GB2500644A

GB2500644A - Turbine with integral generator

Info

Publication number: GB2500644A
Application number: GB1205453.2A
Authority: GB
Inventors: Paul Vigars
Original assignee: Tidal Generation Ltd
Current assignee: Tidal Generation Ltd
Priority date: 2012-03-28
Filing date: 2012-03-28
Publication date: 2013-10-02
Anticipated expiration: 2032-03-28
Also published as: GB2500644B; GB201205453D0

Abstract

An underwater power generating apparatus 4 comprises a generator 8 and a turbine 14. The generator rotor 12 is provided in the body 16 of the rotor. The stator 10 is part of the support means and extends within the generator rotor 12. The turbine 14 comprises a body 16 and at least one blade 18 supported on the body 16 by substantially radial arms 40. There may be electromagnetic components which cause the rotor to magnetically levitate (50, 52 figure 4), and a friction device (54, 56 figure 4) to act as an emergency brake when the electromagnetic device is disabled. The stator 10 may be mounted on an underwater foundation or anchorage 6.

Description

POWER GENERATING APPARATUS

The present invention relates to a power generating apparatus comprising a generator and a turbine. The invention relates particularly, although not exclusively, to vertical axis power generating apparatus for generating electricity from tidal currents.

Background

There is increasing interest in the use of underwater power generating equipment that makes use of the energy of water flows, such as tidal flows. Such equipment is secured to the bed of a body of water, such as a sea, estuary or river, and employs a rotary generator to generate electricity. The generator is driven by a turbine having a rotor and a number of rotor blades placed in the water flow. 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 angle with respect to the direction of current flow at any particular time. Also required for horizontal axis turbines may be upstream operation, pitchable turbine blades, internal dry spaces with seals, power electronics and transformers and auxiliary cooling systems. All of these systems increase the overall weight and cost of the turbine, and reduce its reliability.

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

Summary of the Invention

According to the present invention, there is provided a power generating apparatus comprising: a generator having a stator which defines an axis of the generator and a rotor arranged for rotation about the stator; and a turbine having a body and at least one blade supported on the body, wherein the body provides the rotor of the generator, and is adapted to be mounted for rotation about the stator.

The present invention thus provides a turbine having a "direct drive' arrangement, in which rotation of the at least one turbine blade directly drives rotation of the generator rotor, without the need for intermediate gearing or other ancillary components. This "direct drive' is provided by mounting the turbine rotor for rotation about the generator stator, thus enabling the turbine body to provide the rotor of the generator. This apparatus requires significantly fewer components than conventional turbine apparatus, reducing cost and maintenance requirements.

The stator may be provided in a stator housing, and the body may be adapted for mounting on the stator housing, such that the stator housing extends into an internal aperture of the body.

According to one embodiment, the body may be adapted for mounting on the stator housing in a direction substantially along the axis of the generator. The body may be removable from the stator housing in a direction substantially along the axis of the generator. The body may be adapted for mounting substantially concentrically on the stator housing, with an annular clearance between an external surface of the stator and an internal surface of the rotor.

Bearings may be employed to maintain the clearance.

In use, the axis of the generator may be substantially vertical and the turbine may be maintained on the stator housing by the action of gravity.

The body may be mounted on the stator housing via a bearing. The bearing may comprise an annular bearing which may be formed on or adjacent the stator housing. The bearing may comprise a disc bearing, which may be mounted at one end of the body and may substantially close an end of the body.

The rotor of the generator may be formed within an annular wall of the body of the turbine rotor. Alternatively, the rotor of the generator may be formed on an inner or outer surface of the turbine rotor.

According to one embodiment, the rotor of the generator may comprise an electromagnetic winding.

According to another embodiment, the rotor of the generator may comprise a squirrel cage.

According to a still further embodiment, the rotor of the generator may comprise a permanent magnet, or a plurality of permanent magnets.

The at least one blade may be supported on the body of the turbine via a support arm that may extend substantially radially from the body of the turbine. The blade may be supported by a plurality of support arms extending from the turbine rotor. The turbine rotor may comprise two or more blades, each of which may be supported by one or more support arms and which may be substantially equally spaced around the turbine rotor.

The power generating apparatus may further comprise an emergency brake system.

