How Much Wind And Solar Can Norway’s Reservoirs Balance?

The Skaggerak subsea power cable connects Norway with Denmark. The NorNed cable connects Norway with the Netherlands. By 2019 the Nordlink cable will connect Norway with Germany and by 2021 the NSN cable will connect Norway with the UK. And now Scotland wants to connect with Norway via the NorthConnect link:

Figure 1: Existing, in progress and planned interconnectors with Norway

Why are these countries so anxious to connect to Norway? Because Norway’s hydro reservoirs are regarded as a large-scale storage battery that can be used to smooth out large quantities of intermittent renewables generation. The 2013 Joint Norwegian-German Declaration says as much:

Thanks to its natural endowments and previous investments, Norway possesses 50% of Europe’s entire power storage capacities. Therefore, Norway is in a position to provide large-scale, cost-effective, and emission-free indirect storage to balance wind and solar generation in other countries ….. In times of high wind or solar production, Norway can import cheap electricity from abroad, thereby saving water in its reservoirs. In times of low wind production, Norway can use the stored water to export power at higher prices. In this way, excess wind or solar production can be stored and used later.

On the face of it this looks like a win-win proposition. Germany and its renewables-heavy, storage-challenged neighbors get to store the intermittent wind and solar power they couldn’t otherwise use in Norwegian reservoirs and Norway makes money selling it back to them. But how is it going to work out in practice? Here we look into this question.

First a brief review of Norway’s electricity sector. Figure 2 shows generation by source between 1997 and 2013 (data from Statistics Norway):

Figure 2: Annual generation by source, Norway, 1997-2013

And the table below gives installed capacity and generation totals for 2013, the latest year for which data are available:

Norway’s electricity production remains dominated by hydro (note that this is almost all “conventional” hydro; pumped hydro contributed only 786GWh of generation in 2013.) However, Norway is not a major net power exporter. Figure 3 compares Norway’s export-import balance with its hydro generation over the 17-year period between 1997 and 2013. For ten of these years Norway was a net power exporter and for six years it was a net importer (exports and imports were balanced in 2006).

Figure 3: Annual hydro generation, demand and net imports/exports, Norway 1997-2013

As one would expect the export-import balance is strongly correlated with hydro generation (R squared = 0.92) with net power exports when annual hydro generation exceeds ~120,000GWh and net power imports when it doesn’t.

Figure 4 plots exports and imports separately. Because interconnector flows on the Nordic Grid are governed largely by short-term price differentials Norway still exports “cheap” hydro even in years when it’s a net power importer:

Figure 4: Annual imports and exports, Norway 1997-2013

It would nevertheless be a mistake to conclude that the Norwegians are making no use of the flexibility that hydro offers. Norway in fact already makes copious use of its hydro to balance diurnal and short-term demand fluctuations. Figure 5, which reproduces Statnett’s hourly production, consumption and export-import graphs for the past week, shows how production/consumption imbalances of up to 3GW in both directions were offset by interconnector flows that fluctuated between 2GW of imports and 3GW of exports. Relative to Norway’s 11GW average demand during the week these are large numbers. (During the same week the UK, with an average demand of 28GW, imported between 2.4 and 3.5GW of power and used none of it for load balancing.)

Figure 5:  Hourly electricity production, consumption, exports and imports, Norway, 27th July to 2nd August, 2015.

The question is whether these imports and exports were an artifact of the Nordic Grid’s pricing mechanism or whether Statnett’s generation curve was the closest Norway’s hydro reservoirs could come to matching demand during the week. I suspect it was mostly the former, but there are the following reasons to suppose that it could have been the latter:

• Norway has no significant pumped hydro capacity, so when water goes through a Norwegian dam it doesn’t come back up again. Norway must therefore “store” power by replacing hydro generation with imported power whenever the imported power comes in, thereby preserving water above the dam. This makes the system less flexible than a pumped hydro system, which can be turned on and off at any time.

• Generation from Norway’s hydro plants is further constrained by maximum and minimum acceptable reservoir water levels, minimum acceptable watercourse flow rates and variable permitted release volumes at different times of the year. This adds another layer of inflexibility.

• Norway’s grid presently can’t provide reliable electricity to large parts of Northern and Central Norway. Statnett proposes to spend around 7 billion Euros over the next ten years on grid upgrades, but until they are completed the ability of the Norwegian grid to “wheel” power from place to place will be limited. Another complication is that there are reportedly no fewer than 178 separate grids in the country (Statnett controls only Norway’s “stem net” grid, which transports electricity over long distances. The other 177 are regional and local grids operated by local authorities and county councils.)

For the time being, however, we will ignore these problems and assume that Norway’s reservoirs really are the enormous storage battery many consider them to be. If all goes as planned the Skaggerak, NordNed, NordLink, NSN and NorthConnect links will be charging and discharging this battery with up o 5.9GW of electricity by 2021. Is the battery large enough to provide balancing services for this much input power, which we can reasonably assume will consist dominantly of wind and/or solar spikes? To answer this and related questions I constructed a spreadsheet algorithm that simulates how interconnector flows might work in practice. It makes the following assumptions:

  • Power is exported to Norway from Denmark, Germany, Netherlands and the UK (DGNU for short) during periods of high wind/solar output and imported back to DGNU from Norway during periods of low-wind/solar output.
  • The minimum duration of power flow in either direction is one hour.
  • Power is always available for export from Norway when and in the amounts needed.
  • Annual interconnector flows into and out of Norway are the same.
  • Interconnector flows are adjusted to produce a result as close to constant baseload generation as possible. No attempt is made to balance output against DGNU demand.
  • Power flows along Interconnector links with other countries are ignored.
  • Transmission and efficiency losses are ignored.

Another disclaimer before proceeding. Optimized annual plans of the type you are about to see can be formulated only if complete wind generation data for the coming year are available, which in real life of course they won’t be.

To make the plan as realistic as possible I applied the algorithm to combined DGNU hourly wind output for 2013 (Figure 6, data from PF Bach). The amplitude of the wind spikes greatly exceeds the 5.9GW capacity of the interconnectors, which doesn’t look promising, but we’ll see what Norwegian hydro can do about it anyway:

Figure 6:  Combined hourly wind generation from Denmark, Germany, Netherlands and UK, 2013

Figure 7 plots the surplus wind power sent to Norway during high-wind periods. This is the largest fraction of the spikes that can be sent within the limits imposed by 5.9GW interconnector capacity and the need to balance exports and imports. It represents 34% of total DGNU wind generation during the year:

Figure 7:  Surplus wind power exported to Norway during high-wind periods

Figure 8 shows the 66% of total wind generation that remains:

Figure 8:  Wind generation remaining in Denmark, Germany, Netherlands and UK after export of surpluses to Norway

And Figure 9 shows what Norway sends back to fill in the holes during low-wind periods:

Figure 9: Generation returned to Denmark, Germany, Netherlands and UK from Norway

Summing Figures 8 and 9 then gives Figure 10, which shows what combined 2013 wind generation from DGNU looks like after provision of Norwegian balancing services:

Figure 10: Final “balanced” wind generation

DGNU should be happy with this result. In its journey through Norway’s reservoirs the wildly erratic wind output shown in Figure 6 has been transformed into baseload generation delivered at a constant 7.9GW for 95% of the time (the lowest output over any one-hour period is 6.5GW). The residual spikes above the 7.9GW line, which presumably would have to be curtailed, make up only 15% of total generation, and interconnector utilization is a respectable 62%.

