Aeronautics and astronautics – Kites
Reexamination Certificate
1999-09-20
2001-07-03
Poon, Peter M. (Department: 3643)
Aeronautics and astronautics
Kites
Reexamination Certificate
active
06254034
ABSTRACT:
BACKGROUND—FIELD OF THE INVENTION
This invention relates to a tethered aircraft, specifically to a tethered aircraft system for gathering energy from wind.
BACKGROUND—CROSS REFERENCES TO RELATED PATENTS
This invention includes remotely-controlled angles-of-attack as defined in U.S. Pat. No. 5,931,416, TETHERED AIRCRAFT HAVING REMOTELY-CONTROLLED ANGLE-OF-ATTACK, Aug. 3, 1999; which definition depends, in turn, upon the location of the resultant in U.S. Pat. No. 5,533,694, METHOD FOR LOCATING THE RESULTANT OF WIND EFFECTS ON TETHERED AIRCRAFT, Jul. 9, 1996; both patents to me, Howard G. Carpenter.
BACKGROUND—DESCRIPTION OF THE PRIOR ART
In the present invention the wind blows a tethered aircraft downwind. The rotor of a generator spins and electricity is generated as the downwind travelling aircraft pulls its tether off a drum that drives the rotor. The aircraft is an old time tractor kite with modern day control technology.
Excerpting above cited U.S. Pat. No. 5,931,416, “Kites were used to tow wagons and boats. But the drawback was that there were no means to adjust the flight characteristics of the kites to accomodate gusting and changing winds. Many, it is thought most, of the schemes were tested long before the development of flight controls. Without control apparatus flight becomes erratic in gusting and changing winds. Flight becomes translational and rotational and sometimes crashing. Lives were lost in man lifting operations. The tractors were erratic and there were crashes, sometimes fatal. But, for the most part, after the development of airplanes and the myriad technological advances of this century, profitable applications of kites have declined. So that the application of feedback controls and the like to kites, tethered aircraft, has languished.” It is that tractors without control cannot be an economical part of an energy gathering system; such tractors without control cannot substitute for rotary windmills.
World wide, windmills in wind-farms are a significant source of electrical power. Most are horizontal axis mills atop ground mounted towers. Others are ground mounted vertical axis mills. These mills, wind turbines, are limited by economics to low altitude winds—winds near the ground. The cost to make ground mounted mills higher cannot be recovered by the value of the energy gained from the increased height.
Patents for systems that have neither ground mounted towers or frameworks have issued. These systems extract energy from wind at higher altitude than the height of tower mounted windmills. Significant quantities of the energy of higher altitude winds are not currently gathered. It is not known that any of these patented systems have become economically feasible or technically practical. U.S. patents include:
U.S. Pat. No. 3,924,827, 1975, Lois; U.S. Pat. No. 4,073,516, 1978, Kling; U.S. Pat. No. 4,166,596, 1979, Mouton, Jr. et al; U.S. Pat. No. 4,285,481, 1979, Biscomb, and U.S. Pat. No. 4,309,006, 1982, Biscomb
The Lois patent, APPARATUS FOR EXTRACTING ENERGY FROM WINDS AT SIGNIFICANT HEIGHT ABOVE THE SURFACE, is for a plurality lifting-gas filled, tethered, floating wings whose tethers spin an electrical, ground-anchored, generator as the wings are blown downwind. Each wing may include a tiltable, aerodynamic lifting-wing.
The sail form wings are balloons that float downwind and upwind at more or less constant altitude. When the downwind travel of a wing is finished the other similar wings, travelling downwind, pull it in, by a system of gears and pulleys, for another trip downwind. To maximize power generation the rate of downwind travel is restrained to be about one third the velocity of the wind. On board, modulating flight controls are not included.
The Kling patent, WIND DRIVEN POWER PLANT, is for detailed improvements of dynamos on board captive balloons. Dynamos on captuve balloons is old art. The plant aloft includes an aerostatic suspension body, which is a kind of balloon, a rotor assembly, a current generator, and alignment means. At least one of a plurality of captivating stays includes a power cable from the aircraft aloft to a ground station.
The Mouton, Jr. et al patent, AIRSHIP POWER TURBINE, is based upon an endless belt that is driven by an airborne windmill fan. The belt drives a generator on the ground. The windmill fan is supported aloft by a tubular form gas-filled balloon. The fan, a rotor, is driven by wind to rotate within the center core of the toroidial form balloon which is at high altitude and stayed from the ground. This Mouton patent makes no significant mention of flight controls.
The Biscomb patents, MULTIPLE WIND TURBINE TETHERED AIRFOIL WIND ENERGY CONVERSION SYSTEM and TETHERED AIRFOIL WIND ENERGY CONVERSION SYSTEM, comprise tethered airfoils, balloons, that support a plurality of wind turbines aloft. The turbines and generators are mounted within the lower end of a central tubular vent within the balloon. The wind turbines drive electric generators whose power goes to ground via power cables. In lieu of electric generators turbines drive flexible shafts that are connected to mechanical loads on the ground. A system of stay cables, anchored to the ground, peripherally disposed around the balloon, on powered winches, controls the heading and angle of attack of the balloon.
All of these above patents include lighter-than-air filled balloons. All but one of these patents have aircraft that are stayed; “stayed” meaning that the aircraft does not travel downwind. The one that does have aircraft that travel downwind, the Lois patent, uses the tractor principle of kites. Tractors are old art; carriages and boats and the like are towed across country and water. Tractor kites do work, force through distance, as they drag loads downwind. The presence of balloons in the above inventions indicates that these inventors seek to extract energy from wind at high altitudes; altitudes beyond the reach of windmills on ground mounted towers.
SUMMARY
Energy is gathered from wind by the system of the present invention only while its tethered aircraft travels downwind. The wind blows it downwind. While the aircraft travels downwind its tether is pulled from a windlass drum that is rotationally connected to the rotor of an electricity generator. The rotor of the generator spins and electricity is generated. The windlass drum and generator are anchored to the ground or to a slowly moving carriage.
The system of the present invention includes a cycle for generation of electrical power that is completed when the aircraft is travelled upwind to the site of the beginning of downwind travel where the cycle for generation of power is recommenced.
The downwind travel part of the cycle is at a controlled angle-of-attack that exceeds the stalling angle, reference above U.S. Pat. No. 5,931,416. At the end of downwind travel the unwinding of the tether from the drum is halted.
Three embodiments are included. For all three embodiments the power generating downwind travel part of the cycle is the same. Each embodiment is defined by its unique mode of return of the aircraft to the site of the beginning of downwind travel. The practice of the present invention may include parts of all three embodiments in any one actual cycle.
In the first embodiment, while at the end of downwind travel, when travel is stopped, the wind is caused to blow the aircraft upward to a maximal higher altitude by operating the angle-of-attack remote-control to decrease the angle-of-attack to much less than it had been during downwind travel. At maximal higher altitude another set of controls is operated to initiate and subsequently control the flight of the aircraft to glide upwind from maximal higher altitude downward to the starting point of the cycle power-generating, downwind-travel of the aircraft. The energy consumed in gliding the aircraft back to the cycle starting point is much less than the energy harvested from the power-generating, downwind-travel part of the cycle. Consequently, the cycle of this first embodiment has a net power output.
In the second embodiment the a
Jakel Kevin
Poon Peter M.
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