How to deal with intermittent energy sources

Something quietly remarkable happened in Germany recently. As the country enjoyed a sunny May day, its extensive solar power installations recorded their best ever performance. Solar power hit a new international record of 22GW, equivalent to 20 nuclear power stations.  At one point on Saturday, Germany was almost 50% solar powered.

There’s lots I could say about Germany’s power strategy, both positive and negative, but what I wanted to highlight was the way that renewable energy was accommodated in the system. Averaged over a year, solar power only accounts for 3.5% or so of Germany’s electricity generation, yet at the end of May there were days when solar power was providing ten times that. So far, the national grid has proved it is perfectly capable of handling these extremes.

This illustrated one of the big challenges to renewable energy: they are intermittent energy sources. A coal power station can run as long as you have coal to shovel into its furnaces. Wind power only operates when the wind blows, and solar photovoltaics need cloudless skies to reach their full capacity. Surely, say the critics, too much renewable energy puts us at the mercy of the elements? The greater the percentage of wind or solar in our energy mix, the more likely we are to end up with rolling blackouts. It’s a logical question, but there are solutions.

The grid
The first and biggest answer to this problem is the grid. Power stations feed into a national grid that balances inputs and outputs across the whole country. When demand rises, new capacity is brought online. At night, demand drops off and supply drops accordingly. It’s a highly versatile system, able to handle massive spikes in demand. The famous example is half-time during big football matches. The whistle blows, and everyone goes into the kitchen to switch on their kettles for a cup of tea, or opens their fridge for another beer. The National Grid refers to these as ‘tv-pickups’ and plans ahead for them so that the lights don’t go out.

It’s easy to take functioning power infrastructure for granted. If you’ve lived off-grid or in a developing country, you’ll know the luxury of not having to think about it. When I lived in Madagascar, the power levels dropped so low at night that we couldn’t switch on the TV. If you wanted to watch something that night, you had to remember to turn it on at about five o’clock and leave it on standby. By the time it had got dark and everyone had turned on their lights, there would be enough power to run it but not to turn it on. By day, you had to holler if you were going to boil the kettle. If you forgot, there would be wails from the office as someone lost their homework as the computer blinked off.

Those sorts of eccentricities don’t happen in Britain. At least not any more. The idea of balancing power supplies across the country goes back to 1926, and today the grid incorporates 181 major power stations and thousands of smaller installations. This infrastructure allows us to plug in a variety of variable energy sources, and the broader the network, the easier it becomes.

The supergrid
You can broaden the network beyond our own borders too. Interconnectors already link our grid with France, Ireland and the Netherlands. There are plans to build links to Norway and Belgium too, and a feasibility study was launched last month to see if we could connect to Denmark. Iceland has far more geothermal capacity than it can use itself, and is investigating ways to export it to Britain.

None of this infrastructure is cheap, but the fact that we already have three international links proves that it isn’t prohibitively expensive either. Whether we can afford a Europe wide grid with links to North Africa is another matter, but you can see the advantages of spreading the net as wide as possible. If the sun isn’t shining here right now, it might be in Devon. It might be a calm day in London, but the wind is blowing in Scotland. Expand that principle South to Spain and north to Sweden, and you’ve got a wide variety of conditions.

Stabilising demand
I’ve already mentioned the issue of peaks in demand. Some of these are unusual, like football matches. Others are regular, when people get up and make breakfast, or get home from work in the evening and turn on their lights and cook their supper. Coal power is one of the easiest ways to deal with these large peaks, as they can be switched on quickly. There are renewable energy equivalents, using biomass and incineration (or see hydropower below), but a better approach would be to avoid the extremes in the first place.

That be done through more efficient technologies – if everyone is switching on low-energy light bulbs at twilight, that’s a much lower step in demand than everyone switching on an incandescent. Another way of stabilising demand is through smart appliances that can read demand and respond accordingly. Fridges don’t run constantly, but maintain a steady temperature by switching the cooling mechanism on when needed. A smart fridge would time its cooling cycles to periods of low demand. A smart washing machine would automatically run off-peak when energy prices are cheapest. Samsung, LG and others already offer appliances with this kind of technology.

