WO2010003955A2

WO2010003955A2 - Wind turbine apparatus

Info

Publication number: WO2010003955A2
Application number: PCT/EP2009/058606
Authority: WO
Inventors: Yrjö BLÅFIELD; Heikki BLÅFIELD; Jouko RÄISÄNEN
Original assignee: Cypress Wind Turbines Oy
Priority date: 2008-07-08
Filing date: 2009-07-07
Publication date: 2010-01-14
Also published as: GB0904075D0; GB2461711A; GB0812508D0; WO2010003955A3

Abstract

A wind turbine apparatus is disclosed, the apparatus comprising a generator and a substantially vertical shaft, the shaft being directly mounted to the generator for rotating the generator. At least one lightweight vane member is also provided. The at least one vane member is attached to the shaft to provide a twisted self starting rotor unit. An electronic control apparatus is provided for controlling the speed of rotation of the generator.

Description

Wind turbine apparatus

The present invention relates to production of energy, and in particular, but not exclusively, to wind turbine apparatus and a system comprising at least one wind turbine for localised production of electricity. A method for producing energy from wind is also disclosed.

Wind has been used and is increasingly used as a source of energy, in particular to generate electricity. Wind is a constantly renewable energy source. Wind power is abundant in supply and non-polluting. The bulk of wind energy is produced by means of large horizontal wind turbines. A horizontal wind turbine is provided by a propeller rotating about a horizontal axis. The horizontal turbine is considered to have relatively good aerodynamic efficiency and high tip speeds.

However, to be efficient the propeller has to be of considerable size. Thus the propeller requires a substantially tall tower and also considerable amount of space around the tower. Large propellers are also noisy, the noisiness resulting in particular from high tip speeds. Also, any horizontal turbine has to be oriented to face the wind. Because of these reasons horizontal wind turbines are typically located in particular wind parks in remote locations where issues such as noise and aesthetic considerations are not especially important and where the wind is constant and comes from predictable and stable direction(s). The electricity produced in the wind park sites is then delivered to end users by means of electricity grids, in the same manner as electricity from any other centralized power plant, such as from a coal, nuclear or gas fired power station.

Relatively small horizontal propelled wind turbines for use in roofs or the like have also been proposed. Such wind turbine units are considerably smaller than those used in the wind parks. A consequence of this is that they also produce considerably less energy. Such relatively small scale units have been proposed for use in urban environment, but are regularly objected, in particular because of the noise. A problem with the horizontal wind turbines, regardless the size, is that they have to face the wind in an appropriate direction to effectively produce electricity. Should the direction of the wind change the propeller unit has to be re-orientated accordingly. Due to the size and weight of the unit the change in the direction of the propeller unit is relatively slow. This is not a problem as long as the wind blows steadily from a certain direction. However, in particular in urban environment the wind constantly changes direction and strength, and can be very gusty.

Therefore a small scale wind turbine with a horizontal propeller is not considered to be especially effective in or suitable for ail locations. In particular, the propeller unit with a horizontal rotational axis can be too slow to react to gusts and thus can fail to catch the wind energy contained therein. A gust may have 2 to 10 times more power than a constant wind blow, but a problem with them is that a gust may last only for a few seconds. A gust may also come from any direction. Therefore it would be advantageous to be able to react to a gust as quickly as possible.

Vertical axis wind turbines have been proposed to address the problem in wind direction. In vertical axis wind turbines a rotor assembly rotates typically on bearing assemblies affixed to a rotor shaft and supported by a base. Various types of vertical axis wind turbines have been proposed, the most common types perhaps being the Savonius rotor and the Darrieus rotor. For the basic principles of Savonius type rotors, see e.g. US patents 1 ,697,574 and 1 ,766,765 to Savonius. For the basic principles of Darrieus type rotors, see e.g. US patent No. 1 ,835,018 to Darrieus. A Savonius rotor is typically a self starting rotor whereas a Darrieus rotor requires an electric motor or another additional device for starting. The S-shaped Savonius rotor has been designed to operate in response to wind from any direction and to reduce problems caused by drag on its upwind traveling vane.

These proposals can suffer from poor efficiency and starting problems. The vertical rotors do not rotate fast enough so that a conventional generator could be attached directly to the rotational shaft thereof. Instead, a gear box or another drive system for increasing the speed of rotation may be needed to produce sufficient rotational speeds and appropriate torque to make the vertical turbines economically viable. A problem with the vertical turbines can be the rotor tip velocity which can be considerably less than what is achievable by the propellers of the horizontal wind mills. Therefore the vertical rotors have been considered inefficient. The vertical rotors may also require an additional power source to accelerate the rotor to a velocity at which the rotor can produce positive energy. Also, some of the vertical axis wind mills have utilized rather complex and expensive rotor blade designs. This can make them prohibitively expensive to manufacture, assemble and maintain in relation to the efficiency thereof. The vertical turbines can be erratic in operation and subject to undesirable variations in torque and energy output. That is, changes in wind direction and power, such as sudden gusts, may provide only a few very rapid rotations and thereafter the rotational movement may slow down considerably and provide only a relatively small torque. The vertical rotors have also been prone to vibrations, to extend that they may self-destruct. The requirement for gearbox or another drive arrangement has added not only to the complexity but also to the unreliability.

Therefore, even though vertical wind turbines are capable of operating from wind coming from any direction, there have been various reasons why the vertical wind turbines have not been as widely used in generation of energy from wind as are the horizontal turbines .

Embodiments of the present invention aim to address one or several of the above problems.

