KiteGuy
Posts: 41
Joined: 10/22/2003
From: Newberg, OR, USA
Status: offline
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The main point that you folks have wisely pointed out is that a pendulum in an aircraft is a liability rather than an asset because it will respond to the "g" forces that the aircraft generates, besides performing its intended function of "seeking ground". This is true. and it is the reason why the "pendulum effect" was quickly abandoned as a possibility in the early years of aviation. But if this aircraft were to have a tether it would really now be a high tech kite, and if the kite were attached to a ship, and if both were on a consistent tack, the "g" forces that should be generated should be small. Am I wrong? In which case, the pendulum might stand a chance of correcting the kite's control surfaces to correct the kite's position relative to the ship. In short, I'm thinking that what doesn't work for aircraft may work for kites in certain situations. I would sure appreciate your responses!
I sincerely appreciate your help! If you can point out the pitfalls upfront it can save me a lot of grief later. Thanks much.
But I notice that other people have asked me questions that I have included in a paper on Tethered Airfoils. Only one person asked me for the paper. So maybe I'll go the extra step of coming to them. Below you will find a copy of this paper. I think that it highlights some of the most important aeronautical pursuits that are theoretically possible but that have not been developed yet. I should mention for the moderator's benefit particularly that all of these aeronautical creations that I propose can be developed and prototyped with radio controlled high tech kites that are nothing more than sailplanes with tethers. I presented an earlier version of this paper to the Flight Research Institute (FRI) which was a non-profit offshoot of Boeing. On the basis of this paper alone I was invited to become a Project Leader at the FRI and the Retired Chief of Product Development at Boeing and a Senior Engineering Supervisor at Boeing both volunteered to help me. We sent out a hundred proposals to foundations for funding, but we had not track record. So we received no funding -- despite some of the most credible aeronautical engineer endorse it.
By the way, I know one aeronautical engineer whose speciality is control surface theory, he believes the pendulum may work. But my other friends at Boeing wouldn't even discuss the prospects. They were adamantly convinced that pendulums will not work now or ever.
But because no one asked for the paper, and because the paper answers many questions that are being asked I hope I won't upset the moderator by including the paper in its entirety below. I am leaving out the methods I intend to use to create very large airfoils, very cheap, very fast. I might be persuaded to disclose those details too for those who are willing to sign and notorize a non-disclosure agreement.
I still recommmend that anyone who wants a word version of the paper below email me at wlgerman@verizon.net and put the word "Kite" in the subject line. If you want to collaborate on the development of these projects also include the word "Join". We should be able to make manageable prototypes of all of these projects using radio controlled tethered sailplanes that have computer controlled autopilots on board. I can make the autopilots. I am a software/electronc engineer. I need good qualified aeronautical engineers, mechanical engineers, and electronic engineers to collaborate on these developments.
__________________________________________________________________________
Tethered Airfoils: An Enabling Technology
By Wayne German, wlgerman@verizon.net. October 22, 2003
1. Overview
Occasionally, new technologies are developed that meet global needs and generate considerable revenues in the process. Widely recognized examples are the light bulb, transistor, radio, television, computer, automobile, and airplane. The intent of this paper is to introduce another technology, Tethered Airfoils, whose potential to generate revenue exceeds all of these. The development, marketing, and deployment of this technology could yield the cheapest and cleanest means of: 1) electrical power generation, 2) shipping, 3) transportation, and 4) communication (radio signal relaying).
Each of these four areas could be revolutionized by the introduction of products that incorporate Tethered Airfoils. For the purpose of this paper, Tethered Airfoils are aerodynamically efficient inflatable kites in the shape of wings that have lift to drag ratios of ten to one or greater. Unless stated otherwise, they are extremely light when inflated with air and lighter-than-air when inflated with helium or hydrogen. These airfoils have on board power and autopilots for stable, remotely controllable flight. Most importantly, they provide a means of harnessing wind power to provide the mechanical power required to generate electricity, synthesize fuel, or provide propulsion.
