Provisional Patent Application of
Douglas J. Amick
For
TITLE: TETHERED WIND TURBINE
CROSS-REFERENCE TO RELATED APPLICATIONS: None.
FEDERALLY SPONSORED RESEARCH: None.
SEQUENCE LISTING: None.
BACKGROUND
This invention called "Tethered Wind Turbine" relates to
wind powered devices that generate energy from the wind, specifically to
windmills that are deployed at or above ground or sea level. However, in
another embodiment, this invention could also be used to generate energy from
undersea water currents, being more appropriately called a tethered underwater
current turbine energy generator.
Windmills in recent years have become more effective and
competitive with other energy sources, but most still remain very expensive to
install and maintain. As a result,
their overall cost per installed kilowatt hour is still high enough that they
are only marginally deployed and they contribute only a small amount to the
electrical grid. The primary
method modern windmills use today is a horizontally-mounted, large diameter,
three-bladed propeller that rotates at low revolutions-per-minute over a very
large swept area. The higher
the rotational axis of the propeller can be mounted, the better. The natural speed of the wind increases
proportionally with an increase in the height above the ground. Conventional windmills have very tall
and very strong tower structures.
Typically they have a tubular steel tower that is mounted to a deep
below ground cement base. The
system has to be very carefully engineered and sited appropriately for the
surrounding terrain. The towers must maintain a central stairway or other means
to allow construction and operator access to the upper mechanicals. The tower must accommodate the
heavy gearbox, electrical turbine, and propeller assembly, as well as be strong
enough to withstand gale force winds, and potentially earthquakes. To make the system even more
complicated, the upper nacelle and gearbox/turbine housing must be able to
pivot on a vertical axis, so as to align the propeller correctly with the wind
direction at any time during the day or night. On many windmill systems the individual blades of the
windmill are able to rotate about their individual longitudinal axis, for pitch
control. They can optimize the pitch
of the blades depending on the nominal wind speed conditions that are present
at any one time at the site.
They can also change the pitch of the blade to "feather" the propeller
if the nominal wind speeds are too large. Occasionally the windmill is locked to prevent
rotation, and the blades feathered to prevent major damage to the machine in a
storm. All of this pitch control
technology adds significantly to the cost of windmills. Another major problem with
conventional windmills is damage caused by lightning during thunderstorms. The blades can be upwards of 300 feet
in the air and are a good source for lightning to find a conductive path to the
ground. Some of the more recently
designed windmills use a system of replaceable sacrificial lightning conduction
attractors that are built into each windmill propeller blade. They help channel the lightning away
from the vulnerable composite structure that comprises the blade itself. The fact remains that one of the major
causes of windmill downtime and maintenance costs are caused by lightning
damage. The size of many windmills
is also a major problem for inspection, diagnostics, and repair. Often workmen have to use ropes and
climbing techniques to perform maintenance on the massive machines. It is very expensive and
dangerous. In recent years workmen
have fallen to their death trying to repair the blades. In conclusion, insofar as I am aware,
no current windmill provides competitively inexpensive energy generation
without the major defect of highly priced support tower construction and
maintenance costs coupled with high risk diagnosis and repair of the large
windmill blades themselves.
SUMMARY
The invention, an improved windmill, is a special design
that combines a lighter-than-air structural design with an aerodynamic shape that concentrates the wind´s forces through a relatively-higher-RPM yet
smaller-diameter turbine generator, thus eliminating the need for a fixed
tower. The lighter-than-air machine is tethered to the ground and can therefore
freely align itself optimally with the direction of the prevailing wind
automatically and with no loss in efficiency. The tether also provides the conductive path for the wind
turbine´s electrical energy to travel down to the base station where it can
enter the grid or be used locally.
In one embodiment, the system employs ultra-low weight onboard weather
diagnostic computer technology to be able to smartly know when to remain aloft,
and when to robotically be retracted and returned to the base shelter to
wait-out a potentially destructive storm.
This feature would effectively eliminate the lightning damage problem of
current windmills.
Several advantages of the invention are to provide an
improved windmill, to provide a means of reducing the cost of wind generated
electrical energy, to provide a wind generator with much reduced installation
costs, to provide a wind generator with much reduced problems associated with
maintenance, bird and bat kills, and downtime due to lightning damage, and to
provide a low cost windmill design that is scaleable and that could be
affordable and practical for individual home owners and small community
cooperatives, as well as an attractive alternative to fossil fuels for large
energy companies to use in their electric grid operations. An additional objective would be to
produce an embodiment of the invention that would perform well underwater as a
lighter-than-water, tethered, sea-current turbine generator.
DRAWINGS
FIG. 1
is a perspective left-side view of a tethered wind turbine constructed in
accordance with the invention, showing primarily the left half of the
funnel-shaped wind turbine.
FIG. 2
is a perspective right-side view of the tethered wind turbine of FIG. 1.
FIG. 3
is a longitudinal cross-sectional view of the wind turbine of FIG. 1 and 2,
showing the fluid flow, internal turbine parts, and control module.
FIG. 4
is a perspective front view of the wind turbine of FIG. 1 and 2, showing an
embodiment that uses a rear mounted vertical wing stabilizer.
FIG. 5
is a perspective left-side view of the wind turbine of FIG. 1 and 2, showing
an embodiment of the invention that uses one combination of rear wing
stabilizers and forward mounted lifting wings to improve stability and
performance.
FIG. 6A
is a perspective left-side view of the tethered wind turbine of FIG. 1 and 2
that shows it in operation at a medium height, being tethered to the base
structure on the ground.
