OPTIMIZED RECHARGE-ACTIVATED POTENTIAL ENERGY STORAGE SYSTEM FOR MARINE ENVIRONMENTS

Abstract

The present invention relates to a potential energy storage system (12), comprising: - a tank (18), with a density equal to or greater than the density of the surrounding water (E) in which it is intended to be immersed, comprising: -- a wall (20) delimiting an inner enclosure (I) in which an internal volume of water can be stored; -- a water inlet orifice (22) and a water outlet orifice (24) to allow water to pass into and out of the inner enclosure; -- means for controlling the elevation of the tank (18) in a vertical direction (AZ), comprising: -- a first set of floats (30) at the periphery of the tank (18) forming a flotation interface between this tank (18) and the surrounding body of water (E), and -- an actuator (34) for moving these floats closer together or further apart. Figure 5a

Description

Title of the invention: MARINE POTENTIAL ENERGY STORAGE SYSTEM WITH OPTIMIZED RECHARGE ACTIVATION TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to the field of hydroelectricity. More particularly, it concerns a system for storing energy in potential form for conversion into electrical energy in a marine hydroelectric power plant. TECHNICAL BACKGROUND

[0002] There are five sources of renewable energy: hydroelectric, wind, solar, biomass and geothermal energy.

[0003] Hydropower offers the possibility of being stored as gravitational potential energy, allowing it to be converted into electricity as needed. This results in the ability to modulate electricity production according to demand.

[0004] In practice, hydraulic energy is successively transformed into mechanical energy, by releasing water in the form of a fall passing through a hydraulic turbine, and then into electrical energy via an electric generator connected to the turbine.

[0005] There are many devices for hydroelectric power generation, but the most common solution involves the construction of dams. Depending on the topography, these dams are found on watercourses or built across valleys to transform a suitable natural site into a water reservoir.

[0006] However, notwithstanding their difficulty of integration and their significant ecological impact, dams suffer from a limitation in hydroelectric production capacity linked to available water reserves.

[0007] Recently, hydroelectric power plants located in a marine environment, known as "offshore," have been proposed, which harness the energy of the oceans. As is understood, these power plants do not suffer from a limitation in available water reserves.

[0008] Some of these marine hydroelectric power plants, known as gravity-fed plants, generate energy storage in potential form by means of: - immersing a basin in water to fill it; and - Raising the basin to create a height difference that generates a waterfall usable for electricity generation. This solution is notably described in document KR102287189B1, which proposes equipping such a basin with ballast designed to be filled or emptied with seawater to vary the basin's height.

[0009] However, even though these hydroelectric power plants located in a marine environment offer certain advantages, they generally have a significantly lower operating efficiency than dams due to the low water levels and flow rates generated. Furthermore, the use of a ballast tank requires diverting some of the generated hydroelectric energy to lift the water in the reservoir.

[0010] It follows that the return on investment is uncertain, particularly when also taking into consideration the installation and maintenance costs induced by this architecture.

[0011] The aim of the invention is to propose a solution for storing energy in potential form in a marine environment which makes it possible to release enough energy to justify its integration. Description of the invention

[0012] To this end, the invention relates to a system for storing energy in potential form in a marine environment comprising: - a tank, designed to be immersed in a surrounding body of water which is defined on the surface by a limnimetric height of external water, this tank comprising: — a wall which delimits an inner enclosure of the tank in which an internal volume of water can be stored in isolation from the surrounding body of water; — a water inlet orifice which allows water to pass into the inner enclosure from the surrounding body of water to constitute the internal water volume; — a water discharge opening through which the internal volume of water can be drained out of the inner enclosure; - means for piloting the tank in an up-to-down vertical direction that is normal to the surrounding water surface, these piloting means being configured to selectively raise, lower, and maintain the tank vertically relative to the surrounding water surface, so as to allow — filling the inner enclosure with water by lowering the tank to a level where the inlet opening meets the surrounding body of water; and — to generate a differential in water height between the surrounding body of water and the internal volume of water, by raising the tank; in which: - the tank has a density equal to or greater than the density of water to allow the tank to descend empty into the surrounding body of water; and - The tank elevation piloting system comprises a first set of floats arranged around the periphery of the tank, each forming a flotation interface between the tank and the surrounding body of water, and an actuator for moving these floats in a radial direction, of which: — each float in the first batch of floats having a bearing surface against a respective portion of the tank wall to form a wedge effect in cooperation with the tank; — the actuator is adapted to radially move the floats of the first set of floats by bringing them closer together or moving them away from each other so as to induce a rise of the tank by lifting it by the floats when they come together or induce a descent of the tank by moving the floats away.

[0013] The invention also relates to an energy storage system defined as follows, in which: - the tank has a flared shape; and - the respective support surface of the floats of the first batch is inclined with respect to the tank wall.

[0014] The invention also relates to an energy storage system defined as follows, in which: - the tank has a truncated conical shape; and - the floats of the first batch have a trapezoidal shape and their support surface has an arc-shaped contour which corresponds to the negative of the wall.

[0015] The invention also relates to an energy storage system as defined above, comprising a radial displacement retention device for the floats of the first batch, which does not allow the floats of the first batch of floats to move away during a rise of the tank exerted by the actuator.

[0016] The invention also relates to an energy storage system defined as follows, in which the retention device comprises, for each pair formed by a float from the first batch and the tank wall: - a rack and pinion with rotational capacity, one of which is fitted to the float and the other to the tank, the rack and pinion being meshed together along the relative travel of the float with respect to the tank wall; and - a selective pinion rotation blocking device which blocks pinion rotation in the opposite direction to the direction defined when the tank is raised when the floats of the first batch are brought closer together.