Energy storage
Those living off-grid with their own solar or wind power rely on batteries to make sure that they capture energy when its there, and can use it later. That would be pretty useful in the national grid too, if we could store the solar energy from a sunny day to use it at night. Currently there’s no form of battery big enough to do that, but there are a few other options. One is pumped storage hydropower. When energy is cheap, water is pumped uphill to fill a reservoir. When needed, gates can be opened and it runs back downhill through turbines, generating electricity. This is the renewable energy way of dealing with demand spikes, and also a way of storing intermittent sources. Dinorwig power station is housed underground inside a Welsh mountain, and can bring 1.8GW of power online in 12 seconds.

If you haven’t got a suitable lake, the same thing could be achieved with rail cars, according to a California company. They’re developing a model where surplus energy is used to haul heavy rail cars uphill when wind or solar power is running at full capacity. When it drops off, the cars are released to roll back downhill, generating electricity on the way.

You can also ‘bank’ energy in the ocean, taking advantage of the pressure of the deep sea. A team at MIT suggest that large hollow concrete spheres could be sunk on the seabed near offshore wind turbines. Excess energy would be used to pump out the spheres. When the wind dropped, water would rush back in through a turbine.

Another form of energy storage is solar thermal. I’ve written about it before so I won’t go into detail here, but it essentially stores heat in molten salt, and allows solar power stations to carry on generating electricity through the night. This turns solar energy into a form of constant renewable energy.

Constant renewable energy
Speaking of which, wind and sunshine are intermittent, but there are other natural forces that are much more predictable. Hydropower is one such source, using the steady flow of rivers. There are countries in the world that generate all their electricity from hydropower, and are thus enjoying 100% renewable energy. Hydropower is often overlooked because while it is renewable and clean, it isn’t always environmentally benign and has large capital costs. Large dams are often hugely destructive and displace entire communities. But there is good hydropower too, and I may have to dedicate a separate post to it.

There’s also a whole lot of energy to be sourced from the sea. Harnessing wave power is one approach, but doesn’t count as a constant renewable source because waves are variable. Tidal power does count however, as there’s always a tide. So far, tidal power requires a barrage across a suitable estuary. Like dams on land, dams across estuaries are just as controversial – see the running debate about the Severn Barrage. But there are simpler and smaller ways to harness tidal power too, placing turbines on the sea bed, or using the vertical movement of the tides rather than the vertical. Ecotricity are trialling a hybrid sea technology that uses sea swells to pump water onshore, which is a lot simpler than generating the electricity out on the open sea.

Geothermal provides another source of constant renewable energy. Britain has limited geothermal capacity, and is more useful for providing heat than electricity, but there is still untapped potential. The main reason that geothermal hasn’t been pursued in Britain is that it hasn’t been economical so far, but as the price of energy rises, it is becoming more viable. The Eden Project is pioneering a geothermal plant in Cornwall, the first of what it hopes will be a fairly substantial contribution from Cornwall’s ‘hot rocks’.

Biomass and anaerobic digestion (biogas) are two more renewable energy sources that are often overlooked. Biomass is best reserved for smaller and more localised energy generation, and the current practice of co-firing biomass with coal is a short term option. Biogas is generated from waste, so it doubles up as a useful way of dealing with rubbish otherwise destined for landfill, and its main waste product is a liquid that can be used as fertiliser.

Lowering energy use
Even with these various technologies and techniques, renewable energy can never be a direct swap for fossil fuels. Coal, oil and gas are very dense forms of energy, and deliver a high energy return for energy invested. Renewable energy cannot match it, and if we are to rely on renewable energy more in the future, we will have to reduce our energy use. That’s entirely possible, given how inefficient our houses are, how much electricity is lost in transmission and how low our standards are for appliances.

Quite how far we need to reduce our energy use is debateable, but those assuming we can expand it or carry on as usual aren’t paying attention. The Zero Carbon Britain report, which aims for 100% renewable energy by 2030, assumes a 55% reduction.

In summary, there are ways of managing the intermittent output of certain renewable energy sources. It is a challenge, but it is not an insurmountable obstacle.


