FR2984420A1 - WIND TURBINE MOUNTED ON A ROTATING PLATFORM - Google Patents

Abstract

This installation for converting the mechanical energy of the wind into electrical energy comprises a platform (2), a set of blades (P) with vertical axis connected to the platform so as to cause the platform to rotate under the effect of wind, and at least one electric power generator (7) comprising at least one rotor connected to the rotating platform and at least one stator linked to a fixed structure. It comprises a set of poles (3) erected from a peripheral zone of the platform, on which the blades are respectively fixed.

Description

BACKGROUND OF THE INVENTION The invention relates generally to installations for converting mechanical energy from wind into electrical energy and more particularly relates to floating wind turbines. Wind power is, to date, the second largest source of renewable energy behind hydroelectric power. Currently, wind power exceeds 200 GigaWatts (GW) worldwide, which represents 2% of global electricity production. The annual increase in wind capacity is of the order of 40 GW per year, but this increase tends to be slower for onshore installations. This slowdown is mainly due to the environmental and visual constraints related to these installations. As a result, the construction of wind farms has recently expanded into the sea and into lakes and oceans to provide access to new spaces for the installation of larger turbines. Most offshore (offshore) wind turbines currently rely on foundations laid on the seabed. These installations are however expensive, difficult to dismantle and limited in depth by their technique. It is estimated at 50m the limit depth beyond which it is no longer profitable to build an offshore wind turbine. This limit thus forces the offshore wind market to be restricted to a small portion of the oceans and seas, or even lakes. For Europe, it has been found that 73% of economically exploitable wind resources are at depths greater than 50m. These depths are inaccessible economically and even technically to wind turbines on foundations.

On the other hand, they are for floating wind turbines. Most of the floating wind projects under development are designed for horizontal axis wind turbines, also known as HAWTs (Horizontal Axis Wind Turbines). These wind turbines are generally three-blade wind turbines mounted on a floating structure. The choice of this solution is due to the great experience gained with the operation of HAWT wind turbines, which makes them credible, especially with the financing banks. It has been found, however, that HAWT turbines have not been designed to operate in a marine environment involving significant and disruptive mechanical stresses such as swell, chop and other marine phenomena such that floating wind turbines require increased stability and robustness. A number of documents of the state of the art describe the use of HAWT type floating wind turbines. In this regard, reference may be made to US Pat. No. 7,819,073, US Pat. No. 7,296,971 and US Pat. No. 2001/0037264. The floating wind turbines described in these documents use a set of blades mounted on a floating platform and rely on three float technologies, namely the technology known as Espar, the semi-submersible technology and the TLP technology ("Voltage"). Leg Platforms "), in English. Espar's technology is based on the use of a longitudinally and vertically extending float and the submerged part of the structure is longer than the emergent part, so that the center of gravity of the assembly is below center of flotation to ensure a stable equilibrium and prevent its reversal. Therefore, this technology requires a large draft and is only conceivable for depths greater than 150m. Any lower depth is incompatible with this Espar technology.

The semi-submersible floats consist of three floats connected together by rigid pipes ensuring the robustness of the assembly. This structure allows a lower gite under the effect of the wind that the platforms made according to Espar technology but undergoes, much more sensitive, the oscillations of the surface of the water. In addition, its cost price remains higher than that of other technologies. Finally, the TLP floats are based on the use of tendons arranged between the seabed and a floating structure on which the wind turbine is fixed in order to partially immerse it. The tension generated by the tendons provides maximum stability to the float / wind turbine assembly but offers no flexibility, especially with respect to the effects of waves and tides. This type of platform was originally designed for the oil industry in order to avoid the droning of the drilling platforms and the tearing off the platforms of equipment fixed on the seabed. On the other hand, the TLP floats are unsuitable for supporting the horizontal stresses of the wind which create a cottage of the wind turbine which can generate a relaxation of the tendons in the wind and a surge of the most windward tendon. Furthermore, studies have shown that there is interference between swell oscillations and the rotor rotation frequency of a conventional three-phase HAWT wind turbine. As a result, prototypes using a HAWT wind turbine on a float have shown lower production performance than those observed on land with the same machines at equal wind speeds. Results have shown that such an installation only delivers 81% of the expected production due to interference between the movements of the sea and those of the blades.

