BALLAST SPIRALE

Abstract

The present invention relates to a ballast (32) for ensuring a vertical displacement of a marine structure between two levels of elevation relative to a surface (Se) of surrounding water (E) in which it is immersed, this ballast (32) comprising a spiral conduit (40) which extends radially around a central axis from an external mouth (42e), this conduit (40) being intended to be driven in rotation around this central axis (AX) by being carried by the marine structure so as to extend at least partially immersed in the surrounding water, the ballast (32) allowing a filling of the conduit (40) with surrounding water through the external mouth (42e) in a first direction (R1) of rotation and a draining of water contained in the conduit through the external mouth (40e) in a second direction of rotation, opposite to the first direction (R1) of rotation. Figure for the summary: Figure 5a

Description

Title of the invention: SPIRAL BALLAST TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to the field of actuators for vertically moving a structure or craft in a marine environment relative to the surface of the water. It relates more particularly to a ballast which makes it possible to modulate buoyancy. TECHNICAL BACKGROUND

[0002] Hydraulic energy offers the possibility of being stored in the form of gravitational potential energy, allowing it to be converted into electrical energy as needed.

[0003] In practice, this involves storing a quantity of water at elevation and releasing it in the form of a fall passing through a hydraulic turbine connected to an electric generator. The rotation of the turbine as the water passes over its blades generates mechanical energy which is transformed into electrical energy by the electric generator.

[0004] There are a large number of devices for hydroelectric production, including gravity hydroelectric power stations located in a marine environment, known as “offshore”.

[0005] One operating principle of these hydroelectric power stations in a marine environment is based on the height control of a basin to be: - immersed in the surrounding water and thus lead to its filling; - raised after filling so as to raise the water it contains above the surface of the surrounding water.

[0006] The height differential generated by the elevation of the basin allows the water it contains to be emptied in the form of a waterfall that can be used for generating electricity. The basin is thus lowered and raised cyclically to ensure its filling and emptying respectively.

[0007] To ensure the management of the basin, it was proposed in the document KR102287189B1 to use a conventional type ballast, comprising an enclosure intended to be filled or emptied with sea water to control the overall buoyancy.

[0008] According to this conventional ballast architecture, communication channels controlled by hatches and pumps are provided to selectively ensure an exchange between the enclosure and the exterior in one direction or the other. In practice, this involves allowing the exterior water to flow into the enclosure when the aim is to lower the basin. Once the basin has been lowered to a desired immersion height, the communication channels are obstructed. Conversely, to regain buoyancy positive and thus led to a rise in the basin, water is pumped out to replace it with air.

[0009] This conventional ballast architecture, although functional, nevertheless suffers from certain limitations. Indeed, it requires both a certain level of complexity and a fairly significant energy consumption for the actuation of the pumps and the hatches.

[0010] In particular, document KR102287189B1 calls for additional provision of anchoring to the seabed by means of a chain of controllable length to supplement the ballast in height management, which adds a component of consumption and complexity.

[0011] The electrical energy restored overall by the hydroelectric power station corresponds to the electrical energy that it generates when emptying the basin from which the energy to be supplied for its operation is removed.

[0012] This particularly energy-consuming ballast architecture makes the return on investment uncertain, particularly when one also considers the maintenance costs induced by its complexity.

[0013] The aim of the invention is to at least partially remedy these drawbacks in order to justify such integration of a hydroelectric power station in a marine environment. Statement of the invention

[0014] For this purpose, the invention relates to a ballast for ensuring vertical movement of a marine structure between two elevation levels relative to a surrounding water surface in which it is bathed, this ballast comprising a spiral conduit which extends radially around a central axis from an external mouth, this conduit being intended to be driven in rotation around this central axis while being carried by the marine structure so as to extend at least partially immersed in the surrounding water, the ballast allowing the conduit to be filled with surrounding water through the external mouth in a first direction of rotation and water contained in the conduit to be emptied through the external mouth in a second direction (R2) of rotation, opposite to the first direction of rotation.

[0015] The invention also relates to a ballast thus defined, in which the conduit is bounded between the outer mouth and an inner mouth radially closer to the central axis than is the outer mouth, the ballast further comprising: - a pipeline comprising a first end and a second end, this pipeline being intended to be rigidly supported by the marine structure so that its first end remains exposed between the two elevation levels, and - a rotating contact which fluidly connects the inner mouth to the second end of pipeline.

[0016] The invention also relates to a ballast thus defined, further comprising a series of controllable vents for each selectively allowing or blocking through a fluid communication between the conduit and an exterior to the conduit.

[0017] The invention also relates to a ballast thus defined, comprising: - two transverse flanges which extend parallel in the axial direction; and - a core which connects the flanges by being interposed between them, in which the two flanges and the core jointly delimit the spiral duct.