  1. Jeremy,

    I am no expert, but want to note down the main arguments against the optimistic scenario you present here. All of this is taken from Ted Trainer, whose work Samuel and I have previously pointed out to you. I really don’t have a clue who is right in this debate, but I think Trainer’s view needs more exposure/debate…so here I go.

    The Problem with Intermittency:
    The issue is not whether renewable can technically supply expected 2050 energy demand (i.e at least double current demand), it is whether it can do it a tolerable cost and in a reliable way. The reason why Trainer thinks it will be so costly is due to the problem of intermittency which all renewables face. Given that there are times when there is either no wind or no sun (and sometimes – see below – both!) you have to have enough plant so that BOTH systems can run the entire grid alone. For example, there will be times when wind capacity is contributing almost nothing and will have to sit idle while PV or some other source fills the gap. This means that renewable sources tend to be alternative rather than additive. This increases capital costs immensely. Even if we could meet the capital cost, it is likely there will still be supply gaps when, for example, on consecutive stable cloudy days in winter when there is little wind/sun and yet demand is peaking. The problem would be solved, if we could store large amounts of energy, but this is unlikely – see below.

    Continental Wide Grids?
    It is true the continental wide grids will, to some extent, smooth out the gaps – there will always be wind blowing somewhere. Evidence from Trainer (derived from other studies), however, suggests there would still be many times when the average wind across the whole system was low, and that means the wind system would not be producing much. What this means is that even if the wind is always good in Morocco, or Kazakhstan or Siberia or Western Europe, all these places would have to have the capacity to reliably meet total demand across the entire system. We would therefore have to build four entire systems each big enough to meet demand.

    Smart Grids?
    Trainer argues the value of this strategy depends on the proportion of total load that is flexible, and this is likely to remain quite limited – see here. One major reason seems to be that this really only applies to commercial/domestic heating and cooling, which makes up a relatively small proportion of overall energy demand.

    What about other sources of renewables?
    While other technologies are valuable and/or promising they are unlikely to contribute significantly to very large scale electricity production. The three major suppliers for foreseeable future will be three are wind, photovoltaic solar and solar thermal. If we are prepared to use 1 billion hectares of land to plant biomass energy crops – despite the likely impact on the environment and food prices – we might get the equivalent of 5 per cent world energy demand expected in 2050. All other sources have major technical difficulties, not yet overcome, and in any case are limited. Trainer cites following estimates of global supply potential: Hydro (30% Wave Power (5-10 %) Geothermal (4%) tidal (1%) Ocean currents (450 GW). Note, these percentages are for ELECTRICITY only, not for overall energy demand.

    What about storage?
    Trainer argues it is not possible to store electricity on the required scale to even out the intermittent supply, especially when there can be periods of cloud and calm across a continent lasting for days. You are right that pumped storage is an option, but it won’t do it. Hydro electricity provides only about 15 per cent of world electricity, so it couldn’t meet anything like total demand when there is no wind or sun (even if all dams could be adapted to it and few can be because you need a low and a high storage space). Batteries/compressed air/ammonium/flying wheels are all viable, but not at the scale required and hydrogen as a carrier is likely to be inefficient and therefore expensive. Solar thermal systems can store energy as heat and this is, indeed, the best hope for renewables. Trainer claims data is still limited to draw confident conclusions but, at this stage, he argues winter supply is the major problem. Current technology allows for 17 hour storage at best, but there are times when it will need to provide enough energy for four cloudy days in a row.

    The supply task for a world of affluence running on renewables is huge…
    World energy demand is likely to be at least double current levels by 2050. BUT if everyone in the world lived affluently like us, it would need to be at least 3 times those projections. More importantly, renewables only supply electricity, which currently makes about around 25% of energy demand. So we would have to electrify everything (transport, heat, industry etc) which obviously increases the scale of the task for renewables.

    Trainer’s Conclusion:
    Trainer outlines several possible scenarios for a global energy budget run on renewables…but concludes all of them, even when using very optimistic assumptions, will be too costly. The cheapest scenario would be around $7 trillion which is 11% of 2011 global GDP, or 16 times the early 2000 rich world energy investment for building and maintaining plant – see here. He argues we should be moving to renewables as ‘quickly as possible and that they can enable a satisfactory quality of life for all, but not in energy-intensive consumer-capitalist societies.’