FIG. 6B
is a perspective left-side cutaway view of the invention of FIG. 1 and 2 showing
the typical base structure with the hanger doors open and the tethered wind
turbine retracted to the top of the main pulley.
FIG. 6C
is a perspective left-side cutaway view of the invention showing the typical
base structure with the hanger doors closed and the tethered wind turbine fully
captured for ground storage.
FIG. 6D
is a perspective left-side detail view of the tether component of the invention
of FIG. 1 and 2 showing its typical construction.
FIG. 7A,
7B,
7C
are longitudinal cross-sectional views of the wind turbine of FIG. 1 and 2,
showing the harness pitch retractor at various adjustments, and the resultant
aerodynamic pitch angle of the tethered wind turbine invention.
FIG. 8A
is a perspective left-side view of the tethered wind turbine of FIG. 1 and 2
that shows how in one embodiment of the invention a simple tubular tail boom
(110) could be used to mount rear wing surfaces such as vertical stabilizer
(52) and horizontal stabilizer (56).
FIG.
8B is a longitudinal cross-sectional view of the wind turbine of FIG. 1
and 2, showing how the fluted tail section (112) could be built to allow outlet
air (114) to exit through slots in the tail boom section itself.
FIG.
9A, 9B, 9C, 9D are longitudinal cross-sectional views of the wind turbine
of FIG. 1 and 2, showing how potentially many different section shapes of the
gas inflated structure could be used without materially diverging from the
scope of this invention.
DETAILED DESCRIPTION
FIG. 1 is a perspective view taken from the left side from
the ground standing upwind of the tethered wind turbine constructed in
accordance with the invention.
The funnel shaped front inlet (14) is shaped with an annulus (12) that
directs the oncoming apparent wind into the interior. A lower portion of the invention has attachment
brackets (18) that are used to connect the harness (20) and tether (22) to the
main body casing (10). Large
quantities of wind pass through the inlet (14), the turbine area of the
tethered wind turbine, finally exiting the invention through the outlet
(16). The energy harvesting
invention is lighter than air and thus remains aloft in all wind conditions.
FIG. 2 is
a perspective view taken from the right side from the ground standing upwind
of the tethered wind turbine constructed in accordance with the invention. The wind entering the inlet (14)
passes over the impeller rotor (26).
Energy extraction occurs here at the turbine (24) as is shown near the
narrowest part of the hourglass-like internal shape.
FIG. 3 is
a longitudinal cross sectional view of the tethered wind turbine drawn in accordance
with the invention. Both the interior
and exterior surface profiles, as shown in this view, are designed to be as
aerodynamically efficient as is feasible.
The ring-wing section profile in the preferred embodiment of this
invention optimally would have a very low coefficient of drag. The majority of the physical
aerodynamic shape of the tethered wind turbine is filled with a lifting gas
(40), such as helium. This lifting
gas is contained within sealed polymeric inflated structures (42) made from
polymers such as aluminized polyester film, polyethylene, or other film. The entire tethered wind turbine may
also use an exterior lightweight flexible or lightweight rigid exterior skin
to act as a shape structure and to protect the tethered wind turbine from the
deteriorating effects of ultraviolet solar radiation. One flexible film that would work well ideal for this
purpose in this invention is Tedlar (DuPont) film. A rigid material for the exterior could be composite
material such as carbon fiber matrix or carbon nanotubes matrix. The tethered wind turbine has an intake
flow concentrator nozzle (32) just to the interior of the leading edge annulus
(12). There is a flow expansion
nozzle (34) at the outlet (16) of the invention. Between the concentrator and expansion nozzles there is a
turbine (24) energized electric generator (28). It is also envisioned, though not shown, that the turbine
could mechanically power other types of useable energy conversion and storage
processes. One concept envisioned in this invention is to directly convert the
rotary motion into electricity and use it onboard the tethered wind turbine to
break water into hydrogen and oxygen, delivering the valuable gases to the
ground station through a multi-tubular tether, without any conductive wires at
all. The hydrogen could be stored
in containment vessels on the ground and used for any number of useful purposes. The structure of the tethered wind
turbine is achieved by several elements.
The structural ribs (46) shown support the overall shape of the tethered
wind turbine and spread the loads of the turbine´s (24) and generator´s (28)
mass into the craft in a stable manner.
A light weight way to create the structure of the annulus (12) is shown,
using an inflated toroidal structure (44) that is filled with pressurized
lifting gas (40). There are many
ways to achieve the necessary structure, and what is shown is meant to be an
example of one embodiment of the invention. The rotor impeller (26) is fitted with a streamlined
impeller nosecone (36) and impeller tail cone (38). The electric generator (28) can be any combination of
magnetic rotor or magnetic stator designs, either brush or brushless, and made
of a variety of materials. The
preferred embodiment would use ultra-light-weight rare earth permanent magnets
with brushless DC components and windings that could possibly consist of carbon
nanotube hyper-conductive wires in place of copper to save even more
weight. There are conductive
generator output wires (76) connecting the generator to the harness (20). The harness (20) is secured to
the tethered wind turbine at attachment brackets (18). Said attachment brackets
(18) could be hard mounted to the internal structure or physically attached or
bonded to the outer skin of the tethered wind turbine. The harness (20) can be rigidly
attached, or mounted in such as was as to allow controllable adjustments by mechanical
servo-actuators. One embodiment
of this feature, a harness pitch adjustor (50), is shown and is a way to control
the tethered wind turbine´s angle of attack by lengthening or shortening the
central member of a three point harness (20). The control box (48) is the central brain for the onboard
functionality of the tethered wind turbine, controlling such as the harness
pitch adjustor (50), the flight settings, the generator loading, and any
aerodynamic control surfaces, etc.