[0017] The invention also relates to an energy storage system defined as follows, in which the actuator comprises: - a plurality of anchor cables; - a second set of floats arranged radially around the floats of the first set, each float of the first set cooperating with a float of the second set via at least one cable from the plurality of anchor cables; - a cable winding system designed to control the length of the anchor cables; - a platform held vertically below the tank and floats, and whose position is independent of variations in the height of the tank, for example fixed on a bottom surface of the surrounding body of water; in which each anchor cable connects a float of the second batch to the tank by extending successively from the float of the second batch: - vertically downwards to reach the platform; - radially towards the tank while being held at the level of the platform; - by forming a ramp with vertical and radial components until it reaches the float of the first corresponding batch; and - by straddling this float from the first batch.

[0018] The invention also relates to an energy storage system as defined above, in which the actuator further comprises a cable winding system intended to control the length of the anchor cables, this cable winding system comprising drums integrated each in a respective float of the second set of floats.

[0019] The invention also relates to a hydroelectric power plant comprising: - a potential energy storage system as defined above; - a hydraulic turbine connected to the discharge port to generate mechanical energy as the water drained from the inner chamber of the tank passes through; - a generator that cooperates with the hydraulic turbine to convert mechanical energy into electrical energy.

[0020] The invention also relates to a hydroelectric power plant defined as follows, comprising a structure whose position is independent of variations in the height of the tank, in which: - the hydraulic turbine and the generator are permanently installed on this structure; and - a variable length pipe that connects the discharge port of the energy storage system to the turbine.

[0021] The invention also relates to a hydroelectric power plant as defined above, comprising a plurality of energy storage systems, several pipes of variable length each associated with a separate energy storage system, a hydraulic turbine and a generator; in which the variable length pipes each connect the discharge port of the energy storage system corresponding to a common pipeline that feeds the hydraulic turbine.

[0022] The invention also relates to a hydroelectric power plant as defined above, in of which the variable length pipe is a telescopic pipe made up of several interlocking sections that are movable relative to each other. Brief description of the drawings

[0023] Other features and advantages of the invention will become apparent upon reading the detailed description that follows, for an understanding of which reference should be made to the accompanying drawings in which: [Fig.1] is a schematic diagram of a hydroelectric power plant according to an embodiment of the invention, comprising a hydraulic turbine, an electric generator linked to the turbine and a potential energy storage system comprising a vertically movable tank in a surrounding body of water and equipped with a discharge channel which leads to the turbine; [Fig.2] is a comparative graph illustrating, at iso-volume of liquid contained in a container, the variation in height of liquid depending on the cylindrical or conical shape of the container; [Fig.3] is a discretized cone diagram illustrating the variation in volume as a function of the height of water contained; [Fig.4] illustrates the evolution of a height differential as a function of variations in the height of water contained in the tank and the elevation of the tank relative to the surrounding water surface. [Fig.5a] represents in radial and vertical sections the energy storage system comprising a truncated conical contour tank and a first set of floats movable relative to the tank to control its elevation relative to the according to a preferred mode of the invention, and which illustrates a tank descent actuation mode; [Fig.5b] represents in section the energy storage system corresponding to that of [Fig.5a], illustrating a method of actuation of the floats of the first batch in tank elevation; [Fig.5c] corresponds to a radial projected view of the tank centered on a first-batch float of the energy storage system of Figures 5a and 5b, which illustrates a first-batch float retention device arrangement to selectively allow or prohibit their movement; [Fig.6a] and [Fig.6b] represent in radial and vertical sections the energy storage system equipped with a float displacement actuator according to an embodiment of the invention, comprising a second set of floats and anchoring cables; [Fig.6c] illustrates an example of the design of a system for controlling the length of an anchor cable; [Fig.7a] and [Fig.7b] represent radial section views of the storage system corresponding respectively to figures 5a and 5b, and which illustrate the behavior of a telescopic conveying pipe which connects the tank to the turbine within a hydroelectric power plant according to an embodiment of the invention; [Fig.8a] represents in vertical section a hydroelectric power plant according to a first variant of the invention, which includes a hydraulic turbine, an electric generator linked to the turbine, and three potential energy storage systems which supply a common conduit connected to the turbine; [Fig.8b] represents in vertical section a hydroelectric power plant according to a second embodiment of the invention, which includes a hydraulic turbine, an electric generator linked to the turbine, and five potential energy storage systems which supply a common conduit connected to the turbine; [Fig.9a] is a cycle table of operation of the hydroelectric power plant with three energy storage systems according to [Fig.8a], depending on the tide; [Fig.9b] is a cycle table of operation of the hydroelectric power plant with five storage systems of [Fig.8b], depending on the tide. DETAILED DESCRIPTION OF THE INVENTION

[0024] In the description that follows, identical, similar or analogous elements will be designated by the same reference numerals.

[0025] The idea behind the invention is based on the desire to propose a marine hydroelectric power plant which allows optimized storage of energy in the form of potential energy to convert it into electrical energy, like a dam but without being subject to a limitation of available water.

[0026] A hydroelectric power plant according to a first embodiment of the invention, identified by 10 on [Fig.1], comprises an energy storage system 12, a hydraulic turbine 14 and a generator 16.

[0027] The energy storage system 12 includes a tank 18 intended to be immersed in a surrounding body of water E which is defined at surface Se by a limnimetric height of surrounding water He.

[0028] In the following, we will adopt, by way of non-limiting agreement, vertical and radial orientations related to the tank 18 and identified respectively by the axes AZ and A Y. 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 a direction orthogonal to the radial direction. Therefore, the terms "bottom" B and "top" H are to be considered in the vertical direction, with bottom oriented towards the bottom of the surrounding body of water E at the location of the tank.

[0029] The tank 18 includes a wall 20 which radially delimits an inner enclosure I of the tank and in which an internal volume of water can be contained.

[0030] 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 such an opening at the top of the tank, referred to as the highest vertical section of the tank, as illustrated in [Fig. 1] and identified by 22.