The brake system may comprise a centrifugally operated device or devices which may be formed on the turbine blade or blades.

The brake system may comprise cooperating electromagnetic components which may be formed on the stator and the turbine rotor, the components being operable to levitate magnetically the turbine rotor from a supported position on the stator. Excitation of the braking components may generate a force that acts against the gravitational force holding the turbine rotor body in position on the stator housing.

The electromagnetic components of the brake system may comprise a permanent magnet and a winding. The permanent magnet may be formed on the turbine rotor and the winding may be formed on the stator.

The brake system may further comprise at least one friction pad, which may be formed on an annular end surface of the turbine rotor, and may be operable selectively to engage an annular braking surface formed on or adjacent the stator.

The apparatus may provide a water current power generating apparatus. According to another aspect of the present invention, there is provided a power generating installation comprising a supporting structure and a power generating apparatus according to the first aspect of the present invention, which is adapted for mounting on a supporting structure.

The generator of the power generating apparatus may be adapted for connection to an electrical supply network.

The electromagnetic component of the emergency brake system that is formed on the stator may be energised via the supply network to which the generator is connected.

Brief Description of the Drawings

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the following drawings, in which:-Figure 1 is a representation of a generator stator and foundation; Figure 2 is a representation of an underwater power generation installation; Figure 3 is a representation of a turbine and generator rotor; and Figure 4 is a partial representation of an emergency braking system.

Detailed Description of Embodiments

An underwater power generation installation embodying the present invention will now be described with reference to the accompanying drawings. While the installation is particularly advantageous for underwater applications, it will be appreciated that the present invention may also be embodied in other situations, for example in a wind power installation.

Referring initially to Figures 1 and 2, an underwater power generation installation 2 comprises a power generating apparatus 4 and a foundation 6. The power generating apparatus 4 comprises a generator 8 having a stator 10, and a rotor 12, and a turbine 14 having a turbine body 16 and turbine blades 18. In this example, the foundation 6 comprises at least one support pier 20 and surrounding supporting structure 22. The stator 10 defines an axis of the generator 8.

With particular reference to Figure 1, the stator 10 comprises a stator winding 24 housed within a stator housing 26. The stator housing 26 is sufficiently robust to function as a hub for rotation of the turbine 14, as described in further detail below. The stator winding 24 is preferably canned and/or potted, to protect the winding 24 from the surrounding water. In the example shown, the stator 10 is mounted substantially vertically on an end 28 of the pier of the foundation 6, such that the axis of the generator is substantially vertically oriented.

In one example, the stator 10 is mounted releasably on the support pier 20 via a clamp (not shown). Preferably, such a clamp is sufficiently robust to operate effectively over a significant number of years without requiring intervention. The clamp may however be removed if necessary using a remotely operated vehicle (ROy). This may be desirable to allow for replacement of electrical systems within the stator 10 or replacement of the entire stator component. In another example, the stator 10 is affixed to the foundation in a more permanent manner, for example by the use of a welded joint.

In a preferred example, the foundation 6 is an underwater anchorage of the type disclosed in GB2431 189 to Tidal Generation Limited. Such anchorages offer considerable advantages in cost and ease of installation, as explained in detail in GB2431 189. The generator 8 is connected via cables 30 to an electricity supply network (not shown) which may be a national, international or local network.

Referring now to Figure 3, the turbine 14 comprises a substantially tubular turbine body 16 on which are supported at least two turbine blades 18. The turbine body 16 comprises an annular cylindrical rotor body 32, dimensioned to be received about the stator housing 26. In one example, a first end 34 of the rotor body 32 is closed by an end stop 36, at least an inner surface of which may be formed by a bearing 38. The first end 34 may alternatively be open, or partially open, in order to allow water flow for cooling purposes. The bearing 38 may be of any appropriate shape, suitable for bearing axial loads. For example the bearing 38 may comprise a disk shaped bearing. The bearing 38 may additionally provide lateral support to the turbine rotor body 32, or additional bearings (not shown) may be provided to supply lateral support to the turbine rotor body 32, ensuring the rotor body 32 remains centred upon the stator housing 26.