[0018] The invention also relates to an assembly comprising a marine structure and at least one ballast for vertical movement of the marine structure relative to a surrounding water surface in which it is bathed, thus defined, said at least one ballast comprising a hub centered on the central axis, this hub being rigidly secured to the conduit and carried freely in rotation by the marine structure, the assembly further comprising an actuator for driving the hub in rotation around the central axis.

[0019] The invention also relates to an assembly thus defined, in which the actuator for driving the ballast conduit in rotation by the hub comprises an electric motor and a transmission mechanism which transmits a rotation provided at the output of the electric motor to the ballast hub.

[0020] The invention also relates to an assembly thus defined, further comprising an auxiliary system for driving the ballast conduit in rotation, this auxiliary system comprising: - a mandrel axially aligned on the central axis and rigidly assembled to the hub; - an anchor cable wound around the mandrel and one end of which is attached to this mandrel; - a float which is attached to the other end of the anchor cable; - a platform maintained vertically below the marine structure and whose position is independent of the elevation level of this marine structure relative to the surrounding water surface, for example fixed to a bottom surface of the surrounding body of water; in which the anchor cable connects the float to the mandrel by extending successively from the mandrel: - vertically downwards to reach the platform; - transversely away from the marine structure while being held at the platform level; - vertically upwards to reach the float.

[0021] The invention also relates to an assembly thus defined, in which the marine structure is a tank comprising: - a wall which delimits an interior enclosure of the tank in which it can be stored an interior volume of water isolated from the surrounding body of water, - a water inlet which allows water to pass into the interior enclosure to constitute the interior volume of water when it extends to a level of elevation said to be lowered in relation to the surrounding water surface, - a water discharge opening through which the internal volume of water can be drained out of the internal enclosure.

[0022] The invention also relates to a hydroelectric power station comprising: - a set thus defined, - a hydraulic turbine connected to the tank discharge orifice to generate mechanical energy as the water drained from the inner enclosure of the tank passes when the tank is at a so-called high level relative to the surrounding water surface; - a generator that cooperates with the hydraulic turbine to convert mechanical energy into electrical energy.

[0023] The invention also relates to a method for recharging the inner enclosure of the tank with water between two cycles of production of electrical energy of the hydroelectric power station thus defined; comprising: - a step of lowering the tank by rotating the ballast pipe in the first direction of rotation to fill this pipe with water, to immerse the water inlet orifice in the surrounding water; - a step of introducing water into the inner enclosure through the water inlet orifice to constitute the inner volume of water; and - a step of raising the tank by rotating the ballast pipe in the second direction of rotation to purge this pipe of water. Brief description of the drawings

[0024] Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings in which: [Fig.l] is a schematic diagram of a hydroelectric power station, comprising a hydraulic turbine, an electric generator linked to the turbine and a potential energy storage system comprising a tank vertically movable in a surrounding body of water and provided with a discharge path which opens onto the turbine; [Fig.2] represents in perspective an energy storage system comprising a tank and means for controlling the elevation of the tank, these means comprising a series of ballasts, mounted on the tank, according to an exemplary embodiment of the invention; [Fig.3] is a partial and transverse view of [Fig.2] at the level of a ballast considered; [Fig.4] is a section view AA of [Fig.3] illustrating a spiral-running conduit; [Fig.5] is a cross-sectional view of [Fig.2] in a tank elevation condition relative to the surrounding water surface; [Fig.5a] is a view according to [Fig.4] which illustrates a state in which the duct is completely filled with air; [Fig.5b] is a view consistent with [Fig.4] in a state of filling the conduit with water after rotation over one revolution; [Fig.5c] is a view consistent with [Fig.4] in a state of filling the conduit with water after rotation over two turns; [Fig.5d] is a view consistent with [Fig.4] in a state of half-filling the conduit with water; [Fig.5e] is a view consistent with [Fig.4] in a state of total filling of the conduit with water; [Fig.6] is a cross-sectional view of [Fig.2] in a lowered tank condition relative to the surrounding water surface; [Fig.6a] is a view consistent with [Fig.4] during a water purge of the conduit after several rotations; [Fig.6b] is a view consistent with [Fig.4] during a water purge of the conduit and in a more advanced purge state than in [Fig.6a]; [Fig.7] is a cross-sectional view of the energy storage system equipped with rotational drive actuators according to a first embodiment variant; [Fig.8] is a cross-sectional view of the energy storage system equipped with rotational drive actuators according to a second embodiment variant; [Fig.9] illustrates an alternative embodiment of ballast comprising controllable vents along the conduit. DETAILED DESCRIPTION OF THE INVENTION Hydroelectric power station

[0025] A hydroelectric power station, marked 10 in [Fig.l], comprises an energy storage system 12, a hydraulic turbine 14 and a generator 16.

