NO347728B1

NO347728B1 - A counter-rotating wind turbine and a wind power plant with a counter-rotating wind turbine

Info

Publication number: NO347728B1
Application number: NO20211518A
Authority: NO
Inventors: Stian Valentin Knutsen
Original assignee: World Wide Wind Tech As
Priority date: 2021-12-16
Filing date: 2021-12-16
Publication date: 2024-03-11
Also published as: CN219549022U; NO20211518A1

Description

The present invention is related to a wind turbine with a rotational axis that is substantially perpendicular to the wind direction and usually arranged with a vertical rotational axis and a wind power plant comprising such a wind turbine.

Today wind power accounts for approx. 8-10% of annual installed power capacity globally (c. 750 GW). Wind will play an increasingly important role in the ongoing energy transition towards renewables. The global cumulative installed capacity of onshore wind power is estimated to grow more than threefold by 2030 to 2,000 GW and may increase seven-fold by 2050 to 5,000 GW, and it is expected that the installed wind power capacity will further increase substantially globally towards 2050.

There are two main wind turbine technologies, classified by the orientation of the rotational axis of the wind turbines. Three-bladed horizontal-axis wind turbines (HAWT) with the blades upwind of the tower produce the overwhelming majority of wind power in the world today. These turbines have the main rotor shaft and electrical generator at the top of a tower and is pointed into the wind. The generator is placed on top of a shaft in a nacelle. The technology relating to such wind turbines is mature, and all horizontal turbines produced and installed today have similar design. The HAWTs have increased in size and installed capacity over the past years and now ranges from 1MW to 14MW per turbine.

A vertical axis wind turbine (VAWT) has, on the other side, its rotational axis perpendicular to the wind direction and is typically installed with a vertical rotational axis relative to the ground. This is therefore a type of wind turbine where the main rotor shaft is set transverse to the wind while the main components can be located at the base of the turbine. This arrangement allows the generator to be located close to the ground, with a low center of gravity, facilitating easy access to service and repair. VAWTs do not need to be pointed into the wind, which removes the need for wind-sensing and orientation mechanisms. VAWT has, however, not received the same attention and investments as HAWTs and today accounts for less than 0.1% of installed wind power capacity.

Existing technology relating to VAWTs have certain drawbacks which can explain the very low attention that VAWTs have received so far. Firstly, the efficiency of traditional Savonius VAWT turbines is lower relative to HAWTs as it is mainly a turbine that relies on drag for its operation and the blades downwind do not contribute to power generation. The smaller Darius turbines are also subject to vibrations from torque exerted on the mast, leading to increased wear & tear and needs for maintenance. And lastly and perhaps most importantly, VAWTs have not received anything near the same amount in investments in research and development as HAWTs and is therefore a much less mature technology.

Generally, a problem with existing wind turbines is the gear system which is subjected to large and varying forces. The gear systems therefore must be designed to be capable of withstanding large and varying forces over time and are therefore costly. The wind turbines still require extensive maintenance and monitoring to prevent and to avoid complete breakdown of the gears.

The weather conditions are often severe in locations where wind turbines are installed, and the design of the wind turbines must compensate for the impact of heavy wind and also waves for wind turbines which are installed offshore.

Furthermore, the wind conditions can vary considerably depending on how far from the ground or water surface the wind turbine is mounted.

Publications disclosing relevant prior art are KR 101944098 B, US 2014/105752 A1, US 2010/194112 A1, EP 1096144 A2, WO 2019/129049 A1 and US 2014/145449 A1.

Thus, an object of the present invention has been to develop a wind turbine where at least one and preferably some or all of the problems mentioned above are mitigated.

A further object of the present invention has been to provide a wind turbine where the costs of manufacturing, maintenance and monitoring of the gear system of wind turbines is reduced.

A further object of the present invention has been to provide a wind turbine that can be combined with and/or integrated with other structures to be erected.

A further object of the present invention has been to provide a wind turbine that is suitable to be retrofitted on an existing structure.

A further object of the present invention has been to develop a wind turbine that takes into account the varying wind conditions at the ground or water surface and at some distance from the ground or the water surface.

A further object of the present invention has been to develop a wind turbine with a generator that does not need a gear system.

A further object of the present invention has been to develop a wind turbine with an efficient cooling of the generator.

A further object of the present invention has been to a wind turbine with a simplified construction as compared to the common HAWT wind turbines.

These objects are achieved with a wind turbine as defined in claim 1, a wind power plant as defined in claim 22 and a use of the wind turbine or the wind power plant as defined in claim 29. Further embodiments of the wind turbine are defined in the independent claims.

Hence, there is provided a wind turbine comprising at least a first turbine rotor and a second turbine rotor where the first turbine rotor and the second turbine rotor rotate around the same rotational axis (A), which extends in a longitudinal direction of the wind turbine, and the first turbine rotor and the second turbine rotor are contra rotating. The wind turbine further comprises a generator which comprises a first generator part and a second generator part where the first generator part is mounted on the first turbine rotor and the second generator part is mounted on the second turbine rotor, and where the first generator part comprises at least one generator magnet and the second generator part comprises at least one generator coil for generation of an electric current when the wind turbine is operating, i.e. when the first turbine rotor and/or the second turbine rotor is/are rotating.

The present wind turbine is thus a VAWT, i.e. the rotational axis of the wind turbine is arranged at an angle of about 90 degrees to the direction of the wind, and usually as a vertical axis wind turbine although it is possible to arrange the wind turbine so that the rotational axis is horizontal and at the same time substantially perpendicular to the wind direction. It should be noted that the generator magnet may be a permanent magnet or an electro magnet.

