By Danielle Elliott and Isabel Lyndon
Air travel contributes roughly 2.5% of global carbon emissions, yet it is the fastest growing source of pollution within the transportation sector. According to some estimates, aviation could use as much as one quarter of the world’s remaining “carbon budget” by 2050.More than this, the short-lived non-CO2 pollutants from air travel –– such as water vapour, aerosols, and nitrogen oxides –– contribute to increased warming. Contrails, or the white cirrus cloud that sometimes trail aircrafts, form when water vapor in the atmosphere condenses onto the soot particles released by the aircraft’s engine exhaust. The contrails trap thermal radiation, and even though these clouds usually last only a few hours, their collective warming effect exceeds the impact of CO2 emitted by air travel significantly.
One possible alternative is hydrogen-electric fuel. Hydrogen is a more sustainable fuel source than the internal combustion engines that currently power aircrafts and potentially more efficient than batteries powered by clean electricity. Hydrogen fuel cells have longer life than batteries and can keep generating electricity as long as hydrogen is available.
Hydrogen can be sourced from clean power such as wind or solar – so-called “green” hydrogen – and then passed through an electrolyzer on the way to the fuel cell. The fuel cell then converts the energy stored in the charged hydrogen molecules into propulsion for the aircraft through an electrochemical reaction. These fuel cells can then be stacked to create greater power to fly larger planes.
While hydrogen is a dense fuel, it is also lightweight, so it takes up more space per unit of volume than jet fuel. To manage the density challenge, airports will need to consider innovative logistical solutions to transport and provide immediate fuel delivery to aircrafts, while being cognizant of its potentially dangerous explosive nature. Airports may be able to develop on-site hydrogen production with electrolysis plants to create a storage bank of fuel before it gets delivered to the aircraft. To completely decarbonize, the electricity needs to come from renewable, carbon-free sources.
To help encourage sustainable aviation fuel policies, the aviation industry and UK government formed the Jet Zero Council, which promotes innovative aviation technology that achieves net zero-emissions on commercial flights by 2050. Beyond funding, the group focuses on improving the regulatory framework by using existing policy solutions for green transportation – like the low carbon fuel standard credits in California – to help facilitate the transition to green hydrogen fuel.
Many in the industry believe that passengers can expect to fly on a hydrogen-fueled plane in only a few years, a travel experience that might have the added benefit of quieter flights without the smell of jet fuel.
Val Miftakhov- Twitter
Hydrogen Fuel Cells – Environmental and Energy Study Institute
Hydrogen fuel cells, explained– Airbus
Ethan: This is Ethan Elkind of Climate Break. Air travel contributes 2.5% of global carbon dioxide emissions. To eliminate aviation emissions, Val Miftakhov started ZeroAvia, a company committed to building the world’s first zero-emission 100-person jet that can fly across the Atlantic Ocean by 2030. His planes will run on fuel cells powered by hydrogen.
Dr. Miftakhov: It’s one of the fastest growing areas of transportation and nobody really has a solution for sustainability issues there. So we thought that we would start a company that would solve sustainability of aviation at scale.
Ethan: For Miftakhov, hydrogen fuel offers a greater flight range than batteries, which may be better suited for short-haul flights. It’s also a more efficient fuel overall.
Dr. Miftakhov: Hydrogen is actually three times more energetic than jet fuel on a per kilogram basis. Ethan: But powering planes with hydrogen has its fair share of challenges. For example, it’s hard to manage fuel storage, since hydrogen takes up more volume than the equivalent amount of jet fuel, and more fuel production and stations are needed. But as a test pilot himself, Miftakhov prefers hydrogen.
Dr. Miftakhov: It’s actually easier to fly because the power response is better.
Ethan: Hydrogen fuel also produces benefits for passengers, including quieter flights without the smell of jet fuel. For more information on ZeroAvia and zero-emission airplanes, and for more climate solutions, go to climatebreak.org or wherever you get your podcasts.
