Large scale grid integration of solar power – many problems, few solutions

by Roger Andrews

On Sunday, July 7th, 2013, a day of unbroken sunshine and low demand, solar PV generated approximately 200 GWh of power, over 20% of Germany’s total electricity production for the day. (I’m indebted to CleanTechnica for the bar graphs):

And because peak sunshine and peak demand are more or less coincident on summer Sundays in Germany there was no serious problem admitting all of this solar electricity to the grid:

There was, however, one minor difficulty. The surge of solar power caused generation to exceed consumption for about ten hours and as a result about 13% of it, shown by the orange bars at the bottom of the graph above, had to be exported to other countries in the Central West Europe market region. The graph below moves the orange bars up to the top to illustrate the size of the surplus relative to consumption:

Surpluses like this are of course not large enough to cause a problem, and can in fact be eliminated simply by backing off a little on other forms of generation. But solar supplied only 5.7% of Germany’s total electricity generation in 2013, and if this is as far as it ever gets it’s not going to move Germany very far along the path to sustainable energy. Solar has to get much bigger to do that, and here we will briefly examine some of the obstacles that stand in its way.

How much bigger does solar have to get? Market analysts have predicted that it could ultimately supply 25% of Germany’s electricity, so we’ll use that as the target. Meeting it would require scaling up by a factor of 4.4 relative to 2013, with annual solar generation increasing from ~30TWh to ~130TWh and installed solar capacity from ~35GW to ~ 150GW. We can’t of course predict what consumption will be when and if this happens, but if 150GW of solar PV capacity had been in place on July 7th, 2013, this is what the generation mix would have looked like:

There would have been huge oversupply of solar electricity. Solar would have generated ~800 GWh, representing about half of total German electricity generation for the day, but only about 200 GWh of it could have been admitted to the grid, barely more than was admitted to the grid in 2013, all other things being equal. So in this example expanding PV capacity by a factor of 4.4 would have increased solar penetration by a effectively zero. (Note that the numbers given here and later in the text are scaled off graphs and are therefore approximate, although this does not impact the basic conclusions.)

However, conventional generation would presumably have been cut back to accommodate as much of the solar surplus as possible, and the graph below summarizes the impacts of doing this. By cutting conventional generation to zero between 8 am and 5 pm (wind, hydro and biomass generation are left unchanged) about 450 GWh of solar, representing about 45% of total generation, could have been admitted to the grid. But this still leaves a surplus of about 350 GWh:

And July 7th was a fairly typical summer Sunday. The solar surplus would have been similar on most weekends during the summer of 2013. Weekday surpluses would have been smaller because weekday demand averages 10-15 GW higher than weekend demand, so more conventional generation could have been taken out of service to admit more solar, but weekday surpluses would still be on the order of 150 GWh/day. The average of the weekend and weekday surpluses would be around 250 GWh/day.

A rough calculation based on these numbers indicates that if Germany installs enough PV capacity to supply 25% of its annual electricity consumption, and if no storage capacity or other means of matching production to load is available, and if the load curve remains substantially the same as it is now, about 20% of the solar electricity would have to be “spilt”, meaning that Germany would actually obtain only 20% of its electricity from solar. Additional PV capacity could be added to increase the solar contribution, but most of the added generation would get wasted because there would be nowhere to send it. Clearly the approach of expanding PV generation without anywhere to store the surplus power is not viable.

The question therefore becomes, is there any way of storing solar power surpluses for short-term re-use? Not with solar PV using existing storage technology. But it could be done with concentrated solar power (CSP), which uses heliostats to reflect solar energy into heat-retaining reservoirs containing a fluid (usually molten salt) that delivers steam to conventional turbines both when the sun is shining and when it isn’t. CSP plants can in fact act as load-following or even baseload capacity if enough storage is available, and this capability has been demonstrated at the Gemasolar CSP plant in Spain, which last year completed 36 days of continuous 24/7 operation. (Even Forbes was enthusiastic.)

So why aren’t there more CSP plants? Because a) they aren’t suitable for domestic use and b) they are much more expensive than solar PV plants.

But capital costs are actually not all that much higher. The Gemasolar plant (technical details here) is an example. It has a rated capacity of 19.9 MW and cost 230 million euros to build, which works out to 11,500 euros per installed KW, roughly five times the cost of a 19.9mW PV plant. Ofsetting this, however, is the fact that Gemasolar produces ~110 GWh a year, about three times as much as a 19.9 MW PV plant would produce, and at a much higher load factor (officially 63%, with recent estimates of up to 75%).

How can a solar plant have load factors this high? Because 19.9 MW is the capacity of the turbines, not the capacity of the solar array. The heliostats that melt the salt that produces the steam that drives the turbines in fact have a capacity of 76 MWe (304,750 sq m at 2,172 KWh/sq m/yr), giving an installed cost of slightly over 3,000 euros/KWe, not that much higher than the cost of an equivalent PV array. The 17% load factor calculated using the 76MW number is also comparable to the ~18% average for PV plants in Spain.

On a levelized cost basis, however, CSP electricity is about twice as expensive as PV electricity, with the Fraunhofer Institute estimating levelized costs at 6-10 euros/KWh for PV and 14-19 euros/KWh for CSP. But as Fraunhofer points out: “the advantage of the ability to store energy and the dispatchability of CSP …. was not taken into account.” How big an advantage is this? In the case of Germany very big indeed, because with CSP it could generate 25% of its annual electricity from solar with effectively no spillage at all.

So what’s not to like about CSP? Three things. First, it doesn’t work very efficiently at 50 degrees latitude, but for the purposes of analysis we can consider Germany as a generic example that would apply to sunnier countries closer to the Equator, such as the US.

Second, CSP storage can smooth out only short-term fluctuations. It can’t smooth out the huge seasonal changes in solar output that occur at higher latitudes and which are usually anticorrelated with demand. The next two plots of total monthly electricity generation and solar generation in Germany illustrate the problem (data from Fraunhofer):

Even with solar providing only 5.7% of Germany’s electricity, as it did in 2013, Germany would have to install about 8 TWh of storage to convert the seasonal fluctuations in solar output into continuous baseload generation, and at the 25% level it would need over 30 TWh. Installing this much storage capacity in Germany or anywhere else for that matter is far beyond the bounds of feasibility (current worldwide pumped storage capacity amounts to only 1 TWh). With 25% annual CSP generation Germany would therefore get 40-50% of its electricity from solar in the summer when it least needs it but only about 5% of its electricity from solar in the winter when it needs it most. So while expanding CSP capacity will have a positive overall impact on Germany’s renewable generation mix it will do little or nothing to reduce the requirement for large amounts of conventional backup generation.

Note: Some of the winter shortfall could theoretically be filled by wind power, which is positively correlated with demand over the seasonal cycle in Northern Europe, but integrating large quantities of wind power with the grid poses problems of its own. These problems were discussed in earlier posts here, here and here.

Third, it would be roughly three times cheaper for Germany to add low-carbon generation capacity by building nuclear rather than CSP plants, and nuclear delivers power at a steady rate without the need for storage and whether the sun is shining or not.

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137 Responses to Large scale grid integration of solar power – many problems, few solutions

  1. Euan Mearns says:

    Roger, the issues you describe here are the same that I describe for wind in Scotch on the ROCs. At low levels of penetration, renewables can be accommodated by switching other stuff off – simple load balancing. But once peak renewable supply exceeds demand, which is always going to happen with large scale penetration of a stochastic source, something has to be done with the surplus and there are only three options 1) export, 2) storage and 3) curtailment. Germany can currently export because the level of renewables penetration in the many neighbouring countries is lower and they have capacity to absorb the surplus. But once renewables penetration rises in these neighbouring countries all will have surpluses simultaneously and the energy will have nowhere to go.

    Storage of course solves this problem but it has to be grid-scale, efficient and cheap, otherwise it will be ineffective and expensive to use. The storage issue should ideally be solved in advance. If there was an easy solution it would already have been found. Chemical storage, that is scalable, tends to have a round trip efficiency of about 30%, hence 70% of the worlds most expensive electricity may be wasted. Thermal storage is potentially a better option.

    My guess is that within a couple of years this reality begins to dawn on the renewables enthusiasts (fantasists) which somewhat surprisingly includes many of our electricity utilities and some of our senior scientific advisors.

    • Ed says:

      We haven’t got any alternative but wait for the storage issue to be solved. However to delay the build out of our renewable energy infrastructure (as well as reducing world population) will doom humanity’s future. If the storage issue is not solved then we will just have to adapt our lifestyle to the energy production reality. ie reduce our electricity consumption and only use it when it is available.

      • Euan Mearns says:

        Bbbbbut, what about nuclear?

        • Ed says:

          You keep on making a case for nuclear, Euan, and I’ll keep listening. Keep up the good work on your blog.

        • Exactly. We toured Diablo Canyon nuclear station Wed. Two generators. Two reactors. We stood next to one generator producing >10% of all Calif. power. We could put our arms around its input shaft from the turbines. The generator is no bigger than a stretch Escalade. The two in the turbine hall generate >20% of Calif. power from a few pounds of Uranium per hour. Nothing comes close in power density or cleanliness.

          It’s important to grasp how diminished our environmental problems would now be, if we’d followed this lead: and been deploying 1GWe of nuclear power each week by 1980.

          Now, we need twice as much as we think:

    • Hi Euan: The only stochastic variable affecting solar is cloud cover. Otherwise the amount of incident solar radiation at any place on the Earth’s surface at any time is predictable. And this predictability is the problem. With wind it’s possible to see storage technology eventually coming along that would allow us to smooth out short-term wind surges provided they’re not too large, but with solar we know we have little if any chance of ever being able to store enough energy to smooth out the huge seasonal variations. We’re beaten before we start.

    • Bas says:

      Germany started with a successful battery storage program (= 30% subsidy on the investment) for only small (30% in price before 2020 (mass production & installation).
      It takes most of the evening peak away, though not in the cold dark months; Nov, Dec, Jan.

      For those cold month people can now install a micro-CHP when they have to replace the boiler that heat the house. Most of these micro-CHP use a Sterling engine to generate electricity. The Sterling engine is very quiet and requires not more maintenance than the old boiler.
      It generates only electricity when heat is needed, so only when you are at home in the evening and need heat as well as electricity.

      New nuclear is no real solution as it costs at least two times more than solar+wind+storage, when you compare without the subsidies (especially nuclear gets big subsidies).
      The cost price of electricity produced by old, 100% written off, NPP’s is already higher than that of solar & wind, if all subsidies (direct visible and indirect less visible) for nuclear and solar and wind are accounted for.

  2. Hugh Sharman says:

    Nice paper Roger but I winced every time I read “gWh” rather than GWh! So I winced alot! OK!! I am a pedant and probably very boring!

    Now imagine what will happen if/when Germany’s EU partners go in for solar power in a big way, whether as CSP (almost unthinkable at that price) or PV, where overall costs continue to fall, albeit much more slowly than in recent years.

    PV in Europe is time correlated across the whole of this (rather small) continent. So the expedient of exporting PV peaks, already causing friction with the neighbours, is no longer available. Storage, probably with batteries, becomes the only technically practical option. The costs and massive inefficiencies for storage at this scale, especially if it is to be “inter-seasonal” (as hydrogen) have not been properly thought through.

    There is actually a similar issue with wind power, particularly in NW Europe, where wind output is highly correlated across the region. So inter-connectors, that require a willing buyer and seller at each end, already experience wind surpluses and deficits simultanously. No prizes for guessing why Norway, with almost no wind power, is laughing all the way to the bank every time the wind blows in one of its inter-connected countries, being Denmark, Netherlands and soon, Germany.

    With the present financial arrangement, it buys low cost spot electricity when there are local wind surpluses and sells back balancing power at up to three times that cost.

    • Roger Andrews says:

      Hugh: I grovel at your feet. The source of the solecism, apart from inattention on my part, was the helpful Microsoft word processor that turns lower case letters into capitals when you don’t want them to and vice versa. When I get the chance I’ll go back and change things to preserve my professional integrity 😉

      The main point I was trying to make is that solar is different to wind because of the enormous storage requirements needed to balance out seasonal solar variations, which far exceed the capacity of any known or foreseeable storage technology. Balancing could of course be achieved by linking German solar with an equal amount of solar in New Zealand or Australia, but somehow a Berlin-Auckland interconnector doesn’t sound very feasible either. You’re certainly right in saying that this problem hasn’t been thought through.