An advantage of the present turbine compared to conventional turbines usually installed today, is that the contra rotating turbines do not produce torques that must be taken up by the support structure, such as the tower of the wind power plant. The present wind turbine is therefore well suited to be retrofitted on an existing structure such as the tower of existing horizontal axis wind turbines. Existing wind mill parks may therefore easily be upgraded and made more efficient.

A further advantage of the wind turbine described herein is that there is no need for a gear. This provides for less frictional loss and requirements for cooling. The absence of gears also makes the present wind turbine much more reliable and requires less maintenance as compared to the traditional horizontal axis turbines that are usually built today. This makes the present wind turbine more suitable for use in locations where the weather conditions are harsh, such as off-shore locations. Furthermore, since the wind turbine does not require a gear system, it is also easier to upscale the present wind turbine than traditional wind turbines.

The first generator part is mounted on a radially peripheral first portion of the first turbine rotor facing the second turbine rotor, and the second generator part is mounted on a radially peripheral second portion of the second turbine rotor facing the first turbine rotor. By arranging the generator at the periphery of the turbine rotors, there is less need for cooling since the generator parts will have a large surface which will be naturally cooled by air.

The first turbine rotor may comprise an upper first turbine rotor and a lower first turbine rotor which are arranged on opposite sides of the second turbine rotor in the longitudinal direction of the wind turbine.

The upper first turbine rotor and the lower first turbine rotor are preferably mounted on a first turbine shaft, i.e. a common shaft for the two turbine rotors, which is adapted to be rotatably mounted on a tower of a wind power plant or to an attachment element of a separate structure. For example, the wind turbine may be retrofitted on a tower of an existing wind power plant or at the same time as a separate wind power plant is being built. The second turbine rotor, on the other hand, is preferably rotatably mounted on the first turbine shaft.

The upper first turbine rotor and the lower first turbine rotor are mounted on a first turbine shaft which is adapted to be rotatably mounted on a tower (13) of a wind power plant (10) or an attachment element (54) of a separate structure

The upper first turbine rotor and the lower first turbine rotor may have equal lengths in the longitudinal direction. Alternatively, the upper first turbine rotor and the lower first turbine rotor are made with different lengths in the longitudinal direction, for example due to varying wind intensity at different heights above the ground where the wind power plant is situated.

The upper first turbine rotor and the lower first turbine rotor may have equal diameters.

Alternatively, the upper first turbine rotor and the lower first turbine rotor have different diameters, for example due to varying wind intensity at different heights above the ground where the wind power plant is situated.

Similarly, if the wind turbine is provided with a lower first turbine rotor and an upper first turbine rotor, the lower first turbine rotor may have a smaller diameter and/or a smaller height than the upper first turbine rotor, for example due to varying wind intensity at different heights above the ground where the wind power plant is situated.

If the wind turbine is provided with a lower first turbine rotor and a upper first turbine rotor, the first generator part is preferably mounted on a radially peripheral first portion of the upper first turbine rotor facing the second turbine rotor, and the second generator part is preferably mounted on a radially peripheral second portion of the second turbine rotor facing the first turbine rotor. Alternatively, first generator part may be mounted on a radially peripheral first portion of the lower first turbine rotor facing the second turbine rotor, and the second generator part may be mounted on a radially peripheral second portion of the second turbine rotor facing the first turbine rotor.

The wind turbine may further comprise an outer second turbine rotor which is arranged radially outside the first turbine rotor and is securely attached to the second turbine rotor, for example with support elements such as beams, struts, stays or similar elements that are suitable for supporting the outer second turbine rotor. Thus, the outer second turbine rotor rotates together with the second turbine rotor.

Although it is not shown in the figures, it should also be noted that an outer second turbine may, in the same manner, be attached to the second turbine rotor on the embodiment of the wind turbine shown in figure 3, such that the outer second turbine rotor is arranged radially outside the upper first turbine rotor.

The first turbine rotor and the outer second turbine rotor preferably have substantially the same length in the longitudinal direction of the wind turbine.

If the wind turbine is provided with an outer second turbine rotor, the first generator part is preferably mounted on a radially peripheral first portion of the first turbine rotor facing the second turbine rotor, and the second generator part is preferably mounted on a radially peripheral second portion of the second turbine rotor facing the first turbine rotor. Alternatively, the first generator part may be mounted on a radially peripheral first portion of the first turbine rotor facing the outer second turbine rotor and the second generator part may be mounted on a radially peripheral second portion of the outer second turbine rotor facing the first turbine rotor.

Each turbine rotor preferably comprises at least one support arm which extends in a substantially radial direction relative to the rotational axis of the wind turbine, and preferably at least one turbine blade which is mounted to the support arm.

The at least one turbine blade is preferably rotatably mounted to the at least one support arm. The position of the at least one turbine blade relative to the at least one support arm can thereby be adjusted as the wind turbine, and the at least one support arm, rotates about the rotational axis of the wind turbine.

The at least one turbine blade preferably extends in a direction which is substantially parallel to the rotational axis of the wind turbine. The at least one turbine blade therefore extends substantially in the same direction as the rotational axis of the wind turbine and the longitudinal direction of the wind turbine.

The at least one support arm may comprise a first support arm and a second support arm which are spaced apart in the longitudinal direction of the wind turbine, and the at least one turbine blade may be rotatably mounted to the first support arm and to the second support arm. The at least one turbine blade can therefore be supported at both ends in the longitudinal direction.

