WO2021124361A1

WO2021124361A1 - Marine system for the generation of electric energy from the pitch of floating bodies induced by wave motion

Info

Publication number: WO2021124361A1
Application number: PCT/IT2019/000118
Authority: WO
Inventors: Giuseppe CORONELLA
Original assignee: Fincantieri Oil & Gas S.P.A.
Priority date: 2019-12-18
Filing date: 2019-12-18
Publication date: 2021-06-24
Also published as: EP4077910A1; WO2021124361A8

Abstract

The present invention relates to a marine system (1) for the generation of energy from the pitch of floating bodies induced by the wave motion, comprising: a marine installation (10), which has at least one emerged portion (11) with respect to the sea surface (M) and consists either of a structure firmly fixed to the seabed (F) or of a semi-submersible structure moored to the seabed; one or more WEC devices (20), each of which has a floating hull (21) and is suitable for generating electricity from the pitch motion of its floating hull (21) induced by the wave motion. The floating hull (21) of each of said one or more WEC devices is connected to the emerged portion (11) of said marine installation by means of a respective linkage arm (30), which is movably connected: at a first end portion (31) thereof to the emerged portion (11) of said marine installation (10) by means of a first articulated joint (40) which allows said linkage arm (30) to follow the vertical movements given by the composition of the heave and pitch motions of the floating hull (21) connected thereto; and at a second end portion (32) thereof to said floating hull (21) by means of a second articulated joint (50) which leaves free at least the pitch and yaw motions of said floating hull (21) with respect to said linkage arm (30).

Description

DESCRIPTION

Marine system for the generation of electric energy from the pitch of floating bodies induced by wave motion

SCOPE

[0001]. The subject-matter of the present invention is a marine system for the generation of energy from the pitch of floating bodies induced by wave motion.

[0002]. In particular, the marine system for the generation of energy according to the invention is suitable for the construction of offshore energy parks based on the reuse of disused platforms for the extraction of hydrocarbons.

STATE OF THE ART

[0003]. As is known, the growing need to increase the production of energy from renewable sources has in recent years encouraged the development of devices for the generation of electric energy from wave motion. Such devices are generically identified in the sector by the acronym WEC (Wave Energy Converter).

[0004]. One type of WEC that seems particularly promising is based on the exploitation of the gyroscopic effect of one or more flywheels installed on a floating body. More specifically, the floating body forms an inertial system with the wave motion of the sea. The incident waves induce the pitch motion of the hull and of the flywheel contained within the floating body. The flywheel is connected to an electric generator installed on board the floating body. In turn, the electric generator is connected to the electricity network via umbilical cables for the transfer of the electricity generated.

[0005]. This type of WEC, defined as "inertial system", is described in particular in the International application W02019/111040A1 and the European patent EP2764236B1, to which one should refer for more details. [0006]. Like other types of WECs, inertial system WEC devices must also be moored to the seabed.

[0007]. Mooring a floating body that must be free to pitch in order to produce energy to the seabed poses a number of problems.

[0008]. In general, a mooring ^'system with traditional catenary lines is complex and delicate. It must be designed with sophisticated dynamic simulation software for each individual application as it depends on the particular type of seabed (sandy, rocky, gravelly, etc.), the depth and the state of the sea typical in the installation area.

[0009]. The type of seabed has an impact on the choice of anchorage due to the compactness of the soil and the stresses to which the anchor is subjected. [0010]. The depth has an impact on the total weight of the anchoring system which weighs on the floating body, the elasticity and the damping required. Therefore, the various catenary sections, rope sections, any floating bodies or intermediate ballasts must be studied by means of numerical simulations.

[0011]. The state of the sea is obviously one of the fundamental parameters in the study of the mooring, as it is primarily responsible for the maximum forces that the mooring system will have to withstand.

[0012]. In short, the numerical simulation is performed by imposing as input the stochastic variables of the sea due to the superposition of waves of different periods and heights. The main variables, specific to each zone, are the significant wave height, the wave period and the hundred-year wave condition relating to the most likely maximum wave height during an extreme storm that is likely to occur once every hundred years.

[0013]. The mooring design must first of all withstand the forces imposed by the floating body. In addition to the loads imposed by the wave state on the WEC device, it must also take into account possible wind-induced forces. Another consideration is the compliance of the mooring system, especially with regard to the limitations imposed by the flexibility of the electrical cables and the proximity of any other adjacent EC devices.

[0014]. In general, the conventional mooring types are as follows:

- catenary; - taut elastic;

- tethered surface buoy;

- submerged buoy.

[0015]. There is extensive experience in the use of catenary moorings, including the mooring of semi- submersible oil platforms. For this type of mooring to work effectively, a significant weight per unit of length in the mooring line is required to create an almost horizontal tension on the seabed. Drag-embedment anchors are therefore used to withstand horizontal loads. These moorings require a large area of the seabed.

