Ocean-going ship with active stability

Abstract

A marine structure with improved stability including maneuvering and navigation apparatus and including at least one aerial platform; at least three adjustable-height masts; at least one underwater float equipped with at least one lateral thruster and at least one longitudinal thruster, the platform being lashed to the float(s) by the masts; static ballasting apparatus inside the float(s); servo-controlled dynamic ballasting apparatus located inside the masts; and position and trim control apparatus including at least one sensor and at least one servo-control apparatus for the dynamic ballasting apparatus in order to control, in real time, the position and stability of the marine structure based on swell and wind.

Description

TECHNICAL FIELD

[0001] The invention relates to the field of maritime mobility, in particular support vessels and offshore logistics bases, more specifically vessels dedicated to the maintenance and servicing of floating supports, such as offshore wind farms. The invention is applicable in many maritime fields.PRIOR ART

[0002] A SWATH (Small Waterplane Area Twin Hull) is a catamaran vessel with a small waterline area. This principle was invented by Canadian Frederick G. Creed in 1938. A SWATH is a motorized vessel with two hulls, each of which is deeply submerged. The central platform is connected to the hulls by thin joints at the waterline. The aim is to improve seakeeping in bad weather, especially compared with the conventional catamaran.

[0003] Ballasting is known to be used to stabilize vessels, particularly large ones. Ballasting generally involves loading seawater into tanks, also known as ballasts. This type of ballasting is referred to hereinafter as slow or static ballasting.

[0004] Document DE10336547 describes a vessel comprising a SWATH-type underwater hull comprising a ballast system.

[0005] Patent EP2511168 describes a vessel with a SWATH underwater hull and a static ballast system. Some maintenance vessel projects, such as the “Windkeeper” type, feature ballast systems in the floats (without real-time servo-control) to avoid the effects of swell, but the relative stability of this vessel is compromised as soon as the swell exceeds two or three meters in amplitude.

[0006] Patent US8689720 describes a semi-submersible monohull vessel for retrieving or deploying offshore equipment, comprising a static ballast system in the form of water tanks in the lower part of the hull and in the columns connecting the hull to the platform.

[0007] However, the vessels described do not allow active navigation and stabilization in real time, freeing them from the influence of wind and waves, so that they can navigate and remain at sea in all weather with optimum safety and comfort, particularly in rough seas with waves that can reach heights of over 8 meters.

[0008] There is therefore a need for floating, ballasted marine structures equipped with maneuvering and navigational aids, offering enhanced stability depending on sea conditions and conditions of use, and enabling safe maintenance at sea.SUMMARY OF THE INVENTION

[0009] The invention overcomes the drawbacks of prior art solutions. The solution provided by the present invention is based in particular on a particular geometry of the marine structure combined with a double system of static and dynamic ballasting, making it virtually insensitive to the state of the sea and increasing the stability of said structure.

[0010] To this end, the invention relates to a marine structure with improved stability comprising maneuvering and navigation means and comprising:

[0011] at least one aerial platform (1);

[0012] at least three adjustable-height masts (2);

[0013] at least one underwater float (3) equipped with at least one lateral thruster (4) and at least one longitudinal thruster (5), said platform being lashed to said float(s) by means of said masts;

[0014] static ballasting means inside said float(s);

[0015] servo-controlled dynamic ballasting means located inside said masts;

[0016] position and trim control means comprising at least one sensor and at least one servo-control means for said dynamic ballasting means in order to control, in real time, the position and stability of said marine structure based on swell and wind.

[0017] The marine structure according to the invention may comprise at least two floats, preferably three floats, and at least one profiled crossbeam (6) connecting said floats transversely.

[0018] At least one sensor may provide at least one direct physical measurement of the platform's attitude or height relative to the water surface, or of the structure's absolute or relative position.

[0019] Said dynamic ballasting means may be constituted of at least one air-vacuum or air-filled cylinder (13) inside each mast, each of said cylinders being connected to water injection and ejection means (14).

[0020] Said static ballasting means may be constituted of at least one ballast tank (15) inside each float.

[0021] The marine structure according to the invention may comprise at least one DP2-type servo-control means in position and heading, without anchoring, allowing the platform to maintain itself in a fixed position and to free itself from the influence of wind and waves, and a servo-control means in altitude, pitch and roll enabling it to maintain a substantially zero attitude.

