FLOATING WIND TURBINE WITH CONTROLLABLE YAW POSITION

Abstract

The invention relates to a marine energy production assembly (1) comprising: anchoring means (2); a floating wind turbine (4) comprising a turbine (7) having a fixed axis of rotation (A-A) of a rotor (71) with respect to a floating structure (5) of the floating wind turbine (4), means (8) for determining the wind direction (V);

characterised in that it comprises: means (81) for detecting an orientation of the floating wind turbine (4) with respect to the wind direction (V); means (9) for detecting an inclination of the floating wind turbine (4); means (10) for controlling the inclination of the floating wind turbine (4); a computation unit (11) for transmitting an instruction to the means (10) for controlling the inclination of the floating wind turbine (4) and altering the orientation of the floating wind turbine (4) with respect to the wind direction (V).

Claims

1. Marine energy production assembly (1) comprising: anchoring means (2) for fixing to a seabed (3); a floating wind turbine (4) comprising a turbine (7) having a fixed axis of rotation (A-A) of a rotor (71) with respect to a floating structure (5) of the floating wind turbine (4), the floating wind turbine (4) being linked to the anchoring means (2) and being intended to pivot around them in such a way that the axis of rotation (A-A) of the turbine (7) is substantially parallel to a wind direction (V), means (8) for determining the wind direction (V); characterised in that it comprises: means (81) for detecting an orientation of the floating wind turbine (4) with respect to the wind direction (V); means (9) for detecting an inclination of the floating wind turbine (4) about an axis parallel to the axis of rotation (A-A) of the rotor (71) of the turbine (7); means (10) for controlling the inclination of the floating wind turbine (4); a computation unit (11) for receiving information from the means (8) for detecting the wind direction (V), means (9) for detecting the inclination of the floating wind turbine (4), and means (81) for detecting the orientation of the floating wind turbine (4) with respect to the wind direction (V), so as to transmit an instruction to the means (10) for controlling the inclination of the floating wind turbine (4) and alter the orientation of the floating wind turbine (4) with respect to the wind direction (V).

2. Assembly according to claim 1, characterised in that the means (10) for controlling the inclination comprise a ballast system having: a first reservoir (121) and a second reservoir (122), which are each fixed with respect to a floating structure (5) of the floating wind turbine (4), are fixed on either side of the axis of rotation (A-A) of the turbine (7), and are suitable for acting on the inclination of the floating wind turbine (4); pumping means (123) configured for conveying a liquid or semi-liquid weight from the first reservoir (121) to the second reservoir (122) or vice versa.

3. Assembly according to claim 1, characterised in that the means (10) for controlling the inclination comprise: a mass (13) mounted movably on a floating structure (5) of the floating wind turbine (4); means (14) for guiding the displacement of the mass (13), defining a guide path extending on either side of the axis of rotation (A-A) of the turbine (7); motor means (15) for displacing the mass (13) on the guide means (14).

4. Assembly according to claim 1, characterised in that the means (10) for controlling the inclination comprise means (16) for adjusting the torque of the turbine (7) to vary the torque of the turbine (7) as a function of an instruction from a computation unit (11).

5. Assembly according to any of the preceding claims, characterised in that the means (8) for determining the wind direction comprise a vane.

6. Assembly according to any of the preceding claims, characterised in that the vane is fixed with respect to the floating wind turbine (4).

7. Assembly according to claim 6, characterised in that the vane is fixed with respect to the anchoring means (2).

8. Assembly according to any of the preceding claims, characterised in that the means (9) for detecting the inclination of the floating wind turbine (4) comprise an inertial unit fixed with respect to the floating wind turbine (4).

9. Process for altering the orientation of a floating wind turbine (4), carried out by a marine energy production assembly (1) according to claim 1, characterised in that it comprises the steps of: determining the wind direction (V); detecting the orientation of the floating wind turbine (4) with respect to the wind direction (V); defining an instruction to alter the inclination of the floating wind turbine (4) on the basis of the wind direction (V) and the orientation of the floating wind turbine (4); acting on the inclination of the floating wind turbine (4) by way of said instruction to alter the inclination of the floating wind turbine (4).

