The future of hydrogen-powered air travel

Good Clean Energy is a podcast that tackles one of the most existential questions of our time: how to build a world with abundant, affordable, carbon-free electricity. TAE’s McNiel dives into deep conversations with experts ranging from scientists to innovators to changemakers about the challenges our current electricity systems face and updates on the race for game-changing, clean ways to power our lives.

On this episode, Jim is joined by Paul Eremenko, co-founder and CEO of Universal Hydrogen, a company working toward making hydrogen-powered commercial flight a near-term reality.

• [3:52] The aviation industry’s current carbon footprint
• [5:40] Why sustainable fuels aren’t really all that sustainable
• [7:12] Why electric planes aren’t feasible
• [8:27] Explaining the color spectrum of hydrogen
• [9:22] How hydrogen is safer than jet fuel
• [12:40] Technology for hydrogen fueled aviation
• [17:45] Why you can’t just fill up the existing fuel tanks with hydrogen
• [19:02] The “Nespresso pod of hydrogen”
• [21:23] Universal Hydrogen’s inaugural flight
• [23:20] How the range of a hydrogen craft compares to a regular jet-fuel plane
• [23:50] Major challenge is availability of green hydrogen
• [26:39] The economic competitiveness of hydrogen
• [27:31] A new commercial aircraft configuration
• [34:39] A few ways the aviation industry could look by 2045

INTRO

It’s the year 2035. Well, this would be the first time I’m traveling through an airport to fly on my first hydrogen commercial aircraft. I’m going to Toronto, carbon free.

What gate is it? Let me see.

It’s kind of amazing what has to be done to make all this work. They’ve gotta find a place to get energy from renewables — solar or wind or fusion — and make hydrogen and fill up those bottles and put ’em on a train, and then get that to an airport, and then load it up in the back of the aircraft and plug ’em in. And there you go.

Oh, here it is. I can just see it out the window there. That’s what they’re doing. They’re loading those canisters up into the fuselage. Looks like an ordinary jet. Oh, they’re boarding. Let me go. Let’s get on this plane.

I really like the LED lights, the green hue, it makes you feel like you’re really doing something good for the environment.

So kind of feels like any other flight I’ve taken.

And now I can travel anywhere I want without having carbon guilt. Well, not quite anywhere, because I can’t get across the Pacific or the Atlantic yet. But I could fly domestically. Both U.S. and Europe, Africa. These are the workhorses of commercial aviation. Once we get these single aisle aircraft flying on hydrogen, It’s going to be a carbon-free, green world in the wild blue yonder.

Today I’m joined by the CEO of Universal Hydrogen, Paul Eremenko, who has been instrumental in creating the infrastructure and the systems that are going to take us into carbon-free air travel. He’s going to talk to us about what it takes to produce hydrogen, store it, deliver it, and plug it into an airplane that can carry you carbon-free to wherever you want to go.

I’m Jim McNiel, and this is Good Clean Energy.

Jim McNiel: Paul, welcome to Good Clean Energy. I’m delighted to have you here.

Paul Eremenko: It’s a pleasure. Thanks for the invitation.

McNiel: We’re really excited to dive into the whole world of hydrogen, and I think it’s particularly interesting to be able to do so through the lens of aviation. Could you give us an understanding of what impact commercial aviation has on climate change?

Eremenko: Yeah, absolutely. So aviation is somewhere around three, four, 5% of global CO2 emissions, which doesn’t sound like much. But maybe to put in perspective, it is about the same emissions as the entire country of Germany. So it is a sizable contributor. The other issue that aviation has is it’s the hardest to decarbonize or the slowest to decarbonize. So as other sectors do reduce their carbon emissions to meet Paris Agreement or Paris Agreement-like-targets, aviation doesn’t really have a clear plan for doing so. So it will increasingly stick out like a sore thumb across all of the various contributors to global emissions.

McNiel: Well, what are some of the options to approach either zero or low-carbon aviation?

Eremenko: The most obvious option, and I say it only partially in jest, is to stop flying. The other thing to look at is not just what percent of emissions it is relative to other sectors, but also what’s the growth rate? And aviation traffic volumes have doubled about every 15 years since the birth of the jet age. And so it’s an exponential growth curve, and airplane efficiency has of course improved, but airplane efficiency doubles about every 30 years, so it is a much slower exponential. And so, the sector emission growth continues to increase. And the surest way to curb aviation emissions is to cap traffic volumes. But I think we all agree, not just within aviation but more broadly, that we want people to keep traveling. That air travel has been a force for good in the history of our species.

