2019/20 GB Peak Power Demand

Which energy sources currently meet Great Britain’s peak electricity demand?  Peak demand occurs at ~6pm on weekdays, and the mix of “fuels” as more Wind Power comes on-line is constantly changing. On average today Wind and Nuclear are currently providing roughly equal contributions. However gas  provides by far the most power to the grid and has  become the essential  to balance the increasingly stochastic nature of wind. Randomly occurring wind lulls continue to require a fast ramping up of Gas, while  in emergency situations we  still rely on firing up those dirty  Coal stations to keep the lights on.

Contributions from each energy source at peak demand (6pm). Weekends show up as regular saw teeth. Click on image to see full detail. 

The results shown here are based on a continuous monitoring of the national grid  every hour via the Elexon interface. Peak demand (day)  used in all plots typically occurs at 6pm. This can also be  compared to lowest demand at typically occurring at 3am (night). Shown below are the overall relative fuel type results averaged over the full 13 month period from August 2019 until 7 October 2020.

Average contribution to peak power demand (day) and to lowest demand (night)

The net contribution of wind and nuclear are about equal. Gas is by far the dominant contribution while coal has almost been eliminated as an energy source,  but not quite because it is still needed when wind collapses during peak demand – August 2020. The only zero carbon source that can replace coal is nuclear.  Solar energy makes a small contribution to peak demand mainly because in winter it is dark at 6pm, while in summer the sun’s angle is low at 6pm.

Let’s look a bit more detail at the stochastic nature of wind energy on supply. Remember that if instantaneous power demand cannot be met on then  grid then currently  blackouts will ensue. This already happened in November 2019 when the national grid miscalculated wind output leading to a sudden loss of “inertia”.  A future “smart grid” may  instead decide to avoid this problem by switching off power hungry users or even household systems  unless another energy source other than gas can balance wind power lulls.

Gas is currently used to balance wind energy. The swings in supply can be enormous as highlighted.

Every rise and dip in wind power is matched by a ramp up or down in gas output, aided by accurate weather forecasting. This balancing act is how the grid has managed to absorb a large increase in wind capacity. However, if the UK seriously wants to reach a zero carbon grid by 2040 then somehow we need to stop using gas and find some alternative to balance the inherent stochastic nature if wind energy. Doubling the number of off shore wind farms will only make the balancing worse.

Green energy is all going to end in tears without a solid  nuclear base to run basic basic infrastructure.

Note: This analysis only covers GB since the balancing mechanism does not include Northern Ireland

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3 Responses to 2019/20 GB Peak Power Demand

  1. Jacques Hagoort says:

    Nice and very clear analysis. But you are too pessimistic. The solution is green hydrogen according to EU’s Frans Timmermans and his green friends. We have a generation to make it work. That shouldn’t be that hard.

    • Fabio says:

      only if you have enough power from wind to produce greeeeen hydrogen.
      so wind to cover day by day demand and to produce GH .
      1 million windmills ?
      maybe this is the reason Holland would like to building ten new nuke plant

  2. entropicman says:

    “Green energy is all going to end in tears without a solid nuclear base to run basic basic infrastructure.”

    Nuclear will end in tears too. Best estimate is economically viable reserves of uranium to last 80 years at current consumption.

    I worry about a ropadope at the end of this century as we try to feed 11 billion people with no nuclear and no fossil fuels, while climate change floods our coastlines and disrupts our agriculture..

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