Each turbine rotor of the wind turbine preferably comprises a plurality of support arms, and preferably at least one turbine blade is mounted to each support arm.

The plurality of support arms is preferably evenly spaced out circumferentially relative to the rotational axis of the wind turbine.

Each support arm may also be provided with an outer support arm which is rotatably connected to the support arm at a radially outer part of the support arm. The outer support arms preferably rotates relative to their respective support arms as the wind turbine rotates about the rotational axis of the wind turbine such that the outer support arms at all times has a desired position relative to their respective support arms depending on the wind direction, i.e. the rotational position of their respective support arms in the circumferential direction around the rotational axis of the wind turbine.

The at least one turbine blade is preferably mounted to each outer support arm.

Furthermore, at least one turbine blade may be rotatably mounted to the outer support arm and/or at least one turbine blade may be rotatably mounted to the support arm.

Alternatively, a plurality of turbine blades may be rotatably mounted to each support arm and/or the outer support arm, where the turbine blades are spaced out in a radial direction relative to the rotational axis of the wind turbine along the length of the support arm and/or the outer support arm.

The outer support arm is preferably adapted to be actively rotated relative to the support arm as the turbine rotors are rotating about the rotational axis of the wind turbine.

Furthermore, each support arm is preferably provided with an actuating means which rotates the outer support arm into a desired position relative to the support arm. The actuating means is preferably a motor, such as an electric motor, a hydraulic motor or a pneumatic motor of a type that is commercially available and suitable for effecting the rotational movement of the outer arms relative to their respective support arms as the turbine rotors rotate about the rotational axis of the wind turbine.

The wind turbine preferably comprises a control system which controls the drive devices of the support arms such that each outer arm is rotated to a desired position relative the support arm to which it is rotatably attached, depending on the rotational position of the support arm, as the turbine rotors rotate about the rotational axis of the wind turbine.

Alternatively, the wind turbine may be provided with chains, belts, a cog wheel system, a combination of these or any other similar device which can control the position of the outer arms relative to the respective support arms they are mounted on, and the further the position of the turbine blades relative to the support arms and/or the outer support arms that they are mounted to, as the turbine rotors of the wind turbine are rotating.

The wind turbine may further incorporate spring elements to facilitate the movement of the outer support arms relative to the support arms and/or the movement of the turbine blades relative to the outer support arms and/or the support arms, and/or to help recover at least some of the energy used to effect the rotational movement of the outer support arms relative to their respective support arms, as the outer support arms rotate between a first extreme position and a second extreme position relative to the support arm, i.e. an imaginary line through or imaginary extension of the support arm, as the wind turbine rotates about the rotational axis A during operation of the wind turbine.

The wind turbine may be rotatably mounted on a separate structure, such as a tower structure. The longitudinal direction of the tower structure is preferably substantially parallel to the rotational axis of the wind turbine, i.e. the wind turbine is typically a vertical axis wind turbine when the wind turbine has been installed.

There is also provided a wind power plant comprising a separate structure and a wind turbine as described above, where the wind turbine is mounted on said separate structure.

The separate structure may be an existing structure, i.e. the wind turbine is retrofitted on an existing structure. Alternatively, the separate structure may be a structure under construction, i.e. the wind turbine is mounted on the separate structure as it is being constructed and the wind turbine can therefore be integrated with the separate structure during the design phase.

The separate structure may, for example, be a tower of an existing wind power plant or a wind power plant under construction.

The separate structure may also be a mast, such as a radio mast or a tv mast or a power mast or a mobile mast.

The separate structure may also be a post, such as a lamp post or a telegraph post.

The separate structure may also be a chimney.

There is also provided a method for using a wind turbine as described above and/or a wind power plant as described above, wherein the wind turbine is mounted on a separate structure.

The separate structure may be an existing structure. The separate structure may alternatively be a structure under construction. The separate structure can, for example, be one of the following structures: tower of an existing wind power plant or a wind power plant under construction; a mast, such as a radio mast or a tv mast or a power mast or a mobile mast; a post, such as a lamp post or a telegraph post; a chimney.

In the following, the present invention will be explained in more detail with reference to the figures with a number of non-limiting embodiments, where:

Figure 1 shows a schematic illustration of a wind turbine according to the present invention comprising a first turbine rotor and a second turbine rotor which are contra rotating rotors.

Figure 2 shows a schematic illustration of the second turbine rotor with the windings of the coil of the stator of the electric generator.

Figure 3 shows a schematic illustration of a wind turbine according to the present invention comprising a lower first turbine rotor and an upper first turbine rotor arranged on a common shaft and on either side for the second turbine rotor in the longitudinal direction of the wind turbine.

Figure 4 shows a schematic illustration of a wind turbine according to the present invention comprising a first turbine rotor and a second turbine rotor as shown in figure 1, and an outer second turbine rotor which is securely attached to the second turbine rotor and arranged circumferentially on the outside of the first turbine rotor relative to the first turbine rotor.

Figure 5 shows a schematic illustration of a wind turbine according to the present invention comprising a number of support arms that support at least one turbine blade each, and where the support arms are provided with an outer support arm to which the turbine blades are rotatably attached.

Figure 6 shows a schematic illustration of a wind turbine according to the present invention where four contra rotating turbine rotors are mounted on the tower of a wind power plant.

Figure 7 shows a schematic illustration of a wind turbine according to the present invention where three turbine rotors as shown in figure 3 are mounted on the tower of a wind power plant.