Why sustainable fuels and electric-powered aviation aren’t a good solution

McNiel: I would think the low-hanging fruit would be sustainable fuel. So wouldn’t that be the quickest way to decarbonize commercial aviation?

Eremenko: Well, the thing about sustainable fuels is they’re well-branded, right? Because there’s a lot of oil money behind sustainable fuels, but there’s nothing really sustainable about them. It’s just an offset scheme. So you’re still burning a hydrocarbon, and in the case of aviation, you’re burning the hydrocarbon at 35,000 feet, which is actually significantly worse than burning a hydrocarbon at sea level, because there are non-CO2 emmitants like soot, aerosols and other things that at altitude have a very significant global warming impact. In fact, CO2 is only about one-third of the global warming impact of aviation emissions.

McNiel: There’s nitrous oxide and particulate matter.

Eremenko: That’s right, and the particulates cause cloud formation which in turn has a pretty significant global warming impact. So the thing about sustainable fuels or sustainable aviation fuels is that you’re trying to offset the fact that you’re burning this hydrocarbon at 35,000 feet in the production of the fuel. So you say that I’ll sequester some carbon, some CO2 from the atmosphere. And I’ll combine it with hydrogen that I produce to create a synthetic hydrocarbon. But you could just as well continue to burn fossil fuels and go pay somebody to run a direct air capture system, and it would be functionally equivalent. And so I think this is the thing that a lot of people don’t understand, and I think the oil lobby doesn’t particularly want you to understand very deeply, right? Which is that the sustainable fuels are just an offset scheme — and a relatively expensive one.

“There’s a lot of oil money behind sustainable fuels, but there’s nothing really sustainable about them. It’s just an offset scheme.”

Eremenko: So I think it’s great. Unfortunately, it doesn’t scale, right? So with electric aviation based on a lithium ion battery electric — if you go to the theoretical maximum of what lithium ion electrochemistry can do for you, you’ll get 10 passengers a couple hundred kilometers. And if you try to power an Airbus A320 with batteries, it just won’t take off. Those are too heavy.

McNiel: Yeah, I did a quick look at it and I think to fly a 777, you need like 1.75 megawatts of power.

Eremenko: Oh, much more than that. So an A320 or 737 is about 20 megawatts per side. And I don’t know off the top of my head, a 777, but it’d be considerably more than that. And so then the question is: What’s the energy density of the batteries? What’s the power density of the energy conversion system? And the issue is it’s just too heavy. Could you imagine a battery electric chemistry that’s drastically better than lithium ion? You could, right? There’s no law of physics that prohibits that. But it took lithium ion, what, about 30 years since the late 80s, which was when it was first developed in the lab. So it took about 30 years to get it into mobility applications and aviation is at the very tail-end of mobility applications. And so a new electric chemistry will take a few decades to mature, and we don’t have one in the lab today that promises to solve large commercial aviation.

The color spectrum of hydrogen explained

McNiel: So this all leads us to hydrogen and obviously hydrogen comes in a couple different flavors. Can you kind of explain what the different colors of hydrogen mean and what you’re focused on?

Eremenko: Yeah, absolutely. So there is a color spectrum with an obscure history behind it that tells you how the hydrogen is produced. And my company, Universal Hydrogen, deals principally with green hydrogen, which is hydrogen that is produced using water electrolysis. Which means you run electricity through water with a catalyst and basically break the water into hydrogen and oxygen. And you can use both, as products of that. And as long as you’re using renewable electricity to power the electrolysis process, it’s a totally green cycle. There’s no carbon anywhere in the energy chain.

There’s pink hydrogen which is nuclear produced, and then there’s things like blue hydrogen and gray hydrogen. The easiest way to make hydrogen is by cracking hydrocarbon molecules. So you take methane–

McNiel: –with natural gas, right?

Eremenko: Yeah, exactly. But then you have carbon leftover, and so it kind of defeats the point.

How hydrogen is safer than jet fuel

McNiel: So when people think about hydrogen, I mean, certainly when it comes to my mind, it’s hard not to think about the early days of airship travel with the Hindenburg and what happens when hydrogen meets oxygen meets a spark. How is it different for your approach to commercial aviation?