According to one embodiment there is provided a wind turbine apparatus comprising a generator, a substantially vertical shaft, the shaft being directly mounted to the generator for rotating the generator, at least one lightweight vane member, the at least one vane member being attached to the shaft to provide a twisted self starting rotor unit, and electronic control apparatus for controlling the speed of rotation of the generator by controlling loading of the generator. According to another embodiment there is provided a permanent magnet synchronous generator for a wind turbine apparatus, wherein at least one permanent magnet comprises at least one rare earth metal, the rotor of the generator is mounted on the shaft of the wind turbine apparatus, and the relative positioning of the rotor and the stator of the generator is adjustable.

According to another embodiment there is provided a control apparatus for controlling operation of at least one vertical wind turbine, comprising a wind speed determining apparatus, a processor configured to optimise rotation of the at least one wind turbine based on the information from the wind speed determining apparatus and information of at least one of speed of rotation of the at least one wind turbine and power output of the at least one wind turbine, and an electronic controller configured to control the loading of at least one generator based on information from the processor to optimise the speed of rotation of the at least one wind turbine.

According to an embodiment there is provided a method for controlling a wind turbine adapted to rotate a generator, the method comprising determining wind speed, determining tip speed and/or power output of the wind turbine, and controlling the rotational speed of the wind turbine based on the determined wind speed and the tip speed and/or power output by controliing the loading of the generator by means of an electronic apparatus such that a predetermined relation between the wind speed and tip speed and/or power output is maintained.

According to yet another embodiment there is provided a method of controlling a permanent magnet synchronous generator of a wind turbine apparatus, the generator comprising at least one permanent magnet comprising at least one rare earth metal and the rotor of the generator is mounted on the shaft of the wind turbine apparatus, the method comprising controlling the generator by adjusting the relative positioning of the rotor and the stator of the generator.

In accordance with an embodiment at least one wind turbine apparatus and/or at least one generator are provided for assembly on a roof or on a mast. The turbine apparatus may comprise support structure for mounting to a communications mast. The support structure can be adapted for mounting to a side of a telecommunications mast. The apparatus can be configured to supply power for a base station of a mobile communication system.

In accordance with a more detailed embodiment at least one vane member of a wind turbine apparatus is twisted in the order of 10 degrees relative to a rotor shaft

The generator may comprise a permanent magnet synchronous generator. At least one of the magnets may comprise at least one rare earth metal. At least one permanent magnet may be mounted on the shaft.

The control apparatus may comprise a rectifier adapted to control the loading of the generator. The control apparatus may be adapted to optimise the rotational speed of the wind turbine based on a determined wind speed and tip speed of the vane members and/or power output of the generator. The rectifier may be configured to control the loading of the generator such that a predetermined relation between the tip speed and the wind speed and/or power output is maintained. The rectifier may be adapted to control the loading by modifying the wave form of the sine wave of the voltage generated by the generator.

The wind turbine may be assembled from modules. A module may comprise a vane member and the wind turbine comprises at least two vane member modules. A rotor module may comprise at least two vane members, and the wind turbine comprises at least two rotor modules. If a turbine apparatus comprises a plurality of vane members, each vane member can be arranged evenly about the rotational axis. Each vane member can be mounted 30 to 90 degrees apart from at least one other vane member.

The at least one vane member may be made from at least one of plastic material, composite material, laminate material, fibreglass and aluminium. The relative positioning of a rotor and stator of the generator may be adjustable. The adjustment may be provided by means of a screw or lever, A servomotor may be provided for adjusting the relative positioning of the rotor and the stator. The relative positioning of the rotor and the stator can be adjusted in response to information regarding the output power of the generator. The adjustment may be activated if the adjustment range of the control electronics is exceeded, for example due to very heavy winds. The adjustment can be provided by moving the shaft in vertical direction relative to the generator.

A power generation system comprising at least one wind turbine apparatus and/or at least one generator as described herein may also be provided. The power generation system may be adapted for localised assembly, for example on a roof of a building or in a communications mast. The power generation system may comprise a local grid, means for converting from AC to DC voltage between the at least one wind turbine apparatus and the local grid, a local energy storage connected to the local grid, at least one further local energy production apparatus, and a connection to another grid.

The control apparatus may be configured to load the generator such that a predetermined relation between the tip speed and the wind speed is maintained. The controlling of the loading of the generator may comprise modifying the wave form of the sine wave of the voltage generated by the generator.

A computer program comprising program code means adapted to perform the methods may also be provided.

Embodiments of the invention may provide wind turbine apparatus that is not overly sensible for the wind direction and can react rapidly to changes in direction and/or force of the wind. The disclosed principles enable efficient local production of energy also in urban environment and in isolated locations. The apparatus is considered particularly suitable for mounting on roof tops in urban environment or on tops of other high structures where space and/or weight of the turbine apparatus might become an issue, fore example in telecommunication masts. For better understanding of the present invention, reference will now be made by way of example to the accompanying drawings in which:

Figure 1 shows a system in accordance with an embodiment;

Figure 2 shows a wind turbine in accordance with an embodiment; Figure 3 shows the twisting of the vane of a rotor module relative to the axis thereof;

Figure 4 is a schematic illustration of a possible vane; Figure 5A shows a vane from the side and 5B shows the vane sectioned along the line A-A of Figure 5A;

Figure 6 is a schematic diagram of a control system in accordance with an embodiment;

Figure 7 is a schematic diagram of a system in accordance with an embodiment;

Figure 8 is a flowchart illustrating the operation of one embodiment of the present invention;

Figures 9A and 9B show embodiments where a rotor unit is mounted on a mast; Figures 10A and 10B show units comprising a plurality of vane modules; and

Figure 11 is a sectioned view of a generator in accordance with an embodiment.

