Low Electricity Demand and System Balancing Problems during The UK’s Coronavirus Lockdown

From The GWPF

Date: 04/25/20

Dr John Constable, GWPF Energy Editor

The restrictions on economic and personal activity imposed to address the spread of the coronavirus are reducing electricity demand in the UK to unusually low levels, increasing the difficulties of operating the system, particularly in the presence of embedded solar and wind generation. 

As a result of the restrictions on economic activity and personal movement, designed to reduce the rate of transmission of Covid-19, there are striking anomalies in the British electricity markets. The following chart, drawn by the author from BM Reports data, shows daily electrical energy (MWh) transmitted over the network, and gives evidence of a substantial fall in electricity consumption. Domestic consumption may be rising as a result of the Stay at Home policy, but it is nowhere near offsetting the fall in industrial and commercial consumption.

Figure 1: Daily electrical energy (GWh) transmitted over the British electricity network, from 1st of January to 23rd April 2020 (red line), compared to the historical norm (grey line). Source: Chart by the author, data from BM Reports.

Of course, that decline has to be understood against the background of what is normal for the time year, and the grey line shows that demand normally begins to fall from January onwards. The red line shows that this year was no exception, with the decline beginning even in January well before the first warnings about Covid-19 were given. Furthermore, demand was already low relative to the historical norm for these months, because of unusually warm weather. Consequently, some part of the decline seen towards the end of the charted is to be expected. Nevertheless, even when these factors are taken into account the abrupt nature of the decline in consumption after the 23rd of March is obvious.

Furthermore, there is a clear loss of the familiar structure in the pattern of demand, a feature which is still more evident in the pattern of instantaneous load (MW) on the network by half-hourly settlement period. Compare the following two charts, the first of which graphs load from the 1st of January to the 24th of February, while the second charts the period from the 1st of March to the 23rd of April.

Figure 2. National Demand (the sum of metered generation excluding generation required to meet station load, hydro storage pumping and interconnector exports) by half-hourly settlement period from the 1st of January to 24th February (MW). Source: Chart by the author: National Grid data.

Figure 3. National Demand (the sum of metered generation excluding generation required to meet station load, hydro storage pumping and interconnector exports) by half-hourly settlement period from the 1st of March to 23rd April (MW). Source: Chart by the author: National Grid data.

Before the lockdown the pattern of load is highly but regularly variable, exhibiting repetitive periodicities on several timescales, all patterns well known to the grid operators. The second chart shows the regularly and highly differentiated pattern of electricity demand both falling and becoming temporarily more chaotic as it moves towards a new and less differentiated equilibrium at a lower level. This is not only new and unfamiliar territory for the system operators, but has accelerated the arrival of problems with the large and inflexible renewables fleets, problems for which the system is probably not quite ready.

National Grid ESO’s Summer Outlook for electricity, published on the 15th of April, puts a brave face on the matter, but cannot conceal the difficulties. The ESO’s principal concern is a combination of low demand and a high proportion of inflexible or relatively inflexible renewable generation, leading to system balancing problems. Assuming that demand cannot be increased on request, the operator must prevent hazardous increases in voltage, by reducing generation, while at the same time maintaining sufficient inertia to preserve system stability.

There are already significant reductions in demand, and NG ESO’s medium impact scenario envisages these continuing into the summer with a demand reduction of 7% overnight and 13% during the day. The high impact scenario involves reductions of 13% overnight and 20% during the day. In fact, reductions approaching the high impact scenario are already being observed, with National Grid commenting that in April the UK electricity system served low loads not usually seen until the much warmer, holiday months of July and August. To illustrate this point the Summer Outlook provides a graphic comparing actual demand on the 14th of April with the demand that would otherwise have been expected.

Figure 4: Demand (MW) predicted pre-Covid for the 14th April (yellow line), compared with actual demand (orange line). Source: NG ESO, Summer Outlook (April 2020), p. 6.

The largest demand fall in the chart appears to be in the order of 19%, and generally the currently observed reduction is, as NG comments, “between [the]‘medium impact’ and ‘high impact’ scenarios” considered in the Summer Outlook.

One might on that basis suspect that the summer impact scenarios are overly optimistic, but it is probable that National Grid is expecting the lockdown restrictions to be eased, keeping demand suppression within the bounds of its high scenario. If, on the other hand, the restrictions are maintained or even strengthened then the possibility of demand cuts exceeding 20% are clearly possible.

