Pressure vessel with circumferential reinforcing elements

Abstract

The present invention relates to a pressure vessel comprising a tubular portion and two bottoms (5), the bottoms (5) being arranged at the ends of the tubular portion. The tubular portion comprises a cylindrical wall (1) and a layer of circumferential reinforcing elements (2) wound around the cylindrical wall (1). In addition, the modulus of elasticity of the material of the cylindrical wall (1) is lower than the modulus of elasticity of the material of the first layer of circumferential reinforcing elements (2). The invention also relates to a system for storing and recovering energy comprising a compression means, an expansion means, a heat storage means and a compressed air vessel according to the features described above.

Description

[0001] PRESSURE TANK WITH CIRCUMFERENTIAL REINFORCEMENT ELEMENTS

[0002] technical field

[0003] The present invention relates primarily to the field of compressed air energy storage but could be applied to other pressure vessel systems.

[0004] Electricity production from renewable energy sources, such as solar panels or onshore and offshore wind turbines, is booming. The main drawbacks of these production methods are their intermittent nature and the potential mismatch between production and consumption periods. Therefore, it is important to have a means of storing energy during production to release it during periods of consumption.

[0005] There are many technologies that allow this balance.

[0006] Among them, the best known is the Pumped Storage Water Transfer Station (PSW), which uses two water reservoirs at different altitudes. Water is pumped from the lower reservoir to the upper reservoir during the charging phase. The water is then sent to a turbine, towards the lower reservoir, during the discharge phase.

[0007] The use of different types of batteries (lithium, nickel, sodium-sulfur, lead-acid...) can also meet this need for energy storage.

[0008] Another technology, flywheel energy storage (FES), involves accelerating a rotor (flywheel) to a very high speed and maintaining the energy within the system as kinetic energy. When energy is extracted from this FES system, the flywheel's rotational speed is reduced, according to the principle of conservation of energy. Adding energy to the FES system consequently increases the flywheel's speed.

[0009] Energy storage technology using compressed gas (often compressed air) is promising. The energy produced but not consumed is used to compress air to pressures between 40 bar and 200 bar using compressors (which can be multi-stage). During compression, the air temperature increases. To limit the cost of storage tanks and minimize the compressor's electricity consumption, the air can be cooled between each compression stage. The compressed air is then stored under pressure, either in natural cavities (caves) or in artificial reservoirs.

[0010] During the electricity generation phase, the stored air is sent to turbines to produce electricity. During expansion, the air cools. To prevent excessively low temperatures (-500°C) that could damage the turbines, the air can be reheated before expansion. Such facilities have been operating for several years, such as the Huntorf unit in Germany, which has been operating since 1978, and the Macintosh unit in Alabama, USA, which has been operating since 1991. These two facilities share the characteristic of using stored compressed air to power gas turbines. These gas turbines burn natural gas in the presence of pressurized air to generate very hot (5500°C and 8250°C) and high-pressure (40 bar and 11 bar) combustion gases before expanding them in turbines to generate electricity. This type of process emits carbon dioxide.

[0011] A variant is under development. It is an adiabatic process in which the heat from air compression is recovered, stored, and released back into the air before it is expanded. This is the AACAES technology (from the English "Advanced Adiabatic Compressed Air Energy Storage").

[0012] In an AACAES system, compressed air is stored in a tank independently of heat storage. In such a system, the air is stored at a temperature close to ambient temperature (typically less than 50%).

[0013] Previous technique

[0014] Currently, compressed air tanks, and more broadly, pressure vessels, are closed containers consisting of at least two ends, also called "ends," and possibly connected by an intermediate section, as shown in Fig. 1, where P represents the internal pressure. In this figure, the tank is represented, but not limited to, by a cylindrical section (the r direction being the radial direction and the z direction the axial direction of a cylindrical coordinate system associated with the tank—this system is used in the other figures and will not be detailed in each figure) with an internal diameter D. Thus, this type of tank can be, for example, a sphere made up of two hemispheres or a cylindrical container made up of two ends connected by a cylindrical section. The connections between the different parts are rigid, of the fixed type.