[0031] This tank 18 includes a so-called water inlet opening, formed through the wall 20, which allows water to pass into the inner chamber I from the surrounding body of water E to constitute the internal water volume. As understood, the internal water volume corresponds to a portion extracted from the surrounding water E.

[0032] This inlet port can be equipped with a restriction, such as a non-return valve, to prevent reverse water flow, 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 passage without requiring a restriction.

[0033] In the following, the opening 22 will be considered the intake port, but the invention is not limited to this feature.

[0034] In addition, the tank 18 includes a water discharge orifice, identified by 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 inner enclosure I.

[0035] Within the framework of the invention, the aim is to move the tank 18 along the vertical direction AZ, so as to be: - lowered, that is to say moved vertically downwards, to submerge the inlet passage and thus lead to the filling of the inner chamber I with water; and - elevated, namely moved vertically upwards, after filling the inner enclosure.

[0036] Grooves can 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.

[0037] The filling of the inner enclosure I is complete when the surface of the water contained within it, denoted Si, coincides with the surface Se of the surrounding water extent E.

[0038] Raising the tank 18 leads to a differential in water height, denoted 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.

[0039] Once the tank is raised, the transformation of potential energy into electrical energy consists of draining, through the discharge orifice 24, this volume of stored water so as to form a waterfall that encounters the turbine. As it passes through the turbine 14, mechanical work Em is extracted from the hydraulic energy Eh, and is simultaneously converted into electricity Ee by the generator 16, which cooperates with the turbine 1.

[0040] Energy optimization of the storage system during emptying

[0041] In order to increase the energy recovery potential of the hydroelectric power plant 10, it is aimed, according to a first aspect of the invention, to maximize the height differential AH during the time associated with emptying.

[0042] In the context of a hydroelectric power plant according to the invention, the electrical power P generated by the generator 16 is expressed by the following expression: P = Ç. with: Q denoting the falling water flow rate; p corresponding to the density of water; g, Newton's gravitational constant; and q denoting the efficiency ratio of the hydraulic turbine 14 associated with the generator 16.

[0043] Based on this expression, it is understood that the greater the height differential AH is during emptying, the higher the electrical energy generated.

[0044] In this respect, a first distinctive feature lies in the shape of the tank 18, which is shaped to define an inner enclosure 1 that widens as it extends vertically upwards. With this arrangement, the inner enclosure 1 thus presents a cross-sectional area that increases upwards in the vertical direction.

[0045] With regard to [Fig.2] which illustrates, for a unit of the same volume, the variation in height of a liquid contained either in a cone whose circular base is oriented downwards, denoted hco, or in a cylinder, denoted hcy, when it is purged at the same flow rate, it is observed that: - the height of the liquid in the cylinder is proportional to the volume, that is to say, it behaves as a linear function; and - the height of liquid in the cone follows a curved evolution whose values ​​are greater than those measured in the case of the cylinder.

[0046] This comparative analysis shows that defining an inner chamber I of the tank 18 as conical, and more generally as flared, makes it possible to limit the drop in water level in the tank 18 during a portion of the emptying process. Since the height differential AH is a function of the water level in the tank 18, denoted Hi, and the elevation of the tank relative to the surrounding body of water E, the decrease in height differential AH is therefore slower. In other words, providing a flared shape for the inner chamber I allows, during the same emptying time, for a greater generation of electrical energy to be maintained for a longer period compared to an inner chamber with a non-flared shape. Consequently, a tank 18 defined according to the invention allows for greater electrical power generation.

[0047] In order to further maximize the differential height value AH along the drain, the invention prefers to adopt a frustoconical inner chamber I with a vertical axis. This feature is illustrated in [Fig. 1]. The wall 20 of the tank defines a circular bottom 26. Advantageously, the discharge orifice 24 is positioned at this bottom of the tank to allow maximum drainage of the water contained in the inner chamber I, if necessary.

[0048] In particular, the shape of the truncated cone corresponds to a cone from which most of the portion extending from its apex has been removed. As understood, the aim here is to retain only a minor portion of the cone from its base, that is, less than 50% of the overall height of the cone, and advantageously less than 33%. To understand the benefit of this particular geometry, it is necessary to examine in more detail the variation in water height within a cone by means of a theoretical, stepped division of the volume of liquid contained in the cone into several segments of equal height, as shown in [Fig. 3]. This series of segments is bounded by two termination segments, including a starting segment Td located closest to the cylindrical base of the cone, and an ending segment Tf located closest to the apex of the cone.The initial section Td corresponds to the stage at which the lowering of the liquid surface S is first observable during the emptying. Consequently, the lowering of the liquid surface S at the very end of the emptying is noticeable at the final section Tf.

[0049] It is directly observable that the volume of water V occupied at a given section is greater than the volume of water occupied at the section directly below it. Since the volume to be drained at this section is greater than that at the section below it, a decrease in water level ensues, which accelerates as the height decreases at a constant drainage rate.

[0050] Given that the volume of water occupied at the starting section Td, identified by Vd, is the largest, the water level at the beginning of the draining process varies the least. As can be understood, retaining only the portion of the cone near the base to define the contour of the inner enclosure I allows the water level drop to be minimized, and thus maintains a differential height value AH as close as possible to its maximum value when the tank is raised during draining.

[0051] Shaping the tank 18 so that its internal enclosure I has a frustoconical contour corresponds to the preferred embodiment of the invention. To satisfy this geometric condition, it may be appropriate to shape the tank in a generally frustoconical form and with a wall of constant thickness as in the example of [Fig. 1].

[0052] It should be noted, however, that the invention is not limited to this particular shape, as long as it flares out as it extends vertically upwards to generate a gain in height differential AH. By way of non-limiting examples, the tank 18 can be shaped to delimit an internal enclosure in the shape of a truncated pyramid with a polygonal base, or even a funnel shape without departing from the scope of the invention.

[0053] A second feature aimed at maximizing the height differential AH lies in the means used to raise the tank 18 during emptying.

