DK201600274A1

DK201600274A1 - Underwater Turbine

Info

Publication number: DK201600274A1
Application number: DKPA201600274A
Authority: DK
Inventors: Uffe Bærentsen
Original assignee: Uffe Bærentsen
Priority date: 2016-05-04
Filing date: 2016-05-04
Publication date: 2017-12-11
Also published as: DK179158B1; WO2017190751A1

Abstract

An underwater turbine is disclosed. The underwater turbine comprises a generator, a propeller attached to a shaft and a base member for mounting a mechanical structure, to which mechanical structure the shaft is rotatably mounted. The turbine comprises a base member defining a duct having an opening in each end allowing water to flow through the duct.

Description

Underwater Turbine Field of invention i The present invention relates to an underwater turbine. The present invention more particularly relates to an improved underwater turbine that has an increased size specific power output. The present invention furthermore relates to an underwater turbine capable of applying a generator for land based applications.

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Prior art

Underwater turbines are well known alternatives to land based windmill turbines. One of the advantages of the underwater turbines is that they i are not visible for the people living near them and that the underwater turbines do not make any noise.

There are, however, several drawbacks associated with the use of underwater turbines. First of all, most underwater turbines are not i capable of producing sufficient amounts of power to make it financially appealing to manufacture the turbines. Furthermore, the large scale prior art underwater turbines are extremely heavy and expensive to produce, transport, install and service. i Therefore, it would be desirable to provide an underwater turbine that reduces or even eliminates the above-mentioned disadvantages of the prior art.

There is a need for an underwater turbine having a large size specific i and mass specific power output.

It is an object of the present invention to provide an underwater turbine capable of delivering an increased size specific power output. It is also an object of the present invention to provide an underwater turbine capable of delivering an increased mass specific power output.

It is furthermore an object of the present invention to provide an i underwater turbine that can be produced and installed in an easy and user-friendly manner.

Summary of the invention

The object of the present invention can be achieved by an underwater i turbine as defined in claim 1. Preferred embodiments are defined in the dependent sub claims, explained in the following description and illustrated in the accompanying drawings.

The turbine according to the invention is an underwater turbine i comprising: - a generator; - a propeller attached to a shaft and - a base member for mounting a mechanical structure, to which mechanical structure the shaft is rotatably mounted, i wherein the turbine comprises a base member defining a duct having an opening in each end allowing water to flow through the duct.

Hereby, it is possible to provide an underwater turbine capable of delivering an increased size specific and mass specific power output i compared with the prior art underwater turbines.

Since the base member can be produced on land, the turbine can be produced, launched and installed in an easy and user-friendly manner. i The turbine according to the invention is an underwater turbine comprising a generator of any suitable type and size.

In one embodiment according to the invention, the turbine comprises only one generator. In another embodiment, however, the turbine comprises two generators. i The generator may be arranged in any suitable position, e.g. in a mechanical housing attached to the lower portion of the base member. It is, however, possible to attach the generator in other positions, including at the top surface of the base member. i The turbine comprises a propeller attached to a shaft. The propeller may be of any suitable type, geometry and size. The propeller may be two-bladed, three-bladed or four-bladed by way of example. The turbine may comprise more than one propeller, e.g. two propellers attached to a first shaft and to a second shaft, respectively.

The turbine comprises a base member for mounting a mechanical structure, to which mechanical structure the shaft is rotatably mounted.

The base member is configured to provide a reliable basis for i attachment of the shaft(s). Moreover, the base member is configured to be anchored to the sea floor by means of attachment structures.

The turbine comprises a base member defining a duct having an opening in each end allowing water to flow through the duct. The duct i may have any suitable size and geometry. It is preferred that the duct is configured to provide a free flow through the duct.

In a preferred embodiment according to the invention, the base member is box-shaped and comprises a plane top portion.

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In one preferred embodiment according to the invention, the duct is box-shaped defined by the box-shaped inner geometry of the base member.

It may be an advantage that the shaft extends along the longitudinal axis of the duct of the base member.

Hereby, it is possible to harvest energy from the water in the most optimal manner. Besides, this construction allows for application of two propellers provided in each end of the duct. i It may be beneficial that the shaft protrudes beyond the base member and the duct of the base member, wherein the propeller is mounted in the distal end of the shaft.

Hereby, the propellers can be located in areas that are less turbulent i than the space in the duct defined by the base member. Accordingly, a more efficient (productive) turbine can be achieved.

In one embodiment of the invention, the turbine comprises a gear box for providing a higher rotational speed than the one provided by the i shaft to which the propeller is attached.

It may be an advantage that a coupling is provided between the gear box and the shaft to which the propeller is attached. i It may be advantageous that the turbine comprises a first propeller attached in the distal end of a first shaft, wherein the turbine furthermore comprises a second propeller attached in the distal end of a second shaft. i Hereby, the turbine is capable of harvesting energy from water flowing in two alternating directions (e.g. applying the directions of tide).