A reduction of approaching 20% on spring and summer demand poses real difficulties for control room operators, since they are now working with a generation fleet that is to a large degree non-dispatchable, 23 GW of wind and 12 GW of solar power for example, and may seek to provide energy to system even when not required. Table 2 of the Summer Outlook describes a maximum demand of only 25.7 GW in the high impact scenario, and a minimum demand of 15 GW, a minimum that has already been observed in April. In between these limits, the operator must retain sufficient conventional, rotating plant to provide stabilising inertia, but also find room if required for the 23 GW of wind and 12 GW of solar power, both uncontrollable.

Of the two, it is the solar fleet that is giving NG ESO the most cause for concern. About wind, they can afford to be relatively relaxed since, firstly, output tends to be low in the summer months, and, secondly, they have extensive experience of constraining wind off the system through the Balancing Mechanism (at a cost of £101 million so far this year). That said, it is highly significant that the Summer Outlook refers to the use of an additional instrument, namely “direct trade” (see p 15) to buy wind farms off the system. Bilateral trades of this kind with wind farms have not been used intensively for quite some time, and their return is a sure sign of emergency measures. It’s a topic to watch.

Full article here.

0 0 votes
Article Rating
Newest Most Voted
Inline Feedbacks
View all comments
Planning Engineer
April 25, 2020 2:18 pm

Very interesting. Can’t say I saw that coming. No problem for systems with a food mix of overwhelmingly conventional resources.

Planning Engineer
Reply to  Planning Engineer
April 25, 2020 2:19 pm

Good not food.

Reply to  Planning Engineer
April 25, 2020 7:00 pm

I know that I have problems when I get my food mix wrong.

Reply to  Planning Engineer
April 25, 2020 6:58 pm

It’s almost as though a system engineered by engineers would work much better than a system engineered by politicians.

D Cage
Reply to  MarkG
April 26, 2020 1:16 pm

Yes but on climate change the BBC ensures us that engineers have nothing to offer in the debate on climate change but somehow believe a sour dim witted teenage brat does.

April 25, 2020 2:23 pm

I don’t know what happens to the cost but I suspect the consumer will be in for a rude shock . If the industrial and commercial sector is not using ( and paying for the electricity the power generators will need to make up the difference elsewhere especially if the cost of running the system has gone up due to trying to deal with increased unreliability risk. At times of overall reduced demand prices should be falling just look at what has happened to other commodities especially oil.
Hopefully this experience together with the financial impact of the corona virus measures and the impact of Michael Moore’s film might cause Boris to have a policy rethink about this disastrous renewables path he is taking the UK down.

Reply to  Zigmaster
April 25, 2020 4:28 pm

I wonder what “direct trade” means (and I didn’t go to page 15, wherever that is, to find out). Does it mean the wind operators are paid for their electricity not to be used?
I don’t have to wonder what “disastrous renewables path” means – its obviousness bleeds.

Reply to  Mike Jonas
April 25, 2020 8:21 pm

Mike: yes. Wind operators are regularly paid to stop generating: mostly though it’s when the wind is ideal and they are generating more than the transmission links can handle. It’s cheaper to do that than build bigger links that would only get used to full capacity a couple of times a year for a few hours.

Mad? Yes. That’s renewable energy for you.

Reply to  Leo Smith
April 27, 2020 7:05 pm

It’s not just about the link capacity – the generation must be matched to the demand to prevent damage from over frequency and voltage so with lowered demand, curtailing is going to be much more frequent (since renewables absolutely need to be overprovisioned to come up with the rosy X% of electricity generated today was by wind/solar)

RT Rider
April 25, 2020 2:43 pm

I looked at the ISO’s hourly prices, yesterday, here in Ontario. The average price was around C$13.5 per MWh. Since 11:00 this morning (Saturday) they’ve been giving it away.

Reply to  RT Rider
April 25, 2020 4:03 pm
April 25, 2020 2:59 pm

Paying renewables not generate, that is those operators have politically enforced mandates to make money for their owners. demonstrates that the climate scam was never about CO2 or climate.
Michael Moore’s unmasking the idiocy of renewables to his audience of Lefties will be ignored as well because of discomfort of cognitive dissonance it brings to his climate religion tribe.

