Why hyping solar is bad for renewables

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For a few hours in May this year Germany got over half of its electricity from solar power. A much hyped event that Bill McKibben claimed demonstrates we already have the technology to solve climate change. However, there is a great danger that selectively reporting peak production of different renewable energy sources will lead to public misunderstanding of the relative merits of different renewable energy sources.

Let’s consider Germany. Yes, it got just over 50% of its power from solar on a Saturday afternoon in May. However, for the entire month it only got 10%. May is also a lot sunnier than the rest of the year, and as you can see below was the best Month this year for German solar.

mayIn contrast, solar PV has supplied about 5% of Germany’s electricity this year. A much lower figure than the hype would suggest.  The 50% figure however appears to have become a zombie stat, with a recent New York Times piece claiming that Germany has enough solar to get 50% of its electric from solar (though eventually corrected to say it was only 5%).

Perhaps the most egregious example of this is this is from the energytransition.de website, a website linked to the German Green Party which provides absurd propaganda for the Energiewende.


I don’t think it would be particularly unfair of me to suggest this is intentionally misleading.

[UPDATE: This post actually got me labelled anti-renewables by Craig Morris, one of the authors of the Energy Transition website. I’ll leave it to the reader to decide if this is a fair characterisation.


Why is selective reporting of “record highs” potentially damaging? Let’s consider a simple system with 30 GW solar PV and 30 GW onshore wind. In more or less every country in the world onshore wind will generate significantly more power than solar, at least double in most cases. On the other hand the “record high” recorded for each will be about the same. In simple terms reporting record highs makes solar PV look far better than wind than it really is. This is a problem because in countries such as Germany it is wind power that has the real potential to power countries, and not solar. You can see this by looking at the monthly variation in solar and wind power this year, keeping in mind Germany’s electricity use peaks in Winter, not Summer.

www.ise.fraunhofer.de en downloads englisch pdf files englisch news electricity production from solar and wind in germany in 2012.pdf

Wind has the potential to supply over 50% of Germany’s power. Solar on the other hand cannot, or at least it will require huge energy storage options. The lack of sunlight in winter is a problem that no technological breakthrough can fix.

A final point. Germany getting 50% of its electricity from solar one afternoon may turn out to be less a sign of just how much electricity it can get from solar, but perhaps how little it will get. In May Germany had a total installed solar capacity of 26 GW. Doubling this capacity will clearly lead to it regularly producing more electricity from solar in Summer than it really needs. By coincidence, or not, Germany has recently decided to completely end its feed in tariff for solar panels when installed capacity reaches 52 GW. At this stage it will be producing about 10% of its electricity from solar.

Unless Germany can put large scale energy storage in place, then this appears to be a likely place to end new solar in Germany. The alternative is a flood of useless electricity in Summer, and even more increases to consumer electricity bills. Another alternative is that solar reaches grid parity, and householders continue to buy solar panels in the belief that they this will mean they have to pay less for electricity, all the while pushing up the costs of the electricity they are trying to avoid paying for. An absurd possibility, but maybe not that impossible.

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30 thoughts on “Why hyping solar is bad for renewables

    Rouget said:
    December 20, 2012 at 9:47 pm

    …Meanwhile Germany released a disrete order on “the disconnection of large electricity consumers within the framework of intelligent grids.”.

    Disconnection and intelligent grids in the same sentence. Irony.


    Bernd Gnirss said:
    December 21, 2012 at 1:11 am

    We Germans did the next step already, PowertoGas assemblies were just successfully tested and decentralized GastoPower assemblies deliver power in houses, where the heat is used to warm the houses and power is delivered in the grid… and with the gas you can also drive and fly.

    Robert Wilson on Wind vs Solar in Germany | Lenz Blog said:
    December 21, 2012 at 5:12 am

    […] Robert Wilson just posted on his perception that solar is hyped in Germany by reporting the peak contribution of 50%, while wind has much more potential and does not profit from such favorable reporting. […]

    Jani-Petri Martikainen said:
    December 21, 2012 at 11:01 am

    Nice. Of course things start to look much more interesting if you move from monthly averages to, for example, hourly data. Longer the averaging period smoother the solar and wind output looks. With hourly data PV would consistently produce next nothing most of the time. Also, it would be off interest to see what the German demand is doing. At least here in the north the summer consumption is much lower than the winter demand. At winter it is kind of dark. To keep the lights on demand-production must be non-positive at all times.

      Robert Wilson responded:
      December 21, 2012 at 11:27 am

      German demand does peak in winter, around 6 PM when there is no solar. I’m trying to write a blog on this at the minute, but the German data is a real pain in the ass. Overall though, it seems to be the case that you can get over 50% from wind without a great deal of overcapacity. Obviously you need to back it up heavily with fossil fuels, but not much can be done about that. Greater than 50% in summer requires a lot of overcapacity. 40% may be achievable in Summer, but that just means solar providing 100% and wind etc. being wasted. The absolute maximum in Winter though is about 40%, and this requires an astonishing amount of overcapacity. The evidence seems to indicate that unless Germany gets storage working fast adding much more than 52 GW of solar will cause huge technical problems.

