100% renewables is possible because it was a windy day in Denmark yesterday

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Another Friday, another rant blog from me about bad energy journalism in the Guardian. Shall we dance!

A pet peeve: continually telling people what the record high wind or solar power output was without mentioning what the average is. This results in all kinds of strange beliefs. For example, the internet is now full of people who believe that Germany gets half of its energy needs from solar panels.

Today’s Guardian report tells us that yesterday Denmark got “140% of its electricity deman from wind turbines”.

Here is how it kicks off:

On an unusually windy day, Denmark found itself producing 116% of its national electricity needs from wind turbines yesterday evening. By 3am on Friday, when electricity demand dropped, that figure had risen to 140%.

Interconnectors allowed 80% of the power surplus to be shared equally between Germany and Norway, which can store it in hydropower systems for use later. Sweden took the remaining fifth of excess power.

“It shows that a world powered 100% by renewable energy is no fantasy,” said Oliver Joy, a spokesman for trade body the European Wind Energy Association. “Wind energy and renewables can be a solution to decarbonisation – and also security of supply at times of high demand.”

Let’s think about that. It is windy one day in Denmark, so 100% renewables is not a fantasy. A new logical fallacy appears to have been erected.

I am awake at 2.30 pm therefore being awake 100% of the time is not a fantasy.

Then we have the strange idea that wind farms can be a solution to “security of supply at times of high demand”. How is this so?

Let me compare hourly electricity load with hourly wind farm output in Denmark to see how much security of supply is provided by wind farms.

Below is a scatter plot of hourly wind farm output versus electricity load for each hour from 2011-2014 in Denmark.


When demand is high, you want wind farm output to be high. Clearly you do not want any points in the bottom right hand parts of the graphs. But like it or not lots of points appear at the bottom right.

Look at 2013. Load was at its annual maximum of 6138 MW at the same time as wind farm output was only 115 MW. In other words, electricity demand in Denmark peaked that year at a time when its wind farms were producing at around 2% of their rated capacity.

That is the basic reality of wind farms. Until we figure out how to store the electricity they generate, then wind farms can essentially be relied on to provide zero electricity. You will need things like gas power plants to provide true security of supply for the times when wind is literally not blowing.

As always, numbers should trump wishful thinking and hand waving.


7 thoughts on “100% renewables is possible because it was a windy day in Denmark yesterday

    rhymeafterrhyme said:
    July 11, 2015 at 9:48 am

    “Oh glorious white masts!
    Out of subsidies wrought,
    From a left wing agenda
    So skilfully taught,
    By politicians on a mission
    To change the world,
    Our judgement being clouded
    As the green mist swirled….”



      Robert Wilson said:
      July 11, 2015 at 10:02 am

      Thanks for using the comments section to advertise your bad poetry.


        rhymeafterrhyme said:
        July 11, 2015 at 11:49 am

        Robert you’re welcome
        Your opinion is respected,
        Sorry my rhyme
        Doesn’t get you connected.


    Jeremy Greenwood said:
    July 12, 2015 at 5:42 am

    As I’ve said before, your posts are a [insert deity]send… saving me much time accumulating and presenting the real data clearly, in order to combat half-baked sensationalist innumeracy, and provide rapid high quality analytical feedback to those who care about our increasingly carbonated atmosphere and ocean, yet lack the skills to critically analyse the breathless pieces that pass for environmental journalism from otherwise reputable who ought to know better. May your beard grow ever longer.


      Robert Wilson said:
      July 12, 2015 at 8:27 pm

      If God exists he is probably a complete son of a bitch, so I’m not sure if I take that first sentence as a compliment.


    […] is how it kicks off: – Click here to read the full article […]


    Ferelith Drummond said:
    July 15, 2015 at 9:45 am

    It’s really simple. The wind does not blow when it is very hot nor does it blow when it is very cold. End.


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