Nov. 23, 2022

Ep107: Prof. David Cebon "Thinking in Systems"

David Cebon is Professor of Mechanical Engineering at the University of Cambridge, Director of the Centre for Sustainable Road Freight, and a founding member of the Hydrogen Science Coalition. Prof. Cebon leads Cambridge University Engineering Department’s Transport Research Group and the Department's research theme 'Energy, Transport and Urban Infrastructure'.

Prof. Cebon’s research covers the mechanical, civil, and materials aspects of road transport engineering. He has authored or co-authored more than 150 peer-reviewed papers on the dynamics, safety, and environmental performance of heavy-goods vehicles. He has a strong current focus on vehicle energy consumption and decarbonisation. Prof. Cebon is a Fellow of the Royal Academy of Engineering.

The Centre for Sustainable Road Freight

Hydrogen Science Coalition

Our episode with Simon Morrish, CEO and Founder of Xlinks

Prof. Cebon's blogpost on hydrogen versus heat pumps for heating



Click Here for Edited Highlights


David Cebon

Thanks, Michael. I'm very flattered to be invited, particularly given the esteemed company that I'm joining on your show, and to be compared with David Mackay is certainly a great honour. Thank you.


Michael Liebreich Indeed, and it's always sad to remember his loss because he was such a clear and loud and insightful voice in this space, we would be in a better place, had he been able to continue the work that he was doing, but sadly, it comes to us to try to pick up, and do what we can.


DC Absolutely, he was also a great communicator, and really clearly illustrated the real nub of the issue, understanding the numbers and, communicating the numbers, and the big issues around land use and the challenges of getting to a renewable future. So, I'm a great admirer of David's.


ML Now, I don't want to go down, in the direction of critiquing David McKay's work, but he also I believe, he didn't quite get his head around the extraordinary advances. So, the fact that we've got 15 15 megawatt wind turbines, pushing at 20, the increases in efficiency, and solar and so on. But that's not the issue here today. What I want to do before we dive into some of the areas that you and I have interacted on, what I'd like you to do is give a bit of a thumbnail bio, what is it that you work on, who are you? My audience is a generalist audience, some will know you, and some won't.



DC Well, yes, thanks, Michael. You possibly detect from my accent I come from Australia. I came to the UK in the very early 1980s to do a PhD. And I kind of got stuck and I'm still here. I've worked really my whole career on heavy goods vehicles, believe it or not. Is that a thing that you can work on heavy goods vehicles, as an academic? I worked for 15 years or more on road damage caused by heavy vehicles. Then I worked, spent a lot of time looking at safety and things like braking and rollover and turning and maneuverability. And for the last 15 years or so I've been working on sustainability and decarbonisation of heavy goods vehicles. And of course, as soon as you start to talk about decarbonizing heavy goods, vehicles, at least in the last five years, you come head on with hydrogen, because heavy goods vehicles are one of the early uses being touted by the hydrogen industry. And so I've become very interested in hydrogen for heavy goods vehicles. And that's led me to investigate it for other applications as well.


ML It strikes me that... One of the things I enjoy about reading your work is that you take a whole system approach, so you could be quite happy... you'd probably have a perfectly happy academic career and possibly even be financially better rewarded, if you said, well, let's just use hydrogen for heavy goods vehicles, the hydrogen will be there, and we'll just use it and it'll be fine; it'll be a drop-in, many of the industry structures will remain unchanged. So why have you found yourself having to look beyond the confines of the industry?



DC Well, that's a great question. I think that when you look at decarbonisation, and the energy transition in general, it's essential to take that systems view, particularly when you're looking at carbon, because it's very easy to say, well, look, here's a really fabulously clean solution when we look at it through this sort of window or this boundary. And then if you look at it in the wider sense, you discover that it's actually terrible. And that's definitely the case with hydrogen. If you look at hydrogen, just from the point of view of an individual vehicle, it looks like a pretty good decarbonisation solution. But when you ask the question, where does the hydrogen come from, you get a different answer. And the carbon footprint of hydrogen manufacture, and the implications of hydrogen manufacture are pretty severe, and is what kills it from my point of view.


ML Let's take that statement as a starting point, right? You've got a value chain there from hydrogen production, through to the heavy goods vehicles and other things that you've looked at. But let's take the system thinking as a starting point. Could you describe with the benefit of all the work that you've done, particularly that work on the last 15 years on sustainability? What does the UK energy system look like in a net zero future? And I'm going to assume that most of what you've done is UK based, although you may want to use other examples. Where is that going?