[0026] The energy storage system 12 comprises a tank 18 designed to be immersed in a surrounding body of water E which is defined at the surface Se by a limnimetric height of surrounding water He.

[0027] In the following, vertical and transverse orientations linked to the tank 18 and identified respectively by the axes V and T will be adopted, without limitation. Note that the vertical orientation coincides with the direction normal to the surface Se of the surrounding body of water E. The radial direction is defined as an orthogonal direction to the radial direction. Also, the terms "bottom" B and "top" H are to be considered in the vertical direction, with the bottom oriented towards the bottom of the surrounding body of water E at the location of the tank.

[0028] The tank 18 comprises a wall 20 which radially delimits an internal tank enclosure I and in which an internal volume of water can be contained.

[0029] Note that the inner enclosure I is naturally maintained at atmospheric pressure by means of an opening formed in the wall 20 for this purpose. Advantageously, the wall 20 delimits at the top of the tank such an opening, called the highest vertical section of the tank, as illustrated in [Fig.l] and marked by 22.

[0030] This tank 18 comprises an opening called a water inlet, formed through the wall 20, which allows water to pass into the inner enclosure I from the surrounding body of water E to constitute the inner volume of water. As understood, the inner volume of water corresponds to a portion extracted from the surrounding water E.

[0031] This inlet orifice can be equipped with a restriction, such as a non-return valve, to prevent reverse circulation of water, namely from the inner enclosure I to the surrounding body of water E. Note that the opening 22 formed at the top of the tank can judiciously serve as an inlet route without requiring a restriction.

[0032] Additionally, the tank 18 comprises a water discharge orifice, marked 24 in the example of [Fig. 1], formed in the wall 20 and through which the internal volume of water can be drained out of the internal enclosure I.

[0033] Within the framework of the invention, it is aimed to move the tank 18 in the vertical direction V, to be: - lowered, i.e. moved vertically downwards, to immerse the intake channel and thus lead to filling of the inner enclosure I with water; and - raised, i.e. moved vertically upwards, after filling the inner enclosure.

[0034] Grooves may in particular be formed in the wall 20 to allow water to enter the inner enclosure I through the opening 22 at the top of the tank without requiring total immersion of the tank 18.

[0035] The filling of the inner enclosure I is complete when the surface of the water contained within it, noted Si, is merged with the surface Se of the surrounding water area E.

[0036] The elevation of the tank 18 leads to the generation of a water height differential, noted AH, between the surfaces Si and Se. The volume of water measured between the surfaces Si and Se is thus charged with gravitational potential energy.

[0037] Once the tank is raised, the transformation of the potential energy into electrical energy consists of draining, through the discharge orifice 24, this volume of water stored so as to form a waterfall meeting the turbine. As it passes through the turbine 14, mechanical work Em is extracted from the hydraulic energy Eh, and is converted at the same time into electricity Ee by the generator 16 which cooperates with the turbine 14.

[0038] Elevation control means and ballast structure

[0039] In practice, the mass of water contained in the inner enclosure I opposes the elevation of the tank 18, and conversely the absence of water in the inner enclosure I tends to oppose its immersion to charge it.

[0040] To satisfy this double condition of lowering the empty tank 18 in order to fill the internal enclosure I; and of raising the tank 18 containing water to generate the height differential AH, the energy storage system 12 comprises elevation control means 30.

[0041] The major feature of the invention lies in these means 30 of elevation control, and more particularly in the use of ballast 32 with a particular structure.

[0042] With reference to [Fig. 2], the means 30 for controlling the elevation of the tank 18 relative to the surface Se of the surrounding water E comprise a series of ballasts 32. In this example, the tank 18 has a polygonal shape and the ballasts 32 are identical in having a general disc shape. The ballasts 32 are arranged at regular intervals around the tank 18, like petals of a cyclic flower, each being arranged at a distinct side of the polygonal outline of this tank 18. In particular, the ballasts 32 are each inscribed in a respective vertical plane which intersects the central axis of the tank which is merged with the defined vertical axis V.

[0043] It should be noted that the invention is not limited to the shape of the tank 18 and to the arrangement and / or orientation of the ballasts 32 described on the basis of [Fig. 2]. As a non-limiting example, a parallelepiped shape of tank 18 combined with a linear distribution of ballasts 32 may be used.

[0044] For the description of the structure of the ballast 32 according to the invention, a ballast reference system AX, A Y will also be adopted. It defines axial orientation axes AX and radial A Y. Also, a so-called interior element is also one which is radially closer to the axis AX than is a so-called exterior element.