Ethan: Welcome to Climate Break, bringing you stories of innovative climate solutions being developed at UC Berkeley and around the world shared by the experts themselves. I’m your host, Ethan Elkind, from the Center for Law, Energy and the Environment at UC Berkeley Law. We’re talking about zero emission commercial aviation. Air travel contributes roughly 2.5% of global carbon dioxide emissions, but it’s the fastest growing polluter within the transportation sector. Some reports show that aviation could even take up a quarter of the world’s remaining carbon budget in order to limit warming to 1.5 degrees Celsius by 2050. What’s worse, the short lived non carbon dioxide pollutants from air travel, such as water vapor, aerosols, and nitrogen oxides warmed the planet even more. Contrails, or the white cirrus cloud that sometimes trail aircrafts, form when water vapor in the atmosphere condenses onto the soot particles released by the aircraft’s engine exhaust. The contrails trap thermal radiation. And even though these clouds usually last only a few hours, their collective warming effect exceeds the impact of carbon dioxide emitted by air travel significantly. But physicist Val Miftakhov has a solution: hydrogen electric powered aircrafts. In 2017, he founded ZeroAvia, a company committed to building the world’s first zero-emission 100-person jet that can fly across the Atlantic Ocean by 2030. His engines produce zero emissions and are fit for aircrafts of all sizes.show more
Dr. Miftakhov: I’m a pilot myself, so this is personally relevant, but also wanted to really address the big problem that we have and the sustainability of aviation. It’s one of the fastest growing areas of transportation, and nobody really has a solution for sustainability issues there. So we thought that we would start a company that would solve sustainability of aviation at scale. And after looking at battery electric, turbine hybrids, synthetic fuels, hydrogen turbines and hydrogen electric, we decided that hydrogen electric approach, which is hydrogen fuel cells, electric motors, all of that combined together is probably the best approach to get us the solution at scale.
Ethan: For Miftakhov, hydrogen beats out electricity and batteries as a fuel source, because hydrogen can more easily power long range flights. Battery technology is certainly improving and becoming cheaper, but most batteries need to be recharged and therefore replaced fairly often when used for frequent trips like commercial flights. Unlike batteries, the fuel cells can keep generating electricity, as long as hydrogen is available, without needing to be replaced. The fuel offers other efficiencies, too.
Dr. Miftakhov: The hydrogen is actually three times more energetic than jet fuel on a per kilogram basis. Yeah, very efficient system. And at the same time, you get to use hydrogen as a very, very dense fuel. So actually we can see delivering the same or even better range in aircraft than jet fuel. That’s something that you can’t even think about on the battery side.
Ethan: Here’s how Mr. Miftakhov’s technology works. His planes are powered by fuel cells. Miftakhov sources the hydrogen from clean power, such as wind or solar, so-called green hydrogen. And then passes it through an electrolyzer on the way to the fuel cell. The fuel cell then converts the energy stored in the charged hydrogen molecules into propulsion for the aircraft through an electrochemical reaction. These fuel cells can then be stacked to create greater power to fly larger planes. But while hydrogen is a dense fuel, it is also lightweight. So it takes up more space per unit of volume than jet fuel. Miftakhov and his team are still working on managing this density challenge.
Dr. Miftakhov: So you need more volume in the aircraft if you want to deliver the same range and that becomes a challenge when you’re talking about, okay, how are we going to fly from the United States to England? How are you going to do that? You need more volume. Where are you going to put the fuel? So that’s a challenge. We think that given the volume of fuel that we’ll need, it makes sense to do onsite production of hydrogen at the airports. And it’s going to reduce the amount of logistics that’s involved in the fuel delivery and going to reduce the cost of fuel dramatically so that that can actually compete very well with jet fuel. But that infrastructure needs to be built.
Ethan: Airports can develop onsite hydrogen production with electrolysis plants to create a storage bank of fuel before it gets delivered to the aircraft. To completely decarbonize, the electricity needs to come from renewable, carbon-free sources, which Miftakhov says isn’t a problem for his team.
Dr. Miftakhov: We already have actually a number of eyes with the potential fuel suppliers that are looking to bring zero-emission hydrogen. We are working on our own systems that utilize combined electrolysis systems, all of the battery storage on site and all the other components, fuel and components, to build such installations. You would need a renewable power input from offsite or maybe even onsite. There’s plenty of renewable power these days.
Ethan: An added benefit of using electricity as the primary input: airports can also use it for battery electric aircrafts and other local vehicles, extending these clean energy benefits beyond the aircrafts. Like most new technology, ZeroAvia’s initial prototypes were expensive. But Miftakhov’s team is on track to produce hydrogen electric engines that match the selling price of comparable turbine engines in three years. In the long run, hydrogen powered engines will likely get even cheaper. Without the high pressure, high temperature combustion found in turbine engines, the wear and tear on the system is lower, thereby reducing maintenance costs. And Miftahkhov says that green hydrogen fuel prices are already competitive with jet fuel. All that’s left then to solve is the cost of production.
Dr. Miftakhov: We think that we can meet and beat the incumbent technology, the turbines, on the actual capital cost of the equipment, like how much the engine costs. But you look at the raw materials and you look at the complexity of manufacturing for the modern turbine engine, the complexity of manufacturing is insane. They literally grow single crystal discs and blades and turbine components out of a single crystal of metal because the stresses are so high. So you don’t have any of that on the electrified powertrain. So the cost of production is likely going to be lower as well.
