U.S. patent application number 14/679883 was filed with the patent office on 2015-10-01 for lighter-than-air craft for energy-producing turbines.
The applicant listed for this patent is Altaeros Energies, Inc.. Invention is credited to Benjamin W. Glass.
Application Number | 20150274277 14/679883 |
Document ID | / |
Family ID | 47353094 |
Filed Date | 2015-10-01 |
United States Patent
Application |
20150274277 |
Kind Code |
A1 |
Glass; Benjamin W. |
October 1, 2015 |
LIGHTER-THAN-AIR CRAFT FOR ENERGY-PRODUCING TURBINES
Abstract
A wind-based power generating system provides a wind energy
converter for converting wind energy into another form of energy
using a lighter-than-air craft configured to produce a positive net
lift. The net lift includes both a net aerodynamic lift and a net
buoyant lift. A tethering mechanism is configured to restrain the
lighter-than-air craft with respect to the ground. The
lighter-than-air craft defines an interior volume for containing a
lighter-than-air gas, and the lighter-than-air craft has a fore
section and an aft section. The tethering system has at least one
attachment point on the fore section of the lighter-than-air craft
and at least one attachment point on the aft section of the
lighter-than-air craft. The lighter-than-air craft provides a
stable aerodynamic moment with respect to a yaw axis about a
center-of-mass of the lighter-than-air craft. The craft can be
formed in a variety of aerodynamic profiles/shapes.
Inventors: |
Glass; Benjamin W.;
(Somerville, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Altaeros Energies, Inc. |
Somerville |
MA |
US |
|
|
Family ID: |
47353094 |
Appl. No.: |
14/679883 |
Filed: |
April 6, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13565916 |
Aug 3, 2012 |
9000605 |
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14679883 |
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12579839 |
Oct 15, 2009 |
8253265 |
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13565916 |
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61105509 |
Oct 15, 2008 |
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Current U.S.
Class: |
244/24 |
Current CPC
Class: |
B64B 1/06 20130101; Y02E
10/72 20130101; F03D 9/32 20160501; F05B 2240/133 20130101; F03D
1/02 20130101; F05B 2240/917 20130101; Y02E 10/728 20130101; B64B
1/50 20130101; F03D 13/20 20160501; F05B 2240/922 20130101 |
International
Class: |
B64B 1/06 20060101
B64B001/06; B64B 1/50 20060101 B64B001/50 |
Claims
1. A wind-based power generating system comprising: a wind energy
converter for converting wind energy into another form of energy; a
lighter-than-air craft configured to produce at least one of
neutral net lift and positive net lift to the wind energy
converter, the net lift including a net aerodynamic lift and a net
buoyant lift; and a tethering system configured to restrain the
lighter-than-air craft with respect to the ground, wherein the
lighter-than-air craft defines an interior volume for containing a
lighter-than-air gas, and wherein the lighter-than-air craft has a
fore section and an aft section, wherein the tethering system has
at least one attachment point on the fore section of the
lighter-than-air craft and at least one attachment point on the aft
section of the lighter-than-air craft, and wherein the
lighter-than-air craft is constructed and arranged to generate a
stable aerodynamic moment with respect to a yaw axis about a
center-of-mass of the lighter-than-air craft.
2. The wind-based power generating system of claim 1 wherein the
lighter-than-air craft has a cross-sectional shape at least in part
configured as an airfoil.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of co-pending U.S. patent
application Ser. No. 13/565,916, filed Aug. 3, 2012, entitled
LIGHTER-THAN-AIR CRAFT FOR ENERGY-PRODUCING TURBINES, the entire
disclosure of which is incorporated herein by reference, which is a
continuation-in-part of co-pending U.S. patent application Ser. No.
12/579,839, filed Oct. 15, 2009, entitled POWER-AUGMENTING SHROUD
FOR ENERGY-PRODUCING TURBINES, now U.S. Pat. No. 8,253,265, issued
Aug. 28, 2012, the entire disclosure of which is herein
incorporated by reference, which claims the benefit of U.S.
Application Ser. No. 61/105,509, filed Oct. 15, 2008, entitled
AIRBORNE POWER AUGMENTING SHROUD FOR WIND TURBINES, the entire
disclosure of which is also herein incorporated by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a lighter-than-air craft
for energy-producing turbines. More particularly, the present
invention pertains to craft geometries that can provide with a
stable flight platform for energy-producing turbines.