In view of the foregoing, vertical axis wind turbines, also known as VAWT ("Vertical Axis Wind Turbine") wind turbines, are an interesting alternative to HAWT type wind turbines for the production of wind turbines. floating wind turbines.

VAWT wind turbines have four main advantages over HAWT wind turbines. In the first place, their rotation along a vertical axis makes them insensitive to the direction of the wind and its variation of direction.

Secondly, the barycentre of the forces exerted by the wind on the wind turbine is lower on a wind turbine type VAWT than on a wind turbine type HAWT of the same power with the advantage of reducing the lever lever exerted on the float .

Thirdly, the lower position of the generator of a VAWT type wind turbine compared to that of a HAWT wind turbine reduces the costs and facilitates the maintenance of a VAWT wind turbine. Finally, the generally curved shape of the blades allows a VAWT type wind turbine to oscillate with less loss of aerodynamic efficiency than a wind turbine type HAWT. VAWT wind turbines, however, have certain disadvantages. Their main weakness concerns the lack of robustness of the blades, called Darrieus, generally used. Indeed, all attempts to install wind turbines of several MW of VAWT type power led to self destruction of the turbine under the effect of centrifugal force. In addition, such machines have a relatively low starting torque so that they require a starting aid.

Reference may be made to document US Pat. No. 7,397,144, which describes a floating wind turbine of the VAWT type. This wind turbine however has a number of major disadvantages relating to the fact that the blades are prone to waves and the wear induced by them. In addition, mounting the blades relative to the platform significantly increases maintenance costs and reduces the life of the wind turbine. The object of the invention is therefore to overcome the disadvantages of wind turbines according to the state of the art and, in particular, floating wind turbines type VAWT.

The subject of the invention is an installation for converting the mechanical energy of the wind into electrical energy, comprising a platform, a set of blades with a vertical axis connected to the platform so as to drive the platform in rotation under the effect of the wind. , and one or more electric power generators comprising at least one rotor connected to the rotating platform and at least one stator linked to a fixed structure. This installation comprises a set of masts erected from a peripheral zone of the platform, on which the blades are respectively fixed. Thanks to the mounting of the blades on the masts erected from the platform, the blades of VAWT floating wind turbines are no longer subject to wave impacts, which overcomes the aforementioned drawbacks. The masts also enhance the blades and expose them to stronger and more regular winds, and increase the area swept by the blades. It is thus possible to associate the blades with an angle of attack adjustment device, which would not generally be possible if such a device was subjected to the impact of waves.

In one embodiment, the masts are inclined outwardly of the platform and are held at the platform in rotation by a set of holding arms. In this case, it is advantageous to tilt the masts tangentially with respect to the perimeter of the platform so that the angle between the masts and the platform is reduced and thus allows a lower lever arm between these elements of the structure. In addition, the effects of wind blowing blades on the blades downwind are modulated by the fact that the blades are inclined and their wakes cross only gradually.

According to another embodiment, the masts are inclined towards the inside of the platform in a crossed arrangement, said masts crossing in the vicinity of the vertical axis of rotation of the platform, a device such as a ring or a polygon support unit solidarisant the masts between them and with a hub at the place of their crossing.

According to such a "crossed" configuration, the structure is simplified, lightened and solidified. In one embodiment, the platform is a floating platform on the water, for example on the sea or on a lake, and is associated with an anchoring system acting on the fixed structure.

In this case, the platform is advantageously made in the form of a flat structure whose horizontal dimensions are greater than its vertical dimension. For example, the platform has a toroidal shape and has a generally V-shaped bottom portion in cross section and an outwardly sloped top surface to minimize wave resistance. Advantageously, the lower part of the floating platform is provided with an annular anti-roll bow.

