High-efficiency wind energy converter without gearbox or multi-pole generator

Abstract

A vertical axis turbine having a first rotor and at least one second rotor, the first rotor being configured to rotate around a first rotation axis that is vertical or more vertical than horizontal in use. The first rotor may be configured to be driven and / or rotated by a fluid, such as by wind or water flow, motion. At least one second rotor is disposed on or coupled to the first rotor so that the first rotor is operable to move the second rotor through the fluid, thereby driving the second rotor when the first rotor rotates. The second rotor is operable to drive a power output system. Optionally, the rotation of the first rotor around the first rotation axis moves the second rotor around the first rotation axis. Each second rotor rotates around a corresponding second rotation axis, which may be angled or perpendicular to the first rotation axis of the first rotor, and may be a horizontal axis or at least an axis that is more horizontal than vertical in use. The first and second rotors are configured so that power output is performed by direct drive without the need for a gearbox or a multi-pole generator. The first rotor and the second rotor are configured so that the power conversion in which mechanical power at the first rotor is converted into mechanical power at the second rotor has high efficiency.

Description

Technical Field

[0001] A wind energy converter (WEC) is described herein which may alternatively, but not essentially, be used as a wind turbine to generate electrical power. The invention also relates to related methods of generating electricity from a vertical axis turbine and methods of controlling a vertical axis turbine. Background Art

[0002] A turbine can be driven to rotate and thus perform work. For example, a wind turbine is driven by the wind, and a generator can generate electricity as the turbine rotates. Most wind turbines have blades that are driven by the wind around a horizontal axis. The blades of a horizontal axis wind turbine can face directly into the wind as they rotate, thereby increasing their efficiency.

[0003] Conventional vertical axis wind turbines generate electricity in use by the rotation of a rotor about a vertical axis. Conventional vertical axis wind turbines are designed so that they only operate aerodynamically efficiently if they rotate at relatively low speeds compared to horizontal axis wind turbines, resulting in the rotors of such turbines generating high torques on the main drive shaft. These high torques also require large, heavy and expensive drivetrains for converting the high torque, low speed rotation of the rotor into electricity.

[0004] V-type vertical axis wind turbines include vertical axis wind turbines with blades protruding upward from a center point or V-shaped cross section. This results in the power train being located close to the ground, rather than at a higher altitude. However, the requirement for a large and expensive drive train still exists.

[0005] At least one object of one embodiment of the present invention is to provide an improved vertical axis turbine for generating electrical power having high efficiency and avoiding a gearbox or having a generator with a high number of poles. Summary of the invention

[0006] According to a first aspect, a turbine is provided, comprising a first rotor configured to rotate around a first rotation axis and at least one second rotor. The first rotation axis of the first rotor may be vertical or at least more vertical than horizontal in use. The at least one second rotor may be arranged on the first rotor, contained in the first rotor or coupled to the first rotor. The first rotor may be configured to be driven and / or rotated by fluid motion, such as driven and / or rotated by wind or water flow. The first rotor is operable to drive the second rotor, such as by moving the second rotor through a fluid when the first rotor rotates. (Multiple) second rotors may be arranged on the first rotor, contained in the first rotor or coupled to the first rotor, so that the rotation of the first rotor around the first rotation axis moves (multiple) second rotors, such as around the first rotation axis. (Multiple) second rotors may be operable to drive a power output system, or each second rotor may be operable to drive a corresponding power output system. (Multiple) power output systems may include at least one generator and an optional gearbox. Preferably, the generator may be directly driven by the corresponding second rotor, or alternatively, the generator may be indirectly driven by the corresponding second rotor through a corresponding gearbox.

[0007] Each second rotor may be configured to rotate around a corresponding second axis of rotation. The second axis of rotation of at least one second rotor may be at an angle, such as substantially vertical, to the first axis of rotation of the first rotor. In use, at least one or each of the corresponding second axes of rotation about which the (multiple) second rotors rotate may be or include a corresponding horizontal axis or at least one axis that is more horizontal than vertical. In other words, at least one or each of the second rotors may be a horizontal axis rotor. The first and second rotors may be arranged so that the second axis of rotation of at least one or each second rotor is tangent to the circular trajectory through which the first rotor moves the (multiple) second rotors.

[0008] In an exemplary arrangement, the turbine described above may include a main (first) rotor driven by wind or other fluid flow, and provided with one or more secondary or second rotors driving a power take-off system (preferably directly driven without the use of a gearbox). The (multiple) second rotors may be moved by the rotation of the first (main) rotor, such that the movement of the (multiple) second rotors by the first rotor through the fluid causes the (multiple) second rotors to rotate and thereby drive their respective power take-off systems. There are many such arrangements that do not result in an efficient and effective turbine. The turbine must be appropriately constructed so as to be usable, and the first rotor, (multiple) second rotors and power take-off are selected so that the combined result is a particularly efficient and effective turbine. The selection of many parameters of the turbine (such as torque, tip speed or rotational speed of the first and / or second rotors, power coefficients, etc.) is narrow for a combination of rotors, (multiple) second rotors and power take-offs that is efficient and effective when the power take-off does not require a gearbox or a generator with a large number of pole pairs.

[0009] The maximum aerodynamic efficiency of a horizontal axis turbine (e.g. where the main rotor rotates about a horizontal axis in use) is obtained with a tip speed ratio (i.e. the ratio of the speed of the blade tips to the wind speed perpendicular to the rotor) approaching 7. The combination of horizontal axis second rotor(s) (also operating at a tip speed ratio of 7) mounted on a horizontal axis first rotor (operating at a tip speed ratio of 7) will have a combined tip speed ratio approaching 49. At a wind speed of 10 m / s, the speed of the blade tips is 490 m / s, well in excess of the speed of sound. At a tip speed of 490 m / s, the second rotor(s) operate well beyond the usable operating range of the secondary rotor.

[0010] The rotation of the first rotor causes the (multiple) second rotors to move along a circular path at a forward speed relative to the ground, thereby generating thrust on the (multiple) second rotors. The mechanical power that overcomes the thrust and maintains the rotation of the first rotor and the forward speed of the (multiple) second rotors is the product of the thrust multiplied by the forward speed of the (multiple) rotors. In turn, the (multiple) second rotors deliver mechanical power to the power output device. The transmission efficiency of the mechanical power from the first rotor to the (multiple) second rotors and to the power output device is the ratio of the mechanical power delivered by the (multiple) second rotors to the mechanical power that maintains the rotation of the first rotor. When the second rotor is designed to have aerodynamic characteristics similar to the aerodynamic characteristics of a conventional HAWT rotor and operates at maximum aerodynamic efficiency, the transmission efficiency of the mechanical power from the first rotor to the (multiple) second rotors is close to the theoretical limit of 2 / 3. In order to compensate for such low efficiency, a larger, heavier and more expensive first rotor is required.

