The Cost of Dispatchable Wind Power

In a recent conversation with a politician I was told we needed a lot more pumped storage hydro to store surplus wind power from when the wind blows for use when it is calm.

We have now had several posts on the topic of storing wind power. Recently Roger Andrews was Estimating Storage Requirements At High Levels of Wind Penetration and presented 5 scenarios for the UK where storage varied from 700 to 5000 GWh. I have written a number of posts looking at different pumped hydro storage schemes from FLES O-PAC (8 GWh), Coire Glas (30 GWh) and the concept of Strath Dearn (6800 GWh).

In his post Roger put some numbers on the storage required to transform variable wind into dispatchable uniform baseload. In this post I take a different approach. I calculate how much storage would be required to deliver the diurnal peaks in demand from dispatchable wind – pumped – storage – hydro. I’ve taken this approach for a number of reasons:

  • The daily demand peaks fetch the highest prices and supplying these peaks follows the traditional finance model for pumped storage hydro – buying low and selling high
  • Servicing the peaks as opposed to base load minimises the amount of storage required (the demand peaks represent 18% of total demand in March 2015)
  • Supplying the demand peaks in the UK from wind + storage will allow about 20 GW of conventional generation to be retired
  • Allowing the fossil fuel generators to supply base load allows them to run at optimum efficiency and to minimise their CO2 emissions per unit of electricity produced. By way of contingency it leaves the door open for an all-nuclear base load supply.


UK generation for the month of March 2015 was chosen more or less at random to construct this model (Figure 1). The model results are specific to that month and may not be applied to annual UK generation. Peak demand was of the order 50GW. The night time minima follow a baseline of 30GW (Figure 1) and this was chosen as the value dividing dispatchable from base load supply. Subtracting 30GW from total demand provides a picture of the dispatchable supply to be provided by wind + pumped storage hydro (Figure 2).

The wind model is based on metered wind generation for March 2015 * 1.46 to adjust for unmetered wind [1]. The second multiplication factor in the wind model is a variable used to adjust the amount of wind power on the system that was optimised at 1.76 (Figure 3). The reason for this should become apparent below.

The objective is to make the stochastic wind pattern of Figure 3 match the regular demand pattern of Figure 2 using nothing but wind and pumped hydro storage. Subtracting wind supply from demand produces the pattern of surpluses and deficits shown in Figure 4. In constructing Figure 4 the surpluses and deficits are reduced by a factor of 0.9 to account for round trip storage system losses of 20%.

The model is initiated with the pumped storage reservoirs empty and since it is windy at the beginning of the modelled period, they quickly fill up with water (Figure 5). The storage requirement is calculated by summing the surpluses and deficits across time (Figure 5). The multiplication factor for installed wind was adjusted until we made it through the month using wind and pumped storage alone. The model was optimised with an uplift in installed wind capacity of 1.76 on todays fleet. Effectively wind that matches demand gets used with the surpluses and deficits going into and out of storage.

To get through the month of March the best part of 1092 GWh (1.1 TWh) of storage is required. This is a gigantic amount! The problem of matching wind (Figure 3) to demand (Figure 2) may seem trivial. But the problem lies in the 10 day lull that began on day 16. To get through that on wind and storage alone requires a vast amount of storage.

Figure 1 UK electricity supply and demand for March 2015 as recorded by BM reports and Gridwatch [2]. 30GW has been chosen as the boundary between base load that can be provided by continuous generation from nuclear and coal-fired power stations and variable dispatchable power currently provided mainly by CCGTs (gas). Click charts to get a very large version that will open in a new browser window.

Figure 2 Subtracting 30GW from the total supply / demand curve produces this picture of dispatchable supply that in this model needs to be met by wind and pumped storage hydro alone.

Figure 3 Actual UK wind production for March 2015 grossed up by a factor of 1.46 to account for unmetered wind [1]. It is then grossed up by a further 1.76 in the model in order to provide sufficient energy to service the demand peaks (Figure 2).

Figure 4 Deducting the profile of Figure 2 (demand) from Figure 3 (gross supply) produces this picture of surpluses and deficits that are either used to pump water into storage or used to generate electricity at times of deficit. There are two key observations: 1) there are generating opportunities (revenue opportunities) on 23 of the 31 days of March, but the scale of those opportunities is small compared with the total storage required (see Figure 5 and section on Business Model) and 2) the generating opportunities are centred on day time peak demand and the pumping opportunities are centred on night time off peak demand satisfying the current criteria for storage based on buying low and selling high.

Figure 5 Summing the surpluses and deficits (Figure 4) across time produces this picture of storage required. The maximum total of 1092 GWh is a rather large number. The storage history for this one month can be divided into 4 parts: 1) days 1 to 8 when gross wind supply was in excess of demand and storage was filled quite quickly; 2) days 9 to 15 when gross supply and demand were roughly balanced; 3) days 16 to 25 representing a 10 day lull that emptied storage completely and 4) days 26 to 31 where the wind began to blow again leaving storage 75% full by the end of the month.

