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Blackout risk as low demand for power brings plea to switch off wind farms

May 2, 2020

By Paul Homewood


Little Emily has a scoop:




Her story is behind a paywall at The Times, but this is the gist:


Britain could be at risk of blackouts as extremely low energy demand threatens to leave the electricity grid overwhelmed by surplus power.

National Grid asked the regulator yesterday for emergency powers to switch off solar and wind farms to prevent the grid from being swamped on the May 8 bank holiday, when demand is expected to be especially low.

In its urgent request to Ofgem, it warned of “a significant risk of disruption to security of supply” if the “last resort” powers to order plant disconnections were not granted.


It is of course a problem which I have been warning about for a long time, that when wind and solar power are really ramped up there would be huge surpluses of power at certain times of the year, not to mention days, as well as shortages at others.

In this instance, however, the coronavirus lockdown has suppressed demand, thus bringing forward the issue.

Daily demand this week has fluctuated between about 20 and 30 GW each day. This is probably about 5 GW lower than the same time last year, with the biggest drop seemingly at night time ironically.




Although Emily mentions solar power as an issue, it may well be at night when the risk is greatest.


First, let’s have a look at the Univ of Sheffield Solar site for the last week:




Bear in mind that most solar generation is embedded, that is it is absorbed by local grids rather than transmitted via the National Grid, As such it shows as a drop in demand instead of extra generation. The Sheffield site therefore adjusts the total generation upwards, so as to include the solar contribution.

We can see that total generation drops to around 20 GW at night.

Now if we look at the official grid figures for the last 48 hours (ie excl solar), we see that nuclear is supplying a steady 6 GW, which cannot easily be switched on and off.

Wind is currently under 2 GW, but was up to nearly 6 GW yesterday:



However, we already have 24 GW of wind capacity. If demand drops to 20 GW, and nuclear remains constant, that would mean the system could only absorb 14 GW of wind power, 58% of capacity.

On most days, this would be manageable, but if its a windy day next Friday, all bets are off.


I should not finish without mentioning solar power.

This week it has peaked each day at around 7 GW. At peak solar, ie midday, demand seems to be about 10 GW greater than at night, so on the face of it the grid should cope with the extra generation from solar.

In other words, it is wind power which poses the real problem.


Emily has actually done quite a good job on this one, and her twitter feed mentions that the National Grid are struggling with the legalities of whether they can order generators to switch off. Hence the talk of emergency powers.


What she does not mention is that this will become a regular and much bigger problem in years to come, when wind and solar capacity are expanded.

For instance, under the Committee on Climate Change’s 5th Carbon Budget, the central scenario anticipates 47 GW of wind power capacity and 40 GW of solar just by 2030. (This compares to 24 GW and 14 GW respectively now.)

Even allowing for higher demand for EVs etc, this clearly is not at all manageable at times of low demand.

Even at average loading, 47 GW of wind power would mean an average load of 17 GW, so there would be surpluses on average every night.

Meanwhile 40 GW of solar would probably yield about 20 GW at midday, when the extra demand only appears to be 10 GW.

By 2050, there would need to be much more renewable capacity, of course. The CCC are talking perhaps of 110 to 175 GW of wind/solar.

There is little prospect we could offload any of this to the continent, who would be in a similar position.

Which brings us back to either paying billions a year in constraint payments, or ordering wind and solar farms to switch. Something which radically alter their economics.

  1. GeoffB permalink
    May 2, 2020 7:24 pm

    Doh! I did not see that coming. Did nobody in national grid or ofgem realise that you cannot just keep adding intermittent generation capacity and it will all work out. STOP any more wind farms and solar, get on with closed cycle gas generation. Green idiots.

  2. Joe Public permalink
    May 2, 2020 7:39 pm

    Prof Dieter Helm had the right idea in his ‘Cost of Energy Review’

    “The FiTs and other low-carbon CfDs should be gradually phased out, and merged into a unified equivalent firm power (EFP) capacity auction. The costs of intermittency will then rest with those who cause them, and there will be a major incentive for the intermittent generators to contract with and invest in the demand side, storage and back-up plants. The balancing and flexibility of markets should be significantly encouraged.”

    [My bold]

    Click to access Cost_of_Energy_Review.pdf

  3. Dave Ward permalink
    May 2, 2020 7:58 pm

    “The coronavirus lockdown has suppressed demand, thus bringing forward the issue”

    The potential “Collateral Damage” of the lock-down is finally being admitted: extra deaths from undiagnosed/untreated treated cancer & heart disease, as well as the effect on mental health. Heaven knows how much worse this might become if we are subject to a major grid shut down at the weekend…

  4. May 2, 2020 8:01 pm

    Way back in 2005, Johnathon Porrit (ex FoE) was head of the QANGO Sustainable Development Commission and he publicly stated that there was no limit to the amount of wind power which could be accommodated on the grid. His stupidity and ignorance was obviously not recognised by the government then and any government since. Truly the lunatics have ben in charge of the asylum for a long time.