But we haven’t considered how Norway is positioned to handle the imports and exports. Figure 11 shows hourly exports and imports over the two-week period from June 16th to June 30th, 2013 and compares them with Norway’s electricity demand over the same period in 2015, which would presumably be similar to 2013 demand (data from Statnett). The green-shaded imports from DGNU are fed into the Norwegian grid(s) to offset hydro generation and thereby retain water behind the dams and the red-shaded exports back to DGNU are generated by releasing the retained water:

Figure 11:  Norway’s hourly imports, exports and domestic demand, June 16th – 23rd

To match exports and imports to demand over this period Norway’s hydro generation would have to fluctuate in accordance with the curve shown in Figure 12, and it’s difficult to say whether it could do this without knowing what the impacts of reservoir level and other constraints might be. The range of fluctuation is, however, roughly twice that achieved during normal operations (see Figure 5) so the system could be sailing close to the wind.

Figure 12: Fluctuations in hydro generation needed to match exports, imports and demand, June 16th – 23rd

I next turned to Germany. As stated in the Joint Norwegian-German Declaration quoted at the beginning of the post Germany plans to use Norwegian hydro to balance not only its wind but also its solar, so I ran 2013 hourly wind-plus-solar generation for Germany through the algorithm to see how much difference the 1.4GW Nordlink interconnector might make. Germany’s combined 2013 wind plus solar generation is shown in Figure 13 (solar data also from PF Bach):

Figure 13:  Hourly wind + solar generation, Germany, 2013

And found that a 1.4GW interconnector is far too small to make any significant difference. The output (Figure 14) is in fact almost indistinguishable from the input.

Figure 14:  Final “balanced” wind + solar generation with 1.4GW interconnector capacity

But with five times as much interconnector capacity (7GW instead of 1.4GW) Germany gets near-continuous baseload output at 7.7GW, 12% curtailment and 62% utilization (Figure 15):

Figure 15:  Final “balanced” wind + solar generation with 7GW interconnector capacity

Increasing interconnector capacity would appear to be the solution in this case. Eventually, however, a point will be reached where Norway’s reservoirs will no longer be able to handle Germany’s exports. At the 7GW level they would already be jumping through hoops to handle the solar spikes, which as illustrated in Figure 16 arrive once a day in summer with peak-trough amplitudes usually exceeding 10GW and very steep sides:

Figure 16: Norway’s hourly imports, exports and domestic demand, June 16th – 23rd, German wind + solar

Are there any other potential problems that I haven’t mentioned?

Well yes. First, like many other sources of renewable energy hydro is hostage to the weather. A series of dry years could leave Norway’s reservoirs scrambling to meet domestic demand with nothing left over for anyone else.

Second, we are considering the situation as of 2013. Over the next few decades forests of offshore wind turbines are scheduled to be planted in the North Sea and linked to mainland centers of consumption through the proposed North Sea supergrid. When the wind blows these forests of turbines will deliver far larger amounts of power than the centers of consumption can possibly use, and the bulk of it will have to be wasted if nowhere can be found to store it. But where will this immense amount of storage be found? One thing is for sure; it won’t be Norway.

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89 Responses to How Much Wind And Solar Can Norway’s Reservoirs Balance?

  1. Aidan says:

    Absolutely fascinating. I wonder to what extent peaks in demand can be tempered by ‘smart’ consumption at the domestic/industrial consumer level? Examples are domestic batteries such as Tesla’s new ‘Powerwall’, smart appliances, such as dishwashers etc which operate only when there is sufficient spare power in the system, electric cars whose batteries can be charged ‘when the wind blows’ , and large scale insulated domestic hot water storage.

    • Leo Smith says:

      I wonder to what extent peaks in demand can be tempered

      Its not a hard calculation, though I haven’t done it recently. The answer I arrived at was ‘not very much, really’.

      If you want to wait for a gale to sweep across the country before you can use your car, a little more.

  2. Eoin Licken says:

    Interesting article and analysis.
    One of the underlying assumptions, that DGNU export and import as a block, need not be true. What if UK and Netherlands are exporting while Denmark and Germany are importing? Then Norway becomes an interconnector, and the effect of reservoir pumping or holding capacity is less relevant.
    Put another way, are these connections to Norway simply to use it as a battery, or are they the spokes of a supergrid where Norway is the hub?

    • Willem Post says:

      All are affected by the same weather system, all would be exporting wind energy and Norway could not enough throttle back its hydro plants to use all that energy in its domestic market, especially at night when wind energy is likely to be higher and demand is lower.

  3. dereklouden says:

    If this system is to work at all Norway will need to convert a lot of its conventional hydro to Pumped Storage. This will cost Billions but, unlike us, Norway has the money. We could create more Pumped Storage schemes in the UK but the technology isn’t popular with the UK Government. Given the recent changes to support schemes by DECC and the clear desire to boost nuclear at the expense of all other technologies it won’t happen. No-one will want to invest in UK electricity generation if changes like the CCL alteration can happen without warning. A line was crossed and I fear there is no way back. Now, what was that line by Sir Edward Grey about lamps?

    • Euan Mearns says:

      This is often suggested but seldom backed up with data. To convert conventional hydro to pumped hydro you must have a large lower reservoir. And when you pump that lower reservoir it lowers the level, potentially making the exit river run dry. Its also normal to use the hydro generator as the pump. Hence the lower reservoir must be by the existing power station. Many of these in Norway will currently drain into rivers or fjords (brackish water).

      One of these many fabled renewables half truths that actually needs to be backed up with facts.

      • dereklouden says:

        Hello Euan
        You’re right that the Norwegians currently lack the lower reservoir capacity needed. Many of their schemes currently outflow into rivers. That is where they need to invest. Not all plant could be converted to pumped storage, I very much agree. Loch Ness is a different case. Foyers and Glendoe going flat out won’t move the level up or down a millimetre.

        • Willem Post says:


          What is the incentive for Norway to flood several hundred square miles of its beautiful land area to create meaningful pumped storage of the benefit of RE fantasies?

          People live there, farmers farm there.

          It would displace at least 100,000 people, plus all their wherwithal.

          Not going to happen.

          Eurologists in Brussels should stop propagating their RE fantasies, which cause energy no-nothings to chime in.

    • Leo Smith says:

      The problem with UK pumped storage is that yes, we could have more, but not that much more – maybe a GW or two at best.

      We simply dont have the geography. Thanks to Slartibartfast the Norwegians do.

      And whilst its a good thing if a pumped storage costs less than the equivalent nuclear plant, a windmill/solar farm and pumped storage always costs more.

      So it is better to build the nuke.

      • Peter Lang says:

        The cost of electricity from nuclear can be estimated as LCOE of the plant plus the LCOE of the grid to serve it (LCOE of the grid is negligible for nuclear (<$2/MWh).

        However, the cost for wind plus pumped hydro is the LCOE of all the following components:
        Wind farms
        pumped hydro facility (which needs to sell power at about 4 x what it bought it fro from the wind farms)
        normal grid (roughly 50% addition to the LCOE of wind at 30% wind energy penetration)

        All in all, I'd expect the LCOE of wind plus pumped hydro to be at lest 5x and perhaps 10x the cost of nuclear.