      Hopefully I can get a more in depth blog on this written, but the data currently is slowing it down.

        patb2009 said:
        March 26, 2013 at 3:00 am

        The other options are 1) Germany developing low cost
        battery storage such as Ambri technologies is working on, or 2) Germany working on highly variable industrial demand. If certain processes such as Aluminum or Glass smelting could be added in, subject to them tolerating large swings in supply of electricity, this power could be consumed in energy intensive commodity production.

    Jani-Petri Martikainen said:
    December 21, 2012 at 11:23 am

    Ok, I checked some numbers. In january 2011 the maximum conventional production was about 63GWe which was also about the same as their maximum demand. At summer conventional production drops to bit less than 50GWe. That should indicate the seasonal variation of their demand. There is easily a factor of 5 separating summer month PV production from the winter month. Wind production is somewhat higher at winter, but we are talking about tens of percentage point differences (and large monthly variation) from the summer. Nothing as drastic as for PV of course.

    pmaidowski said:
    December 21, 2012 at 12:17 pm

    Robert, your argument points to some good observations – storage will of course be crucial. But the system needs to be based on a second/minute/hourly&monthly basis, and discussing monthly averages in general terms doesn’t go deep enough.

    You’re right in saying that wind and solar need to complement each other. But you quote the above graph out of context, turning the message on its head (for up-to-date and comprehensive information, see http://www.ise.fraunhofer.de/de/veroeffentlichungen/studien-und-positionspapiere/aktuelle-fakten-zur-photovoltaik-in-deutschland, in German). The two graphs on page 27 (one of them the same you quoted) show that wind and solar have complemented each other very well during the first 10 months of 2012 (graph 20) and that they have done so throughout 2011 as well (graph 21).

    What’s more, you do get a few basic facts wrong: PV has already reached grid parity in Germany for private consumers! That’s why it’s indeed urgent to finally support flexible storage solutions (in a way that doesn’t unduly burden private consumers/small businesses and especially non-PV owners – an issue that Germany so far has done rather poorly). ISE also published a comprehensive May 2012 study about Germany, Spain and Northern Africa. On a more general note, they find that grid parity for onshore wind, PV and CSP has already been reached. (Also in German: http://www.ise.fraunhofer.de/de/presse-und-medien/presseinformationen/presseinformationen-2012/erneuerbare-energietechnologien-im-vergleich, http://www.ise.fraunhofer.de/de/veroeffentlichungen/veroeffentlichungen-pdf-dateien/studien-und-konzeptpapiere/studie-stromgestehungskosten-erneuerbare-energien.pdf)

    (PS: On second thoughts, I’ll blog about this some time soon, showing the graphs that I can’t upload in this comment)

      Robert Wilson responded:
      December 21, 2012 at 12:28 pm

      I can’t read German so these docs aren’t so helpful.

      I don’t see how I am turning these graphs on their head. Are you saying that I am wrong in claiming wind is a far greater resource in Germany? A simple look at the facts shows that, without storage, wind can provide more than 50% of Germany’s power, whereas solar stands zero change of doing this. In fact it’s very hard to see how solar can provide more than 20% of power without large scale storage options.

      “Grid parity” may or may not have been reached. However, it is far from clear if this is a good thing. Solar can displace absolutely no fossil fuel capacity, unless storage works out. Grid parity may just result in piles of excess electricity flooding the market in summer, with gas companies having to be subsidised. Overall it will simply increase the cost of electricity to people who don’t have solar panels. Stealing from the poor to give to the rich.

    Reiner Grundmann @ReinerGrundmann said:
    December 21, 2012 at 12:57 pm

    Even more important than average v peaks are the troughs (v peaks). Every system will break at its weakest point.

    Nick said:
    December 21, 2012 at 12:57 pm

    Good article although it’s worth bearing in mind that wind energy IS solar energy since it’s the sun that powers the weather systems here on earth.


      Robert Wilson responded:
      December 21, 2012 at 1:02 pm

      Yes, it is pedantic. Fossil fuels are also solar power. As our biofuels.

        Carl Hellesen said:
        December 29, 2012 at 12:14 pm

        Even nuclear power is “solar”. Maybe not our sun though. The uranium we mine was produced in an exploding star many billion years ago…

    Proteos said:
    December 23, 2012 at 1:33 pm

    You are very right on one count: emphasis on hourly production records is plainly misleading. One has to look at a bigger picture: how much demand does each means of production covers, correlation with demand, etc.

