Water current power generation systems

An underwater structure includes a power generation unit, which includes a main body, a mounting portion which extends from the main body and which defines a mounting axis, and a support structure adapted for engagement with a bed of a body of water, and support housing. The mounting portion defines a substantially continuous mounting surface which extends substantially completely around the mounting portion, and the support housing defines a substantially continuous support surface which extends substantially completely around the support housing. The mounting surface and support surface are arranged to abut one another substantially continuously when the power generation unit is mounted on the support structure. The mounting portion and the support housing are adapted to cooperate with one another for mounting of the power generation unit on the support structure in any polar orientation about the mounting axis.

The present invention relates to water current power generation systems, and in particular to such systems which employ removable power generation units.

BACKGROUND OF THE INVENTION

It is widely known that easily accessible resources of fossil fuels are declining. In addition, the impact of the use of fossil fuels upon the environment has become increasingly apparent. As a result of this, it has become imperative that viable alternative energy sources are used as effectively and efficiently as possible. The use of turbines to capture the power of water flow, such as tidal, river and ocean current flows is becoming a viable source of alternative energy. The turbine equipment used to capture such water flow energy typically includes a shaft driven generator connected using a drivetrain to a rotor assembly. The rotor assembly includes a plurality of rotor blades that are driven by the water flow, so as to turn an input shaft of the drivetrain.

In order to be economically practical, multiple water current turbine devices need to be deployed in a suitable area. For example, a tidal turbine farm may have tens to hundreds of turbines. The turbines are preferably arranged in an array having multiple rows of multiple turbines. The turbine array could be deployed in a tidal flow area, a river flow, an ocean current, or any other suitable water current area. Although it is preferable for the turbines to be arranged in an array, geography, bathymetry and other factors may mean that a turbine farm has another arrangement.

Such turbine equipment needs to be secured to the bed of a body of water, such as a sea, estuary or river. Conventional underwater turbines used to drive electrical generators are mounted on a horizontal rotational axis and require a significant amount of ancillary features, in order to maximise energy capture. One such feature that is essential for efficient energy generation is yaw capability: it must be possible to direct the turbine to the most effective orientation with respect to the direction of current flow at any particular time.

Installation, maintenance and servicing of underwater power generation apparatus, particularly in deep sea environments, are highly costly and time consuming procedures. It is therefore desirable to simplify the construction and deployment of underwater power generation apparatus, lowering capital cost and reducing the frequency with which in service intervention is required.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided an underwater structure comprising a power generation unit including a main body, a mounting portion which extends from the main body and which defines a mounting axis, a connection carrier, and a connector mounted on the connection carrier, and a support structure adapted for engagement with a bed of a body of water, and including a support housing, a support connection carrier attached to the support housing, and a support connector mounted on the support connection carrier, the support connector being adapted for releasable engagement with the connector of the power generation unit, wherein the mounting portion defines a substantially continuous mounting surface which extends substantially completely around the mounting portion, and wherein the support housing defines a substantially continuous support surface which extends substantially completely around the support housing, the mounting surface and support surface being arranged to abut one another substantially continuously when the power generation unit is mounted on the support structure, and wherein the mounting portion and the support housing are adapted to cooperate with one another for mounting of the power generation unit on the support structure in any polar orientation about the mounting axis.

In one example of such a structure, the power generation unit includes connection actuation means operable to move the connection carrier substantially parallel to the mounting axis, and to rotate the connection carrier about the mounting axis. In one example of such a structure, the connection actuation means is provided by a single actuator.

In one example of such a structure, support structure includes support connection actuation means operable to move the support connection carrier substantially parallel to the mounting axis, and to rotate the support connection carrier about the mounting axis.

In one example of such a structure, the support connection actuation means is provided by a single actuator.

In one example of such a structure, the support connection carrier is removable from the support housing.

In one example of such a structure, wherein the support connection carrier includes engagement means operable to engage releasably with the support housing so as to enable releasable engagement of the support connection carrier with the support housing. In one example of such a structure, the support connection carrier is provided a substantially planar plate.

In one example of such a structure, the connection carrier is provided with a predetermined amount of positional float with respect to the mounting portion.

In one example of such a structure, the connection carrier is provided with a predetermined amount of positional float with respect to the actuation means.

In one example of such a structure, the connection carrier includes a locating portion which is acted upon by the actuation means, and a secondary carrier which carries the connector, the secondary carrier being provided with a predetermined amount of positional float with respect to the locating portion.

In one example of such a structure, the connector is provided with a predetermined amount of positional float with respect to the secondary carrier.