[0015] Furthermore, these tanks are most often made of steel to withstand high pressures. Given the large storage volumes and high pressures, the cost of constructing these large-volume pressure tanks is very high, primarily due to the amount of steel required.

[0016] In a closed cylindrical tank, bottom effects, resulting from the application of internal pressure on the tank bottom, generate tensile forces in the longitudinal direction and therefore axial stresses oll, as illustrated in Fig. 1. Regardless of the shape of the bottom (flat, domed, hemispherical, etc.), the bottom effects of this type of tank generate the following average longitudinal stress in the current part of the tank: [Math 1]

[0017] PD?

[0018] sii =

[0019] 4 t (Di + t)

[0020] Where P is the pressure applied in the reservoir

[0021] D, : the internal diameter of the tank

[0022] t: the thickness of the tank wall at the cylindrical part

[0023] When the pressure tank has thin walls, we obtain:

[0024] [Math 2]

[0025] A thin-walled pressure tank is defined as a pressure tank whose thickness is very small compared to its diameter (small thickness compared to its diameter means a ratio t / Di<5%).

[0026] Furthermore, we know the principle of prestressed concrete pipes, pipes mainly intended for fluid transfer (sanitation, water transfer, etc.) with low service pressures (less than 20 bar and most often less than 5 bar).

[0027] French patent application FR 3 055 942 A1 relates to the current section of composite steel and prestressed concrete pipes.

[0028] However, all these different solutions generate large mass tanks and high manufacturing costs.

[0029] To overcome the aforementioned drawbacks, the present invention relates to a pressure tank comprising a tubular section and two ends, the two ends being positioned at the ends of said tubular section. The tubular section comprises a cylindrical wall and at least one first layer of circumferential reinforcing elements. The first layer of circumferential reinforcing elements is wound around the cylindrical wall, which serves as a rigid base for the winding, such that the modulus of elasticity of the material of the cylindrical wall is lower than the modulus of elasticity of the material of the first layer of circumferential reinforcing elements.

[0030] Summary of the invention The invention relates to a pressure tank, comprising a tubular part and two bottoms, said two bottoms being positioned at the ends of said tubular part, said tubular part comprising a cylindrical wall and at least a first layer of circumferential reinforcement elements, said first layer of circumferential reinforcement elements being wrapped around said cylindrical wall, The modulus of elasticity of the material of the cylindrical wall is less than the modulus of elasticity of the material of said first layer of circumferential reinforcement elements.

[0031] Preferably, the modulus of elasticity of the material of the cylindrical wall is at least 10% lower, preferably at least 30% lower, than the modulus of elasticity of the material of said first layer of circumferential reinforcement elements.

[0032] According to one embodiment of the invention, at least one of said two bottoms is a domed bottom, preferably spherical or hemispherical.

[0033] Advantageously, the reservoir includes at least a second layer of axial reinforcement elements, said axial reinforcement elements extending in the axial direction and / or said axial reinforcement elements including burial in the ground of said pressure reservoir.

[0034] According to a variant of the invention, said axial reinforcement elements of said second layer continue at the level of the domed bottom towards the axial end of said domed bottom, forming a star on said domed bottom.

[0035] Advantageously, at least a second layer of axial reinforcement elements is positioned inside the inner cylinder defined by said cylindrical wall, said axial reinforcement elements of said second layer being regularly distributed over the circumference of said cylindrical wall.

[0036] Preferably, at least a second layer of axial reinforcement elements is positioned outside said tubular part, said axial reinforcement elements of said second layer being regularly distributed over the circumference of said tubular part.

[0037] Advantageously, the material of said circumferential reinforcing elements of said first layer is a polymer, preferably an aramid fiber, a nylon polyamide, a polypropylene, or a polyethylene, and even more preferably a high-strength polyethylene. Preferably, the material of said cylindrical wall is a metallic material, preferably a steel, or a polymer.

[0038] According to one embodiment of the invention, said circumferential reinforcement elements of said first layer are embedded in a protective layer.

