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Makani Power is developing Airborne Wind Turbines (AWT) to extract energy from the powerful, consistent winds at high altitudes. Makani’s AWT is a rigid wing that flies at altitudes between 300 and 600 meters. Turbines on the leading edge of the wing face into the wind as it flies and generate energy, which is transmitted to the ground along a tether. Makani AWTs will produce energy at an unsubsidized real cost competitive with coal-fired power plants, the current benchmark of the lowest cost source of power.
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The subcomponents of Makani’s 10 kW Airborne Wind Turbine (AWT) prototype. The wing flies in circles navigated by the autonomous controllers running on state of the art avionics system. Power is extracted by wing mounted rotors by slowing the wing down. Generated power is transmitted down the tether to the ground station. The bank of lights on the ground station is illuminated to dissipate excess power.
The Makani AWT operates using the same principles as a wind turbine. As wind moves air across turbine blades, their airfoil shape forces them to rotate perpendicularly to the wind. The blades are attached to a central hub and rotate as the wind blows, driving a central generator that produces electricity.
Like a sailboat with a large sail on a tall mast, wind turbines are more effective when they have longer blades to access larger areas. However, as conventional wind turbines grow in size, manufacturers are fast approaching the limits of possibility given the strength and cost of current materials.
In the Makani system the blade is a wing, anchored to the ground by a tether so that it is free to fly in large circles. The wing flies across the wind by the same principles that cause a wind turbine to rotate. This system makes the Makani AWT much more materials efficient: there is no tower, hub or nacelle.
Image: A composite of fifty-six images of a 10 kW prototype wing in flight under autonomous control.
Why airborne wind? The Makani Airborne Wind Turbine (AWT) can reach the stronger and more consistent winds at higher altitudes, allowing for cost effect deployment across 85% of the United States, a five-fold increase over conventional turbines. The AWT is also 90% lighter than current offshore wind turbines, which means that it can be economically installed offshore, even in deep water.
Makani is lighter and has fewer complex components than conventional turbines so it is cheaper to build and install, even offshore. In addition, the efficiency of the wing means that it has better low wind performance, which leads to higher capacity factors both on and offshore, 60% and 70% respectively. This means AWTs will make more power for less money than conventional turbines. The AWT will reach costs competitive with coal.