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Flying
Without Fuel by Tacking in the Air
(And other Objectives)
By Wayne German, wlgerman@verizon.net,
11/19/2003
| Ships that have sails can tack over
water, but ships equipped with high tech inflatable kites, Tethered
Airfoils, could do it more efficiently and at greater speed. If a
hydrofoil replaced the ship, these craft could tack to any destination
and arrive faster than the speed of the wind. Tethered Airfoils could
also act as Air Tugs causing freighters to tack across oceans and save
as much as 15 billion dollars of fuel costs annually. A pair of
Tethered Airfoils could tack in the air by having one airfoil in higher
faster winds and the other airfoil in lower slower winds. If
one airfoil were in the jet stream and the other just below it, then the
craft could tack hundreds of miles an hour without consuming fuel and yet
be able to transport people and freight anywhere around the world between
unimproved open fields. Also by tacking, it would be possible to
maintain position in the jet stream and use an on board wind turbine
to generate electricity with which to synthesize helium, then transport
the helium to a power station. Over Japan, 3.72 Kilowatts (4.99 horsepower),
flow through each square foot of the jet stream. This is equivalent
to 714 Kilowatts (958 horsepower) flowing through an area the size of a
soccer goal. However, the power that a wind turbine generates
is proportional to the area that it sweeps per unit time. So a small turbine
could generate considerable power in the jet stream if it sweeps through
a large area in a short period of time.
These are the dreams of Wayne German,
a software engineer by vocation, and an aeronautical engineer by
avocation. After more than twenty years of dreaming and researching
Wayne submitted an article, “Tethered Airfoils: An Enabling Technology”,
to the Flight Research Institute which was a non-profit offshoot of
Boeing. On the strength of that one paper alone Wayne was invited
to become a Project Leader at the Flight Research Institute, and the Retired
Chief of Product Development at Boeing and a Retired Engineering
Supervisor at Boeing, both volunteered to participate on the project.
Proposals were sent to organizations and foundations to obtain funding
to develop prototypes, but without a track record no funds were received.
Wayne’s
colleagues at the Flight Research Institute wrote in their review of some
of these proposals:
"As a result of our studies of your
invention we have concluded that your concept is fundamentally sound
and we believe that your goals can be achieved by step-by-step demonstrations
and that each step can be accomplished within a reasonable effort."
It is now Wayne’s belief that much of
this early prototype development can be done by knowledgeable people
volunteering their time and/or resources to participate as members of the
Tethered Airfoil Research And Development group (TARAD) over the Internet,
if not in person. Particular skills that would be required would
be knowledge in aeronautics, mechanics, software, electronics,
marketing, proposal writing, website development, project leading,
management, public relations, and assisting all of the above (i.e. students
or other motivated individuals). Knowledgeable retired individuals
would particularly be encouraged to participate. Project issues
would be determined by voting. Wayne believes that a number of these
goals could be accomplished with just a few thousand dollars, if
not hundreds of dollars.
Wayne
believes Oregon would be a good state in which to begin these developments
for the following reasons:
1)
Oregon has beaches where four-wheel drives could pull very large kites
at constant velocity to monitor their design and the functioning
of their control surfaces.
2)
At the Yakima Test Firing Range Wayne has an agreement in principle to
be able to fly kites as high as the jet stream -- free from any possible
aircraft interference.
3)
The Columbia River Gorge would be an excellent place to test the ability
to cause a boat to tack over water. Any kite system that
can successfully tack in the Gorge can tack anywhere.
4)
We have technical people from Boeing and Intel nearby to provide guidance
and input, and
5)
The Evergreen Aviation Museum in McMinnville Oregon may offer facilities
and a place to meet.
The
first three goals that Wayne would like to accomplish in Tethered Airfoil
development would be to:
1)
Develop methods to construct Tethered Airfoil wings, and methods to manipulate
their control surfaces,
2)
Use a Tethered Airfoil to tack into the wind and with the wind with a small
motorboat or kayak, and
3)
Demonstrate that a Tethered Airfoil can generate more electricity flying
downwind at a high angle of attack than it consumes flying back upwind
at a low angle of attack, and then demonstrate that a Tethered Airfoil
can generate far more energy flying corkscrews and figure 8’s downwind
instead.
If you have questions, or comments,
or wish to participate, or receive a copy of the paper “Tethered
Airfoils: An Enabling Technology” you are encouraged to contact Wayne German
at wlgerman@verizon.net |
Tethered
Airfoils: An Enabling Technology
(This is a text version of a Word document of the same name. You
may request it at the email address below.)
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
funneled -- 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 jet stream
blows (eastward in the Northern Hemisphere) the vessels could pull large
Tethered Airfoils into the jet stream. Once in the jet stream, 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 jet stream
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 jet stream 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
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