News

Milestone Flights, September and November 2011

In recent months Makani has met two critical flight milestones in first-of-kind demonstrations as per the requirements of the ARPA-E sponsored Wing 7 project. Both of these flights occurred at Makani’s test site on the Alameda Naval Air Station.

Milestone 4 stipulated autonomous transition from crosswind flight to hover mode. In this demonstration, the wing moves rapidly from high-speed, circular flight back into stationary hover flight and remains stationary for over a minute before landing. This demonstration shows the wing’s ability to regain stationary hover flight before landing to a perch.

Makani first met Milestone 4 on September 1st. During the short flight, the wing transitioned autonomously from hover into crosswind flight, performed six loops and, at a command from our controls team, autonomously transitioned back into hover. While hovering, the wing remained stationary, supporting the fully extended tether for over a minute under full autonomous control.

The next step was to show that the wing could autonomously launch and land. For Milestone 5, the Makani team demonstrated that Wing 7 can hover on and off of a perch under full autonomous control and without any human input. Milestone 5 has now been repeated multiple times and under variable and sometimes gusty conditions.

The first demonstration of Milestone 5 was completed on a windy day in mid-November. The wing autonomously launched from the perch, reeled out and hovered for over a minute before reeling itself in to autonomously land on a perch. As per the milestone, the test was repeated after a four minute rest period. Throughout the day, winds varied from 3 to 11 m/s (7-25 mph). This is within our design and simulation envelope, and we were pleased to see Wing 7 repeatedly and precisely land back into the perch interface despite shifts in wind speed and direction.

  • AWT

    A wind based energy generation device with at least one airborne element. The Makani AWT consists of a rigid wing with mounted turbines that flies in circles across the wind at 300 meters (1,000 feet) above ground level.

    Airborne Wind Turbine

    A wind based energy generation device with at least one airborne element. The Makani AWT consists of a rigid wing with mounted turbines that flies in circles across the wind at 300 meters (1,000 feet) above ground level.

    Airborne Wind Turbines

    A wind based energy generation device with at least one airborne element. The Makani AWT consists of a rigid wing with mounted turbines that flies in circles across the wind at 300 meters (1,000 feet) above ground level.

    Autonomous Controller

    An on-board computer that controls the flight path of the wing by changing the position of the control flaps.

    Avionics

    The electronic backbone of the AWT. Avionics include the sensors, actuators, controllers and communication systems that keep the wing flying on its desired path.

    Capacity factor

    The average power output divided by the name plate power output of a power plant. Capacity factor demonstrates the frequency with which a power plant is running at its name plate capacity.

    COE

    Cost of Energy or the total cost to generate energy that is fed into the grid.

    Firming Power

    The outside power generation needed to stabilize the flow of electricity to the grid when an inconsistent resource, like wind or solar, creates less electricity than needed.

    Ground Station

    The base station for the AWT, includes a winch for retrieval of the wing and storage of the tether.

    Car vs. AWT

    A typical compact car weighs about 1.2 tons and produces about 30 kW during the 10 seconds it takes to slow from 25 m/s (50 mph) to a stop. Each cubic meter (~1.2 cubic yards) of air weighs only .0012 tons and a good wind day might be traveling at 25 mph (11 m/s), so Wing 7 would have to to interact with 350 cubic meters of air (about 23 dump trucks worth) every second to extract an equal amount of power. In reality it is not as efficient to design an AWT to completely halt the air it interacts with, so we design our AWTs to exert a smaller force on an even larger body of air.

    Material efficiency

    Material efficiency refers to how much power is output in relation to the raw material needed for construction of the generator.

    Rated power

    The amount of power a plant delivers when operating at full capacity.

    Rated capacity

    The amount of power a plant delivers when operating at full capacity.

    Rotors

    The rotors capture the accelerated wind as it rushes across the wing and convert it into electrical power with small, direct drive generators. The hybrid rotors can act as propellers as well as turbines, allowing the wing to stay aloft if the wind dies.

    Turbines

    The rotors capture the accelerated wind as it rushes across the wing and convert it into electrical power with small, direct drive generators. The hybrid rotors can act as propellers as well as turbines, allowing the wing to stay aloft if the wind dies.

    Tether

    The tether is made of high strength fibers surrounding a conductive core. The tether carries the traction force of the wing and transmits the electrical power to the ground station.

    Tethered

    The tether is made of high strength fibers surrounding a conductive core. The tether carries the traction force of the wing and transmits the electrical power to the ground station.

    Usable land

    Factors that influence whether land is usable include site geography, ecology, and wind patterns, for example.