FIG. 4 is
a perspective front view of the tethered wind turbine and shows an embodiment
of the invention that includes a vertical stabilizer (52) mounted at the top
and to the rear of the craft. The
full front of the impeller rotor (26) and impeller nose cone (36) are visible
and are described visually as having 5 blades. Any
number of impeller rotor (26) blades would be acceptable and part of the intent
of this invention. The outer
casing (10) of the lighter-than-air is shown, as well as the flow concentrator
nozzle (32) and the annulus (12).
Attachment brackets (18) secure the harness (20) to the tethered wind
turbine. The harness (20) is also
shown secured to the tether (22).
FIG. 5 is
a perspective left side view of the tethered wind turbine. Showing an embodiment
built in accordance with the invention that uses a number of aerodynamic lifting
and control surfaces to enhance the overall stability and performance of the
wind energy extracting craft. Vertical
stabilizer (52) and horizontal stabilizers (56) act to further help keep the
longitudinal axis of the turbine (24) aligned with the apparent wind
direction. These aerodynamic
surfaces can be either passive, or actively controlled with the use of
stabilizer control surfaces (54).
A wing (58) is shown in this embodiment and can add additional lift to
the tethered wind turbine to help it remain at altitude even when the wind
conditions attempt to blow the craft downwind and downward. Wing control surfaces (60) are shown
and help control roll as needed.
These control functions are envisioned to be fully controlled by the
onboard control module (48).
FIG. 6A ,
6B, and 6C show the tethered wind turbine as a system that is managed from
a base shelter structure (68). This
base shelter structure (68) would be pre-built and carried to the site or it
could be built on the site. It
would also be installed atop housing or buildings or concealed below grade.
FIG. 6A is
a left-side perspective with cutaway view of the tethered wind turbine and
base shelter structure (68) showing the invention in operation.
The tethered wind turbine is flying at a reasonable height above the
ground, downwind of the base shelter structure (68), and is constrained by the
tether (22). The craft can be
expected to float freely downwind in any direction as a result of changes in
true wind direction. The total
airspace occupied by the tethered wind turbine in the long term can be
described as an inverted cone emanating from the tether main attachment at the
robotic control torus (72). The
top diameter and half angle of the inscribed cone is dependent on many
variables such as the total buoyancy force of the invention, maximum wind
speed, amount of active flight controls used to maintain altitude, and active
tether extension/retraction deployed, and turbine generator load levels. To send the tethered wind turbine to
a higher or lower altitude while in flight, the tether (22) is unwound or
wound-up on the tether retractor reel (74) by the tether retractor mechanism
(64). The cutaway view of the base
shelter structure (68) also shows a wish-bone launch arm (100) that swings up
when the tethered wind turbine is about to be launched and also swings down
when the craft is retrieved and tucked into the base shelter structure (68) for
safe storage. This wish-bone
launch arm (100) mechanism may be
shaped differently, such as having one leg instead of the wish-bone shape, but
all versions act as a lever to initially move the tethered wind turbine up out
of the base shelter structure (68) or down within the its walls. The entire base shelter structure (68)
sits on a site pad (98).
FIG. 6B is
a perspective cutaway view of the tethered wind turbine near the middle phase
of the launching process, or the retrieving for storage process. In
the latter, the tethered wind turbine has been pulled down out of the sky to
a point where the harness (20) touches and interacts with the robotic control
torus (72). It shows the base
shelter structure (68) with its hinged bay doors (92) opened wide. The wish-bone launch arm (100) is in
the upright position and the launch arm actuators (102) are fully
extended. Energizing the reel
motor (66) causes the rotation of the tether retraction reel (74), which is
bi-directional in this embodiment of the invention. It rolls the tether retraction reel (74) in one direction
to wind-up (retract) the tether (22) and rotates the reel in the opposite
direction to unwind the tether (22), allowing the buoyant tethered wind turbine
to ascend upward into the airspace above.
The control of the reel motor (66) is accomplished with the logic that
is built into the retractor control module (62). Also shown are the reel-to-power box cables (78) that
deliver electricity from the tether (22) to the power control/conditioning box
(70) where the electrical characteristics are tailored to meet desired output
specifications of a particular application. Power from the tethered wind turbine invention is delivered
to the end use through the output plug box (96).
FIG. 6C is
a perspective left-side cutaway view of the entire tethered wind turbine and
base shelter structure (68) as a system that has been put into the storage
mode where the inflated casing (10) and other components are safe from excessive
weather conditions such as lightning, turbulent high winds, and wintry blizzards. In this state, the tether (22) is fully wound-up by the
tether retractor mechanism (64) onto the tether retractor reel (74). The wish-bone launch arm (100) is in
the lower position and the launch arm actuators (102) are fully retracted. The hinged bay doors (92) are shown in
the closed position.
Meteorological sensors (104) on the base shelter structure (68) monitor
the air-space and keep the tethered wind turbine safely contained until
conditions are appropriate for launching in the future.
