Hydro Balancing Wind in the UK

There’s nothing that renewables advocates like to discuss more than building power lines, lots of them. And a favourite subject is to build very expensive power lines between the UK and Scandinavia so that we, like the Danes, can balance variable wind generation  off their controllable hydro. Every country in Europe wants to do this.

The UK of course has its own suite of hydro dams with 1.7 GW capacity, most of it in Scotland. And so you would think that before we begin to dream about balancing our wind power off Scandinavian Hydro we would start by utilising our own hydro to maximum effect before hand (Figure 1). Nothing could be further from the truth.

Figure 1 If UK hydro were being used to balance wind, a negative correlation between the two would be expected since hydro generation should be turned down or switched off altogether when the wind blows. If anything there is a positive correlation suggesting that UK hydro is not being used to balance wind power at all. Data points are 5 minute intervals for the whole of 2012. Data sources BM reports from Gridwatch.

Another way to look at the data is of course as time series as shown for January 2012 in Figure 2. From this it is perfectly evident that UK hydro is not turned down or off when the wind blows nor is it turned up when the wind doesn’t blow. It is more or less kept running the whole time with minor fluctuations made to meet diurnal demand pattern.

Figure 2 Click chart for very large readable version. The x-axis is at 5 minute intervals for the month of January 2012, the labels are spaced on a daily basis. There is precious little evidence from this that UK hydro is being used to balance variable wind. Data sources BM reports from Gridwatch.

The picture for January 2014 is pretty much the same although there is a hint that hydro may be run a little harder during windless spells (Figure 3). It is never turned off and it never gets close to generating 1.7 GW the supposed name plate capacity.

Figure 3 Click chart for very large readable version. The axis is as described for Figure 2. In January 2014, hydro is still producing all the time and does not get much above 1 GW output. The diurnal variance that helps meet peak daily demand is still evident. The scale of wind variability has grown to dwarf hydro output.

Most of UK hydro is owned by utility Scottish and Southern Energy (SSE). They presumably are running their assets according to engineering and economic prerogatives. The positive correlation shown in Figure 1 most likely shows that both hydro and wind production are higher during wet and windy periods that occur mainly in winter months. The small diurnal variations in hydro are down to SSE selling some of their power into high priced, peak demand periods.

So why is the UK not using indigenous hydro to balance wind choosing instead  to make curtailment payments to wind producers when the wind blows too much? I don’t know the answer. I suspect that turning hydro off would cause our rivers to run dry and producing flat out would produce floods. It must also be noted that wind is now producing over 6 GW of variable range in output (Figure 3) that dwarfs the maximum output of our hydro suite. Hydro balancing wind in the UK seems to be yet another empty Green promise.

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20 Responses to Hydro Balancing Wind in the UK

  1. Joe Public says:

    Wouldn’t the sudden changes of water flow rates detrimentally affect the little fishes that live downstream?

    Maybe it’s a ‘wildlife preservation’ decision?


    • roberto says:

      You get the point correctly.
      On a bigger scale that’s what happens downstream of the dozen or so of larger dams along the Yang-Tze river and the Three Gorges Dam… there’s plenty of literature on that… a real environmental disaster in the making… see for reference the articles on Environmental Research Letters… they are Open source.


  2. Glen Mcmillian says:

    More than likely the answer in in a nutshell is that the regulatory authorities are not mandating the two resources be used in such fashion.There are various reasons why this might be so,some good ones and one less so.

    The less so one would be that the hydro owners aren’t interested for reasons involving their own bottom line.

    The good ones probably boil down to the apparent fact that there is not enough hydro to properly balance wind without changing the down stream flows below hydro reservoirs too much too fast.

    Water released today offset a lack of wind can leave a reservoir too low to produce as needed over the next few days or weeks and water flow held up beyond a certain point would overfill the reservoir as well as get the public to screaming about an empty river.

    Running at or near nameplate would almost for sure deplete a reservoir very quickly in most cases and would mean burning coal or gas on following days.

    Euan is probably right.The hydro resource in the Uk is probably too small to really matter in terms of balancing wind power.

    Personally I remain convinced that long distanced power transmission lines built today will prove to be bargains compared to the risks of possibly irregular deliveries of gas and coal at exorbitant cost in the future.

    A power line to Scandinavia looks to be a better and safer investment than a larger Navy and Army.Invading countries that do not want to export to you is a VERY expensive undertaking.

    Now as to just how much UK wind could be balanced by Scandinavian wind is concerned I have no real idea.

    But one thing is for sure. Such power line can be maintained more or less indefinitely once built. Navy ships have to be scrapped every thirty years or so due to wear and obsolescence.