[0039] Advantageously, said circumferential reinforcement elements of said first layer and / or said axial reinforcement elements of said second layer have a circular, substantially circular or rectangular cross-section.

[0040] According to one variant, the tank includes at least one sliding connection between said cylindrical wall and at least one of said two bottoms.

[0041] Preferably, said sliding connection is positioned between the outer diameter of said cylindrical wall and the inner diameter of said bottom.

[0042] Preferably, said sliding connection is positioned between the outer diameter of said bottom and the inner diameter of said cylindrical wall.

[0043] According to one embodiment of the invention, at least one of said two funds is embedded in the ground.

[0044] The invention also relates to an energy storage and recovery system comprising at least one compression means, at least one expansion means, at least one heat storage means and at least one compressed air reservoir as defined above.

[0045] List of figures

[0046] Other features and advantages of the system according to the invention will become apparent from the following description of non-limiting examples of implementations, with reference to the figures attached and described below.

[0047] Figure 1, already described, represents a cylindrical pressure tank according to the prior art.

[0048] Figure 2 illustrates, schematically and without limitation, one embodiment of a pressure tank according to the invention. Figure 3a illustrates, schematically and without limitation, one embodiment of a pressure tank according to the invention, comprising a layer of circumferential reinforcing elements with a rectangular cross-section.

[0049] Figure 3b illustrates another embodiment of a pressure tank according to the invention, comprising a layer of circumferential reinforcement elements of circular cross-section.

[0050] Figure 4 illustrates, schematically and without limitation, an embodiment of a pressure tank according to the invention, comprising a layer of circumferential reinforcement elements embedded in a resin.

[0051] Figure 5 illustrates, schematically and without limitation, an embodiment of a pressure tank according to the invention, comprising a layer of circumferential reinforcement elements and a layer of axial reinforcement elements, as well as domed bottoms.

[0052] Figure 6 illustrates, schematically and without limitation, an embodiment of a pressure tank according to the invention, comprising a layer of circumferential reinforcement elements and a layer of axial reinforcement elements, as well as flat bottoms.

[0053] Figure 7 illustrates, schematically and without limitation, an embodiment of a pressure tank according to the invention, comprising a layer of circumferential reinforcement elements and a layer of axial reinforcement elements, as well as flat bottoms.

[0054] Figure 8 illustrates, schematically and without limitation, another embodiment of a pressure tank according to the invention, comprising a layer of circumferential reinforcement elements and two layers of axial reinforcement elements, as well as flat bottoms.

[0055] Figure 9 illustrates, schematically and without limitation, an embodiment of a pressure tank according to the invention, comprising a layer of circumferential reinforcement elements and two layers of axial reinforcement elements, as well as sliding connections with the bottoms.

[0056] Figure 10 schematically and without limitation illustrates an embodiment of a pressure tank according to the invention, comprising a layer of circumferential reinforcing elements and a layer of axial reinforcing elements, as well as sliding connections with the ends. Figure 11 schematically and without limitation illustrates an embodiment of a pressure tank according to the invention, comprising a layer of circumferential reinforcing elements and two layers of axial reinforcing elements, a sliding connection with one of the two ends and a fixed connection with the other end.

[0057] Figure 12 illustrates, schematically and without limitation, an embodiment of a pressure tank according to the invention, comprising a layer of circumferential reinforcement elements and a layer of axial reinforcement elements, a sliding connection with one of the two bottoms and a fixed connection with the other bottom.

[0058] Figure 13 illustrates, schematically and without limitation, an embodiment of a pressure tank according to the invention, comprising a layer of circumferential reinforcement elements, a sliding connection with one of the two bottoms and a fixed connection with the other bottom, the bottoms being buried in the ground.

