If there’s ever an example of mistaken groupthink then the case of working out the task of finding the cheapest and most efficient way of long-term storage of renewable energy could well be one of the most shining examples. Hydrogen is the default choice it seems, but defaults can be wrong!
The point of the e-fuels or hydrogen is to power gas engines or turbines to provide electricity when there is a long-term shortage of wind or sun. (Batteries etc can cope with intra-daily fluctuations, but are too expensive for inter-annual storage). Inter-annual storage is needed because the amount of wind power available one year can be significantly different to that available in another year, and such stores will also cope with low wind weeks or fortnights etc.
As self-assured advanced green ‘experts’ we’ve become cosy (too cosy!) in our body of received knowledge that renewable e- fuels (that is synthetic fuels made from renewables) are necessarily always bad because of the inefficiency of the production process. That’s because in addition to the losses involved in electrolysing water with renewable electricity to produce hydrogen you also have losses in extracting C02 from the air (using renewable electricity) and combining this with the hydrogen to produce the synthetic methane. That means e-fuels will, on the basis of this calculation, use the renewable energy half as efficiently compared to H2 production.
So far this looks like a slam-dunk in favour of using H2 (which is then used to generate electricity when there is not enough wind etc). Except for one (enormous) detail. That is the cost and efficiency of the storage system itself. Two unalterable facts come into play here. First is that mass for mass methane is a lot more energy dense than hydrogen. Second, on top of that, a lot more volume is required to store a given mass of H2 than methane.
Put those two things together and methane requires EIGHT TIMES LESS storage capacity compared to hydrogen. Now the sheer relative inefficiency of space use in underground (yes, underground is what we’re talking about) storage of hydrogen compared to methane blows H2 as a long storage system out of the water by comparison. This is even when full account is taken of the relatively inefficient way that e-fuels are produced.
The cost balance is very clear; methane storage wins by a large margin. In fact the superficially looking energy efficiency advantage of the H2 storage system won’t look the same at all when an account is taken of all that extra energy needed to prepare the eight times as much storage space needed for hydrogen compared to methane.
Our LUT team who did our 100% renewable UK model did the maths and costs on this very carefully. You can see the calculations for inter-annual storage on pages 34-40 in the summary – see link HERE. See page 38 in particular. Now they have taken all the detailed costs for the various elements and you can see how they pan out. If you want to look at more cost assumptions, see the Appendices at the end of our report, link HERE
So why are the great and the good missing this? Well one very big reason is that the storage requirements for 100%RE systems are not being taken seriously. To be honest, there’s a hell of a lot of wishful thinking and lazy dismissal flowing around, and not nearly enough serious research being done at all on the subject of 100%RE. So why are we so clever, eh? It’s not a matter of cleverness. The reason that the LUT team came up with this is that they were set a puzzle – a bit of a competition if you like – that is not just ‘how do you come up with a system that delivers enough interannual storage in a system mostly fuelled by wind and solar’, but how to do it as cheaply as possible – we built in a comparison with the Government’s plans to use nuclear power and CCS.
Sometimes a bit of lateral thinking upends established thinking. How long it will take for serious researchers to realise our point, I don’t know. Most people don’t like to stand out too much I suppose. But we don’t care about that! We’ve looked at the system costs of all the elements and concluded that a 100% renewable energy system is much cheaper in achieving net zero by 2050 compared to the Government’s plans.
By the way if you think I’m one of those guys who think e fuels or even H2 are a good bet for heating or transportation, then you are dead wrong. Electric cars and heat pumps are the best ways to go by far. But that’s not what we’re talking about here at all. I’ve got no particular yen for e-methane – it just looks like a better overall long-term storage system than using H2. Of course it may be that something else is even better – I’ve heard positive things about using methanol as an e-fuel storage mechanism, for example (that needs less storage space). But we didn’t have enough time to look at methanol.
But really we need a lot more research institutions and the Government to sponsor research into the best options for 100%RE systems. Even the cosiest establishment figure should realise that with nuclear development going slow, slow, slow, and CCS not doing much to deliver either, a system depending essentially on 100% RE is something that badly needs to be looked into.
Come to our seminar on April 22nd when the model and the issues surrounding the objective of 100percent renewables for the UK it will be extensively discussed. We shall also be discussing the UK Government’s Energy Bill and what we need to speed the UK’s energy transition.
Confirmed speakers so far include: introduction by Caroline Lucas MP, Jonathon Porritt (Forum for the Future), Charmian Larke (Atlantic Energy), Professor Christian Breyer (LUT University), Professor Mark Barrett (UCL), Professor Nick Eyre (University of Oxford), Dr Doug Parr (Greenpeace), Alethea Warrington (Possible), Rianna Gargiulo (Friends of the Earth and Divest UK), Alison Downes (Stop Sizewell C) Ian Fairlie and David Toke (both 100percentrenewableuk) and Dave Andrews (Claverton Group)
You can either attend the event in-person (that’s better as you can talk to people, be social and make contacts),
£20 admittance to the in-person event at Conway Hall, London, SIGN UP HERE
or if or if you cannot attend in person it is £30 admittance to the virtual (online) version of the event SIGN UP HERE
See our recently published report on 100 per cent renewable in the UK by 2050
14 thoughts on “Why storing renewables as synthetic green methane is much cheaper and efficient than using green hydrogen”
Interesting. But can you explain where you get your 8x less storage capacity figure from? H2 density is an eighth that of CH4 at 25C, 1atm, but it has 2.5x the energy density by weight so I make that a 3x difference?
Looking forward to your analysis of methanol. Proponents like it because it can be converted a wider variety of e-fuels (including methane). The inefficiencies of e-fuels (including carbon capture) are easily resolved by an overbuild of wind and solar with a small fission backbone (community owned of course)
I’m confused. Mass for mass, hydrogen has much more energy than methane (the opposite of what you say). How do you arrive at the EIGHT TIMES figure above?
Excellent points and there’s also the need for something to decarbonize aviation. It would be helpful to identify acronyms before page 70.
the figures are out there – if you don’t believe me, ask a Chemistry Professor
the figures are out there – ask a Chemistry Professor if you don’t believe me
the figures are ought there – I’ve relied essentially on the advice of a Chemistry Professor and the technical knowledge of our LUT team
the figures are ought there – I’ve relied essentially on the advice of a Chemistry Professor and the technical knowledge of our LUT team. I understand that you have also got to take into account the fact that a given mass of hydrogen occupies a much larger space than a given mass of methane
So 1m3 of H2 at room temperature and pressure will have a weight of 0.09kg. With an energy density of 120MJ/kg this will be 10.8MJ.
1m3 of CH4 will have a weight of 0.72kg. With an energy density of 50MJ/kg this will be 36MJ – a little over 3x…
ok but you are not taking into account the differences in volume taken up by the gases
I’ve compared the same volume of each gas…? 1 cubic metre…
the gases occupy different volumes for the same mass
The calorific value of hydrogen is about 12000kJ/m3 that of Nat gas about 38000 This as others say above is about a factor of three. Believe me this is right
you haven’t taken account of the fact that the same calorific volume of H2 as CH4 occupies a lot more volume