[0016]. In taut elastic moorings, the synthetic fiber ropes, which are in practice floating in a neutral manner, remain essentially straight and rely on the elasticity of the material to provide the necessary deformability. This function will be used as part of this flexible mooring design. The differences between catenary and taut line moorings may be summarized as follows: "The main difference between a catenary mooring and a taut line mooring is that where the catenary mooring reaches the bottom of the sea horizontally, the taut line mooring reaches the bottom of the sea at a vertical angle. This means that in a taut line mooring the anchoring point must be able to withstand horizontal and vertical forces, whereas in a catenary mooring the anchoring point is only subject to horizontal forces. In a catenary mooring, most of the restoration forces are generated by the weight of the mooring line" (Vryhof Anchors, 2010)

[0017]. In surface buoy ^' moorings, a surface floating structure is used to keep the mooring lines taut, thus reducing the lifting movement. However, this type of mooring operates in the volatile region on the sea surface, being subject to turbulence and the combined action of waves and wind. The buoyancy characteristic of a structure to maintain tension in the mooring line is adapted in this design through the use of a submerged buoy thus avoiding the worst of the surface interaction.

[0018]. Submerged buoy moorings combine aspects of taut elastic and tethered surface buoy moorings. This type of mooring provides tension to the mooring line using a submerged buoy. The buoyancy provided by the buoy is sufficient to keep the floating device neutral in the desired working position.

[0019]. A distinct advantage of this system is that it minimizes the excursion, i.e. it keeps the footprint of the entire system to a minimum. [0020]. Reliability will also be a key feature of any project. This will be achieved by maximizing the life of the mooring eguipment and minimizing costly maintenance operations. [0021]. The final design of a mooring system must also take into account the years of expected life in order to calculate a thickness margin that takes into account corrosion, fatigue stress and wear due to operational or accidental abrasion. [0022]. All the systems described above necessarily require underwater installation operations, normally carried out with the aid of specialized surface means and divers or underwater means.

[0023]. Regardless of the mooring system used, during its operational life the mooring system requires difficult regular underwater inspections and maintenance operations to verify its integrity.

[0024]. The problems related to possible interference between the mooring lines and the submarine electrical cable for transporting the electricity produced by the WEC device should not be overlooked.

[0025]. The above makes the whole process of mooring a WEC device extremely laborious and expensive, not only at the time of installation, but also during its operational life. [0026]. In the (most likely) case that the WEC devices are arranged in rows to form a single marine station (Wave Farm), one may assume a likely scale economy of the mooring. This solution limits, but certainly does not eliminate, most of the difficulties and burdens set out above .

[0027]. Finally, it should be noted that, for a WEC device that bases its electricity generation efficiency on pitch freedom, the constraint imposed by the mooring could be limiting.

[0028]. To date, there are no marine systems for the generation of energy from the pitch of floating bodies induced from wave motion that would allow the aforesaid operational and cost limitations linked to mooring to be overcome, or at least significantly reduced.

PRESENTATION OF THE INVENTION

[0029]. The object of the present invention is to provide a marine system for the generation of energy from the pitch of floating bodies induced by wave motion that allows one or more WEC devices to be moored less onerously in terms of installation and maintenance than traditional solutions.

[0030]. A further object of the present invention is to provide a marine system for the generation of energy from the pitch of floating bodies induced by the wave motion that allows the effects, in particular damping, of mooring on the pitch motion of the WEC device to be reduced.

[0031]. A further object of the present invention is to provide a marine system for the generation of energy from the pitch of floating bodies induced by wave motion that is economically feasible net of the manufacturing costs of the WEC device.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032]. The technical features of the invention, according to the aforesaid objects, are clearly apparent from the contents of the claims provided below and the advantages thereof will become more apparent in the following detailed description, made with reference to the accompanying drawings, which represent one or more purely illustrative and non-limiting embodiments thereof, wherein:

[0033]. - Figure 1 shows an elevation view of a marine system for the generation of energy from the pitch of floating bodies induced by wave motion according to a first preferred embodiment of the invention;

[0034]. - Figure 2 shows a perspective view of a marine system for the generation of energy from the pitch of floating bodies induced by wave motion according to a preferred embodiment of the invention;

[0035]. - Figure 3 shows a plan view of the system of Figure 2;

[0036]. - Figure 4 shows an elevation view of the system in Figure 3 according to the arrow IV shown therein;

[0037]. - Figures 5a, 5b and 5c show the relative movements between a WEC device and the marine mooring installation due to the vertical components of the pitch and heave motion induced by wave motion on the WEC device; [0038]. - Figure 6 shows a plan view of the system of

Figure 4 according to a cross-section plane VI-VI indicated therein;

[0039]. - Figure 7 shows an enlarged view of a detail of

Figure 6 highlighted in the box VII indicated therein and relating to an intermediate support structure for a WEC device on the marine mooring installation; [0040]. - Figure 8 shows an elevation view of the detail in Figure 7 according to the arrow VIII shown therein; [0041]. - Figure 9 shows an enlarged view of a detail of

Figure 8 relating to a fixed arm of the intermediate support structure for a WEC device on the marine mooring installation;

[0042]. - Figure 10 shows an enlarged view of a detail of Figure 7 relating to a fixed arm of the intermediate support structure for a WEC device on the marine mooring installation; [0043]. Figure 11 shows a perspective view of the detail illustrated in Figure 7;

[0044]. - Figure 12 shows an enlarged view of a detail of Figure 8 relating to a movable linkage arm of a WEC device on the marine mooring installation;

[0045]. - Figure 13 shows an enlarged view of a detail in Figure 7 relating to a movable arm connecting a WEC device to the marine mooring installation;

[0046]. - Figure 14 shows an enlarged view of a detail of Figure 13 highlighted in the box XIV indicated therein and relating to a second articulated joint arranged to connect the movable linkage arm and the WEC device;

