WO2014180628A1

WO2014180628A1 - Alignment of a wave energy converter relative to the surrounding body of water

Info

Publication number: WO2014180628A1
Application number: PCT/EP2014/057467
Authority: WO
Inventors: Alexander Poddey; Michael Hilsch; Nik Scharmann; Johannes Nitzsche; Matthias Lenssen; Benjamin Hagemann
Original assignee: Robert Bosch Gmbh
Priority date: 2013-05-06
Filing date: 2014-04-14
Publication date: 2014-11-13
Also published as: DE102013007667A1

Abstract

The invention concerns a method of operating a wave energy converter (1) for converting energy from a wave movement of an undulatory body of water, the wave movement having a propagation direction, the wave energy converter (1) comprising a lever arm (4), which is mounted so as to rotate about a rotor rotational axis (x) and bears a coupling body (3), and an energy converter (2, 7) which is coupled to the rotatably mounted lever arm (4). The wave energy converter (1) is aligned relative to the wave movement such that, during operation, the rotor rotational axis (x) forms an angle (φ) which is not 90° with the propagation direction of the wave movement.

Description

Alignment of a wave energy converter to the surrounding waters

description

The present invention relates to a method for operating a wave energy converter for converting energy from a wave motion of a wavy body of water into another form of energy.

State of the art

Wave power plants (wave energy converters) use the energy of ocean waves to generate electricity. Newer design approaches use rotating units (rotors), which convert the wave motion into a torque. At these hydrodynamic buoyancy bodies (ie bodies that generate a buoyancy in flow around, such as buoyancy profiles and / or Flettner rotors using the Magnus effect) can be used as coupling body, by means of which from the oncoming wave buoyancy forces and the arrangement the coupling body is generated on the rotor a moment which can be converted into a rotational movement of the rotor. By a superimposed flow from the orbital flow of the wave motion and the rotation of the rotor itself buoyancy forces on the coupling bodies, whereby a torque is introduced into the rotor. From DE 10 201 1 105 169 A1, DE 10 201 1 105 177 A1, DE 10 201 1 105 178 A1 and DE 10 201 1 105 170 A1, a plant concept is known in which the buoyancy of a flowed-up lift rotor, So one of a hydrodynamic lift generating coupling body is converted into a rotational movement. GB 2 226 572 A discloses a wave energy converter with Flettner rotors. It is desirable to improve the operation of generic wave energy converters and / or to reduce the complexity / cost of electricity of the equipment.

Disclosure of the invention

According to the invention, a method for operating a wave energy converter for converting energy from a wave motion of a wavy body of water into another form of energy, a computing unit for carrying it out, and a wave energy converter having the features of the independent claims are proposed. Advantageous embodiments are the subject of the subclaims and the following description.

Advantages of the Invention The invention makes it possible to operate a wave energy converter relatively inexpensively, but nevertheless with relatively high energy yield. This is achieved by dispensing with the vertical alignment of the axis of rotation to the current propagation direction of the waves of the wavy body of water (corresponding to a parallel orientation of the axis of rotation to the wave crests) previously required (such as the introductory documents or US Pat. No. 7,686,583 B2). Instead, the wave energy converter is aligned with respect to the wave motion that (at least temporarily or constantly) during operation, the rotor rotational axis with the propagation direction of the wave motion includes an angle not equal to 90 °. This gives rise to the possibility of developing a significantly simplified system, which dispenses with a particularly active Azimuthausrichtung.

At a specific location, the characteristics of the ocean waves can vary over the year - this also applies in particular to the propagation direction of the incoming waves. As described in the article "Wave power variability over the northwest European shelf seas", Applied Energy 106 (2013) 31-46 and shown in Figure 13, these can vary by large angles of about 100 °.

So far, it has been assumed that a wave energy converter is preferably to be aligned in each case such that the axis of rotation is largely parallel to the currently incoming wave crests (and thus largely perpendicular to the wave propagation direction or wave propagation direction). speed of advancement) in order to achieve optimum energy yield. Otherwise, the orbital flow is not oriented perpendicular to the coupling bodies, so that they can not optimally change the flow. In practice, this will mean that a wave energy converter, depending on the location over an angular range of about 100 ° or more (about the vertically oriented z-axis) must be rotatable in order to be optimally aligned for possible wave movements.