2. The Potentials of Tethered Airfoil Technology
The potential applications for Tethered Airfoil technology are numerous. Some of the applications that should be possible are listed below. The applications that could most easily be developed are listed first followed by those that would require more skill and experience.
2.1. Wind power generators that use reciprocating airfoils to produce electricity on the ground.
2.2. Water pumps that use reciprocating airfoils to pump water for irrigation.
2.3. Sailing craft that have a Tethered Airfoil to tack into the wind or with the wind -- the airfoil being held aloft by aerodynamic lift, or buoyancy (helium or hydrogen), or both.
2.4. Recreational airships that fly over water without fuel by tacking in the air while being attached by tether to submerged hydrofoils.
2.5. Paraglider wings and ultralight aircraft that could use buoyant lift, and/or the methods of manufacture that will be discussed later in this proposal to greatly reduce cost.
2.6. Passive self-regulation of altitude using highly pressurized lighter-than-air structures.
2.7. Ship and vessel propulsion assistance with minor retrofitting.
2.8. Energy conserving tugs that could deploy Tethered Airfoils to pull unmodified vessels across oceans.
2.9. Land Based High altitude wind power generators that use reciprocating Tethered Airfoils to tap winds as high as the jet stream to produce electricity at a generator on the ground.
2.10. Sea Based wind power generators (low or high altitude) to produce electricity at a boat or barge.
2.11. Flight without fuel over land or water by using an airfoil at lower altitude tethered to another airfoil at a higher altitude to harness the power available in the differential velocities of the two altitudes.
2.12. Radio signal relaying by hovering indefinitely in the air while using excess wind to generate electricity to relay radio signals.
3. Conceptual Descriptions of Products Incorporating Tethered Airfoil Technology
3.1. Wind Power Generators
Wind power generating systems can be developed using reciprocating Tethered Airfoils. Using two airfoils and a tether that passes from one airfoil through an electrical generator on the ground to the other airfoil, power could be generated if one airfoil flew at a high angle of attack (nose up) while the other flew at a low angle of attack (nose into the wind or slightly down). The airfoil flying at a high angle of attack would have greater lift and drag, which would cause it to be blown downwind and upward while pulling the other airfoil upwind and downward. Electricity would be generated as the cable is pulled and the generator is forced to spin.
As the airfoil having the lower angle of attack approaches sufficiently close to the generator, remote control could cause it to assume a high angle of attack and cause the airfoil further downwind to assume a low angle of attack. This would cause the upwind airfoil to fly downwind and the downwind airfoil to fly upwind. Periodically changing the angles of attack would, therefore, cause the two airfoils to reciprocate in the sky producing power on the ground. Between strokes, as the airfoils change their angles of attack, and as the cable changes its direction of travel, there would be a brief time when no power would be generated. Therefore, in Tethered Airfoil wind farms the flights of all the airfoils should be synchronized so that as few as possible would change direction at the same time. This would ensure that the power generated at the farm would be as even and continuous as possible.
Note that only the pitch, or angle of attack, would have to be controlled remotely -- not the yaw and roll. This should make the design and development straightforward. Adjusting the tether bridle position fore and aft should provide the level of control required for this application. The Tethered Airfoil could be designed to passively correct for yaw and roll -- much the same way that single string kites do today.
A single Tethered Airfoil could produce electricity if a flywheel or external electrical power is used to winch the airfoil in on the upwind stroke. The airfoil would produce more power on the downwind stroke flying in a high lift, high drag mode than would be required to winch it back in on the upwind stroke.
The amount of power that a Tethered Airfoil could generate is not proportional to the size of the airfoil. It is proportional to the area swept by the airfoil per unit time -- just as in wind turbines. A small airfoil that quickly traverses a large area would generate more power. But Tethered Airfoils could generate far more power than wind turbines because they could sweep a greater area for an equivalent cost since they would not have the cost of the tower, nor be limited to the sizes that towers can accommodate.
