FR2960266A1 - Vertical-axis marine turbine for generating electricity, has flexible bearing structure bearing vertical-axis turbine units and comprising cable including strands interlaced with each other to resist torsional stress - Google Patents

Abstract

The marine turbine (1) has a flexible bearing structure bearing vertical-axis turbine units (20-23) e.g. Achard turbine units. The bearing structure has a cable comprising strands interlaced with each other to resist torsional stress. The bearing structure is made of a material chosen from steel, aramid fibers such as poly para-phenylene terephthalamide, and polyamide such as polyamide-11. Ballast is provided at an end of the bearing structure to maintain the bearing structure. The bearing structure is connected to an alternator whose stator is connected to an electric cable (60).

Description

i

HYDROLIENNE WITH A FLEXIBLE CARRIER STRUCTURE

The present invention relates to the field of tidal turbines.

Horizontal axis tidal turbines are known. A tidal turbine 101 with horizontal axis is for example shown in Figure 1. This tidal 101 is formed of a rigid carrier structure 110, 111 on which are mounted turbines 120, 121 horizontal axis. Each turbine 120, 121 is associated with an alternator 128, 129 arranged along the rigid axis of the corresponding turbine. The tidal turbine 101 shown in FIG. 1 is a coastal tidal turbine, a part of which the carrying structure leaves out of the water 15 for its description with respect to floating craft likely to sail in the vicinity. There are also other types of horizontal axis tidal turbines whose design differs depending on whether they are intended to be installed in the mouth of a river or on the high seas. Vertical tidal turbines are also known. A tidal turbine 101 with a vertical axis is for example shown in Figure 2. It is the tidal turbine project HARVEST. This tidal turbine 101 is formed mainly of a rigid carrier structure 110 comprising a stack of several turbines 120, 121, ..., 12n, in this case Achard turbines. The carrier structure 110 is external to the turbines 120, 121. These turbines 120, 121 are integral with the same axis 12 of vertical rotation, rigid. As a result, the electricity generation can be carried out, for all the turbines, with a single alternator located at one of the ends of the carrier structure 110. This is not possible with a horizontal axis tidal turbine. .

Furthermore, the vertical axis turbine developed in the HARVEST project is flexible, the carrier structure 110 being made in sections. Each section can in particular be associated with a turbine.

Thus, with the same design, it is possible to adapt to the different water levels encountered, as the case may be, in the coastal zone, in the mouth of a river or on the high seas. Unfortunately, horizontal axis tidal turbines or existing vertical axis, rigid, may be subjected to high forces related to marine currents. These efforts can lead to the rupture of the supporting structure. An object of the invention is to limit this risk of rupture. Another object of the invention is both to limit this risk of rupture and to maintain a good energy conversion efficiency. To achieve at least one of these objectives, the invention provides a tidal turbine comprising a carrier structure for at least one turbine, characterized in that the carrier structure is flexible. The tidal turbine according to the invention may provide other technical features of the invention, taken alone or in combination: the carrier structure forms the axis of rotation of the at least one turbine; the supporting structure is formed of at least one cable comprising several strands braided together in order to withstand torsional forces; - The carrier structure is made from at least one of the following materials: steel, aramid fibers such as poly-para-phenylene terephthalamide or polyamide such as polyamide-11; - It provides a ballast at one end of the supporting structure; It comprises at least one means for generating a traction force along the axis of the supporting structure;

said at least one means comprises a buoy integral with the support structure, at the upper end of said structure; said at least one means for generating a traction force along the axis of the supporting structure comprises at least one buoyancy means mounted on said at least one turbine; said at least one turbine has a variable diameter to generate a tensile force along the axis of the carrier structure; the blades of said at least one turbine are arranged so that a current transverse to the axis of the carrier structure generates a traction force along the axis of said structure; the carrier structure is connected to an alternator inserted in a housing at the base of said structure. The invention also proposes an assembly comprising a platform located out of the water and a tidal turbine according to the invention, in which the carrying structure of the tidal turbine is connected, at a first end, to an alternator situated on the platform, and is secured, at a second end, to a weight intended to maintain said vertical structure. Other features, objects and advantages of the invention will be set forth in the following detailed description, with reference to the appended figures: FIG. 3 shows a vertical axis turbine according to the invention, in operation; FIG. 4 shows a vertical axis tidal turbine according to the invention, folded, before its installation on site; 5 shows another vertical axis turbine according to the invention, in operation. The following description is mainly made with reference to FIG. 3. In this FIG. 3, the tidal turbine 1 is used as a vertical axis hydrotreater. We will see below that the tidal turbine 1 can also be used as a horizontal axis hydrotreater.

