Season 6 - L’avion solaire

Episode 1 - Erm… What's this device?

When advocating for clean mobility, of course, dilemmas arise. Last summer, the weather in Brittany was similar to the Maldives. So for a scorcher of a 2023 summer, you rented a place in Morbihan. Problem is, despite what the climate-optimists on TV suggest, climate change is not fun. And what was meant to be a tropical European getaway, feels more like a bleak October break. Spending all the time inside, you finish all your holiday reads and start looking up flights to Thailand and the Dominican Republic. As for your future carbon footprint, well, it’s best not to think about it. Don’t worry, we’ve all been there.

What if we told you that there is a plane capable of travelling 40,000 kilometres – roughly the circumference of the Earth – without using the slightest drop of kerosene. That would tempt you, right? Of course. Well actually, a vehicle delivered this feat in 2015: the Solar Impulse 2 plane, which was piloted by André Borschberg and Bertrand Piccard. “If it has the wingspan of a Boeing 747, its weight does not exceed that of a family sedan. Its huge wings are made from a composite material made of carbon fibres that are covered by 17,000 solar cells; the latter provide its four propeller motors with the necessary energy during the day and allow it to power four lithium batteries for night flights,” says Oxford University researcher Neil Ashton in an article in The Conversation. In short, it’s a technological marvel, powered only by the sun’s rays.

But despite its extraordinary record, this solar plane isn’t the first of its kind (the clue’s in the name: Solar Impulse 2). In fact, the idea of ​​an aeroplane powered by solar cells dates back to the 1970s. The oil shock of 1973 had just upturned the world economy, and some clever people thought it might be time to switch to a more abundant, less expensive source of energy (and yes, a cleaner one). The one they found didn’t actually cost anything. In 1974, Sunrise I made its first flight in the form of an unmanned prototype 9.76 metres wide, weighing 12.3 kilograms and equipped with 4096 photovoltaic cells. Then came Sunrise II in 1975, Solaris and Solar One in 1976. In the 1980s, technology progressed with the Gossamer Penguin, an aircraft which carried a pilot. There was also the Sunseeker, which crossed the United States in twenty-one stages.

A few other models appeared here and there, including NASA's Helios model, until the Solar Impulse project earned its stripes as a means of travel. Still, it stayed relatively under the radar. The impact of the oil shock had been absorbed and black gold began to reign over the world again, so people lost interest in flying planes with solar energy (energy that had no impact on the climate by the way). Sure, plenty of powerful people would have lost out if planes flew without kerosene. But that’s only one explanation for the general disinterest in solar aircraft. The other is that at this stage of the development of the technology, no one had managed to create an aircraft capable of carrying a large number of passengers.

That doesn’t mean it’s useless technology. Far from it. In addition to producing solar-powered drones capable of flying for over 64 days without stopping, such as the Airbus Zephyr S, this technology has some amazing potential. As Gérard Feldzer, engineer, pilot and president of Aviation Sans Frontières, explains: “as far as large aircraft are concerned, it is unimaginable with the technology at our disposal. But there are other interesting applications. At Aviation Sans Frontières, we could be the first customers for small planes operating with solar technology or hybrid technology”. Aviation is essential, right? But even flying can and should be decarbonised.

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