It may be advantageous that the first propeller attached in the distal end of the first shaft is optimized for energy harvesting water having a first flow direction, and that the second propeller attached in the distal end of the shaft is optimised for energy harvesting water having a i second (preferably opposite) flow direction.

It may be an advantage that the first shaft and the second shaft extend through opposite portions of the duct comprising the space defined by the base member.

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It may be advantageous that a first shaft protrudes beyond the front end of the base member and the duct of the base member, wherein the propeller is mounted in the distal end of the first shaft, and that a second shaft protrudes beyond the (opposite) back end of the base i member and the duct of the base member, wherein the second propeller is mounted in the distal end of the second shaft.

It may be beneficial that the turbine comprises a base member having a bottom portion and a top portion and side structures extending between i the bottom portion and the top portion and hereby forming the duct.

This construction is easy to produce, assemble and install. It is possible to use modules to produce the base member, so that the base member can be produced by combining the modules. The modules may comprise i grid structures.

It may be an advantage that the shaft extends basically parallel to the longitudinal axis of the duct and/or of the base member. i Hereby, it is possible to optimise the power productivity of the turbine.

It may be an advantage that the shaft is provided in the lower portion of the base member, preferably attached to the bottom portion of the base member, either on the top side or the back side of the bottom portion. i Hereby, it is possible to avoid turbulence present near the top of the base member. Accordingly, the power productivity of the turbine can be increased.

It may be an advantage that the ratio between the area As swept by the i propeller and the cross-sectional area Ac of the duct is as large as possible so that As/Ac can be maximised. Hereby, the power productivity of the turbine can be maximised.

It may be an advantage that the base member comprises buoyancy i members having buoyancy structures.

Hereby, buoyancy can be achieved in order to position the turbine in a preferred level/height (e.g. distance from the sea floor) in the water. i It may be beneficial that the buoyancy members extend between the top portion and the bottom portion. Hereby, a stable and reliable construction can be achieved. Moreover, access to the buoyancy members can easily? be provided e.g. through a lid member provided in the top of the buoyancy members.

It may be an advantage that the upper portion of the base member is configured to extend above the water level when the turbine is installed. i Hereby, there is access to the base member. This is an advantage during installation and service, where the turbine can be accessed from the top and where the turbine can be lifted by attaching attachment members provided at its top to lifting means (e.g. a lifting crane of a service ship). Moreover, it is possible to provide visual signal members (e.g. lights) and radar reflectors on the portion of the base member that is above the water level.

It may be advantageous that the buoyancy members comprise a number of buoyancy structures each formed as an elongated structure having a uniform cross-section. i Hereby, standard components (e.g. box-shaped steel components) may be applied to construct the buoyancy members. Moreover, it is easier to produce and to join the buoyancy members with the adjacent structures and a working deck is provided. i It may be an advantage that the buoyancy structures have a rectangular cross-section (e.g. a square cross-section). This geometric shape is an advantage when the buoyancy structures have to be welded together to form a one-piece body. i It may be beneficial that the the buoyancy member(s) comprise a number of buoyancy structures provided with a through-going tube member, wherein the tube members are configured to provide access for attachment structures such as chains or wires extending through the tube members for anchoring the base member of the turbine.

Hereby, the turbine can be anchored to the sea floor and there can be access to the chains or wires from the top of the turbine. The tube members are preferably configured to provide easy access for chains, wires or alternative attachment structures for the purpose of anchoring i the base member of the turbine to the sea.

It may be an advantage that the buoyancy member comprises a number of buoyancy structures joint (e.g. being welded together) to form a one-piece body.

It may be advantageous that the first tube member and a second tube i member extend through the two second outermost buoyancy structures.

It may be beneficial that the generator is arranged on the top portion of the base member.

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It may be advantageous that a connection shaft connects the generator and the shaft.

Description of the Drawings i The invention will become more fully understood from the detailed description given herein below. The accompanying drawings are given by way of illustration only, and thus, they are not limitative of the present invention. In the accompanying drawings:

Fig. 1A shows a schematic perspective front view of a base i member according to one embodiment of the invention;

Fig. IB shows a schematic perspective front view of a turbine according to one embodiment of the invention applying the base member shown in Fig. 1A;

Fig. 2A shows a schematic top view of a turbine according to one i embodiment of the invention;

Fig. 2B shows a schematic front view of the turbine shown in Fig. 2A;

Fig. 3 shows a schematic front view of a turbine according to one embodiment of the invention installed in the sea; i Fig. 4A shows a schematic perspective front view of a turbine according to one embodiment of the invention;

Fig. 4B shows a schematic perspective front view of a turbine according to another embodiment of the invention;

Fig. 5A shows a two-bladed propeller according to one embodiment of the invention;

Fig. 5B shows another two-bladed propeller according to one embodiment of the invention;