    The wider Picture:
    The renewable/energy issues is just one reason why we should give up on the quest for affluence/growth. This quest depends on global injustice, generates war/conflict, and doesn’t improve the quality of our lives. Neither should we bother trying to reform this greed/growth society – it can’t be done. Instead we should start where we live, in our towns and suburbs, DOING IT OURSELVES, building the alternative local co-operative economies of the future. We will be ignored for a while but when the beast starts to crumble people might start listening…we just need to have the alternatives in place and ready to ramp up.

  2. Johnathan, thank you for your detailed reply. I’m specifically addressing the issue of intermittency here, as it came up as a sticking point in a recent debate on the blog. I haven’t gone into the bigger debate over if/how society would run on renewable energy. If I had, you’d see a much fuller expansion of my final point – that renewable energy can never replace fossil fuels.

    I’ve read Trainer’s calculations in the Simplicity Institute paper, and like him, I’m a renewable energy realist. There’s no way we can run a consumer economy on renewable energy. Renewable energy only makes sense with a massive downscale of our energy use, and is incompatible with the current growth model of economics.

    That’s why I champion renewable energy, but also simpler living, transition towns, and a postgrowth economy.

  3. Hey Jeremy – fair enough. Yes I kinda missed your statement at the end about the need to reduce overall demand! Still, I think Trainer’s arguments are important for the movement to discuss because they directly challenge the optimistic case that, in my experience, the overwhelming majority of greens adhere too. Keep up the good work; really enjoy your blog.

    1. Yes, I think the environmental movement has kept quiet about the fact that we need to downsize, and goes for the easy wins of ‘green growth’. I should write up Trainer’s conclusions as a separate post too.

  4. Jeremy:

    I’m glad you’ve decided to deal specifically with the important renewable/intermittency problem. In a sense, this interesting (and, as usual for MWH, balanced) post is a response to my final contribution to the comment thread on your earlier post about the cost of renewables:

    Jonathon makes some interesting and pertinent comments above. And I don’t think you’ve really answered my concern about wind energy: that we are risking power outages – and power outages are horribly dangerous. I appreciate, of course, that you’re looking at the much broader renewable picture, but I don’t think that does much to assuage that concern. I’d like to expand on this in more detail but cannot do so now as I’m preparing for a trip that will mean I’m away from my computer for 10 days.

    I look forward to returning to this discussion when I get back.

    1. That’s right, this is in reply to our previous discussion.

      As for power outages, I lived in countries with frequent power cuts for 12 years and I disagree that they’re ‘horribly dangerous’. Even in this country, places such as hospitals have backup generators – but they are horribly frustrating and inconvenient and they should be avoided at (almost) any cost.

      For us to get to the state of regular power outages because of wind power though, you would have to have a government who let that happen. They would need to believe in wind power above all else, believe that clean energy was more important than reliable energy. That’s not going to happen.

      Since generation capacity is built by energy companies rather than the government, you’d also need radical green power companies. They would also need to believe that clean energy was more important than a consistent supply. That’s never going to happen either.

      You’d also be assuming that efficiency and smart technology doesn’t keep up with the expanding scope of renewable energy, and that there are no breakthrough renewable technologies in the pipeline. Which would be a little ironic, since you’re the one who usually tells me that I’m the pessimist and need to have more faith in human ingenuity.

      It is quite possible that we are headed for power outages in future, but it is far more likely to be because our gas supplies are interrupted, because we have a nuclear backlash, or because we just fail to deal with runaway demand.

      More likely still is that power outages will be personal rather than collective, as poor people can no longer keep up with rising bills and see their power cut off or their pre-paid credit run out.

      In fact, that latter scenario is practically guaranteed if we insist on tying ourselves to ever more expensive gas rather than investing in renewable energy.

    1. Yes, there are optimists out there. There are those in the Chinese solar industry who apparently believe that the next generation of solar cells will solve the problem entirely and we’ll wonder what all the fuss was about.
      But since energy use is so tied to growth, neverending growth requires neverending energy sources, so even the optimists have a challenge on their hands. We need to transform the economy as well as the energy landscape.