Eremenko: So Jim, I guess the first comment I would make is that the Hindenburg has very little bearing on the safety of hydrogen aviation.

McNiel: That’s good to hear.

Eremenko: It was a very long time ago. The hydrogen was used for a very different purpose. It was not used for propulsion. It was used for lift and there is some debate over whether the hydrogen ever actually ignited in the Hindenburg. There’s a strong thesis that it was the doping on the side of the airship that It was surprisingly a fairly survivable accident. So a number of people in the cabin actually survived. And if the hydrogen had ignited, they probably wouldn’t have. And of course, it’s emblazoned in people’s memory because of the video reel, which was rare in that era, and it is a very stark and touching video of course.

But think about things like TWA 800. Much more recent. And it was an explosion of a jet fuel tank, because it was not properly inerted. So look, aviation is hard. Flying is hard and you need a combustible source of energy in order to fly in most cases. So, certainly hydrogen is combustible, but actually the fundamental properties of the fuel make it much safer than jet fuel.

McNiel: In what way? How is that possible?

Eremenko: Yeah, so there’s a couple of different aspects to it. So one is that hydrogen only burns in certain concentrations from about 4% to about 75%, right? And so the trick to hydrogen safety in all mobility applications, not just aviation, is either to keep the hydrogen concentration below 4% or 5% or above 75%. And so when hydrogen is stored, you want it to be in a very, very high concentration so there’s no air or oxygen in that mix. And if you do have a hydrogen leak, you want to vent, vent, vent. You don’t want to confine the leak. You want to immediately drive the concentration below the flammability limit. And so that’s pretty manageable. Hydrogen detectors are reliable. There’s many different technologies for it, so you can use redundant ones.

The other thing about hydrogen is if you do have an accident, hydrogen doesn’t pool, even in liquid form, which is probably how you would store it for large commercial airplanes. It evaporates very quickly and immediately rises, because it’s significantly lighter than air. So as a result, the fires don’t spread. So you have very little secondary damage. And one of the places where we’ve seen this is with hydrogen cars. So there are hydrogen cars on the road today here in California. There’s a Toyota Mirai, there’s a Honda Clarity, there’s a Hyundai, I think. And the safety record of those cars is actually much, much better than gasoline-powered cars.

McNiel: Well, it’s also better than electric cars, isn’t it? We’ve had much more electric cars burst into flame because of lithium ion batteries than we have hydrogen cars, right?

Eremenko: Yeah, absolutely. And the fundamental reason for that is that, in an accident, the hydrogen does not pool. It does not spread. It’s very localized. It rises. So if it does ignite, there’s a column of flame. Hydrogen also emits very little infrared radiation when it burns. So it doesn’t tend to ignite secondary fires nearly as much as gasoline fires. As we’ve been going through the process of working hand-in-hand with the FAA to develop what’s called a certification basis — which is the criteria by which hydrogen airplanes will be certified. We’re the first applicant, as far as I know, to be developing the certification basis — we’re finding that the physics are on our side.

How hydrogen will factor in existing plane technology

McNiel: And I think that that also leads to what’s probably an obvious question, is that when we talk about hydrogen as a combustible, people would think, “OK, I’m going to use it like I do gasoline or diesel.” But the cars in California are fuel cell cars, right?

Eremenko: They sure are.

McNiel: And so does that mean you’re building a fuel cell plane, or are you building turbines that burn hydrogen?

