Renewable Energy Storage and Power-To-Methane

In recent posts here, here and here Euan Mearns and I have published estimates of the amount of storage needed to integrate intermittent renewable energy with the UK grid in meaningful quantities. All of them point to the same conclusions:

1. The volume of storage needed to convert intermittent renewable energy into dispatchable energy is very large, with estimates running in the 1 to 5 terawatt-hour range even at modest levels of renewables penetration. (Note that these estimates are confirmed by an independent estimate from David Mackay detailed in this comment.)

2. Pumped hydro is the only large-scale, commercially-proven technology that has the potential to handle such storage volumes, but there’s no realistic prospect that the UK could add anything like this much new pumped hydro (total UK pumped hydro storage capacity is presently only 0.03TWh).

In short, the UK will have very considerable difficulty integrating large amounts of intermittent renewable energy into the grid if a solution to the storage problem can’t be found.

And most other countries are in the same position.

Yet there are studies which claim to have developed scenarios that allow the UK and other countries to be powered largely or entirely by renewable energy by or before the middle of the century. The authors of these studies are aware that an energy storage problem exists, so clearly they believe they have found a solution to it. What might it be? To find out we will briefly review the results of two such studies, one for France and the other for the UK:


In April 2015 the French Environment and Energy Agency ADEME completed a report entitled “Vers un mix eléctrique 100% renouvelable en 2050” which purports to show how France can generate 100% of its electricity from renewable sources by 2050 without the lights going out. The report has not yet been issued because ADEME apparently wrote it without authorization and its conclusions are ruffling feathers, but a leaked copy (in French) is available here. ADEME developed the 100% scenario by juggling 14 separate sources of renewable energy, three different types of energy storage, interconnector flows with neighboring countries, demand management, hourly generation data based on five different future meteorological scenarios and four different energy mixes in 21 individual French regions.

I began the review by making an independent estimate of energy storage requirements for ADEME’s 100% renewables scenario, which I did by applying ADEME’s 2050 mix of 63% wind, 17% solar, 13% hydro and 7% thermal plus ADEME’s assumed 14% reduction in demand, to actual 2014 generation data (details in the Addendum at the end of the post). I came up with 20TWh, a truly enormous amount, and went away feeling confident that ADEME would not have allowed for anything like this much in its study.

Which just goes to show how wrong you can be. A more detailed reading of the report revealed that ADEME in fact allows for at least 46TWh of storage, well over twice my estimate.

And where does all this storage come from? ADEME provides the following details:

Short-term (diurnal) storage: Batteries, adiabatic compressed air energy storage, others. 12GW installed capacity, 6 hours duration. Implied storage capacity = 72GWh

Short/medium term pumped hydro storage (STEP in French): 7GW capacity, 32 hours duration. Implied storage capacity = 224GWh.

Long-term (seasonal) storage: Power-to-gas (methane)-to-power. 17GW capacity, storage capacity ~46TWh (implied ~2,700 hours duration).

The 224GWh of pumped hydro capacity by 2050 is probably achievable (according to Eurelectric France already has 184GWh) but the 72GWh of short-term battery, ACAES and “other” storage probably isn’t without a major breakthrough in battery technology (72GWh = 10 million Tesla 7kWh units) and rapid commercialization of CAES. These, however, are bit players compared to ADEME’s long-term storage, which I quantified at ~46TWh by summing the bars on Figure 34 of the ADEME report:

ADEME Figure 34:  Inter-seasonal storage (red) and releases (blue) from gas-to-methane storage (note that the plot begins in June)

This huge amount of storage is achieved entirely by storing renewable energy in the form of methane gas. Surplus renewable electricity is used to make hydrogen, the hydrogen is combined with CO2 to make methane and the methane is stored in tanks before being fed to gas-fired plants to fill demand during periods of renewable energy deficit.

Can power-to-methane storage be made to work? We will discuss that shortly. But the  100% renewables scenario won’t work if it can’t, because without it France will be unable to meet demand when the wind doesn’t blow. ADEME’s Figure 112 (modified by the author) shows methane released from storage providing no less than a quarter of France’s total electricity consumption – and up to half of it for short periods – during a simulated windless week in February 2050:

ADEME Figure 112: Contribution of storage to France’s electricity supply during a simulated windless week in late February 2050. The red-shaded area shows combined releases from all three categories of storage

(Figure 112 also shows France obtaining another ~10% of its power from imports during the week. This isn’t a storage-related issue, but where these imports will come from given that the wind probably won’t be blowing anywhere else in Western Europe isn’t made clear.)

United Kingdom

The latest version of the Centre for Alternative Technology’s study “Zero Carbon Britain” can be accessed here . The study claims to show how the UK can totally decarbonize its electricity sector by 2030 while at the same time more than doubling its electricity generation, which is a bit of a stretch, but we will review it anyway. Here’s CAT’s proposed 2030 generation mix (note that the UK generated 359TWh in 2013):

The CAT report doesn’t address the question of the feasibility of installing the additional ~250GW of renewable capacity needed to meet these totals by 2030 nor does it discuss the cost, which would probably exceed £1 trillion. But we’ll assume it all gets installed. And having installed it, what does the report have to say about storage? First it correctly identifies the problem:

As most of the energy in our scenario is from variable sources there is often a mismatch between supply and demand, with both large surpluses and shortfalls. Adding more electricity generating capacity would increase surplus electricity production without significantly reducing the problem of shortfalls. (Demand management) and combining different renewable sources of energy helps but doesn’t completely solve the problem.

And presents supporting graphics:

Then it touches on the shortcomings of some other storage technologies:

  • Pumped hydro: Not enough of it
  • Batteries: Not cost-effective
  • Hydrogen: Explosive, hard to store, no infrastructure

Then it gives specifics:

Our scenario combined various short term energy storage mechanisms (hours to days) with the capacity to store up to 60TWh of carbon neutral synthetic gas for months or years.

And once again the carbon-neutral synthetic gas is methane.

So CAT comes up with the same long-term energy storage solution as ADEME – power-to-methane – and with a comparable storage requirement.

I didn’t discuss power-to-methane storage in previous posts because it seemed much too far away from large-scale commercialization and also probably too inefficient and uneconomic to be given serious consideration. On the other hand it’s not limited by the availability of topographically- or geologically-suitable sites, as is pumped hydro, CAES and FLES, or by the prohibitive cost of battery storage, and as such it represents effectively the only option for storing surplus renewable energy in large enough quantities to support high levels of renewables penetration. So now we will take a closer look at the question:

Will power-to-methane work?

Using the ADEME scenario as an example the following things must happen before it does.

The technology must be commercialized: This will be a major undertaking because at present there is only one small commercial power-to-methane plant in operation in the world – the 6.3MW ETOGAS plant in Germany, which produces methane by chemically combining hydrogen from electrolysis with CO2 from a neighboring biogas plant. The electrolysis process works with intermittent renewable energy – an advantage – but while the plant consumes 6MW of electricity it outputs only about 3MW worth of methane. The graphic below, reproduced from the ETOGAS article linked to above, summarizes system performance over a 20-hour period of operation with intermittent power delivery:

And when this energy loss is allowed for we find that over five thousand ETOGAS-sized plants will be needed to fuel the 17GW of gas-fired capacity ADEME considers necessary to support 100% renewables generation (which itself appears to be an underestimate. 17GW of capacity would have to operate at a 166% capacity factor to generate the 19,000GWh projected in February – see ADEME Figure 34 above.) An energy storage system that works at only 50% efficiency – less when downstream losses are taken into account – is of course inefficient but still preferable to having no storage system at all.

CO2 feedstock for the methane plants must be obtained: This is another potential roadblock. If ETOGAS consumes 2,800 tons of CO2 a year then roughly 15 million tons of CO2 will be needed to support 2050 methane production. ADEME claims that this CO2 will be obtainable from “numerous possible sources” but there are actually only two –biogas and carbon capture & storage. By 2020 France is projected to have 740 biogas generation plants with 315MW of installed capacity, but these would still supply only about 150,000 tons/year of CO2 even if all of it were captured, and CCS isn’t applicable even if it could be commercialized because ADEME’s 2050 scenario doesn’t allow for any.

An extensive pipeline network must be constructed: The CO2 needed to make the methane, which would come from thousands of small biogas plants, must be transported to the methane plants and the methane must then be transported to the gas-fired power plants. ADEME proposes an extensive pipeline network that doesn’t presently exist but which it assumes will exist (donc on présuppose l’existence) by 2050. But France’s transition to 100% renewables would have to begin long before that, so work on the pipeline network would have to start soon. And it would be embarrassing if there wasn’t enough gas to fill it once it was finished.