  5. Another publication that may give useful background is Chris Goodall’s book, ‘Ten Technologies to Save the Planet’. I found this quite a useful, insight-giving discussion of the major low-carbon energy technologies.

  6. I wonder how much backup was required for the ‘50% solar’ output, though? You only need a passing cloud or two to reduce the output dramatically, and ‘spinning reserve’ has to be on hand to pick up the deficit. No way to run a grid efficiently, IMO.

    1. Sure, you need backup, but the fuel for solar power is free, and the fuel for a gas or coal power station is increasingly expensive. So running on clean and free energy for even a portion of the day is worth the hassle of incorporating it.

  7. “the fuel for solar power is free”

    Not really, if you have to have reserve power available all the time you’re using it to cover the intermittent output. Doesn’t have to be gas or coal either – nuclear works quite well, too 🙂

    1. No, the fuel (sunshine) is free, and it takes a lot less energy to keep a power station on standby than to run it at full power. So it is still better to use that renewable energy when it’s there, and Germany has just proved that it can be done.
      I haven’t gone into it here, but much of Germany’s solar boom is in direct response to post-Fukushima nuclear scepticism, and I think that’s somewhat misguided. If you have nuclear capacity, that’s probably the best way to maintain the base load at the moment (the other 50%), while coal and gas maintain the balance, since they can be switched on and off much more quickly.

  8. Fair enough, but what happens if you remove the subsidies? The sunshine might be free, but the electricity isn’t!

    1. Take away the fossil fuel subsidies and factor in the externalities of all the tech and let’s see what happens. Having said that once peak oil and debt sets in we won’t have the resources or subsides to do business as usual anyway.

  9. I fully accept that fossil fuels are finite, but they’re not running out just yet and a measured response is called for, not a panic. The panic is predicated on the evilness of CO2, which it isn’t.

    1. No one’s calling for panic, and I think this post is a pretty good example of a measured response, though I do say so myself.

      Have you seen the price of wholesale gas over the last ten years? This isn’t just about supplies running out or about CO2, though both of those matter – it’s about rising demand and rising prices too.

  10. Jeremy: I’m back and, as promised, I’ll continue this discussion.

    You claim that power outages are not “horribly dangerous”. Well that may be true of a developing economy but it’s not for an advanced developed economy where affordable, reliable energy is an essential. See this one-minute video: No energy means no water, no trains, no phone systems, no computers, no traffic controls, no petrol stations, no factories, no airports, no central heating, no street lights, no refrigeration, no sewerage … Had, for example, the UK’s energy depended substantially on the wind last February, thousands in the UK would have died of frostbite and our ruined economy suffered yet another severe blow. Few people appreciate the fragility of a modern city: in periods of extreme heat or cold, it’s electricity that prevents disaster. And, throughout the UK (onshore and offshore), the wind typically doesn’t blow in periods of extreme heat or cold. See this:

    That’s not a problem today because, despite all that investment and all those expensive subsidies, wind is such a tiny contributor to our energy mix and, by increasing the contribution from coal and gas, the Grid can easily cope when wind fails. It seems, however, that that will change: the Government asserts that, within just a few years (too soon for that human ingenuity to find solutions), much of our coal and nuclear capacity is to be phased out and renewables (inevitably mostly wind) are to become a substantial part of our energy supply.

    That would mean serious risk of Grid failure, the consequences of which would be intolerable and tragic. And that’s why support for wind energy is little more than impractical, sanctimonious piety.

        1. Then I fail to see why you keep repeating the same point over and over again, as if you’re the only person who’s thought about power shortages.

  11. I’m repeating the point because current Government (and Opposition) policies mean that in just a few years we face the real, but seldom recognised, risk of power outages. For the reasons I’ve spelled out, your “first and biggest answer to this problem” – the grid – is unlikely to be able to cope when many coal and nuclear plants have been phased out and we are substantially dependent on wind. For a modern economy to return to the energy position of 1926 would be dreadful. Even if a Europe-wide grid was planned for the next few years (it’s not) it would not be a dependable solution: atmospheric high pressure with little or no wind is commonly widespread throughout much of Europe. On a calm day in London, the wind often does not blow in Scotland or in the North Sea (for example the wind, from all UK sources onshore and offshore, is currently contributing less than 1% to our energy needs) or in Spain or in Sweden.