        Furthermore, nuclear plus pumped hydro would be far more economical that wind plus pumped hydro and would allow nuclear power to provide over 80% of a country's electricity (if the pumped hydro sites are available). This would reduce the CO2 emissions intensity of electricity by around 90% (as is the case in France). Furthermore, as most informed people know, nuclear power is about the safest way to generate electricity. Doe any readers of Energy Matters no know that?

        So, why does any informed person argue for wind and solar power for mainstream grid connected electricity generation? It beats me.

        • Willem Post says:


          I agree 100%.

          It would be good to create a table of various combinations so folks get to see the systems approach of LCOE.

          This site should have it as a permanent exhibit to nip in the bud any fantasy ideating.

        • Leo Smith says:

          So, why does any informed person argue for wind and solar power for mainstream grid connected electricity generation? It beats me.

          Either because they are (deliberately) misinformed, or their worldview operates on a completely different set of metaphysical assumptions.

          The green view amongst those I have talked to amounts to a complete distrust of big business and somewhat government, total fear of nuclear power, and an almost total aversion to mathematics.

          The renewable energy movement has keyed accurately into that world view by portraying renewables as small scale, even community sized projects, talking ‘powered homes’ not gigawatts, being heavy on emotional terms like ‘renewable’ and ‘sustainable’ which are never defined, and comparing apples and oranges.

          I am afraid this basic ignorance and religion-like view extends to educated scientists as well.

          Ultimately the green view is that we dont actually need energy beyond a bit to heat our homes with, and since nuclear is by definition big, scientific and therefore capitalistic and scary, all we have left is renewables, since carbon fuels are now also demonized.

          And since the green view is ultimately a Left view, what it costs is simply not an issue: whatever it takes, and provided the whole world is equally disadvantaged, who cares? We all sink into egalitarian dark ages together….

        • Knut says:


          I understand all the arguments for nuclear, trust me.

          But when I see posts like this from nuclear fans, suggesting that everyone else are idiots, I can’t help but ask whether you have a blind spot yourself.

          As you say, statistically, nuclear power has been pretty safe so far. But politicians who plan ahead now have to take a new factor into account. Yes, I am talking about terrorism. Looking decades ahead, how much would it cost to secure hundreds of nuclear plants against drone-equipped evildoers?

          Put that in your LCOE and give me the numbers.
          Compare it to LCOE for wind/solar and storage with plausible predictions for cost reductions (decades out) built in.

          Then call us idiots.

          • Peter Lang says:


            I didn’t mean to call or imply that anyone is an idiot. I don’t know what I said that gave that impression.

            I do not agree with the arguments about nuclear proliferation risk. So let’s leave that out of the discussion, there are orders of magnitude greater risks from bad energy policy decisions than nuclear proliferation risk. The risk of wind and solar not being able to meet the expectations of the proponents by 2050 is around 50/MWh (expected monitory value).

            I am considering policy for century timescale. My main argument is that policy has to address the concerns of those concerned about cutting GHG emissions. And we have to consider that fossil fuels are limited. Also, renewables, like wind and solar, are not sustainable – that is, they can not supply sufficient energy to power modern society as well as reproduce themselves. So they can make only a minor contribution to global energy supply and are entirely dependent on fossil fuels or nuclear to sustain them. Hydro capacity is limited and it’s share of global energy will decline over this century.

            Conversely, nuclear fuel is sufficient to supply all the world’s energy for thousands of years in breeder reactors. And nuclear is well proven as capable of meeting requirements.

            Therefore, over the course of this century, it would seem it is likely to become the main source of global energy supply. There is also the potential for orders of magnitude reduction in cost and for unlimited transport fuels (petrol, diesel, jet fuel, etc.), with no change in our distribution and storage systems for these fuels.

            I can provide links to support all this if interested, but not easy with the iPad I am using while on holidays.

          • Knut says:

            Peter, (for some reason, I’m unable to reply to your post, (perhaps the site only allows so many levels) so I do it here),

            You didn’t say “idiot”, but your post ended: “So, why does any informed person argue for wind and solar power for mainstream grid connected electricity generation? It beats me.” That’s what I was reacting to.

            To the rest: the blind spot I was referring to was not nuclear proliferation. It is attacks upon nuclear power plants. Or waste storage facilities. Or fuel transports.

            Now consider how these things are to be protected in a future where everyone and their uncle can put a drone capable of carrying hundreds of kilos of TNT in the air.

            See it now?

          • Peter Lang says:


            It’s off topic for this thread. However, I do not agree this is a significant risk because the consequence is small. If you think it is large you’d need to explain the consequence in objective terms and quantify it in terms of fatalities per TWh of electricity produced by nuclear power. And compare that objectively with other technologies that can meet requirements in 2030, 2050, 2100. We have 60 years showing that nuclear power is the safest way to generate electricity. Provide objective evidence that is going to change, not just more scaremongering, doomsday
            scenarios and straw man arguments.

          • robertok06 says:


            ” It is attacks upon nuclear power plants. Or waste storage facilities. Or fuel transports.”

            Power plants? Done already… rocket-propelled grenades against the Superphenix reactor… did absolutely nothing to it.

            Waste and/or storage facilities? Be my guest, dear terrorist… you’ll have to dig 500 m underground, and then try to blow up a Castor made of 15 cm of concrete, with inside 10 cm of copper, and inside of it a vetrified matrix with the waste… with the vetrified part being able to sustain >2000 C temperatures.

            The terrorist attack is a fake problem. One could imagine of having a team of 400 armed security personnel on duty 24h/24 on a site with, say (for the sake of an numerical example) 4x 1.4 GWe reactors (there are several already like this in France now))… they produce >40 TWh of electricity/year…. so 40 billion kWh/y… adding 0.5 cents to the cost of each kWh would mean 200 millions/year, to pay salary, equipment, training, pensions, etc… of the said 400 security people…. 1/2million each. I’d sign in immediately… 🙂
            Where’s the problem?

  4. Willem Post says:


    You are the master of quick and good analysis.

    There likely will be an economic trade-off between the costs of greater inter-connection capacity, Norway’s hydro balancing capacity, curtailment of wind and solar energy to contain the weather-induced energy spikes and traditional balancing. What a can of worms it has become!

  5. Peter Lang says:

    Another excellent analysis, Roger. Thank you.

    A couple of points:

    1. I understand the US Pacific Northwest used to assume that existing hydro generation capacity would be able to balance and equal amount of wind generation capacity. However, they are now finding that the ration is more like two or perhaps 3 hydro to support 1 wind (I don’t recall if this comparison is on the basis of GW capacity or GWh of energy). But it is an interesting rule of tub based on empirical evidence in an area with a lot of hydro and trying to accommodate a lot of wind and solar.

    2. If Norway can make money out of building pumped hydro storage sites, I am sure they will do so. They have the ideal topography. But, I’d suggest to Norway’s negotiators, they may want to consider requiring 100% year secure contracts with export price guarantees for the full life of each pumped storage project. Because, most pragmatists believe the wind energy ‘revolution’ will blow over soon (along with CAGW and solar).

    • Wind and hydro don’t seem to get along too well in the Pacific Northwest:

      FERC ruled in December 2011 that the federal transmission operator must stop curtailing wind generators in favor of its own hydropower without compensating the wind projects for lost production tax credits, renewable energy credits, and revenue from power purchase agreements. Under its original Environmental Redispatch Protocol, BPA had traditionally curtailed thermal power generators who, although not generating, did experience a saving in fuel costs.