Incentives to build energy storage capacity must be provided: Anyone who has studied renewable energy knows how important energy storage is, but governments still haven’t caught on. They pay generous subsidies to producers who deliver non-dispatchable renewable energy to the grid whether the grid needs it or not but none worth speaking of to energy storage projects. As a result the storage capacity needed to make the renewable energy dispatchable isn’t getting built, and it won’t get built until governments begin to recognize the need for it and apply appropriate market stimuli. At this time no progress is being made towards building the infrastructure necessary to support large-scale power-to-methane operations.

Clearly the chances that power-to-methane storage can be deployed on the necessary scale within the XX-percent-renewables-by-20YY time frames that many governments have committed themselves to are not good. Power-to-methane is clearly not an option the world can hang its renewable energy future on.

But what about power-to-hydrogen? This is something I haven’t looked into, but CAT doesn’t think it will work:

In principle, hydrogen can be stored and then used directly to produce electricity using gas turbines or fuel cells. However, hydrogen is a very light gas that needs to be highly compressed for storage. It is also quite corrosive and can even corrode metal. It is possible to store relatively large amounts of hydrogen (a few 100GWh) over long periods of time, for example in salt caverns. However, compared to natural gas (primarily methane) hydrogen is difficult to store and transport and there is almost no existing infrastructure suitable for it.

And ADEME doesn’t mention it at all.

So if power-to-methane isn’t feasible, what’s left? We are back to the only approach that can be guaranteed to work – keeping enough conventional backup generation to fill demand when the wind doesn’t blow and the sun doesn’t shine. With this approach the lights stay on even at high levels of renewables penetration, but the system would be highly inefficient and probably ruinously expensive.

ADDENDUM: Estimation of storage requirements for the ADEME 100% Renewables by 2050 Scenario:

Procedures were:

2050 hourly generation was estimated by factoring actual 2014 hourly generation from the Paul-Frederik Bach data base to match ADEME’s generation mix (63% wind, 17% solar PV, 13% hydro, 7% thermal – assumed to be biomass operating as baseload and delivering a constant 7GW). Factors used were wind = 16, solar = 15, hydro = 0.81.

2050 hourly demand was estimated by factoring actual 2014 demand by 0.86 to match ADEME’s assumed 14% demand decrease.

The Gridwatch data for France between November 2014 and the present were used to approximate average hourly hydro generation in 2050 (the Bach data base gives no data for hydro).

2050 generation by source obtained by factoring 2014 generation is shown in Figure A1:

Figure A1: Hourly generation by source for ADEME 2050 100% renewables scenario

Figure A2 sums generation from all four sources and superimposes it on 2050 demand.

Figure A2: Total generation versus demand, ADEME 2050 100% renewables scenario

Figure A3 plots generation surpluses and deficits relative to demand:

Figure A3: Generation surpluses & deficits, ADEME 2050 100% renewables scenario

And Figure A4 shows net storage requirements through the year, estimated by accumulating the surpluses and deficits shown in Figure A3. An 80% overall efficiency is assumed, with 10% of the energy lost during the storage cycle and 10% lost during the release cycle.

Figure A4: Storage requirements, ADEME 2050 100% renewables scenario

Figure A4 shows that 17TWh of storage will be needed if the renewables mix is to fill demand at all times during 2050, but this is still only just enough to keep the lights on in December. 20TWh of storage would probably be safer.

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79 Responses to Renewable Energy Storage and Power-To-Methane

  1. Fred says:

    My view was always that a liquid as storage mechanism was more practical than a gas. In particular cells utilising developed Fischer-Tropsch to generate hydrocarbons from recycled plastics and solar holds out the hope of generating petrol to power ICE in cars as well as energy storage – allowing a smoother transition route to plug in hybrids as well. Couple that with flow batteries for short term storage and a massively distributed architecture, and you have a hope of a practical solution.

    However, people should be piling money into this area now to push up efficiencies and push down prices – and they aren’t.

    Oh, and PS “which I quantified at ~46GWh by summing” should be 46TWh I think.

  2. donb says:

    Roger, I am impressed by your realistic analysis of this and related issues. Keep it up.

  3. cafuccio says:

    Five thousands power to gas plants !!!
    Note also that this scenario requires not less than fifty thousands onshore wind turbines
    Ha ha ha

  4. Phil Chapman says:

    According to CAT’s table, they expect to generate 58 TWh per year from PV solar, or an average power of 6.6 GW, from an array with a peak power of 75 GW. The ratio of average to peak power is thus 8.8%.

    A peak power of 75 GW implies solar arrays with a total area of 350 to 500!! At $1.50/peak watt, the array capital cost will be $112.5 billion (by “billion” I mean the American definition, 1000 million). Amortizing that sum over 30 years @ 6% requires annual payments of $8.2 billion, or about 14 cents for each kWh produced.

    My guess is that adding storage will at least double these costs, to a total of order $225 billion, or about 30 cents/kWh.

    I am astonished that anybody would consider a project on this scale without even mentioning space-based solar power.

    In geosynchronous orbit (GSO), the ratio of average to peak power is 95.2%, for an array that remains perpendicular to the equatorial plane (i.e., that does not track the sun in declination). The calculated efficiency of microwave power transfer to Earth is about 50%, so the average power to the terrestrial grid, divided by the peak power in GSO is about 47%. The sun shines (almost) all the time in GSO, so no energy storage is required.

    Given the scale of manufacture needed to make a significant contribution to energy needs, there is absolutely no reason why array costs should be greater for use in space than on Earth. The solar constant in space is 1.36 kW/sq m, compared to 1 kW/sq m at best on Earth; this means that PV cells that cost $1.50/peak watt on Earth will cost c. $1.10/peak watt in GSO, or $2.34/watt delivered to the grid. Providing 6.6 GW thus involves an array capital cost of $15.4 billion.

    It is a widespread delusion that spaceflight is intrinsically expensive. Neglecting atmospheric drag, etc., the delta-V needed to launch from the equator into low orbit (altitude 100 nautical miles) is 7.6 km/s, which means imparting a kinetic energy of 7.9 kWh/kg. If we could buy that energy in the form of electricity, it would cost about $1/kg.

    At present, launch costs about $5,000 kg. The reason is easy to understand: if an airline threw away the aircraft after every flight, crossing the Atlantic would also be expensive. The present flight rate does not justify building reusable launch vehicles (although SpaceX is working on it). Spaceflight is expensive only because it is infrequent – and it is infrequent because it is so expensive. Sunsats provide an economically justifiable way to resolve this chicken-and-egg dilemma. Studies show that the traffic required to build sunsats on a scale sufficient to make a dent in energy needs will lead quickly to reusable launch vehicles and learning-curve effects that reduce the launch costs to <$250/kg. Very little new technology is required.

    Studies also show that we can build sunsats with a mass <7 kg per kW to the terrestrial grid. The propellant needed to transfer the satellite to GSO adds 10% to this mass. Delivering 6.6.GW to the grid thus requires launching satellites with masses totaling c. 51,000 metric tons, at a cost of c. $12.7 billion.

    The estimated cost of the solar array, delivered to GSO, is thus $15.4 + $12.7 = $28.1 billion. The savings in array area offset the launch costs, by a very wide margin. Amortizing over 30 yrs @ 6% gives an annual payment of $2.04 billion, which will contribute 3.5 cents to the cost/kWh.

    Of course this calculation is too simplistic, and it leaves out many costs (especially the microwave transmitting antenna and the rectenna on Earth for converting the power to the grid), but the lesson is obvious. Because (1) there is no night or weather in GSO; (2) sunlight is stronger there; (3) maintenance is easier (no dirt or snow or shadows or bird excreta on the array); and (4) no energy storage is needed, space-based solar power is cheaper (no, make that MUCH CHEAPER) than terrestrial solar power.

    (Incidentally, the reduction in launch costs due to building sunsats will give us the whole solar system as the domain of our species. That’s a pretty good bang for a buck – and the nation(s) that get that message first will not only dominate energy supply in this century but also lead the way to a true interplanetary society (and thus dominate the human future for centuries to come). It looks like it might be China: according to the China Academy of Space Technology (CAST) in 2011, “the state has decided that power coming from outside of the earth, such as solar power and development of other space energy resources, is to be China's future direction.”)