Figure 1 shows an embodiment of the present invention, where a plurality of vertical wind turbines 10 are provided in an assembly 2 that is mounted on a roof of a building 1. The building 1 can be any building, for example an office, a factory, a municipal building, for example a school or hospital, or a residential building. The building can be located in any location, although it is considered that the invention provides a particular advantage in urban or otherwise tensely built areas. It is also noted that the construction in which a system and/or wind turbine apparatus in accordance with the present invention is mounted can be any other construction as well, for example a mobile phone mast, urban illumination mast, a bridge, an oil rig, a ship and so forth. A vertical turbine apparatus can also be placed on a ground, particularly on a high ground, such as a hill top.

The system 2 comprises of a plurality of vertical wind turbines 10. In principle the number of wind turbines can be any appropriate number depending on capacity requirements, space available and other circumstances. The inventors consider that in certain roof top conditions, such as on top of an office building, around ten wind turbines might be preferred, subject to the size of the building, wind conditions and local electricity needs.

Each wind turbine 10 is provided with vane members 20 connected to a shaft 28. The shaft 28 is mounted directly into a generator 26 without any drive apparatus there between, thus providing a direct drive. More detailed examples for the vanes, shafts and generators will be described below.

Each generator is connected to a control unit 12. The control unit 12 is for controlling the generators and the energy production of the system. The control unit may comprise at least one rectifier. The operation and various components of the control unit 12 will also be described in more detail below.

Figure 2 shows an example of a wind turbine rotor 10 in accordance with the embodiment. More particularly, Figure 2 shows a twisted vane structure which is assembled from three modular rotor elements 20, 22 and 24. The three modules can be manufactured to be identical. Each module is attached to a shaft 28 which in turn is mounted on bearings for rotation and directly into the generator 26.

In the shown embodiment further support for the rotating structure is provided by supporting poles 29 supporting the structure from the top. However, such a supporting structure may not be necessary in all constructions.

In a vertical wind turbine structure two opposite forces affect the turbine. The straighter the vane is the more power it can generate from the wind. However, the straighter the vane the more the device will vibrate. If the blade or vane is totally straight, the structure may become dangerous and in any event self-destructive because the straight vane can cause so much vibration that the device breaks. Therefore an optimal vane is shaped as straight as possible, but twisted or warped so that the vane does not cause a level of vibration that could break the device.

In the shown rotor the vanes are twisted by about 10 degrees relative to the shaft. This is considered as optimal warping to provide best possible efficiency while avoiding breakage due to vibration. The warping is also small enough so as not to cause significant loss of power. The warping of about 10 degrees enables use of vanes with a relatively small surface area. This, in turn, enables light vanes, which, in turn, enables utilisation of gusts more efficiently. The light weighted vanes also enable turbines which start to produce energy in lower wind speeds than what was possible with the heavier vanes of the prior art turbine structures. Also, the overall weight of the apparatus is reduced, thus facilitating easier transport and assembly. Also, assembly on structures that are not originally designed to carry substantial weights may be facilitated.

The twisted structure of Figure 2 is also advantageous in that a vane of the rotor is never in the worst case scenario position. That is, regardless of the direction of the wind, a portion of the surface of the S-shaped vane is always in such orientation that it will cause rotation of the rotor. This assists further in optimising the use of gusts and similar blows of wind from unpredictable directions and with unpredictable forces.

Figure 3 shows one module of a rotor. Figure 3 also shows schematically the warping α « 10° of the vane members of a module relative to the vertical shaft. Such a warping of each of vane members is also illustrated in Figure 10A showing a rotor comprising six vane members.

Figure 4 shows an example of a vane 20 as seen from above. Figures 5B shows a cross-sectional view of a vane 20 of Figure 5A along line A-A. As shown in Figures 4 and 5B, the tip of the vane 20 can be bent relatively heavily to provide a S-shaped vane module. The vane members of the rotor can be manufactured from an appropriate lightweight material. The material can be, for example, appropriate plastic, fibre glass, composite material or aluminium. Laminated structures may also be used. The lightness of the material is important in decreasing the moment of inertia of the rotor. It is noted that the shaft itself in the centre of rotation is not a substantial cause of moment of inertia, and therefore its weight is of lesser significance. As it is of more importance that the vane member is lightweight, the shaft can be manufactured from heavier materials, for example steel. In accordance with an embodiment the weight of the vane per surface area is constantly low from the shaft to the tip of the vane. In accordance with another embodiment the weight per surface area decreases from shaft to the tip. The decrease may be linear or be provided in steps.

The lightness of the rotor makes control of the wind turbine apparatus easier to provide. The apparatus is also easier to transport and assemble, and can be mounted on a variety of structures. The lightness also facilitates load control by a rectifier or other electronic controller apparatus, as will be explained in detail below. A lightweight rotor and an electronic control apparatus such as a control apparatus comprising a rectifier enables provision of control that reacts rapidly to changes in the wind forces, speeds and/or directions. Therefore the wind turbine can be driven optimally regardless of the changes in the wind, and the apparatus can react rapidly to sudden changes in the wind conditions such as to sudden gusts.

Figure 5B also shows how a vane 20 can be constructed from a multiple of parts and/or materials 52, 54, 56. For example, different materials can be used to provide a body or frame of the frame, a coating layer thereon and the different surface areas such as the curved tip area 58 and the substantially straight area 59. A vane can be manufactured by laminating material or materials together. At least a part of the vane may be produced by means of injection moulding.