In the context of the invention, it has now surprisingly been found that deviations from the described orientation in this angular range lead to less energy losses than feared, with small deviations in the single-digit or low double-digit angular range even an increase in the energy yield can be observed. The angle between the axis of rotation and the wave propagation direction preferably deviates at least temporarily by at least 1 °, preferably at least 3 °, particularly preferably at least 5 ° or 7 ° and / or at most 25 °, preferably at most 20 °, very particularly preferably at most 17 ° or 15 ° from 90 °.

When carried out in a wave tank experiments with obliquely impinged rotating Wellenenergiekonverterermodellen could be found that the decrease in power at oblique flow is significantly lower than initially expected (see Figure 2). Surprisingly, even a slight increase in the energy yield in some wave states could be found for smaller angles of rotation. The result is a slightly twisted system (angle between the axis of rotation and incoming wave crests, for example at least 3 ° and / or at most 25 °) the possibility to increase the efficiency of the system. This could be due to an increase in the flowed effective coupling body width by the skew.

An at least temporary or permanent deviation from the propagation direction during operation can also be achieved by applying to one (active and / or passive)

Azimuthnachführung, so on an orientation of the rotor axis of rotation with respect to the propagation direction of the wave motion (or with respect to the wave crests), is omitted. This eliminates the need for appropriate Aktorik other forms of attachment of fasteners for a wave energy converter, which can be designed simpler and more robust. This gain in simplicity and ruggedness can reduce costs associated with investment and operating and maintenance costs, possibly lower yields at times sharply biased Clearly overcompensate flow. In this embodiment, it is provided to completely dispense with the Azimuthnachführung the wave energy converter. Instead, in this embodiment, the wave energy converter is mounted in such a way that it is oriented in accordance with the propagation direction of the (in particular high-energy) waves prevailing at the respective location (rotation axis substantially perpendicular to the propagation direction). As a result, particularly simple and robust anchoring concepts can be realized. The propagation directions of the waves occurring at the respective location can be determined, for example, over a longer period of time. From this, a prevailing propagation direction at the respective location can then be determined. For example, there are locations where the propagation direction of the incoming waves distributed over the year in a range of less than or equal to 90 °, or in which only a small proportion of incoming waves from significantly different directions enters and / or on which the waves with strong deviating propagation direction have only a small share of the incoming wave energy at this site. For these locations is particularly the waiver of Azimuthnachführung.

In an equally preferred embodiment, it is provided that the rotor axis is operated in a targeted manner rotated to the vertical configuration - preferably in combination with an (active and / or passive) Azimuthnachführung. It is thus preferably an (active and / or passive) control of the angle between the axis of rotation and wave propagation direction instead. This allows the observed increases in efficiency to be achieved. The optimal deviation from the vertical orientation may depend on the wavelength and / or frequency and on the expected overlaying of different sea conditions at the installation site. A passive azimuth tracking is, for example, a rotatable attachment of the wave energy converter to a suspension, e.g. Mooring or monopile, according to a banner in the wind. An active one

Azimuth tracking can be achieved, for example, by generating a torque about the vertical, cf. DE 10 201 1 105 170 A1, or be realized by rotation about a stationary suspension.

In an advantageous embodiment, the Azimuthnachführung is carried out so that they only for larger deviations from the preferred oblique flow (eg deviations above a deviation threshold of, for example, 10 ° -15 ° from the preferred angle not equal to 90 ° between the rotor rotational axis and the wave propagation direction) ak - closely followed. This reduces the tracking effort considerably. In other words, during operation, an actual value of the angle is detected and regulated to a setpoint value of the angle, with a setting intervention taking place only if a control error between the actual value of the angle and the setpoint value of the angle exceeds a deviation threshold value.