DC Well, that's a great question. The first thing is that to decarbonize the UK's economy, we really need to electrify everything that can possibly be electrified. And that means to me, certainly, the big elephants, transportation, ground transportation, and heating, they need to be electrified. If you don't electrify those, you end up with really dramatically increased energy demand. And in a way, which we can talk about, which is really not achievable, in my view. So you have to electrify. It needs to be clearly renewable. Offshore wind, and onshore wind, increasingly, will be a big part of that; some solar, there is the nuclear fleet still exists, and that's important to keep that running. I have my doubts as to whether the country will be able to build much more nuclear, because I think it's kind of politically very difficult, long term. It's too expensive, at this point compared to renewables. I think, for all those reasons, nuclear is not likely to increase, but we'll keep it going. So they're the big components. The challenge with that mix is that, with electricity, getting supply and demand to match, and that's a problem on two scales for the UK. One is the daily demand cycles, and availability of renewables. To meet those differences between supply and demand, I think we'll do a few different things. The first is that we'll over build some renewables, and to some extent, we will curtail, probably; over build and curtail. To some extent, that's an economically reasonable thing to do. Not a huge amount, but there'll be some of that. The second thing that I think we will do is increasing demand management. And, you know, there's some great examples of that like Octopus, where the electricity industry can manage demand, manage pricing, to level out demand, and I think that's the second thing. And the third thing is that we will have to have some storage and there will be a modest amount of storage to solve this particular problem of day to day fluctuation of supply and demand, the amount of storage needed is not that high, and can be achieved using a combination of technologies, and we can talk about what those what those technologies might be. But at the end of all of that, you end up with a system which has got firmed power across a day, or a couple of days, maybe you have storage so that you have a day or two when the renewables are down, you have a day or two of storage. You then have the problem of summer to winter. And the winter usage, the winter consumption of electricity in the UK is currently about, on average, eight gigawatts higher than summer consumption, something like that, over a period of about 200 days, which is essentially the winter period. So the UK uses more power in the winter than in summer, and the question is, how do you do that, how do you solve that problem? This is... that's not the only problem, but it's one that you have to solve. One approach is to build salt caverns and fill 'me up with hydrogen. That's one approach that's been proposed. The amount of that required is pretty mind boggling, because if you integrate that eight gigawatts by 200 days, you end up with 16 terawatts, at the current consumption rate, and that's really large. And my calculation is that would take something like 160 of the largest salt caverns, 500,000 cubic metres salt caverns, running at 200 bar. It's a mind boggling project to make enough storage to do the UK's winter / summer seasonal storage. And actually I don't think it's practical, because of course, not only does the UK have to do it, but Germany has to do it and the Netherlands and France and everybody else has to do the same thing. If we go for this idea that what we're going to do is simply store all the energy that we need in the... the whole world has got to be building salt caverns full of storage by 2050. Frankly, it's not a thing that's going to happen. I think it's ridiculous. I think it's a ridiculous concept,


ML Although just to be clear, that is on the basis of essentially sizing the system for the summer, and then preparing for the winter. So now you're going to tell us what we should do instead?



I am going to tell you what we should do instead. So the other thing of course, there's a number of other assumptions in what I've said. The first and most important is that it doesn't account for the fact that our electricity demand is going to increase dramatically. And we will need a lot more electricity in the summer to power all those heat pumps. So, you know, my number is probably out by a factor of two or three in terms of storage that you would need. My opinion here is that the answer is to import the energy using high voltage DC interconnects. If you do that, at the current electricity consumption rate, that eight or ten gigawatts is perfectly doable. There's a HVDC connection in China returns 12 gigawatts, and it's 3000 kilometres long. So 12 gigawatts and 3000 kilometres would get you from North Africa to the UK. And they've got all that excellent, firm wind and solar power in North Africa.


ML David, just to be clear, we had an episode on Xlinks, which is 3.6 gigawatts doing exactly that. We had Simon Morrish on the show, I can't remember which number the episode was [92], we can put it in the show notes. And I'm an investor, so this is music to my ears: DC says I'm gonna make lots of money because that's a great idea. But that's 3.6 gigawatts which is about 8% of the UK's peak power now. Okay, power will grow, that might become 5% or 4%. But how many percent of UK power would you feel comfortable coming from North Africa in undersea cables, given particularly what we've seen with what happened to Nord Stream 2 just a few weeks ago,



DC You clearly have to diversify. You don't want to be dependent on one source. I think the amount needed, the current amount needed, is about double that. So, it's not a huge amount. And that just covers the winter-summer difference, right. So assuming we've got enough renewables and storage, to manage day to day, we just need to increase the average, and that would require current consumption about double what Xlinks is going to provide. I think the world needs to have diversified and interconnected electricity systems.


ML Can I ask why do you go with HVDC for that eight gigawatts? Why don't you just oversize and say, well, you know what, we're just going to do overcapacity, we're going to curtail more during the summer, we're going to maybe store what we can, we're not going to do this ridiculous, you know, 160 hydrogen in salt cavern storage, because it's simply unfeasible as quite correctly point out. Why don't you just oversize, and then, you know, it's right size for the winter, and it's oversized for the summer? But we're not dependent on somebody else's cable from somewhere else, which everybody else, by the way is going to be competing to do as well.



DC I think that is a perfectly reasonable thing to consider. And it's all about optimising the economics, isn't it, the economics and the energy security. The current situation, I've got to say, from an energy security point of view, this is a way better solution than what we've currently got. We're currently importing 50% of our gas, and it's coming from our friends in, you know, all kinds of places where we don't really want gas to be coming from.


ML And Norway, and our own...



DC Sure, but it's 60% imports. And it's dirty, what's coming in, right.


ML But... I'm going to throw a scenario at you, which you will have heard before, which is what the Germans call the dunkelflaute, which I call the dark doldrums. And that is where there are some weeks of very low wind production. And when I say very low, I don't mean that there's eight gigawatts that could drop out; we can see times lasting many days, where wind output, even when you've built out, you've got the law of large numbers, you could be, I'm gonna say, if we've electrified everything, and our demand is now not 50 gigawatts, but it's now 80 gigawatts. What happens when you're missing 50 gigawatts of supply because of a weather situation that might last, you know, three, four days, a week, maybe even longer?