[0011] However, many of the above disadvantages may be reduced, eliminated or advantageously employed in a system that includes a vertical axis first rotor driven by wind or water current, but in which the first rotor moves one or more second rotors through air or other fluid, and in which the rotation of the second rotors due to the movement of the second rotors through the air or other fluid drives the power take-off, rather than the main / first rotor driving the power take-off.

[0012] The aerodynamic efficiency of a vertical axis turbine is generally lower than that of a corresponding horizontal axis turbine. In addition, the rotational speed tends to be slower and the torque higher. In practice, these characteristics can be a problem in conventional vertical axis turbines, because the reduced aerodynamic efficiency relative to a corresponding horizontal axis turbine generally results in a larger vertical axis turbine to produce the same power as an equally rated horizontal axis turbine, with associated disadvantages, such as in terms of cost, weight and complexity. In addition, the higher torque on the drive shaft used to couple the rotor to the power take-off results in a heavier and more expensive drive train.

[0013] In a system comprising a vertical axis first rotor and one or more second rotors, many of the above-mentioned disadvantages of known vertical axis turbines may also be reduced, eliminated or advantageously used.

[0014] In an exemplary arrangement, a specific design of a vertical axis first rotor is combined with a specific design of a (multiple) second rotor to reduce, eliminate or advantageously use the disadvantages of a vertical axis wind turbine and the disadvantages of a (multiple) second rotor. Aerodynamic considerations impose a maximum value on the tip speed of the blades of the second rotor. In addition, when each secondary rotor directly drives a generator without the need for a gearbox or multi-pole generator, generator considerations impose a minimum value on the rotational speed of the second rotor.

[0015] In a first exemplary arrangement, the rotor comprises an upper portion with two upper blades in a V shape and a lower portion with two lower blades in an inverted V shape. A secondary rotor and optionally an associated generator are attached to the tip of each lower blade. Each secondary rotor directly drives an associated generator, which may have 4 pole pairs and a nominal frequency of 25 Hz, without the need for a gearbox. The rotor speeds of the first and second rotors are variable, increasing with wind speed. The mechanical power P delivered by the first rotor is F Related to the ambient wind speed, at rated wind speed V RThe first rotor has the greatest aerodynamic efficiency at a tip speed ratio of 4.65. The second rotor operates at a tip speed ratio of 3.13, with an aerodynamic power coefficient of 0.27 and an aerodynamic thrust coefficient of 0.3375. The combined tip speed ratio (i.e., the product of the tip speed ratios of the first and second rotors) is 14.57. The mechanical power extracted from the wind by the first rotor is proportional to the ambient wind speed V R and the rotation speed of the second rotor about, that is When the rotation speed of the second rotor is 39.21 rad / s and the rated wind speed is 12.66 m / s, the tip speed of the secondary rotor is 184.3 m / s and the mechanical power extracted from the wind by the first rotor is 5.99 MW. When the turbine is operated with the second rotor rotation speed varied, the second rotor delivers 5.02 MW (i.e. 84% of the mechanical power extracted from the wind by the first rotor) of mechanical power to the generator at a wind speed of 12.66 m / s, increasing to 5.50 MW (i.e. 92% of the mechanical power delivered by the first rotor) at a wind speed of 20 m / s. The first rotor has an area of ​​12351 square meters and a maximum value of the aerodynamic power coefficient of 0.39. The second rotor has a combined area of ​​138.8.

[0016] In a second exemplary arrangement, the rotor comprises an upper portion having two blades in a V shape and a lower portion having two blades in an inverted V shape. Two secondary rotors and optionally associated generators are attached to the tip of each lower blade. Each secondary rotor directly drives an associated generator, which may have 4 pole pairs and a nominal frequency of 25 Hz without the need for a gearbox. The second rotor has maximum aerodynamic efficiency at a tip speed ratio of 4.65. The second rotor operates at a tip speed ratio of 3.13 with an aerodynamic power coefficient of 0.27 and an aerodynamic thrust coefficient of 0.3375. The mechanical power extracted from the wind by the first rotor is When the rotation speed of the second rotor is 39.21 rad / s and the rated wind speed is 11.79 m / s, the tip speed of the secondary rotor is 171.6 m / s and the mechanical power delivered by the first rotor is 8.41 MW. The second rotor delivers 7.05 MW (i.e., 84% of the mechanical power delivered by the first rotor) of mechanical power to the generator at 11.79 m / s, increasing to 7.91 MW (i.e., 94% of the mechanical power delivered by the first rotor) at a wind speed of 20 m / s. The first rotor has an area of ​​21,470 square meters and a maximum value of the aerodynamic power coefficient of 0.39. The second rotor has a combined area of ​​242.3 square meters.

[0017] In the first and second exemplary arrangements, the selection of the rated wind speed and the tip speed of the second rotor determines all other parameters, including the mechanical power delivered by the first rotor, the mechanical power delivered to the generator by the second rotor, the area of ​​the first rotor and the combined area of ​​the second rotor. Modifying either exemplary arrangement by increasing the rotational speed of the second rotor while keeping the rated wind speed constant reduces the power delivered to the generator, the area of ​​the first rotor and the combined area of ​​the second rotor by the same factor (i.e., the square of the ratio of the rotational speeds). The rotational speed of the second rotor in the second arrangement is increased from 39.21 rad / s to 46.46 rad / s, and the mechanical power delivered by the first rotor is reduced from 8.41 MW to 5.99 MW. Modifying either of the exemplary arrangements by increasing the number of blades comprising the lower portion of the first rotor from 2 to 3 while keeping the number of secondary rotors attached to the tips of the blades and the total mechanical power delivered to the generator the same increases the rotational speed of the secondary rotor to 48.02 rad / s and the nominal frequency of the generator to 30 Hz.

[0018] The combined efficiency of the first and second rotors in delivering mechanical power to the generator is between 84% and 94%. This high combined efficiency is obtained by having a first rotor with high aerodynamic efficiency (maximum value of the aerodynamic power coefficient of 0.39 at a tip speed ratio of 4.65) and a second rotor with low aerodynamic efficiency (value of the aerodynamic power coefficient of 0.27 at a tip speed ratio of 3.13 and a ratio of the aerodynamic power coefficient to the aerodynamic thrust coefficient of 0.8). The tip speed ratio at which the first rotor has maximum aerodynamic efficiency is higher for a V-type vertical axis turbine than for an H-type rotor, and for a V-type rotor it is easier to obtain a value of 4.65. A value of 0.8 for the ratio of the aerodynamic power coefficient to the aerodynamic thrust coefficient can be obtained by designing the secondary rotor to maximize the mechanical power extracted from the wind speed while keeping the blade root bending moment constant. The value of 0.27 for the aerodynamic power coefficient at a tip speed ratio of 3.13 is within the normal range for low-efficiency rotors designed according to this criterion.

[0019] The special arrangement that results in an efficient and effective turbine has the following characteristics.

[0020] The first (main) rotor is rotatable about a generally vertical axis of rotation and is configured to move one or more secondary rotors having generally horizontally oriented axes of rotation.

[0021] The first rotor may include at least one upper blade and / or at least one lower blade.