[0047]. - Figures 15 and 16 show two sectional views of the detail of Figure 14 respectively according to the cross-sectional planes XV-XV and XVI-XVI indicated therein;

[0048]. - Figure 17 shows a side view of the connection structure of a WEC device on the marine mooring installation according to an alternative embodiment of the invention;

[0049]. - Figure 18 shows an enlarged view of a detail of Figure 17 according to the arrow XVIII shown therein, relating to a counterweight system of the movable arm connecting a WEC device to the marine installation;

[0050]. - Figure 19 shows a perspective view of a movable linkage arm and the associated WEC device connected thereto in an alternative embodiment of the invention;

[0051]. - Figures 20 and 21 show respectively a side orthogonal view and a plan view of the movable linkage arm illustrated in Figure 19 according to the two arrows XX and XXI shown therein;

[0052]. - Figure 22 shows an enlarged view, partially transparent, of the detail inserted in the box XXII of Figure 20 and related to a second articulated joint placed between the movable linkage arm and the EC device; and

[0053]. - Figure 23 shows a cross-sectional view of the second articulated joint illustrated in Figure 22 according to a cross-sectional plane XXIII - XXIII shown therein. [0054]. The elements or parts of elements in common between the embodiments described hereinafter will be indicated at the same numerical references.

DETAILED DESCRIPTION

[0055]. The subject-matter of the present invention is a marine system for the generation of energy from the pitch of floating bodies induced by wave motion.

[0056]. The marine system for the generation of energy from the pitch of floating bodies induced by wave motion according to the invention has been indicated collectively at 1 in the accompanying drawings. [0057]. According to a general embodiment of the invention, illustrated for example in Figure 1, the marine system 1 comprises:

[0058]. - a marine installation 10, which has at least one portion 11 emerged above the sea surface; and

[0059]. - one or more WEC (Wave Energy Converter) devices 20, each of which is equipped with a floating hull

21 and is suitable for generating electricity from the pitch motion of its floating hull 21 induced by wave motion.

[0060]. The aforesaid marine installation 10 may consist either of a structure firmly fixed to the seabed F (as shown in the accompanying Figures) or of a semi- submersible structure moored to the seabed.

[0061]. Preferably, the aforesaid marine installation 10 is transparent or substantially transparent to the waves. The marine installation's transparency to the waves is intended to avoid, or at least to contain as much as possible, perturbations on the wave motion due to the presence of the marine installation and which could reduce the energy of the wave motion potentially exploitable by the aforesaid WEC devices 20. In particular, the marine installation 10 is made with a truss structure typical of the platforms firmly fixed to the seabed by means of vertical or subvertical structural posts 12a connected to each other by diagonal cross bars 12b; in the case of a semi-submersible platform, it is typically supported by a variable number of semi-submerged columns that support the emerged zone of the unit by resting on the submerged hulls.

[0062]. In particular, the marine installation 10 may be an offshore platform.

[0063]. Advantageously, the marine installation 10 may be a disused offshore platform, e.g. a disused offshore platform for hydrocarbon extraction or drilling.

[0064]. As will be discussed in greater detail below, the marine system 1 according to the invention is suitable for the construction of offshore energy parks based on the reuse of disused platforms, e.g. platforms for the extraction of hydrocarbons.

[0065]. The aforesaid one or more WEC devices 20 of the marine system 1 are devices suitable for generating electric energy using the gyroscopic effect of one or more flywheels installed on its floating hull.

[0066]. More specifically, the floating hull forms an inertial system with the wave motion of the sea. The incident waves induce the pitch motion of the hull and of the flywheel contained inside the floating body. The flywheel is connected to an electric generator installed on board the floating body. In turn, the electric generator is connected, directly or indirectly, to an electricity distribution network or to an electricity consumer, by means of umbilical cables for the transfer of the electricity generated. [0067]. This type of WEC, defined as "inertial system", is described in particular in the International application W02019/111040A1 and in the European patent EP2764236B1, which are fully incorporated here as a reference and to which we refer for more details on the operation of the WEC device 20.

[0068]. Here we limit ourselves to specifying the following. Each of the aforesaid WEC devices 20 is provided within the floating hull with at least one gyroscope connected to an electric generator. According to the dimensions of the floating hull, the WEC device may also comprise a larger number of gyroscopes, preferably an even number, usually two or four. The frame of the gyroscope, appropriately connected to an electric generator, may rotate around the longitudinal axis of the hull (i.e. the roll axis, perpendicular to the pitch axis) while the rotor (or flywheel) is left free to rotate, preferably under the control of an electric motor. The floating hull, subjected to wave motion, is subject to pitch. The pitch motion then generates a first angular speed, called of pitch. The rotor, or flywheel, has in turn its own angular speed of rotation. The combination of the two angular speeds generates a torque, called gyroscopic torque, which is able to put the gyroscope in oscillation around the roll axis, providing mechanical energy to the generator that will transform it into electricity. As mentioned above, the operation of the WEC device 20 is therefore based on an inertial system with the wave motion.

[0069]. According to the invention, the floating hull 21 of each of said one or more WEC devices 20 is connected to the emerged portion 11 of the aforesaid marine installation 10 by means of a linkage arm 30.