The Cost of 1.1 TWh of Storage

In recent posts I’ve examined a number of different pumped storage concepts and this allows us to put some numbers on the cost:

FLES : O-PAC Flat land large scale electricity storage is an underground concept with a unit storage volume of approximately 8.4 GWh and a cost of €1.8 billon [3]. 130 such units would be required at a cost of €234 billion (£167 billion)

Coire Glas is a conventional pumped storage concept located on the Great Glen of Scotland using a natural lake (Loch Lochy) as the lower reservoir. Storage is 30 GWh and cost £800 million [4]. 37 facilities like Coire Glas would be required at a total cost of £29.6 billion.

Strath Dearn is a concept for a mega storage project on the Great Glen. With a capacity of 6800 TWh this single unit would do with bucket loads of capacity to spare [5]. Cost is unknown but the engineering is on the scale of the Three Gorges Dam that cost $26 billion (£16.8 billion).

The Tesla Battery has a capacity of 10 kWh and a cost of £2,267 each [6]. 110 million batteries would be required at a cost of £249 billion.

Business Model

Throughout this discussion it is important to bear in mind that we are discussing the wind power and storage needs to meet peak demand and not total demand. In March 2005, total UK demand for electricity was 26.9 TWh. Peak demand (that part over 30 GW) was 4.9 TWh or 18.2% of the total. To service that requires 31.18GW (12.133*1.46*1.76 [1]) installed wind capacity and 1.1 TWh of storage. The 31.18 GW of installed wind is almost double today’s figure. Figure 3 shows that it is frequently producing 15 GW output (operating at about 50% load) and that having sufficient storage allows this to service up to 20 GW of peak demand.

It is creating a lucrative business model for the 1.1 TWh of storage that is the problem. The model allows for 1.8 TWh of generation from storage over the 31 days of March from 1.1 TWh of storage capacity. The average is 0.058 TWh per day yielding notional utilisation of 5.3% per day while the current pumped storage model aims for utilisation closer to 70% per day. Current pumped storage operates on the diurnal supply demand cycle offering the opportunity to make money to repay high CAPEX every day. Adapting this to a new supply model of storing electricity for weeks clearly requires a new business model that the current “free market” is not able to deliver.

Looking at the storage options detailed in the previous section, the mega concept like Strath Dearn may appear most attractive on the basis of cost, but it is unlikely to be able to respond to the rapid swings of the diurnal demand cycle. It is also extremely unlikely that any organisation in the UK would be willing or able to sink so much capital into a single facility such as this. I’m unsure if a facility like Coire Glas would be able to respond rapidly to the diurnal demand cycle while FLES O – PAC is designed specifically with rapid response in mind. It is clear that a combination of Coire Glas and FLES O – PAC could do the job where large storage like Coire Glas does the heavy carrying while FLES O-PAC provides the rapid close to market response.


The Scottish, UK and EU parliaments have set in motion a set of energy policies that require a large amount of energy storage if the policies are going to make any form of rational sense. Having intervened in the market to create significant opportunity for wind and solar power in particular, the business opportunity for storage quite simply is not there. That is why the storage situation in the UK has not changed for decades. It is naive and quite simply wrong to assume that the existing finance model for storage based on the diurnal demand cycle can be adapted to fit the multi week cycle presented by the passage of cyclonic weather systems across Europe.

The various parliaments mentioned above have created the situation in the UK where we already have about 17.7 GW of installed wind and no means of managing this without using flexible fossil fuel generating plant as the balancing mechanism. The policy to date has created a dependency on fossil fuels that it was designed explicitly to end.

Governments need to confront the high cost of energy storage that they have created through misguided policy decisions and decide how this cost is going to be met. The capital sums involved are substantial and the number of companies able to raise this capital is limited. And there are substantial risks to making an investment for 100 years when policy may change on a whim

An argument can be made that energy storage is of strategic importance and should therefore be built by the State. The cost of 1.1 TWh that is required today and which will take over a decade to build will be of the order £30 to £170 billion. This investment would be in strategic infrastructure that may serve the nation for a century or more. It would reduce the nation’s dependency upon imported fossil fuel. This would enhance energy security and the nation’s trade balance. It is unrealistic to expect the private sector to pay for these services to the State, especially since the current business model cannot enable the investments required. It is time for politicians to either step up to the plate and finance the misguided policies properly in order to make them effective. Or to recognise the mistakes of the past and to follow a different path.


[1] Clive Best Untangling UK Wind power production
[2] Leo Smith Gridwatch
[3] Energy Matters, Euan Mearns Flat-land Large-scale Electricity Storage (FLES)
[4] Energy Matters, Euan Mearns The Coire Glas pumped storage scheme – a massive but puny beast
[5] Energy Matters, Euan Mearns The Loch Ness Monster of Energy Storage
[6] Energy Matters, Roger Andrews How Much Battery Storage Does a Solar PV System Need?

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66 Responses to The Cost of Dispatchable Wind Power

  1. 121 Dinorwigs at 9.1GWh each gives 1.1TWh at a cost of 120 times £425 million = £51 billion. These, however are ~1980 pounds. In today’s money the cost would be over £200 billion.

    I suspect that capital costs for projects like Coire Glas may be underestimated. They often are at the predevelopment stage.

    • Euan Mearns says:

      Coire Glas is made cheap by using Loch Lochy as lower reservoir. But this then places constraints on scalability since this disrupts the hydrology of the Loch – River – Caledonian Canal system. I still don’t see how Coire Glas can ever make money and doubt it will be built. The only way to make a scheme like this pay is for the consumer to pay for companies to store energy. I didn’t do the sums but I think the cost will be of order magnitude higher.