Unlike standard wind turbines, Tethered Airfoils would not require expensive towers, specially designed low speed generators, and would not be subject to the strong vibrations that have so often caused premature failures. Most importantly, they could fly at higher altitudes to harness more powerful winds. On average, over flat land, the wind is twice as powerful at every five-fold increase in altitude. So a Tethered Airfoil flying at only 500 feet would encounter twice the wind power as a wind turbine 100 feet off the ground. At a half mile the Tethered Airfoil would encounter more than four times as much wind power. This effect can be greatly magnified by terrain that causes the air to be funnelled -- as is generally found at the best wind farm sites.
Obviously, Tethered Airfoils that fly at high altitude would need to be assigned their own airspace a safe distance away from commercial flight paths. They might obtain permission to fly in the restricted airspace over wilderness areas because they do not pollute or make noise. Alternatively, the vast areas that exist offshore would provide excellent sites for both low and high altitude wind farming (as will be discussed) later. But initially, windy rural areas would provide good lower altitude proving grounds.
Inflated with helium, these Tethered Airfoils would simply float up in exceptionally calm winds. But in places, such as Minnesota, where the winds are constant and strong close to the ground it may prove practical to develop Tethered Airfoil Generators that rely exclusively on aerodynamic lift rather than buoyant lift. Inflated only with air, they could be developed to automatically launch from a stand when the winds blow sufficiently strong and be winched down quick enough to maintain controllable flight when the winds are exceptionally calm.
While the jet stream offers the greatest potential power per unit area, it may be more practical to fly larger Tethered Airfoils at lower altitudes. This would reduce the cost and drag of the tethers, but would require larger or more numerous airfoils to generate a like amount of power.
Even in typical installations, wind power used in conjunction with hydropower or fossil fuel plants could reduce the long-term rates at which these plants use water or fuel. These plants on the other hand, could provide backup power during periods of calm winds when these wind power generators would produce little or no power.
3.2. Water Pumps
Tethered Airfoils can be used to pump water as well as to generate electricity. The specific application of pumping water is mentioned here for three reasons. First, it would not require a generator. Pulling the tether could drive the pump directly. Second, water pumps do not require a consistent power source. If the winds cause short-term variations in the amount of water that is pumped there is no problem provided that daily or weekly quotas are met. Third, many nations require or could benefit by the use of good cheap water pumps.
Many underdeveloped nations need power to pump irrigation water. Studies conducted in Sri Lanka, Kenya, Cape Verda, and the Sudan show that windmills can be cost effective compared with diesel engines for pumping water. If windmills are considered cost effective, Tethered Airfoils should prove superior because they can extract power from much stronger winds and sweep through a far greater airspace. (As mentioned previously, the power that may be generated is proportional to the area swept per unit time).
3.3. Custom Sailing Craft
A lighter-than-air Tethered Airfoil and a watercraft having a small wetted surface could be tethered together to make a very fast and efficient sailing craft. Canoes and kayaks with centerboards or catamaran hulls would make good choices. Tethered Airfoils suitable for this purpose would need to have remotely controllable pitch and roll so that they could fly "out to the side" as well as downwind. These Tethered Airfoils would not require remotely controllable yaw. These airfoils could be designed (perhaps with a delta wing shape) to ensure that the Tethered Airfoil would always fly with nearly zero yaw with respect to the wind. (The purpose for flying "out to the side" is to generate a force perpendicular to the direction of the wind just as sails do when tacking into the wind.)
The Tethered Airfoils that have been discussed previously require pitch control only (nose up or down) The purpose of this control is to: 1) generate varying tether tensions by adjusting the lift and drag characteristics of these airfoils, or 2) to adjust the height of the Tethered Airfoils in the sky. Tethered Airfoils that could be used to provide propulsion into the wind (as well as with the wind) require roll control as well. These airfoils must be able to fly out to the side as well as overhead and downwind. The best Tethered Airfoil for this purpose would be one that could be directed to assume a relative position in the sky with respect to a hull -- in response to remote control -- and then hold that position indefinitely without requiring power. It appears that such control may be possible (and patentable).