The vane modules can be designed such that by appropriate combinations thereof it is possible to provide an optimum wind catching surface of a rotor and optimally sized rotors depending on the local conditions and needs. In the Figure 2 embodiment three rotor modules are assembled together to provide the complete rotor. For example, in a relatively windy area one module may be enough to produce 2 kW of power whereas in another location two, three or even a greater number of similar modules may be required for the production of the same amount of electricity. Similarly, if more power is needed to be output, for example if 4 kW is desired, two or three or even more modules may be needed to provide a useful rotor.

The modular structure provides various advantages. The modules are easier to transfer, assemble, and maintain than a rotor manufactured as a single piece. An appropriate dimensioned rotor can be easily designed and produced to suit the local conditions while savings can be obtained in manufacture of parts thereof, since only one type of rotor module design may be needed. The modularity can be improved further if the vane members 11 are designed to be identical and the module structure is designed such that the vane members 11 can be mounted to the central shaft 28 at the place of assembly.

A module in can be affixed together and to other modules by various manners. For example, the vanes and/or modules can be affixed to each other and/or a possible separate shaft member by screws and/or snap-lock type locking. This enables easy assembly and re-assembly, if needed. The vane members and/or the modules, or at least a part thereof, can also be fixed permanently, for example by gluing or another type of adhesion, welding and so on.

The efficiency of the wind turbine can be based on the optimised shape thereof and use of electronics to control the operation of the generator 26. For example, as shown in Figure 6, a controller apparatus 12 can comprise a rectifier 14 for controlling the loading of the generator 26. The rectifier 14 can be used to adjust the rotational speed of the rotor to correspond the wind condition so that optimised production of energy is provided. For example, the loading of the generator can be increased in heavy wind and decreased in light wind. The change of loading can be provided rapidly in case of gusty winds. An example for the control operation is shown in the flow chart of Figure 8.

The control can be based on wind measurements by a wind measurement unit 16 and measurements of the rotational speed of the wind turbine (expressed e.g. as Rotations Per Minute, RPM) by a speed measurement unit 17, see also steps 100 and 102 of Figure 8. The measurement results are fed into an appropriately programmed processor 15 of the control apparatus for processing at steps 104 to 108.

In accordance with an embodiment the load control can be based on continuous optimization of the output power of the wind turbine apparatus based on feed-back information regarding power output. The power output feedback can information can be utilised by the controller in addition to or as an alternative the wind speed and tip speed information. The power output feedback information can comprise determined, preferably measured, output power of the generator, or a power level measurement elsewhere in the system, for example at the point where the generated electricity is fed into a local grid. The rotational speed of the rotor or rotors can be adjusted based on the feedback of the measured power levels such that the output power of the generator or generators is driven as close to the maximum for the current wind speed as possible. Thus it is possible to maintain optima! efficiency even if this can be achieved only in a relative narrow tip speed to wind speed ratio range,

In accordance with a preferred embodiment the processor 15 is configured to maintain the tip speed of the rotor in a predefined level. In accordance with a preferred embodiment the speed is maintained at a level that is slightly less than is the speed of the wind. Thus, if there is a detected change in one of the monitored speeds the optimising operation is triggered and new control parameters are determined at 106. The loading of the generator is then controlled accordingly at 108. The load control can comprise modifying by the rectifier 14 the wave form of the sine wave of the AC voltage generated by the generator. The rectifier can modify the sine wave form by means of vectorisation so as to increase or decrease the generated breaking force. The control can be based on predetermined optimum values. For example, the processor may map the measured wind and rotor speeds to a table of predetermined optimum values. The predetermined values can be obtained for example by simulations and/or tests, and stored in a memory 18 of the control apparatus.

Because of the software aided control the control apparatus can respond rapidly to any changes in the wind, and to sudden gusts. In the test is has been found that with appropriate predictive software the control can react to the changes in the wind with a very little if no noticeable delay. This can provide significant advantage since it is estimated that while a gust typically lasts for only a few seconds, e.g. 2 to 5 seconds, it contains 2 to 10 times more power than a steady blow. It is also estimated that in urban environment about 20 % of the time there can be gusts rather that just a steady blow. Thus the capability of rapidly reacting to gusts can provide significant improvement in the efficiency of energy production.

In accordance with an embodiment the turbine apparatus generates the energy required to power the electronic control apparatus. Thus no external energy source may be needed, but the apparatus can be made self-sufficient. In such case the rotor needs to rotate such that it produces enough power so that the control electronics can operate in a satisfactory manner. A point of consideration in here is that if the rotation produces less energy than is required to operate the control electronics, the power demand by the electronics can brake down any rotational movement. This is so because the torque generated by the wind is not necessarily enough to rotate the generator sufficiently to overcome the braking force by the power demand. In such case the rotor would not even start, unless an additional power source or other starting assistance is provided. To address this the controller apparatus may be configured such that no power generated by the generator is consumed by the control electronics unless a predefined condition is satisfied. Instead, the rotor is allowed to freewheel until the predefined condition is satisfied. The predefined condition may based on, for example, a power output and/or rotational speed and/or windspeed. For example, it can be defined that the rotational speed and/or windspeed has to reach a certain threshold speed before the control electronics is switched to an active state and/or can start consuming any power generated by the generator. !n accordance with a non-limiting example a windspeed threshold can be set to 3 m/s and/or rotation threshold can be set to 38 rpm in a system where a 38V and 3Hz generator is used.

It is noted that various different activation thresholds may be used and that the threshold may be based on various different parameters, or be based on a combination of various parameters. According to a possibility at least one condition, or a predefined number of conditions of a plurality of conditions, need to be satisfied before the electronics can start consuming the generated power to prevent the control electronics from braking the rotation at too low wind and/or rotational speeds.