Firsts indicated in the figures, the rotational axis A of all embodiments of the wind turbine 12 is arranged at substantially a right angle, or perpendicular, to the wind direction. Hence the rotational axis A of the wind turbine 12 is substantially vertical relative to a horizontal ground 56 or the surface of the sea 56 (see figures 6 and 7). The wind turbine 12 is therefore a vertical axis wind turbine (VAWT). It should could also be mentioned that the longitudinal direction of the wind turbine 12 extends in the same direction as the rotational axis A.

In figure 1 a wind power plant 10 according to the present invention is shown comprising a wind turbine 12. The wind turbine 12 is mounted on a tower 13, which can be a tower 13 of an existing structure, such as an existing wind power plant, but can also be a mast, post, chimney or any other suitable existing structure on which the wind turbine 12 can be retrofitted. The wind turbine 12 may also be mounted on a tower 13, or similar structure, as the tower is being built.

The wind turbine shown in figure 1 comprises a first turbine rotor 16 which is rotatably mounted on the tower 13 about a rotational axis A, and a second turbine rotor 23 which is also rotatably mounted on the tower 13 about the same rotational axis A.

The first turbine rotor 16 is supported on at least one, but preferably two or more first turbine rotor bearings 31 which allow the first turbine rotor to rotate about the rotational axis A and ensure that external forces on the first turbine rotor 16 is taken up and transferred to the tower 13.

Similarly, the second turbine rotor 23 is supported by at least one, but preferably two or more second turbine rotor bearings 32 which allow the second turbine rotor to rotate about the rotational axis A and ensure that external forces on the second turbine rotor 23 is taken up and transferred to the tower 13.

The first turbine rotor 16 and the second turbine rotor 23 are arranged such that they rotate in opposite directions about the rotational axis A when the wind turbine 12 is operating, i.e. the first turbine rotor 16 and the second turbine rotor 23 are contra rotating turbines.

As indicated in the figures, the rotational axis A of the wind turbine 12 is arranged at substantially a right angle, or perpendicular, to the wind direction. Hence the rotational axis A of the wind turbine 12 is substantially vertical relative to a horizontal ground 56 or the surface of the sea 56 (see figures 6 and 7). The wind turbine 12 is therefore a vertical axis wind turbine (VAWT).

The wind turbine 12 is provided with a generator 35 for production of electric power. The generator 35 comprises a first generator part 36 which comprises the magnets of the generator 35, and a second generator part 38 which comprises the windings of the generator 35. The first generator part 36 can be mounted on the first turbine rotor 16 as shown in figure 1, such that the first generator part 36 faces the second turbine rotor 23. The second generator part 38 can be mounted on the second turbine rotor 23 as shown in figure 1, such that the second generator part 38 faces the first turbine rotor 16.

In figure 2, the second turbine rotor 23 is schematically shown with the second generator part, including its windings, mounted on the second turbine rotor 23.

Alternatively, the second generator part 38 that comprises the windings of the generator 35, is mounted on the first turbine rotor 16, and the first generator part 36 that comprises the magnets of the generator 35, is mounted on the second turbine rotor 23.

The generator 35 is preferably mounted on a radially peripheral portion of the turbine rotors 16, 23, i.e. at the outer portion of the turbine rotors 16, 23 relative to the rotational axis A. This will provide a greater relative speed between the magnets of the first generator part 36 and the windings of the second generator part 38. Hence, as indicated in figure 1, and also in figures 3-4, the first generator part 36 is mounted on a radially peripheral first portion 17 of the first turbine rotor 16 facing the second turbine rotor 23, and the second generator part 38 is mounted on a radially peripheral second portion 24 of the second turbine rotor 23 facing the first turbine rotor 16.

As shown in figure 1, the wind power plant 10 is further provided with a slip ring 41 which is mounted on the second turbine rotor 23. The wind power plant 10 is further provided with brushes 42 which are mounted on the tower 13 and cooperate with the slip ring 41 so that electric power produced by the generator 35 can be exported from the wind turbine 12 and transferred to any desired external location.

In figure 3 there is shown an embodiment of a wind turbine 12 according to the present invention which is slightly different from the wind turbine 12 shown in figure 1.

Instead of a single first turbine rotor 16, the wind turbine 12 shown in figure 3 comprises an upper first turbine rotor 19 and a lower first turbine rotor 20. The upper first turbine rotor 19 and the lower first turbine rotor 20 are both mounted on a first turbine shaft 21.

The upper first turbine rotor 19 and the second turbine rotor 20 are spaced apart in the longitudinal direction of the wind turbine 12, i.e. in the direction of the rotational axis A, and the second turbine rotor 23 is arranged between the upper first turbine rotor 19 and the lower first turbine rotor 20.

The second turbine rotor 23 is securely mounted on a second turbine shaft 25. The second turbine shaft 25 is rotatably mounted on the first turbine shaft 21 as indicated in figure 3. The second turbine shaft 25 is supported by at least one, but preferably two or more second turbine rotor bearings 32 which allow the second turbine rotor to rotate about the rotational axis A, in the opposite direction of the upper first turbine rotor 19 and the lower first turbine rotor 20, and to ensure that external forces and loads on the second turbine rotor 23 is taken up and transferred to the first turbine shaft 21 and subsequently to the tower 13. The upper and lower first turbine rotor 19, 20 and the second turbine rotor 23 are therefore contra rotating turbines.

