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Misconceptions About Battery Storage

January 27, 2019

By Paul Homewood



There is a very common misconception that battery storage can solve the problems of intermittency arising from renewable energy sources.

For instance, there was this little exchange on the Telegraph article today about wind farms along the HS2 route to power the trains:




What the public at large, represented by Mr Truth, don’t seem to understand is just how limited the amount of energy that can be stored really is.

As we know, Elon Musk sold his 100MW battery storage system to South Australia a couple of years ago. 100MW sounds impressive, but as his own specifications made clear the maximum output was only 129 MWh. And for this tiny amount of storage, the Australians paid an estimated A$150m, about £80m.

Hornsdale Battery Storage – South Australia

The only way to increase this capacity is keep building more and more batteries.


To put storage into perspective, let’s take a typical 5MW wind turbine, the sort we see plastered across the countryside.

Based on utilisation of 28%, one turbine would, on average, generate 1022 MWh/month.

Now, suppose that we had a month with relatively little wind, and output declined to 10% of capacity. This is not an unrealistic assumption, as we went a full week earlier this month with wind power down to that sort of level.

In this scenario, output during the month would fall to 365 MWh, leaving a shortfall of 657 MWh against the norm.

If this single wind turbine was to provide enough storage to make good this shortfall, how many Tesla batteries would be needed?


Tesla’s South Australian storage system can provide, as we have seen, 129 MWh. So we would need five of these, at a cost of £400m.

Remember, this is to guarantee supply for just one tiny wind turbine.

The Australian scheme consists of around 600 Tesla Powerpacks, each rated at 210 KWh, and each about the size of a large fridge.

Our local 5MW wind turbine need some 3000 of these. Apart from filling up the countryside with millions of fridges, the cost of providing this sort of storage would kill wind projects stone dead, if they had to pay the cost themselves.


It may be that to need such large reserves of power would be a rare event, a reliable grid needs to cater for all contingencies.


Meanwhile, Claire Perry whittles on about smart grids and storage, and a gullible public falls for it.

  1. dearieme permalink
    January 27, 2019 5:36 pm

    “100MW sounds impressive, but as his own specifications made clear the maximum output was only 129 MWh.” There’s a confusion of units there.

    • January 27, 2019 6:50 pm

      Yes, that’s why people get confused about it, because they don’t understand the difference between capacity and output

      • Curious George permalink
        January 27, 2019 7:00 pm

        California specifies a battery storage capacity in megawatts. No kidding. I would prefer gallons.

      • January 27, 2019 8:18 pm

        Or between power and energy. I have been examining what energy ministers have been saying from Ed Miliband through to Claire Perry and I am certain that not one of them knows the difference between power and energy. It’s no wonder the country is in a mess when we’ve had all these PPEs etc in charge.

      • David James Styles permalink
        January 28, 2019 11:15 am

        In Jillian Ambrose’s piece here (now behind a paywall) she goes the whole article quoting MW, not once MWh.

  2. Saighdear permalink
    January 27, 2019 5:44 pm

    You really do feel like throttling some of these people….. How DO YOU get the message across about the King’s new clothes?

  3. January 27, 2019 5:54 pm

    Taken to its inevitable outcome – next they will be saying you don’t really want a reliable grid and never really had one anyway.

    Ms Zibelman said load shedding was common practice around the world. “All countries that I’m aware of, and again, I have been in the business for 30 years, and over periods of time you run into these systems like you have, where you have generators that go off and you have to do load shedding,” she said. “We can’t afford … 100 per cent reliability over all hours and all circumstances, but we do like to plan that for what we see these extreme weather events that we have enough reserves available. That’s really what we’re working towards.”

    • It doesn't add up... permalink
      January 27, 2019 10:51 pm

      Except of course Zibelman is working away from having a reliable grid. She wants lots of renewables, and closing down dispatchable coal stations. Indeed, it’s precisely because the closed down the Hazlewood coal fired station not so long back that Victoria ran into problems with inadequate supply and rolling power cuts. The Zibelman plan cost Australians an extra A$1bn over just two days of hot weather.