    • A C Osborn says:

      Phil, like you I believe that mankind should be looking forward and not back, most of today’s Science was “Science Fiction” 50-60 years ago.
      However more modern Science Fiction is not being realised due to the ending of the original Space Race which the USA won and then basically withdrew from serious exploration. Based on the original space progress many thought that we would be on the Moon and Mars by now, but instead NASA spends it’s billions on Climate Change.
      They are being overtaken in Space by India, China, France and Russia, but there again those countries coming to space later are re-inventing the wheel, rather than joining a Human collaboration to really push forward.

      The major problem with Beamed Solar Power is that it can be used as a very nasty weapon.

      The Solar System is totally awash with energy, minerals and resources, but instead of going for it man is still squabbling over territory, Religion & Climate Change.
      Arthur C Clarke will be turning in his grave.

      • Phil Chapman says:

        All SPS designs I know about use an encrypted pilot transmitter at the rectenna as the phase reference for the microwave beam, so it can’t be pointed anywhere else — and anyway the peak power density in the beam (e.g., 230 W/sq m) is too low to harm people or anything else.

        A large power supply in GSO could of course be used to power a laser weapon. The power required is tiny compared to the optimal output of a sunsat, which is about 2 GW to the grid. Ten or twenty megawatts is enough to attack other sunsats or any other satellites, to start forest fires or to ignite firestorms in cities, and perhaps to destroy launch vehicles, ICBMs and aircraft in flight. Three sunsats equipped with laser weapons, equally spaced in longitude, could conceivably be used to deny other nations access to space. The laser technology is not quite ready yet, but it’s close. This could be a cheap route to global military domination.

        I don’t know that China (or any other nation) would be interested in such naked aggression, but I believe in the ancient military doctrine that a potential enemy must be judged in terms of his capabilities, not his intentions. I am therefore appalled that we are doing nothing while China is steadily moving toward this kind of capability.

        At the very least, we need a strong international treaty with verifiable limits on lasers in space (e.g., limits on allowable apertures and spectral characteristics), with provisions for in situ inspection of sunsats. I would be happier if some or all of the reliably Good Guys (by which I mean the US, Canada, Australia, the UK, some but not all members of the EU, perhaps a few others) would get there first with a fleet of sunsats, and also prepare but not deploy suitable laser weapons, so that we could make it clear that we would win decisively in any race to establish a dominant military capability in space. Of course potential opponents would not trust our intentions, but they would not start an arms race as long as the outcome of such an effort was absolutely predictable: the Good Guys would win and thus become the gatekeepers for all space activities.

        In my opinion, international competition about vital interests in space is not damaging but beneficial. It doesn’t have to include shooting at each other, and it’s not a waste of resources but a primary source of real progress. We would not have had Apollo without fear of the USSR. One of the reasons for the lack of progress in space is that after Apollo NASA was persuaded by fuzzy-minded idiots that cooperation with the Russians was better than competition. One result was the Apollo-Soyuz Test Project, whose only achievement was to demonstrate the feasibility of an astronaut and a cosmonaut shaking hands in zero-g. NASA wasted a perfectly good Cold War, and then perpetuated the folly by making the International Space Station a cooperative rather than competitive international venture.


        • Peter Lang says:


          I know nothing about spaced based and haven;’t looked into it. However, I don’t understand how the transmission of such power can be viable. Surely if it was viable there’d be no need for solar panels and massive batteries on satellites. We’d simply beam the power they need up to them. And we could reduce our electricity transmission and distribution costs by replacing the transmission system with beams of GW of power. Surely, if it was feasible to beam power from space to Earth stations it would be well developed already as a means to transmit on Earth. Why hasn’t it been adopted already? What are the proven costs?

    • Phil: You have already forgotten more about working in space than I am ever going to know, so I have no way of gainsaying the numbers you present. And if they are correct then yes, space-based solar power is indeed something we should be looking into.

      Which prompts the question – why aren’t we? With the US Military currently fixated on the need to adapt to climate change one would think that funding for something like this would be fairly easy to get.

      • A C Osborn says:

        The answer is simple, it is not really about climate change or clean energy or even cheap energy, as madam Christiana Figueres has already told us.
        It is about UN Agenda 21, power and control.

    • Angus says:

      Tom Murphy did an analysis of this in Do The Math:
      His conclusion was that there is not sufficient benefit over ground based solar to make it worthwhile.

  5. Euan Mearns says:

    Roger, Great post. I think the real killer is energy efficiency. If you take renewable electricity and use it in an electric resistance heater you get almost 100% of the energy as heat. Now let’s imagine that we want to use the power to methane gas to heat our home. We need to 1) make the H2 by electrolysis of water – that uses and loses energy; 2) we need to somehow capture CO2 from a decarbonised electricity system – that uses and loses energy; and 3) we need to combine the H2 + CO2 to make CH4 and water – that uses and loses energy. Just imagine, we start with water as one of our raw materials and we end up making water from the process.

    I’m guessing all this will have a similar energy budget to Audi’s e-diesel that I looked at some months back. Its the same process without the polymerisation stage. I found that the process was about 50% energy efficient – i.e. the EROI is about 0.5, 50% of the input energy is lost as low grade heat.

    And it gets worse. We then need to convert our CH4 back to electricity in a CCGT where about another 50% of the energy is lost.

    So the overall system efficiency is about 0.5*0.5 = 25% efficient. So we need about 4 times as many wind turbines than if we simply used the electricity directly. I was wondering if this harsh reality is built into the French and British models you refer to?

    Simply using the H2 would be more efficient, but you don’t need to spend much time looking at the cost of H2 storage to find out that is also a non-starter. And in fact, for the e-diesel, about 75% of the energy consumption was involved in making the H2.

    There is an “urban myth” that society needs an EROI of 7 or above to function as it does. Wind has EROI of about 20. If we use wind via the storage route the chained EROI drops to 5.

  6. JerryC says:

    And all this to justify scarring the landscape with windmills. 🙁

    • ColA says:

      No JerryC, this includes installing thousands more bird choppers to terrify every man woman and child – Dog, this is horrifying !! 🙁 ;-(

  7. clivebest says:

    We forget that there are only two sources of energy on earth – solar and geothermal and both are produced by nuclear reactions. Solar is fusion and geothermal is fission. Renewable energy is an illusion. The lifetime of a wind turbine is at most 15-20 years. Solar panels degrade rapidly and need continuous cleaning. Neither should really be termed renewable until it can be proven that they can both renew themselves and provide sufficient power for a modern society.

    • glen Mc Millian says:

      I believe the life of newer wind turbines is much closer to thirty years than fifteen or twenty. In any case as older turbines wear out they are can be replaced individually at a relatively small fraction of the cost of putting one up from scratch.

      The thing that amuses me in reading the comments here is that the folks who believe renewable energy is unworkable never seem to spend any time thinking about the undeniable fact that fossil fuels are a depleting resource – the supply remaining growing less every year – even as the population continues to grow.

      I am somewhere between ambivalent and pro in terms of nuclear power but I think the odds of at least one more serious nuclear accident happening within the next ten or fifteen years is pretty high. If such an accident results in a few thousand people dieing and another large area being declared off limits, nuclear power is probably politically dead in Western countries from that day forward.

      Fusion power is not apt to become a commercial reality in the lifetime of anybody reading this blog today.

      Better be getting used to the idea of using renewables – expensive it is true – but not so expensive as doing without – to stretch fossil fuel supplies as far as possible while we learn to live on a lot less energy per capita.

      I could invest the price of just one fairly cheap new car in improving my own personal energy efficiency and live just as well on half as many kilowatt hours as I do now.

      We will adapt to more expensive energy and living with a lot less of it per capita.

      We don’t have any choice.

      Constantly focusing on how much it costs today without considering what can be done about it is shortsighted to say the least.

      When the fossil fuel supply fecal matter hits the fan we will collectively start doing things differently. No sooner. The mindset of the typical person who comments here is proof aplenty of this assertion.

      I would think seriously about moving if I lived in a country almost wholly dependent on imported energy.

      The English people had more to do with bringing about the Industrial Revolution than anybody else – largely because of the immense coal resource. I am pretty sure the last English coal mines will shut down within the next decade.

      There is a Pennyslvania state park where the modern oil industry was born.

      This sort of thing bears thinking about.

      • A C Osborn says:

        Ed, English Coal Mines are only closing due to the low cost of Gas and the skewed market prices due to renewable subsidies.
        There are hundreds of years of Coal under the UK.

      • clivebest says:

        Actually the industrial revolution started mainly because of steel. Steel is an alloy of Iron and carbon and using coking coal made steel production much easier.