Description

[0066] Further features and advantages of the invention will become more clearly apparent upon reading the following description of a preferred embodiment of the invention, given by way of illustrative, non-limiting example, and the accompanying drawings, in which:

[0067] FIG. 1 is a schematic side view of a marine energy production assembly according to the invention;

[0068] FIG. 2 is a schematic top view of a structure of a floating wind turbine of the marine energy production assembly according to the invention in a first embodiment;

[0069] FIG. 3 is a schematic top view of a structure of a floating wind turbine of the marine energy production assembly according to the invention in a second embodiment;

[0070] FIG. 4 is a schematic side view of a marine energy production assembly according to the invention in a variant embodiment;

[0071] FIG. 5 is a diagram showing the development of the yaw angle in different usage scenarios of the floating wind turbine of the marine energy production assembly according to the invention during a testing programme;

[0072] FIGS. 6a to 6d are schematic illustrations of the floating wind turbine of the marine energy production assembly according to the invention, during the testing programme, in a top view in FIGS. 6a and 6c and a front view in FIGS. 6b and 6d.

[0073] FIG. 1 shows a marine energy production assembly 1 according to the invention.

[0074] The energy production assembly 1 comprises: [0075] anchoring means 2 for fixing to a seabed 3; [0076] a self-orientating floating wind turbine 4.

[0077] The anchoring means 2 comprise a buoy 21 and a device 22 for anchoring the buoy 21 to the seabed 3.

[0078] The floating wind turbine 4 comprises: [0079] a floating structure 5; [0080] an aerial structure 6 mounted on the floating structure 5; [0081] a turbine 7 carried by the aerial structure 6.

[0082] The floating structure 5 comprises at least three floats 51, in the present case four floats 51.

[0083] The floats 51 are linked to one another via a lattice 52 formed of girders 521, for example metal girders 521.

[0084] The aerial structure 6 comprises four legs 61. Each leg 61 has a first end 62 fixed with respect to one of the floats 51 and a second end 63 fixed with respect to the turbine 7.

[0085] The turbine 7 comprises a rotor 71 and a nacelle 72 on which the rotor 71 is mounted in rotation about an axis of rotation A-A which is fixed with respect to the floating structure 5 of the floating wind turbine 4.

[0086] In general, the rotor 71 is formed of a central hub on which blades are mounted in rotation. The blades are mutually independent so as to be orientable in real time if necessary, in particular so as to vary the wind resistance of the rotor 71 and thus the torque of the turbine 7. For reasons of clarity, a rotor is referred to in the following rather than an assembly of a central hub and blades.

[0087] As is shown in FIG. 1, the turbine 7 is fixed to the aerial structure 6 by cooperation of the nacelle 72 with the second end 63 of the legs.

[0088] Finally, the floating wind turbine 4 is linked to the anchoring means 2 by joining means 53, and more particularly by at least one mooring.

[0089] The moorings make it possible for the floating wind turbine 4, during the operation thereof, to turn around the buoy 22 of the anchoring means 2 so as to position itself in a wind direction V (represented by arrows in FIG. 1). In the case of a single mooring, the centre of yaw rotation of the floating wind turbine 4 is the connection between the mooring and the floating wind turbine 4.

[0090] In other words, the buoy 2 forms an axis of rotation about which the floating wind turbine 4 turns to produce energy.

[0091] With respect to the floating wind turbine 4, an orthonormal coordinate system is defined so as to comprise: [0092] an X-axis parallel to the axis of rotation A-A; [0093] a Y-axis perpendicular to the X-axis and extending in a port-starboard direction of the floating wind turbine 4; [0094] a Z-axis forming a right trihedron or orthonormal coordinate system with the X- and Y-axes.

[0095] Relative to this orthonormal coordinate system, three angles of rotation are defined, namely a roll angle about the X-axis, a pitch angle about the Y-axis, and a yaw angle about the Z-axis.

[0096] During energy production, the floating wind turbine 4 is subjected to external forces which tend to destabilise and incline it.

