UK Electricity Supply Capacity

[JohnW2]

Given recent discussions about 'power shedding' etc., does anyone know roughly what is the current limit of UK electricity generation+import capabilities? In particular, does the red sector on the Gridwatch 'total demand' dial, starting at about 65 GW, represent that 'limit', I wonder? (the below from a few minutes ago) ...

The total demand seems to be generally between 25 GW and 35 GW, and only very rarely appreciably over 40 GW ....

In passing, and interestingly, for the last few days the amount of UK electricity derived from coal has been zero.

Kind Regards, John

 

[SimonH2]

Demand does vary significantly wirh weather - the lst few days have been quite warm so demand will have been down. 65GW is about the value I recall - but it too varies, for example some plants shut down during summer for planned maintenance.
The old NETA bmreports page was much better for visualising things - but the information is still there, just less easy to see.

 

[JohnW2]

Demand does vary significantly wirh weather - the lst few days have been quite warm so demand will have been down.

There clearly must be some variation, but I have to say that I've always been a bit surprised that there is not a lot more seasonal variation or variation with weather changes. Demand in the last few days has, in fact, been pretty similar to what it was over the 'very hot' Easter weekend.

65GW is about the value I recall ....

That certainly seems consistent with that red sector on their dial - so demand is currently usually roughly half of the theoretical maximum supply (and virtually never more than about 60% of that theoretical maximum)?

Kind Regards, John

 

[bernardgreen]

In particular, does the red sector on the Gridwatch 'total demand' dial, starting at about 65 GW, represent that 'limit', I wonder?

65 Gwatts seems low for the amount of power needed

There are about 25 million homes in the UK 65,000,000,000 watts (65 GWatts) divided by 25,000,000 gives an average of 2600 watts per home. But that does not take into account the power used for industrial and other non residential purposes.

Department for Business, Energy and Industrial Strategy (BEIS)
UK ENERGY IN BRIEF 2018

 

[Harry Bloomfield]

Given recent discussions about 'power shedding' etc., does anyone know roughly what is the current limit of UK electricity generation+import capabilities? In particular, does the red sector on the Gridwatch 'total demand' dial, starting at about 65 GW, represent that 'limit', I wonder? (the below from a few minutes ago) ...

Best to talk to the gentleman who provides the Gridwatch pages http://www.gridwatch.templar.co.uk/. Better known as The Natural Philosopher he resides in the uk.d-i-y newsgroup, he has considerable expertise and knowledge of capacity issues.

 

[JohnW2]

65 Gwatts seems low for the amount of power needed

Intuitively, I'd be inclined to agree, but if one looks at the various figures available on-line (all of which are very similar), it would seem that 65GW is not far off double the actual total demand for electricity in recent times.

There are about 25 million homes in the UK 65,000,000,000 watts (65 GWatts) divided by 25,000,000 gives an average of 2600 watts per home. But that does not take into account the power used for industrial and other non residential purposes.

All true - but, as I've said, all available figures seem to suggest that average total (residential + all other) demand is generally no more than about 30 GW.

I realise that you are presumably talking about 'peak' demand, but if a home used anything like an average of 2,600 W (over 24h), their electricity bills would be astronomical - an average of 2,600 W continuous would at, say, 16p/kWh) cost around £3,644 per year. The average domestic electricity usage in 2017 was around 3,700 kWh/year, equating to an average consumption of about 420W (and about £592 p.a. at 16p/kWh).

The UK's total (domestic plus everything else) annual electricity consumption in 2017 is said to have been 348 tWh, equivalent to an average consumption of about 39.7 GW.

The official government figure are somewhat lower than these, and require a bit of arithmetic, since usage is expressed in units of ktoe (kilotonnes of oil equivalent), 1 ktoe being about 11.63 GWh. Reading from the Chart 1.06 of page 9 of the summary for 2017 (click here) , it seems that the total UK electricity consumption in 2017 was around 20,000 ktoe., which equates to about 233 TWh/year, an average of about 26.5 GW.

Department for Business, Energy and Industrial Strategy (BEIS) .... UK ENERGY IN BRIEF 2018

Those figures for electricity generation capacity are amazingly high (about 3 times) in relation to what appears to be current usage/demand! In particular, the 40.6 GW of 'renewable' generation capacity in 2017 would have been, alone, numerically enough to service the entire UK demand on nearly all days in 2018! [I say 'numerically', since there is obviously considerable variability in 'renewables', particularly in that solar generation is only possible during daylight hours!]

Kind Regards, John

 

[SimonH2]

In terms of "keeping the lights on" you more or less have to disregard renewables. The figures for renewables are a total of rating plate capacity - not actual output. There's never the right conditions for all windmills and solar PV to operate at 100%, and as we know, we can have prolonged periods in winter (about 2 weeks in Dec 2010) when there's hardly any wind and short days - right when demand is highest.
In practice, what's happened is we now pay a number of large plant operators to stay open who would have just closed and scrapped the plant. Without such payments, many plants aren't economic because of the way renewables get first bite of the cherry and (as we're seeing now) effectively block some plant from having any income for a lot of the time. The wind lobby don't seen keen to mention that hidden cost

 

[JohnW2]

In terms of "keeping the lights on" you more or less have to disregard renewables. The figures for renewables are a total of rating plate capacity - not actual output. There's never the right conditions for all windmills and solar PV to operate at 100%, and as we know, we can have prolonged periods in winter (about 2 weeks in Dec 2010) when there's hardly any wind and short days - right when demand is highest.