Fig. 5C shows a three-bladed propeller according to a first embodiment of the invention;

Fig. 5D shows another three-bladed propeller according to another embodiment of the invention;

Fig. 5E shows a four-bladed propeller according to a first embodiment of the invention;

Fig. 5F shows another four-bladed propeller according to another embodiment of the invention;

Fig. 6A shows a schematic top view of a buoyancy member according to one embodiment of the invention;

Fig. 6B shows a schematic top view of a buoyancy member according to another embodiment of the invention;

Fig. 6C shows a schematic cross-sectional side view of a buoyancy structure of a buoyancy member according to an embodiment of the invention;

Fig. 6D shows a schematic perspective side view of a grid structure according to an embodiment of the invention;

Fig. 6E shows a schematic perspective side view of a grid structure according to another embodiment of the invention;

Fig. 7A shows a side view of a turbine according to one embodiment of the invention;

Fig. 7B shows a side view of a turbine according to another embodiment of the invention;

Fig. 8A shows a schematic perspective side view of a turbine according to one embodiment of the invention;

Fig. 8B shows a schematic side view of the turbine shown in Fig. 8A;

Fig. 9A shows a schematic front view of the turbine according to one embodiment of the invention;

Fig. 9B shows a schematic side view of a gear box coupled to a propeller according to one embodiment of the invention and

Fig. 10 shows a schematic front view of a turbine according to another embodiment of the invention.

Detailed description of the invention

Referring now in detail to the drawings for the purpose of illustrating preferred embodiments of the present invention, an underwater turbine 2 of the present invention is illustrated in Fig. 1.

Fig. 1A illustrates a schematic perspective front view of a base member 4 according to one embodiment of the invention. The base member 4 comprises a bottom portion 6 having a plurality of first rod members 14 extending parallel to each other within a first plane. The bottom portion 6 furthermore comprises a plurality of second rod members 16 extending parallel to each other within a second plane extending parallel to the first plane. The first rod members 14 and the second rod members 16 are connected by a plurality of cross members 18.

The base member 4 comprises a top portion 8 having a plurality of first rod members 14 extending parallel to each other within a first plane. The top portion 8 furthermore comprises a plurality of second rod members 16 extending parallel to each other within a second plane extending parallel to the first plane. The first rod members 14 and the second rod members 16 are connected by a plurality of cross members 18.

The base member 4 is intended to be installed in the water (e.g. in a sea, a lake or a river). When installed in the water, the bottom portion 6 and the top portion 8 are intended to extend horizontally.

The base member 4 furthermore comprises a first buoyancy member 10 and a second buoyancy member 12 each extending perpendicular to the bottom portion 6 and the top portion 8 of the base member 4.

The first buoyancy member 10 comprises a plurality of buoyancy structures 10', 10" extending parallel to each other. The buoyancy structures 10', 10" are box-shaped and may be manufactured in steel or fibre-reinforced plastic. Accordingly, the adjacent buoyancy structures 10', 10" can be welded to each other or fixed to each other by alternative mechanical means. In one preferred embodiment according to the invention, the first buoyancy member 10 comprises a plurality of buoyancy structures 10', 10" welded together to form a one-piece body.

Like the first buoyancy member 10, the second buoyancy member 12 comprises a plurality of buoyancy structures 12', 12" extending parallel to each other. Each of the buoyancy structures 12', 12" has an elongated box-shaped geometry. The buoyancy structures 12', 12" bay be produced in steel or fibre-reinforced plastic like the buoyancy structures 10', 10" of the first buoyancy member 10.

The buoyancy structures 10', 10", 12', 12" of the first buoyancy member 10 and the second buoyancy member 12 may be filled with a filler media such as expanded polystyrene or another low density material. The buoyancy structures 10', 10", 12', 12" may be provided as air-filled airtight containers.

The bottom portion 6, the top portion 8 and the buoyancy members 10, 12 of the base member 4 forms an opening O. When the base member 4 is installed in the water, water will flow through the opening O.

Fig. IB illustrates a schematic perspective front view of a turbine 2 according to one embodiment of the invention applying a base member 4 as the one shown in Fig. 1A. The turbine 2 comprises a first propeller 20 attached to a first shaft 22 rotatably mounted to a mechanical structure 24. The turbine 2 also comprises a second propeller 20' attached to a second shaft 22' rotatably mounted to a mechanical structure 24'.

Each of the mechanical structures 24, 24 comprise a gear box and a generator. The mechanical structures 24, 24 are arranged on the top side of the bottom portion 6 of the base member 4. Hereby, electricity can be generated to the land through electric cables (not shown) in order to supply the power to power consumers.