      The wind generators, who have no fuel costs, filed a complaint with FERC in June 2011 urging it to stop BPA from using its transmission monopoly power to curtail competing generators in an “unduly discriminatory manner.” BPA began limiting the output of non-hydroelectric energy in May 2011 due to high flows creating an oversupply of hydropower.

      The agency said it acted to protect salmon and steelhead from high dissolved gas concentrations in spilled water that bypasses turbines. It said the action also maintained the reliability of the power grid and avoided shifting costs to BPA customers.

      • Peter Lang says:

        Thank you. You are clearly well on top of all this. A commenter on some energy web sites, harrywr2, is very knowledgeable about electricity industry in USA and especially about wind, hydro , coal , gas and nuclear. I haven’t seen him post on energy matters yet. He can say a lot more about the issues with wind and hydro in the pacific NW. I can’t contribute much at the moment because I am still travelling.

  6. Euan Mearns says:

    Roger, I believe it is the case that Norway’s balancing capacity is limited by its own power consumption. For June (your fig 16) 11 to 14 GW, somewhat higher in winter. This is because Norway balances external renewables by using the imports instead of its own stored water. The balancing service cannot go beyond its own consumption.

    With current and planned inter connectors (5.9 GW) we are almost half way there to that capacity. So is this a good thing? Well we already have about 129 GW of installed wind in Europe. This puts the current and projected balancing capacity of Norway into perspective. Its not even a half measure its a 1/20th measure. Renewables advocates keep advocating these 1/20th solutions in the hope that they add up to a whole, which they don’t do.

    We also need to question the business model whereby Norway buys cheap surplus wind from the UK and sells it back at inflated cost when it is calm. Why would we want to enter into a business deal like this?

    • Peter Lang says:

      “We also need to question the business model whereby Norway buys cheap surplus wind from the UK and sells it back at inflated cost when it is calm. Why would we want to enter into a business deal like this?”

      Exactly. Denmark does it. Over half the electricity it generates from wind is not consumed in Denmark. It’s exported to Norway. Then Denmark buys back electricity from the grid (at the average emissions intensity of the overall grid) at five times the cost. Result: Denmark has the highest electricity prices in EU and also some of the highest CO2 emissions electricity. It’s a joke. See Slide 14 here: “How much does it cost to reduce carbon emissions”

    • I believe it is the case that Norway’s balancing capacity is limited by its own power consumption

      Correct, Euan. But I think reservoir level and flow rate restrictions etc. are likely to limit balancing capacity before the power consumption limit is reached. This wouldn’t be the case if Norway’s hydro capacity was all pumped but it’s almost all run-of-river (run-of-fjord?)

      The Germans, however, have a solution. From the Joint Norwegian-German Declaration:

      What needs to happen for Norway to assume its role? Offering more balancing power implies taking two measures: reinforcement of the power grid with transmission cables inside Norway and linking Norway to other countries; and a more intensive use of existing hydropower reservoirs. The latter does not imply building new dams, but rather accepting a more frequent and/or intensive oscillation of the water levels in some reservoirs and, in some cases, in the rivers below them.

      • Euan Mearns says:

        Correct, Euan. But I think reservoir level and flow rate restrictions etc. are likely to limit balancing capacity before the power consumption limit is reached.

        Agreed, suggesting that the existing and planned inter connectors (5.9 GW) may be close to the maximum balancing capacity.

        • Knut says:

          As the post says, minimum consumption is about 11GW, and hydro capacity is about 31GW. So why would reservoir level and flow rate restrictions be the limiting factor?

          It’s important to realize that very little of the 31GW is run-of-river. I can’t point to a written source for this claim, but to the best of my knowledge, absolutely all the major hydro installations are dams. They can all be turned to zero, at the same time, for days, with no problem.

          Obviously the dams fill up eventually, but they can handle huge volumes. It’s important to realize in this context that the dams were originally built to handle seasonal (not weekly or daily) variations. Water inflow is great in the summer/fall (when all the snow melts) and small in winter (when it snows rather than rains). So the dams are essentially dimensioned to carry the whole Norwegian power consumption through the winter (in a dry year). When you change the problem to one of balancing weekly swings in European wind, you are shooting sparrows with cannons.

          • robertok06 says:

            “When you change the problem to one of balancing weekly swings in European wind, you are shooting sparrows with cannons.”

            Mmmmh… EU-29 consumes about 2300 TWh/y… average of 6.3 TWh/day… but in winter it can be easily 50% higher, under particular weather conditions (very cold polar front)…. so around 10 TWh is a good estimate of a high electricity demand day
            Norway in no way has 10 TWh of storage on a daily basis to deliver…not even probably on a weekly basis.

            Correct my numbers if you think that I’m wrong, please.


          • Knut says:


            There are two physical measures here: a) the wattage Norway can absorb from DGNU (absent pumped storage) in a given second, and b) the storage capacity (water volume) of Norway´s dams.

            My point was that a) is the limiting factor for how much Norway can do to balance swings in DGNU wind, as opposed to b). You hit ceiling a) before you hit ceiling b). I was not saying that Norway can balance the entire European power supply.

            By the way, though, as Lars points out further down, the capacity of all the dams put togheter is about 84TWh. So about 8 days´ worth of European consuption, if your estimates are right. That is really quitte a lot.

            So again, even with pumped hydro, the point remains: the limiting factor is the wattage that can be absorbed/produced in a given second, not the storage capacity of the dams.

      • Knut says:

        Very little of it is run-of-river. It’s mostly dams.

        Really this question is quite simple. Without pumped storage, the balancing capacity is limited by Norway’s minimum power consumption. As you say, it is around 11GW. “A bit more in the winter” is a serious understatement, though.

        Obviously, if 11GW interconnectors are built, they work both ways, so they could balance 22GW of wind.

        But: if Norway builds a significant number of windmills ourselves (we haven’t yet, but there are plans), and if they are in the same weather system as, say, Germany, these must be subtracted from the balancing capacity. Though, are we sure northern Norway and Bavaria, say, tend to be in the same weather system?

        On the point of internal power connections: this problem is not as big as the post suggests. Most of the dams are in the west of Norway, close to where the UK and Scot interconnectors will start. The distance to the south, where the German interconnectors will start, isn’t great either. When you read about weakness in the internal Norwegian connections, this is mostly concerning connections northwards, which we can all but ignore in this context.

        • Knut: With 11GW of interconnectors you can send 11GW from Europe to Norway all the time or 11GW from Norway to Europe all the time. But if you want to send wind from Europe to Norway and get an equal amount of hydro back you have 11GW going one way for half the time and 11GW going the other way for half the time. So all you actually get is 5.5GW of balancing capacity.

          • Knut says:

            Aha. We are defining “balancing capacity” differently.

            I don’t see the relevance of your measure, though. Since the 11GW northwards is timed when the wind blows, and the 11GW southwards is timed when it doesn’t, the net is that the arrangement gives you (a little more than) 11GW of stable power in the south from wind + the interconnectors.

            This connects with another issue in your original post. You assume that Norway needs to import about as much as it exports. Historically, that has been the case, but going forward, all experts predict a power surplus in Norway+Sweden in 2020 due to a buildout of new “green power”, induced by the Norwegio-Swedish “green certificates” scheme.

            However, and sadly for us in this context, much of this will be wind and run-of-river hydro (there aren’t any good spots left to build dams).

            So: that assumption of yours is probably wrong, but also my assumption that Norway in the future could import 100% of consumption when the wind blows in Germany.