      • Bas says:

        So the German Energiewende scenario includes:
        – more wind than solar (wind blows more in the autumn and winter);
        – a fair amount of biomass/waste + hydro (together ~15%);
        – grid extension. E.g. when the wind blows in the north then it is quiet in N-Spain and vice versa.
        – storage; pumped storage, batteries, power2gas and power2fuel
        – Further development of Geo-thermal. They have some, but the potential is big.
        Further development requires more advances in earth sensing technology (bigger computers, more smart computer programs, better sensors needed). So reliable predictions can be made about the amounts of hot water a mile deep, it’s temperature and it’s composition).

        • Math Geurts says:

          Unfortunately, untill now half of the high costs of the Energiewende went to the premature deployment of PV. At the moment that most jobs in solar factories were already lost and even more jobs in installment would be lost it appeared to be political suicide to confess that this was not a smart choice in a country far from the Equator.

          As a result of the fear for such a clear confession many German homeowners prefer to stay addicted to the hopium of small scale PV, now “new” i.e. with subsidized batteries.

  3. roberto says:


    as far as I know, Germany’s storage of surplus electricity under increased PV and wind capacities is expected/planned to be accomplished mainly via Norwegian pumped hydro.
    There is a nice paper by Eurelectric, 2013 or 2012, which deals with the potential storage capability of each EU country, plus non-EU ones like Switzerland, Norway and Turkey, the latter having the bigger potential, if I remember well…. if I find the time to look for it I’ll post the link here.
    CAES, hydrogen and/or methanol obtained via electrolysis or other electrochemical process have, on paper, large potentials too, but bigger losses (H2,methanol,etc…) and bigger physical constraints (CAES)… and bigger costs too.
    In those cases the problem shifts to acceptance of the Norwegian people to become the storage of Germany… a very profitable operation but would require drilling thousands of km of tunnels to connect different storage lakes, with lots of new ones being created… already now some Norwegians are asking why they should accept their countryside to be dramatically changed like that.
    In the case of Turkey, the main problem would be to transport the tens of GW from Germany to Turkey, and back… possibly months later (storage in May-Aug to be used in Nov-Feb)… with huge transport losses (several 1000s km distance), plus the evaporation from the lakes (a far from being negligeable issue!). Economically would be a disaster, environmentally difficult to implement (how many countries along the path

    Cheers,and keep up with the good job… this blog is great!


    • Bas says:

      You forget Switzerland and Austria. As with Norway those countries mainly do ‘virtual’ storage.
      If electricity is cheap at the spot market, they import and throttle their own hydro production.
      If it is expensive, they open the gates and produce max. which is exported.
      Nice earnings.

      This behavior is one of the reasons the 35 pumped storage facilities in Germany make losses.
      All building of new pumped storage has stopped (even installations that were half way were stopped), as predictions are that they cannot compete at all after 2025 as by then battery storage will also be very cheap.

  4. Hugh Sharman says:


    Norway has not got a single kW of pumped hydro. However, its system is roughly 99% hydro which can be readily turned up and down, therefore this 15 GW system can effectively act as a giant “battery” which is what it does for windy little Denmark.

    Problems arise in dry years when Norway relies on fossil and nuclear neighbours to keep its own lights on!!

    A 1.6 GW inter-connector will soon connect Germany with Norway, so Norway’s possibilities for storing German’s 35 GW of PV and 32 GW of wind power are limited to 1.6 GW.

    Norwegians are pretty reluctant to build any new hydropower.

    As regards Turkey, acting as Germany’s energy store, I believe Turkey will other more important things to do, energy-wise for its own people! That’s a new one for me!

    • Lars Evensen says:

      Mr. Sharman: Fyi Norway has about 1,5 GW of pumped hydro, all of it integrated with ordinary hydro power stations. In addition, the “passive” storage and deliver capacity (non pumped hydro) estimated to be available by importing surplus electricity from the continent when the wind is blowing and sun shining and exporting hydro in the opposite situation is estimated to be around 10 GW. This could be an important contribution to balance the central European and even British grid short term, ie. for a few days. Likewise, 6-7 GW could probably be added for Sweden. There is of course also a potential for a lot more pumped storage in both countries.

      Mr. Roberto: However this article discusses the problems with solar pv power and among others the seasonal changing nature of pv. Norway and Sweden combined have 84 + 33 (= 117) TwH hydro storage capacity. Although a huge “battery”, this is mainly meant for storing electricity for the winter season when demand is very high in both countries. There is no chanse that the Nordic reservoirs can act as seasonal storage for European solar power whatsoever, and frankly, Turkey doing so seems like an even wilder dream to me.

      • Roger Andrews says:


        Norway and Sweden combined have 84 + 33 (= 117) TwH hydro storage capacity.

        Thanks for the data. These numbers include both conventional and pumped hydro capacity and not just pumped hydro, correct?

        Do you happen to know how they were calculated?

        • Lars Evensen says:


          These numbers are given by NVE (the Norw. equivalent e.g of the British Ofgam) in their weekly reports where among others the status (ie. water levels and corresponding available power stored) of the Nordic reservoirs is given.
          84 + 33 TwH storage is of course a theoretical level demanding that all reservoirs are 100% full which never happens, but in wet years they sometimes reach 90%+ just before the winter season.

          Yes, they include pumped and conventional hydro, but pumped is miniscule in comparison. The numbers are calculated for each reservoir system with their associated hydro power station(s) and multiplied for water levels, actually for each elspot area. This link should give you an idea of it if you watch graphs. Nordic reservoir level patterns btw. are remarkably similar to US natural gas storage graphs.

          • roberto says:

            “84 + 33 TwH storage is of course a theoretical level demanding that all reservoirs are 100% full which never happens, but in wet years they sometimes reach 90%+ just before the winter season.”

            Even under these optimistic assumptions, filling to the top and emptying to the bottom all possible and conceivable reservoirs of Scandinavia… 117 TWh is equivalent to LESS than 20 days of storage of the average EU electricity consumption (2200 TWh/year,right?)… meaning it wouldn’t work once all/most big countries move to this bogus “renewable” scheme…. PV needs to store over 3-4 months in order to get it back (70% of it, no more!) during the period Nov-Feb!… there’s no way to escape to seasonal variability, unless some green genius finds a way to straighten the tilted axis of rotation of the earth (which would make things much worse, by the way…).

            The craziest thing of them all is that the greens want to cut down all of the 900 TWh generated in EU by nuclear!… unbelievably stupid.


          • Euan Mearns says:

            Lars, are you able to say what peak Norwegian and peak Swedish electricity demand is. And also what the peak capacity is for each country. The way this system works, the import balancing capacity of Norway and Sweden will be limited to their own consumption since they switch off hydro and run on imported wind and solar when such surplus is available. Once Norway is running on 100% imported renewable surplus it cannot import any more (without pumping). Similarly, export capacity will be limited to their max production capacity less their own consumption, adjusted for the capacity of inter connectors and storage.

            As already pointed out by many commenters, this system of balancing wind off Scandinavian hydro works well for tiny Denmark. But it is impossible to store a summer surplus of solar for use in winter time in this way.

          • Thanks for the graphs Lars:

            I speak no Norwegian but I interpret Figure 1 to mean that total hydro storage – i.e. the amount of water above Norwegian dams – changes by +/-50 TWh in an average year because of changes in seasonal electricity demand. Is this right?

          • Hugh Sharman says:

            and rain and snow melt of course!!

          • Euan Mearns says:

            Roger, part of the story is that dams are emptied in winter when it is cold and precipitation falls as snow and they fill in the spring and summer as the weather turns milder and the snow melts and it rains, rains, rains in west Norway.

          • Lars Evensen says:


            Peak Norwegian demand is about 24,5 GW in an extremely cold period, normal peak in the winter about 20-22 GW. Practical maximum production capacity about 26 GW with 25 GW of it hydro, the remaining gas powered plants.

            For Sweden I think the peak consumption number is pretty much the same or slighly higher at 26 GW. If they are fortunate with no trips of big hydro generators I think they can produce about 13,5 GW hydro. In the last years they have had lots of problem with their aging nuclear generators so 8,5 GW is the realistic maximum level, again if they are “lucky”. That makes 22 GW. In addition you can add about 4-5 GW from conventional thermal (coal, peat, wood and oil), mainly CHP.

            You are totally correct in your assumptions. And the balancing capacities in the existing system of both countries will be rather limited during the winter and virtually non existent in peak periods of the day then. During the rest of the year capacities are present. Storing solar power seasonally is pure fantasy.

            However, if more generators with pumping capacity along with more connectors are built, I think the Nordic reservoirs have the ability to balance part of the European grid for days at a time, not just hours like most continental pumped hydro. This will cost huge sums of money, the interesting question will be who will foot the bill for all this.
            I don`t know about the Swedes, but the Norw. public is extremely sceptical about this to say it the least.


            Yes, 50 TwH is about correct.

      • Hugh Sharman says:

        Thanks Lars, I stand corrected!

    • roberto says:

      What? No pumped hydro in Norway? How do you think that Denmark balances its wind production?

      Anyway, the paper I was referring to should be this one…,d.ZGU

      … and this one too is not so bad:

      … that’s where Turkey’s potential comes into play… it’s not that I had made it up myself!

      As far as costs related to new pumped hydro projects is concerned, there is a very recent project in southern Italy, in Campolattaro, by the swiss RWE company… 10 GWh total storage capability (average daily electricity consumption in Italy is 850GWh)… so this stores 17 minutes of italian consumption… 6 years to build and 600 million Euros spent… I let you reach the obvious conclusions…

      (it’s in Italian, but the numbers are clear)



      • Hugh Sharman says:


        Thank you.

        Denmark depends on Sweden and Norway’s hydropower lakes, not pumped hydro, to balance its wind power.

        I stand corrected by Lars Evensen (scroll up) who points out that stretching the normal definition of pumped hydro a bit, there is 1.5 GW of “pumped hydro” in Norway. This achieved by interconnecting various existing hydro-power lakes which are at different levels. There is no pumped hydro in the classic sense of a purpose-built, upper and lower lake and this is not much used to balance Denmark.

        Lars seems to believe Norway can balance roughly 10 GW of European renewables. I respect his view, of course, but have vivid memories (here in Denmark) of “dry years” (eg spring 2010-2011) when Norway needed months of high net imports of fossil and nuclear power to prevent those lakes from emptying. When push comes to shove, Norway will protect its own security of supply.

        Its existing inter-connectors with Sweden, Netherlands (1 GW) and (tiny) Denmark (2 GW by December this year) will shortly be increased by 1.6 GW when the German – Norway inter-connector is commissioned will enable all parties to assess whether there will be a practical upper limit or not.

        I, conclusion, think all of us in this forum seem to agree that ~15 GW/84 TWh Norway cannot be Europe’s wind power battery. We just have different ways of saying the same thing!

        I agree that this is a very informative and interesting energy blog!!

        • roberto says:


          Thank you.

          Denmark depends on Sweden and Norway’s hydropower lakes, not pumped hydro, to balance its wind power.”

          What do you mean “not pumped hydro”??? It IS pumped hydro!… they pump water UP in their lakes/reservoirs/dams and get it back later…with a roundtrip efficiency of 75%…meaning each heavily incentivized MWh of Danish wind looses 25% of it on the road to Norway and back.

          Intermittent sources are inherently inefficient, from start to finish…


          • Hugh Sharman says:

            No Roberto!

            The rain falls, the snow melts and the Norwegian, purpose-built-with-dams, hydropower lakes fill up. When they draw down water, they generate electricity. The hydropower can be turned up and down very rapidly to balance the imports and exports of electricity flowing through the inter-connectors.

            Lars has explained that very clearly!

          • Lars Evensen says:

            Roberto, you are totally wrong here. The relatively small Norw. pumped hydro scheme was originally not constructed to balance the grid or export/import, but is largely a seasonal pumping to prevent water losses when demand is low. This was the original reason for building pumped hydro here, but in recent year with Danish and German wind power it can also be used to import very cheap surplus energy from them to refill some reservoirs of course.

            Like many have pointed out, the only good reason why Denmark can integrate so much wind power is because they are surrounded by three much larger power systems that can give them back-up when the wind is not blowing, or as a place to get rid of excess wind power at times also. The “success” (?) of the Danish system can thus not be copied anywhere in the World. How the Nordic system works can easily be seen in the link below, and spot market pricing is the main factor for the direction of the energy flows.
            As of writing we have the rare situation that Denmark sends surplus power to both Sweden and Norway during daytime, although it is actually surplus German power because of the trophical storm “Bertha”.


