U.S. patent application number 12/441276 was filed with the patent office on 2009-12-24 for polymeric concrete for wind generator towers or other large structural applicatons.
Invention is credited to Paulo Luis Cardoso Osswald, Daniel Da Fonseca Farias Rodrigues, Paulo Manuel Ferreira Sobral, Ana Margarida Goncalves Terra, Alexandre Francisco Malheiro De Aragao, Celia Maria Moreira Parente Novo, Andre Ferreira Vieira.
Application Number | 20090313913 12/441276 |
Document ID | / |
Family ID | 38924495 |
Filed Date | 2009-12-24 |
United States Patent
Application |
20090313913 |
Kind Code |
A1 |
Malheiro De Aragao; Alexandre
Francisco ; et al. |
December 24, 2009 |
POLYMERIC CONCRETE FOR WIND GENERATOR TOWERS OR OTHER LARGE
STRUCTURAL APPLICATONS
Abstract
The present invention relates to towers for wind generators or
other large structural applications and uses a new construction
concept, based on polymeric concrete. Polymeric concrete is
composed of thermosetting resin and aggregates such as sand or
gravel. Polymeric concrete has low maintenance costs and
exceptional high resistance to corrosion, thus justifying its main
usage in non-structural applications. Additionally, polymeric
concrete has been used as mortar in the rehabilitation of civil
structures, especially retrofitting of bridges and heritage
buildings. Its advantages for these applications are the adherence
to the traditional materials, higher compressive strength than
traditional concrete and low specific weight. The tower (1),
according to the invention, is built of two or more superimposed
ring sections (2) in conical or cylindrical shape, each ring (2)
being built of one or more shell segments and the said segments
being fixed by means of mechanical and/or chemical couplings, and
being made of prefabricated polymeric concrete.
Inventors: |
Malheiro De Aragao; Alexandre
Francisco; (Braga, PT) ; Goncalves Terra; Ana
Margarida; (Porto, PT) ; Vieira; Andre Ferreira;
(Matosinhos, PT) ; Moreira Parente Novo; Celia Maria;
(Matosinhos, PT) ; Ferreira Sobral; Paulo Manuel;
(Porto, PT) ; Farias Rodrigues; Daniel Da Fonseca;
(Maia, PT) ; Cardoso Osswald; Paulo Luis; (Porto,
PT) |
Correspondence
Address: |
CERMAK KENEALY VAIDYA & NAKAJIMA LLP
515 EAST BRADDOCK RD SUITE B
Alexandria
VA
22314
US
|
Family ID: |
38924495 |
Appl. No.: |
12/441276 |
Filed: |
September 13, 2007 |
PCT Filed: |
September 13, 2007 |
PCT NO: |
PCT/IB2007/053696 |
371 Date: |
September 8, 2009 |
Current U.S.
Class: |
52/40 |
Current CPC
Class: |
F05C 2225/00 20130101;
F03D 13/20 20160501; Y02E 10/728 20130101; Y02P 70/50 20151101;
F05B 2240/912 20130101; Y02E 10/72 20130101; Y02B 10/30 20130101;
F03D 13/25 20160501; E04H 12/12 20130101; F05B 2230/50 20130101;
F05B 2280/4003 20130101 |
Class at
Publication: |
52/40 |
International
Class: |
E04H 12/12 20060101
E04H012/12 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 13, 2006 |
PT |
103562 |
Claims
1. A tower to support on-shore or off-shore wind generators or
other large structures, wherein the said tower is formed by two or
more superimposed ring sections, each ring comprising one or more
shell segments, which are affixed by means of mechanical and/or
chemical connection and made of pre-cast polymeric concrete, which
is composed of a thermosetting resin with an aggregate of at least
60% weight dry sands and/or gravel.
2. The tower, according to claim 1, comprising a conic, cylindrical
or prismatic external shape.
3. The tower, according to claim 1, wherein between two
superimposed rings, the bottom has the top end shaped like a step
comprising, from inside-out, firstly a bottom surface, then an
inclined middle surface, and thirdly a top surface, and in that the
top ring, in its turn, comprises in each pair of superimposed
rings, has a bottom end shaped as an inverted step that matches the
counterpart surfaces of the bottom ring.
4. The tower, according to claim 1, wherein further aggregates up
to a maximal content of 20% weight of the polymeric concrete are
used, to enhance chemical and/or physical properties.
