Swapping jet powered planes for alternative power sources is possible, but complicated.
Aircraft are a vital part of the way we organise society, nationally and internationally, from world summits to quick international delivery to foreign holidays and sports tours. Now, because of the need to mitigate climate change and stop burning fossil fuels, many of the things we have come to take for granted in the last 60 years are up for grabs.
While aviation is not one of the biggest contributors to the atmospheric carbon load, it is the one that is growing as demand for air travel increases.
Currently, jet aircraft (the backbone of world aviation) are powered by kerosene-fired jet engines. While this fuel can run a wide variety of different engines to undertake everything from short to long haul flights, the application of renewables in this field is trickier. As a result, there needs to be considerably more development and perhaps more variety in the types of drive used to get an aircraft into the sky.
One solution would be electricity provided by batteries. The big issue here is that any aircraft must be weight conscious, but batteries are heavy…and they stay heavy. Nor can they last long enough to send an aircraft anything more than a few hundred miles. Luckily, this is all that is needed for short range flights of up to 500 miles, with nine to 15 seats per plane. Such an aircraft powered by battery and electric motors would require a battery weighing anything up to five tonnes. At the lower end of this scale, the lack of size and noise of vertical take-off and landing (eVTOL) machines currently in development, make them ideal for short hop journeys to and around cities. A company called Volocopter already has a small aircraft for just such a role and is readying itself to provide such a service during the Paris Olympics.
Closer to home, in Coventry’s Westminster Car Park - next to the railway station and only ten minutes from the city centre - has already been developed into the world’s first ‘vertiport’ for eVTOL aircraft. While it is not yet operational, it will provide a blueprint for 200 other vertiports around the world. Initially, only ‘expensive people’ could afford such a service. With the passage of time, such services will become more affordable to others.
Longer haul flights are beyond the reach of batteries and there are several potential methods that could fill the gap. One (albeit temporary) solution might be a sustainable aviation fuel, such as synthetic kerosene, although this is carbon-neutral not carbon-zero.
Hybrid aircraft, as with hybrid cars, would use a mix of energy sources. For example, a kerosene powered engine driving a generator could power electric motors. The conventional engine could be used on take-off and landing, two key moments requiring a lot of power. Cruising at high altitude would then be powered electrically. Possibly with batteries or another form of electrical power.
Alternatively, hydrogen (coincidentally a by-product of refining oil) could in some form be a fuel of the future. So-called ‘green’ hydrogen, perhaps sourced from offshore wind power to hydrolyse water, would be needed in large quantities. The ‘H’ in H2O could then be used to generate electricity to power an aircraft over a much greater range than possible with batteries. Alternatively, the hydrogen could be burned in an engine. These ideas are all currently the subject of intense research and development.
There have been many examples since the industrial revolution of transition from one technology to another; for example, horses giving way to motorcars, sail ships superseded by steam ships, propeller driven aircraft overtaken by the jet engine. With green powered air-travel, we are on the cusp of another.
John Turton - IET Aerospace Executive Team member
If you found this blog interesting, on 13 September 2023 at 12:30pm BST, register for our webinar on:
With speakers from Airbus, Rolls-Royce and Volocopter, it will keep you up to date with the latest developments in hybrid and electric aircraft.