[0022] The at least one second rotor may be configured such that the power take-off is a direct drive (ie without a gearbox), or a semi-direct drive (ie with a single-stage gearbox).

[0023] The power take-off may be configured to provide variable speed operation of the first and second rotors, wherein the rotational speed of the first rotor increases with wind speed until a rated wind speed is reached.

[0024] The first rotor may be configured to operate at or near a maximum value of its aerodynamic power coefficient below rated wind speed.

[0025] The first rotor may be configured to have maximum aerodynamic efficiency at a tip speed ratio value in the range of 4 to 5 (the normal range for a vertical axis turbine).

[0026] The combined first and second rotors may be configured to have a high efficiency in delivering mechanical power to the generator when at least one of the second rotors operates at a low efficiency.

[0027] The at least one second rotor may be configured to operate at a tip speed ratio in the range of 3 to 4 at wind speeds below rated.

[0028] The at least one second rotor may be configured to operate at a high value of the ratio of the aerodynamic power coefficient to the aerodynamic thrust coefficient below rated wind speed, wherein the value is higher than 0.75.

[0029] The first and second rotors may be configured to have a product of a tip speed ratio of the first rotor and a tip speed ratio of the second rotor in the range of 14 to 16 below rated wind speed, and to have a tip speed of the second rotor in the range of 0.4 to 0.6 times the speed of sound at rated wind speed.

[0030] The characteristics of the first rotor (particularly the values ​​of the tip speed ratio and the aerodynamic power coefficient) and the characteristics of the second rotor (particularly the values ​​of the tip speed ratio, the aerodynamic power coefficient and the aerodynamic thrust coefficient) are all subject to strict constraints. When selecting the values ​​of the rated wind speed and the rotational speed of the second rotor, the values ​​of all remaining variables, including the area of ​​the first rotor and the complete area of ​​the second rotor, are determined. Although the value of the rated wind speed itself is limited to the range of 11 m / s to 13.5 m / s, and the nominal rotational speed of the generator should also be limited to greater than 20 Hz, there is still sufficient design flexibility to obtain an efficient and effective turbine as shown in the first and second exemplary arrangements.

[0031] The first rotor may be configured to operate at its maximum aerodynamic coefficient (C pmax) or close to its maximum aerodynamic power coefficient. It should be understood that the maximum aerodynamic power coefficient (C pmax ) varies with the design and construction of the first rotor and associated blades, but can be easily determined by a skilled person for any given rotor and blade construction / design.

[0032] The at least one second rotor may be configured to operate such that a ratio of an aerodynamic power coefficient to an aerodynamic thrust coefficient has a value above 0.75 below a rated wind speed.

[0033] The at least one second rotor may be configured to operate such that the tip speed ratio is in the range of 3 to 4 below rated wind speed.

[0034] The first rotor and the at least one second rotor may be configured such that a rated wind speed is in the range of 11 m / s to 13.5 m / s.

[0035] The first rotor and at least one second rotor may be configured such that the rotational speed of the second rotor(s) is high enough to drive (e.g. directly drive) the power take-off. However, if the rotational speed of the second rotor is too high, the value of the ratio of the aerodynamic power coefficient to the aerodynamic thrust coefficient will be less than 0.75. The first rotor and / or at least one second rotor may be configured such that the product of the tip speed ratio of the first rotor and the tip speed ratio of the second rotor is in the range of 14 to 16, and the tip speed ratio of the second rotor is in the range of 0.4 to 0.6 times the speed of sound at rated wind speed.

[0036] The power take-off may be configured such that the rotational speed of the generator is greater than 20 Hz at rated wind speed.

[0037] The first rotor may include at least one upper blade and / or at least one lower blade.

[0038] The turbine may be configured to operate as a wind turbine and / or a tidal stream turbine. It will be appreciated that, in use, the axis of rotation of the first rotor may be vertical, or may be within 10° of vertical, or may be closer to vertical than horizontal. If the angle of the first rotor is adjustable or changeable, then in use, the axis of rotation of the first rotor may be vertical, or may be within 10° of vertical, or may be closer to vertical than horizontal, in at least some or all of the adjustable or changeable angles of the rotor.

[0039] At least one second rotor may be configured to convert power from the rotation of the first rotor into rotation of the second rotor. The second rotor may be configured so that under all operating conditions at least 80% of the mechanical power extracted from the wind by the first rotor is delivered to the generator, i.e. the turbine may have a high efficiency in use.

[0040] The first rotor may be configured to have maximum aerodynamic efficiency at a tip speed ratio value in the range of 4 to 5 (a normal range for vertical axis turbines).

[0041] At least one second rotor may be configured to drive a power take-off system. For example, at least one second rotor may be configured to drive an electric generator. Each of the one or more second rotors may be configured to drive a power take-off system. The power take-off system may include an AC generator. The AC generator may be a generator having a number of pole pairs, such as 8 pole pairs or less or 4 pole pairs or less. The power take-off system may be a synchronous generator, such as a 25Hz 4-pole pair 2.5MW synchronous generator.

[0042] Due to the rotation of the at least one second rotor, the power take-off system can generate power in use. For example, the rotation of the at least one second rotor in use can drive an associated power take-off system, which can generate power, such as electricity. The power take-off system can be driven by the second rotor in use, such as a direct drive.

[0043] Direct drive may mean that the power take-off system rotates at the same speed as the at least one second rotor.For example, in use, each rotation of the at least one second rotor may result in one rotation of the power take-off system.

[0044] The power take-off system may be coupled (such as directly coupled) to the second rotor. For example, the coupling between at least one second rotor and the power take-off system may advantageously not include a gearbox. In other words, the turbine may be a gearbox-less or direct drive turbine.

[0045] The power take-off may be configured to provide variable speed operation of the first and second rotors, wherein the rotational speed of the first rotor increases with wind speed until a rated wind speed is reached.

[0046] At least one second rotor may be arranged on at least one of the blades or included in at least one of the blades. The lower blades may include or be provided with at least one second rotor. The lower blades may each include or be provided with a second rotor. At least some of the lower blades may each include or be provided with more than one second rotor. The turbine may be configured so that in use (e.g. during the entire operation of the turbine) the second rotor is 25m or lower above ground or sea level.

[0047] The at least one second rotor may comprise a second axis of rotation, for example a substantially horizontal axis of rotation in use.The at least one second rotor may be, comprise or be included in a turbine, such as the second turbine.

[0048] The turbine may comprise at least one support structure. The at least one second rotor may be arranged on or included in the at least one support structure. The at least one support structure may comprise or be provided with at least one second rotor. The at least one support structure may each comprise or be provided with a second rotor. At least some of the at least one support structure may each comprise or be provided with more than one second rotor.