The tidal turbine 1 according to the invention comprises a carrier structure 10 for at least one turbine 20 with a vertical axis. Preferably, and as shown in FIG. 3, several turbines 20, 21, 22, 23 with a vertical axis are arranged along the carrier structure 10. In this figure, the turbines represented are "Achard" type turbines, but other types of turbines can be used such as Darrieus or Gorlov turbines. The supporting structure 10 is flexible. It can therefore deform and incline relative to the vertical under the effect of marine currents. FIG. 3 shows the bearing structure 10 inclined at an angle α with respect to the vertical axis 13 passing through the base of the supporting structure. The turbines 20, 21, 22, 23 are mounted on the carrier structure 10 so that the latter forms the axis of rotation of the turbines 20, 21, 22, 23, this axis of rotation being connected to an alternator to generate a current electric. For this purpose, the carrier structure 10 is preferably a cable capable of withstanding torsional forces about its axis when it is rotated by the turbines. In this case, the turbines 20, 21, 22, 23 may be equipped with a deformable mechanical system capable of gripping the cable 10 and thus make a frictional fitting connection. One could also imagine that fixing points, for example of the shackle type, are arranged on the cable 10, to which the turbines can be secured. Several types of cables can be envisaged. Preferably, a cable 10 is used with several strands braided together. The cable 10 may be made from at least one of the following materials: steel, aramid fibers such as poly-para-phenylene terephthalamide or polyamide such as polyamide-11.

For example, for a tidal turbine of 50kW rotating at 3tr / s, it is possible to envisage a steel cable with a diameter of 40 mm, formed of several braided strands between them. The braided strands between them make it possible to limit the twisting forces around the axis of the cable, the torsional torque being in this case of the order of 2500 N.m. It should be noted that the cable could be of variable diameter along its axis. The steel in question may be a stainless steel, galvanized or steels wrapped in a waterproof sheath. Preferably, the cable 10 forming carrier structure will be continuous over its entire height. In this case, all the turbines 20, 21, 22, 23 are mounted on the same cable 10. The rotation of each turbine then creates a torque that is added to the other pairs created by the other turbines mounted on the cable. The torque transmitted to the cable 10 therefore corresponds to the sum of the torques generated by each turbine. This design is advantageous because it avoids the torque generated by a turbine being transmitted to the other turbines. Indeed, with a continuous cable, the torque produced by each turbine passes only through the cable 10 forming the carrier structure. Alternatively, it is conceivable to provide several cables, each cable connecting at least two turbines. Thus, if the tidal turbine 1 has n turbines, it is possible to envisage up to n + 1 cables. In this case, a turbine makes it possible to mechanically connect two cables. The torque generated by a turbine is then transmitted to the other turbines which make it possible to connect two cables together. Therefore, it is then necessary to size each turbine so that it provides sufficient mechanical resistance to withstand the currents, but also the torques transmitted by the other turbines. The turbines will usually be made of steel. However, if the installation area of the tidal turbine 1 is subjected to low currents, it can be provided to make them plastic.

When the tidal turbine 1 is subjected to a current transverse to the axis of the cable 10 forming a carrier structure, the cable 10 bends. This bending is necessary to limit the risk of rupture of the tidal turbine 1. However, excessive bending of the cable 10 is detrimental to the efficiency of the turbines and therefore the tidal turbine 1. To limit this phenomenon of loss of efficiency, it is therefore sought to limit the bending of the cable 10, that is to say to reduce the angle but without making it zero. For this purpose, the tidal turbine 1 comprises means for exerting a tensile force along the axis of the cable, from bottom to top. The function exercised by this means can be obtained in different ways. The simplest is to implement a buoy 50 secured to the upper end of the cable 10. 15 This buoy 50 can be rigidly mounted relative to the cable 10. In this case, it is rotated with the cable 10 when the turbines 20, 21, 22, 23 rotate. To limit the drag forces of the buoy 50, and therefore losses on the cable, it is preferable to choose a buoy 50 having a shape of revolution, for example a spherical shape. This buoy 50 is generally installed under the surface of the water. In this case, the tidal turbine 1 is entirely located under the surface of the water, at a distance from the upper surface to the draft of any vessel likely to sail over the tidal turbine 1. As a variant, the buoy 50 could be mounted on the cable 10 in a pivot connection or ball joint. Alternatively, or in addition, the blades of at least one turbine 20 may be arranged so that a current transverse to the axis of the cable 10 generates a vertical tensile force from bottom to top. For this, one solution is to provide a turbine 20 having, in its upper part, a larger diameter than in its lower part. The lower part of a turbine 20 is the one that is closest to the seabed.

Another solution is to provide a suitable hydrodynamic profile of the turbine blades 20. This solution is mastered by the skilled person and is therefore not described in more detail.