BACKGROUND OF THE INVENTION
[0003] Though wind energy is increasingly popular, especially with
the threat of global climate change, the cost of energy from wind
farms is still not competitive with that of more conventional power
sources. Additionally, most of the top-tier wind farm sites have
already been taken, forcing new developments to move to less
favorable environments which will make the large scale deployment
of wind energy all but impossible with current technology.
[0004] Windmills in recent years have become more effective and
competitive with other energy sources, but most still remain very
expensive to install. As a result, their overall cost per installed
kilowatt (kW) is still high enough that they are only marginally
deployed and contribute only a small amount to the "electrical
grid."
[0005] The primary configuration of modern windmills is a
horizontally-mounted, large diameter, three-bladed propeller that
rotates at low revolutions-per-minute (rpm's) over a very large
swept area. The higher the rotational axis of the propeller can be
mounted, the better, as the natural speed of the wind increases
with an increase in the height above the ground. Conventional
windmills thus have very tall and very strong tower structures.
Typically, they have a tubular steel tower that is mounted to a
deep, subterranean 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.
[0006] 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
anyone 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.
[0007] Another major disadvantage 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.
[0008] 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.
[0009] There have been a number of proposals for more efficient
and/or cost effective means of harvesting the wind's energy in
order to combat the high price of wind energy. There has been
considerable effort put into developing diffuser-augmented wind
turbines, which have considerably higher power output for a given
size rotor than conventional turbines. However, the cost of the
diffuser has not justified their commercial implementation.
[0010] Some effort has also been made to develop high-altitude wind
harvesters, as high-altitude winds are considerably stronger than
ground level winds and are present almost everywhere. In one
example of this effort, it has been proposed to provide tethered
wind turbines that are deployed at or above ground level. See US
Published Application 20080048453 to Amick, the disclosure of which
is incorporated herein by reference in its entirety.
[0011] However, no conventional windmill yet addressees the
foregoing problems while providing for cost-effective wind-energy
production.
SUMMARY OF THE INVENTION
[0012] The present invention addresses problems encountered in
prior art apparatus, and encompasses other features and advantages,
through the provision, in an illustrative embodiment, of a
lighter-than-air (LTA) craft for an airborne wind-turbine for
converting wind energy into another form of energy, the craft being
disclosed in an illustrative embodiment as a shroud having a
ring-like shape having an airfoil cross-section and defining an
interior volume for containing a lighter-than-air (LTA) gas. For
the shroud embodiment the shroud includes a central opening
oriented along a longitudinal axis of the shroud, and is further
configured to produce an asymmetric moment of left and right
lateral sections thereof, which asymmetric moment yields a
restoring moment that automatically orients the longitudinal axis
of the shroud substantially optimally relative to a prevailing wind
direction. In addition to the shroud structure other geometries are
considered as falling within the scope of the present invention
including, inter alia, craft that supports turbines or other
mechanisms for converting kinetic wind energy into other useful
forms of energy.
