U.S. patent application number 13/707913 was filed with the patent office on 2013-06-20 for system of anchoring and mooring of floating wind turbine towers and corresponding methods for towing and erecting thereof.
This patent application is currently assigned to Andreas Graf. The applicant listed for this patent is Andreas Graf. Invention is credited to Andreas Graf.
Application Number | 20130152839 13/707913 |
Document ID | / |
Family ID | 45350695 |
Filed Date | 2013-06-20 |
United States Patent
Application |
20130152839 |
Kind Code |
A1 |
Graf; Andreas |
June 20, 2013 |
SYSTEM OF ANCHORING AND MOORING OF FLOATING WIND TURBINE TOWERS AND
CORRESPONDING METHODS FOR TOWING AND ERECTING THEREOF
Abstract
A system of floating and weight-stabilized wind turbine towers
with separately floodable compartments and aerodynamic overwater
encasement and the appertaining semisubmersible mooring structures
including anchorage on the seabed, a horizontally floating
underwater mooring meshwork and an actinomorphic buoy-cable-mooring
to the wind turbine towers. Also, a method to transport wind
turbine towers from the manufacturing plants on-shore to the final
off-shore destination by towing the vented towers in a horizontal
position with towboats. Further, a method to erect the wind turbine
towers at the final destination, including the assembly of the wind
turbines. The worldwide potentials of off-shore wind farming in
deep waters to produce electricity in an ecologically and
economically sound way in order both to satisfy men's requirements
and to help to reduce the need to rely on critical fossil and
nuclear resources being immense.
Inventors: |
Graf; Andreas; (Pieterlen,
CH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Andreas Graf; |
Pieterlen |
|
CH |
|
|
Assignee: |
Graf; Andreas
Pieterlen
CH
|
Family ID: |
45350695 |
Appl. No.: |
13/707913 |
Filed: |
December 7, 2012 |
Current U.S.
Class: |
114/125 ;
114/242; 114/293 |
Current CPC
Class: |
B63B 21/50 20130101;
F05B 2240/96 20130101; F03D 13/10 20160501; Y02E 10/727 20130101;
F03D 13/40 20160501; F05B 2240/95 20130101; F05B 2240/93 20130101;
Y02P 70/50 20151101; F03D 13/25 20160501; B63B 43/06 20130101; Y02E
10/72 20130101 |
Class at
Publication: |
114/125 ;
114/293; 114/242 |
International
Class: |
B63B 21/50 20060101
B63B021/50; B63B 43/06 20060101 B63B043/06; B63B 21/56 20060101
B63B021/56 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 15, 2011 |
EP |
11193848.6 |
Claims
1. System of anchoring and mooring of floating wind turbine towers
in waters typically deeper than 30 meters, forming a
windpark-structure, comprising: anchors, vertical mooring lines,
border mooring lines, major buoys, a floating meshwork, and
ropes.
2. System according to claim 1, wherein each wind turbine tower
comprises an upper part exposed to the winds, a submerged lower
part or shaft, compartments, a sliding ring, a stabilizing bottom
weight, an aerodynamic encasement with openings, a water-air-pipe
system and connective valves.
3. Method for towing the wind turbine towers with one single or
several vented compartments in horizontal position with towboats
from on-shore construction and assembling sites to the off-shore
sites of electricity production.
4. Method for erecting wind turbine towers at a final destination
by flooding successively one or more compartments, starting with a
compartment next to a lower end respectively next to a stabilizing
bottom weight of a shaft, until an upper part of each wind turbine
tower reaches a working level from which the entire nacelle is
mounted to a top end of the respective wind turbine tower and from
which also blades are fixed.
5. Method according to claim 4, further comprising the following
step: after having fully assembled the wind power station one or
more compartments are at least partially vented until the wind
power station reaches its final operational position to produce
electrical energy.
6. System according to claim 1 further including signal buoys.
7. System according to claim 1 wherein the ropes have weights.
8. System according to claim 2 wherein the compartments includes a
center compartment.
9. Method according to claim 3 wherein the compartments includes a
center compartment.
10. Method according to claim 4 wherein the final destination is an
off-shore site of electricity production.
