Estimating Storage Requirements At High Levels of Wind Penetration

In recent posts and comments there have been a number of back-of-the-envelope estimates – including some from yours truly – of how much pumped hydro storage would be needed to bridge some of the low-wind periods that have been registered in the UK. Here I take a closer look at the question of how much wind power storage would be needed at the high-penetration grid scale.

And I find that estimating how much storage is needed is not a trivial exercise. It is in fact a very complicated one, and we get quite different results depending on what it is we want to achieve and how we go about achieving it. Within limits (usually high ones) we can make the storage requirement pretty much what we want it to be. For any given scenario there is in fact no correct answer.

Here I consider the following scenario. There are many others:

By February 20XX the UK is generating enough wind power to supply an average of 25GW to the grid. The goal is to use pumped hydro storage to convert all of this wind power into dispatchable baseload generation, whereupon wind will supply almost 60% of UK electricity consumption for the month.

The pumped hydro system consists of a lower and upper reservoir of the same size. It loses and gains no water, has no charge/discharge limitations and is 100% efficient (the results can be factored to allow for lower efficiencies).

Demand in February 20XX is the same as in February 2013. Wind generation in February 20XX is increased by a factor of twelve relative to 2013 values (25GW divided by the 2.08GW average generation in February 2013) so that it averages 25GW in 20XX, which works out to 100GW of installed wind capacity at a 25% overall load factor. (I chose February 2013 partly because I’ve used it as an example before, partly because it’s a fairly typical winter month and partly because analyzing the data for all of 2013 was too burdensome. Other months will, however, give different results, and the numbers provided here should be considered in that light.)

Economic considerations are ignored.

Figure 1 summarizes the position in February 20XX (data from Gridwatch). Demand is the same as in February 2013 and wind generation is factored up from 2013 as described above. I’ve assumed that load-following gas plants will supply the variable demand not covered by wind. The requirement is to convert the erratic blue wind generation curve into the flat line at 25GW:

Figure 1:  UK wind generation and demand, February 20XX

Let’s look at how we might do this.

The 2,750GWh Option:

We will begin with the simplest case – an empty upper storage reservoir which fills when wind generation exceeds 25GW and empties when it falls below 25GW. If we’re lucky this option will supply enough power to maintain wind generation at the 25GW level all through the month. Figure 2 shows what happens:

Figure 2:  Upper reservoir storage and output to grid, 2,750GWh option, February 20XX

Because of the surplus of wind power during the first week the upper reservoir fills rapidly and by February 6th/7th it has accumulated 2,750GWh of storage. After that, however, it’s all downhill until the reservoir runs dry on February 27th, whereupon the system is no longer able to deliver 25MW to the grid and it’s lights out.

So let’s try starting with the upper reservoir full instead of empty:

Figure 3:  Upper reservoir storage and output to grid, 2,750GWh option, reservoir starts full, February 20XX

It makes no difference. All that happens is that the surplus wind generation in the early part of the month gets wasted, or “curtailed”, because the upper reservoir is already full and it has nowhere to go, and after that there simply isn’t enough wind generation to keep the reservoir topped up.

The 3,100GWh Option:

What next? We could try increasing reservoir capacity, but there’s only enough wind power to put 2,750GWh of storage into the upper reservoir to begin with, so increasing capacity above this level won’t achieve anything. We could, however, increase the size of the upper reservoir and start with it full instead of empty, and when we do this we find that the system is capable (barely) of supplying 25GW all through the month when the storage capacity is increased to 3,100GWh:

Figure 4:  Upper reservoir storage and output to grid, 3,100GWh option, reservoir starts full, February 20XX

But we still finish the month with the upper reservoir only 10% full. Can we guarantee that there will be enough wind in March to fill it back up again? No, we can’t. So to be on the safe side we have to increase the capacity of the upper reservoir further. Let’s make it 5,000GWh, a good, round and hopefully safe number:

The 5,000 GWh Option:

Figure 5: Upper reservoir storage and output to grid, 5,000GWh option, reservoir starts full, February 20XX

Now we have 2,000GWh left in storage at the end of the month. But we’ve lost 3,000GWh during the month, and if this rate of decline continues the upper reservoir will dry up around the middle of March. To be on the safe side it seems that we might need even more than 5,000GWh …..