  5. Harry Passfield permalink
    May 2, 2020 8:04 pm

    Makes me wonder where she gets her ideas…I figure the she’s a fan of Michael Caine.

  6. JimW permalink
    May 2, 2020 8:22 pm

    Its the grid frequency that will first trigger the problem, that could well be during the daytime.

  7. jack broughton permalink
    May 2, 2020 8:29 pm

    Is not the problem that underlies this the ability of the synchronous generators to maintain frequency if the proportion of “unreliables” exceeds its limit of somewhere between 40 and 50% power. Otherwise the CCGTs would be switched off leaving only Drax and nuclear to give any frequency control. I thought that the constraint payments allowed unloading of the “unreliables” at a massive price of course, but I suppose that they need powers to actually have them removed from the grid.

    Interesting times when Emily makes a criticism of the foolish policies that have been developed over the last 20 years.

  8. Tim Spence permalink
    May 2, 2020 8:52 pm

    The national grid (transmission and distribution) is a unique entity and the most reliable in the world, until that is, some genius decides you can have thousands of erratic sources feeding it, what could possibly go wrong?

    And it’s not just Solar that doesn’t plug into the transmission grid, it’s wind power too. So in reality, neither is transmissable or in other words can be despatched to another region of the country. Result … Chaos.

  9. MrGrimNasty permalink
    May 2, 2020 9:28 pm

    As I remarked on the other thread, at the moment the forecast is favourable for very little wind generation at all on Friday (the recent wind power slump for several days was with similar conditions nationally as forecast), but picking up somewhat on Sat/Sun – I’d guess at the moment in the range 2-4GW, before almost dead calm returns.

    Looks like they got out of jail, but forecasts have been rubbish recently, so who knows!

    • Up2snuff permalink
      May 3, 2020 4:25 pm

      Had a power cut in the south-east recently, only relatively momentarily – half an hour max., if that – and I cannot now remember which day it was. The wind had dropped and I guess something tripped on the London Array off Herne Bay.

    • MrGrimNasty permalink
      May 3, 2020 7:14 pm

      Changing already – Friday still looks flat but could be a rapid transfer to swift persisting northerlies for the w/e – especially in Scotland at first (with all their onshore), maybe it will get interesting!

  10. Graeme No.3 permalink
    May 2, 2020 11:18 pm

    South Australia has been there, starting with a State-wide blackout. Lately the wind farms are being ‘constrained’ when the wind blows strongly, to balance supply with demand.
    The ‘equation’ used is total demand minus the minimum necessary conventional generation plus the amount that can be sent via interconnector to Victoria = allowable wind generation.
    Total demand is reduced by solar generation, and the State Govt. has blindly pushed more household schemes including subsidised household batteries. (The ‘payback time’ for the initial cost has been calculated as aound 27 years).
    Our regulations allow the authority to shut down a wind farm (or 2 or 3) without payment. The result has been that the Capacity Factor for wind has dropped by just over 10%, affecting their economics.
    The other problem is frequency stability; despite all assurances about the “big battery’ (essentially useless) this has caused the local grid controller to start installing ‘synchronous generators’ – basically rotating flywheels or think coal fired power stations without the coal. So extra cost to provide what was supplied for free by reliable generators who were driven out of business.
    Sadly I think you in the UK are going to have to have a longish blackout before your grid can be painfully (and expensively) stabilised.

    • Frosty Oz permalink
      May 3, 2020 12:28 am

      Two important differences between Australian and UK markets:
      – in Australia, the market price can go to negative $1,000MWh, and if a wind farm wants to operate it has to bid and pay to generate; and
      – if system security requires a generator to be constrained off, there are no constraint payments.

    • Gerry, England permalink
      May 3, 2020 11:42 am

      There is some truth in your final sentence Graeme but I think the blackout last August has given them an early warning. The two reports do show an understanding of what went wrong but the test will be if they have prepared well enough for all possibilities.

      • Graeme No.3 permalink
        May 3, 2020 1:08 pm

        An understanding maybe, but are your politicians willing to prepare?
        The improvement in grid stability has come from
        1. More diesel generation (some of which has to shut down soon).
        2. Synchronous generation (flywheel type) and
        3. the ability to switch wind farms OFF (without as Frosty Oz above notes payment for not producing). Further they get a subsidy (Certificate compulsorily purchased by retailers) dependent on them producing.
        Originally about $A 85 per MWh, it has dropped recently to about $30 (see politicians boasting about the increase in supply). Since the original price almost paid for the cost of producing, they could bid very low prices and undercut conventional producers. Under the weird system in place it is the highest price accepted that applies, so wind farms were (in the vernacular) “making a motsa”. With too many wind farms bidding and shutdowns they don’t make the money they feel entitled to get.

        This latter is of considerable annoyance to wind farm proprietors and they have been loud in calling for an interconnector to another State. Our politicians have agreed to pay for such, ignoring that the State is to all purposes bankrupt and the money has to come from the Federal Govt. who may not be that keen as they work out how to pay for all their own reckless promises during the CoVid crisis.
        The reality is to send electricity to Wagga Wagga (the extreme reach) so they get that subsidy.