[0045] In the example of figures 2, 3 and 4, the ballasts 32 each comprise a central body provided with: - two transverse flanges 34 which extend parallel in the axial direction; and - a core 36 which connects the flanges 34 by being interposed between them.

[0046] The core 36 comprises a guide wall 38 shaped to extend in a spiral around the axis AX which corresponds to the central axis of the ballast. This guide wall 38 advantageously has a thickness and a width, measured respectively in the radial direction and in the axial direction, which are constant in a ribbon-like manner.

[0047] By spiral, it is meant in the sense of the invention that the wall 38 gradually approaches the axis AX by swirling. Preferably, the guide wall 38 uniformly approaches the axis AX so as to have a constant pitch. This architecture is modeled on the Archimedes spiral model.

[0048] To ensure overall cohesion of the central body, the core 36 is held by a built-in connection to the flanges 34 which extend axially on either side thereof. This built-in connection can be achieved by any conventional assembly technique provided that linear contact, in other words continuity of material, is ensured between the flanges 34 and the wall 38 along its extent. For example, the core 36 may comprise two tabs which follow the profile of the wall 38, for example in the form of a sheet metal, extending it on either side and perpendicularly, so as to come into plane support against the flange directly opposite and thus allow assembly by screwing.

[0049] The flanges 34 advantageously have a circular shape and are superimposable in the axial direction.

[0050] The flanges 34 and the wall 38 of the core 36 are dimensioned so that the spiral wall 38 does not extend transversely beyond the flanges. In other words, it is intended that the wall 38 remains inscribed in the axial alignment of the flanges 34.

[0051] With this arrangement, the guide wall 38 and the transverse flanges 34 jointly delimit a spiral path conduit 40.

[0052] In the example of [Fig. 3], the conduit 40 has at all points a parallelepiped shape in radial section, understood that the wall 38 extends normal to the flanges 34. It should be noted however that the invention is not limited to this particular arrangement, and allows any type of profile in section of the conduit 40. By way of non-limiting example, the conduit 40 can have a chevron shape, obtained by folding the wall 38 along its median.

[0053] This conduit 40 is limited to the radial ends of the guide wall 38 of the core 36, at the level of which two mouths are defined, including a mouth called external 42e and a mouth called internal 42i.

[0054] It is advantageously recommended according to the invention that these two openings 42e, 42i communicate with the outside so as to allow controlled movement of fluid along the conduit 40, without which it would be subject to a pressure difference.

[0055] The external mouth 42e, located at the peripheral contour of the conduit 40, allows as such communication with the outside.

[0056] As regards the communication of the inner mouth 42i with the exterior, it is recommended to form an orifice 44 in one of the flanges 34. This orifice 44 is formed passing through in the axial direction while being centered on the central axis AX. The diameter of this orifice 44 is advantageously fixed so as to allow fluid circulation between the conduit 40 and the exterior only or at least mainly through the internal mouth 42i.

[0057] In addition to this orifice 44, the ballast 32 comprises a pipe 46 and a rotating connection 48. The rotating connection 48 is installed in axial alignment with the central axis AX and at the interface between the pipe 46 and the flange 34 provided with the orifice 44. By definition, this rotating connection 48 ensures communication between the conduit 40, through the orifice 44, while allowing relative movement around the central axis AX of the central ballast body, formed by the association of the two flanges 34 and the core 36, relative to the pipe 46.

[0058] The pipe 46 runs from the rotating connection 48, oriented in the radial direction, to an end 50 open to the outside. In particular, the pipe is shaped so that this end 50 extends at the level of or radially beyond the external mouth 42e.

[0059] From an integration point of view, the ballasts 32 are designed to be mounted in rotation on the tank 18, each around their respective central axis AX. According to the arrangement illustrated in the appended figures, the transverse flanges 34 are each extended axially, and externally to the core 36, by a hub 54. In addition, the tank 18 comprises a series of yokes 58, each of which supports in rotation the hubs 54 of a ballast 32.

[0060] In detail, each yoke 58 comprises two parallel legs 59 which are sufficiently spaced from each other to interpose the corresponding ballast 32 when the hubs 54 each extend through an opening 62 formed in the leg 59 directly opposite.

[0061] It is preferred according to the invention that the ballasts 32 equip the tank 18 of the energy storage system 12 by being oriented so that their respective central axis AX extends perpendicular to the vertical direction V. In addition, the pipe 46 of each of the ballasts 32 is held by a fixing element of the tank 18 so as to extend vertically at its end 50 which communicates with the outside.