The controller can also determine that the power produced by the generator has dropped to a level that is not enough to power the control electronics in appropriate manner. Upon determination of this, for example based on a deactivation threshold, the controller may switch itself off or to a standby state, and allow the rotor to rotate freely. The activation threshold and deactivation threshold may be set to same level or have different values.

The data processing functions of the control apparatus 12 may be provided by means of one or more data processor entities. Appropriately adapted computer program code product may be used for implementing the embodiments, when loaded to a data processing apparatus, for example a computer or a processor. All required data processing may be provided in the controller apparatus 12, or the control functions may be distributed. The program code product may be stored on and provided by means of an appropriate carrier medium such as semiconductor memory, a disc, card or tape. A possibility is to download the program code product via a data network. At least a part of the control may be provided by means of an appropriate software in a server.

The generator 26 can be a three phase permanent magnet generator and more particularly a permanent magnet synchronised alternative current generator. The magnets may be attached directly to the rotor shaft 28. The magnets can be made from materials comprising at least one rare earth metal. The rare earth metals are a group of metallic elements possessing closely similar chemical properties. The rare earth metals are trivalent but otherwise similar to alkaline earth metals. The group consist of the lanthanide elements 57 to 71 , plus scandium (21) and yttrium (39). Examples of appropriate materials include rare earth metal alloys like neodymium alloyed with iron and boron. Molybdenum, or molybdenum alloys may also be used. Permanent magnets are commonly known as super magnets. The rare earth metal magnets or supermagnets comprising rare earth metals are commercially available, and are therefore not described in any further detail herein than by mentioning that the rare earth metal magnets enable efficient production of electricity already in slow rotational speeds. Possibility of energy generation in slow speeds provides advantage in that it produces less noise than what emits from the horizontal wind turbines. In addition, they are relatively light weight compared to the size of the generator and are therefore suitable for use on top of structures where weight might become an issue, Permanent magnets comprising rare earth metals can also be made relatively compact and are thus suitable for applications where only limited space is available.

The generator transforms the breaking energy into alternative current which can be transformed into direct current before converting to grid. The transformation can be provided, for example, by a rectifier. The direct current electricity can be used immediately and/or stored e.g. in batteries for later use. The direct current from batteries or directly from rectifier can be transformed to AC voltage suitable for e.g. public grid. The transformation can be provided, for example, by an inverter.

The gusts can cause sudden blows to the structure. Traditionally these blows have been one of the reasons why wind turbines with gear boxes or other drive arrangements have been prone to brakeage. In the herein proposed arrangement the shaft is connected directly to the generator, thus reducing the amount of components that could fault. In accordance with an embodiment the permanent magnets are mounted directly on the rotor shaft and the stators of the generator are mounted in the generator body. This eliminates the need for any breakable gears or joint between the rotor shaft and the rotor of the generator.

Figure 7 shows a further embodiment comprising a plurality of vertical wind turbines and at least one energy producing unit of another type. More particularly, Figure 7 shows a system where a part of the energy can be produced by vertical wind turbines, for example by about ten wind turbines 10 each producing 2 to 4 kW. The system can further comprise e.g. solar panels 32 connected to the local grid 30. Other types of energy producing entities may also be connected to the grid 30, such as fuel cells 34, a diesei generator 36 and so on. The fuel cells 34 may be based on hydrogen technology. The system may also include at least one energy storage, for example batteries 40, for storing the energy produced. Control functions such as overload resistor 38 may also be provided.

The local or internal grid 30 can be direct current grid. In the example the direct current grid is shown to be designed to have maximum voltage of 700V₁ but it is noted that this is an example only. The electricity provided by the wind turbine generators is fed into the grid 30 under control of rectifiers and by means of frequency converters 31.

An inverter 46 is provided for facilitating the supply or output for the local use of the energy from the local grid 30. The local direct current grid 30 can also be connected to a public or national grid 42. Energy produced by the local system can be supplied from the grid 30 into the grid 42 by means of an inverter 44.

It is also possible to use the system such that electricity is received from the national grid 42 in the local system 30. That is, instead of connecting a house directly to the national grid, the electricity is the taken out for the local use via the local system 30 rather than directly from the national grid. This can be advantageous for example in conditions where the voltage in the national grid varies greatly, as the local system can be used to smoothen the peaks. Also, effects of power cuts can be either avoided or at least reduced due to the local production of energy and/or the batteries 40. The quality of the electricity is improved since rather than being taken directly from the national grid which is not under local control the electricity can be taken out from the local system which is under direct control of the end user. This can have significant benefits for users such as hospitals and/or businesses with high tech computing apparatus requiring constant supply of good quality electricity and so forth.

An advantage of locating the wind turbines in urban environment and/or on roof tops on buildings as shown in Figure 1 is that the energy is produced where it is needed and thus transfer losses can be avoided. The system can be designed to supply a single building, either partially or entirely depending on the need for energy, wind conditions and the size of the system. For example, the system could be designed to produce 20 kW to 40 kW, although this is only a non-limiting example. The system can also be used as an auxiliary, emergency energy supplying system. For example, the system could be used during power cuts for producing energy to elevators, emergency exits, computers, communications equipment, life supporting devices in hospitals and so forth.

Each turbine unit can be made relatively lightweight. For example, turbine units weighting 20 to 300 kilograms can be provided. Such units can be mounted on various locations, for example on top of a mobile phone base station mast 90 or any other mast, see Figure 9A. In accordance with a possibility shown in Figure 9B the turbine unit 10 can be mounted on a side of a mast 90. A reason why of a light weight vertical rotor unit of the present invention is suitable for mast assemblies is that, unlike a horizontal wind mill, the rotating diameter of the vertical unit is not large relative to the size of the mast and thus the unit does not extend very far from the mast. Because of this no additional support and/or strengthening of the mast may be required. A plurality of side mounted turbine units can be provided in a mast. The units may all be mounted on one side where the wind conditions are considered most preferable, or at least two turbine units can be mounted on different sides of a mast.