  11. May 2, 2020 11:30 pm

    “Little Emily has a scoop:”

    does she use it for ice-cream ?

  12. Gamecock permalink
    May 3, 2020 1:14 am

    ‘In its urgent request to Ofgem’

    National Grid isn’t in charge of the grid.

    Good luck!

  13. Jamie Thomas permalink
    May 3, 2020 8:30 am

    The wind situation is made worse by the fact that the output of a wind turbine varies with the cube of the wind speed – an erratic and intermittent source!

  14. Dodgy Geezer permalink
    May 3, 2020 8:53 am

    It’s very simple.

    Order them to switch off, and pay them their full running costs plus a sizable profit. If they complain, pay them a gigantic profit.

    It has been obvious for some time that the wind farms are nothing to do with the effective provision of energy for the country, and everything to do with providing free money to favoured individuals.

    We might as well accept this now…

  15. May 3, 2020 9:23 am

    Overtime for interconnectors?

    • May 3, 2020 10:11 am

      Or get the wind mills to turn backwards!

      • Up2snuff permalink
        May 3, 2020 4:30 pm

        Paul, I understood that they can feather the blades on the turbines, just as a multi-engine propeller aircraft would do when an engine went down. Is that not so?

  16. Ben Vorlich permalink
    May 3, 2020 11:03 am

    I had a short email conversation with the webmaster at last week. I was trying to make sense of the renewable data. This was the reply to the original question.

    “Two issues. Solar power is not included in the downloadable data as part of demand.

    Exported power – negative values on the interconnectors are alos not added to demand.

    If you ignore solars and exported power you should get a close balamce.”

    So I asked for clarification on the Solar PV

    “No one can distinguish between power that isn’t drawn off the grid and power that is ‘exported to the grid’ except the person doing it. The grid has meters on major power stations and at a few places on its backbone, – what is going in at the 33KV level and below is something it doesn’t meter.”

    So presumably those managing the grid can only guess at how a windy sunny day affects demand by guesswork.

    • May 3, 2020 11:17 am


      Also about a third of wind power is embedded as well.

  17. Gerry, England permalink
    May 3, 2020 11:30 am

    Does anyone else look at the power generation graph and wonder how the hell have we ended up with FIFTEEN sources of power? If that doesn’t say something about the surreal world of our electricity supply I don’t know what does.

  18. Adam Gallon permalink
    May 3, 2020 9:29 pm

    Wind’s slumped to a meagre 0.85GW tonight.

    • MrGrimNasty permalink
      May 3, 2020 11:26 pm

      Ridiculously low demand, yet pelleted forest is in the red part of the dial!

  19. May 4, 2020 10:20 pm

    And any RE fan will vigorously claim that wind and solar are the cheapest energy forms. They have preferential treatment. They can deliver when they want at guaranteed prices. A thermal power plant will produce electricity when it’s needed, not when the plant operator is funny. As wind and solar cannot do that, they should be made to pay for modifying their power towards what the consumers need and not when the vagaries of the weather give us.

  20. Whanaby Borton permalink
    May 5, 2020 9:42 am

    doesn’t seem like renewable uk knows how the electricity grid works

  21. May 6, 2020 1:31 pm

    Hiya, simple question… why can’t the grid turn off the ‘dirty’ sources of energy instead of sacrificing ‘green’ solutions such as wind and solar?

    • Frosty Oz permalink
      May 7, 2020 8:55 am

      Paola, South Australia tried this (shutting down coal in favour of wind). They encountered 3 main problems:
      – replacing power from AC turbines with power from DC-AC inverters reduced the inertia in the system, leaving potentially high rates of change of frequency, with the frequency changing faster than they could control by conventional means (ultimately leading to system failure);
      – replacing AC power with DC inverter power reduced the system strength (its ability to resist high current flows when faults arise), to the extent where conventional fault protection systems were insufficient; and
      – when the wind slowed down, additional fast-start gas generation was required to meet the demand.

      If your “green” generation could be AC turbine-based, such as hydro (or pumped-hydro), or solar thermal power, then some of these problems would be less.

      South Australia eventually solved its problems by installing massive batteries, installing special fast-switching under-frequency relays, installing fast-start diesel generation, and mandating gas generation to continue to run until they can install synchronous condensers with fly-wheels (spending about US$100M on those alone).

      So, it can be done. But it ain’t cheap.

    • Stuart Brown permalink
      May 7, 2020 9:55 am


      Simple answer – we tried that last August in the UK and the grid fell over. People were trapped in tube trains for hours.

      For the reasons Frosty details above.

  22. Harold Gordon Ambler permalink
    May 7, 2020 9:31 am

    Octopus energy have just asked me to switch everything on between 1pm and 4pm on Sunday. For this they will pay me 2p per kWh. They tell me it’s to make Britain greener!

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