Posts Tagged ‘Wind Versus Nuclear’

Wind versus Nuclear: The real story in pictures

November 3, 2014
Graph showing the electricity generated by nuclear and wind power (in gigawatts) every 5 minutes for the months of September and October 2014. The grey area shows the period when wind power exceeded nuclear power.

Graph showing the electricity generated by nuclear and wind power (in gigawatts) every 5 minutes for the months of September and October 2014. The grey area shows the period when wind power exceeded nuclear power. (Click Graph to enlarge)

For a few days in October 2014,  wind energy consistently generated more electricity in the UK than nuclear power. Wow!

You may have become aware of this through several news outlets. The event was reported on the BBC, but curiously the Daily Mail seems not to have noticed .

Alternatively, you may like me, have been watching live on Gridwatch – a web site that finally makes the data on electricity generation easily accessible.

I was curious about the context of this achievement and so I downloaded the historically archived data on electricity generation derived from coal, gas, nuclear and wind generation in the UK for the last three years. (Download Page)

And graphing the data tells a powerful story of the potential of wind generation – but also of the engineering challenges involved in integrating wind power into a controllable generating system.

The challenges arise from the fluctuations in wind power which are very significant. The first challenge is in the (un)predictability of the fluctuations, and the second challenge is coping with them – whether or not they have been predicted. Both these challenges will grow more difficult as the fraction of wind energy used by the grid increases over the next decade.

As an example, consider in detail an event earlier in October shown in the graph at the top of the page

Graph showing the electricity generated by nuclear and wind power (in gigawatts) every 5 minutes for the months of September and October 2014. The grey area shows the period when wind power exceeded nuclear power.

Detail from the graph at the top of the page showing how earlier in October, wind power went from an impressive 6 GW to less than 1 GW in a period of around 18 hours . (Click Graph to enlarge)

The grid operators have a wind forecast running 6 to 24 hours ahead and would have planned for this. The forecasts are typically accurate to about 5% and so at the high end that amounts to a margin of error of 0.3 GW – which is within the reserves that the grid can cope with routinely.

However the fluctuations in wind power are becoming larger as the amount of wind power increases. The graph below shows the monthly averages of electricity produced by Wind and Nuclear since May 2011. Also shown in pink and light blue are the data (more than 300,000 of them!) taken every 5 minutes.

Monthly averages of electricity produced by Wind and Nuclear since May 2011. Also shown in grey are the data (more than 300,000 of them!) taken every 5 minutes. It is clear that the fluctuations in wind power are large - and getting ever larger. (Click Graph to enlarge)

Monthly averages of electricity produced by Wind and Nuclear since May 2011. Also shown in pink and light blue are the data (more than 300,000 of them!) taken every 5 minutes. It is clear that the fluctuations in wind power are large – and getting ever larger. (Click Graph to enlarge)

Incorporating wind energy is a real engineering challenge which costs real money to solve. Nonetheless, as explained in this excellent  Royal Academy of Engineering report, we expect capacity to double to ~20 GW by 2020, and to at least double again by 2030. So these problems do need to be solved

Because wind-generated electricity supply does not respond to electricity demand, as the contribution of wind energy grows we will reach two significant thresholds.

  • When demand is high, unanticipated reductions in wind-generated supply could exceed the margins within which the grid operates.
  • When demand is low, unanticipated increases in wind-generated supply could exceed the base supply from nuclear power which cannot be easily switched off

These challenges will require both economic and engineering adaptations. At the moment, because the marginal cost of wind power is so low, we basically use all the wind power that is available.

However, it is possible to ‘trim’ wind turbines so that they do not produce their maximum output. In a future system with 40 GW of wind generating capacity, we might value predictability  and controllability over sheer capacity. Then as the wind falls, the turbines could adjust to try to keep output constant.

These challenges lie ahead and are difficult but entirely solvable. And their solution will be essential if we really want to phase out fossil fuels by 2100.

But for the moment wind is providing on average about 2 GW of electrical power, which is around 6% of UK average demand. This is a real achievement and as a country we should be proud of it.

Perhaps someone should tell the Daily Mail.


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