The side mounted unit is considered particularly advantageous as the supporting structure thereof can be made lighter and simpler than that of the top mount. As shown in Figure 9B, the side mount of a turbine unit can be provided for example by means of A-shaped supports at the top and bottom of the structure. For example, when testing the different mounting possibilities it was found that when a top mount unit comprising the mounting structure weighted about 300 Kg a similarly sized side mount unit could be made with a mounting structure such that it only weighted about 200 Kg.

The rotating shaft of the turbine can be supported by bearings on the mounts or supports at the upper and lower end of the rotor unit such that the lover support is placed between the turbine and the generator. By means of it is possible to reduce the loading of the bearings of the generator. The loading of the generator can also be reduced by means of a flexible joint between the shaft and the generator. For example, a rigid shaft of the rotor unit and a shaft of the generator can be connected by means of a yoke or by a connector made from flexible material such as rubber. The flexible joint can be particularly advantageous in a side mount to mast. A reason for this is that the mast may bend and/or vibrate on wind, and this may otherwise stress the bearings of the generator or even break the generator.

Also, when mounting the turbine unit onto a mast it may not be possible to use as accurate assembly methods and equipment as it is possible for example when working on a roof top. The stress caused by such inaccuracies can also be mitigated by the flexible joint and/or suitable bearing assembly on the rotor shaft.

An optional shield plate or screen may be provided on top of the rotor unit to shield the rotor from debris, dirt, ice or similar falling from above the rotor, for example from the upper parts of the mast or other structures that may be located above the turbine unit. An advantage of use of a substantially self-sufficient energy generation unit in a mobile phone base station mast or similar communications mast structure is that the mast can be located even in locations where external electricity is not easily available. Also, as mentioned above, a vertical turbine unit can be used as an emergency power source, for example when the ordinary power source such as power cabling is damaged by a storm or for other reasons. Although most base station sites of mobile telecommunication systems are provided with batteries to cover such emergency situations, these last only for a limited time. Even a relatively low power turbine unit in accordance with the present invention can used to at least lengthen this time, and in many instances to provide enough power for the communications equipment to prevent it from becoming inoperable as a result of a power cut.

Similarly to the roof top assembly, a mast unit may be connected to at least one battery and/or electricity grid. The energy production and supply can be arranged in various manners. The energy supply can be controlled to switch between different modes. For example, a turbine unit mounted in a mobile telecommunications mast may have a mode where all electricity produced is supplied solely to a base station unit or units mounted in the mast. In another mode the electricity is supplied to a battery unit, wherefrom it can then be supplied to one or more base station units. In a third mode any excess eiectricity is supplied to a power grid. The switching may be controlled by means of a computerized control system such that the turbine unit and/or the battery unit is operated in an optimal manner.

The rotor assembly can be provided with a braking mechanism. The brake can be mechanical, for example a disc brake, a drum brake or the like. The braking mechanism may also be based on an electronic control arrangement. For example, the controller can "lock" the generator and thus prevent the turbine shaft from rotating. The locking can be provided e.g. by short circuiting the generator. The braking mechanism may be used for example as a safety mechanism when any work, maintenance or other work, needs to be done in the vicinity of the rotor to prevent it from rotation. The braking mechanism may be particularly advantageous in situations where the turbine unit is mounted on a mast, for example a telecommunications mast as shown in Figures 9A and 9B. Particular advantage may be provided if the vertical rotor unit is mounted on a side of the mast, and where work may need to be done in a location that is above the unit.

Figures 1OA and 1OB show a possible assembly 10 of three vane modules 20, 22, 24 relative to each other. As can be seen from the top view of Figure 1 OB, the vane modules of the rotor unit 10 can be arranged about 120 degrees apart such that a wind blow from any direction will start the rotor and that at least one vane is always in an optimal position relative to the wind blow as the rotor rotates. As an arrangement consisting of three vane modules provides six vane members, there is a vane member in every 60 degrees when viewed from the top. However, another number of vane members can be provided and evenly distributed about the rotational axis. It is considered the that the separations is preferably from 30 to 90 degrees. Even positioning of a plurality of vane members may provide advantage in reducing vibration as the unit as a whole is subjected more evenly to wind coming from a direction. Particularly good results in view of vibration can be achieved in embodiments where the shape of each of the vane members and modules arranged in such a fashion corresponds to that shown in Figures 2 to 5 and explained with reference thereto.

The rotor assembly of Figures 10A and 10B can be advantageously used for example for assembly on top or side of a telephone or other mast, or other structure where vibration may be a problem. It is noted that the vane modules can be in different order than that shown in Figure 1 OA. The order of the vane modules can be used to adjust the turbine unit, and more particularly its vibration characteristics, to the wind conditions of the site. This may have particular importance if more than three vane modules are used in a rotor.

Furthermore, each of the plurality of vane members may be provided with a space for advertisement or similar. Because a vane member of the plurality of rotating vane members is always visible, the advertisement or similar will also be visible regardless the rotational position of the rotor unit. Power during hard winds may increase to such level that is exceeds the power handling capabilities of the electronics. Traditionally this problem has been solved by stopping the rotor or releasing the generator from the rotor. In accordance with an embodiment the relative positioning between the rotor and the stator is adjusted to control the output power and/or heating of the generator. For example the distance between the generator stator and rotor can be increased to reduce the power during hard winds. In a generator where permanent magnet or magnets are mounted directly on the shaft of the wind turbine the rotor to stator distance can be controlled, for example, by pressing the end of the shaft by a screw or by a lever to move the shaft in vertical direction. The relative movement between the stator and rotor can be provided by a servomotor. The rotor to stator distance can be controlled based on feedback information regarding the generator power.