DC Well, I think that's a very useful question to ask. And my personal response to that what you do is you keep your combined cycle gas turbines, CCGT capability, in a form where you can spin it up, if necessary. And the advantage of that... First of all, of course, we're approaching this future from a current situation where we've got all this kit operating, and we're gradually using it less and less, right? So that's going to happen out into the foreseeable future, to 2050, we'll use it less and less. But we have the option, we can decommission it, or we can keep it. Now all of the sunk energy and sunk carbon cost, and sunk capital cost is there, right? So you're just talking about maintaining these things, keeping them ticking over so that you can fire them up, if necessary. My opinion is that that's a far better thing to do, than spinning up a whole big hydrogen economy. And you know, all those salt caverns and sort of ridiculous fantasy ideas that have been proposed for how to do this. Much better to keep the CCGT fleet if you need it for a couple of days, a year or a couple of weeks a year. So, you know, you spin it up. And frankly, Michael, if, when I die, we've got to the point where we just use the CCGTs for a week or two in the year, and that's the sum total of our carbon emissions, I will die a very happy man.


ML Okay, but if I was a, I don't know, I'm not sure that my impersonation of an Extinction Rebellion or a Just Stop Oil protests is particularly good, but I would say, you know, that is, you know, that is the typical side-stepping of the issue, we've got to stop burning stuff, you're saying we should keep this kit. And you all know what's going to happen next is whoever's got that kit is going to want to use it, and they won't be wanting to use it two days a year or a week, a year, they will be trying to use it, you know, 30%, 40%, 50% of the time, we're going to go nowhere like that. How do you answer that?



DC Well, the first thing I'd say is, in this regard, the perfect is the enemy of the good. If the perfect solution is to completely switch off all fossils as quick as we possibly can, and to fire up this hydrogen economy in order to make that work, it will make things much worse. And the Extinction Rebellion, people I think can probably have that explained, to see just how much worse the decarbonisation process will become if we've got to do it all with hydrogen rather than just by electricity. So, the world needs to, what we need to do, is to decarbonize as quickly as we possibly can. The last few percent are important, they will become increasingly important. But the problem now is not that last few percent. People, you know... the argument that we have to focus on how to abate sectors is ridiculous. What about the easy to abate sectors? We need to... let's get the easy to abate sectors done! And that means heating and transport get electrified. So I think that's where we need to, we need to focus. It will be the case that, you know, the possibility of what you've suggested is that gas will be used more than it needs to be. That does exist, and we need to think about how to manage that, perhaps through some sort of regulation to prevent it from happening. But I think the quickest way to get where we need to go is to electrify as fast as we can and to not have the dunkelflaute being the tail that's wagging the whole big dog, right? Let's deal with the dunkelflaute by just keeping those CCGT's available if we need them, and do everything else by electricity as quickly as we can. Very good. And I


ML Very good. And I have to concede that I also... if I could leave this world, or leave this country, at a point where, you know, we've dealt with 95% of the problem, and we've only got 5%, which is very intractable, but you know, I've got really smart kids, you know, there are lots of smart students that you teach, and, you know, they need to have something to work on, right? Let's try and stay at the system level for a moment and talk about hydrogen. The UK currently uses - I believe - it's 770,000 tonnes of hydrogen every year. And that is overwhelmingly - and I mean 99% plus overwhelmingly - from fossil fuels. What is your vision...? That's used, for those in the audience who are newer to this, that's in fertilisers, it's chemical feedstocks, and it's also in refineries for doing things like hydrocracking, so we get the right mix of diesel and petrol out of a barrel of oil. What is your vision for hydrogen in that - you know, we accept your overall architecture - what is hydrogen going to be doing? And then we can get on to what it's not going to be doing.



DC Yes. Well, certainly it's going to be doing fertiliser, isn't it? We've got to feed a population now of 8 billion people, so fertiliser is number one on my list for hydrogen. And, you know, if politicians want to do something, right now, this minute, what I would say is make that grey hydrogen that's being used for fertiliser green, and do whatever you need to do, because there is no alternative to that.


ML I'm going to jump in here, I'm going to challenge you on that because here's the problem with that, is you said make the grey hydrogen, make the grey fertiliser green, right, but that means you've got some renewable energy, right? And if you do, why wouldn't you put it in a heat pump or an electric car? You'd displace far more carbon by not doing the fertiliser first.



DC All of those things need to be electrified. While there's controversy about heat pumps and transport, there can be no controversy about green hydrogen for fertiliser. I mean, I think that the other aspect of fertiliser is there's of course much more efficient methods of agriculture, which don't involve spreading fertiliser around the place, and we should be clearly encouraging that sort of more efficient farming as well.


ML I feel very... that was a bit unfair, because I said, let's talk about hydrogen, not the other things that it shouldn't be doing, and then I kind of shot in a chip shot from the side there. But you're right. And of course, the other thing is that the green fertiliser could easily be imported from a Morocco or a Chile or Namibia or an Australia or whatever. And I personally believe we're going to do a lot of that. But it was, I think that point that you made about fertiliser, perhaps... I know that if we just left this out there, you use the word we've certainly got to continue using fertiliser with 8 billion people.... And there are those out there that would say "no, we don't, we're going to do completely different types of agriculture." Do you have a sense of how quickly we could do that?



DC I'm not an agriculture expert in any sense of the word. So I couldn't really comment


ML That's great, we found a system boundary, but I can tell you, it's gonna be decades and decades. I think you'd agree with that.