[0097] Among these external forces, the current and the swell bring about disorientation of the floating wind turbine 4 which impairs the electrical energy productivity.

[0098] Moreover, when the wind exerts a thrust on the turbine, the wind turbine has a tendency to pitch, in other words to pivot about the Y-axis.

[0099] When the swell is aligned with the wind V, it influences the pitch of the wind turbine in an alternating, cyclical manner. This means that, with the crests and troughs of the wind, the floating wind turbine is displaced and then returns to position cyclically.

[0100] When the swell is perpendicular to the wind, the first-order forces (the most significant ones), in other words in general the main components of the forces, generate an alternating, cyclical roll.

[0101] Since the roll forces about the Y-axis average to zero at the first order (the displacement (on a crest) being cancelled by the return to position (in a trough)), they do not push the floating wind turbine 4 about the Y-axis, nor do they alter the yaw angle of the floating wind turbine 4 with respect to the wind turbine.

[0102] The second-order forces (considered in detail) potentially generate a drift force on the floating wind turbine 4, in the form of a yaw angle.

[0103] By contrast, a current about the Y axis may be harmful, especially if the current is strong. This is explained in particular by the drag generated by the current on the floating structure 5 of the floating wind turbine 4.

[0104] Specifically, the floating wind turbine 4 is then positioned off-axis, impairing the electrical energy production yield thereof.

[0105] To reduce the influence of the swell and the current on the productivity of the floating wind turbine 4, the invention aims to alter the position of the centre of effort P. The centre of effort P of the floating wind turbine 4 is defined as the barycentre of the sum of all the forces associated with the wind V which are applied to the aerial structure 6 (principally to the rotor 71).

[0106] As the centre of effort P is altered, the floating wind turbine 4 is displaced about the Y axis, and a yaw angle α1 is generated.

[0107] One of the reasons behind this mechanism is that the wind vector V passing through a centre of yaw rotation of the floating wind turbine 4 (for example the anchoring means) has to be collinear with the wind thrust force P.

[0108] This yaw angle α1 makes it possible to correct misalignment with the wind V or to create misalignment with the wind V if it is desired to orientate the slipstream of the floating wind turbine 4 in a specific direction (for example to prevent it from being directed towards another floating wind turbine 4 positioned downstream, disrupting the yield thereof).

[0109] In other words, an acceptable yaw angle α1 is intentionally created so as to prevent disturbance to the operation of an adjacent floating wind turbine 4 located downstream in the flow direction of the wind V.

[0110] Acceptable is understood to means that the yaw angle α1 created does not impair the production yield of the intentionally off-axis floating wind turbine 4.

[0111] To make it possible to correct or create the yaw angle α1, and thus to make a good production yield of the floating wind turbine 4 possible, the production assembly 1 comprises: [0112] means 8 for determining the wind direction V; [0113] means 81 for detecting an orientation of the wind turbine with respect to the wind direction; [0114] means 9 for detecting an inclination of the floating wind turbine 4; [0115] means 10 for controlling the inclination of the floating wind turbine, shown schematically in FIGS. 2 and 3; [0116] a computation unit 11 which communicates with the determination means 8, the detection means 9 and the control means 10.

[0117] The means 8 for determining the wind direction V are for example in the form of a vane, and the means for determining the orientation of the floating wind turbine 4 with respect to the wind direction V are for example in the form of a camera orientated in the direction of the wind V and intended to capture the position of a coordinate system.

[0118] By way of example, the camera is fixed with respect to the mooring means and the coordinate system is fixed with respect to the floating wind turbine 4.

[0119] The means 8 for determining the wind direction V may be mounted on the floating wind turbine 4, as shown in FIG. 1, or on the mooring means 2 and more particularly on the buoy 21, as shown in FIG. 4.

[0120] The means 9 for detecting the inclination of the floating wind turbine 4 are for example in the form of a compass or accelerometer, and are positioned on the floating wind turbine 4. Preferably, the means 9 for detecting the inclination of the floating wind turbine are in the form of an inertial unit.

