Vertical-axis hydro turbine

Abstract

A rotor for a vertical-axis hydroelectric turbine, comprising a blade support structure extending from a central shaft of the rotor and designed to rotate around the central shaft, a blade pivotally coupled to the blade support structure, and a control mechanism comprising a spring and a damper for regulating an angle of attack of the blade as a function of a rotational position of the blade support structure, wherein the spring and the damper are suitable for improving the energy extraction efficiency of the rotor depending on the hydrodynamic forces acting on the blade.

Description

Field of the invention

[0001] The present invention relates to the field of vertical-axis hydroelectric turbines, and more specifically to a rotor for such a turbine.Background of the invention

[0002] The invention relates to the field of vertical-axis hydroelectric turbines, in particular to the field of blade control for such turbines. Vertical-axis hydroelectric turbines are widely used for generating electricity from flowing water, such as in rivers or tidal currents.

[0003] A challenge in designing vertical-axis hydroelectric turbines is optimizing the energy extraction efficiency of the rotor. The energy extraction efficiency depends on various factors, including the shape and orientation of the blades relative to the flow direction of the water. The orientation of the blades is typically characterized by the angle of attack, which is the angle between the chord line of the blade and a tangential direction.

[0004] In the state of the art, various solutions are proposed for controlling the angle of attack of the blades in order to improve the energy extraction efficiency. Frequently, a control mechanism is used that adjusts the angle of attack of the blades depending on the rotational position of the rotor. Various control mechanisms are described in the state of the art. For example, WO2023068925A1 describes a control mechanism comprising a damper with a first damping coefficient in a first direction of rotation of the blade and a second damping coefficient, different from the first damping coefficient, in a second direction of rotation of the blade. This document further describes a spring for keeping the blade away from extreme positions to prevent damage to the blade.

[0005] Despite the various solutions already proposed, it remains a challenge to further improve the energy extraction efficiency of vertical-axis hydroelectric turbines. There is therefore still a need for innovative solutions that can take the performance of such turbines to a higher level.Summary of the invention

[0006] It is an object of embodiments of the present invention to improve the control mechanism of a vertical-axis hydroelectric turbine. This object is achieved by a rotor for a vertical-axis hydroelectric turbine according to the invention.

[0007] It is an advantage of embodiments of the present invention that the energy extraction efficiency of a vertical-axis hydroelectric turbine can be improved by using a control mechanism with a spring and a damper.

[0008] In a first aspect, the present invention relates to a rotor for a vertical-axis hydroelectric turbine. The vertical-axis hydroelectric turbine comprises a blade support structure extending from a central shaft of the rotor and designed to rotate around the central shaft. The vertical-axis hydroelectric turbine further comprises a blade pivotally (or rotatably) coupled to the blade support structure. The vertical-axis hydroelectric turbine further comprises a control mechanism comprising a spring and a damper for regulating an angle of attack of the blade as a function of a rotational position of the blade support structure, wherein the spring and the damper are suitable for improving or optimizing the energy extraction efficiency of the rotor depending on the hydrodynamic forces acting on the blade, and preferably also the centrifugal forces.

[0009] It is an advantage of embodiments of the present invention that the blade can mechanically assume an advantageous or optimal position. It is an advantage of embodiments of the present invention that the mechanism can be simple. It is an advantage of the combination of the spring and damper that a very accurate dependence of the angle of attack as a function of the rotational position can be achieved.

[0010] Said improvement can mean that the control mechanism can provide, or provides, an energy extraction efficiency higher than that of an alternative vertical-axis hydroelectric turbine not according to the present invention, such as an alternative vertical-axis hydroelectric turbine from the state of the art (thus without the control mechanism according to embodiments of the present invention), such as an alternative turbine with a tangentially oriented, fixed blade. The energy extraction efficiency can, for example, be higher than if the blade were fixed at an angle of attack of 0º.

[0011] In embodiments, the blade pivots around a shaft located ahead of a location at one-third of a blade chord length measured from a leading edge in the direction of a trailing edge of the blade. This ensures effective tracking of the optimized path of the blade. From calculations, the inventors have determined that an optimized path can be better followed in these embodiments. Herein, located "ahead of" the location is understood as located, relative to the location, in the direction pointing from the trailing edge towards the leading edge. The blade highly preferably pivots around a shaft located behind the leading edge of the blade. Herein, located "behind" the leading edge is understood as located, relative to the leading edge, in the direction pointing from the leading edge towards the trailing edge.

[0012] The spring and damper are typically connected to the blade. The spring and damper are typically connected to the blade support structure. This allows, for example, consistent damping and suspension of the blade to be achieved with every movement and at every angle of attack of the blade. The spring and damper are preferably configured so that they are coupled to the blade when it is in a neutral position, e.g., when it has an angle of attack of 0º. In embodiments, the spring and damper are configured to provide suspension and damping of movements of the blade around a neutral position (i.e., around the angle of attack of 0º) of the blade, preferably around any angle of attack within a range from -10º to 10º, more preferably around any angle of attack within a range from -20º to 20º, most preferably for (e.g., around) any angle of attack that the blade can reach. Movements around the neutral position are typically movements along or through the neutral position, wherein the spring and damper are typically configured so that they also provide damping and suspension of movements of the blade when the blade is in the neutral position. The spring and damper are preferably configured so that they control the blade even when it moves around the neutral position, e.g., when moving around the angle of attack of 0º. This means that good control of the blade can be achieved by combining a spring and a damper, even for small angles of attack, in contrast to configurations - such as in the case of end stops - where the spring and / or damper only adjust the blade when the blade is at an extreme angle.

[0013] The spring and / or damper may be adjustable (that is, the spring constant and / or damping coefficient may be respectively adjustable), which can make it possible to optimize the spring and / or damper for a certain flow velocity. Preferably, the damper (which may consist of one or more damper elements) is a double-acting damper. In embodiments, the damping coefficient of the damper during compression of the damper is preferably substantially equal to the damping coefficient of the damper during extension of the damper. In preferred embodiments, a first damping coefficient of the damper for rotation of the blade in a first direction of rotation relative to the blade support structure is equal to a second damping coefficient of the damper for rotation of the blade in a second direction of rotation relative to the blade support structure. The first direction of rotation is typically different from, such as opposite to, the second direction of rotation. The first direction of rotation may for example be towards smaller (or more negative, or clockwise) angles of attack and the second direction of rotation towards larger (or more positive, or counterclockwise) angles of attack, or vice versa. This means that damping can be the same for opposite directions of rotation, i.e., regardless of whether the direction of rotation is a rotation towards smaller or larger angles of attack. In combination with the spring, embodiments according to the present invention can achieve good control of the blade even when a single, symmetric damper (for example consisting of a single damper element) is used.

[0014] In preferred embodiments, the damper may comprise one or more shock absorbers (e.g., where each shock absorber is a damper element). These are typically non-linear: as the shock absorber is compressed further, resistance to speed increases progressively.

[0015] Preferably, the spring is a symmetrical spring or a double-acting spring. In embodiments, the spring constant of the spring during compression of the spring is preferably substantially equal to the spring constant of the spring during extension of the spring. In preferred embodiments, a first spring constant of the spring for rotation of the blade in a first direction of rotation relative to the blade support structure is equal to a second spring constant of the spring for rotation of the blade in a second direction of rotation relative to the blade support structure. This means that suspension can be the same for opposite directions of rotation of the blade.

[0016] Preferably, the spring and damper are connected to the blade at a location behind the shaft around which the blade pivots, i.e., on the trailing-edge side of the blade relative to the shaft. However, this is not essential.

[0017] In embodiments, end stops are provided for limiting the angle of attack of the blade. This prevents the blade from adopting extreme angles of attack which could limit the energy extraction efficiency. These end stops may typically be present adjacent to or on top of or in addition to the spring and damper; that is, the vertical-axis hydroelectric turbine may comprise the spring, the damper, and the end stops. In other words, in embodiments, the end stops are different from the spring and the damper, i.e., in embodiments, the end stops do not comprise the spring and the end stops do not comprise the damper. The damper and spring typically have another function than the end stops. The end stops typically serve to keep the blade away from extreme angles of attack when the blade is reaching the extreme angles of attack. In contrast, the damper and spring typically serve to constantly dampen and provide suspension for movements of the blade (e.g., movements resulting from the hydrodynamic force acting on the blade) in order to provide the blade with a good or optimal angle of attack as much as possible. Therefore, the damper and spring typically dampen and provide suspension for movements of the blade even when the blade has not yet adopted an extreme angle of attack, such as when the blade is located around the neutral position, e.g., when it has an angle of attack of around 0º.