        It’s not about renewables or fossil fuels or nuclear. It’s about which mix makes sense. Those wind turbine towers need coal to make them. They need fossil fuels to mine iron ore, copper and make plastics. Solar cells need rare earth’s to make them mined using fossil fuels and transported by diesel. Have you ever seen an electric JCB or earth mover?

        Those fossil fueals will be needed for a very long time – possibly thousands of years, so we should preserve them rather burh them.

        In the end we will have to use nuclear power. We should first understand some of the myths about it.

        Chernobyl killed 25 firemen immediately. The most recent study estimates only 500 early cancer deaths total for the whole of Europe’s population.

        Fukushima killed no-one. There are no risks of radiation induced early deaths. The evacuation of the area caused unneccesary alarm. People could safely return to live nearby now.

        Radiatioactive waste disposal is a political problem rather than a health issue. It seems incredible to worry about leakage 10,000 years in the future when we supposedly are doomed by global warming by 2100.

  8. ristvan says:

    I have been working on a CE post on storage technologies, and have done the hydrogen storage calculations ignoring the physical H storage problems. H2 from electrolysis (a small portion, 4%,of industrial hydrogen is made this way) is ~75% efficient. Ballards 1MW PEM fuel cell is 40 +- 2% efficient according to its specifications. So net efficiency is only 30%. Ruinous.
    One might consider methane storage as an alternative form of carbon capture and recycling, without the sequestration.

    • How might this bear on the ETOGAS graphic in the text, which shows 50% net efficiency from an operating power-to-methane plant?

      • ristvan says:

        I spent yesterday evening working up actual numbers based on a paper they published last year abailable open access. The 50 % is deceptive for two reasons. First, it omits energy inputs for the whole system. Second, it ignores methanation losses. Lets ignore the CO2 supply issue you highlight, and just do a system energy balance.
        First, produce hydrogen by water electrolysis. 4% of industrial hydrogen is made that way today, with energy efficiency (E in, H out)of about 75% on a lower heating balue basis. Second, capture CO2. The international CCS org paper says CCS parasitic loads are 20-30%. Assume 20% for CC alone. Third, combine H2 and CO2 over nickel catalysts at 200-550C. The methanation process is exothermic, and only about half the 20% energy ‘loss’ can be recycled back into the process stream to preheat the input gasses. The process is also only 95% conversion efficient even after three passes through the catalytic reactor (only 70% for one pass at Etogas, so they go through 3 reactors). Finally, assume the methane fires a CCGT to regenerate electricity. Those are about 60% efficient in 500MW units (GE’s Flex 500 is 58% at minimum 40% load, 60% at 85% load, and 61% loaded at 100% of rated capacity).

        So the net round trip efficienty is 0.75 (electrolysis) * 0.8 (CC) * 0.9 (exothermic methanation heat loss) * 0.95 (incomplete catalysis) * 0.6 (CCGT). Net 31%. Ruinous. All Etogas methane storage does is solve the hydrogen storage problem at the expense of a thermodynamically inefficient, costly second chemical conversion step.

        • Graeme No.3 says:


          The 75% figure for electrolysis efficiency is for the continuous high pressure process. This can’t compete economically with the cracking of methane to form hydrogen.

          The efficiency for intermittent hydrolysis is between 38 and 45%, which puts the overall efficiency between 17 & 19%.
          Between breeding unicorns and breeding mules in expense.

          • Peter Lang says:

            Graeme No.3 It great to see you posting here.

            Others might be interested in this humourous and informative few comments that reveal Graeme No.3’s industrial chemical engineering experience.
            First comment:

          • Graeme No.3 says:

            Peter Lang:

            Thank you, I had almost forgotten the exchange. I might add it wasn’t pleasant at the time, the public servants were quite impossible but, as happened, easily fooled. I might also add that the firm is down to about 20 personnel now (advice from another ex-employee earlier this year).

            I can’t help wondering how much of current government policies is based on exasperated responses feeding them nonsense, just to get them off the company’s back.

          • Peter Lang says:

            Graeme No.3

            Thank you for your reply. Sorry I missed it when you wrote it.

            I guess the reduction in the size of the company could be part of the general trend in Australia and other developed countries to push manufacturing out of our countries and replace it with service industries – such as massage centres, discussion groups and other such highly productive services etc.

      • ristvan says:

        Roger, it occured to me after posting mycalculations that your Etogas graphic must be about right for the electricity to methane half of the storage cycle. 0.5 But include CCGT electricity generation to get back to where one started (the point of ADME is to store renewable electricity to be reproduced when needed) and you get 0.5 * 0.6 = 30% round trip efficiency. I calculated 31% doing the math the hard way, process block by block. Regards on a very good post.

        • ristvan: Thanks. I think that clears it up. We are looking at a 30% round-trip efficiency, which as you say is ruinous.

          It brings up another point too. ADEME’s Figure 34 shows an almost exact balance between stored and released power. So they’ve either underestimated stored power by a factor of three or overestimated released power by the same factor.

  9. Peter Lang says:

    Roger Andrews,

    I am a new follower of your posts. ‘The Difficulties Of Powering The Modern World With Renewables’ and ‘Renewable Energy Storage and Power-To-Methane’ are excellent, clear, concise explanations of the real world realities of electricity generation systems that are needed to meet the requirements of modern industrial societies.

    Could I suggest a follow up analysis and post:

    What kind of energy system would supply low emissions electricity at least cost?

    • All costs in, say, 2014 US$/MWh
    • Must meet current electricity system requirements
    • Assume current costs or projected costs to 2020 but no further out than that

    Break the costs down into these three major components:
    • Generation (including the fair market cost for land area)
    • Energy storage if it is needed to meet the current reliability requirements
    • Transmission – (transmission to intermittent renewable plants must have the capacity to carry the full name plate capacity of the renewable energy plant, even though their capacity factor is very low on average).

    I did a simple example of such a comparison for Australia’s National Electricity Market, for four mostly renewables and one mostly nuclear scenarios here:

    Figure 6 compares capital costs, cost of wholesale electricity and CO2 abatement cost (i.e. with transmission costs additional to the existing grid) for the five scenarios.

    Figure 5 compares the CO2 emissions intensity of the systems for these five scenarios

    Figures 7 compares my very rough estimate (limit analysis) of the transmission cost (capital cost and cost of electricity) for the five scenarios.

    You can download the explanation of the renewables scenarios from here and my spreadsheet for the four renewables scenarios from here:

    The inputs for the mostly nuclear scenario are in the Appendix in the first link; here it is again for convenience:

    • Peter: Today marks the first anniversary of my 37th birthday and I just got back from a celebratory dinner and it’s getting late and shortly I’m off to bed. But your scenarios look very interesting and I will take a close look at them tomorrow. So don’t go away.

    • Euan Mearns says:

      Peter, I had a quick look at your report. Here is link to my 2050 pathway for UK. High nuclear came out as the cheapest and least impact.

      • Peter Lang says:


        Thank you. Excellent post. Our thinking is closely aligned on strategy (but I’d differ on a few relatively minor points points). Lots we could discuss, perhaps on future posts.

        I played with the DECC calculator some years ago and followed David Mackay’s various scenarios as he developed and optimised them further after publication of his book. However, I’ve put more of my effort into looking at the Australian costs and emissions intensity. There have been many studies in Australia and CSIRO has two calculators which are useful for reality checks, but they do not include some important inputs and parameters. I could summary some results from these calculators in comments if there is interest. However, I am looking forward to Roger’s analysis (and yours?) – but perhaps you’ve posted the link to your DECC analysis to hint that it’s already done and you don’t intend to tackle it again at this stage?

        I am not clear if your analysis and DECC’s takes into account the full system costs, and properly takes into account the issues of intermittency.

        I’ll post some more in separate comments. [let me know if I am posting too much].

      • Peter Lang says:


        As you have highlighted the requirements for the electricity system must be defined as a starting point for such an analysis. I have a different order for the essential requirements for the electricity system (for all countries, even the poorest countries with minimal electricity grids as I see this debate being about solutions for cutting global GHG emissions, not just individual countries emissions). For convenience of anyone else who may be following this, I’ll post your priority order first, and then mine.

        You say:

        My priorities in designing our energy future in very approximate descending order of priority are as follows:

        Health and safety
        Security of supply
        Total environmental impact

        I say:

        1 Energy supply requirements

        The most important requirements for energy supply are:

        1. Energy security (refers to the long term; it is especially relevant for extended periods of economic and trade disputes or military disruptions that could threaten energy supply, e.g. 1970’s oil crises [1], world wars, Russia cuts off gas supplies to Europe).