[0062] By this arrangement, it is intended that the end 50 of pipe 46 remains emerged at all times, in particular when the tank 18 is vertically lowered, to allow communication between the conduit 40 and the ambient air, in the manner of a diving snorkel. As shown in [Fig. 2], the means 30 for controlling the elevation of the tank 18 may additionally comprise an additional float 66 to ensure this. This float 66 is advantageously in the form of a circular buoy centered vertically on the tank 18, to act uniformly on the whole 32 ballasts.

[0063] Tank movement and ballast filling / purging dynamics

[0064] With reference to figures 5a to 5e, the operating principle of a ballast 32 from the situation of [Fig.5] for which it is intended to lower the tank 18, namely to move it vertically downwards B, to allow filling with water of the internal enclosure I.

[0065] Considering a case in which the conduit 40 is exclusively filled with air, as shown in [Fig.5a], it acts as a conventional float to keep the tank 18 elevated relative to the surrounding water surface Se.

[0066] By rotating it on one turn in a direction RI, defined as the direction in which the outer mouth 42e advances, the conduit 40 will capture a volume of water VI at the level of the outer turn Spe marked in bold in [Fig.5b]. The outer turn corresponds to the peripheral section of conduit 40. This volume of water VI rushes into the conduit 40 through the outer mouth 42e when the latter is immersed on the turn.

[0067] By continuing the rotation on another turn following RI, a second volume of water V2 will be captured in the conduit 40 at the passage of the external mouth 42e in the surrounding water E. During this turn, the conduit 40 will move relative to the first volume VI already contained, which amounts overall to considering a displacement of this first volume towards the center of the spiral to find itself in the adjacent turn, which is noted Spe-1 and delimited in bold on [Fig.5c]. The first volume VI of water arranged in this adjacent turn Spe-1 is thus maintained vertically above the second volume V2 which is contained in the external turn Spe.

[0068] At this stage, all or part of this first volume VI is above the surface Se of the surrounding water, in other words it is not part of the surrounding water E. This emerged part of the volume V1 thus reduces the buoyancy of the ballast, which causes the tank 18 to naturally descend vertically to return to equilibrium.

[0069] Thus, the conduit 40 will gradually fill with water as the turns follow RI, and the tank will consequently descend.

[0070] Note that a self-amplification effect of the descent of the tank 18 is observed. Indeed, as the conduit 40 submerges, the angular path of the external mouth 42e when it is submerged increases, leading to the capture of more water.

[0071] In practice, air was trapped at each turn between two volumes of captured water. This air does not participate in the descent of the tank 18. This particularity is particularly clearly visible in [Fig.5d] which corresponds to the case for which all the turns contain water and air.

[0072] Nevertheless, this air will gradually decrease in the conduit 40 by continuing the rotation in the direction RI. Indeed, the successive volumes of water (VI, V2, ...) which occupy the conduit 40, as well as the air trapped between them, will be discharged into the ambient air by the pipe 46 which extends the inner mouth 42i, to the benefit of ever greater volumes of water entering through the outer mouth 42e under the self-amplification effect described. The ballast 32 then acts as a pump which imposes during the rotation of its conduit 40 a displacement of water from the outer mouth 42e towards the inner mouth 42i.

[0073] When the reverse is intended to raise the tank 18, in particular after a step of filling its internal enclosure I as illustrated in [Fig. 6], it is a question of rotating the conduit 40 in the direction opposite to the direction RI, noted R2 in figures 6a and 6b. Following this direction of rotation R2, the water contained in the conduit 40 will travel from the internal mouth 42i to the external mouth 42e, being replaced by air sucked in from the outside by the pipe 46.

[0074] As understood, the conduit 40 empties water progressively in a radially interior-exterior direction, passing successively from the state illustrated in [Fig.6a] to that of FIG. 6b to regain positive buoyancy. In other words, as the conduit 40 empties water, the proportion of air it contains increases, which increases the buoyancy of the ballast 32 and consequently leads to the progressive vertical raising of the tank 18.

[0075] In view of the above, the specific spiral conduit structure 40 according to the invention grants the ballast 32 a double functionality: - a ballast effect by means of filling with water, which requires the tank to descend to compensate for the difference in height between the water contained in the conduit 40 and the surrounding water surface Se. In such a case, the ballast 32 according to the invention acts in the manner of a ballast commonly called “reverse type”; - an aid to the flotation of the tank by means of a water purge of the conduit 40, which instead fills with air in order to keep the tank 18 above water, in the manner of a so-called “conventional” ballast.

[0076] It is thus possible to modulate the height of the tank 18 as needed by means of a simple mechanical rotation drive in one direction or the other around the central axis AX of the ballast body, having the effect of modifying the proportion of water and air contained in the conduit 40. Ballast actuation

[0077] The rotational drive of the ballast body, defining the conduit 40, can be provided by a drive actuator 60.