[0018] In embodiments, the control mechanism is designed so that the angle of attack is negative during at least a first part of the rotational positions in which the blade support structure is oriented upstream. This optimizes the energy extraction in this part of the rotation.

[0019] In embodiments, said first part of the rotational positions comprises at least rotational positions with an angle between a flow direction of water, if present, and the blade support structure - measured from the upstream direction in the direction of rotation of the blade support structure - of 45°, preferably from 0° to 65°, more preferably from -90° to 90°.

[0020] In embodiments, the control mechanism is designed such that the angle of attack is substantially a constant angle from -5º to 5º, preferably from 0º to about 3º, during at least a second part of the rotational positions in which the blade support structure is oriented downstream. This minimizes the influence of disturbances in the flow pattern at the rear of the turbine.

[0021] In embodiments, said second part of the rotational positions comprises at least rotational positions with an angle between a flow direction of water, if present, and the blade support structure - measured from the upstream direction in the direction of rotation of the blade support structure - of 180º, preferably from 135º to 225º, highly preferably from 90º to 270º.

[0022] In a second aspect, the present invention relates to a vertical-axis hydroelectric turbine comprising the rotor according to embodiments of the first aspect.

[0023] The vertical-axis hydroelectric turbine typically uses rotation, or a continuous rotational movement, or rotation in one direction of rotation (e.g., where complete rotations (that is, rotations of 360º) are made without alternating with rotation in a reverse or opposite direction of rotation), of the blade support structure around a central shaft. This rotation is typically driven by lift or drag acting on the blade or blades (e.g., induced by water flow along the rotor or along the blade, or hydrodynamic forces exerted on the blade). This rotation can be converted into electricity, for example by coupling the central shaft to a generator.

[0024] In embodiments, the vertical-axis hydroelectric turbine is a Darrieus turbine. This type of turbine is particularly suitable for application of the invention.

[0025] In a third aspect, the present invention relates to the use of the rotor according to embodiments of the first aspect for converting energy from flowing water into electricity. This achieves efficient energy conversion, in other words high energy extraction efficiency.

[0026] Specific and preferred aspects of the invention are included in the appended independent and dependent claims. Features of the dependent claims may be combined with features of the independent claims and with features of other dependent claims as appropriate and not merely as expressly set out in the claims.

[0027] To summarise the invention and the advantages achieved relative to the prior art, certain objects and advantages of the invention have been described above. It is of course to be understood that not necessarily all these objects or advantages can be achieved by each specific embodiment of the invention. Thus, for example, persons skilled in the art will recognise that the invention may be embodied or implemented in a manner that achieves or optimises one advantage or group of advantages as provided herein, without necessarily achieving other objects or advantages that may be provided or suggested herein.

[0028] The aspects above and other aspects of the invention will be apparent and elucidated with reference to the embodiment(s) described below.Brief description of the figures

[0029] Fig. 1 is a schematic depiction of a rotor according to embodiments of the present invention. Fig. 2 is a schematic depiction of a vertical-axis hydroelectric turbine according to embodiments of the present invention. Fig. 3A is a schematic horizontal cross section of a vertical-axis hydroelectric turbine according to embodiments of the present invention, wherein the angle of attack and the rotational position are indicated. Fig. 3B is a plot of the angle of attack as a function of the rotational position, as calculated by the inventors using CFD calculations, for a rotor according to embodiments of the present invention.

[0030] The figures are only schematic and not limiting. In the figures, the dimensions of some parts may be exaggerated and not to scale for illustrative purposes. Dimensions and relative dimensions do not necessarily correspond to actual embodiments of the invention.

[0031] Reference numerals in the claims should not be interpreted as limiting the scope of protection.

[0032] In the different figures, the same reference numerals refer to the same or similar elements.Detailed description of illustrative embodiments

[0033] The present invention will be described with reference to particular embodiments and with reference to certain drawings; however, the invention is not limited thereto but is limited only by the claims.

[0034] The terms first, second, third and the like in the description and in the claims are used to distinguish between similar elements and not necessarily to describe an order, either temporally, spatially, in rank or in any other way. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are suitable for operation in a different order from that described or shown herein.

[0035] Furthermore, the terms upper, lower, above, front, and the like are used in the description and claims for descriptive purposes and not necessarily to describe relative positions. It should be understood that the terms used in this way may be interchangeable under certain circumstances and that the embodiments of the invention described herein are also suitable for operation in accordance with other orientations than those described or depicted herein.

[0036] It should be noted that the term "comprises", as used in the claims, is not to be construed as limited to the means described thereafter; this term does not exclude other elements or steps. It can therefore be interpreted as specifying the presence of the stated features, values, steps or components referred to, but does not exclude the presence or addition of one or more other features, values, steps or components, or groups thereof. Thus, the scope of the expression "a device comprising means A and B" should not be limited to devices consisting only of components A and B. It means that with regard to the present invention, A and B are the only relevant components of the device.

[0037] Reference throughout this specification to "one embodiment" or "an embodiment" means that a specific feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, occurrences of the phrases "in one embodiment" or "in an embodiment" at various places throughout this specification do not necessarily all refer to the same embodiment, but may do so. Furthermore, the specific features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art, based on this disclosure, in one or more embodiments.

[0038] Similarly, it should be appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together into a single embodiment, figure or description thereof for the purpose of streamlining disclosure and aiding in the understanding of one or more of the various inventive aspects. In any case, this method of disclosure should not be interpreted as reflecting an intention that the invention requires more features than those explicitly stated in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all the features of a single previously disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing alone as a separate embodiment of this invention.

[0039] Furthermore, while some embodiments described herein include some, but not other, features included in other embodiments, combinations of features of different embodiments are intended to be within the scope of the invention, and constitute different embodiments, as would be understood by those skilled in the art. For example, in the following claims, any of the described embodiments may be used in any combination.

[0040] The description provided here highlights numerous specific details. In any case, it is to be understood that embodiments of the invention can be implemented without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order to keep this description clear.

[0041] As used herein, and unless otherwise specified, the term "blade support structure" refers to a structure that supports the blade and can connect it to the central shaft of the rotor such that the blade can rotate around the central shaft. Examples of blade support structures comprise, but are not limited to, spokes, arms, beams, or other suitable structural elements extending from the central shaft.

[0042] As used herein, and unless otherwise specified, the term "energy extraction efficiency," or energy conversion efficiency, refers to the ability of the turbine to convert the hydraulic energy from flowing water into mechanical energy within the turbine, or ultimately into electrical energy after conversion of the mechanical energy within the turbine into electricity. It can be measured as the percentage of available hydraulic energy that is actually utilized by the turbine, i.e., converted into mechanical energy or (ultimately) energy in the form of electricity (although the latter again depends on the efficiency of a generator for converting mechanical energy into electricity). A higher efficiency means that the turbine can capture more energy from the water and is therefore more effective in driving pumps or generators. This is often expressed as a percentage and can vary depending on the specific type of turbine and the operating conditions.

[0043] As used herein, and unless otherwise specified, the term "control mechanism" refers to a mechanism that regulates the angle of attack of the blade as a function of the rotational position of the blade support structure. The control mechanism comprises at least a spring and a damper. Examples of control mechanisms include, but are not limited to, mechanical, hydraulic, pneumatic, or electromechanical systems that comprise the spring and damper and can adjust the angle of attack of the blade.

[0044] As used herein, and unless otherwise specified, the term "rotational position" refers to the angular position of the blade support structure relative to a reference point, such as the flow direction of the water. The rotational position is typically measured in degrees, where 0° corresponds to the position where the blade support structure is oriented upstream and parallel to the flow direction (i.e., the upstream direction) and 180° corresponds to the position where the blade support structure is oriented downstream and parallel to the flow direction (i.e., the downstream direction), and where the rotational angle increases in the direction of rotation of the blade support structure or of the blade (i.e., as the blade moves with the (round) leading edge of the blade facing forward).