[0049] There may be more than one second rotor. At least one second rotor may be mounted on or included in the blades of the first rotor. The at least one second rotor may be attached or mounted on a separate rotating structure coupled to the first rotor so that the separate rotating structure can be rotated by the first rotor (e.g., by the rotation of the first rotor). At least some or all of the second rotors may have the same distance along the blades of the first rotor and / or be in the same relative position on the blades of the first rotor, wherein the second rotors are supported and / or coupled to the blades of the first rotor. At least some or all of the second rotors may be at and / or near the tips of the blades of the first rotor, wherein they are supported at the tips of the blades of the first rotor. The tip of the blade may be the end farthest from the axis of rotation of the first rotor, such as the distal end of the blade. At least some or all of the second rotors may be at the same distance and / or radius from the first axis of rotation of the first rotor (e.g., which is substantially vertical in use).

[0050] At least some or all of the second rotors may be in the same relative position relative to the first axis of rotation of the first rotor. For example, at least some or all of the more than one second rotors may be arranged rotationally symmetrically around the first axis of rotation of the first rotor. At least some or all of the more than one second rotors may follow the same path in use. At least some of the more than one second rotors may be arranged in a plane or configured to rotate in a circle substantially perpendicular to the first axis of rotation of the first rotor.

[0051] The first rotor may be driven in use by a fluid such as air (e.g. wind) or water acting on the upper and / or lower blades. The upper and / or lower blades may be configured, configurable, reconfigurable or dynamically reconfigurable to maximize the rotational efficiency of the first rotor.

[0052] At least some of the upper and / or lower blades may be aerodynamically and / or hydrodynamically designed. At least some of the upper and / or lower blades may be at least partially thin in shape, such as being airfoil or hydrofoil in shape. For example, at least some of the upper and / or lower blades may be thin in shape along at least a portion of the blade length.

[0053] The turbine may include two or more upper blades. The turbine may include two or more lower blades. The turbine may include the same number of upper blades as lower blades. The tips or distal ends of some or all of the upper and / or lower blades may be free or unconnected, e.g., not connected to other of the upper and / or lower blades.

[0054] The upper blades and the lower blades may be constructed or configurable to at least partially balance the turbine. For example, each upper blade may be paired with a lower blade, and each upper blade and lower blade pair may be located in a plane. The plane in which the upper blade and lower blade pair are located may be parallel to the first rotation axis of the first rotor. The upper blades and / or the lower blades (such as the upper portion and the lower blade pair) may be arranged symmetrically (such as rotationally symmetrically) around the rotation axis of the first rotor. The moments generated on the main bearing from the upper blades and from the lower blades act in opposite directions and are therefore partially canceled.

[0055] The turbine may include a support or tower for supporting the first rotor. The first rotor may be attached (e.g., rotatably attached) and / or fixed to the top of the tower or support. The first rotor may be fixed and / or attached to the tower at a first bearing. The first axis of rotation of the first rotor may be in a position along the axis of the tower.

[0056] The first rotor may rotate on a first bearing. Blades, such as an upper portion and / or a lower blade, may be attached and / or fixed to the first bearing. The blades may be arranged and / or may be configured to reduce and / or minimize a tipping moment acting on the first rotor and / or the first bearing. For example, a tipping moment from an upper blade acting on the first bearing may be substantially or completely offset by a tipping moment from a lower blade acting on the first bearing. The tipping moment acting on the first bearing due to the upper blade in use may act in a direction opposite to the tipping moment acting on the first bearing due to the lower blade in use.

[0057] At least one second rotor may include at least one second blade, for example five second blades. At least one second blade may drive at least one second rotor to rotate in use, for example, rotate around a corresponding second rotation axis in use. At least one second blade and / or the second rotor may be driven by the rotation of the first rotor. For example, in use, the rotation of the first rotor may drive at least one second rotor by a fluid (such as water and / or air), and the fluid may act on the second rotor and / or at least one second blade to rotate the second rotor. At least one second blade may be configured to rotate, rotate and / or drive at least one second rotor.

[0058] The at least one second rotor may have a rotor solidity of less than 0.07 to 0.09 (eg, 0.082). The rotor solidity refers to the ratio of the total area of ​​the rotor blades to the rotor swept area.

[0059] At least some of the blades may be arranged and / or configured to extract energy from a fluid acting on the blades.At least some of the upper portion and / or the lower portion and / or the second blades may be arranged and / or configured to extract energy from a fluid acting on the blades.

[0060] At least some of the blades (e.g., blades of the first rotor) may be pitchable. Preferably, at least some of the upper blades and / or lower blades of, for example, the first rotor may be pitchable. At least some of the blades may be individually pitchable. At least some of the blades may be full-span pitchable. At least some of the blades may be substantially straight and / or linear. At least some of the blades may be pitchable about their linear or longitudinal axis, for example, rotating about their linear or longitudinal axis. The turbine may include an actuator that is operable to pitch the blades. The actuator may be at or coupled to the base of at least some of the blades. For example, the actuator may be at or coupled to the end of at least some of the blades that is closest to the first bearing. Each blade may be operated by a corresponding actuator. Each upper and / or lower blade without the second rotor may be operated by an actuator. Each upper blade and / or lower blade without the second rotor may be pitchable. The actuator may be replaceable and / or accessible in use, such as readily accessible, for example from a base of the turbine in use.

[0061] The at least one second blade may be configured to extract energy from the fluid acting upon them.

[0062] The first rotor may include a support member. The support member may be attached and / or fixed to the first bearing. The blades (such as the upper blades and / or the lower blades) may be attached and / or fixed to the support member.

[0063] The support member may be substantially planar and / or may be or include a longitudinal or elongated support member. The support member may be or include a rod, a circle, a triangle, a square or other polygon. The support member may be a polygon (such as a regular polygon) having the same number of angles as the number of pairs of upper and lower blades. The support member may include a plurality of rods, and each rod may support at least one upper blade and / or at least one lower blade. The support member may be substantially horizontal and / or perpendicular to the axis of rotation of the first rotor in use.

[0064] The support member may be aerodynamically and / or hydrodynamically shaped. The support member may be at least partially thin in shape, such as airfoil or hydrofoil in shape. For example, the support member may be thin in shape along at least a portion of the length of one of its rods. The support member may be rotationally symmetrical.

[0065] For example, the upper and / or lower blades of the first rotor may be attached and / or fixed at or near an end (e.g., each end) of the support member. For example, a corresponding upper blade may extend generally upward and / or outward from each end of the support member, and a corresponding lower blade may also extend generally downward and / or outward from each end of the support member. The upper blades may be tilted or angled away from each other, for example, when they extend from the support member. The lower blades may be tilted or angled away from each other, for example, when they extend from the support member. The upper and / or lower blades may be mounted on the support member so that they are rotationally symmetrical around the axis of rotation of the first rotor. The upper blades may be attached to the upper surface of the support member in use. The lower blades may be attached to the lower surface of the support member in use.

[0066] The turbine and / or the first rotor may be rotationally symmetrical, for example rotationally symmetrical about an axis of rotation of the first rotor.

[0067] The upper blade may rotate above the tower in use. The lower blade may rotate around the tower in use. The upper blade and / or the lower blade may protrude away from the tower. The tip of the upper blade and / or the lower blade may be further from the axis of rotation (e.g. which is vertical in use) than the base of the blade (which is, for example, attached, attachable and / or fixed or fixable to the first bearing and / or support member).

