RENEWABLE ENERGY CONVERSION APPARATUS

Abstract

The apparatus described is a buoyant energy converting apparatus for converting energy obtained from renewable ocean energy sources to useful energy, comprising: a wind energy converter; a buoyant platform arranged to support the wind energy converter in a body of water having a surface and a bed; and a connection member, the connection member being positioned between the wind energy converter and the buoyant platform, the buoyant platform comprises an in-use configuration in which the buoyant platform is submerged in the body of water. In the in-use configuration the connection member protrudes through the surface of the body of water such that the wind energy converter is located substantially above the body of water. The apparatus further comprises a wave energy converter. The apparatus aims to provide a device having increased stability in stormy conditions, a more consistent supply of power and improved cost and ease of maintenance.

Claims

1. A buoyant energy converting apparatus for converting energy obtained from renewable energy sources to useful energy, the apparatus comprising: a wind energy converter; a buoyant platform arranged to support the wind energy converter in a body of water, the body of water having a surface and a bed; and a connection member, the connection member being positioned between the wind energy converter and the buoyant platform, wherein the buoyant platform comprises an in-use configuration in which the buoyant platform is submerged in the body of water, and wherein in the in-use configuration the connection member protrudes through the surface of the body of water such that the wind energy converter is located substantially above the body of water; wherein the apparatus further comprises a wave energy converter in communication with the buoyant platform, the wave energy converter being arranged to convert wave energy from the body of water to the useful energy.

2. A buoyant energy converting apparatus of claim 1, wherein the apparatus further comprises a service configuration, wherein in the service configuration the buoyant platform is substantially on the surface of the body of water with all serviceable elements of the apparatus above the water, and the apparatus is connected to a mooring means.

3. A buoyant energy converting apparatus of claim 2, wherein in the service configuration, the wind energy converter is arranged to convert wind energy to the useful energy.

4. A buoyant energy converting apparatus of claim 1, wherein the apparatus further comprises a transport configuration, wherein in the transport configuration the buoyant platform is substantially on the surface of the body of water, wherein the apparatus is not coupled to a mooring means, and further wherein the apparatus is able to stably free float on the surface of the body of water.

5. A buoyant energy converting apparatus of claim 1, wherein the wave energy converter comprises a wave energy capturing member coupled to a wave energy converting member, wherein the apparatus further comprises a storm configuration, and wherein in the storm configuration, the wave energy capturing member is positioned at, within, or proximate the buoyant platform.

6. A buoyant energy converting apparatus of claim 1, wherein the wave energy converter comprises a working depth at which the wave energy converter provides an optimal energy conversion; and further wherein buoyant platform in the in-use configuration comprises a buoyant platform depth; and wherein the buoyant platform depth is substantially the same as the working depth.

7. A buoyant energy converting apparatus of claim 1, wherein the wind energy converter and wave energy converter are arranged to convert each of wind energy and wave energy to a respective interim form of energy, wherein the respective interim forms of energy are transferred to a common secondary energy conversion apparatus; wherein the secondary energy conversion apparatus is arranged to combine the interim forms of energy, and export the combined interim forms of energy as a single form of desired output energy.

8. A buoyant energy converting apparatus of claim 7, wherein the apparatus is arranged to convert either the wind energy or the wave energy to mechanical energy using one or more pulleys and gears; is further arranged to transfer the mechanical energy to the common secondary energy conversion apparatus; and wherein the secondary energy conversion apparatus is arranged to convert the mechanical energy to a different form of energy prior to exporting said different form of energy from the apparatus.

9. A buoyant energy converting apparatus of claim 7, wherein the apparatus is arranged to convert either the wind energy or wave energy to hydraulic energy using one or more hydraulic actuators; is further arranged to transfer the hydraulic energy to the common secondary energy conversion apparatus; and wherein the secondary energy conversion apparatus is arranged to convert the mechanical energy to a different form of energy prior to exporting said different form of energy from the apparatus.