[0054] In practice, to raise the tank 18 during emptying, it is necessary to generate a vertical force directed upwards and of greater intensity than the resultant weight of the tank, namely greater than the sum of the weight of the empty tank and the weight of the water contained in the inner enclosure I.

[0055] In this regard, the invention provides for the use of flotation means which generate a vertical force under the effect of Archimedes' principle. These means are specifically designed to be able to lift the tank 18 under limiting conditions, namely when the inner chamber I is completely filled, in order to generate a height difference AH regardless of the volume of water contained in chamber I.

[0056] The use of such flotation devices is particularly advantageous for two reasons:

[0057] On the one hand, given that these flotation devices maintain the tank in a state of equilibrium with respect to the surrounding water surface Se, they allow for the generation of a height differential AH that is independent of variations in the surrounding water level He that may exist, particularly under the effect of the tide. The generation of electricity by means of the drained water passing through the turbine 14 is therefore not subject to any parasitic effect of the tide.

[0058] Furthermore, these flotation devices also compensate for the drop in water level inside the enclosure I, measured at the surface Si, during emptying. Indeed, since the volume of water contained within the tank 18 decreases during emptying, this results in a progressive reduction of the mass to be lifted. This reduction in mass induces a progressive and spontaneous rise of the tank as the water is discharged, under the effect of the vertical force generated by the flotation devices.

[0059] As is understood, compensation for the drop in water height is observed by the rising of the tank under the effect of the decrease in the mass of water contained in the enclosure I, which would not be the case with the use of lifting means of the freight elevator type at a fixed height value, independent of the surface Se of surrounding water E.

[0060] In view of the foregoing, it is envisaged according to the first aspect of the invention to: - to shape the inner enclosure I of the tank 18 in the form of an upward flare, advantageously in the form of a truncated cone, to limit the fall of water level in the inner chamber I during draining; and - to ensure the elevation of the tank 18 by means of flotation which generates a lifting force on the tank 18 which raises the tank as the inner chamber I empties.

[0061] This combination makes it possible, by optimizing the shape of the tank 18, for example the angle of the truncated cone in such a case, and the force exerted by the flotation means, to generate a height differential AH that is both high and tends to remain constant throughout all or most of the emptying process. With this solution, it is possible to produce electrical energy at full potential throughout the emptying process.

[0062] This behavior is illustrated in [Fig. 4] for a specific case of emptying a tank lasting six hours, the height of which, measured between the bottom 26 and the opening 22 at the top of the tank, is six meters. It can be observed that the elevation Hc of the tank by the flotation means, simultaneously with the decrease in the total mass of the tank over the time t associated with the emptying, compensates for the drop in water height Hi in the inner chamber I, tending towards a height differential AH whose value tends to be constant.

[0063] It should be noted that a variation in the cross-section of the discharge orifice 24 can be considered to provide an additional component to the management of the balance of the height differential AH along the drain.

[0064] Similarly, it can also be assumed that the force exerted by the flotation means is adjustable, these flotation means being able, for example, to take the form of ballasts. However, the invention is not limited to this solution, and allows the use of floats exerting a constant lifting force.

[0065] Energy optimization of the storage system between two emptying operations

[0066] Overall, the electrical energy produced by the power plant 10 corresponds to the electrical energy generated Ee at emptying, from which is deducted the energy to be supplied to carry out a cycle of descent and ascent of the tank 18.

[0067] On this basis, a second aspect of the invention aims to limit as much as possible the energy required to supply the vertical movement of the tank 18 in order to increase the energy recovery potential of the hydroelectric power plant 10.

[0068] In this regard, another particularity of the invention lies in the means used to control the elevation of the tank in the vertical direction relative to the surrounding body of water surface Se.

[0069] The mass of water contained in the inner enclosure I opposes in practice the raising of the tank 18, and conversely the absence of water in the inner enclosure I tends to oppose its immersion to load it.

[0070] To satisfy this dual condition of lowering the empty tank 18 to fill the inner chamber I; and of raising the tank 18 containing water to generate the height difference AH, the energy storage system 12 comprises means of piloting in elevation, including: - the tank itself, which is formed at a density equal to or higher than the surrounding water so that it can flow when empty; and - a first batch of 30 floats which are radially movable relative to tank 18.

[0071] In the example of Figures 5a and 5b, the floats 30 of the first set are radially arranged around the periphery of the tank 18, advantageously spaced two by two at a regular interval. They are delimited by a hull shaped with an inclined side 32. This inclined side 32, intended to form a bearing surface against the tank 18, advantageously has a shape that at least partially follows the contour of the flared tank 18.

[0072] In the example of figures 5a and 5b, the tank 18 has a truncated conical shape and the floats 30 of the first batch have an overall trapezoidal shape, each presenting a conical surface 32 with a circular arc profile in vertical section, which corresponds to the negative of the wall 20.

[0073] These floats 30 are movable radially in directions SI and S2, referred to as moving away and coming closer respectively, between: - a first position, illustrated in [Fig. 5a], in which they are spaced apart to allow tank 18 to submerge naturally for filling; and - a second position, illustrated in [Fig. 5b], in which they are brought together to raise them entirely or substantially above the water level surface. They are held in this second position while awaiting drainage and during this drainage stage.

[0074] As understood, the floats 30 of the first batch act as muscles, allowing the tank 18 to descend or rise. In the second position, since they maintain the tank 18 in an elevated position, they assume the role of flotation means as defined in the first aspect of the invention dedicated to the energy optimization of the storage system during emptying. Thus, the floats 30 perform a dual function, acting both as flotation means, cooperating with the tank 18 to keep it afloat, and as actuation means to perform a descent and ascent cycle of this tank 18.

[0075] In view of the above, the floats 30 of the first batch are dimensioned and designed so as to form a flotation interface between the filled tank 18 and the surrounding body of water E.