[0068] The upper blades may generally protrude upwards in use. The upper blades may protrude generally upwards from the support member and / or the first bearing in use. The upper blades may protrude at an angle relative to the vertical in use. For example, the upper blades may be at an angle of less than 90 degrees to the vertical in use, preferably at an angle of 0 to 45 degrees to the vertical in use, more preferably at an angle of 15 to 40 degrees to the vertical in use, more preferably at an angle of 25 to 35 degrees to the vertical in use.

[0069] The lower blades protrude generally downwards in use. The lower blades may protrude generally downwards from the support member and / or the first bearing in use. The lower blades may protrude at an angle relative to the vertical in use. For example, the lower blades may be at an angle of less than 90 degrees to the vertical in use, preferably at an angle of 0 to 50 degrees to the vertical in use, more preferably at an angle of 25 to 50 degrees to the vertical in use, and more preferably at an angle of 45 to 50 degrees to the vertical in use.

[0070] The lower blades may, in use, be at a greater acute angle to the vertical than the acute angle made by the upper blades with the vertical in use. The lower blades may, in use, be at a less acute angle to the vertical than the acute angle made by the upper blades with the vertical in use. The upper portion and the lower blades may, in use, be at the same acute angle to the vertical.

[0071] The upper blade may be longer than the lower blade. The lower blade may be longer than the upper blade. The lower blade may be of the order of two thirds the length of the upper blade or less.

[0072] The upper blade may be up to 200 m long, preferably in the range of from 50 m to 150 m long, more preferably in the range of from 80 m to 120 m long, for example 100 m long. The lower blade may be up to 140 m long, preferably in the range of from 35 m to 105 m long, more preferably in the range of from 55 m to 75 m long, for example 65 m long.

[0073] The upper and / or lower blade tips may have the same radius from the axis of rotation (eg which is substantially vertical in use).Alternatively, the upper and / or lower blade tips may have different radii from the axis of rotation (eg which is substantially vertical in use).

[0074] The at least one second rotor can be on at least one upper blade and / or preferably on at least one lower blade, so that the at least one second rotor can rotate about the rotation axis of the first rotor with a radius up to the radius of the tip of the upper blade and / or the radius of the tip of the lower blade.

[0075] The upper blades may all be identical, such as the same length and / or profile. The lower blades may all be identical, such as the same length and / or profile. The at least one second blade may all be identical, such as the same length and / or profile.

[0076] At least some or each of the upper blades may be different from at least some or each of the other upper blades. For example, there may be two first upper blades that are identical to each other, and two second upper blades that are identical to each other but different from the first upper blades. Some upper blades may differ from some other upper blades in at least one or more or all of the following: their shape, size, length, angle to the vertical, number of second rotors and / or whether they are variable pitch.

[0077] At least some or each of the lower blades may be different from at least some or each of the other lower blades. For example, there may be two first lower blades that are identical to each other, and two second lower blades that are identical to each other but different from the first lower blades. Some lower blades may be different from some other lower blades in at least one or more or all of the following: their shape, size, length, angle to the vertical, and number of second rotors.

[0078] The first rotor may comprise a power take-off system.The first rotor may comprise more than one power take-off system, such as more than one generator.

[0079] The first bearing may advantageously not include a power take-off system.The first bearing may advantageously not include a drive train, such as a conventional turbine drive train.

[0080] At least one second rotor may be removable and / or replaceable in use, for example to minimize the time and effort spent on maintenance and repair. When the turbine is upright and / or in use, at least one secondary rotor may be accessible, such as easily accessible. For example, when the turbine is upright and / or in use, at least one second rotor may be accessible from the plane of the ground, sea level or the base of the tower, for example, at least one second rotor may or may always be no more than 25m from the ground or sea level in use. When the axis of rotation of the first rotor is substantially vertical, the turbine may be considered to be upright. At least one second rotor may be at a lower height, for example, below (such as substantially below) the first bearing and / or support member.

[0081] The turbine may be connected to a power system. The power system may include a rechargeable power source, such as a battery and / or battery pack. The power system may include an electrical grid, such as a national grid.

[0082] The turbine may include one or more wind speed and / or direction measuring devices, such as anemometers, LIDAR, vanes, and / or the like.

[0083] The turbine can be configured to use at least one second rotor and associated (multiple) power output systems to determine the direction of the prevailing wind. When the at least one second rotor rotates into the wind, the power generated increases and / or is at a maximum, and when rotating away from the wind, the power generated decreases and / or is at a minimum. Thus, the turbine is operable to analyze the changes in the power generated by the at least one second rotor and the associated power output system in order to determine the direction of the prevailing wind.

[0084] The turbine may comprise a power connector. The power connector may comprise a transformer, such as a rotary transformer or a non-rotating or conventional transformer, which may be connected by means of slip rings or the like. The power connector may advantageously comprise a variable frequency transformer or an electrical connector. The power connector may be housed in and / or near the tower, for example in and / or near the base of the tower, or in a hub of the turbine. The power connector may connect the turbine to an external power system, such as a power grid, for example a national grid. The power connector may be accessible from the base of the tower in use, such as easily accessible.

[0085] The turbine may include a power converter and / or power electronics. The power converter and / or power electronics may connect the power output system to the power connector. The power converter and / or power electronics may regulate the power output system, the power connector, and / or the power transferred between the power output system and the power connector.

[0086] The power converter and / or power electronics can control the power connection. For example, the frequency of the AC power to the rotary transformer can be controlled to achieve a high efficiency connection (greater than 98%) to the external power system.

[0087] The power converter and / or power electronics may control the turbine. For example, the power electronics may control the power output and rotational speed of the generator by using or by appropriately controlling and / or varying the frequency of the AC power supply to the generator. For example, at wind speeds below rated, the second rotor speed may be controlled to achieve maximum power generation, and at wind speeds above rated, the second rotor speed may be controlled to achieve rated power generation.

[0088] The turbine may include a pitch actuator. The pitch actuator may pitch at least some of the blades. The pitch actuator may control at least some of the blades, such as at least the upper blades of the first rotor, to pitch periodically according to the rotational position of the blades relative to the prevailing wind direction. For example, the pitch actuator may be configured to control the pitch of at least some of the blades to maximize energy below rated wind speed, adjust the rotational speed and / or provide overspeed protection above rated wind speed. The pitch actuator may be housed in and / or near the root of the upper blades of the rotor. The pitch actuator may be accessible from the base of the tower in use, such as easily accessible.

[0089] The center of mass of the turbine may be lower in use. For example, the power connector and power electronics may be housed at and / or near the base of the tower, which may lower the center of mass of the turbine, closer to the base of the tower in use.

[0090] The tower may be supported by a platform. The platform may be floatable and / or tetherable. The turbine may be configured to reduce the weight and / or size of the platform relative to a conventional floating turbine platform.

