GB2525967A

GB2525967A - Wave energy converter with energy source for actuator

Info

Publication number: GB2525967A
Application number: GB1503857.3A
Authority: GB
Inventors: Frederik Loraing; Benjamin Hagemann; Matthias Lenssen; Yukio Kamizuru
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2014-03-07
Filing date: 2015-03-06
Publication date: 2015-11-11
Also published as: DE102014204249A1; GB201503857D0

Abstract

A wave energy converter comprises a rotor 4 which is driven by wave movement relative to a stator 18. The rotor 4 has a vane 3 which is driven by wave movements. The angle of the vane 3 is controlled by an actuator 5, which is powered by an energy source. The energy source may comprise a generator with permanent magnets 10b mounted on the stator and coils 10a on the rotor. Magnets 10b may be supplemented or replaced by electromagnets, e.g. to supply power when the rotor is not moving. Power is therefore supplied to the rotor without requiring slip-rings. A Flettner rotor may be used in place of vane 3, in which case the actuator controls the rotational speed for the Flettner rotor. The main generator 40, 41 may be positioned alongside the power supply to the rotor.

Description

Wave energy converter with energy source for actuator

Description

The present invention relates to a wave energy converter.

Prior art

Wave power stations (wave energy converters) utilise the energy of sea waves to produce electrical energy. Recent design approaches in this regard use rotating units (rotors) which convert the wave movement into a torque.

Hydrodynamic buoyant bodies (i.e. bodies which generate lift when there is a flow around them, such as, for example, lift profiles and/or Flettner rotors using the Magnus effect) can be used on these as coupling bodies, by means of which lift forces are generated from the inflowing wave and a torque is generated by the arrangement of the coupling bodies on the rotor, which torque can be converted into a rotational movement of the rotor. A superimposed inflow from the orbital flow of the wave movement and the intrinsic rotation of the rotor results in lift forces on the coupling bodies, as a result of which a torque is applied to the rotor. In sea waves the water particles move on largely circular so-called orbital paths (in the form of an orbital movement or orbital flow, both terms also being used synonymously) . In this case, the water particles move under a wave crest in the propagation direction of the wave, under the wave trough opposite the wave propagation direction and in both zero crossings upwards and downwards, respectively. In this regard, a plant concept is known from DE 10 2011 105 169 Al, DE 10 2011 105 177 Al, DE 10 2011 178 Al and DE 10 2011 105 170 Al, in which the lift cf a lift device against which there is a flcw, that is tc say a hydrodynamic lift-generating coupling body, is converted into a rotational movement. A wave energy converter with Flettner rotors is disclosed in GB 2 226 572 A. It is desirable to improve the operation of wave energy converters and/cr reduce the complexity/current producing costs of the plants.

Disclosure of the invention

According to the invention, a wave energy converter for converting energy from a wave movement of a fluid into another form of energy with a stator and at least one rotor rotatably mounted about the stator, having the features of Claim 1, is proposed. Advantageous configurations are the subject-matter of the subclaims and the following

description.

Advantages of the invention A particular aspect of the invention is the measure to assign -in the case of a wave energy converter, at least one energy-delivering component of an energy source for supplying energy to an actuator for a coupling body which is adjustably, in particular rotatably, fastened to the rotor by means of the actuator -to a rotating assembly comprising at least the rotor of the wave energy converter, i.e. to fasten it in or to this asserntly. This results in a particularly simple construction and a reduced maintenance requirement, in particular in view of the rough conditions on the high seas, since no slip rings or rotary transmission leadthroughs are required for supplying energy to the actuator. For, the energy-delivering component of the energy source rotates with the actuator. As a result, the operation is improved and/or the complexity/current producing costs are reduced.

The energy source for supplying energy to the actuator is preferably an electrical generator with an energy-delivering electrical component and an energy-consuming magnetic component which rotate relative to one another.