    • Joe Public says:

      “Personally I remain convinced that long distanced power transmission lines built today will prove to be bargains compared to the risks of possibly irregular deliveries of gas and coal at exorbitant cost in the future.”

      Unless of course you’re blessed with plentiful indigenous supplies, as we in the UK are.

      • Glen Mcmillian says:

        Maybe I am all wrong but it seems to me from just about everything I have read that the UK simply does not have ” plentiful indigenous supplies” any more and certainly does not have supplies that are proven to be economically extractable adequate to last very long into the future.

    • roberto says:

      “Personally I remain convinced that long distanced power transmission lines built today will prove to be bargains compared to the risks of possibly irregular deliveries of gas and coal at exorbitant cost in the future.”

      Bargains only if it’s gonna be a matter of transporting back and forth few GWs (with losses of the order of 5-6%/1000 km distance, plus 25-30% for the pump-up/re-generate electricity cycle of pumped hydro in Norway… I’ll let you figure the overall losses!) … but the UK greens would wish to transport TENS and TENS of GWs at once!… because this is what is going to be like in a future where nuclear and coal (and possibly gas as well?) are zeroed… which, by the way, it is almost exactly what the german green intelligentsia is wishing to do… but… “Houston, THEY have a problem here!”… there’s not enough lake space or willingness to do so in Norway or on Norway’s citizens… so UK and DE and all the others better think of some alternative based on known physical laws (and common sense) rather than ideological zeal… because the latter will never, ever work in the real world.
      Never did, and never will, no way.


      • Glen Mcmillian says:

        I don’t know how efficient pumped hydro is in Norway but at facility near where I live Smith Mountian Lake the efficiency is said to be about eighty five percent. Losses are usual all over transmission systems and to be expected.Ten percent is the figure I usually see quoted for our American domestic grid.

        HVDC lines are supposed to suffer only small losses over a distance of a thousand kilometers or more but I cannot remember just how big at the moment.

        But we should keep in mind that in debates such as this one a lot of partisans on both sides are going to exaggerate their case for shock value and because exaggeration leaves more room for negotiation later. I am a renewables advocate as well as a nuclear advocate myself.

        But there are ” greens” out there that do advocate the shuttering of coal and nuclear power altogether. Those who do so are living in cloud la la land. It isn’t going to happen.

        And the renewables industry is going to continue to grow no matter how the antirenewables faction presents its case. The people of the world are able to understand there is more to the cost of electricity than just the monthly bill and that a higher bill is partly offset by local employment and local tax collections on renewable infrastructure and that home grown is economically safer than imported.Beyond that the investment community is mostly convinced that in the end game renewables are going to be cheaper than fossil fuel generation as renewables cost falls and fuel costs rise.

        Those who are just systematically opposed to renewables are in cloud la la land for all practical purposes because building enough nukes to replace fossil fuels is probably an economic impossibility within the time frame available and doing so is for damned sure a political impossibility. The anti nuke forces are very well organized and highly skilled in the politics of obstructing the construction of nukes.They are also very numerous.

        I don’t expect very many new nukes to be built anytime soon in western countries. I don’t think any body does – not really!!!!

        Antirenewables parties are in la la land because they are basing their arguments on the continued assured availability of fossil fuels at affordable prices.

        A very basic knowledge of the history of the energy industry and geology in combination with some understanding of political history- meaning primarily wars and nationalism etc- indicates that afford able fossil fuels are growing scarce and will continue to become harder to extract and more expensive to buy over the long term.And even if the foreign exchange needed to pay is available the supply may still not be there for sale.

        I personally sure would not want to be a German beholden to Russia for my energy. The Russians have long memories.

        I used to watch trains headed for Newport News go by loaded with top quality coal headed to Japanese steel mills on the far side of the world. No more. We mostly have to import that grade of coal now- the kind needed to make the very best grades of steel.

        The DELIVERY costs of midwestern American coal to power plants in our southern states runs about five times the actual mine site cost of the coal.The cost of running trains is as about as low as it will ever get given that railroads are a mature technology.

        The construction of very high capacity power lines -hvdc lines- is just now beginning to wear long pants.The price of new technologies tends to fall quite a bit over a period of years.Renewables cost will continue to fall and methods used to store intermittent energy will be invented as time passes.

        We are probably past the point of net available energy in this country – the US- because after allowing for higher mining costs in our legacy fields and high transportation costs from our newer fields plus the lower quality of mid western coal the higher tonnage is not enough to compensate for the lower quality and additional costs of transportation.Our mid western coal is pretty sorry stuff compared to the good hard coal we used to mine nearby here close by West Virginia.The local papers tell us that we can expect most of our mining jobs to vanish in another ten to fifteen years and not because of any war on coal. The remaining coal is going to be too deep to mine it at a profit.