[0070]. As shown in the accompanying Figures, each linkage arm 30 is movably connected at a first end portion 31 thereof to the emerged portion 11 of said marine installation 10 by means of a first articulated joint 40, which allows the linkage arm 30 to follow the vertical movements given by the composition of the heave and pitch motions of the floating hull 21 connected thereto.

[0071]. Moreover, each linkage arm 30 is movably connected at a second end portion 32 thereof to the floating hull 21 via a second articulated joint 50 which leaves at least the pitch and yaw motions of the floating hull 21 free with respect to the linkage arm 30.

[0072]. Due to the invention, in the marine system 1 each of said one or more WEC devices 20 should no longer be moored directly at the seabed F and at the same time is less subject to the damping effects of mooring on its own pitch motions, which are essential for energy generation. [0073]. The solution of the invention makes it possible to moor one or more WEC devices in a much less expensive way from the point of view of installation and maintenance than the traditional solutions currently provided for such WEC devices.

[0074]. In effect, it should be noted that the mooring system of each individual WEC device on the marine installation 10, as it consists of the aforesaid movable linkage arm 30, is always located above the water level. In this way, the need for underwater operations is eliminated. This makes it extremely easy to install, inspect and maintain the mooring system of each individual WEC device.

[0075]. The problems linked to mooring are therefore shifted from the mooring of a plurality of WEC devices to the movable connection of such WEC devices to the marine installation 10. This leads to a significant simplification in terms of design and maintenance of mooring/connection systems. In effect, the structure and the articulated joints of the linkage arms may be designed and manufactured according to established mechanical engineering methods for heavy industrial components and may therefore be sized and manufactured with great reliability. As far as installation and periodic maintenance operations are concerned, machinery and dry work directly from the marine installation 10 are sufficient, without requiring specialized vessels for underwater activities. This avoids the complex procedures associated with the laying of underwater mooring lines and the inspection and maintenance thereof during their operational life. The end result is to transform all the typically complex, dangerous and expensive maritime operations into the activities typical of a land-based industrial system known to be simpler, safer and more economical.

[0076]. This advantageous effect is enhanced in the (preferred) case wherein the marine installation 10 is used as a mooring for a plurality of WEC devices, and in particular in the (particularly preferred) case wherein the marine installation 10 consists of a pre-existing structure, such as a disused offshore platform.

[0077]. Secondly, as already highlighted, the solution of the invention further makes it possible to reduce the effects of mooring on the pitch motion of the WEC device. [0078]. In this respect, it should in effect be noted that, due to the aforesaid two articulated joints 40 and 50, the aforesaid movable linkage arm 30 does not actually affect the pitch motions of the floating hull, thus substantially cancelling the damping impact of the mooring on the functionality of the WEC device 20.

[0079]. In particular, due to the fact that the linkage arm 30 and the respective articulated joints 40 and 50 are arranged substantially always above the water level, the damping effects of the viscosity of the water, which intervene in traditional underwater mooring systems, are eliminated.

[0080]. Finally, in the particularly preferred case wherein a pre-existing structure (such as, for example, a disused platform) is used as a marine installation 10, the marine system 1 is also much more economical than a traditional mooring solution, net of the manufacturing costs of WEC devices. The traditional underwater moorings of the individual WEC devices are, in effect, simply replaced by individual movable linkage arms, which may be constructed and installed much more economically.

[0081]. Advantageously, the linkage arm 30 consists of a rigid structure and is suitably sized to withstand the mechanical stresses that are imposed thereon by the WEC 20, when subject to wave motion, and that the linkage arm must discharge onto the marine installation 10.

[0082]. For example, as illustrated in the accompanying Figures, the linkage arm 30 may have a truss structure. [0083]. In particular, since, due to the two articulated joints 40 and 50, the linkage arm 30:

- is free to follow the vertical movements given by the composition of the heave and pitch motions of the floating hull 21 attached thereto; and

- in turn leaves free at least the pitch and yaw motions of the floating hull 21 connected thereto, the linkage arm 30 should be sized to withstand substantially only the stresses related to blocking surge and sway motions of the WEC device on the waterplane and, if necessary, to withstand also the stresses related to blocking roll motions.

[0084]. Preferably, the second articulated joint 50 may be configured to also leave the roll motions of the floating hull 21 free with respect to the linkage arm 30, so as to further reduce the stresses that the linkage arm 30 has to withstand.

[0085]. According to the embodiment illustrated in the accompanying Figures, each linkage arm 30 may consist of a beam which extends along a single longitudinal axis of development B-B between the first end portion 31 and the second end portion 32.

[0086]. According to alternative embodiments not illustrated in the accompanying figures, the linkage arm 30 ^'may also have different configurations with respect to the beam, dictated by specific requirements for connecting to the marine installation. For example, the linkage arm 30 may have a V configuration, wherein the vertex of the V defines the second end portion 32, while the two free ends of the two branches of the V define two first end portions 31. In this case, each of these two first end portions is connected to the marine installation by means of a respective first articulated joint. These two first articulated joints define axes of rotation aligned with each other to allow the linkage arm to follow the vertical motions given by the composition of the heave and pitch motions of the floating hull 21 connected thereto at the vertex of the V.

[0087]. The linkage arm 30 may be connected to the marine installation 10:

- directly, or

- indirectly, at an intermediate support structure 70 which in turn is fixed to the marine installation 10, as illustrated in the accompanying Figures, and supports the first articulated joint 40.

