Electric-powered passenger aircraft: reality, hype, or distant future?
You've undoubtedly read about drone taxis that can transport one or two people within the same city. Although developments like these are (almost) a reality, they don't yet meet the needs of large-scale commercial transportation. There's a huge gap between what's currently possible and what we should be able to offer in the not-so-distant future. This is particularly important in the context of pollution: aviation CO2 is 2.5% in 2019 but could rise to 10% in 2050 if nothing is done about it. Not to mention noise pollution and sustainable energy (eventually, we will run out of oil).
In some countries, an awareness of these matters is already reflected in consumer behavior. In Scandinavia, for example, people who hop on long-haul flights are frowned upon because they actively take part in pollution practices. An understandable development in the European Union, whose legislation stipulates that aviation CO2 should be decreased by 75% in 2050. This means we'll need to come up with viable solutions in the next three decades. The question is, what are the options for passenger flights, and which of them is most feasible?
Electric-, solar-, and fuel-cell-powered: the options at a glance
The first question that comes to mind is whether there's an aircraft-version of a Tesla car. The problem is, batteries are much heavier. Whereas kerosene is consumed and thus lightens the weight during the flight, batteries maintain their weight all the way through. On top of that, the energy density and efficiency of batteries versus kerosene are factor 40, meaning you'd need lots of batteries to get from A to B. Even if batteries are heavily improved, they'll never match the current 'kerosene system,' so unfortunately, this is not an option.
Then, there's the concept of a solar-power aircraft. Technically, it works – an individual tested it by flying around the world in a one-person airplane for over a year. But it’s not the large-scale solution we're looking for.
So how about a fuel-cell-powered aircraft? The idea is to convert hydrogen to electricity so you need less fuel. This process, however, costs a lot of energy, and although hydrogen isn't heavy, it is difficult to store, requiring a high-pressure or very cold environment and lots of space. An alternative is to use hydrogen in current aircraft engines, which would be doable if it weren't for the storage issues.
What's the likeliest short-term outcome?
For short-haul flights with airplanes that carry 5 to 10 passengers, batteries are, in fact, an option. Small electric aircraft for air taxis will become reality within the next few years, as they avoid noise and air pollution.
In the meantime, the big players such as Boeing and Airbus are working on solutions, aiming for a hybrid system. This could mean an aircraft has 2 jet engines and 2 electric-powered engines. During take-off, the latter will provide an extra boost, while a mix of traditional fossil fuel and bio fuel will be used for continuous stretches at altitude. The gas turbine can be simpler, lighter, and more efficient, as it only needs to operate at a limited rotational speed. This could save 30% of kerosene, meaning emissions will be significantly reduced. Of course, we've still got a long way to go to get to 75%. But it's definitely a step in the right direction!