The energy-delivering component is the winding in which a voltage is induced, and the energy-consilming component is the component providing the magnetic field. This is a particularly expedient configuration for many applications. :15

The rotor advantageously has a largely horizontal rotor rotational axis. The rotor is advantageously driven by the orbital flow. In other words, through the wave movement of the water, more precisely its orbital flow, a torque (in the context of this invention referred to as torque" or "rotor torque") is produced which acts on the rotor.

The term Thoupling body" is to be understood in this context as any structure by which the energy of an inflowing fluid can be coupled into a rotor movement or a corresponding rotor torque. As explained below, coupling bodies can be configured in particular as lift devices (also referred to as "blades") , but also comprise drag devices or Flettner rotors (i.e. cylinders with additional intrinsic rotation) Particularly preferably, coupling bodies from the class of lift devices are used which, upon an inflow at an inflow angle, produce besides a drag in the direction of the local inflow, in particular a lift force directed substantially perpendicular to the inflow. These may, for example, be lift devices with profiles according to the NACA (National Advisory Committee for Aeronautics) but the invention is not limited to such profiles.

Particularly preferably, Eppler profiles can be used. In the case of a corresponding rotor, the local inflow and the associated inflow angle result from a superimposition of the orbital flow and a local or instantaneous wave inflow direction, the rotational speed of the lift device at the rotor and the angle of incidence of the lift device.

According to one embodiment, the actuator is configured to adjust an angle of incidence of the coupling body. As a result, the orientation of the coupling body can be optimised with regard to the locally existing inflow conditions.

According to a further embodiment, the actuator is configured to adjust a coupling body geometry of the coupling body. For this purpose, the coupling body can have, for example, flaps similar to those on aircraft wings and/or be configured to change the lift profile geometry (so-called "morphing") to influence the inflow.

According to a further embodiment, the actuator is configured to rotate the coupling body with a desired rotational speed. As a result, Flettner rotors can be used as the coupling body.

According to a further embodiment, the actuator is configured to change the position of the coupling body relative to the lever arm, in particular the radial distance. By changing the radial distance, the machine can be adapted to different wave states or in very high waves the coupling body can be protected from emerging. Moreover, the dimensions of the rotor can thereby be reduced, which is beneficial for installation and transportation. By changing the angular position of the rotor arms, for example by folding down the rotor arms, emergence of the coupling body can likewise be avoided and the dimensions can be reduced.

According to a further embodiment, the energy-delivering component has a coil for converting mechanical energy into electrical energy. It is thereby achieved with simple technical means that mechanical rotational energy of the rotor can be converted into electrical energy for supplying the actuator. In addition, by continuously changing a magnetic field passing through the coil of the energy-delivering component, for example by corresponding operation of an electromagnet, a current can be induced in the energy-consuming component even when the rotor is at a standstill.

According to a further embodiment, the actuator has an electric motor which is connected in a force-transmitting manner to the coupling body. Tt is thereby achieved that an electric motor, such as, for example, a stepping motor or a synchronous motor, can be used for adjusting the coupling bodies.

According to a preferred embodiment, the actuator is a hydraulic, pneumatic, mechanical or electromechanical actuator.

According to a further embodiment, the rotor has a rotor base and a lever arm extending from the rotor base, the lever arm being of hollow form. This allows the energy-delivering component and/or the actuator to be arranged at least partially inside the lever arm, which is particularly space-saving and moreover protects the elements arranged there.

According to a further embodiment, the energy-consuming component of the energy source for supplying energy to the actuator is assigned to the stator of the wave energy converter. It is thereby achieved that the actuator has further, stationary components which do not have to be arranged to be rotatable with the rotor. Thus, the actuator has a particularly simple and low-maintenance construction.

According to a further embodiment, the energy source for supplying energy to the actuator is configured as an electrical generator with an electrical component as energy-delivering component and a magnetic component as energy-consuming component.