The sectional view of Figure 11 shows a possibility for providing control of the relative positioning between a rotor 72 and stator 74 of a generator 70. The rotor axle 73 is supported by appropriate bearing arrangement allowing rotational and axial movement of the axle 73 relative to the frame of the generator 70. The bearings can be provided, for example, by means of slide bushings 71. As the rotor

72 is attached to the axle 73 and the stator 74 is fixedly mounted to the frame by means of appropriate support arrangement 75, vertical movement of the axle 73 will cause change in the positioning of the rotor relative to the stator.

In the embodiment of Figure 11 the axial movement is provided by means of an adjustment screw 76 bearing at the end of the axle 73. The screw can be actuated by a motor 78, The motor 78 in turn can be controlled by an appropriate controller. The controller can be integrated for example with a load controller apparatus as described above, or provided by means of a separate controller unit. Other possibilities for the actuation and adjustment are also possible. A non-limiting example of the adjustment range is 3mm.

In accordance with a possibility the stator 74 is movable. For example, the stator supports 75 can be configured such that it is possible to move the stator vertically relative to the rotor 72. In accordance with a possibility the entire generator is moved relative to the shaft, thus moving the stator elements fixed to the body of the generator. A servomotor or pneumatic/hydraulic mechanisms can be provided in connection with adjustable supports to provide an adjustment mechanism that can be controlied by an electronic controller.

Increasing the distance between the rotor and the stator reduces magnetic effect and thus the generator produces less power. An advantage is that even during very high gusts system can generate maximum power without exceeding its capacity. Also, the output power can be limited to a level that should not damage the control electronics.

In accordance with a further embodiment a gap or gaps are provided between the vane member and the rotor shaft while the vane member is shaped such that a portion of the wind coming towards the vane surface can pass between the vane surface and the shaft and is guided to press against the back surface of the opposite vane member. The vane members can be attached to the shaft for example by means of appropriate fish bone structure or the like structure allowing the wind the pass the gap whilst maintaining the rigidity of the vane module.

It is noted that the above disclosed use examples are not exhaustive. In addition to local energy production on top of buildings, telephone or illumination masts or other high structures, the wind turbine apparatus can be assembled e.g. on moving platforms such as ships and military vehicles. Furthermore, instead of assembly on a side of structures such as a communication systems mast, a turbine unit can be mounted on a side of any other structure, such as any tower like structure, side wall of a tall building, side of a bridge and so forth.

It is also noted herein that while the above describes exemplifying embodiments of the invention, there are several variations and modifications which may be made to the disclosed solution without departing from the spirit and scope of the present invention as defined in the appended claims.

Claims

1. A wind turbine apparatus comprising: a generator; a substantially vertical shaft, the shaft being directly mounted to the generator for rotating the generator; at least one lightweight vane member, the at least one vane member being attached to the shaft to provide a twisted self starting rotor unit; and electronic control apparatus for controlling the speed of rotation of the generator by controlling loading of the generator.

2. A wind turbine apparatus as claimed in claim 1 , wherein the at least one vane member is twisted in the order of 10 degrees relative to the shaft.

3. A wind turbine apparatus as claimed in claim 1 or 2, wherein the generator comprises a permanent magnet synchronous generator.

4. A wind turbine apparatus as claimed in ciaim 3, wherein the generator comprises at least one magnet comprising at least one rare earth metal.

5. A wind turbine apparatus as claimed in claim 3 or 4, wherein at least one permanent magnet is mounted on the shaft.

6. A wind turbine apparatus as claimed in any preceding claim, wherein the control apparatus comprises a rectifier adapted to control the loading of the generator.

7. A wind turbine apparatus as claimed in claim 6, wherein the control apparatus is adapted to optimise the rotational speed of the wind turbine based on at least one of a determined wind speed, a tip speed of the vane members, and output power.

8. A wind turbine apparatus as claimed in claim 7, wherein the rectifier of the control apparatus is configured to control the loading of the generator such that a predetermined relation between the tip speed and the wind speed is maintained.

9. A wind turbine apparatus as claimed in claim 7 or 8, wherein the rectifier is adapted to control the loading by modifying the wave form of the sine wave of the voltage generated by the generator.

10. A wind turbine apparatus as claimed in any preceding claim, wherein the wind turbine is assembled from modules,

11. A wind turbine apparatus as claimed in claim 10, wherein a module comprises a vane member and the wind turbine comprises at least two vane member modules.

12. A wind turbine apparatus as claimed in claim 10 or 11 , wherein a rotor module comprises at least two vane members, and the wind turbine comprises at least two rotor modules.

13. A wind turbine apparatus as claimed in any preceding claim, wherein the ratio of weight to surface area of the at least one vane member decreases in function of distance from the shaft.

14. A wind turbine apparatus as claimed in any preceding claim, wherein the at least one vane member is made from at least one of plastic material, composite materia!, iaminate material, fibreglass and aluminium.

15. A wind turbine apparatus as claimed in any preceding claim, wherein the control apparatus is further configured to be activated and/or deactivated based on detection that at least one condition is satisfied.

16. A wind turbine apparatus as claimed in claim 15, wherein the at least one condition comprises a threshold.

17. A wind turbine apparatus as claimed in claim 16, wherein the threshold comprises a threshold for at least one of windspeed, speed of rotation, and power output.