DC I think the transfer to green fertiliser is you know, that's a doable thing. It is a massive job. I mean, just decarbonizing existing hydrogen uses is a massive job. As you say, that 700 million tonnes [sic] in the UK... Have I got that right?


ML 770,000. 94 million, globally, but we are relatively small compared to places like China and Brazil and the US and so on. So we're just under a million tonnes.



DC Across the world, that is a massive, massive issue. And, you know, one of the first ones that needs to be tackled. I mean, the other uses, a lot of those petrochemical uses will go away as we stop using fossil fuels for transport and so on. There will be a residual chemical use for polymers, which is something like 10% or 15% of that. And then there will be... and the other industrial uses for glassmaking, possibly for steel. I think steel is the interesting one for me, because it's such a big number, it's like 7% or 8% of world emissions, carbon emissions. It's such a huge amount. And think of that, I mean, it's the same scale as the trucking industry, which I'm interested in. It is a huge amount. And one of the possibilities for steel, steel reduction is hydrogen; it's not the only one, but it seems to be a front runner at the moment. And that would require a massive, massive amount of hydrogen.


ML And of course, for the listeners, I think by now are probably familiar with my hydrogen ladder, which I've talked about on a number of episodes and present it in all sorts of fora. And those uses that you started with, fertiliser, hydrocracking, methanol, chemical feedstocks, that's the 94 million tonnes that's already being used, we've got to green it, it's row A. Row B has steel on it, it also has shipping, because that seems to be one of those very difficult areas. It's very unclear how we're going to decarbonize the fuel used in ships without somehow going through hydrogen. Do you agree with that? Or have you found some other cunning pathway?


DC I'm a sailor myself, I think that's a good solution. Shipping is probably the most difficult to abate sector, I think, in the end. It's relatively small, it's a couple of percent of carbon emissions. And so, it is not the one where I would start. And I think that's important. It's important we start with the easy to abate sectors. Now where you end up with shipping... You know, I have my opinions and I certainly know, if I was the king of the world, I would say that all biofuels should go into shipping. Now that's not a straightforward thing to do.


ML Not aviation?


DC No, well my reason reasoning for that is... So for a start, I don't believe in hydrogen for aviation, I believe in drop-in replacement fuels, so sustainable aviation fuel or biofuel are the two possibilities. If I was king of the world, I would say I would reserve the biofuels for shipping, which is much, much more cost constrained. So shipping, you know, they use bunker fuel, it's the lowest of the low, it's the stuff that comes out of the cracking column just before the bitumen that we make roads from. And it's really, really cheap. To go to something which costs 10 times more, shipping, it's very difficult, which would be a synthetic fuel. So biofuels are much more in the realms of feasible economics, for shipping. On the other hand, aviation, I think, is less price sensitive. People can, it's largely people, rich people being transported around the place, and it has much more price flexibility, or, quote price elasticity. So I would say that, if you've got a choice of where you use a biofuel, it would be better off in shipping. The problem of course, if you do that, you know, somebody once said to me, look, once the biofuel is available, aviation will gobble it up; aviation will be able to pay more for it, and that will leave shipping nowhere. So that's why you need to be king of the world because...


ML Aviation in your world, a King David, King David of the World, aviation would then be using a very expensive, but presumably that would be an e-fuel? So, hydrogen and Direct Air Capture or something that's non-biological, because if it was bio, you'd put it into shipping?


DC Yeah, I think so. I mean, possibly you have some biological feedstocks for your...


ML Okay. And now, so there are... I'm glad we found one use case beyond the replacement, which is then the aviation, the sustainable aviation fuel based on an e-fuel. And, you know, maybe if we sort of tried harder, we might find one or two niches. But I want to move on to that hydrogen. Is it all green? Or is there any space at all for blue or any of the other rainbow of colours, colours that we're told - pink and red and turquoise and whatever - that we're supposed to get excited about?


DC Well, that's a very good question. I think the most important one is yellow, which nobody talks about. What is yellow hydrogen?


ML Yellow is from solar, right?


DC No. Well, I don't know, in my rainbow.


ML Yellow is just from electricity?


DC From electricity from grid electricity.


ML I was a good student when I was at Cambridge. I almost was in the right year to study under you, but not quite.


DC I don't think, I don't think we had that rainbow back then.


ML Okay, so it's electrical hydrogen, is what you want to see?


DC Well. So, I mean, it's nice to talk about green, but then you're talking about dedicated, new renewable assets. We do need lots of dedicated renewable assets. But in the end, when you build those, it's an opportunity. You know, if you use it for making hydrogen, you're not making something else. So the opportunity cost is decarbonizing the rest of the electricity grid. And I think that's... So, I'm a believer in actually when we make, when we use electricity, using grid average carbon. And that means that rather than the marginal, additional wind turbine. So it's important to consider the average carbon intensity of the grid when you're thinking about the future. And that's where you...


ML Let me make sure I've understood, and that might, you know, for the audience... So what you're saying is, you know, if we insist it has to be green, then we'll build some wind farms and some solar to make green hydrogen. But then we might not use, that might displace some renewables elsewhere in the systems. So actually, it's not as clean as it kind of looks, is that a fair statement?