11. Method according to claim 5 wherein there are plural
compartments and more than one compartment is vented.
12. Method according to claim 5 wherein at least one compartment is
fully vented.
13. Method according to claim 5 wherein a water level in at least
one compartment is above a surrounding water level and the water
within the at least one compartment is simply being released.
Description
TECHNICAL FIELD
[0001] The present invention relates to an off-shore windfarming
structure based on floating and weight-stabilized wind turbine
towers with compartments and aerodynamic overwater profile, moored
by ropes, a net of horizontally floating underwater cables and
vertical lines anchored on the seabed, altogether forming a
windpark, and the methods to erect these structures. The system is
suitable to carry down- or upwind operating wind turbines typically
comprising nacelles, horizontal axles and radially mounted blades
as well as to serve as guiding structure for electrical
transmission cables from the wind turbine towers to the collector
stations of the windpark.
BACKGROUND OF THE INVENTION
[0002] Worldwide energy consumption is increasing steadily and
rapidly. The international community strives, therefore, to
introduce and expedite non-fossil and non-nuclear energy production
in order to slow down climatically critical CO.sub.2 emissions and
to avoid risks and consequential costs of nuclear energy. Solar
energy, hydro and wind power as well as gas and ethanol made from
biomass present valuable alternatives in combination with efforts
to increase the efficiency of powered or fueled devices and to slow
down the increase of energy consumption.
[0003] Due to large areas worldwide exposed to strong and steady
seasonal or all-the-year winds, the potentials of wind power are
enormous. The efficiency of wind turbines with two or three blades
and horizontal axles is high and can hardly be improved due to the
laws of physics. However, larger turbines are being planned:
whereas the most productive turbines of today have the capacity to
generate up to 5 Megawatts, turbines of 10 or more Megawatts are
expected to be installed in some years from now.
[0004] There exist both large on-shore and off-shore windparks. in
both cases the towers, on top of which nacelles and blades are
mounted, are positioned on piles anchored on the seabed or the
ground of a lake. Alternatively, towers can be mounted on platforms
held in place by a structure on the lake ground or seabed
(hereinafter, the term "seabed" stands for both "the ground of a
lake" or "(the) seabed").
[0005] Various systems of floating or semisubmersible structures as
bases of off-shore wind turbines are being developed and tested.
For this purpose the technology of fixedly anchored off-shore and
land-based wind turbines has been adapted. Transmission of
electrical power under water is only feasible with direct
current.
[0006] The installation of windparks on the open sea has the
following advantages compared to near-shore and land-based
windparks: immense marine areas suitable for windfarming off the
shores of major consumer nations (often with important
agglomerations close to the shore) are still not exploited for
windfarming, winds unimpaired by topography, trees or buildings,
unperceivable noise emission, virtual invisibility for coast
dwellers and negligible impact on birdlife (since routes of
migratory birds rarely lead across oceans) and underwater fauna (if
not with a positive impact by making fishing with nets inefficient
or impossible).
[0007] The disadvantages of off-shore windparks (regardless of
whether the towers are fixedly anchored in the seabed or whether
they are freely floating [though not drifting] or whether they are
semisubmersible) are the necessity to operate with high voltage
direct current (HVDC) transmission over very long distances until
power can be converted onshore into alternative current to be fed
into the grid, the exposure of wind turbines and their supporting
structures to aggressive saliferous air and spindrift as well as
the fact that shipping or towing of modules or entire off-shore
wind power units including their platforms to the energy production
sites and the assembly and/or erection of existing systems is
complicated and cost-intensive. Mono-piles of wind turbine towers
fixedly anchored are exposed to enormous leverage forces at or near
the seabed. Both fixedly anchored and semisubmersible wind turbine
towers are exposed to the forces of breaking waves, whereas
floating wind turbines are still exposed to up- and downward
motions. Especially floating and--to a lesser
extent--semisubmersible wind towers tend to wobble when towers
incline under wind load because of the changing angular momentum.
This leads to a disturbed running of mechanics, increasing material
fatigue, in particular of the bearings of the nacelle freely
rotating around its own axis.