Waves are caused by the interaction of wind and water surface, whereby the wind sweeps over the water surface over longer distances (Fetch) and thereby generates waves. These waves spread over long distances in the oceans. Therefore, it is possible that at some point wave systems operate from two or more directions, ie from geographically different places of origin. In this case, the wave motion has at least two propagation directions. According to a further embodiment of the invention, the wave energy converter in sea states consisting of the above-mentioned superposition of two or more spatially separated wave systems., With an angle of incidence between the incident wave systems of preferably <120 °, more preferably <90 °, most preferably <45 ° and very exceptionally particularly preferred <30 ° operated, ie the rotor axis of rotation includes with the at least two propagation directions of the wave motion in each case an angle not equal to 90 °. The wave systems are characterized by the spectral magnitudes Hs (significant wave height) and Te or Tp (period duration). To calculate the optimal alignment of the system, vectors are generated per wave system with direction of the wave propagation direction and length = Hs ² Te. In addition, since the wave energy converter has different conversion efficiencies for different wave systems (in particular wavelengths), the vectors can be weighted (multiplied here) with the conversion efficiency in order to favor the wave systems which promise particularly high conversion efficiencies. For example, by vectorial addition of the vectors associated with the wave systems, the direction of the resulting propagation direction can now be determined. The system should then be oriented so that this resulting propagation direction is preferably perpendicular to the rotor axis of rotation or has an above-described deviation from the vertical orientation. As a result, in total, a significantly larger amount of energy can be absorbed than is possible with a conventional alignment with one of the overlapping components. This solution can advantageously be combined with the embodiment without azimuth tracking, in which case the resulting output The direction of propagation of a long-term wave motion (eg over one year) is determined and used for the orientation of the wave energy converter.

An arithmetic unit according to the invention, e.g. a control unit of a wave energy converter is, in particular programmatically, arranged to perform a method according to the invention.

Also, the implementation of the invention in the form of software is advantageous because this allows very low cost, especially if an executing processing unit is still used for other tasks and therefore already exists. Suitable data carriers for providing the computer program are, in particular, floppy disks, hard disks, flash memories, EEPROMs, CD-ROMs, DVDs and the like. It is also possible to download a program via computer networks (Internet, intranet, etc.). Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

The invention is illustrated schematically with reference to an embodiment in the drawing and will be described in detail below with reference to the drawing.

figure description

FIG. 1 shows a preferred embodiment of a wave energy converter according to the invention in a perspective view.

Figure 2 is a diagram of a relationship between removable power and

Angular rotation between wave crest line and rotor axis for a model test. Detailed description of the drawing

FIG. 1 shows a wave energy converter 1 with a rotor base 2, a housing 7 and four coupling bodies 3 fastened to the rotor base 2 via lever arms 4. The lever arms 4 are arranged on each rotor side in a basic position at an angle of 180 ° to one another. The wave energy converter 1 is placed for operation below the water surface of a wavy body of water - for example, an ocean. The coupling bodies 3 are profiled in the example shown, but may also be used as Flettner rotors, i. Cylinder with additional self-rotation, be executed. Conveniently, there is at least one degree of freedom for each of the coupling bodies 3 to adjust the orientation (e.g., "pitch angle," i.e., the angle between chord and tangential velocity) of the respective coupling body, thereby affecting the interaction between the body of water and the coupling body. The degree of freedom of the adjusting devices is described here by adjusting 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 adjusting devices are preferably hydraulic and / or electromotive and / or pneumatic adjusting devices. Preferably, the wave energy converter 1 also sensor 6 for detecting the current adjustment. The components 2, 3, 4, 5, 6 are components of a rotor 1 1, which rotates about a rotor axis x. This is oriented largely horizontally. In normal operation, the rotor is completely submerged.