10. A buoyant energy converting apparatus of claim 1, wherein the apparatus is arranged to convert either the wind energy or wave energy to a first form of energy; is further arranged to transfer the first form of energy to a common secondary energy conversion apparatus; and wherein the secondary energy conversion apparatus is arranged to convert the first form of energy to a second form of energy prior to exporting said second form of energy from the apparatus.

11. A buoyant energy converting apparatus of claim 1, wherein the wind energy converter; a wind energy primary converter and a wind energy transfer means.

12. A buoyant energy converting apparatus of claim 1, wherein the wave energy converter comprises; a wave energy primary converter; a wave energy transfer means; and a wave energy secondary converter.

13. A buoyant energy converting apparatus of claim 1, wherein the buoyant platform comprises an in-use configuration in which the buoyant platform is submerged in the body of water, and wherein in the in-use configuration the connection member protrudes through the surface of the body of water such that the wind energy converter is located substantially above the body of water.

14. A buoyant energy converting apparatus of claim 13, wherein in the in-use configuration, the wave energy capturing member is positioned at or proximate the surface of the body of water.

15. A buoyant energy converting apparatus of claim 1, wherein the wave energy converter comprises a wave energy capturing member coupled to a wave energy converting member, and wherein the wave energy capturing member is coupled to the wave energy converting member by an adaptable coupling member defining a distance between the wave energy capturing member and the wave energy converting member.

16. A buoyant energy converting apparatus of claim 1, wherein the wave energy converter comprises a wave energy capturing member coupled to a wave energy converting member, and wherein the wave energy converter is arranged to convert relative movement between said energy converting member and said wave energy capturing member to the useful energy.

17. A buoyant energy converting apparatus of claim 1, wherein the wave energy converter comprises a wave energy capturing member coupled to a wave energy converting member, and wherein the wave energy capturing member comprises a float.

18. A buoyant energy converting apparatus of claim 13, wherein in the in-use configuration, the apparatus is arranged to convert both wave energy and wind energy to the useful energy.

19. A buoyant energy converting apparatus of claim 1, wherein the buoyant platform comprises an adaptable depth-setting means arranged to define, over a predetermined range: a depth between an uppermost surface of the buoyant platform and the surface of the body of water.

20. A buoyant energy converting apparatus of claim 19, wherein the adaptable depth-setting means comprises a tether for tethering the buoyant platform to the bed of the body of water, wherein the buoyancy of the buoyant platform is arranged to provide an adequate tension in the tether, and wherein the adequate tension provides a stability to the buoyant platform when in the in-use configuration.

21. A buoyant energy converting apparatus of claim 20, wherein the stability and tension in the tether is arranged to substantially inhibit movement of the buoyant platform.

22. A buoyant energy converting apparatus of claim 19, wherein the tether comprises a substantially non-elastic material.

23. A buoyant energy converting apparatus of claim 1, wherein at least a portion of the connection member comprises a rigid open framework arranged to permit passage of water substantially through the connection member.

24. A buoyant energy converting apparatus of claim 1, wherein the housing comprises a storage cavity arranged to store equipment such as plant; motors; electricity generation means.

25. A buoyant energy converting apparatus of claim 1, wherein at least one of: a. the buoyant platform length; b. the buoyant platform width; and c. the buoyant platform diameter; is selected from the range 20 to 200 metres.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0087] Specific embodiments will now be described by way of example only, and with reference to the accompanying drawings, in which:

[0088] FIG. 1 shows an isometric view of a first example embodiment of a buoyant energy converting apparatus in accordance with the present invention;

[0089] FIG. 2a shows a close-up isometric view of the first example embodiment of the buoyant energy converting apparatus from FIG. 1;

[0090] FIG. 2b shows a close-up isometric view of an alternative to the first example shown in FIG. 2a;

[0091] FIG. 3 shows a lateral view of the first example embodiment of the buoyant energy converting apparatus from FIG. 1 in a service configuration;

[0092] FIG. 4 shows a lateral view of the first example embodiment of the buoyant energy converting apparatus from FIG. 1 in an in-use configuration;

[0093] FIG. 5 shows a lateral view of the first example embodiment of the buoyant energy converting apparatus from FIG. 1 in a survival, or storm, configuration;