In Fig. 1A and Fig. 1 B, both the first buoyancy member 10 and the second buoyancy member 12 comprises eight buoyancy structures 10', 10", 12', 12" that are welded together to form a one-piece body. It is, however, possible to make buoyancy members 10, 12 that comprise fewer buoyancy structures 10', 10", 12', 12" e.g. 1-4 or 4-8 buoyancy structures 10', 10", 12', 12".

Fig. 2A illustrates a schematic top view of an underwater turbine 2 according to one embodiment of the invention, whereas Fig. 2B illustrates a schematic front view of the turbine shown in Fig. 2A.

The turbine 2 comprises a base member 4 provided with a bottom portion 6 and a top portion 8 mechanically connected by a first buoyancy member 10 having a plurality of box-shaped buoyancy structures 10', 10" attached to each other and a second buoyancy member 12 having a plurality of box-shaped buoyancy structures 12', 12" attached to each and extending along their longitudinal axes Y, Y\

The turbine 2 comprises a first propeller 20 attached to a shaft 22 rotatably mounted to a gear-box, and a generator provided in a first box-shaped mechanical structure 24. Likewise, the turbine 2 comprises a second propeller 20 attached to a shaft 22 rotatably mounted to a gear-box and a generator provided in a second box-shaped mechanical structure 24'. The shafts 22, 22' extend along the longitudinal axis X of the base member 4. The longitudinal axes Y, Y' extend parallel to the longitudinal axis X of the base member.

The first propeller 20 and the second propeller 20' are provided outside the base member 4. Accordingly, the distal portion of the first shaft 22, and the second shaft 22' protrude from and beyond the base member 4 in a manner in which they extend through the opening O. Hereby, the propellers 20, 20' are located in areas that are less turbulent than the space S in the duct 52 defined by the base member 4.

The first shaft 22 and the second shaft 22' extend through opposite portions of the duct 52 comprising the space S defined by the base member 4. The first propeller 20 is configured to start rotating when a flow is present. In Fig. 2A, a first flow having a first direction Di towards the first propeller 20 is illustrated. Likewise, a second flow having a first direction D2 towards the second propeller 20' is illustrated in the opposite end of the base member 4.

The mechanical structures 24, 24 comprise a gear box and a generator and are arranged on the top side of the bottom portion 6 of the base member 4. Electric power generated by one or more generators can be supplied to power consumers on the land by means of electric cables (not shown).

It can be seen that the ratio between the area As (indicated by a dotes circle) swept by the propeller 20 and the cross-sectional area Ac (indicated by a dotes rectangle) of the duct 52 is large. It is preferred to maximise As/Ac in order to maximise the power productivity of the turbine 2.

Fig. 3 illustrates a schematic front view of an underwater turbine 2 according to one embodiment of the invention installed in the sea. The turbine 2 comprises a base member 4 having a bottom portion 6 and a top portion 8 mechanically connected to each other by means of a first buoyancy member 10 and a second buoyancy member 12.

The turbine 2 has an opening O to a space S defined by the base member 4. The turbine 2 comprises a first propeller 20 attached to a shaft 22 rotatably mounted to a gear-box and a generator provided in a first box-shaped mechanical structure 24.

The base member 4 comprises a bottom portion 6 having a plurality of first rod members 14 extending parallel to each other within a first plane and comprises a plurality of second rod members 16 extending parallel to each other within a second plane extending parallel to the first plane. The first rod members 14 and the second rod members 16 are connected by a plurality of cross members 18.

The base member 4 is installed in the water 28 of a sea; however, the base member 4 may alternatively be installed in a lake or a river by way of example. As it can be seen in Fig. 3, the bottom portion 6 and the top portion 8 extend horizontally, whereas the first buoyancy member 10 and the second buoyancy member 12 extend vertically.

The uppermost portion of the base member 4 is arranged above water level 26. Accordingly, the top of the base member 4 is provided in a height H above water level 26.

The base member 4 is anchored to the sea floor 34 by means of attachment members formed as chains 30, 32 having proximal ends 30', 32' and distal ends 30", 32".

The proximal end of the first chain 30 is attached to a first underwater anchorage 36, whereas the proximal end of the second chain 32 is attached to a second underwater anchorage 36'. The underwater anchorages 36, 36' are heavy structures that are kept in place on the sea floor by their weight. In practice, it may be an advantage to apply more than two chains 30, 32 (e.g. four).

The chains 30, 32 extend through pipe structures extending through the first buoyancy member 10 and the second buoyancy member 12, respectively. These pipe structures are filled with water. The distal portion of the chains 30", 32" are prevented from falling down through the pipe structures by means of a first locking member 38 and a second locking member 38', respectively.

Fig. 4A illustrates a schematic perspective front view of a turbine 2 according to one embodiment of the invention. The turbine 2 basically corresponds to the one illustrated in Fig. 3. The turbine 2 comprises a base member 4 having a bottom portion 6 and a top portion 8 mechanically connected to each other by means of a first buoyancy member 10 having a longitudinal axis Y and a second buoyancy member 12 having a longitudinal axis Y' extending parallel to the longitudinal axis Y.