In one example of such a structure, the connector is provided with a predetermined amount of positional float with respect to the connection carrier.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A water current power generation system1is shown inFIG. 1and comprises a support structure2located on a bed3of a body of water. A power generation unit4, such as a turbine device, is mounted on the support structure2. In this example, as the water current flows past the power generation unit4, a rotor assembly turns, thereby driving an electrical generator, or other power converter apparatus, provided in the power generation unit4. In one example, the power generation unit4is buoyant, and is winched down to the support structure2.

FIG. 2illustrates the power generation unit4ofFIG. 1in more detail. The power generation unit4comprises a main body10, on which is rotatably mounted a rotor assembly12. The rotor assembly12operates to drive an electricity generator, or other power generation apparatus, housed in the main body10. The power generation unit4is adapted for releasable mounting on the support structure2, and includes a mount14to provide this releasable mounting.

The attachment of the mount14to the support structure is shown in more detail inFIG. 3. The main body10, from which the engagement portion14extends, is not shown inFIG. 3for the sake of clarity. The mount14defines a mounting axis M for the power generating unit4.

The mount14has a mounting flange15which engages with an associated support flange21provided by the support housing20. The mounting and support flanges15and21allow the power generating unit4to be affixed to the support structure2in an appropriate manner. For example, the power generating unit4may be substantially rigidly fixed to the support structure2during power generation, and may be rotatable with respect to the support structure2during a re-orientation procedure.

FIG. 4is a schematic cross-sectional view of an example mount30for a power generation unit4. This example mount30is provided with a tapered mounting portion31which is substantially circular in cross-section, and which provides an aperture therethrough. In the example shown inFIG. 4, the mounting portion31is in the form of a truncated cone, but could be provided by any suitable shape. It will be appreciated that the mounting portion31need not be tapered nor circular in cross section, but may be provided by any suitable shape. For example, the mounting portion31may be provided by a hollow cylinder, or by a hollow prism.

The mounting portion31has, at a distal end thereof, a mounting flange32, which defines a substantially circular and substantially continuous mounting surface. In the example shown inFIG. 4, an attachment flange33is provided for attaching the mount30to the main body of the power generation unit. The mount30can be bolted, welded, or fixed in any other suitable manner, to the housing10, and may not require the provision of the attachment flange33.

A connection carrier35is provided within the mounting portion31, and carries any appropriate number of electrical, optical and other connectors38. The precise nature and number of connectors38carried by the connection carrier35is not material to examples of the present invention. InFIG. 4, the connection carrier35is shown in a first, unconnected, configuration.

The connection carrier35may be provided by any suitable shape and configuration. The exemplary connector carrier shown inFIG. 4comprises a carrier shaft (or locating portion)35aonto which is mounted a carrier plate35b. The connectors38are carried by the carrier plate35b, on a mating surface of the carrier plate35b.

The connection carrier shaft35is mounted on actuation means39, such as one or more hydraulic or electrical actuators. The actuation means39serve to move the connection carrier35in a direction substantially parallel to the mounting axis M. The actuation means39also operate to rotate the connection carrier35about that axis M. The actuation means may be provided by any suitable arrangement of equipment. In one example, the actuation means comprises a linear actuator linked to the carrier shaft35aby a linkage arrangement, and a rotary actuator that operates directly on the carrier shaft35a. In another example, the actuation means includes an actuator that engages the carrier plate35bfor rotation of the connection carrier35. The actuation means may be located in any convenient location in the mounting portion31, and/or in the main body10of the power generation unit4.

The connection carrier35is provided with at least one alignment pin, such as the two alignment pins36and37shown inFIG. 4, which extend from the carrier plate35b. As will be described in more detail below, the alignment pins serve to enable accurate alignment of the connection carrier35on the support structure2.

Connector cables40are connected with the connectors38, and are routed through a cable management system41before connecting to cables42from the power generating apparatus.

FIG. 5illustrates a schematic cross-sectional view of a support housing50provided on the support structure2. The example support housing50shown inFIG. 5is substantially cylindrical, and defines a circular aperture therethrough. It will be readily appreciated that, as for the mounting portion31of the power generation unit4, the support housing50can be of any suitable shape and cross section.

The support housing50includes a support flange51which defines a substantially circular and substantially continuous support surface onto which the mounting surface of the mount30abuts when the power generating unit4is mounted on the support assembly2.

A support connection carrier52is provided in the support housing50. The support connection carrier52extends across the aperture of the support housing50, and carries support connectors59for connecting to the connectors38of the connection carrier35of the power generating unit4. Alignment apertures60and61are arranged to receive the alignment pins36and37of the power generating unit. It will be appreciated that any number of alignment pins and associated apertures can be provided. In one example, the alignment holes60and61have conical openings configured to allow for some level of initial misalignment of the alignment pins.

It is to be noted that the alignment pins may be provided on the support connection carrier, and the corresponding alignment apertures on the connection carrier of the mounting portion. It will be readily appreciated that each of the carriers may be provided with both alignment pins and alignment apertures, with corresponding apertures and pins being provided on the other of the carriers.