      Three Gorges number I dare say is way too low distorted by currency conversion and low wages in China. But it took 20 years to build. If our engineers had foresight they would have started building storage a decade ago. Instead today’s engineers have bull shit, and that’s all.

      • Roger Andrews says:

        Dinorwig was “made cheap” too by having a ready-made lower reservoir (Llyn Peris) and a ready-made upper reservoir (an abandoned slate quarry).

        So why is Coire Glas so much cheaper in terms of $/GWh?

    • Andrew Lee says:

      The simplest way to give us more pumped storage is not to build new pumped storage plants but to retrofit existing hydropower dams to allow them to store water when there is high levels of wind power available.

      Refit the dams to allow a slightly variable water level and instead of being constantly powered on, they only produce power when there is no wind power on the grid.

      This doesn’t require secondary dams. Ideally we would fit extra turbines to the dams to increase their potential power generation with all the extra water we have stored when there are high wind conditions. It probably also needs different control systems than currently to allow the grid operators to manage output of the water supply

      • Euan Mearns says:

        In most cases it can’t be done. Many UK power stations drain into rivers and you need a large lower reservoir to pump water from. Sloy is an example of a conventional hydro scheme being adapted to pumped hydro where Loch Lomond is the lower reservoir.

        These would be adjoined to two of the existing pipes, allowing water to be pumped back from the powerhouse on Loch Lomond all the way to Loch Sloy. With the 2 pumps running for 6 hours at a time, 432,000 m3 of water would be pumped out of Loch Lomond, resulting in only a 6mm fluctuation in the water level! The purpose of this pumped storage extension will be to take advantage of excess energy in the grid during evenings and times of low demand, to help the grid in times of especially high demand. The cost of this proposed work is £40m and it would provide an extra 200GWh to the grid. Work on this installation is due start in late 2012 and is due for completion within 27 months.

    • Lars says:

      121 Dinorwigs would have a generator capacity of almost 240 GW and you could cut that by a factor of 9 I suppose to suit UK`s needs to balance wind and sun energy according to Euan`s scheme in this post, so that cost estimate is way off.

      UKs main problem is like almost everywhere else, there are no suitable locations for a scheme like that at a reasonable cost both geologically, financially and environmentally. That guy with the Strath Dearn idea would probably object to this claim.

      • Euan Mearns says:

        Lars, you are confusing instantaneous supply with storage. 10 Dinorwigs would be run till empty, then the next 10, then the next 10 till all were empty and then they would be filled up again when the wind started blowing.

        • Willem Post says:

          Reservoir banks can become unstable due to frequent filling and emptying.

        • Lars says:

          Euan, noone would construct 121 Dinorwigs with 2 GW of power combined with a few GWhs of storage for each plant.

          I was thinking of the fact that Roger multiplied Dinorwigs with a factor of 121 and arrived at a certain cost for that (£200 billion in today`s money). That cost INCLUDES about 240 GW of generators, that`s what I meant when I said cost estimate is way off. In your post you assume that only 20 GW of generators will be necessary, thus only 10-11 Dinorwigs are necessary when talking about generators, not 121.

          Generators and associated equipment is a major cost factor for any hydro development be it conventional or pumped. Assuming you found a suitable site(s) to store 1,1 TWh (in one or a few reservoirs) with 20 GW capacity in total the cost would be huge but perhaps affordable. Apart from geology and environmental concerns I suppose it boils down to a question of profitability for private investors in such a scheme. As everybody here probably knows it`s not like a conventional hydro reservoir, you start with the drawback of having lost about 20% energy when pumping the water uphill.

  2. Another way of looking at it is cost per GWh. Dinorwig comes in at £47 million as-spent, which works out to about £140 million in today’s money. FLES comes in at £214 million, Coire Glas at £27 million and Strath Dearn at £2.5 million using your £16.8 billion Three Gorges number. Quite a spread.

  3. Roberto says:

    One thing to mention here for those who live in countries other than the UK is that the geniuses in the EU parliament/Commission have set up a policy which basically points everything, storage-wise, on one non-EU country, i.e. Norway, which does not have to abide to diktats from Strasbourg, our tantrums of the green intellighentsia…
    A recipe for failure.


    • Willem Post says:

      I lived in Norway for 3 years, and one of my relatives, who works for Norsk-Hydro, tells me Norway has no interest in balancing anything beyond Denmark, as it would imply very large storage reservoirs in many areas of Norway, where people are living in a healthy environment.

      So whatever Brussels is dreaming is pie in the sky.

      There will be more HVDC interconnection between countries, which will benefit Germany the most, as it is the RE king with more and more hours of larger and larger quantities of surplus energy; “all dressed up, with no place to go”

      • Lars says:

        Willem, please forgive me for being a bit sarcastic here, but did you live in the inner part of Oslo? Your claim “…as it would imply very large storage reservoirs in many areas of Norway, where people are living in a healthy environment” is so far out of touch that I start to wonder. These “very large” storage reservoirs are already here and I live next to one of them by chanse.