Eremenko: So both are possible. And I think we will see both in aviation. What we are developing for our first product is, we are actually a hydrogen logistics company. So we deliver hydrogen as a service in this convenient modular capsule type form factor that basically makes it compatible with existing intermodal freight, with containerized freight on trains, trucks, boats, And then compatible with existing cargo handling equipment at airports. So that’s really the core of what we do at Universal Hydrogen, but building a hydrogen infrastructure, hydrogen distribution network without an end application, and just the hope that if you build that they will come is not a very good fundable investable business model for a startup. So for the first product, we felt that we needed a fully permissionless business model. And so we are developing a conversion kit for regional airplanes to accept our modules and to fly on hydrogen. And those are about two megawatts per side, in terms of power consumption. And so in the two megawatt class, you can get away with fuel cells. In particular, sort of the mature fuel cells that are out there, which is called low-temperature PEM: low-temperature proton exchange membrane. And this is what you see in forklifts, this is what you see in the Toyota Mirais, in some of the trucks. That’s a well-matured technology that’s relatively straightforward to certify for aviation use. Bigger airplanes, as you look towards the A320 and 737s, you will have to burn hydrogen. When you get to the 20 megawatt scale, a fuel cell is just too heavy. There have been hydrogen jet engines. The first hydrogen airplane, crude airplane, manned airplane, to fly was in the 1950s and that was based on a hydrogen jet engine. My old company, Pratt & Whitney, actually developed a number of hydrogen engines, a couple of, I should say, hydrogen engines back in the 50s for various military programs. The Soviets flew an airliner on hydrogen with a converted jet engine in the 1980s.

So it’s been done before. There’s nothing fundamentally different about a hydrogen-burning jet engine than a jet fuel-burning jet engine. You have to change the fuel injectors a little bit. You wanna shorten the combustor, so there are a few tweaks. But the overall architecture of the engine stays the same. So there’s very little doubt that you can build a hydrogen jet engine with the existing technology base.

McNiel: When you burn hydrogen, you still produce nitrous oxide, but you don’t produce as much as say, kerosene or jet fuel.

Eremenko: So the nitric oxides, or NOx as they’re called, are really not a function of the fuel. When you burn anything in air, it’s the nitrogen in air reacting with the oxygen to produce NOx, which is not a strong greenhouse agent. It’s mostly a smog agent, which is still not great. And so that problem is not fundamentally different when you burn hydrogen versus when you burn jet fuel. And there’s a variety of technologies for trying to reduce NOx. In a hydrogen jet engine, you would shorten the combustor. Hydrogen has a much faster flame speed, and you don’t want the flame to dwell, which is when you get all the NOx production. So that’s why you would have to shorten the combustor. But it is not fundamentally different, right? So, the NOx problem is there regardless of what you’re burning. And there is a suite of technologies that the industry has developed to mitigate NOx.

McNiel: So where does the fuel cell make sense and where do you have — you’re saying you have to switch to a hydrogen turbine when you get to the bigger single-aisle aircraft or the narrow body aircraft? You’re not going to the super, like A380 kind of stuff, the 777 stuff. You’re doing mostly the single-aisle aircraft, right?

Eremenko: So our first target is the regionals. So this is like ATR 72, and this is where you can do it with fuel cells.

McNiel: All the prop stuff.

Eremenko: And the crossover point is in the couple-megawatt class. So, we’re comfortable that we can deliver a two megawatt class system. That’s what we flew back in March. When you start getting into 3, 4, 5, megawatts, just the increased weight of the fuel cell starts to kill you, and starts to cut into the airplane’s performance. And certainly by the time you get to the single-aisle or narrow-body class, it has to be a jet engine.

McNiel: And so the way it actually comes down to the conversation about energy density, right? So what’s the energy density of hydrogen versus jet fuel?

Eremenko: So, I think it’s important to differentiate gravimetric energy density, which is energy per unit weight, versus volumetric, which is energy per unit volume. And so from a gravimetric perspective, hydrogen is actually the lightest energy carrier, the most weight-efficient energy carrier outside of nuclear fuels. From a weight perspective, hydrogen is the most weight-efficient energy carrier outside of nuclear fuels.

McNiel: Is that including its capsule or its container?

Eremenko: No, of course that’s the raw hydrogen itself, you do have to factor in the tankage. For liquid hydrogen, the tankage is such that it is still superior to jet fuel, even if you include the tankage.

The “Nespresso pod of hydrogen”

McNiel: The first question is why couldn’t you just fill up the existing fuel tanks with hydrogen?

Eremenko: So the fundamental reason is that you don’t want the hydrogen to gasify, and it only stays liquid at these very cold cryogenic temperatures. In order to minimize the warming or the boil off, the gasification of hydrogen would create, you want to minimize the surface area to volume. And the minimum surface area for a given volume is the sphere. But the sphere has very poor packing efficiency. So you compromise on a cylinder with hemispherical end caps.

McNiel: It looks a bit like a scuba tank.