Or maybe we don’t need anything like as much. There’s another way of doing it.

The 1,200 GWh Option:

Instead of beefing up storage we increase installed wind capacity. We can in fact eliminate the dip in output shown in Figures 2 and 3 by increasing it by only 3%, but this still leaves us with a near-empty upper reservoir at the end of the month. Clearly we won’t have solved the storage problem until we have a combination of installed capacity and storage that keeps the lights on and maintains the upper reservoir at a safe and reasonably stable level. How much capacity do we have to add to get it?

It turns out that we need to increase installed wind capacity by 50%, from 100GW to 150GW, before we achieve the desired result (Figure 6. Note that I start with the upper reservoir empty to avoid having to curtail the surplus wind energy during the first week). We’ve lowered the storage requirement back down to 1,200GWh and the month ends with the upper reservoir full, but we’re still sailing close to the wind. On February 19th the upper reservoir almost dries up. Obviously we need a reserve margin:

Figure 6:  Upper reservoir storage and output to grid, 1,200GWh option (150GW installed wind capacity), February 20XX

But how large should the reserve margin be? Enough to cover a day without wind (24 hours times 25GW = 600GWh)? Or should it be two days? Or three days? A week?

The 700 GWh Option:

If we double installed wind capacity from 100 to 200GW we can cut the storage requirement even farther to 700GWh, although still with no allowance for a reserve margin. Doubling capacity leads to a high level of wind power curtailment, as shown in Figure 7:

Figure 7:  Upper reservoir storage and output to grid, 700GWh option (200GW installed wind capacity), February 20XX

Time to sum up. We have identified five different options for storing wind power that give pumped hydro storage requirements of anywhere between 700GWh and 5,000GWh. Which is the best?

There isn’t one. In all probability none of them is even feasible, if only because it’s highly unlikely that the UK will have access to this much pumped hydro storage at any time in the foreseeable future, if ever. And even if it did all of the options would be to a greater or lesser extent hostage to the UK weather, which as residents will tell you is not to be trusted.


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39 Responses to Estimating Storage Requirements At High Levels of Wind Penetration

  1. Wow. Should be req’d reading (and comprehension) by policy makers.

  2. Flocard says:

    In the second part of a work titled “What Sea Winds Deliver” (2011) after discussing with grid engineers, I tried to estimate the storage (energy volume, in-pumping power, out-pumping power)

    I used data nearly two years from the wind park Robin Rigg off the coast of Scotland-England which I could get courtesy of Eon Renewables France

    The erratic character of the production would have made a storage matching the consumption needs over such a long period costly and non practical.

    Thus in this work I rather investigated what would be needed to smooth out the production in order to reduce the power gradients and not generate too difficult problems for the grid.

    I also would like to point out a very interesting and much more elaborate work along similar lines by Dr Wagner using german data (offshore wind, onshore wind solar).

    • PhilH says:

      Could you give a link or reference for that last-mentioned study?

      • Flocard says:

        Sorry for the delay in answering this question. I missed it.

        Only the French version of my work is posted on the web.

        For the english version contact me at

        For the work of Dr Wagner which must be posted somewhere (he sent it to me directly) and has been published in the Europhysics journal
        (Dr Wagner a specialist of fusion was for a long time the chairman of the “Energy” section of the European Physical Society)
        I can only give you his e-address. I am sure he will be ready to either send you his work or give you an e-reference.