[0045] As used herein, and unless otherwise specified, the term "end stops" refers to mechanical limiters that restrict the maximum and minimum angle of attack of the blade. Examples of end stops comprise, but are not limited to, physical stops, bumpers, or other suitable means for maintaining the rotation of the blade within a desired range.

[0046] As used herein, and unless otherwise specified, the term "spring" or "spring system" refers to one or more spring elements, such as one or more coil springs. The coil spring is typically a spiral spring that, when compressed, springs back. A spring system typically consists of one or more spring elements that exert a force on an object when compressed or extended. The spring constant (also known as the stiffness constant) of the spring or spring system determines how much force the spring exerts per unit of displacement. The greater the spring constant, the stiffer the spring. Springs or coil springs are typically formed from a metal, although they may also be formed from other materials, such as plastic. The spring may comprise multiple spring elements (e.g., multiple coil springs), but these together form the "spring."

[0047] As used herein, and unless otherwise specified, the term "damper" or damper system refers to one or more damper elements, such as one or more shock absorbers or impact absorbers. As a person skilled in the art will appreciate, a damper element typically consists of a cylinder, a piston, and a damping fluid (such as oil, although it may also be a gas). The piston moves in the cylinder, through the damping fluid present in the cylinder, thereby creating resistance to the movement of the damping fluid. Damping absorbs energy and prevents infinite motion. A damper is typically associated with a damping coefficient. The damping coefficient is defined as the ratio between a force generated by the damper system as a result of a relative speed between two components of the damper system. The damper may comprise multiple damper elements (e.g., multiple cylinders with pistons and damper fluid), but these together form the "damper."

[0048] In a first aspect, the present invention relates to a rotor for a vertical-axis hydroelectric turbine. The vertical-axis hydroelectric turbine comprises a blade support structure extending from a central shaft of the rotor and designed to rotate around the central shaft. The vertical-axis hydroelectric turbine further comprises a blade pivotally coupled to the blade support structure. The vertical-axis hydroelectric turbine further comprises a control mechanism comprising a spring and a damper for regulating an angle of attack of the blade as a function of a rotational position of the blade support structure, wherein the spring and the damper are suitable for improving the energy extraction efficiency of the rotor depending on the hydrodynamic forces acting on the blade.

[0049] In a second aspect, the present invention relates to a vertical-axis hydroelectric turbine comprising the rotor according to embodiments of the first aspect.

[0050] In a third aspect, the present invention relates to the use of the rotor according to embodiments of the first aspect for converting energy from flowing water into electricity. This achieves efficient energy conversion.

[0051] We now refer to Fig. 1, which shows a schematic depiction of a vertical-axis hydroelectric turbine (6) according to embodiments of the present invention. The vertical-axis hydroelectric turbine (6) comprises a rotor (5) according to embodiments of the present invention. The rotor (5) comprises a plurality of blade support structures (7) extending from a central shaft (8). The rotor (5) is in this case designed to make complete rotations (e.g., rotations through 360º) around the central shaft (8). This may mean that the rotor (5) can rotate at least through a rotation angle of 360º, preferably to an unlimited extent, in both directions of rotation without mechanical restriction or returning to an initial position. The rotor (5) is preferably designed to always maintain the same direction of rotation around the central shaft (8). In the present example, the central shaft (8) is a physical central shaft (8) that is coupled to the blade support structure (7). The central shaft (8) is further coupled to a generator (10).

[0052] However, it is not essential that the rotor (5) itself comprise a physical central shaft (8). For example, when the rotor (5) is not coupled to a generator (10), the central shaft of the rotor (5) may, according to embodiments of the present invention, be an imaginary (or virtual) central shaft where a physical central shaft (8) (which in this case need not be part of the rotor (5)) can be coupled to the blade support structures (7) of the rotor (5).

[0053] Each blade support structure (7) is designed to rotate around the central shaft (8). A blade (9) is pivotally coupled to each blade support structure (7).

[0054] We now refer simultaneously to Fig. 2, which shows a schematic horizontal cross section of a part of the rotor (5) according to embodiments of the present invention. The blade (9) pivots or rotates around a shaft (1b) located ahead of a location (1a) at one-third of a blade chord length measured from a leading edge (90) in the direction of a trailing edge (91) of the blade (9). Furthermore, in this example, a weight is placed on the rear side of the blade (9) (e.g., behind the location where the shaft 1b is located), which causes the rear side to be pushed outward by centrifugal force during rotation of the rotor or of the blade support structure (7).

[0055] End stops (2) are provided for limiting the angle of attack of the blade (9). A control mechanism consisting of a spring (4) and a damper (3) was used to regulate the angle of attack of the blade (9) as a function of the rotational position of the blade support structure (7). The spring (4) and damper (3) can be coupled to the blade support structure (7), for example, as in this example, via a structure (70) such as a rod or bar that is attached to the blade support structure (7). In this case, the end stops (2) and the control mechanism have different functions: while the end stops only serve to keep the blade away from extreme angles of attack, the function of the control mechanism is to optimize the angle of attack in order to achieve good energy extraction efficiency. The spring (4) and the damper (3) are, in this example, configured to provide suspension and damping of movements of the blade (9) around a neutral position of the blade (9). For this purpose, it is possible, inter alia, to connect the spring (4) and the damper (3) to the blade (9) when the blade (9) is in the neutral position. In addition, the type of damper (4) and the type of spring (3), and the damping coefficient of the damper and the spring constant of the spring, can be designed such that the damper (3) and spring (4) also provide damping and suspension of movements of the blade (9) around the neutral position of the blade (9). In this case, the neutral position may be a tangential position of the blade, or a position for which the angle of attack (δ) is equal to 0º.Example: Optimization of the angle of attack of a blade in a vertical-axis hydroelectric turbine

[0056] The inventors conducted research into optimizing the energy extraction efficiency of a vertical-axis hydroelectric turbine according to embodiments of the present invention. The objective was to optimize the angle of attack of the blade as a function of the rotational position of the blade support structure, taking into account the hydrodynamic forces acting on the blade.

[0057] We now refer to Fig. 3A, which shows a schematic horizontal cross section of a blade (9) according to embodiments of the present invention, wherein the angle of attack (δ) and the rotational position (β) are indicated. The rotational positions (β) for the angles 0º, 90º, 180º, and 270º (or -90º) are indicated in FIG. 3A.

[0058] The experiment used a model of a rotor with a blade support structure extending from a central shaft of the rotor. The blade was pivotally coupled to the blade support structure. A control mechanism consisting of a spring and a damper was used to regulate the angle of attack (δ) of the blade (9) as a function of the rotational position (β) of the blade support structure (not shown in Fig. 3A).

[0059] In this case, the angle of attack (δ) is the angle between the chord line (92) of the blade (9) and a tangential direction (93). The angle of attack (δ) is typically 0º. when the chord line (92) is directed tangentially (93) and when the blade (9) is oriented in the direction of rotation (11) of the blade (i.e., with the (e.g., rounded) leading edge 90 oriented in the direction of rotation 11). (If the chord line 92 is directed tangentially 93 but the blade is oriented against the direction of rotation, i.e., with the (e.g., pointed) trailing edge 91 directed in the direction of rotation, the angle of attack is therefore 180º.) This tangential direction (93) is typically perpendicular to a direction from the central shaft (8) to the (local) shaft (1b) of the blade (9). The tangential direction for a particular rotational position is typically the direction in which the blade (9) moves around the central shaft (8) from the particular rotational position. The tangential direction therefore depends on the rotational position of the blade (9) (and is independent of the angle of attack δ of the blade 9). The tangential direction typically touches the arc along which the blade (9) moves around the central shaft (8).

[0060] In the case of a negative angle of attack (δ) (or an angle of attack of 0º (e.g., through -90º) to -180º, i.e., from 180º to 360º), the trailing edge (91) is typically closer to the central shaft (8) than when the blade (9) is located in a tangential position - for which δ = 0 - and / or the leading edge (90) is typically further away from the central shaft (8) than when the blade (9) is located in a tangential position. (In FIG. 3A, the angle of attack δ of the right blade is therefore negative.)

[0061] In the case of a positive angle of attack (δ) (or an angle of attack of 0º. (e.g., through 90º) to 180º), the trailing edge (91) is typically further away from the central shaft (8) than when the blade (9) is located in a tangential position - for which δ = 0 - and / or the leading edge (90) is typically closer to the central shaft (8) than when the blade (9) is located in a tangential position.

