Patent Application
20110316282
The invention relates to an underwater powerplant having a disconnectable nacelle according to the preamble of the independent claims, in particular for obtaining power from a tidal current.
Underwater power plants which are implemented without a dam structure and having free flow around them, and are used for obtaining energy from a tidal current, are known. Such freestanding plants can also be used for flowing bodies of water. For such plants, a water turbine driven by the current flows around the nacelle and drives an electrical generator housed inside the nacelle at least indirectly. The nacelle is mounted on a support structure, which can either be placed on a foundation on the body of water floor or can be implemented as a floating unit. The mounting of the nacelle on the support structure can be implemented as rigid. Alternatively, the nacelle is fastened on the support structure so it is rotatable in such a way that tracking of the water turbine is possible in the case of a varying inflow direction.
To execute a plant service and to simplify the installation, a modularly constructed underwater powerplant has been proposed by EP 1 366 287 A1, for example. A foundation is first erected from individual components on the body of water floor, having a support structure constructed thereon. The nacelle is subsequently lowered along a guide cable configuration to the support structure. A connection cable, which originates from the electrical generator or the power-electronic components in the nacelle, is laid by service divers in a guide channel on the support structure. This type of installation is complex and hazardous because of the use of the service divers. Further raising of the nacelle to execute a plant service above water proves to be correspondingly difficult.
To simplify the cable guiding, it was proposed by GB 2 437 534 A for a modular underwater powerplant that a rigid pipe connecting piece be used on the nacelle, which receives and protects a first portion of the connection cable. The constructive outlay for implementing the connecting piece is a disadvantage in such a design. In addition, this plant part interferes with the handling of the nacelle. This relates to the initial installation and to maintenance work, which is executed on board a water vehicle. For this case, the connecting piece protruding from the housing of the nacelle will result in a correspondingly large-dimensioned crane and handling system onboard the water vehicle.
A connection cable which is external after the plant installation represents a component which is susceptible to wear because of the continuous movement due to the surrounding current. These fatigue problems cannot be entirely overcome even by components of a cable protection system which are attached in segments. In addition, the cable located in the current can result in vibrations. Furthermore, a fastening on the support structure is to be provided, which ensures a sufficient distance from the orbit of the water turbine during operation. This is complex.
Further problems of the known, modular underwater power plants result in the case of a rotatable linkage of the nacelle to the support structure to track the water turbine in relation to a variable-direction inflow. For this case, excessively strong twisting of the connection cable originating from the nacelle is to be avoided. For actively motorized azimuthal rotational devices, a continuous change of the rotational direction, in the simplest case a back-and-forth movement, can be executed to avoid these problems. However, passive azimuthal rotation devices are preferred to simplify the system. To avoid the twisting for such a device, it was proposed by DE 10 2007 002 338 B3 that the azimuthal rotation be synchronized with the intrinsic rotation of a centrally running connection cable. However, this is connected with an additional design effort for coupling the rotational movements of the nacelle and the connection cable.
The invention is based on the object of specifying a modular underwater powerplant having a nacelle which is removably fastened on a support structure, whose coupling and decoupling is simplified. In particular, the connection cable for transmitting the electrical power generated by the electrical generator in the nacelle is to be reliably protected during installation and removal and during normal plant operation. For a refinement, the nacelle is to be able to execute a rotation around the support structure in the coupled state, in order to be able to follow a direction change for the inflow, without cable twisting being able to occur.
To achieve the object, the inventors have recognized that a modular underwater powerplant should transmit the electrical power generated by the electrical generator in the nacelle inductively and accordingly in a contactless manner to the support structure. For this purpose, an inductive transmission device can be provided between the nacelle and the water turbine, which is detachable and thus allows coupling and decoupling of the nacelle to and from the support structure. The inductive transmission device can be implemented by a transformer for a first design. In the case of a directionally-rigid coupling of the underwater powerplant to the support structure, a transformer can be used, whose primary side is assigned to the nacelle and whose secondary side is assigned to the support structure. The use of a plurality of such transformers is conceivable, which can be implemented as a part of or in the area of the coupling device for connecting the nacelle to the support structure.
To implement an underwater powerplant having a nacelle linked so it is rotatable on the support structure, the inductive transmission device according to the invention is also designed having parts movable rotatably to one another. A preferred embodiment is the use of a rotary transformer, which is implemented as an electrical generator, for example, as an asynchronous machine having a wound rotor, which is fixedly braked.
