacing it with gas?

        Coal and gas have comparatively low capital costs (so they can afford to run on a bit lower capacity factor). What exactly is going to cover winter demand? Imports from German coal?


    jmdesp said:
    November 19, 2014 at 4:42 pm

    Yes, by replacing with gas. Replacing an older, around 35% efficient coal plant by a modern 60% efficient gas one, is the most cost effective way of reducing CO2 emission. As the gas one is only used during peak winter season, it doesn’t emit so much CO2 all year round (here installing some wind makes sense by producing more in winter, so lowering the required load factor of this gas unit).

    And the need for external imports in a once every 10 years event like February 2012 does not have any significant impact on what the average CO2 emission is. France is a net exporter on the sum of all it’s frontier almost all year round, even if they are many days where it’s a net importer from Germany, that’s actually in order to be able to export more at a higher price on other frontiers.


      ppp251 said:
      November 19, 2014 at 5:13 pm

      Sounds reasonable and it isn’t that different from Denmark, which also plans to phase out coal and keep natural gas for the time being.


        jmdesp said:
        November 19, 2014 at 6:18 pm

        Except that the 2013 start point for France is 1,5% of the mix from coal, with until now a high of only 2,68% in October. With those numbers, yes no coal is within reach. With the danish numbers, not at all. Nuclear and hydro are the reason for the huge difference.


    jmdesp said:
    November 19, 2014 at 6:19 pm

    Sorry those are the up-to-now 2014 numbers, not 2013. December won’t change in a big way.


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