Eremenko: Exactly. So that’s how you end up with hydrogen storage in the fuselage. And then the fueling operation is quite complex for two reasons. One is that from a volumetric perspective, hydrogen is much worse than jet fuel. And this is also to your previous comment, Jim, that maybe we can elaborate a little bit, which is the much larger airplanes — 787, 777, A380s — are very difficult today to do with hydrogen and that’s a volume issue. But, in the fueling operation, volume just makes it slower. And it’s about a factor of four worse than jet fuel from a volume perspective. So it’ll be about a factor of four slower from a fueling perspective, and that means that you go from a 20 minute fueling operation to an hour and 20 minutes and it wreaks havoc on the turnaround time in the unit economics of the airplane.

McNiel: Which is why your, let’s call it, cartridge approach, or I think what you said on Bloomberg is you’re like the Nespresso of hydrogen?

Eremenko: I have used that analogy before. Yes. It’s the Nespresso pod. That’s right. It’s a convenient form factor. We don’t grow the coffee. We buy the coffee, we put it in a convenient form factor, we get it to the consumer and we’re building the first coffee machine to work with our capsule. But in general, we are in the capsule-as-a-service business, not in the coffee maker business.

McNiel: So you use the existing cargo infrastructure to deliver these capsules to an aircraft. It flies to its destination. You pull out the empties, you put in a new full one, and the empties go back to be recharged.

Eremenko: That’s right. And so that solves the fueling time problem. It also solves a loss problem. Hydrogen transfers tend to be lossy, both because the molecule is very small and prone to escaping around sort of fittings and fixtures and connectors. But more importantly, because you have to purge the target vessel that you’re fueling of the gaseous hydrogen that’s warmed and evaporated from liquid form. So you constantly have to purge it until you have cooled the target vessel to this cryogenic temperature. And that purging is a very lossy process, right? So we solve all of that with a modular fueling approach.

McNiel: If you were able to succeed in converting the regional propeller aviation space to hydrogen, what impact would that have on aviation overall? How much of the commercial aviation is turboprop.

Eremenko: So the turboprop fleet is about 2,400 airplanes. So it is not huge and they don’t fly very far. So in the end, the impact will be a couple percent of all aviation emissions. So in itself, regional aviation does not solve aviation emissions. What solves for aviation emissions is the next category of airplanes, which is the narrow-body or single-aisle. So the 737 and A320 today, and that class of airplanes produces over half of all aviation emissions.

McNiel: That’s the workhorse of aviation.

Eremenko: Because there’s so many of them, they fly so frequently. It is the workhorse. All of the intra-European flights, all the intra-North American flights and all the intra-Chinese flights are basically single aisles. And so those are huge markets. And so it is not the very large, very long-range airplanes that produce most of the emissions. And that’s good news because the narrow-body and single-aisle is very much addressable by hydrogen. Whereas the larger airplanes would require some novel technology development.

Universal Hydrogen’s inaugural flight

McNiel: So you recently flew your inaugural flight. Can you walk us through what that was like and what that experience felt like to you as someone who is pioneering this technology?

Eremenko: Yeah, So we flew on March 2 of this year, the largest airplane ever to be powered by fuel cells. And it was in Moses Lake, Washington, which is a very historic airport. It was a Shuttle Abort site. Boeing does a lot of their flight testing out in Moses Lake. It’s kind of in the middle of nowhere in southeast Washington state. And this was a long time coming, so we were certainly a couple months late. And so those few months of delay, we were always on pins and needles and saying, “Hey, are we going to fly next week? Are we going to fly the week after next? When is it going to happen?” So the anticipation was very, very high. And it was a magical day.

I’ve been through a few first flights in my career, when I was at Airbus and when I was at United Technologies and prior to that at a couple of other aviation companies. And a first flight is always just an incredibly special experience. In aviation, unlike in other sectors, first flights usually work, so we do a lot of work up front. We did a lot of ground testing, a lot of taxi testing, and we had been running a test rig with this hydrogen powertrain for the better part of a year prior to that. So we were quite confident by the time the day a first flight rolled around that it was going to work. But that doesn’t in any way detract from just that feeling when the airplane starts going down the runway and when the wheels leave the ground, there’s nothing like it. It’s hard to describe. It’s one of those things that typically happens a few times in one’s career if you’re in aviation, if you’re lucky. And it is a moment that you remember for the rest of your life.