A Tethered Airfoil should be able to passively maintain a new relative position in the air in response to a single radio control request to change the tether bridle position, flaps, wing warping, or center of gravity. Using this technique to change the attitude of the airfoil would cause the airfoil to select a different position in the sky. This, in turn, would cause the tether to be pulled in a different direction -- causing a new tack to be taken. If the airfoil could maintain this new position indefinitely after it had made these changes, it would be highly desirable, because power would only be required when changing tacks -- not to maintain the course of a tack. Even more important, is the fact that if it could passively self-correct it's own position it would be immune to brief system power failures or shutdowns. It would still continue to fly just as well on the same tack.
Members of the Flight Research Institute have demonstrated the feasibility of water skiing upwind or downwind with a Tethered Airfoil at the Columbia River Gorge. They also won first place in a speed sailing competition in England -- racing against craft having similar sail area. Even though the airfoil and hydrofoil were inefficient off-the-shelf kites and skis, they won by the greatest margin of the day.
While the principle of tacking into the wind with Tethered Airfoils may sound unique, it has actually been accomplished and documented as early as 1827 by G. Pocock. (The Samoans used it even earlier.) It appears that as soon as Orville and Wilbur Wright showed that it was possible to fly without a tether, virtually all scientific research into the applications of Tethered Airfoil flight ceased. Back then, the only way that an operator could remotely control a Tethered Airfoil, was by applying varying tensions on additional drag-inducing cables. The winds that kept the airfoil aloft also acted upon these control cables. When a wind gust would cause an airfoil to start diving to one side, different tensions would result in the control cables. Often, these different tensions would cause the airfoil to dive even more. These airfoils often flew out of control and crashed. What is surprising, is that in 176 years nothing has changed.
Tethered Airfoils that rely on cables for their control will always be unreliable and prone to crash. To the best of my knowledge, no one has yet put an inexpensive autopilot and an aerodynamically efficient Tethered Airfoil together. I hope to work with others to be the first to achieve this goal. With such equipment there is no reason why Tethered Airfoils would not be every bit as stable, controllable, reliable, and useful as airplanes.
Tethered Airfoils could provide propulsion for small boats. Attached to the gunwales negligible listing moment would be generated. In fact, traveling with the wind, the airfoil could help pull the hull of smaller boats out of the water, thereby reducing drag. Motor boats, sailboats, hydrofoils, canoes, kayaks, sailboarders, skiers (both water and snow) -- all could be accommodated with a handful of different models. Unlike sails, Tethered Airfoils need not be custom made for each boat or application. No heavy masts, ballast, special ship design, or expensive retrofitting would be required. Like sails on a sailboat, Tethered Airfoils could provide power for all points of tack except dead into the wind. They would be better than sails because they would have an aerodynamically superior shape -- higher lift to drag ratios -- and therefore be able to tack much closer into the wind. They would also have access to the stronger winds aloft. They would have one cable, requiring one winch, and take up no deck space (mounted externally to a track on the gunwales).
Over land, the available wind power doubles with every five-fold increase in altitude. This factor can be much greater over water when the wind causes the waves to crest and the waves cause more pronounced boundary layer effects. So Tethered Airfoils could tap much more powerful winds than sails.
If a motor boat were outfitted with a Tethered Airfoil that flew at 500 feet (where the winds at sea are often three to four times as strong as at the top of most masts and towers) it could outrun most sailboats -- without engine power. Naturally, If the winds became too strong the airfoil could be tied down or deflated. For example, fishing fleets could race to their fishing grounds with their airfoils at high altitude and troll with their airfoils slightly overhead.
Motor boats under power could use Tethered Airfoils to provide a component of thrust in the direction they wished to travel. Suppose that a captain desired to travel east and decided to use an airfoil to help reduce fuel consumption. Suppose further that the wind was blowing such that his Tethered Airfoil pulled strongest in a northeasterly direction. He could accomplish his goal by directing the motors to cause an equally powerful thrust in a southeasterly direction. If the captain wished to travel east at 20 knots, the motors would only need to propel the boat at 14 knots. Depending on the ship and the sea conditions, this thirty percent reduction in motor propulsion speed could result in a fifty percent reduction in fuel consumption -- yet he could travel just as fast as if he had used motor power only.