            I agree this is a very interesting blog, and with a plethora of commentators alternating between the most wildly optimistic RE “fanatics” to more pessimistic ones.

          • Bas says:

            Norway simply throttles its (hydro) electricity production. So when imported electricity is cheap the country lives on imported electricity. So they consume imported electricity immediately.
            When the price is high in NL/Germany/Denmark they produce with all (hydro) capacity in order to earn as much money as possible (the interconnection capacities are the bottleneck).

            Thought that Oregon in USA does something similar.

            According to my definition this is not pumped storage as no pumps involved.

          • Willem Post says:

            I suggest, before making uninformed comments, you google hydro power to learn about the different configurations, then google hydro power in Norway to learn about ITS pumped storage capacity, MW, which is next to nothing. That means no upper and lower reservoirs, etc.

            In Spain and Portugal there is significant pumped storage capacity, which is used when Atlantic weather fronts pass over the Iberian peninsula to store a part of the wind energy, with the other part being consumed.

  5. Glen Mcmillian says:

    An excess of unneeded and non storable wind or solar power costs nothing other than the lost opportunity to use it.The real question is how much it will cost or save to integrate a larger solar capacity into the German and western European grid.

    Engineers and economists in the past have rightly based their calculations on running whatever utility capacity is built at pretty close to max most or all of the time with only a little back up capacity off line as the usual state of affairs.

    But in other lines of work and business it is quite common to have substantial extra capacity that is idle most or all of the time.If you go to a big construction job you will find bulldozers and trucks and cranes sitting around more than they are being used. I have tractors on my farm adequate to meet my maximum needs. They sit in the shed almost all the time with only one of them being used a few hours on a weekly basis year around.

    If that twenty five percent of capacity does ever get built then it will be utilized to whatever extent it does produce everyday of the year.In Germany it will not produce much more than half of its potential day in and day out due to the cloudy weather and long nights winter time will result in even less production.

    The VAST majority of days there will be no problem with surplus production.

    If the engineers can solve the load balancing problem and if the pv industry can supply say just fifteen percent of German needs on an annual basis then that means saving close to fifteen percent of the countries expense for imported fossil fuels.Over time the implications of such savings are simply enormous in terms of the prosperity and actual security of the German people.

    I read a lot of history and politics and I can assure anybody interested in such things that the Russians have not forgotten WWII and that they will not forget WWII for at least another thirty or forty years when the children of the people who lived thru it are dead.

    I am not a cornucopian believer in technology but I do believe that the problems associated with the intermittency of renewable energy are manageable thru both technical innovation and changes in lifestyle.

    The real potential for saving our ” business as usual” way of life over the next few decades lies not in more generation but in more efficient use and less waste of the electricity we are generating already.

    Given time the solutions will come. LED lights use less than a third of the energy old incadescents use and substantially less than fluorescents. Insulation can be retrofitted to older houses and buildings and newer ones can be built to use hardly any energy at all for heating and cooling.

    Renewable energy at three times the costs we are used to paying today will still be affordable if we can achieve three times the efficiency in the use of it. That is probably beyond being accomplished but maybe doubling efficiency is within reach.And we may have to just get used to a somewhat curtailed lifestyle in terms of energy use.

    I may be wrong but I am confident that in ten years the price of a compact battery electric car with a hundre mile range will be comparable to that of an ordinary car and that such cars will be quite common and selling as fast as they can be built.Such cars and electric water heaters could suck up and store a substantial amount of fuel cost free solar electricity on a really good sun day.Refrigeration machinery including home refrigerators could be easily built to accommodate the use of cheap solar power and draw hardly any power at all on cloudy days.There must be dozens of ways to take advantage of fuel cost free electricity when it is available once it IS available. The question becomes one of the chicken and the egg.Which is first to arrive?

    And while they are simply to expensive to contemplate as storage these days batteries may become cheap enough to install them in individual homes sooner or later.The falling cost of batteries and the increasing efficiency of appliances in homes may eventually result in a boom in the battery industry and employment of electricians who can install and tie them into the grid.Batteries could eventually serve very well in storing a few percent of a households weekly consumption of electrical energy. Such savings add up.e

    Taken all around the thing that disappoints me about this article is that it focuses on Germany as if Germany makes or breaks the case for solar power.

    But we all know that Germany is is poorly situated both geographically and climatically in terms of solar power.

    Now if about ten million industrious German craftsmen and engineers could be transplanted to let us say the great state of Texas…. solar power would in my estimation look pretty damned good on paper and spreading out across the empty countryside.

    Incidentally I am in favor of building as many new nukes as can be gotten thru the permitting and financing bottlenecks. Speaking again as a long time observer of people and politics I can say with confidence that not nearly enough are going to be built to alleviate our fossil fuel depletion troubles over the next few decades- not here in the West at any rate.

    • Willem Post says:

      “An excess of unneeded and non storable wind or solar power costs nothing other than the lost opportunity to use it.”

      That is pure nonsense, as it costs at least 34 eurocent per kWh to generate PV solar energy (average of legacy costs) under the ENERGIEWENDE program; the energy is “sold”, wholesale, at 3-4 eurocent/kWh or lower. See page 29

      • Glen Mcmillian says:

        The average cost of all solar production is not the proper metric to use.The only value lost is the production on a day it cannot be used. And so far as I know it is all being used and probably all that is ever going to be generated probably WILL be used because as solar capacity continues to grow so will the capacity of the grid and businesses and consumers to continue to use it.

        It costs a certain amount per hour in dollars to run my tractors over the life of the tractor.That figure including fuel if I assume fuel costs are constant at present levels for a couple of decades comes to about thirty dollars per hour not including my personal time.My tractors are among the smaller ones used commercially. Some farmers have tractors that cost well over a hundred dollars per hour to operate.

        If I use them a few days less per year the overall average cost of owning and running them in comparison to the amount of work I do with them changes by only a trivial amount.The same situation applies when solar generation is considered.

        The amount of solar electricity that will not be well utilized on a day when and if a day comes that it cannot be utilized is going to be trivial in comparison to the total annual output.

        Ways will be found to put it to good use before it is produced in any serious excess quantity for any appreciable amount of time.

        Just about every kind of business has excess capacity that is poorly utilized. Stores sit empty most nights. Hotels are seldom full more than a few days out of the year on average.Cars and trucks sit many more hours than they are driven and not too many manufacturing facilities run around the clock and around the calendar.

        I believe the time is coming when excess electrical generating capacity on good days will be looked at in just the same fashion as I look at my larger tractor. It is there so that I can do what I must do on the days I need it. The rest of the time it just sits there.

        The situation with solar power is going to be better though because however much the solar industry can generate any given day will certainly be put to good use in saving on fossil fuel purchases on that day.

        • Willem Post says:


          “The only value lost is the production on a day it cannot be used”

          Based on my 30 years of experience in the utility sector, I have to say sorry, but utility industry accounting does not work that way. This is something that would never pass by the CPAs in the utility sector.

          However, for RE aficionados, who usually have no, or near-zero, experience in the utility sector, such creative accounting appears to be no problem.

          “And so far as I know it is all being used..”

          But the article clearly states, and the PRODUCTION graphs show, some of it is exported!!

      • Willem Post says:


        The below table shows the lack of solar energy in Vermont during winter months. About a 4 to 1 variation from summer to winter. Germany’s irradiance is about 20% worse.

        PV solar energy is almost not “present” in Germany, in winter.

        It also shows, for 12 months, the New England on-peak rates, $/kWh, and the on peak value of the energy, $/month.

        The average of the on peak rates is 8.14 c/kWh, solar-energy weighted it is 6.98 c/kWh; both are high because of the gas shortage last winter. Normally, they would be about 7 c/kWh and about 6 c/kWh, respectively.


        Solar energy occurs during the ISO-NE defined “On-Peak” period of 7 AM – 11 PM. The cost of energy of any large SPEED solar facility up to 2.2 MW, connected via a substation, to Vermont’s high voltage grid, should be compared against the solar-energy, weighted-average, wholesale price, as follows:

        1) Determine the local irradiance, kWh/m2/d, for 12 months. See URL.

        2) Monthly irradiance x the days of each month = monthly solar energy production, kWh. The annual solar energy production is 1,265 kWh per kW of panels. That is for NEW, CLEAN panels, snow/ice-free, facing solar south, at the proper fixed angle. Most owners get less.

        3) Monthly wholesale rate, $/kWh x monthly solar energy production = monthly solar energy value, $/mo. The annual solar energy value $88.36
        Open July 8, 2014, “Monthly Data by Load Zone” spreadsheet, go to bottom of page, click on VT tab, monthly wholesale prices, $/kWh, appear.

        4) Divide ($88.36/yr)/(1265 kWh/yr) = $0.0698/kWh. This is the solar energy-weighted, annual-average wholesale price. This value is high, because of the winter gas shortage; a more likely value would be about $0.065/kWh.
        PV solar is disruptive, variable, intermittent energy, that requires special coddling and balancing for accommodating it to the grid, as Germany has found out in the Bavaria, etc. Therefore, it is worth LESS than 6.50 cents/kWh.


  6. Willem Post says:


    This is an excellent article with good graphics that clearly makes the point many of us have made during the past few years and as more of us will make in the future. Only by repetition will the truth of RE follies finally sink in.

    NOTE: The only reason Denmark has been able to maintain its expensive wind folly and its associated worldwide wind PR campaign is because of Norway’s and Sweden’s hydro plants.

    I like the way you connected it with CSP, which even in rich Germany would be an economic non-starter. Even in poor Spain, which much greater irradiation, it is too expensive for its economy.

    For Germany, modular nuclear, supplemented with 5 to 10% wind, 5 to 10% solar, 5 to 10% biomass, 5% hydro is the most economical way to go for the next 150 years.

    Economical storage should be invented and deployed during that time. It would minimize the use of the world’s diminishing fossil fuel, including Russian gas.

    • Ed says:

      150 years ! Humans need to survive the next 50 first. World population increasing to over 9 billion while oil available on the export market goes down to zero.

      • Glen Mcmillian says:

        Hi Ed

        It became perfectly obvious to me some time back that the regulars here don’t believe in fossil fuels ever running short or resource wars or resource nationalism or give any thought to the necessity of paying for imported fossil fuels in the event they do continue to be available on a regular basis.

        • Ed says:

          It’s human nature Glen; bit like having cancer. Cancer happens to someone else, not me. Fossil fuel depletion will happen to future generations, not to me. When the first symptoms appear, you deny it. When diagnosed, it is a shock but you still hope for the best. Technology will come to your rescue. Renewables, nuclear. Perhaps, perhaps not. Perhaps it may be terminal. Finally you come to terms with it what ever the outcome.

          PS I don’t have cancer, by the way. Just clearing that up. ….. or do I. No, just kidding.

          • Euan Mearns says:

            Ed, this is a peak oil blog with a difference. I believe we have entered an era of energy resource constraint that may well be acting on society like a cancer. But I also believe that human and social adaptability perhaps offers the best opportunity to find a way through. It is absolutely certain that Earth will have a maximum carrying capacity of human beings and an optimum one. But where do those boundaries lie? 7 billion, 9, billion, 20 billion?

            There is a large multitude of very complex issues that go way beyond CO2 emissions will fry the planet and we need to return to Medieval living to survive. I’m not saying you are an advocate of that, but where does the truth and the right balance between humans and nature and the planet lie?

          • roberto says:

            Well, you may be right, on the other hand you and all the other RE fanatics (if you are one of them, of course) are just proposing to cure the said cancer with wishful thinking and some “natural” ointments, rather than undergoing some unavoidable life-saving surgery.

            The green mantra says “just install enough PV and wind and everything’s going to be fine”.
            No, it won’t!… the bottom-up approach is known the be wrong… you simply can’t make use of ANY extra watt*hour past a maximum penetration of this two technologies… that’s already known since years and years, but the green intellighentsia running the show over here in EU has been good at keeping it off the screens of the non-technical people… they hope that when it will turn out to be the case there will be already enough PV and turbines that they will simply be impossible to discard and go back to other more effective ways of de-carbonizing the production of electricity while containing the cost of the kWh.

            After all, all you need to do is to look at the CV of those who decide!… literature, history, law… that’s what they’ve studied in college… practically all of them!… Connie Hedegaard?… Maria van der Hoeven?… Segolene Royal (and her precedessors)?… a real tragedy.