The turbine 2 has an opening in each end and space defined by the base member 4. The turbine 2 comprises a first propeller 20 attached to a shaft 22 rotatably mounted to a first box-shaped mechanical structure 24. The turbine 2, moreover, comprises a second propeller 20' attached to a shaft 22' rotatably mounted to a second box-shaped mechanical structure 24'.

The mechanical structures 24, 24' are connected to a generator 40 by means of a first connection member 42 and a second connection member 42'. The connection members 42, 42' may provide a hydraulic connection between the mechanical structures 24, 24' and a generator 40. The generator 40 is provided (e.g. attached to) the top side of the top portion 8 of the base member 4.

The base member 4 is adapted to be installed in the water 28 of a sea, a lake or a river in a manner in which the bottom portion 6 and the top portion 8 extend horizontally, whereas the first buoyancy member 10 and the second buoyancy member 12 extend vertically.

The uppermost portion of the base member 4 is configured to be arranged above water level so that the top of the base member 4 is provided in a non-zero height above water level. Hereby, the generator 40 can be kept out of water. Furthermore, the electrical connection can be established between one or more electric cables and the generator. Accordingly, the electric cables can be connected and disconnected in an easy and user-friendly manner without using a diver.

By bring the uppermost portion of the base member 4 above water level, the propeller is arranged in a depth in which the water flow is larger. Accordingly, a higher power output can be achieved.

The base member 4 is anchored to the sea floor 34 by means of attachment members formed as chains 30, 32 having proximal ends 30', 32', 32"" and distal ends 30", 30'", 32", 32'".

The proximal end of the first chain 30 is attached to a first underwater anchorage 36. The proximal end of the second chain 32 is attached to a second underwater anchorage 36'. The proximal end of the third chain 32 is attached to a third underwater anchorage 36", whereas the proximal end of a fourth chain is not visible in Fig. 4A.

The underwater anchorages 36, 36', 36" are configured to be kept in place on the sea floor by their heavy weight. Additional chains may be used to restrict the turbine from drifting or floating away.

The chains 30, 32 extend through water-filled pipe structures extending through the first buoyancy member 10 and the second buoyancy member 12. The distal portion of the chains 30", 32", 32'" are prevented from falling down through the pipe structures by means of a locking members 38, 38'.

During installation and service, the turbine 2 can be lifted up by using the chains 30, 32.

Fig. 4B illustrates a schematic perspective front view of a turbine 2 according to another embodiment of the invention.

The turbine 2 comprises a base member 4 having a bottom portion 6 and a top portion 8 mechanically connected to each other by means of a first wall portion 50 having a first longitudinal axis Y and a second wall portion 50' having a second longitudinal axis Y'. The first wall portion 50 and the second first wall portions 50' are provided in opposite ends of the base member 4. The first longitudinal axis Y and the second longitudinal axis Y' extend parallel to each other and to the longitudinal axis X of the base member 4.

The turbine 2 has an opening in each end of a through-going boxshaped duct defined by the bottom portion 6, the top portion 8 and the first wall portion 50 and the second wall portion 50'.

The turbine 2 is provided with a first propeller 20 attached to a shaft 22 rotatably mounted to a first box-shaped mechanical structure 24. The turbine 2, furthermore, comprises a second propeller 20' attached to a shaft 22' rotatably mounted to a second box-shaped mechanical structure 24'.

The mechanical structures 24, 24' each comprise a generator. However, in one embodiment it may be possible to connect both shafts 22, 22' to the same generator.

The base member 4 is configured for installation in the water 28 of a sea, a lake or a river in such a manner that the bottom portion 6 and the top portion 8 extend horizontally, whereas the first wall portion 50 and the second wall portion 50' extend vertically.

The uppermost portion of the base member 4 is adapted for being arranged above water level so that the top of the base member 4 is provided in a non-zero height above water level.

Fig. 5A illustrates a schematic front view of a two-bladed propeller 20 according to one embodiment of the invention, wherein the first blade 44 corresponds to the second blade 44'.

Fig. 5B illustrates a schematic front view of a two-bladed propeller 20 according to another embodiment of the invention, wherein the first blade 44 also corresponds to the second blade 44'.

Fig. 5C illustrates a schematic perspective front view of a three-bladed propeller 20 according to one embodiment of the invention. The propeller 20 comprises a first blade 44, a second blade 44' and a third blade 44" of equal geometry.

Fig. 5D illustrates a schematic perspective front view of a three-bladed propeller 20 according to another embodiment of the invention. The propeller 20 comprises a first blade 44, a second blade 44' and a third blade 44" of equal geometry.

Fig. 5D illustrates a schematic perspective front view of a four-bladed propeller 20 according to an embodiment of the invention. The propeller 20 comprises a first blade 44, a second blade 44', a third blade 44" and a fourth blade 44'" of equal geometry.