According to a further embodiment, the magnetic component has a permanent magnet. It is thereby achieved that no energy supply to the magnetic component is required to provide a magnetic field, so that a particularly simple and low-maintenance energy source is provided for the actuator.

According to a further embodiment, the wave energy converter has a hollow shaft which extends parallel, in particular concentrically, to the rotor rotational axis, wherein the further component is arranged inside the hollow shaft. This is particularly simple and of low maintenance and also in particular space-saving.

Preferably, the wave energy converter has an energy store for indirectly cr directly supplying the actuator. This advantageously results in energy being available even when the rotor is at a standstill, in order, for example, when using Flettner rotors as the coupling body, to bring these first to a certain rotational speed before the rotor starts to rotate.

According tc cne alternative, the energy stcre is assigned to the stator. This has the advantage that the energy store, which usually has a relatively high mass, does not have to rotate jointly. The energy supply to the actuator can in this case take place via the energy-delivering component and the energy-consuming component when the former is configured as a coil and the latter as an electromagnet.

According to another alternative, the energy store is assigned to the rotating assembly comprising at least the rotor of the wave energy converter. This results in a simpler construction, since no electromagnet is required for supplying energy to the actuatcr.

Further advantages and configurations of the invention can be found in the description and the appended drawing.

Cf course, the features which are mentioned above and which are to be explained below can be used not only in the respectively specified combination but also in other

B

combinations or alone without departing from the scope of the present invention.

The invention is illustrated schematically in the drawing using exemplary embodiments and is described in detail below with reference to the drawing.

Description of the figures

Figure 1 shows a preferred embodiment of a wave energy converter according to the invention with two coupling bodies in a perspective view.

Figure 2 shows two rotors for converting energy from a wave movement with disc-shaped rotor bases in a perspective view.

Figure 3 shows a schematic sectional representation of a quadrant of the wave energy converter with an actuator according to a first exemplary embodiment.

Figure 4 shows a schematic sectional representation of the wave energy converter with an actuator according to a second exemplary embodiment.

Detailed description of the drawing

In the figures, identical or identically acting elements are specified with identical reference symbols. For the sake of clarity, the explanation will not be repeated.

Figure 1 shows a wave energy converter 1 with a rotor base 2, a housing 7 and four ooupling bodies 3 which are respectively attached via lever arms 4 to the rotor base 2.

The lever arms 4 are arranged on each rotor side in a starting position at an angle of 1800 to one another. The wave energy converter 1 is placed for operating below the water surface of a body of water where there is wave action, for example an ocean. In the example shown, the coupling bodies 3 are embodied in a profiled fashion, but can also be embodied as Flettner rotors, i.e. cylinders with additional intrinsic rotation. An actuator 5 with at least one degree of freedom is expediently available for each of the coupling bodies 3 in order to change the orientation (for example pitch angle, i.e. the angle between the profile chord and the tangential speed) of the respective coupling body and therefore influence the interaction between the body of water and the coupling body. The degree of freedom of the actuators is described here by adjustment parameters (pitch angle) . Alternatively, in the case of Flettner rotors as coupling bodies the rotational speed of the Flettner rotors can also be adapted. The actuators are preferably hydraulic and/or electromotive and/or pneumatic actuators. Preferably, the wave energy converter 1 also has a sensor system 6 for sensing the current adjustment. The components 2, 3, 4, 5, 6 are components of a rotor 11 which rotates about a rotor rotational axis x. The latter is largely horizontally orientated. In normal operation, the rotor 11 is completely submerged.

The rotor 11 is mounted so as to be rotatable relative to the honsing 7. Tn the example shown, the housing 7 is connected in a rotationally fixed fashion to a stator of a directly driven generator for generating current, and the rotor 11 (here the rotor base 2) is connected in a rotationally fixed fashion to a rotor of this directly driven generator. It is also possible advantageously to provide a transmission between the rotor base and the generator rotor. A provided means of attaching the wave energy converter 1 to the sea bed, which can also be done by means of a mooring system and preferably by a monopile, for example, is not illustrated.