SUMMARY OF THE INVENTION
[0008] In view of the above, an object of the present invention is
to provide a system of structures to carry floating off-shore wind
turbines (operating in up- or downwind position) and to make the
transport of these wind turbine towers and of the turbines to the
energy production sites and the erection and maintenance of towers
on site more efficient and, therefore, less expensive than existing
systems.
[0009] According to the present invention, these and other
objectives are achieved in particular through the features of the
independent claims. In addition, further advantageous embodiments
follow from the dependent claims and the description.
[0010] Furthermore, the system according to the present invention
does not require the nacelle to be mounted on bearings on top of
the tower. Instead, the entire tower (including the turbine and the
submerged stabilizing shaft) can align itself and the turbine
according to the wind direction since the tower is being placed in
a slide ring (typically based on polymers) near the water surface
and since the overwater cross-section of the tower is
aerodynamically encased.
[0011] The aerodynamic encasement of the tower above the water
level serves as wind vane and reduces also the wind load impacting
on wind turbine towers and helps, subsequently, to reduce the drift
forces impacting on the entire windpark system. Additionally, the
aerodynamic encasement helps to maintain the dynamic balance
between forces caused by the angular momentum of the rotating
turbines and the aerodynamic forces impacting on the encasement
and, thereby, to avoid wobbling movements of the tower.
[0012] The submerged shaft of the tower stabilizes the wind turbine
tower with the mounted turbine due its self-weight and the ballast
enclosed in the lower end of the shaft. Typically, the submerged
shaft above the bottom weight and the upper tower comprise several
compartments separately connected to a pump (typically on-board of
ships) to either pump gas (typically air) into the compartments or
to pump water out of the flooded water- and airtight compartments
(respectively tanks). Typically, if more than two compartments
exist, the center compartment will float just below the water
surface when in final energy production position, will be the one
with the largest cubage and might be featuring a considerable
larger diameter than the upper tower and the lower shaft. The
facility for manipulating and controlling the specific weight of
the wind turbine towers is on the one hand used to tow towers in a
horizontal, floating position from and to the energy production
sites. On the other hand, the towers can be erected and the nacelle
mounted by flooding successively the bottom compartments on site
until the top of the tower reaches the working position for the
installation of nacelle and blades e.g. with the help of ship
cranes. Alternatively, the nacelle, possibly with one blade, could
be mounted already on-shore, lowered onto and fastened to a
separate buoy or ship (whereas the tower and shaft would float
horizontally without such support) and towed to the final energy
production site. In case, the nacelle and blades are mounted on
site, the tower can be lifted into the final position by pumping
air into the upper compartment(s) after having installed the
nacelle and blades on the working level. The floating wind turbine
units are integrated to a windpark.
[0013] The mooring system of the wind park consists of weight
anchors or other anchorage systems, vertical mooring lines, chains
or cables to these anchors. Typically, the anchors are positioned
in a triangular or quadrangular, regular pattern on the seabed.
Semisubmersible buoys or tanks containing gas or foams (hereinafter
called major buoys) to generate buoyant force maintain the mooring
lines, chains or cables in an upright and taut position. Typically,
the vertical mooring lines, chains or cables are either entirely
coated or encased with corrosion-resistant and buoyancy generating,
light materials or with separate buoys fixed in regular (typically
short) distances to generate buoyancy and keep them in a floating
under water position and, thereby, helping to reduce the physical
strain caused by the self-weight of the mooring lines, chains or
cables.
[0014] Anchors with connected mooring lines, chains or cables are
lowered to the seabed together with the major buoys. The mooring
lines, chains or cables are prepared or cut to length in order all
major buoys float on the same depth under the water surface.
Typically, the major buoys will be placed several meters below the
floatation depths of very large ships in order the windparks do not
constrain shipping traffic or reduce interference with the latter
as much as possible.