DC I think that's absolutely right. And at the scale that people are talking about, for hydrogen, it's a really massive amount of green electricity needed... you can't build that massive amount of electricity, and also do all the other stuff we've been talking about decarbonizing,


ML Because the assumption behind what you're saying is that the you can't just build more renewables. Because I have this discussion quite a bit with, you know, on Twitter and elsewhere, where, you know, I'm very clear that the supply chain for renewables is constrained; the supply chain, the rare earth minerals, the land use, which of course Professor MacKay always talked about, the planning process; all of these things are constrained and therefore, you just don't have infinite renewable electricity to do this and this and this. And in fact, the A and the B rows of my ladder, the top two, between them would use more than five times all the wind and solar ever built to date, if we were trying to do that.


DC That's a great calculation. I think that's absolutely right. I agree with you entirely. There's a little calculation that I've done on this is, I've done a few, but one is around heating, right. So if you wanted green hydrogen for heating in the UK, you would need an installed capacity, installed wind turbine capacity, offshore wind capacity of 385 gigawatts. Now, that's about 10 times the current average electricity demand of the country. That's just to heat homes using green hydrogen boilers, because of all of the losses in that chain. So the idea that you're going to decarbonize the grid while also building out 40 times more renewables than we currently have. Well, you know, we currently have, we currently have 11 gigawatts of offshore wind, we're talking about 395 gigawatts of wind to heat homes.


ML You've got this great graphic, which compares - I don't know how, I you think you came to 270 gigawatts or something like that on the graphic; I'm not sure. Was it, or was it 380? But anyway, it contrasts it with the amount that you would need to build in order to heat the same number of homes using heat pumps. Can you give us the numbers on that?


DC Yeah, well, so. So the calculation is that on average in the winter, the UK uses 70 gigawatts of heat. UK homes take 70 gigawatts of heat. Now, to generate that 70 gigawatts of heat, if you go via a hydrogen route, you've got a green hydrogen route, you start off with a large amount of wind, offshore wind or renewables, you will actualize at about 75% efficiency. And then you have to compress it and transport it and so on, and finally, burn it in your hydrogen boiler, condensing boiler. And the total losses through that are about 50%. So that means that you need, if you want 70 gigawatts, you need about 140, 150 gigawatts of renewable electricity. And to get that renewable electricity at the grid factor of the North Sea, my calculation is about 385 gigawatts of installed capacity. So that 385 gigawatts, give you 70 gigawatts of actual heat. Now, the heat pump, on the other hand, is a miracle of modern engineering. To get that 70 gigawatts of heat, two thirds of it can come from the environment, from... pumped out of the environment from the heat pump.


ML Possibly three quarters, because the technology continues to improve.


DC Exactly, exactly. So that depends on the so-called coefficient of performance of the heat pump, depends on the technology that you're using there. The upshot of that... so you just need enough electricity to run those heat pumps. And where do I end up? I've forgotten what the numbers are... I think that the total installed capacity is about 60 gigawatts of offshore wind turbines. It's a sixth of what you need. So I need to get those numbers straight. I should have put the graphic on the screen.


ML What we'll do, David, what we'll do is we'll put a link, in fact into the... I mentioned the Hydrogen Science Coalition, which I'm not sure if, I think I mentioned in my introduction, if not, it's an important thing that you've done and we'll link to that and we can link to the specifics with the numbers in the show notes. You know, all of that so you've got a ridiculous amount of offshore wind that you will have to build if you want to do green hydrogen for heating, ridiculous, completely inconceivable. Okay. That's a fantastic reason to do blue hydrogen, isn't it?


DC Right. So blue hydrogen is interesting, Michael, and you and I have disagreed on this in various ways. But let me tell you my take on blue hydrogen. So the problem with blue hydrogen is that... well, there are numerous, numerous problems. The first problem is, of course, that hydrogen is not as energy intense, doesn't have the calorific value of the gas that you make it from. So you take methane, you reform it with hot steam, you take the carbon... and the carbon is the good stuff, right? I think people think that hydrogen is the good stuff and methane; actually, it's carbon, which is the good stuff, it has the highest energy to burn it. So you strip off the good stuff, you mix it with oxygen and turn it into CO2 and put it down a hole on the ground, and you're left with this much lower calorific value, hydrogen. Now, what that means is that if you want to provide the same amount of energy through using hydrogen instead of methane, you have to start with a lot more methane, you have to start by importing 40% or 50% more methane in the first place. So the very first thing that happens is our energy security problem gets a whole lot worse, because now instead of importing 50% of all our gas, we have to import 60% or 65% of all our gas. So energy security is an issue. And the cost, of course, there's the cost of importing all that energy. The other problem is, with blue hydrogen, is that it's not necessarily as clean as we might hope. And this is where we don't necessarily agree, but let me tell you the three issues. The first issue is the fugitive methane emissions, the upstream methane emissions. In really, really good gas fields, the really, really good gas can have 0.1% fugitive emissions; this is emissions through flaring, venting and leakage. I don't know if you've seen the fabulous BBC documentary about Big Oil Versus the World. But there's some amazing footage of methane leakage in US fracking industry. Just showing the amount of methane that's going up into the atmosphere. So the worst places in the world, that can be three 3% or more. So that's the first problem, is that some of the gas coming in is very dirty.


ML And to point out to the audience, it's an incredibly powerful greenhouse gas. So, when you get to 3% or 4% loss, you might as well not bother, you might as well just use coal or whatever, you're done.


