Gleaming solar cells and churning turbines have become familiar sights on the renewable energy landscape, but they could be about to be joined by a third: a tether extending up hundreds of metres into the heavens. Ftero, a group of eight research students at ETH Zurich, are among the first people to explore the potential of airborne energy: generating power by harnessing the wind at high altitudes. “The idea comes from playing with kites as kids, and the force on your rope,” explains the group’s Lorenz Affentranger.
Ftero’s prototype plane, attached to a generator on the ground, ascends to around 400m and begins a predetermined circle flight path, initially driven by the wind; the torque created on the tether unwinding produces the energy. Neat concept, but Ftero – as part of their project – also have to persuade investors.
“People are quite resistant to renewable,” says Affentranger, “they always think it’s a good idea in principle, but investing is often an extra step they aren’t willing to get into.” They’ve been approaching Swiss energy and consulting firms, stressing that airborne is the renewable form of the future because it’s capable of bigger power output than wind turbines.
Other players are moving into the airborne energy sphere, including Google. The internet giant purchased Makani Power in 2013, which uses a slightly different technique – generating power on board the craft with propellors and transmitting it down the cable. It’s not feasible for Ftero, who can’t afford to crash prototypes full of expensive electronics in the testing phase.
Instead, they’ve built up from planes bought in toyshops to a 5m wingspan prototype due to be presented at a conference in May, tinkering with their flight algorithm in a spirit of old-school Wright Brothers-style innovation. As Affentranger says before offering the group’s innovation advice, “I’m having so much fun this semester”.
Don’t be afraid of being first
“No one really has a fixed idea of how to do airborne, which is the best situation. Every idea can be explored. The technology is still at this point where you have to look at every single aspect, even if it seems a bit messy. The best ideas often come from the areas you least expect.”
Make like David Attenborough
“We’re inspired by the natural world. Traditional planes move through using ailerons on the wings, changing the aerodynamic flow. But it’s really inefficient to only use a mechanical part. So we want to have a wing structure that flexes automatically with the wind flow – the way birds’ wings work.”
Know your USP
“Ours is mobility, because we can mount the plane on a truck and drive it to wherever energy is needed, be it a mountain resort or a refugee camp that’s just been set up.”