[0013] In accordance with another feature of the present invention
there is provided a wind-based power generating system that
includes a wind energy converter for converting wind energy into
another form of energy; a lighter-than-air craft configured to
produce a neutral or positive net lift to the wind energy
converter, the net lift including a net aerodynamic lift and a net
buoyant lift; and a tethering system configured to restrain the
lighter-than-air craft with respect to the ground. The
lighter-than-air craft defines an interior volume for containing a
lighter-than-air gas, and the lighter-than-air craft has a fore
section and an aft section. The tethering system has at least one
attachment point on the fore section of the lighter-than-air craft
and at least one attachment point on the aft section of the
lighter-than-air craft, and the lighter-than-air craft is
constructed and arranged to generate a stable aerodynamic moment
with respect to a yaw axis about a center-of-mass of the
lighter-than-air craft.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The invention description below refers to the accompanying
drawings, of which:
[0015] FIG. 1 depicts an exemplary wind-turbine system
incorporating the inventive shroud according to an illustrative
embodiment;
[0016] FIG. 2 is a cross-sectional view of an exemplary shroud
according to an illustrative embodiment of the present
invention;
[0017] FIG. 3 is a vertical cross-sectional view of the exemplary
shroud of FIG. 2;
[0018] FIG. 4 is a diagrammatic vertical cross-sectional depiction
of an exemplary shroud according to a further illustrative
embodiment of the present invention;
[0019] FIG. 5 is a diagrammatic vertical cross-sectional depiction
of an exemplary shroud according to a still further illustrative
embodiment of the present invention;
[0020] FIG. 6 is a diagrammatic horizontal cross-sectional
depiction of the inventive shroud illustrating the principle of
operation of the shroud configuration producing the asymmetric
moment of left and right lateral sections thereof;
[0021] FIG. 7 depicts another embodiment of the present invention
with a different craft style;
[0022] FIG. 8 depicts an illustrative embodiment similar to that
shown in FIG. 7 but with added aerodynamic structures;
[0023] FIG. 9 depicts an illustrative embodiment similar to that
shown in FIG. 8 but with a different tether system;
[0024] FIG. 10 depicts an illustrative embodiment similar to that
shown in FIG. 8 but with still a different tether system;
[0025] FIG. 11 depicts a further illustrative embodiment of the
present invention employing a novel craft having upper and lower
wing sections;
[0026] FIG. 12 depicts still a further illustrative embodiment of
the present invention employing a single wing section;
[0027] FIG. 13 depicts an embodiment similar to that shown in FIG.
12 but supporting multiple smaller turbines; and
[0028] FIG. 14 depicts still another illustrative embodiment of the
present invention employing a single wing section, but with no side
walls or upper and lower wing sections.
DETAILED DESCRIPTION
[0029] Referring now to the drawings, wherein like numerals refer
to like or corresponding parts throughout the several views, the
present invention is generally characterized as a lighter-than-air
craft that can be constructed and arranged as a power-augmenting or
non-power-augmenting shroud for an airborne wind turbine for
converting wind energy into energy (e.g., electrical energy), such
as, for instance, an airborne wind-turbine of the type disclosed in
above-incorporated US Published Application 20080048453 to
Amick.
[0030] In the following description reference is made to the use of
a lighter-than-air (LTA) shroud. Illustratively, FIGS. 1 and 2
depict such a shroud arrangement. However, in other embodiments
disclosed herein the turbines or other wind converters are
illustrated as supported from other structures, referred to herein
generally as "craft". For other structures refer, for example, to
FIGS. 7-14.
[0031] The shroud 1 is a "lighter-than-air" (LTA) shroud, and is
thereby dimensioned to define an internal volume 2 capable of
holding a sufficient volume of lighter-than-air gas to provide
buoyant lift for overcoming the weight of the airborne components
of the wind turbine system comprising the "Lighter-than-air" (LTA)
shroud, wind turbine and related components, and tether, and
maintaining the wind turbine at heights substantially above ground
level where wind speeds are generally higher (see FIG. 2). To this
end, the material of the shroud is preferably impermeable to egress
of a suitable lighter-than-air gas contained therein, such as, by
way of non-limiting example, helium, and is, furthermore,
impermeable to ingress of outside air. According to the exemplary
embodiment, fabrication and operation of the shroud can utilize
materials, subsystems and processes such as those used in other
"Lighter-than-air" (LTA) devices (e.g., aerostats). In the
exemplary embodiment, a mechanism is also provided for maintaining
the volume of lighter-than-air gas at acceptable pressure, and
further for substantially maintaining the shape and size of the
shroud, in varying atmospheric conditions. Such a mechanism can
include, by way of non-limiting example, internal ballonets,
subdividing the internal volume of the shroud to define multiple
internal compartments, etc.
[0032] Referring to FIG. 1, the shroud 1, along with all other
associated airborne components of the wind turbine system of which
it is a part, can be lowered and raised from a base station 10 by
employing a tether 11. Any conventional mechanism, including such
as disclosed, for example, in Amick, US Publication Number
2008-0048453, can be employed to provide for the selective raising
and lowering of the shroud 1 via the tether 11.
[0033] Once airborne, the tethered shroud 1 passively floats
downwind of the base station. As wind direction changes, the drag
force on the shroud 1, by virtue of its design as explained further
herein, causes the shroud 1 to passively change its location with
respect to the base station 10, thereby automatically maintaining a
down-wind position with respect to the new wind direction.