It is typically reported that by assisting propulsion with standard sails, fuel consumption can be reduced by a fourth. But since Tethered Airfoils can harness winds having greater power, Tethered Airfoils could save much more fuel. Since Tethered Airfoils could be attached at the gunwales they could never pull the boat over -- just along. So, unlike sails, Tethered Airfoils would never need to be furled to prevent capsizing. Tethered Airfoils should always be able to make use of the best winds -- at altitudes where there is over four times as much power available.
The Tethered Airfoils for sailing applications could be inflated with lighter-than-air gases such as helium or hydrogen so that they would simply float up in exceptionally calm winds. Alternatively, they could be inflated with air in which case they would need to launch and land as the winds would permit. As the winds would become strong enough, or as a boat having an alternative propulsion source would pull, an air inflated Tethered Airfoil could be launched by letting out the tether. To land the airfoil when desired, or in the event of exceptionally calm winds, a winch could pull the Tether back in again at a sufficient velocity to maintain stable flight.
Airfoils that are inflated with air would be advantageous because they could readily be deflated and conveniently stored on board when not in use. Also, there is additional cost and logistics involved in obtaining, storing, and transferring lighter-than-air gases. As elegant as it would be to have lighter-than-air Tethered Airfoils pull boats, in general it would probably be more practical to use air inflated Tethered Airfoils.
3.4. Recreational Airships that Fly Over Water without Fuel
As soon as Tethered Airfoils are developed that can pull hydrofoils reliably, passengers could fly in gondolas attached to airfoils rather than sail in hulls over the water. The principles of operation would be just the same. The only difference is that the hydrofoil would now be remotely controlled rather than the airfoil. Such a craft should have a much smoother ride. The tether would dampen Wave action before it was transmitted to the gondola. In the event that the wind stopped, the gondola would simply float -- being held up by the buoyant lift of the lighter-than-air airfoil.
This configuration could render a truly efficient sailing craft because a lighter-than-air airfoil could support the passengers, cargo, and all other components of the craft except for the hydrofoil that would be required for tacking. In other words, the craft could be made very efficient by the elimination of the hull and all unnecessary water drag. Having a high sail, very little drag, and always being "up on the hydrofoils" such a craft could sail even in the lightest of winds. For truly high speed, the airfoil could fly at high altitudes. For passenger comfort without cabin pressurization, the gondola could be attached to the tether a reasonable distance above the ocean.
Nearly this same level of comfort and efficiency could be obtained by using Tethered Airfoils that are inflated with air. In this case, the Tethered Airfoil and gondola would have to launch and land as the winds would permit. But this would probably not be a very big penalty because they would land when the winds would provide little or no propulsion and when the water would be calm. The one disadvantage in using air rather a lighter-than-air gas to inflate the airfoil is that some of the aerodynamic and hydrodynamic lift generated by the airfoil and hydrofoil would have to be used to lift the gondola and wing. Normally, a relatively small percentage of the power would be required to lift the gondola and wing. The vast majority of the power would still be available to provide propulsion.
As the winds would start to pick up, this craft could be launched by releasing tether from a spool in the hydrofoil. In many cases this would be sufficient to cause the gondola and wing to take to the air. But if the winds at low altitude were insufficient, the gondola and the airfoil would float on the water downwind from the hydrofoil. When the tether would be let out sufficiently, the tether could be winched back in briefly and strongly to cause enough tension in the tether between the hydrofoil and the airfoil to pull the airfoil into the sky. Once in the sky, under the influence of greater wind power, the winch could stop pulling and gradually let out more tether so that the gondola and airfoil could ascend to the altitudes that would allow tacking.
3.5. Paraglider Wings and Ultralight Aircraft
Tethered Airfoil construction techniques should enable the construction of high performance inflatable paraglider wings and ultralight aircraft. Standard Paraglider wings are ram-air inflated. This causes drag to be generated at the leading edge. Also during flight, standard paraglider wings can easily be deformed into less efficient shapes. Tethered Airfoils should be at least as light, but they should form much more rigid and well-defined airfoil shapes. It should also be possible to use these techniques to make inflatable ultralight aircraft.