According to yet another characteristic of the installation according to the invention, the blades are blades of three-blade wind turbines HAWT type and are each associated with an angle of attack adjustment device thus allowing to benefit from the technical maturity and low cost of HAWT wind turbine blades and their angle of attack adjustment systems. It will be noted that the fixed structure in which said stator is arranged can be mounted on an anchoring device, the anchoring system comprising, for example, an assembly of at least one rigid or flexible link, a weighting device or floatation acting on the links and a set of chains extending from the weighting or flotation device and provided with end anchors. The fixed structure supporting the stator can be submerged and have an adjustable flotation on command. The installation according to the invention may comprise means for storing the kinetic energy generated during the rotation of the platform. The energy storage means may comprise a set of weights displaceable along the arms, including the holding arms and be connected to one or more counterweights by one or more pulleys. It may also provide a set of ballast boxes, for example inside the float, intended to be filled with water during the rotation of the platform under the effect of centrifugal force or a pumping system.

According to a feature of the invention, the installation may include a so-called wind turbine (Savonius type, for example) and / or a motor placed on the platform and intended to cooperate with the blades mounted on the poles to provide a torque complementary at startup or at low speed. It is possible to provide a stabilizing fin placed on the fixed structure and / or a stabilizing drift placed under water, integral with the fixed structure. We can still provide wings between the platform and the top of the masts and at least one auxiliary float connected to the hub to maintain the flotation and verticality of the installation in case of complete immersion. Other objects, features and advantages of the invention will appear on reading the following description, given solely by way of nonlimiting example, and with reference to the appended drawings in which: FIGS. 1 and 2 illustrate examples of an installation for transforming the mechanical energy of wind into electrical energy according to the invention, respectively in profile and in perspective; Figure 3 is a section illustrating the shape of the floating platform of the installation of Figure 2; FIGS. 4 and 5 illustrate exemplary embodiments of an installation for transforming mechanical energy from wind into electrical energy according to another embodiment; Figure 6 is a diagram illustrating the structure of the electric power generator; Figure 7 illustrates various embodiments of a processing plant according to the invention. A first embodiment of a plant for transforming the mechanical energy of the wind into electrical energy, indicated by the general reference numeral 1, will firstly be described with reference to FIGS. 1 and 2. This installation is based on FIG. use of a wind turbine type VAWT, that is to say comprising a set of blades, such as P, mounted on a platform. The blades P are mounted on the platform 2 via a set of respective masts, such as 3 extending in the embodiment shown in Figures 1 and 2 radially externally from the platform and, so as to raise the area of attachment of the blades P on the masts 3 above the water level so as to prevent these attachment areas are subjected to the impact of waves.

The wind turbine is here provided with three blades P. It will be noted, however, that it is not beyond the scope of the invention when using a different number of blades. It can also be seen in FIGS. 1 and 2 that the wind turbine is here a floating wind turbine and is particularly intended to be installed at sea and more particularly in areas for which the depths are greater than 50 m. However, it is not beyond the scope of the invention when the installation 1 is intended to be implanted on lakes, streams or water reserves, or even on ice.

The platform 2 is in the form of a flat float, generally toroidal shape, whose horizontal dimensions are greater than the vertical dimensions. Thus, the platform 2 has a diameter much greater than its height by a coefficient that can reach and exceed 10 so as to provide good stability to the installation. The platform 2 advantageously has in the lower part an annular anti-roll bow E contributing to the stability of the platform. P blades are erected from the platform 2 and are connected thereto so that the rotation of the blades generate a consecutive rotation of the platform and, with relatively low losses, the installation using water as that lubricant. The masts 3 are held with respect to the hub 8 by means of a first set of arms 4 fixed at the two mutually opposite ends, upper and lower of the masts 3 to ensure their radial retention and to transmit the rotation to the platform and at the hub. A second set of holding arms 5 extending between the platform 2 and the upper end zone of the masts 3 ensures the maintenance of the latter and transmits the rotational movement. Finally, another set of holding arms, such as 6, are arranged so as to connect in pairs the upper ends of the masts and thus secure them together and stiffen the structure.