5. The tower, according to claim 1, wherein a reinforcement of
composite materials is used within the polymeric concrete wall
along one or more superimposed rings.
6. The tower, according to claim 1, wherein a reinforcement of
steel cables is used within the polymeric concrete wall along more
than two superimposed rings.
7. The tower, according to claim 1, wherein reinforcement steel
walls are used in the outer and/or inner surfaces.
8. The tower, according to claim 1, wherein casting takes place
on-site.
9. The tower, according to claim 2, wherein between two
superimposed rings, the bottom has the top end shaped like a step
comprising, from inside-out, firstly a bottom surface, then an
inclined middle surface, and thirdly a top surface, and in that the
top ring, in its turn, comprises in each pair of superimposed
rings, has a bottom end shaped as an inverted step that matches the
counterpart surfaces of the bottom ring.
10. The tower, according to claim 2, wherein further aggregates up
to a maximal content of 20% weight of the polymeric concrete are
used, to enhance chemical and/or physical properties.
11. The tower, according to claim 3, wherein further aggregates up
to a maximal content of 20% weight of the polymeric concrete are
used, to enhance chemical and/or physical properties.
12. The tower, according to claim 2, wherein a reinforcement of
composite materials is used within the polymeric concrete wall
along one or more superimposed rings.
13. The tower, according to claim 3, wherein a reinforcement of
composite materials is used within the polymeric concrete wall
along one or more superimposed rings.
14. The tower, according to claim 3, wherein a reinforcement of
composite materials is used within the polymeric concrete wall
along one or more superimposed rings.
15. The tower, according to claim 2, wherein a reinforcement of
steel cables is used within the polymeric concrete wall along more
than two superimposed rings.
16. The tower, according to claim 3, wherein a reinforcement of
steel cables is used within the polymeric concrete wall along more
than two superimposed rings.
17. The tower, according to claim 4, wherein a reinforcement of
steel cables is used within the polymeric concrete wall along more
than two superimposed rings.
18. The tower, according to claim 2, wherein reinforcement steel
walls are used in the outer and/or inner surfaces.
19. The tower, according to claim 3, wherein reinforcement steel
walls are used in the outer and/or inner surfaces.
20. The tower, according to claim 4, wherein reinforcement steel
walls are used in the outer and/or inner surfaces.
Description
TECHNICAL DOMAIN
[0001] The present invention relates to towers for wind generators
or other large structural applications and applies a new
construction concept, based on polymeric concrete.
STATE OF THE ART
[0002] Wind generators have gained wide acceptance as an
alternative source for the production of renewable and clean
energy. In recent years, state of the art wind energy converters
had a dramatic development in energy output/production, by using
longer blades and more powerful generators. Rotor diameter of state
of the art units has reached 120 m and generator power has reached
5 MW. Wind generators are supported to a convenient height by
towers, in order to expose them to a convenient wind flow and
prevent interaction between the rotor blades and the ground. The
towers themselves are adequately attached to the foundations. The
development trend described above requires increased hub height,
and tower height for the same state of the art unit has reached 120
m.
[0003] These towers must support the increased weight of the energy
converters, withstand the wind forces on the whole unit and provide
adequate mechanical resistance to the dynamic behaviour of the
generator, including stiffness and fatigue wear for a minimum 20
year life time. Thus they are a demanding design project
representative of engineering state of the art for supporting large
and heavy structures at extreme heights.
[0004] The same energy converters have also been applied off-shore,
where wind flows are more convenient and where there are fewer
implications with ground occupancy. The supporting towers have been
attached to steel pylons or concrete foundations that reach above
maximum sea water level.
[0005] The towers have a significant impact in the overall cost of
the wind generator unit and several solutions have been proposed
both to support the development trend to higher hub heights and to
reduce the costs in manufacture, transport, assembly and
maintenance, which become more and more relevant with increasing
height. A variety of construction methods, from guyed poles, steel
wall, steel lattice, concrete wall, hybrid steel wall &
lattice, hybrid concrete & steel wall to composite materials,
have been proposed for wind towers. A viable solution has to
provide necessary mechanical resistance both to static and dynamic
loads at increasing heights and prove cost-effectiveness in
manufacture, transport, assembly and maintenance.