3.6. Passive Self-Regulation of Altitude
Using the proprietary construction methods that will be discussed near the end of this paper, highly pressurized lighter-than-air balloons (or airfoils) could be manufactured that could passively stabilize their altitudes in free-flight without being restrained by tethers. These construction methods could be used to make lighter-than-air balloons that would prevent the internal gases from expanding as the balloons would rise. As a consequence, if these balloons were free to ascend or descend they would come to rest at the altitude that would have the same density as the over-all balloon. If these balloons rose higher -- perhaps due to momentary gusts -- they would be heavier than the surrounding air so they would settle back down. Likewise, if they were lower, they would be lighter than the surrounding air so they would rise. They would always passively return to the altitude whose density is equal to that of the balloon. In short, they would require no monitoring, control, or power to automatically self-regulate their own altitudes. If they were in no hurry they could float to destinations downwind consuming no power. This might be a useful plan in hauling freight inexpensively.
This technique was once used to make a weather balloon that passively stayed aloft for numerous circumnavigations of the globe. Interestingly, this technique has never been used to maintain the altitude of lighter-than-air man-lifting balloons.
To date, all lighter-than-air man-lifting balloons require continual monitoring and adjustments of altitude. This is because the air in these balloons expand during ascent and compress during decent. If they start upward, they continue upward at an accelerating rate, until helium is released to cause them to descend again to the desired height. But once they start to descend they continue to descend at an accelerating rate, until ballast is released to cause them to ascend again. These balloons continually rise and fall requiring continual releases of helium and ballast to compensate.
In standard airships or blimps, the lifting gas is free to expand or compress to come to equilibrium with the surrounding air. So as the airship descends, the gases compress. This would cause the airship envelope to become limp were it not for ballonets. Ballonets are special internal air pressure compensating balloons that inflate during descents to maintain a small but uniform positive pressure in the airship. Unfortunately, a ballonet requires a fan to maintain a slight positive pressure. The fan in turn requires a power source. Present day airships do not regulate altitude by alternately releasing helium and ballast like balloons. That would be too costly. Instead, they use the aerodynamic forces of thrusters to maintain altitudes when the airship has a different density than the surrounding air. These thrusters are used to provide an upward force when the airship is heavier than the surrounding air and a downward force when the airship is lighter. This method requires engines that continually consume fuel.
It would be better if airships were designed to withstand high internal pressures (such as up to 5 psi). To ascend, air could be released from an internal ballonet. The loss of this air, and the expansion of the helium that would result in the adjacent chambers, would lower the overall density of the airship, which would cause it to rise to the altitude having the same density -- and no higher. To descend, a fan would be required to draw air back into the ballonet. This additional air, and the compression of the helium that would result, would cause the airship to descend to the altitude that would have the same density -- and no lower.
Such an airship would never need to discard helium or ballast, or consume fuel to maintain a specific altitude. It could also be smaller because it would not need the extra buoyancy required to lift ballast or the additional fuel required to maintain altitude. In the course of adjusting altitude, this airship would only need to consume power when using the fan to draw in additional air to descend. It would require no power to maintain a specific altitude or ascend. It could float indefinitely downwind at a specific altitude without requiring any altitude monitoring or control.
3.7. Ship and Vessel Propulsion Assistance
If freighters and ocean going vessels used even relatively simple and inefficient Tethered Airfoils they could realize dramatic reductions in the costs of fuel. When traveling the direction that the jetstream blows (eastward in the Northern Hemisphere) the vessels could pull large Tethered Airfoils into the jetstream. Once in the jetstream, these airfoils could simply pull the vessels downwind. A 50 percent reduction in the cost of fuel one direction on a large freighter would save hundreds of thousands of dollars annually. Efficient Tethered Airfoils might be able to save significantly more because they could provide propulsion assistance on the return upwind trip as well.
Some freighters have been designed to use metal sails to provide propulsion assistance with the wind or into the wind. They are designed to save as much as 60 percent of the cost of the fuel. Like all sails, these metal sails cause the vessels to list to one side when the winds blow. Listing causes all decks and cargo bays to have sloping floors. To prevent capsizing, the metal sails are "furled" by folding. They require special ship designs to accommodate the masts, ballasts, and the forces that the sails generate.
