Everything you need to know about Green aviation technology in 2 minutes

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As the world grows perilously close to mass environmental catastrophe, mass jet air travel is no longer appropriate. Fortunately, the Electric Age of air travel has already begun: the world’s first fully electric commercial aircraft took its first flight last week. But is it plausible and what are the other key Green aviation technologies out there? We spoke to Tim Robinson from Editor in Chief of Aerospace – the flagship magazine of the Royal Aeronautical Society.

Electric engines/hybrid-electric

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Electric pretty well for smaller aircraft (eg motorised gliders, two seat trainers) – and hybrid-electric types – are getting bigger all the time, with the market gravitating to an ideal 19-seat.

Biggest advantage – (as well as zero carbon and reduced noise) is operating costs. Electric motors could deliver 50-75% reduction in operating costs – opening up the possibility of cheap, clean, quieter aircraft flying point-to-point from smaller airfields.

Disadvantage. Range and battery weight. Unfortunately, kerosene is still more energy dense than batteries – so you will never see an all-electric 777 or A380 any time soon – the weight of the batteries would simply be too much. Even if you had batteries that were 30 times as energy dense as the ones we have today – it would mean a single-aisle aircraft like an A320 would be able to carry half its payload for one fifth of its range, compared to a jet-powered airliner – a big drawback. Electric or hybrid/electric aircraft also may have to fly slower than current jets to optimise battery power – which may mean a change in the productivity or how many legs an airline can fly in one day. Hybrid-electric though might offer the way forward for single-aisle airliners. Electric aircraft also weigh the same on landing as when they take-off – so will fuel savings be undermined by needing stronger landing gear and a beefier structure?

Likelihood of happening – accelerating fast with Canadian seaplane operator just flown a re-engined 1940s vintage electric de Havilland DHC-6 Beaver this week. In the UK, a Twin Islander is to be retrofitted with electric engines, while Eviation Alice – a new design – stole the show at the Paris Air Show in 2019. Industry meanwhile is already looking at larger hybrid-electric airliners in the 2030s.

 

Hydrogen

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At the research stage – although one company is set to trial a six-seat hydrogen fuel-cell/electric aircraft in the UK in 2020.
Advantages – Very clean fuel (only produces water ) – more energy dense than kerosene, acts as heatsink to absorb excess heat of electrics.
Disadvantages – volume, cryogenics storage, Hindenburg flashbacks, fuel infrastructure, did we mention Hindenburg again?
Will it happen? Perhaps more of a longer-term solution. Hydrogen make the perfect fuel for rockets, but airlines are understandably nervous about turning Heathrow into Cape Canaveral with cryogenics fuel storage. Hydrogen also takes up more volume than kerosene, making for bulbous Guppy-like concepts with higher drag (although a blended wing body aircraft may solve this).
Airships

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Concept mostly well understood, but suffers from ‘snigger’ factor (Flying Bum headlines) and a feeling that fixed wing technology overtook them in the 1930s for very good reasons, not just pictures of an unlucky Zeppelin burning its passengers to death (other aircraft were crashing with frequency too at that time). Beloved by steampunks and Philip Pullman, current next generation airship projects are underway in US, UK, China, Russia and France.

Advantages – uses less fuel than equivalent aircraft, can carry very heavy loads, and (with electric power – there is lots of space for solar panels) could conceivably be a very green or zero carbon mode of mass aerial transport.

Cons Slow – will the travelling public accept that journeys will take far longer? Constrained more by the weather than fixed-wing aircraft. Needs space for landing/docking (eg a mast).

Will it happen? A niche market at the moment in heavylift and VIP sightseeing, airships were heading for a Renaissance as military ISR platforms when the US generals got cold feet and backed out. An accident involving Airlander (a slow-speed crash, ironically demonstrating the types safety) has set back the UK’s big hope for lighter-than-air revival. However, there are some encouraging signs – a recent British Airways study saw travellers express an interest in flying slower if it could be made greener.

Quick wins

Environmental quick wins. There are many technologies or operational concepts that don’t require inventing super-efficient battery or convincing an airline that airships are back.

ATM (air traffic management) – especially in Europe. Despite sharing a currency, many countries in the EU are very reluctant to share or at least make their airspace more efficient. The result is that airlines spend an in-ordinate amount of time weaving around empty military flying areas, restricted zones etc or stuck in the hold when you get to your destination. The technology is here for flying direct – so why can’t we?

Sustainable aviation fuels – drop-in alternatives such as biofuels is already happening and many airlines have conducted trials with blends. The technology is here, but the sticking point is the cost compared to regular jet fuel. This will come down as more sustainable fuel production facilities come online – but could be incentivised to happen far quicker by governments.

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Flying in formation – Airbus (and others) have noticed that migrating geese fly together in formation not because it looks cool, but because it saves energy. By surfing the lead aircraft’s vortex from up to 3km away, the fuel burn could be reduced by 5-10% (a big saving considering that say A320’s ‘Sharklets’ winglets save 3.5%). Challenge here is in the operational aspect and getting airlines to synchronise their flights this closely – but Airbus believe it could be rolled out in the mid-2020s.

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Electric vehicles at airports – a personal bugbear. The latest eco-efficient airliner drops you off at a budget terminal. The stairs are down, the weather is good and it would take literally 60 seconds to walk to the terminal. However, for some strange reason, instead a dirty diesel bus will sit alongside for 15minutes chugging particulates into the atmosphere until everybody has deplaned, only to chug over to disgorge everyone. There’s also solar panels at airports and even tapping into geothermal energy to melt ice and snow on runways – that could make for net zero airports.

Ditch the inflight magazines and duty free to save weight – some have already cottoned on to this, but why are we flying acres of dead trees around, booze, perfume and trinkets that no-one buys? Surely put the magazine content on IFE and have the passenger pick up the duty free when then land? It’s not like they are going to be smoking 200 Benson & Hedges during the flight, is it?

Avoid contrails – (or persistent contrails in the atmosphere) can cause radiative forcing – making the planet hotter. However, weather modelling and real-time communications means that airliners could be vectored around (or under) particular cold fronts where these high-altitude contrails form. Only a tiny number of flights would be affected – but the impact on the formation of these persistent contrails would be huge.

What should I asked you?
That aviation meeting the challenge of climate change is not just about making Guardian readers feel ethically smug when visiting their Tuscan villa every weekend. The 2% of CO2 produced by aviation is likely to get larger in comparison with other industries as they electrify and go green. Unfortunately, fossil fuel is almost perfect for aviation – energy dense, works at low temperatures, stored easily etc and the physics make replacing it on bigger aircraft a challenge.

Climate change and aerospace is also not just a challenge for civil aviation – it also has implications for military operators – just look at the extreme storms that have wrecked US air bases recently. Climate change also means adapting to reduced take-off performance in hot areas, stronger jetstream and clear air turbulence.

Finally (and the boring bit when ‘selling’ what aviation is doing already) is that there is no one silver bullet of technology or operations that is the answer. Increased efficiency of current engines, electrification, operational changes, new materials will all make a difference – but it won’t be overnight.

However, as in the past when given a big challenge (flying the Atlantic, breaking the sound, travelling to them) aerospace steps up to the challenge and scientists and engineers manage the impossible. The zero-carbon challenge is just the latest one.

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One comment

  1. brian

    I thought you were going to have a zero emission list of aircraft. Starting out with a passenger glider, Benefits: full employment for pilots as you would need zillions of them with current technology. Disadvantages: slow

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