• Photos: Eurocontrol; Lakov Kalinin /

20.09.2023 By: Andreas Haug

Artikel Nummer: 46479

A 7 km flying carpet?

Eurocontrol presents one of its ’Think Papers’ on alternative fuels. The research scene into alternatives to fossil fuels – including electric batteries, hydrogen, methane and ammonia – is lively. There’s still no solution for decarbonisation in sight for long-haul flights, however, according to the conclusion of a recent Eurocontrol study.

Only 10% of flights departing from or arriving in the EU and the UK are longer than 3,000 km and are operated with more freight-friendly wide-body aircraft. Today, however, they account for half of all CO2 emissions caused by aviation. By 2050, this figure is expected to rise to 60% – if major technical progress isn’t made.

The production of SAF is still in its infancy, so Eurocontrol has taken a close look at the advantages and disadvantages of truly alternative propulsion systems. Its ‘Think Paper 21’ has concluded that the disadvantages outweigh the advantages for every potential solution, as an illustration using a fictitious Airbus A380 with alternative propulsion systems and energy sources impressively illustrates.

Weight and volume problems

Trucks powered purely by electricity are already conquering an ever greater share of the road haulage market. Even with the current state of battery technology, however, the take-off of an electric long-haul aircraft is impossible, due to the 5,000 t of lithium-ion batteries required, plus 17 t for efficient electric motors and their cooling systems.

In addition, the range the aeroplanes could currently offer would be insufficient; the risk of fire would be high; and energy consumption in airports would be anything but CO2-neutral.

Liquid hydrogen (98 t), which could be processed into electricity in on-board fuel cells (242 t), is also eliminated from the list of possibilities by the fact that it meeds 1,376 m3 of volume. If liquid hydrogen were burned directly in the engines its weight would be reduced to 52 t and its volume to 730 m3, it’s true, which would be enough to take off and land.

This still leaves the problem of a lack of cryogenic tanks and other infrastructure on the ground. In addition, significant quantities of contrails would be ‘painted’ in the sky, whose effects on the climate and on the environment are currently being investigated by several bodies, with Eurocontrol also set to start it’s own analysis soon.

Methane, ammonia, solar power

In principle two further gases also present potential fuels. Methane is attractive due to its small space requirement (259 m3); its weight of 109 t is 10 t less than the weight of kerosene currently carried; and its performance comes quite close to that of jet fuel.

Its production costs are exorbitant, however, and the climate impact of methane once it enters the atmosphere is 30 to 83 times more severe than that of CO2. Liquid ammonia is heavier (345 t), requires more space (506 m3) and is highly toxic, especially once it is a vapour.

The potential of ‘clean’ solar power, on the other hand, represents a complete utopia. In order to provide enough energy, an Airbus A380 would have to pull a 7.4 km long and 80 m wide carpet of panels behind it.


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