The first turbine shaft 21 is rotatably mounted on the tower 13 about the rotational axis A. The first turbine shaft 21 is supported on at least one, but preferably two or more first turbine rotor bearings 31 which allow the lower first turbine rotor 20 and the upper first turbine rotor to rotate about the rotational axis A and ensure that external forces and loads on the lower first turbine rotor 20, the upper first turbine rotor 19 and the second turbine rotor 23 are taken up and transferred to the tower 13.

As in the embodiment shown in figure 1, the generator 35 comprises a first generator part 36 comprising the magnets of the generator 35, and a second generator part 38 comprising the windings of the generator 35. The first generator part 36 can be mounted on the upper first turbine rotor 19, preferably on a peripheral first portion 17 of the upper first turbine rotor 19 as indicated in figure 3, and the second generator part 38 can be mounted on the second turbine rotor 23, preferably on a peripheral second portion 24 of the second turbine rotor 23, or vice versa.

Obviously, as an alternative, the first generator part 36 may be mounted on the second turbine rotor 23, preferably on a peripheral second portion of the second turbine rotor 23, and the second generator part 38 may be mounted on the lower first turbine rotor 20, preferably on a peripheral first portion of the lower first turbine rotor 20, or vice versa.

Although not shown in figure 3, the wind power plant 10 is further provided with a slip ring which can be mounted on the upper first turbine rotor 19 or the first turbine shaft 21, and brushes which are mounted on the tower 13 above the wind turbine 12. The brushes cooperate with the slip ring so that electric power produced by the generator 35 can be exported from the wind turbine 12 and transferred to any desired external location.

In figure 4 there is shown a further embodiment of a wind turbine 12 according to the present invention. The wind turbine 12 comprises a first turbine rotor 16 which is rotatably mounted on the tower 13 about the rotational axis A, and a second turbine rotor 23 which is also rotatably mounted on the tower 13 about the same rotational axis A.

The wind turbine 12 is further provided with an outer second turbine rotor 28. As indicated in figure 4, the outer second turbine rotor 28 is arranged radially on the outside of the first turbine rotor 16 relative to the rotational axis A and extend around the first turbine rotor 16 in the circumferential direction of the wind turbine 12.

The outer second turbine rotor 28 is supported by at least one, but preferably a plurality of support elements 28 as indicated in figure 4. The support elements 28 are securely attached to the second turbine rotor 23 and to the outer second turbine rotor 23, for example by welding or with bolts, screws or any other suitable fastening means. The second turbine rotor 23 and the outer second turbine rotor 28 therefore rotate together as a unit when the wind turbine 12 is operating. The first turbine rotor 16 and the second and outer second turbine rotors 23, 28 are therefore contra rotating turbine rotors.

As for the other embodiments of the present invention, the generator 35 comprises a first generator part 36 which comprises the magnets of the generator 35, and a second generator part 38 which comprises the windings of the generator 35. The first generator part 36 can be mounted on the first turbine rotor 16 as shown in figure 4, such that the first generator part 36 faces the second turbine rotor 23. The second generator part 38 can be mounted on the second turbine rotor 23 as shown in figure 4, such that the second generator part 38 faces the first turbine rotor 16.

As for the other embodiments of the present invention, the generator 35 is preferably mounted on a radially peripheral portion of the turbine rotors 16, 23, i.e. at the outer portion of the turbine rotors 16, 23 relative to the rotational axis A. This will provide a greater relative speed between the magnets of the first generator part 36 and the windings of the second generator part 38.

Hence, as indicated in figure 4, the first generator part 36 is mounted on a radially peripheral first portion 17 of the first turbine rotor 16 facing the second turbine rotor 23, and the second generator part 38 is mounted on a radially peripheral second portion 24 of the second turbine rotor 23 facing the first turbine rotor 16.

Although not shown in figure 4, the wind power plant 10 is further provided with a slip ring which is preferably mounted on the second turbine rotor 23. The wind power plant 10 is also provided with brushes which are mounted on the tower 13 and cooperate with the slip ring so that electric power produced by the generator 35 can be exported from the wind turbine 12 and transferred to any desired external location.

The wind turbine 12 can be provided with a well known type of construction comprising a number of support arms which extend outwards in a radial direction relative to the rotational axis A. The support arms are preferably evenly spaced out around the wind turbine 12 in the circumferential direction of the wind turbine 12 around the rotational axis A.

Each support arm may support a single turbine blade which is rotatably mounted to a radially outer portion of the support arm. Alternatively, each support arm may support a plurality of turbine blades spaced out along the support arm with a desired distance between them.

Each support arm preferably comprises an upper support arm and a lower support arm. The turbine blade, or the turbine blades, is then arranged between the upper support arm and the lower support arm and is rotatably mounted to the upper support arm and the lower support arm in a manner well known in the art. When the wind turbine 12 is in operation, the turbine blades of the support arms are continuously rotated to a desired position relative to their respective support arms depending on the rotational position of the wind turbine in order to provide the largest possible and/or desirable wind thrust on the wind turbine 12.

Instead of using the well known design of turbine rotors described above, an alternative turbine rotor as shown in figure 5 may be employed.

In figure 5 there is shown a possible version of the wind turbine 12 comprising eight support arms 45 which are securely attached to a central turbine rotor support element 14 of the wind turbine 12. The support arms 45 are evenly spread out in the circumferential direction around the tower 13. As indicated in figure 5, the wind turbine 12 may be provided with 8 support arms 45, but the wind turbine 12 may of course be provided with any number of support arms 45 which would be suitable for any given wind power plant 10.