[0076] Also, according to the invention, it is aimed at moving the floats 30 of the first batch in an overall movement, in a manner analogous to a diaphragm, to distribute the load and thus maintain control of the balance.

[0077] As will be understood, the invention makes judicious use of the flared shape of The tank 18, as described in the first aspect of the invention, is moved vertically by means of a radial displacement of floats 30 that cooperate with it, each acting as a wedge. The interface between the floats 30 of the first set and the tank 18 forms an inclined plane that allows the vertical force required to lift the filled tank to be converted into a reduced radial force.

[0078] With this solution, there follows a limitation of energy loss in the hydroelectric power plant 10.

[0079] It is suggested according to the invention to provide a system for holding the floats 30 in position against the wall 20 of the tank, namely a system which always guarantees contact between the float and the wall regardless of the level of elevation of the tank 18. Such a system adds a component of operational safety by preventing a float from tipping over or escaping.

[0080] According to another feature, the means for raising the tank 18 may include a radial retention device 31 that prevents the floats 30 of the first batch from moving unexpectedly in the direction SI away from the tank when the aim is, on the contrary, to raise the tank 18 and hold it in the raised position. This device acts so as to force the floats 30 to move only in the direction S2 in such a case.

[0081] According to a preferred embodiment, such a retention device 31 may include, for each of the pairs formed by a float 30 and the wall 20 against which it is supported, at least one rack 31a, at least one pinion 31b which meshes with the rack 31a, and a system 31c for selectively locking the rotation of the pinion 31b.

[0082] In the example of [Fig. 5c], the wall 20 of the tank 12 is equipped, for each float 30, with two vertically oriented racks 31a, and additionally, the floats 30 are equipped with a pair of pinions 31b that protrude on either side to mesh with one of the racks 31a. In this example, the rack 31a is installed on the wall 20 of the tank 18, while the pinion 31b is fitted to the float 30 in question, but a reverse arrangement can be used without departing from the scope of the invention. The direction of rotation of the pinion 31b is determined by the selective locking system 31c, which only allows rotation in the direction corresponding to the movement of the float in the direction S2 as illustrated in [Fig. 5b] during a tank raising step.

[0083] With this arrangement, the movement of the floats 30 in the S2 approach direction follows an incremental logic: as long as the selective locking system 31c does not allow the associated pinion 31b to rotate freely, it prevents the tank 18 from descending. It follows that the energy storage system 12 is not affected during the raising of the tank 18 in the event of parasitic force exerted on one or more floats 30. in the opposite direction to direction S2.

[0084] Such a selective blocking system 31c as described may be an active system which is controlled by servo control or a passive system which activates / deactivates autonomously according to the relative position of the floats 30 with respect to the tank 18.

[0085] It should also be noted that the retention device, by its function, contributes to increasing the energy recovery potential of the hydroelectric power plant 10. Indeed, by mechanically blocking the radial movement of the floats 30 in the opposite direction to S2, it limits the radial force to be applied to these floats 30 to just what is necessary to raise the tank 18. In other words, the retention device makes it possible to isolate the actuation of the floats 30 from external parasitic constraints which could lead to having to apply a greater radial force to achieve the raising of the tank.

[0086] As regards the actuator for moving the floats 30 of the first batch, noted 34, it is configured to move the floats 30 of the first batch by exploiting tidal energy, namely by taking advantage of the natural change in height He of the surrounding body of water E.

[0087] As is understood, by means of this exploitation of tidal energy, external to the system, the aim is to be able to operate the floats 30 of the first without batch without needing to draw the hydroelectric energy generated by the power plant 10 according to the invention.

[0088] With reference to Figures 6a and 6b, this actuator 34 is formed by the combination of: - anchor cables 36; - a second batch of 38 floats; and - a 40-foot underwater platform.

[0089] The floats 38 of the second batch are arranged radially around the tank 18 and the floats 30 of the first batch. They are in the form of coils and are advantageously connected in pairs so as to form together a ring of revolution with a vertical axis.

[0090] The underwater platform 40 is held vertically below the tank 18 and the floats 30, 38 of the first and second batches, and its position is independent of variations in the height of the tank and the radial displacement of the floats 30 of the first batch. In practice, it is advisable to fix this platform 40 to the bottom Te of the surrounding body of water E.

[0091] As regards the anchor cables 36, they each cooperate with a float 30 of the first set and connect a float 38 of the second set to the tank 18. Each cable 36 extends serpentinely from the float 38 of the second set to which it is attached towards the tank 18 along the following path: - it extends the float 38 of the second batch by diving to reach the underwater platform 40; - it is held along a portion of the platform 40 by adopting a radial orientation directed towards the tank 18. The platform 40 can be equipped with a slide in which the cable is held, or with rings through which the cable passes; - it rises, forming a ramp with a vertical and radial component that is at least partially parallel to the wall 20 of tank 18 until it comes into contact with a radially external slice of a float 30 from the first corresponding batch; and - it overlaps said float 30 of the first batch before being fixed at the top of tank 18. Overlapping of float 30 is understood as following the contour of the float located outside the water.

[0092] From a kinematic point of view, considering the tank 18 lowered for filling as illustrated in [Fig.6a], and the anchor cables 36 in tension, a rise in the surface height Se of surrounding water under the combined effect of the gravitational forces of the Moon and the Sun, tends to raise the floats 38. It is understood that the floats 38 of the second batch, which float on surface Se, are led to follow the rise in water height He under the effect of the Archimedes' thrust, denoted Fa, to which they are subjected.

[0093] It should be noted that the actuator 34 is not strictly limited to the architecture described above. For example, several floats 30 from the first batch can cooperate with the same float 38 from the second batch, or several floats 38 from the second batch can be assigned to the actuation of the same float 30 from the first batch.