          • Knut: Yes, we’re defining it differently. I suggest we leave it at that. 🙂

            The Norwegio-Swedish “green certificates” scheme targets adding 26.4GWh of renewables generation in Norway and Sweden by 2020, which works out to about 8GW in terms of new installed capacity. I don’t know how close Norway and Sweden are to achieving this, but 8GW is only a fraction of the ~60GW of wind power that’s already going north in my DGNU example (~100GW if I add in solar). So I’m not sure it would make all that much difference, although I haven’t done the sums.

        • robertok06 says:

          “Though, are we sure northern Norway and Bavaria, say, tend to be in the same weather system?”

          Bavaria has almost NO wind turbines!… Bavaria is the heaven of photovoltaics, wind is mainly concentrated in the north of DE… therefore it gets the same weather conditions as DK, NO, SE, BE, NL… a couple of hours later than UK, IR, most of the time.

  7. One of the side issues that bears on the future use of Norwegian hydro is the emissions-reduction plan Norway recently submitted to the UNFCCC in advance of the Paris-Conference, which binds Norway to a 40% reduction in GHG emissions by 2030 – the same as the EU28. Norway can’t meet this target by decarbonizing its electricity sector because it’s already decarbonized, and 40% decarbonization of its oil and gas, industrial, transportation and/or agricultural sectors within the next 16 years is a goal achievable only in computer simulations. So how does Norway plan to meet it?

    The aim is to fulfil the emission reduction target as a collective delivery with the EU and its member states. Norway will enter into a dialogue with the EU on an agreement for the collective delivery of the climate target.

    Although it doesn’t spell it out Norway clearly intends to use its hydro to earn carbon offsets from the EU. The problem is that to earn enough offsets to reduce its emissions by 40% it would have to process far more power through its reservoirs than they could possibly handle. But Norway is one of the “greenest” countries in Europe and is unlikely to be deterred by such considerations.

    • Euan Mearns says:

      Norway is one of the “greenest” countries in Europe

      In 2014, Norway produced 85.6 million tonnes of oil and 97.9 million tonnes of nat gas. I’ve not done the sums, but I’m pretty sure that on a per capita basis (perhaps even on an absolute basis) Norway will be the biggest producer of CO2 in Europe. If they were really serious about cutting global CO2 they would leave their remaining oil and gas reserves in the ground – like it seems the USA intends to do with coal, maybe, for a couple of years at least.

      • Norway isn’t the biggest per-capita CO2 producer in Europe – Luxembourg wins hands down – but it is above average. This is partly because of its O&G sector and partly because of the heavy industry cheap hydro attracts. (Note that Norwegian oil and gas that gets exported and consumed elsewhere isn’t included in Norway’s emissions.)

        But Norway still has a strongly liberal perspective on green issues. It has a CO2 tax and an emissions trading scheme and in 2012 it purchased over 20 million UN carbon offsets so that it could outperform its Kyoto target (there’s dedication for you). At one point Norway also had a goal of reducing emissions to zero by 2050 but I’m not sure whether it still stands.

        • Hugh Sharman says:

          No Roger! Bunkum! Greenwash! You must have written the foregoing just to annoy me personally!

          I assume Euan is correct (he always is) in stating that in 2014 Norway produced and mostly exported 85.6 million tonnes of oil and 97.9 million tonnes of nat gas from which, since the 1960s, it has become one of the richest per capita nations in the history of mankind.

          So assuming that all these hydrocarbons turned into CO2 (a pretty fair estimate) Norway exported 105 tons of CO2 per capita in 2014.

          • Peter Lang says:

            Go to Global Carbon Atlas, select emissions, then units, then either territorial or consumption to compare countries by emissions produced or consumed in country. Rank countries in table or histogram.

          • So when we look at per-capita production rather than per-capita consumption we find that the Norwegians are the world’s number one carbon polluters (although the Kuwaitis might run them close). Life is full of surprises 🙂

  8. jacobress says:

    Fig 10 shows DGNU + Norway can get a steady “base load” supply from wind, of 7.9 GW.
    DGNU have, now, (combined) maybe 60GW wind capacity already installed. So, you need about 8 times capacity + inter connectors + Norway – to get a steady baseload supply from wind.

    Plus: this base-load is limited – you can’t expand it, no matter how many more turbines you build.
    Correct ?

    • DGNU had about 50GW of installed wind capacity in 2013, so the ratio would be closer to six.

      By adding wind turbines and beefing up interconnectors in proportion you can make your baseload generation as large as you want. With 100GW of wind capacity and 11.8GW of interconnectors you would in theory double your baseload output to 15.8GW. The problem is that you would also double the amplitude of the swings in Figure 11, and I’m not sure Norway’s hydro installations could handle that.

      • Peter Lang says:


        I don’t understand how a country (e.g. UK) can get more base load power from wind and Norwegian hydro than the capacity of the interconnector (excluding base load generators in that country or other interconnectors). When the wind isn’t blowing the maximum power from Norway would be limited by the capacity of the interconnector. Am I misunderstanding something?

        • I was wondering when someone was going to ask that. Here’s the way it works using my DGNU baseload case as an example:

          Hour 1: DGNU generate 20GW. 7.9GW of this goes to baseload, 5.9GW goes to Norway and the remaining 6.2GW gets curtailed.

          Hour 2: DGNU generate 10GW. 7.9GW goes to baseload, 2.1GW goes to Norway and there’s no curtailment.

          Hour 3: DGNU generate 5 GW. All of it goes to baseload and 2.9GW comes back from Norway to make up 7.9GW.

          Hour 4: DGNU generate 2GW. All of it goes to baseload and 5.9GW is imported from Norway to make up 7.9GW.

          Hour 5: DGNU generate 1GW. 5.9 GW is imported from Norway, making only 6.9GW. This is one of the 5% of occasions when the 7.9GW threshold isn’t met.

          With 5.9GW available from Norway you can always make 7.9GW as long as DGNU wind generation is 2GW or more.

          • Peter Lang says:

            Thank you for that explanation. I understand now, how you did it. Am I incorrect that there are
            times when wind generates virtually no power In the UK? That is certainly the case in the Australian National Electricity Market, which claims to be the largest grid in the world by areal extent. So I would expect base load power to be always available.

          • robertok06 says:

            @Petr Lang

            “Am I incorrect that there are times when wind generates virtually no power In the UK?”

            Yep!… it happens very often… right now the Gridwatch site linked on this page gives 0.57 GW from wind!…and it has been like that (even lower earlier in the day) since last midnight… 16 hours and counting.

            There’s no way that this could work, practically.

          • Peter Lang says:


            I should have finished my previous comment with a clearer statement. I suggest for wind plus storage to be classed as base load, it should be able to produce power 100% of the time. There will be times when generators and transmission systems fail that bring the availability of Norwegian energy storage system to well below 95% availability. Therefore, my suggestion is for Hour 6 = 0 GW is the one that should be the base load. And this is limited by interconnector capacity as well as the energy storage capacity of the reservoirs for the worst case scenario of low inflows over a long period and sustained high electricity consumption.

            When you do the cost analysis I suspect the nuclear option plus gas for peak and intermediate generation would be by far the leas cost option. But probably not with the EPR power stations.

  9. Hugh Sharman says:

    An excellent post, by the way! Very thought provoking!