        For new pumped hydro in Norway NO single new reservoir would need to be constructed and that`s a fact. If you don`t believe me I would gladly refer you to CEDREN`s report which have identified at least 20 existing sites with an upper and lower reservoir where at least 20 GW of new pumped hydro could be constructed and where the level of water would be changed by maximum 2 cms/hour up and down (which was one of the main critierias for identifying suitable reservoirs).

        In my view Norwegians are a bit concerned but for different reasons. They are not concerned about the reservoirs, they are already here and additional generators, tunnels etc. would be out of view inside mountains. The visible part would be expanded grids to the interconnectors, and that`s a concern for many of course. Decreased access to some of these lakes/reservoirs due to more dangerous ice conditions in winter is another concern for a few people loving ice fishing etc.
        But above all we fear that more interconnectors mean higher electricity prices, it`s as simple as that.

  4. Aidan says:

    It is excellent to see this huge question of storing intermittent renewable energy being given the attention it deserves.

    I must explain that I am NOT an engineer, but would like to throw this proposal into the ring;

    First, the UK is said to have around 40%of Europe’s wind power potential.
    Second, it also has some spectacular tidal flows – such as that between the Scottish mainland and Orkney.
    third, it has some pretty high tidal variations in seal level.

    Renewables are currently seen as either/or options; wind, or tidal, or solar etc and storage somewhere else.

    please don’t laugh, but why not build combined wind/tidal flow/tidal rise&fall units, each including energy storage?

    instead of expensively building offshore wind turbines from the seabed up, why not base them on a huge flotation chamber, tethered to the seabed? In order to make the most of the huge capital expense, fitting the unit with underwater turbines could catch that power, and there also has to be a way of harnessing the energy involved in the tide lifting such a device. The flotation chamber would be the energy store, with the turbines etc creating either pressure or a vacuum within the flotation chamber. The stored vacuum (or pressure?) could be released through a turbine when needed.

    These units could be mass-produced relatively cheaply in shipyards and floated out to their chosen location, or moved to different locations if necessary. They could be exported to maritime regions worldwide.

    I hope that I have explained this possibility reasonably lucidly. I would like to hear whether it is naive and silly, or whether I have just wasted the greatest patenting opportunity in history?

    • Euan Mearns says:

      Aidan, I don’t think you have missed a patenting opportunity. Using lots of different types of renewable energy to smooth supply is just another of those “renewable myths”. When you look at real data it takes 5 minutes to conclude that it won’t work. Your mobile offshore devices, if they are producing electricity, require a cable to connect them to the grid. HUGE cost.

      What may make sense, and is something I’ll move on to, is combining storage with tidal power. Tides are much more regular than wind and I suspect will require much less storage to make them dispatchable. Its just that we have GW of wind alreadt and zero tidal. We have probably already put all our eggs in the wrong basket.

    • Leo Smith says:

      Aidan, you are certainly being less silly than most renewable aficionados. However in the end all that probably matters is the cost benefit analysis of any particular solution, and how much the natural price market has been distorted by government intervention, which is at this point in time, massively.

      Without hopefully demean Euan’s work, which is detailed accurate and very helpful I myself made some far faster leaps to conclusions using techniques learnt in engineering management when trying to decide between options for technical expenditure.

      That technique is simple. It is a single rational algorithm, and I hope this pseudo code makes it clear …

      Best-solution-cost=cost of existing solution;
      Best technology = existing solution.
      for(each possible alternative)
      solution cost+= cost of investigated bit;
      if(solution cost > Best solution cost)
      discard this alternative;
      while (costs not fully explored);
      Best technology = this alternative.

      What this is in essence is a way of investigating any given technology, or suite of complementary technologies only as far as is needed to work out its already more expensive and offers no advantages over an earlier identified one.

      When I applied this metric to UK generation, the answer was that we already had the best mix of technologies – coal, gas and such hydro as was reasonably cheap to deploy, plus a nuclear baseload facility.

      And that was because a reasonably free market had dictated that mix.

      If you decided not to use coal, the answer was simple: Use more nuclear – and in fact that works out as not that expensive, at least ex of government regulation and politically inspired anti-nuclear legislation.

      So my algorithm dropped out nuclear power as simply the best way to decarbonise, assuming decarbonisation was what was desired.

      I investigated all other technologies – intermittent renewables – not in full, but enough to demonstrate they were in fact, watt hour for watt hour, more expensive than nuclear,

      When I went to look at all the other pluses and minuses that might affect a decision, nuclear also came out very well. Its very good on import bills – especially if you process your own fuel – yellow cake is dirt cheap really, but manufactured fuel rods are not. It allows excellent energy security. There is estimated to be 10 years plus of potential fuel stored at Sellafield already in terms of Plutonium and other uranium isotopes.

      And once you make an investment in fuel and waste processing and reprocessing, you might as well leverage the cost by building as many nuclear power stations as you need to meet at least the minimum baseload figures typically about 25GW or so.

      More than that starts to bend the solution cost, as nukes that have to throttle back to not oversupply (in the absence of storage, which is better for nukes than renewables actually) are stuck with exactly the same* O & M and Capex costs as those that run flat out, but just earn less, so have to raise prices to compensate.

      Whenever I did these various exercises in Yet Another Renewable Technology (YARP??) it became clear that the costs imposed by intermittency itself were enough to completely nail the coffin, already constructed of expensive low energy density technologies , completely shut.

      If windmills without additional technology to compensate for intermittency already exceeded the cost of nuclear, there was little point in investigating the overall cost of solutions with storage.