The support arms 45 preferably extends outwards in a substantially radial direction from the tower 13. At the radially outer end portion of the support arms 45 an outer support arm 50 is mounted as indicated in the figure. The outer support arms 50 are articulated, i.e. they are rotatably attached to respective support arms 45 with a joint device 51 which allows the outer support arms 50 to rotate relative to the support arms 45.

The joint devices 51 can be provided with actuating means so that the rotation of the outer support arms 50 relative to the support arms 45 can be controlled such that the outer support arms 50 are continuously rotated to a desired position relative to their respective support arms 45 as the wind turbine 12 is rotating. As indicated in figure 5, the desired position of the outer support arms 50 relative to their respective support arms 45, will change during a full rotation of the turbine rotor about the rotational axis A and depends on where in the rotational cycle of the turbine rotor the support arms 45 are located at any given time.

The actuating means can be a motor, such as an electric motor, or a hydraulic device, such as a piston/cylinder assembly, or a mechanical system comprising chains or belts, or any other suitable actuating means which is capable of rotating the outer support arms 50 relative to their respective support arms 45.

As indicated in figure 5, a turbine blade 47 is rotatably mounted to an outer end portion of the outer support arms 50, preferably with respective turbine blade joint devices 48. It should be mentioned that two or more turbine blades 47 may be mounted to each outer support arm 50 spaced out along the outer support arm 50. One or more turbine blades may also be mounted to the support arm 45 spaced out along the support arm 45.

The turbine blade joint devices 48 are preferably also provided with actuating means so that the rotation of the turbine blades 47 relative to the outer support arms 50 can be controlled such that the turbine blades 47 are continuously rotated to a desired position relative to their respective outer support arms 50 as the wind turbine 12 is rotating and the outer support arms 50 are rotating relative to their respective support arms 45. The actuating means can be a motor, such as an electric motor, or a hydraulic device, such as a piston/cylinder assembly, or a mechanical system comprising chains or belts, or any other suitable actuating means which is capable of rotating the turbine blades 47 relative to their respective outer support arms 50.

The wind turbine 12 may also incorporate spring elements to facilitate the movement of the outer support arms 50 relative to the support arms 45 and/or the movement of the turbine blades 47 relative to the outer support arms 50 and/or the support arms 45, and/or to help recover at least some of the energy used to effect the rotational movement of the outer support arms 50 relative to their respective support arms 45as the outer support arms 50 rotate between a first extreme position and a second extreme position relative to the support arm 45, i.e. an imaginary line through or imaginary extension of the support arm 45, as the wind turbine rotates about the rotational axis A during operation of the wind turbine.

Although not shown in the figures, each outer support arm 50, preferably comprises an upper outer support arm and a lower outer support arm, and optionally, but preferably, each support arm 45 is provided with an upper support arm and a lower support arm, even if no turbine blade is mounted to the support arms 45. The turbine blade 47, or the turbine blades, is/are then arranged between the upper outer support arm and the lower outer support arm and is rotatably mounted to the upper support arm and the lower support arm in a manner well known in the art.

The wind turbine shown in figure 5 is provided with eight support arms 45 and eight respective outer support arms 50 which are rotatably mounted to respective support arms 45 with a joint device 51. A brief description of the rotation of the outer support arms 50 relative to their respective support arms 45 as the wind turbine 12 rotates counter clockwise due to the wind indicated with the arrow P.

When the wind turbine 12 is in operation, the turbine blades of the support arms are continuously rotated to a desired position relative to their respective support arms depending on the rotational position of the wind turbine in order to provide the largest possible and/or desirable wind thrust on the wind turbine 12. The rotation of the outer support arms 50 relative to the support arms 45 at various positions during the rotational movement of the wind turbine 12, is indicated with arrow V in each of the eight positions, i.e. for each of the eight outer support arms 50 as the wind turbine 12 is located in this specific position in its continuous counter clockwise rotational movement.

A turbine blade 47 of the turbine rotor shown in figure 5 is generating power as it moves from the position shown with letter A until it reaches the position shown with the letter E. In the position indicated with the letter A, the outer support arm 50 is located in its first extreme position where it is rotated clockwise relative to a straight line through support arm 45 indicated with broken line B. As the turbine rotor rotates counter clockwise, the outer support arm 50 located in position A starts its rotation, indicated by the arrow TB, relative to the support arm 45 towards its second extreme position relative to the support arm 45.

Between the positions indicated by letters A and C, the lift force on the turbine blade 47 is larger than the opposing forces caused by the headwind and the turbine blades 47 contribute to the power generation. By rotating the outer support arms 47 in the direction indicated with arrow TB from position A the lift force on the turbine blades 47 is increased.

In the position indicated with the letter C, the outer support arm 50 has been rotated relative to the support arm 45 so that they lie on a straight line, and continues to be rotated towards the second extreme position relative to support arm 45 as indicated by arrow VC. In the position indicated with the letter E, the outer support arm 50 is located in its other extreme position relative to the support arm 45.

The angle that the outer support arms 50 makes with a straight line through their respective support arms 45 when the outer support arms 50 are located in the first extreme position or the second extreme position, can vary from one turbine rotor to another, and from one wind turbine 12 to another, but can be any angle in the range 0-45 degrees. The support arms 45 and/or the outer support arms 50 and/or the joint devices 51 may further be arranged with adjustable stop devices which makes it possible to adjust the first extreme angle and/or the second extreme angle that the outer support arms 50 makes relative to the support arms 45 to a desired angle depending on, for example, prevailing wind and weather conditions.

