VERTICAL AXIS WIND WIND

Abstract

The present invention relates to a wind turbine (1) comprising a base (2), a shaft (3) extending along a vertical axis (A) and rotating about said vertical axis (A) relative to the base (2), a rotor (4) fixed to the shaft (3) comprising at least two arms (5, 6) each extending along a respective horizontal arm axis (B1, B2) and at least one blade (11, 12) mounted at the end of each arm (5, 6), characterized in that it further comprises at least one propeller (7-10) mounted on each arm (5, 6) and capable of rotating about a horizontal propeller axis (P1, P2), via a one-way bearing, and in that each one-way bearing allows the rotation of the associated propeller (7-10) when the wind (W) blows from the rear or the front of this propeller (7-10), but prevents the rotation of this same propeller (7, 10) when the Wind blows from the opposite direction. Abbreviated figure: Figure 5.

Description

Title of the invention: WIND TURBINE WITH VERTICAL AXIS FIELD OF THE INVENTION

[0001] The present invention relates to a vertical axis wind turbine. PREVIOUS ART

[0002] It is known to produce electricity from the force of the wind by means of a wind turbine. Said wind turbine can rotate relative to a fixed base, containing a generator. Depending on the orientation of the axis of rotation, two types of wind turbines can be distinguished.

[0003] Most wind turbines developed in recent decades are horizontal axis wind turbines (HAWTs) with a growing trend towards gigantism. This trend leads to a centralized energy production model with very high operating costs, visual and noise pollution, bird casualties and inefficient land use due to strict safety regulations. For all these reasons, HAWTs are not very popular and will never find their place in urban areas.

[0004] Vertical axis wind turbines (VAWTs) are an attractive alternative because they can produce more power with less space, are safe for birds, much quieter, and have lower operating costs because critical components are located at ground level, making them easier to maintain. The compactness of VAWTs makes them better suited to urban environments and local energy production and management—i.e., microgrids or local power grids.

[0005] VAWTs also have very interesting characteristics for floating offshore wind farms. This rapidly expanding market makes it possible to exploit previously inaccessible offshore wind resources, with much higher wind quality offering very high energy production potential. Here, VAWTs make it possible to significantly reduce operating costs compared to HAWTs, on the one hand for the installation and maintenance of the stability of the wind turbines, and on the other hand for the accessibility of critical components on the surface and not at the top of a 200 to 300 m high tower.

[0006] Yet, the vertical axis wind turbine industry has been plagued to date by historical malfunctions of high-power Darrieus turbines, which have proven difficult to implement on a large scale. As a result, improvements to the design of the most popular VAWTs, namely the H-type Darrieus models, are welcome in order to increase their profitability and their power density for a given footprint.

[0007] On the other hand, the phenomenon of "wind milling" is well known in aeronautics as the ability of a propeller to be passively rotated by an air flow, the kinetic energy of the rotation of the propeller being able in turn to be transmitted to a mechanical device, the engine in the case of an aircraft. SUMMARY OF THE INVENTION

[0008] The inventor has now developed a power generation system based on a VAWT wind turbine, which uses propellers to exploit the "wind milling" phenomenon in order to amplify the rotational movement of the wind turbine and therefore increase its power. This alternative system also benefits from a self-starting capacity and a very simple structure.

[0009] The invention relates to a wind turbine comprising a base, a shaft extending along a vertical axis and rotatable about said vertical axis relative to the base, a rotor fixed to the shaft comprising at least two branches each extending along a respective horizontal branch axis and at least one blade mounted at the end of each branch, characterized in that it further comprises at least one propeller mounted on each branch and rotatable about a horizontal propeller axis via a unidirectional bearing, and in that each unidirectional bearing allows the rotation of the associated propeller when the wind blows from the rear or the front of this propeller and prevents the rotation of this same propeller when the wind blows from the opposite direction.