    Your suggested “solutions’ – such as pumped storage hydropower, solar thermal and large dams – cannot apply nationally even if they were planned (they’re not). Tidal, wave and geothermal power are interesting – but, again, nothing is planned that could possibly be ready on time. And anyway they all have serious disadvantages. Biomass and anaerobic digestion (biogas) are unlikely to make anything more than a tiny contribution.

    Solar power cannot do much for the UK and nor is much planned. So a move to renewables means a move to more wind. And that puts us at grave danger of power outages with all the consequences I have spelled out. It’s a point that cannot be too often repeated.

  12. Return to 1926? That’s a rather alarmist notion, don’t you think?

    The only renewable energy target I’m aware of is to hit 15% by 2020, and we’re unlikely to even hit that. Plenty of places are well beyond that already, including Germany, which is at 20% – and 40% of that is wind power. So what are you afraid of exactly? Other countries are proving that this can work.

    Your point can be too often repeated actually, as you’ve just proved. The more times you repeat it without bothering to look at the objective realities of renewable energy, the more you sound like someone who is simply blinded by a hatred of wind turbines.

    1. Well, the Germans are getting increasingly scared of renewables. See, for example, the current edition of the news magazine FOCUS entitled, “Energy End! Why it is unaffordable and threatens to ruin the country.” You can find it here (in German): An extract:

      “Not only the costs have become major obstacles, but also the technical feasibility of renewable energies is missing, especially wind and solar, which lack the infrastructure elements for taking the power to the markets that need them. These elements include power transmission lines, back-up energy systems for when the sun isn’t shining and the wind isn’t blowing, and power storage systems. Costs costs costs.”

      Renewables are described as having “highway bridges without highways”. And FOCUS warns that Germany’s once super stable power grid, once a model of stability and reliability, is now on the brink of collapse. “If next winter turns out to be a harsh one and the power fails and leaves citizens out in the cold, then there are going to be lots of angry people. Germany’s social powder is tinder dry.”

      Not perhaps the best example of an objective reality “proving that this can work”, Jeremy.

      1. Further to the above.

        In an article yesterday, Professor Fritz Vahrenholt (a father of Germany’s environmental movement and the director of RWE Innogy, one of Europe’s largest renewable energy companies) said, “In the UK and Germany, for example, power-station closures and huge expenditure for backup of volatile wind or solar energy or harmful ethanol production will raise energy prices massively and even threaten power cuts: the economic cost will be crippling, all driven by fear.”

      2. FOCUS also quotes an interesting comment from senior SPD official (and notable green), Sigmar Gabriel. Having described Germany’s handling of its power system as being as precarious as “operating on an open heart”, he added, “900 interventions to prop up the power grid in what was a relatively mild winter makes me nervous.”

  13. “continental wide grids”

    Don’t they require superconductors? Transmission losses are noticeable even over distances in the UK, and I seem to recall that the proposed link to Iceland is unlikely to go ahead for that reason.

  14. Germany’s in post-Fukushima panic mode, I only use them as an example because I began the article with their solar news. Don’t like Germany, try Portugal at 29%, Denmark at 26%, Sweden, 60%, Spain, 18% … They’re all done it differently, some better than others, and there will be sceptical voices in all those countries that you could Google up to support your views.

    To suggest that it would be dangerous to move beyond our lowly 7% is sheer paranoia, and in denial of the reality of the technology.