[0088]. In particular, the intermediate support structure 70 may have the function of freeing the positioning and sizing of the linkage arms 30 from the configuration of the marine installation 10. For example, the intermediate support structure may allow the distance of the WEC device from the marine installation 10 to be increased without requiring a corresponding oversizing of the respective linkage arm 30.

[0089]. The insertion of an intermediate support structure 70 into the marine system 1 is also particularly useful for adapting a disused offshore platform as a marine installation 10 for the marine system 1.

[0090]. As will be shown below, in the preferred case wherein the marine system 1 comprises a plurality of WEC devices 20, the intermediate support structure 70 may be configured as a connecting structure between the linkage arms in order to balance between them the stresses that the individual linkage arms transmit to the marine installation 1.

[0091]. Preferably, as shown in the accompanying Figures, and in particular in Figures 3 and 4, the linkage arm 30 is connected to the floating hull 21 of the respective WEC device near a stern or bow end of the floating hull 21. In this way, it gives the WEC device the ability to self-orient with respect to the waves, i.e. the ability to arrange itself independently with its stern-bow axis orthogonal to the main front of the wave motion, so as to capture the maximum energy content thereby produced. [0092]. Preferably, the aforesaid first articulated joint 40 consists of at least one cylindrical hinge with the axis lying preferably on a substantially horizontal plane (i.e. parallel to the surface of the flat sea). In this way, the aforesaid first articulated joint 40 allows the linkage arm 30 to follow only the vertical movements given by the composition of the heave and pitch motions of the floating hull 21 connected thereto, and to completely block the horizontal motions, i.e. the surge and sway motions of the WEC device 20.

[0093]. In particular, as illustrated in the accompanying Figures, and in particular in Figures 10 and 11, the first articulated joint 40 may consist of two cylindrical hinges having axes aligned with each other and horizontal and connecting the first end 31 of the linkage arm 30 directly to the marine installation 10, or indirectly thereto, at an already cited intermediate support structure 70.

[0094]. In accordance with an embodiment not illustrated in the accompanying Figures, the aforesaid second articulated joint 50 may consist of a spherical hinge. This hinge blocks all the translations along the three axes, leaving the rotations around the three axes free. The spherical hinge binds the translative motions of the WEC device (heave, surge and sway) to those of the movable linkage arm 30, while leaving the rotational motions of the WEC device (pitch, yaw and roll) free.

[0095]. In accordance with an alternative embodiment, illustrated in the accompanying Figures, the second articulated joint 50 may consist of a cardan joint 51 and a rotational decoupling joint 52.

[0096]. Similar to a spherical hinge, this assembly also blocks all the translations along the three axes, leaving the rotations around the three axes free. The assembly of the cardan joint 51 and the rotational decoupling joint 52 binds the translative motions of the WEC device (heave, surge and sway) to those of the movable linkage arm 30, while leaving the rotational motions of the WEC device (pitch, yaw and roll) free.

[0097]. More specifically, as illustrated in particular in Figures 14, 15 and 16, the aforesaid cardan joint 51 consists of a four-arm cross with two by two orthogonal arms and a first fork 51a and a second fork 51b, each of which engages two opposite arms of the cross rotationally, thus defining a turning pair. The two turning pairs define respectively a first cardan axis a-a and a second cardan axis b-b orthogonal to each other. Each of these two forks 51a and 51b has its own support body 51a' and 51b', which defines a support axis c-c and d-d orthogonal to the cardan axis defined by the respective fork. The cardan joint 51 is connected (directly or indirectly) to the floating hull 21 of the WEC device and to the linkage arm 30 at the support body 51a' or 51b' respectively of the first fork 51a and the second fork 51b. The aforesaid rotational decoupling joint 52 is kinematically associated with the support body 51a', 51b' of one of the two forks 51a, 51b of said cardan joint 51, around the respective support axis c-c or d-d. The rotational decoupling joint 52 may therefore be interposed between the cardan joint 51 and the linkage arm 30 or between the cardan joint 51 and the floating hull 21 of the WEC device 20.

[0098]. In accordance with a preferred embodiment illustrated in the accompanying Figures, the rotational decoupling joint 52 is interposed between the cardan joint 51 and the linkage arm 30.

[0099]. More specifically, as illustrated in particular in Figures 14-15 and 22-23, the cardan joint 51 has:

[00100]. - the first fork 51a rigidly fixed to the floating hull (21) at its support body 51a' arranged with the respective support axis c-c orthogonal to the waterplane of the floating hull 21; and

[00101]. - the second fork 51b rotationally connected to the linkage arm 30 around the support axis d-d of its own support body 51b' by means of said rotational decoupling joint 52.

[00102]. In particular, the aforesaid first fork 51a is oriented so that the cardan axis a-a thereby defined is parallel to the waterplane of the floating hull 21 and transverse to the longitudinal axis X of the floating hull 21. This ensures the fixed alignment of one of the cardan axes along the pitch axis. Thus, the pitch motions, which are predominant in the operating life of the WEC device, take place by involving only one cardan axis B-B and not through the composition of overlapping rotations of the cardan joint 51 and the rotational decoupling joint 52. Thus, the mechanical stresses, particularly fatigue stress, on the two joints 51 and 52 are reduced.

