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High Altitude Wind Power HAWP
High Altitude Wind Power (HAWP) and Airborne Wind Turbines (AWT)
The power of the wind at high altitudes is much stronger and more consistent than what is typically available nearer to the ground. However, getting access to this excellent source of energy and harnessing it for electrical use presents obvious challenges. Various types of design responses to that challenge have emerged in recent decades and there are many start-up companies engaged in perfecting HAWP.

Many types are in some way derivative of kite technology and can trace their historic origins to designs for sailing vessels or for land traction vehicles from the late 18th century. While the use of the wind for directional navigation is obvious, the problem for single point installations for electrical energy generation is that the kite must be pulled back to a starting position with less energy than it required to travel from the origin point.

Douglas Selsam conceived of the ladder mill in 1977 to make use of high altitude winds. It is a series of kites arranged like a ladder in a loop formation. The shape of the individual kites changes based on their location in the loop so that they are either fully harnessing the wind or creating minimum drag resistance on their return journey. In this way, the loop can be designed to constantly rotate. With kite-type HAWP, the conversion of energy is typically done at the ground level, the movement of the tether cable providing the kinetic energy.

Other types of HAWP devices (airborne turbines, or AWT) use light-than-air balloons (aerostats) that rotate between two cables, or small glider-like machines that are designed to fly in a constant circle or figure-eight. In these technologies the conversion of energy to electricity is performed in the sky.

While there are still some hurdles to large scale implementation, HAWP certainly has the potential to be a very cheap and consistent source of energy at very high capacities. And the state of the technology right now is in such a wide transition (as opposed to ground-mounted HAWT technology that has become conventional with one type predominating) that it is offers a potential source for artists to provide new interpretations.