Figure 2 illustrates two embodiments of the wave energy converter 1 with a disc-shaped rotor base 2 without lever arm. These embodiments each have two coupling bodies 3 which are mounted on one or both sides on the rotor base 2.

The coupling bodies 3 are coupled to the actuator 5 which are formed for active adjustment of the angle of incidence of respectively one of the coupling bodies 3. when the coupling bodies 3 are mounted on both sides, the second side can be rotatably mounted, but alternatively an attachment of the actuator 5 on both sides is also possible. Additionally, sensors 6 for determining the angle of incidence are provided.

At the rotor base 2, an energy converter 8 engages on a rotor shaft 9, which converter has a directly driven generator 40, 41 in the present exemplary embodiment.

With the aid of Figure 3, in which a detail (substantially a quadrant; axes of symmetry are represented in dot-dash lines) of a wave energy converter is shown in a plan view from above, it can be seen that in the present exemplary embodiment the actuator 5 is supplied by an energy source with an energy-delivering, here electrical component lOa and an energy-ccnsuming, here magnetic compcnent lob.

The electrical component lOa and the magnetic component lOb are in this case formed to supply together the actuator 5 with electrical energy. For this purpose, the electrical component iCa in the present exemplary embodiment has a coil 13 for converting mechanical energy of the rotating rotor 11 into electrical energy, which coil is arranged on the rotating rotor 11, while the magnetic component lOb has a magnet 14 which is arranged stationarily on the wave energy converter 1. In the present exemplary embodiment, the magnet 14 is a permanent magnet, such as, for example, a rare-earth magnet, which consists essentially of ferromagnetic metals (iron, cobalt, rare nickel) and rare-earth metals (in particular neodymium, samarium, praseodymium, dysprosium, terbium, gadolinium) -Also yttrium may assume the role of a rare-earth metal. Such a magnet is distinguished in that it exhibits simultaneously a high magnetic remanent flux density and a high magnetic coercive field strength and hence a high magnetic energy density. Thus, in the operation of the wave energy converter 1, the magnet 14 induces a magnetic field in the coil 13, a voltage being induced in the coil 13 by the relative movement of the coil 13 on the rotor 11 of the wave energy converter 1 in relation to the stationary magnet 14. It can be provided that the magnet 14 alternatively or additionally has an electromagnet, in order thereby to be able to supply the actuator 5 with energy even when the rotor is at a standstill. In this case, an energy store 12 for supplying the electromagnet (and hence indirectly for supplying the actuator 5) is necessary, which energy store is expediently assigned to the stator. This has the advantage that the energy store, which usually has a relatively high mass, does not have to rotate jointly. Alternatively or additionally, an energy store 12' for supplying the actuator 5 may be assigned to the rotor.

A converter unit 33 (e.g. so-called power electronics) converts the voltage induced in the coil 13 and frequency, so that a voltage and frequency is available, with which an electric motor 15 of the actuator 5 is supplied with electrical energy via a supply line 16, which motor is connected in a force-transmitting manner to the coupling body 3, in order to change the angle of incidence of the coupling body 3. In the present exemplary embodiment, the electric motor 15 which is connected in a force-transmitting manner to the coupling body 3 is arranged inside the lever arm 4. Figure 2 shows that the coupling bodies 3 can be suspended adjustably between respectively two or more lever arms 4.

For the radial and axial force transmission between a rotating assembly 17, such as, for example, the rotor, and a fixed assembly 18 of the wave energy converter 1, e.g. the stator, an axial and radial bearing 19a, 19b (e.g. media-lubricated) is provided.

Furthermore, the fixed assembly 18 of the wave energy converter 1 in the present exemplary embodiment comprises a generator winding 40, which inductively cooperates with magnets 41, such as, for example, electromagnets or permanent magnets, on the rotor 11 and thus allows a conversion of mechanical wave energy into electrical energy. The generator winding 40 and the magnet 41 formed as an electromagnet or permanent magnet can constitute an external rotor generator or an internal rotor generator.