[0010] Particular characteristics or embodiments, usable alone or in combination, are:

[0011] - the rotor is axisymmetric, the propellers are mounted axisymmetrically, likewise that the blades are mounted axisymmetrically,

[0012] - a propeller has an angle of attack between 15 and 75°, preferably between 30 and 60° and preferably around 45°,

[0013] - the propellers are mounted in countercyclic pairs: a pair of propellers comprises a primary propeller rotatable by means of a unidirectional primary bearing and a secondary propeller, sharing the same horizontal propeller axis, said secondary propeller rotatable in the opposite direction, by means of a unidirectional secondary bearing,

[0014] - all primary bearings are identical, all primary propellers are identical, all secondary bearings are identical and all secondary propellers are identical,

[0015] - the secondary propellers are smaller than the primary propellers,

[0016] - the secondary propellers are driven by motors,

[0017] - the angles between a horizontal branch axis and a horizontal helix axis cor respondent are equal,

[0018] - each horizontal helix axis is generally perpendicular to the branch axis corresponding horizontal,

[0019] - the axisymmetric rotor is a DARRIEUS rotor of type H, comprising a blade identical, mounted axisymmetrically at the end of each branch and in which the propellers are mounted axisymmetrically on blades and / or on branches,

[0020] - the propellers are mounted on the trailing edge of the blades,

[0021] - the number of branches is between 2 and 8. DESCRIPTION OF FIGURES

[0022] The invention will be better understood on reading the following description, which is purely illustrative and with reference to the appended figures in which:

[0023] [Fig.l] represents, in a schematic front view but without the blades at the end of the horizontal branches, a first embodiment, in the start-up phase, illustrating a charging cycle,

[0024] [Fig.2] shows, in a schematic front view, the embodiment of the [Fig.l] without the blades at the end of the horizontal branches, in the operating phase, illustrating an alternating cycle of charge and discharge,

[0025] [Fig.3] shows, in perspective, a Darrieus or H rotor, with two blades,

[0026] [Fig.4] shows, in top view, the embodiment of [Fig.3],

[0027] [Fig.5] shows, in top view, another embodiment with primary propellers,

[0028] [Fig.6] shows, in top view, another embodiment, with propellers primary and smaller secondary propellers,

[0029] [Fig.7] shows, in front view, another embodiment, with multiple propellers arranged on blades and / or on branches. DETAILED DESCRIPTION OF THE INVENTION

[0030] With reference to [Fig.l], the invention relates to a wind turbine 1. Said wind turbine 1 comprises a base 2. Said base 2 is generally fixed and attached to the ground or to a roof. The wind turbine 1 further comprises a shaft 3. Said shaft 3 extends along a vertical axis A. The wind turbine 1 thus belongs to the family of Vertical Axis Wind Turbines (VAWT). Said shaft 3 is rotatable about said vertical axis A relative to the base 2.

[0031] The wind turbine 1 further comprises a rotor 4. This rotor 4 is preferably axisymmetric. Throughout the present invention, the axisymmetry is with respect to the axis A. The rotor 4 is fixed to the shaft 3. The rotor 4 comprises at least two branches 5, 6. The rotor 4 may comprise more than two branches 5, 6. The branches 5, 6 are preferably arranged axisymmetrically, i.e. 2 branches at 180°, 3 branches at 120°, 4 branches at 90°, 5 branches at 72°, etc. Each of said branches 5, 6 extends along a respective horizontal branch axis B1, B2.

[0032] The wind turbine 1 further comprises at least two propellers 7 to 10. Said propellers 7 to 10 are preferably arranged axisymmetrically with respect to the axis A, mounted on each branch 5, 6. Due to the axisymmetric symmetry characteristic, the number of propellers 7 to 10 is a multiple of the number of branches 5, 6, with the same number of propellers 7 to 10 on each branch 5, 6. A propeller 7 to 10 can rotate about a respective horizontal propeller axis PI, P2, by means of a one-way bearing. The one-way bearing is such that the associated propeller can rotate when the wind blows from behind the propeller and it prohibits rotation of the propeller when the wind blows from in front of the propeller.