McNiel: And to be clear, this was a hydrogen fuel cell producing electricity that was turning an electric motor that was spinning your props.

Eremenko: That’s exactly right. The hydrogen engine, the fuel cell engine is our design, our integration, our test rig and ultimately will be our product that we will deliver to airlines for this retrofit.

McNiel: Now, do you expect to have the same range for these aircraft as a regular jet fuel or kerosene fueled engine will have.

Eremenko: So you can. It’s a tradeoff between the number of seats you want in the airplane and the range of the airplane, because we are storing the hydrogen modules in the fuselage, not in the wing. And so as a result, we have to remove a few rows of seats. In our case, we’ll remove three rows of seats from the airplane, and that gives us about a thousand kilometer range. That’s as far as these airplanes ever actually fly in service.

Major challenge is availability of green hydrogen

McNiel: So what are the major challenges of you making this a commercial success?

Eremenko: Well, for the regional product, we have a pretty clear path to market. We have a very large order book, I think it’s 247 airplanes to date across 16 airlines in 12 countries. And we expect to be FAA certified in 2025, maybe the latter portion of 2025. And then get IASA (International Aviation Safety Assessment) and other countries’ certifications in 2026. And it’s off to the races. The key issue is hydrogen supply in the early years. So today there’s very little green hydrogen produced in the world. There is a huge number of projects underway that take two to three years to come to fruition.

McNiel: Does the IRA (Inflation Reduction Act) recently passed have any impact on the production of green hydrogen?

Eremenko: Yeah. The IRA was probably the most important thing to happen in the green hydrogen world. It’s a massive $3 per kilo subsidy for green hydrogen production that’s good to 2042–

McNiel: –to 2042?

Eremenko: Yeah. Yeah, And so it’s been massively catalytic for starting new projects in the U.S. for hydrogen production and the U.S. really leapt ahead from being a laggard in this space to being the leader and actually causing a lot of consternation in Europe and other parts of the world, in terms of being a capital and talent drain as a result of the IRA.

McNiel: But is it work towards making hydrogen competitive with kerosene?

Eremenko: It sure does. Yeah. When people talk about the cost of hydrogen, you always have to be like “cost where?” Because there is no global spot market, because there is no hydrogen infrastructure today, there is no global spot price, there’s no global market. It is very regional and largely driven by the cost of the renewable electricity that powers the electrolysis process.

McNiel: And to be clear, the hydrogen we’re talking about that’s impacted by the Inflation Reduction Act is green hydrogen?

Eremenko: That is correct.

McNiel: Which is the only hydrogen you’re dealing with?

Eremenko: Yes, with a small caveat of the fact that we are quite open to nuclear-produced hydrogen, which is called pink. And in fairness, the IRA does have some provisions for non-green hydrogen, and the subsidy is reduced depending on the carbon intensity of the hydrogen production process. For green hydrogen, it’s the biggest subsidy, which is $3 per kilo. And in some parts of the world, if you can get electricity at 3 cents per kilowatt hour or so, which is doable in many places, especially if you co-locate with a source of electricity production and you’re willing to take off-peak renewables, you can get 3 cents per kilowatt hour, then you can get $3 per kilo hydrogen with no subsidy and you can get free hydrogen with the IRA subsidy. Now you can’t do that everywhere, and as a practical matter there’s not very many places where you can go for free hydrogen today. But in terms of the structural sort of cost stack, the IRA erases a good chunk of it. And with the war in Ukraine and all of the geopolitical turmoil that’s driven up oil prices, we should be at a crossover point between green hydrogen and jet fuel in the next couple years.

“We should be at a crossover point between green hydrogen and jet fuel in the next couple years.”

Eremenko: It is, and we set that as a constraint for ourselves when founding the company. The unit economics had to work for the first product with no subsidies and no carbon taxes on the jet fuel side, it just had to work. And that includes the loss of seats. And we had a very spirited discussion about whether we were too early as a company. And ultimately we decided that 2025-2026 was probably the right moment to target. We do want to be first in the market because we do have this modular product that we need to have the industry coalesce around as a standard. So for that purpose, you do want to be first, but you don’t wanna be too early such that you’re reliant on your customers to pay a significant green premium because of course that reduces your addressable market.

McNiel: When we talk about the big overseas carriers, the big wide bodies that you mentioned earlier — the 380s and 787s and so forth — is there a scenario in which they use hydrogen like in a hybrid form so that they can boost the efficiency of their aircraft with low-carbon solutions?