When the outer support arms 50 are moving between the positions indicated with letters C and I, they have tailwind, and between the positions indicated by the letters E and G the turbine blades 47 are in fact normally moving faster than the wind so that the turbine blades 47 experience headwind. To counteract this headwind, the outer turbine blades 47 are rotated in the opposite direction again and the speed of the turbine blades 47 is less than the wind speed and the turbine blades 47 do contribute to the power production during this stage.

Starting from the position indicated with the letter E, the outer support arm 50 is rotated in the direction indicated with letter VE relative to the support arm 45, i.e. in the opposite direction of the wind direction P, until the outer support arms 50 reach their first extreme position again, i.e. the outer support arms 50 have the same position relative to the support arms 45 in the positions indicated with the letters A and G.

Between the positions of the outer support arms indicated with letters G and K, the turbine blades 47 will again be subjected to a lift force that contributes to power generation. To increase the lift forces on the turbine blades 47, the outer support arms 50 are rotated relative to their respective support arms 45 from the first extreme position they have in position G, in the direction indicated with arrow TG, to the second extreme position they have in the position indicated with the letter K.

As the turbine rotor rotates so that the outer support arms 50 move from the position indicated with the letter K to the position indicated with the letter A, the outer support arms 50 are rotated in the direction indicated with arrow VK and VL relative to the support arms 45, from the second extreme position of the outer support arms 50 in the position indicated with the letter K to the first extreme position of the outer support arms 50 in the position indicated with the letter A. As can be seen in figure 5, the outer support arms will be closer to each other during this stage and the outer support arm(s) in front will to a certain extent cover the trailing support arm(s) and the result is that in total less headwind is created on the outer support arms 50.

The wind turbines 12 shown in figures 1-5 can be mounted on various types of towers, mast, poles, chimneys or other types of suitable structures. The wind turbines 12 can be retrofitted on separate, existing structures. Alternatively, one or more wind turbines according to the present invention is integrated in a support structure, such as a tower, as the support structure is being built. Such a separate structure can be a tower of an existing wind power plant or a wind power plant under construction. The separate structure may also be a mast, such as a radio mast or a tv mast or a power mast or a mobile mast, or it can be a post, such as a lamp post or a telegraph post, or it can be a chimney, for example a chimney on a power plant.

In figures 6 and 7 two examples of wind power plants 10 are shown comprising wind turbines 12 according to the present invention.

In figure 6 a wind power plant 10 is shown comprising a separate structure 53 in the form of a horizontal axis wind power plant comprising an attachment structure 54 in the form of a tower. The attachment structure 54 may be erected on the ground 56 or arranged in a body of water with a water surface 56. Two contra-rotating wind turbines 12 according to the present invention, each comprising a first turbine rotor 16 and a second turbine rotor 23 as described above, are shown mounted on the attachment structure 54, i.e. the tower 54. In figure 6, two wind turbines are mounted on the attachment structure 54, i.e. the tower of the wind power plant in this case, but any desired number of wind turbines 12 may be mounted on an attachment structure. When a number of wind turbines 12 are stacked on top of each other, each may be adapted to the distance above the ground or water surface 56 that they will be mounted to account for varying wind conditions, turbulence etc. which depends on the location of the wind power plant, the surrounding terrain and the distance above the ground 56.

In figure 7 a wind power plant 10 is shown comprising a similar separate structure 53 to the one shown in figure 6. The separate structure 53 is a horizontal axis wind power plant comprising an attachment structure 54 in the form of a tower 54. The attachment structure 54 may be erected on the ground 56 or arranged in a body of water with a water surface 56. A contrarotating wind turbine 12 according to the present invention, comprising an upper first turbine rotor 19, a lower first turbine rotor 20 and a second turbine rotor 23 as described in connection with figure 3 above is shown mounted on the attachment structure 54, i.e. the tower 54. In figure 7, one wind turbine 12 is mounted on the attachment structure 54, i.e. the tower of the wind power plant in this case, but again, any desired number of wind turbines 12 may be mounted on the attachment structure 54. Again, when a number of wind turbines 12 are stacked on top of each other, each may be adapted to the distance above the ground or water surface 56 that they will be mounted to account for varying wind conditions, turbulence etc. which depends on the location of the wind power plant, the surrounding terrain and the distance above the ground 56. In addition, the upper first turbine rotor 19 and the lower first turbine rotor 20 may be designed differently to accommodate different wind conditions and turbulence that the upper first turbine rotor 19 and the lower first turbine rotor 20 may experience since they are located at different heights above the ground or water 56.

Claims

1. A wind turbine (12) comprising at least a first turbine rotor (16) and a second turbine rotor (23) where the first turbine rotor (16) and the second turbine rotor (23) rotate about the same rotational axis (A), which rotational axis (A) extends in a longitudinal direction of the wind turbine (12), and the first turbine rotor (16) and the second turbine rotor (23) are contra rotating, the wind turbine (12) further comprising a generator (35) which comprises a first generator part (36) and a second generator part (38) wherein the first generator part (36) is mounted on the first turbine rotor (16) such that it faces the second turbine rotor (23) and the second generator part (38) is mounted on the second turbine rotor (23) such that it faces the first turbine rotor (16), and wherein the first generator part (36) comprises at least one generator magnet and the second generator part (38) comprises at least one generator coil for generation of an electric current when the wind turbine (12) is operating,

characterized in that the first generator part (36) is mounted on a radially peripheral first portion (17) of the first turbine rotor (16) facing the second turbine rotor (23), and the second generator part (38) is mounted on a radially peripheral second portion (24) of the second turbine rotor (23) facing the first turbine rotor (16).

