Wind has the potential to power the world 100 times over, but only 4% of the world’s electricity comes from conventional wind power. Worldwide, hundreds of millions of people live within 25 miles of a coastline where winds are strong and steady, but two-thirds of coastal waters are too deep for conventional wind energy systems that sit on the seabed. It’s in areas like these, where conventional wind energy technologies don’t make economic or geographic sense, that energy kites have the greatest potential.
Over the last ten years, Makani has been prototyping and testing energy kites that can generate electricity by efficiently harnessing energy from wind resources that aren’t accessible or cost-effective today.
The Makani energy kite is an aerodynamic wing tethered to a ground station. As the kite flies in loops, rotors on the wing spin as the wind moves through them, generating power that is sent down a tether to the grid.
The airflow acting on a moving kite is many times faster than the wind experienced by a stationary object. This powerful apparent wind spins the kite’s rotors, generating a large amount of electricity.
The kite’s airframe has to handle loads of 7-15 Gs.
Data from GPS and other sensors help the software steer the kite.
Onboard computers running custom flight controller software guide the autonomous kite’s flight path.
8 stacked rotors are spun by the wind in crosswind flight. Each drives a permanent magnet motor/generator that generates electricity onboard.
1200V DC silicon carbide motor controllers handle high voltages efficiently with minimal mass.
Makani started in 2006 when a group of devoted kitesurfers had the novel idea that kites might be able to harness enough wind energy to power the world. The earliest kites were made of fabric and closely resembled kiteboarding gear. Testing these early prototypes proved that the kites needed more efficiency and control than fabric could afford. This led to the idea of rigid kites that could support onboard rotors to harness apparent wind for higher lift and more energy production.
After building rigid kites, their next step was to test small-scale kite prototypes in a broad range of wind and environmental conditions. Here, the team had to solve some major technical problems like how to transition between vertical hover flight, and how to generate energy in crosswind flight when the kite flies in acrobatic loops.
In December 2016, after many generations of prototypes, the team put the knowledge gained from years of testing into a commercial-scale carbon-fiber kite with the wingspan of a small jet plane. The newest kite is capable of generating up to 600 kilowatts of electricity, which is 30 times more energy than the previous prototype and enough to power about 300 homes.
In 2018, the team installed a new ground station for flights at Parker Ranch in Hawai’i, where they’re running autonomous all-modes flights with their kite — another critical milestone on the path to commercial success.
While at X, Makani evolved from a proof-of-concept kite to a commercial-scale prototype. The team is now an independent business within Alphabet working to accelerate access to new offshore wind areas. Makani has partnered with Shell to bring energy kites to offshore environments and remains focused on testing and refining the system to scale commercially so that more people around the world can have access to clean, affordable wind power.