        • Ed says:

          Just to add. You are right. Many of the people making comments on this site are in the “cancer, I don’t have cancer, I’m not wasting money on cancer treatment” camp. As they would put it “energy scarcity, we won’t have energy scarcity for hundreds of years, I don’t want to spend money on renewable energy capacity”

        • It became perfectly obvious to me some time back that the regulars here don’t believe in fossil fuels ever running short …

          Glenn: Please read some of the recent posts on this topic. You will find that the “regulars” are very much aware of the fact that fossil fuels will eventually run short.

          • Glen Mcmillian says:

            I am guilty of ”artistic license” today more honestly referred to as exaggeration. You are correct of course.

  7. Daniel Simon says:

    This post poses an interesting hypothetical problem that is at least 20 years into the future, and then assumes a complete lack of creativity and intelligence on the part of a very smart country.
    Seems like electric vehicle batteries, fridges/freezers and hot water tanks could easily soak up the extra load–that is if the Germans aren’t smart enough to come up with an even better use, maybe shift some night-load back to daytime…they could grow carrots in the basement if worst came to worst.

    And by the way William Post, if you assume Germany were to install 4x as much solar as it currently has, the cost of the solar will be (34 + 3Y)/4 where Y = is currently something like 10 eurocents and falling. so maybe 16 eurocents at most.

    • Could you please explain how “electric vehicle batteries, fridges/freezers and hot water tanks could easily soak up the extra load” for:

      1. A summer daytime generation surplus of 450 gigawatt-hours

      2. A cumulative summer generation surplus of 30 terawatt-hours

      Thank you

      • Glen Mcmillian says:

        Vehicle batteries hot water heaters and such are by themselves not going to soak up a really good days excess solar generation unless electric vehicles become the norm and maybe not even then. But it is reasonable to expect industry to find ways to take advantage of some of that excess and probably almost all of it – if and when it materializes.

        Some possibilities that occur to me are batteries installed in homes and businesses that can be cheaply charged so that fossil fuel plants can be further throttled back to some minor but useful extent.Many industries spend a lot of money on fuel to generate heat to operate whatever machinery they use- installing electric heaters to supplement coal fired and gas fired furnaces at such industrial sites might prove to be quite economical depending on how much ” surplus” solar juice is available.It seems likely to me that some pumped storage facilities will be built because although they are expensive they work like a charm to balance loads so long as they are not out of water in the upper reservoirs.

        And while I am on expert in such matters by any stretch of the imagination I am encouraged to think that very large batteries based on relatively new technologies but common and affordable materials can be built at reasonable cost in the not so distant future.Such batteries will be big enough and durable enough to withstand thousands of charge discharge cycles and so useful in shifting loads from peak solar and wind hours to peak load hours- assuming of course that they prove to be affordable. There is little doubt that they can be built.

        It might even prove practical to just dump any solar electricity energy not immediately needed into an underground water reservoir that is used in the winter to supply heat to a large scale ground source heat pump.

        Some industrial processes will probably prove to be worth operating them preferentially when cheap solar or wind power is available in preference to more expensive fossil fuel generation.

        We do most of our irrigation here in the US with diesel when using deep wells as the water source but if very cheap electricity were more widely available in farm communities farmers would switch to electrically powered pumps. Irrigation is not so sensitive to time frames that starting and stopping the flow is a big problem as a general rule. So long as the pumps run enough hours in a week it doesn’t really matter which hours – assuming you have enough pumps of course to meet your needs without running all of them continuously.

        It may be necessary to move a lot of water in the future a good long way to supply European farms and cities and if small reservoirs adequate to meet a week or twos needs are built close to the final destination of the water it will be economical to pump it to the extent possible with wind and solar power.If the reservoirs and pipelines and pumps are large enough it might be possible to use wind and solar power exclusively to do the pumping perhaps supplemented with off peak nuclear.

        The decision making tipping points involving capital cost and variable costs in undertakings involving energy are changing and in the future fuel cost are going to be far more important than they are today in comparison to fixed capital costs.

        A perhaps overdrawn example is this : My old delivery truck is only used a day a week and sits six days but it has long been paid for and if gasoline were still cheap I would drive use it at least ten more years since a day a week is only roughly equivalent to two years of more or less daily use.

        But I am going to get rid of it soon and buy a truck that uses less fuel because the potential fuel savings are more than enough to offset the increased capital expense of a newer ( more efficient) truck -even though I use it only one day a week.

        If I used the old truck three or four days a week the fuel savings would be so compelling I would necessarily have gotten a new truck years ago.Of course the analogy fails at some point because if I actually had been using the old truck on a daily basis it would long since have been worn out beyond repair.

        Efficiency, conservation, storage and improvisation are going to take us a long way toward solving the intermittency issue.

        In the end unless the public can be persuaded to go nuclear on the grand scale we are just going to have to get used to living with whatever intermittency problems persist.

        All the old folks I know used to swear they would never give up their full sized American cars and trucks for compacts but over the last twenty years most of them have in fact switched to much downsized and far more efficient cars and trucks.Their kids are continuing the movement to downsizing and I expect that by the time I am ninety or so the biggest cars around are going to be about the size of todays compacts.The littlest ones are going to be about the size of enclosed go-carts and getting well over a hundred mpg on gasoline or diesel and the first forty or fifty miles on battery power.Half of us will be walking or riding bicycles or buses by then even here in the US.

        • roberto says:

          “Half of us will be walking or riding bicycles or buses by then even here in the US.”

          Glenn: I don’t know where in the USofA you are based, but after having lived and worked in Texas and Tennessee for several years, I can guarantee you that your statement will never become reality!

          No way that “the masses” will ride bycicles and buses in Dallas between April and October, it is simply unbearably hot most of the day (and often at night)… same for TN, and all of the southern states?… cycyling in Mississippi in scorching summer heat/humidity???… would kill people by the thousands/day!


    • Willem Post says:

      You did not read the referenced article. The LEGACY costs of PV solar are about 34 eurocent/kWh end 2013, per official data.

      Under ENERGIEWENDE, new PV solar systems, built in 2014 sell their energy at about 15 eurocent/kWh

      • Bas says:

        Small (rooftop) solar systems get 12.8cent/KWh.
        Bigger installations (<10MW) get 9.8cent/KWh.
        Tariffs still going down with 1%/month.

        • Math Geurts says:

          “Essentially, the main issue is that people who consume their own solar power but do not go completely off grid still need the grid. But grid costs are passed on to consumers in Germany as a surcharge per kilowatt-hour of power consumed, not as a monthly fee. So those who need the grid, but do not consume much power pay less.”

          “The term “grid parity” often raises the question of “parity with what?” As the study points out, solar has not reached parity with the grid if, by that, we mean that going off-grid (a solar array with battery systems) is cheaper than a solar roof that uses the grid as a battery.

          The authors have quite a straightforward proposal to solve the problem: a flat fee for a grid connection at around 250 euros for a family of four, equivalent to slightly more than 20 euros a month. While such a flat fee would reduce the incentive for power conservation, it would make the entire bookkeeping process easier, and – more importantly – would more equitably reflect the actual costs per household.

          I’ll leave the conclusion up to the authors, who end their study with the following statement: “We have to realize that PV arrays are only affordable from the owner’s viewpoint; a macroeconomic calculation leads to a different outcome, particularly in terms of an equitable sharing of the cost burden.”

          And now German owners of solar roofs are fond on subsidies for batteries.

        • Willem Post says:

          As a result of these low compensation values, PV MW installed per month has decreased; 2000 MW may not be achieved in 2014.

    • roberto says:

      Hi Daniel,

      funny, your name is exactly the same as my former french neighbour… who also thinks that PV is a great technology…
      The problem is that the 10 Eurocent value is bogus!… there is no such thing!… it’s an ad/commercial for/from the PV industry.
      One should quote the REAL kWh, available 24/24h, 365/365d… not only when the sun shines at noon!… and if one takes into account all of the necessary steps required for PV (and wind as well) to replace coal/lignite/gas/nuclear in a highly industrialized country such as Germany, the real cost of the kWh is way above the “16 eurocents at most” that you have quoted… make it double if not more.

      Batteries are not a solution for an entire country, no way, and hot water storage as well…. that’s wishful thinking… thermodynamics kills the efficiency of the process.

      Just think: all the efforts to de-carbonize the production of electricity in Germany made so far (more than 72 GW of combined PV and wind) will be zeroed when, in 10 years or so, the remaining 11 reactors will all be stopped… 90 something TWh/years to replace… in fact they will be mostly replaced by gas/coal/lignite… no way PV and wind will be able to do it… in 10 years???


      • Bas says:

        Germany’s efforts are not directed towards de-carbonize.
        The targets of the Energiewende (in order of priority):
        1. All nuclear out (done in 2022);
        2. 80% of consumed electricity renewable in 2050.
        Renewable share now 30%.
        Intermediate targets: 35% in 2020; 45% in 2025; 55% in 2030.
        Ultimately 100% renewable. In 2065? Discussions to upgrade the 2050 target is ongoing.
        3. Less GHG – CO2
        4. Cheap electricity
        5. Democratization of control over and production of electricity
        6. More robust. Thanks to highly distributed generation, they have already by far the most reliable grid in the world (<15min/year total customer outage time).

        Since 2001 Germany stopped already the 10 of its 19 nuclear reactors while decreasing FF produced electricity substantially. The electricity production increase by renewable is more than the production decrease of nuclear.
        So wind+PV (now 17%) together with other renewable, will indeed replace that 90TWh and also some coal.

        The real costs of wind+solar+storage in 2023 (fastest a new nuclear can start):
        Based on the German situation:
        – Only guaranteed FIT for 15yrs(wind) or 20yrs (solar). Not inflation corrected.
        Av. FiT now €90/MWh. FiT’s for new installations going down with ~4%/a.
        So in 2023 average FiT ~€63/MWh while going down further…
        Storage costs in 2023 ~€40/MWh. With 30% to be stored*), the av. storage addon is €12/MWh.
        So total costs in 2023 ~€75/MWh, going down further.

        Compare that with the planned Hinkley C nuclear plant (corrected for the subsidies):
        – inflation corrected guaranteed FiT for all produced electricity during 35years. Based on £92.50/MWh in 2012 prices. With 2% inflation that is £115 in 2023 (=€138/MWh) +
        – Major investment subsidy of £10billion, worth ~£800mln/a (=€31/MWh) +
        – accident liabilitiy limitation subsidy, waste and decommission liability subsidies, etc. =~€10/MWh
        So total costs in 2023: €179/MWh going up with inflation during 35years.

        • Math Geurts says:

          The term “grid parity” often raises the question of “parity with what?” As the study points out, solar has not reached parity with the grid if, by that, we mean that going off-grid (a solar array with battery systems) is cheaper than a solar roof that uses the grid as a battery.

          The authors have quite a straightforward proposal to solve the problem: a flat fee for a grid connection at around 250 euros for a family of four, equivalent to slightly more than 20 euros a month. While such a flat fee would reduce the incentive for power conservation, it would make the entire bookkeeping process easier, and – more importantly – would more equitably reflect the actual costs per household.

          I’ll leave the conclusion up to the authors, who end their study with the following statement: “We have to realize that PV arrays are only affordable from the owner’s viewpoint; a macroeconomic calculation leads to a different outcome, particularly in terms of an equitable sharing of the cost burden.” (Craig Morris)

          However: the solar sector is begging for subsidies on batteries.

    • Willem Post says:


      If frogs had wings…..

      Germany has no plans to install 4x as much as it currently has, so the 16 eurocent/kWh is not relevant.

      For EEG-2, Germany plans to add 2.0 to 2.5 GW/year by the end of 2030, 16 years, or 32 to 40 GW

  8. Lars, Hugh, Roberto, Euan et al.

    Thanks for your stimulating contributions!

    I probably should have made it clear in the post that the kind of storage I was talking about was new pumped hydro dedicated to storing surplus solar energy. Existing hydro and pumped hydro is already taken.

    Here’s another perspective on the scale of the storage needed. In December 2013 Euan posted an article on the proposed Coire Glas pumped storage project in Scotland, which would have a capacity of 30GWh and cost £800 million to build. To store a 450GWh solar surplus overnight we would need fifteen Coire Glases costing £12 billion. To store a 30 TWh summer surplus for winter re-use we would need a thousand costing £800 billion.