[0078] According to a first variant embodiment illustrated in [Fig.7], this drive actuator 60 comprises an electric motor 62 and a transmission mechanism 64.

[0079] The transmission mechanism 64 ensures the rotational coupling, and optionally a torque reduction, between the electric motor 62 and the hub 54 of the ballast 32 in question. The electric motor 62 and the transmission mechanism 64, represented diagrammatically by a dotted power transmission line, are carried by the tank 18 of the storage system 12. The ballast 32 conduit 40 is thus driven in rotation by the drive actuator 60 in the direction RI or the direction R2 depending on the direction of rotation generated at the output of the electric motor 62.

[0080] As understood, the means 30 for controlling the elevation of the tank 18 comprise a number of actuators 60 corresponding to the number of ballasts 32 which equip the tank 18, each cooperating with a ballast hub 54. The actuators 60 advantageously operate in concert, at least for this given application, namely simultaneously by providing a rotation in the same direction around the central axis AX of the ballast, to result in a vertically balanced descent or rise of the tank 18.

[0081] The electric motors 62 in practice consume a portion of the electrical energy generated overall by the power station 10 during the discharge of the inner enclosure I with water to drive the ballast bodies in rotation during each cycle of descent and ascent of the tank 18.

[0082] On this basis, a second variant embodiment is proposed aimed at reducing the energy consumed by the electric motor 62. According to this variant illustrated in [Fig.8], each drive actuator 60 additionally comprises an auxiliary rotation system 66.

[0083] This auxiliary system 66 is configured to exploit tidal energy, namely by taking advantage of the natural change in height He of the surrounding body of water E. In detail, this system 66 comprises for each ballast 32: - a mandrel 68 axially aligned on the central axis AX and rigidly assembled to an axle 54; - an anchor cable 70 wound around the mandrel 68 and one end of which is attached to this mandrel 68; - a float 72 which is attached to the other end of the anchor cable 70; - an underwater platform 74.

[0084] The underwater platform 74 is held vertically below the tank 18, at a position independent of variations in height of the tank 18. In practice, it is advisable to fix this platform 40 to the bottom Te of the surrounding body of water E.

[0085] In the example of [Fig.8], the same underwater platform 74 is common to all of the auxiliary systems 66, but an arrangement in which each auxiliary system 66 comprises a separate platform 74 can be retained.

[0086] As regards the anchor cable 70, it extends in a serpentine fashion from the mandrel 68 to which it is attached at one end towards the float 72 to which it is attached at another end according to the following path: - it extends the mandrel 68 around which it is wound by diving vertically to join the underwater platform 74; - it is held along a portion of the platform 74 by adopting a transverse orientation moving away from the tank 18. Note that the platform 74 can be equipped with a slide in which the cable 70 is held, or with rings through which this cable passes; - it rises vertically from the platform to the float 72 which extends transversely at a distance from the tank 18 and the ballast 32 with which it cooperates.

[0087] Considering the tank 18 lowered for filling as illustrated in [Fig.8], an increase in the surface height Se of the surrounding water under the combined effect of the gravitational forces of the Moon and the Sun, tends to cause the float 72 to rise. It is understood that the float 72, which floats on the surface Se, is led to follow the increase in the water height He under the effect of Archimedes' thrust, noted Fa, to which it is subjected.

[0088] This Archimedes thrust corresponds to a force oriented vertically upwards and applied to the end of the cable 70 attached to the float 72. In reaction, it tends to pull the section of cable wound around the mandrel 68 vertically downwards, which leads to it being unwound by imposing a rotation of the ballast body 32.

[0089] This solution thus allows spontaneous rotation of the ballast body, by judiciously using the tidal effect.

[0090] In the example of [Fig.8], the tide is rising when the aim is to raise the tank 18. In such a case, it is a matter of winding the cable 70 onto the mandrel 68 so that the rise of the float 72 drives the ballast body in rotation in the direction R2 ensuring the emptying of water from the conduit 40.

[0091] Note that a reverse arrangement can also be adopted, namely winding the cable 70 onto the mandrel 68 so that the natural rise of the float 72 drives the ballast body into rotation in the direction RI when a descent of the tank 18 is defined when the tide rises.

[0092] As understood, the auxiliary system 66 makes it possible to totally or partially replace the electric motor 62 in one direction of rotation, RI or R2, while the electric motor 62 fully ensures rotation in the other direction. “Totally” is understood to mean that the auxiliary system 66 ensures the actual driving of the ballast body in a predefined direction of rotation. The term “partially” refers to the case where the Archimedes thrust applied to the float 72 is not of sufficient intensity to drive the ballast body in rotation as such, but makes it possible to reduce the rotation torque to be applied by the electric motor 62 to the hub 56, and therefore its consumption. Controllable events

[0093] The dynamics of filling the ballast ducts 40 with water 32 have been described on the basis of figures 5a-5e and 6a-6b without taking into consideration the pressure within it.