[0033] For example, [Fig.l] shows a rotor 4 with two branches 5, 6, each branch 5, 6 carrying a single propeller 7, 8. The wind W blows from the back of an observer. The first propeller 7 (receiving the wind W from behind) can rotate (here clockwise) around its axis PL. On the contrary, the second propeller 8 (receiving the wind W from the front) cannot rotate, because it is blocked by its unidirectional bearing. Thus arranged, the wind turbine 1 can rotate (here counterclockwise) around its axis A when a wind W blows from any direction.

[0034] Such an arrangement alleviates the common problem of self-starting of vertical axis wind turbines (VAWT). [Fig. 3] shows a perspective view of a typical H or Darrieus type vertical axis wind turbine (VAWT), with a rotor 4 comprising two branches 5, 6 and each branch 5, 6 holding a blade 11, 12. The blades attached to the end of each branch may, depending on the type of vertical axis wind turbine, be curved, straight, helical or even hyperboloidal.

[0035] As illustrated in [Fig.4], showing a top view of the same Darrieus VAWT, when starting from a static position, it can encounter a given angle with respect to the wind direction W, where the force applied by the wind W to the first blade 11 creates a momentum around the axis A which is exactly the opposite of the momentum created by the force applied by the wind W on the second blade 12. In this case, the two momentums oppose and cancel each other out. The rotor 4 then remains static.

[0036] On the contrary, with the wind turbine 1 of the invention, in the configuration of [Fig.l], the second propeller 8, blocked by its unidirectional bearing, offers greater resistance to the wind W than the first propeller 7, which can rotate freely, and thus offers less resistance to the wind W. Such asymmetry, created by the unidirectional bearings, guarantees that the rotor 4, even when starting from a static position, will start to rotate.

[0037] The arrangement of the invention, comprising at least two propellers 7-8, mounted axisymmetrically on the rotor 4, can be called a “kinetic battery”. Such an arrangement offers the following advantages:

[0038] As illustrated in [Fig.l], the wind turbine 1 is just starting from a static position. The W wind blows from the observer's back. As explained previously, due to the unidirectional bearings, only the first propeller 7 can be rotated by the W wind, while the W wind cannot rotate the second propeller 8.

[0039] As the first propeller 7 is rotated by the wind W, it accumulates kinetic energy. This functions as a “charge” cycle. After a 180° rotation, the rotor 4 arrives in the configuration of [Fig.2], with the first propeller 7 now on the right and the second propeller 8 now on the left. Due to its inertia, the first propeller 7 continues to rotate. However, it is now facing the wind W. The wind W will then attempt to stop the first propeller 7. As the first propeller 7 rotates against the wind W, it offers more resistance to the wind W. This results in a greater impulse for the rotation of the vertical axis. This functions as a “discharge” cycle of the kinetic energy accumulated by the first propeller 7, energy which is then transferred to the rotary motion of the rotor to increase its capacity to produce electrical energy.

[0040] At the same time, the second propeller 8, initially static, now receives the wind W from behind, and thus its unidirectional bearing now allows it to start rotating. This is its load cycle.

[0041] This occurs periodically, each propeller 7-8 alternately charging when the other is discharging and discharging when the other is charging.

[0042] According to another characteristic, a 7-10 propeller has an angle of attack of the order of 45°.

[0043] According to another characteristic, in order both to comply with the preceding 45° characteristic and to enhance the invention, a 7-10 propeller benefits from being designed according to a divided-blade rotor as defined in US patent 7,396,208.

[0044] According to another characteristic, the more inertia the propeller has, the more energy it can accumulate since the load cycle accumulates kinetic energy in the rotating propeller 7-10. Accordingly, the propellers 7 to 10 are preferably made of heavy materials in order to give them greater inertia. Thus, the propellers 7 to 10 are preferably made from a metallic material.

