UK Electricity Supply, September 2015

Scotland has had a dreadful summer. Our rivers have been in flood for most of the year. But then along came September and with high pressure stable over the North Sea we are now enjoying an Indian Summer. And so is much of Northern Europe. This is good for the soul, but as we shall see dreadful for both wind and hydro production. We imported more electricity in September (9%) than was produced by wind (6%).

According to DECC, the UK had 10.9 GW of installed wind at end May 2015. At 08:35 on 26th September this massive wind park managed to produce 0.134 GW. That works out at 1.2% load. The maximum for the month was 5.3 GW, 48.6% load, at 06:05 on 12th September. The average wind load for the month was 16%.

Hydro has operated well below capacity all month with an average load of 9% (compare with 41% in January this year). Imports via inter-connectors have been full on all month with average load of 68%. Nuclear had average load of 74%.

According to DECC, the UK had 81 GW of generating capacity at end May of which 10.9 GW was wind. With 70.1 GW of dispatchable capacity (excluding 4 GW inter-connectors), and peak winter demand of the order 55 GW, there does not seem to be a risk of blackouts caused by lack of capacity this winter unless natural gas supplies are disrupted.

Figure 1 UK electricity supply for September 2015. Data from BM reports via Gridwatch. Click chart to get a large, readable copy. There have been three UK-wide wind lulls this month; 7th-8th, 13th to 19th and 26th to ongoing. The bulk of generation has come from nuclear, coal, gas (CCGT) and imports (see Figure 3) which are probably mainly rooted in French nuclear.

Figure 2 Same data as plotted in Figure 1, not stacked. Gas (CCGT) and coal have done the bulk of load following. Note how wind has died to near zero on three occasions.

Figure 3 Pie chart showing the share of generation by type. Other = biomass, though I’m unsure if this is pure biomass or biomass co-fired with coal.

Figure 4 The capacity numbers come from DECC dukes5_10 and are for end May 2015. 

Figure 5 Maximum and minimum statistics by type. The “other” category (biomass) has been run at high capacity all month (min/max=0.6). Hydro max of 599 MW compares with installed capacity of 1742 MW. Despite the  dull and wet summer, there is now a drought pending. Note how max total demand is double minimum total demand (min/max = 0.51).

The River Tay in Perthshire was once world famous for its salmon runs. The river has been in flood all summer. The river hosts several hydro schemes and is rarely this low and the sky is rarely this blue.

The view from my cottage, sunset on 30 September. We had frost this morning, 1 October.

My dogs are heavily into renewable heat.

This entry was posted in Energy and tagged , , , , , , . Bookmark the permalink.

31 Responses to UK Electricity Supply, September 2015

  1. Dave Rutledge says:

    Hi Euan,

    Good summary. Brings back memories of a pleasant walk.


  2. Lars says:

    To me the the most worrisome for the UK in the years ahead looks to be the closures of coal power. Only 13 GW left and more to disappear soon means an overreliance on CCGT. As far as I remember British storage capacity for natural gas is only 4 TWh and domestic production dwindling. Coal is easier to store and ship around and I would not bet that the UK can get enough natural gas in all circumstances. “Diversification” and “energy security” are obviously words lost to the current British leadership.

    And I almost forgot to say, wind power just proves how useless it is in these statistics. Providing 5,76% of monthly power on average with more than 10 GW installed, blah!

    • Euan Mearns says:

      I suspect there is a lot of smoke and mirrors. There is an additional 7 GW of coal + bio. So they throw a few sticks into the fire and pretend its Green. And the post-Fukushima gas shortage has alleviated somewhat with a Japan nuke coming on and global demand softening. And in UK we will have large Lagan field coming on soon. The CURRENT momentum is with glut, not shortage.

  3. 70.1GW of installed capacity to service 55GW of peak demand gives a false impression of the UK’s reserve margin this coming winter. Without Nat Grid’s purchase of “reserve supplies” it would reportedly be down to 1.2%.

  4. PhilH says:

    Not entirely pedantically, this posting refers to the GB electricity supply, rather than the UK’s.

    More significantly, the DECC stats that put UK wind capacity at 10.9 GW at end May 2015 can only be counting part of the fleet, as last week’s latest Energy Trends from DECC puts it at 13.748 GW (8.723 on shore + 5.025 offshore) at end June 2015. Of this just over 13 GW is in GB (nearly 0.7 GW being in NI).