    • Dave Ward permalink
      January 28, 2019 11:01 am

      “Where you have generators that go off and you have to do load shedding”

      That might be the case in Africa, but I believe the UK grid once had in the region of 20% spare capacity, and now it’s often down to 2%, so her claim is bull****

  4. January 27, 2019 5:57 pm

    I’ve long said, nothing will help our energy supply system become more robust until we remove the pollution … from our knowledge base.

  5. ben Dussan permalink
    January 27, 2019 6:13 pm

    Well, it seems that the intended purpose of wind and solar power is to accordingly reduce the use of fossil fuel power generation.

    It also seems that the current state of the art of battery storage is “too” expensive, with the “hope” that they will become reasonably expensive in some unknown distant/near future.

    And an interesting question is what is more “expensive”: to maximize generation, and storage, of wind and solar power, or to pay for the continuing use of fossil fuel and nuclear power and their collateral damage to the environment and all living creatures on earth?

    • January 27, 2019 6:54 pm

      What collateral damage?

      But you are missing the point. It is not a matter of cost, it is that battery storage is simply incapable of solving the intermittency problem

    • Harry Passfield permalink
      January 28, 2019 10:52 am

      Ben, you do understand that if you’re using wind power to charge batteries you can’t use that power for utility use. It’s going to be one or the other. In other words, it’s only worth charging batteries – if it is at all a good strategy (not, IMO) – if you have an excess of power being generated, but, if you have an excess you don’t need wind turbines in the first place.

  6. Ian Magness permalink
    January 27, 2019 6:20 pm

    Another crucially important aspect of windmill engineering that the Mr Truths need to understand (but don’t) is that because they only produce any usable power in a relatively narrow windspeed range BUT, even then the actual power output can vary hugely with changing windspeeds, they will always be a very expensive form of power because they need reliable, dispatchable power sources as cover, almost all of the time.
    To elucidate on the speeds, if you chart output v wind speed of the average windmill, not a great deal of power is produced before 10 miles per hour, output then rises very rapidly to about 25mph before levelling out at about 30mph. If wind speeds continue to rise above about 30mph, you continue to get good output at the same rate until, calamity!, the windmills have to be shut down at around 55mph for operational and safety reasons.
    However, it gets worse. The nature of a nation-wide electricity grid is that it needs stable, predictable power for such trivial things as houses, schools, hospitals, the internet, telecommunications, factories and, yes, even railways. That wonderful, 10mph to 30mph zone mentioned above, however, is notable because its power output gradient is very steep, so regional winds fluctuating up or down even by as much as 5mph cause significant changes in windmill array power output which, in turn, causes all sorts of grid management problems. Having, for instance, nuclear or CCGT power stations as back-up is not only very expensive but you simply cannot just turn them on or off at the speed at which weather systems develop.
    In short, windmills may well have good uses, perhaps for specific cases where power output does not have to be stable. For country-wide electricity grids, however, until and unless we get economic, scaleable, long-lasting battery arrays using a revolution in battery technology clearly not even remotely close now, windmill arrays are simply not fit-for-purpose for powering a national electricity grid. Indeed, whether the requirement is for as yet un-invented battery arrays, or constant back-up from dispatchable power stations the reality of wind forming a material part of our national grid simply must mean very, and unnecessarily, expensive electricity.

  7. Frank Everest permalink
    January 27, 2019 6:59 pm

    Another thing these battery storage enthusiasts forget is that the batteries need charging after use. And guess where the electricity will come from? If it’s from the wind farm, then there won’t be any spare to use for actual consumption, so the net effect is nearly zero, and that’s after ignoring the losses incurred in charging and discharging.
    Overall, the average power into the batteries is a bit more than the average power which can be extracted. So what’s the point of having them at all?