[0022] The marine structure according to the invention may comprise electric motors to ensure propulsion as well as position and heading control.

[0023] The marine structure according to the invention may comprise autonomous electricity production means selected from wind turbines, photovoltaic panels, aeroturbines and energy storage means.

[0024] The marine structure according to the invention may comprise electrical power generation means, allowing the longitudinal and lateral thruster(s) of said float(s) to be at least partially electrically powered.

[0025] The marine structure according to the invention may comprise at least one nuclear fuel generator.

[0026] The marine structure according to the invention may further comprise sail propulsion means.

[0027] The aerial platform may be aerodynamically shaped to minimize the drag generated by absolute and relative wind, and can be much thinner than its length to limit its frontal area and windage.

[0028] The marine structure according to the invention may comprise means for adjusting the height of the platform with respect to the float(s).

[0029] The invention also relates to the use of the marine structure according to any of the variants described for the handling or maintenance of equipment on the open sea.LIST OF FIGURES

[0030] Further features and advantages of the device according to the invention will become apparent from the following description of non-limiting examples of embodiments, with reference to the appended figures described below.

[0031] FIG. 1 shows a 3D view of a marine structure according to the invention.

[0032] FIG. 2 shows a profile view of a marine structure according to the invention.

[0033] FIG. 3 shows a 3D view of a marine structure according to the invention, of modular design and wherein the base comprises three floats.DESCRIPTION OF THE EMBODIMENTS

[0034] In the rest of the text, “draft” refers to the height of the submerged part of a vessel or marine structure, which varies based on the load carried. It corresponds to the vertical distance between the waterline and the lowest point of the hull.

[0035] The trim of a vessel or marine structure is the ratio of the difference between the aft and forward drafts of a vessel or marine structure to its length. The trim reflects the longitudinal inclination of the vessel or marine structure, and determines its smooth operation. A vessel has equal draft, or no difference draft, when its forward and aft draft are the same: no trim.

[0036] “Static ballast” means a slow-moving ballast system in the form of seawater tanks distributed throughout the hull of the marine structure, in the case of the present invention in the floats at the bow and stern of each float.

[0037] “Dynamic ballast” is a ballast system with near-instantaneous volume variation, enabling it to compensate for movements generated by the sea, wind and shifting loads in real time.

[0038] The invention relates to a ballasted marine structure comprising an aerial part, said structure being provided with navigation and maneuvering means. The movements of this marine structure are similar to those of a vessel. In particular, the marine structure according to the invention can navigate, maneuver and position itself precisely on the open sea (or high sea) in all types of weather, offering great stability, increased safety and comfort for its passengers.

[0039] The marine structure according to the invention comprises both, one or more submerged floats equipped with remote-controlled ballasts, and a superstructure or aerial platform rigidly attached to said floats by means of sturdy, streamlined watertight masts. The aerial superstructure (or upper aerial part) can take the form of a platform, structure or nacelle, depending on the application.

[0040] The design of the marine structure according to the invention, comprising one or more submerged floats, makes it possible firstly to extract the buoyancy and lift zone of the vessel from the turbulent zone of the surrounding elements (sea, wind) by submerging it at depth. In particular, the invention makes it possible to dissociate the buoyancy zone from the living zone by separating them on either side of the turbulent surface zone.

[0041] In the remainder of the description, the marine structure according to the invention is a structure comprising two floats (FIGS. 1 and 2), but it would not be outside the scope of the invention to increase or decrease the number of floats.

[0042] The present invention can be used with one or more floats. FIG. 3 shows a three-float structure.

[0043] With most of the volume of the upper aerial part (platform) positioned several meters above the water's surface, and the buoyancy equipment (floats) positioned several meters below the surface, the entire marine structure is intrinsically insensitive to sea surface movements. In addition, the emerged part of the masts advantageously represents 50% of their total length. For a platform resting on 20 m masts, the submerged length and the emerged length are each advantageously 10 m above the average water surface level, making the aerial part relatively insensitive to waves of up to 10 m from trough to crest. The height of the aerial section can be adjusted at any time by means of quick ballasts (dynamic ballasts), whose equilibrium position can be controlled and set in real time based on the navigation, safety or comfort conditions required.