Fig. 5E illustrates another schematic perspective front view (seen from the other side) of the four-bladed propeller 20 shown in Fig. 5D.

The turbine according to the invention may apply any of these propellers 20. Furthermore, it is possible to apply two propellers 20 of different types.

Fig. 6A illustrates a schematic top view of a buoyancy member 10 according to one embodiment of the invention. The buoyancy member 10 comprises eight buoyancy structures 10', 10" joint (e.g. being welded together) to form a one-piece body. The buoyancy structures 10', 10" are box-shaped and may be manufactured in steel or fibre-reinforced plastic.

It can be seen that a first tube member 46 and a second tube member 46' extend through the two outermost buoyancy structures 10', 10". The tube members 46, 46' are configured to provide access for chains, wires or alternative attachment structures for anchoring the base member 4 of the turbine 2 to the sea floor (see Fig. 3 and Fig. 4A).

Fig. 6B illustrates a schematic top view of a buoyancy member 12 according to another embodiment of the invention. The buoyancy member 12 comprises eight buoyancy structures 12', 12" joint (e.g. being welded together) to form a one-piece body. Like the buoyancy structures 10', 10" shown in Fig. 6A, the buoyancy structures 12', 12" are box-shaped and can be produced in steel or fibre-reinforced plastic.

The first tube member 46 and a second tube member 46' extend through the two second outermost buoyancy structures 12', 12". The tube members 46, 46' are configured to provide access for chains, wires or alternative attachment structures for the purpose of anchoring the base member 4 of the turbine 2 to the sea floor like illustrated in Fig. 3 and Fig. 4A.

Fig. 6C illustrates a schematic cross-sectional side view of a buoyancy structure 10' of a buoyancy member according to an embodiment of the invention. The buoyancy structure 10' is provided with a through-going tube member 46 extending along the longitudinal axis of the buoyancy structure 10'. A chain 30 extends through the tube member 46. The chain 30 has a proximal end 30" that is prevented from falling through the tube member 46 by means of a locking member 38 attached to one of the chain members of the proximal end 30" of the chain 30.

Fig. 6D illustrates a schematic perspective side view of a grid structure 48 according to an embodiment of the invention. The grid structure 48 comprises a plurality of first rod members 14 extending parallel to the longitudinal axis of the grid structure 48. The grid structure 48 moreover comprises a plurality of second rod members 16 extending perpendicular to the longitudinal axis of the grid structure 48. The grid structure 48 furthermore comprises a plurality of cross members 18 extending perpendicular to the longitudinal axis of the grid structure 48 and connecting the rod members 14, 16 of the grid structure 48.

Fig. 6E illustrates a schematic perspective side view of a grid structure 48' according to another embodiment of the invention. The grid structure 48' comprises a plurality of first rod members 14, second rod members 14', and third rod members 16 extending parallel to the longitudinal axis of the grid structure 48. The grid structure 48 moreover comprises a plurality of cross members 18 connecting the rod members 14, 14', 16 of the grid structure 48.

The grid structures 48, 48' shown in Fig. 6D and in Fig. 6E may be used in the base member of the turbine according to the invention. Any other suitable type of grid structures may be used.

Fig. 7A illustrates a side view of a turbine 2 according to one embodiment of the invention. The turbine 2 comprises a buoyancy member 12 having a first tapered portion 64 and a second tapered portion 64'. Accordingly, the upper portion of the base member is shorter than the upper portions of the turbines illustrated in Fig. 1-4. The turbine 2 comprises a first blade 20 attached to a first shaft 22 and a second blade 20' attached to a second shaft 22'.

Fig. 7B illustrates a side view of a turbine 2 according to another embodiment of the invention. The turbine 2 comprises a buoyancy member 12 provided with a first tapered portion 64 and a second tapered portion 64'. The lower portion of the base member is shorter than the upper portions of the turbines illustrated in Fig. 1-4. The turbine 2 comprises a first blade 20 attached to a first shaft 22 and a second blade 20' attached to a second shaft 22'.

Fig. 8A illustrates a schematic perspective side view of a turbine 2 according to one embodiment of the invention. The turbine 2 comprises a box-shaped base member 4 comprising a bottom portion 6, a top portion 8, a first buoyancy member 10 and a second buoyancy member 12 extending between the bottom portion 6 and the top portion 8. A first propeller 20 is attached to a first shaft that is rotatably attached to a first mechanical structure 24 provided on the upper surface of the bottom portion 6 of the base member 4. The turbine 2 also comprises a second propeller attached to a second shaft that is rotatably attached to a second mechanical structure 24' provided next to the first mechanical structure 24. A first pipe 42 with a connection shaft extending through it is provided between the first mechanical structure 24 and a generator 40 provided on the top side of the top portion 8 of the turbine 2. Likewise, a second pipe 42' with a connection shaft extending through it is provided between the second mechanical structure 24' and the generator 40. Hereby, the generator 40 can be installed above the water level (provided that the top portion of the base member 4 is arranged above water level- as shown in Fig. 3). Accordingly, a cheaper and less demanding generator (compared to prior art underwater turbine generators) can be applied. Moreover, the electric connection between the generator and the electric cable can be provided above the water level.