  3. Dave Ward says:

    I agree with Rob Schneider as regards the “reading” part, but I doubt that any of us think the “comprehension” aspect would be remotely achievable! They would say “we can just start up a few gas fired plants when needed” – completely forgetting that you don’t simply turn on the petrol and ignition as if they are 2kW portable gensets. Germany is already showing what happens when conventional generation is forced to run at part load or not at all.

    As for the UK scenario – since some 50% of wind generation (and a large part of the potential hydro storage sites) are in the North, yet most consumption is in the South, the small matter of vastly increasing the grid capacity between the two needs addressing. Once again, Germany is showing this is not a straightforward matter, with growing numbers of protests over the number of HV lines required.

    As for matters of efficiency and finance – Rogers numbers would obviously need “tweaking” to cover pumping and transmission losses, and would the wind farm operators STILL expect to be paid for all the curtailed generation?

  4. JerryC says:

    Seems obvious that demand management is how a “decarbonised” electricity system will be made to function. There simply won’t be a grid producing reliable electricity for the general public 24/7, ordinary people will have to make do with having power when weather conditions permit. The elite and well-connected will be able to make other arrangements, of course.:-)

    • Willem Post says:

      Ordinary people will have to learn doing without a lot of goods and services, not just energy, considering what it is going to cost to get from existing conditions to conditions with near-zero fossil energy.

      The costs of operation, maintenance, replacement parts, enhancements of the new power systems will be 3-4 times existing costs, and all goods and services will be much more expensive.

  5. PhilH says:

    > The requirement is to convert the erratic blue wind generation curve into the flat line at 25GW

    Why? No reason is given for trying to shoe-horn a variable source into the mould of a baseload source, while ignoring all the other things going on in the electricity system.

    A more realistic study would be to add in the production (in 20xx) from, say, 80GWp of PV (a 3kWp system on half of homes, plus a similar amount on non-domestic buildings, and a few solar farms), 2GWp of non-storage hydro (at least some of which is surely dispatchable), 5GWp of wastes & biomass thermal generation (at least some of which may be dispatchable), and the suite of tidal lagoons (taken from Euan’s work in last post). You could try it with or without the planned nuclear, and with or without the existing & planned international interconnectors.

    The resulting storage requirements would surely be much less. I can imagine it would be a lot more work, but the actual amount (storage capacity & output capacity) needed in such a realistic scenario would be of interest to me, and, potentially, of use to the powers-that-be.

    • Why use a 25GW baseload case? Because it’s a simple way of getting a handle on order-of-magnitude storage requirements. And I’m not the only one who does it. David Mackay assumes baseload generation in his analysis of tidal pumped hydro linked to on the Swansea Bay post.

      A more realistic study would be etc. etc. The resulting storage requirements would surely be much less.. Would they? Could you give us some numbers?

      Incidentally, I ran another scenario that I didn’t report in which I estimated storage requirements for matching wind power to demand rather than smoothing it out into baseload generation. It approximately doubled the amount of storage required.

      • PhilH says:

        Daily GB demand in Feb would be about 1000 GWh. The 100 GWp of wind, with 25% LF, provides 600 GWh/d for comparison. The 80 GWp of PV I’d guesstimate would give 70 GWh/d in Feb. The set of tidal lagoons generating 30 TWh/yr would give 82 GWh/d on an avg day. The 2 GWp of hydro might run at 75% LF on winter days when wanted (and 25% on unwanted days) to give 36 GWh/d. The 5 GWp of thermal might run at 75% LF on winter days when wanted (and 25% on unwanted days) to give 90 GWh/d. This totals 277 GWh/d, or nearly 12 GW(avg), ie nearly half the wind’s average.

        There’s currently 4GW of international interconnectors, with plans for at least another 5GW within a decade. But let’s assume the low-wind days in GB coincide with low wind & high demand elsewhere, so we get no net flow, except for the 1.4GW one with Norway, who have to supply others as well, so can only send us 1 GW averaged over the day, say 24 GWh/d. This takes the total to about 300 GWh/d, about half the wind’s average, so only half the wind power is needed to get the 25 GW(avg) modelled.