[0121] The computation unit 11 is intended to acquire information from the means 8 for determining the wind direction and the means 9 for detecting the inclination of the floating wind turbine 4, so as to transmit an instruction to the means 10 for controlling the inclination of the floating wind turbine 4.

[0122] In a first embodiment, shown in FIG. 2, the means 10 for controlling the inclination of the floating wind turbine 4 comprise a ballast system 12 having: [0123] a first reservoir 121 and a second reservoir 122; [0124] pumping means 123.

[0125] More specifically, the first reservoir 121 and the second reservoir 122 are each fixed with respect to the structure 5 of the floating wind turbine 4 and are arranged either side of the axis of rotation A-A of the turbine 7.

[0126] When one of the first reservoir 121 and the second reservoir 122 is filled with a larger amount than the other, it can act on the inclination of the floating wind turbine 4 and in particular on the roll angle, in other words pivoting the floating wind turbine 4 about the Y-axis.

[0127] By contrast, when no force is acting to alter the inclination of the wind turbine 4, the first reservoir 121 and the second reservoir 122 may each be filled or else each be emptied. Each reservoir thus has the same mass as the other, in such a way that the floating wind turbine 4 is stabilised automatically.

[0128] The pumping means 123 are configured for conveying a liquid or semi-liquid weight from the first reservoir 121 to the second reservoir 122 or vice versa.

[0129] Preferably, the weight is water pumped directly from the sea by the pumping means 123. The pumping means 123 are further configured to make it possible to discard the water contained in each of the first reservoir 121 and the second reservoir 122 so as to make it possible to empty them completely.

[0130] In addition, the pumping means are controlled by the computation unit 11 as described below.

[0131] In a second embodiment, shown in FIG. 3, the means 10 for controlling the inclination of the floating wind turbine 4 comprise: [0132] a mass 13; [0133] means 14 for guiding the displacement of the mass 13; [0134] motor means 15.

[0135] The mass 13 is mounted movably on the structure 5 of the floating wind turbine 4.

[0136] More specifically, the mass 13 is mounted movably on the means 14 for guiding the displacement of the mass 13, which are in turn fixed with respect to the structure 5 of the floating wind turbine.

[0137] The guide means 14 define a guide path extending on either side of the axis of rotation A-A of the turbine 7.

[0138] In a first embodiment, the guide means 14 take the form of a straight rail 141 extending substantially perpendicular to the axis of rotation A-A of the turbine 7. The mass 13 can therefore be displaced on this straight rail 141 so as to go from left (port) to right (starboard) or vice versa.

[0139] In a second embodiment, the guide means 14 are in the form of a circular rail 142, the central point of which is located on a vertical axis passing through a centre of gravity of the structure 5 of the floating wind turbine 4, in such a way that, in the absence of the mass 13, the circular rail 142 does not by itself influence the inclination of the floating wind turbine 4.

[0140] The mass 13 can therefore be displaced on this circular rail 142 to go from left (port) to right (starboard) or vice versa.

[0141] To make it possible for the mass 13 to be displaced on the guide means 14, the motor means 15, for example a motor coupled to one or more wheels, are mounted fixed with respect to the mass 13.

[0142] Each wheel of the motor means 15 is thus intended to cooperate with the guide means 14 by friction or by meshing, for example. In the case of cooperation by meshing, each wheel of the motor means 15 is a toothed wheel, and the guide means 14 comprise either a toothed line (for the straight rail 141) or a toothed crown (for the circular rail 142).

[0143] When the motor means 15 are actuated, they provide the displacement of the mass 13 along the guide means 14.

[0144] The motor means 15 are controlled by the calculation unit 11 so as to be actuated.

[0145] In a third embodiment, shown in FIGS. 1 and 4, the means 10 for controlling the inclination comprise means 16 for adjusting the torque of the turbine 7.

[0146] More specifically, the means 16 for adjusting the torque of the turbine 7 are positioned in the nacelle 72 of the turbine 7, and act, for example via a transmission, on the rotational speed of the rotor 71, so as to vary the torque of the turbine 7 as a function of an instruction from the computation unit 11.

