Utilising high altitude winds

There is an enormous amount of energy hidden in the winds over our heads. At an altitude of 30,000 feet (9,000 meter), the wind energy is twenty times as large as at sea level. The “laddermill” is a new and novel idea to harness this immense energy resource.

The laddermill consists of a large number of kites on an upward and downward motion. The kites used are of a breed between regular kites and airplanes. Whereas a kite climbs relatively easy, getting a kite down requires a force pulling in the cable. An airplane, on the other hand, requires large engines to gain altitude. Decreasing altitude is much easier, as the aircraft can glide to the ground. The kites used in the laddermill, generally called “kiteplanes”, combine the ascension characteristics of kites with the descension characteristics of aircraft. By creating a large loop of kiteplanes ascending and descending, a rotation can be created. In turn, this rotation can be coupled to a generator to create energy. The loop of kiteplanes can ultimately go up to 30,000 feet, which would generate approximately 100MW.

The cable is an important part of the system and consists of strong fiber materials such as Dyneema. The kiteplanes themselves need to be both large in surface area as well as light in construction weight. Structural principles such as inflatables are being investigated. The control of the kiteplanes can be done by a pressure differential in the inflatable members. Its control will ultimately be automated using flight computers.

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