[0094] FIG. 6 shows an isometric view of a second example embodiment of a buoyant energy converting apparatus in accordance with the present invention;

[0095] FIG. 7 shows an isometric view of a third example embodiment of a buoyant energy converting apparatus in accordance with the present invention;

[0096] FIG. 8 shows an isometric view of a fourth example embodiment of a buoyant energy converting apparatus in accordance with the present invention;

[0097] FIG. 9 shows a lateral view of the fourth example embodiment of the buoyant energy converting apparatus from FIG. 8 in a survival, or storm, configuration;

[0098] FIG. 10a shows a close-up isometric partial cutaway view of an alternative example embodiment of the buoyant energy converting apparatus from FIG. 1;

[0099] FIG. 10b shows a close-up isometric cutaway view of an alternative to the first example embodiment shown in FIG. 10a;

[0100] FIG. 11 shows a close-up isometric partial cutaway view of an alternate example embodiment of the buoyant energy converting apparatuses from FIGS. 10a and 10b;

[0101] FIG. 12 shows a further close-up isometric partial cutaway view of the example embodiment shown in FIG. 11;

[0102] FIG. 13 shows an isometric view of a fifth example embodiment of a buoyant energy converting apparatus in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0103] Referring to FIG. 1, an isometric view of an example embodiment of a buoyant energy converting apparatus 100 in accordance with the first aspect of the present invention is shown, positioned within a body of water (not shown) having a surface (not shown) and a bed. The apparatus comprises a wind turbine 3, a buoyant platform 7 and a connection member 9 therebetween. The wind turbine 3 comprises an elongate tower 6 having a first end coupled to a nacelle 5 having a longitudinal axis arranged orthogonally to the longitudinal axis of the tower 6, the nacelle 5 housing a rotational generator (not shown). Coupled to, and extending from, the generator are a plurality of blades 4 arranged in a plane substantially parallel to the longitudinal axis of the tower 6. The tower 6 further comprises a second end coupled to a first end of the connection member 9.

[0104] The connection member 9 comprises a lattice framework forming a substantially rectangular frustum, said first end of which having a first end aspect ratio, and a second end having a second end aspect ratio, wherein the first end aspect ratio is smaller than the second end aspect ratio. The second end of the connection member 9 is coupled to a central region of an uppermost surface of the buoyant platform 7.

[0105] The buoyant platform 7 comprises a planar structure comprising a substantially rectangular lattice framework 21, and positioned approximately at each of the four corners of the lattice framework 21 is a float (buoyancy chamber) 22, seen more closely in FIG. 2. The longitudinal axis of the buoyant platform 7 is oriented substantially orthogonal to the longitudinal axes of the connection member 9 and the wind turbine 3.

[0106] FIGS. 1 to 5 illustrate a first example embodiment of a combined wind and wave energy converting apparatus in accordance with the present invention.

[0107] In said FIGS. 1 to 5, the apparatus 100 is shown positioned in a body of water having a surface 1 and a bed 2 the apparatus comprises a wind turbine 3 which further comprises turbine blades 4, a nacelle 5 and a mast 6. The apparatus further comprises a buoyant platform 7 upon which is a plurality of wave energy converters 8 and connection member 9 upon which the wind turbine 3 in mounted.

[0108] The apparatus further comprises a machinery room 10 that is positioned at the top of the connection member 9 and contains power conversion apparatus to convert the energy captured by the wave energy converters and the wind turbine into electricity in a format suitable for export from the machine, for example grid compliant electricity.

[0109] The apparatus also comprises moorings 11 that further comprise of anchors 12 positioned on the sea bed 2, mooring lines 13 and depth setting means 14. The mooring lines 13 are typically flexible lines could be either ropes or chains or a combination of the two. The depth setting means would typically be a winch or a chain puller.