DC Right. So that's my second number. So we've got one number, which is the percentage of fugitive emissions, 0.1% for really great, 3% for really [bad]... and 1.5% average in the world or something like that. Number two, is how bad do you think methane leakage is? And there's different opinions. Some people say we should consider methane on a 100-year basis, which means that it's 24, 25 times worse than carbon dioxide. Some people say we should consider it on a 20-year basis, in which case it's 86 times worse than carbon dioxide. I don't understand the 100-year basis, because the stuff is only resident in the atmosphere for 12 years. So... and I think that we've got real problems now, with all of this. We're not going to leave it for 100 years for our children to deal with. So my opinion is that we should be using the 20-year basis which is 86. The third issue is the Carbon Capture and Storage in the blue hydrogen manufacture. The current technology that's around is capturing about 50% of carbon emissions. It's thought that if you change from SMR, steam methane reforming, to ATR autothermal reforming, that you can get that to be much better, maybe 90%. But they don't exist, those plants don't exist in the world. So the debate around blue hydrogen on the one hand, you can take the worst of those three numbers, you can take the existing level of methane emissions, you can take the global warming potential, 20-year global warming potential, and you can say well, look, we're going to convert existing grey hydrogen plants to blue and the best we'll do is 50%, 60%, 70%. Or you can say, well, the future is going to be... we'll only use certified methane from a 0.1% leakage source - I don't see how we can get around the 86 - but we will only use plants which capture a really high level, 90%-99%. Now, if you manage to do all that, you will have hydrogen, which is fairly clean. If you don't... you won't. In fact, you'll have it being pretty dirty. Now, I think we agree on all of that. So where we don't agree is, what is reasonable to assume for the future? Do we assume kind of retrofitting business-as-usual technologies and the fact that there's all this methane leakage in the world and... Or do we assume that we can get to this fabulous, clean future world?


ML And maybe that's, maybe that is the nub of it, in that I don't assume anything; I think it's up to us to decide, us as society, us as thought leaders, academics, commentators, whatever I am, to say, you know, look, if you want to do lots of hydrogen, you can't do it all green, we've talked about that. You have to do, if you really want to do a lot - and by the way, I think we have to do a lot, because of shipping and aviation and the stuff at the top of the ladder - and therefore, we have to do it clean. And that means not 90% autothermal, but I actually think that the standard and you know, you and I have talked about what a clean hydrogen standard needs to look like, really ought to be probably 0.2% fugitive methane and 95% plus carbon capture. And if they can't do that, then I think that should all be just shut down and walked away from, so I think we would agree on that.


DC So we would agree on that. BEIS, the Department of Business and Energy and whatever else they are, doesn't... is not, you know, they've got a standard, which is effectively 2.4 kilogrammes of carbon dioxide per kilogramme of hydrogen. Now, just to put that into context, if you just make grey hydrogen, it generates about 10 kilogrammes of carbon dioxide per kilogramme of hydrogen. If you go for the BEIS standard 2.4, it's about 75% less. My calculation is if you use BEIS, that BEIS blue hydrogen standard for heating, that within about three or four years, it will be dirty, just with the current rate of decarbonisation of the electricity grid, it will, within a few years, that blue hydrogen standard will be obsolete, and will actually... any plants that are built to that standard will be a carbon source, a problem carbon source.


ML And this is a classic example of regulatory capture where the industry says, well, you know, it's better than what we do today, so it's a start, whereas it's actually a dead end; it does not, it is not compatible with a net zero future, it's gonna leave you with too many emissions to buy offsets. David, I'm just conscious of the time because we did talk about trying to get you out at the top of the hour, and we have to talk about transport and trucks, which we've not started on. And let's just do the following: let's assume that everybody agrees that fuel cell cars are done, they're just not going to happen. There are still some people who say yes, and BMW is doing a pilot, and is going to make a few and I think that... Let's just assume that we all agree that they're going to have horrible sales figures and stop doing that. And the same with Stellantis, and the same with Toyota and whatever. But now trucks, there's a lot of people saying ah, but the truck, the heavy goods vehicle is the absolute natural use case for hydrogen. So how do you, what do you say to that?


DC I'll give you a very quick, potted version. The first thing is the hydrogen truck costs twice as much as an electric, battery electric truck. Why is that? They're both actually battery electric trucks. They both have electric drivetrain, a battery, an inverter. The difference between them is that the electric truck has a bigger battery, the battery electric truck, and the hydrogen truck has a hydrogen fuel cell, hydrogen tanks, hydrogen delivery equipment - all expensive and actually rather heavy. And that really increases the cost. So just at current prices, you can go and buy a truck unit for a 44 tonne truck, it'll cost you £300,000, in the battery electric version, £600,000 in a hydrogen fuel cell version.


ML And now I'm gonna say, ah experience curve.


DC Yeah, well, that may be, but in the end, it's capital expensive, much more expensive. Its capital is much more expensive technology than just adding the battery. And experience curves on that additional battery, of course, are being brought down way faster, because of the whole electric vehicle industry. So on capital cost, you're at about double, on energy costs, you're at about three times, because of the inefficiencies of using hydrogen. So here we go, I've got an industrial partner, I got lots of industrial partners in the logistics industry. I say to my industrial partner, okay, you can have this Vehicle A, which costs you x to buy and y to run. And you can have this Vehicle B, which costs you 2x to buy and 3x to run. Which one are you going to buy? Well, it's quite clear, you buy the one on which costs you half on capital, and a third on running costs, as long as it will do the logistics that you need it to do. That is the question.


