Electric planes may seem futuristic, but they’re not too far-fetched, at least for short hops.
Two-seater Velis Electros have quietly gained popularity throughout Europe, electric seaplanes are being tested in British Columbia and larger planes are coming. Air Canada announced on September 15, 2022, that it will purchase 30 electric hybrid regional aircraft from Sweden’s Heart Aerospace, which is expected to bring the 30-seat aircraft into service by 2028. Analysts at the US National Renewable Energy Laboratory note that the first 50- to 70-seat hybrid electric aircraft could be ready shortly after. They say that by the 2030s, electric aviation could really take off.
That’s important for climate change management. Around 3% of global emissions come from the aviation industry today, and with more passengers and flights expected as populations grow, aviation could generate 3 more carbon dioxide emissions. -5 times by 2050 than before the COVID-19 pandemic.
Aerospace engineer and assistant professor Gökçin nar develop sustainable aviation concepts, including hybrid-electric aircraft and hydrogen fuel alternatives, at the University of Michigan. We asked her about key ways to cut aviation emissions today and where technologies like electrification and hydrogen are headed.
Why is aviation so difficult to electrify?
Airplanes are some of the most complex vehicles out there, but the biggest problem with electrifying them is the weight of the batteries.
If you were to try to fully power a 737 with batteries today, you would have to get all the passengers and cargo out and fill that void with batteries just to fly in less than an hour.
Jet fuel can hold about 50 times more energy than a battery per unit mass. So you could have 1 pound of jet fuel or 50 pounds of batteries. To bridge that gap, we need to make lithium-ion batteries lighter or develop new types of batteries that hold more energy. New batteries are in development, but they are not yet aircraft-ready.
An electric alternative is hybrid.
While we may not fully electrify a 737, we can get some fuel-burning benefits from batteries in larger jets by using the propulsion system. hybrid. We are trying to make that happen in the short term, with a target of 2030-2035 for smaller regional aircraft. The less fuel you use to fly, the less greenhouse gas emissions you will emit.
How does hybrid aviation work to cut emissions?
Hybrid electric aircraft are similar to hybrid electric cars in that they use a combination of batteries and aviation fuel. The point is that no other industry has weight restrictions like we do in the aerospace industry.
That’s why we have to be very smart about how and to what extent we are breeding the propulsion system.
Using batteries as a power source during take-off and climbing are very promising options. Taxiing to the runway using only electric power can also save a significant amount of fuel and reduce local emissions at airports. There is a point between the extra weight of the battery and the amount of electricity you can use to get the net fuel benefit. This optimization problem is at the heart of my research.
Hybrid vehicles will still burn fuel while flying, but it could be significantly less than relying solely on jet fuel.
I see hybridization as a medium-term option for larger jets, but a short-term solution for regional jets.
In the period 2030-2035, we focus on hybrid turbofan engines, usually regional aircraft with 50-80 passengers or used for freight. These hybrids can cut fuel use by about 10%.
With hybrid electric, airlines can also make more use of regional airports, reducing congestion and the time larger planes have to idling on the runway.
What do you expect to see in the near future from the sustainable aviation industry?
Shorter term, we will see more use of sustainable aviation fuels, or SAFs. With today’s engines, you can pour sustainable aviation fuel into the same fuel tank and burn it. Fuels made from corn, oilseeds, algae and other fats have been used.
Sustainable aviation fuels could reduce aircraft net carbon dioxide emissions by around 80%, but limited supplies and greater use of biomass for fuel could compete with food production and lead to to deforestation.
A second option is to use synthetic sustainable aviation fuel, which involves capturing carbon from the air or other industrial processes and synthesizing it with hydrogen. But it’s a complicated and expensive process and doesn’t have a high scale of production yet.
Airlines can also optimize their operations in the short term, such as route planning to avoid flying nearly empty planes. That could also reduce emissions.
Is hydrogen an option for the aviation industry?
Hydrogen fuel has been around for a long time, and when it’s green hydrogen – produced with water and electrolyzed with renewable energy – it produces no carbon dioxide. It can also hold more energy per unit mass than a battery.
There are two ways to use hydrogen in aircraft: instead of conventional jet fuel in engines, or combined with oxygen to power hydrogen fuel cells, which then generate electricity to power the vehicle. plane.
The problem is volume — hydrogen gas takes up a lot of space. That’s why engineers are looking at methods like keeping it cool so it can be stored as a liquid until it ignites as a gas. It still takes up more space than jet fuel and the containers are also heavy, so how to store, handle or distribute it on board is still being studied.
Airbus is doing a lot of research on hydrogen combustion using an innovative gas turbine engine with the A380 platform, and aims to have the technology mature by 2025. Ant will begin testing a 34-seat, hydrogen-powered aircraft for short hops in the next few years.
Given the wide range of options, I see hydrogen as one of the key technologies for sustainable aviation.
Can these technologies meet the aviation industry’s emissions reduction targets?
The problem with aviation emissions is not their current levels – it’s the fear that their emissions will increase rapidly as demand increases. By 2050, we could see three to five times more carbon dioxide emissions from aviation than before the pandemic.
The International Civil Aviation Organization, an agency of the United Nations, often defines industry goals, looking at what is possible and how aviation can cross the line.
Its long-term goal is to cut net carbon dioxide emissions by 50% by 2050 compared to 2005 levels. Achieving that will require a combination of different technologies and optimizations. I don’t know if we can achieve it by 2050, but I believe we must do everything we can to make the future of aviation environmentally sustainable.
Gökçin Çınar is an assistant professor of Aerospace Engineering at the University of Michigan