[0094] In practice, due to the spiral path of the conduit 40, the pressure of the air trapped between each volume of water (VI, V2, ...) increases with each subsequent turn RI, it being understood that the space allocated to it reduces as it approaches the internal mouth 42e. [Fig.9] illustrates this phenomenon in the form of a gray level gradient.

[0095] Under the effect of this overpressure, the water is pushed further towards the inner mouth 42e as the revolutions increase, which generates uncertainty and can harm the ideal operation of the ballast 32.

[0096] To overcome such a phenomenon, it is advantageously provided according to the invention to equip the ballasts 32 with controllable vents 78. In the example of [Fig.9], these vents 78 are distributed in several batches of radially aligned vents 78. This multiplication makes it possible to limit the angular positions of the ballast body for which no vent is accessible for the air confined in the duct 40.

[0097] These vents 78 are thus controllable so as to selectively authorize or block fluid communication between the interior and the exterior of the conduit 40.

[0098] Note that the control of the vents 78 can be controlled according to their position but also according to the state of vertical movement of the tank 18. In the example of [Fig.9], it is intended to allow air to pass through the vents which are both exposed and arranged at the level of an air pocket in the conduit 40 to allow pressure relief during the vertical descent of the tank 18. In this example it may additionally be desired to open the vents 78 which are submerged to accelerate the immersion of the ballast body and therefore of the tank 18.

[0099] Conversely, during a step of hoisting the tank 18, it may be advisable to open the vents 78 when they emerge so as to allow a discharge of water from the conduit 40 also through these vents. As understood, such a discharge of water through the vents 78 limits the time associated with emptying the water from the conduit to result in a faster hoisting of the tank 18.

[0100] In view of the above, it should be noted that by limiting the time required to vertically raise or lower the tank 18, these controllable vents 78 provide the possibility of reducing the consumption of the electric motors 62, by limiting their activation time.

[0101] The invention has been described as relating to a ballast 32 whose body, formed of two flanges 34 which enclose a core 36 on either side, delimits a conduit 40 to spiral path. It should be noted in general that the invention is not limited to the constituent elements of the ballast body 32 as described, since it defines such a conduit 40 with a central axis AX around which it is driven in rotation. For example, it may be chosen, as an alternative to the ballast body as described on the basis of FIGS. 3 and 4, to directly shape the conduit 40 by winding a tube on itself. The hubs 54 may be fixed to the conduit 40 thus formed, for example by welding.

[0102] Also, the ballast 32 is not limited to the use of a pipe 46 and a rotating contact 48 as described to form a fluid passage bridge between the exterior and the interior mouth 42i of the conduit 40. In practice, the ballast 32 according to the invention may be devoid of these elements, and more generally of a direct communication path between the interior mouth 42i and the exterior of the ballast, to the detriment of its effectiveness. Indeed, in such a case, the time associated with filling or emptying the conduit 40 with water is increased due to the fact that the water and the air must flow in opposite directions, and therefore hinder each other, to ensure a replacement of one by the other through the exterior mouth 42e.

[0103] The ballast 32 according to the invention is generally of simple and robust construction. The structure of the ballast 32 is generally non-working, i.e. is not subject to significant forces. This particularity is all the more true if the ballast 32 is equipped with controllable vents 78 which ensure operation at substantially atmospheric pressure in the conduit 40.

[0104] The invention has been explained as relating to a ballast 32 which can equip an energy storage system 12 in potential form. It should be noted, however, that the ballast according to the invention is not limited to this particular application. In practice, it can be used to modulate the height of any maritime installation or craft provided that it allows the conduit 40 to be at least partially submerged during its operating life. For example, a series of ballasts 32 according to the invention can be used to equip a floating marine platform, such as a drilling or wind turbine mast support platform, in order to compensate for uneven mass distribution linked to load variations, wind or waves.In another example, such ballast can be used to equip surface vessels to optimize navigation, such as correcting heel or trim, or controlling sinking in the water according to the mass of the cargo so as to keep the propeller that propels them submerged.

[0105] The ballast 32, in particular in its form equipped with a pipe 46 and a rotating contact 48, can also be used as a hydraulic pump for any application. Indeed, a rotation in the direction RI of the conduit 40 ensures a water pumping effect at the level of the external mouth 42e to collect it at the level of the end 50 of the pipe 46.