[0034] Tether 11 is secured to shroud 1 at fore F and aft A
attachment points so that the shroud's center of pressure is
located downwind of the tether's fore F attachment points. Tether
11 is further attached to the shroud 1 at a location so that the
aerodynamic forces on the shroud 1 passively restore the minimum
radius section thereof to be oriented approximately normal to the
direction of airflow. The passive stability and control of shroud 1
can, optionally, be further improved by moving the shroud's center
of pressure aft through the employment of aft stabilizers, such as
flat winglets or fins (depicted as structures W in FIG. 1), on the
exterior of shroud 1. Furthermore, the center of buoyancy and
center of gravity of shroud 1 (taking into account the wind turbine
components disposed therein) are both located between the fore F
and aft A tether attachment points and as close to each other as
possible. Note that the wings (or where relatively small in
reference to the overall surface size--winglets) or fins on any of
the embodiments described herein can be implemented in accordance
with a variety of arrangements. As shown, three wings or fins W are
employed in a triangular orientation. Alternatively four or more
wings or fins can be employed in an appropriate geometrical
arrangement (e.g. an orthogonally crossing pattern of four fins, a
pentagonal arrangement, etc.)
[0035] While capable of employment at a variety of scales, it is
contemplated that shroud 1 can be dimensioned to accommodate wind
turbines with minimum rotor diameters of approximately 5 to 10
meters (e.g. 6 meters), and is highly variable. Likewise, the
number and arrangement of rotor blades is also highly variable.
[0036] Referring also to FIG. 2, the shroud 1 passively maintains
the wind turbine system approximately aligned with the direction of
wind at heights above ground level, while increasing the power
output of the enshrouded wind turbine by increasing the upstream
size of the captured stream tube 3 through aerodynamic diffusion of
the airflow therethrough. To these ends, the shroud 1 is
essentially characterized by a ring-like shape the cross-section of
which is an airfoil shape with (except where the airfoil is
symmetric) the high-pressure surface 4 oriented toward the shroud
exterior and the low-pressure surface 5 oriented towards the shroud
interior (the captured stream tube 3) with the chord oriented in
the direction of airflow at a geometric angle of attack
(.alpha..sub.geometric) equal to or greater than zero. According to
the exemplary embodiment, the airfoil sectional thickness is in the
range of from approximately 12% to approximately 30%, while the
chord/radius ratio is approximately 1-5.
[0037] It is contemplated that, optionally, shroud 1 can further
comprise additional lift surfaces, such as wings W, disposed on the
exterior of shroud 1. Wings or winglets on any of the embodiments
herein can extend approximately horizontally from opposing sides of
the craft and/or can define a slight acute upward or downward angle
(as shown in FIG. 1). The term "approximately horizontal" shall be
deemed to include such acute angles--e.g. up to an angle of
approximately 20-40 degrees with respect to the horizontal plane
perpendicular to gravity and parallel to the flat ground.
[0038] Still referring to FIG. 2, shroud 1 is further shaped such
as to provide a circular section (denoted by line 6) of minimum
radius approximately normal to the wind flow and a divergent
section downstream (i.e., aft of the wind turbine 20) thereof. The
enshrouded wind turbine 20 is placed such that the turbine blades
sweep out this minimum radius circular section 6 as they rotate.
The foregoing design passively augments the power conveyed through
the enshrouded wind turbine by increasing the mass flow of air
through the enshrouded wind turbine 20.
[0039] The drag force on shroud 1 increases parabolically as the
wind speed increases, and this additional force tends to lower the
height of the shroud 1. Compensation against this drag force is
provided for by an equivalent increase in lift force, and to this
end shroud 1 is, in one embodiment, shaped to provide additional
lift force through positive net aerodynamic lift produced by
utilization of high local lift airfoils proximate the bottom 51
(relative to the base station) of shroud 1 and low local lift
airfoils proximate the top 52 (relative to the base station) of
shroud 1 (see also FIG. 3). Consistent with aerodynamic principles,
these airfoil sections are constructed and arranged to produce high
or low lift through any combination of high or low lift
coefficients, and larger or smaller local chord lengths or angles
of attack. Note that in various embodiments herein, the LTA
shroud/craft geometry can alternatively be constructed and arranged
to produce a neutral lift or a small positive net lift so long as
the lift derived from buoyancy is sufficient to maintain sufficient
suspension of the power-generating assembly.