ML One second, why is the hydrogen three times as expensive? You sort of you put that out there, and I'm going to have... the comments are going to be full of people saying, no, no, no, it's all going to become cheap; look at Plug Power and ITM and they're all going to electrolyze, it's going to be free.


DC It's... when you look at the simple thermodynamics of converting renewable electricity to hydrogen and running it in a fuel cell vehicle, you end up with about a quarter, slightly less, than a quarter of the energy you started with, with the renewable electricity. You go through electrolysis, compression, transportation, fuel cell, drivetrain... you end up with about a quarter of the energy you started with. If you do that for an electric vehicle, you end up with about 70%. And the ratio of those two is near enough a factor of three.


ML The way I put it is, it doesn't matter how cheap your cake is, the ingredients are always cheaper.


DC Exactly, exactly right. The ingredients for electricity are much cheaper.


ML And also, you haven't touched on maintenance costs. I suspect that's something else that you're gathering data on.


DC I think maintenance costs are a big issue. I mean... a fuel cell vehicle is way more complicated, more issues, moving parts, expensive platinum catalyst - all that stuff is much more expensive. So the real question, Michael, is, can you do the logistics with a battery electric vehicle?


ML You say the logistics: do you mean the loading and unloading? Or do you mean the charging and the fueling?


DC The charging and the distance you need to travel without time penalty, and that's the critical thing, right? Logistics is a highly time dependent thing. You can't add time penalties, significant time penalties with charging of vehicles. And so the question is, can you do UK current logistics without time penalties with electric vehicles? And the answer to that is we've been researching that for a couple of years, and have concluded that it is perfectly possible to do current UK logistics, all current UK logsitics, using battery electric vehicles by charging at rest stops, and by charging at warehouses, when vehicles, turning around for typically 20 minutes or half an hour, by fast charging on these locations, and even using overhead power lines, which is another story. You can do logistics with electric vehicles.


ML Presumably the starting point, which you didn't mention, is that these trucks are parked somewhere at night, or for some period of each day, and you start with slow charging there, and then you're doing top ups along the way. I don't want to put words in your mouth.


DC Yeah, well, not all vehicles do that. Some vehicles run 24/7, with alternating drivers, and you have to be able to deal with those as well. So we do need to have enough time during the day to charge vehicles. But we think that it is, is possible to run a logistics system on electric vehicles only. And given that there's no incentive to buy hydrogen powered vehicles, which have much higher capital costs and much higher running costs.


ML But doesn't that put an enormous onus on these rapid chargers? I mean, we're talking about vehicles that will charge at what half a megawatt? Maybe a megawatt? And then you might have 20 of them, all in a truck park outside - I don't know, Dover, or outside you know, the logistics triangle in the centre of the country or over at Felixstowe - how on earth are you going to get? I mean, isn't that just an enormous pulse that goes on to the grid because you've got these 20 trucks arrive, they've all got to charge at the same time. How do you get around that?


DC Well, it's pretty well continuous. But if you wanted to do, to refuel those trucks with hydrogen, you would need three times that amount of electricity.


ML That's if the hydrogen is locally generated.


DC That's if the hydrogen is locally generated. Well, so hydrogen distribution is one of the things which is not talked about. But there's an interesting little statistic: if you take a diesel fuel tanker, and you want to replace it with a bunch of hydrogen tube trailers, operating at 700 bar - compressed hydrogen at 700 bar - do you know how many of those tube trailers it takes?


ML I shudder to think... You're about to tell us though.


DC I am about to tell you; it's 18. So you need to replace every fuel tanker with 18 hydrogen tankers.


ML And that's because hydrogen, although there's lots of energy per kilo, but there's lots of cubic metres per kilo as well.


DC Exactly. And at 700 bar, you've got thick steel pressure vessels to hold it, and they're quite heavy. So getting that hydrogen around the country by tube trailer is non-trivial. And then so you say, well, alright, let's do it by pipeline. To which I would say, well, how many of the existing refuelling stations are connected by gas pipelines, even if you were able to use them? And so then you end up with electrolyzing at the refuelling station. And if you're going to do that, you need three times the amount of electricity.


ML It's also being promoted as a great solution, because the grid is constrained, there's all sorts of local DNO areas, Distribution Network Areas on the electrical grid, that haven't got the capacity. And of course, if you say, well, we'll bring in, we're bringing in hydrogen, [inaudible] and then well, we'll make it locally. But that doesn't solve your problem, it makes it worse. Just, if we've got time, I would love to have you talk about the catenaries, because that's where you and I first met. I got hold of, somebody sent me a draft of a paper you wrote about catenaries - so this is charging on some of the major motorways of the UK. And it seems very sort of Heath Robinson, and ridiculous, and absurd, that we're gonna have... they're gonna look like tramways. But your calculations are that it makes a whole hell of a lot of economic sense. Talk us briefly through that, and then I'll let you go.