[0006] The industry has used mainly steel towers, made of
cylindrical or conical sections of metal wall, flanged at the
extremities, the sections being bolted together on site. However,
as increased tower height implies bolder dimensioning of the tower
diameter, of the wall thickness, or both, in order to assure the
necessary stiffness, this solution has met increasing limitations
due to materials costs and also manufacture and transport
limitations due to dimensions, as a diameter of 4.2 m is the
maximum allowed in many roads due to over-crossings. This is the
main reason why the standard steel tower height for the multi-MW
generators today is still 80 m, which was the state of the art 10
years ago.
[0007] Towers of steel lattice construction were used for smaller
towers in the past and have also been proposed for higher towers.
Lattice towers need more ground space and imply more time
consumption for on site assembly. They also have increased
inspection and maintenance costs. A variant hybrid construction,
made of a lower section of steel lattice and an upper section of
steel wall, has been proposed as in DE 103 39 438 A1, but it
requires expensive joints.
[0008] Proposals have been made in order to improve the steel wall
tower construction presently used by the industry. The construction
of the tower has been proposed in variable forms, including various
numbers of ring sections and shell segments, as in WO 2004/083633
A1. Other proposals are based on a more complex wall profile, as in
EP 1561883 A1, providing more stiffness but requiring additional
and costly operations both for production and on site assembly.
Hybrid variants with a concrete lower section, as in WO
2005/015013, improve the load-bearing capacity and easiness of
attachment to the foundation, thus allowing higher towers, but they
present increased costs and fail to solve the maintenance
issues.
[0009] Furthermore, all the steel wall and lattice solutions
require maintenance of the tower during the project lifetime of the
wind generator, due to corrosion. Although corrosion usually
appears late in the 20 year life-cycle of the on-shore tower,
control and maintenance of corrosion spots on the external wall or
in lattice construction entail important costs and risks. In more
aggressive environmental conditions, such as off-shore towers,
corrosion becomes an even more important concern and implies
increased maintenance costs and risks.
[0010] A different approach is that of concrete towers, made of
pre-cast concrete sections reinforced with pre-tensioned cables.
They have been used for towers with heights of about 95 m and
higher, as in DE 100 33 845 A1 and DE 101 60 306 B4 and they have
the advantage of a better weathering resistance. However, this
solution is considerably heavier than the one of steel wall, with
corresponding higher logistic costs and longer on-site assembly
time.
SUMMARY OF THE INVENTION
[0011] The present invention provides a solution for building large
scale towers, including towers beyond 80 m height, reducing
substantially the maintenance needs, avoiding the logistics
restrictions of the maximum transportable diameter and reducing the
production costs of the current state of the art steel tower
solutions, through the application of polymeric concrete.
[0012] Polymeric concrete is composed of thermosetting resin and
aggregates such as sand or gravel. Polymeric concrete has low
maintenance costs and exceptional high resistance to corrosion,
justifying its main usage in non-structural applications and in
small size parts where corrosion is the main problem.
Complementary, polymeric concrete has been increasingly used in
recent years in the rehabilitation of civil structures, especially
retrofitting of bridges and heritage buildings using polymeric
mortar. Its advantages for these applications are the adherence to
the traditional materials, a compressive strength higher than
traditional concrete and low specific weight.
[0013] Ongoing research has shown that an adequate amount of
aggregates such as dry sands with a fine grain and gravel, with
proper sizes, combined with low viscosity resin, can provide very
good adhesion and compression properties preserving the other
advantages of polymeric concrete. The nature of polymeric concrete
allows adequate reinforcement through addition of fibre reinforced
plastic materials or steel, thus complementing its mechanical
properties, namely flexure strength. Thus, polymeric concrete can
be successfully employed as a basis material on its own for large
structures. Applied to towers for wind generators and other
structural applications, the casting process of polymeric concrete
allows plasticity in form modelling in a very cost-effective way,
thus allowing adaptation and optimization of the structural design
to loads and logistic restraints, while contributing with its
chemical properties to reduce maintenance costs.
[0014] Towers for large structural applications typically have a
base diameter of more than 4 m and reach heights above 50 m,
supporting heavy loads. Examples of towers for large structural
applications are towers for windmills, lighthouses or pillars
supporting highways in viaducts. For all of these polymeric
concrete can be used as the base material, presenting advantages in
lower maintenance and in lower logistics and production costs.
[0015] The polymeric concrete is prepared by thorough mixing of the
binder and filler materials in adequate ratios, and adding the
hardener to promote the complete polymerization. Large scale
production of polymer concrete is performed in proper equipment.