[0040] In addition, or alternatively, to the higher
coefficient-of-lift airfoil sections at the bottom of shroud 1, the
shroud can be configured to operate at a positive angle of attack
(.alpha..sub.shroud) (FIG. 4), and/or to employ larger airfoil
sections at the bottom relative to those at top (FIG. 5).
[0041] A mechanism can be provided to dynamically control the angle
of attack of the shroud (.alpha..sub.shroud) to provide lower or
higher lift as necessary through, by way of an illustrative
example, dynamic lengthening and shortening of the fore F and/or
aft A attachment point harness lines. Such a mechanism can, for
instance, comprise one or more mechanical winches disposed, for
instance, at the juncture 12 where tether 11 comprises the separate
lines extending to the fore F and/or aft A attachment points.
According to this embodiment, each such winch operates to
selectively shorten the length of the associated line extending to
one or more of the fore F and/or aft A attachment points.
Alternatively, such a mechanism can be provided at or proximate the
base station, according to which embodiment it will be appreciated
that tether can comprise a plurality of separate lines extending
between the base station and each of the fore F and/or aft A
attachment points.
[0042] Referring to FIGS. 2 and 6, shroud 1 is configured to
produce an asymmetric moment of left and right lateral sections
thereof, which asymmetric moment yields a restoring moment that
automatically orients the longitudinal axis of shroud 1 (defined
along the centerline through stream tube 3) substantially optimally
relative to the prevailing wind direction. This is particularly
beneficial for higher frequency variations in wind direction, as
the shroud 1 will passively "weather-vane" about the base station
10 in conditions of low frequency variations in wind direction.
Generally speaking, this restoring moment is produced by the
asymmetric moment of the left and right shroud sections, which are
operating at different "angles of attack" when shroud 1 is yawed
with respect to the prevailing wind direction. More particularly,
the airfoil sections of shroud 1 are, in the exemplary embodiment
of the invention, shaped such as to produce a "locally nose-down"
moment about the airfoil quarter-chord. In the event of a non-zero
yaw angle (.theta.yaw.noteq.0), such as occurs when wind direction
shifts, the upwind shroud sections operate at a local angle of
attack, .alpha..sub.upwind=.alpha..sub.geometric+.theta.yaw, which
is greater than the downwind shroud sections angle of attack,
.alpha..sub.downwind=.alpha..sub.geometric-.theta.yaw, and
subsequently the upwind shroud sections produce a larger "locally
nose-down" moment (M.sub.u), than the downwind shroud sections
(M.sub.d). This asymmetric aerodynamic moment sums to produce a net
restoring moment (M.sub.restoring) that points shroud 1 in the
direction of the wind.
[0043] It will be understood from the foregoing disclosure that the
asymmetric moment described above can be tailored to ensure an
appropriate response to wind variations by employing airfoils with
higher or lower moment coefficient.
[0044] While the disclosure heretofore has comprehended a shroud
for an airborne wind-turbine, it is contemplated that the inventive
shroud can, with only modest modification from the foregoing
disclosure, be employed in an underwater environment as part of a
water-turbine. According to such an illustrative embodiment, the
power-augmenting shroud and associated, enshrouded water turbine
can be secured to a suitable base, such as, for instance, a tether
or tower, whereby the shroud is permitted to pivot in the water so
as to automatically orient itself substantially optimally relative
to a prevailing water direction.
[0045] As with the embodiment of the shroud described above for
employment in a wind-turbine system, the shroud according to this
embodiment of the invention is likewise configured to produce
rotation about an axis of rotation upstream of the center of
pressure and substantially perpendicular to the longitudinal axis
of the shroud, so as to automatically orient the longitudinal axis
of the shroud substantially optimally relative to a prevailing
water direction.
