UK Peak power 2019-2021

Electricity is a power source that runs the modern world. Meeting the instantaneous power demands of the UK  is the responsibility of the National Grid (ELEXON).

The balancing of available energy supply with the instantaneous power demand as logged  by ELEXON  provides a live snapshot of which fuel type provides the power required  needed  to match demand. Energy security requires that demand must  always be met. I have been monitored ELEXON data since December 2016. Peak demand in general always occurs around 6pm each evening so I use this value to compare the relative importance of different energy sources needed to provide energy security. The values provided by ELEXON  are for centrally ‘metered’ power supply and do not include smaller ‘feed-in’ sources. In addition unmetered ‘feed in’ wind farms are estimated to add ~46% to the larger metered wind farms. This correction is applied to the overall results below. Elexon changed format during the winter 20/21 so I missed a couple of months logging before I realised the problem. Despite this the results give a very similar picture to previous years.

Daily fuel contributions to peak power (6pm), The upper red trace is total demand.

The 2 year average contribution for each fuel  to peak power are given in the table below below

Fuel % Contribution
Gas 44.03%
Nuclear 16.443%
Wind 15.9%
French Imports 4.85%
Dutch Imports 2.0%
Bio(DRAX) 6.3%
Coal 2.9%
Hydro/Pumped 2.o%
Solar Metered ~4%

This result is shown graphically below which compares the peak power(6pm)  with the low power demand(4am) . Note how at night the weather dependent wind power increases its percentage as gas is turned down. Nuclear is basically always on and still outperforms wind in both scenarios despite the last operational station being completed in 1995 (Sizewell B).

Shown in red are the relative contributions to UK peak power. Blue shows the contribution at 4am

This analysis shows that it is not feasible to run UK on renewable energy alone. The only realistic zero carbon energy future is one that depends on a steady baseload of nuclear energy. Wind Energy needs a storage method that can iron out large fluctuations and avoid discarding excess power during high wind speeds especially at night. Otherwise we will always depend on Natural Gas as back up for wind lulls as shown below.

Gas and Wind output are perfectly anti-correlated. Gas is turned up or down depending on the output of Wind power. This balancing is needed to meet peak demand.

Alternative storage for wind energy is pumped hydro, green hydrogen or even green methane. However it is not clear the last two processes are economic.

About Clive Best

PhD High Energy Physics Worked at CERN, Rutherford Lab, JET, JRC, OSVision
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13 Responses to UK Peak power 2019-2021

  1. I am not a climatologist so my comments should be read in that light.

    Is this news? I thought your penultimate paragraph was now generally accepted.
    Although this is the case now, surely the objective is to find ways to make it not the case, and work towards that? One pathway might be to explore the contribution micro power generation can make. Highly localised wind and tidal projects for instance.

    • Clive Best says:

      There are District Network Operators who handle the local power network in your area. So if you install solar panels on your roof or a farmer connects up a small wind farm the power is fed into the DNO who pay you the feed in tariff. This energy production actually appears as a reduction in demand because it is used by other people connected to the DNO. It is all invisible to the National Grid. So some of what you describe is actually happening now I think. This may be the reason why the national peak demand has fallen from say 10 years ago.

      • Adam Abdelnoor says:

        Thanks Clive. I expect micro and nano projects are going to become more significant. And they also have two additional virtues – they reduce centralised control and distribution making them more future-proof, and they are in-line with another important change towards increased localisation of infrastructure and production generally, on a subsidiarity where possible basis, reducing power used for unnecessary transportation.

  2. Joe Public says:

    Hi Clive

    The contribution by Bio (Drax) shown in the Day/Night chart is puzzling.

    Renewables have priority access to market, and exactly as wind’s *%* contribution to lower night demand results in an increased *%*, I’d have expected a similar relative *%* increase during nighttime from burning firewood.

  3. Joe Public says:

    “Alternative storage for wind energy is pumped hydro, green hydrogen or even green methane. However it is not clear the last two processes are economic.”

    The Reuter’s “Germany’s Uniper feeds wind power-to-methane into gas grid” article all but confirms your supposition.

    Conspicuous by its absence is any reference to the amount of wind generated electricity (kWh from what kW capacity) needed to produce the plant’s “14,500 kilowatt hours (kWh) of energy” via methane output per day.

    It’ll have a significant negative ERoEI.

  4. Phil Toler says:

    The sheer scale of the net zero challenge is mind boggling. The Elexon data shows that UK wind generation falls to around 5% of capacity for periods of at least 6 days, several times a year. The government plan is to get wind capacity to 126GW by 2050. 5% of 126 would be 6.3GW during several weeks in each year. During these calm weeks I would be interested to hear views on how peak winter demand of 40GW will be met.

  5. David Appleby says:

    Thank you for documenting these numbers so clearly. It helps to quantify the scale of the “net zero” challenge. I believe that the answer to the absence of BIO generation overnight is that the wood chips are quite expensive after the processing, drying and shipment across the Atlantic to Drax (and not obviously very green either).

    For the future in the UK, I agree with you that we need much more nuclear capacity. For energy storage, I favour a combination of green Hydrogen plus green CH4, which can be fed back into the existing gas grid infrastructure. There is a big engineering challenge in making Hydrogen by electrolysis, and the process will always be inefficient because of the heat generated. However, as long as the electricity comes from an offshore wind surplus, that can be tolerated. Possibly, the bigger problem is capturing sufficient atmospheric CO2 to react to CH4. Perhaps they should start with pilot plants to recover CO2 from the waste gases from cement manufacture and steel making, to get the technology more mature.

  6. Rob says:

    Lets hope there is going to be enough supplies of gas this winter

  7. tygrus says:

    The data doesn’t match the CliveBest data & I’m confused as how each calculate their sub-totals. I downloaded the gridwatch data & there are obvious data quality issues. I tried to contact the owner via email but was bounced because of filtering rules (obviously not in their list of friends).
    I was wanting to have hourly data to run a few simulated years & various scenarios as to how much storage or other tech would be needed as fossil fuels were removed.
    I was hoping to do it with Australian data but that’s also hard to get a good historical record.

    • Clive Best says:

      I think the reason they differ for wind power is because I correct the Elexon numbers to include so-called “embedded” wind farms. These are small wind farms which feed-in power to the local transmission network. This appears nationally as drop in demand. This is exactly the same story as for solar energy. This too is not metered nationally but appears as a reduction in the visible demand. The solar figures that I and Gridwatch use are actually theoretical calculations made by the University of Sheffield based on sunshine available over the UK.

      See for the details on the wind farm corrections I make.

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