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What does this summer tell us about the role for nuclear in the UK’s future energy mix?

The proposed nuclear power station Sizewell C. Nuclear is crucial for the UK’s low carbon energy needs, says Humphrey Cadoux-Hudson | Credit: EDF

Humphrey Cadoux Hudson, Managing Director, Nuclear Development | EDF

5 min read Partner content

EDF says low wind conditions this summer demonstrate the need for nuclear as part of the future energy mix.

The Covid-19 pandemic has disrupted not only the UK’s economy and society, but also the electricity system.

Faced with extreme unanticipated circumstances, including the lowest-ever national demand for electricity, National Grid, the Electricity System Operator, has taken unprecedented actions to ensure the continuous provision of power.

This includes reductions in output from wind turbines, gas plants and interconnectors, and, in the case of nuclear, a longer-term arrangement to reduce output.

The ability to deliberately reduce nuclear and other energy sources has provided important help in managing these difficult conditions.

Many generators cannot offer this assistance, including some onshore wind, solar and small gas, as the System Operator cannot turn them down even when it would be beneficial.

While the turn down of nuclear may have helped the system to operate, it has come at an environmental cost as gas generation has increased in its place.  

Unfortunately, there is another factor increasing carbon emissions: this summer’s long periods of very low wind (which often happens in our summers, for example in 2018 the UK experienced a two week wind drought). When the wind has been low, sometimes for days at a time, gas has made up the difference. In combination with the reduced nuclear output, the consequence is that gas has regularly been 40-50% of the UK’s mix and as high as around 60%. Last week, the UK had to turn coal on.

[Example of a low wind week this summer. Source: EDF] [Example of a low wind week this summer. Source: EDF]

In the future, more wind farms and storage will help manage low wind periods. EDF is investing in both, but they will not be the complete solution. Having more wind farms on the system provides little benefit at times when there is no wind to blow them. Battery storage is too expensive to fill the gap when the wind is low for more than a few hours, let alone a few days.

This summer has shown how more interconnectors will not solve the issue either. Periods of low wind are often correlated across Northern Europe – as they have been in 2020. If the UK were to import power from other European countries when its wind turbines weren’t generating, the imported energy is likely to have been generated by gas or even coal because the wind wasn’t blowing in Europe either. While displacing domestic with imported gas power might look good for the UK’s carbon accounts, the global warming damage is the same.    

While wind has been low for much of the summer, the good news is that solar output has been high and the nuclear power stations that have been kept running have consistently produced low carbon power. This illustrates the importance of a diversity of technologies in our system to meet our decarbonisation goals. There are key roles for lots more wind, solar and more batteries - and a vital role for nuclear, to provide a significant chunk of non-weather dependent low carbon power.

Germany and California both demonstrate the potential consequences of attempting to decarbonise without nuclear. Since 2011, Germany has been enforcing the early closure of its nuclear power stations  while undertaking a huge renewables build programme. The unintended, if not unsurprising, consequence is that coal remains the foundation of the German electricity mix and carbon emissions remain stubbornly high.

In today’s exceptional circumstances, the electricity system can’t accommodate the full output of Sizewell B nuclear power station. The technical fix for this is straightforward, not expensive and is needed for a decarbonised system.

National Grid has a target to make the grid capable of operating with 100% low carbon electricity by 2025.

Rather than demonstrating that nuclear has no place in the future mix as some critics claim, this summer’s events have emphasised its importance for deep decarbonisation and security of energy supply.

Not only is nuclear compatible with this target, but it is necessary to make it possible. Nuclear provides an important mechanical benefit to the system called ‘inertia’ which wind and solar do not. Inertia acts like a shock absorber, helping the grid absorb constantly occurring changes in electricity demand and supply.

As the system needs inertia to work, a 100% low carbon mix is not possible without nuclear, even when there is lots of wind and solar.

Many nuclear plants can also offer flexibility. In France, the system relies on a lot of nuclear power and the nuclear fleet’s output turns up and down in response to demand. The EPR power stations that will be built at Hinkley Point C and, hopefully, at Sizewell C will also be capable of flexible operation.

Nuclear is crucial if the UK is to achieve Net Zero. It provides low-carbon electricity irrespective of the weather or time of day and will allow the system to operate without fossil fuels.

Rather than demonstrating that nuclear has no place in the future mix as some critics claim, this summer’s events have emphasised its importance for deep decarbonisation and security of energy supply.


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