In the example shown, support arms 40 extend substantially radially from the rotor body 32 to support the turbine blades 18. Each turbine blade 18 may be supported by at least two arms 40. In another example, the turbine blades 18 may be supported by direct connection of the blade with the rotor body 32, or may have any appropriate number of suitable support members.

Encased within the annular wall of the rotor body 32 is the generator rotor 12. The generator 8 may be of any suitable construction or type and may for example comprise an inductive design, a permanent magnet design, a brushless exciter design or any other generator design. In the example shown, the rotor 12 of the generator 8 comprises a winding 42 which is entirely housed within the body 32 of the turbine rotor 16. In another example, the generator rotor 12 may be provided by a squirrel cage construction. In a still further example the generator rotor 12 may comprise one or more permanent magnets. The winding 42, squirrel cage or other rotor components are preferably canned and/or potted to protect them from ingress of water.

At a second end of the rotor body 32, an annular end surface 44 is defined. The annular end surface 44 abuts at least one bearing 46 provided on the end 28 of the foundation pier immediately adjacent the stator 10. The bearing 46 may be a substantially continuous annular bearing or may comprise a plurality of discrete bearings arranged around the pier 20.

The turbine 14 is mounted on the stator 10 in a manner illustrated in Figure 2. The turbine rotor body 32 is received over the stator housing 26, the two components defining an annular clearing 48 therebetween. In use, the annular clearing 48 is flooded by water from the body of water within which the apparatus is installed. The turbine 14 is supported on the stator 10 via the end stop 36 and bearing 38, together with the annular bearing 46 which engages the annular end surface 44 of the rotor body 32. In operation, water flowing past the installation 2 exerts a force on the turbine blades 18, causing the turbine 14 to rotate. As the generator rotor 12 is provided within the rotor body 16, rotation of the turbine 14 directly causes rotation of the generator rotor 12, which cooperates with the stator 10 to generate electricity. The generator 8, comprising rotor 12 and stator 10, may comprise an induction, permanent magnet, brushless excited or any other suitable generator type.

The turbine 14 is mounted on the stator 10 in a direction along the axis of the generator 8.

When the stator is positioned so that the axis is substantially vertical, the turbine 14 can simply be lowered into place on the stator 10, such that the stator housing 26 extends inside the internal aperture of the rotor body 32, as described above. The turbine 14 is then maintained in position on the stator by virtue of the effect of gravity. That is, the weight of the turbine 14 keeps it in place on the stator 10. Such an arrangement allows for more straightforward deployment techniques than for existing designs of water current turbines.

If at any time it is necessary to dismantle the apparatus 4, it will be appreciated that the turbine 14 may simply be lifted off the stator 10, vertically separating the generator rotor 12 and stator 10.

Operation of the power generating apparatus 2 can be managed via a control system which, according to various embodiments, may be based on appropriate control and measured parameters. The apparatus may be designed to allow rotation at runaway speed, and thus not require a brake. However, emergency braking may be provided via centrifugally operated devices on the turbine blades 18, and/or on the support arms 40.

The apparatus 4 may further comprise a failsafe brake system, such as that illustrated in Figure 4. The brake system of Figure 4 comprises a cooperating electromagnetic coil 50 and permanent magnet 52, together with friction pads 54 and an annular brake surface 56.

The coil 50 is mounted in the first end 58 of the stator 10, and is powered via the connection through the pier 20 to the electrical supply network. The permanent magnet 52 is mounted in the end stop 36 of the turbine body 16 and is thus opposite the coil 50 when the turbine 14 is mounted in position on the stator 10. Friction pads 56, which may comprise a single annular friction pad 56, are formed on the annular end surface of the rotor body 32. With the turbine 14 at rest on the stator 10, the friction pads 54 engage an annular braking surface 56 formed on the end 28 of the pier 20 immediately adjacent the stator 10. In use, when the generator 8 is correctly connected to the electrical supply network! electrical current is fed to the coil 50, thereby energising the electromagnet and repelling the permanent magnet located in the turbine body 16. The repulsion is sufficient to levitate the turbine 14 by a small distance, thus disengaging the friction pads 54 from the braking surface 56. In this levitated condition, the turbine 14 is able to rotate freely as driven by the water current, thus driving the generator 8. Should connection to the electrical network be lost for any reason, the power flowing to the coil 50 is lost, and the turbine 14 settles back under gravity to rest on the stator 10, thereby re-engaging the friction pads 54 on the braking surface 56 and thus retarding rotation of the turbine 14. The buoyancy of the turbine 14 may be designed to optimise the levitation and braking effects of the brake system.