    • Lars says:

      It`s an excellent post regarding the calculations, but the headline`s assumption is unfortunately wrong from the start because Roger mixes the reservoir capacity`s potential (84,3 TwH) with the present and planned interconnector availability from Norway to DGNU (the Skagerrak interconnector is 1,7 GW btw., not 1 GW) and the present generator capacity available.

      Who ever stated that Norway can become a true “battery” in the sense reported in the press without pumped hydro?

      These present and planned HVDC interconnectors to DGNU (in total 5,2 GW, the Scottish interconnector is not in the planning) are ALL the Norwegian grid can handle up till 2021. I have never seen anyone state anything else, and first and foremost not Statnett.

      Roger quotes from the joint Norw.-German declaration, but he omits a very important sentence further down:

      “By making its storage capacities available, Norway can help replace large amounts of fossil and nuclear generation in other countries with wind and solar energy. Of course, Norwegian storage can only be a part of the solution.”

      Yes, PART of the solution, from the German perspective at least they realise this. Please note, I do not take any stand here whether more wind and solar makes sense at all.

      It would be far more interesting if Roger could scale up his calculations to one of CEDREN`s scenarioes where Norway possesses an additional 20 GW of pumped hydro.

      He will find lots of information available here:

      Two articles of special interest might be:

      • Leo Smith says:

        “Who ever stated that Norway can become a true “battery””

        …Understood that there are primary and secondary batteries. Norway is either a primary battery, or a secondary one that gets recharged by rainfall. 🙂

        IF you have hydro that is not adequate in terms of rainfall to meet average demand, but is adequate in terms of peak capacity to meet peak demand, adding wind or solar to it makes good sense.

        Not as much sense as adding nuclear – Switzerland has the lowest carbon intensity along with france in Europe with an ideal mix of nuclear and hydro (both countries are trying to get rid of the nuclear energy that gives them that advantage).

        Hydro is a massively good and useful way to follow peak demand, and as much baseload demand as there is rainfall. Adding more baseload generation capacity is the ideal way to augment it – adding intermittent renewables is one of the worst, but its better than nothing.

        • Lars says:

          I know you are a nuclear fan also and I won`t argue against nuclear. It`s up to you Brits to decide which way to go with your sources of electricity in the future.

          But regardless of you developing 20-30 GW of new nuclear or not I can`t see how a couple of interconnectors to Scandinavia (2,8 GW) could harm British interests. In fact one of France`s few problems with nuclear is that it`s so cheap it has created a large market for electric resistance heating meaning trouble when they have a spell of very cold weather like in February 2013. With new nuclear you could face the same problem and a few interconnectors could come in very handy, and also for exporting surplus power of course.

          • Peter Lang says:


            From my perspective what makes sense is the mix of technologies that is best able to meet requirements for the life of the plants. The most important requirements are, arguably, energy security, reliability of supply and cost of electricity.

            France has demonstrated that a generator mix with near 80% nuclear can meet requirements for a large industrial country and do so with near the least cost electricity and near the lowest CO2 emissions intensity in Europe. That’s got to be near ideal. Pumped hydro, if cheap, would be an ideal match with nuclear to provide peak power. So, I agree the interconnectors you suggest, if coupled with sufficient pumped hydro energy storage capacity in Norway, could make sense – IF the economics makes sense. But does the economics make sense, or is gas peak and intermediate generation a cheaper option?

          • Lars says:

            Peter, I agree 100% with your first statement about cost, reliability and energy security. I didn`t realise you are Australian before now, but it`s amazing you don`t have nuclear power with all your uranium resources. Correct me if I am mistaken.

            About your second part, I doubt that gas peak and intermediate generation would be cheaper. Hydro, whether conventional or pumped has much shorter ramp up time than CCGT and is far cheaper than OCGT from what I know. The World`s longest HVDC interconnector so far, the NorNed between Norway and the Netherlands had a pay back time for it`s construction costs in less than two years actually. With the huge elspot price difference at the moment between Norway and the Netherlands it has been running flat out in direction south for years now, so it`s actually providing base load not balancing.

            France has a lot of hydro and hydro storage which the UK don`t, that`s a major difference. If the UK were to have a lot of new nuclear interconnector hydro could be a good part solution for balancing and security I suppose.

          • Peter Lang says:


            Thank you. The Australian public is very strongly antinuclear. Australia is the only G20 country that doesn’t already have nuclear or is in the process of getting it.

            Regarding the cost of pumped hydro versus gas for intermediate and peak power, it would depend on the country. Clearly, hydro and pumped hydro would be ideal for countries that have viable sites. But Australia doesn’t.

            By the way, just for interest, here is a conceptual study for a pumped hydro scheme between two existing reservoirs in the Australian snowy mountains scheme. It’s 9 GW average capacity and 400 GWh energy storage capacity. There is one major technical issue, and a few other lesser issues, that make it not feasible.

          • Leo Smith says:

            Interconnectors would not of themselves do anything but good to anyone.

            The only issue is the cost and the benefit.

            Are they value for money? Or do they use up scarce resources that could better be deployed elsewhere?

            This is a problem I constantly run into arguing policy with ‘greens’ To me, as an engineer, the best solution is the one that fits the human physical needs at the lowest possible cost in any way you wish to interpret cost.

            To a Green the best solution is one that ignores human physical needs, and meets political and ideological and human emotional needs instead, with no regard for the cost, human or otherwise of implementing it.

            I accept that emotional needs are in a sense real human needs, but pandering to them is not ever a good way to address them.

          • robertok06 says:

            ” In fact one of France`s few problems with nuclear is that it`s so cheap it has created a large market for electric resistance heating meaning trouble when they have a spell of very cold weather like in February 2013. ”

            Back in 2013 almost nothing happened!… the thing you report is a urban legend, frequently used by anti-nuclear people (note: I’m not saying you are one of them). The reality is that during a week or so France did not export and had to import from neighbouring countries at a much higher price… meaning they lost some money. No big deal.

            I’d take that any year in the future, rather than having to look out every morning to see wether there are clouds and/or wind or not.

            I just read on an energy blog in italian an interview with B Burger, of the Fraunhofer Institut, where he claims that in the future Germany will store electricity under the form of heat… and claims that this will be a “high efficiency” technology… beats me if I understand how they plan to do it, to beat the Carnot INefficiency with low-quality heat???? It’s simply crazy.

      • Lars:

        Comments that set me straight are always welcome!

        Having said that, let me respond to some of yours.

        Roger mixes the reservoir capacity`s potential (84,3 TwH) with the present and planned interconnector availability from Norway to DGNU

        I have in fact assumed that Norway’s reservoir capacity is infinite. I mention that power delivery to and from Norway will be limited by how fast reservoir levels etc. can be allowed to vary but don’t make any allowance for that either because I can’t quantify it.

        the Skagerrak interconnector is 1,7 GW btw., not 1 GW) ……. present and planned HVDC interconnectors to DGNU (in total 5,2 GW, the Scottish interconnector is not in the planning) are ALL the Norwegian grid can handle up till 2021. It would be far more interesting if Roger could scale up his calculations to one of CEDREN`s scenarioes where Norway possesses an additional 20 GW of pumped hydro.

        Thanks for the correction on Skaggerak. But all reducing combined link capacity from 5.9 to 5.2GW does is cut baseload generation from ~7.9 to ~7.3GW. Adding 20GW of pumped hydro makes no difference. Transmission is limited by link capacity, not hydro capacity. Although with more hydro you could of course add more links.