[0062] As shown in the figure, a negative angle of attack may correspond to a clockwise rotation of the chord line (92) of the blade (9) - through an angle δ of less than 180º - relative to the neutral angle of attack of 0º, within the plane of rotation of the blade support structure in which, viewed from a direction perpendicular to this plane, the blade support structure itself rotates counterclockwise (as is the case in FIG. 3A). A positive angle of attack in this case corresponds to a counterclockwise rotation of the chord line (92) - also through an angle of less than 180º - relative to the neutral angle of attack, viewed from the same direction.

[0063] The rotational position (β) is typically an angle between a flow direction (11) of water and the blade support structure. Alternatively, the rotational position (β) can be defined as an angle between said flow direction (11) and a direction from the central shaft (8) to the (local) shaft (1b) of the blade (9). The rotational position (β) is typically measured in degrees, where 0° corresponds to the position where the blade support structure - or the direction from the central shaft (8) to the (local) shaft (1b) of the blade (9) - is oriented upstream and parallel to the flow direction, and 180° corresponds to the position where the blade support structure - or the direction from the central shaft (8) to the (local) shaft (1b) of the blade (9) - is oriented downstream and parallel to the flow direction. In this case, the rotational position (β) is measured from the upstream direction in the direction of rotation of the blade support structure, i.e., of the blade. The direction of rotation is typically the direction in which the leading edge of the blade (9) is oriented when at rest, particularly in the absence of hydrodynamic forces and centrifugal forces.

[0064] The inventors performed CFD (computational fluid dynamics) calculations to determine the optimal angle of attack (δ) for the blade under the influence of hydrodynamic forces. Centrifugal forces were not included in the calculations at this stage: although these are of course present in practice, they do not play a role in the CFD calculations as long as the movement of the blade is specified in these calculations. An optimization procedure is then performed in which the combination of the positions of pivot point, spring and damper, plus any required centrifugal weight, is determined that best approximates the intended blade position (δ) during rotation (β).

[0065] These calculations showed that the pivot point or rotation point of the blade (9) was best located ahead of the typical location (typically used in the state of the art) at one-third of a blade chord length in order to effectively follow the optimal path. The exact location depends on the spring and damper, and can be determined using an optimization procedure. In practice, it is typically from 10 to 30%, such as from 15 to 25%, such as at about 20%, of the distance from the leading edge to the trailing edge of the blade.

[0066] We now refer to Fig. 3B, which shows a plot of the angle of attack (δ) depending on the rotational position (β), as calculated by the inventors using CFD calculations, for a rotor (5) according to embodiments of the present invention. The plot shows the desired relationship between the rotational position (β) and angle of attack (δ) for improving the energy extraction efficiency of rotor (5).

[0067] The CFD calculations showed that the angle of attack (δ) is ideally negative during at least a first part of the rotational positions (β) in which the blade support structure is oriented upstream (or rotational positions in which -90° < β ≤ 90º). A negative angle of attack typically corresponds to a condition in which a trailing edge (91) of the blade is located closer to the central shaft (8) than a leading edge of the blade. A positive angle of attack typically corresponds to a condition in which a trailing edge of the blade is located further from the central shaft (8) than a leading edge of the blade. Said first part comprised at least rotational positions (β) - measured from the upstream direction in the direction of rotation of the blade support structure - from 0º to 45º (or 0 ≤ β ≤ 45º), preferably from 0º to 65º ( i.e., 0 ≤ β ≤ 65º), most preferably from -90º to +90º. The angle of attack (δ) can preferably assume a minimum of -10º to -20º, in this example of -15º, with a rotational position (β) falling in the range of 0º. to 50º.

[0068] At the rear of the turbine (i.e., downstream of the central shaft), where disturbances in the flow pattern often occur, the blade was set to a nearly fixed position to prevent the influence of these disturbances on the operation of the rotor. The control mechanism was adapted such that the angle of attack (δ) was from 0º. to 3º, or substantially 0º, during at least a second part of the rotational positions (β) in which the blade support structure was oriented downstream (i.e., rotational positions in which 90º < β ≤ 270º). This second part comprised rotational positions (β) - measured from the upstream direction in the direction of rotation of the blade support structure - from 135º to 225º (i.e., 135 ≤ β ≤ 225º), preferably from 90º to 270º (i.e., 90 ≤ β ≤ 270º).

[0069] Because the turbine rotates at an almost always constant tip speed ratio (TSR), that is, proportional to the flow rate of water (i.e., 2 times faster rotation at 2 times higher flow rate), Fig. 3B is always applicable. The spring and damper can be set for maximum rotational speed. Until the spring and damper are controllable or adjustable, a different and slightly less optimized angle of attack (δ) at lower flow rates is thus accepted. However, the spring and / or damper may be (manually or automatically) adjustable (i.e., the spring constant and / or the damping coefficient may be respectively adjustable), allowing the spring and / or damper, i.e., the spring constant and / or the damping coefficient, to be optimized for a specific flow rate. The calculations also showed that these preferred angles of attack can (also) be approximated well when using a symmetrical damper and a symmetrical spring. Therefore, for robustness, efficiency and simplicity of implementation, it is preferred that a first damping coefficient of the damper (3) for rotation of the blade (9) in a first direction of rotation relative to the blade support structure is equal to a second damping coefficient of the damper (3) for rotation of the blade (9) in a second direction of rotation different from the first direction of rotation.

[0070] The inventors concluded that this angle of attack (δ) as a function of the rotational position (β) is best approximated, or obtained, when using a control mechanism with a spring and damper. Only a damper, or only a spring, was typically found to be unable to approximate this dependence well. In this regard, it is also highly desirable to optimize the location of the pivot point of the blade, preferably in conjunction with a centrifugal weight on the rear side of the blade.

[0071] If the angle of attack(δ) (determined via CFD calculations) as a function of the rotational position (β) is closely approximated or followed, the energy extraction efficiency of the vertical-axis hydroelectric turbine can be improved.

[0072] The preceding description provides details of certain embodiments of the invention. However, it should be clear that no matter how detailed the preceding appears in terms of text, the invention can be applied in many ways. It should be noted that the use of certain terminology in describing certain features or aspects of the invention should not be construed as implying that the terminology herein is redefined so as to be limited to specific features of the characteristics or aspects of the invention with which this terminology is linked.

Examples

Embodiment Construction

[0033]The present invention will be described with reference to particular embodiments and with reference to certain drawings; however, the invention is not limited thereto but is limited only by the claims.

[0034]The terms first, second, third and the like in the description and in the claims are used to distinguish between similar elements and not necessarily to describe an order, either temporally, spatially, in rank or in any other way. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are suitable for operation in a different order from that described or shown herein.

[0035]Furthermore, the terms upper, lower, above, front, and the like are used in the description and claims for descriptive purposes and not necessarily to describe relative positions. It should be understood that the terms used in this way may be interchangeable under certain circumstances and that the embodi...

Field of the invention

[0001] The present invention relates to the field of vertical-axis hydroelectric turbines, and more specifically to a rotor for such a turbine.Background of the invention

[0002] The invention relates to the field of vertical-axis hydroelectric turbines, in particular to the field of blade control for such turbines. Vertical-axis hydroelectric turbines are widely used for generating electricity from flowing water, such as in rivers or tidal currents.

[0003] A challenge in designing vertical-axis hydroelectric turbines is optimizing the energy extraction efficiency of the rotor. The energy extraction efficiency depends on various factors, including the shape and orientation of the blades relative to the flow direction of the water. The orientation of the blades is typically characterized by the angle of attack, which is the angle between the chord line of the blade and a tangential direction.

[0004] In the state of the art, various solutions are proposed for controlling the angle of attack of the blades in order to improve the energy extraction efficiency. Frequently, a control mechanism is used that adjusts the angle of attack of the blades depending on the rotational position of the rotor. Various control mechanisms are described in the state of the art. For example, WO2023068925A1 describes a control mechanism comprising a damper with a first damping coefficient in a first direction of rotation of the blade and a second damping coefficient, different from the first damping coefficient, in a second direction of rotation of the blade. This document further describes a spring for keeping the blade away from extreme positions to prevent damage to the blade.