[0015] Either together with the lowering of anchors, of mooring
lines, chains or cables and of the major buoys or after successful
positioning of anchors and major buoys, horizontal floating lines
or typically cables are fixed to the majors buoys to form an
immense triangular or quadrangular underwater floating meshwork,
hereinafter called floating meshwork, with the major buoys serving
as platform for the joints of the fishing-net-like, horizontally
floating meshwork. As with the vertical mooring lines, cables or
chains described above, the cables of the floating meshwork are
typically either entirely coated or encased with
corrosion-resistant and buoyancy generating, light materials or
with separate buoys fixed in regular (typically short) distances to
generate the buoyancy needed to avoid any vertical sagging of the
meshwork cables, lines or chains and subsequent contracting of the
entire floating mooring system of the wind park.
[0016] Finally, in the corner regions of the floating meshwork and
in a certain distance from the major buoys the wind turbine towers
are positioned, usually by tying the slide ring with three,
typically equally long ropes to the floating meshwork, whereupon
one joint would be on the major buoy and the two other connections
would be on the cables of the floating meshwork. The wind turbine
towers form hence the center of an actinomorphic
buoy-cable-mooring. Typically, the angles between ropes would be
120.degree. if no drift is interfering. One or several wind turbine
towers are fixed next to each major buoy. Typically, the final
distance between single wind turbine towers would be the same
regardless of whether clusters of several wind turbine towers are
arranged around major buoys or whether only one single wind turbine
tower is fixed to a major buoy. The optimal distance between single
wind turbine tower units depends on the size of the wind turbine
and the all-season wind regime and would typically be several
hundred meters.
[0017] The method should allow conventional onboard ship cranes,
towboats, cable layer ships and/or heavy lift ships to be used,
but, as may be the case, with certain modifications.
[0018] The described system of off-shore windparks is applicable
particularly in waters deeper than 30 meters.
[0019] Electric surplus energy could be used to fill compressed
underwater-air-stores of adiabatic systems. In times of power
shortages compressed air can be released and be used to generate
electricity again. Alternatively or additionally, electric surplus
energy could be used on shore to produce H.sub.2 gas through water
electrolysis and followed by methanisation of CO.sub.2 gas from
coal- or gas-based thermic power plants. The methane gas could then
be distributed using existing gas pipelines and stored using
existing gas storage facilities. Alternatively or additionally,
electric surplus energy could be used to pump water back up to
reservoirs of hydroelectric power plants, to charge batteries or to
fill other suitable energy storages. In case of lacking facilities
to store or transmit electric surplus energy from windparks, wind
power turbines can be shut down within short time--contrary to
conventional thermic and nuclear power plants.
[0020] If designed for a sufficiently high mechanical load
capacity, the floating meshwork can be used to moor other
structures than wind turbine towers like e.g. floating fish farms
or floating platforms for compressors, engines, turbines,
generators, couplings, hoses, tubes and other structures and
devices necessary to operate adiabatic systems. Furthermore, the
horizontal mooring lines can serve as guiding lines along which
electrical cables (typically with a relative density similar to
water) can be fixed.
[0021] Other objectives, features and advantages of the present
invention will appear from the following detailed disclosure, from
the attached claims as well as from the drawings.
[0022] Generally, all terms used in the claims are to be
interpreted according to their ordinary meaning in the technical
field, unless explicitly defined otherwise. All reference to
"a/an/the [element, device, component, part, methods etc.]" are to
be interpreted openly as referring to at least one instance of said
element, device, component, part, methods etc., unless explicitly
stated otherwise. The steps of any method disclosed herein do not
have to be performed in the exact order disclosed, unless
explicitly stated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The above, as well as additional objects, features and
advantages of the present invention will be better understood
through the following illustrative and non-limiting detailed
description of preferred embodiments of the present invention, with
reference to the appended drawing, where the same reference
numerals will be used for similar elements.
[0024] FIG. 1 is a schematic side view of the floating off-shore
windpark system of the present invention, whereas
[0025] FIG. 2 is the schematic bird's view of the same windpark
system.
[0026] FIG. 3 depicts a schematic side view of a single floating
wind turbine tower installed in upright operational modus (position
in which energy is produced).
[0027] FIG. 4 depicts a schematic perspective view onto a part of
the floating meshwork with major buoys and the anchorage on the
seabed, but without wind turbine towers.
[0028] FIG. 5 is the schematic cross-section view of the wind
turbine tower above and next to the center compartment, which is
below the water surface when in operational modus.