Binder and filler have separate hoppers and their mixture is
promoted through a screw mechanism. Granulometry and viscosity are
controlled to assure the adequate flow of the resulting mixture and
the final mechanical characteristics of the polymeric concrete. The
finished mixture is then filled into a mould and compacted through
vibration. The moulds are made of steel and/or other adequate
materials. After polymerization the final product is removed from
the mould.
DESCRIPTION OF THE FIGURES
[0016] The annexed drawings exemplify a solution according to the
invention:
[0017] FIG. 1 shows a tower (1) made of several superimposed
horizontal sections, or rings (2), of cast polymeric concrete, with
convenient wall thickness.
[0018] FIG. 2 shows a cross-section of one section (2), or
ring.
[0019] FIG. 3 shows the cross-section of another section(2), or
ring, being built of 3 shell segments (3), joined together, using
appropriate chemical bonding, like structural glue (4).
[0020] FIG. 4 shows how two superimposed rings (5) and (6) are
joined together using appropriate chemical bonding, like structural
glue (7), between conveniently fitted ends, respectively (8) and
(9), of the adjoining sections or rings. The same figure shows an
example of a reinforcing element (10) within the polymeric concrete
wall (11), used to adequately increase stiffness of the tower and
decrease risk of fatigue failure. The casting process not only
allows modelling the internal wall surface, but also allows fitting
into the wall any kind of fixtures needed for installation of the
internal cabling system, stairs, platforms, etc.
[0021] FIG. 5 shows an inserted fixture (15) to fix cables, or
other means of handling the sections or rings, inserted into the
polymeric concrete wall (16) of a segment or ring.
DETAILED DESCRIPTION OF THE INVENTION
[0022] The tower, according to the invention, is built of two or
more superimposed ring sections in conical or cylindrical form,
each ring being built of one or more shell segments, these segments
are joined by means of mechanical and/or chemical bonding and made
of pre-cast polymeric concrete.
[0023] The segments are moulded after mixture of the binder and
filler materials, as described above. The binder is a thermosetting
resin like polyester resin, epoxy resin, phenolic resin, vinyl
ester resin or others. Before filling the moulds with polymer
concrete, chopped fibres mixed with the thermosetting resin can be
sprayed onto the mould external wall, to enhance the tensile
resistance of the segment.
[0024] The rings have specially designed ends in order to assemble
into each other when building a tower. Between two superimposed
rings, as seen in FIG. 4, the one in the bottom has the top end
shaped like a step with, from the interior to the exterior, first a
bottom horizontal surface (12), second a inclined middle surface
(13), and third a top horizontal surface (14). In turn, the top
ring, in each pair of superimposed rings, has a bottom end shaped
as an inverted step (12', 13', 14') matching the corresponding top
end surfaces of the bottom ring. This kind of assembly makes the
structure more stable because, as the top ring assembles with a
bottom ring, both inclined middle surfaces 13 and 13' of the rings
are uniformly pressed against each other, this way pressing the
structural glue interposed between the two surfaces. Surfaces 12
and 12', or 14 and 14', are joined by press fit due to the top ring
weight or are also glued. Furthermore, this configuration provides
a conveniently extended interface for application of the structural
glue at assembly, which can be subjected to shear stresses,
enhancing its effect in providing the necessary stiffness and
mechanical resistance of the tower. To optimize the joining
efficiency and to decrease the tensions applied, the surface 13 and
13' are positioned near the internal surface of the ring.
[0025] To help stabilise the tower even more, a post tensioned
reinforcing element (10), such as a steel or a polymeric cable, or
a composite profile, can be used within the polymeric concrete wall
(11) in order to increase the stiffness of the tower and decrease
risk of fatigue failure. To optimize mechanical efficiency, this
reinforcement is positioned near the external surface of the ring
and is stressed when fixing the top ends at assembly. Furthermore,
if this reinforcing element extends through two or more adjacent
rings, it can be used as a mechanical joining method between these
rings, complementing or substituting the structural glue.
[0026] These advantages are valid both for cylindrical and conical
tower segments.
[0027] It should be clear that the described embodiments are simply
examples of execution of the present invention. Variations and
modifications, that are obvious to a person skilled in the art, can
be made within the scope of the invention and are still protected
by the following claims.
* * * * *