[0005] Despite the various solutions already proposed, it remains a challenge to further improve the energy extraction efficiency of vertical-axis hydroelectric turbines. There is therefore still a need for innovative solutions that can take the performance of such turbines to a higher level.Summary of the invention

[0006] It is an object of embodiments of the present invention to improve the control mechanism of a vertical-axis hydroelectric turbine. This object is achieved by a rotor for a vertical-axis hydroelectric turbine according to the invention.

[0007] It is an advantage of embodiments of the present invention that the energy extraction efficiency of a vertical-axis hydroelectric turbine can be improved by using a control mechanism with a spring and a damper.

[0008] In a first aspect, the present invention relates to a rotor for a vertical-axis hydroelectric turbine. The vertical-axis hydroelectric turbine comprises a blade support structure extending from a central shaft of the rotor and designed to rotate around the central shaft. The vertical-axis hydroelectric turbine further comprises a blade pivotally (or rotatably) coupled to the blade support structure. The vertical-axis hydroelectric turbine further comprises a control mechanism comprising a spring and a damper for regulating an angle of attack of the blade as a function of a rotational position of the blade support structure, wherein the spring and the damper are suitable for improving or optimizing the energy extraction efficiency of the rotor depending on the hydrodynamic forces acting on the blade, and preferably also the centrifugal forces.

[0009] It is an advantage of embodiments of the present invention that the blade can mechanically assume an advantageous or optimal position. It is an advantage of embodiments of the present invention that the mechanism can be simple. It is an advantage of the combination of the spring and damper that a very accurate dependence of the angle of attack as a function of the rotational position can be achieved.

[0010] Said improvement can mean that the control mechanism can provide, or provides, an energy extraction efficiency higher than that of an alternative vertical-axis hydroelectric turbine not according to the present invention, such as an alternative vertical-axis hydroelectric turbine from the state of the art (thus without the control mechanism according to embodiments of the present invention), such as an alternative turbine with a tangentially oriented, fixed blade. The energy extraction efficiency can, for example, be higher than if the blade were fixed at an angle of attack of 0º.

[0011] In embodiments, the blade pivots around a shaft located ahead of a location at one-third of a blade chord length measured from a leading edge in the direction of a trailing edge of the blade. This ensures effective tracking of the optimized path of the blade. From calculations, the inventors have determined that an optimized path can be better followed in these embodiments. Herein, located "ahead of" the location is understood as located, relative to the location, in the direction pointing from the trailing edge towards the leading edge. The blade highly preferably pivots around a shaft located behind the leading edge of the blade. Herein, located "behind" the leading edge is understood as located, relative to the leading edge, in the direction pointing from the leading edge towards the trailing edge.

[0012] The spring and damper are typically connected to the blade. The spring and damper are typically connected to the blade support structure. This allows, for example, consistent damping and suspension of the blade to be achieved with every movement and at every angle of attack of the blade. The spring and damper are preferably configured so that they are coupled to the blade when it is in a neutral position, e.g., when it has an angle of attack of 0º. In embodiments, the spring and damper are configured to provide suspension and damping of movements of the blade around a neutral position (i.e., around the angle of attack of 0º) of the blade, preferably around any angle of attack within a range from -10º to 10º, more preferably around any angle of attack within a range from -20º to 20º, most preferably for (e.g., around) any angle of attack that the blade can reach. Movements around the neutral position are typically movements along or through the neutral position, wherein the spring and damper are typically configured so that they also provide damping and suspension of movements of the blade when the blade is in the neutral position. The spring and damper are preferably configured so that they control the blade even when it moves around the neutral position, e.g., when moving around the angle of attack of 0º. This means that good control of the blade can be achieved by combining a spring and a damper, even for small angles of attack, in contrast to configurations - such as in the case of end stops - where the spring and / or damper only adjust the blade when the blade is at an extreme angle.

[0013] The spring and / or damper may be adjustable (that is, the spring constant and / or damping coefficient may be respectively adjustable), which can make it possible to optimize the spring and / or damper for a certain flow velocity. Preferably, the damper (which may consist of one or more damper elements) is a double-acting damper. In embodiments, the damping coefficient of the damper during compression of the damper is preferably substantially equal to the damping coefficient of the damper during extension of the damper. In preferred embodiments, a first damping coefficient of the damper for rotation of the blade in a first direction of rotation relative to the blade support structure is equal to a second damping coefficient of the damper for rotation of the blade in a second direction of rotation relative to the blade support structure. The first direction of rotation is typically different from, such as opposite to, the second direction of rotation. The first direction of rotation may for example be towards smaller (or more negative, or clockwise) angles of attack and the second direction of rotation towards larger (or more positive, or counterclockwise) angles of attack, or vice versa. This means that damping can be the same for opposite directions of rotation, i.e., regardless of whether the direction of rotation is a rotation towards smaller or larger angles of attack. In combination with the spring, embodiments according to the present invention can achieve good control of the blade even when a single, symmetric damper (for example consisting of a single damper element) is used.

[0014] In preferred embodiments, the damper may comprise one or more shock absorbers (e.g., where each shock absorber is a damper element). These are typically non-linear: as the shock absorber is compressed further, resistance to speed increases progressively.

[0015] Preferably, the spring is a symmetrical spring or a double-acting spring. In embodiments, the spring constant of the spring during compression of the spring is preferably substantially equal to the spring constant of the spring during extension of the spring. In preferred embodiments, a first spring constant of the spring for rotation of the blade in a first direction of rotation relative to the blade support structure is equal to a second spring constant of the spring for rotation of the blade in a second direction of rotation relative to the blade support structure. This means that suspension can be the same for opposite directions of rotation of the blade.

[0016] Preferably, the spring and damper are connected to the blade at a location behind the shaft around which the blade pivots, i.e., on the trailing-edge side of the blade relative to the shaft. However, this is not essential.

[0017] In embodiments, end stops are provided for limiting the angle of attack of the blade. This prevents the blade from adopting extreme angles of attack which could limit the energy extraction efficiency. These end stops may typically be present adjacent to or on top of or in addition to the spring and damper; that is, the vertical-axis hydroelectric turbine may comprise the spring, the damper, and the end stops. In other words, in embodiments, the end stops are different from the spring and the damper, i.e., in embodiments, the end stops do not comprise the spring and the end stops do not comprise the damper. The damper and spring typically have another function than the end stops. The end stops typically serve to keep the blade away from extreme angles of attack when the blade is reaching the extreme angles of attack. In contrast, the damper and spring typically serve to constantly dampen and provide suspension for movements of the blade (e.g., movements resulting from the hydrodynamic force acting on the blade) in order to provide the blade with a good or optimal angle of attack as much as possible. Therefore, the damper and spring typically dampen and provide suspension for movements of the blade even when the blade has not yet adopted an extreme angle of attack, such as when the blade is located around the neutral position, e.g., when it has an angle of attack of around 0º.

[0018] In embodiments, the control mechanism is designed so that the angle of attack is negative during at least a first part of the rotational positions in which the blade support structure is oriented upstream. This optimizes the energy extraction in this part of the rotation.

[0019] In embodiments, said first part of the rotational positions comprises at least rotational positions with an angle between a flow direction of water, if present, and the blade support structure - measured from the upstream direction in the direction of rotation of the blade support structure - of 45°, preferably from 0° to 65°, more preferably from -90° to 90°.

[0020] In embodiments, the control mechanism is designed such that the angle of attack is substantially a constant angle from -5º to 5º, preferably from 0º to about 3º, during at least a second part of the rotational positions in which the blade support structure is oriented downstream. This minimizes the influence of disturbances in the flow pattern at the rear of the turbine.

[0021] In embodiments, said second part of the rotational positions comprises at least rotational positions with an angle between a flow direction of water, if present, and the blade support structure - measured from the upstream direction in the direction of rotation of the blade support structure - of 180º, preferably from 135º to 225º, highly preferably from 90º to 270º.

[0022] In a second aspect, the present invention relates to a vertical-axis hydroelectric turbine comprising the rotor according to embodiments of the first aspect.

[0023] The vertical-axis hydroelectric turbine typically uses rotation, or a continuous rotational movement, or rotation in one direction of rotation (e.g., where complete rotations (that is, rotations of 360º) are made without alternating with rotation in a reverse or opposite direction of rotation), of the blade support structure around a central shaft. This rotation is typically driven by lift or drag acting on the blade or blades (e.g., induced by water flow along the rotor or along the blade, or hydrodynamic forces exerted on the blade). This rotation can be converted into electricity, for example by coupling the central shaft to a generator.

