Laddermill
Airborne wind turbine using a loop of power kites.
A laddermill kite system is an airborne wind turbine that uses a long string or loop of power kites. The loop or string of kites, called the ladder, is launched by the lifting force of the kites until it reaches a height determined by designers and operators, with some considering heights of about 30,000 ft. The concept is not height-dependent and may use one endless loop, two endless loops, or more such loops.
Did You Know?
- A rotating loop LadderMill project was designed and developed by the Dutch ex-astronaut and physicist Wubbo Ockels.
- The LadderMill concept was developed with the aim to convert wind energy at altitude into electricity on the ground in an environmental and cost effective manner.
Operating modes
Engineers have proposed two main ways to operate a laddermill. In the first, kites pull upward on a long tether, spinning a generator to produce electricity. Once the tether reaches its full extension, the kites' wing angle is adjusted to reduce lift, allowing the tether to be reeled back in—either by reversing the generator as a motor or through another method. When the tether is fully rewound, the kites' angle returns to maximum lift and the cycle repeats. In the second design, kites are attached to a continuous loop. Kites on one side generate lift, while those on the opposite side do not, because their angle of attack shifts as they pass the loop's top. This imbalance rotates the loop, and the resulting motion drives a generator.
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