FIG. 6D is
a perspective detail view of the tether (22) itself. Within
the outer casing (82) of the tether are two critical components. They are the main tensile members (84) and the electrical
wires. Both the positive
conductor wires (86) and negative conductor wires (88) are sheathed in an
insulation jacket that prevents shortÐcircuiting and power drainage. Ideally, the main tensile members (84)
and the positive conductor wires (86) and negative conductor wires (88) would
be comprised of carbon nanotubes materials. Although these materials are not a requirement, the use of
carbon nanotubes materials in these components of the tether (22) would greatly
enhance the overall performance of the tethered wind turbine. That is because the tether (22)
itself is a parasitic weight loss acting against the tethered wind turbine´s
buoyancy. Carbon nanotube
materials would make the tether (22) itself many times lighter and allow the
tethered wind turbine to fly much higher using less lifting gas (40). Electrical conductance of nanotube wires
would be many times higher than copper and would enhance overall efficiency
greatly. In lieu of carbon
nanotubes materials, many other materials would also work well. Some examples are copper core
conductors, Spectra ™ fiber tensile members, Kevlar ™ fiber tensile members,
or polyester fiber tensile members.
FIG. 7A,
7B, and 7C are longitudinal cross-sectional views that show how pitch attitude
of the tethered wind turbine interacts with the apparent wind. In FIG. 1 the
aerodynamic shape of the inflated casing (10) is a ring-wing that is in a
neutral angle of attack.
FIG. 7B shows
the tethered wind turbine in a negative angle of attack (106). This
maneuver is accomplished by various means.
Shown in this view the harness pitch adjustor (50) has let out some
length of the central line of the harness (20) causing the buoyant rear end of
the inflated casing (10) to be moved upward relative to the front end. In this state the flying ring wing is
going to descend. Another
way to accomplish this negative angle of attack (106) is by using the
aerodynamic control surfaces of the horizontal stabilizer (56) or the wing
control surface (60).
Conversely, as is shown in FIG. 7C,
the harness pitch adjustor (50) has pulled in the central line of the harness
(20) causing the rear end of the inflated casing (10) to be moved downward
relative to the front end. This
positive angle of attack (108) would cause the flying ring-wing tethered wind
turbine to ascend, and allow the energy harvesting turbine system to increase
electrical output without as much loss of altitude. The
higher loading of the turbine would mean more total drag on the impeller rotor
(26), and a tendency to descend. This
could be balanced-off or improved by calling for an even larger positive angle
of attack (108) maneuver, and a tendency to ascend.
FIG.
8A is a perspective left-side view of the tethered wind
turbine showing how in one embodiment of the invention a tubular tail boom
(110) could be used to mount rear stabilizer wing surfaces.
FIG.
8B is a longitudinal cross-sectional view of the wind
turbine of FIG. 1 and 2, showing how the fluted tail section (112) could be
built to allow outlet air (114) to exit through slots in the tail boom section
itself.
FIG.
9A shows a longitudinal cross-section of the wind
turbine of FIG. 1 and 2 that has a elongated profile of the airfoil-shaped
inflated casing (10) of the invention.
FIG. 9B is a potential shape that embraces a very short longitudinal
airfoil profile of the inflated casing that may be efficacious due to its large
annulus (12) outside diameter relative to its turbine diameter and air outlet
(16) outside diameter. A prominent
feature of this embodiment of the invention is the large concentration ratio of
the front inlet (14) flow concentrator nozzle (32). It appears the concentration ratio is nearly 6 to 1, or
higher. FIG. 9C shows almost the
opposite inlet (14) style. That
is, it shows a very minor attempt to concentrate the wind at the inlet (14)
flow concentrator nozzle (32). The
concentration ratio is nearly 1 to 1.
FIG. 9D is a longitudinal cross-sectional view of yet a different
section shape and construction style.
In this view the bulk of the lifting gas (40) within the inflated casing
(10) is located in the annulus (12) of the front inlet (14). The remainder of the flow concentrator
nozzle (32) in this embodiment is analogous to a wind-sock, comprising a thin
cone-shaped wall, whether of rigid or flexible material. As with a wind-sock, the cone-shape
become more pronounced by the wind flowing through it, All of these gas inflated structures
and many more could be designed and manufactured without materially or
significantly diverging from the scope of this invention.
REFRENCE NUMERALS
OPERATION --
FIG. 1, 2, 3, 4, 6, 7
FIG. 1 and FIG. 1 show the component of the tethered wind
turbine invention that extracts energy from wind currents. The inflated casing (10) is filled with
helium or other lifting gas (40) which makes the tethered wind turbine lighter
than air. It also is shaped to
scoop-up and aerodynamically force large amounts of air to move through its own
interior. The inflated casing (10)
is shaped like an airfoil wing that has been bent all the way around into a
ring. At the front, a
funnel-shaped inlet (14) is surrounded with an annulus (12) at the leading
edge. Together they direct
oncoming apparent wind into the central part of the ring-wing shape and into a
smaller and smaller opening. The
wind then passes into the mouth of a rotary engine turbine (24), and finally
exits out the rear outlet (16) to return to the atmosphere.
NO NEED FOR A GEARBOX
The flow concentrator nozzle (32) gradually directs a large
cross-sectional area of slower-moving air to a smaller cross-sectional area,
but higher velocity duct full of air.
The laws of aerodynamics say that air moving two times faster will carry
eight times more energy. It is
apparent that an aerodynamically shaped device that can concentrate and
accelerate the apparent wind in a controlled manner will be very helpful in
extracting energy from the wind.
It is the intent of this invention to use the flow concentrator nozzle
(32) to make a large cross-sectional area of slower-moving air to move through
a smaller cross-sectional area at a higher velocity through the turbine
(24). This reduces the size of the
physical hardware of the turbine (24) and enables it to operate at a higher
speed without the need for an up-ratio gear-box.
FIG. 3 shows
that the turbine (24) is mounted centrally in the inflated casing (10). Air
currents can flow through it imparting energy to the turbine (24). The kinetic energy of a flowing fluid
(30), such as flowing wind, is converted into mechanical or electrical energy
by causing the blades of the impeller rotor (26) on the turbine (24) to rotate
as it passes through. Output of
electrical energy harvested from the wind will be maximized when the wind
throughput of the turbine is maximized.