For cooling the generator arrangement, both the rotating assembly 17 and the fixed assembly 18 of the wave energy converter 1 can have guide vanes and/or bores (neither of which are shown) which provide a defined coolant flow, e.g. water. Furthermore, in the present exemplary embodiment, there is provided a membrane (not shown) which provides a volume and electrolyte equalisation between an otherwise sealed medium and the surrounding sea water. The fixed assembly 18 of the wave energy converter 1 can moreover have further electrical and power-electronics components, such as, for example, a control (not shown in Figure 3) for controlling the actuator 5. Finally, there is provided a transmission element 32 which is configured to transmit forces and moments, to be supported towards the sea floor, into a foundation (not shown) In the present exemplary embodiment, a hollow shaft 20 extends parallel and concentrically to the rotor rotational axis x, which shaft likewise is part of the rotating assembly 17 and substantially serves to connect the lever arms. Arranged inside the hollow shaft 20 is a bracing element 21 which connects fixed assemblies 18 arranged on both sides. The assemblies 18 are here braced with a kind of nut 31 against a projection 30 of the bracing element 21. It is also conceivable for the drive train to be attached only to one side of the machine, Only mechanical components would then be installed on the opposite side of the axis of symmetry.

In the present exemplary embodiment, the rotor 11 has two rotor blocks 34 arranged on both sides, only one of which is shown in Figure 3. Attached to the rotor blocks 34 are the lever arms 4, between which the coupling bodies 3 are adjustably suspended. The hollow shaft 20 is configured such that it connects the rotor blocks 34.

Between the rotor blocks 34 and the stator 25 is provided the axial and radial bearing 19a, 19b. The axial and radial bearing 19a, 19b can be configured in a manner sealed off from the outside, i.e. from the sea. Alternatively, the axial and radial bearing 19a, 19b can also be configured to be open and thus water-lubricated.

The stator 25, shown in Figure 3, of the wave energy converter 1 with the magnetic component lOb is of rotationally symmetrical configuration. The rotor 11 with the energy-delivering component ba is configured, in the present exemplary embodiment, as an external rotor. In other words, during assembly of the wave energy converter 1, the stator 25 and the two assemblies 18 is/are inserted into the rotor 11 configured as an external rotor from both sides. For fixing the stator 25, the latter is fixed on both sides using the bracing element 21.

Figure 4 shows a second exemplary embodiment of a wave energy converter, which differs from the first exemplary embodiment according to Figure 3 in that a plurality of components are accommodated in the hollow shaft 20. In this case too, the stator has a hollow axle 18, which at the same time defines the rotational axis drawn as a dot-dash line.

Tnside the hollow axle 18 the magnetic component lOb, namely the magnet 14, of the energy source for supplying energy to the actuator, and the generator winding 40 of the energy converter are stationarily arranged, while in the hollow shaft 20 the energy-delivering component ba, namely the coil 13, of the energy source for supplying energy to the actuator 5, and the magnet 41 of the energy converter are arranged. Between hollow shaft 20 and hollow axle 18 are arranged radial bearings 19a which can be open to or sealed off from the sea. Expediently, bearings are also present in order to take up axial forces. Furthermore, in the present exemplary embodiment, a control 23 for controlling the wave energy converter is accommodated inside the hollow axle 18.

In operation, as described above, an orbital flow results in a rotation of the rotor 11. Thus, the coil 13 in which the fixed magnet 14 induces a voltage rotates. Electrical energy is therefore provided, with which the electric motor can be driven in order to change the angle of incidence of the coupling body 3 if necessary, for example if the inflow conditions have changed. An operation of the wave energy converter 1 with optimal angles of incidence of the coupling bodies 3 is thus possible.

On the other hand the magnet 41 rotates, so that a voltage is induced in the generator winding 40, which can then be extracted by the wave energy converter.