      And if solar was more expensive than windmills, there was little point in deploying that either.

      In short my stance from being completely technology neutral, was moved by the cost benefit analysis towards a rabid anti-intermittent-renewable stance. No technology yet matches nuclear in terms of basic generation costs, and when the externalised costs are added on to cope with intermittency, it’s simply not worth even considering.

      And that of course is the inconvenient truth the Green persuasion won’t accept: That if decarbonised energy is what you want, then nuclear power is far and away the best option by a really significant margin, and money spent on developing it and on fuel and waste recycling and treatment will be well spent.

      ALL this discussion about making renewables dispatchable wont lead to cost effective solutions at all. All it does is flesh out the position I arrived at very quickly: Namely that intermittent renewable energy is, except in rare and exceptional cases**, a crock of shit, and should be shunned like the plague by any nation that actually wants to do more than devote most of its GDP to generating enough energy to stay civilised.

      * Obviously costs of running dispatchable nukes are not really exactly the same, but fuel costs are low, and saving a bit of fuel doesn’t really save much, and the potential poisoning of underrun fuel means more frequent fuel changes are needed anyway.

      ** Two exceptions spring to mind: New Zealand is an isolated country with a lot of hydro electric potential and a lot of places no one goes either, and the hydroelectric capacity is greater than the rainfall it receives. Under these circumstances windmills built near dams will actually serve to reduce the amount of rainfall needed and the dams and reservoirs act as innate dispatchability. That is you cant get any more energy out of their hydro than rain that fills them, so it can be topped up with windpower when available, and if the cables between dam and windmill are short, they dont add much extra cost to the overall solution.

      The second possible site that could benefit from massive deployment of solar power, is the Boulder (Hoover) dam in the USA. Its a hydro place that represents a big store of energy, but not enough to run flat out all year. The lake (Mead) is surrounded by uninhabited and pretty ugly desert, and its cloudless nearly all year. Adding solar to that would generate a few useful GWh every day.

      BUT it should be emphasised that ex of government and political meddling, both these examples would benefit more from tacking a nuclear power station onto the hydro instead of renewables, as Switzerland does, with the ‘nuclear baseload, hydro load following’ providing some of the lowest carbon and cheapest electricity in the world. Nuclear is generally always cheaper, but the two examples above – where natural storage already exists – represent the least worst case of renewable deployment.

      Note that the storage doesn’t have to be rechargeable from electricity, in order to be useful. Hydro is a dispatchable power source that is not constrained by the capacity of its turbines, but by rainfall, in general. It can always be utilised to fill profitable peak demand when other technologies are not available. Neither is there a heat up/cool down energy loss when starting or stopping.

  5. Askja Energy says:

    I find this discussions about cost of pumped hydro very interesting. It would make it even more interesting to also focus on levelized cost pr/ electricity unit produced (such as GBP/MWh or USD/MWh).

    • Euan Mearns says:

      That’s an interesting web site.

      Agree that levelised cost is a good metric, but I am a humble geologist and not an economist.

      What is the proposed capacity of Ice Link? What will it cost? And where will the economic benefits for the UK lie? I have on going correspondence with Hugh Sharman about the Denmark – Norway links where the Danes sell low and buy high and the Norqwegians are laughing all the way to the bank. Denmark has the highest cost electricity in Europe.

      • Olav says:

        From the danish A dane is complaing about Norway bying cheap and selling expansive.
        “Han påpeger, at nordmændene kan glæde sig over, at den gennemsnitlige eksportpris for vindmøllestrøm er nede på ca. 157 kroner pr. MWh.
        Til sammenligning må danskerne importere norsk vandkraft til en pris på næsten 212 kroner pr. MWh, når vindmøllerne har stået stille”

        .157 is a good price when you have surplus. He can buy it back when really needed for 212. I would say he has the benefif of storage to a very fair price. Doubt he can find a storage to a lower price.
        The private housholders entering German PV now is less fortunate. The grid may pay 6 eurocent and after sunset he has to buy it back for 24.

        Well danish housholds has high el price, but danish industry pay low price. All PSO (Vindmill support) and part of other taxes is levelied on housholds only. Similar system exist everywhere, but the danish has taken the top spot. Electricity taxes on housholds are used to finance the budget for everything else. The Dane finance officials does see battery storage as a bad idea offcause.

      • Willem Post says:


        It is true Denmark sells at low wholesale prices (mostly at night) when it needs to export energy (during stronger winds combined with lower demand), and buys at high wholesale prices (mostly during the day) when it needs to import energy (during weaker winds combined with higher demand).

        The benefit to Norway is more water staying in reservoirs, less through the turbines, because of the Danish energy inflow (mostly at night) which typically takes place at lower wholesale prices than they might otherwise be.

        Norway saves some wear and tear, but almost all other costs of its power system remain unchanged.

      • Askja Energy says:

        Hi Euan,
        The capacity is likely to be close to 1,000 MW.
        The cost is expected to be 2.5-3.3 billion USD.
        Economic benefits from UK would be great, as the cable would give the Brits access to renewable energy that is substantially less costly than they are paying for new CfD contracts in UK.
        Norway is indeed profiting greatly from their subsea cables.
        For more info please note this link:
        Best regards from Reykjavík.
        Ketill Sigurjonsson.

