Three facts about wind generation of electricity in the UK:

(1) Headlines exclaim that the UK has beaten its own record and produced 55% of its demand from renewables alone.

(2) Similar headlines (here and here) boast of the average contribution of renewable power over the year (2020 is likely to be a record) and demonstrate the real and laudable displacement of coal and consequent dramatic (world-leading) reductions in GHG emissions.

(3) No headlines, but very real – days when wind and solar don’t contribute and these cause significant perturbations to the grid, price spikes and CO2 emissions rise.



All of these are factually correct – but depending how they are presented (or ignored) can significantly change the narrative.

The Ugly Average

We all know about the intermittent nature of wind and solar so points : (1) the “Good” and (3) the “Bad” above are not really new or news

But the “Ugly” is hidden in the innocuous use of the word “average” in point (2).

When looking at an average value one can be mislead into complacency. There is an old joke about a divorcing couple who seem to be having an amicable split and agree that each should get exactly half of their assets. The punchline being that when they split the use of the swimming pool, one partner ends up with exclusive use of the bottom half.

The average has been respected but the utility is not equal.

In much the same way the headlines about percentage generation as an average over the year disguise a problem of utility. Solar power is most generative in the summer – just when energy demand reaches seasonal lows in Europe. Wind on the other hand can be better matched – winter storms like the recent Storm Bella generate power when it is needed on winter evenings. However, as I have discussed here (The Cold Night of Forgetting) winter anticyclonic conditions can create very long windless periods exactly when it is cold and dark. We haven’t had a really cold winter since 1963 – but when the next one happens – as it inevitably will due to natural variations in seasonal weather, it will put huge strain on the electricity system.

I think about this when walking our dog. A dog that our son begged for and promised to walk everyday come-what-may. To be fair he does some percentage of the dog walking – but when it is cold, dark and rainy – guess who does 100% of the walking duties?

A lot of not much is still not much.

Although the analogies above are a bit flippant, the problem is very real. We can celebrate an average but at the same time understand that the utility is not equal.

On cold winter evenings when we need heat and light – our electricity is dominated by traditional sources – gas, nuclear and coal.

In the example here from the UK, solar is obviously absent and the 23 GW of installed wind capacity (source) is generating about 1.5 GW.

If we increase the installed wind to 40 GW the contribution would be 2.6 GW using a simple extrapolation.

To replace gas and coal (26 GW), and ignoring the 10% that is imported… on this specific day, we would need close to 400 GW of installed wind capacity. Include replacing nuclear and it would be 490 GW.

Thus, to replace gas, coal and nuclear with respect to current electricity demand (ignoring the 2x-3x that home heating and EVs would imply) would require installing 20x the existing capacity of wind generation. If of course we ditch gas home heating – we would be closer to France – which has electricity demand of over 80 GW – so double everything again. And then add electrification of transport and industry and multiply up further…

This looks to be pretty unrealistic – however, the rapid advances in size and capacity of individual turbines may mean that significant capacity increases can occur with less footprint that one would have calculated just a few years ago. It is however, still a monumental project, and opens a whole raft of questions. IF and I repeat, “if” we get even close to covering low-wind days, there would be an equally massive over-supply for much of the year – and there are interesting discussions around what could be done with this “super” energy. Its incorrect to think of it as free, but once (if) built, it is an intriguing question.

Hype toolkit: Beware average values

As a general rule, be very wary of “average” electricity generation numbers, especially when in celebratory headlines. Whilst factually correct (and indeed inherently a massive achievement), the average tells us nothing about how we manage energy security for the times we need it the most.

Not surprisingly, the all important utility can be seen in price signals. |Renewable energy went negative in the spring of 2020 as solar and wind met low demand, and prices have spiked with increasing frequency end 2020 and into 2021 as absent renewables leave a hole in the supply side. (Image source)