[0147] During operation, the calculator 11 receives information from means 8 for determining the wind direction and means 9 for detecting the inclination of the floating wind turbine 4, so as to combine said information and determine an instruction for controlling the inclination of the floating wind turbine 4.

[0148] The calculation unit 11 then transmits the control signal to the control means 10 using ad hoc means, the control means then acting directly on the inclination of the floating wind turbine by: [0149] filling or emptying one or both of the first reservoir 121 and second reservoir (FIG. 2); [0150] displacing the mass 13 on the guide means 14 (FIG. 3), and/or [0151] adjusting the torque of the turbine 7 (FIG. 4).

[0152] Although this is not shown in the drawings, the floating wind turbine 4 could comprise a plurality of different control means 10. Specifically, it is possible to combine at least two, or even all three, of the above-mentioned embodiments.

[0153] For example, the floating wind turbine 4 could comprise first control means 10 in the form of ballasts (FIG. 2) and/or second control means 10 in the form of displacement of a mass (13) on the floating structure 5 (FIG. 3) and/or third control means 10 in the form of means 16 for adjusting the motor torque (FIG. 4).

[0154] Referring to FIG. 5, experimental tests were carried out where the exploitation conditions of the wind turbine represent a rare situation which obstructs the operation of the floating wind turbine, for example a swell during a storm.

[0155] These tests aim in particular to study the behaviour of the floating wind turbine 4 when the roll angle (rotation of the floating wind turbine 4 about the X-axis in FIGS. 1 to 4) is altered.

[0156] The behaviour of the floating wind turbine 4 is shown schematically in FIGS. 6a to 6d.

[0157] In FIGS. 6a and 6c the floating wind turbine 4 is schematically represented by a straight line extending between a point A and a point B, and in FIGS. 6b and 6d the floating wind turbine 4 is in a front view. The point C in FIGS. 6a and 6c represents the centre of rotation of the floating wind turbine 4.

[0158] In FIG. 6a, the floating wind turbine 4 is sketched in an optimum operating configuration; in other words, no storm or current is being applied to the floating wind turbine 4. Thus, the vector of the wind direction V and the wind thrust P are aligned, and no yaw angle is generated.

[0159] For each test, represented by one of the lines C1 to C3 on the graph of FIG. 5, the development conditions of the floating wind turbine 4 are the same, namely with a very significant storm (a scenario not representative of general normal production conditions) being produced at 90° to the wind direction V.

[0160] Line C1 shows that in these conditions, without control of the roll angle α2, the floating wind turbine 4 has a yaw angle of approximately 30°. The floating wind turbine 4 is thus substantially parallel to the surface of the water (meaning that the segment AB is horizontal in FIG. 6b).

[0161] In these development conditions, the wind direction V and the wind thrust P are no longer aligned.

[0162] By modifying the centre of effort P using the control means 10, the floating wind turbine 4 is displaced about the Y-axis and the yaw angle α1 is generated (FIG. 6c).

[0163] One of the reasons for this mechanism is as follows: the vector of the wind direction V passing through a centre of yaw rotation of the floating wind turbine 4 (for example the anchoring means) has to be collinear with the wind thrust force P.

[0164] This intentionally created yaw angle α1 thus makes it possible to correct the misalignment with the wind V, increasing the production yield of the floating wind turbine 4.

[0165] Line C2 represents the floating wind turbine 4 in these same conditions except that a weight is added at point A of the floating structure 4 by the control means 10 (the addition of weight being sketched in FIG. 6d). It is then found that the yaw angle α1 is between 5° and 10°.

[0166] Finally, line C3 shows the floating wind turbine 4 still in the same conditions except that a weight twice as great as for line C2 is added at point 1 of the floating structure 4. It is then found that the yaw angle is between 0° and 5°.

[0167] These tests thus make it possible to verify that the yaw angle α1 can be controlled by one of the means 10 for controlling the inclination of the floating wind turbine 4 which were described above, these control means 10 thus influencing the roll angle α2 of the floating wind turbine 4.