[0024] In embodiments, the vertical-axis hydroelectric turbine is a Darrieus turbine. This type of turbine is particularly suitable for application of the invention.

[0025] In a third aspect, the present invention relates to the use of the rotor according to embodiments of the first aspect for converting energy from flowing water into electricity. This achieves efficient energy conversion, in other words high energy extraction efficiency.

[0026] Specific and preferred aspects of the invention are included in the appended independent and dependent claims. Features of the dependent claims may be combined with features of the independent claims and with features of other dependent claims as appropriate and not merely as expressly set out in the claims.

[0027] To summarise the invention and the advantages achieved relative to the prior art, certain objects and advantages of the invention have been described above. It is of course to be understood that not necessarily all these objects or advantages can be achieved by each specific embodiment of the invention. Thus, for example, persons skilled in the art will recognise that the invention may be embodied or implemented in a manner that achieves or optimises one advantage or group of advantages as provided herein, without necessarily achieving other objects or advantages that may be provided or suggested herein.

[0028] The aspects above and other aspects of the invention will be apparent and elucidated with reference to the embodiment(s) described below.Brief description of the figures

[0029] Fig. 1 is a schematic depiction of a rotor according to embodiments of the present invention. Fig. 2 is a schematic depiction of a vertical-axis hydroelectric turbine according to embodiments of the present invention. Fig. 3A is a schematic horizontal cross section of a vertical-axis hydroelectric turbine according to embodiments of the present invention, wherein the angle of attack and the rotational position are indicated. Fig. 3B is a plot of the angle of attack as a function of the rotational position, as calculated by the inventors using CFD calculations, for a rotor according to embodiments of the present invention.

[0030] The figures are only schematic and not limiting. In the figures, the dimensions of some parts may be exaggerated and not to scale for illustrative purposes. Dimensions and relative dimensions do not necessarily correspond to actual embodiments of the invention.

[0031] Reference numerals in the claims should not be interpreted as limiting the scope of protection.

[0032] In the different figures, the same reference numerals refer to the same or similar elements.Detailed description of illustrative embodiments

[0033] The present invention will be described with reference to particular embodiments and with reference to certain drawings; however, the invention is not limited thereto but is limited only by the claims.

[0034] The terms first, second, third and the like in the description and in the claims are used to distinguish between similar elements and not necessarily to describe an order, either temporally, spatially, in rank or in any other way. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are suitable for operation in a different order from that described or shown herein.

[0035] Furthermore, the terms upper, lower, above, front, and the like are used in the description and claims for descriptive purposes and not necessarily to describe relative positions. It should be understood that the terms used in this way may be interchangeable under certain circumstances and that the embodiments of the invention described herein are also suitable for operation in accordance with other orientations than those described or depicted herein.

[0036] It should be noted that the term "comprises", as used in the claims, is not to be construed as limited to the means described thereafter; this term does not exclude other elements or steps. It can therefore be interpreted as specifying the presence of the stated features, values, steps or components referred to, but does not exclude the presence or addition of one or more other features, values, steps or components, or groups thereof. Thus, the scope of the expression "a device comprising means A and B" should not be limited to devices consisting only of components A and B. It means that with regard to the present invention, A and B are the only relevant components of the device.

[0037] Reference throughout this specification to "one embodiment" or "an embodiment" means that a specific feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, occurrences of the phrases "in one embodiment" or "in an embodiment" at various places throughout this specification do not necessarily all refer to the same embodiment, but may do so. Furthermore, the specific features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art, based on this disclosure, in one or more embodiments.

[0038] Similarly, it should be appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together into a single embodiment, figure or description thereof for the purpose of streamlining disclosure and aiding in the understanding of one or more of the various inventive aspects. In any case, this method of disclosure should not be interpreted as reflecting an intention that the invention requires more features than those explicitly stated in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all the features of a single previously disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing alone as a separate embodiment of this invention.

[0039] Furthermore, while some embodiments described herein include some, but not other, features included in other embodiments, combinations of features of different embodiments are intended to be within the scope of the invention, and constitute different embodiments, as would be understood by those skilled in the art. For example, in the following claims, any of the described embodiments may be used in any combination.

[0040] The description provided here highlights numerous specific details. In any case, it is to be understood that embodiments of the invention can be implemented without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order to keep this description clear.

[0041] As used herein, and unless otherwise specified, the term "blade support structure" refers to a structure that supports the blade and can connect it to the central shaft of the rotor such that the blade can rotate around the central shaft. Examples of blade support structures comprise, but are not limited to, spokes, arms, beams, or other suitable structural elements extending from the central shaft.

[0042] As used herein, and unless otherwise specified, the term "energy extraction efficiency," or energy conversion efficiency, refers to the ability of the turbine to convert the hydraulic energy from flowing water into mechanical energy within the turbine, or ultimately into electrical energy after conversion of the mechanical energy within the turbine into electricity. It can be measured as the percentage of available hydraulic energy that is actually utilized by the turbine, i.e., converted into mechanical energy or (ultimately) energy in the form of electricity (although the latter again depends on the efficiency of a generator for converting mechanical energy into electricity). A higher efficiency means that the turbine can capture more energy from the water and is therefore more effective in driving pumps or generators. This is often expressed as a percentage and can vary depending on the specific type of turbine and the operating conditions.

[0043] As used herein, and unless otherwise specified, the term "control mechanism" refers to a mechanism that regulates the angle of attack of the blade as a function of the rotational position of the blade support structure. The control mechanism comprises at least a spring and a damper. Examples of control mechanisms include, but are not limited to, mechanical, hydraulic, pneumatic, or electromechanical systems that comprise the spring and damper and can adjust the angle of attack of the blade.

[0044] As used herein, and unless otherwise specified, the term "rotational position" refers to the angular position of the blade support structure relative to a reference point, such as the flow direction of the water. The rotational position is typically measured in degrees, where 0° corresponds to the position where the blade support structure is oriented upstream and parallel to the flow direction (i.e., the upstream direction) and 180° corresponds to the position where the blade support structure is oriented downstream and parallel to the flow direction (i.e., the downstream direction), and where the rotational angle increases in the direction of rotation of the blade support structure or of the blade (i.e., as the blade moves with the (round) leading edge of the blade facing forward).

[0045] As used herein, and unless otherwise specified, the term "end stops" refers to mechanical limiters that restrict the maximum and minimum angle of attack of the blade. Examples of end stops comprise, but are not limited to, physical stops, bumpers, or other suitable means for maintaining the rotation of the blade within a desired range.

[0046] As used herein, and unless otherwise specified, the term "spring" or "spring system" refers to one or more spring elements, such as one or more coil springs. The coil spring is typically a spiral spring that, when compressed, springs back. A spring system typically consists of one or more spring elements that exert a force on an object when compressed or extended. The spring constant (also known as the stiffness constant) of the spring or spring system determines how much force the spring exerts per unit of displacement. The greater the spring constant, the stiffer the spring. Springs or coil springs are typically formed from a metal, although they may also be formed from other materials, such as plastic. The spring may comprise multiple spring elements (e.g., multiple coil springs), but these together form the "spring."

[0047] As used herein, and unless otherwise specified, the term "damper" or damper system refers to one or more damper elements, such as one or more shock absorbers or impact absorbers. As a person skilled in the art will appreciate, a damper element typically consists of a cylinder, a piston, and a damping fluid (such as oil, although it may also be a gas). The piston moves in the cylinder, through the damping fluid present in the cylinder, thereby creating resistance to the movement of the damping fluid. Damping absorbs energy and prevents infinite motion. A damper is typically associated with a damping coefficient. The damping coefficient is defined as the ratio between a force generated by the damper system as a result of a relative speed between two components of the damper system. The damper may comprise multiple damper elements (e.g., multiple cylinders with pistons and damper fluid), but these together form the "damper."

