Makani
Harnessing wind energy with kites to create renewable electricity
Makani set out to unlock access to new sources of clean, affordable wind power by developing novel energy kite technology. Over 13 years, the team developed kites that flew in loops to generate electricity, sending power down a tether to the grid. Despite strong technical progress,the road to commercialization proved longer and riskier than hoped. Makani wound down in 2020 and shared its technology, designs, patents and insights in hopes of advancing the airborne wind industry.
Untapped Wind Potential
Makani began in 2006 with a bold idea from a group of devoted kitesurfers: What if kites could harness enough wind energy to power the world? At the time, wind accounted for only 5% of the world's electricity. By replacing the massive steel towers of conventional wind turbines with lightweight hardware and smart software, the team hoped to unlock access to wind resources that were previously too expensive or impractical to reach with traditional wind technology.
Makani spent 13 years developing energy kites that generated electricity by flying in loops and sending power down a tether to the grid.
From Riding Waves to Harnessing Wind
Makani’s earliest prototypes were fabric-based and closely resembled kiteboarding gear. Testing quickly revealed that fabric kites lacked the efficiency and control needed for large-scale energy generation.
The team pivoted to rigid kites capable of supporting onboard rotors, allowing them to harness apparent wind for higher lift and more energy production.
From there, the team built and tested small-scale kite prototypes in a broad range of wind and environmental conditions. Here, the team tackled key challenges like transitioning between vertical hover flight and generating energy in crosswind flight— where the kite flies in acrobatic loops to maximize power outputs.
How the Energy Kite Worked
At take off, propellers on the kite acted like helicopter rotors — taking off and lifting it off the ground station. Once airborne, the kite climbed to a height of 1,000 feet, before shifting into a “crosswind flight”—a looping motion that doesn’t require additional energy output.
This phenomenon — which can be observed when flying a kite on a windy day —allows air to flow through the rotors, turning them into mini wind turbines that generate energy that is then sent to a specially-engineered tether on the ground. A flight computer managed the kite’s path, keeping it stable even in turbulent winds and ensuring a controlled return to the ground station.
Video: First Crosswind Flight of a Utility Scale Energy Kite - Makani M600
An Aerodynamic Wing Tethered to a Ground Station
The kite rests on a ground station ready for launch.
The kite climbs to a desired altitude, and positions itself downwind. The rotors initially consume a small amount of energy to produce thrust.
The kite then transitions into crosswind flight. Aerodynamic life allows the wing to fly autonomously in loops optimized for maximum power generation by our flight controller.
Wind propels the kite around the loop. The rotors spin, driving onboard generators to produce electricity that is transferred back to the ground via the tether.
Kite Design
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.
1200V DC silicon carbide motor controllers handle high voltages efficiently with minimal mass.
8 stacked rotors are spun by the wind in crosswind flight. Each drives a permanent magnet motor/generator that generates electricity onboard.
Taking Wind Energy Higher
After years of iteration, the team developed the M600, a utility-scale, carbon-fiber kite with the wingspan of a small jet. This advanced kite could generate enough energy to power about 300 homes. The team ran a number of successful tests including flying the world’s first offshore flight of an airborne wind turbine off the coast of Norway, with support from their partner Shell.
Sharing Makani
In 2020 Makani’s journey came to an end. To share their lessons and insights with the airborne wind community, the team created The Energy Kite Collection—a comprehensive archive of technical reports, designs, code repositories, flight controls, and flight logs. They also created a film documenting their 13-year effort building energy kites.
Video: Pulling Power from the Sky: The Story of Makani [Feature Film]