    And if that didn’t work we could always store the surplus in 25 billion, 100-ampere-hour twelve-volt car batteries. 😉

  9. Carl Hellesen says:

    Being a swede its kind of amusing to listen to continental Europe’s plans for Scandinavian hydro. I heard a radio interview with a german guy a few months ago, and he explained how Germany wanted to balance their wind and solar with Swedish and Norwegian hydro. In the end he added that it of course only works if we don’t build lots of wind power ourselves.

    Unfortunately for the german guy, in about a months time we will have a new government with the greens, and they are very keen on replacing reactors with wind power.

    And to complicate things further, people here have started to realise that hydro power has an environmental impact as well, and the permits for most hydro power stations were issued something like 100 years ago when the word environment hardly existed.The idea now is to revoke all permits for the hydro stations and let them reapply under today’s environmental laws.

    No one knows exactly what will happen, but the consensus seems to be that our hydro power will have to follow a more “seasonal flow” in order to keep minim flows in the rivers etc. Since the reservoirs are mostly filled by snow melt during late spring / early summer I guess we will have more limited opportunities for seasonal storage in the future. And I also guess that “reversing” the rivers to store german solar and wind power would be out of the question.

    I don’t know what the discussions in Norway are like, but its likely that the prospects for continental Europe to balance their intermittent power with Scandinavian hydro are limited. Rather the opposite, at least Sweden will probably need continental Europe’s fossil power to balance our own future system with a crippled hydro power and wind instead of nuclear.

    • Hugh Sharman says:


      That is very alarming news. You should read the latest posting at which chronicles the fast-closing, fossil-fuel fired, dispatchable capacity in and around our part of the world, including Germany. I live in Denmark.

      I trust the sturdy good sense of your compatriots not to be panicked into following the Germans into premature closure of your nukes. Nor unnecessarily degrading your excellent hydro capacity.

      Of course, Hitler was terribly keen on exploiting Norway’s hydro….so there is nothing new!

      • Lars Evensen says:


        the Danish TSO Energinet needs to come to its senses and create a capacity market as Bach says. I shall read Paul Frederic Bach`s new article with great interest. He has previously advocated keeping Denmark`s extensive network of small and medium CHPs as a partial solution to balance the grid by installing electric heaters that can soak up excess wind power when needed and substitute a lot of coal consumption in that process.

        This is a possibility that is little discussed elsewhere (?) and I wonder why. Both Denmark, Sweden and Germany have a very extensive network of district heating and why don`t heat it with surplus power at times? Perhaps it is the continental aversion against using electricity for heating purposes that comes to play here, considering it as “wasting”?

        Speaking of the dire situation in Denmark, just a couple of hours ago the relatively small coal fired plant “Avedøreværket” (250 MW) was ordered to cancel/postpone its planned maintenance “due to shortage of effect” as they put it. Pretty remarkable since it after all is the low load summer season still.

        I will give an answer to Carl Hellesen`s somewhat pessimistic outlook for Nordic hydro and nuclear later.

      • Carl Hellesen says:


        I guess its not so much a question of premature closure. 4 of the reactors have already passed, or will soon pass, 40 years of age. Its likely that they will have to close within 10 years anyway. This as the new strategy of the antinukes in Sweden today. Make sure that it is financially impossible to build new reactors and let time close the existing ones.

        And when they close it will be too late to plan for new reactors any. Instead we will probably end up with a wind + gas system in addition to the hydro.

    • Euan Mearns says:

      Carl, what makes you presume Sweden will have Greens sharing power?

      • Carl Hellesen says:

        Not sure I understand the question.

        • Euan Mearns says:

          You said:

          Unfortunately for the german guy, in about a months time we will have a new government with the greens, and they are very keen on replacing reactors with wind power.

          The Swedish election is next month. The result is unknown, but you are claiming to know that The Greens will be a part of the government. On what basis are you making this presumption?

          • Carl Hellesen says:

            Aha, you mean that kind of power. I was thinking about voltage times current. Stupid…

            Well, its very trendy to vote green these days. And frankly, people don’t care about energy politics, they just want their organic latte served and power coming out of their sockets.

            The way the polls look like today the current center/right government is toast. Further, the greens have issued an ultimatum that they will vote against any attempt to form a government of which they are not a part of. The only possibility I see to form a stable government without the greens will be a grand coalition a la Germany. But I don’t see that working here. So, we will most likely get a green/left government. Of course, anything could happen, but…

          • Carl Hellesen says:

            The green/left side gets about 50% in the polls, and the presently ruling center/left coalition about 37%. The remainder is roughly 3% for the feminist party (but limit for parliament is 4%) and 10% for the nationalist part, which nobody wants to touch. Historically, the polls have been rather accurate, so thats why most people assume that the next government will include the greens.

    • Willem Post says:


      It would be good if someone would put out a status report of the physical set up of the Swedish hydro plants, including the PRESENT ability to do balancing and what modifications would be required to do future balancing.

      Ditto for the Norwegian hydro plants.

      From the comments, it looks like each of us know a little about these hydro plants, but that knowledge should be pooled.

      This to snuff out any wishful/fantasy “thinking” on part of RE aficionados, including on this site, who have “hand waving” solutions for integrating/storing large quantities of German, et al, variable wind and solar energy.

    • Lars Evensen says:


      I disagree with you about the potential for Scandinavian hydro taking a big part in balancing the European grid, although I can mainly answer for Norway not Sweden. The Germans see the potential because there IS a potential, it`s as easy as that. Nobody is claiming it is the whole solution, nobody says it`s going to be cheap or without environmental costs, and let`s make one thing clear: We are talking about short time balancing up to a few days perhaps a bit more. Seasonal balancing is utopia.

      In disagreement with you I believe the Nordic power situation looks very good towards 2025 and beyond. Saying that Sweden will retire its nuclear reactors in a relatively short time is going against history. I think it was around 1990 you had a referendum which turned in favour of shutting all Swedish nuclear reactors within 2010. I remember my aunt`s husband who is now a retired electrical engineer described this a “pure fantasy” and “totally unrealistic”, and he was right. Reality struck and the Swedes are not even so negative to nuclear power as back then from what I have read.
      You also had the statement by former prime minister Göran Persson a few years back that “Sweden will be fossil free by 2020” which we now of course can say is equally unrealistic. This is exactly how countries behave when fantasy must give way to realism. It will be very interesting to see what will happen to the remaining German reactors.

      But here is why the Nordic power outlook is so good in the time ahead. Essentially we have to countries with power surpluses (Norway/Sweden) and two with deficits, Finland and Denmark. Especially Finland is totally dependent on imports from Sweden, Norway (via Sweden mainly) and Russia. The Russians however mainly provide night time power and no peak power. Finland`s situation will improve greatly when the new Olkiluoto 3 reactor is commissioned (hopefully) in 2016. It`s 1600 MW reactor will almost remove Finland`s power deficit and reduce greatly the need for peak power from its neighbours. This will likely lead to spot prices more similar to Sweden`s and will also reduce Swedish and Norwegian hydro operator`s profit. Part of this power (about 2500 MW on average now in the North and South) will have to go elsewhere!

      In Sweden I take it for granted that all the nuclear reactors will remain at least until 2025, and the hydro output will remain virtually unchanged. However thousands of mw new wind power will be developed, Sweden is soon overtaking Denmark as it is. With Sweden being a long-stretched country there is obviously a rather strong non-correlation between Northern Swedish wind output compared to the South and with Danish/German wind. Granted, Swedish wind power cannot be counted on to balance the European grid of course, but it has the potential to save water in the reservoirs which can be used more for balancing purposes! As it is now Sweden has a power surplus of about 15 Twh in a “normal” year, and this will increase in the years ahead.

      For Norway the situation is similar, we will have an increased surplus in the years ahead on average. But due to the nature of a 96% hydro system`s need for precipitation we have seen that since 1990 we have had two years of surplus for every year of deficit. However, a year of power deficit does not mean that balancing services to the Continent cannot be provided as long as we can import at low load times and save water, or pump it back.

      In Norway a lot more hydro and wind power will be developed until 2020-2025. I can give you some numbers from NVE (the water and power directorate in Norway).

      Hydro power:
      – 2970 MW of concessions given ready to be developed providing about 15 Twh of new power.
      – 584 MW of probable concessions providing 1,8 Twh.
      – 3077 MW applied for, potentially providing about 9 Twh. Given history about 60-70% of these will be granted.
      – 472 MW reported but not yet sent formal application, appr. 1 Twh.

      A lot of these schemes are small hydro smaller than 10 MW. Some of them are only run of river, some have small ponds capable of providing power at peak times to increase the value for its owners and a few are large hydro plants in the 100 MW + class. Some of them are also upgrades to existing plants/modernization providing more effect and/or more MWh.

      Wind power:
      – 6676 MW of concessions ready to be developed providing about 18,6 Twh.
      – 7203 MW applied for but not decided, potentially 21 Twh. Probably 50-60% will be granted?
      – 300 MW newly arrived applications, potentially 1 Twh.
      – 9365 MW planned not applied for, potentially 27 Twh.

      With these numbers it is easy to see all this power is not going to be consumed inside Norway, it must be exported. Norwegian hydro and wind producers are extremely eager to see more interconnectors developed, because if not it means prices will be even more suppressed than they are now. In fact, some of these schemes, although granted, will not be developed unless we see more interconnectors, and that goes especially for wind power.

      What about balancing services? Norway at present has these connectors:

      1 GW to Denmark, by December this year 1,7 GW (Skagerak 1-4).
      0,7 GW to the Netherlands (NorNed)

      2,1 GW to Sweden in the South, about 1 GW in the North.
      0,1 GW to Finland (plans for development).
      0,05 GW to Russia, only used for imports.

      New DC:
      1,4 GW to Germany (NordLink)
      1,4 GW to Germany possible (NordGer)
      1,6 GW to the UK (Britnor?)
      0,7 GW to the Netherlands possible (NorNed 2).

      With the new hydro developments in particular it should be quite possible to provide balancing services even with all the proposed interconnectors developed. The problem is mainly the internal grid in Norway which is constantly being upgraded from 300 to 420 KV.

      I cannot go into a discussion on the full possibilites for more pumped hydro, but the potential is very large. Of course there are constraints with regard to water levels, erosion, some hydro plants send water to the sea, size of reservoirs and their inter linkage and nature conservation in general.
      I can give one small example out of dozens of possibilites. There is one concrete plan for pumped hydro at the moment which hangs on the development of new interconnectors. Norway`s largest power station in terms of annual production but not effect (Tonstad/Sira-Kvina kraftselskap) wants to double its effect from 980 MW to 1960 MW by installing two new 480 MW reversible turbines. This power station is not far from either the Skagerrak interconnector to Denmark, the one to Holland and the coming interconnector to Germany.

      • Carl Hellesen says:


        First, I should make it clear that I’m speaking entirely about Sweden as I don’t know much about the Norwegian system. You think I’m pessimistic, and that there is a large potential. Of course there is a potential to do wonderful things as you say. However, there is a reality as well, and here the environmental impacts from using hydro to balance the system are already considered too large. Really, its been discussed a lot the last year. I’m not saying our hydro won’t be able to provide balancing in the future, just that it might be less effective than today.

        Considering this, what do you think would happen if a politician said that we shall further damage our local environment by building pumped hydro stations to help the Germans balance there wind power?

        You also say “In Sweden I take it for granted that all the nuclear reactors will remain at least until 2025, and the hydro output will remain virtually unchanged”.

        Actually no. EON, who owns three reactors in Oskarshamn have already applied for permission to close one of the units. It will be 50 years old by 2022, and they have stated that they want to close it before that. The swedish radiation protection agency has also said that the industry should not count on more than 50 years of operations for the older units. Apparently the PWRs in Ringhals have problems with embrittlement of the pressure vessels. This leaves us with 1/3 of the capacity gone by 2026.

        A few months ago the director general of our grid operator also warned in a debate article that within 10 years there will be a power deficit of about 3 GW in south of Sweden. It’s already too late to have new reactors running by then, so the gap will have to be filled by something else. Wind power is growing fast as you said, but it needs to be backed up by something, and natural gas is probably the only alternative you can find political support for. This is what history tells us by looking at the closure of the two Barsebäck reactors close to Malmö.

        • Lars Evensen says:


          thank you for the answer, very interesting, particularly about the nuclear reactors.

          If what you say about them is correct that begs the question why on Earth do you spend billions of Swedish krona to upgrade them (safety measures, effect upgrades and more) if they are due to be closed in a relatively short time anyway? For instance, the Oskarshamn 2 reactor has been undergoing maintenance and upgrades for “ages” now and is not due to come back until 2015 sometime. Others are already upgraded or there are plans, or am I totally wrong here?