According to other examples of the invention, the magnetically operated braking system may be realised in alternative constructions. For example, both the electromagnetic coil 50 and the permanent magnet 52 may be located in other positions and orientations than those described above. Additionally, the permanent magnet 52 may be replaced by a ferromagnetic element. In one example, the electromagnetic coil may form part of a solenoid, which may be an inside out solenoid, and via which the rotor body is displaced under an electromagnetic force. The electromagnetic force that causes the displacement needed to disengage the braking system may be a repulsive force as described above or may be an attractive force, depending upon the particular arrangement of the electromagnetic coil and cooperating magnet or ferromagnetic element.

The present invention provides a very simple and robust installation that offers considerable advantages over known alternatives. The combined effect of these advantages is to reduce the cost of energy generation. Thanks to the simplicity of the structure, resources can be directed into making the few components as reliable and efficient as possible, thus ensuring that intervention during the operating life of the installation is not required. Significant capital cost reductions and improvement in reliability are achieved owing to the removal of so many systems that are necessary in convention horizontal axis apparatus. The power generating apparatus of the present invention requires no split rings or subsea connection using wet-mate connections. The apparatus also does not requile any dry space or seals, making it highly suitable for deep water sites in particular. The apparatus can be designed to support turbines of varying sizes to suit different sites, all using a common generator and foundation structure. The versatility of the apparatus ensures it may be equally suited to shallow sites as to deep water, or to any other conditions specific to particular geographical areas.