Reply to  Joel O’Bryan
April 25, 2020 3:05 pm

Pro-Choice, selective, opportunistic religion… they’ll get over it.

mario lento
April 25, 2020 3:10 pm

Pretty much, as the grid demand is low enough that wind and solar comprise a significant portion of energy, the ultra reliable baseload has a hard time fixing the problems of the unreliable intermittent green energy.

This makes sense!

John in Oz
April 25, 2020 3:19 pm

As demand is lower, I expect to hear the pro-renewable lobby to claim loudly and proudly that the wind and solar generation is meeting and/or exceeding this demand during this crisis and this is why we need more of the same.

They will say nothing about the timing difference between generation and demand, the fragility of the system nor the overall cost of maintaining and operating such a variable source.

Reply to  John in Oz
April 27, 2020 7:20 pm

Giles Parkinson is already doing victory dances over South Australia’s renewables generation mix aided by the Hornsdale battery. No mention of the massive gas use to paper over the gaps, of course.

April 25, 2020 3:22 pm

Solar and wind uncontrollable? I was of the belief that wind generation could be controlled by “feathering the props” and applying the brakes. I see many, many turbines in a non-generation mode (no blade rotation) at nearly every wind farm I pass.
Are not those turbines controlled by the grid operators, or is it the individual wind farm operators that can trun them off and on?

Reply to  fxk
April 25, 2020 6:43 pm

You can turn them off at will. You just can’t turn them on when you want to.
They decide for themselves when they can come on.

Steve Richards
Reply to  fxk
April 26, 2020 12:15 am

Yes, they can point off wind and apply the brakes but the problem is the contract between wind turbine owner and the grid. Which states that I generate power you will pay me whether you can take it away or not. That way the farm owners have a reliable income averaged out over a year. Shame about us electrical users though!

April 25, 2020 3:30 pm

Lets screw the Plebs through their electricity bills. They’ll never notice it. So far this has turned out to be correct. Fortunes are being enlarged and made on a few extra dollars from almost everyone. That’s always been the surest means to the biggest accumulations of wealth. In Planet of the Humans biomass gets a well deserved beating. I happened to spend about 6-8 weeks in Vermont on business living out of a hotel. Another guest and I got into a complimentary breakfast discussion over his biomass heating business which he was trying to sell to public institutions. That was about 2012. As I countered his obvious meaningless sales hype with detailed questions he became agitated. Don’t think I laid a glove on his determination but also hope I didn’t help him sharpen his pitch to more important and less critical audiences. He was in it for the money and nothing but the money.

Reply to  troe
April 25, 2020 11:59 pm
Gordon Dressler
April 25, 2020 4:11 pm

The last paragraph of the above WUWT article gives the folks at the Oxford Dictionary of English a new CYA-phrase to enter: “direct trade”.

john rattray
April 25, 2020 5:10 pm

One of the problems with renewable energy is the intermittency factor, especially between seasons. This requires a substantial overbuild to service peak periods with low generation. For example in South Australia wind farms produce about 9% of nameplate generation during peak demand (hot still weather) and solar has about 5% due to the peak being late in the afternoon. Alternatively during periods of low demand, for instance solar noon weekends during Autumn, then wind farms often produce up to 80% of name plate capacity with solar doing about the same. This gives a system operator only one option – turn off controllable generation. However when large amounts of generation are not controllable (i.e. roof top solar) this option is no longer available. The inevitable consequence is system collapse once uncontrollable generation exceeds system demand. In South Australia this is likely to be a risk under N-2 scenarios from 2021 given the current rate of growth in small PV installations (up to 1 MW).

In my view this will require either:
– the system operator being able to turn off non market generation (probably a physical and political impossibility); or
– Spend massive sums on new controllable load ( e.g. pumped hydro or batteries) . Something that is not in the business plans of those who are causing the problem.

Perhaps we should apply the principle of “polluter pays”?

Reply to  john rattray
April 27, 2020 7:25 pm

No, it is quite enough for the (non-hydro) renewable generators simply to be treated in EXACTLY the same manner as thermal and hydro generators for bidding day ahead to supply power and the fines for shortfalls. They can hedge with contracts to batteries (ha!) and gas peakers if they want to avoid the fines.

Right now they get a free pass for being able to produce as much or as little as they are able forcing the rest of the system (including the demand side) to suck up the associated costs.