[0110] The wave energy converters 8 are typically positioned on the uppermost surface of the buoyant platform 7, each comprising an energy capturing float 15, a plurality of coupling members 16, and a plurality of pulleys 17 that guide coupling members 16 and establish a geometrical relationship with the float 15 in order to optimise energy capture. In an in-use configuration, depicted in FIG. 4, the energy capturing floats 15 of the apparatus 100 are positioned at an optimum height H′ relative to the upper surface of the buoyant platform 7, such that an angle A is produced between the coupling member 16 and the upper surface of the buoyant platform 7, said angle being required for optimal energy capture. An example of a typical optimal angle would be 45 degrees, with a range of suitable angles being 15 to 75 degrees. The optimal height H′ provides for sufficient clearance between the upper surface of the buoyant platform 7 and the underside of the float 15. Said clearance is a distance which provides optimal wave energy capturing by the energy capturing floats 15. An optimum distance might be selected from the range of 15 m to 50 m.

[0111] Each coupling member 16 takes the form of a flexible line and is coupled to an energy converter 18.

[0112] Typically, each energy converter 18 would comprise a drum around which the coupling member 16 is wound which is in-turn linked to a rotational generator. The rotational generator, depicted as an example on the end of each drum 17, can also act as a winch to allow the length of the coupling member 16, and therefore the depth of the float 15, to be adjusted. The drum could also be enabled to be driven by a separate winch or other adjustment means (not shown) to allow the length of the coupling member 16 to be adjusted independently of the rotational generator.

[0113] The nacelle 5 of the wind turbine 3 contains an energy converter (not shown) that would typically be a rotational electrical generator.

[0114] The rotational generators for the wind turbine and the wave energy converters 18 can be any type of generator but would typically be electric generators. Each generator would be part of a common electrical system (not shown) that would connect the electrical output from each generator to a final power conversion stage to allow the apparatus to export power in the required format through a single power output cable 23. The final power conversion stage would comprise of components such as inverters and transformers and is housed in the machinery room 10 to enable easy access for maintenance. The machinery room 10 would also contain a control and communication system (not shown).

[0115] Referring to FIG. 4, the example embodiment of a buoyant energy converting apparatus 100 of FIG. 1 is shown in an in-use configuration during mild sea conditions. In the in-use configuration shown, the buoyant platform 7 is submerged beneath the surface 1 of the body of water 150, with the mooring lines 13 of the depth-setting member 14 affixed to their respective anchoring members 12 on the bed 2 of the body of water 150. In the in-use configuration shown, the connection member 9 is shown protruding through the surface 1 of the body of water 150, such that the wind turbine 3 is above the surface 1 of the body of water 150, and is not in contact with the body of water 150. The connection member 9 is shown having a cavity 10 (in this case a machinery room 10) which remains substantially above the surface 1 of the body of water 150 and is arranged to accommodate equipment (not shown). In the in-use configuration shown, the floats 15 of the wave energy converter are positioned proximate the surface 1 of the body of water 150 to capture wave movement.

[0116] Referring to FIG. 5, the example embodiment of a buoyant energy converting apparatus 100 of FIG. 1 is shown in a storm or survival configuration during a storm, depicted in the embodiment shown by large waves. In the storm configuration shown, the buoyant platform 7 is positioned substantially as it is in the in-use configuration, submerged beneath the surface 1 of the body of water 150, with the mooring lines 13 of the depth-setting member 14 affixed to their respective anchoring members 12 on the bed 2 of the body of water 150. As with the in-use configuration of FIG. 4, in the storm configuration shown in FIG. 5, the connection member 9 is shown protruding through the surface 1 of the body of water 150 as defined by the depth of the buoyant platform 7 within the body of water 150 (determined by the length of the mooring lines 13). The connection member 9 is thus positioned such that the housing 10 is positioned at a housing height H″ relative to the mean sea level L, housing height H″ ensuring that the housing remains above the surface 1 of the body of water 150. The wind turbine 3 is thus also positioned above the surface 1 of the body of water 150 at all times, and is not in contact with the body of water 150. The floats 5 of the wave energy converters 8 are positioned at the buoyant platform 7 in the storm configuration and are thus optimised for minimum resistance of the apparatus 100 against the large waves, minimising forces on the apparatus 100 and tension of the mooring lines 13 of the depth-setting member 14, and maximum stability of the apparatus 100.