        2. Reliability of supply (over periods of minutes, hours, days, weeks – e.g. NE USA and Canada 1965 and 2003 [2])

        3. Low cost energy – energy is a fundamental input to everything humans have; if we increase the cost of energy we retard the rate of improvement of human well-being.

        Policies must deliver the above three essential requirements. Lower priority requirements are:

        4. Health and safety

        5. Environmentally benign

        1.1 Why health and safety and environmental impacts are lower priority requirements than energy security, reliability and cost

        This ranking of the criteria is what consumers demonstrate in their choices. They’d prefer to have dirty energy than no energy. It’s that simple. Furthermore, electricity is orders of magnitude safer and healthier than burning dung for cooking and heating inside a hut. The choice is clear. The order of the criteria is demonstrated all over the world and over thousands of years – any energy is better than no energy.

        • Euan Mearns says:

          Peter, I have no axe to grind on ranking priorities. In fact the priorities may vary from country to country. I have grown up on a diet of health and safety and so placed it high. You make a good point about looking at health risks through the energy use chain – wood fires in mud huts is not good. China has provided some prosperity with cheap dirty coal and is now looking to provide better prosperity with cleaner coal. Energy systems and society need time to evolve together.

          • Peter Lang says:

            Thanks Euan,

            I think we are in close agreement on important strategic issues.

            India’s energy and climate change challenge:

            Any electricity is better than no electricity. At the moment 400 million people in India have no electricity at all. Across the world it is about 1.3 billion (from memory).

            If the leading nuclear countries and the IAEA can remove the impediments that are thwarting the development of nuclear power the cost of electricity from SMR’s will come down to less than the cost of electricity from fossil fuels (over several decades). As this happens nuclear will become the least cost option for new and replacement generation capacity. The savings in infrastructure would be enormous for developing countries. They’d still need an electricity grid. But they would not need pipelines, railways, ports and ships to transport fossil fuels. 20,000 times less fossil fuels would need to be transported with the LWR reactors and up to 2 million times less with breeder reactors.

      • Peter Lang says:

        Using the CSIRO eFuture calculator to compare the least cost options to reduce CO2 emissions by 2050 for scenarios with and without nuclear permitted (Australia’s are scared stiff of nuclear), and adding estimates for grid costs, decomissioning, waste disposal, accident insurance and the expected monetary value (EMV) of the risk that technologies will not be able to meet the requirements by 2050, I get the following costs:

        The estimated total system cost of electricity (in 2014 A$) for the two options are:

        No nuclear = $244/MWh
        With nuclear = $91/MWh

        Therefore, the cost of electricity for the ‘nuclear not-permitted’ option is 2.7 x higher than the ‘nuclear permitted’ option. And emissions would be 3.2 times higher with nuclear not permitted.

        The risk that renewables will not be able to do the job is the major risk that those concerned about GHG emissions should be most concerned about, not the costs of nuclear waste disposal, decommissioning, accident insurance etc. all of which are negligible compared with the LCOE and the risk that renewables do not deliver the benefits claimed by their proponents.

      • Euan & Peter

        I’ve done a lot of work on energy scenarios since I last looked at the DECC calculator and it’s now apparent to me that it gives highly misleading results. It throws jigsaw puzzle pieces on the table until the space is filled without making any attempt to fit them together, and the result is a scenario which looks good on paper but which has no chance of working in practice, particularly when the scenario includes high levels of renewables generation.

        It would be an interesting exercise to take a high-renewables-penetration DECC scenario that meets UK emissions targets, convert it to hourly generation by factoring actual Gridwatch generation and compare it to demand for, say, 2013 or 2014. I’d be willing to bet the UK would be freezing in the dark for much of the time during the winter.

  10. Gaz says:

    All, as ever, interesting comments, my conclusions after watching all this unfold, a process in gradulisation is happening, two steps forward one step back – so barely anyone noticed (obsessed with media induced political correctness, house prices & whatever else is served up for consumption). The de-industrialisation of the country & the west continues unabated.

    It occurred to me and many others that this is intent, de-industrialisation & equality (equally poor) for all – a new world order if you like, that goes under the name of globalisation!

    Renewables are a boondoggle and a wild goose chase and co2 is a meaningless (from AGW stance) trace gas essential for life on earth – an opposite meme is portrayed daily via the media/schools etc.

    More so, fossil fuels are running out – disaster is just round the corner! Again false imho…

    So the public are feed dog-crap for info and forget (as H/T Roger points) that a hundred years ago life was very different and harder!

    We are really heading back to feudalism & surfdom if we let them – set and frame all the arguments, and we spend all day and night arguing who’s religion is best!

    Best to all!

    • ristvan says:

      Gaz, you might want to read Gaia’s Limits and Blowing Smoke. Both ebooks available Amazon Kindle, Apple iBooks, B&N Nook, KoBo… Yes, CAGW is way overblown. No, we will not ‘shortly’ run out of fossil fuels.
      BUT we will shortly hit peak oil production including all unconventional sources (IMO) between 2020 and 2025, despite the present temporary overabundance from US fracked shale. That means growing scarcity, sharply rising prices, and economic disruption thereafter. Many separate essays on details in the energy portion of Blowing Smoke. And, taking the long view, very difficult to substitute for liquid transportation fuels. Gaia’s Limits lays out all the scenarios including electrification, hybridization, intermodal, biofuels, gas and coal to liquids. The one bright note is that Siluria Technologies OCM pilot plant has now been successfully operational for 6 months. If that same hurdle can be passed with their ETL (presently works fine at large lab scale) then shale gas buys several decades of liquid synfuels. The TRR of shale gas is now about 15%; for shale oil it is only 1.5%.

  11. ColA says:

    We need to start educating Australians and growing our nuclear industry. I am particularly interested in Liquid Fluoride Thorium Reactors (LTFR) they have been around for nearly 70 years (tossed over for Uranium’s bomb). Thorium is abundant in most countries and easily mined, LFTRs are FAILSAFE, they can use old Uranium/Plutonium but NOT very useful for making bombs, waste is minimal and not as radio active as current LWRs
    The Yanks successfully ran and proved an experimental in the 60’s (for 6,000hrs?) India (and China?) are well advanced in developing this technology and we sit here squabbling about bird choppers and poisonous CO2 fertiliser! Thats gotta be a Cassandra Paradox!!

    • Flocard says:

      I believe there is a sort of mythology around thorium fueled reactors. There are attributed virtues which do not withstand close examination. I believe this mythology has to do with the fact that even those who think that nuclear energy has to be part of the world energy future share many misgivings of the anti-nuclear associations. They believe (wrongly in my opinion) that Th-fueled recators will resolve most problem. I belong to the group of people who think that for some countries without energy resource (such as France) nuclear energy will be necessary for a long time, I have worked on Th reactors (fast molten salt reactors). many of their so-called virtues do not really exist. Many other problems which took decades to be solved (or nearly solved) for the U-cycle are still unsolved. These problems have nothing to do with nuclear energy but with chemistry, material science, safety design and security design.

      Myth 1 : inexhaustible resource. People tend to forget that Thorium only exists in nature as the isotope Th232 (or Th2 to shorten). Uranium exists in the forms of two isotopes U235 (or U5) which is a small fraction of natural uranium and U238 (or U8) which comprises the largest part. The Uranium which starts reaction is U5 which is said to be “fissile”. while U8 which is only “fertile” has to swallow one neutron to transform (in two steps) in plutonium Pu239 (Pu9) which again is fissile and can burn in the reactor. Th2 is the equivalent of U8 (U3 would be for Th2 what Pu9 is for U8). There is no fissile material in the thorium mineral. Thus to initiate a Thorium reactor one needs to have added some fissile material which could be U5 (from the same mine which ) or Pu9 (from standard reactors) or other fissile materials to be found for instance in the radioactive waste od standard reactors. The resource in Th is as inexhaustible as the resource in U8. Moreover the U8 resource has one advantage : it is already on shelf in countries which have a nuclear industry. Indeed U8 is presently considered a “waste” to be separated from natural uranium to get the U5 enriched fuel for standard reactors. As an example presently the stock of U8 stored in France corresponds to about one thousand year of present energy production in fast reactors. Note that the former rare-earth industry has also left on shelf in France for about 100 years nuclear energy in the form of Th2. Thus if fast reactors are considered a possible option, the uranium resource is certainly huge. I am not a geologist but I tend to believe that the U8 resource is of the same order as the Th2 resource