So every effort to streamline the interior surfaces is very important
and has been attempted to be shown in this preferred embodiment of the
invention.
NO TOWER NEEDED
In most places on earth, the wind speed, and thus potential
kinetic energy that could be harvested is distributed in a gradient relative to
ground, which could be described as increasing as one moves to a higher
altitude. Unlike most windmills
currently available, the tethered wind turbine of this invention operates
without a tower. It simply does
not need a tower. The preferred
embodiment of this invention uses a tether (22) to hold the inflated casing
(10) and its turbine (24) from Wind-Assisted downwind with the force of available
winds.
NO NACELLE NEEDED
The tethered wind turbine also has no need for a complicated
rotating nacelle as is currently used in the prior art to align properly with
the direction of the true wind.
The tethered wind turbine has a unique ability to keep itself aligned
properly to the wind automatically, even in changing wind conditions. The inflated casing (10) will naturally
drift to the most downwind position in the sky, being restrained only by the
tether (22). Just like the rudder
on an airplane, the invention directs itself in response to the changing wind´s
direction.
FLYING THE TETHERED WIND TURBINE
FIG. 6A is
a view looking downwind at the invention while it is operating. The
tether (22) can be let-out, or pulled-in, in a controlled way so as to position
the inflated casing (10) in the most favorable part of the natural wind velocity
gradient. That is an altitude
where the energy extracted from the wind can be maximized.
As is shown in FIG. 6A,
6B, 6C the tethered wind turbine invention uses a base shelter structure (68)
to store the lighter-than-air device during inclement weather conditions, violent
lightning, periods of non-use, or for routine maintenance.
FIG. 6A shows
the tether (22) after it has been let out and the hinged bay doors (92) are
closed.
The retractor control module (62) remains idle while the production of
energy aloft in the turbine (24) proceeds uninterrupted. The electrical power sent down
the tether (22) travels through the tether retractor mechanism (64), through
the reel-to-power box cables (78), and into the power conditioner box
(70). At this stage the
electricity is adjusted to a form that is compatible with the end user
electrical specifications and exits the system through the output plug box
(96).
FIG. 6B shows
the tethered wind turbine in the middle stage of launching or retracting. At
this stage the tether (22) is fully retracted, the wishbone launch arm (100)
is in the upright position and the hinged bay doors (92) are wide open. If in launching mode, the tether
(22) would be let out, the lighter-than-air inflated casing (10) would ascend
slowly upward. If in the
retracting stage, the robotic control torus (72) would rotate the inflated
casing (10) until the craft aligned properly with the hinged bay doors (92) and
then ready the system for final stage.
FIG. 6C shows
the final stage of the tethered wind turbine when the inflated casing (10)
is in the completely stored mode. The wishbone launch arm (100) is in the
lowered and horizontal position resting underneath the inflated casing
(10). The hinged bay doors (92)
are closed and the entire system is in standby mode.
CONTROLLING THE TETHERED WIND TURBINE
The preferred embodiment of the invention would have a smart
logic circuitry built into it. The
control module (48), shown in FIG. 3,
would make many decisions about when, where and how to fly the tethered wind
turbine. The onboard automatic-pilot feature of the control
module (48) would send control voltage signals to various aerodynamic control
mechanisms to tune the flight of the tethered wind turbine and thereby achieve
a desired ascent trajectory and altitude.
At launch, there would be software programmed to fly the
lighter-than-air tethered wind turbine in a controlled, stable ascent. The tethered wind turbine´s ascension
could be stable in zero-wind conditions, or, even in rough and gusty wind
conditions. This auto-pilot
feature to maintain straight and level flight during fluctuating of wind
currents broadens the potential application to many geographic locations that
otherwise may not have been feasible.
CONTROLLING THE ANGLE OF ATTACK
Controlling the angle of attack of the inflated casing (10)
is essential for flight control.
By controlling the angle of attack, the flying ring-wing-like tethered
wind turbine would be able to ascend on command to a predetermined altitude to
achieve the best position in a given environment. Once at the favorable altitude the tethered wind turbine would
electronically load-up the electrical generator (28) to increase electrical
output.
As shown in FIG 7A, 7B, 7C one way this invention controls
the angle of attack, the flight, and ultimately the altitude, of the inflated
casing (10) is to change the characteristics of its attachment at the top of
the tether (22). The
attachment as shown in this embodiment of the invention utilizes a three-point
flexible harness (20). It has a
method to adjust it as so as to change the angle of attack and therefore the
amount of lift on the inflated casing (10). It is the intent of this invention to use the tether´s (22)
harness pitch adjustor (50) device to vary the overall amount of lift on the
inflated casing (10) and thereby control the altitude it operates at. The harness pitch adjustor (50) does
this by extending or reeling-in the center rear harness tension member with a
servo motor mechanism. By
adjusting the harness (20) attachment in the above described way the overall
angle of attack and hence the total lift of the ring-wing-like inflated casing
(10) is controlled. The desired
altitude is either dialed into the control module (48) or determined
automatically by a software algorithm that takes into account several
variables.
The benefit using the harness pitch adjustor (50) as
envisioned in this invention to control angle of attack of the inflated casing
(10), a larger amount of electrical output would be achieved with less loss of
altitude. In the absence of any
angle of attack flight controls such as the harness pitch adjustor (50), higher
loading of the turbine (24) would mean increased drag on the blades of the
impeller rotor (26), an increased total drag on the inflated casing (10), and a
general tendency for it to descend.