[00103]. The yaw movements, important for allowing the orientation of the WEC device with respect to the waves, are carried out through the composition of overlapping rotations of the two joints 51 and 52. The yaw movements are less frequent than the pitch movements, however, and generally occur in weather conditions that are expected to be more favorable. In effect, the wave motion is produced by a progressive increase in the wind which normally precedes it. The wind gradually increases rising from low intensity and aligns the WEC devices 20 with the respective floating hulls 21 with the still relatively calm sea in the direction of the next wave motion which will gradually rise to follow. In this way the alignment of the WEC devices takes place when the vertical pitch and heave motions are almost zero and the second articulated joint 50 must withstand only the mechanical forces resulting from the yaw movement.

[00104]. In the case (not preferred and not illustrated in the accompanying figures) wherein it is preferred that the yaw movements of the WEC device occur involving only one axis of the second articulated joint, the rotational decoupling joint 52 is interposed between the cardan joint 51 and the floating hull 21 and is arranged with the rotation axis G-G orthogonal to the waterplane of the floating hull 21. In this case, the pitch,movements are made through the composition of overlapping rotations of the two joints 51 and 52.

[00105]. Preferably, the rotational decoupling joint 52 comprises a cup-shaped housing body 53, which is rigidly attached either to the second end 32 of said linkage arm 30 (as illustrated in particular in Figures 14-15 and in Figures 22-23), or to the floating hull. Inside the cup^¬ shaped body 53 one or more bearings 54 are arranged, suitable to support rotationally the support body 51a' or Sib' of one of the two forks 51a or 51b, keeping the support axis c-c or d-d aligned with the axis of the cupshaped housing body 53, which defines the rotation axis G- G of the joint 52.

[00106]. Preferably, as illustrated in Figures 19, 20 and 21, in the case wherein the rotational decoupling joint 52 is interposed between the cardan joint 51 and the linkage arm 30, the rotational decoupling joint 52 is connected to the linkage arm 30 in such a way that the cup-shaped housing body 53 is axially angled with respect to a longitudinal axis B-B of said linkage arm 30. This reduces the width of the angle of misalignment between the yaw axis and the rotation axis G-G of the joint 52. This promotes a quicker response of the cardan joint 51 to the yaw movements of the floating hull 21 of the WEC device. [00107]. Advantageously, as illustrated in Figures 17 and 18, the linkage arm 30 may be fitted with a counterweight 33, which is arranged at the first end portion 31, to balance around the aforesaid first articulated joint 40 at least part of the weight of the linkage arm 30, thus preventing it from discharging onto the floating hull 21. Thus, the possible damping effect of the pitch motions by the linkage arm 30 is cancelled or at least significantly attenuated. Thus, the energy absorption of the wave motion by the movements of the linkage arm is prevented, or at least significantly reduced.

[00108]. The marine system 1 for the generation of energy from the pitch of floating bodies induced by wave motion may be equipped with a single WEC device 20, as illustrated in Figure 1. [00109]. Preferably, as illustrated in Figure 2 and as already highlighted, the marine system 1 comprises a plurality of WEC devices 20, thus configuring collectively a Wave Energy Farm. As already mentioned, this configuration enhances the advantages of the invention, in particular when a disused offshore platform is used as a marine installation to which each of said WEC devices may be connected via a respective linkage arm.

[00110]. According to the preferred embodiment shown in Figures 2, 3 and 4, the WEC devices 20 are spatially distributed around the marine installation 10 of the marine system 1 and are each connected thereto via a respective linkage arm 30.

[00111]. Preferably, the linkage arms 30 of said plurality of WEC devices 20 are all connected each through their first articulated joints 40 to a single intermediate support structure 70 which is rigidly fixed to the marine installation 10 and develops in a closed loop around said marine installation 10. [00112]. Advantageously, configuring the intermediate support structure 70 as a closed-loop (preferably polygonal in shape) makes it possible to balance at least part of the forces (in particular shear forces) transmitted by the movable linkage arms to the respective first articulated joints 40, to the advantage of the static and dynamic stability of the entire construction. [00113]. In particular, the aforesaid closed-loop intermediate support structure 70 is fixed to the emerged portion 11 of the marine installation 10 by means of:

- a plurality of fixed arms 71, preferably extending over the plane of said intermediate support structure 70; and

- a plurality of lifting stays 72.

[00114]. Preferably, as illustrated in Figure 3, the fixed arms 71 and the reinforcement stays 72 are at least of the same number as the movable linkage arms 30 and connect the intermediate support structure 70 to the marine installation at least at each of said first articulated joints 40, i.e. at least at the points of greatest mechanical stress. It is also possible to provide additional fixed arms and stays to support the intermediate structure in different positions from those of the first articulated joints 40.

[00115]. As illustrated for example in Figures 2, 3 and

4, the marine installation 10 of the marine system 1 may consist of a disused offshore platform.

[00116]. More specifically, this offshore platform comprises a bearing structure 12 which extends vertically from the seabed until it emerges from the sea surface with the emerged portion 11 thereof. In particular, this bearing structure 12 may consist of a truss comprising posts 12a connected to each other by diagonal cross bars 12b. Generally, this bearing structure 12 supports one or more decks 13 at the top, which in particular may be arranged on several planes.

[00117]. In the marine installation 1 consisting of this offshore platform, the closed loop intermediate support structure 70 is arranged below said one or more decks 13 so as not to require any dismantling, even partial, of the decks.