[0091] According to a second aspect, there is a method of generating power using the turbine of the first aspect.

[0092] The generated power may be generated by and / or extracted from the rotation of the at least one second rotor.

[0093] The method may include exposing the turbine to a fluid that may act on the upper blades and / or the lower blades to drive the first rotor. The fluid may be air and / or water. For example, wind energy and / or wave energy may propel the upper blades and / or the lower blades to drive the first rotor. The upper blades and / or the lower blades may be configured to extract energy from the fluid acting on the upper blades and / or the lower blades.

[0094] The method may comprise configuring the upper blades and / or the lower blades such that the tip speed ratio and the rotational speed of the first rotor are high in use, for example a tip speed ratio in the range of 4 to 5.

[0095] The method may comprise configuring the first rotor and / or the at least one second rotor such that the tip speed ratio and the rotational speed are low in use, for example the tip speed ratio is in the range of 3 to 5. The maximum tip speed of the at least one second blade in use may be high, for example 160 m / s to 200 m / s, for example 180 m / s at rated wind speed.

[0096] The method may include arranging the turbine so that the first rotor drives at least one second rotor through a fluid (e.g., through air or water) by the rotation of the fluid. The fluid may act on the at least one second rotor to drive the at least one second rotor. For example, the fluid may act on a second blade of the at least one second rotor to rotate the at least one second rotor.

[0097] The rotation of at least one second rotor can drive at least one power output system, which can generate power, such as electricity. The at least one second rotor can drive the power output system without a gearbox or a multi-pole generator. For example, the rotation of at least one second rotor can directly drive the at least one power output system. In use, the rotation of at least one second blade can directly drive the power output system.

[0098] The power generated by the at least one second rotor can be cyclic, sinusoidal and / or periodic. For example, as the first rotor rotates, the at least one second rotor can be driven alternately against the fluid flow and with the fluid flow. The power generated by the at least one second rotor can be greater when the at least one second rotor is driven against the fluid flow than when the at least one second rotor is driven with the fluid flow. The cyclic, sinusoidal and / or periodic power generated by the at least one second rotor can increase the efficiency of the power generated by the second rotor. For example, the cyclic, sinusoidal and / or periodic power generated by the at least one second rotor can increase the energy extracted from the fluid acting on the at least one second rotor. For an amplitude of A and an average flow velocity of The sinusoidal variation of the fluid velocity on the second rotor increases the energy extracted by a factor of The determination of the periodic, sinusoidal and / or periodic power generated by the at least one second rotor may be used to determine the direction of the prevailing wind.

[0099] The cyclic, sinusoidal and / or periodic power generated by the at least one second rotor may be used to calculate and / or determine the speed and / or frequency of rotation of the first rotor.

[0100] The power generated by the first rotor may be cyclic, sinusoidal and / or periodic. The point of maximum power generation formed by the first rotor may coincide with the point of minimum power generation formed by the at least one second rotor. The cyclic, sinusoidal and / or periodic nature of the power generated by the at least one second rotor may be reduced by the out-of-phase cyclic, sinusoidal and / or periodic power generated by the first rotor.

[0101] According to a third aspect, there is a method of controlling a turbine of the first or second aspect.

[0102] The turbine may be configured to have maximum efficiency under certain conditions. For example, the turbine may be most efficient in extracting energy from the fluid acting on the turbine when the fluid is at a certain desired velocity or within a certain desired velocity range blowing toward the turbine. Under these conditions, the turbine may be rated to produce maximum power. The turbine may be rated or may be configured to extract maximum energy from the fluid acting on the turbine under these conditions.

[0103] For example, when the turbine is operated as a wind turbine, the turbine may be configured to operate most efficiently at wind speeds below a rated wind speed in the range of 11 m / s to 13.5 m / s. The turbine may be configured to generate megawatts of power, such as multiple megawatts of power, such as up to 10 MW, such as 5.9 MW.

[0104] When the turbine is operated as a wind turbine, the method may include configuring the at least one second rotor to operate most efficiently at an effective wind speed of up to 65 m / s, for example 59 m / s. The effective wind speed of the at least one second rotor is the sum of the wind speed and the relative speed of the at least one second rotor when the first rotor is rotating. The method may include configuring the at least one second rotor to generate megawatts of power, such as up to 5 MW, for example 2.5 MW.

[0105] The method may include pitching at least some of the blades (e.g., upper blades and / or lower blades without a second rotor). The method may include pitching the upper blades. The method may include pitching the upper blades to fix the orientation of each upper blade relative to the fluid flow when the first rotor rotates. For example, the upper blades may be pitched periodically. At least some of the blades may be pitched at the same frequency as the rotation of the first rotor. When the turbine is operating below its maximum rated energy, for example, when the wind blows toward the turbine at less than a specific desired speed or a specific desired speed range, at least some of the blades may be pitched. Pitching at least some of the blades (such as the upper blades) may increase the energy generated by the turbine. For example, pitching at least some of the blades (such as the upper blades) may increase the energy extracted from the wind blowing toward the turbine.

[0106] At least some of the blades may be pitched to increase or optimize the efficiency of energy transfer from the fluid acting on the vertical axis turbine to the turbine relative to energy transfer from the fluid to the vertical axis turbine when the blades are not pitched and / or have a fixed pitch relative to the rotation of the turbine. For example, at least some of the blades may be pitched to increase or optimize the speed of rotation of the first rotor. When the turbine is operated as a wind turbine, at least some of the blades may be pitched to fix the orientation of those blades relative to the wind. For example, at least some of the blades may be pitched periodically to maximize energy transfer from the wind to those blades.

[0107] The method may include determining the direction of a fluid flow acting on the turbine. The direction of the fluid flow may be determined based on the position of the first rotor when the cyclic, sinusoidal and / or periodic power generated by the at least one second rotor is at a maximum. For example, when the power generated by the at least one second rotor is at a maximum, the at least one second rotor is driven directly into the fluid flow by the first rotor.

[0108] The frequency and / or speed of pitching at least some of the upper blades and / or lower blades may be based on the cyclic power generated at the at least one second rotor. For example, at least some of the upper blades and / or lower blades, such as the upper blades, may be pitched at the same frequency as the power generated at the at least one second rotor.

[0109] At least some of the blades may be pitched to reduce the efficiency of energy transfer from the fluid acting on the turbine to the turbine relative to energy transfer from the fluid to the turbine when the blades are not pitched and / or have a fixed pitch relative to the rotation of the turbine. For example, at least some of the blades may be pitched to reduce the rotation speed of the first rotor and / or stop the rotation of the first rotor. At least some of the blades may be pitched to provide overspeed protection. For example, at least some of the blades may be pitched to prevent the first rotor from rotating too fast, such as to prevent damage to the first rotor and / or the first bearing.

[0110] The method may include controlling the rotor speed of at least one second rotor. The method may include controlling the rotor speed of each second rotor individually. The rotor speed of at least one second rotor may be controlled by controlling the frequency of the voltage on at least one second rotor (on the power output system of at least one second rotor). The drag of at least one second rotor may be used to control and / or influence the rotational speed of the first rotor.