Pat from kerbob
April 25, 2020 8:31 pm

Miserable sindu day here in Alberta so the bird choppers are operating full on
This page is very useful, especially when we are in the middle of a -30c high pressure system in winter or +35 in summer, and zero wind


Pat from kerbob
Reply to  Pat from kerbob
April 25, 2020 8:32 pm

Miserable saturday

How can autocorrect produce such crap, Apple laughing at us

April 25, 2020 9:56 pm

This is a good article but from the comments it seems that some of the important detail has not been fleshed out enough.
First of all let me say something about solar power in the UK.There is quite a lot of it, but none of it is metered centrally by the grid, and, as far as I know none of it is under central control. If you look at the demand curve graphs you will see that there is a big midday notch. I have been monitoring, via my website, Gridwatch, (https://gridwatch.org.uk) the same data as is used here, since 2011. There never was a midday notch until solar power came along, and this ‘notch’ is actually the effect of millions of domestic solar panels and a few commercial solar farms kicking in and feeding local demand. As far as the central monitoring is concerned this represents a fall in ‘seen’ demand and so ‘the notch’. A couple of years back Sheffield University, in a zeal for all things renewable, starting publishing their estimate of total GB solar power, based I think on sampling a few sites who agreed to share their output figures. I now incorporate that data with suitable caveats on the same website and database.

This solar power is absolutely ‘wild’ on the grid. As far as domestic panels go, there is absolutely no way to control the output centrally at all. I am less sure about the few commercial solar farms as to what their contractual arrangements are and whether (like wind) they can be ‘constrained off the grid’.

Wind farms are similarly wilful in their output, although both solar and wind are reasonably predictable to within a couple of GW several hours ahead, and a couple of GW is something the grid should be able to cope with – typically, if there is a massive and sudden shortfall if a power station trips out, the pumped hydro at Dinorwig and the small hydro sets get an alarm and can be up to power in seconds. So long as they can ‘hold the fort’ for half an hour or so without running out of water, that is enough to get the gas sets up and running. Similarly a sudden drop in demand is catered for by the inverse – hydro stops and then gas sets are shut down.

Contrary to popular belief not much ‘spinning reserve’ is kept online. I suspect that what actually happens is that the hydro plants are used to modulate very small and rapid fluctuations in demand over the timescale of minutes.

This however is not the instability which is the matter of concern here, what is a matter of concern is the grid frequency – nominally 50Hz± not a lot. Traditionally this was held to 50Hz exactly on average over the day so that synchronous electric clocks kept proper time, but minor fluctuation was tolerated. And a major part of that stability was inherent in the design of the generating plant – massive turbines and rotors in the alternators held to 3000rpm (for 3 pole designs) represent a surprising amount of stored kinetic energy. More than the average battery installation for sure, and in the case of – say – lightning striking a main grid link and shorting it – this is what supplies the overload current until the arc self extinguishes. Then of course we have electric trains which are constantly stopping and starting with power flows to and from the grid (most these days push braking energy back into the grid) .

This is all well and good until – because renewables have priority on the grid – there is hardly any conventional generation on the grid at all. Peak solar and a bit of wind is capable of putting over 16GW onto the grid and typically when Europe has a surplus in summer, we will be importing another 4GW via the undersea high voltage DC links. So that’s 20GW of ‘unconventional’ generation on a grid whose maximum total demand is in the middle of the day scarcely 30GW. Typically there will be a 3GW of wood burners at Drax plus about 6-8GW on nuclear power on the grid. And all the coal, gas and hydro shut down.

And this is where the problems start to get nasty. All those renewables, and the DC power under the sea, feeds the grid via inverters. Electronic circuits that chop the DC and shove it through high frequency transformers to generate an approximate 3 phase sinusoidal waveform that is fed to the grid via chokes and capacitors to improve the waveform . And this has to be in phase with the grid and locked to its frequency.
How do they know what the frequency is? They monitor it of course.

And what happens if the frequency, now hardly controlled by spinning turbines, drops due to a temporary overload?


And instead of 2GW lost from the grid, because a reactor has tripped, that’s 20GW, and a total cascading blackout across the entire country.
That is the problem that is concerning engineers, myself included.
It’s mentioned but not explained in this report.

In between these limits, the operator must retain sufficient conventional, rotating plant to provide stabilising inertia, but also find room if required for the 23 GW of wind and 12 GW of solar power, both uncontrollable.