[00118] . The closed-loop intermediate support structure 70 is connected to the emerged portion 11 of said bearing structure 12 by means of the aforesaid fixed arms 71 at a first height and via the stays 72 at a second height higher than the first. In particular, the stays 72 may be anchored to one or more of the aforesaid decks 13.

[00119]. In particular, the fixed arms 71 may consist of beams with a truss structure.

[00120]. Advantageously, the aforesaid fixed arms 71 may be anchored to the aforesaid bearing structure at the posts 12a of the truss by means of anchor clamps 12c. The clamps must be designed and sized on a case-by-case basis to suit the particular central structure, which may have more varied dimensions, and the structural loads resulting from the particular geometric and physical configuration of the marine system 1. These anchor clamps 12c may be configured to support also two or more of said fixed arms 71. The use of these anchor clamps 12c facilitates the connection of the intermediate structure 70 to offshore platforms equipped with bearing structures comprising posts or column structures.

[00121]. Advantageously, the marine system 1 for generating energy from the pitch of floating bodies induced by wave motion comprises at least one power line (not shown in the accompanying Figures) suitable for interconnecting the marine system 1 to an electrical distribution network or at least one electricity consumer, so as to make the power generated by said one or more WEC devices 20 available.

[00122]. Preferably, this power line is shared by all WEC devices 20 in the marine system 1 so as to use a single underwater umbilical cable. However, it is also possible to provide two or more independent underwater power lines. [00123]. Preferably, as illustrated in Figures 19 and 20, each of said one or more WEC devices 20 is electrically connectable to said at least one power line through an electrical cable 60 extending from the WEC device to the marine installation 10 passing through the respective linkage arm 30. This avoids having to equip each WEC device 20 with an independent underwater electricity transmission cable thereof, with advantages in both the installation and maintenance stages.

[00124]. Advantageously, as shown in Figures 22 and 23, the aforesaid electrical cable 60 passes from the WEC device 20 to the linkage arm 30 through an electric swivel joint 61 associated with the rotational decoupling joint 52 of the second articulated joint 50. This prevents the rotations due to yaw motions from causing the electrical cable 60 to twist on itself.

[00125]. In particular, the electrical cable 60 is fed into the rotational decoupling joint 52 following a generous amplitude curve to prevent roll, pitch and heave movements from damaging the same electrical cable.

[00126]. In this way it is possible to disconnect the electrical cable 60 from all the relative motions between the WEC device and the linkage arm 30 avoiding abrasions, twisting, bending and fatigue damages.

[00127]. The electrical cable 60 may only be used for the transfer of electricity, or also as a line for the passage of control and command signals of the on-board instruments of the WEC device 20. In particular, all the control and automation channels necessary for the management of WEC devices may run on optical fibers incorporated in the aforesaid electrical cable 60.

[00128]. Preferably, due to the proximity of the WEC devices to the marine installation 10 (less than 50 m), the transfer of controls and commands may alternatively be performed by radio between a single WEC device and a substation arranged on board the marine installation 10 and from there to a control center on shore via underwater cable together with the energy produced. In this way it is possible to simplify the design of the electric swivel joint 61, which may be configured only for the passage of the electrical cable 60 used only for the transfer of electricity.

[00129]. The WEC devices 20 may be advantageously equipped on board with all the instruments and equipment (converters, rectifiers, etc.) necessary for the processing of the electricity generated. In this case, the electricity generated by the various WEC devices is simply transferred to the aforesaid power line without any intermediate transformations.

[00130]. Alternatively, the marine system 1 may comprise on board of the marine installation 10 an electrical station (not illustrated in the accompanying Figures) to which all the WEC devices 20 are connected and which carries out all the operations necessary for processing the electricity generated by the individual WEC devices. In this way, the WEC devices 20 may lack at least part of the electricity transformation equipment. This leads to cost savings both in the purchase and in the installation and maintenance of WEC devices. Moreover, the larger components normally have a greater electrical efficiency.

* * *

[00131]. The invention provides numerous advantages, some of which have already been highlighted above.

[00132]. The marine system 1 for the generation of energy from the pitch of floating bodies induced from wave motion according to the invention allows one or more WEC devices to be moored less expensively in terms of installation and maintenance than the traditional solutions available. [00133]. The marine system 1 according to the invention makes it possible to reduce the effects of mooring on the pitch motion of each individual WEC device, thus avoiding negative effects on the functionality of the WEC device and on the efficiency of energy generation.

[00134]. The marine system 1 according to the invention is also economically feasible net of the manufacturing costs of the WEC devices. This applies in particular in the (preferred) case wherein the marine installation 10 is used as a mooring for a plurality of WEC devices, and in particular in the (particularly preferred) case wherein the marine installation 10 consists of a pre-existing structure, such as a disused offshore platform.

[00135]. In particular, the marine system 1 for the generation of energy according to the invention is suitable for the construction of offshore energy parks based on the reuse of disused platforms for the extraction of hydrocarbons.

[00136]. The invention thus conceived therefore achieves the foregoing objects.