18. A wind turbine apparatus as claimed in claim 16 or 17, wherein the condition is satisfied when the generator produces enough energy to power the electronic control apparatus.

19. A wind turbine apparatus as claimed in any preceding claim, comprising a plurality of vane members, each vane member being arranged evenly about the rotational axis and 30 to 90 degrees apart from at least one other vane member.

20. A permanent magnet synchronous generator for a wind turbine apparatus, wherein at least one permanent magnet comprises at least one rare earth metal, the rotor of the generator is mounted on the shaft of the wind turbine apparatus, and the relative positioning of the rotor and the stator of the generator is adjustable.

21. A generator as claimed in claim 20, wherein the relative positioning is adjusted by means of a screw or lever.

22. A generator as claimed in claim 20 or 21 , comprising a servomotor for adjusting the relative positioning of the rotor and the stator.

23. A generator as claimed in any of claims 20 to 22, wherein the relative positioning of the rotor and the stator is adjusted in response to information regarding the output power of the generator.

24. A generator as claimed in any of claims 20 to 23, comprising means for axially adjusting the relative position of the stator and rotor.

25. A control apparatus for controlling operation of at least one vertical wind turbine, comprising a wind speed determining apparatus; a processor configured to optimise rotation of the at least one wind turbine based on the information from the wind speed determining apparatus and information of at least one of speed of rotation of the at least one wind turbine and power output of the at least one wind turbine; and an electronic controller configured to control the loading of at least one generator based on information from the processor to optimise the speed of rotation of the at least one wind turbine.

26. A control apparatus as claimed in claim 25, comprising means for determining at least one of the speed of rotation of the at least one wind turbine and the power out of the at least one wind turbine, wherein the control apparatus is configured to load the at least one generator such that a predetermined relation between the tip speed and/or power output of the at least one wind turbine and the wind speed is maintained.

27. A control apparatus as claimed in claim 25 or 26, the control apparatus is configured to be activated and/or deactivated based on detection that at least one condition is satisfied.

28. A control apparatus as claimed in claim 27, wherein the at least one condition comprises a threshold for at least one of windspeed, speed of rotation, and power output.

29. A control apparatus as claimed in claim 27 or 28, wherein the condition is satisfied when the generator produces enough energy to power the electronic control apparatus.

30. A control apparatus as claimed in any of claims 25 to 29, configured to adjust the relative positioning of a rotor and a stator of the at least one generator.

31. A control apparatus as claimed in claim 30, comprising an adjustment mechanism configured to move the shaft of the wind turbine relative to the stator of the generator.

32. A wind turbine apparatus, comprising a plurality of vane members, each vane member being twisted in the order of 10 degrees in the vertical direction relative to the rotational axis thereof and being arranged substantially evenly about the rotational axis such that each vane member is spaced 30 to 90 degrees apart from at least one other vane member.

33. A wind turbine apparatus as claimed in claim 32, comprising a plurality of modules, each of the modules comprising two vane members.

34. A wind turbine apparatus as claimed in claim 32 or 33, comprising at least six vane members such that the at least six vane members are evenly distributed about the rotational axis.

35. A power generation system comprising at least one wind turbine apparatus as claimed in any of claims 1 to 19 and/or 32 to 34 and/or at least one generator as claimed in any of claims 20 to 24 and/or a control apparatus as claimed in any of claims 25 to 31.

36. A power generation system as claimed in claim 35 adapted for localised assembly on a roof of a building or on a mast.

37. A power generation system as claimed in claim 36, comprising a support structure for mounting to a communications mast.

38. A power generation system as claimed in claim 37, wherein the support structure is adapted for mounting to a side of a telecommunications mast.

39. A power generation system as claimed in any of claims 35 to 38, configured to supply power for a base station of a mobile communication system.

40. A power generation system as claimed in any of claims 35 to 39, comprising a local grid; means for converting from AC to DC voltage between the at least one wind turbine apparatus and the local grid; a local energy storage connected to the local grid; at least one further local energy production apparatus; and a connection to another grid.

41. A method for controlling a wind turbine adapted to rotate a generator, comprising determining wind speed; determining tip speed and/or power output of the wind turbine; controlling the rotational speed of the wind turbine based on the determined wind speed and the tip speed and/or power output by controlling the loading of the generator by means of an electronic apparatus such that a predetermined relation between the wind speed and tip speed and/or power output is maintained.

42. A method as claimed in claim 41 , wherein the controlling comprises maintaining the tip speed in a level that is slightly less than the wind speed.

43. A method as claimed in claim 41 or 42, wherein the controlling of the loading of the generator comprises modifying the wave form of the sine wave of AC voltage generated by the generator.

44. A method of controlling a permanent magnet synchronous generator of a wind turbine apparatus, the generator comprising at least one permanent magnet comprising at least one rare earth metal, the rotor of the generator being mounted on the shaft of the wind turbine apparatus, comprising adjusting the relative positioning of the rotor and the stator of the generator.

45. A method as claimed in claim 44, wherein adjusting the relative positioning comprises adjusting the distance between the rotor and stator by means of a screw or lever.

46. A method as claimed in claim 44 or 45, wherein the adjusting comprises vertically moving the shaft.

47. A method as claimed in any of claims 41 to 46, comprising controlling output power of the generator based on feedback information.

48. A method of supplying power to telecommunications equipment mounted on a mast, comprising the steps of any of claims 41 to 47 and operating the wind turbine in the mast.

49. A computer program comprising program code means adapted to perform any of steps of any of claims 41 to 48 when the program is run on a data processing apparatus.