        This is just looking at the problem at a resolution of one day. I’d be really interested to see what that does to the storage required – both using average daily values (as above), and also using actual weather (ie, sunshine for the PV; crudely, I would guess sunshine is negatively correlated with wind) and tides. (I don’t ask much, do I?)

        I’m more concerned by the results of your demand-following scenario, and think that worthy of a full write-up.

        • PhilH. Thanks for the numbers, but one-day resolution doesn’t solve the problem of storing stochastic wind generation over the longer-term, and adding large amounts of solar and tide power makes the problem even more intractable because of the seasonal solar and spring-neap tidal fluctuations. And as far as interconnectors are concerned we don’t have to assume that low-wind days in GB will coincide with low wind days elsewhere. We already know they will:

          I didn’t write up the demand scenario partly because filling 100% of UK demand with wind power is not a realistic option and partly because as I mentioned before you can get a good idea of what the results look like simply by doubling the Y scales on the graphs in this post.

          • Leo Smith says:

            What emerges from all this is that the solution to power generation needs to be looked at ultimately on a cost benefit basis.

            When Dinorwig was built, the engineers already dispatching large coal plant at relatively high capital cost and poor fuel efficiency, and seeing nuclear plant surpass it for base load, calculated that the cost of Dinorwig would obviate the need to build one extra thermal plant, needed to purely cover the ‘Coronation Street peak’ – that blip in demand just after dusk when consumers witched on lights, the telly, and the cooker and the kettle.

            If we take cost benefit as our guide – and engineers always tend to – we get perfectly reasonable mixes of power generation optimised to cover ‘99.999 years out of 100 uptime’, at the lowest cost.

            Unfortunately, the mix does not include a single windmill or solar plant, except perhaps in some remote location where the cost of grid connection exceeds the cost of storage for intermittent renewables.

            If we then start to add in assumed externalised costs for carbon emissions, the mix changes towards predominantly nuclear, but it still does not include any intermittent renewables.

            I know it is fashionable to look at each and every renewable option and storage and pick them apart one by one to discover that they won’t actually cut the mustard, but the reality is that there is a simple yardstick that can be applied to everything, and that is cost benefit. If a given solution set is more expensive than another one that offers equivalent performance. there is no point in pursuing its analysis further. My own analysis suggests that so long as we have nuclear, it is in each and every case far lower cost than any renewable option – at least in the context of UK and most of N European power generation.

            My reasoning is simple: If wind is already more expensive than nuclear without storage, then it isn’t going to be cheaper once storage is added.

            Whereas at the time of Dinorwig, nuclear plus coal plus storage was cheaper than all nuclear and coal…

      • Willem Post says:

        I am pleased a narrowing of options is developing.

        The two main ones are reduce the world’s population to about one billion, the same level as in 1800, and reduce per capita energy consumption by 4 times, the same level as in 1800, and reduce the per capita consumption of other goods and services by a factor of about ten to fifteen.

        That may not save the rest of the fauna and flora, but it would be better than doing everything else.

    • Leo Smith says:

      The resulting storage requirements actually get much worse.

      From the point of view of organising dispatchable power, renewable energy is just another fluctuation in demand.

      The only place that renewables really ‘work’ is where there is a huge base already of dispatchable power that is already paid for and which can be dispatched with no cost penalty.

      E.g. massive hydroelectric installations in NZ for example.

      In Euan’s model these represent a storage that is recharged without wind by e.g. snow melt in spring.

      The Great Fraud of renewables is in considering that a non dispatchable power source has the same value as a dispatchable one. In reality this is nonsense in anything approaching a free market. Excess wind power that can’t be stored and can’t be used has no value at all.

      Wind power that can be used is worth only as much as its competition is charging that that point.

      If we had stuck broadly to market constrained systems, there wouldn’t be a single windmill, and we would all be better off.