[0046] Unlike the embodiment of the invention for airborne
employment, however, it will be appreciated that the underwater
variant is not necessarily filled with a "lighter-than-air" gas,
although buoyancy of the shroud (including in combination with any
enshrouded turbine components) is required where the shroud is
tethered to a base station. This is contrasted with embodiments
where the shroud is pivotally connected to a rigid tower secured to
the underwater floor or other substrate, in which case buoyancy of
the shroud is plainly not required. Further according to such
embodiments, it is likewise appreciated that changes on the
shroud's angle-of-attack can be effected employing other than fore
and aft tether attachment points such as heretofore described.
[0047] Lighter-than-Air (LTA) Craft for Support of Wind
Converters
[0048] Reference is now made to further embodiments of the present
invention such as illustrated in FIGS. 7 through 14. These other
embodiments disclose the use of turbines or other wind converters,
as supported from other structures, referred to herein as a craft
or a "lighter-than-air" (LTA) craft. Where earlier disclosed
embodiments describe the use of an encompassing shroud, the
embodiments illustrated in FIGS. 7 through 14 disclose other craft
for the support of turbines or other wind converters, including,
but not limited to, semi-circular structures, winged structures and
open structures. The LTA craft structures of the present invention
provide aerodynamic and buoyant lift; corrective yaw moment (in
conjunction with any aerodynamic structures present, and not
necessarily due to an asymmetric moment); and a mounting for a wind
energy converter (but not necessarily "around" the turbine). These
embodiments also illustrate various tether arrangements, in
particular arrangements with 1, 2 or 3 (or more) primary tethers;
fore and aft tether attachment points, and side-side attachment
points. In one embodiment there are employed three primary tethers.
Single and multiple turbine arrangements are disclosed and highly
variable within ordinary skill.
[0049] Additional features include a tail or other structure which
extends the aerodynamic structures (specifically vertical and
horizontal stabilizers or control surfaces) substantially
downstream of the rest of the craft; winglets or horizontal
stabilizers arranged to improve stability and rotational damping
about a pitch axis; a different mechanism for the actuation of the
tether system, which is either on the ground and independent for
each primary tether, or with an actuator at the tether bridle point
which shortens or lengthens the bridle/harness lines to impart a
desired rotation position (pitch, roll) to the craft; different
forms of the wind energy converter such as a single wind turbine,
multiple wind turbines, or an aerovoltaic converter.
[0050] Reference is now made to FIG. 7 which depicts a craft 31
with a closed perimeter made up of two semi-circles 30A and 30B
with a straight section 32 in between. The top and bottom portions
are asymmetric, relative to the mid-plane. In this particular
embodiment there are three turbines 34 that are mounted within the
closed perimeter defined by members 30A, 30B and 32. FIG. 7 also
illustrates a tether system that employs three primary tethers
extend from the ground station 38 to the craft 31. This includes
tethers 35, 36 and 37. Tether 35 is a fore tether with attachment
at a fore location of the craft 31. Tethers 36 and 37 are
respective aft tethers with attachments at an aft location. The aft
tether attachments are spaced apart and secured to the craft 31 on
the left and right sides thereof of the craft 31. In FIG. 7 the
three turbines are schematically illustrated, but can, for example,
be as shown at 20 in FIG. 1. The attachment location for the
tethers is at an outer surface of the craft. Refer, for example, to
the afore-mentioned Amick '453 publication for an illustration of
an attachment used at the shroud.
[0051] Reference is now made to FIG. 8 which depicts an embodiment
similar to that shown in FIG. 7 but with added aerodynamic
structures. Thus, this figure shows the craft 31 with the same
features as illustrated in FIG. 7 wherein like reference numbers
are used for common components. FIG. 8 depicts a craft 31 with a
closed perimeter made up of two semi-circles 30A and 30B with a
straight section 32 in between. The top and bottom portions are
asymmetric, relative to the mid-plane. In this particular
embodiment there are three turbines 34 that are mounted within the
closed perimeter defined by members 30A, 30B and 32. FIG. 8 also
illustrates a tether system that employs three primary tethers
extend from the ground station 38 to the craft 31. This includes
tethers 35, 36 and 37. Tether 35 is a fore tether with attachment
at a fore location of the craft 31. Tethers 36 and 37 are
respective aft tethers with attachments at an aft location directly
from the base station. The aft tether attachments are spaced apart
and secured to the craft 31 on the left and right sides thereof of
the craft 31. In this embodiment two additional fins 33
(aerodynamic structures) have been added on the top section of the
craft 31 for improved corrective yaw moment for yaw stability.
