Kites in search of the safest winds in the world
SkySails actually started in 2001 with a different goal: to build flexible kite wings to pull ships at sea. The shipping industry has traditionally relied on a crude, polluting fossil fuel called bunker fuel, and the idea was that a wing could, like the sails of old, help to greatly reduce a ship’s fuel requirements.
Now, with stricter requirements from the UN’s International Maritime Organization for ships to reduce emissions, other companies, including an Airbus spin-off, are making fenders to help tow massive ships . But in 2015, SkySails focused on power generation with SkySails Power.
SkySails’ system – like several others in development – relies on a parachute-like wing of about 150 square meters (1,600 square feet) to ride on the wind. There are no turbines in the air and the tether is not an electric wire. Instead, power is generated on the ground, from the tug on the line. “The winch brake generates electricity,” says Fagiano. The software flies the kite autonomously in a figure-eight pattern to get the strongest possible pull to generate power. The system then changes the wing’s flight pattern so that it can be pulled with minimal resistance, expending some energy to pull it up. This pattern repeats itself, creating far more energy than it consumes.
It sounds simple and the power generation system is pretty standard. But Stephan Brabeck, director of technology at SkySails, says it took the team about seven years to perfect the flight software, in particular so that the wing could safely land and launch autonomously. They have now made and sold five units, Brabeck says, with Maurice’s being the first in operation. They believe the wing will have to land about 14 times a year due to heavy rain, unsuitable winds or thunderstorms. The occasional hurricane, which an airborne system can if nestled on the ground, is what makes the island unsuitable for traditional wind turbines, says aerospace engineer Brabeck.
The sails are less intrusive on the horizon than traditional turbines and quieter too, Brabeck says. And they make economic sense, he says, for anyone currently paying more than $0.30 (23p) per kilowatt hour from diesel generators. But there are challenges. Wind turbines can kill or injure migratory birds, and how birds will react to these kites “hasn’t been very well studied yet,” Fagiano says. SkySails has ongoing studies. Tethering such a system, Archer notes, could theoretically trigger drones or even small planes. And if a tether breaks or the guidance system fails, a system can crash to the ground.
This might not be a big deal for a soft wing, but other companies are looking for hard wings that are more like a hang glider than a paraglider. These may be more efficient and have better control, but crashes may be a bigger problem, making them a better bet for offshore use. “Essentially, they are airplanes,” Fagiano explains. “They will have to achieve a level of reliability close to civilian aircraft.”