DC Indeed, thanks Michael. So, the first thing is of course electricity much prefers to be transported in wires than in boxes. So, it's much more effective to move it to the vehicle than have the vehicle carry it. The basic kind of technology that we're talking about is the sort of system that is used to power trams and trolleybuses in cities, and is well proven and in fact has been well proven in a bunch of trials in Germany running on the motorway, as being safe and effective for trucking as well. The big advantages of it, first of all that, of course, it's the most efficient way that you can power a vehicle, because you don't even have to take electricity in and out of the battery, it comes straight from the grid, straight from the wind turbine, transmitted straight to the vehicle, into the convertor and into the motor; that's the most efficient way that you can run a vehicle. Nearly 80% of the electricity ends up at the wheels, which is fabulous. So the carbon emissions are the smallest, the battery sizes are the smallest, and that's highly beneficial because of constraints on the battery supply chain and so on. And the carbon emissions are lowest, and the effect on the trucking is the least, because you have the smallest possible battery. So that means that if you're running heavy loads, for example, you're carrying steel or something like that, which would otherwise be constrained by the weight of the battery - so you wouldn't be able to carry as much stuff as you want because of the battery - you don't have that constraint, because you've got small batteries. You have small batteries to take the vehicle from the motorway to the warehouse, you know 10, 15 kilometres away, so it drops its pantograph and runs on battery power to its destination, runs back and charges while on the on the motorway. So all of those things are a big, big benefit. The total cost of installing such a system on the UK's motorways would be about £20 billion. Well, actually, our recent little hiatus in government cost us more than £20 billion. That's quite clear. So instead of having that hiatus, they just put it into the transport industry, we could have decarbonized all the trucks much more effectively. £20 billion pounds sounds like a huge amount of money. But you can compare it with £28 billion, which is the Department of Transport's budget for roads for the period 2020 to 2025. So we're spending about 50% more than that, than the £20 billion, in the current budget for roads. So it's right within the realms of a practical project. But the big advantage is that it makes, it can be done quite quickly, it is the lowest carbon, lowest cost, most efficient system for the country.


ML And presumably, we're not talking about every road. I mean, £20 billion doesn't sound like a lot, and I know that when I first saw your paper, I said just double it, just without... I hadn't even read the paper, and I said it seems too low, just double it. But you're really only talking about the small number of motorways, that... because it is for those longer distance trucks, which are not on every road, are they?


DC That's absolutely right. So, they do spend some time, some of those trucks do spend time tramping around the wilds of Scotland and Norfolk and so on. And you do need to have some static chargers, and larger batteries on a small proportion of vehicles that do those kinds of journeys. But the majority of vehicles which just run up and down the motorway, warehouse to warehouse, can be powered entirely by such a system. When you stand next to a system in Germany, and you see it, it just works. You think well, that's obvious, of course that works. It's brilliant.


ML And presumably, the £20 billion, or if I'm right £40 billion, which by the way, I also think is a relatively small amount of money. But you know, maybe my perspective is distorted by what we spent during the pandemic and various...


DC Maybe they're paying you too much at Bloomberg, Michael.


ML Yes, exactly, earning too much. No, but presumably, the trucks pay for themselves because they then become cheaper. So you don't need to worry about... that number is only the infrastructure, but actually, you don't need to start adding, well, you've got some equipment on each truck. But that would be less than a hydrogen fuel cell or a much bigger battery that would otherwise be needed?


DC That's exactly right, it's the cheapest thing you can do to the truck, right? You take this battery electric platform with a small battery, and you put a £10,000 pantograph on the roof. And that's really a low cost, compared to all the other things you can do, that's a very low cost addition.


ML And you're charging... You said that the electricity can go straight into the motor, but you are also charging as you go? It's not all going into the into the motors, it's also going into that smaller battery, presumably?


DC Yes, and so that's important, because it means that you don't have to charge at the warehouse, it means you don't have to have a big grid connection at the warehouse, which is expensive and time consuming and complicated. And it also means you don't have to stop at the warehouse; there are plenty of operations where the track unit drops its trailer at the warehouse and goes off again, doesn't have half an hour to stop and charge. And it can just charge on the motorway. So it means that the vehicles never have to stop, they can keep, they can keep running without having stuff to charge.


ML Systems thinking: cheaper trucks, more expensive road maintenance and road infrastructure, but not having to do, building out all of this hydrogen fueling stations, hydrogen pipelines, and some way of making hydrogen, which is inevitably going to be more expensive, because you can't make... you can't you can't make a cake cheaper than its ingredients. So, fabulous stuff.


DC Let me say...


ML I'll let you go, because you're the one that's time constrained.


DC Let me just say one final thing. Because of the energy efficiency of this approach, it saves a lot of money. And it's financially viable, financially the most attractive for the vehicle owner, but it can also, the infrastructure can be paid for by private finance. So although it's cost £20 billion to build the infrastructure, it can be privately financed, and it just needs another sort of government...


ML That would be presumably, your calculations... That presumably works because, on a total cost of ownership, total cost of operations basis, it will be cheaper than diesel? And therefore there ought to be a financial bit of wizardry that my mates in the City of London can do, that should not even hit the Treasury's budget. Is that right?


DC Well actually, what it means, because of that energy efficiency, is that the Treasury can run raise revenue through electricity sales, to account for some of the diesel tax that they're not, that they won't be getting. So, rather than subsidising hydrogen, they're generating revenue from electricity sales from the same vehicles, and everybody comes out, everybody comes out a winner.


ML Fabulous. You could say, well, what's not to like? But of course, we are not gas network operators or gas extraction distribution companies, because I'm sure that if they were on this call, then they would find plenty of things not to like about it. I'm gonna let you go; I would have loved for you to talk about Direct Air Capture, and how many Rolls Royce Trent engines it would take to actually remove some carbon from the atmosphere. I think we're gonna have to leave that, perhaps if we have you back for a later episode. David, it's a huge pleasure as always to talk to you and to have you. I'm thrilled that you came on Cleaning Up here today.


ML Thanks, Michael, it's been a pleasure.