        Fossil fuels simply are not always going to be available at affordable prices. Sometimes when the international political landscape is troubled they are simply not going to be available at all for extended periods of time.

        China is well on the way to sewing up Asian supplies in the ground and under the water.The US may or may not have gas to export depending on how well our industry does over the long term and how our people feel about exporting it after we experience a couple of price spikes.

        I don’t think any body seriously contemplates invading either China or Russia to grab their oil and other resources the way we westerners used to take over countries as colonies.If there is going to be a new colonial era the Chinese are going to be the masters of it.

  3. Ted says:

    Though the flooding/run dry scenario does not applt to the 440MW of Cruachan or the Sloy hydro which both run into major lochs. You would have thought both would be switched of when wind was high and that Cruachan would even pump up before wind farms were paid to stop producing.

  4. Euan: According to your graphs UK hydro is being used dominantly as baseload capacity with a load factor of ~750/1700MW = ~44%, which according to DOE is the “typical” load factor for hydro plants (http://www.jcmiras.net/surge/p130.htm). With all the other variables that figure into the equation, like fluctuations in water supply, flood control requirements, environmental restrictions etc. it seems that hydro plants can’t do any better than this.

    And the reason it’s being used as baseload rather than load-following capacity may be that rapid cycling to accommodate wind surges can crack the dam:


  5. In most places where renewables have a fair penetration, natural gas is being used to balance intermittent renewables. This is very much to the consternation of utilities in Germany, such as E.ON, whose natural gas fired power plants are being used to balance renewables and are being run at lower capacity factors than their investments require for an adequate return. In addition, broad grid connections can be very helpful as well. Denmark exports excess renewables’ production to other European countries, using the grid to balance production variability. Companies that manufacture energy systems are designing fast response turbines, including natural gas turbines and hydropower turbines (for hydro storage), to handle responding to intermittent renewables. Check out this post on the subject: http://bit.ly/1zcsxB5

    • roberto says:

      From your link:

      “In Germany, several notable data points have been achieved with solar power and wind power. On May 25, 2012, Germany hit a peak in solar generation capacity of 22.15 GW, producing 189.24 GWh on that day, contributing fourteen percent (14%) of the country’s total electricity requirement. Germany added 1,008 new turbines in 2012, connecting an additional 2,439 MW in new wind capacity to the grid.”

      … PV in Germany is an oxymoron… for the few days when the sun shines there’s plenty of many more days when the sun is nonexistent!… and all this for more than 30 Eurocents/kWh, that’s there real and only notable point of the Enertgiewende… 29 Eurocents/kWh for the german electricity customers!… second only to “windy” Denmark…

      Germany will go NOWHERE with PV and wind… NOWHERE!… it is physically impossible, as well explained by several recent papers in the literature… especially if all of this is done for decarbonizing the production of electricity… a pure nonsense.


  6. I think there is a difference between using the UK’s 1.7 GW of rain fed hydro plants for balancing by just varying their flow rate as you describe and using hydro reservoirs for pumped storage of surplus power e,g from wind/ the grid. The UK has the 1.8 GW Dinorwic scheme and some other smaller pumped storage projects including the 440MW plant at Cruachan which I hear is to be extended to 1GW. I’m told Dinorwic was built initially as back up in case Sizewell B failed, but with lots of gas plants then emerging, it lost its place in the balancing market . But this is the sort of thing that could earn it’s keep under the new capacity market scheme. Though there evidently isn’t much potential for more. If I read it right, a report for the EU estimated that UK’s maximum feasible was ~ 6 TWh.

  7. Lars Evensen says:

    “If UK hydro were being used to balance wind, a negative correlation between the two would be expected since hydro generation should be turned down or switched off altogether when the wind blows.”

    I suppose there are several factors at play here. First, could it be that wind power still is such a minor player in the large British electricity market that it doesn`t bring prices much down if it blows at lot like it does in Denmark and northern parts of Germany? If prices are sufficiently low this should cause hydro plants with reservoirs to stop producing and save their water awaiting higher prices. Of course this is also dependent on reservoir levels for any given producer. If your reservoir is full you don`t want to stop producing, that means you will have a “water loss”.
    2012 was an extremely wet year in Scandinavia, probably that was the case in Britain too?

    Glen McMillan has a point when he says “more than likely the answer in in a nutshell is that the regulatory authorities are not mandating the two resources be used in such fashion”.
    If,theoretically the whole British electricity market had one single owner it would obviously be in their interest to curtail hydro production instead of shutting windmills down. But with many players in the market it is probably a case of imperfect competition, or the prices aren`t low enough to encourage hydro operators to stop producing.

