UK-based aircraft engine manufacturer Rolls-Royce successfully ran one of its aero aircraft engines on hydrogen. The company speaks of a new aviation milestone, but how far along are we in the journey toward sustainable aviation?
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A converted traditional aero engine running on hydrogen
Rolls-Royce carried out their tests in cooperation with British airliner EasyJet using a converted conventional aero engine.
The companies have set out to demonstrate that hydrogen can efficiently and safely generate power for civilian aero engines. They view their successful test as proof that they are on the right track with their plans for CO2-neutral aviation in 2050.
The test was conducted at the outdoor testing facility MoD Boscombe Down, in Wiltshire, UK. The team used a Rolls-Royce AE 2100-A turboprop engine, a relatively old aircraft engine that is mostly used for shorter flights.
The team stated in a joint press release that they are now working towards a test with a more modern Pearl 15 jet engine (commonly used in private jets). They are also planning a second set of tests and aim for actual flight tests in the longer run.
Different types of hydrogen
There are many different types of hydrogen. Most of the hydrogen that is currently produced is so-called 'grey hydrogen.'
Grey hydrogen is created from methane or natural gas via SMR (Steam Methane Reforming). Here high-pressure steam (H2O) reacts with natural gas (CH4), resulting in hydrogen and CO2.
Grey hydrogen is sometimes converted into 'blue hydrogen' by capturing and storing the CO2 released in the production process. It is often touted to be a clean fuel. However, Stanford and Cornell-based scientists think it may harm the climate even more than actually burning fossil fuel.
If we aim for true carbon-free hydrogen production, there are only two real options: green hydrogen or purple hydrogen.
Green hydrogen is created using renewable electricity (wind, solar, etc.) via the electrolysis of water. Purple hydrogen is created via the same method but by using nuclear power instead of renewable electricity. (Purple hydrogen is sometimes also referred to as red hydrogen or pink hydrogen.)
It will require a lot of new infrastructure and production facilities, but green hydrogen is the way to go - (Image Credit: petrmalinak via Shutterstock / HDR tune by Universal-Sci)
Why are there no hydrogen planes yet?
A hydrogen-powered aircraft engine isn't a new concept. The first experimental tests with hydrogen as a fuel were carried out all the way back in the 1950s. However, the current tests are of a different order as we are slowly edging toward actual commercial viability.
Nevertheless, there are still many practical problems that need to be solved in order to make flying on hydrogen viable on a commercial scale.
Hydrogen packs a lot of energy into a small amount of mass; however, one of the issues is that hydrogen fuel takes up about four times more volume for the same amount of energy compared to conventional kerosene. More volume means that the plane needs to be bigger and heavier.
In addition, it is challenging to keep hydrogen to keep in liquid form. You either need to keep it under high pressure or cool it to maintain its liquid form. Keeping the fuel under pressure requires very sturdy, heavy tanks, whereas cooling uses up additional energy, reducing the plane's efficiency.
Therefore, in order to accommodate hydrogen fuel, aircraft will have to be redesigned entirely. The European aircraft manufacturer Airbus is currently working on several concept aircraft with hydrogen propulsion.
Airbus expects the first commercial hydrogen aircraft to come onto the market around 2035, although it thinks the majority of aircraft will remain reliant on kerosene-powered jet engines until at least 2050
All in all, it seems that (after almost 70 years since the first tests) we are actually making some progress toward viable commercial hydrogen-powered planes, which is excellent. However, it remains to be seen if 2035 is a realistic target.
As always, we will keep you posted on developments.
Sources and further reading
Blue hydrogen is often hyped as clean, but in actuality, it might be even worse than burning coal (Universal-Sci)
Why aren’t there electric airplanes yet? (Universal-Sci)
Why battery-powered vehicles stack up better than hydrogen (Universal-Sci)
How green is blue hydrogen? (Energy Science & Engineering)
Rolls-Royce and easyJet set new world first (Rolls-Royce press release)
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