[0029] FIG. 6 depicts a schematic side view of a horizontally
floating wind turbine tower ready for transport by towboats.
[0030] FIG. 7 depicts a schematic perspective view onto parts of
the windpark with floating triangular meshwork, major buoys,
vertical moorings, anchorage on the seabed and one mounted wind
turbine unit per major buoy.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OR EMBODIMENTS OR
BASIC VERSIONS OF EMBODIMENTS
[0031] FIG. 1 is a schematic side view of the floating off-shore
windpark system of the present invention. The reference number 1 is
a floating wind turbine unit comprising a wind turbine tower 13
(cf. FIG. 3) moored to a semi-submersible major buoy 8 and the
adjacent semisubmersible, horizontally floating cables, chains or
lines 2a (in the following only called horizontal lines 2a) of the
floating meshwork 2. The reference number 3 is a vertical mooring
chain, cable or line (in the following only called vertical mooring
lines 3) connected typically to a weight-anchor 5 on the seabed 7.
At the edges of the windpark the major buoys 8 and with it the
entire floating meshwork 2 would typically be transversely braced
by border mooring lines 4 to achieve an optimal reduction of side
drift of the windpark system. The reference number 6 depicts the
water surface and maximal swell amplitude.
[0032] FIG. 2 is the schematic bird's view of the same windpark
system. The reference number 9 is a singular wind turbine tower
forming the center of an actinomorphic buoy-cable-mooring. The
reference number 10 are the lines, cables or ropes (in the
following called the ropes 10) to which the wind turbine towers 13
are tied to. Optionally, relatively light ropes 10 (contrary to
e.g. steel cables or chains) could be tensed by mounting a weight
11 either freely sliding on or fixed approximately in the middle of
the rope in order to avoid unwanted coiling of the ropes around the
underwater parts of the wind turbine tower 13b (e.g. in case of
jammed sliding rings 14). Optionally, at each joint where the ropes
10 are fixed to the floating meshwork 2, including the major buoys
8, signal buoys 12 floating on the water surface can be tied to
clearly indicate the triangular range (around wind turbine towers)
within which ships with considerable floatation depths may not
circulate.
[0033] Typically, the mooring lines 2a, 3 and 4 are either entirely
coated or encased with corrosion-resistant and buoyancy generating,
light materials or with separate buoys fixed in regular (typically
short) distances to generate buoyancy and help, thereby, to avoid
the physical strain caused by the self-weight of the mooring lines
2a, 3 and 4 and to avoid vertical sagging and subsequent
contracting of the entire horizontally mooring system of the
floating meshwork 2. Mooring lines 3 and 4 encased or equipped with
buoyancy generating materials can be dimensioned for smaller drag
forces than as if these lines would not be self-floating.
[0034] Usually, anchors 5 with connected mooring lines 3 and 4 are
lowered to the seabed together with the major buoys 8. The mooring
lines 3 and 4 are cut to length in order all major buoys float in
the same depth under the water surface. Typically, the major buoys
will be placed several meters below the floatation depths of very
large ships in order the windparks do not constrain shipping
traffic or in order to reduce interference with the latter as much
as possible.
[0035] FIG. 3 depicts a schematic side view of a single floating
wind turbine tower 13 installed in upright operational modus and
fixed within the floating meshwork 2. The wind turbine tower
consists of an upper part 13a, reaching above the water surface 6,
and a lower part 13b, hereinafter called tower shaft, which is
submerged. Typically, the diameters of both the upper and lower
part of the wind turbine tower will be conically reduced towards
the upper respectively lower end for reasons of static
optimization.
[0036] The wind turbine tower consists of one, but typically
several compartments 15, whereupon the center compartment 15a will
for stability reasons float just below the water surface (when in
operational modus), will have an important cubage or will be the
one with the largest cubage and might be featuring a considerable
larger diameter than the upper tower 13a and the lower shaft
13b.