    When you look at all aspects, cost is something you can’t ignore. And in Germany, solar is probably around a LCoE of €200/MWh for new big installations (~1MW peak) in Bavaria while wind is more like €90/MWh in Lower Saxony.
    But solar has an edge over wind: it’s more correlated to intraday demand than wind. Some modicum of solar PV is thus interesting whatever you have in the system. If, say, you have decarbonized baseload, it’s not very interesting to add more wind because it will produce at random in low or high consumption hours. Solar only produces during the day, when demand is (nearly) always higher than the hours before it. At 30GW, Germany can cover a large part of this intraday swing on sunny summer days. Again, it becomes a question of price: if the price is low enough it makes sense to install a lot of solar PV, as you will avoid fuel consumption and GHG emissions. So if the price of PV would be €50/MWh, it would be a very good policy, but much less so at €200/MWh (and downright ridiculous at more than €500/MWh as in the past).
    Wind has more a winter/summer variation, but it’s still only a fuel saver like solar PV is. The big question is how far does it get you towards decarbonization if you install the technical maximum (to the limit of security of supply). And so long it’s only a fuel saver, you can’t save on standing capacity.

      Robert Wilson responded:
      December 23, 2012 at 1:56 pm


      My post was focusing more on the technical limits, not economics. Certainly the economics currently argue more for wind than solar. Right now in Germany electricity from solar is actually increasing faster than that from wind.

      On a pure technical basis, you could get over 50% from wind. Solar on the other hand, without storage, does not seem capable of getting over 20%. If you based it on cost effectiveness, Germany would be investing the money in wind instead of solar.

        Proteos said:
        December 23, 2012 at 2:25 pm

        Even from a technical point of view, wind will not get you everywhere. It’s completely random from day to day, but will help you more in winter. So it’s more a baseload replacement or seasonnal capacity replacement. But if you do not want any overflow (= forced disconnection), you won’t get to 50% of production. The Danes seem to have hit a ceiling at 25%, so between 25 and 33% storage in some form start to look mandatory.
        Solar on the other hand is only there during the day, so should be limited to the intraday swing.

        So to answer the question with which of solar or wind to start, it all boils down to how much money you have at hand and how much bang for the buck you’ll get. Germany started with a ~75% fossil based system, so any new renewable capacity is an opportunity to reduce GHG emissions. And of course, decarbonizing baseload will have a much bigger effect than decarbonizing peaks, because there’s a lot more energy in the baseload than in the peaks (hence the names). But there’s a toolbox problem here: you won’t solve all DIY problems with hammers only! Much the same, you won’t solve all power problems with wind only.
        To date, there are only two zero carbon means of production that vary intraday in step with demand: dam hydro and solar. Of course, hydro is technically much better, but not every country has mountains. If you want to reach 80% zero carbon generation, I think you will want to use solar, if its price is not ridiculous!

        So in terms of decision making, the technical limitations are not all that counts. The real problem of the policies towards solar PV is not that the potential of fuel saving is low, but that it costs so much for so little progress.

        Robert Wilson responded:
        December 23, 2012 at 4:22 pm


        This is getting a bit off topic from the original post, which was mostly about wind being able to provide more power in Germany than solar. I am not claiming wind will sort out the problem, and have blogged previously saying it won’t. Likewise, I am very skeptical that Germany will be able to decarbonise entirely with renewables. Population density appears to be too high to make this socially acceptable.

        To you points though. It’s certainly true that somewhere around 25-30% wind penetration will result in periods of overflow. The exact figure of course will vary a bit by country. For solar however this is far lower. Probably between 10 and 15%. And also, because solar is much spiky overflow is much more of a problem for solar than wind. (I’m planning a post on this issue in the next month or so.) However, looking at the numbers in the UK getting 50% of power from wind does not actually appear to result in that much overflow. Roughly 10% based on current wind production/demand (though I need to check my figures.)

        Reaching 80-90% renewables in Germany does seem technically possibly. The problems with it are economic and social. The social fundamentally is the big problem. You somehow covers massive amounts of land in wind turbines. Then you need to think about storage, which is a far from trivial issue. They’ll need to have maybe 70 GW ready for when it is not windy, and that’s assuming today’s level of demand. In future it will likely need to be higher. The only alternative is to build large amounts of CCS. But again, there are big social and political problems here.

        It’s quite clear their decision to withdraw from nuclear has reduced their chances of decarbonising by an incredible amount.

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    A snapshot of German wind power | Carbon Counter said:
    February 1, 2013 at 5:38 pm

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    Dr Green said:
    March 18, 2013 at 6:16 am

    The 50% solar energy figures of Germany may seem to be an eyewash today, however this is actually possible. Although it would take a few more years to reach those numbers.

    solar energy in Nigeria said:
    April 23, 2013 at 6:31 pm

    Firstly i thank Germany solar power, I think solar energy in Nigeria seals 70% solar in Nigeria. I save money and fuel.

    Niels Kjaer-Pedersen said:
    May 8, 2013 at 7:38 pm

    Solar energy appears to be one of the most powerful and reliable sources of renewable energy. Drawbacks are potential limits of access to required manufacturing materials.

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