[0044] The marine structure according to the invention comprises static ballasting means (also called static ballasts) distributed inside the float(s) and servo-controlled dynamic ballasting means (also called dynamic ballasts) distributed inside the masts.

[0045] In one embodiment, seawater tanks distributed in the floats at the front and rear of each float serve as static or slow ballast, while dynamic ballast tanks in the connecting masts allow the trim and altitude of the platform to be adjusted in real time, to compensate for movements generated by the sea, as well as longitudinal and transverse load displacements on the structure.

[0046] The underwater floats are advantageously equipped at their ends with longitudinal and transverse thrusters, allowing the vessel to be maneuvered with great efficiency, longitudinally, transversely and rotationally.

[0047] The active stability of the entire marine structure, owing in particular to the dynamic ballast tanks and the servo-control system, ensures a high level of comfort on board and optimum safety for the personnel and equipment carried.

[0048] This ability to cope calmly with heavy and rough seas increases the range of use and intervention of the marine structure according to the invention, whatever its end use.

[0049] Preferably, the aerodynamic shape of the aerial part also minimizes the drag generated by absolute and relative wind, and therefore the energy required to move it or keep it in position during strong wind conditions. The geometry of the marine structure according to the invention thus advantageously reduces the frontal area of the aerial or emerged part (comprising the emerged part of the masts and the platform). In the present invention, aerodynamic shape means that the shape of the aerial part is such that the air only slightly opposes its movement; in particular, the platform has a flattened, rounded shape at its ends to limit its frontal surface and its exposure to the wind. This optimizes the flow of air over its surfaces.

[0050] In one embodiment, the support masts of the platform allow hybrid sail propulsion.

[0051] The aerial platform rests via at least three masts (e.g. four masts) on a base comprising at least one submerged float (e.g. two floats). The submersion depth of the float(s), and therefore the height of the platform from the water surface, can be adjusted to suit sea conditions and requirements, such as docking or securing the platform to the float or wind turbine tower in the case of offshore wind turbines.

[0052] For greater flexibility, e.g. to reduce draft and lower the center of gravity in port, the platform height can also be adjusted with respect to the floats. The marine structure according to the invention can comprise means for adjusting the height of the platform on the masts. These adjustment means allow the platform to move up or down with respect to the floats.

[0053] In one embodiment, the adjustment means comprise a mechanism consisting of a vertical rack and pinion system on the masts. Apart from the phases of raising and lowering the platform on the racks, the mechanism can be completely locked to guarantee the rigidity and safety of the assembly.

[0054] The position and attitude of the marine structure according to the invention are permanently controlled by a servo-control system to guarantee the stability of the platform in all conditions, whether in rough sea conditions or to compensate for load transfers during handling or wind-generated forces. The servo-control system guarantees anchorage-free position and heading maintenance, whatever the wind direction in relation to the platform axis, as well as permanent stability in altitude, pitch and roll. The complete system is based on a passive safety approach: the platform is stable by design and returns to a stable state in the event of total system failure. The servo system includes several degraded modes, guaranteeing safety at all levels.

[0055] The immediate-response servo-controlled dynamic ballast technology according to the invention allows active stability of the marine structure, making it suitable for marine structures of all sizes and loads.Applications

[0056] In particular, the invention can be applied to all sectors requiring a stabilized means of movement and / or a stabilized platform at sea, such as platforms for scientific exploration and data collection, or passenger transport under optimum conditions, or even platforms for air logistics deployment (transport, maintenance, helicopter take-off and landing, or take-off and recovery of stratospheric vehicles and spacecraft).

[0057] Without limitation, the vessel according to the invention can be used and adapted for multiple uses, by adjusting the dimensions and on-board equipment: SOV (Service Operations Vessel) chosen from offshore service vessels, cargo and personnel transport, offshore living quarters, surveillance and intervention vessel, autonomous vessel, helideck, diving and underwater exploration base, rescue vessel, pollution control vessel, vessel or base for deployment and recovery of underwater drones and remotely operated vehicles (ROV), marine aquaculture base, marine hospital, weather station, military vessel, solar-powered eco Yacht, cruise ship, groundable residential vessel at low tide, amphibious vessel, refloating crane vessel, etc.

[0058] The ratio between the length and width of the vessel according to the invention is not fixed and is not a limiting factor. Typically, the invention can be applied to vessels with lengths of between 10 and 200 meters, and widths of between 4 and 100 meters.