[0094] This Archimedes' thrust, to which the floats 38 of the second group are naturally subjected, corresponds to a force oriented vertically upwards applied at the end of the cable 36. In reaction, it tends to pull on the other end of the anchor cables 36, which is connected to the tank 18. The particular serpentine path of the cables 36 then converts this vertical upward tensile force into a radial pressing force along S2, which is applied to the floats 30 of the first group by the overlapping effect of the floats 30 of the first group by the cables 36.

[0095] Conversely, a lowering of the water height He results in a descent of the floats 38 of the second batch, naturally leading to a displacement of the floats 30 in the direction SI, and a natural immersion of the tank 18.

[0096] The actuator can be equipped, for each anchor cable 36, with a control system 41 of the corresponding cable length. This system, an example of whose arrangement is illustrated in [Fig. 6c], allows adaptation to the tidal coefficient, i.e., to the variations in amplitude of the different tides, so as to maintain control of the forces exerted on the floats 30 of the first set. It comprises, for each anchor cable 36: - a drum P, or chuck, around which the corresponding cable 36 is wound; and - an electric motor M which can rotate the drum in one direction or another to reduce / increase the length of the cable 36 by winding / unwinding around the drum.

[0097] The drum P and the electric motor M of the pilot systems 41, each associated with a respective cable 36, can advantageously be arranged at either end of the cable 36, namely either fixed to the tank 18 or fixed to the float 38 of the second batch. Preferably, these elements are encapsulated in the float 38 of the second batch with which the cable 36 cooperates, as illustrated in the example of [Fig. 6c].

[0098] It should also be noted that such a piloting system 41 for the length of the anchor cables 36 can compensate for a lack of tidal energy, namely by simulating the effect of a rise or fall in the water level He of the surrounding area. As understood, winding each of the cables 36 around the drum P reduces their length to provide the effect of a rise in water level He and thus cause the tank 18 to rise. Conversely, unwinding the cables 36 reverses the direction of the forces, which naturally induces a displacement of the floats 30 away from the tank by reaction to the natural immersion of the tank 18.

[0099] As understood, with the particular arrangement of the actuator 34, the tidal force alone may be sufficient to move the floats 30 of the first batch. The piloting system 41, with the length of the anchor cables 36, can add an additional component to the pressing force exerted on the floats 30 of the first batch in the event of a low tide. Also, the motors M of the piloting system 41, with the length of the cables 36, can be used to raise the tank 18 even in the event of a tide. In other words, the piloting system 41, with the length of the cables 36, makes it possible, by means of an energy expenditure, to overcome the effects of tides when necessary in order to maintain control of the filling / emptying cycle of the tank 18.

[0100] Finally, it should be noted that the floats 30, 38 are not limited to the shapes described based on the figures. The substantially trapezoidal shape of the floats 30 in the first batch is particularly suitable when the tank 18 has a radial conical or frustoconical cross-section. However, the floats 30 can be shaped differently within the scope of the invention, particularly to adapt to a different external shape of the tank 18, provided that they have a bearing surface against a respective portion of the wall 20 to create a wedge effect. As will be understood, the tank 18 is not limited to a particular external geometry to form a flare, as in the case of the frustoconical shape. Any shape can be used as long as a complementary tank-float relationship is possible to raise or lower the tank 18 vertically when they move radially towards or away from each other.

[0101] Structure and operating cycle of the hydroelectric power plant

[0102] Regarding the positioning of the turbine 14 and the generator 16, they can be fixed to the tank 18 or installed on a structure whose position is independent of variations in the height of the tank. For example, they can be mounted on the platform 40, in the case of the embodiment of the actuator 34 described with reference to Figures 6a and 6b.

[0103] The installation of the turbine 14 and the generator 16 on a structure separate from the tank 18 requires the use of a variable length conduit which connects the discharge port 24 of the energy storage system 12 to the turbine 14.

[0104] According to a preferred embodiment of the invention, with reference to Figures 7a and 7b, this variable-length conduit, denoted 42, is formed by the combination of several interlocking sections 44, 46 mounted to move relative to each other. In the example of Figures 7a and 7b, the conduit 42 comprises two sections 44, 46, one of which is fixed to the tank and the other connected to the turbine 14. With this arrangement, it is understood that the conduit 42 has a telescopic character to maintain a continuous connection from the discharge port 24 to the turbine 14 despite variations in the height of the tank 18. The variations in the height of the tank 18 can be induced by variations in the surrounding water level He according to tidal cycles, as well as by the passive raising of this tank 18 during emptying by flotation means, as stated above.

[0105] It should be noted that the invention is not limited to this telescopic conduit architecture, and allows for the consideration of other connection solutions, such as an accordion-shaped tubular flexible hose.

[0106] The hydroelectric power plant 10 has been described according to a first embodiment as comprising a turbine 14, a generator 16 and a single energy storage system 12. It follows from the detailed description that it is necessary to respect a vertical displacement and water loading time of the tank 18 before electrical power can be generated by emptying.

[0107] Alternatively, and particularly to meet a continuous need for electricity production, the hydroelectric power plant 10 may include several energy storage systems 12 whose discharges feed a single shared turbine 14. In the example of [Fig. 8a], the hydroelectric power plant 10 includes three energy storage systems 12, indexed a, b, and c, but an architecture with two or more than three energy storage systems 12 may be used without departing from the scope of the invention.

[0108] The multiplication of energy storage systems 12 supplying discharge water to the same turbine tends to a more constant electrical production, given that when one tank 18 is refilled with water, another can be emptied at the same time.

[0109] In such a hydroelectric power plant architecture 10 according to the invention, at each energy storage system 12 is associated with a conduit 42 of respective variable length which connects the corresponding discharge orifice to a common pipeline 50 supplying the turbine 14.

[0110] Generally speaking, a day has two complete tidal cycles. Each cycle corresponds to the succession of an increase in water level He, called "rising tide" of a duration of approximately six hours, and a decrease in water level, called "falling tide", of equivalent duration.