[0045] According to another characteristic, as shown in [Fig.6], the propellers are mounted in countercyclic pairs, each pair of propellers comprises a primary propeller 7, 8 which can rotate thanks to a unidirectional bearing and a secondary propeller 9, 10, sharing the same horizontal propeller axis PI, P2, said secondary propeller 9, 10 being able to rotate in the opposite direction, thanks to a unidirectional secondary bearing. The primary propellers 7, 8 and secondary propellers 9, 10 are mounted independently on the same horizontal propeller axis PI, P2. They have no mechanical connection between them. In order to respect the axisymmetric characteristic, all the primary propellers 7, 8 rotate in the same direction. Similarly, all the secondary propellers condaries 9, 10 rotate in the same opposite direction.

[0046] In order to rotate the secondary propellers 9, 10 in opposite directions, the secondary one-way bearing is reversed with respect to the primary one-way bearing, and the pitch of the secondary propeller 9, 10 is reversed with respect to the pitch of the primary propellers 7, 8 as well.

[0047] In order to respect the axisymmetric characteristic, all the primary unidirectional bearings are identical to each other, all the primary propellers 7, 8 are identical to each other, all the secondary unidirectional bearings are identical to each other and all the secondary propellers 9, 10 are identical to each other.

[0048] The double propeller allows for better efficiency, in the sense that it offers a better wind-catching surface. The primary propellers 7, 8 can be of any size, larger or smaller, compared to the secondary propellers 9, 10.

[0049] According to a preferred characteristic, the primary propellers 7, 8 have the size of the secondary propellers 9, 10.

[0050] According to another preferred characteristic, the secondary propellers 9, 10 are smaller than the primary propellers 7, 8. The secondary propellers 9, 10 are arranged in such a way that they first encounter the wind W from the front, before the primary propellers 7, 8. The fact that the secondary propellers 9, 10 are smaller, allows the primary propellers 7, 8 to see the wind W, despite the presence of the secondary propellers 9, 10, at least for the area not covered by the secondary propellers 9, 10.

[0051] According to another feature, the secondary propellers 9, 10 are driven by motors. Such motors require little electrical power and can be powered by photovoltaic panels or films exploiting the available surfaces of the wind turbine 1. This feature is advantageously combined with the fact that the secondary propellers 9, 10 are smaller than the primary propellers 7, 8. This feature allows the secondary propellers 9, 10 (then driven by a motor) to rotate faster than the primary propellers 7, 8, in order to further increase wind resistance. This then also increases the airflow towards the primary propellers 7, 8, so that the primary propellers 7, 8 accumulate more kinetic energy. This feature also facilitates the automatic starting of the wind turbine 1.

[0052] According to another characteristic, the unidirectional bearings are configured and mounted so as to allow rotation of a propeller 7-10 when the wind W comes from the rear of the propeller 7-10 and so as to prohibit rotation when the wind W comes from the front of the propeller 7-10. This advantageously creates an asymmetry which facilitates self-starting, whatever the initial direction of the wind W.

[0053] As shown in Figures 1 and 7, each horizontal helix axis P1, P2 is generally perpendicular to the corresponding horizontal branch axis B1, B2.

[0054] According to another characteristic, the axisymmetric rotor 4 is a Darrieus rotor of the type H, as shown in [Fig.3]. It comprises an identical blade 11, 12, mounted axisymmetrically at the end of each branch 5, 6 and propellers 7-10 mounted axisymmetrically on the blades 11, 12, as shown in Figures 5-7 and / or on the branches 5, 6, as shown in [Fig.7].

[0055] According to another characteristic, the propellers 7 to 10 can be mounted on any part of the blades 11, 12.

[0056] According to a preferred characteristic, the propellers 7 to 10 are mounted on the trailing edge of the blades 11, 12, as shown in FIGS. 5, 6.