This suboptimal condition could be improved by the use of the harness
pitch adjustor (50) of this invention, as described above.
There is one balance of forces that naturally occurs with
the tethered wind turbine invention.
If winds escalate while the invention is operating, the overall forces
increase on the inflated casing (10).
The natural reaction is for it to be drawn farther downwind and
arc-tangentially lower according to the radius struck by the length of tether
extended at that time. Other
things remaining equal, the craft moves down to a lower altitude and hence a
lower energy level in the natural wind velocity gradient. This will reduce forces on the inflated
casing (10) and result in a convergence toward a natural equilibrium.
CONTROLLING THE GENERATOR
The control module (48) also sends control signals to the
tethered wind turbine´s electric generator (28) circuitry. For example, in favorable wind
conditions the kinetic energy of the moving air flow develops lift on the turbine
(24) blades, turning the impeller rotor (26) and electric generator (48). The only thing resisting the impeller
rotor (26) turning motion is the amount of load, or field resistance, that the
electric generator (28) demands at a given point in time. The load setting is a controllable
variable that the control module (48) can monitor and adjust. The tethered wind turbine utilizes the
generator loading configuration to maximize power output but at the same time
retain adequate air stability and altitude. The more load levied on the impeller rotor (26), the more
overall wind drag will be developed on the craft. The total induced drag on the lighter-than-air inflated
casing (10) shows up as a tensile force on the tether (22) along a vector in
the downwind direction. The
tension in the tether (22) is resisted by a mass below. The control module (48) ideally should
balance power output versus positional stability and drag management. The control module uses
electronic hardware and software as is necessary to accomplish this goal.
CONTROL OF ELECTRICAL OUTPUT
The control module (48) also may condition the electricity
that is output by the electric generator (28). In may invert the voltage up to a higher voltage for the
purpose of efficiently transferring the generated power down the tether (22) to
the base shelter structure (68) below.
There would be lower line losses experienced if the electricity
traveling down the tether (22) were voltage-adjusted higher. The control module (48) would handle
this function.
In summary, the control module (48) of the tethered wind
turbine performs the following functions:
á
controls straight and level flight of the inflated
casing (10) using aerodynamic control surfaces
á
controls straight and level flight of the inflated
casing (10) using harness pitch adjustor (50)
á
controls load levels applied to electric generator (48)
á
converts or inverts voltages as necessary to optimize
efficient energy transfer down the tether (22)
OPERATION of
ADDITIONAL EMBODIMENTS Ð FIG. 5
There are actually two ways this invention proposes to
accomplish varying the angle of attack so as to control the flight and altitude
of the inflated casing (10). The
first way to would be to use automatic electrical control of the harness pitch
adjustor (50) as described above.
In an additional embodiment of the invention, angle of
attack would be controlled using additional wings, stabilizers and other
aerodynamic control surfaces. The
net affect would be increased control of total lift of the inflated casing (10)
and an ability to control its altitude.
FIG. 5 shows
one such additional embodiment of the tethered wind turbine invention using
aerodynamic control surfaces of many types. These include any and all types of
active or passive in-stream surfaces as are typically found on, but not limited
to, conventional aircraft such as a horizontal stabilizer (56), vertical
stabilizer (52), stabilizer control surface (54), and any type of wing (58),
or wing control surface (60). It
is unlikely that all of these would be necessary.
It is also the intent in this additional embodiment of the
invention, for inflated casing (10) to use its aerodynamic surfaces to soar to
higher heights than would otherwise be possible in an effort to counteract the
craft´s downward altitude tendency caused by power extraction induced drag of
the turbine (24).
It should be noted that the inflated casing (10) of the
tethered wind turbine could be secured to ground through a less sophisticated
tether system and it will still be a valuable energy extracting machine in the
sky. Or it could be outfitted to
operate somewhat autonomously with its own internal smart-chip controller and
sophisticated controls for its harness pitch adjustor or its aerodynamic wing
control surfaces (60). The
latter would probably come closer to maximizing energy production efficiency,
but would likely cost more to manufacture. It is a trade-off.
The tethered wind turbine invention as described in this document leaves
room to cover both.
ADAPTING TO WEATHER
It is envisioned that an additional embodiment of the
invention would have a micro-meteorological analysis module (104) onboard that
could automatically obtain samples and or use sensors to collect enough data in
real time to be able to judge the likelihood of lightning or other hazardous weather
conditions. With knowledge of the
meteorological facts, including but not limited to, data on humidity,
precipitation, temperature, atmospheric pressure, the presence of ozone, or
audio-visual signatures, the tethered wind turbine could be programmed to do
certain things. It would run the
data through a decision formula that could prompt actions such as immediately
descending the inflated casing (10) to a safer altitude by reeling in the
tether (22). Other times in truly
inclement weather, it could fully retract the invention to the safety of the
base shelter structure (68).
This could all be done automatically and would prevent catastrophic
failures as otherwise could be experienced from such hazards as lightning
strikes, tornado-like wind currents, or destructive hail. The meteorological analysis module
(104) could optionally be located in the base shelter structure (68) or other
place not onboard the inflated casing (10).
OPERATION of
ALTERNATIVE EMBODIMENTS FIGs. 8, 9
FIG. 8 A shows an alternative design of the tethered wind
turbine that utilizes a very simple boom and rear stabilizer arrangement. It represents a direct and simple
method of construction.
FIG. 8B shows another more fanciful arrangement where the
exit of air from the turbine (24) is through a number of slots in the sidewalls
of the tail structure.