    All the figures cited above are just from the major power sources connected to the GB National Grid and their Balancing Mechanism. Only 8.403 GW of GB’s 13 GW wind capacity is monitored amongst this according to the BM Reports main page of graphs, though 8.972 GW according to its PowerPark Modules spreadsheet, and it was that fraction that produced the 0.134 GW minimum output. Pro rata, the whole GB fleet would have produced about 0.2 GW, ie about 1.5% load, which is indeed almost as minimal as the figures in the second paragraph above. The figures for wind in Fig 4 above need to be increased, pro rata, to about 1800 GWh for the month, about 2500 MW avg, and 0.23 capacity factor (CF).

    Similarly for hydro – for which I can’t find more accurate figures than the statement on the BM Reports page that, at least as of 2011, only about 50% of GB’s hydro is included in the monitoring. Hydro has changed relatively little in recent years, so that’s probably still reasonably accurate. So the figures for hydro in Fig 4 above need to be roughly doubled to about 200 GWh for the month, about 300 MW avg, and about 0.2 CF.

    Most significantly, the National Grid and their Balancing Mechanism don’t monitor solar at all. The UK now has about 8.5 GW of PV solar, very little of which is in NI, so GB probably has about 8.25 GW. In September its output peaks at about 5 GW on the sunniest days, like the past few, and is obviously 0 GW each night (, and in an averagely sunny September would generate about 600 GWh in the month, about 800 MW on average, and about 0.1 CF (to be added to Fig 4 above).

    So the total RE (Wind+PV+Hydro+Biomass) generation would be about 1800+600+200+1144 = about 3750 GWh for the month, and about 2500+800+300+1589 = about 5200 MW on average. Both figures are not far short of the figures for coal, in what was evidently a month with relatively low wind speeds. Wind thus provided about 7.5% of GB’s total electricity for September, and PV about 2.5%.

    • Euan Mearns says:

      Thanks for that Phil. I will try to make this more sophisticated in future. I know Clive Best did a post on this. But it begs the question why it is so hard for BM to not report all the data accurately. There doesn’t seem a lot of point in reporting at all, if it is just partial data.

      My figure 1 has a curious V shape at mid day. Do you think that could be filled with solar?

    • Euan Mearns says:

      So does anyone want to help me make a solar model for the UK? Phil’s link to solar forecast didn’t have a handy “download all our data” button. Do you think they would send it to me? The only data I can see is Leo’s French data. Is it possible to proxy that to UK?

  5. Rob says:

    Why is the capacity factor for wind so low 0.16 I keep hearing the can achieve 30-40%
    Link claims 50% the New Normal

    • Euan Mearns says:

      Rob, part of the reason is mis match between production figures and the wind capacity it is connected to. See Phil’s comment. To achieve 50% would require climate engineering to make the wind blow most of the time. Or as is often the case, someone simply makes up the numbers.

    • PhilH says:

      Wind varies day-to-day, month-to-month and year-to-year. From the figures I’ve seen, I get the impression that average load factors (LFs) for turbines in the UK are typically 25-30% (or 0.2-0.3) for onshore and 30-35% for offshore, with a rough overall average of about 30%.

      The law of averages says that for every below-average, 20% (see my revision above) month like Sept 2015, there’ll be an above-average, 40% month, or two above-average, 35% months, etc. In NW Europe, winter months, when we use more electricity & energy in general, tend to be windier than average, and summer months, when we use less, less windy than average.

      As to achieving 50+% LFs, it will depend on the wind regime at the site you’re interested in. I suspect that article refers mainly to the US, where there’s a much larger choice of locations than the UK, some of which will have such excellent wind regimes. I get the impression there’s also an effect from the increasing range of turbine designs available, particularly higher towers & longer blades, which allow better selection of a design best suited to harvesting the range of wind speeds at a given site.

      • A C Osborn says:

        ” In NW Europe, winter months, when we use more electricity & energy in general, tend to be windier than average, and summer months, when we use less, less windy than average.”.

        That is not my experience in Europe, Spring & Autumn are windier in Europe and Winters are quite often troubled with freezing “Blocking Highs” which totally becalms much of Europe for days on end, just when Electricity is most needed.

  6. Hugh Sharman says:

    Well said, PhilH!

    Has anyone an explanation for why, at, NGrid is only declaring 8403 MW? This has stayed constant for well over a year despite the steady stream of new wind projects being triumphantly announced at

    • PhilH says:

      I’m guessing that National Grid and their Balancing Mechanism control & monitor only the large-scale generation sources, including wind farms, connected to the high-voltage national grid. Their webpage has been stuck at 8403MW since Feb 2014, since when the offshore farms West of Duddon Sands (389MW), Gwynt y Mor (576MW), Westermost Rough (210 MW) & Humber Gateway (219 MW) have been commissioned. Even if there have been no onshore wind farms large enough to need to be connected to the high-voltage national grid, something’s not up-to-date. Whether the displayed wind generation actually comes from just the 8403MW of the main page, or the 8972MW of the PowerPark Modules spreadsheet (which does include those 4), or the 10333MW from adding those new 4 to the 8403MW, or some other selection of wind farms, I’ve no idea. Does anyone from National Grid read this blog?