[0059] Similarly, the ratio between the width and height of the vessel of the invention is not a limiting factor. Depending on the requirements and specifications for each possible use and destination, mast height and overall vessel height can be defined primarily with the aim of ensuring, on the one hand, reduced sensitivity to sea conditions, and on the other hand, stability (in the sense of possible overturning) through all the conditions defined in the specifications. Typically, the invention relates to vessels with mast heights ranging from 2 to 40 meters. Smaller masts can be used on coastal vessels.

[0060] For certain applications of the invention, in particular those requiring increased displacement speed, the shape of the submerged floats can vary according to the displacement speed of the vessel: with a view to reducing drag, the specific design of the profiled submerged floats allows the steering system to reduce the frontal surface area of the floats by varying their volume. The resulting reduction in buoyancy is advantageously offset in displacement by the lift generated by the horizontal control surfaces provided for this purpose.

[0061] The architecture of the marine structure according to the invention, which is similar in principle and in its two-float design to a SWATH underwater hull, offers good stability in difficult sea conditions.

[0062] The base of the marine structure according to the invention advantageously comprises at least one, or even two profiled crossbeams connecting the floats. Compared with conventional underwater hulls or architectures, the underwater hull technique with reduced waterline surface reduces wave sensitivity and offers good seakeeping. The solution provided by the present invention consists in positioning the floats lower below the surface in a stable layer of water, and this position is adjusted by ballasting and by orienting the profiled crossbeams according to the sea state, both when sailing and when the vessel is stationary.

[0063] Preferably, two control systems are used:

[0064] A DP2-type servo-control (in reference to IMO circular: MSC.1 / Circ.1580—Guidelines for vessels and units with dynamic positioning (DP) systems) in position and heading, without anchoring, enabling the platform to maintain a fixed position and to free itself from the influence of wind and waves. In the case of a floating wind turbine, the servo-control allows the platform to follow the wind turbine as it moves around the anchors, if necessary.

[0065] Altitude, pitch and roll (trim and heel) servo-control, allowing the intervention team to handle heavy loads on the platform or from the float of a floating wind turbine, and to carry out maintenance in the workshop under optimum safety conditions in difficult sea and wind conditions.

[0066] The system is thus based on two ballasting principles:

[0067] conventional static ballasts, which are used to compensate for slow load variations, such as those caused by fuel weight reduction and the load of on-board equipment and personnel.

[0068] dynamic ballasts with near-instantaneous volume variation for immediate response, arranged in such a way as to compensate in real time for load transfers at the platform due to the effects of waves, wind and the handling of heavy loads on the platform.

[0069] The system comprising dynamic ballasts with quasi-instantaneous volume variation and the associated servo-control means constitute one of the technical specificities of the invention. By virtue of their immediate response, these dynamic ballasts can compensate in real time for movements generated by variations in the forces exerted on the system.

[0070] The system is based on a passive safety approach: in the event of partial or total system failure, the platform returns to a stable position. Static ballasting is provided by the submerged float(s), most of which are filled with air to ensure passive buoyancy. Servo-controlled dynamic ballasting is carried out according to the chosen safety approach, either by adding mass (seawater) above surface level, or by removing mass below surface level. The volume used for said dynamic ballasting is a specifically dedicated volume in the masts. Advantageously, each mast has at least one vertical cylinder, preferably two vertical cylinders, the base of which extends down to the lower level of the floats. Two embodiments may be envisaged.

[0071] In a first embodiment, the cylinders are under partial vacuum, which naturally raises the water level above the waterline surface. The floating equilibrium point of the vessel is based on this level of water above the water surface in the cylinders. In the event of total system failure, passive safety naturally causes the floats to rise to the surface of the water and float the entire vessel.

[0072] In another embodiment, the cylinders are under positive air pressure, which naturally lowers the water level below the waterline surface in the dedicated cylinders. The floating equilibrium point of the vessel rests on this water level above the water's surface. In the event of total system failure, the passive safety system naturally sinks the floats to bring the platform down to the water's surface. By design, the platform is advantageously floating.

[0073] The static ballasting means inside said float(s), as well as the servo-controlled dynamic ballasting means inside said masts, include water or air filling and emptying means of the pump or solenoid valve type, or vertical nozzle thrusters, as well as air pressure control means of the compressor or vacuum pump type.