    • Curious George permalink
      January 27, 2019 8:25 pm

      What’s the point of storing potatoes in autumn to eat them later?

      • January 31, 2019 6:11 am

        Just try to imagine a battery that will collect enough summer sunshine in Ireland to keep you warm in the winter. It makes going out to the bogs, cutting “turf”, and stacking it in the rain in Donegal to dry look quite a practical way to feed your fires.

  8. arfurbryant permalink
    January 27, 2019 7:26 pm

    Basically, having wind power as a national energy system is the equivalent of buying a plug-in Electric Vehicle and then paying a chauffeur to follow you in your ICE vehicle for you to use when your battery dies…

    • Ian Magness permalink
      January 27, 2019 7:40 pm

      Except, arfur, you would expect your expensively charged-up EV actually to work most of the time, even if it’s only for a while. For reasons outlined in my comment above, windmills don’t work most of the time, are totally unpredictable and if they get too excited, you have to turn them off! EVs are, in many ways, easier to understand than windmills, although both are just as stupid in the wider context of a developed country’s more significant energy sources and uses.

      • arfurbryant permalink
        January 27, 2019 8:07 pm

        Point taken Ian. Can I say it was a best-case analogy?😉

    • January 28, 2019 12:22 pm

      That is what our sad little authoress planned for with her electric car and her cell phone full of apps to find charging stations as she traversed mountainous terrain. She had to call someone to tow her instead if having the tow truck follow her. Sad story.

  9. beowulf permalink
    January 27, 2019 8:54 pm

    For the benefit of those not from Oz, only 4 Days ago when South Australia had its latest blackout, the fabulous Tesla mega-battery managed just 3 hours output at 30MW — a drop in the bucket. It then began recharging itself at the peak of the power shortage because it has contractual obligations to maintain frequency or some such. What a bloody joke. Its main function is not to support the grid, but to game the system for its owners by buying low and selling high.

    • January 27, 2019 10:09 pm

      Any links?

      • It doesn't add up... permalink
        January 27, 2019 11:13 pm

        Here’s the battery’s activity and the regional spot price:

        You can download the 5 minute data from the csv link. It discharged at 29.6MW from 15:30 to 18:30 on the 24th, exhausting the charge it had taken on between 1 a.m. and 4 a.m. It did make over A$1m over the two days.

    • Hivemind permalink
      January 28, 2019 8:05 am

      Something is wrong with these numbers. The battery can only supply peak load for 5 minutes. It is physically incapable of providing 30 MW for 3 hours!

      • beowulf permalink
        January 29, 2019 11:31 am

        How so? Unless my maths is wrong, 5 mins X 30MW = only 2.5 MWh from a 129MWh battery. How is it physically incapable of exceeding that?

        Regardless, the Nemlog record in the link above shows the 3 hour block of constant discharge at a shade under 30MW, then re-charging in bursts from 8pm.

        The battery when built was theoretically able to single-handedly power all of South Australia for about 4 minutes at average demand if it could discharge that quickly without self-destructing and discharge right down to zero (which it can’t). Is that the source of confusion in your 5 minute comment?

    • 3x2 permalink
      January 29, 2019 8:07 pm

      […] because it has contractual obligations to maintain frequency or some such.

      Frequency is the grid.

      The overall load on the grid dictates the frequency and, in an ideal world, the output of all reliable sources.

  10. Bruce of Newcastle permalink
    January 27, 2019 9:39 pm

    The other problem that the activists don’t talk about is that batteries only last about 8 years.

    So South Australia is in for a rude shock in about 6 years time when they are up for another £80m for a replacement battery. Then £80m more in 14 years time…

    It’s very difficult to increase the lifetime of batteries because of the chemistry and their complexity.

    • January 28, 2019 12:23 pm

      What is the source of the energy necessary to produce said replacement batteries?