It can be seen that a first cable 52 is electrically connected to the generator 40 by means of a first plug 54 and that a second cable 52' is electrically connected to the generator 40 by means of a second plug 54'.

The turbine 2 comprises a first hatch 56 provided on the top of the first buoyancy member 10 and a second hatch 56' provided on the top of the second buoyancy member 12. There is access into the buoyancy structure of the buoyancy structure 10, 12 through the first hatch 56 and the second hatch 56'. A first transport pipe 60 extends between the hollow buoyancy structure 10' of the first buoyancy member 10 and the first mechanical structure 24. Hereby, there is direct access to the mechanical structure 24 through the hollow buoyancy structure 10' of the buoyancy member 10 via the first transport pipe 60. Accordingly, it is possible to service the mechanical structure 24 by opening the hatch 56.

Likewise, a second transport pipe 60' extends between the hollow buoyancy structure 12' of the second buoyancy member 12 and the mechanical structure 24'. Hereby, there is direct access to the mechanical structure 24' via the hollow buoyancy structure 12' of the buoyancy member 12 through the second transport pipe 60'. Accordingly, it is possible to service the mechanical structure 24' by opening the hatch 56'.

In the top surface of the first buoyancy member 10 and the second buoyancy member 12, openings 58, 58' are provided. There is access through the first buoyancy member 10 and the second buoyancy member 12 by means of the openings 58, 58'. Accordingly, chains or wires extending through the openings 58, 58' can be used to anchor the turbine 2.

Fig. 8B illustrates a schematic cross-sectional side view of the turbine 2 shown in Fig. 8A. The turbine 2 comprises a base member comprising a bottom portion 6, a top portion 8, a first buoyancy member having a buoyancy structure 10' and a second buoyancy member having a buoyancy structure 12' extending between the bottom portion 6 and the top portion 8. A first hatch 56 and a second hatch 56' is rotatably mounted to the top of the first buoyancy structure 10' and the second buoyancy structure 12', respectively. There is access to the mechanical structure 24 via a ladder 62 provided in the first buoyancy structure 10' and further through the first transport pipe 60. Furthermore, there is access to the other side of the mechanical structure 24 via a ladder 62 provided in the second buoyancy structure 12' and further via the second transport pipe 60'. A first propeller 20 is attached to a first shaft that is rotatably attached to a first mechanical structure 24 provided on the upper surface of the bottom portion 6 of the base member. A first pipe 42 with a connection shaft extending through it is provided between the first mechanical structure 24 and a generator 40 provided on the top side of the top portion 8 of the turbine 2. Hereby, the generator 40 can be installed above the water level when the top portion of the base member 4 is arranged above water level (as shown in Fig. 3).

It can be seen that a first cable 52 is electrically connected to the generator 40 by means of a first plug 54.

Fig. 9A illustrates a schematic front view a turbine 2 according to one embodiment of the invention. The turbine 2 comprises a base member 4 having a top portion 8 and a bottom portion 6. The turbine 2 comprises moreover comprises a first buoyancy member 10 and a second buoyancy member 12 sandwiched between the top portion 8 and a bottom portion 6. A generator 4 (or two generators) 40 is attached to the top portion of the top portion 8. A connection member 42 extends between the mechanical structure 24 to which the shaft at which the propeller 20 is attached to is rotatably mounted. The connection member 42 mechanically supports the base member 4. A shaft (not shown) extends through the connection member 42 for mechanically connecting the shaft with a generator 40. A transport pipe 60 extends between the hollow buoyancy member 10 and the mechanical structure 24. Hereby, there is direct access to the mechanical structure 24 through the hollow buoyancy member 10 via the first transport pipe 60. Accordingly, it is possible to service the mechanical structure 24 though the transport pipe 60.

Similarly, a transport pipe 60' extends between the hollow buoyancy member 12 and the mechanical structure 24. Hereby, there is direct access to the mechanical structure 24 through the hollow buoyancy member 12 via the second transport pipe 60'. Accordingly, it is possible to service the mechanical structure 24 transport pipe 60'.

Fig. 9B illustrates a schematic side view of a gear box 68 coupled to a propeller 20 according to one embodiment of the invention. The gear box 68 is connected to a propeller 20 via a coupling 66. A shaft 22" mechanically connects the gear box 68 and the coupling 66, whereas another shaft 22 connects the propeller 20 and the coupling 66.