Claims

Claims

1. Ballast (32) for ensuring vertical movement of a marine structure (18) between two elevation levels relative to a surface (Se) of surrounding water (E) in which it is immersed, this ballast (32) comprising a spiral conduit (40) which extends radially around a central axis (AX) from an external mouth (42e), this conduit (40) being intended to be driven in rotation around this central axis (AX) while being carried by the marine structure (18) so as to extend at least partially immersed in the surrounding water, the ballast (32) allowing filling of the conduit (40) with surrounding water through the external mouth (42e) in a first direction (RI) of rotation and emptying of water contained in the conduit through the external mouth (42e) in a second direction (R2) of rotation. rotation, opposite to the first direction (RI) of rotation.

2. Ballast (32) according to claim 1, in which the conduit (40) is bounded between the outer mouth (42e) and an inner mouth (42i) radially closer to the central axis (AX) than is the outer mouth (42e), the ballast (32) further comprising: - a pipe (46) comprising a first end (50) and a second end, this pipe (46) being intended to be rigidly supported by the marine structure (18) so that its first end (50) remains emerged between the two elevation levels, and; - a rotating contact (48) which fluidically connects the inner mouth (42i) to the second pipe end (46).

3. The ballast (32) of claim 1 or 2, further comprising a series of controllable vents (78) each for selectively allowing or blocking through fluid communication between the conduit (40) and an exterior to the conduit.

4. Ballast (32) according to any one of the preceding claims, comprising: - two transverse flanges (34) which extend parallel in the axial direction; and - a core (36) which connects the flanges (34) by being interposed between them, in which the two flanges (34) and the core (36) jointly delimit the spiral conduit (40).

5. Assembly (12) comprising a marine structure (18) and at least one ballast (32) for vertical movement of the marine structure (18) relative to a surface (Se) of surrounding water (E) in which it is bathed according to any one of the preceding claims, said at least one ballast (32) comprising a hub (54) centered on the central axis (AX), this hub (54) being rigidly secured to the conduit (40) and carried freely in rotation by the marine structure, the assembly further comprising an actuator (60) for driving the hub (54) in rotation around the central axis (AX).

6. An assembly according to claim 5, wherein the actuator (60) for driving the ballast conduit (40) in rotation (32) by the hub (54) comprises an electric motor (62) and a transmission mechanism (64) which transmits a rotation provided as an output of the electric motor (62) to the ballast hub (54) (32).

7. Assembly (12) according to claim 6, further comprising an auxiliary system (66) for rotating the ballast conduit (40) (32), this auxiliary system (66) comprising: - a mandrel (68) axially aligned on the central axis (AX) and rigidly assembled to the hub (54); - an anchoring cable (70) wound around the mandrel (68) and one end of which is attached to this mandrel (68); - a float (72) which is attached to the other end of the anchoring cable (70); - a platform (74) held vertically below the marine structure (18) and the position of which is independent of the elevation level of this marine structure (18) relative to the surface (Se) of the surrounding water (E), for example fixed on a bottom surface (Te) of the surrounding body of water (E); in which the anchor cable (70) connects the float (72) to the mandrel (68) by extending successively from the mandrel (68): - vertically downwards to reach the platform (74);- transversely away from the marine structure (18) while being held at the level of the platform (74); - vertically upwards to join the float (72).;

8. Assembly (12) according to any one of claims 5 to 7, in which the marine structure (18) is a tank comprising: - a wall (20) which delimits an interior tank enclosure (I) in which an interior volume of water can be stored in isolation from the surrounding body of water (E), - a water inlet orifice (22) which allows water to pass into the inner enclosure (I) to constitute the inner volume of water when it extends to a level of elevation said to be lowered relative to the surface (Se) of the surrounding water (E), - a water discharge orifice (24) through which the inner volume of water can be drained out of the inner enclosure (I).

9. Hydroelectric power station (10) comprising: - an assembly according to claim 8, - a hydraulic turbine (14) connected to the discharge orifice (24) of the tank (18) to generate mechanical energy (Em) when the water drained from the inner enclosure (I) of the tank (18) passes when the tank is at a so-called high level relative to the surface (Se) of the surrounding water (E),; - a generator (16) which cooperates with the hydraulic turbine (14) to convert the mechanical energy (Em) into electrical energy (Ee).

10. Method for recharging the inner enclosure (I) of the tank (18) with water between two electrical energy production cycles (Ee) of the hydroelectric power station (10) according to claim 9; comprising: - a step of lowering the tank (18) by rotating the ballast (32) conduit (40) in the first direction (RI) of rotation to fill this conduit (40) with water, to immerse the water inlet orifice (22) in the surrounding water (E); - a step of introducing water into the inner enclosure (I) through the water inlet orifice (22) to constitute the inner volume of water; and - a step of raising the tank (18) by rotating the ballast (32) conduit (40) in the second direction (R2) of rotation to purge this conduit (40) with water.

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