[0111] Considering the hydroelectric power station 10 of [Fig.8a], equipped with the three energy storage systems 12a, 12b, 12c, it is possible to achieve a continuous generation of electrical energy by means of a descent / ascent actuation of the tanks 18 using only tidal energy.

[0112] As a reminder, the configuration of actuator 34 as defined allows the tank to rise spontaneously when the surrounding water surface height Se increases, and conversely, to descend when the surrounding water surface height Se decreases. Based on this, it is preferable to begin filling a tank at the beginning of the rising tide, when the surrounding water surface height Se is at its lowest.

[0113] Following this principle, continuous electrical energy production is obtained by means of the operating cycle as shown in [Fig. 9a]. As can be seen from this figure, it is; - to condition the 18 tanks so that their emptying and refilling takes place over a period of 6 hours each; - to stagger the emptying of the tanks of the three energy storage systems 12a, 12b, 12c, so as to always maintain a tank in a state of emptying during each rising or falling tide; and - to refill with water the two tanks which need to be refilled during a given rising tide, namely the tanks which were emptied during either the rising tide or the falling tide which preceded this given rising tide.

[0114] A hydroelectric power plant 10 with three energy storage systems 12a, 12b, 12c thus makes it possible to achieve continuous electrical power generation. However, it remains advantageous to increase the number of energy storage systems, i.e., to include more than three equipping the same hydroelectric power plant 10.

[0115] Indeed, the multiplication of energy storage systems allows a shorter emptying time for each of the tanks, since several of them can be consecutively emptied in whole or in part during the same tidal phase.

[0116] Fig. 8b illustrates another example of power plant architecture 10, equipped with five energy storage systems 12a, 12b, 12c, 12d and 12e.

[0117] For a given tank filling time of six hours, the optimized emptying time is set at three hours in the case of this variant with five storage systems. For a power plant with four energy storage systems, the optimized emptying time would be four hours.

[0118] With reference to the attached [Fig.9b] which illustrates an example of the operating cycle of the hydroelectric power plant equipped with five energy storage systems 12a, 12b, 12c, 12d and 12e of [Fig.8b], it should be noted that: - two tanks are successively emptied during the same tidal phase, each for three hours; - The refilling of a tank can be interrupted at the end of a rising tide phase and then resumed at the beginning of the next rising tide phase; as seen, in particular, for system 12d between the first and second rising tide phases. This scenario is necessary when the tank is emptied at the beginning of a rising tide phase and there is still time to begin refilling it.

[0119] As understood, the greater the number of systems 12 equipping the hydroelectric power plant 10, the shorter the required emptying time. This reduction in emptying time then allows for a reduction in the capacity of the tanks 18, which makes it possible to reduce the size of the internal containment I. In practice, this translates into the possibility of manufacturing tanks, equipping the same power plant 10, with a smaller radius as their number increases. As understood, increasing the number of storage systems 12 reduces the space required for their respective installation.

[0120] Such a reduction in tank size, made possible by increasing the number of storage systems 12 equipping the same power plant 10, therefore allows for a reduction in the size of the flotation devices used to keep these tanks 18 elevated above the surface. Indeed, the mass to be lifted is all the less significant the smaller the tank. In the example shown in the figures, this corresponds to a reduction in the size of the floats 30.

[0121] Finally, it should be noted that the invention is not limited to the arrangement of the storage systems 12 of the hydroelectric power plant 10. The aim in practice is to favour the most compact arrangement possible. A trefoil arrangement, namely in which the tanks of the hydroelectric power plant 10 are inscribed in a circle as shown in [Fig. 8a], or a herringbone arrangement as in the example in [Fig. 8b], marked by a staggered positioning on either side of the common pipeline 50 which they supply with discharge water, are particularly interesting.

[0122] In view of the above, multiplying the energy storage systems equipping the same hydroelectric power plant 10 offers several advantages, in particular It reduces bulk and simplifies manufacturing.

[0123] In this regard, it is planned according to the invention to preferentially use a hydroelectric power plant arrangement with five energy storage systems.

[0124] In the preceding description, two aspects aimed at optimizing the energy recovery of the storage system were described. The first aspect concerns optimization during emptying by means of a flared shape of the inner chamber I of the tank and flotation means allowing a height differential to be maintained between the internal volume of water and the surrounding water. The second aspect concerns the actuation of the tank's raising / lowering via a wedge-effect float / tank cooperation that does not require energy expenditure.

[0125] It is particularly advantageous to combine these two aspects to strive for the most optimized hydroelectric power plant 10. Nevertheless, these aspects can be considered independently of each other without departing from the scope of the invention.

[0126] With regard to the first aspect of the invention aimed at optimizing energy recovery, the energy storage system according to the invention: - is not limited to the specific morphology of tank 18 as described on the basis of [Fig.4], since it allows us to delimit an inner enclosure I whose cross-sectional area increases upwards H in the vertical direction AZ; - is not limited to the nature of the flotation means used to keep the tank 18 elevated relative to the surface Se of the surrounding water body so that the internal volume of water remains at the surface Si higher than the surface Se of the surrounding water body E.

[0127] It should be noted that the increase in the cross-sectional area of ​​the tank is not restricted to a constant value. In other words, the increase in the cross-sectional area of ​​the inner enclosure I can be linear, as in the case of a truncated cone as described, but also variable along its height. The air can also grow discontinuously, namely increasing, remaining stable, and then increasing again, the resultant always corresponding to a cross-sectional area that increases upwards in the vertical direction AZ. As can be understood, the inner enclosure I can have a distorted shape whose cross-sectional area increases, but not constantly, upwards.