[0117] An example of a wave energy converter 8 is shown in FIG. 12, the wave energy converter 8 comprising an energy capturing float 15, energy conversion means 17, and a coupling member 16 coupling the float 15 to energy conversion means 17. The coupling member 16 comprises a flexible line wound around a drum within the energy conversion means 17, the drum being driven by a winch arranged to adjust the distance between the float 15 and the buoyant platform 7. As the floats 15 are moved by waves they alternately extend and contract their respective coupling members 16 and actuate the respective energy conversion means 17, enabling the apparatus to generate power. This type of wave energy converter is exemplary, and other types of wave energy converters could be used on the apparatus.

[0118] Also shown in FIG. 12 are mooring winches 14 arranged in pairs of one vertical mooring line 13 (shown) and also arranged to provide one angled mooring line (not shown) on the corners of the buoyant platform 7, however other winch positions are possible.

[0119] The wave energy converter in the described embodiments should be considered as being for the purpose of exemplification only. For the purpose of illustration, a wave energy converter similar to the Marine Power Systems WaveSub® has been described. Additional embodiments comprising different wave energy converters will be conceivable, some examples of which will be described in more detail below:

[0120] Referring to FIG. 6, a second embodiment 51 of the invention is envisaged which is similar to the first embodiment in all aspects except the energy capturing member of the wave energy converters comprises a buoyant disc 52 slideably affixed to a mast 53 and arranged to move freely up and down the mast 53 with the motion of the waves. Embodiments will be appreciated wherein the floating discs are instead immovably affixed to the top of slideable mast similarly arranged to provide energy capture and conversion through a pressure differential. Equivalent numbering as that for the embodiment of FIGS. 1 to 5 will be used where appropriate. In the second embodiment 51 the buoyant discs 52 are each in communication with a corresponding coupling member (not shown) which may include a hydraulic ram and an energy transmission line (not shown) that transmit the corresponding captured and/or converted energy and establish a geometrical relationship with the buoyant discs 52 in order to optimise energy capture. In the embodiment shown, the apparatus 51 comprises a buoyant platform 7 positioned at a depth such that the upper surface of the mast 53 is an optimal clearance distance from the sea surface 1. Said clearance distance provides optimal wave energy capturing by the energy capturing discs 52. An optimum clearance distance for said mast 53 might be selected from the range of 10 m to 50 m.

[0121] A third embodiment 54, similar to the second embodiment 51, is shown in FIG. 7, wherein the features are substantially the same and equivalent numbering thereof is used. In the fourth embodiment 54 of FIG. 7, the buoyant discs 52 are exchanged for elongate floats 55. The apparatus 54 comprises a buoyant platform 7 positioned at a depth such that the upper surface of the floats 55 is an optimal clearance distance from the sea surface 1. Said clearance distance provides optimal wave energy capturing by the energy capturing floats 55. An optimum clearance distance for said floats 55 might be selected from the range of 15 m to 40 m.

[0122] Each wave energy converter in the embodiments of FIG. 6 and FIG. 7 takes the form of a pressure differential wave energy converter, and may comprise for example, a hydraulic ram used to capture wave energy from the wave energy capturing discs 52 or floats 54. Such hydraulic mechanisms would transfer the hydraulic energy to an energy converter in the housing 10 by way of energy transfer lines. Alternatively, coupling members may be used which take the form of a flexible line and is guided via pulleys to an energy converter 18 that is located in the machinery room 10. The machinery room 10 is always above the water and therefore the energy converters 18 can be in a dry environment. Each energy converter may comprise a drum around which the coupling member is wound which is in-turn linked to a rotational generator. The rotational generator (not shown) can also act as a winch to allow the length of the coupling member, and therefore the depth of the buoyant discs 52 or elongate floats 55, to be adjusted. The drum could also be enabled to be driven by a separate winch or other adjustment means (not shown) to allow the length of the coupling member to be adjusted independently of the rotational generator. An example can be seen in FIG. 12. Other embodiments of energy capture, transfer and conversion using a pressure differential device will be appreciated, and may for example comprise a membrane arranged to transmit mechanical or kinetic energy, potentially using a hydraulic energy transmission mechanism as described above, as a result of a pressure differential.