    • Euan Mearns says:

      This is what I get from BM reports.

      They have 12900 GW of wind on that table, higher than the 10929 I used from DECC. Using the higher number will result in even lower load. No surprising really. Earlier today when I checked we were turning out 0.5 GW of wind. I’m guessing the figure will actually be negative as turbines draw power from the grid to keep moving. Nuclear powered wind turbines 😉

      Their number for Hydro is not too different to what I used BM=1570 v DECC=1742. This will boost the hydro load a little. 1570 sounds like the SSE Scottish hydro number.

    • Euan Mearns says:

      Summary of wind installed capacity from DECC (May), BM and Renewables UK. The offshore actually looks fairly consistent. I guess I need to assume that the BM numbers are those that need to be applied to their production reports? Doing so, the September average load for the UK wind drops to 13.7%.

    • PhilH says:

      I’m dubious that what’s in the Elexon image you reproduce above corresponds to what’s reported on the BM Reports webpage.

      Firstly, wind: Since the BM Reports webpage started displaying that it was monitoring 8403MW in Feb 2014, the maximum wind output has been 6835MW (on 9 Dec 2014). Crudely you’d expect that for every 1% LF interval there’d be a 99% LF interval, but probably because the strongest areas of wind (low pressure systems) aren’t as extensive as the weakest areas of wind (highs) the max might be more like (waves hands as justification) 80% LF, which would correspond to a 100% total capacity being monitored of about 8500MW. If it were 10900MW, 6835MW would only be 63%; if 12900, only 53%; if 13300, only 52% – these 3 cases seem far too low for an instantaneous maximum as some whole months can average LFs over 50% for some UK wind farms. So I reckon the total capacity being monitored was actually something like the 8403MW or 8972MW figures.

      Secondly, it has 3 categories that don’t appear at all in the BM Reports webpage graphs: ‘Solar’ ‘Biomass’ & ‘Other renewable’, as distinct from the ‘Other’ category, which is reported (it’s not clear to me what’s included in that if it’s not solar, biomass or other renewables – non-renewable types of waste?)

      • Euan Mearns says:

        Clive Best has the answer:

        Untangling UK Wind power production

        BM @ 12900/1.46 = 8836 MW metered

        1766 MW average for Sep, average load = 20%

        Note that Clive grosses up metered wind by this factor which explains why his value right now is 0.3 GW and Leo’s is 0.21 GW. Its quite amazing that it is totally flat calm across the UK including the offshore areas.

  7. Gaz says:

    En route to Bristol airport recently, few large Tur(d)bines moving in the complete absence of any wind, and from memory Gridwatch was showing F/all Wind generation 0.56gw…

    As mentioned, the Tur(d)bines are parasites on the network – what a waste of space!

  8. Hugh Sharman says:

    Capacity factor of UK renewables can be downloaded at, table DUKES 6.5

    On shore wind 26.5% offshore 37.5% during 2014

    I am surprised to see that UK PV is 11.2%

  9. Günter Weber says:

    Dear Euan,

    many people who are into renewables (me too) are hoping for some kind of balancing of wind power production throughout Europe. It would be nice if you could contrast the wind power production in UK, Spain and Germany (to have 3 regions with a certain distance to each other that all have a significant wind capacity) for a certain period of time.
    Here you could obtain data for Germany and some neighbouring countries:
    Unfortunately, I did not find a source for Spain yet.

  10. KenB says:

    Scotland has a huge potential for wind and hydro particularly in winter when demand is greatest. I believe Shetland Isles holds the world record for load factor of something like 67% over a yr.

    On the other hand with Spain pv producing 1.5 kwh/kwp to the UKs 1.0 over a yr. and 2.0x in winter.

    On another hand France has Nuclear to sell cheaply.

    Norway has more than enough hydro storage.

    Dont see why renewables have to justify themselves all the time ,it is the fossil fuel burners that need to justify themselves-it is them that have caused the pollution,health problems and global warming,which they are still not paying for.

    In any case onshore wind leccy is cheaper than any other NEW production just need to get it connected to the grid.

    • Andy Dawson says:

      “Norway has more than enough hydro storage”

      Norway’s got about 14GW of hydro – against its own demand of 10-11GW.

      Which sounds like it’ll be able to provide 3GW – presumably to meet demand at times of low renewables output from Denmark, Germany, Sweden, the UK…..

      Am I the only one that can see an issue?

Comments are closed.