The support connection carrier52also includes a cable connector57arranged to connect the support connectors59to an input/output cable58. The cable58is used to export generated power from the power generating apparatus. For example, the cable may be used to export electricity generated by the power generating apparatus to a grid connection. In an alternative application, the export cable may be used to transfer hydraulic fluid from the power generating apparatus. The cable58can also include control and measurement cables.

In the example shown inFIG. 5, the support connection carrier52is removable from the support housing50, and is held in place using locking actuators53and54, which serve to move engagement features55and56into engagement with an inner surface of the support housing50. Such an arrangement enables the support connection carrier52to be removed from the support housing50for maintenance purposes, without the need to remove the whole support structure, or support housing, or to undertake complex underwater cutting and welding operations.

FIG. 6illustrates the mount30ofFIG. 4located on the support housing50ofFIG. 5in a first, unconnected, configuration. The mount30is brought into contact with the support housing50, so that the mounting and support surfaces defined by the attachment flanges32and51respectively abut one another. The connectors38of the power generation unit and the support connectors59remain unconnected at this stage.

FIG. 7shows a second configuration in which the connection carrier35has been moved axially in a direction substantially parallel to the mounting axis M, such that the connectors38and alignment pins36and37are engaged with associated connectors59and alignment apertures60and61on the support connection carrier52. The actuator39is operated to move the connection carrier35into connection with the support connection carrier52.

Before the connection carrier35is moved into position axially, it may need to be rotated in order that the alignment pins36and37are substantially aligned with the alignment holes60and61respectively. A motor for providing this rotation may be provided within the mounting portion31, or the rotation may be achieved by the actuation means39.

As the connection carrier35moves into connection with the support connection carrier52, the connectors38meet with the corresponding connectors59to complete the electrical/hydraulic, optical and/or control connections between the power generating unit4and the cable58.

FIG. 8illustrates another example of a mount30located on the support housing50. In this example, the mounting portion31includes a locating portion63which extends from an end region of the mounting portion31. The locating portion63extends from within the mounting portion31past the mounting flange32. The locating portion63is coaxial with the mounting portion31, and is provided with an aperture therethrough. The locating portion63is tapered so as to aid location of the power generating unit on the support structure. As the power generating unit is lowered into place on the support structure, the distal end of the locating portion63, which is narrower than the aperture of the support housing50of the support structure, is able to enter the support housing structure50with a degree of positional freedom. That is, the accuracy of location of the distal end of the locating portion63is not as fine as that required to locate the mounting and support flanges32and51. As the power generating unit continues to be lowered onto the support structure, the locating portion63centres the mount30on the support housing50, such that the mounting and support surfaces abut one another. It will be appreciated that a similar locating portion could be provided by the support housing50instead of by the mount30.

The mounting surface transfers the load of the power generation unit onto the support surface, and hence into the support structure. The substantially circular and substantially continuous nature of the mounting and support surfaces serves to distribute the loads around the support housing, and to remove, or substantially reduce, the occurrence of point loading on the support housing.

The substantially circular and substantially continuous nature of the mounting surface of the power generation unit and of the support surface of the support housing, in combination with the rotatable connection carrier of the power generation unit, also enables the mounting portion30to be located on the support housing50in any polar orientation with respect to the mounting axis M.

The ability to mount the power generation unit on the support structure in any polar orientation (that is, without discrete mounting locations) simplifies the deployment of the power generation unit to the support structure. This is because there is no requirement to orient the unit as it descends into its mounting position on the support structure.

The mounting and support surfaces allow the power generation unit to rotate with respect to the support structure, so that the unit can be oriented appropriately for power generation, irrespective of the orientation of the unit when it was first deployed to the support structure.

Due to the high loading associated with the rotor and tidal flow, it is preferable to use a clamping arrangement, such as that shown in UK Patent Number 2448710. Such a clamp arrangement allows the power generating unit to be oriented for power generation for an initial tide direction, and then re-oriented when the tide turns.

In addition, this polar mounting freedom of the power generation unit enables the location and orientation of the support structure to be simplified, since the polar orientation of the support housing is not important when the power generating unit can be mounted, and then operated, in any polar orientation with respect to the support structure.

The mounting arrangements described above are particularly advantageous for use with a single cable winch deployment system, such as that described in UK Patent Number 2431628. In such a configuration, a winch cable tube or aperture is provided substantially aligned with the mounting axis. In one example, a tube is provided through the connection carriers, through an arm of the actuation means, and then through the main body of the power generation unit.

In a practical example of an arrangement that follows the principles of those described above, a degree of positional freedom, or “float” is desirable for at least some of the components. In this context, the term “float” is used to mean that a component has some flexibility of movement about a nominal mounting position, without the need for specific adjustment intervention. This positional float is provided in order to allow for manufacturing and positioning tolerance.