[0074] Servo-control is based on direct physical measurements: of attitude (e.g. using an inertial unit providing attitude parameters, longitudinal and transverse inclination and gyrocompass), of platform height relative to the water surface (e.g. height is measured by an algorithm based on signals received from water pressure sensors and / or proximity sensors of the LIDAR or ultrasonic type), of geolocation (GNSS: Global Navigation Satellite System), other sensors (position, inclination, wind speed, temperature, etc.) if required.

[0075] The servo-control means can comprise an automated control unit equipped with navigation and position-keeping software, receiving information from the various sensors and controlling actuators. The servo-control means can comprise a man-machine interface for on-site or remote control of some or all of the functions. In particular, speed, position, heading, yaw angle and structure height can be controlled manually or automatically.

[0076] The main actuators used can be as follows:

[0077] longitudinal thrusters (e.g. one or two per float, fixed or on an adjustable pod depending on the application)

[0078] lateral or transverse thrusters (e.g. a bow thruster and a stern thruster on each float)

[0079] pumps and solenoid valves for filling and emptying static ballasts

[0080] vertical nozzle thrusters to adjust the water level in each dynamic ballast cylinder (typically two thrusters per mast)

[0081] horizontal front and rear control surfaces

[0082] a steerable pod or rudder on each float

[0083] a compressor and vacuum pump to adjust pressure levels in the static and dynamic ballast tanks.

[0084] Integrating degraded modes into the servo system right from the design phase ensures the required level of safety for all types of use, taking into account the failure(s) of sensors, actuators or the servo means themselves. The first degraded modes include the failure(s) of a longitudinal thruster, one or more lateral thrusters, one or more ballast control pumps, the trim sensor, one or more sensors for measuring platform height, etc. The architecture of the automated control unit is advantageously fail-safe, based for example on redundant control units. The automated control unit architecture is advantageously fail-safe, based for example on redundant computers.

[0085] The dynamic ballasting means can operate:

[0086] in passive mode: the partial vacuum is adjusted in the cylinders, with water exchanges with the outside via calibrated pressure drops located at the base of the cylinders (the system works like a damper)

[0087] in active mode: each cylinder is equipped with a pump to dynamically control the water level in real time.

[0088] The main advantage of this technical choice is to minimize energy consumption while guaranteeing optimal stabilization and safety. The entire servo system is designed to enter safety mode automatically in the event of one or more faults. The system has a number of degraded modes, particularly if the buoyancy of the floats is compromised, as the aerial superstructure is buoyant by design.

[0089] An non limitative example of an SOV vessel is shown in FIG. 1. The vessel comprises a streamlined aerial platform (1) located 12 meters above the waves and sea spray.

[0090] This platform (1) is securely attached by four masts (2) to an underwater chassis comprising two floats (3), four lateral thrusters (4), rotating and steerable shrouded longitudinal thrusters (5) (known as “pods”) and two profiled crossbeams (6) with hydrodynamic and aerodynamic profiles to facilitate the forward motion of the vessel. In FIG. 1, the platform (1) is equipped with a helipad (7).

[0091] Propulsion of the vessel is provided by two electric pods (5) powered by containerized generators (8). Pods are rotating, shrouded thrusters that provide propulsive thrust in the desired direction, including forward if necessary, allowing the vessel to be propelled backwards without reversing the direction of rotation or pitch of the propeller. On-board service power is provided by LFP-type battery packs stored in 20-foot containers (9), and recharged by 1200 m2 of photovoltaic panels and 2 or 3 vertical-axis wind turbines by virtue of a crane or wind turbine support structural axis (10).

[0092] FIG. 2 is a profile view of the structure according to the invention showing an embodiment wherein the platform (1) is equipped with a helipad (7) under which the command bridge (11) is located. The platform comprises a nacelle (12) with a living quarters, workshops and storage areas on three levels and a peripheral open passageway.

[0093] FIG. 2 details the double ballast system, including:

[0094] servo-controlled dynamic ballasting means in the form of cylindrical vertical dynamic ballasts (13) located inside the masts (2), which are filled and / or emptied by vertical thrusters (14);

[0095] static ballast means in the form of static ballast tanks (15) inside the floats (3).