[0111] When the turbine is operating above its maximum rated energy, for example when the wind blows towards the turbine above a certain desired speed or a certain desired speed range, the rotor speed of the first rotor may be variable and controlled by collectively pitching the upper blades. The upper blades may be pitched in response to relatively low frequency changes in wind speed to control the rotor speed of the first rotor. The rotor speed of the at least one second rotor may be controlled in response to relatively high frequency changes in wind speed, for example by controlling the frequency of a voltage on the at least one second rotor.

[0112] When the wind blows toward the turbine above a certain desired speed or a certain desired speed range, some of the power of the rotating first rotor may be stored in a reserve, such as in a flywheel, a compressed air storage device, an electrochemical battery, and / or the like. Later, when the wind speed has dropped, power may be drawn from the reserve.

[0113] The method may include monitoring the power generated by the turbine. The method may include controlling the turbine in response to the power generated by the turbine. The power generated by the turbine may be monitored by power electronics and / or control of the turbine may be performed by power electronics. The power electronics may be controlled by a programmable computer.

[0114] It should be understood that in any other aspect or embodiment of the present invention, the various features and / or combinations of features defined according to any aspect of the present invention or below with respect to any specific embodiment of the present invention may be used separately or individually, alone or in combination with any other defined features.

[0115] Additionally, the invention is intended to cover apparatus configured to perform any of the features described herein with respect to methods and / or methods of using or producing, using or making any of the apparatus features described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0116] At least one embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0117] Figure 1 A perspective view of a vertical axis turbine is shown;

[0118] Figure 2 A plan view of a vertical axis turbine is shown;

[0119] Figure 3 A wind farm showing vertical axis turbines; and

[0120] Figure 4a and Figure 4b The plan shapes of the upper blade, the lower blade and the second blade are shown. DETAILED DESCRIPTION

[0121] Throughout the following description, the same reference numerals will be used to identify the same parts.

[0122] Figure 1 A vertical axis turbine 5 is shown having a tower 10 and a first rotor 12. The first rotor 12 is attached to the tower 10 at a first bearing 13. The first rotor 12 rotates on the first bearing 13. The first bearing 13 is at the top of the tower 10. The first rotor 12 has a support member 15. The first rotor 12 is attached to the first bearing 13 at the center of the support member 15.

[0123] Two upper blades 20 are attached to the support member 15, and the upper blades 20 are inclined upward and protrude away from the tower 10. Two lower blades 25 are attached to the support member 15, and the lower blades are inclined downward and protrude away from the tower 10. The upper blades 20 and the lower blades 25 are attached to the support member 15 by attachment points 30. The attachment points 30 for the upper blades 20 include actuators that enable the upper blades 20 to be pitched. Since the first rotor 12 rotates relatively slowly in use, the pitch of the upper blades 20 is also relatively slow, and therefore the duty cycle of the actuator is low. Therefore, the actuator has a lower maintenance cost.

[0124] The lower blades 25 include respective second rotors 35 and associated generators 37 at the ends of the lower blades 25. The second rotors 35 include second blades 40. The second rotors 35 are each configured to drive an associated generator 37. The second rotors 35 face in opposite directions so that rotation of the first rotor 12 causes the two second rotors 35 to be driven in the same orientation along the same path in use.

[0125] The upper blades 20, lower blades 25 and support member 15 are configured so that when wind blows toward the vertical axis turbine 5, the first rotor 12 rotates clockwise about the first bearing 13 (although it should be understood that a configuration in which the direction of rotation is reversed may be provided). This rotation drives the second rotor 35 through the air. The air acts on the second blades 40 of the second rotor 35, which causes the second rotor 35 to rotate. This in turn provides power for the generator 37 driven by the second rotor 35. Thus, the first rotor 12 is used to rotate the second rotor 35, and the rotation of the second rotor 35 drives the generator 37. Thus, it is the rotation of the second rotor 35, rather than the rotation of the first rotor 12, that primarily drives the generator 37.

[0126] Compared to conventional horizontal axis wind turbines, the horizontal axis second rotor 35 is unusually designed to have a lower C P Value and higher C P With C T The second rotor 35 is also designed to operate at a high tip speed of the order of 160 m / s. If the tip speed of the second rotor 25 is much higher, the second rotor 35 will become incompatible with the required higher lift and lower drag aerodynamic characteristics.

[0127] When the second rotor 35 is operated at a relatively high tip speed with a relatively short second blade 40, the second rotor 35 rotates at a relatively high speed, for example up to 50 rad / s. This results in each of the second rotors 35 being able to directly drive a corresponding associated electric generator 37 without the need for a gearbox or a multi-pole generator. This simplifies the second rotor 35 and thus reduces the cost of the second rotor 35.

[0128] Because there is no power take-off system at the first bearing 13, no large, heavy and expensive drive train is required at the first bearing 13. This greatly simplifies the vertical axis turbine 5 and greatly reduces its cost.

[0129] The power electronics 41 are included at the bottom of the tower 10 and are easily accessible. Since the power electronics 41 are easily accessible, maintenance costs are relatively low. The power electronics 41 are used to monitor and control the vertical axis turbine 5 and the power generated by the vertical axis turbine 5.

[0130] The power electronics 41 are connected to a power connector 42. The power connector 42 connects the vertical axis turbine 5 to a power system 43, such as a national grid.

[0131] Since the power electronics 41 are located at a lower height, they can be easily accessed from the level of the base of the tower 10. This provides for simple and low-cost maintenance.

[0132] Figure 2 Shows Figure 1 A plan view of the vertical axis turbine 5. The axis of rotation 45 of the first rotor is shown by a dotted line.

[0133] The tips of the upper blades 20 and the lower blades 25 are at the same distance from the rotation axis 45 of the first rotor, and rotate at the same radius from the rotation axis 45 of the first rotor. The second rotor 35 is at the tip of the lower blade 25. The second rotor 35 is at the same height as the base of the tower 10. The second rotor 25 is at the same distance from the rotation axis 45 of the first rotor, and rotates at the same radius from the rotation axis 45 of the first rotor.

[0134] Since the second rotor 35 is located at a relatively low height (e.g., 25 m or 20 m or less from the ground or sea level), they can be easily accessed from the plane of the base of the tower 10. Since the second rotor 35 is also lightweight and replaceable, the second rotor 35 can be easily replaced. This provides simple and low-cost maintenance.

[0135] The upper blades 20 form a smaller acute angle with the vertical direction than the lower blades 25. The upper blades 20, the lower blades 25 and the support member 15 lie in a plane.

[0136] Figure 3 An offshore wind farm 105 is shown of vertical axis turbines 5. A tower 10 supports a first rotor 12 above the ocean 110. The tower 10 may be supported by a floating platform or fixed to the sea bed.