[0048] In a first aspect, the present invention relates to a rotor for a vertical-axis hydroelectric turbine. The vertical-axis hydroelectric turbine comprises a blade support structure extending from a central shaft of the rotor and designed to rotate around the central shaft. The vertical-axis hydroelectric turbine further comprises a blade pivotally coupled to the blade support structure. The vertical-axis hydroelectric turbine further comprises a control mechanism comprising a spring and a damper for regulating an angle of attack of the blade as a function of a rotational position of the blade support structure, wherein the spring and the damper are suitable for improving the energy extraction efficiency of the rotor depending on the hydrodynamic forces acting on the blade.

[0049] In a second aspect, the present invention relates to a vertical-axis hydroelectric turbine comprising the rotor according to embodiments of the first aspect.

[0050] In a third aspect, the present invention relates to the use of the rotor according to embodiments of the first aspect for converting energy from flowing water into electricity. This achieves efficient energy conversion.

[0051] We now refer to Fig. 1, which shows a schematic depiction of a vertical-axis hydroelectric turbine (6) according to embodiments of the present invention. The vertical-axis hydroelectric turbine (6) comprises a rotor (5) according to embodiments of the present invention. The rotor (5) comprises a plurality of blade support structures (7) extending from a central shaft (8). The rotor (5) is in this case designed to make complete rotations (e.g., rotations through 360º) around the central shaft (8). This may mean that the rotor (5) can rotate at least through a rotation angle of 360º, preferably to an unlimited extent, in both directions of rotation without mechanical restriction or returning to an initial position. The rotor (5) is preferably designed to always maintain the same direction of rotation around the central shaft (8). In the present example, the central shaft (8) is a physical central shaft (8) that is coupled to the blade support structure (7). The central shaft (8) is further coupled to a generator (10).

[0052] However, it is not essential that the rotor (5) itself comprise a physical central shaft (8). For example, when the rotor (5) is not coupled to a generator (10), the central shaft of the rotor (5) may, according to embodiments of the present invention, be an imaginary (or virtual) central shaft where a physical central shaft (8) (which in this case need not be part of the rotor (5)) can be coupled to the blade support structures (7) of the rotor (5).

[0053] Each blade support structure (7) is designed to rotate around the central shaft (8). A blade (9) is pivotally coupled to each blade support structure (7).

[0054] We now refer simultaneously to Fig. 2, which shows a schematic horizontal cross section of a part of the rotor (5) according to embodiments of the present invention. The blade (9) pivots or rotates around a shaft (1b) located ahead of a location (1a) at one-third of a blade chord length measured from a leading edge (90) in the direction of a trailing edge (91) of the blade (9). Furthermore, in this example, a weight is placed on the rear side of the blade (9) (e.g., behind the location where the shaft 1b is located), which causes the rear side to be pushed outward by centrifugal force during rotation of the rotor or of the blade support structure (7).

[0055] End stops (2) are provided for limiting the angle of attack of the blade (9). A control mechanism consisting of a spring (4) and a damper (3) was used to regulate the angle of attack of the blade (9) as a function of the rotational position of the blade support structure (7). The spring (4) and damper (3) can be coupled to the blade support structure (7), for example, as in this example, via a structure (70) such as a rod or bar that is attached to the blade support structure (7). In this case, the end stops (2) and the control mechanism have different functions: while the end stops only serve to keep the blade away from extreme angles of attack, the function of the control mechanism is to optimize the angle of attack in order to achieve good energy extraction efficiency. The spring (4) and the damper (3) are, in this example, configured to provide suspension and damping of movements of the blade (9) around a neutral position of the blade (9). For this purpose, it is possible, inter alia, to connect the spring (4) and the damper (3) to the blade (9) when the blade (9) is in the neutral position. In addition, the type of damper (4) and the type of spring (3), and the damping coefficient of the damper and the spring constant of the spring, can be designed such that the damper (3) and spring (4) also provide damping and suspension of movements of the blade (9) around the neutral position of the blade (9). In this case, the neutral position may be a tangential position of the blade, or a position for which the angle of attack (δ) is equal to 0º.Example: Optimization of the angle of attack of a blade in a vertical-axis hydroelectric turbine

[0056] The inventors conducted research into optimizing the energy extraction efficiency of a vertical-axis hydroelectric turbine according to embodiments of the present invention. The objective was to optimize the angle of attack of the blade as a function of the rotational position of the blade support structure, taking into account the hydrodynamic forces acting on the blade.

[0057] We now refer to Fig. 3A, which shows a schematic horizontal cross section of a blade (9) according to embodiments of the present invention, wherein the angle of attack (δ) and the rotational position (β) are indicated. The rotational positions (β) for the angles 0º, 90º, 180º, and 270º (or -90º) are indicated in FIG. 3A.

[0058] The experiment used a model of a rotor with a blade support structure extending from a central shaft of the rotor. The blade was pivotally coupled to the blade support structure. A control mechanism consisting of a spring and a damper was used to regulate the angle of attack (δ) of the blade (9) as a function of the rotational position (β) of the blade support structure (not shown in Fig. 3A).

[0059] In this case, the angle of attack (δ) is the angle between the chord line (92) of the blade (9) and a tangential direction (93). The angle of attack (δ) is typically 0º. when the chord line (92) is directed tangentially (93) and when the blade (9) is oriented in the direction of rotation (11) of the blade (i.e., with the (e.g., rounded) leading edge 90 oriented in the direction of rotation 11). (If the chord line 92 is directed tangentially 93 but the blade is oriented against the direction of rotation, i.e., with the (e.g., pointed) trailing edge 91 directed in the direction of rotation, the angle of attack is therefore 180º.) This tangential direction (93) is typically perpendicular to a direction from the central shaft (8) to the (local) shaft (1b) of the blade (9). The tangential direction for a particular rotational position is typically the direction in which the blade (9) moves around the central shaft (8) from the particular rotational position. The tangential direction therefore depends on the rotational position of the blade (9) (and is independent of the angle of attack δ of the blade 9). The tangential direction typically touches the arc along which the blade (9) moves around the central shaft (8).

[0060] In the case of a negative angle of attack (δ) (or an angle of attack of 0º (e.g., through -90º) to -180º, i.e., from 180º to 360º), the trailing edge (91) is typically closer to the central shaft (8) than when the blade (9) is located in a tangential position - for which δ = 0 - and / or the leading edge (90) is typically further away from the central shaft (8) than when the blade (9) is located in a tangential position. (In FIG. 3A, the angle of attack δ of the right blade is therefore negative.)

[0061] In the case of a positive angle of attack (δ) (or an angle of attack of 0º. (e.g., through 90º) to 180º), the trailing edge (91) is typically further away from the central shaft (8) than when the blade (9) is located in a tangential position - for which δ = 0 - and / or the leading edge (90) is typically closer to the central shaft (8) than when the blade (9) is located in a tangential position.

[0062] As shown in the figure, a negative angle of attack may correspond to a clockwise rotation of the chord line (92) of the blade (9) - through an angle δ of less than 180º - relative to the neutral angle of attack of 0º, within the plane of rotation of the blade support structure in which, viewed from a direction perpendicular to this plane, the blade support structure itself rotates counterclockwise (as is the case in FIG. 3A). A positive angle of attack in this case corresponds to a counterclockwise rotation of the chord line (92) - also through an angle of less than 180º - relative to the neutral angle of attack, viewed from the same direction.

[0063] The rotational position (β) is typically an angle between a flow direction (11) of water and the blade support structure. Alternatively, the rotational position (β) can be defined as an angle between said flow direction (11) and a direction from the central shaft (8) to the (local) shaft (1b) of the blade (9). The rotational position (β) is typically measured in degrees, where 0° corresponds to the position where the blade support structure - or the direction from the central shaft (8) to the (local) shaft (1b) of the blade (9) - is oriented upstream and parallel to the flow direction, and 180° corresponds to the position where the blade support structure - or the direction from the central shaft (8) to the (local) shaft (1b) of the blade (9) - is oriented downstream and parallel to the flow direction. In this case, the rotational position (β) is measured from the upstream direction in the direction of rotation of the blade support structure, i.e., of the blade. The direction of rotation is typically the direction in which the leading edge of the blade (9) is oriented when at rest, particularly in the absence of hydrodynamic forces and centrifugal forces.

[0064] The inventors performed CFD (computational fluid dynamics) calculations to determine the optimal angle of attack (δ) for the blade under the influence of hydrodynamic forces. Centrifugal forces were not included in the calculations at this stage: although these are of course present in practice, they do not play a role in the CFD calculations as long as the movement of the blade is specified in these calculations. An optimization procedure is then performed in which the combination of the positions of pivot point, spring and damper, plus any required centrifugal weight, is determined that best approximates the intended blade position (δ) during rotation (β).

