Plane taking off

‘Light, environmentally friendly’ liquid hydrogen proposed as aircraft fuel

Using hydrogen to fuel passenger aircraft deserves serious consideration as a potential solution to the problem of emissions, according to Dutch physicist Professor Jo Hermans, who compared the energy efficiency of modes of transport ranging from bikes to flights.

In a paper published in the journal MRS Energy and Sustainability, Prof Hermans of Leiden University concludes there are numerous advantages involved in using liquid hydrogen for air transport – most notably that it is so light.

Kerosene is currently used to power jet planes, and Hermans acknowledges that, in terms of cost and sheer convenience, this fuel is at present impossible to beat.

But he writes: “It is a defect that kerosene is so irrationally cheap, which triggers much unnecessary air travel. A worldwide tax on kerosene - if at all politically possible - should be something to pursue.”

In his paper, the academic, who has authored several popular science books with titles like Physics is Fun, adds: Given the severe weight limitations for fuel in aircraft, liquid hydrogen may be a viable alternative in the long run.”

He discounts the potential of having solar-powered planes as this would be all but hopeless without revolutionary changes in aircraft design, writing, Direct use of solar power is within reach for cars, provided that customers are willing to accept a lower degree of comfort. By contrast, for aviation purposes the direct solar power option seems to be beyond hope.”

Hydrogen is highly flammable and must be stored and handled with care, but Hermans believes taking necessary precautions would be perfectly feasible within the context of an already tightly regulated airport environment.

He points out that losses through ‘boil-off’ are also much less of an issue when using liquid hydrogen to fuel planes, as opposed to in cars.

For road transport, Hermans argues that liquid hydrogen is not a viable option due to safety issues around handling.

Electric vehicles offer the most promising solution, he believes. However, the challenge is to improve the performance of batteries to prolong the driving time, as well as improving the performance of supercapacitors for more rapid charging of the batteries.

Direct driving using solar power is difficult, Hermans finds, even under a clear sky, but he concludes solar family cars will be feasible in future if consumers are willing to sacrifice on comfort.

Transport makes up around 20 per cent of energy use globally – a figure that appears set to grow over coming decades.

One of the most efficient ways to reduce energy use in future, Hermans writes, is to reduce our mobility - for example, through having shorter distances between the workplace and home.

In other words, urban planning provides an important key, he concludes.

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