Ethan: And they may be safer too, when people think of hydrogen fuel. The 1937 Hindenburg disaster often comes to mind. The infamous German passenger airship explosion used hydrogen fuel and deterred engineers and the public from using hydrogen in aviation. But Miftakhov believes that hydrogen fuel is actually safer than jet fuel.
Dr. Miftakhov: It’s really about building the safety system around the fuel. Jet fuel is not inherently a safe substance either. Any substance that packs a lot of energy is going to have safety concerns. Right. So it’s about the system that you build around it that ensures safety. Handling protocols or systems, failsafe and so forth. Hydrogen actually has some good properties from a safety perspective relative to jet fuel. So, for example, if you have a jet fuel spill and the vapors go in the air, they’re relatively heavy, they tend to cluster around the fuel spill, which means that any kind of ignition source creates an initial explosion and then you have the fire of the fuel itself. Typically any kind of collision events with the ground or another aircraft creates those kinds of situations. Whereas hydrogen is so lightweight that if you have a leak in a tank, for example, an advance outdoors, it dissipates immediately. So it’s very, very hard to maintain combustible, explosive concentration of hydrogen in open air. And, of course, all of the aircraft operate over there. Then auto ignition temperature or ignition temperature of hydrogen is quite high, compared to jet fuel. That means that if you have hard brakes, for example, on your aircraft and you have a fuel spill right after landing, the jet fuel, if it gets the vapors or fuel itself gets in contact with that, it’s going to catch fire. Hydrogen has 500 C ignition temperature, jet fuel, 200 C. So you need to be much, much hotter in order to auto ignite hydrogen. And a few of those things. So, safety profile is different. In some ways, it’s better than jet fuel, and we just need a system around it. And the good thing is that the industry has used hydrogen for ages. Actually, almost 100 million tonnes is produced a year of hydrogen and used in fertilizer industry refineries, industrial processes, all kinds of things. Actually, every gallon of gasoline that you put in your vehicle likely went through the hydrogenation process with hydrogen that is used in a refinery to produce lighter fractions of crude oil. So tons and tons, millions of tonnes of that is used. They are stored, they are transported, they are consumed. So the industry knows how to do it. The safety protocols exist.
Ethan: So what can policymakers do to support this transition to decarbonized aviation? Miftakhov says U.S. policymakers could increase funding for hydrogen fuel research and projects. In the United Kingdom, ZeroAvia is part of the recently formed Jet Zero Council, an alliance between the aviation industry and UK government actors to deliver innovative aviation technology that achieves net zero emissions on commercial flights by 2050. Beyond funding, Miftakhov suggests improving the regulatory framework, using existing policy solutions for green transportation, like the low carbon fuel standard credits in California.
Dr. Miftakhov: They don’t have to necessarily invent a completely new scheme to do it. You just say, okay, well, this worked for ground vehicles. Let’s just extend it into the air vehicles. Similar type of. Maybe focus more on the commercial vehicle side, like for trucks, for example, there are some good programs.
Ethan: Passengers can expect to be able to fly on a hydrogen-fueled plane in only a few years. Commercial operation for 10 to 20 seat aircrafts will be available in three years. And another three years, 50 to 80 seat planes, and then possibly 100 seat aircrafts by 2030. What to expect? A quieter ride without the smell of jet fuel.
Dr. Miftakhov: Then it’s going to be significantly quieter, especially inside, because a lot of the noise that gets inside of the vehicle is produced by the engines themselves, because they’re hard coupled to the airframe, the air noise from the propellers and so forth. You can isolate it easier inside the cabin than the engine noise. And obviously with electric motors you have zero engine noise. So it’s actually much quieter inside as well, especially in the smaller aircraft. So the experience of the thing is going to be quite a bit better and there’s less vibration as well.
Ethan: There are also added benefits for the pilot. Miftakhov himself has been test piloting ZeroAvia’s aircrafts.
Dr. Miftakhov: It’s actually easier to fly because the power response is better and the little linearity of response is better, because you can control it in a much finer way. And actually, electric powertrain lends itself to – also automation much better because you get, it’s all electronic control systems that manage flow of electrons versus flow of fuel, and that can be made much more precise, much more robust. And for automation for very fine control levels, but very frequent controls, this is much better than fossil fuel. So it’s also future proof in that way.
Ethan: For more information on ZeroAvia, zero-emission airplanes, and other interviews with climate experts discussing groundbreaking research, you can visit our website at climatebreak.org. We’ve gathered resources there to help you remain up to date on the latest climate change solutions. I’m your host, Ethan Elkind. See you next time on Climate Break.show less