[0065] These calculations showed that the pivot point or rotation point of the blade (9) was best located ahead of the typical location (typically used in the state of the art) at one-third of a blade chord length in order to effectively follow the optimal path. The exact location depends on the spring and damper, and can be determined using an optimization procedure. In practice, it is typically from 10 to 30%, such as from 15 to 25%, such as at about 20%, of the distance from the leading edge to the trailing edge of the blade.

[0066] We now refer to Fig. 3B, which shows a plot of the angle of attack (δ) depending on the rotational position (β), as calculated by the inventors using CFD calculations, for a rotor (5) according to embodiments of the present invention. The plot shows the desired relationship between the rotational position (β) and angle of attack (δ) for improving the energy extraction efficiency of rotor (5).

[0067] The CFD calculations showed that the angle of attack (δ) is ideally negative during at least a first part of the rotational positions (β) in which the blade support structure is oriented upstream (or rotational positions in which -90° < β ≤ 90º). A negative angle of attack typically corresponds to a condition in which a trailing edge (91) of the blade is located closer to the central shaft (8) than a leading edge of the blade. A positive angle of attack typically corresponds to a condition in which a trailing edge of the blade is located further from the central shaft (8) than a leading edge of the blade. Said first part comprised at least rotational positions (β) - measured from the upstream direction in the direction of rotation of the blade support structure - from 0º to 45º (or 0 ≤ β ≤ 45º), preferably from 0º to 65º ( i.e., 0 ≤ β ≤ 65º), most preferably from -90º to +90º. The angle of attack (δ) can preferably assume a minimum of -10º to -20º, in this example of -15º, with a rotational position (β) falling in the range of 0º. to 50º.

[0068] At the rear of the turbine (i.e., downstream of the central shaft), where disturbances in the flow pattern often occur, the blade was set to a nearly fixed position to prevent the influence of these disturbances on the operation of the rotor. The control mechanism was adapted such that the angle of attack (δ) was from 0º. to 3º, or substantially 0º, during at least a second part of the rotational positions (β) in which the blade support structure was oriented downstream (i.e., rotational positions in which 90º < β ≤ 270º). This second part comprised rotational positions (β) - measured from the upstream direction in the direction of rotation of the blade support structure - from 135º to 225º (i.e., 135 ≤ β ≤ 225º), preferably from 90º to 270º (i.e., 90 ≤ β ≤ 270º).

[0069] Because the turbine rotates at an almost always constant tip speed ratio (TSR), that is, proportional to the flow rate of water (i.e., 2 times faster rotation at 2 times higher flow rate), Fig. 3B is always applicable. The spring and damper can be set for maximum rotational speed. Until the spring and damper are controllable or adjustable, a different and slightly less optimized angle of attack (δ) at lower flow rates is thus accepted. However, the spring and / or damper may be (manually or automatically) adjustable (i.e., the spring constant and / or the damping coefficient may be respectively adjustable), allowing the spring and / or damper, i.e., the spring constant and / or the damping coefficient, to be optimized for a specific flow rate. The calculations also showed that these preferred angles of attack can (also) be approximated well when using a symmetrical damper and a symmetrical spring. Therefore, for robustness, efficiency and simplicity of implementation, it is preferred that a first damping coefficient of the damper (3) for rotation of the blade (9) in a first direction of rotation relative to the blade support structure is equal to a second damping coefficient of the damper (3) for rotation of the blade (9) in a second direction of rotation different from the first direction of rotation.

[0070] The inventors concluded that this angle of attack (δ) as a function of the rotational position (β) is best approximated, or obtained, when using a control mechanism with a spring and damper. Only a damper, or only a spring, was typically found to be unable to approximate this dependence well. In this regard, it is also highly desirable to optimize the location of the pivot point of the blade, preferably in conjunction with a centrifugal weight on the rear side of the blade.

[0071] If the angle of attack(δ) (determined via CFD calculations) as a function of the rotational position (β) is closely approximated or followed, the energy extraction efficiency of the vertical-axis hydroelectric turbine can be improved.

[0072] The preceding description provides details of certain embodiments of the invention. However, it should be clear that no matter how detailed the preceding appears in terms of text, the invention can be applied in many ways. It should be noted that the use of certain terminology in describing certain features or aspects of the invention should not be construed as implying that the terminology herein is redefined so as to be limited to specific features of the characteristics or aspects of the invention with which this terminology is linked.

Examples

Embodiment Construction

[0033]The present invention will be described with reference to particular embodiments and with reference to certain drawings; however, the invention is not limited thereto but is limited only by the claims.

[0034]The terms first, second, third and the like in the description and in the claims are used to distinguish between similar elements and not necessarily to describe an order, either temporally, spatially, in rank or in any other way. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are suitable for operation in a different order from that described or shown herein.

[0035]Furthermore, the terms upper, lower, above, front, and the like are used in the description and claims for descriptive purposes and not necessarily to describe relative positions. It should be understood that the terms used in this way may be interchangeable under certain circumstances and that the embodi...

Claims

1. A rotor (5) for a vertical-axis hydroelectric turbine (6), comprising: a blade support structure (7) extending from a central shaft (8) of the rotor (5) and designed to rotate around the central shaft (8), a blade (9) pivotally coupled to the blade support structure (7), and a control mechanism comprising a spring (4) and a damper (3) for regulating an angle of attack (δ) of the blade (9) as a function of a rotational position (β) of the blade support structure (7), wherein the spring (4) and the damper (3) are suitable for improving the energy extraction efficiency of the rotor (5) depending on the hydrodynamic forces acting on the blade (9).

2. The rotor (5) according to claim 1, wherein the blade (9) pivots around a shaft (1b) located ahead of a location (1a) at one-third of a blade chord length measured from a leading edge (90) in the direction of a trailing edge (91) of the blade (9).

3. The rotor (5) according to any one of the preceding claims, wherein end stops (2) are provided for limiting the angle of attack (δ) of the blade (9).

4. The rotor (5) according to any one of the preceding claims, wherein the control mechanism is designed so that the angle of attack (δ) is negative during at least a first part of the rotational positions (β) in which the blade support structure (7) is oriented upstream, wherein the negative angle of attack (δ) corresponds to a condition in which a trailing edge (91) of the blade (9) is located closer to the central shaft (8) than a leading edge of the blade.

5. The rotor (5) according to claim 4, wherein said first part of the rotational positions (β) comprises at least rotational positions (β) with an angle between a flow direction of water, if present, and the blade support structure (7) - measured from the upstream direction in the direction of rotation of the blade support structure (7) - of 45°, preferably from 0° to 65°, more preferably from -90° to 90°.

6. The rotor (5) according to any one of the preceding claims, wherein the control mechanism is designed such that the angle of attack (δ) is from -5º to 5º, preferably in the range of 0º. to 3º, or substantially 0º, during at least a second part of the rotational positions (β) in which the blade support structure (7) is oriented downstream.

7. The rotor (5) according to claim 6, wherein the second part of the rotational positions (β) comprises at least rotational positions (β) with an angle between a flow direction of water, if present, and the blade support structure (7) - measured from the upstream direction in the direction of rotation of the blade support structure (7) - of 180º, preferably from 135º to 225º, highly preferably from 90º to 270º.

8. The rotor (5) according to any one of the preceding claims, wherein a first damping coefficient of the damper (3) for rotation of the blade (9) in a first direction of rotation relative to the blade support structure is equal to a second damping coefficient of the damper (3) for rotation of the blade (9) in a second direction of rotation that is different from the first direction of rotation.

9. The rotor (5) according to any one of the preceding claims, wherein the spring (4) and the damper (3) are configured to provide suspension and damping of movements of the blade (9) around a neutral position of the blade (9).

10. A vertical-axis hydroelectric turbine (6) comprising the rotor (5) according to any one of the preceding claims.

11. The vertical-axis hydroelectric turbine (6) according to claim 10, wherein the vertical-axis hydroelectric turbine (6) is a Darrieus turbine.

12. Use of the rotor (5) according to any one of claims 1 to 9 for converting energy from flowing water into electricity.

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