      • Gerry, England permalink
        January 28, 2019 2:02 pm

        A donkey in a wheel?

      • January 30, 2019 1:00 pm

        Around here, we call it coal.

  11. Joe Public permalink
    January 27, 2019 10:00 pm

    Musk’s Hornsdale Power Reserve ‘Big South Australian Battery’ AKA BSAB

    “100MW sounds impressive, but as his own specifications made clear the maximum output was only 129 MWh.”

    That’s the battery, not the storage availability into the grid for when the wind doesn’t blow.

    While total battery power is 100MW, energy flows are capped at 30MW, with the remaining 70MW held in reserve to provide frequency control services for the highly intermittent wind sources, contributing to the security of the grid.

    30MW represents just 1% of possible peak demand

    However, it *is* very good / excellent at providing those frequency control services.

    • Joe Public permalink
      January 27, 2019 10:04 pm


      “…. not the storage availability into the grid for when the wind doesn’t blow.”

      Meant not the *power* availability into the grid for when the wind doesn’t blow.

    • It doesn't add up... permalink
      January 27, 2019 11:20 pm

      The 70MW is supposedly under the control of the SA government – but it doesn’t last long as they only have 30MWh or so of storage for it. Maybe just enough time to fire up the diesel gensets they procured expensively (and were forced to use at full capacity). The rest of the battery is for FCAS and price arbitrage. They seem to be allowed to recharge at up to 40MW. Round trip losses are of the order of 20%.

    • Hivemind permalink
      January 28, 2019 8:14 am

      It may not be much use as a fix for the intermittency of wind power, but it is great as a propaganda device to the intermittent wind industry!

  12. Colin Megson permalink
    January 27, 2019 10:22 pm

    I worked it out at £632 billions-worth of Powerpack 2 to ‘drag’ low-wind cfs up to the annual average, for a not over-significant 13 day period last year. It would have taken 7,541,350 Powerpack 2s and they would have occupied 2.85 km x 2.85 km. I couldn’t bring myself to even think about the waste issue!

  13. It doesn't add up... permalink
    January 27, 2019 11:38 pm

    Batteries aren’t meant for serious storage. Their role is providing some help with grid stabilisation, taking advantage of their fast reaction time. They aren’t even used to fill in the gaps on wind power. Here’s a fortnight of the BSAB alongside the 300MW Hornsdale wind farm in South Australia at 5 minute resolution (click to see expanded chart):

    Now serious storage is a different matter altogether. I calculate that if the UK were to go for a 100% wind/solar grid, we would need storage of the order of 35TWh, most of which would only be drawn on in a really bad year for renewables generation, but a chunk of which would be needed just annually to cover seasonal variations. The cost, even as pumped storage, would be horrendous – and where do you put 3,900 Dinorwigs at £425m each in 1980s money anyway? Beef up demand for electric heating (a real seasonal shocker) and electrified transport, and the sums get truly horrendous.

    • Harry Passfield permalink
      January 28, 2019 11:29 am

      IDAU: I know it’s only a whimsical calculation but does that 35TWh needed to create the energy stored in the batteries come from existing windfarms or have you calculated fr the number of extra turbines needed to create it? A 100% solar/wind grid would need to be capable of supporting (a significant proportion) the country’s power needs PLUS the needs of the batteries being charged for when they are needed.

      • It doesn't add up... permalink
        January 28, 2019 11:44 am

        I assumed 75% round trip efficiency by crediting the store with only 75% of surplus generation, using 30 years of hourly wind and solar data from Staffel and Pfenniger which is supposedly derived from weather and satellite data reanalysed and calibrated with actual outputs in more recent times, and required that the whole balance over the 30 years with demand being met.The store has to be capable of redelivering over 90% of peak demand, and of absorbing a summer solar peak. The wind to solar ratio was adjusted to minimise storage required.