As indicated above, the assembly formed by the platform 2 and the blades P linked to the platform via the respective masts 3 constitutes a rotating assembly under the effect of the force of the wind. The installation also comprises one or more electric power generators 7 each comprising a rotor connected to a hub 8 from which the first set of holding arms 4 extends so as to be rotatably connected to the platform 2 and a fixed stator (not visible in Figures 1 and 2) linked to a fixed structure 9 via a shaft 10, itself associated with an anchoring system comprising a set of chains, such as 11, endowed with each of a weighting or flotation device 12 and provided with an end anchor 13, for example of the suction type. With this arrangement, the stator, linked to the mooring system comprising the shaft 10, the fixed structure 9 and the anchoring system is maintained in a fixed position relative to the terrestrial reference, independently of the movements of the swell, while the platform carrying the blades is rotated relative to the stator under the effect of wind. Thanks to the horizontal dimensions of the platform 2, significantly greater than its vertical dimension and thanks to its embodiment in a toroidal shape having a vertical axial symmetry corresponding to the axis of rotation of the blades P, a solid and robust emergent assembly is obtained. It should be noted that the diameter of the platform can typically reach 40 to 60m, while being able to reach or even exceed 100m, so as to obtain a much greater stability than the Espars technologies, semi-submersible floats and TLP technologies. As can be seen in FIG. 3, the platform 2 advantageously has a toroidal shape, the vertical section of which has a generally V-shaped lower portion 14 to minimize friction with water, or even with ice, when the platform is intended to be implanted on ice, and an upper part 15 inclined outwards to reduce the catch waves. The platform 2 advantageously has in the lower part an antiroll bow E. The height of the platform can typically reach 4 to 8m, while can exceed 10m. These dimensions make it possible to obtain a low draft. As regards the blades, it will be noted that these, thanks to their mounting on the platform via the masts 3, may be constituted by conventional blades used in particular for three-blade wind turbines type HAWT. Advantageously, it will be provided to mount each blade P on a mast 3 by means of a variable-pitch angle-of-attack adjustment device 16 in order to ensure at all times the maintenance of an optimum angle of attack for each blade relative to its apparent wind. Note that the blades can reach or exceed dimensions of the order of 75m. Thus, the installation 1 comprises, for example, in one embodiment, a float having a diameter of the order of 40 to 60m, and a height of the order of 4 to 8m, blades having a height of 1m. order of 75m, and masts with a height of about 20m. As seen in FIGS. 1 and 2, the blades P are substantially inclined outwards, in particular because of the inclination of the masts 3.

In the embodiment illustrated in FIGS. 1 and 2, it will also be noted that the masts 3 are also inclined tangentially to the perimeter of the platform 2 so that the angle between the masts and the float is reduced and thus allows a smaller arm to lever between the masts and the platform 2. In addition, the inclination of the masts modulates the wake effect of the blades relative to each other. In the embodiment illustrated in FIGS. 1 and 2, the masts 3 extend in a "cantilever" configuration, being radially inclined outwards. In the embodiment illustrated in FIGS. 4 and 5, in which elements identical to those of FIGS. 1 to 3 are designated by the same reference numerals, the masts 3 are arranged in a crossed configuration and intersect in the vicinity of the axis. vertical rotation of the platform. In this embodiment, there is the floating platform 2 of toroidal shape, the masts 3 erected from a peripheral zone of the platform 2 and the blades P fixed on the masts 3, as well as the generator or generators. electrical energy 7 each comprising a rotor connected to a hub 8 connected in rotation to the masts 3 and a stator associated with the anchoring system comprising the shaft 10, the structure 9 and the docking system comprising the chains 11, the weights or the floats 12 and the end anchors 13. According to this crossed configuration, the masts 3 are secured to each other and to the hub by a device such as a ring or a holding polygon 17 and extend upwardly, so that that the trajectory of their vertices form a circle of radius that can exceed that of the platform 2. According to this configuration, whose operation is identical to that mentioned above, the installation has a simplified structure, lightened and increased strength. Note however that in the embodiments described above with reference to FIGS. 1 to 5, the blades P can be connected to the mast 3 by means of an angle of attack adjustment device 16. Similarly, the The blades can be inclined tangentially to the perimeter of the platform 2 in order to modulate the wake effect of the blades relative to each other. It will be noted that in the embodiments described above with reference to FIGS. 1 to 5, the fixed structure 9 to which the stator is connected constitutes an immersed assembly. However, it is not beyond the scope of the invention when this fixed structure 9 has emerged. The structure of the generator 7 of the installation 1 will now be described with reference to FIG. 6. It will be noted that FIG. 6 corresponds to an installation provided with masts arranged in a cantilevered configuration. Note however that the description of the generator or generators also applies to the embodiment of Figures 4 and 5. This description also applies to embodiments in which this (these) generators is (are) emerged (s). ), either immersed (s). Similarly, the description of the generator or generators applies to embodiments in which the fixed structure 9 is either emerged or immersed.