Claims

1. A marine system (1) for the generation of energy from the pitch of floating bodies induced by wave motion, comprising:

- a marine installation (10), which has at least one emerged portion (11) with respect to the sea surface (M) and consists either of a structure firmly fixed to the seabed (F) or of a semi-submersible structure moored to the seabed;

- one or more WEC devices (20), each of which is equipped with a floating hull (21) and is suitable for generating electricity from the pitch motion of its floating hull (21) induced by the wave motion, characterized in that the floating hull (21) of each of said one or more WEC devices is connected to the emerged portion (11) of said marine installation by means of a respective linkage arm (30), which is movably connected:

- at a first end portion (31) thereof to the emerged portion (11) of said marine installation (10) by means of a first articulated joint (40), which allows said linkage arm (30) to follow the vertical movements given by the composition of the heave and pitch motions of the floating hull (21) connected thereto; and

- at a second end portion (32) thereof to said floating hull (21) by means of a second articulated joint (50) which leaves at least the pitch and yaw motions of said floating hull (21) free with respect to said linkage arm (30).

2. A marine system according to claim 1, wherein said second articulated joint (50) is configured to leave free also the roll motions of said floating hull (21) with respect to said linkage arm (30).

3. A marine system according to claim 1 or 2, wherein said linkage arm (30) is connected to said floating hull (21) near a stern or bow end of said floating hull (21).

4. A marine system according to any one of the preceding claims, wherein said first articulated joint (40) consists of at least one cylindrical hinge with axis lying preferably on a substantially horizontal plane.

5. A marine system according to any one of the preceding claims, wherein said second articulated joint (50) consists of a spherical hinge.

6. A marine system according to any one of claims 1 to 4, wherein said second articulated joint (50) consists of the assembly of:

- a cardan joint (51) and

- a rotational decoupling joint (52).

7. A marine system according to claim 6, wherein said cardan joint (51) comprises two turning pairs defining respectively a first cardan axis (a-a) and a second cardan axis (b-b) orthogonal to each other, said two turning pairs being supported respectively by a first fork (51a) and a second fork (51b), each of said two forks (51a; 51b) having its own support body (51a', 51b') which defines a support axis (c-c; d-d) orthogonal to the cardan axis defined by the fork, and wherein said rotational decoupling joint (52) is kinematically associated with the support body (51a', 51b') of one of the two forks (51a, 51b) of said cardan joint (51).

8. A marine system according to claim 7, wherein said cardan joint (51) has:

- the first fork (51a) rigidly fixed to the floating hull (21) at the support body (51a') thereof arranged with the respective support axis (c-c) orthogonal to the waterplane of the floating hull (21); and

- the second fork (51b) rotationally connected to the linkage arm (30) around the support axis (d-d) of its support body (51b') by means of said rotational decoupling joint (52).

9. A marine system according to claim 8, wherein said first fork (51a) is oriented so that the cardan axis (a-a) thereby defined is parallel to the waterplane of the floating hull (21) and transverse to the longitudinal axis (X) of the floating hull (21).

10. A marine system according to claim 8 or 9, wherein said rotational decoupling joint (52) comprises a cup shaped housing body (53) rigidly fixed to the second end (32) of said linkage arm (30).

11. A marine system according to claim 10, wherein said cup-shaped housing body (53) is axially angled with respect to a longitudinal axis (B-B) of said linkage arm (30).

12 . A marine system according to any one of the preceding claims, wherein said linkage arm (30) is equipped with a counterweight (33) which is arranged at the first end portion (31) of said linkage arm (30) to balance around said first articulated joint (40) at least part of the weight of said linkage arm (30).

13. A marine system according to any one of the preceding claims, wherein said linkage arm (30) has a truss structure.

14. A marine system according to any one of the preceding claims, comprising at least one power line suitable to interconnect said marine system (1) to an electricity distribution network or to an electricity consumer, wherein each of said one or more WEC device(s) (20) is electrically connectable to said at least one power line by means of an electrical·cable (60) extending from said WEC device to said marine installation (10) passing through the respective linkage arm (30).

15. A marine system according to any one of claims 6 to 11 and claim 14, wherein said electrical cable (60) passes from said WEC device (20) to said linkage arm (30) through an electric swivel joint (61) associated with the rotational decoupling joint (52) of the second articulated joint (50).

16. A marine system according to any one of the preceding claims, wherein the linkage arm (30) is connected to said installation (10) by means of an intermediate support structure (70), which is rigidly fixed to said installation (10).

17. A marine system according to any one of the preceding claims, comprising a plurality of said WEC devices (20) which are spatially distributed around said marine installation (10) and are each connected thereto via a linkage arm (30) thereof.

18. A marine system according to claim 17, wherein the linkage arms (30) of said plurality of WEC devices (20) are all connected each through their first articulated joint (40) to a single intermediate support structure (70) which is rigidly fixed to the marine installation (10) and develops in a closed loop around said marine installation (10).

19. A marine system according to claim 18, wherein said intermediate support structure (70) is fixed to the emerged portion (11) of the marine installation (10) by means of:

- a plurality of fixed arms (71), preferably extending over the plane of said intermediate support structure

(70); and

- a plurality of lifting stays (72), wherein preferably the fixed arms (71) and the reinforcement stays (72) are at least of the same number as the movable linkage arms (30) and connect said intermediate support structure (70) to the marine installation at least at each of said first articulated joints (30).

20. A marine system according to any one of the preceding claims, wherein said marine installation (10) is transparent to the waves.

21. A marine system according to any one of the preceding claims, wherein said marine installation (10) is a disused platform, preferably an offshore platform for the extraction of hydrocarbons.