    • Saighdear permalink
      January 28, 2019 12:49 pm

      Uhuh, I’m listening ….. and IF it worked, and others were to follow…. What then? sufficient resources in world to supply? etc etc.
      I instruct my students: BEFORE you start a process, How Do you STOP it ?
      Politicians and the MSM should think about that BEFORE they spit out so much junk.

    • 3x2 permalink
      January 29, 2019 8:31 pm

      Beef up demand for electric heating (a real seasonal shocker) and electrified transport, and the sums get truly horrendous.

      Not ‘horrendous’ but completely impossible. Add in some home heating and cooking and the fact that idiots are only too happy to ‘skyrocket’ electricity prices …

      You get Brexit and Trump. People have had enough of little girls speaking at ‘Davos’ and Governments around the world listening to some kind of ‘focus group’ style politics

  14. January 28, 2019 3:47 am

    Reblogged this on Wolsten and commented:
    It really is astonishing that politicians are simply unable to understand simple projections like this. And it isn’t just the land requirement of course, there is the obvious environment disaster waiting at the end of life when it comes to disposal as well as the huge risk of fires during operation.

    • A C Osborn permalink
      January 28, 2019 11:37 am

      And the use of masses of rare earth materials to start with.

    • Gerry, England permalink
      January 28, 2019 2:06 pm

      Dr North once said that he used to respect people in prestigious positions such as politicians. Then when he started meeting some of them he was left wondering how they got through the day, such was their ignorance and stupidity.

  15. January 28, 2019 3:50 am

    Reblogged this on Climate Collections.

  16. January 28, 2019 8:22 am

    Reblogged this on ajmarciniak.

  17. keith permalink
    January 28, 2019 10:12 am

    I’m not sure it’s the gullible public falling for it, I think it is mostly the press who will not admit the facts and tell the public what is going on. They are probably afraid of the Bob Ward Stasi.
    The other fact is though, would any company or industry buy a piece of kit that is only 28% efficient? I think the answer is No., Would any motorist buy a car that only achieves a performance level of 28% of what the manufacturer claims. Again the answer must be No. And yet our stupid Government seems to think to use and expand on using an energy generating process that is only 28% efficient is the way forward.
    God, forbid when are we going to get rid of these idiots?

    • January 28, 2019 11:04 am

      I think you have made a fallacy there, plenty of processes are relatively inefficient
      eg the amount energy in a fuel that gets converted to motive force in a vehicle
      or heat for your home in an open fire.
      The issue with wind turbines/solar is their intermittenty , which means their electricity in incomparable with electricity that is reliable.

    • A C Osborn permalink
      January 28, 2019 11:28 am

      Keith, you are correct about the public, just look at the majority of comments on any Wind/Solar/Battery article in the MSM.
      They are negative with agreat deal of knowledgable people giving facts and even quoting Paul on occassions.

  18. Jules permalink
    January 28, 2019 12:58 pm

    Is that the same sort of ‘truth’ the Telegraph were printing about the First Lady?

  19. January 28, 2019 2:55 pm

    The BBC radio five science programme (aka Thought For The Day from the new Planet Saving religion) gave an (almost) unrestricted platform to Prof Stuart Haszeldine, who has now apparently overcome the slight problem of being a professor of something that doesn’t exist (Carbon Capture and Storage).

    His latest wheeze, also something destined never to exist, is to store compressed air in rocks using electricity from those lovely offshore wind farms, which then generates electricity by expansion:

    The BBC presenter mentioned at the end that the cost would be “several times” higher than electricity from conventional sources, the poor guy has probably been handed his P45 and outed as a denier on social media.

    • Dave Cowdell permalink
      January 28, 2019 5:18 pm

      Prof Hazeldine was interviewed with Piers Corbyn on LBC 9th October,Corbyn stated that no scientific paper exists that proves CO2 drives global temperatures. Hazeldine gave Venus as proof, composed mainly of CO2 being much hotter than earth . Of course Venus has a “heavy” atmosphere and is much closer to the sun. There you go.