      Myth2 : waste is less radioactive. both reactors will have the same short term radioactive waste as this waste is dominated by the fission product. The medium term radioactivity of the present reactor waste is dominated bu Pu9. If no fast reactor is being built to burn it, the medium term radioactivity of our present reactors will be larger by a factor 5 to 10 over that of a Th fueled reactor. If fast reactors are built (do not forget that they are the equivalent of Th reactors) the radioactivity of the Th-cycle waste slightly exceeds that of a Fast reactor waste. Any how in the medium long and long term there is no avantage (smaller radioactivity of the waste) in the Th cycle over the U cycle

      Myth3 : no bomb. I have attended security sessions. Once started the Th-cycle produces a fissile material U233 (analogue of Pu239). Bombs with about the same critical masses can be made from any fissile material of the actinide region. The question is more a matter of handling (intrinsic radioactivity). As far as I know for military people all these products are considered security dangers

      Unsolved problems 1 : chemistry. A Th nuclear cycle (Th2-U3) is the equivalent of a fast reactor cycle (U8-Pu9). In other words reprocessing is a necessity (although suposedly made on the nuclear reactor site in the present Th design, it is the equivalent of the reprocessing performed at the La Hague site for the U-cycle. The chemistry for the Th is more difficult than that of the U-cycle and is very far from reaching the 99,99 % efficiency with chemical agents which can be regenerated and are not using polluant chemical (only H, C, N and O atoms avoiding heavier elements)

      Unsolved problem 2 : material science. Reactor science is less a science of nuclear engineers than of plumbing and thermician engineers. Molten salt reactors are using highly corrosive substratum. In addition they work at a much higher temperature which pushes the alloys (they have to bbe Ni based) to their limit. Safety demonstration i still very far to be achieved.

      Unsolved problem 3 : safety design. A molten salt reactor cannot rely on the experience on safety design acquired through thousands of years of experience with standard and even fast reactors. An entirely new safety design has to be developped and made approved by safety authoriries.

      Unsolved problem 4 : security. The separation unit associated with the reactor will manipulate stuff which could become a danger in hands of terrorist whether they want to make a bomb or more simply to disperse it creating, in not real harm, at least panic given the general state of mind concerning radioactivity danger (as compared to other even more harmful dangers which are commonly accepted).

      • Peter Lang says:

        This is a really excellent comment. Thank you. Here is a UK National Nuclear Laboratories report to the UK government on viability of thorium reactors in the near term: ‘Comparison of thorium and Uranium fuel cycles’

        “I am not a geologist but I tend to believe that the U8 resource is of the same order as the Th2 resource.”

        There is four times more thorium than uranium in the Earth’s upper continental crust. But both elements are in huge quantities compared with what will be needed to power humanity for millennia. Nuclear fuel, in concentrations that will be extractable, is effectively unlimited

      • Euan Mearns says:

        Hubert, many thanks for this most informative comment – but where does the truth lie?

        I believe this mythology has to do with the fact that even those who think that nuclear energy has to be part of the world energy future share many misgivings of the anti-nuclear associations.

        I think this is quite true. I am supposed to know a bit about radioactivity etc, but find it impossible to judge the data / evidence on safety and the viability of the various technologies. I even a wrote a post a year ago:

        • Flocard says:

          Ar CNRS we really worked hard on the subject. We were invited to participate in the GenerationIV forum to analyze this option which was one of the four main lines of work retained. We also were in charge of preparing the documents on Th for the Sustainable Nuclear Energy-Technical Platform supported by EU and Euratom

          When I say that there are unsolved problems I am no saying that they are insolvable problems. On the other hand the amount of work on molten salt reactors is minuscule compared to number of man-hour work on the U cycle.

          It is generally said that the fact that a large amount of initial work was conducted by the military essentially for powering submarines and that this oriented decisively the future of nuclear energy. That is certainly true but only partially. The fact that the coolant and moderator in present reactors is water (a liquid which has been abundantly studied) played also an important role. The choice of Na as coolant in the fast reactors has also very solid motivations (a liquid at moderate temperatures, a high enough boiling temperature, very good thermal exchange potential; moderate density and thus constraints on pumps, minimal corrosion and chemical interaction with standards steels, …)

          With molten salt, one enters an completely unchartered physico-chemical space both for the fluids and the vessel and pipes. Not to mention the very high temperatures.

          It is said that the chinese are now working on it. Nothing of the sort can be expected to happen in the (extended) western world where presently nuclear energy is being killed (Germany, Switzerland, Japan), on the defensive (France, USA), trying to recuperate a competence it has willingly lost (UK, Japan in some undecided future). The western nuclear industry and research which still exists does not have the strength (the will ?) to investigate new options. They are only able to maintain a research effort on optimisation of what presently exists.

          Note that with Th another option is being seriously investigated. I mentionned that in present reactors U5 starts the reaction. Via the Pu9 route a small fraction of the U8 (in the fuel Uranium is only enriched in U5 up to say 3%, the rest is U8) is also burnt.
          Along that some other Pu9 is also produced and not burned. The ratio of fissile material in the burnt fuel over the fissile material in the initial fuel is typically 35%. The higher this ratio the close one gets to “even regeneration” (which corresponds to a ratio equal to one). One can show that (for reasons which have to do with nuclear physics) if one mixes Th2 into the fuel of reactors very close in their structure (water cooled and moderated) to those operating today one can significantly increase the ratio (from 35% to say 60-70%). This is considered an interesting option because in a way it amounts to extending the not so important U5 resource (the fissile part of the mineral) by a factor 2 without any major change in an already well tested nuclear reactor technology.

          Note that the problem is now displaced to chemistry. One has to develop a spent-fuel reprocessing industry capable of handling simultaneously the U-cycle (with Pu9) and the Th-cycle (with U3) along with the various radioactivity problems (there is a dangerous gamma-ray in the Th2-U3 chemistry which has no equivalent in the U8-Pu9 chemistry)

          The indians who because of their initial refusal to adhere to the non proliferation treaty (they wanted a bomb just as Israel, Iran now – and Pakistan which signed the treaty but built the bomb nevertheless) were shut out of the world uranium trade, were the first to investigate thoroughly this Th option. They first relied on Candu reactors to bypass the question of U-enrichment (and have easy access to Pu9 for their bomb because of the technical features of the Candu technology). At the same time they launched the most extensive effort ever made on Th-cycle chemistry. A good deal of the world chemical expertise is there.
          I assume that their policy has changed now that following agreement with the US congress, India has now open access to the Uranium trade.

          I did’nt mention Russia which has also a lot of expertise and is very active on all fronts and options but not so much on Th-cycle (although their chemists are extremely good in particular on the subject of molten salts). May be Russia will collaborate with China on that technology.

          • With molten salt, one enters an completely unchartered physico-chemical space both for the fluids and the vessel and pipes. Not to mention the very high temperatures.

            Molten salt seems to be working in concentrated solar power plants:


          • Flocard says:

            They are not the same salts.

            In solar power plants the salts are only used as heat storage more or less in a static way (or in a slow moving way). The volume (the mass of salt) is not really a problem (although it probably explains why these solar plants are so expensive and have not commercially suceded). The benefit of extending the electricity production into the night does not compensate for the complexity of the system (a large fraction of the stored energy is lost)

            In molten salt reactors the salts act as carriers of the nuclear fuel (which is dispersed within the salt) and thermal carrier. It is crucial that the salts resist the large radiation level inside the reactor (not too many transmutation and destruction of molecules) while being able to transfer rapidly their heat content (generated by the fissions) while they rapidly (in less than 10 seconds) cycle out then back into the core of the reactor.

            The salts must also be amenable to gaseous extraction through He injection of some of the most harmful fission products which would otherwise poison the reactor (diminish the efficiency of the nuclear reactions).

            Other fission product extractions and reprocessing is less demanding in terms of volume and time response.

            Finally the temperature range is more demanding in reactors, typically 700°C or more. It is sometimes presented as an advantage due to the improvement of the Carnot efficiency. On the other hand the alloys for the vessels, the pipes, the valves and the heat exchangers must resist to corrosion (mechanical and chemical) by salts on their internal face and to chemical coorosion by oxygen at such temperatures on the outside face. Standard steels or composite materials for high temperature turbines do not face the same material challenge

            The salts considered in reactors are fluor based (F) not chlorine (Cl) as is often the case for heat storage in solar plants.