Tethered Airfoils in contrast could provide greater power from higher altitudes and yet cause negligible listing. Little or no retrofitting would be required because Tethered Airfoils could pull the vessels at the same attachment points that tugs would use. Even if these Tethered Airfoils were not lighter-than-air they could be self-launched into the apparent wind generated by these ships at sail.
Between territorial waters there are no governmental bodies that regulate how high Tethered Airfoils would be allowed to fly. As low as a ten percent reduction in the worldwide consumption of fuel by freighters would save billions of dollars annually -- not to mention the environmental benefit of reduced pollution and less global warming.
3.8. Energy Conserving Tugs
Special tugs could be designed for the express purpose of manipulating Tethered Airfoils to pull ships across oceans. This would have the advantage that the large vessels would not have to manipulate the Tethered Airfoils directly. All the tasks associated with providing propulsion assistance could be handled by a tug specially designed to do the job. Tethered Airfoils suitable for this purpose would probably not have to be lighter-than-air. The tug could sail into the wind, pulling even a heavier Tethered Airfoil into the air. A heavier-than-air airfoil would have to fly exclusively by aerodynamic lift, but it could still land safely even in calm winds by being pulled in fast enough to ensure stable flight back down.
3.9. Land Based High Altitude Wind Power Generators
Most appealing is the prospect of harnessing winds in the jetstream where the wind power is often hundreds of times greater than at the top of masts and towers. Technical and political hurdles would have to be overcome, but as Tethered Airfoil technology matures and gains acceptance jetstream wind farming may prove practical.
At each site, the local terrain and the proximity to the jetstream will determine whether it would be best to fly more airfoils at lower altitude or fewer airfoils at higher altitude. Mountains or other land formations that funnel wind may favor lower altitudes. One such mountain range exists in Hawaii. This range runs perpendicular to the prevailing winds and funnels winds up and over. (Hawaii also has expensive electricity and a state government that has recently invested millions in wind energy development in a single year.)
Obviously, Tethered Airfoils that fly at high altitude would need to be assigned their own airspace. They could be assigned airspace far from the commercial flight paths. In rural Kansas, for example, strong constant winds at ground level would assure that the Tethered Airfoils could self-launch and self-land inflated only with air. Alternatively, they might obtain permission to fly in the restricted airspace over wilderness areas because they do not pollute or make noise.
Many Third World countries are crossed by the jet streams of the northern and southern hemispheres. They might desire to relinquish airspace to produce inexpensive electrical power. If the winds at ground level are insufficient to launch these Tethered Airfoils, they could be filled with helium or hydrogen so they would always be in flight even in calm winds.
(Ever since the Hindenburg blew up, people have been reluctant to use hydrogen in lighter-than-air aircraft, but it should be noted that the Hindenburg contained the hydrogen in "gold beater's skin" -- the intestines of calves beaten thin -- nothing to be compared with today's multi-layered plastic films.)
A number of articles have been written about the feasibility of developing wind power generating systems that could tap the power of the jetstream. But the systems described in these research papers consist of wind turbines mounted on large metal wings that are tethered with special power conducting cables. The wings use the turbines as thrusters for launching and landing. The complexity and manufacturing costs are staggering; yet the amortized costs of the electrical power generation are considered favorable (in the 7.5 - 9.5 cent per kilowatt range nearly twenty five years ago).
However, it would be much simpler and less expensive to design a system that would:
1) have an ordinary land based generator,
2) have inexpensive inflatable fabrics that can be quickly deflated and stored away during periods of excessive wind,
4) bounce rather than crash in an accident,
5) contain virtually no costly and fragile high tech components,
6) require no heavy turbines or metal cables to conduct lightning,
7) never need to land during light winds,
8) provide a much greater return on investment because the same costs could be used to construct larger Tethered Airfoils that could extract power from a greater area.
Over much of the United States the average potential power of the air that flows through one square meter of the jet stream exceeds 10 kilowatts. Drag on the tether and airfoil(s) will, of course, limit how much of this potential power |
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