          About the Barsebäck reactors they were closed due to pressure from the Danes since they were so close to Copenhagen, only 20 kms or so. Obviously a slight touch of Danish hypocricy there since they gladly import Swedish (nuclear) power whenever they need too… 🙂
          Effect upgrades on the remaining reactors have already replaced the effect from the decommissioned Barsebäck plant btw. (1200 MW).

          You said “A few months ago the director general of our grid operator also warned in a debate article that within 10 years there will be a power deficit of about 3 GW in south of Sweden”

          I agree this sounds alarming, but the South of Sweden (if we include elspot area 3 and 4) already has a large power deficit which is filled from area 1 and 2. Like I said, the new Finnish nuclear reactor will remove the need for a lot of Swedish (and Norw.) hydro in the North which can be sent southwards.

          To me natural gas seems like a bad solution for new power given the situation now. In the 80s and 90s (after the Swedish referendum on nuclear energy demanding a closure by 2010) there were plans to build a natural gas pipeline up the Norw. Skagerrak coast and further down the Swedish west coast, but it was abandoned. Again, was this because reality set in about the nuclear?

          About the hydro plants and prospects for balancing I can only listen to what you say because I don`t know the details of the Swedish debate.

          You say “Considering this, what do you think would happen if a politician said that we shall further damage our local environment by building pumped hydro stations to help the Germans balance there wind power?”

          This is actually a very interesting statement and again I can only provide some insights into the Norw. situation. Here local communities frequently have a large share in power operators (and also local grid operators) and many of them are actually more or less depending on hydro revenues every year to balance their budgets, that`s the case where I live for instance. More revenues from balancing services would likely be welcomed by politicians but destruction of environment be opposed by the public and greenies. But in the end it will be up to the “National hydro and water directorate” (NVE) to decide if the benefits of upgrades and pumping schemes are larger than the possible negative environmental effects. In most cases they will have the final say unless it is appealed to the ministry of energy of which it is a branch.

          So far at least the main concern of the average Norwegian citizen, to the extent that he/she is interested, is that more interconnectors will lead to higher power prices which is undesirable given that heating with electricity is so dominant here. There is a misunderstanding among the public that the interconnectors will only be used for exports (and thus higher prices) and the fact that you can also import cheap surplus energy with them is clearly not understood by many.

  10. BLOG’S AUTHOR SAID: “The question therefore becomes, is there any way of storing solar power surpluses for short-term re-use? Not with solar PV using existing storage technology.”

    Solar energy can be “stored” by pumping water uphill, and then releasing it into turbines downhill during periods when the sun is down, or dim. Living near Niagara Falls as I do, enables me to witness this practice, as they do this very thing there so as not to damage the tourism aspect of the falls, by pumping water uphill at night, when grid demand is low, and then releasing it during the day, when it is high. Clever, no?

    • Euan Mearns says:

      Merida, in Europe it is sunny in summer (when demand for electricity is low) and not so sunny in winter (when demand for electricity is high). The commenters here are all fully aware of the merits of pumped hydro storage. The whole point of the post and the discussion is that the volume of storage required to store the summer surplus for use in winter is impossibly large.

  11. Math Geurts says:

    A very interesting discussion which delivered some usefull data.

    Let’s assume that PV wil become a lot cheaper than today, that batteries will become a lot cheaper than today, that Norway and Sweden could deliver considerable more balancing services to Europe, that Germany will be able to convince its population that they have to accept extension of transmission lines to use that service, that night-time load can be shifted to day time, that most cars will be electric cars, etc. etc., then remains the uncomfortable fact that, far from the equator like in Germany and almost all of Europe, the sun delivers on average during a summer day about 6 times as much energy as during a winter day. Unfortunately, on the contrary, the overall demand for energy one average could be more than 3 times as much during a winter day (data needed). Even cars consume on average more energy during a winter day.

    So the title could be: large scale integration of solar power, far from the equator: many problems, for the worst of those there is only one “solution”: enormeous seasonal storage. That solution will not be hydropower, pumped or not.

    Even when there are no more fossil fuels left, far from the equator it is not likely that solar energy will contribute very much to the energy supply.

    • Unfortunately, all of the major electricity-consuming regions are some way away from the Equator. I would guess a weighted average of somewhere between 45 and 50 degrees.

    • Bas says:

      You describe one of the main reasons that Germany is developing power2gas plants. The gas can be stored easily in available caverns deep in the earth. Storage capacity enough.*)
      Development goes slow. On the other hand, there is enough time. It will only be needed after 2050 when renewable share will reach ~90% (I assume they will increase the 2050 target, they did that last year already with the 2030 target).

      The main issue is that the yield of the whole process is rather low; ~25%.
      With PV-solar electricity of ~2.5cnt/KWh in ~2040, that implies that the electricity generated from such storage would cost ~10cnt/KWh (some wind in USA is already reaching 2cnt/KWh levels).
      That is still ~half of the price for the electricity that nuclear Hinkley C generates at that time (guaranteed price with 2% inflation then 19cnt/KWh + subsidies: total price then 23cnt/KWh).

      *) Bavaria and other states have already such seasonal storage (my rough estimation; enough for ~3 months) for the situation Russia stops with the delivery of gas. And The Netherlands can put it into the caverns of its big natural gas fields, which has a capacity of many years for the whole of NW-Europe.

      • Math Geurts says:

        Right, after batteries there is a new hopium. The fact that increasing the renewable target (incl. large scale integration of solar) in rather flat, densely populatied countriy far from the Equator will only be possible with deployment of power-2-gas plants, is the reason that the German government de facto appears to be reluctant to increase the 2050 target.

        No doubt. Fraunhofer’s solar researchers are fond of this kind of challenges.

  12. Math Geurts says:

    Roger, it is not that bad, except for Europa.


    Quito 0,13
    Singapore 1,17
    Nairobi 1,17
    Kuala Lumpur 3,09
    Bogota 4,36
    Manila 14,36
    Arica (Chile) 18,29
    Hongkong 22,18
    Dubai 25,15
    Riyadh 25,45
    Miami 25,47
    Brisbane 27,28
    Houston 29,40
    Austin 30,15
    Cairo 30,30
    Shanghai 31,12
    Phoenix (Arizona) 31,52
    Perth 31,58
    Santiago de Chile 32,50
    Tripoli 32,53
    Newcastle (NSW) 32,55
    Baghdad 33,20
    Casablanca 33,26
    Marrakesh 33,27
    Tel Aviv 33,32
    Sydney 33,52
    Beiroet 33,53
    Cape Town 33,55
    Los Angeles 34,30
    Buenos Aires 34,36
    Adalaide 34,55
    Heraklion 34,20
    Canberra 35,18
    Tokio 35,41
    Valetta 35,54
    Auckland 36,51
    Gibraltar 36,80
    Sevilla 37,22
    San Fransico 37,46
    Melbourne 37,48
    Athens 37,58
    Lisboa 38,43
    Washington 38,53
    Palermo 38,70
    Valencia 39,29
    Wilmington, Delaware 39,44
    Beijng 39,54
    Madrid 40,23
    New York 40,40
    Napoli 40,50
    Tirana 41,19
    Barcelona 41,23
    Roma 41,53
    Boston 42,20
    Hobart 42,52
    Marseille 43,17
    Sapporo 43,30
    Toronto 43,38
    Burlington (Vermont) 44,28
    Bordeaux 44,50
    Milano 45,28
    Montreal 45,30
    Quebec City 46,48
    Bern 46,57
    Ulan Bator 47,55
    München 48,08
    Vienna 48,12
    Paris 48,51
    Vancouver 49,16
    Kiev 50,27
    Bruxelles 50,50
    Praha 50,50
    London 51,31
    Amsterdam 52,22
    Berlin 52,31
    Nottingham 52,57
    Belfast 54,37
    Newcastle-upon-Tyne 54,58
    Edinburgh 55,55

  13. Pingback: Recent Energy And Environmental News – August 18th 2014 | PA Pundits - International

  14. Math Geurts says:

    Large scale intergation of pv in Japan

    “Easy PV” is solar power that can be integrated into the grid without leading to “negative” residual load. For the sake of the “easy PV” argument, we’ll ignore that Japan is home to the world’s largest existing grid-level storage capacity in the form of 25 GW of pumped hydro.

    High peak summer demand

    Japan is a great nation for solar power. It has more sunshine than Germany (that’s an easy one, I admit), it has densely packed urban areas and a domestic solar industry with a very long tradition. Most importantly, its electricity demand usually peaks during the summer around noon. The Japanese record for peak summer demand occurred on July 24th 2001; it stands at 182.7 GW.”

    For Germany things are much more difficult.

    -Electricity demand peaks on winter days around 18.00.
    -Considerably lower yield of PV, specially in winter months.
    -Residual load has to remain positive, to protect the economy of domestic lignite power plants
    -For the time being additional residual load needed for remaining nuclear plants.
    -Much less grid-level storage in the form of pumped hydro.

    -For the time being Germany has one “solution”: exporting power during summer peak PV hours, as long as but neighbours have not installed their own “easy PV”.
    -Incl. this solution max. PV = 52 GW.

  15. Hugh Sharman says:

    Gentlemen (are there no ladies reading this blog? If not, why not? Euan?)

    I generally concur with a policy of installing stochastic renewables into OECD grids up to the point where integration is relatively costless. This is mostly because all OECD countries have highly developed grid systems developed over the last hundred years ago. This is because affordable fossil fuel supplies will not last much longer. It is already much, much too expensive for OECD countries to use even residual oil for the generation of power, for example, let alone kerosene or diesel fuel when coal and local natural gas are available. By simple observation, I’d say that limit is in the order of 15% by TWh annual penetration.

    This is more in countries like Portugal, Spain and Japan that have high levels of already built electricity storage i.e. pumped storage! Denmark of course is a very special case for the reasons already stated.

    However, in most of the poorly developed world, electricity still depends on diesels where the fuel cost alone can be $200 – $300/MWh and to be “economic”, the power companies must charge up to 50% over the fuel cost to recover the total costs of generation.

    Most of Africa, for example, has little to no rural power grid.

    It may (just) make sense to improve “central” power generation, transmission and distribution infrastructure where these exist already. But at today’s actual prices for PV (where the sun shines) and windpower (where the wind blows), and with reliable and robust electricity storage prices actually falling, and electricity-efficient lighting and machinery, it would be as stupid to create OECD-style electricity systems as foisting these countries off with land-line telephony rather than “mobiles”.

    Most of the human race still lives miserable lives which would be transformed by access to electricity in the same way that their lives have already been transformed for the better by mobile telephony! Let’s raise our eyes a bit to the much large picture! “Horses for courses”, as we say!

    • Bas says:

      Fully agree!

    • Math Geurts says:


      Obvious, on global scale solar will be extremely very important and in many parts of Africa there will possiibly never be a big power grid. But relative costless integration of solar power – the issue here – will be very limited in a region far from the Equator like Europe. Actually, only because of overcapacity, integration of 52 GW PV in Germany (about 9% of their demand), seems to be not too expensive, as long as neighbouring countries don’t install their real “easy share”.

  16. Hugh Sharman says:

    Bas, you write “…Germany started with a successful battery storage program (= 30% subsidy on the investment) for only small (30% in price before 2020 (mass production & installation).” My best understanding of domestic electricity storage (3 – 6 kW) in Germany is that a complete installation costs in the range €10,000 (lead acid) – €16,000 (lithium). This puts a complete solar installation incl storage far outside the budget of the ordinary German, even with the subsidies.

    BTW, I also understand the uptake of the grant for home storage has been very poor.

    Maybe you will be kind enough to bring us up-to-date on the situation, post election?

    Thanks in advance, Hugh

    • Math Geurts says:

      (Subsidized) battery storage for small systems only prevents distributed PV from overloading small local grids in Germany.

      It’s hopium to consider this as a way of large scale integration of solar power because p.14 of shows that small systems (in Germany < 10 kW) contribute considerably less than 15% of all PV in Germany. The contribution of systems < 6 kW will be less than 5%

      • Willem Post says:

        The problem with current thinking and proposed “solutions” is it is based on existing energy use patterns.

        Below is a small write-up regarding housing that use very little energy for heating, cooling and electricity. Such housing can be off the grid at relative minor cost. As PV solar and batteries become less costly these minor costs will be even less.

