The lighter the better.

This motto has always applied in aviation.

In this respect, it is only logical to examine the smallest atom to see whether it is suitable as a fuel for aircraft turbines, especially since hydrogen can be produced from regeneratively generated electricity and water with comparatively low losses.

John Winterhagen

Editor in the economy, technology and engine department

  • Follow I follow

At the end of November, the engine manufacturer Rolls-Royce announced the first results of a development cooperation with the airline Easy Jet.

The AE2100A turboprop turbine was used in the underlying tests.

This type of machine normally powers the Saab 2000 short-haul aircraft, albeit fueled with kerosene.

With various test bench tests, it should first be demonstrated that reliable operation of the turbine with hydrogen is even possible.

Both the fuel system and the core engine were designed to match the thermodynamic and chemical properties of the new fuel, although Rolls-Royce does not disclose the details of the changes.

space issues

In principle, the operation of gas turbines with hydrogen is considered to be manageable.

Both GE and Siemens Energy are already supplying power generation units that can be operated 100 percent with gas.

A specific feature of aviation is the exhaust gas behavior: Subsequent exhaust gas cleaning is technically not possible, which is why raw nitrogen oxide emissions can be reduced solely by internal engine measures.

Hydrogen combustion not only works at very high temperatures, but usually also with excess air, which promotes the formation of nitrogen oxides.

However, the project partners are confident that the emissions can be reduced by further tests that are already planned, similar to what has been achieved in the past for kerosene operation.

Compressed to 200 bar

The big challenge for hydrogen aircraft is probably not the combustion, but the storage of the gas.

Rolls-Royce carried out the test series with hydrogen compressed to 200 bar.

What sounds like a lot is well below the 700 bar that is already used in the automotive industry for small series.

But even then, one cubic meter of gaseous hydrogen only achieves 1332 kilowatt hours.

A cubic meter of kerosene, on the other hand, produces around 10,000 kilowatt hours.

In order to complete comparable distances, the tanks would have to be larger, the wings are not sufficient for the containers.

That is why Airbus recently announced that it would try cryogenic hydrogen storage.

This uses very low temperatures of less than 252 degrees Celsius, at which the hydrogen is present as a liquid.

Compared to 700 bar storage, the energy content per volume unit is then doubled.

It remains to be seen whether that will be enough for civil aviation.

Despite the associated conversion losses, it could prove advantageous for their balance sheet to process hydrogen into synthetic kerosene and allow more passengers on board.