    1. No, Jeremy, you specifically cited Germany as a country that proves “that this can work” before asking me what I was “afraid of exactly” and as a prelude to accusing me of not “bothering to look at the objective realities of renewable energy”. Well, I answered those points precisely, using your chosen example. German experience shows that wind power may well not work and is a perfect illustration of what I am afraid of. My links (none of which incidentally were derived from Google) show that, unlike you I suspect, I am well aware of the objective realities. A consequence of Germany’s decision to abandon nuclear power is that people, including the left and many environmentalists, have been obliged to face up to the hard reality of wind energy’s weakness – that it’s a feel-good luxury that’s fine so long as reliable conventional power sources are there to do the real grunt work of providing a steady base supply. Here’s an objective “reality of the technology” for you: at present, on a quietly breezy day, wind power (onshore and offshore) is contributing a mere 180 MW to the UK’s overall demand of 39.6 GW – less than 0.5%. And that’s despite all that investment and all those subsidies.

      The uncomfortable truth is that, as I said yesterday, support for wind energy is little more than impractical, sanctimonious piety.

  15. How many times have you mentioned your little live wind meter? I get it. And I’m bored of repeating the same points, that wind power is not the only renewable source of energy, that renewable energy is not a direct swap, that we need to drastically reduce our energy use to make it work, etc etc etc …

    Germany is not a model for use to imitate note for note, as it’s on a politically motivated panic retreat from nuclear power – not something we’re doing here if you’ve read the energy bill, nor something I advocate by the way. But it does prove my point that you can incorporate intermittent sources of energy, which is what this post is about. It proves that we can expand considerably beyond our current level of renewable energy, something you seem irrationally terrified of.

    I’m suggesting we can do better than 7%, and there are a dozen countries in Europe that prove that’s perfectly possible.

    I can’t be bothered making this point again, so let’s stop wasting each other’s time, shall we?

    1. I daresay you are bored of reading about the unreliability of wind power. Unfortunately your being bored doesn’t make it untrue – and burying your head in the proverbial sand won’t make the truth go away. And of course wind power isn’t the only renewable source of energy. But, as I’ve pointed out several times, it’s essentially the only one our politicians have decided to back.

      You’ve completely missed my point about Germany. So I’ll repeat it: a consequence of Germany’s decision to abandon nuclear power is that people, including the left and many environmentalists, have been obliged to face up to the hard reality of wind energy’s weakness – that it’s a feel-good luxury that’s fine so long as reliable conventional power sources are there to do the real grunt work of providing a steady base supply. My objection (one of several – not least the environmental damage done by the extraction and processing of rare earth minerals) to wind power is that we can no longer afford to indulge in feel-good luxuries, especially when we are planning to decommission coal and nuclear plants.

      I could select any of your dozen countries to illustrate the same point. But I don’t suppose you’re really interested. So I’ll leave it at that.

  16. “Fridges don’t run constantly, but maintain a steady temperature by switching the cooling mechanism on when needed. A smart fridge would time its cooling cycles to periods of low demand. A smart washing machine would automatically run off-peak when energy prices are cheapest”

    Eh? So it doesn’t matter if your freezer warms up a bit (and lets the salmonella develop) when the wind’s not blowing? Or your washing machine scratches its head before starting, telling you to wait before you can wash your clothes? I’m off to buy a generator…

  17. “Germany, which is at 20% – and 40% of that is wind power”

    So wind power is 8% and solar is 3.5% (in OP) so what’s the rest? Are you confusing capacity of renewables with their real-world performance? Who measures this stuff?

    Wind is always being quoted here in the UK as ‘enough to supply X homes’ which really means that the average home consumption of around 1.5kW can be met when all the windmills are at full output, not the average output of 20-30% of that produced over time, or the peak requirements of homes on winter evenings with all appliances blazing. For that, you need real power stations, and although I appreciate that a bit of wind’n’solar has part to play, its lack of reliability rules it out as a major source.

    1. 20% hydro, 20% biomass, and the rest is solar and biogas, and that’s production, not capacity.

      The average wind turbine operates at about 30% efficiency overall, and any sensible estimate of future wind power takes that into account. The average coal power station or nuclear power station is on for less than half the time too, by the way.

      1. Actually, newer turbines run at 35-47% of capacity. 30% is a long-term average including older, smaller, increasingly obsolete designs. One of the reasons wind turbines are often not reaching their putative 20 year life is because they are being replaced at 15-17 years by far more efficient models. And the gains still continue. I’m no wide-eyed techno-optimist about wind, but the scare campaigns are just as silly.

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