2. The wind turbine according to claim 1,

wherein the first turbine rotor (16) comprises an upper first turbine rotor (19) and a lower first turbine rotor (20) which are arranged on opposite sides of the second turbine rotor (23) in the longitudinal direction of the wind turbine (12).

3. The wind turbine according to claim 2,

wherein the upper first turbine rotor (19) and the lower first turbine rotor (20) are mounted on a first turbine shaft (21) which is adapted to be rotatably mounted on a tower (13) of a wind power plant (10) or an attachment element (54) of a separate structure (53).

4. The wind turbine according to claim 3,

wherein the second turbine rotor (23) is rotatably mounted on the first turbine shaft (21).

5. The wind turbine according to one of the claims 2-4,

wherein the upper first turbine rotor (19) and the lower first turbine rotor (20) have different diameters and/or different lengths in the longitudinal direction of the wind turbine (12).

6. The wind turbine according to one of the claims 2-5,

wherein lower first turbine rotor (19) has a smaller diameter and/or a smaller length than the upper first turbine rotor (20).

7. The wind turbine according to one of the claims 2-6,

wherein the first generator part (36) is mounted on a radially peripheral first portion (17) of the upper first turbine rotor (19) or the lower first turbine rotor (20) facing the second turbine rotor (23), and the second generator part (38) is mounted on a radially peripheral second portion (24) of the second turbine rotor (23) facing the upper first turbine rotor (19) or the lower first turbine rotor (20).

8. The wind turbine according to one of the claims 1-7,

wherein the wind turbine (12) comprises an outer second turbine rotor (28) which is arranged radially outside the first turbine rotor (16) and is securely attached to the second turbine rotor (23).

9. The wind turbine according to claim 8,

wherein the first turbine rotor (16) and the outer second turbine rotor (28) have substantially the same length in the longitudinal direction of the wind turbine (12).

10. The wind turbine according to one of the claims 1-9,

wherein each turbine rotor (16, 19, 20, 23, 28) comprises at least one support arm (45) which extends in a substantially radial direction relative to the rotational axis (A), and at least one turbine blade (47) which is mounted to the support arm (45).

11. The wind turbine according to claim 10,

wherein the at least one turbine blade (47) is rotatably mounted to the at least one support arm (45).

12. The wind turbine according to claim 10 or 11,

wherein the at least one turbine blade (47) extends in a direction which is substantially parallel to the rotational axis (A).

13. The wind turbine according to one of the claims 10-12,

wherein the at least one support arm (45) comprises a first support arm and a second support arm which are spaced apart in the longitudinal direction of the wind turbine (12), and wherein the at least one turbine blade (47) is rotatably mounted to the first support arm and to the second support arm.

14. The wind turbine according to one of the claims 10-13,

wherein each turbine rotor (16, 19, 20, 23, 28) comprises a plurality of support arms (45), and wherein at least one turbine blade (47) is mounted to each support arm (45).

15. The wind turbine according to one of the claims 10-14,

wherein each support arm (45) is provided with an outer support arm (50) which is rotatably connected to the support arm (45) at a radially outer part of the support arm (45).

16. The wind turbine according to claim 15,

wherein at least one turbine blade (47) is mounted to each outer support arm (50).

17. The wind turbine according to claim 15 or 16,

wherein at least one turbine blade (47) is rotatably mounted to the outer support arm (50) and/or at least one turbine blade (47) is rotatably mounted to the support arm (45).

18. The wind turbine according to one of the claims 15-17,

wherein a plurality of turbine blades (47) is rotatably mounted to each support arm (45) and/or the outer support arm (50), spaced out in a radial direction relative to the rotational axis (A) along the length of the support arm (45) and/or the outer support arm (50).

19. The wind turbine according to one of the claims 15-18,

wherein the outer support arm (50) is adapted to be actively rotated relative to the support arm (45) as the turbine rotors (16, 19, 20, 23, 28) are rotating about the rotational axis (A).

20. The wind turbine according to claim 19,

wherein each support arm (45) is provided with a motor which rotates the outer support arm (50) into desired positions relative to the support arm (45).

21. The wind turbine according to claim 20,

wherein the wind turbine (12) comprises a control system which controls the motors of the support arms (45) such that each outer arm (50) is rotated to a desired position relative the support arm (45) to which it is rotatably attached, depending on the rotational position of the support arm (45), as the turbine rotors (16, 19, 20, 23, 28) rotate about the rotational axis (A).

22. A wind power plant (10) comprising a separate structure (53) and a wind turbine (12) according to any one of the claims 1-21, wherein the wind turbine (12) is mounted on the separate structure (53).

23. The wind power plant according to claim 22,

wherein the separate structure (53) is an existing structure.

24. The wind power plant according to claim 22,

wherein the separate structure (53) is a structure under construction.

25. The wind power plant according to one of the claims 22-24,

wherein the separate structure is a tower (13) of an existing wind power plant or a wind power plant under construction.

26. The wind power plant according to one of the claims 22-25,

wherein the separate structure (53) is a mast, such as a radio mast or a tv mast or a power mast or a mobile mast.

27. The wind power plant according to one of the claims 22-25,

wherein the separate structure (53) is a post, such as a lamp post or a telegraph post.

28. The wind power plant according to one of the claims 22-25,

wherein the separate structure (53) is a chimney.

29. Use of a wind turbine according to any one of the claims 1-21 and/or a wind power plant according to any one of the claims 22-28 on an existing structure.