Alternatively, or in addition, the turbines 20, 21, 22, 23 of the tidal turbine 1 may comprise a buoyancy means, for example a buoy.

As mentioned previously, when the turbines 20,

to 21, 22, 23 turn under the effect of the current, they drive the cable 10 on which they are mounted. The cable 10 is thus rotated about its axis. For this purpose, it is understood that the blades of each turbine are oriented to rotate all in the same direction.

Whatever the variants envisaged, we understand

15 that the tidal turbine 1 is subjected to a drag force from the current flowing around its various elements, and a vertical traction force to counteract the drag force to maintain the tidal turbine in a vertical position.

Thus, if we consider N turbines each generating a vertical tensile force L ,,, a buoy 50 generating a vertical traction force FZ and neglecting the drag force of the cable 10 relative to those of the N turbines, each turbine i is inclined at an angle α; with respect to the vertical, such that:

tan (ai) = Fy (1) where: Fyi = Efyk with fy, k the drag force to which the turbine k is subjected, and k = i N FZ i = FZ + 1 fz k is the traction force cumulative buoy 50 (Fi) and k = i

all the turbines located above the turbine i.

It should be noted that if the angle a; is low, then tan (a,) ai and if ff, i = 0 for each turbine i (for example due to an absence of buoy at each turbine) then the angle represented in FIG. 3 is such that N that. a = E a; k = 1 As previously stated, the vertical traction force resulting from the buoy 50, and / or, as the case may be, the turbines themselves and / or the buoyancy means associated with these turbines must not be too great by compared to trail efforts. Indeed, if this were the case, the flexibility of the cable 10 would have only limited utility, since the latter

lo would always be held vertically.

The dimensioning of the cable 10 must therefore take into account the number and nature of the turbines, as the site of implantation of the tidal turbine. As such, the simplest variant of the invention remains that of the buoy 50 as the only element generating a vertical traction force.

Indeed, if, once installed, the tidal turbine 1 is too flexible (yield loss) or, on the contrary, not enough (increased risk of rupture), it is easy to change the buoy.

The alternator (not shown) is inserted in a housing 40 located at the base of the cable 10. The rotation of the cable 10 thus drives the rotor of

The alternator, whose stator is connected, at the output, to an electric cable 60 connected to an electrical network.

It is therefore understandable to use a cable 10 capable of withstanding the torsional torque imparted by the turbines.

Housing 40 also includes a ballast (no

25 shown), intended to maintain the tidal turbine 1 on the seabed, without possible displacement.

To this end, the skilled person will understand that the ballast must have a mass to prevent the rise of the tidal turbine on the surface of the water and, at the same time, sized to prevent any

30 slip on the seabed.

The sizing of the ballast is therefore done on a case by case basis. It is necessary to take into account the mass of the tidal turbine and the force of Archimedes which will be exerted on the tidal turbine. It is also necessary to take into account the location of the tidal turbine and more precisely, the force of the currents that exert a drag force on the housing and the nature of the seabed, which exerts a resistance force to the drag force. . The ballast solution is particularly interesting because it allows easy recovery of the housing 40, for example by a robot that grasp the housing to go up to the surface. This facilitates maintenance operations because there is no anchoring means to remove from the bottom soil. Alternatively, or in addition, it would however be possible to provide means for mechanical anchoring of the housing on the seabed. For example, we can plant piles in the soil of the seabed 15 connected by cables to the housing 40. Alternatively, or in addition, it is also possible to provide suction means creating a suction effect on the housing 40. Carrier structure 10, which will generally be a cable, is therefore a central element of the invention. Indeed, this structure is flexible so that the tidal turbine 1 adapts to the currents to which it is subjected, without breaking. In addition, the carrier structure 10 is able to withstand a torque to transmit a rotational movement generated by the turbines, to an alternator. The buoy 50, and / or any other means described above having the same function, then has the main purpose of adapting the intrinsic flexibility of the cable to the particular conditions encountered at the installation site of the tidal turbine 1 to obtain a good compromise between the flexibility of the tidal turbine as a whole and its performance. Due to the flexibility of the cable 10 forming the carrier structure of the turbines, the turbine 1 according to the invention can be folded. This is very advantageous because, suddenly, it takes up little space on a boat intended for its installation. FIG. 4 represents a tidal turbine according to the invention, folded. Moreover, the actual installation of the tidal turbine 1 5 is very easy. It can be done as follows. A tool provided on the installation boat of the tidal turbine seizes the housing 40 weighted, the position on the surface of the water and down into the water under its own weight until the part of 10 cable connecting the ballasted housing to the first turbine is stretched. A second tool, of the same nature as the first, then grasps the portion of cable located between the first turbine and the next turbine. The second tool then positions the first turbine on the surface of the water and down into the water until the cable portion connecting the first turbine to the next turbine is stretched. The first tool then loose the ballast. This is the second tool that ensures the maintenance of the tidal turbine. The first tool being free, it then performs the same operations as the second tooling for the next turbine and so on until the tidal turbine is fully immersed. The descent into the water is carried out turbine by turbine using two tools that take turns to lower the tidal turbine into the water, one of the tools now still tidal turbine. The tidal turbine 1 may be the subject of other variants described below. According to one variant, it is conceivable for the vertical axis turbine 1 to be attached to a fixed surface installation 30, namely a platform such as an oil platform. Such a tidal turbine 1 is shown in FIG. 5, with "Achard -" type turbines.