            Note that also there have been problems with salts in solar plants despite the fact that the material science constraints are not as exacting as in reactors. Leaks in the piping system are certainly to be avoided also in solar plants but their consequence is not so great as regards safety. Any nuclear safety authority will ask for a demonstration that a leak can’t happen or can be controlled in a matter of split seconds in a molten salt reactor. We are very far from that.

            Otherwise, molten salts reactors have virtues of course. Otherwise they would not have been considered for such a long time in the sixties up to the beginning of the eighties when the US finally chose the standard Na technology for their pre-industrial prototype of fast reactor which in the end never really achieved much and was abandoned. They are also among the systems considered by the generation IV international forum.

            Right now in the mouth of their proponents the molten salt reactors have only advantages (which are real and that I could spell out); still this (having only advantages) is a characteristics shared by all the electricity producing systems which do not yet work.

          • Peter Lang says:


            Excellent information. Much appreciated.

          • roberto says:

            “Molten salt seems to be working in concentrated solar power plants:”

            Incidentally, in THOSE molten salts, which have a mix of salts containing, among other things, potassium, the amount of stored radioactivity thanks to the natural K-40 is so large that, by applying the standards forced to nuclear power plants, they should require the salt containers to be encased in triple armored concrete domes, as required for nucleare power plants.


    • Euan Mearns says:

      Thorium is abundant in most countries and easily mined

      ColA – you make some good points here. But when we talk about abundance it is normally in a relative sense and Th is a rare trace element. It commonly occurs in an accessory mineral called monazite that is a phosphate mineral. It has high density and is EXTREMELY hard and resistant to weathering. Hence monazite is often concentrated by sedimentary processes that can sort minerals according to density.

      Monazite is near indestructible in the lab. Hence, dissolving it to extract the Th is no simple process. It also contains high concentrations of the Rare Earth Elements (REE) and is hence implicated in the environmental and health degradation in China where most of our REE come from.

      So bottom line, Th is not scarce and it can be mined, but it is not simply lying around everywhere waiting to be picked up. Certain U minerals on the other hand are easily soluble in dilute acid and can be “mined” by acid leaching of surface strata.

      Roger is a mining geologist and its possible he knows more about this than I do 😉

      • Euan: I put on my mining geologist hat and took a quick look at thorium, and as far as I can determine there are no thorium mines per se. The small amounts of thorium that are produced are by-products of rare earth mining. So while thorium probably is “relatively abundant” in most countries – with the emphasis on “relatively” – we don’t really know whether it can be “easily mined” or not. As you point out, uranium is a lot easier to process than monazite.

        I’ll add another word of caution. Unless we commercialize fast neutron reactors we probably don’t have enough uranium to support a major nuclear expansion. I haven’t looked into how much thorium we have.

  12. Peter Lang says:


    I agree we need to educate Australian about nuclear. Australia is the only member of the G20 that doesn’t have nuclear power and has no plans to start. We have lots of cheap, high quality, low sulphur coal close to our major demand centres. So, for nuclear to be viable, the cost will have to cone down a .long way. Here’s how I suggest that could be done:

    How to make nuclear cheaper

    Nuclear power will have to be a major part of the solution to significantly reduce global GHG emissions. It seems it will have to reach about 75% share of electricity generation (similar to where France has been for the past 30 years) and electricity will have to be a significantly larger proportion of total energy – this could reduce the emissions intensity by around 90%.

    To achieve that, the cost of electricity from nuclear power will have to become cheaper than from fossil fuels.

    Here’s my suggested way to get to nuclear cheaper than fossil fuels:

    1. The next US Administration takes the lead to persuade the US citizens nuclear is about as safe as or safer than any other electricity source US can gain enormously by leading the world on developing new, small modular nuclear power plants; allowing and encouraging innovation and competition; thus unleashing the US’s ability to innovate and compete to produce and supply the fit-for-purpose products the various world markets want.

    2. The next US President uses his influence with the leaders of the other countries that are most influential in the IAEA to get the IAEA representatives to support a process to re-examine the justification for the allowable radiation limits – as the US announced in January it will do over 18 months “‘WNN 20/1/15, ‘Radiation health effects’

    3. Once the IAEA starts increasing the allowable radiation limits for the public this should be the catalyst to reducing the cost of nuclear energy.

    a. it will mean radiation leaks are understood to be less dangerous than most non experts believe > less people will need to be evacuated from accident effected zones > the cost of accidents will decline > accident insurance cost will decline;

    b. the public progressively reconsiders the evidence about the effects of radiation > they gain an understanding it is much less harmful than they thought > fear level subsides > opposition to nuclear declines > easier and less expensive to find new sites for power plants > increased support from the people in the neighbourhood of proposed and existing power plants > planning and sight approval costs decline over time;

    c. The risk of projects being delayed during construction or once in operation declines; > all this leads to a lowering of the investors’ risk premium > thus reducing the financing costs and the fixed O&M costs for the whole life of the power plants;

    d. Changing perceptions of the risks and benefits of nuclear power leads to increasing public support for nuclear > allows the NRC licensing process to be completely revamped and the culture of the organisation to be changed from “safety first” to an appropriate balance of all costs and risks, including the consequences retarding nuclear development and rollout by making it too expensive to compete as well as it could if the costs were lower (e.g. higher fatalities per TWh if nuclear is not allowed to be cheaper than fossil fuels).

    4. NRC is revamped – its Terms of Reference and its culture are changed. Licensing period for new designs is greatly reduced, e.g. to the equivalent of the design and licensing period for new aircraft designs.

    5. Small modular reactors are licensed quickly. New designs, new versions, new models, and design changes are processed expeditiously. This will lead to more competition, more innovation, learning rate continually improves so that costs come down.

    6. The efficiency of using the fuel can be improved by nearly a factor of 100. That gives some idea of how much room there is to reduce the cost of nuclear power over the decades ahead.

    7. Eventually, fusion will be viable and then the technology life cycle starts all over again – but hopefully the anti-nuke dinosaurs will have been extinct for a long time by then.

    • Euan Mearns says:

      Peter, we (the OECD) are currently in the grip of anti-capitalists. How this came about will be something for historians to muse over. Don a Green cloak and claim to be saving the Planet and Humanity from Humanity and it seems anything is possible. Wave the climate sensitivity = 4 flag and dispense with the need for any evidence whatsoever to support it leads to an anti – FF lobby. Then wave a radiation will kill everyone flag and that leads to an anti – nuclear lobby. And then wave away all the harmful impacts and economic suicide associated with new renewables and that leads to the pro – renewable lobby.

      Am I correct in my summation that it is the same people who see climate melt – down, who are anti FF, who are anti-nuclear and who are pro-renewables. And these same people who have contorted the meaning of the terms “science” and ‘logic” beyond the recognition of “old timers” like us who seem to view the way the world works through a totally different lens.

      • Peter Lang says:


        I agree with you. I often say that progress is being blocked by those who call themselves ‘Progressives’.

      • Leo Smith says:

        You are describing my sister to a T. You should throw in an Arts degree, Vegetarianism, add homeopathy as well, and of course she is married to a German.

  13. Proteos says:

    Just to add a few words:
    * for the long term storage, the amount of delivered electricty is about 20TWh in the ADEME scenario. It is written plainly in a footnote somewhere in the report. This requires 60TWh of inputs.
    * the name plate capacity of the long term storage is minimized by playing on shorter term storage technos to be used as reserves for the long term storage. Imports seem to be used too to fill in the long term storage. Note that, for exemple, the amount of gas produced in June amounts to a capacity factor of about 80% for the electricity to gas facilities. In other words, they are running continuously, whereas solar power is expected to provide a large part of the stored energy in June.
    * I think you misunderstand figure 34 in the ADEME report. if you have 17GW of gas to electricity in the system, with an efficiency of 60%, you need about 19000GWh of gas to run it continuously for 28 days. That’s what is implied by the scale on the left: “PCS” stands for Higher Heating Value

    I agree with the grist of what you say, in that the biggest issue with large scale electricity storage is only proven with hydro power today. All other technologies are extremely expansive and limited to small scale prototypes.

  14. frédéric Livet says:

    Main difficulty in methane storage is the low efficincy of the cycle:
    -hydrolysis: less than 70%
    -“Sabatier” (or similar reaction to obtain hydrocarburs) about 70%
    -Re-obtainig electricity:<60%

    Total efficiency is <30%. This means that the cost of re-generated electricity is 3-4 times hogher than the initial cost (and renewables are in the 100$/MWh range). The usual argument is that this electricity should be lost and has a marginal zero cost. In this case, how is financed the high investement cost of the renewables? This subtility between cost and price is illusory!

