Assistant Professor of Aerospace Engineering, University of Michigan Michigan (USA), September 21 (The Conversation) Electric planes may seem futuristic, but they are not that far off, at least for small jumps.
Two-seater Velis Electros are already buzzing quietly Europeelectric seaplanes are being tested in British Columbia and larger planes are coming.
Air Canada announced Sept. 15 that it will purchase 30 hybrid-electric regional jets from Sweden’s Heart Aerospace, which plans to field its 30-seater aircraft by 2028.
The analysts of US National Renewable Energy Laboratory note that the first 50-70-seat hybrid-electric transport aircraft could be ready soon after. In the 2030s, they say, electric aviation could really take off.
This is important for the management of climate change. About 3% of global emissions come from aviation today, and with more passengers and flights expected as the population grows, aviation could produce three to five times more carbon dioxide emissions than by 2050 than before the COVID-19 pandemic.
Aerospace engineer and assistant professor Gokcin Cınar is developing sustainable aviation concepts, including hybrid-electric aircraft and hydrogen alternative fuels at the University of Michigan.
We asked her about the main ways to reduce emissions from aviation today and where technologies such as electrification and hydrogen are headed.
Why is aviation so difficult to electrify?
Airplanes are among the most complex vehicles, but the biggest problem with electrifying them is battery weight.
If you were trying to fully electrify a 737 with today’s batteries, you’d have to remove all passengers and cargo and fill that space with batteries just to fly for less than an hour.
Jet fuel can hold about 50 times more energy than batteries per unit mass. So you can have 1 pound of jet fuel or 50 pounds of batteries.
To close this gap, we must either lighten lithium-ion batteries or develop new batteries that contain more energy. New batteries are being developed, but they are not yet ready for aircraft.
An electrical alternative is hybrids.
While we may not be able to fully electrify a 737, we can achieve fuel economy benefits from the batteries of larger jets by using hybrid propulsion systems.
We are trying to make this happen in the short term, with a 2030-2035 target for small regional aircraft. The less fuel is consumed during the flight, the less greenhouse gas emissions there are.
How does hybrid aviation work to reduce emissions?
Hybrid electric airplanes are similar to hybrid electric cars in that they use a combination of batteries and aviation fuels. The problem is that no other industry has the weight limits that we have in the aerospace industry.
That’s why we have to be very smart about how and to what extent we hybridize the propulsion system.
Use batteries as Powerful take-off and climb assistance are very promising options. Taxiing to the runway using only electric power could also save a significant amount of fuel and reduce local emissions at airports.
There is a balance between the added weight of the battery and the amount of electricity you can use to get net fuel benefits. This optimization problem is at the center of my research.
Hybrids would still burn fuel during flight, but that could be considerably less than just relying entirely on jet fuel.
I consider hybridization as a medium-term option for large aircraft, but as a short-term solution for regional aircraft.
For 2030 to 2035, we are focusing on hybrid turboprops, typically 50-80 passenger or freighter regional aircraft. These hybrids could reduce fuel consumption by around 10%.
With electric hybrids, airlines could also make more use of regional airports, reducing congestion and the time large planes spend idling on the runway.
What do you expect from sustainable aviation in the short term?
In the shorter term, we will see more use of sustainable aviation fuels, or FAS. With today’s engines, you can dump sustainable aviation fuel into the same fuel tank and burn it. Fuels made from corn, oilseeds, algae and other fats are already in use.
Sustainable aviation fuels can reduce an aircraft’s net carbon dioxide emissions by around 80%, but supply is limited and using more biomass as fuel could compete with food production and drive deforestation .
A second option is to use sustainable synthetic aviation fuels, which involves capturing carbon from the air or other industrial processes and synthesizing it with hydrogen. But it is a complex and expensive process that does not yet have a large production scale.
Airlines can also optimize short-term operations, such as route planning to avoid flying nearly empty planes. It can also reduce emissions.
Is hydrogen an option for aviation?
Hydrogen as a fuel has been around for a very long time, and when it comes to green hydrogen – produced with water and electrolysis powered by renewable energy – it does not produce carbon dioxide. It can also hold more energy per unit mass than batteries.
There are two ways to use hydrogen in an aircraft: either instead of regular jet fuel in an engine, or combined with oxygen to power hydrogen fuel cells, which then generate electricity to power the plane.
The problem is volume – hydrogen gas takes up a lot of space. That’s why engineers are looking at methods like keeping it super cool so it can be stored as a liquid until it’s burned off as a gas.
It takes up even more space than jet fuel and storage tanks are heavy, so how to store, handle or distribute it on aircraft is still being worked out.
Airbus is doing a lot of research on hydrogen combustion using modified gas turbine engines with an A380 platform, and aims to have mature technology by 2025.
Australian airline Rex plans to start testing a 34-seat hydrogen-electric aircraft for short hops in the next few years.
Due to the variety of options, I consider hydrogen to be one of the key technologies for sustainable aviation.
Will these technologies be able to meet the emission reduction objectives of the aeronautical industry?
The problem with aviation emissions isn’t their current levels – it’s the fear that their emissions will grow rapidly as demand grows.
By 2050, we could see three to five times more carbon dioxide emissions from aviation than before the pandemic.
Its long-term goal is to reduce net carbon dioxide emissions by 50% by 2050 compared to 2005 levels. Achieving this will require a mix of different technologies and optimization.
I don’t know if we will be able to reach it by 2050, but I believe that we must do everything to make the aviation of the future ecologically sustainable.
Disclaimer: This article is syndicated by PTI from The Conversation