(I have never actually seen more than 12GW of wind , ever, and certainly not when the sun is shining, so he hasn’t got that bit right .There may be a reported 23GW of wind nameplate capacity, but at any time at least 15% is broken awaiting repairs, or constrained off, or simply not getting enough (or getting too much) wind. Yes if the wind is too strong they shut down to prevent damage)

In other words what this post is about is to explain why the operator must ‘retain stabilising inertia’ and what it is and the consequences of not doing so.

When renewable energy first came out I tried to explain the problems to people who didn’t want to listen
The first and easiest problem is power density. the late Professor David Mackay wrote the definitive book on that (which I helped him get published), called “without the hot air” which was the go-to book to see how much renewable energy there was for a given land or sea area. That alone should have been enough to condemn it out of hand as Michael Moore seems to have finally realised.

The problem he didn’t tackle, which I took on, was the problem of intermittency – that renewable energy is not only diffuse (low energy density, so needing BIG constructions over a lot of land or sea area) – but also variable Or as the term is used intermittent. Or to be pejorative unreliable.

Many ‘greens’ think the problem is one ofpredictability, but it isn’t, Whether you know in advance whet the sum will shine the tides will come on or the wind will blow is not the point. It’s having to start up a gas set when they don’t, and the excess of gas that it uses, which partially negates the carbon gains from not using it for 6 hours and letting it cool down, but also requires that you build an maintain the gas sets which are now runs so rarely that the capital cost of them and the necessary maintenance and staffing is not longer paid for out of generation income, so you have to start charging more money…and that as Professor Hughes pointed out, you end up in the situation where instead of nice (but expensive) efficient CCGT stations the temptation is to build cheap OCGT sets that use nearly twice the gas, or even worse, in the UK case, Diesel sets, because they are the cheapest to put in if you are only ever going to use them a couple of days in winter. Add in the carbon cost of building windmills on massive concrete pylons, and really – and this is borne out by total emission figures – there is no net carbon gain from renewables at all in the UK. Only where you have hydro power to offset, can you really make wind and solar work to reduce carbon emissions. And Britain does not.
Plus the fact that renewable energy has high peak to mean flow, you need to build expensive grid links to e.g. Scottish offshore power stations to transport the peak flows to the urban centres in England, but when the wind stops blowing these are idle. More expense for no return.

Renewables themselves by themselves may be cheap, but the cost of making them reliable and delivering them to the consumer is very expensive.

So that was the two reasons why renewables were pointless, the third one, why they are in fact actively dangerous, is what this article is all about, coincidentally exacerbated by the COVID19 lockdown and concomitant low demand.

(And whilst hospitals may have emergency generators, losing grid power is not something that happens without cost there, either)

What the current move to put batteries on the grid is all about is not keeping the grid alive when the sun goes down and the wind stops blowing – that is truly beyond any battery – but to provide active frequency stabilisation in the event of overload. Again, what was built in to conventional power stations has to be added to renewable generation ( increasing the cost and carbon cost and pollution cost), to make it work properly.

To summarise:
Renewable energy must always use a lot of real estate and have a negative impact on the environment because its source energy is diffuse. This makes it expensive.

Renewable energy alone is either inadequate (biofuel, hydro) or intermittent, and therefore must always be supplemented by another form of energy adding considerably to the overall cost of energy and negating its effect on CO2 reduction. In addition grid links must be uprated to carry peak loads or the wind companies paid not to generate them. The consumer pays. The renewable companies do not.

Renewable energy alone is unable to provide grid frequency stability because it has no stored rotational energy: So that too has to be bolted on (using batteries?) again at increased cost to the consumer (but never the renewable operator).

In short, when you hear someone declare that renewable energy is cheap, ask them who pays for its impact on the grid?

Reply to  Leo Smith
April 25, 2020 10:00 pm

damn I missed a closing block quote: Mods if possible insert that after the send of the second line. I HATE not being able to edit long posts…

John Edmondson
Reply to  Leo Smith
April 26, 2020 1:16 am

Right on the money Leo. As usual. The bottom line is? A much higher chance of blackouts whilst we are in the Covid low demand scenario.

Thanks again,

John Edmondson

Old planning engineer
Reply to  Leo Smith
April 26, 2020 2:00 am

In the Australian context large generators have to meet certain standards in order to be able to connect to the grid. One of those standards is the ability to be able to ride through faults. Typically in a high voltage fault you get phase angle changes, voltage dips and frequency changes. Large professionally designed and tested installations should have to prove that they can indeed meet these standards, at least in first world countries.