        ”By making its storage capacities available, Norway can help replace large amounts of fossil and nuclear generation in other countries with wind and solar energy. Of course, Norwegian storage can only be a part of the solution.”

        Electricity consumption in the EU28 is presently around 3,000TWh/year. According to my calculations processing wind power from DGNU through Norwegian reservoirs via 5.2GW of interconnectors would add ~14TWh/year. To claim that this will help replace “large amounts of fossil and nuclear generation” is misleading to put it charitably.

        Thanks for the Cedren links. I’ll check through them as time permits to see if anything of interest drops out.

        • Lars says:


          “I mention that power delivery to and from Norway will be limited by how fast reservoir levels etc. can be allowed to vary but don’t make any allowance for that either because I can’t quantify it.”

          This is estimated by CEDREN. They have chosen lower and upper reservoirs where water level will rise/sink by a maximum of 13 cms/hour which according to them is seen as acceptable for salmon and other criterias. If the water and energy authorities will accept this is another case. Thus they have established that 20 GW can be developed with new tunnels etc. between existing reservoirs. If you lower the criteria of course potentially a lot more but with more environmental damage.

          “Adding 20GW of pumped hydro makes no difference. Transmission is limited by link capacity, not hydro capacity. Although with more hydro you could of course add more links.”

          Of course. Who would construct 20 GW of pumped hydro in Norway without the corresponding links? That would be one of the most meaningless projects in the history of mankind 🙂

          It may look as I am a big fan of this scheme but I am not, I am just quoting research that claims it is possible. I don`t want all those new pylons most of all.

          • Peter Lang says:


            You mention that CEDREN estimates 20 GW of pumped hydro is likely to be viable in Norway, assuming the interconnectors are economically viable too. Can you tell me what is the estimated energy storage capacity of the pumped hydro plants, in TWh. It is defined by the storage capacity of the smaller of the top and bottom reservoir.

          • Lars says:

            Peter, that`s a bit complicated to answer. In have not found reservoir storage capacity in GWh/TWh for most reservoirs in Norway on the internet. In most cases it is only given in cubit meter content of water, not energy content unfortunately. CEDREN doesn`t tell directly either, but I calculated the upper reservoir energy content by multiplying the effect of the power plant with running days until the reservoir is empty. Thus I arrived at 7763 GWh reservoir capacity. I was a bit puzzled by this number and thought my calculations were wrong because the reservoirs in the study include the biggest one in Norway, Lake Blåsjø which in itself has a capacity of 7800 GWh, more than what I concluded. But I soon realised it is because the new pump storage power station associated with Lake Blåsjø will have a higher head than the existing power station and thus will never be able to drain the lake empty. It will only be able to drain maximum 2352 GWh from the reservoir if I am right. It makes a lot of sense since it will increase the total output from the reservoir slightly on an annual basis. This could be the case with several of the other reservoirs also.

            But this is only part of the story. CEDREN has developed 3 scenarioes with different effects and pumping. Of the new capacity only part is with pumping, the rest is co-called “effect power stations”, in reality just adding more installed capacity to existing power stations without pumping.
            So please note, the 7763GWh/7,76 TWh of upper reservoir capacity is solely for the pumped storage power stations, not the “effect” power stations.

            Scenario 1: New power 11200 MW with 5200 MW pumping and 6000 MW effect

            Scenario 2: New power 13600 MW with 9200 MW pumping and 4400 MW effect

            Scenario 3: New power 20000 MW with 10000 MW pumping and 10000 MW effect.

            I did not calculate the lower reservoir energy content but it is much smaller. In some cases these lower reservoirs are actually not the lowest in the power system but also function as upper reservoirs for power stations further down.

          • Peter Lang says:


            Thank you for the estimates of energy storage capacity for CEDREN’s 20 GW pumped storage. I’d suspect they may have designed the smaller reservoir for about 10 hours generation at full power on average. Therefore, a lower limit might be 200 GWh of storage for 20 GW capacity. They’d probably assume pumping each night for say about 6 hours giving about 4 h storage each night. So they could not generate 10 hours at full power every night. This would be the case if the power for pumping is supplied by base load plants.

            I find it hard to understand how the economics could make sense if the power for pumping is to be supplied by intermittent renewables; large amounts of energy would need to be stored during part of the year to use when demand is high and wind power generation is low. The cost of the system for very low capacity factor would mean it wouldn’t be financially viable if pumping was to be using high cost, intermittent, unreliable power

          • I think one of the purposes of the pumped hydro would be to provide balancing capacity for wind. Although with all that untapped hydro potential I can’t imagine why Norway would want to install any wind turbines in the first place.

          • Peter Lang says:


            I don’t see how it can be anywhere near financially viable. To pay for pumped hydro you need to sell a lot of energy at a high price margin between buy and sell price. A rule of thumb is that buy price needs to be at least 4x sell price and use it to near full capacity for most days of the year. That means reliable , low price power every night. Wind doesn’t supply reliable low cost power every night.

            If you pump and store energy during periods of excess wind and generate from storage during months of low wind power, the pumped storage plant would have a very low capacity factor and would need enormous storage capacity in both reservoirs.

            Norway may have well located natural lakes with large surface area and high head in close proximity. If no manufactured reservoirs it may be feasible, but I suspect it would be in the order of 3x better cost-benefit if it was to be powered by base load and recharged nearly every night of the year.

          • Lars says:

            Peter, about the economic viability of this scheme (I know you addressed Roger but I`ll give a brief answer), I think you think too much in terms of an “ordinary” pumped hydro scheme, ie. where you essentially have you recharge the upper reservoir every night. In the CEDREN scheme that will not be the case. The smallest reservoirs will take days and the biggest ones weeks to empty even at full production. In addition all are reservoirs with natural inflow. Recharging will potentially take place not only during the night, but at any time the oversized German (and other countries) wind and solar system yield too much to be used in Germany itself or in other countries.

            This is happening frequently, I notice this week`s Blowout link to an article about Germany`s neighbours having to protect themselves from the power flows from wind and solar. This is reflected in the highly erratic pricing of German power, sometimes even with negative wholesale prices.

            Having said that I think nobody has made serious calculations yet. CEDREN`s study does not involve the economic viability, just the technical side from the reservoir point of view. I hardly think all these new pumped hydro and “effect power stations” will be built.

          • Peter Lang says:

            Lard thank you again. I do understand all of what you said. However it is not persuasive for me. It’s about the energy flows. I need to understand CEDREN financial and cash flow results, assumptions and methodology, but just at a very high level. I need to know that this has been done by accepted competent financial analysts. We need to be able see that the capital cost of the scheme, including the interconnectors, plus the annual operating costs can Be paid by annual revenue over an acceptable amortisation period.

            More simply, can the annual revenue pay the LCOE each year?

          • Peter Lang says:

            Lars, another way to roughly evaluate the comparative financial viability of pumped storage recharged with intermittent renewables versus reliable base load, is to compare on the basis of three factors:

            1. Average Capacity factor of the two alternatives,

            2. Average Buy/sell price of electricity,

            3. Capital cost per kW.

            If parameters 1 and 2 are equivalent or higher for the option with intermittent renewables, and parameter 3 is equivalent this option may be viable.

            For the option recharged by reliable base load power each night and assuming say 4 h generation at full power every day of the year, the capacity factor would be 16.7%. Is the option recharged by intermittent renewables higher than this? Recall that the recharge would be done over months of high wind power and drawdown would be over months of low wind period. So, can the capacity factor be higher than for the option recharged by base load?