[0137] The lower blades 25 protrude downward toward the sea 110, and the second rotor 35 is at the tip of the lower blades 25. Therefore, the second rotor 35 is at a relatively low height and relatively close to the surface of the sea 110. Therefore, since the second rotor 35 is not at a considerable height, it is relatively simple to maintain and / or replace the second rotor 35 from the ship.

[0138] Figure 4a The planar shapes of the upper blade 20 and the lower blade 25 are shown. Both the upper blade 20 and the lower blade 25 are thicker at the base than at the tip. The base of the lower blade 25 is thicker than the base of the upper blade 20. The upper blade 20 is longer than the lower blade 25.

[0139] Figure 4b There is shown a planar shape of the second blade 40. The second blade 40 has a similar planar shape to the lower blade 25, but the second blade 40 is much smaller than the lower blade 25.

[0140] In the examples described above, the first and second rotors are configured so that power output is performed by direct drive without the need for a gearbox or a multi-pole generator. The first and second rotors are configured so that power conversion in which mechanical power at the first rotor is converted into mechanical power at the second rotor has high efficiency.

[0141] Although various examples have been provided above, it should be understood that the present invention is not limited to these specific examples, but is instead defined by the claims. For example, it will be understood by those skilled in the art that the turbine can be scaled up or down to different sizes, and the dimensions given herein are exemplary only. Similarly, it should be understood that geometric terms are interpreted purposefully. For example, blades are three-dimensional objects, and the fact that they can be linear and / or straight does not prohibit, for example, tapering along the length of the blade. The upper and lower blade pairs can be planar, but it should be understood that the upper and lower blade pairs do not exist alone in a two-dimensional plane, but can be planar as real three-dimensional objects. The axis of rotation of the first rotor is described as being substantially vertical in use, and it should be understood that this relates to an axis of rotation in such use, which may deviate from being completely vertical in use, for example, at an angle of less than 15° to the vertical direction.

[0142] Those skilled in the art will appreciate that the turbine disclosed above is equally applicable to onshore and offshore wind turbines, and that the turbine described may be used elsewhere, for example as a tidal stream turbine. In addition, if the turbine disclosed above is used as a wave turbine, it will be appreciated that minor modifications of the embodiments shown in the drawings may be necessary, such modifications falling within the scope of the present disclosure. For example, Figure 1The first rotor may have to be turned upside down horizontally so that the second rotor is on the upper blades rather than the lower blades. This will advantageously bring the second rotor closer to the surface of the water, which will provide the benefits of easier access and lower maintenance costs.

Claims

1. A vertical axis turbine comprising a first rotor and at least one second rotor; The first rotor is configured to rotate about a first rotation axis, wherein the first rotation axis is vertical; The at least one second rotor is disposed on, contained in, or coupled to the first rotor such that the first rotor is operable to move the second rotor when the first rotor rotates; and the second rotor being operable to drive a power take-off system, in, The tip speed ratio is in the range of 3 to 4 at the rated wind speed of the at least one second rotor in use, The first rotor and the second rotor have a combined tip speed ratio of from 14 to 16 at wind speeds below rated wind speed, and The at least one second rotor has an aerodynamic power coefficient (C) greater than 0.75 in use at wind speeds below rated. P ) and the aerodynamic thrust coefficient (C T )ratio.

2. A vertical axis turbine according to claim 1, wherein: The first rotor has a tip speed ratio in the range of 4 to 5 in use below rated wind speed; The first rotor and at least one second rotor have a combined tip speed ratio of 15 at wind speeds below rated, and / or The first rotor has a maximum aerodynamic coefficient of force (C pmax ) within 5% of the aerodynamic power coefficient; and / or The blades of the at least one second rotor have a maximum tip speed in use at their rated wind speed in the range of 0.4 to 0.6 times the speed of sound; and / or The rated wind speed is in the range of 11 m / s to 13.5 m / s in use.

3. The vertical axis turbine according to claim 1, wherein: The power output system includes a generator.

4. The vertical axis turbine according to claim 1, wherein: The at least one second rotor comprises at least one second blade, and rotation of the at least one second blade, in use, directly drives the power take-off system.

5. The vertical axis turbine according to claim 1, wherein: The first rotor includes at least one upper blade and at least one lower blade.

6. A vertical axis turbine according to claim 5, wherein: The at least one second rotor is disposed on or comprised in one or more of the lower blades.

7. The vertical axis turbine of claim 5, wherein: The vertical axis turbine includes a tower supporting the first rotor; said at least one upper blade projecting upwardly and away from said tower; as well as The at least one lower blade projects downwardly and away from the tower.

8. A vertical axis turbine according to any one of claims 5 to 7, comprising two or more upper blades and two or more lower blades, wherein the upper blades and / or lower blades are rotationally symmetric about the rotation axis of the first rotor.

9. A vertical axis turbine according to any one of claims 5 to 7, wherein: The overturning moment of the at least one upper blade acting on the first rotor in use is in an opposite direction to the overturning moment of the at least one lower blade acting on the first rotor in use.

10. A vertical axis turbine according to any one of claims 5 to 7, wherein: At least some of the at least one upper blade and / or the at least one lower blade are variable pitch.

11. A vertical axis turbine according to any one of claims 5 to 7, wherein: The upper blades and / or lower blades are free or unconnected at their distal ends or tips.

12. A vertical axis turbine according to any one of claims 1 to 7, wherein: The power take-off system is driven directly by at least one second rotor without being driven via a gearbox and / or the first rotor rotates on a first bearing and the first bearing does not include a drive train.

13. A vertical axis turbine according to any one of claims 1 to 7, configured such that the second rotor is, in use, located 25m or less above ground or sea level during the entire operation of the turbine.

14. A vertical axis turbine according to any one of claims 1 to 7, wherein: An electrical connection is also included, and wherein the second rotor and / or the power take-off system can be controlled by appropriately controlling the electrical connection.

15. A vertical axis turbine according to claim 14, wherein: The electrical connection comprises a variable frequency transformer, and the second rotor and / or the power output system can be controlled by appropriately controlling the variable frequency transformer.

16. A vertical axis turbine according to any one of claims 1 to 7, wherein: The turbine is operable to analyse changes in power generated by the at least one second rotor and associated power take-off system to determine the direction of prevailing winds.

17. A method of generating power using a vertical axis turbine according to any one of claims 1 to 16, comprising: Providing the turbine so that the fluid acts on the upper blades and / or the lower blades to drive the first rotor, such that: The rotation of the first rotor drives the at least one second rotor through the fluid; as well as The fluid acts on the at least one second rotor to drive the at least one second rotor.

18. The method according to claim 17, wherein: The fluid is air and / or water.

19. The method according to claim 17 or 18, wherein: The generated power is generated by the rotation of the at least one second rotor.

20. The method according to claim 17 or 18, wherein: The power generated is electricity.

21. A method of controlling the rotation of a first rotor of a vertical axis turbine according to any one of claims 1 to 16 in use, or a method of controlling power generated by a method according to any one of claims 17 to 20, comprising: pitching at least some of the blades of the first rotor; and / or The frequency of an electrical connection to the power take-off system is varied.

Images