A new commercial aircraft configuration

Eremenko: I think there’s a couple of options, and it’ll be interesting to see how the industry plays out in that respect. There are hybrid solutions where you can have a hydrocarbon fuel and hydrogen, and for instance, carry your reserves in hydrocarbon, and carry your primary mission fuel in hydrogen. Because typically, an airliner will not dig into the reserves, you can in most cases, fly zero emissions. And you only start producing CO2 if you’re cutting into your reserve fuel. So that’s one scenario. Another scenario is hydrogen-ammonia hybrids. An ammonia you can think of as a liquid carrier for hydrogen that’s a lot more volume-efficient than just cryogenically, liquified hydrogen, but less weight-efficient. And so by blending hydrogen and ammonia, you can sort of tweak and trade off volumetric and gravimetric energy density against each other. And Ammonia fundamentally is just a hydrogen carrier. Then a third class of options for those airplanes for that segment is to go to a different airplane configuration instead of a tube and wings, as most airplanes are today, go to a blended wing body. So more like a flying wing configuration.

McNiel: Like a delta wing.

Eremenko: Exactly. And then you have a lot more volume to play with for storing hydrogen, trying to address sort of hydrogen’s achilles heel, which is a volumetric energy density.

McNiel: So this looks like a B-1 bomber.

“We in aviation have not been prone to making big step changes.”

Eremenko: It could, yes. And so there are concepts both from Boeing and from Airbus for a blended wing body airliner. It has a lot of advantages, but it is quite a significant departure. And for an industry that’s been driven by incrementalist thinking since the birth of the jet age, it’s a pretty massive step. The good news is that the wide body category, so these long-range airplanes, 777, 787, A380s and 350s, are not due for a clean sheet sort of new replacement until the 2040s because the 350 and the 787 are relatively new airplanes.

McNiel: So why haven’t we seen a delta wing concept for a commercial aircraft?

Eremenko: Well, concepts are cheap. And we have seen such concepts, both from Boeing and from Airbus. If you look up Airbus ZEROe, one of their zero emissions concepts is a blended wing body, kind of a flying wing configuration. Boeing has actually, together with NASA, flown a subscale demonstrator of a blended wing body. So this is not a new idea. It’s been around for a while. The issue is that going from a concept to a full-scale aircraft program is a very big chasm, if you will, and the industry is very risk averse. We in aviation have not been prone to making big step changes. We’ve been tweaking incrementally from one variant to the next. And so it would really take a different kind of leader than what we’ve seen at the C-suites of the aerospace companies in the past in order to make that kind of change.

McNiel: Well, why does it work for the B-1 bomber and not for commercial aviation? Why did they go with that configuration?

Eremenko: Because the military customer fundamentally is less risk averse.

McNiel: But what’s the advantage?

Eremenko: So the advantage is aerodynamic efficiency and volumetric efficiency. So the airplane has better aerodynamics overall if it’s a flying wing because some weird stuff happens at the juncture between a wing and the tube fuselage in a conventional airplane. By eliminating that area, you overall get aerodynamically efficient design and you have more volume.

McNiel: Which means you’re basically just getting better lift overall, right?

Eremenko: That’s right. It’s called lift-to-drag ratio, L/D. And so you get better L/D, you get more volume, which in a bomber is good because you want to be able to carry bombs.

McNiel: More bombs.

Eremenko: And then the third aspect is the radar cross section, which is not a factor for commercial airplanes, but for military airplanes, such an airplane is easier to make stealthy.
I just wanna emphasize, Jim, that we don’t need to solve the wide body problem in order to get aviation on a path towards the Paris Agreement, because the narrow body is most of the emissions and the narrow bodies are due for a replacement in the relatively near future around the mid 2030s. And both of those families of airplanes are very old. And we saw this manifest itself in a very unfortunate way with the 737 max disasters in the last couple years, because Boeing was torturing a very old airplane family to try to create a new derivative design. And layering a sort of bandaid on top of bandaid on top of bandaid. Eventually, things didn’t go well. And so it’s very clear that Boeing cannot do another derivative in the 737 family. And the A320 is a little bit younger, but if Boeing moves to a new clean sheet airplane, Airbus has to as well or the A320 family will stop selling. So I think both companies have a publicly stated strategy of a new clean sheet airplane in that family for around 2035 entry into service, which means a program launched in the late 2020s, because it takes five, seven years to design and build a new airplane. And so that’s the opportunity, and that does not require an exotic configuration. It does not require any new energy storage technology. It will be a slight stretch in order to accommodate the hydrogen. And by stretch, I mean physically lengthening the fuselage to accommodate the hydrogen storage. But it’s not a huge stretch. It’s a couple meters. And companies like GE are already working on hydrogen engines.