            The sell price would need to be at least four times higher than LCOE for the option recharged by base load to be viable. Is that likely? I doubt it is, given that wind power is much higher cost than off peak base load power.

            The option recharged by renewables would need orders of magnitude more storage, so the storage would have to be in natural lakes, not man made dams. If dams are required, the capital cost would be far higher for the option recharged by intermittent renewables.

            This explains why my gut feeling tells me the option recharged by intermittent renewables is highly unlikely to be viable. New Pumped hydro energy storage is rarely economically viable anywhere nowadays, except in a vey few very favourable locations. Little new pumped hydro capacity has been built for decades.

        • Lars says:

          “Electricity consumption in the EU28 is presently around 3,000TWh/year. According to my calculations processing wind power from DGNU through Norwegian reservoirs via 5.2GW of interconnectors would add ~14TWh/year. To claim that this will help replace “large amounts of fossil and nuclear generation” is misleading to put it charitably.”

          Roger, sorry but I am not sure if I understand this. First you are talking about balancing and now total consumption in the EU28?

          Are you saying that 5,2 GW of hydro can only balance 14 TWh/year of wind and solar?
          Does it mean that 25 GW of conventional + pumped hydro (CEDREN`s estimates) can balance about 67 TWh of wind/solar turning it into base load?

          • Lars: What I’m saying is that 5.2GW of interconnectors will balance only 14TWh/year. With the 2013 wind data (the 2012 wind data give very similar results, incidentally) an average of 1.6GW of wind power flows north through the interconnector during the year and an average of 1.6GW flows back south, and 1.6GW*8760 hours = 14,016GWh, or 14TWh.

  10. Owen says:

    Does anyone know if the interconnectors will provide synchronous or non synchronous power ?

    • Leo Smith says:

      If you mean will they be DC, the answer is yes. The losses associated with high power cables in conductive seawater offset any losses in the AC->DC->AC conversion process.

      To be sure the cables have only reactive (capacitative) coupling to each other and to the sea, but that is more than enough to create very large put of phase current flows that interact with the cables resistance to produce heat.

      By using DC, all those AC losses are eliminated.

  11. jacobress says:

    Another interesting question: Norway has 31 MW capacity hydro, but only about 14 MW peak demand.
    What caused them to build so much hydro capacity (dams) – much more than they can use ?

    • Lars says:

      No Jacob, wrong numbers. Peak demand is 22+ GW in winter, maximum ever about 24,5 GW.

      Since electric resistance heating and electric heat pumps are the dominant sources of heating the difference between summer and winter consumption is very large. That is why the abundance of reservoirs and hydro capacity was developed in the first place. Since water inflow is very low during the cold season it is the only way to store enough power.

      You can see a graph of typical drawing and filling of the reservoirs according to season here:—per-prisomrade/

      • Lars: As you may have noticed from Figure 5 I’ve already been into the Statnett web site, but speaking not a word of Norwegian I can’t figure out what the graphs are. But the drawing and filling one you link to is interesting enough to bring up now that I know what it is (I’ve put percent on the Y axis and week on the X-axis, which I think is right). It suggests that Norway’s reservoirs would have the most difficulty handling wind & solar surges in or around April when water levels are at a minimum, correct?

        • Lars says:

          Roger, first here is link to Nordpoolspot which has an overview of Norwegian, Swedish and Finnish reservoir levels in thousand GWhs on a weekly basis. Here you have the exact numbers for each week and it may be more useful:

          I think the answer to your question is a definite no. For instance this year the minimum level (for Norw. reservoirs) occurred in week 18 with a comfortable 24829 GWh left. In addition you have to factor in the snow level reservoir that is about to melt at that time. Snow level reservoir is calculated by the Norw. Water Directorate and some power companies and used in the planning of hydro production. For a critical situation to arise BOTH reservoir level and snow level would have to be minimal at the time you mention.

          Combining this with the graph from Statnett you will see that the lower line is the minimum level between 1993 and 2014. A minimum level of 17,3% still gives 17,3 x 84,3 TWh = 14583 GWh left.

          Another thing to factor in is that all the interconnectors developed or in planning towards DGNU are placed in elspot area 2 (South-West Norway). This area has a combined reservoir capacity of 32725 GWh + the largest hydro capacity. This area usually has smaller swings in reservoir levels than the other ones also.

          • Lars: Thanks for the Nordpool data. It looks like the kind of thing I’m looking for but I can’t figure out what the numbers in the left column, like 29-15 and 51-14, mean. Can you tell me?

        • jacobress says:

          If there is a wind surplus in winter (as is usually the case), Norway can use more imported (wind) electricity in winter, when their demand is highest, thus saving water in the dams, just when inflow is low and water scarce. Makes sense.

          • Lars says:

            That`s true Jacob. Denmark usually has a power surplus in winter both because wind production is higher and they have to run their CHPs to produce both heat and electricity. Especially at night and weekends. Sending surplus production to Norway and Sweden and receiving peak power and balancing services in return makes a lot of sense AS LONG AS they have chosen the path of wind turbines of course :))

      • Peter Lang says:

        Larson, you said ” Peak demand is 22+ GW in winter, maximum ever about 24,5 GW.”

        For comparison, the max and min demand in Australia’s National Electricity Market is about 17 GW and 34 GW.

        Therefore, 20 GW of cheap nuclear running at 85% average capacity factor and 20 GW of pumped hydro and/or gas generation would meet base load and peak power with 6 GW reserve capacity.

        However, to be economic compared with Australia’s cheap coal the LCOE of nuclear in Australia would have to be reduced by a a large margin. And we’d need Small Modular Reactor plants of less than about 500 MW per unit for most states’ electricity grids. Reactors of about 180 MW would be ideal, like the mPower, if cheaper than coal. That’s what is needed, ASAP.

  12. Lars says:

    Roger, it`s week number 29 in 2015, week number 51 in 2014 and so on. The GWh reservoir storage number is for the end of each week of course.

    • Thanks Lars. I was hoping they would be hourly data 🙁

      What I’m trying to find out is whether Norway’s existing hydro facilities can achieve and sustain ramp rates of ~3GW/hour for several hours, which is what they would have to do to support exports of “smoothed” wind power in the DGNU case. Ramp rates of over 5GW/hr are needed to smooth out the solar spikes in the Germany wind + solar case. I’m not sure these would be achievable.

      • Lars says:

        Roger, perhaps the best way to find out about ramping capabilities is to contact Statkraft, the biggest hydro producer. I have no idea if they are willing to supply such information but you could give it a try.

        On the linked page I suggest you send an email to the spokesperson for press contact first (Knut Fjerdingstad), maybe he can direct you to personell who can answer your question.

  13. Olav says:

    Some interesting links.
    below an easy to read Norwegian reservoir info.
    Next how low a good hydro inflow can press price down. Looks like Latvia and Litauen lack interconnectors to Sweden.
    Next El price during the day in Denmark, The evening cooking time usually result in maximum price.
    This effect is worse elsewhere where solar is the big renewable source.

  14. ducdorleans says:

    assumption “Power is always available for export from Norway when and in the amounts needed.” is a very critical one !

    that “always available power” has to come from either hydro or pumped hydro

    does anyone have any idea
    – what the total energy stored in Norwegian hydro is ?

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