        Energy-Efficient Housing a la PASSIVHAUS: Energy efficiency will go nowhere regarding buildings without a very strict, state-wide-enforced, building code. In Denmark, a recently passed law requires NEW residential buildings must be zero-energy. Vermont should follow THAT example.

        Here is an example of what CAN be done, AND it would be invisible, AND it would maximize fossil fuel and CO2 reduction, AND it would REDUCE energy bills of already-struggling households and businesses!!!

        If one had a properly-oriented, free-standing house about as efficient as a Passivhaus, then energy requirements for heating, cooling, and electricity would be minimal, even in cold climates. For living off the grid, in a near-zero-CO2 mode, the house would need to be equipped with:

        – A roof-mounted, PV solar system + a battery system for electrical energy storage + an electric heater in the hot water storage tank to get rid of any excess electricity, plus
        – A roof-mounted, thermal solar system + a hot water storage system + a system to get rid of any excess thermal energy.
        – A whole house duct system to supply and return warm and cool air, with air-to-air heat exchanger to take in fresh, filtered air and exhaust stale air at a minimum of 0.5 ACH, per HVAC code.
        – For space cooling, a small capacity, efficient AC unit would be required on only the warmest days.
        – For space heating, an electric heater, about 1.5 kW (about the same capacity as a hairdryer) for a 2000 sq ft house, in the air supply duct, would be required on only the coldest days.

        NOTE: As space heating and cooling would be required for just a few days of the year, an air-source heat pump would be excessive and too expensive.
        NOTE: A future plug-in vehicle could be charged with DC energy from the house batteries by bypassing the vehicle AC to DC converter.

        • Math Geurts says:


          Of course new houses and building should be designed to minimize (all) energy consumption. But in Europe, with a stagnating population, most of the houses for 2050 have already been build now and are “stone” buildings.

          The zero-energy houses in Denmark are (only) zero energy on a yearly base. In Denmark there is the, in Europe on the long run, exceptional situation, that there is relatively too much power available in winter, because of CHP (whether or not biomass) and wind. Additional PV is welcome in Denmark.

          The main and most persevering problem with large scale integration of photovoltaics in most countries far from the Equator is the summer peaking generation and the winter peaking demand. A net zero energy building equipped with a lot of PV will (outside Denmark) not be helpfull to solve this problem.

          • Willem Post says:


            Thank you for your comment.

            Regarding thermal energy, a friend of mine, with a near Passivhaus-standard house (not certified), installed vacuum thermal solar units that produce ample thermal energy in winter to heat his energy sipping house. Often it is 25 – 30 F below freezing.

            Regarding solar, with enough lead-zinc battery capacity, kWh, AND his little electricity use,
            he has adequate electricity from his PV solar system, even in winter when irradiance is as low as 1/4 of maximum summer irradiance.

            NOTE: In Denmark and Germany, about 20% more panel surface would be required.

            He does not use heat pumps, as they would be overkill and expensive.

          • Math Geurts says:

            As long as somebody is completely off grid I am fine with everything. If on-grid in Germany it would be nice to have zero-energy houses which deliver to the grid in the winter and take from the grid in the summer.

            In Germany on average the yield of PV during the period november-january is about 1/6 of the 3 max. summer months.

          • Willem Post says:

            Irradiance in Munchen at 42 deg from vertical year round facing south.

            Jan……..1.88 kWh/m2/d

            max/min ratio 4.68/1.46 = 3.2, not 6.

            Multiply times the number of days in each month and one gets the total kWh from 1 m2 of panels for the year.


          • Math Geurts says:


            Even in this place in Portugal, 38 degrees, summer yield = about 5 times winter yield.

          • Willem Post says:


            Thank you for your comments.

            To be off the grid, I added a 2 kW gasoline-powered DC generator to cover too low PV solar and thermal energy production, and revised my write up as follows:

            Energy-Efficient Housing a la PASSIVHAUS: Energy efficiency will go nowhere regarding buildings without a very strict, state-wide-enforced, building code. In Denmark, a recently passed law requires NEW residential buildings must be zero-energy. Vermont should follow THAT example.

            Here is an example of what CAN be done, AND it would be invisible, AND it would maximize fossil fuel and CO2 reduction, AND it would REDUCE energy bills of already-struggling households and businesses!!!

            If one had a properly-oriented, free-standing house about as efficient as a Passivhaus, then energy requirements for heating, cooling, and electricity would be minimal, even in cold climates. For living off the grid, in a near-zero-CO2 mode, the house would need to be equipped with:

            – A roof-mounted, PV solar system + a lead-zinc battery system + a hot water storage tank with DC electric heater + a system with DC pump and water-to-air heat exchanger.
            – A roof-mounted, vacuum thermal solar system. Vacuum systems produce hot water even during the minimum winter irradiance periods, whereas standard tube systems do not.
            – A gasoline-powered, 2 kW DC generator with 50-gallon storage tank to provide electricity in case of too little PV solar and thermal solar energy during winter, due to fog, ice, snow, etc.
            – Any excess electricity would bypass the already-full batteries and go to the electric heater of the HW tank. Any excess thermal energy would be exhausted from the HW tank to the outdoors.
            – A whole house duct system to supply and return warm and cool air, with an air-to-air heat exchanger to take in fresh, filtered air and exhaust stale air at a minimum of 0.5 ACH, per HVAC code.
            – For space cooling, a small capacity, high-efficiency AC unit would be required on only the warmest days, as the house will warm up very slowly.
            – For space heating, a DC electric heater, about 1.5 kW (about the same capacity as a hairdryer) for a 2000 sq ft house, in the air supply duct, would be required on only the coldest days.

            NOTE: As space heating and cooling would be required for just a few days of the year, an air-source heat pump would be overkill and too expensive in this case.
            NOTE: A future plug-in vehicle could be charged with DC energy from the house batteries by bypassing the vehicle AC to DC converter, provided the batteries have adequate remaining storage capacity, kWh, for other electricity usages.
            NOTE: The PV solar and thermal solar systems need to be oversized to ensure adequate electrical and thermal energy during winter when the monthly minimum winter irradiance is about 1/4 – 1/6 of the monthly maximum summer irradiance.


          • Math Geurts says:

            Of course it is possible to go off-grid with the back-up of a gasoline powered CHP generator. It has been done, and you can do it today, even without photovoltaics.

            In my opinion, the issue here is that a large contribution of solar power to the energy supply of a country causes a lot of problems, specially if that country is far from the Equator. In my opinion, grid integration could be less problematic than off-grid solutions as long as a grid is available and not becomes overloaded during supply peak.

            There are more options to solve the problem if one is grid connected. Some battery storage at home could be a smart part of the solution. The key is that every grid connected generator has the obligation to deliver some “capacity”, whether fysically or “contractual”.

          • Willem Post says:

            What my write-up shows is to what extend PV solar system households are dependent on the grid. Not having them pay to maintain the grid is absurd.
            Building zero-energy buildings that are free-standing energy wise is a smart approach to distributed generation which would require minimal fossil fuels, the direction we need to go into in the future.
            CHP would not be the entirely right answer.

          • Math Geurts says:


            According to figure 2 in this link power consumption in Vermont is higher on a winter day. That is definitely not the case in almost all of Europe.


          • Willem Post says:

            Figure 2 shows 28,000 MW, red, on August 2, 2006 and 23,000 MW, blue, on January 15, 2004, Per ISO-NE.Which one is higher?
            Please explain the relevance of your comment to my original comment.

            I am well aware, there is no way RE can provide enough energy at reasonable cost for building heating, cooling, and electricity. That is why my starting point is a house built to Passivhaus standards (not “Certified Passivhaus”, as that costs about $3000 for testing), and go from there.

          • Math Geurts says:


            You are right: the power demand is higher in the summer (and somewhere in the afternoon) than in the winter. In almost all of Europe the winter peak is higher than the summer peak.

            The relevance is that, because of this seasonal mismatch, large scale integration of solar power, is more difficult in Europe. That is the reason that Germany is desperately researching P2G. To be considered as storage however P2G has to be followed by G2P.

          • Willem: Here’s a plot of monitored monthly output from two ~8KWe solar systems in München (data from SunnyPortal). A summer-winter difference of a factor of six looks about right:

    • Bas says:
      Btw. We don’t talk about lead-acid batteries here.

      Taking into account the generally expected substantial price decreases, you can expect that in 2020 most new rooftop (household) PV installations will have such storage.
      Realize that German households can get loans for such investments at low interest rates.

  17. Hugh Sharman says:

    Matt, Thanks for that useful ppt and surprising information (to me) about the rather small contribution of <10 kW roof-top solar to German electricity demand/consumption.

    Bas, you should take anything you read at with a very "large pinch of salt". Especially its happy-clappy but crappy forecasts.

    I have been at PV and el-storage exhibitions in Germany where lead acid battery sales were very busy! Do you have any recent sales prices for domestic-scale lithium (and lead and/or other) el-storage installations? German language links are fine!

  18. Bas says:

    20mln households installing 5KW each, implies 100GW of new PV. So then we have the Fraunhofer projected PV capacity of ~140GW in 2050 (producing ~22% of all electricity).

    With millions of such batteries to install, installation prices will go down very much as well as the price of the batteries and associated electronics.

    Then it will become beneficial for bigger PV installations to install similar batteries (I estimate in ~2025). Especially if the owners consume electricity in the evening (shops, some factories, etc).

    That amount of batteries will take the evening peak away. Partly even in the dark months!

    Thanks for the nice ppt.

    I don’t have recent prices. I live in NL.
    For us storage is not very advantageous (yet) as the share of wind & solar is very low.

    The system does not respond quite well on my PC (Rather difficult to post a response, so I stop).
    Not sure why. I use FF with windows 8.1.

    • Math Geurts says:

      Bas, you are right about 100 GW in stead of 10 GW. 19 million homes to go. They will all save on grid costs, levies and taxes. Unfortunately grid costs and expenditures of the government will not go down. Maybe former solar factories can be transformed into battery factories.

      Even then, it is a cumbersome integration of 22% of all electricity in a country where electricity makes up 28% of the consumption of all energy. Compare this to 40% for the U.S. where a considerably higher share of solar can be integrated at least less cumbersome.

      How much time need German politicians to openly confess that solar will not be the winning horse for Germany, although Germany betted a lot of money on it?

      Btw. Storage is not advantageous in the Netherlands because de facto there is still a feed-in payment of about 22 cent/kWh. Every country has to right to make is own mistakes. It is not obligated to learn from the mistakes of your neighbours. Fortunately we had hardly any solar factories, so we need not to close them.

    • Euan Mearns says:

      Bas, long standing problem that I don’t know how to fix. With nested comments you can only go 5 deep. And sometimes the size of the reply box gets very small and the submit button disappears.

    • Bas says:

      I saw a price indications for Li-ion at Wikipedia 4.5KWh for €5900,=:
      4.5Kwh seems to me more than enough for a long evening at home.

      Based on the German situation:
      If you consume 2.5KWh/evening, then you save 2.5x(32-12cent)= ~50cnt/evening.
      32cnt for electricity from the grid, assuming future price increases, 12cnt for electricity you deliver to the grid.
      That is 365*€0,50 = €180/year. That is 3% without and 4.3% yield with the 30% investment subsidy.
      So you need the 30% subsidy, as well as some optimism and/or idealism. But there are substantial numbers of green Germans that have that.

      I would say that it takes a ~60% price decrease before it becomes mainstream (without subsidy). Assuming same long term price decrease as solar (8%/a) and FIT decreases, it will be ~2023 before rooftop solar with battery storage is mainstream.

      Regarding scarcity of materials (your Peterson link).
      I think that with the emerging mass market, that will not become an issue.
      The story reminds me to the mix of fantasy and reality in the David McKay stories, or the Club or Rome simulation studies (according to them we should not drive any car by now as all oil is finished).

      this Wikipedia page gives good overview of storage options:

      Thanks for your response. So I tried again!

      • Math Geurts says:

        Two problems.

        The small problem: on many winterdays a small PV system will not produce 2,5 kWh excess to store.

        The big problem: the difference between 32 cent and 12 cent is caused by avoiding taxes, levies and costs for grid use. Unfortunately overall grid costs will not become lower. The government needs the same tax income.
        The result: the “saving” of the idealistic Green German has to be payed by other Germans. For society the only advantage of this battery is to avoid an overload of the local grid which would not occur anyway without distributed PV.