  6. It doesn't add up... says:

    The obvious solution is to change the climate so that we are subject to constant zephyrs of around Force 4-5. A further tweak would see the blowhard winds timed to coincide with rush hours, dying back overnight, and being stronger in winter. After all, if we’re trying to change the climate, why not achieve what we need in doing so?

    Flocard’s approach is of course correct in so far as it goes. The problem is that a proper economic evaluation would produce very low levels of wind and solar penetration, especially when considering the global scale, since all we appear to have achieved by attempts to be saintly is to shift energy consumption to other countries with higher emissions per joule produced, thus increasing global emissions and defeating the objective. Perhaps more worrying is that policy makers appear to be considering this to be a viable alternative:

    • ducdorleans says:

      lol … and so true …

      if we can manage climate, why not manage it correctly ?

  7. Craig Crosby says:

    It seems to me that the obvious answer must be to reduce demand for power, and become truly sustainable as a culture. This goes for Britain, the US, Russia, as well as China, India, and sub-Saharan Africa. For all.

    And this means a reduced population. One that, if the facts enunciated by this article are correct will be accomplished one way or another. Unfortunately, given the human species’ proclivities, it will be done by nature, with most of the homo sapiens objecting and resisting to the end.

    Agreeing that wind power will not sustain any society, and that solar is limited in far northern or far southern climes, hydro likely maxed out, and geo-thermal limited in locale, it seems obvious to me that, for a time, some nuclear power will be needed, even if simply to sustain whilst populations decline. The only real question is, for how long will that suffice, and will that be long enough.

    The idea that high emission power production and transmission can endure indefinitely, and similarly that climate warming emissions are limitless are equally flawed. At some point, continued fossil fuel mining will end through economic necessity, and with them co2 emissions. By then, we had best be at a numerically sustainable population, and ready with the alternatives lest our survivors freeze as nature returns to her cyclical ice ages.

    Hopefully we (as a species) will endure to see the day.

    • ducdorleans says:


      “It seems to me that the obvious answer must be to reduce demand for power” … please give the good example by not posting anymore, or just stay away from the internet … remember that all of your posts cost a few millijoules (if not joules) that – if not posted – Roger doesn’t have to store anymore …

      “And this means a reduced population.” … what is the formula – given the diameter of the earth, and the resources we have – to come to the exact or approximate number of people that our sphere can support ? … and if the result of that calculation is smaller than the number now present, who will decide where we have to reduce, when, and who has to “go” …

      maybe you should again give the good example and commit seppukku ..

      • Craig Crosby says:

        I have no idea the point of your response. Other than to be extremely rude, and more than a bit condescending.

        If you have some valid objection to my comment, by all means have at it. Telling those with whom you disagree (I am not sure that you do) to go kill themselves is obscene.

        Euan: If this is representative of your site, please remove me from your list of subscribers. I thought better of you.


        • ducdorleans says:

          Craig, you might have to bear with my English from time to time as it is not my first language …

          but you wrote “… answer must be to reduce demand for power … And this means a reduced population. ”

          correct me if I’m wrong, but I understand this as:
          1, actually, our main problem is overpopulation
          2, by “correcting” that, reduced demand for power – and solutions to all our other problems – will automatically ensue …

          if I sound a bit “rude”, it is because for some 10 years, I’ve been reading the same “reduced population absolutely necessary” here on fora in Belgium, and for 10 years I’ve been asking the same question, without getting ANY answer …

          I try again hereunder:

          1. since you write that population should be reduced, and since we know what the present population amounts to, I conclude that you know either exactly, or more or less, what the “ideal population number” of our earth is … the “sustainable” number to use a popular word …

          2, I therefore (now) politely ask you to share the formula that you use to come to that “ideal popuplation number” ?

          3. or absent a formula, your idea for the ideal or sustainable number of people that can live on this earth atm ?