        • Euan Mearns says:

          Ketill, thanks for info and link. My immediate reaction is that a 1 GW link is not much. 5 GW and it begins to get interesting. And Iceland, that vast empty wilderness, could become a power house for the UK. I need to spend some time thinking about the comparison of investment in inter-connectors and storage. But 1 GW 24/7 for £1.5 billion looks incredibly cheap compared with the storage options. But then someone needs to build the dams and geothermal plant in Iceland too.

          • Willem Post says:

            Iceland has several aluminum plants and may want to keep its energy for more such plants and export the aluminum instead.

    • A C Osborn says:

      I am intrigued by the 44% efficiency in 2014.
      How it managed it I don’t know, according, to that nice interactive gadget it is managing about 1.5% at the moment, 23Kw of 1800Kw capacity.

  6. peter2108 says:

    Here is a link to a recent pumped storage scheme in Portugal The UK DECC projections show no increase in planned pumped storage out to 2035.

  7. The logical solution to the business model problem is to have the wind & solar producers deliver their power to the grid in a dispatchable form. But there are two reasons this wouldn’t work:

    1. The needed storage capacity doesn’t exist.

    2. The added cost would make wind and solar uneconomic if it did exist.

  8. Ed says:

    Here’s another possible piece in the storage “solution”. Back of an envelope calculations and ignoring all practicalities.

    Each of the 25 million homes in Britain buys four 85 Ah batteries. 4 x 85 = 340 Ah. 340 Ah x 12v = 4 kWh of storage per home.

    25 million x 4 kWh = 0.1 TWh of storage

    Cost: 1 battery @ £70, 4 batteries @ £280 per household. £7 Billion in total

    • Ed says:

      Oh, I forgot. £7 Billion every 5 or so years because lead batteries don’t last long. 🙂

      • roberto says:

        You are an optimist!… no lead battery can stand 5×365 deep discharges… they would need to be replace much earlier than once every 5 years, I think.

    • JerryC says:

      Don’t you have to buy everyone an inverter, too?

      • Ed says:

        Yep, that too plus a multitude of other “minor” details, like how we manufacture all these batteries without fossil energy in 100 years time. 🙂 Just put it out there as a thought experiment rather than a serious suggestion, Jerry.

        • Ed says:

          On reflection, I wonder if lead batteries can be recycled or reconditioned so they may not cost £7 Billion every 5 years to replace. On top of that, I have very high hopes for the new flow batteries that are being developed to become available within 10 years which should have much longer lifespans and be cheaper.

          • roberto says:

            The 10 year time span is not OK, unfortunately, as per greenwash propaganda dogmatic view that “we need to do something immediately or else global warming will kill us all”.

    • It doesn't add up... says:

      But the calculation above calls for 1.1 TWh of storage, so that’s £77bn in cost – and finding somewhere to put 44 batteries in each home is not easy.

      • Ed says:

        44 batteries under the bed – no problem ! 😉 I did make it clear in the original comment that it was only a tentative partial solution. Like renewable energy, which will come from a number of sources, storage will also come in a number of ways.

        Also, the way we use energy will have to change. Wave goodbye to electric showers whenever you want. Welcome in smart meters, electricity rationing. etc.

    • Willem Post says:

      Lead acid batteries should rarely be charged/discharged beyond 50%, preferably 25%
      Charging loss is about 10%, discharging loss about 10%

      Here is a battery system for an off-the-grid, 2000 ft2, energy-efficient house from this article

      Provided to house…………………………………….10.00 kWh/d AC
      Provided by 10 kW PV system…………………….4.00 kWh/d AC
      Provided by 3 kW generator………………………..3.00 kWh/d AC
      From DC to AC inverter…………………………….3000 Wh/d AC
      Inverter loss factor……………………………………..0.90
      To inverter………………………………………………..3333 Wh/d DC
      Wiring loss factor……………………………………….0.90
      From battery……………………………………………..3704 Wh/d DC
      Battery discharge loss factor………………………..0.90
      From battery adj’d for discharge loss……………4115 Wh/d DC
      Autonomy period…………………………………………..4 days
      From battery during autonomy period…………16461 Wh DC
      Depth of Discharge factor……………………………0.30; a low value for longer life
      Charge in Battery…………………………………… 54870 Wh DC
      Temperature loss factor……………………………….0.90
      Charge in battery adj’d for temperature………60966 Wh DC
      System voltage……………………………………………..48 V
      Battery system capacity……………………………..1270 Ah
      Battery aging factor…………………………………….0.85
      Battery system capacity adj’d for aging………..1494 Ah

      Battery system to have 2 strings in parallel; each string with 12 batteries in series

      Rating of selected battery……………………………750 Ah
      Battery strings in parallel…………………………………2; three strings is acceptable, if necessary
      Battery system rating…………………………………1500 Ah
      Battery voltage………………………………………………4 V
      Batteries in series…………………………………………12
      Total number of batteries……………………………….24

      Battery cost = 1,500 Ah x $350/100 Ah = $5,250, plus the cost of wiring, charge/discharge controller, 48 V to 120 AC inverter, mounting rack, and installation, for an installed total cost of about $10,000.