        • Bas says:

          “… winterdays a small PV system will not produce 2,5 kWh excess to store.”
          Two solutions:
          – A bigger PV installation. That will occur as PV will become much cheaper.
          – A micro CHP installation when you replace your boiler. That produces electricity in combination with heat. So it delivers electricity the moment your PV solar with storage doesn’t (in the cold evening), and does not when you are not at home (assuming you than put the thermostat lower).

          “…“saving” of the idealistic Green German has to be payed by other Germans.”
          So the less idealistic Germans may also take care for their own electricity and invest as indicated! A good thing.
          Poor Germans can get loans for that against very low interest rates.

          The good thing is that such investment creates commitment towards energy.
          Hence less energy will be wasted.

      • Bas says:

        Looking at the Li-ion price, I now understand the interest in lead-acid batteries.
        You get same capacity with lead-acid batteries for 10% of the price (~€600,=)…

    • Bas says:

      “….How much time need German politicians to openly confess that solar will not be the winning …?”
      No German politician said that.
      They commit to the Energiewende scenario, which is adapted slightly ~ every 4years after the elections. The Energiewende scenario is the result of expensive studies in the nineties by scientists and consultancy firms. It predicts the best way to go towards 80% renewable in 2050, which is ~1.5% more renewable each year. They had already ~5% renewable (mainly hydro) in 2000.

      The Energiewende is based on a number of technologies:
      1- PV-solar and wind; and
      2- biomass and waste burning;
      3- Geothermal, power2gas, etc.
      The technologies under 2 and 3 can compensate some of the variability of solar and wind.
      Together with the 20% fossil fuel burning left in 2050, it is more than enough to keep their highly reliable electricity supply up.
      The presentations at this Fraunhofer page will give you more insight:

      Our government did learn to much from the Germans, .
      Here the FiT is the same rate as the rate you pay, but (very important) only until you reach break-even (same KWh delivered back as you bought). Compensation for all you deliver above that is open for negotiation with your utility. Often you get ~3-5cent/KWh for that. Some utilities pay nothing, so you then may switch to a better paying utility.

      And our government made no promise at all. So they can change the arrangement tomorrow and have no burden of guaranteed payments! This insecurity also causes that PV-solar takes off slowly here.

      May be the rules change after next elections and you do not get any money for the electricity you deliver to the grid. Or they adapt the Spanish rule that you have to pay extra to the utility because you have PV-solar, even if your PV-solar is not connected to the grid. So it becomes beneficial to take the solar panels off the roof. That is the Spanish situation since the right wing won last elections; hence you don’t see rooftop solar in Spain, only utility scale solar (the utilities have major influence in Spain now, as politicians earn lot of money advising them, etc).

  19. Hugh Sharman says:

    Bas, as regards electro-chemical storage technology, Moore’s Law does not work within the Periodic Table.

    For “high tech” (read any “lithium”) batteries, that use scarce or relatively scarce metals, the greater the demand, the higher the cost of the constituent metals. Therefore, even as non-material manufacturing costs fall with mass production (read Tesla Giga factory), the global commodity price of lithium, cobalt, managanese and even scarcer materials rises.

    If you have the time and inclination (warning: you may not like what you read), I can thoroughly recommend John Petersen’s forensic but witty analysis at!

    Actually, I don’t entirely agree with John’s analysis, believing that el-storage solutions (batteries) using lead and zinc (metals cost about $2/kWh) will arrive in time to save EVs but halt the ludicrous share price rise at Tesla!

    • Bas says:

      Moores law doesn’t work either with PV-solar. Still the price decrease during last 50years has same characteristics.
      The issue is that mass production creates similar price decreases. With millions of similar units you can automate the whole production line. Hence you complicated electronic equipment very cheap.

  20. Bas says:

    PV-magazine has published a calculator so you can calculate the optimal storage capacity for your household:

    • Math Geurts says:

      For this discussion it is more interesting what is optimal for society than what is optimal for “green” “idealism”.

      • Bas says:

        Society is you and me and …

        Anyway, it shows the viability of the battery storage by the rooftop owner / consumer.
        And it makes people:
        – more independent; and
        – more aware of the energy they consume, hence less wasted energy.
        Both are good for society.

        • Math Geurts says:

          The summit of satisfaction: to oblige others to pay the bill for your “idealism”.

          • Bas says:

            Nuclear does it far better or worse (just how you see it).

            Nuclear transfers their risks to the population by limiting their liability for:
            – accidents to ridiculous low level. Which is a subsidy of ~8cnt/KWh paid by you and me (insurance premium based on the nuclear accident & caused damage history);
            – dangerous waste to 100year, so our next generations can pay. A subsidy of ~2cnt/KWh.

            In addition new nuclear, such as Hinkley, get:
            – loan guarantees £10billion, worth ~4cnt/Kwh; and
            inflation corrected high price for all produced electricity during 35years. With 2% inflation that price will be 14cnt/KWh at the start in 2023 and 21cnt/KWh in 2040 halfway the guarantee period.
            While the future market shows that wholesale price in 2023 will be <7cnt/KWh.

            That is real transfer of costs, risks and burden to the citizen / tax-payer!

          • Math Geurts says:

            Nuclear is nobody’s idealism but at least every citizen has to pay and has the advantages (just how you see it)

            Let’s limit the discussion to different options for renewable energy:

            summary of small scale PV + battery:

            “Based on the German situation:

            If you consume 2.5KWh/evening, then you save 2.5x(32-12cent)= ~50cnt/evening.
            32cnt for electricity from the grid, assuming future price increases, 12cnt for electricity you deliver to the grid.
            That is 365*€0,50 = €180/year. That is 3% without and 4.3% yield with the 30% investment subsidy.

            So you need the 30% subsidy, as well as some optimism and/or idealism. But there are substantial numbers of green Germans that have that.”

            “The big problem: the difference between 32 cent and 12 cent is caused by avoiding taxes, levies and costs for grid use. Unfortunately overall grid costs will not become lower. The government needs the same tax income.
            The result: the “saving” of the idealistic Green German has to be payed by other Germans. For society the only advantage of this battery is to avoid an overload of the local grid which would not occur anyway without distributed PV”

            “Anyway, it shows the viability of the battery storage by the rooftop owner / consumer.
            And it makes people: – more independent”

            More independent. Something like a bit pregnant?
            30% subsidy = nearly 2000 Euro

            Conclusion: the summit of satisfaction: to oblige others to pay the bill for your “indepency”?

            For readers from the U.S. aware of discussions about (un-)fairness of netmeetering.
            That is really peanuts compared to this game of avoiding taxes, levies and paying for grid costs!

          • Bas

            Nuclear transfers their risks to the population by limiting their liability for accidents to ridiculous low level. Which is a subsidy of ~8cnt/KWh paid by you and me (insurance premium based on the nuclear accident & caused damage history)

            Can you supply some backup for your 8 cent/KWh number? Applying it to world nuclear generation since 1965 (77,000 TWh) gives the sum of $6.2 trillion, which strikes me as being a.little high relative to the actual “nuclear accident and caused damage history” over that period.

  21. Bas says:

    Made that calculation already some years ago. Couldn’t find the XLS anymore.
    Still know starting points:
    I based the calculation of the insurance premium on the costs of all accidents in 14,000reactor years.
    The two most important were:
    – Chernobyl; I incl. also the costs in W-Europe, etc. Assigned a number for the extra Down’s, malformations, etc. as shown by different studies (the costs of deaths are relative small compared to e.g. extra Down syndromes and other malformations). That delivered an amount in the range of ~€2-6trillion.

    – Fukushima; I’m not sure about the sum. I remember that the property loss (value loss of houses and land, etc) was there more important. And more estimations involved as the true scale not clear yet and Japanese government actively frustrates research (Japanese scientists published complaints; somewhat similar as with Chernobyl, Belarus put their most important radiation scientist for a year in prison when his group came with more serious health damage).

    Then I divided the total damage by the 14.000 reactor years and then by the number of KWh a reactor produced per year.

    You can state that reactors are now safer, however they are also older now. And even the new EPR and AP1000 cannot stand an attack by a 200ton airliner.

    Realize further that we were very lucky with Chernobyl and Fukushima:
    – Fukushima because 97% of the winds went to the ocean. If the came from the north Tokyo would be emptied.
    – Chernobyl because the winds went towards the ’empty’ country-side in the north. If to the south, then Kiev would have been evacuated for next centuries.

    I think that the insurance premium should be differentiated dependent on the damage an accident may cause.
    A NPP in the desert should pay a low amount, while e.g. Indian Point should pay a very high amount as an accident there can result in a full ‘permanent’ evacuation of New York (that would deliver 10trillion?).

    • Math Geurts says:

      I admit. You have done a lot of calculations to defend the satisfaction to oblige others to pay the bill for your “idealism”.

  22. Bas: Thank you. But estimates in the 2-6 trillion euro range for the health effects of Chernobyl are way out of line with the authoritative 2006 “Chernobyl Forum” report, which cites 28 radiation deaths, maybe up to 4,000 additional cancer cases and no evidence of an increase in birth defects. It doesn’t even mention Down’s syndrome.

    • Euan Mearns says:

      Why would it mention Down’s syndrome? A chromosome not genetic defect I believe?

      • Bas says:

        Chromosome is part of the DNA. Increased risk for Down and malformations, due to enhanced radiation was already well known from the fifties. So since the sixties the womb of (especial pregnant) women is protected for X-ray.

        But look into the study I referenced.
        It is a rock-solid design due to very lucky circumstances in Bavaria (1000miles away), where some districts got Chernobyl fall-out in different amounts and other similar districts got none (local rainfall). As they took all birth (~a million) no sampling confounding, etc. Results are highly significant (p<0.0001 for some important hypothesis).

        There are many more studies that show similar (also serious cleft-lips, perinatal death, etc), however none had those lucky circumstances which allowed for such rock-solid design.

    • Bas says:

      That IAEA report was produced with the intention to make nuclear viable again.
      So they excluded all health damage reports and studies of not direct involved people (all western studies, incl. those of Finland, Sweden, Germany, Belarus, etc.
      Even Ukraine government protested that the report delivered a far to optimistic picture.

      The argument used that for regions at greater distances no proof for a causal connection.
      The fact that there was a highly significant strong correlation with the amount of fall-out and disorders, was dismissed.
      They came up with only direct deaths and illness that was very visible and couldn’t denied.

      Now the New York Academy of Science publishes a book summarizing ~5,000 studies (some low, some excellent quality) written by 3 radiation professors from Russia & Belarus, which concludes about 1million death due to Chernobyl until 2006.

      I think about 100,000 and 900,000 after 2006 (most still have to come) as low level radiation has the same long latency before harm shows as smoking, asbestos, etc (~2 to 6 decades).
      No smoker gets cancer in the first 10 years of his smoking! Similar with low level radiation.

      • “This collection of papers, originally published in Russian, was written by scientists who state that they have summarized the information about the health and environmental consequences of the Chernobyl disaster from several hundreds of papers previously published in Slavic language publications. In no sense did Annals of the New York Academy of Sciences or the New York Academy of Sciences commission this work; nor by its publication does the Academy validate the claims made in the original Slavic language publications cited in the translated papers. Importantly, the translated volume has not been formally peer‐reviewed by the New York Academy of Sciences or by anyone else.”

        Sounds a little shaky.


        • Bas says:

          Of course. As you can imagine nearly the whole nuclear world in USA attacked NYAS and tried to induce the top of NYAS to remove the publication. As an Example; Atomic insight spend an article to that.

          They succeeded partially as NYAS added the disclaimer.
          Such statement: “… the translated volume has not been formally peer‐reviewed …” is rather unusual as scientific publications are formally peer reviewed, but books mostly not (thought that the paper version was published by Wiley; they do a review before publication).

          And of course the official nuclear scientific world of Russia, Belarus (and may be Ukraine, though that is not clear for me) denounce it, as it would hamper further development of nuclear due to the extra precautions they than have to take. Remember that Russia already had such major accident in the fifties, similar large exclusion zone (now wild life park), luckily the wind was steadily north into nearly unpopulated regions.

          • I find that Alexey V. Yablokov, the primary author of the NYAS publication, is a co-founder of Greenpeace Russia. That explains everything to my satisfaction.

  23. Math Geurts says:

    “Is Germany’s Energy Transition a case of successful Green Industrial Policy? Contrasting wind and solar PV”

    “We find mixed evidence that Germany reaches its green industrial policy aims at reasonable costs. Wind energy seems to perform better against all policy objectives, while the solar PV sector has come under intense pressure from international competition”

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