          4, then, if (only if) that ideal number is smaller than the present number, what are your ideas to travel from the present number to that ideal number ?

          and again my apologies …

          • Leo Smith says:

            Ideal human population zero. World now 100% ‘natural’

            Or maybe we let a few hinter gatherers stumble around picking shellfish off an african beach.

            Heck it probably beats living in London, anyway.

    • Leo Smith says:

      Do I hear the sound of cat bells* tinkling in the sunlight?

      Never mind who is going to bell the cat, who is going to march the surplus populations off to the gas chambers?

      No, the answer is massive nuclear, a high standard of living and education and hope this is enough to curtail population voluntarily and willingly.

      Enforcing ‘Green’ solutions takes us inevitably towards that which in the Green Mind is the ‘right’ world. One that does not contain humans.


  8. Donb says:

    Perhaps the easiest solution would be to change-out the politicians.

  9. roberto says:

    @roger andrews

    “Time to sum up. We have identified five different options for storing wind power that give pumped hydro storage requirements of anywhere between 700GWh and 5,000GWh. Which is the best?

    There isn’t one.

    Actually there is one, if other than hydro forms of large-scale storare are implemented… transform the excess wind power into H2 or some other combustible form of storage… and then use this H2/CH4 and burn it in thermal power units… the conversion/generation losses are humongus… but in greenwash policy this is not an issue…


    • Leo Smith says:

      Well yes…there are a thousand ways to store energy in small quantities, with terrible efficiency and creating a public danger far far worse than an out of control Chernobyl, and no doubt the Greens will propose every one of them.

      I would like to make a point. Even without renewable stuff, energy storage has the potential to reduce the need for generation capacity to cover peak demands. And take power ‘off grid’ as well.

      At every turn what counts is the cost of this vis-à-vis the alternatives.

      What is wrong with intermittent renewable energy is not that solutions dont exist, but that with any metric you choose apart from weird political and religious ideology, renewable energy is part of a solution set that is to be rejected on cost and environmental impact grounds.

      It is the worst alternative possible, with and without storage.

      Massive storage enables us to build just enough generating capacity to meet averaged annual demand and use storage to cover all the peak demands. Irrespective of renewable clutter, that by itself would halve the amount of primary generating capacity we would need. From around 70GW in total including all emergency stuff to about 35GW.

      It is the arrogance and stupidity of the young that they consider that no one has thought of this before. Of course we have. If it were that easy we would all be doing it. In fact the problem of energy storage is almost intractable, which is why we depend so mightily on fossil hydrocarbon fuel. In an oxygen rich atmosphere, hydrocarbon fuel is the best all round store of energy we have for most applications.

      The final nail in the coffin is this: If we can’t build solar wind wind plant that competes effectively with nuclear, without storage, we have no hope of building it with storage and hoping it will be competitive.

      In short we don’t need to analyse solutions that we already know can never be cost effective .

  10. S.C. Schwarz says:

    What we are witnessing is a relatively rare event in human history: A civilization (ours) is voluntarily destroying itself in a spasm of religious hysteria. While we de-industrialize the Chinese, the Indians, and others, can hardly believe their good luck. All they have to do is wait and then they can take over the ruins of our countries.

    The world’s population is not going back to pre-industrial levels. The people filling all those cities just won’t be us.

    • Leo Smith says:

      For years and years the Mayans sacrificed the odd chap, to the delight of the crowds, in order that the sun would rise, the crops would grow, and that Quetzalcoatl would be kept happy.

      Then the white man arrived, and under severe threat they sacrificed more and more…in the end all that was left was white men, and the peasants who slunk off into the woods shaking their heads sadly..

      Its actually quite a common event: Fiddling while Rome burns. When the problem you have been handed defies solution by the organisation you are a part of, and cannot exist without.

  11. Graeme No.3 says:

    “Economic considerations are ignored”. They always are by the green gulls.

    A minor matter, more wind turbines surely means a drop in the capacity factor, as poorer sites have to be used.

    Rather than trying to provide a workable solution using “renewable” electricity it might be cheaper to move the UK south about 500 miles.