[0037] The ropes 10 are fixed to the slide ring 14 (typically based
on polymers) near the water surface and usually to two horizontal
lines 2a of the floating meshwork 2 and one major buoy 8. The
reference number 16 is the stabilizing weight enclosed in or
attached to the lower end of the shaft 13b. The reference number 17
is the nacelle including generator and typically a gearbox. The
reference number 18 is a turbine blade. A tower 13 advantageously
comprises three blades 18, but any other number is of course
possible. The plane of these turbine blades 18 is typically
parallel to (or in line with) the plane of the shaft 13b, but it is
also absolutely thinkable to have blades 18 being in a plane
inclined with respect to the plane of the shaft 13b. It is
furthermore possible to offer the possibility of a dynamic
adjustment of the plane, e.g. by means of an electrically
controlled motor.
[0038] The electrical cable leading to (respectively away from) the
wind turbine tower 13 exits at the bottom tip of the shaft 13b and
is not visually depicted on none of the Figures. To avoid coiling
of electrical transmission cables due to the rotation of the wind
turbine tower around its own axis with changing wind directions
sophisticated conventional mechanical solutions are adopted.
[0039] FIG. 4 depicts a schematic perspective view onto a part of
the floating meshwork 2 with major buoys 8 and anchorage 5 on the
seabed 7, but without wind turbine towers.
[0040] FIG. 5 is the schematic cross-section view of the upper part
of the wind turbine tower 13a above and next to the center
compartment 15a (if such is foreseen). The depicted cross-section
would be close to the water surface 6 of a wind turbine tower 13 in
operational modus.
[0041] The reference number 19 is the aerodynamic encasement of the
wind turbine tower 13a exposed to the winds. The aerodynamic
encasement 19 will either feature an invariable diameter or its
diameter may be conically reduced from the bottom towards the top
of the wind turbine tower 13a. The clear space between the
encasement and the tower is not hermetically sealed. This is
indicated by the dashed line symbolizing openings 20.
[0042] FIG. 6 depicts a schematic side view of a horizontally
floating wind turbine tower 13 with compartments 15 not flooded,
but vented and ready for transport by towboats. During towing the
aerodynamic encasement 19 is flooded through the openings 20 and
will serve as keel preventing the wind turbine tower 13 from
rolling over its own axis. The reference number 21 is a water
respectively air pipe system through which compartments 15
(including compartment 15a) both in the upper tower 13a and in the
shaft 13b can be flooded and vented. Hoses mounted to pumps on
ships can be connected to the connective valves 22 and air can be
pumped to vent the compartments or water filled in order to flood
the compartments 15 and press the air out. Typically, two
pipes--one inlet and one outlet pipe--lead to each of the floodable
compartments 15. If a multitude of compartments exist, the one or
the ones next to the top end of the wind turbine tower 13a need not
to be equipped for flooding and ventilation.
[0043] Finally, FIG. 7 depicts a schematic perspective view onto
parts of the windpark with a floating triangular meshwork 2, major
buoys 12, vertical mooring lines 3, border mooring lines 4,
anchorage 5 on the seabed 7 and completely assembled wind turbine
tower units 1 in operational modus, each of these units 1 tied to a
major buoy 12 and adjacent horizontal lines 2a by ropes 10.
Optionally and depending on the width of the meshes of the floating
meshwork 2, the size of the wind turbine units 1 and the
environmental conditions (wind regime, water depths, maximum swell
amplitude, water currents, topography of seabed 7) more than one
wind turbine tower unit 1 could be positioned around each mayor
buoy 12 and the adjacent four (applicable for quadrangular floating
meshwork 2) or six (applicable for triangular floating meshwork 2)
horizontal lines 2a. In FIG. 7, wind turbine tower units 1 along
the left border of the windpark are not or not yet mounted to major
buoys 12 and the adjacent horizontal lines 2a.
[0044] Although the present disclosure has been described with
reference to particular means, materials and embodiments, one
skilled in the art can easily ascertain from the foregoing
description the essential characteristics of the present
disclosure, while various changes and modifications may be made to
adapt the various uses and characteristics as set forth in the
following claims. In particular, it is important to mention that
any one of the components of the windpark can be exchanged by a
similar component, fulfilling the same or a similar functionality.
Furthermore, it is also possible to leave out one or more of the
components of the windpark (e.g. one of the more components of the
wind turbine tower 13). without jeopardizing the spirit of the
present invention.
* * * * *