    Secondly, all you do is looking at the graphs and see the numbers, but we have absolutely no information on reservoir/precipitation levels, electricity prices or whether the hydro production comes from run off river or stored hydro for instance.

  8. Luís says:

    Hi Euan,

    You assertion “If UK hydro were being used to balance wind, a negative correlation between the two would be expected” is completely at odds with the data I am acquainted with. This is mostly due to the weather: the wind blows stronger when low pressures come through, usually bringing warm air from the south and the rains from the sea. At an annual, monthly and daily resolution, wind generation correlates positively wind wind. Even at an hourly basis, such correlation would only arise if all the hydro-electric elements connected to the grid had back pumping infrastructure. This is usually not the case.

    Another aspect that is evident from your post is the punitive size of the hydro-park in Scotland. The top 5 dams in Portugal have more installed capacity than the whole park in Scotland. This hints at a disperse park composed by micro to small sized dams where back pumping may not be feasible (financially and/or technically).

    You have to pick on the renewables some other way.

    • Euan Mearns says:

      Luis, In Scandinavia where they balance Danish wind hydro is incrementally switched off when it is windy and they use Danish wind instead. And when its not windy they switch more hydro on to cover domestic use and exports to Denmark. This must create a negative correlation between Norwegian hydro production and Danish wind consumption. This negative correlation is absent in the UK data. UK hydro is quite transparently not being used to balance wind. The main reason, if we switched it off, the rivers would run dry and all the fish would die.

      In most cases it is not possible to use conventional hydro as pumped hydro (back pumping) since this requires a large lower reservoir that is normally lacking in the UK. And in any case, the design of Scottish hydro is quite peculiar with networks of water tunnels in the mountains (gravity fed) channeling water into catchments where it is not supposed to be in order to gather enough water for a power station.

      You have to pick on the renewables some other way.

      I am not picking on renewables but simply pointing out that the Green argument that wind can be balanced off hydro does not stack up in the UK.

      • Pedro A. Prieto says:

        Luis, I am more in the side of Euan in this matter. In Spain, hydro is relatively well endowed and offers a potential close to wind in yearly output (installed power: 19.4% hydro and 22.3% wind; generation to the electric grid: 14.2% hydro and 21.2% wind in 2013). The problem is that our dams are already filling more than 90% of the main river basins (Ebro to the Mediterranean but Duero -Douro-, Tajo -Tejo-, Guadiana and Guadalquivir to the Atantlic through Portugal. But it is out of sight to think that one day the 100% renewable program (not only for elecricity, but specially if for primary energy, as Greenpeace proclaims) hydro could simply balance wind at certain levels. Portugal would probably put much more claims that it is already producing to Spain for altering the current river courses at its will. Not to talk about problems with river life and increasing use of water flows for domestic, industrial and more than any other thing, agriculture. If you see the Tajo-Segura water channel transfer, a water that should end at Lisbon and ends in our South Eastern deserts of Murcia and Almeria, to satisfy production of vegetables and fruits for most of Northern Europe, including UK and up to Finland, in a surprising case of water export from our deserts to wet and humid Northern European countries, embbeded in the exported products, you will probably fall in tears, when noticing that this channel carries more flow than Tajo river itself in summer.

        What we are already doing to the fisheries (if any remaining there, in the absolutely polluted main rivers), with so many blockings and seawage treatment plants and what we are doing pouring 4 GWth to the Tajo River from the 2 GWe nuclear power station of Almaraz, just to name two reactors from the 7 we have, is something to be seriously revisited.

        We have limits, including modern renewables, if we pretend to live in the same BAU conditions.


        Pedro, living 40 Km from Almaraz and fearing what would happen to the almost completely filled pools of wasted fuel rods, if we have a serious draught of the type of Biblic Joseph, with the seven lean cattle (seven continuous years of draught), considering that we can only extract rods to place them in dry casks (to get them refrigerated passively by air and avoid the melting of the material into corium), when they have been cooled enough and this takes from 5 to 10 years.

  9. roberto says:

    On hydro balancing elsewhere… interesting:



  10. Hugh Sharman says:

    Euan, in the UK, wind and rain come together. Of course, wind capacity so far exceeds combined hydro and conventional hydro that its balancing effect is miniscule anyway as I tried my best to point out at http://euanmearns.com/the-balancing-capacity-issue-a-ticking-time-bomb-under-the-uks-energiewende/

  11. A C Osborn says:

    I wonder how long it will take the Energy Generators and Gas Suppliers who are being financially restricted in favour of Wind & Solar to realise the power (pun intended) that they will hold in the future.
    What do you think will happen if they get together and decide to just switch off their equpiment?
    Or to just start taking their equpiment off line for “Essential” maintenance?

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