[0059] Description of the implementation methods

[0060] The invention relates to a pressure tank. This tank comprises a tubular section and two ends, each end of the tubular section. The ends allow the pressure tank to be sealed airtight and define a volume for fluid storage. The tubular section includes a cylindrical wall and at least one first layer of circumferential reinforcing elements, wound around the cylindrical wall, which serves as a rigid base for the winding. The modulus of elasticity of the material of the cylindrical wall is lower than the modulus of elasticity of the material of the first layer of circumferential reinforcing elements. Consequently, deformation of the cylindrical wall tends to bring the cylindrical wall into contact with the circumferential reinforcing elements, which thus contribute to resisting pressure forces.Therefore, the thickness of the cylindrical wall can be reduced because the circumferential stresses related to internal pressure are absorbed by both the cylindrical wall and the circumferential reinforcement elements. Reducing the thickness of the cylindrical wall lowers the cost of the tank. Furthermore, the cylindrical wall ensures a seal against the internal fluid, preventing contact between the internal fluid and the circumferential reinforcement elements.

[0061] Advantageously, the modulus of elasticity of the cylindrical wall material can be at least 10%, and preferably at least 30%, lower than the modulus of elasticity of the material of the first layer of circumferential reinforcement elements. This facilitates the transfer of pressure forces by the circumferential reinforcement elements, further reducing the thickness of the cylindrical wall. In one variant, at least one of the two ends can be domed, preferably hemispherical. These shapes reduce the mass of the ends while ensuring resistance to internal pressure. A domed end is, by definition, the opposite of a flat end, having a concave shape directed outwards from the pressure vessel.

[0062] According to one embodiment of the invention, the pressure tank may include a second layer of axial reinforcement elements, these axial reinforcements extending in the axial direction (corresponding to the axis of the tubular portion of the tank). Alternatively or in addition, axial reinforcement elements may include burying at least both ends of the pressure tank in the ground. Indeed, when the tank is subjected to internal pressure, a force called "bottoming effect" tends to generate axial stresses in the tubular portion of the tank. The axial reinforcement elements allow the bottoming effect to be absorbed and thus prevent the cylindrical wall from bearing these stresses alone. Therefore, the cylindrical wall may not participate, or may only participate minimally, in absorbing the bottoming effects.

[0063] When the tank includes at least one dished bottom and at least one second layer of axial reinforcement elements, the axial reinforcement elements of the second layer may extend along the dished bottom towards its axial end, forming a roughly star-shaped pattern on the dished bottom. In this way, the axial reinforcement elements contribute to the transfer of stresses in the dished bottoms.

[0064] According to one embodiment of the invention, at least a second layer of axial reinforcement elements can be positioned inside the inner cylinder, and the axial reinforcement elements of the second layer can be evenly distributed around the circumference of the cylindrical wall. This configuration allows for good distribution of forces among the different axial reinforcements.

[0065] According to another embodiment of the invention, at least a second layer of axial reinforcement elements can be positioned outside the tubular section, and the axial reinforcement elements of the second layer can be evenly distributed around the circumference of the tubular section. This configuration allows for simpler manufacturing and does not hinder internal inspection of the tank. This embodiment can be combined with the embodiment in which a second layer of axial reinforcement elements is positioned inside the tank. Thus, mechanical resistance to bottom effects can be improved.Advantageously, the material of the circumferential reinforcement elements of the first layer can be a polymer, preferably an aramid fiber (notably known as "Kevlar"), a nylon polyamide PA, a polypropylene PP, a polyethylene PE or PES, for example "Dyneema®", and more particularly a high-strength polyethylene, generally known as "HDPE". These materials provide good tensile strength and therefore good resistance to the circumferential stresses of the pressure vessel.

[0066] Preferably, the cylindrical wall material can be a metallic material, preferably steel, or a polymer. This improves the seal against the internal fluid.

[0067] According to one embodiment of the invention, the circumferential reinforcement elements of the first layer can be embedded in a protective coating. This coating can protect the circumferential reinforcement elements from chemical and / or physical damage, thereby improving the system's resistance to, for example, moisture, ultraviolet radiation, or an aggressive external environment. This protective coating can be applied, for example, by spraying or injecting a material. This coating could be, for example, a resin such as an epoxy resin.