FIG. 9A, 9B, 9C, and 9D show how the tethered wind turbine
invention could still perform as explained above but with different ring-wing
cross-sectional profiles. FIG. 9A
is an elongated version of the preferred embodiment of this invention. FIG. 9B is a more exaggerated version
with the turbine (24) located very near to the air outlet (16) and the flow
concentrator nozzle (32) exhibiting a larger concentration of cross-sectional
area ratio. FIG. 9C shows a
profile that has the turbine (24) located near the leading edge annulus (12)
with a very small concentration of cross-sectional area ratio. FIG. 9D is profile with most of the
inflated part reserved to the front annulus (12) itself.
ADVANTAGES of the TETHERED WIND TURBINE
It can be seen that the tethered wind turbine of this
invention:
á
Provides a new way to extract the kinetic energy from
the wind.
á
Allows use of a smaller, lighter-weight, higher-speed
turbine generator that does not need for an expensive and bulky up-ratio
gearbox between the impeller rotor (26) and the electric generator (28).
á
Operates without the need for a tower.
á
Has no need for a complicated rotating nacelle to align
rotating blades with the wind.
á
Uses lift generated from its overall shape or from
horizontal wings so that it can operate higher aloft than would otherwise be
possible while extracting energy from the wind.
á
Has a control module that can monitor flight and
weather variables and then react to control trajectory, position, stability,
altitude, generator loading levels and power output.
á
Has the capacity to retract the tether (22) and
inflated casing (10) to a lower altitude or ultimately all the way into the
base shelter structure (68) to avoid damage from lightning or severe weather.
CLAIMS
1.
A wind turbine machine for extracting energy from wind,
comprising:
(a) a
buoyant, lighter-than-air device,
(b) an
exterior skin of said lighter-than-air device with means to contain a lifting
gas,
(c) a
concentrating inlet of said exterior skin which is shaped aerodynamically to
direct naturally occurring air flows striking said lighter-than-air device in
such a way as to accelerate the velocity of said air flows within said
concentrating inlet,
(d) a
means, including a rotary turbine engine, for converting kinetic and inertial
energy of said accelerated air flows into useable energy,
(e) an
outlet of said exterior skin of said lighter-than-air device which is shaped
aerodynamically to allow the said accelerated air flows to exit the device,
(f) means,
including an electromechanical tether connected to said lighter-than-air
device, for said lighter-than-air device to be held against the force of the
wind and the force of said lighter-than-air device´s buoyant force,
(g) means,
including an electromechanical tether connected to said lighter-than-air
device, for said useable energy to be transferred to the ground,
whereby, said lighter-than-air device with said
means for converting kinetic and inertial energy of said accelerated air flows
into useable energy can ascend to an altitude where wind conditions are more
favorable, and utilize wind currents of a large cross-sectional area by
concentrating them within said concentrating inlet shape into a small-diameter,
high-speed wind turbine within the center of said lighter-than-air device that
simultaneously is used to contain said lifting gas.
2. The
wind turbine machine of claim 1 wherein the said lighter-than-air device is
shaped aerodynamically to develop lift thereby being a lifting body by virtue
of its overall shape.
3. The
wind turbine machine of claim 1 wherein said exterior skin is designed in such
a way as to give a means for passive flight stability to said lighter-than-air
device including, but not limited to, passive stabilizer aerodynamic surfaces
such as non-articulating horizontal, vertical, v-shaped or ring-wing
stabilizers.
4. The
wind turbine machine of claim 1 wherein said exterior skin is designed in such
a way as to give a means, including active articulating aerodynamic control
surfaces of any shape or size, for active flight stability to said
lighter-than-air device.
5. The
wind turbine machine of claim 1 wherein said exterior skin is designed in such
a way as to give a means, including aerodynamic wing surfaces of any size or
shape, for developing lift from said air flows striking said lighter-than-air
device.
6. The wind turbine machine of claim 5
wherein the lift obtained from said means is controlled and used to offset drag
forces experienced by said means for converting kinetic and inertial energy
when said accelerated air flows travel through the interior of said
lighter-than-air device.
7. The
wind turbine machine of claim 1 wherein said means for said lighter-than-air
device to be held against the force of the wind is connected with an adjustable
harness means to control pitch angle of attack of said lighter-than-air device,
the purpose of such adjustment being useful for maximizing energy output and
improving flight stability of said lighter-than-air device.
8.
The wind turbine machine of claim 1 wherein the means for converting
kinetic and inertial energy of said accelerated air flows into useable energy
is an impeller rotor driven turbine coupled to an electrical generator that
splits water into oxygen and hydrogen gases, of which said oxygen and hydrogen
gases are pumped down said tether through tubing to storage containers at the
base end of said tether.
9. The
wind turbine machine of claim 1 wherein a primary tensile strength member of
said tether is constructed of carbon nanotube materials.
10. The
wind turbine machine of claim 1 wherein said electrical conducting members of
said tether are constructed of carbon nanotube materials.
11. The wind
turbine machine of claim 10 wherein said primary tensile strength member of
said tether are constructed of carbon nanotube materials.
12. The
wind turbine machine of claim 1 wherein the lighter-than-air device is made
using Tedlar film material in said exterior skin.
13. The
wind turbine machine of claim 1 wherein said exterior skin of said
lighter-than-air device uses aluminized polyester film material to contain said
lifting gas.
14. The
wind turbine machine of claim 1 wherein said lighter-than-air device is
tethered to a base shelter structure on the ground.
15. The
wind turbine machine of claim 14 wherein a tether retractor mechanism exists to
pull-in and let-out said tether from time to time, as is needed.
16. The wind
turbine machine of claim 15 wherein said retractor mechanism is installed on a
tower.