Claims

Claims: 1. A power generating apparatus comprising: a generator having a stator which defines an axis of the generator and a rotor arranged for rotation about the stator; and a turbine having a body and at least one blade supported on the body! wherein the body of the turbine provides the rotor of the generator, and is adapted to be mounted for rotation about the stator.
2. Apparatus as claimed in claim 1, wherein the stator is provided in a stator housing, and wherein the body is adapted for mounting on the stator housing, such that the stator housing extends into an internal aperture of the body.
3. Apparatus as claimed in claim 2, wherein the body is adapted for mounting on the stator housing in a direction substantially along the axis of the generator.
4. Apparatus as claimed in claim 3, wherein the body is removable from the stator housing in a direction substantially along the axis of the generator.
5. Apparatus as claimed in claim 3 or 4, wherein, in use, the axis of the generator is substantially vertical and the turbine is maintained on the stator housing by the action of gravity.
6. Apparatus as claimed in any one of claims 2 to 5, wherein the body is mounted on the stator housing via a bearing.
7. Apparatus as claimed in claim 6, wherein the bearing comprises an annular bearing formed on or adjacent the stator housing.
8. Apparatus as claimed in claim 6 or 7, wherein the bearing comprises a bearing, mounted at one end of the body and substantially closing an end of the body.
9. Apparatus as claimed in any one of the preceding claims, wherein the rotor of the generator is formed within an annular wall of the body of the turbine.
10-Apparatus as claimed in any one of the preceding claims, wherein the rotor of the generator comprises an electromagnetic winding.
11. Apparatus as claimed in any one of claims 1 to 9, wherein the rotor of the generator comprises a squirrel cage.
12. Apparatus as claimed in any one of claims 1 to 9, wherein the rotor of the generator comprises a permanent magnet, or a plurality of permanent magnets.
13. Apparatus as claimed in any one of the preceding claims, wherein the at least one blade is supported on the body of the turbine via a support arm that extends substantially radially from the body of the turbine.
14. Apparatus as claimed in any one of the preceding claims, further comprising an emergency brake system.
15. Apparatus as claimed in claim 14, wherein the brake system comprises cooperating electromagnetic components formed on the stator and the turbine rotor, the components being operable to levitate magnetically the turbine rotor from a supported position on the stator.
16. Apparatus as claimed in claim 15, wherein the electromagnetic components of the brake system comprise a permanent magnet and a winding.
17. Apparatus as claimed in claim 16, wherein the permanent magnet is formed on the turbine rotor and the winding is formed on the stator.
18. Apparatus as claimed in any one of claims 14 to 17, wherein the brake system further comprises at least one friction pad, formed on an annular end surface of the turbine rotor, operable selectively to engage an annular braking surface formed on or adjacent the stator.
19. Apparatus as claimed in any one of the preceding claims, wherein the apparatus provides a water current power generating apparatus.
20. A power generating installation comprising a supporting structure and a power generating apparatus as claimed in any one of the preceding claims adapted for mounting on a supporting structure.
21.An installation as claimed in claim 20, wherein the generator is adapted for connection to an electrical supply network.
22. An installation as claimed in claims 19 or 20, when dependent upon one of claims 14 to 18, wherein the electromagnetic component of the emergency brake system that is formed on the stator is energised via the supply network to which the generator is connected! or via a dedicated power supply connection.
23. An apparatus, installation or system substantially as described herein with reference to, and as shown in, the accompanying drawings.Amendments to the claims have been filed as follows Claims: 1. A power generating apparatus comprising: a generator having a stator which defines an axis of the generator and a rotor arranged for rotation about the stator; a turbine having a body and at least one blade supported on the body; and comprising an emergency brake systemAcooperating electromagnetic components formed on the stator and the turbine rotor, the components being operable to levitate magnetically the turbine rotor from a supported position on the stator, wherein the body of the turbine provides the rotor of the generator, and is adapted to be mounted for rotation about the stator.2. Apparatus as claimed in claim 1, wherein the stator is provided in a stator housing, and wherein the body is adapted for mounting on the stator housing, such that the stator housing extends into an internal aperture of the body. C')3. Apparatus as claimed in claim 2. wherein the body is adapted for mounting on the Lç) stator housing in a direction substantially along the axis of the generator.4. Apparatus as claimed in claim 3, wherein the body is removable from the stator O housing in a direction substantially along the axis of the generator.5. Apparatus as claimed in claim 3 or 4, wherein, in use, the axis of the generator is substantially vertical and the turbine is maintained on the stator housing by the action of gravity.6. Apparatus as claimed in any one of claims 2 to 5, wherein the body is mounted on the stator housing via a bearing.7. Apparatus as claimed in claim 6, wherein the bearing comprises an annular bearing formed on or adjacent the stator housing.8. Apparatus as claimed in claim 6 or 7, wherein the bearing comprises a bearing.mounted at one end of the body and substantially closing an end of the body.9. Apparatus as claimed in any one of the preceding claims, wherein the rotor of the generator is formed within an annular wall of the body of the turbine.10. Apparatus as claimed in any one of the preceding claims, wherein the rotor of the generator comprises an electromagnetic winding.11. Apparatus as claimed in any one of claims 1 to 9, wherein the rotor of the generator comprises a squirrel cage.12. Apparatus as claimed in any one of claims 1 to 9, wherein the rotor of the generator comprises a permanent magnet, or a plurality of permanent magnets.13. Apparatus as claimed in any one of the preceding claims, wherein the at least one blade is supported on the body of the turbine via a support arm that extends C') substantially radially from the body of the turbine.LI') 14. Apparatus as claimed in claim 1, wherein the electromagnetic components of the of the brake system comprise a permanent magnet and a winding. N-200 15. Apparatus as claimed in claim 14, wherein the permanent magnet is formed on the turbine rotor and the winding is formed on the stator.16. Apparatus as claimed in any one of claims 1 to 15, wherein the brake system further comprises at least one friction pad, formed on an annular end surface of the turbine rotor, operable selectively to engage an annular braking surface formed on or adjacent the stator.17. Apparatus as claimed in any one of the preceding claims, wherein the apparatus provides a water current power generating apparatus.18. A power generating installation comprising a supporting structure and a power generating apparatus as claimed in any one of the preceding claims adapted for mounting on a supporting structure.19. An installation as claimed in claim 18, wherein the generator is adapted for connection to an electrical supply network.20. An installation as claimed in claims 17 or 18, wherein the electromagnetic component of the emergency brake system that is formed on the stator is energised via the supply network to which the generator is connected, or via a dedicated power supply connection.21. An apparatus, installation or system substantially as described herein with reference to, and as shown in, the accompanying drawings. C')LUN