The rotor 1 1 is rotatably mounted relative to the housing 7. The housing 7 is rotatably connected in the example shown with a stator of a directly driven generator for generating electricity, the rotor 1 1 (here the rotor base 2) is rotatably connected to a rotor of this directly driven generator. It may also be advantageous to provide a gearbox between rotor base and generator rotor. An arithmetic unit, which is adapted to perform a method according to the invention, is disposed within the housing 7 and serves to control the operation of the wave energy converter 1. Not shown is an intended attachment of the wave energy converter 1 to the seabed, for example by a Mooringsystem and preferably by a Monopile can be done. In the context of the invention, a deviation of the previously required orthogonality between the rotor axis (x-axis) and the propagation direction of the incoming waves is now accepted. Conventionally, the wave energy converter is aligned so that the propagation direction of the incoming waves lies in the yz plane. In the context of the invention, a deviation is now accepted or even adjusted by an angle φ, ie the propagation direction of the incoming waves includes the angle φ with the yz plane. The angle φ also occurs in a corresponding manner between the wave crest lines (perpendicular to the propagation) and the rotor axis (x axis). In FIG. 2, a power P generated by a wave energy converter model is plotted against the angle φ in [°]. These are measurement results which were determined in experiments with a wave energy converter model flown at an angle φ in a wave tank. At this angle of attack were tested from 0 ° - 42 °, which results in symmetry reasons an opening angle of 84 °, which already covers all incoming waves at many potential locations of wave energy power plants. It can be seen that the power decrease with oblique flow is relatively small. In particular, a rotation of up to about 25 ° does not lead to an excessive decrease in performance. Surprisingly, for smaller angles of rotation (in the present example in a range of about 13 °) even an increase in the power generated could be determined.

Claims

Claims 1. A method of operating a wave energy converter (1) for converting energy from wave motion of a wavy body of water, the wave motion having a propagation direction,

wherein the wave energy converter (1) has a lever arm (4) rotatably mounted about a rotor rotational axis (x) and carrying a coupling body (3), and an energy converter (2,7) coupled to the rotatably mounted lever arm (4),

characterized in that the wave energy converter (1) is aligned with respect to the wave motion, that during operation, the rotor rotational axis (x) with the propagation direction of the wave motion includes an angle (φ) not equal to 90 °.

2. The method of claim 1, wherein the angle (φ) at least 1 °, preferably at least 3 °, more preferably at least 5 °, most preferably at least 7 ° and / or at most 25 °, preferably at most 20 °, more preferably at most by 17 °, most preferably at most by 15 ° deviates from 90 °.

3. The method of claim 1 or 2, wherein the angle (φ) is set so that in comparison to a vertical alignment between the rotor rotational axis (x) and propagation direction of the wave motion increased conversion of energy is achieved.

4. The method according to any one of the preceding claims, wherein the Wellenenergiekonver- ter (1) is not aligned during operation with respect to the propagation direction of the wave motion.

5. The method according to claim 4, wherein a propagation direction of the wave motion resulting over a period of time is determined and the wave energy converter (1) is aligned with respect to the wave motion such that during operation the rotor rotational axis (x) forms an angle with the resulting propagation direction of the wave motion (φ) equal to 90 °.

6. The method according to any one of the preceding claims, wherein the wave energy converter (1) is arranged rotationally fixed with respect to the surrounding water.

7. The method according to any one of claims 1 to 3, wherein detected during operation, an actual value of the angle (φ) and is controlled to a desired value of the angle (φ).

8. The method of claim 7, wherein a control intervention takes place only when a control error between the actual value of the angle (φ) and setpoint of the angle (φ) exceeds a deviation threshold.

9. The method according to claim 1, wherein the wave movement has at least two propagation directions, wherein the wave energy converter is aligned with respect to the wave movement such that during operation the rotor rotational axis with the at least two propagation directions of the wave movement respectively forms an angle. φ) not equal to 90 °.

10. The method of claim 9, wherein from the at least two propagation directions, a resultant propagation direction is determined and the wave energy converter (1) is aligned with respect to the wave motion, that during operation, the rotor rotational axis (x) with the resulting propagation direction of the wave motion at an angle (φ) equal to 90 °.

1 1. arithmetic unit, which is adapted to perform a method according to any one of the preceding claims.

12. Computer program with program code means which cause a computing unit to perform a method according to one of claims 1 to 10, when they are executed on the computing unit, in particular according to claim 1 1.

13. A machine-readable storage medium with a computer program stored thereon according to claim 12.

Wave energy converter (1) for converting energy from a wave motion of undulating body of water, comprising a rotatably mounted around a rotor axis of rotation (x) th lever arm (4) carrying a coupling body (3), one with the rotatably mounted lever arm (4) coupled energy converter (2,7) and a computing unit according to claim