Also, two additional winglets 39 (aerodynamic structures) have been
added on the respective right (30B) and left (30A) sections of the
craft, to add additional lift and stabilize the pitch and yaw
moment, as needed.
[0052] Reference is now made to FIG. 9 which depicts an embodiment
similar to that shown in FIG. 8 but with an alternate tether
system. Thus, this figure shows the craft 31 with the same features
as illustrated in FIG. 7 wherein like reference numbers are used
for common components. FIG. 9 depicts a craft 31 with a closed
perimeter made up of two semi-circles 30A and 30B with a straight
section 32 in between. The top and bottom portions are asymmetric,
relative to the mid-plane. In this particular embodiment there are
three turbines 34 that are mounted within the closed perimeter
defined by members 30A, 30B and 32. FIG. 9 also illustrates a
tether system that employs two primary tethers that extend from the
ground station 38 to the craft 31. In FIG. 9 there is a primary
fore tether 35 and a bridled tether 40 that includes a juncture
point 41 that splits into bridles 42A and 42B. The additional
aerodynamic structures illustrated in FIG. 9 can also be any
combination of fins, winglets, wings, stabilizers, and other known
structures, that can be added to the outer surface of the craft. In
FIG. 9 the three turbines are schematically illustrated, but can be
as shown at 20 in FIG. 1.
[0053] Reference is now made to FIG. 10 which depicts an embodiment
similar to that shown in FIG. 8 but with still a further alternate
tether system. Thus, this figure shows the craft 31 with the same
features as illustrated in FIG. 8 wherein like reference numbers
are used for common components. FIG. 10 depicts a craft 31 with a
closed perimeter made up of two semi-circles 30A and 30B with a
straight section 32 in between. The top and bottom portions are
asymmetric, relative to the mid-plane. In this particular
embodiment there are three turbines 34 that are mounted within the
closed perimeter defined by members 30A, 30B and 32. FIG. 10
illustrates a tether system that employs one primary tether 44 that
extends from the ground station 38 to the craft 31. In FIG. 10 the
tether 44 splits at the juncture point 45 into three separate
bridles 46, 47 and 48. The tether incorporates a bridle point and
bridles, having one attachment point on the fore section (tether
46) and two attachment points on the aft section (tethers 47 and
48) of the craft. The aft attachment points are located on the left
and right sections of the craft 31. The additional aerodynamic
structures illustrated in FIG. 10 can also be any combination of
fins, winglets, wings, stabilizers, and other known structures that
can be added to the outer surface of the craft. In FIG. 10 the
three turbines are schematically illustrated, but can be as shown
at 20 in FIG. 1.
[0054] Reference is now made to FIG. 11 which depicts a further
embodiment of the present invention employing a novel craft having
upper and lower wing sections. In this particular embodiment there
are no side walls (it is not a closed perimeter, as in the previous
embodiments). Thus, in FIG. 11 the craft 51 has an upper wing
section 50 and a lower wing section 52. The upper and lower
sections are different in structure relative to each other. For
example, the top or upper section may have a smaller cross-section
than the bottom or lower section. In this particular embodiment
there are four turbines 54 that are mounted between the upper and
lower sections 50, 52. In this embodiment there are three separate
primary tethers 56, 57 and 58 that commonly extend from the ground
station 59 to the craft 51. FIG. 11 also illustrates the tethers as
one fore tether 56 with an attachment point to the craft and two
aft tethers 57, 58 each with an attachment point to the craft at a
more aft location. The aft tether attachments are on respective
left and right attachment points 53 and 55 of the craft. This
embodiment should also employ fins or other aerodynamic structures
(not shown, but similar to those illustrated in FIGS. 8-10) for
corrective yaw moment for yaw stability.
[0055] Reference is now made to FIG. 12 which depicts a further
embodiment of the present invention employing a novel craft 61
comprised of a single wing section 62. There are no side walls or
"upper" and "lower" section. A single turbine 64 is mounted on top
of the wing section 62. In this embodiment there are provided three
primary tethers 65, 66 and 67 that extend from the ground station
68 to the craft 61. FIG. 12 also illustrates the tethers as one
fore tether 65 with an attachment point to the craft and two aft
tethers 66, 67 each with an attachment point to the craft at a more
aft location. The aft tether attachments are on respective left and
right attachment points of the craft in a similar manner to that
illustrated in FIG. 11. This embodiment should also employ fins or
other aerodynamic structures (not shown, but similar to that
illustrated in FIGS. 8-10) for corrective yaw moment for yaw
stability.