Indeed - it certainly seems to me that those BEIS figures posted by bernard are potentially quite misleading.

Having said that, I think it would be totally wrong to completely ignore renewables, given that they currently have the potential to service much of our current demand, particularly during hours of daylight, and are continuing to increase. Whilst there will obviously be occasional periods like you mention (over 8 years ago), when there is little wind and short days, things will more-often-than-not 'work out' reasonably well.

We could, of course, never rely on only 'renewables', but they are coming to be an increasingly important contributor. Given the inevitable eventual exhaustion of fossil fuels, an ultimate future based on 'renewables' plus nuclear (ideally fission) would seem pretty inevitable (albeit beyond any of our lifespans).

Kind Regards, John

 

[bernardgreen]

it certainly seems to me that those BEIS figures posted by bernard are potentially quite misleading.

It is annotated to be installed capacity. No wind = no output but the "installed capacity" is still there but doing nothing worth while.

 

[JohnW2]

It is annotated to be installed capacity. No wind = no output but the "installed capacity" is still there but doing nothing worth while.

Indeed - but (a) many people will not notice that (feint on my monitor!) annotation and (b) it seems to make little sense to tot up that 'installed capacity' (which, as has been said, will rarely/never be realised, even during daytime, and never at night) with the other ('true capacity') figures.

Kind Regards, John

 

[SFK]

Quoting from https://assets.publishing.service.g...m/uploads/attachment_data/file/736152/Ch5.pdf

Over 2017 the total installed capacity (for both transmission and distribution networks) for the UK was 106 GW, an increase of 6 per cent on 2016. From this total UK capacity, 96 per cent was connected in Great Britain and 4 per cent in Northern Ireland.
For Great Britain, [in 2017] it is estimated that 71 GW was connected to the transmission network, which accounts for 70 per cent of the Great Britain total capacity. This was slightly lower than the 71 per cent in 2016, due to increases in distribution connected renewables capacity.

 

[JohnW2]

"... Over 2017 the total installed capacity (for both transmission and distribution networks) for the UK was 106 GW, an increase of 6 per cent on 2016. From this total UK capacity, 96 per cent was connected in Great Britain and 4 per cent in Northern Ireland.
For Great Britain, [in 2017] it is estimated that 71 GW was connected to the transmission network, which accounts for 70 per cent of the Great Britain total capacity. This was slightly lower than the 71 per cent in 2016, due to increases in distribution connected renewables capacity.

Thanks, that attempts to explain the reason for the different sets of figures we're seeing - but I'm not really sure what it is saying

What exactly is the difference between "total installed capacity (for both transmission and distribution networks)" and "connected to the transmission network". Are they saying that there is some 30+ GW of "installed capacity (for both transmission and distribution networks)" which is not "connected to the transmission network" (which would sound rather odd!), or what?

Kind Regards, John

 

[SFK]

My reading of this (and happy to be corrected) is

The GB + NI network can handle a max of 106GW at any time.

Estimated that 71GW of Production (power stations etc) is actually connected to this network.

So there is 35GW of spare Distribution capacity. So the Distribution Network has ability to have more Production Capacity (Power stations/solar etc) built / switched on if needed.

Do not know value of spare or offline Prodution Capacity.

 

[JohnW2]

My reading of this (and happy to be corrected) is ... The GB + NI network can handle a max of 106GW at any time. ... Estimated that 71GW of power stations are actually connected to this network. .... So the network as ability to have more Power stations built / switched on if needed. .... So there is 35GW of spare distribution capacity.

Oh, I hadn't even thought of that possible interpretation! The implication seemed to be that the data related to generation, not just distribution, capacity!

However, if one looks at the BEIS figures that bernard posted earlier today, what is charted as "Electrical Capacity" showed similar figures for 2017 to the ones you mentioned, but with the 'Renewables' component (but not for any other component) having increased dramatically during the preceding decade - the implication surely being that that was actual potential 'renewable' generation capacity, not distribution capacity?

Kind Regards, John

 

[Harry Bloomfield]

My reading of this (and happy to be corrected) is

The GB + NI network can handle a max of 106GW at any time.

Estimated that 71GW of power stations are actually connected to this network.

So the network as ability to have more Power stations built / switched on if needed.

So there is 35GW of spare distribution capacity.

Do not know value of spare or offline Prodution Capacity.

I equally I might be wrong, but I would read the 106 as the absolute maximum capacity, full input from renewables and all other capacity in full working order. Renewables will rarely if ever produce 100% of their rated input to the grid. Conventional generation likewise is never 100% available, generators etc., will be taken off line for repair and refurbishment etc.. The likelihood is that the 106GW at any one time, might be actually as low as 55GW of available capacity to meet demand. The distribution network is designed to work with input and output scattered around it, it could not for instance cope with all southern UK generation being stopped and a net export from northern generators, so how they arrive at a figure of 35% spare capacity I don't know. Maybe that is an average taking into consideration the entire national grid system? Some section running at full capacity, some with considerable spare capacity?