17. The wind
turbine machine of claim 15 wherein said retractor mechanism is installed on
top of a building.
18. The wind
turbine machine of claim 15 wherein said retractor mechanism is installed on a
vehicle.
19. The wind
turbine machine of claim 15 wherein said retractor mechanism is installed on a
watercraft.
20. The wind
turbine machine of claim 15 wherein said retractor mechanism is installed on a
sea buoy.
21. The
wind turbine machine of claim 1 wherein there is a control module on said
lighter-than-air device that automatically pilots the craft in order to
maintain stable flight and proper altitude.
22. The
wind turbine machine of claim 1 wherein said control module monitors and
adjusts load levels applied to said means for converting kinetic and inertial
energy of said accelerated air flows into useable energy.
23. The
wind turbine machine of claim 1 wherein said control module monitors
meteorological data from a plurality of sensors and decides to retract the
lighter-than-air device into a base shelter structure during those times when
certain logical criteria are met, including but not limited to those times when
there are severe storms or extreme winds or lightning.
24.
A lighter-than-air ring-wing flying in the earth´s
atmosphere with a low-coefficient-of-drag section profile, having an annulus
with a funnel-like wind concentrator shape at the front inlet, said inlet made
to direct oncoming apparent wind into a turbine rotary engine within said ring-wing,
said turbine made to extract kinetic energy from said wind flowing through it,
and an outlet for air, which has moved through said turbine and is now in a
lower energy state, to be expelled from said ring-wing.
25. The
ring-wing of claim 24 wherein said ring-wing is held from drifting downwind by
means of a tether that is affixed to a mass which is held stable by the force
of gravity, including a mass fixed to ground.
26. The
ring-wing of claim 24 wherein said ring-wing has aerodynamic control surfaces
attached to it that imparts aerodynamic stability to said ring-wing.
27. The
ring-wing of claim 24 wherein said ring-wing has aerodynamic lift surfaces
attached to it that impart aerodynamic lift to said ring-wing, allowing for
said ring-wing to climb to higher altitudes and achieve higher energy output
than would be possible without said aerodynamic lift surfaces.
28. The
ring-wing of claim 24 wherein said ring-wing has a pitch adjustor harness on
said tether attached to it that can be adjusted as needed to impart aerodynamic
lift to said ring-wing by varying the angle of attack of the entire ring-wing
that said pitch adjustor harness would affect, allowing for said ring-wing to
climb to higher altitudes and achieve higher energy output than would be possible
without said pitch adjustor harness.
29. A wind
energy harvesting device that has special qualities and shape that perform dual
purposes of acting as a wind amplifying shroud shaped to speed-up air flowing
through an internally mounted turbine, and, to simultaneously enclose a
lighter-than-air lifting gas that serves to lift said wind energy harvesting
device to an altitude where wind currents are more powerful.
30. A
lighter-than-water ring-wing flying in the earth´s rivers or oceans with a low-coefficient-of-drag
section profile, having an annulus with a funnel-like fluid flow concentrator
shape at the front inlet, said inlet made to direct oncoming apparent fluid
flow into a turbine rotary engine within said ring-wing, said turbine made to extract
kinetic energy from said fluid flow flowing through it, and an outlet for said
fluid flow, which has moved through said turbine and is now in a lower energy
state, to be expelled from said ring-wing.
31. The
ring-wing of claim 30 wherein said ring-wing is held from drifting downstream
by means of a tether that is affixed to a mass which is held stable by the
force of gravity, including a mass fixed to the seafloor.
32. The
ring-wing of claim 30 wherein said ring-wing has hydrodynamic control surfaces
attached to it that imparts hydrodynamic stability to said ring-wing.
33. The
ring-wing of claim 30 wherein said ring-wing has hydrodynamic lift surfaces
attached to it that impart hydrodynamic lift to said ring-wing, allowing for
said ring-wing to climb to higher altitudes and achieve higher energy output
than would be possible without said hydrodynamic lift surfaces.
34. The
ring-wing of claim 30 wherein said ring-wing has a pitch adjustor harness on
said tether attached to it that can be adjusted as needed to impart
hydrodynamic lift to said ring-wing by varying the angle of attack of the
entire ring-wing that said pitch adjustor harness would affect, allowing for
said ring-wing to climb to higher altitudes and achieve higher energy output
than would be possible without said pitch adjustor harness.
ABSTRACT
The tethered wind turbine uses an aerodynamic,
flow-concentrating shape and lighter-than-air construction utilizing a lifting
gas and an electrically conductive tether fixed to ground to reap energy from
the wind at low or high altitude.
The design has no need for the large, expensive, bulky and unsightly
tower structures, pivoting nacelles, or gearboxes presently used in
conventional horizontal axis windmills.
The tethered wind turbine of this invention easily and passively floats
aloft downwind to a direction and position that is aligned with the wind. The invention uses sensors and control
modules to fly gracefully at an optimal altitude in most wind regimes and also
to ascend/descend when appropriate to seek shelter from extreme weather
conditions. Ideally, the tethered
wind turbine of this invention would utilize carbon nanotube materials in its
tether for both structural and conductive purposes. The ring-wing section profile in the preferred embodiment of
this invention optimally would have a very low coefficient of drag. A major benefit of this invention
is potentially much lower cost per installed kilowatt capacity and a lower
operating cost per kilowatt hour delivered to the end user.
Tethered Wind Turbine - FIGURES
 |
|
 |
|
 |
|
 |
|
 |
|
 |
|
 |
|
 |
|
 |
|
 |
|
 |
|
 |
|
 |
|
 |
|