[0056] Reference is now made to FIG. 13 which depicts a further
embodiment of the present invention employing a novel craft 71
comprised of a single wing section 72. In this embodiment four
turbines 74 are mounted on top of the wing section 72. In this
embodiment there are provided three primary tethers 75, 76 and 77
that extend from the ground station 78 to the craft 71. FIG. 13
also illustrates the tethers as one fore tether 75 with an
attachment point to the craft and two aft tethers 76, 77 each with
an attachment point to the craft at a more aft location. The aft
tether attachments are on respective left and right attachment
points of the craft in a similar manner to that illustrated in FIG.
11.
[0057] Reference is now made to FIG. 14 which depicts a further
embodiment of the present invention employing a craft 81 comprised
of a wing structure 82. In this embodiment three turbines 84 are
mounted on top of the wing structure 82. In this embodiment there
are provided three primary tethers 85, 86 and 87 that extend from
the ground station 88 to the craft 81. FIG. 14 also illustrates the
tethers as one fore tether 85 with an attachment point to the craft
and two aft tether 86, 87 each with an attachment point to the
craft at a more aft location. The aft tether attachments are on
respective left and right attachment points of the craft in a
similar manner to that illustrated in FIG. 11. In this embodiment
there are essentially no side walls and the wing structure is
essentially open. The wing can illustratively incorporate a
dihedral angle, which improves roll stability. Three wind turbines
84 are shown mounted on top of the wing structure 82. Also of note
in this embodiment is the addition of a tail structure 83 with
vertical and horizontal stabilizers. It should be clear that the
number of turbines provided to such an embodiment can be widely
varied based upon the size of individual turbines employed and the
carrying volume/form-factor of the craft.
[0058] Likewise, it is appreciated and expressly contemplated that
the dimensions and other geometries/measurements, such as airfoil
sectional thicknesses, chord/radius ratio, and others provided as
illustrative examples of the above-disclosed embodiment of the
airborne variant of the inventive shroud are not necessarily
applicable to the underwater embodiment, the dimensions and other
measurements of which can be varied according to specific
applications.
[0059] It should be clear that the various embodiments of an LTA
craft and/or LTA shroud provide highly desirable platforms for
mounting one or more wind-energy converters (e.g. turbines). These
shapes allow for neutral or positive aerodynamic lift, via their
aerodynamic geometry for greater stability and overall lift
capability. Likewise, these craft effectively locate the wind
converters at an elevation where they can operate most effectively,
while allowing relatively quick retrieval for service or to avoid
severe weather conditions.
[0060] The foregoing has been a detailed description of
illustrative embodiments of the invention. Various modifications
and additions can be made without departing from the spirit and
scope of this invention. Features of each of the various
embodiments described above can be combined with features of other
described embodiments as appropriate in order to provide a
multiplicity of feature combinations in associated new embodiments.
Furthermore, while the foregoing describes a number of separate
embodiments of the apparatus and method of the present invention,
what has been described herein is merely illustrative of the
application of the principles of the present invention. For
example, the buoyant fluid used to inflate the LTA shroud/craft is
highly variable, and can include conventional helium, hydrogen
mixtures of helium and hydrogen, hot air or another heated gas, or
any other fluid that provides buoyancy in relation to the
surrounding fluid environment. Likewise, while various embodiments
show single or multiple tethers on the fore or aft position of the
craft, it is expressly contemplated that the number and placement
of tethers and/or bridles is highly variable. Thus, while various
embodiments describe multiple tethers on the fore section at
discrete/different locations, and a single tether at the aft
section, in alternate embodiments, a single tether can be located
on a fore section and a plurality of tethers can be located at
discrete/different locations on the aft section. Also additional or
alternative tethers can be provided at other locations along the
craft or connected to certain structures, such as wings or
winglets. Accordingly, this description is meant to be taken only
by way of example, and not to otherwise limit the scope of this
invention.
* * * * *