You are correct in stating that when generators cannot meet those standards then you get a system blackout as evidenced by the system collapse in South Australia a few years ago. That however was not caused by inverter software but badly configured protection software that tripped off after three and in some cases two faults in quick succession.

In my opinion, it’s sensible to assume that all large inverter based units can ride through a cleared fault provided that the system fault level is reasonable at the point of connection (2 or 3 times nameplate capacity). When the fault level drops below this from either continued growth in inverter installations, retirement of thermal plant or N-1 conditions then it is the job of the system operator to close down the inverters until the problem is remedied. This is happening a lot in Australia at the moment, accompanied by a lot of howls from people who have been on sold a pup of an installation.

The real problem is the little guys, roof top PV sold with dodgy cheap inverters than cannot ride through fault conditions and therefore turn themselves off at the first sign of trouble. As penetration of these units increases so does the risk of substantially increasing load following the fault due to the disappearance of the unmonitored PV generation. Usually these units start to ramp back on after 1 minute, so slow acting emergency generation (fast start gas for instance) is unlikely to be of any assistance. It’s difficult to quantify how much roof top PV as a percentage of total load is necessary before things start getting iffy. Part of the difficulty is in knowing just how many dodgy inverters there are installed as this requires local testing and not believing the test certificates out of China; a politically fraught issue. In Australia, a cross fingers and hope attitude is being taken.

My feeling is that a solution will require a mixture of large batteries / synchronous condensers and rapid ramping hydro (< 1 minute). bigger question is who is to pay?

Planning Engineer
Reply to  Old planning engineer
April 26, 2020 9:51 am

You sound credible, but I don’t know whose older. Hydro is the best and I much prefer synchronous condensers to batteries.

Reply to  Old planning engineer
April 26, 2020 10:59 am

There is nothing an all nuclear grid cannot do that cannot be done worse and at far greater expense and with more environmental destruction by adding renewable energy to it.
Nuclear isn’t a< solution.
It's THE solution.

Planning Engineer
Reply to  Leo Smith
April 26, 2020 3:54 pm

Nuclear could work fine if there is a balance spot between safety needs and safety requirements. Current US regulations and requirements increase costs, complexity and challenges to overburdensome levels. If they don’t need to be that onerous and if that could be accomplished politically, I agree a nuclear future addresses CO2 concerns and allows a stable grid.

Gerry, England
Reply to  Leo Smith
April 26, 2020 5:31 am

It has often been said that for the UK the biggest risk of grid failure is not during the winter months when demand might outstrip the supply but during the summer – or warmer – months when the amount of unreliable generation forms an increasing percentage of the supply. And of course last year we had a demonstration of how fragile the grid is when the blackout came following the lightning strikes.

Gordon Dressler
Reply to  Leo Smith
April 26, 2020 8:04 am

Leo Smith posted: “This however is not the instability which is the matter of concern here, what is a matter of concern is the grid frequency – nominally 50Hz± not a lot. Traditionally this was held to 50Hz exactly on average over the day so that synchronous electric clocks kept proper time, but minor fluctuation was tolerated.”

I wonder if the intent of originally stabilizing electrical grid frequency to enable clocks to keep accurate time is a fact, or just an urban myth.

It seems much more reasonable that a very precisely-controlled AC grid frequency is absolutely necessary for any grid that employs two or more generators. If any one generator operated at, say, 50.1 Hz while another one (or more) operated at 50.0 Hz, then assuming at time=0 they were perfectly synchronized, within 5 seconds (without any frequency adjustment), the 50.1 Hz generator would be trying to push AC power that would be 180-degrees out of phase into the connected grid . . . not good! Obviously, any generator operating at a greater frequency deviation (say, 52 Hz, again without frequency correction) would drift out of phase even faster.

So, it seems much more reasonable that holding grid frequency to a very narrow range was mandatory from the start to enable multiple generators simultaneously connected to it to have a reasonable time-deadband in which the generators (with their associated spinning inertia, considering the earliest forms of AC power generation: turbines) could perform automatic frequency control “tweaking” to avoid supplying AC power that is out of phase with the rest of the grid. Note that being ±5 degrees, or even ±10 degrees out-of-phase is likely an acceptable amount of inefficiency of power input into the grid, as long as it doesn’t continue to grow higher.

