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How does it work?

Overview

The Makani Airborne Wind Turbine (AWT) is a tethered wing outfitted with turbines. It flies between 250 and 600 meters (800 and 1,950 feet), where the wind is stronger and more consistent. Makani is developing a 600 kW AWT, for utility scale generation at a cost below conventional solar and wind.

The Makani AWT operates like a wind turbine. Air moving across the turbine blades forces them to rotate, driving a generator to produce electricity.

Due to its speed, the tip of a conventional wind turbine blade is the most effective part and is responsible for most of the energy produced. The Makani AWT takes advantage of this principle by mounting small turbine/generator pairs on a wing that itself acts like the tip of a traditional turbine blade. The wing flies across the wind in vertical circles, fixed to the ground by a flexible tether.

Wing Operation Diagram – Click to open fullscreen

Offshore Diagram of the Makani Wing

Technical Spotlight

Makani has developed hybrid rotors with symmetrical, uncambered foils that let them generate energy as a turbine or apply thrust like a propeller.  The rotors are used as propellers to keep the wing aloft during short lapses in the wind, allowing the wing to stay aloft if the wind dies.

Hybrid Rotors

Read on: Development Plan

  • 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.