[0123] Referring to FIG. 8, an isometric view of a fourth embodiment 56 of the invention is shown similar to that of the second embodiment, and equivalent numbering is used where appropriate. In the fourth embodiment 56 of FIG. 8, the wave energy converter 57 comprises a paddle 58 arranged to rotate about a hinge in a reciprocal fashion between a first position in which the paddle 58 is adjacent to the buoyant platform 7 at a first principal surface of the paddle 58, and a second position in which the paddle 58 is adjacent to the buoyant platform 7 at a second principal surface of the paddle 58, wherein the first principal surface opposes the second principal surface. In such a way, the paddle 58 my reciprocally rotate about the hinge with the flow of the waves, and consequently drive a rotational generator (not shown). Embodiments will be appreciated wherein the rotational generator will be contained with a machinery room 10 located atop the connection member. FIG. 9 shows the third embodiment of FIG. 8 in a storm configuration, wherein the paddles 58 are positioned adjacent the buoyant platform 7.

[0124] In an alternative embodiment (not illustrated) the energy conversion apparatus may be fixed or have a structure suited to the combination of a wind energy conversion system and a tidal power generation system.

[0125] The embodiments described show a typical horizontal axis wind turbine, although additional embodiments will be appreciated wherein other types of wind energy capturing devices are used as, as part of, and/or within the wind energy converter, such as, for example, a vertical axis wind turbine, or a kite powered generator system.

[0126] The structure of the device is designed so that only relatively thin framework is in the wave zone when the apparatus is in its in-use configuration, reducing wave loads on the device.

[0127] To survive storms the floats of the wave energy converter can be retracted against the main structure of the buoyant platform, leaving a large gap between the floats/platform and the wind turbine tower, through which large surging storm waves can pass with minimal loads on the device.

[0128] The depth-setting member depicted in the described embodiments comprises four vertical mooring lines and four angled mooring lines to provide a high level stability to the barge platform. Additional embodiments will be appreciated wherein alternative mooring layouts are possible.

[0129] The energy transport means in the embodiment shown takes the form of a power umbilical, which exports power from the device to an underwater energy storage member, which in the embodiment shown is a junction box. From the junction box a further cable (not shown) delivers the energy to land.

[0130] In the transport configuration shown in FIG. 3, all moving parts of the apparatus and connections are above the surface of the body of water, and can be accessed for maintenance. The floats on the buoyant platform, which are buoyancy tanks on the embodiment shown, provide the buoyancy needed to float the entire apparatus, and are of fixed buoyancy. Additional embodiments will be appreciated wherein the buoyant portions of the buoyant platform are of either fixed or variable buoyancy.

[0131] Whilst in the transport configuration, if the apparatus is in the desired location and the power umbilical is connected, the wind turbine can remain operational when the wave energy converters are not. This allows, for example, maintenance to be carried out on the wave energy converters whilst the wind turbine still generates power.

[0132] In the in-use configuration described and shown in FIG. 4, the buoyant platform is submerged to a level which allows the wave energy converters to function and generate energy. The wave energy converters may be on or close to the surface of the body of water and can be moved by waves. The wind turbine remains clear of the water in this configuration and can be accessed for maintenance whilst the wave energy converters continue to generate power.

[0133] Embodiments may be appreciated wherein the depth-setting member, or parts of the depth-setting member are preinstalled at the desired location of the apparatus prior to transport of the apparatus to said site. In such an example situation, to deploy the apparatus in the into its in-use configuration from its transport configuration, the apparatus is connected to preinstalled mooring lines which are attached to the bed of the body of water by respective anchoring members. The mooring lines are adjusted in length by winches on the depth-setting member. The winches reel-in the mooring lines to pull the buoyant platform beneath the surface of the body of water, overcoming the buoyancy in buoyant portions of the buoyant platform, to position the buoyant platform at a required depth.

[0134] In the storm configuration, the floats of the wave energy converters are retracted further underwater and preferably secured against the buoyant platform. The depth of the floats underwater in the storm configuration is such that they are protected from large forces that could otherwise be experienced on or close to the sea surface in storm waves. The connection member protrudes through the surface of the body of water such that it is high enough above the surface that storm waves are unable to reach the wind turbine tower. Therefore, the only part of the device that is ever exposed to storm waves is the framework of the connection member, which is made from a lattice structure, comprising beams having a thin cross section which allows waves to pass freely through its structure without experiencing high forces.

[0135] Alternative embodiments to that shown in FIGS. 1 to 5 are shown in FIGS. 10a and 10b. In FIG. 10a, the nacelle 5 of the wind turbine 3 contains gearing 19 that turns a driveshaft 20 that runs down the mast 6 to an energy converter 18 in the machinery room 10. The energy converter 18 would typically be a rotational electrical generator.

[0136] In FIG. 10b the wind energy converter and wave energy converter 15, 16, 17 convert wind and wave energy respectively to an interim form of energy, such as hydraulic or mechanical energy which is then transmitted to the machinery room 10 by hydraulic or mechanical means, to energy generators 18 housed within the machinery room 10. This has the advantage that more of the complex machinery is housed in a location that is simpler to engineer (e.g. not subsea) and simpler to access for maintenance (e.g. not subsea and not at the top of a wind turbine mast).

[0137] The buoyant platform 7 and connection member 9 comprises a substantially rectangular lattice framework 21 and positioned approximately at each of the corners of the lattice framework 21 is a buoyancy chamber 22. The buoyancy chambers 22 ensure the apparatus has a net positive buoyancy. Whilst the illustrated embodiment of the apparatus is shown with a substantially rectangular platform 7, it can be appreciated that other shapes, such as triangular or circular are possible.

[0138] The apparatus further comprises a power export cable 23 arranged to transfer energy generated by the apparatus to an undersea connector 24. The undersea connector 24 would typically be further connected to a fixed seabed cable (not shown) or an energy storage means (not shown).

[0139] Referring to FIG. 11, an alternative embodiment of the invention is shown. The alternative embodiment is similar to the embodiment shown in FIGS. 10a and 10b in all aspects except the energy transfer mechanism from the wind turbine 3 to the machinery room 10.

[0140] The alternative embodiment of the invention uses a drive belt 25 running down the inside of the turbine mast 6 instead of the driveshaft 20 of the first embodiment. The drivebelt 25 is driven by a pulley 26 in the nacelle 5 of the turbine and is connected to another pulley 27 in the machinery room 10 which turns a rotational energy converter 18.

[0141] It can be appreciated that the belt drive could be substituted for a chain drive and operate in a very similar manner.

[0142] Embodiments will be appreciated wherein the energy transfer mechanism from the wind turbine 3 and the wave energy converters 8 to the machinery room 10 is hydraulic. A hydraulic system might for example use a hydraulic generator in the nacelle 5 that converts the rotational energy in the wind turbine 3 into hydraulic energy which is transferred to an energy converter 18 in the machinery room 10 by hydraulic lines running down the inside of the mast 6.

[0143] The wave energy converter 8 comprises corner pulleys 17 that guide the coupling members 16 directly to hydraulic generators (not shown). The hydraulic generators connected by hydraulic lines to secondary energy converters in the machinery room 10.

[0144] An alternative embodiment, shown in FIG. 10b may utilise a common secondary energy converter that converts hydraulic energy from both the wind turbine 3 and the wave energy converters 8 to electricity.

[0145] In the embodiments previously described, the wind energy converter comprises a horizontal axis wind turbine. Additional example embodiments will be appreciated, such as that shown in FIG. 13, wherein the wind energy converter comprises a vertical axis wind turbine.

[0146] It will be appreciated that the above described embodiments are given by way of example only and that various modifications thereto may be made without departing from the scope of the invention as defined in the appended claims. The housing described may contain all or part of either or both of the wind energy converting member or the wave energy converting member. The wave energy converting members may be the most crucial components to locate in the housing due to maintenance requirements in some situations.