Fig. 10 illustrates a schematic front view a turbine 2 according to one embodiment of the invention. The turbine 2 comprises a base member 4 having a top portion 8 and a bottom portion 6. The turbine 2 comprises moreover comprises a first buoyancy member 10 and a second buoyancy member 12 sandwiched between the top portion 8 and a bottom portion 6. A generator 40 is attached to the top portion of the top portion 8. A propeller 20 is attached to a shaft rotatably attached to a mechanical structure 24 attached to the lower side of the bottom portion 6 of the base member 4. A connection member 42 extends between the mechanical structure 24 and the generator 40. An electric cable 52 is detachable attached to the housing of the generator 40 by means of a plug 54. A shaft extends through the connection member 42 and hereby mechanically connects generator 40 and the mechanical structure 24.

The height h of the base member 4 is low in this embodiment, since the first buoyancy member 10 and the second buoyancy member 12 are short. Hereby, a light and more compact turbine 2 can be achieved.

List of reference numerals 2 Turbine 4 Base member 6 Bottom portion 8 Top portion 10, 12 Buoyancy member 10', 10", 12', 12" Buoyancy structure 14, 14', 16 Rod member 18 Cross member 20, 20' Propeller 22, 22', 22" Shaft 24, 24' Mechanical structure 26 Water level 28 Water 30, 32 Attachment member 30', 32' Proximal end 30", 30'", 32", 32'" Distal end 34 Sea floor 36, 36' Underwater anchorage 38, 38' Locking member 40 Generator 42, 42' Connection member 44, 44', 44", 44'" Blade 46, 46' Tube member 48, 48' Grid structure 50, 50' Wall portion 52 Duct 54, 54' Pipe with connection shaft 56, 56' Hatch 58, 58' Opening in pipe member 60, 60' Transport pipe 62, 62' Ladder 64, 64' Tapered portion 66 Coupling 68 Gear box O Opening S Space H, h Height X, Y, Y' Longitudinal axis

As, Ac Area

Claims

1. An underwater turbine (2) comprising: - a generator (40, 24, 24'); - a propeller (20, 20') attached to a shaft (22, 22') and - a base member (4) for mounting a mechanical structure (24, 24'), to which mechanical structure (24, 24') the shaft (22, 22') is rotatably mounted, characterised in that the turbine (2) comprises base member (4) defining a duct (52) having an opening (0) in each end allowing water to flow through the duct (52),

2. An underwater turbine (2) according to claim 1, characterised in that the shaft (22, 22') extends along the longitudinal axis (X) of the duct (52) of the base member (4),

3. An underwater turbine (2) according to claim 1 or claim 2, characterised in that the shaft (22, 22') protrudes beyond the base member (4) and the duct (52) of the base member (4), wherein the propeller (20, 20') is mounted in the distal end of the shaft (22, 22').

4. An underwater turbine (2) according to one of the preceding claims, characterised in that the turbine (2) comprises a first propeller (20) attached in the distal end of a first shaft (22), wherein the turbine (2) furthermore comprises a second propeller (20') attached in the distal end of a second shaft (22').

5. An underwater turbine (2) according to one of the preceding claims, characterised in that the turbine (2) comprises a base member having a bottom portion (6) and a top portion (8) and side structures (10, 12) extending between the bottom portion (6) and a top portion (8) and hereby forming the duct (52).

6. An underwater turbine (2) according to one of the preceding ciaims, characterised In that the shaft is provided in the lower portion of the base member (4), preferably attached to the bottom portion (6) of the base member (4) either on the top side or the back side of the bottom portion (6).

7. An underwater turbine (2) according to one of the preceding claims, characterised in that the base member (4) comprises buoyancy members (10, 12) having buoyancy structures (10', 10", 12', 12").

8. An underwater turbine (2) according to one of the preceding claims 5-7, characterised in that the buoyancy members (10, 12) extend between the top portion (8) and the bottom portion (6).

9. An underwater turbine (2) according to one of the preceding claims, characterised in that the upper portion of the base member (4) is configured to extend above the water level (26) when the turbine (2) is installed.

10. An underwater turbine (2) according to one of the preceding claims, characterised in that the buoyancy members (10, 12) comprise a number of buoyancy structures (10', 10", 12', 12") each formed as an elongated structure having uniform cross-section.

11. An underwater turbine (2) according to one of the preceding claims 8-10, characterised in that the buoyancy members (10, 12) comprise a number of buoyancy structures (10', 10", 12', 12") provided with a through-going tube member (46, 46'), wherein the tube members (46, 46') are configured to provide access for attachment structures (30, 32) such as chains or wires extending through the tube members (46, 46') for anchoring the base member (4) of the turbine (2).

12. An underwater turbine (2) according to one of the preceding claims 5-11, characterised In that the generator (40) is arranged on the top portion (8) of the base member 4.

13. An underwater turbine (2) according to claim 12, characterised in that a connection shaft connects the generator (40) and the shaft (22, 22'),