[0057] Wind turbine 1 is most often used to drive a generator to produce electricity.

[0058] According to another characteristic, photovoltaic cells (not illustrated) can be mounted on all surfaces of the rotor 4, whether it is the blades 11, 12 and / or the branches 5, 6. This allows additional electrical production. One or the other of these two sources of electricity can be diverted at least partially to drive the possible motors of the propellers 7 to 10.

[0059] The figures represent a two-arm rotor 4. According to another characteristic, the number of arms 5, 6 is at least 2 and can be extended to any number. The limitation comes only from the size. A reasonable maximum number is 8.

[0060] The invention has been illustrated and described in detail in the drawings and the preceding description. This description should be considered as illustrative and given by way of example and not as limiting the invention to this description alone. Several alternative embodiments are possible. List of reference signs

[0061] 1: wind turbine,

[0062] 2: base,

[0063] 3: tree,

[0064] 4: rotor,

[0065] 5, 6: branch,

[0066] 7-10: propeller,

[0067] 11, 12: pale,

[0068] A: axis of rotation,

[0069] Bl, B2: axis of the branches,

[0070] PI, P2: propeller axis,

[0071] W: wind.

Claims

Claims

1. A wind turbine (1) comprising a base (2), a shaft (3) extending along a vertical axis (A) and rotatable about said vertical axis (A) relative to the base (2), a rotor (4) fixed to the shaft (3) comprising at least two branches (5, 6) each extending along a respective horizontal branch axis (B1, B2) and at least one blade (11, 12) mounted at the end of each branch (5, 6), characterized in that it further comprises at least one propeller (7-10) mounted on each branch (5, 6) and rotatable about a horizontal propeller axis (PI, P2), via a unidirectional bearing and in that each unidirectional bearing allows the rotation of the associated propeller (7-10) when the wind (W) blows from behind or in front of this propeller (7-10), but prohibits the rotation of this same propeller (7,10) when the wind blows from the opposite direction.

2. The wind turbine (1) according to claim 1, wherein the rotor (4) is axisymmetric and the propellers (7-10) and the blades (11,12) are mounted axisymmetrically.

3. The wind turbine (1) according to any one of claims 1 or 2, wherein the angles between a horizontal branch axis (B1, B2) and a corresponding horizontal helix axis (PI, P2) are equal.

4. The wind turbine (1) according to any one of claims 1 to 3, wherein each horizontal helix axis (PI, P2) is generally perpendicular to the corresponding horizontal branch axis (Bl, B2).

5. The wind turbine (1) according to any one of claims 1 to 4, wherein the axisymmetric rotor (4) is a Darrieus rotor of type H, comprising an identical blade (11, 12), mounted axisymmetrically at the end of each branch (5, 6) and propellers (7-10) mounted axisymmetrically on blades (11, 12) and / or on branches (5,

6. O). The wind turbine (1) according to claim 5, wherein propellers (7-10) are mounted on the trailing edge of the blades (11, 12).

7. The wind turbine (1) according to any one of claims 1 to 6, wherein a propeller (7-10) has an angle of attack of between 15 and 75°, preferably between 30 and 60° and most preferably about 45°.

8. The wind turbine (1) according to any one of claims 1 to 7, wherein the propellers are mounted in countercyclic pairs, each propeller pair comprising a primary propeller (7, 8) rotatable through a primary one-way bearing and a secondary propeller (9, 10), sharing the same horizontal propeller axis (PI, P2), said secondary propeller (9, 10) being rotatable in opposite directions, through a secondary one-way bearing.

9. The wind turbine (1) according to claim 8, wherein all primary one-way bearings are identical, all primary propellers (7, 8) are identical, all secondary one-way bearings are identical and all secondary propellers (9, 10) are identical.

10. The wind turbine (1) according to claim 9, wherein the secondary propellers (9, 10) are smaller than the primary propellers (7, 8).

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