[0096] Below the nacelle (12) is a tilting bridge (16) for launching and retrieving speedboats (2×10 m rigid inflatable boats) and ROVs (Remotely Operated underwater Vehicles).

[0097] At least one of the masts can include a structural pin (17) on the masthead for attaching a vertical-axis crane or wind turbine.

[0098] The rear deck of the nacelle offers 350 m2 of open space for craning and handling maintenance equipment, and an articulated retractable bridge (18) for transferring personnel and equipment to the wind turbines.

[0099] The overall balance and height of the platform above the water is adjustable by means of static ballast tanks (15) distributed horizontally in the floats (3).

[0100] Position and trim control means comprising at least one sensor and at least one servo-control means for said dynamic ballasting means allow control, in real time, of the position and stability of the marine structure based on swell and wind.

[0101] Dynamic balancing, which compensates for load displacements and maintains a level trim, is servo controlled by an electronic device which drives vertical thrusters (14) which rapidly fill and empty the vertical dynamic ballasts (13) distributed in the four masts (2). The means of filling / emptying quick ballast tanks are referred to as “vertical thrusters”, in that they add a thrust component (by action / reaction) when they eject water from the ballast tanks, creating a vertical downward force that adds punctually to the variation in ballast tank buoyancy, making the system as a whole more responsive.

[0102] The steerable and rotating shrouded longitudinal thrusters (5), four lateral thrusters (4) and dynamic ballasts (13) coupled with satellite navigation software provide precise maneuvering and the ability to maintain a geostationary position without anchoring.

[0103] This type of vessel design means that large platforms can be envisaged, with displaced weights lower than those displaced by conventional vessels of the same size, thus saving energy when moving the vessel.

[0104] Advantageously, the design of the vessel is based on modularity and redundancy of construction elements, aimed at limiting manufacturing costs (including for transporting modules) while enabling a wide range of vessel sizes to be covered. A modular construction method can thus be envisaged.

[0105] For example, as shown in FIG. 3 for a marine structure comprising three floats and six masts, the masts and floats can be made up of modular elements: modular float elements (19) and modular mast elements (20) enabling different vessel concepts and architectures to be implemented. Modular elements are identical, repeatable elements of short length (with respect to the length of the vessel, generally imposed by the standard dimensions of the construction materials), which can be assembled together to obtain a variable total length, at lower cost, according to need. This approach optimizes the cost of purchasing certain materials such as sheet metal (6 or 12-meter modules, for example), and facilitates transport by land or sea.EXAMPLE

[0106] A non-limiting example of a floating device (maintenance vessel for offshore wind turbines) according to the invention is described in the present example.

[0107] The proposed system is a marine structure in the form of a stabilized platform (incorporating the control cell, living quarters, workshop, store, handling equipment and electrical power generation units) moving above the water surface, making it possible to travel to and remain for extended periods in areas far from the coast (of the order of 100 km), the aim being to enable continuous offshore wind turbine maintenance, whatever the sea conditions. The platform is equipped with:

[0108] a storage capacity for equipment and spare parts (warehouse),

[0109] a maintenance workshop

[0110] heavy handling equipment (30 t)

[0111] a wind turbine securing system

[0112] a means of access to the wind turbine

[0113] a comfortable living cell for 24 / 7 operations by intervention teams

[0114] launch / retrieval and piloting cells for airborne and underwater drones

[0115] In its basic configuration, the platform is 48 m long, 38 m wide and has a total height (draft plus air draft) of 30 m. Draft is variable, and can be temporarily reduced to 6 m to allow access to shallow draft areas. The height of the platform in relation to the water surface is continuously adjustable to suit requirements (by virtue of ballasts), walk-to-work (pedestrian bridge raised and deployed to the required height to provide access to the wind turbine), load handling between the wind turbine and the platform, docking, stowing, launching of ROVs or tender boats, and constraints (wave height). The platform can also be placed on the water to significantly increase handling capacity (in this case, it is no longer stabilized and behaves like a barge).

[0116] The volumes of the underwater floats (empty ballast tanks) are 500 m3 each, giving the whole vessel a maximum buoyancy of 1,000 tons.

[0117] The platform offers an open working area of 350 m2. A telescopic handler can handle heavy loads (up to 30 tons) without compromising the platform's stability. This equipment can also be used to handle a load between the wind turbine and the platform.