In this case, it is conceivable that the tidal turbine 1 is no longer fully disposed under the surface of the water. The cable 10 forming the carrier structure of the turbines 20, 21, 22, 23 is then connected, by its upper part, to an alternator located on the platform. It is therefore understood that the tidal turbine 1 is attached to the platform. A ballast 70 can always be provided in the lower part of the cable 10, floating in the water. The main function of the ballast is then to participate in the maintenance of the tidal turbine 1 in a position as vertical as possible, for the reasons already mentioned above. The ballast is then driven by the rotation of the cable 10 about its axis. In this case, the invention relates to an assembly comprising a platform located out of the water and a tidal turbine 1 according to the invention, in which the cable 10 of the tidal turbine 1 is connected, by a first end, to a alternator located on the platform, and is secured by a second end to a ballast for holding the cable 10 in a vertical position. According to another variant, particularly useful when the water level is insufficient, it is possible to install the tidal turbine 1 according to the invention horizontally. A low water level is particularly encountered in a river mouth. The tidal turbine 1 is thus a horizontal axis turbine, in which the turbines are also horizontal axis. According to this variant, no buoy is provided because they 25 would not allow to exert a tensile force along the axis of the cable, that is to say here, horizontally. On the other hand, it is always possible to plan the turbine so that it generates a traction force along the axis of the cable. This, however, is of limited value because, in order to maintain the tidal turbine on the bottom, each end of the cable is anchored in the ground with mechanical moorings such as piles.

Indeed, the distance between the mechanical moorings then makes it possible to adjust the tension of the cable so that it retains a certain flexibility. 25

Claims (12)

CLAIMS, 1. Hydrolienne (1) comprising a carrier structure (10) for at least one turbine (20, 21, 22, 23), characterized in that the carrier structure (10) is flexible. 2. Hydrolienne (1) according to claim 1, wherein the carrier structure (10) forms the axis of rotation of said at least one turbine (20, 21, 22, 23). 3. Hydrolienne (1) according to one of the preceding claims, wherein the carrier structure (10) is formed of at least one cable comprising several strands braided together to resist torsional forces. 4. Hydrolienne (1) according to one of the preceding claims, wherein the carrier structure (10) is made from at least one of the following materials: steel, aramid fibers such as poly-para-phenylene terephthalamide or polyamide such as polyamide-11. 5. Hydrolienne (1) according to one of the preceding claims, wherein there is provided a ballast at one end of the carrier structure (10). 6. Hydrolienne (1) according to one of the preceding claims, comprising at least one means for generating a tensile force along the axis of the carrier structure. 30 7. Hydrolienne (1) according to the preceding claim, wherein said at least one means comprises a buoy (50) integral with the carrier structure (10), at the upper end of said structure (10). 8. Hydrothermal (1) according to one of claims 6 or 7, wherein said at least one means for generating a tensile force along the axis of the carrier structure (10) comprises at least one buoyancy means mounted on said at least one turbine (20, 21, 22, 23, 24). 9. Hydrolic (1) according to one of claims 6 to 8, wherein said at least one turbine (20, 21, 22, 23) has a variable diameter to generate a tensile force along the axis of the carrier structure . 10.Hydrolienne (1) according to one of claims 6 to 9, wherein the blades of said at least one turbine (20, 21, 22, 23) are arranged so that a current transverse to the axis of the carrier structure (10) generates a tensile force along the axis of said structure. 11.Hydrolienne (1) according to one of the preceding claims, wherein the carrier structure (10) is connected to an alternator inserted into a housing (40) located at the base of said structure. 12. An assembly comprising a platform located out of the water and a tidal turbine (1) according to one of claims 1 to 6, wherein the carrier structure (10) of the tidal turbine (1) is connected, by a first end, to an alternator located on the platform, and is secured by a second end, a ballast (70) for maintaining said structure (10) vertical. 30