As seen in Figure 6, the generator or generators 7 each comprise at least one rotor R, and at least one stator S incorporating a set of coils B. The rotor R incorporates a set of magnets A regularly arranged around the set of coils B.

The set of coils B is, for its part, placed at the end of the shaft 10, which is associated with two stabilizing bearings 25 and 26 guided by ball or roller bearings 27 and 28. the rotation of the rotor with respect to the stator, and in particular during the rotation of the magnets A with respect to the coils, an electric current is generated. It is advantageous to provide a conductive cable C disposed in the shaft 10, connected to the set of coils B and through the fixed structure 9 to evacuate the electrical energy produced during the rotation of the platform. It will be noted that the invention which has just been described uses a wind turbine of the VAWT type rotationally fixed to a floating platform and provided with blades traditionally used in wind turbines of the HAWT type having a dimension of the order of 75 m. This installation is capable of producing electrical energy of the order of 5 MW or more.

Note also that the embodiment in which the fixed structure is immersed under water, at a depth of the order of less than 20m, is advantageous insofar as, otherwise, the links used to connect the fixed structure the ballast or flotation device may come to hit the platform .. Note however that the invention is not limited to the embodiments that have been described. Referring to Figure 7, in which the various variants can be applied to both the "cantilever" structure and the "crossed" structure, it can be seen that it is possible to provide a stabilizing fin 30 at the top of the generator 7 and linked for example to the shaft 10 so as to avoid rotation relative to the terrestrial reference of the fixed part of the installation. This fin may be seconded or replaced by a drift underwater (not shown).

Note also that the installation can also be provided with means to provide a complementary torque helping start the installation. It will be possible, for example, to place on the rotary cylinder 8 a "Savonius" type wind turbine and / or a motor. In addition, wings can also be installed between the platform 2 and the top of the masts 3. Note also that the installation can be provided with means for storing the kinetic energy generated during the rotation of the platform under the effect of the blades P of the wind turbine. According to a first example, it will be possible to provide weighting devices, such as 32 movable along the radial arms and associated with one or more counterweights 33. Thus, during the rotation of the platform, the weighting devices are solicited by force centrifugal and tend to move away from the vertical axis of rotation. Conversely, during the slowing down or shutdown of the installation, these weights are recalled towards the central axis by the (or the) counterweight and release the corresponding kinetic energy. As shown in FIG. 7, in the "cantilever" configuration, the weighting devices are advantageously displaceable along the holding arms 4.