McNiel: And like you said, it’s already been done and proven.

Eremenko: It has absolutely, and so, there is a very significant sort of low-hanging fruit opportunity with no significant tech risk to put hydrogen in service and solve in one fell swoop, half of aviation emissions problems by 2035.

McNiel: Do you think hydrogen can succeed without the need to impose a carbon tax on aviation space?

Eremenko: Well, I think it depends on the evolution of oil prices. I think if we continue to see the kind of geopolitical turmoil that’s been driving up oil prices and therefore jet fuel prices without carbon taxes, then we’re going to be at cost parity in the next couple years, with or without the IRA. I think that if oil prices drop significantly, then we’ll need some artificial way of inflating them, in essence, in order for green alternatives like hydrogen to be competitive. Between two-thirds and three-quarters of the cost of hydrogen is electricity and the rest is the amortization and servicing of the electrolyzer.

McNiel: OK, so when you get to really — like you said, you were talking about 3 cent kilowatt power — when you get to really, really cheap electricity, hydrogen changes a lot.

Eremenko: Absolutely. Absolutely. But it is important to note, Jim, hydrogen unlike fossil fuels, hydrogen is not a source of energy, it’s just an energy storage mechanism. The same is true for sustainable fuels or synthetic fuels as well. They’re not naturally occurring, you should think of it as a battery. And it takes some energy to charge the battery with clean electricity. It is an energy storage mechanism, which is ironic, because hydrogen is the most abundant element in the universe, but it is not naturally occurring on earth.

McNiel: Well, it is — just not in this pure form.

Eremenko: That’s right.

McNiel: Usually I ask this question in going out to 2035, but in your case, I’m going to extend it to 2045. If you could imagine your industry in the year 2045, what’s it going to look like?

Eremenko: Well, I think there’s a few choices that the industry has to make. And so one is the choice that we just talked about, which is, is the next narrow-body, next single-aisle going to be a hydrogen airplane? And that’s a decision that has to be made in Seattle and in Toulouse. So two different decisions–

McNiel: Boeing and Airbus.

Eremenko: Boeing and Airbus that could go in two different directions, and it will be really unprecedented in the history of that duopoly if they go in different directions. So for instance, if Boeing makes a sustainable fuel hydrocarbon airplane and Airbus does a hydrogen airplane, that would be really interesting, because we’ve never seen that divergence in the duopoly. But hopefully they both go hydrogen. I think there’s a variety of other technologies. So for instance, I do think that we will see single-pilot operation in the next generation of aircraft. So probably in that narrow body, that single aisle will be a single pilot airplane, which essentially means that it is an autonomous airplane

McNiel: It’s a single pilot with a robot.

Eremenko: And the single pilot is mostly there for comfort, for psychological comfort. And then I think we’ll continue to see improvements in — which have been far too slow to come — in the cabin, in passenger comfort, how we conceptualize the air travel experience.

McNiel: Oh, God willing. Oh my word. Please.

Eremenko: Right?

McNiel: Please.

Eremenko: Well, and Jim, my earlier point about the fact that the industry is really trapped in this incrementalist mindset is there’s no better illustration of it than the fact that if you look at an airplane cabin in the early days of aviation, in the 1930s, 1940s, 1950s, it was people strapped to a seat. And then we bring a substandard sleeping experience, working experience, entertainment experience, culinary experience right to your seat. Why does it have to be that?

McNiel: I wish it wasn’t.

Eremenko: So again, I think it’s an illustration. Right now I’m trying to tackle it in a different space, which is the fuel and propulsion space, but it’s a manifestation of the same incrementalist mindset.

McNiel: Well listen, Paul, this has been fascinating. Thank you so very much. and I wish you the best of success.

Eremenko: It’s my pleasure. Thanks for having me here.