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What happens in an extended wind lull?

Extended Wind Lulls

The intermittency of wind is already a huge problem in the UK. It used to be said that "it's always windy somewhere", but that was proved to be untrue a long time ago. Lulls in wind can cover virtually the whole of the UK, and can last for hours, days, weeks or even be prevalent over periods of a month or longer.

When total wind power was small this was a problem that could be resolved using "spinning reserves" of fossil fuels, notably gas. However, as total wind power has increased, lulls in the wind have started to cause bigger and bigger gaps to fill. As wind power increases, we will need to use not only gas to fill the gap, but we will be increasingly dependent on interconnectors. By carefully setting our available gas power and managing its use we can help, but we have limited control over interconnectors, both in terms of availability and the source (fossil fuel or otherwise) of the electricity we are importing. And, as the available wind power increases still further and the gaps get larger and larger, we will increasingly not be able to fill the gap and power cuts will become more likely. Other sources - notably nuclear - are to decline, whilst others just will not have enough available power to make up the difference.

This problem will be made even worse by the fact that by 2050 the National Grid figures show that GB electricity demand will have greatly increased.

The UK will have an increasing number of power cuts, and they will tend to last longer.

Here is an example of what happens now when there is little wind for a protracted period of time.


September 2019

Throughout the month of September 2019 almost all UK electricity demand was frequently met by CCGT (i.e. gas) and nuclear, with some support from interconnectors and biomass and a couple of minor sources. There was little wind during that month, and on several days there was virtually none.

Wind Lulls in 2020

If we assume that a wind lull is when wind is supplying less than 5% of demand, the table below shows the extent of wind lulls in 2020.

Incidence of wind lulls in 2020
MonthTotal Hours <5%No. of LullsNo. of Lulls >5 hoursNo. of Lulls >10 hoursMaximum Lull (hours)
January32.553112.5
February1211112
March3953121
April7065422
May124127432.5
June137.553388.5
July58.584320
August78135221.5
September62.595321
October36.583213.5
November8193245.5
December48.543225.5
TOTAL780854528 

Although demand has been significantly reduced since March due to lockdown and reduced commercial activity, there were wind lulls of almost a day or more every month, with June showing one very extended lull of over 3½ days. No current or proposed storage capacity could cope with such long periods without any significant generation. (It should be noted that wind lulls do not significantly decrease as the capacity of operational wind turbines is increased.)

The National Grid’s Future Energy Scenarios (FES) published in 2020 proposes massive increases in operational wind capacity (over six times current capacity in one scenario) through to 2050 with significant reductions in gas (to zero in one scenario) and nuclear.

It is hard to see what the UK would have done in 2020 without gas and nuclear, and to contemplate what will happen if any of the scenarios in FES 2020 are adopted.

It is also a rather sobering thought to consider how much storage Great Britain will need to cover these frequent extended periods of low wind.

How will the UK cope with low wind days, weeks and months in 2030 and 2050?