“In Great Britain, the National Grid is the system operator that is responsible for maintaining the frequency response of the power system within acceptable limits. Two main levels define these limits: the operational limit, which is equal to ± 0.2 Hz (i.e. 49.8 Hz to 50.2 Hz), and the statutory limit, which is equal to ± 0.5 Hz (i.e. 49.5 Hz and 50.5 Hz). Under a significant drop in the frequency (i.e. below 49.2 Hz), a disconnection by low-frequency relays is provided for frequency control of both the generators and demand.” — source: https://link.springer.com/article/10.1007/s40565-018-0441-1

Reply to  Gordon Dressler
April 26, 2020 10:55 am

Gordon: It doesn’t work like that.
What happens is that if the whole grid goes down, one generator – probably Dinorwig – starts up and is stabilised to 50hz. Then other generators are spun up and a synchroscope not only matches frequency but also phase: That is the grid is not only frequency locked, it’s PHASE locked. Once phases match the generator is connected to the grid. As generator power increases the phase starts to lead on that generator and net power flows into the grid from the generator. If power is reduced the grid will DRIVE the generator. That’s what spinning reserve is – generators spinning and locked to the grid but not generating any power into it.

In this respect once connected ALL the spinning turbines are in effect one single phase- and frequency- locked entity. So as load increases frequency drops and the generators slow down, as more power is fed into them the phase starts to advance on them and that adds more power to the grid, and the frequency starts to rise again. Generators can never be at different frequencies.Just slightly different phases.

And that is why the USA is split into three grids. The time delay from coast to coast is enough to mean operating as a phase locked network results in lots of currents flowing around that don’t do anything other than heat wires…

mario lento
Reply to  Leo Smith
April 26, 2020 11:58 am

A couple of things. Voltage drives current and power. Phase imbalance in AC current leads to reactive power, which is out of phase with real power. Complex indeed, think of your class in complex variables –makes my head hurt.

Gordon Dressler
Reply to  Leo Smith
April 26, 2020 1:53 pm

“Generators can never be at different frequencies.”

Why then is there a specification for such tight control on grid FREQUENCY (i.e., the operational limit of ± 0.2 Hz)? Based on what you assert it would not matter if the grid operated at 48 Hz or 52 Hz, since according to you “a synchroscope not only matches frequency but also phase” for each individual generator.

And, by definition, a power source cannot possibly be phase-locked to a AC grid unless it is first frequency-matched.

Reply to  Gordon Dressler
April 27, 2020 7:36 pm

Gordon, the frequency of AC affect more than clock. Transformers and AC motors are directly affected by fluctuations plus all the synchronous generators that are connected.

Large fluctuations cause cascading issues including synchronous generators falling offline and transformer output under or over voltage which can cause serious physical damage and danger.

Gordon Dressler
Reply to  Gordon Dressler
April 30, 2020 10:19 am

Analitik, if you read back to my OP on April 20 at 8:04 am, I think you will see that I was trying to make that exact point . . . that tight frequency control was not, and is not, instituted so that electrified clocks can keep accurate time.

Reply to  Leo Smith
April 27, 2020 7:28 pm

Thanks for the detailed response, Leo. I hope those who aren’t familiar with power grids take the time to read through it so they can respond to any greenwashed friends harping on about renewables

April 26, 2020 12:14 am

Hummm, call me Mr Picky but the text says “The following chart, drawn by the author from BM Reports data, shows daily electrical energy (MWh)”, the chart logo says “Daily electrical energy (GWh) transmitted over the British electricity network”. OK, just a units scale mix up? But the chart is a line graph that tracks at a time intervals much finer than a day. A graph of daily energy would be a bar graph in one-day chunks. So the Y axis must be Watts (power) not MWh or GWh (energy = Joules), i.e. not only the scale but the units are wrong.
What else is wrong???

Phillip Bratby
April 26, 2020 1:19 am

We have been warning UK politicians about the looming problems of too much uncontrollable, intermittent and unreliable, asynchronous renewable generation for years. But our warnings have fallen on deaf ears.

April 26, 2020 1:20 am

UK has enough windmills to generate well over 10GW with decent wind (that’s just the metered).

Since Thursday the whole lot has produced next to nothing, becalmed countrywide.

If that is not uncontrollable, unreliable, not dispatchable, I don’t know what is.