According to a second example, it will be possible to provide a set of compartments, such as 31, within the platform 2, these compartments 31 being intended to be filled with water during the rotation of the platform 2 in a natural way because of the centrifugal force or artificially by means of pumps, to modify the rotational moment of the platform. Thus, wind energy being by nature intermittent, it is possible to store the kinetic energy by filling the water tanks and thus increase the moment of rotation of the float to, in case of wind drop, reduce the moment rotation of the float by removing the water contained in the floats. The compartments 31 may also be filled for the purpose of ballasting, and thus stabilize the structure or to totally immerse it to protect it in the anticipation of a cyclone or a typhoon. An auxiliary float connected to the stator and sufficiently bulky to provide dynamic floatation when the wind turbine is fully submerged and a communication and control device for controlling the submerged wind turbine from the surface can be provided.

In case of the use of an odd number of blades, the compartments diametrically opposed to each blade can be ballasted to compensate for the preponderance of aerodynamic forces during the recovery of the blades facing the wind and avoid oscillations of the platform during its rotation.

Claims (19)

REVENDICATIONS1. Installation for converting the mechanical energy of the wind into electrical energy, comprising a platform (2), a set of blades (P) with vertical axis connected to the platform so as to drive the platform in rotation under the effect of wind, and at least one electric energy generator (7) comprising at least one rotor (R) connected to the rotating platform and at least one stator (S) connected to a fixed structure (9), characterized in that it comprises a set of masts (3) erected from a peripheral zone of the platform, on which the blades (P) are respectively fixed. 2. Installation according to claim 1, characterized in that the poles (3) are inclined outwardly of the platform (2) and are retained at the platform in rotation by a set of holding arms. 3. Installation according to claim 1, characterized in that the masts are inclined towards the inside of the platform in a crossed arrangement, said masts intersecting in the vicinity of the vertical axis of rotation of the platform (2), a device support (17) solidarisant the poles (3) and a hub (8) at the point of their point of intersection. 4. Installation according to any one of claims 1 to 2, characterized in that the poles (3) from which the blades extend, are inclined tangentially relative to the perimeter of the platform. 5. Installation according to any one of claims 1 to 4, characterized in that the platform is a floating platform on the water and is associated with an anchoring system (11, 12, 13) acting on the fixed structure. 6. Installation according to claim 5, characterized in that the platform is formed in the form of a flat structure whose horizontal dimensions are greater than its vertical dimension. 7. Installation according to any one of claims 1 to 6, characterized in that the platform has a toroidal shape and has a transverse cross-section a generally V-shaped lower portion and an upper surface inclined outwardly. 8. Installation according to claim 7, characterized in that the lower part of the platform comprises an annular anti-roll bow (E). 9. Installation according to any one of claims 1 to 8, characterized in that the blades are three-axis horizontal wind turbine blades and are each associated with a device (16) for adjusting the angle of attack. 10. Installation according to any one of claims 5 to 9, characterized in that the fixed structure (9) on which is disposed said stator is mounted on an anchoring device comprising a fixed structure immersed or emerged, a set of links rigid or flexible, a weighting or buoyancy device acting on the links and a set of chains extending from the weighting or flotation device and provided with end anchors. 11. Installation according to claim 10, characterized in that the fixed structure supporting the stator is immersed and has an adjustable flotation on command. 12. Installation according to any one of claims 1 to 11, characterized in that it comprises means for storing the kinetic energy generated during the rotation of the platform (2). 13. Installation according to claim 12, characterized in that the energy storage means comprise a set of weights (32) movable along the arms and connected to one or more counterweights (33). 14. Installation according to claim 12, characterized in that the platform comprises a set of ballast boxes to be filled with water during the rotation of the platform. 15. Installation according to any one of claims 1 to 14, characterized in that it comprises a so-called wind turbine and / or a motor connected to the fixed structure. 16. Installation according to any one of claims 1 to 15, characterized in that it comprises a stabilizer fin (30) placed on the fixed structure. 17. Installation according to any one of claims 1 to 16, characterized in that it comprises a stabilizing drift placed under water, integral with the fixed structure. 18. Installation according to any one of claims 1 to 17, characterized in that it comprises wings between the platform (2) and the top of the masts. 19. Installation according to any one of claims 1 to 18, characterized in that it comprises at least one auxiliary float connected to the hub (8).