      Such a 5-day event may occur only a few times during winter. At other times, PV solar generation would be greater and the battery discharge % would be less, which reduces battery capacity reduction due to aging. Energy generation would be sufficient for DHW heating (supplementing the LP heater of the DHW system) and for most of the plug-in vehicle charging.

      • Ed says:

        Thanks, Willem. That is a very comprehensive reply. Lets hope the new generation of flow batteries being developed will provide the breakthrough that we need.

  9. Confused Mike says:

    Whilst digesting the maths of matching storage size to surplus renewable generated power is there the challenge of who receives the CfD for the power when it is eventually dispatched. The wind farmer owner assumed he would get it when it was generated but what happens if it is stored and then dispatched later ?
    The storage site economics relies on buying (surplus) power at low prices – not CfD enhanced – and then supplying it when the market price is high.

    How does that work with Electricity Market Reform?

    • Euan Mearns says:

      Mike, you have every right to be confused. In this opaque labyrinth of electricity supply that has been painted for us I haven’t a clue how this would work. Its true that if storage were to store wind then it would already be the most expensive electricity on the market. And you maybe need to multiply its price by 10 to pay someone to store it for a week.

    • It doesn't add up... says:

      You should start by asking how does it work now?

      From last year’s DUKES (next one due end July)

      5.44 Plant load factors measure how intensively each type of plant has been used. The load factor of nuclear stations in 2012 at 74 per cent was 3.1 percentage points higher than in 2012, due to increased availability of stations. However, it was 6.3 percentage points below the peak load factor of 80.1 per cent in 1998. With generation from gas at its lowest level since 1996, the CCGT load factor
      fell to a record low of 28 per cent. This was following reductions in each year since 2009, from 2008’s eight-year high of 71.0 per cent. Between 2012 and 2013, the load factor for coal fired power stations increased by 1.5 percentage points, to 58 per cent.

      5.45 Load factors for natural flow hydro and wind (as well as other renewables) can be found in table 6.5. Slightly higher wind speeds in 2013 resulted in an increase in the overall wind load factor (on an unchanged configuration basis) of 3.1 percentage points, from 29 per cent in 2012 to 32 per cent in 2013. Onshore wind rose from 26 per cent to 29 per cent, while offshore wind increased from 36 per cent to 39 per cent, higher than the load factor for CCGT stations in 2013. Rainfall (in the main hydro areas) fell in the first three quarters of 2013 compared to 2012, leading to a fall in the hydro load factor
      (on an unchanged configuration basis) of 4.1 percentage points, from 36 per cent to 32 per cent in 2013.

      Pumped storage use is less affected by the dry weather and the load factor fell successively from 2009 to 2011, from 2008’s peak [15.3%], as lower peak time demand for electricity and lower prices deterred its use. In 2013, the load factor decreased by 0.3 percentage points, to 12 per cent.

      So Dinorwig has been used more than 20% (3.3/15.3) less even as wind penetration has increased, because it has been cheaper to meet the now shallower peak from coal. That may of course change now that coal has been made uneconomic, but CCGT could be the first candidate to replace it. Also notable is the low utilisation of normal hydro plant – constrained by rainfall and snowmelt relative to installed capacity. It is of course used as a fast reaction peaker, as well as a filler for low/below forecast wind.

    • roberto says:

      Well, clearly, everybody wants the biggest slice of the pie possible… so wind farm gets paid for the electricity it produces, regardless of what fraction of it can be integrated at time of production… same for the owner of the pumped-hydro system (or battery)… the term “losses” in green jargon does not exist, at least not from their point of view… the populace will cope with that via fat electricity bills… very fat ones.

  10. Knut says:

    I would imagine any scheme of wind+storage would involve building some surplus generating capacity, with curtailment when the reservoirs are full. I assume the cost of windmills can be estimated at least roughly (taking expected cost reductions into account). It should be fairly easy math to figure out the most rational combinations given different estimates of storage cost. Have you tried to run the numbers on this?

  11. Rob says:

    Would it be possible to calculate all in costs for wind power in terms of £ per MWh
    to allow comparisons of other energy sources
    For example current costs using gas for balancing and costs including more storage
    Also at what point do we require more storage instead of using fossil fuels

  12. A great breakdown of the financial challenges. It is also important to look at the energy needed to build both the “renewable” power source and the storage mechanism compared to what the system will deliver back over its lifetime. From memory the “renewable” appliances themselves return about 7 times the energy required to make them (this doesn’t calculate transport to site or installation). Take away the energy needed to build the storage system and maintain and repair it, and you don’t have much left over to power people’s homes!

  13. Nial says:

    How much do you think a Thorium plant is going to cost when the Chinese have cracked it?


    • roberto says:

      It will cost more than an equivalent U/Pu one, since for Th reactors the necessary radio-chemistry tools and knowledge are way less developed than those for the U/Pu cycle.
      That Th-based reactors would/could be much less expensive than U/Pu ones is an urban legend, nothing more…. the radioprotection requirements would be exactly the same.

      • Nial says:

        Roberto, one of the American universities had an experimental thorium reactor running for thousands of hours in the sixties/seventies. This suggests it might be cheaper and more scalable that a U/Pu reactor?

        On the other hand I am an electronic engineer and know sod all about nuclear reactors so perhaps not.


  14. Willem Post says:


    You may be interested in this analysis of pumped storage in Norway using EXISTING reservoirs.