Gerry, England
Reply to  MrGrimNasty
April 26, 2020 5:42 am

Looking like a change of weather pattern from Tuesday to westerly low pressure which will push up output but possibly increase demand if it brings cooler weather. They will soon be pleading with us to turn appliances on to save the grid.

April 26, 2020 7:33 am

I am watching the Baltic States largest windfarm mostly sitting doing nothing for about a week, thanks to a whopping great Anticyclone, and an absence of rain for a week.
The Wonder mills are some of the largest in the EU, with simply gigantic towers and blades.

They just about started turning today finally after a light breeze came, and the other side of the sea will be the same in Finland, as we share the same weather.

What annoys the heck out of me is having to pay a 20% supplement on my electricity bill for something that patently doesn’t work, was put up without asking, has been erected an illegally close distance to the town, generates huge amounts of low freq noise pollution, and on top of that has been touted by the rotten nuts in Brussels as a way to produce power from “non polluting sources” when we have 100yrs of oilshale in the ground, and 100s of billions worth of low grade uranium (the most radioactive state in the EU).

It was also touted as a way for the Baltic states to get energy “independence” from Russia.
A lie, – because ALL the oil and gas comes from over the border like it always has.

Can someone send me some of Mr Nobel’s pet creation so that I can remove 1 or 2 of the eyesores during the summer white nights, when the wind is usually as calm as death?

April 26, 2020 7:35 am

Look here you lot.
The science is settled.
Renewable energy is (was/will be) a big bag of sh*t.

Crispin in Waterloo
April 26, 2020 9:41 pm

Speaking of low Demand: Sunday in Ontario


For 7 hours today electricity fed into the grid had to be accompanied by a payment (negative payment). For 8 hours they accepted it for free (no payment) and for the rest of the day the max per MWh was under CDN $8.00 (0.94 to 7.76).

Wind provided roughly 20% during some hours. Do the wind energy companies get paid for power even if the nuclear power stations have to pay $3/MWh for them to take it? What is in the contract? Is there a level playing field?

Gordon Hughes
April 30, 2020 5:28 am

I would like to add some economic context to the comments here. Some of you may know that I have published a number of papers questioning the economics of renewable generation, especially wind, but that does not mean that renewable generation is always uneconomic. There are plenty of circumstances in which solar and wind power make sense. The problems are caused by the naive or incompetent policies that have accompanied the implementation of large subsidies for renewable generation.
A few of the issues:
1. To accommodate renewables in a large scale electricity it is necessary to move away from paying primarily for energy to paying for a variety of grid services. The engineers refer to frequency control, reactive power, etc – mostly provided by large spinning turbines – but there are a variety of other services required to meet the needs of most complex energy systems. Batteries are not enough, and storage/pumped hydro is strictly limited in densely populated markets.
2. The UK & Europe have resisted the introduction of nodal pricing for transmission which is fairly widespread in the US and elsewhere. This is a large hidden subsidy for wind farms in remote areas.
3. As far as I am aware all solar and about 50% of wind in the UK is embedded – i.e. outside grid monitoring and control. The situation is worse in Germany. The consequence is that variations in output appear as short term fluctuations in demand, greatly complicating management of the system. John highlights the difficulties in the UK but they are far worse and more expensive in Germany.
4. Much of this shows up in what in the UK are called BSUoS (balancing costs). This are not properly passed on to either generators or consumers. The UK government wants people to use smart meters to switch on equipment when energy prices are low. The problem this creates is that system or balancing costs are high at such times and increase with the level of demand, so they are promoting behaviour that deliberately destabilises the system.
I could add more but the central point is that it is daft to pay for generation solely via prices per MWh of output, especially ones that are fixed independently of demand and system stability as is the case for most renewable subsidies/contracts. This worked as long as renewable generation was less than 10% of output. It is now 20-30% of annual output in several European countries and much higher at some times of year. In the new regime there is no option other than to unbundle generation services and devise what will (unfortunately) be much more complex contracts for all parties.
Large grid-connected solar plants make economic sense in certain parts of the world, provided that they pay the associated system integration & stability costs. It is less clear where wind power is economic – probably it is ok in Texas but not offshore in Europe – but wind operators have resisted any notion that they should pay for the costs that they impose on electricity systems. That has to change.

May 7, 2020 1:36 am

Large fluctuations cause cascading issues including synchronous generators falling offline and transformer output under or over voltage which can cause serious physical damage and danger.


%d bloggers like this: