GB2540274A

GB2540274A - Multi-Rotor device with a polygonal structure, for harnessing sea currents

Info

Publication number: GB2540274A
Application number: GB1611676.6A
Authority: GB
Inventors: López Pineiro Amable; Nunez Rivas Luis; Andrés Somolinos Sanchez José
Original assignee: Universidad Politecnica de Madrid
Current assignee: Universidad Politecnica de Madrid
Priority date: 2014-02-11
Filing date: 2015-02-03
Publication date: 2017-01-11
Anticipated expiration: 2035-02-03
Also published as: ES2461440A1; WO2015121517A1; GB2540274B; GB201611676D0; ES2461440B2

Abstract

The invention relates to a multi-rotor device with a polygonal structure, for harnessing sea currents, comprising an assembly of extractable generating units (1) and driving units or floats (2) supported by a main structure in the shape of a polygon and complemented by a stabilisation structure using lattices (20, 21) or guys (22), in the centre of which a central dome (7) can be arranged. The device is attached to the bottom by means of anchoring cables (10), the length of which can be regulated by means of winches (9). The driving units (2) have ballast tanks which change the drive and orientation of the device as they are filled or emptied. As a result of the combined action of ballasts and winches, the device rotates and orients itself autonomously when the tide changes, the rotors always operating with optimum orientation and depth according to the current.

Description

MULTI-ROTOR DEVICE WITH A POLYGONAL STRUCTURE FOR THE UTILIZATION OF

MARINE CURRENTS

DESCRIPTION

FIELD OF THE INVENTION

The present invention is included in the field of marine renewable energies, and more particularly it refers to a second generation device for the utilization of energy from marine currents, both inertial and tidal currents.

Background of the invention

Nowadays, there is a strong interest on marine renewable energies utilization. Among these, the utilization of the currents generated by general water flow from the oceans and by tides, can significantly contribute to the “energy mix” and help achieve the energetic objectives linked to climate change. At a worldwide level, the energy obtained from the marine currents is estimated to be about 800 TWh/year.

Currently, there are several designs and prototypes of generators to obtain energy from currents. Generally, it is considered that first generation generators are those mounted on the sea-bed (limited to depths of about 40 m), second generation ones (ideal for greater depths, where the best locations are found) are those being floating or submerged which are attached to the sea bed by means of specific anchoring system, and third generation ones being designed for marginal areas in which the current speed is very low.

Among the second generation devices, there are designs having a single generator and rotor, or designs having several ones, wherein the developments from Oceanflow (Evopod), Hydratidal (Morild), Tidalstream (Triton) and Soermar-UPM (GESMEY) can be distinguished. A key element of these devices is the generating units, consisting of a rotor and the electromechanical energy conversion unit (PTO) which, when featuring reduced power (between 30 and 300 kW), can be used as modular units, allowing maintenance operations by removing thereof. Among developments of these units, those from Tocardo, Schotell and Verdant Power are to be distinguished.

Among patents related to second generation devices, the three granted to the R&D group from the UPM (Technical University of Madrid), being also the applicant of the present new patent, can be distinguished: ES 2284411 B2, ES 2341311 B2 and ES 2367616 B2, showing different variants of a single-generator device, and, on the other hand, those patents referring to multi-rotor floating or submerged devices, such as GB2471874A, GB2450962A, WO2012175955A1 and WO2013066897A2. In the latter, the generators are supported by structures which make the afloat maintenance process complicated, since they are not designed to damp the movements induced by waves, and have problems for the operation thereof under conditions of currents that change direction, such as those generated by tides.

Because of all that, an interest has arisen in designing a second generation multi-rotor device which: optimizes the structure weight, adapts to the currents direction and makes the transport and maintenance operations easier, thus reducing the economical, operational and maintenance costs as much as possible through the life cycle thereof.

This object is achieved by means of the invention as defined in claim 1. Preferred embodiments of the invention are defined in the dependant claims.

Description of the invention

The present invention refers to a multi-rotor device with a polygonal structure for the utilization of marine currents which comprises a plurality of removable modular generating units and a plurality of driving units or floats, in an amount similar to that of the generating units.

The device object of the invention has the peculiarity that the generating units and the driving units are positioned according to a polygonal arrangement, at the sides and/or vertices of said polygonal arrangement, each generating unit and each driving unit alternating with respect to each other so as to reduce the stress in the structures. Additionally, the device is characterized in that, first main connecting elements and complementary connecting elements are provided for the connection of the generating units and the driving units, and second main connecting elements for the connection of at least the driving units with the polygon centre, all of them being configured to provide the resulting polygonal structure with rigidity, such that the device will be able to operate in a vertical position to obtain energy or float on the water surface for the transportation thereof and for afloat maintenance operations. Therefore, the device works, usually, being totally submerged while in operation and can float during maintenance and transport operations.

Thus, as the generating units and the driving units are supported by simple structures, afloat maintenance process becomes easier, since said simple structures have been designed to help damp the movement induced by the waves in said units, and work properly even when there are changes in the currents direction, as it happens with tides. Therefore, the device is suitable for the utilization of energy from marine currents of any type, in areas of half and big depth.

Therefore, the assembly (connecting units and elements) of the present invention is designed for reducing the costs of the life cycle of a marine power plant, allowing an easier mass production of elements of a reasonable weight and size, an easier transportation and mounting thereof, allowing the use of low cost maritime means of transport and maintenance, and increasing the assembly availability and utilization factor.

In a first aspect of the invention, the driving units can be arranged in the polygon vertices and the generating units will be arranged equally distanced between two consecutive driving units at the midpoint of the corresponding polygon side. Likewise, and alternatively, the generating units will be arranged in the polygon vertices and the driving units will be arranged equally distanced between two consecutive generating units at the midpoint of the corresponding polygon side. Both arrangements are suitable for the object of the present invention.

In another aspect of the invention, a central dome, being located at the geometrical centre of the polygon, can be provided which will be connected to the driving units and/or the generating units by means of the second main connecting elements, with complementary equipment being provided within the central dome, preferably including anchoring control and ballasting equipment, electronic converters, switchgear and controlgear and several systems. Additionally, in the central dome and/or in some of the driving units and/or generating units located at different points in the polygon, corresponding winches can be provided, the anchoring cables of which attach the device to the seabed. The main role of said anchoring cables and winches is simply to allow an intentional variation in the immersion depth of the device structural assembly, in collaboration with the driving units.

In another aspect of the invention, each one of the generating units may be connected through respective cables having a fixed length, to a submerged rotating buoy, which in turn is fixed to the sea bed by means of an anchoring system, said submerged rotating buoy automatically adapting to the direction of the current. That is, the rotating buoy makes the device structural assembly rotate in case said rotation is necessary, or for maintenance or transportation operations, or for changes in the direction of the water current. Initially, the buoy from patent ES 2367616 B2 from the same applicant can be used as a buoy.

Regarding the generating units, each of them can be provided with a rotor having several blades and a watertight body including the elements for converting the hydrokinetic energy into mechanical energy. Furthermore, each one of said generating units are removable units located in the periphery of the device polygonal structure, and are configured to be serviced while floating or to be substituted by others by means of a crane associated to a vessel.

Therefore, each generating unit is modular and removable and will be generally referred to as UGEX. Furthermore, each generating unit is internally made up of an electromechanical power train, including the rotational electric generator, and each unit is connected to the device through an umbilical cable to a connector allowing the connection and disconnection thereof while floating.

On the other hand, each driving unit or float incorporates ballast tanks configured to change its float level and that of the device, wherein some of said driving units comprise complementary equipment. More particularly, each driving unit is provided with conical hydrodynamic (fairwater) nose and tail bodies, inside of which a series of ballast tanks are arranged which, upon being filled or emptied with water, can control the hydrostatic forces and, consequently, adjust the position and orientation of the device, both being submerged and floating. Referring to the complementary equipment, it can consist of electronic converters, ballast and anchoring winches control equipment. The sectioning and separation of the driving units or floats has a positive influence in the device behaviour in the sea when it is floating, during transportation, installation and, above all, during maintenance. The driving units can rotate according to a horizontal axis, being configured in such a way that, when the current direction changes, as a consequence of the tidal cycle, said driving units can rotate over the horizontal axis thanks particularly to the ballast tanks, keeping the desired depth with the assistance of the anchoring system. When the driving units are in a horizontal position, by emptying ballast and casting the anchoring cables off, the device is allowed to come up to the surface for maintenance and transport operations.

In another aspect of the invention, the device can be provided with a water ballast control system to control each of the driving units and/or the central dome, and with an anchoring control system, which comprises anchoring winches and cables, wherein the combined operation thereof allows controlling the device depth and orientation, thus optimizing the energy obtained and/or reducing the fatigue stress. In particular, this anchoring system consisting of the winches and anchoring cables, which can be used both in the central dome and in some of the driving units or floats, allows adjusting the length of the anchoring cables that attach the device to the sea bed by means of the aforementioned winches, which are submersible, in such a way that the device can operate at different depths, taking advantage of the optimum speed of the current, change height during the rotation required when the current changes direction within each tidal cycle, and come out to the surface and submerge during installation, afloat maintenance and disassembling operations. In turn, the ballast control system, by controlling the total volume and position of the dome and/or the driving units, makes it possible for the device to keep its main plane vertical while in operation, counteracting the torque produced by rotors and that from the hydrodynamic resistance, to rotate to a horizontal or inverted position upon tidal changes, and to stay horizontal on the surface during maintenance or transportation, showing stability and a good movement response to waves, being the depth thereof adaptable.

In another aspect of the invention, the plurality of generating units and driving units can be arranged according to a regular polygon wherein the driving units are located in the vertices of the polygon, these being connected to each other through first lattice structures acting as first main connecting elements, and the generating units are located in the midpoints of said first lattice structures forming the polygon. The preferred use of lattice structures will serve as a way to reduce hydrodynamic resistance during transport, and it will make construction and assembly easier. Additionally, the central dome may be arranged in the core of said polygon, connected to the driving units through second lattice structures acting as second main connecting elements, with guy-wires being provided which connect to the second lattice structures and act as complementary connecting elements. These second lattice structures and the aforementioned guy-wires are mainly intended to make the device structure rigid.

In another aspect of the invention, and alternatively, all the driving units may be connected to a central point through first guy-wires acting as second main connecting elements, and wherein the adjacent generating units are connected to each other through pairs of second guy-wires acting as complementary connecting elements. That is, in this case, the dome has been left out and guy-wires are used in substitution of the second lattice structures. Said guy-wires together provide stability against deformation of the ring formed by the polygon sides, and access to the central area is not required, so three-blade rotors can be used in the generating units. Thus, it is possible to achieve a somewhat more flexible structure, and to adapt movement of both the generating units and the driving units to high intensity currents, without damage being caused to the device.

In another aspect of the invention, and advantageously, the regular polygon used in the device may be a hexagon, this concrete shape not being limitative in any case. Another possible arrangement may consist of the plurality of generating units and driving units being positioned according to rectangular polygonal arrangements that are subdivided into at least a pair of square areas, wherein the driving units are positioned in the square vertices being connected to each other through first lattice structures acting as a first main connecting element, and the generating units are positioned in the midpoints of said first lattice structures forming the polygon, with only second lattice structures, which act as second main connecting elements, being provided at the exterior sides of the device perimeter, between any of the generating units and said structures with a central support. This alternative arrangement can be equally efficient as any other regular polygonal distribution, in terms of easiness of the management of functioning, maintenance and transport operations of the device structure assembly.

The use of the basic side modules (UGEX generating unit, driving unit or float and set of lattice structures and guy-wires), allows great freedom of configurations which make it easier to adapt the design adaptation to the conditions of each location. This modular concept also makes the construction, transport and mounting process easier.

Brief description of the drawings

The following is a brief description of a series of drawings which will help understand the invention better and which specifically refer to two embodiments of said invention presented as a non-limiting example thereof.

Figure 1 shows a perspective view of the multi-rotor device with a polygonal structure for the utilization of marine currents object of the invention, as a first embodiment of the invention wherein the device has a hexagonal shape and is provided with a central dome.

Figure 2 is a schematic view of the preferred configuration of one of the polygon sides of figure 1, in which a lattice structure is provided, in the centre of which one of the generating units is arranged.

Figure 3 shows an elevation view of the multi-rotor device with a polygonal structure for the utilization of marine currents, object of the invention, of figures 1 and 2, in a plane perpendicular to the current direction, for the case of generating units having two-blade rotors.

Figure 4, shows a perspective view of the multi-rotor device with a polygonal structure for the utilization of marine currents, object of the invention, as a second embodiment of the invention in which the central dome is not provided, in which two central driving units will hold inside thereof the conversion and control equipment, including the anchoring winches, wherein the two upper driving units plus the lower two are also work as ballast tanks, in which, for connecting the generating units and/or the driving units with the centre of the device, guy-wires are used instead of lattice structures, and in which the generating units are provided with three-blade rotors.

Figure 5 shows a perspective view of the multi-rotor device with a polygonal structure for the utilization of marine currents, object of the present invention, as a third embodiment of the invention in which an auxiliary buoy is used as an anchoring means, in which winches within the driving units are not required, and in which the anchoring cables, with a fixed length, are engaged in the generating units supports, instead of being engaged in the driving units.

Figure 6 shows a perspective view of the multi-rotor device with a polygonal structure for the utilization of marine currents, object of the present invention, as a fourth embodiment of the invention in which the base polygon is a rectangle subdivided so as to determine two square areas to build up a more complex structure, and in which generating units have not been provided in the inner sides, and wherein a higher number of anchoring cables have been used.

Figure 7 shows a plan view of the anchoring solution, for the multi-rotor device with a polygonal structure for the utilization of marine currents of figures 1 to 3, with two anchoring cables, each one of them being operated by an independent winch.

Figure 8 shows an elevated view of the operation for changing the orientation of the device of figure 7, including the different positions the device takes when the current changes direction.

Figure 9A shows a plan view of the maintenance operation of a generating unit being part of the multi-rotor device with a polygonal structure for the utilization of marine currents, object of the present invention, wherein said maintenance operation consists of replace one unit with another one, using a crane mounted on a vessel.

Figure 9B shows an elevated view of what is depicted in figure 9A.

Figure 10A shows a plan view of a bigger maintenance operation if the central dome equipment which is part of the multi-rotor device with a polygonal structure for the utilization of marine currents, object of the present invention, wherein said maintenance operation requires the use of the crane, removing for that one of the generating units and partially sinking the device, such that a catamaran type vessel can run above this side.

Figure 10B shows an elevated view of what has been depicted in 10A.

Figure 11 is a schematic view of the components of one of the generating units which are part of the multi-rotor device with a polygonal structure for the utilization of marine currents, object of the present invention.

Figure 12 is a schematic view of the components of one of the driving units or floats which are part of the multi-rotor device with a polygonal structure for the utilization of marine currents, object of the present invention.

In the above figures there have been identified a series of references corresponding to the elements detailed below, without this implying any limitation at all: 1. generating units 2. driving units 3. polygon sides defining the device position 4. polygon vertices defining the device position 5. first main connecting elements 6. complementary connecting elements 7. central dome 8. second main connecting elements 9. winches 10. anchoring cables 11. cables for connecting to a submerged rotating buoy 12. submerged rotating buoy 14. rotor of each of the generating units 15. rotor blades of each of the generating units 16. watertight body of each of the generating units 17. energy conversion elements of each of the generating units 18. ballast tanks of each of the driving units 19. complementary and auxiliary equipment included inside one of the driving units 20. first lattice structures 21. second lattice structures 22. guy-wires 23. first guy-wires 24. second guy-wires 25. square areas 26. central support 27. operation with rightward current 28. submerged horizontal position 29. operation with leftward current 30. vessel 31. crane 32. support sleeve of the generating units in the lattice structure 33. elements for anchoring the anchoring cables to the sea bed 34. rotor core of the generating units 35. watertight horn of the generating units 36. main axis of the generating units 37. multiplier of the generating units 38. thrust bearing of the generating units 39. generator of the generating units 40. electrical brake of the generating units 41. first watertight chamber of the driving units 42. access hatchway of the driving units 43. second watertight chamber of the driving units.

Description of the invention

The multi-rotor device with a polygonal structure for the utilization of marine currents, object of the present invention, as it can be appreciated, for example, in figures 1 and 2, consists of a set of generating units 1 being modular and removable (UGEX), and a set of driving units 2 or floats, almost conical (fairwater), connected through structures which are preferably lattice structures 20, 21 and through guy-wires 22. As it can be appreciated in figure 11, each UGEX features a watertight body 16 of an almost cylindrical shape, having the electrical and mechanical conversion elements 17 inside thereof, and a rotor 14 outside thereof, preferably a two or three-blade 15 one, featuring a fixed pitch, and is attached to the structure by means of a cylindrical support or sleeve 32 inside which there is arranged the electrical and signal connection system between the UGEX and the device (not shown in the figures). More particularly, and as it can be appreciated in figure 11, the conversion elements 17 are formed, in turn, by a rotor core 34 from which the blades 15 start (not shown), from a watertight horn 35 being coupled to a main axis 36, in the same way as the rotor core 34, there being also inserted in said main axis a multiplier 37 and a thrust bearing 38, which is related to a generator 39 which is provided with an electrical brake 40. All the conversion elements 17 mentioned are contained in the watertight body 16, preventing water from entering inside thereof so as not to damage the conversion elements 17.

Figure 12 shows how the driving units 2 or floats are divided inside into a series of ballast tanks 18 which when ballasted with water, to a greater or lesser extent, allow regulation of the assembly drive and hydrostatic torque, and thus control of the depth and orientation thereof. Inside the driving units 2 or floats there may be a first watertight chamber 41 in which different complementary and auxiliary equipment 19 is placed, such as for example, electronical converters, pumps, compressors, electrical switchgear, instrumentation and control systems, etc. In the upper area of the driving units 2 an access hatchway 42 has been provided for access to the auxiliary and complementary equipment 19. In the lower area of the driving unit a second watertight chamber 43 is provided, inside which there is arranged a winch 9 in which the corresponding anchoring cable 10 is wound up. This set of generating 1 and driving 2 units can be arranged according to different distributions, being possible for those units to be placed on the polygon sides 3 or on the vertices 4 thereof.

As it can be seen in figures 1 and 3, wherein a first embodiment of the invention has been depicted, the structure represented consists of a regular polygon, particularly a hexagon, in the vertices 4 of which the driving units 2 are arranged, being connected to each other through first lattice structures 20, in the midpoint of which the generating units 1 are arranged, the driving units 2 being connected, in turn, to a central dome 7 provided in the geometrical centre of the hexagon, through second lattice structures 21, wherein the structure is completed by guy-wires 22 which connect each other, at the midpoint thereof, to second lattice structures 21 and therefore describe a hexagonal shape, making the device structural assembly significantly rigid. The central dome 7 is connected to anchoring cables 10 being attached to the sea bed by means of corresponding winches 9 placed inside the spherical end of the dome (not visible in the figure), which can adjust the depth of the assembly. On the other side, figure 2 represents one of the sides 3 of the polygon forming the device structural assembly, wherein the driving units 2 are arranged at both ends joint by one of the first lattice structures 20, and in the midpoint of which a generating unit 1 is provided being connected to said first lattice structure 20 by means of a support or sleeve 32.

Figures 4 and 5 show, respectively, a second and a third embodiment of the invention which are variants of the first embodiment keeping the hexagonal shape thereof. Regarding figure 4, the central dome 7 has been left out and the second lattice structures 21 of figurel have been substituted by first guy-wires 23 which connect the driving units 2 or floats to the geometrical centre of the hexagon, and also connect the generating units 1 with said geometrical centre. Furthermore, the guy-wires 22 of figure 1 have been left out, and instead of them, in order to make the assembly more rigid, pairs of second guy-wires 24 have been provided, which are intended to connect the generating units 1 to each other. In the case of figure 4, the choice is a “direct” anchoring system having two anchoring cables 10 which connect two driving units 2 or floats to the sea bed, and that adjust the device immersion depth with the help of winches 9 (not visible in the figure) placed inside the spherical end of said driving units 2. In contrast, the choice in figure 5 is a third embodiment depicting an “indirect” anchoring system, in this case several generating units 1 being connected, by means of connecting cables 11, to a submerged rotating buoy 12 and this, in turn, to the sea bed by means of a pair of anchoring cables 10. The submerged rotating buoy 12 is described in patent ES 2367616 B2 of the same applicant. Therefore, the connecting cables 11 between the buoy 12 and the device have a fixed length and the device winches may be eliminated. In the case fixed pitch blades are used, the current has to come only from one direction. But, in the case of tidal currents, in which there exists a change in the current direction between ebb and flood, it is essential to rotate the device, so when using a submerged rotating buoy 12 the alignment is produced automatically.

Figure 6 shows a fourth embodiment of the device in which the base polygon is a rectangle subdivided to determine two square areas 25 in order to form a more complex structure. More particularly, in this case the structural assembly consists of six driving units 2 or floats connected to each other through first lattice structure 20, and the generating units 1 are placed between each pair of driving units 2, in the midpoint of the structures 20, with a total of six generating units 1. In this case, a central support 26 is provided which is connected to the intermediate driving units 2 from the long sides of the rectangle by means of first lattice structures 20. In turn, the generating units 1 are connected to each other by means of second lattice structures 21 diagonally positioned with respect to the sides of the rectangle constituting the device structural assembly. In this case, a greater number of anchoring cables 10 has been used; concretely four being connected to the driving units 2 situated on the rectangle vertices.

Figure 7 shows a plan view of the anchoring solution for the multi-rotor device with a polygonal structure for the utilization of marine currents of figures 1 to 3, with two anchoring cables 10, each one of them controlled by an independent winch 9 (not visible). The anchoring cables 10 are connected to the sea bed through anchoring elements 33.

It should be noted that in all figures and in order to generalize in the main claim, the first main connecting elements 5 have been designated as first lattice structures 20, the second main connecting elements 8, depending on the embodiment, as second connecting elements 21, or first guy-wires, and the second connecting elements 6, depending on the embodiment, as guy-wires 22 or as second guy-wires 24.

As it can be seen in figure 8, while in operation, the device has the main plane thereof in a vertical position and with the rotor axis in the current direction. If this flows rightwards, the balance position 27 is reached at a depth which is a function of the current speed (higher on the surface than at the bottom), the anchoring cables length and the net device drive. Thus, it is possible to operate nearer the surface when the current speed is low and there are few waves, increasing depth with bad conditions of the sea or higher speeds. Thus, the annual quantity of energy obtained can be maximized and fatigue stress can be reduced. The rotors arrangement “downstream” of the device produces a self-alignment with the current direction.

When the current speed lowers, and thus the hydrodynamic forces, the device is rotated by transferring ballast water from the lower floats to the upper ones, so it changes from a vertical orientation to a horizontal 28 one, with part of the anchoring cable being reeled in if the device is not intended to go up much more.

When the current direction changes completely, a new ballast transfer makes the device rotation complete, which adopts the operation position 29, wherein the depth is adjusted again with the help of the winches.

In order to carry out with maintenance operations, taking advantage of intervals of low current speed and moderate waves, once the device is submerged and horizontally positioned, part (or all) of the ballast water is emptied and the anchoring cable is cast off, such that it will emerge softly, being held in the position depicted in figures 9A and 9B. In the base position for maintenance, using a small vessel 30, it is possible to access the floats having equipment within, through the access hatchways situated in the cones. In order to change the generating unit 1 UGEX, the bolts attaching thereof to the sleeve 32 have to be removed, the umbilical cable thereof has to be disconnected and the generating unit has to be lifted by a crane 31 into the vessel 30. Assembling of the reserve generating unit 1 UGEX is carried out inversely.

In the case any of the winches is to be serviced, from the initial operation position 27 a counter-rotation is generated, such that the rotors are left upside-down. Subsequently, by casting cable off and reducing ballast, the device emerges.

It can be seen that under floating conditions, the set of floats act as a half-submersible platform, such that the movement induced by waves will be reduced. Furthermore, by controlling the amount of remaining ballast, the period of the device movement resonance can be adjusted in such a way that it does not coincide with that of significant waves.

As it can be seen in figures 10A and 10B, in the case of an embodiment having the central dome 7, access thereto is more complex. For light equipment inspection or substitution tasks, access can be achieved from the maintenance vessel 30 by hoisting out a tender (for example a pneumatic boat) that can go through the blades of a generating unit 1 UGEX and a driving unit 2 or float. In order to do that, it is required that the device does not protrude too much from water, and that one of the rotors has the two blades thereof in radial direction. In case of a bigger maintenance in the central dome 7, in order to move heavy equipment, the vessel 30 can get closer if it is a catamaran or the like, previously removing one of the generating units 1 UGEX and submerging the device up to a suitable depth, as it can be seen in figure 10.

The driving units 2 or floats and the generating units 1 UGEX, and even the central dome 7, which may have equipment within watertight chambers, may be provided with an access hatchway situated in the conical end thereof.

Steel will be used as a preferred material for all these elements, although it is possible to use composite materials for the most voluminous bodies, especially for the driving units 2 or floats. The structure of the bodies forming the generating 1 and driving 2 units, must be pressure resistant and it will preferably consist of a nose fairing (ellipsoidal cap), a cylinder and two truncated cones for the watertight area and a tail fairing.

In the case of figure 6, where the alternative embodiment having a submerged rotating buoy 12, the winches 9 (not visible in the figure) adjusting the anchoring cables 10 length, are provided inside said buoy 12 instead of being in the device. A preferred use of an attaching system using lattice structures 20, 21 formed by tubes, with the designs shown in figures 1 to 6, makes it possible for the assembly to be mounted with limited means, featuring less resistance for sea transport and improving the dynamic behaviour under floating conditions. For the mounting thereof, fundamentally, it is only necessary to attach a series of tubes with a butt joint, which can be carried out by means of portable welding robots.

For example, each of the driving units 2 or floats and the central dome 7 can be factory assembled, installing all the equipment therein and welding, in each of them, small tube sections from the structures they are going to be attached to. On the other hand, the generating units 1 UGEX watertight units and the rotor 14 blades 15 are manufactured. The third manufacturing block consists of the structural assemblies of the lattice structures 20 and 21 and the guy-wires 22.

When mounted, the whole assembly is in a horizontal position, with the rotors upward and, after performing the floating tests, the device is transported to the place it will operate in by means of a tug.

At the same time, the anchoring system will have been installed at the sea bed with the anchoring elements 33 (piles, suction anchor, gravity bases, etc.) and the anchoring cables 33 attached, at the free ends thereof, to driving units 2 so that they can be accessed. The power supply line (not depicted), which has to be dynamic and be provided with a submergible connector, but dry mounted, will have been installed at the accessible end thereof on the surface. When the device arrives the ends of the anchoring cables 10 are joined to guide cables being pre-rolled in the winches, and the power supply cable is connected, adopting a situation similar to that of a maintenance operation. Disassembling is carried out inversely.

Claims

1. Multi-rotor device with a polygonal structure for the utilization of marine currents, comprising a plurality of modular removable generating units (1) and a plurality of driving units (2) with floating and ballasting features, characterized in that the generating (1) and driving (2) units are supported by a three dimensional structure, consisting of lattice flat frames delimiting a polygonal profile in the sides and vertices of which the generating units and the driving units are provided, in alternate positions and separate to each other; the driving units of which feature enough floating and ballasting capability so as to generate the rotation of the three dimensional structure around a horizontal axis, by means of a ballasting variation of the driving units situated at each side of said horizontal axis.

2. Device according to claim 1 characterized in that the driving units (2) are provided in the vertices (4) of the polygonal profile and the generating units (1) are provided in an intermediate point of the sides of the polygonal profile.

3. Device according to claim 1 characterized in that the generating units (1) are provided in the vertices (4) of the polygonal profile and the driving units (2) are provided in an intermediate point of the profile sides.

4. Device according to claim 1 characterized in that it comprises a central dome (7), situated in the geometrical centre of the polygonal profile, the dome of which is connected to the driving units (2) and/or to the generating units (1) by means of flat lattice structures.

5. Device according to claims 1 and 4 characterized in that the central dome (7) and at least part of the driving units (2) and/or generating units (1) are provided with winches (9), whose anchoring cables (10) attach the device to the sea bed.

6. Device according to claims 1 and 4 characterized in that at least part of the generating units (1) and/or driving units (2) are connected by means of respective cables (11) to a submerged rotating buoy (12) which, in turn, is attached to the sea bed through an anchoring system.

7. Device according to claim 1 characterized in that the three dimensional structure has a hexagonal profile.

8. Device according to claim 1 characterized in that the three dimensional structure has a square profile.