    Based on ON-PEAK and OFF-PEAK electric rate differentials, none of the cases are profitable.

    For Denmark, Norway and Germany, about 15,000 – 20,000 MW of pumped hydro storage, plus 42,000 MW of transmissions would be required, by 2050.

    The water level rise/fall rate in reservoirs was kept at about 13 cm/hr for analysis.

  15. Olav says:

    Finding 100 sites for Pumped Hydro ashore in UK is impossible unless the big one at Loch Ness is used. Old coal mines can perhaps be used as an alternative but keeping the tunnels and cavities underground stable is very difficult. Digging new cavities has enormous costs. The cheapest solution is Norwegian and Icelandic reservoirs- Lower and upper lakes are already there only extra generating capacity is needed. If not enough differential in buying and selling power is offered then no other storing solutions will work economically.
    But if UK must do something by themselves the could wall in a big slice of the ocean. Swansea is about 10 km wall at 100 million £ a kilometer including generators. Has to be a shallow area to limit the wall height. May I suggest Dogger Bank…. If you double the length of a circular wall then the enclosed area quadruples so the Swansea cost a enclosed km2 will go down. The cost will also go down due to the enormous scale of such a project. Wind power does mainly emptying the pool. Simultaneously is generators producing by letting water in as “load following” above base level. Average head is only 10m but friction losses from long tunnels on ordinary Pumped Storage is avoided. Generator clusters along the south eastern perimeter has interconnectors to UK east coast so much land line grid is avoided. Tidal range is low but it can be utilized to some extent. But the fishermen will not be happy any enclosure of a sea area (this is the case at Swansea too) will destroy that area as productive fishing area unless some advanced ideas for fish farming comes up..
    Am in Aberdeen now.. Time for a beer at Prince of Whales.

  16. Jeff says:

    A more sensible approach is to reduce and spread energy demand, especially peaks. There are various ways of doing this including variable pricing, demand management, insulation and technology change. As a start, if each of 20 million houses used just one fewer 60W incandescent bulb, using a 10W LED bulb instead, the saving is 1GW. Replacing 20 incandescent bulbs per-household with LEDs would cost about £100 – or £1bn for 20 million homes. That is a lot easier than building pumped storage.

    • Lars says:

      “…As a start, if each of 20 million houses used just one fewer 60W incandescent bulb…”

      Jeff, aren`t those low hanging fruits already picked? How many incandescent bulbs are left? They must be disappearing by the thousands in Europe each day. I have a few left in my household but only in lamps that are rarely used.

      Besides I don`t think you solve all the problems of intermittency with renewables by doing this including the other measures. The peaks are reduced as has already been the case in the UK, but the diurnal, weekly and seasonal swings will still not correspond to the erratic output of renewables.

      Demand management ok, but are we supposed to cook our coffee and wash our clothes only when the wind is blowing? I see your points, but having read this extremely thorough blog for a couple of years with lots of articles adressing this I am convinced it is by far not enough.

      • Jeff says:

        You are right. I haven’t bought bulbs for so long that I didn’t realize incandescents are no longer available. I know these measures don’t solve the problem of intermittent supply, but mustn’t it be easier and cheaper if only one of supply and demand is highly variable hour by hour?

    • roberto says:

      Demand management is another issue that I really don’t understand… and personally I would never, ever accept to use electricity at times decided/chosen by others, other than running the washing machine after 10pm as I’ve done in France… no way to accept that my fridge does not start its compressor because my neighbour wants to charge his Tesla Model S…
      How’s industry going to cope with demand management? Is BMW or Mercedes in the Country of Energiewende going to accept not to run their production lines because there is no wind for a week, in January, and for some reason pumped-hydro is limited? Don’t think so!

    • Willem Post says:

      An even better approach would be to upgrade building codes for houses, as in Sweden, etc.,

      Older 2000 ft2 houses in New England have PEAK space heating demands of about 45 – 55 Btu/ft2/h, requiring up to 125,000 Btu/h of output from the heating system.

      Newer, standard, 2000 ft2, houses in New England have PEAK space heating demands of about 20 – 25 Btu/ft2/h, requiring up to 60,000 Btu/h of output from the heating system

      Here is the URL of a 1,232 ft2 tight house with a PEAK space heating demand of 10,500 Btu/hr, or 8.5 Btu/ft2/h; an equivalent 2000 ft2 house would have a PEAK space heating demand of about 2000/1232 x 10500 = 17,045 Btu/hr.

      – Heating: two Mitsubishi, Mr. Slim, ductless, minisplit, heat pumps (one downstairs @ 12,000 Btu/hr, and one upstairs @ 9,000 Btu/hr), installed cost about $5,250.
      – Ventilation; a Lifebreath 155 ECM energy-recovery ventilator.
      – Electricity: a grid-connected, PV system, 5.7 kW, roof-mounted with Fronius IG 5100 inverter, installed cost about $22,000 less subsidies.

      The PEAK heating demand of a 2000 ft2 Passivhaus would be about 10 W/m2 x 186 m2 = 1.86 kW, or 6,348 Btu/hr, or 3.2 Btu/ft2/h, i.e., a 2 kW, thermostat-controlled, electric heater in the air supply duct COULD be the heating system!!

  17. Jeff says:

    that should have been £2bn…

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