    • Euan Mearns says:

      Frederic, I think I left a comment to this effect. The wind electricity is already paid for with subsidy and would be wasted so Green logic dictates that is tantamount to free. All these crazy schemes will work at low level penetration and politicians will driven around in Green cars. Try to scale it and the cost will go through the roof.

      Nothing Greens like more than environmental destruction and waste 😉

  15. David MacKay says:

    Great post! You could extend it into a third country by looking at the German Energiewende (which means “Energy banana”); I recall that the Energy banana depends very heavily on synthetic methane. I don’t know if they have detailed where they would get the required carbon atoms from.

    In the German transport sector there seem to be two camps: VW Audi assert that they will make zero-carbon cars powered by synthetic methane; and BMW assert that they will make zero-carbon cars powered by fossil-free hydrogen.

    Since a hydrogen store is likely to be more efficient (having fewer chemical steps) than a methane store, it might be a good idea to look further at the question of how much hydrogen can be stored. Perhaps multiple TWh of hydrogen _can_ be stored in salt caverns? (I don’t know why CAT asserted that only ‘small’ amounts could be stored thus.)

    • David: Thank you.

      I took a quick look at the requirements for storing hydrogen in caverns.

      According to the Energy Storage Association “Very large amounts of hydrogen can be stored in man made underground caverns of up to 500,000m3 at 200 bar (2,900psi), corresponding to a storage capacity of 167GWh hydrogen (100GWh electricity).”

      Two hundred caverns of this size would be required to store the 20TWh of energy that I estimate would be required to support ADEME’s scenario and maybe as many as five hundred to store ADEME’s implied ~46TWh. As to the practicability of excavating this many salt caverns in France, it all depends on whether there are enough soluble salt formations, and I can’t find any information on that. There may be, there may not.

      It would also be desirable to locate the hydrogen-manufacturing plants and the hydrogen-fired power plants next to the caverns to avoid the problems involved in transporting hydrogen over long distances.

      On the face of it storing methane in tanks seems like a much simpler option, but as I discuss in the post it would be desirable to locate the methane plants next to the biogas plants that supply them with CO2 to avoid the problems involved in transporting CO2 over long distances.

      Ain’t no free lunch on this one. Banana peels really are slippery 😉

      • Peter Lang says:

        “There are two types of cavern storage – salt caverns (natural formations) and rock caverns (natural and constructed). Salt caverns are developed by flushing the salt deposits from underground deposits leaving a cavern that can then be used to store oil. Rock caverns require excavation to develop the underground storage facility. The IEA Report gives the following development costs for cavern storage (initial capital cost):
         Salt caverns USD8-12/bbl (or USD50-75/m3)
         Rock caverns USD15-31/bbl (or USD94-195/m3)
        It is only worth developing underground storage if the facility is of sufficient size. The IEA note a minimum storage capacity of 1.5 million m3.
        In the Asia Pacific region, Korea has rock cavern storage and Singapore is currently developing a rock cavern storage facility. In Singapore’s case the incentive is to free up land currently used for above ground storage. The publically released cost of developing the Singapore rock cavern has been given as SGD890 million which works out as USD75-80/bbl (~USD490/m3). This is two to three times higher than the upper end of the IEA Report estimate. The Japan/Vietnam study paper on floating storage gives a construction cost for underground cavern storage of USD466/m3 more in line with the Singapore cost than the IEA Report estimate .”

        Perhaps ~US$500/m3 is a reasonable round figure to use for estimating the capital cost for underground storage.

    • Peter Lang says:

      Cavern Storage costs: Appendix 2

       Salt caverns: USD50-75/m3

       Rock caverns: USD94-195/m3

      • Thanks Peter, good stuff.

        If we assume an average IEA cost of $100/m3 and if I’ve done my sums right then ADEME’s implied 46TWh of storage would cost $23 billion, expensive but not totally out of line when we consider that France’s lights would go out if it wasn’t there.

        But if we assume your estimate of $500/m3 then the cost goes up to $115 billion, which certainly would raise some eyebrows.

        And do these costs include the associated infrastructure, or are they just the cost of excavating the caverns? .

        • Peter Lang says:


          I expect the $500/m3 would apply to the full. cost of the oil storage facility, including infrastructure (but I haven’t checked the sources for those figures).

          Instead, I looked at the cost of excavation, including rock support and water control, for three 12.7m diameter tunnels for a conceptual study for a 9 GW, 400 GWh pumped hydro storage facility connecting two existing large reservoirs in the Australian Snowy Mountains scheme. The unit cost used for the tunnels was A$155/m3. The unit rate would be lower for larger caverns. This should be escalated by around ~15% for inflation since 2009 and by about 30% to US$ due to exchange rate changes. So, I , all in all, I suspect the IEA estimate of around $100 to $200/m3 for rock caverns is probably in the right ball park.

          You and other readers may be interested in this post on the conceptual study for the Tantangara-Blowering pumped hydro scheme. The reviewer’s comments (at the end of the post, before the comments) may be particularly interesting to you and others with an interest in energy storage.

          P.s.:The project is not viable, either technically or economically.

    • Peter Lang says:

      “VW Audi assert that they will make zero-carbon cars powered by synthetic methane”

      Audi (and the US Navy) claim they can produce petrol, diesel, jet fuel and other hydrocarbon fuels from seawater for US$3-$6/gallon using existing commercially available technology. These cost estimates assume the hydrogen is produced by electrolysis. The costs could come down enormously (e.g. by 50% or more) if the hydrogen is produced by high temperature nuclear reactors.

      Nuclear fuel is effectively unlimited in the upper continental crust at concentrations that will be commercially viable (eventually). Combine effectively unlimited cheap electricity and unlimited sea water and we have potentially unlimited hydro carbon fuels for transport … and no need to incur the enormous costs of changing the current infrastructure.

      Furthermore, every country can have secure energy supplies. They can store nuclear fuel sufficient for many years of their energy needs in warehouses or small underground bunkers.

      Every way we look at it, nuclear looks likely to be the predominant source of energy in the future. All we need to do to make progress is to remove the massive regulatory impediments that are blocking progress by making it many times more expensive than it should be.

  16. alexjc38 says:

    Ideally, this comment would best go with your excellent post “Eigg – a model for a sustainable energy future” last September – I’ve put together a transcript of BBC’s Costing the Earth (20 May, this year) about renewables on Eigg, which does also mention hydrogen as a possible future storage mechanism for the island:

    • Peter Lang says:


      IMO, those who are genuinely concerned about reducing global GHG emissions (and are also concerned about the well being of humanity in the short, medium and long term) should stop advocating for renewables. We should advocate for economically rational and sustainable technologies and policies. Renewables are not sustainable so it is highly unlikely they will be able to provide a major proportion of global energy needs, either now or in the future. Therefore, they will not be able to play a major role in reducing global GHG emissions.

      The reason renewables are not sustainable is that their ERoEI is too low to provide sufficient energy to power modern society as well as reproduce themselves:

      The consequence of advocating for renewables is that we are delaying genuine progress … by decades. The Australian Renewable energy Target requires Renewables provide 23.5% of our electricity generation by 2020. We’ll have to raise the proportion fo electricity generated by wind power from 4.5% in 2014 to about 15% in 2020 – i.e. triple the amount of wind energy in 4.5 years. Incentivising renewables to substitute for fossil fuels in Australia is forcing new high cost capacity to cause fossil fuel plants to shut down. It will take two or three decades before we will be in a position where we need sufficient new capacity to make nuclear power a viable option to consider. So we are stalling real progress to cut emissions.

      For those not aware, intermittent renewables are much less effective than nuclear at reducing GHG emissions. Reneweables require back up and because of their intermittent nature, they do not fully displace the emissions when they displace energy from thermal generators. In Ireland in 2011. renewables were just 53% effective at reducing emissions per MWh generated by wind . In Australia wind was 78% effective in 2014 (when wind contributed just 4.5% of electricity) and projected to be about 60% effective by 2020 when wind provides about 15% of energy . Nuclear power, on the other hand tends to be more than 100% effective (because it replaces baseload coal, and the highest emissions intensity coal).

      To put a figure on the risk renewables will not be able provide a large proportion of global electricity in 2050, I’ve estimated risk at $54/MWh. That cost needs to be added to all the other costs of electricity supplied by renewables (LCOE for generation, their full share of grid costs, decomissioning, etc).

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