An induction machine having a rotor feed to implement a rotary transformer is particularly preferred.
An alternative embodiment of the invention provides implementing the electrical generator, which is at least indirectly driven by the water turbine in operation, as separable and to dispense with a separate inductive transmission device. The rotor of the electrical generator 6 is assigned to the nacelle 2 and the stator of the electrical generator 6 is assigned to the support structure. Accordingly, the electrical generator is implemented as separable and can correspondingly be assigned to the two halves of the coupling device. The two parts can be separated or connected in the submerged state.
For installation, the support structure is first sunk with the generator stator. In a subsequent installation step, the revolving unit having the rotor is placed on the support structure, the coupling device allowing renewed detachment and decoupling of the revolving unit. In the case of a plant service, the revolving unit having the generator rotor is raised to the water surface, while the generator stator remains in the support structure, since these plant components are to be viewed as essentially maintenance-free.
The above-mentioned embodiment of the invention having a separable electrical generator is advantageously implemented having a flooded air gap. Furthermore, the bearing components are advantageously designed as water-lubricated friction bearings, so that the revolving unit is coupled to the initially exposed rotor of the electrical generator underwater. Furthermore, to simplify the coupling, complementary guide units are provided on the revolving unit and the water turbine, which cause self-centering.
The invention is described in greater detail hereafter on the basis of exemplary embodiments in connection with illustrations in the figures. In the specific figures:
According to the invention, the modularly constructed underwater powerplant 1 has an inductive transmission device 7, which is used for the purpose of transmitting the electrical power generated by the electrical generator 6 in a contactless manner from the nacelle 2 to the support structure 4. For this purpose, the inductive transmission device 7 can comprise a transformer 9, whose primary side 10 is assigned to the nacelle 2 and whose secondary side 11 is assigned to the support structure 4. The inductive transmission device 7 can be part of the coupling device 15, as shown, or can be implemented in proximity thereto. Because of the self-centering of the coupling device 15 caused by the complementary guide elements 14, the partial components of the transformer 9, which are guided toward one another during the coupling, can be precisely positioned to one another on the primary site 10 and the secondary site 11. In this way, it is possible to reduce the distance to be bridged in a contactless manner or to provide components which interlock like teeth for the primary side 10 and the secondary side 11, which improve the efficiency of the inductive power transmission.
To implement a simple coupling ability, the inductive transmission device 7 is implemented in such a way that its components are encapsulated in relation to the surrounding water, but the air gap area of the electrical generator is flooded after the coupling.
A rotary transformer represents a possible embodiment for the inductive transmission device 7, which is particularly used to implement a rotatable mount for the nacelle 2 on the support structure. It can be implemented as an asynchronous machine having a wound rotor, which is fixedly braked for a specific operating position. The fixing brake used for this purpose is preferably implemented so it can be disengaged, so that an azimuthal rotation of the nacelle can be executed. Correspondingly, for this case, the primary side of the rotary transformer moves in relation to the secondary side fixed on the support structure during tracking of the nacelle.
For the mentioned rotary transformer, the absolute value of the secondary voltage is unchanged in relation to the primary voltage. Only the phasing is variable as a function of the rotational position. The rotary transformer is particularly preferably implemented as an induction machine having rotor feed, whose components are protected against the corrosive action of the surrounding water by a corrosion protection element, such as a can, or using a casting compound, so that operation in the surrounding water is possible.
In detail,
Upon coupling of the revolving unit 16 to the support structure 4, a conical receptacle 12 in the support structure 4 is used for a first centering. Furthermore, a centering device 23 is provided on the revolving unit 16, which causes the final centering in the end phase of the coupling together with a complementarily shaped receptacle in the support structure 4. Furthermore, the diagonally placed bearing 22 supports the self-centering, so that the required tolerances of the air gap 19 are maintained between the generator rotor 17 and the generator stator 18. The air gap 19 and the areas in which the bearings 20, 21, 22 are implemented are preferably flooded using surrounding water. Electrical components of the frequency inverter 24 and the electrically conductive parts of the generator 6 are encapsulated.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2008 059 891.7 | Dec 2008 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2009/008315 | 11/23/2009 | WO | 00 | 6/27/2011 |