[0118] Submersible floats are equipped with electric motors to ensure propulsion as well as position and heading control.

[0119] The electric motors can be powered by diesel generators of proven reliability. The generators are containerized (functional, modular and removable) in their standard containers (20 feet or 40 feet), making them interchangeable depending on the technologies selected. In this way, the power supply can be modified and entrusted to a hydrogen fuel cell to generate on-board electricity and power the engines. This conversion from diesel generator to fuel cell takes place at lower cost, since propulsion is already provided by electric motors.

[0120] The platform allows the deployment of 1200 m2 of photovoltaic panels, generating electrical energy stored in containerized MegaPack batteries. In the case of a fuel cell-based power supply, the electrical energy generated by the photovoltaic panels is converted into hydrogen for storage and reuse via the fuel cell.Advantages of the Invention

[0121] The platform is able to intervene at any time, in any type of weather, with autonomy in terms of energy, human resources and logistics, guaranteeing the success of maintenance or repair operations on the high sea. The platform makes it possible to reach any offshore area at reasonable speed (10 to 20 knots), to get as close as possible to equipment, such as a floating wind turbine, and to follow its movement in position and heading, to transfer an intervention team to the float of the wind turbine, to handle heavy loads and bring them back on board to be able to intervene in complete safety. The living cell allows the crew to be fully autonomous, in optimum comfort conditions, for the duration of the mission.

[0122] In one embodiment, the marine structure according to the invention is energy autonomous, in that it comprises autonomous electricity production means chosen from wind turbines, photovoltaic panels, aeroturbines-and energy storage means (including batteries and hydrogen storage for fuel cells). The longitudinal and transverse thrusters of said float(s) can be at least partly electrically powered by electrical energy generation means, hybrid operation also being possible by further implementing sail propulsion means. In one embodiment, a nuclear fuel generator can be used.

[0123] Of course, the invention is not limited to the examples just described, which are given by way of illustration only.

Claims

1. A marine structure with improved stability having maneuvering and navigation means and comprising:at least one aerial platform;at least three adjustable-height masts;at least one underwater float equipped with at least one lateral thruster; and at least one longitudinal thruster, said platform being lashed to said float(s) by means of said masts;static ballasting means inside said float(s);servo-controlled dynamic ballasting means located inside said masts, andposition and trim control means comprising at least one sensor and at least one servo-control means for said dynamic ballasting means in order to control, in real time, the position and stability of said marine structure based on swell and wind.

2. The marine structure according to claim 1, comprising at least two floats, and at least one profiled crossbeam connecting said floats transversely.

3. The marine structure according to claim 1, wherein at least one sensor provides at least one direct physical measurement of at least one of the platform's attitude or height relative to the water surface, of the structure's absolute position or a relative position of the structure.

4. The marine structure according to claim 1, wherein said dynamic ballasting means consist of at least one air-vacuum or air-filled cylinder inside each mast, each of said cylinders being connected to water injection and ejection means.

5. The marine structure according to claim 1, wherein the static ballasting means consist of at least one ballast tank inside each float.

6. The marine structure according to claim 1, comprising at least one DP2-type servo-control means in position and heading, without anchoring, allowing the platform to maintain itself in a fixed position and to free itself from the influence of wind and waves, and a servo-control means in altitude, pitch and roll enabling it to maintain a substantially zero attitude.

7. The marine structure according to claim 6, comprising electric motors to ensure propulsion as well as position and heading control.

8. The marine structure according to claim 1, comprising autonomous electricity production means selected from wind turbines, photovoltaic panels, aeroturbines-and energy storage means.

9. The marine structure according to claim 1, comprising electrical power generation means, allowing the longitudinal and lateral thruster(s) of said float(s) to be at least partially electrically powered.

10. The marine structure according to claim 9, comprising at least one nuclear fuel generator.

11. The marine structure according to claim 9, further comprising sail propulsion means.

12. The marine structure according to claim 1, wherein the aerial platform is aerodynamically shaped to reduce the drag generated by absolute and relative wind, and is thinner than its length to limit its frontal area and windage.

13. The marine structure according to claim 1, comprising means for adjusting the height of the platform with respect to the float(s).

14. A use of the marine structure according to claim 1 for the handling or maintaining of equipment on the open sea.

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