    • JerryC says:

      That’s a terrible idea! Move the UK 500 miles south and you instantly achieve the dreaded 2 degrees centigrade warming that’s supposed to kill everyone. Better move it north instead. Maybe invade Svalbard and have everyone move up there.

      • Leo Smith says:

        If you just want to be 0.1C cooler, build houses on stilts…what is the adiabatic lapse rate again?

  12. Graeme No.3 says:

    Your suggestion will raise the ire of the green gulls. There are polar bears on Svalbard.
    Do you want them to die from gross indigestion?

    Besides, most people from the UK are used to heading south in their holidays. There would be complaints from various EU members if the hordes were diverted away from the harvesting grounds.
    Only the green (noisy, always squawking, always wanting to be fed) gulls would volunteer to go north as the world cools.

  13. Will we have a grid in 20 years? One has to remember that renewables +
    storage only needs to beat retail prices, not wholesale prices to have an
    economic advantage (people and companies will simply go off grid). Deutsche
    Bank put out a report 27 February 2015 in which they predict that by 2030
    renewables + storage will have this advantage in 80% of the world. Deutsche
    Bank is impressed with the decreasing cost of solar power and the decreasing
    cost of lithium ion batteries. Personally I am very impressed with the
    possibilities of heat pumped electrical storage (see for
    example Isentropic Ltd.). Once
    engineers figure out how to efficiently transform temperature differences
    into electricity, all sorts of possibilities

  14. ducdorleans says:

    Roger’s “2,750GWh Option” in perspective …

    Coo ( ) is Belgium’s (only) pumped hydro power station. (“only” because also Les Eaux du Lac d’Heure makes a small contribution.

    It can generate 1,150Mw for 5 hours, and thus can store 5.75Gwh …

    To get to Roger’s storage, 2750/5.75 = 478 Coo’s are then needed …

    Now, since demand here is only about 1/5 to 1/6 of UK’s, only about 80 are needed …

    piece of cake !

    • Another perspective would be 393 million 7kWh wall-mounted Tesla storage batteries costing $2.75 trillion installed, although financing could be problematic.

      • ducdorleans says:

        that is an even better comparison, because I would have difficulty on estimating the present cost of 1 Coo !

        the GDP of the UK being around that same number, this storage would cost all the wealth accumulated in the country during 1 year every 4 or 5 years … which indeed could lead to problematic financing …

        the solution here is to negotiate a rebate at Elon’s webshop …

  15. David MacKay says:

    Your calculations agree with my back-of-envelope estimates. In SEWTHA Ch 26 I said “imagine we had 33 GW of wind capacity, delivering on average 10 GW”; I reckoned that ballpark of 1000 GWh of storage would be needed; and that it wasn’t credible that this could be created using pumped storage, in the UK, unless there were a radical change in attitude to pumped storage in the landscape, and even then it would be a push. However, there are other storage options coming along the R+D path – pumped heat electricity storage (e.g. Isentropic); compressed air storage; and of course electrolysers to make hydrogen which could then deliver peak winter heating demand (rather than being used to generate electricity). This last idea seems worth looking into even if we had a wind-free grid – for example if one had only nukes and CCS power stations, you might find the cost optimum is to use sparse capacity in summer to make zero-carbon hydrogen, then deliver winter heat-demand-peaks with the hydrogen.

    • David: Thanks for checking out my calculations. Your ball-park estimate of 1,000GWh for 33GW of wind capacity is to all intents and purposes the same as the first number I came up with – 2,750GWh for 100GW of wind capacity.

      I don’t know enough about the potential of hydrogen storage to comment on it intelligently, but even if it turns out to be a viable option it will obviously take many years to commercialize it on the necessary scale.

      And at present batteries, CAES, flywheels and thermal storage have a total global installed capacity of about 12GWh, enough to keep the world’s lights on for fifteen seconds. These technologies clearly have a long way to go too.

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