FIG. 9illustrates a first example of float, in which the actuation means39are able to float in position with respect to the mount30. InFIG. 9, this floating coupling is illustrated by mounting elements100, which are illustrative only. The elements100can be provided by any suitable means, for example flexible mountings or slot and pin arrangements. Using the arrangement ofFIG. 9, the whole of the actuation means and connection carrier assembly is able to float in position with respect to the mount30. Following initial rotational alignment, as the actuation means39moves the connection carrier35linearly, the alignment pins (not shown inFIG. 9for clarity) are brought into engagement with the corresponding alignment apertures. If there is any misalignment of the pins and apertures, the alignment pins cause the actuation means and connection carrier assembly to move with respect to the mount, as those pins are brought into alignment with the apertures. The respective shapes of the alignment pins and alignment apertures serve to bring the pins into alignment with the apertures through the linear action of the connection carrier35. The float provided to the actuation means and carrier assembly by the mounting elements100enable the lateral, rotational and angular position of the carrier plate35bto be aligned correctly with the corresponding support connection carrier to enable the connectors to engage with one another.

FIG. 10illustrates another example of the provision of float to the connection carrier35. In this example, the actuation means39are fixed substantially rigidly with respect to the mount30, and the connection carrier35is able to float with respect to the actuation means39. This float is illustrated by the elements101. In this example, the float may be provided by specifying bearings between the actuation means39and the carrier shaft35athat have a required amount of play. In this way, the carrier shaft35aand the carrier plate35bare able to move with respect to a nominal mounting position by the action of the alignment pins aligning and engaging with the alignment apertures.

FIG. 11illustrates another example of the provision of float to the connection carrier. In this example, the actuation means39are fixed substantially rigidly with respect to the mount30, and the carrier shaft35ais located in the actuation means39using bearing having substantially no play. As such, the carrier shaft35aand carrier plate35bare moveable linearly, and are rotatable, with respect to the mount30substantially without float. A secondary carrier35cis mounted on the carrier plate35bon mounting elements102. The mounting elements102are illustrative only and may be provided by any suitable arrangement. The mounting elements102allow the secondary carrier35cto float with respect to the carrier plate35b. The secondary carrier plate35ccarries the alignment pins and connectors (not show for clarity), and so the float provided to the secondary plate35cenables the alignment of the alignment pins and connectors carried by the secondary carrier35c.

FIG. 12illustrates the connection carrier35, comprising the carrier shaft35a, and the carrier plate35b, and illustrates another example of the provision of float. Alignment pins36and37extend from the carrier plate35bwithout the provision of float. The connectors38are mounted on the carrier plate35bby way of mounting elements103that allow a predetermined amount of float for the connectors38. As the carrier plate35bis brought into engagement with the support connection carrier of the support structure, the mounting elements103allow the connectors38to align correctly with the support connectors of the support structure.

FIG. 13illustrates the connection carrier35making use of the float techniques illustrated inFIGS. 11 and 12. As such, a secondary carrier plate35cis provided on the carrier plate35b, and is able to float with respect to the carrier plate35b. In addition, connectors38are mounted on the secondary carrier plate35cby way of elements that allow float of the connectors with respect to the secondary carrier plate35c. Alignment pins36and37extend from the secondary carrier plate35csubstantially without float. In this way, as the connection carrier is brought into engagement with the support connection carrier, the alignment pins engage with the alignment apertures. If there is any slight misalignment, the action of the alignment pins engaging with the apertures causes the secondary carrier plate35cto move (laterally, rotationally, and/or angularly) such that the alignment pins are able to engage fully with the apertures. As the connectors38come into engagement with the support connectors, the mounting elements103allow the connectors to align correctly, taking up any minor misalignment.

It will be appreciated that the float provision ofFIGS. 9 to 13may be used individually, or in any suitable combination, depending upon the requirements and specific design of connection carrier. The provision of positional float enables the action of the alignment pins engaging with the alignment apertures to cause alignment of the connectors to allow for manufacturing or fitting tolerances of the connection carriers. Providing the individual connectors with float then enables any connector-related misalignment to be taken up and overcome.

FIG. 14illustrates an example of mounting of a connector38on the carrier plate35bor on the secondary carrier plate35c. The connector38is attached to the carrier plate35b/35cvia a flexible attachment means65. The attachment means65allows a predetermined amount of lateral float66of the connector38, and also allows a predetermined amount of angular float67of the connector38. In such a manner, an amount of lateral and angular mismatch can be taken into account when the connectors are brought into connection with support connectors on the support connection carrier. It will be readily appreciated that the support may be provided with such positional freedom in addition to, or in place of, that provided to the connectors of the power generation unit.