  20. January 28, 2019 3:30 pm

    And of course all these batteries will need to be stored in air conditioned rooms to keep them in top condition.

  21. stiffstef permalink
    January 28, 2019 3:45 pm

    Interested to see what everyone thinks of the development of liquid metal batteries? Hopefully a quantum leap better that the existing batteries. Although it doesn’t solve the discharge/re-charge issue apart from some old fashioned over engineering.

    • dave permalink
      January 30, 2019 7:01 pm

      “…what everyone thinks…”

      If it “works,” it will be implemented somewhere, and we can then evaluate its true usefulness.
      The basic science is not new. But new technology, most emphatically, does not have to use new science.

      Personally, I have been aware of him for about ten years – ever since I watched the MIT video lectures of his freshman course on materials and electro-chemistry. Can’t say I took to the man, although I found the lectures interesting, and recommend them.

  22. saparonia permalink
    January 28, 2019 5:03 pm

    I think it would be worth making the mines safe to open.

  23. JCalvertN permalink
    January 28, 2019 9:23 pm

    Flywheel energy storage is feasible and maybe would be better . . . .

  24. Robin Guenier permalink
    January 29, 2019 12:38 pm

    Paul: although it may be OK for Claire Perry to whittle on, I suggest problems arise when she witters on. (Sorry!)

  25. January 31, 2019 6:03 am

    I think that these things are doing a magnificent job, if you own fossil carbon interests, of casting discredit upon the proposition that it’s time you were replaced.
    Far too many of my fellow environmentalists are too ignorant or stupid stupid to see, as Michael Shellenberger, James Hansen, and Alex Cannara know that civilian nuclear is the only solution.

  26. January 31, 2019 6:06 am

    It’s the arithmetic, stupid! Look at the depths of the troughs in any record of wind power production, and how many days it lasts.

  27. January 31, 2019 6:20 am

    Pumped hydro storage, at Bath County in Virginia, is the biggest AC electricity storage in the world. Look it up if you like.
    There is no battery imaginable with output capacity of that facility’s 3030 MW, and its storage capacity is 24,000 MWh.
    If you compare that with what’s needed for the troughs in a flourishing wind or solar location, you can be sure storage will ever be enough.
    THEREFORE, it is Impossible to fight Global Oceanic Warming and Acidification, with ANYthing other than Civilian Nuclear.
    Note that, as the Thorcon Power company website says, this is needed World Wide.

  28. Dave Wild, Somerset permalink
    January 31, 2019 8:27 pm

    In 1962, a major high pressure area sat across the UK. In broad terms,”snow* started falling on Boxing day 1962and started melting ate Easter – March 1963″. There was barely a whiff of wind across most of the British Isles, and temperatures were consistently lower than I can ever remember. Across that period there was absolutely NO wind, and would have been very little solar electricity. Mr Musk’s batteries might have lasted a few hour – if there were lots of the – but, three months? Renewable energy fanatics dream on..

    * I walked to school with 8ft snowdrifts along the side of the road. They didn’t melt, just stayed there for the whole period.

    • dave permalink
      February 1, 2019 9:53 am

      As I once wrote here: after a foot of fresh snow had fallen, I walked along the frozen River Cam, at night in early 1963, between the Colleges, which were softly lit up. It was beautiful. One does not feel the cold at that age.

      There was a lot of cloud cover during this period, but the ground-directed radiation from this ‘blanket’ could only slow, and not stop, the overall temperature from dropping. As a physicist, I understood this perfectly well.

      When the lawns finally emerged, the grass was in a terrible state – because lazy undergraduates had peed in the snow there, instead of making a chilly trip to the bath-house.

      I almost hope that – after the coal stations have been demolished – another winter like that of 1962/3 or 1947/8 comes to the UK. I will be in the Med, laughing my head off!

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