[0128] Regarding the second aspect, the invention is not limited to the nature of the vertical displacement actuator used, since it allows for selectively ensuring: - a descent of the tank 18 to a level in which the inlet orifice 22 meets the surrounding body of water E, allowing the inner enclosure I to fill until the water level at the surface is balanced between the surface Si of the internal water volume and the surface Se of the body of water; and; - an elevation of the tank 18 by lifting it, allowing the internal volume of water to be emptied out of the internal enclosure I when the surface Si of the internal volume of water is higher than the surface Se of the surrounding water body.

[0129] Throughout the detailed description, the storage system 12 has been described as relating to a component of a hydroelectric power station 10. It should be noted that the invention is not limited to this particular application, the storage system 12 being able to be used for other purposes, such as, for example, as a water tower placed in a lake to irrigate adjacent crops.

Claims

Claims

1. System (12) for storing energy in potential form in a marine environment comprising: - a tank (18), intended to bathe in a surrounding body of water (E) which is defined on the surface (Se) by a limnimetric height of external water (He), this tank (18) comprising: — a wall (20) which delimits an internal tank enclosure (I) in which an internal 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 from the surrounding body of water (E) to constitute the inner volume of water, — a water discharge orifice (24) through which the internal volume of water can be drained out of the internal enclosure (I); - means for controlling the elevation of the tank (18) in a vertical up-down direction (AZ) which is normal to the surface (Se) of the surrounding body of water (E), these control means being configured to selectively raise, lower and maintain the tank vertically relative to the surface (Se) of the surrounding body of water, so as to allow: — filling the inner enclosure (I) with water by lowering the tank (18) to a level in which the inlet orifice (22) meets the surrounding body of water (E); and — to generate a water height differential between the surrounding body of water and the internal volume of water, by raising the tank (18); and in which: - the tank (18) has a density equal to or greater than the density of water to allow this tank to descend empty into the surrounding body of water (E); and - the means for controlling the elevation of the tank comprise a first batch of floats (30) arranged on the periphery of the tank (18) to each form a flotation interface between the tank (18) and the surrounding body of water (E), and an actuator (34) for moving these floats (30) in a radial direction (AY), including: — each float (30) of the first batch of floats comprising a bearing surface (32) against a respective portion of the tank wall (20) to form a wedge effect in cooperation with the tank (18); — the actuator (34) is adapted to radially move the floats (30) of the first batch of floats by bringing them closer or moving them radially away from each other so as to induce a rise in the tank (18) by lifting it by the floats (30) when they come closer or to induce a descent of the tank by moving the floats (30) apart.

2. Energy storage system according to claim 1, wherein: - the tank (18) has a flared shape; and - the respective bearing surface (32) of the floats (30) of the first batch is inclined opposite the wall (20) of the tank (18).

3. Energy storage system according to claim 1, wherein: - the tank (18) has a truncated cone shape; and - the floats (30) of the first batch have a substantially trapezoidal shape and their bearing surface (38) has an arc-shaped profile which corresponds to the negative of the wall (20).

4. Energy storage system according to claim 1, comprising a device for retaining the floats of the first batch in radial displacement, which does not allow the floats (30) of the first batch of floats to move away during a rise of the tank exerted by the actuator (34).

5. Energy storage system according to claim 4, in which the retention device comprises for each pair formed by a float (30) of the first batch and the wall (20) of the tank (18): - a rack and a pinion with rotation capacity, one of which equips the float and the other equips the tank, the rack and the pinion being meshed together along the relative movement path of the float with respect to the tank wall; and - a device for selectively locking the pinion in rotation which blocks a rotation of the pinion in a direction opposite to the direction defined during the rise of the tank when the floats (30) of the first batch are brought closer to each other.

6. Energy storage system according to any one of claims 1 to 5, wherein the actuator (34) comprises: - a plurality of anchor cables (36); - a second batch of floats (38) arranged radially around the floats (30) of the first batch, each float (30) of the first batch cooperating with a float (38) of the second batch via at least one cable (36) of the plurality of anchor cables (36); - a cable winding system provided to control the length of the anchoring cables; - a platform (40) held vertically below the tank (18) and the floats (30, 38), and whose position is independent of variations in height of the tank (18), for example fixed on a bottom surface (Te) of the surrounding body of water (E); in which each anchoring cable (36) connects a float (38) of the second batch to the tank (18) by extending successively from the float (38) of the second batch: - vertically downwards to reach the platform (40); - radially towards the tank (18) while being held at the level of the platform (40); - by forming a ramp with a vertical and radial component until it reaches the float (30) of the corresponding first batch; and - by overlapping this float (30) of the first batch.

7. Energy storage system according to claim 6 wherein the actuator (36) further comprises a cable winding system provided for controlling the length of the anchor cables, this cable winding system comprising drums each integrated into a respective float (38) of the second batch of floats.

8. Hydroelectric power station (10) comprising: - a system (12) for storing energy in potential form according to one of the preceding claims; - a hydraulic turbine (14) connected to the discharge orifice (24) to generate mechanical energy (Em) when the water drained from the inner enclosure (I) of the tank (18) passes through; - a generator (16) which cooperates with the hydraulic turbine (14) to convert the mechanical energy (Em) into electrical energy (Ee).

9. Hydroelectric power station (10) according to claim 8, comprising a structure whose position is independent of variations in height of the tank (18), in which: - the hydraulic turbine (14) and the generator (16) are fixedly installed on this structure; and - a variable length pipe (42) which connects the discharge port (24) of the energy storage system (12) to the turbine (14).

10. A hydroelectric power plant (10) according to claim 9, comprising a plurality of energy storage systems (12), a plurality of variable-length conduits (42) each associated with a separate energy storage system (12), a hydraulic turbine (14) and a generator (15). neratrix (16); wherein the variable length pipes (42) each connect the discharge port (24) of the corresponding energy storage system (12) to a common pipe (50) which supplies the hydraulic turbine (14).

11. Hydroelectric power station according to claim 8 or 9, in which the variable length pipe (42) is a telescopic pipe formed of several sections (44, 46) nested and movable relative to each other.

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