[0068] Furthermore, the circumferential reinforcement elements of the first layer and / or the axial reinforcement elements of the second layer can have a circular, substantially circular, or rectangular cross-section. A circular cross-section is simple to manufacture and therefore can be less expensive, particularly when using ropes consisting of one or more strands twisted together. The rectangular shape is advantageous because the wrapping of the circumferential reinforcements around the cylindrical wall forms a nearly continuous layer. For example, the rectangular shape can be achieved using flat braided strands, which have the advantage of being easy to manufacture. Thus, this reinforcement shape allows for optimization of the thickness of the tubular section of the tank and its pressure resistance, and avoids local effects of the cylindrical wall between the turns of the circumferential reinforcement elements.

[0069] According to an advantageous embodiment of the invention, the pressure tank may include at least one sliding connection between the cylindrical wall and at least one of the two ends. The internal pressure of the tank creates a bottoming effect by applying pressure to the ends. This bottoming effect generates an axial tensile force in the tubular section of the tank. The sliding connection reduces or even eliminates this bottoming effect in the tubular section by allowing at least one of the ends to slide axially.

[0070] According to one embodiment of the invention, the sliding connection can be positioned between the outer diameter of the cylindrical wall and the inner diameter of the base. This configuration allows for simpler installation with a base that surrounds the tubular part.

[0071] According to another embodiment of the invention, the sliding connection can be positioned between the inner diameter of the cylindrical wall and the outer diameter of the bottom. This embodiment makes it possible to cancel the effect of the bottom on the tubular part.

[0072] Advantageously, at least one of the two bottoms can be embedded in the ground. This allows the ground to absorb bottom effects, simplifying the tank's design and therefore its manufacture.

[0073] The invention also relates to an energy storage and recovery system comprising at least one compression means, at least one expansion means, at least one heat storage means, and at least one compressed air reservoir as described above. Such a reservoir reduces the cost of the energy storage and recovery system.

[0074] Figure 2 illustrates, schematically and without limitation, one embodiment of the device according to the invention. The pressure tank comprises a tubular portion and two flat ends 5. The flat ends 5 could be replaced by domed ends, such as hemispherical ends. The tubular portion comprises a cylindrical wall 1, for example a membrane, and one or more layers of circumferential reinforcing elements 2. For clarity, the layers of circumferential reinforcing elements 2 are shown only on a portion of the cylindrical wall 1. Preferably, the layers of circumferential reinforcing elements 2 cover the entire axial length of the cylindrical wall 1. A layer may consist of one or more circumferential reinforcing elements 2. A circumferential reinforcing element 2 may, for example, be a rope wound around the cylindrical wall 1.The rope offers a good strength-to-weight ratio. Multiple layers can be used, each additional layer comprising at least one circumferential reinforcement element wrapped around the previous layer. This improves pressure resistance while limiting the tank's weight and manufacturing cost. Using multiple layers of circumferential reinforcement elements is particularly advantageous for large-volume pressure tanks, especially those with large diameters (greater than 2 m) and / or high internal pressures (greater than 100 bar), such as those used for energy storage and recovery systems.

[0075] In figure 2, F represents the direction of winding of the circumferential reinforcement elements 2 around the cylindrical wall 1.

[0076] Advantageously, the material of the cylindrical wall 1 has a lower modulus of elasticity than that of the material of the circumferential reinforcement elements 2. Thus, the circumferential deformation of the cylindrical wall 1 is greater than that of the circumferential reinforcements 2, which tends to press the cylindrical wall 1 against the circumferential reinforcement elements 2 and to distribute the pressure forces appropriately between the cylindrical wall 1 and the circumferential reinforcement elements 2. Furthermore, the tensile strength of the circumferential reinforcement elements 2 can be greater than the tensile strength of the cylindrical wall 1. Consequently, the mechanical strength of the tank is essentially ensured by the circumferential reinforcement elements 2.The cylindrical wall 1 can then have its function limited to ensuring a seal for the fluid contained in the pressure tank, the sheet of circumferential reinforcement elements 2 not necessarily being sealed on the one hand and the cylindrical wall 1 thus preventing contact between the internal fluid and the circumferential reinforcement elements 2, limiting for example their degradation.

[0077] Figure 3a schematically and non-limitingly illustrates an embodiment of the invention in which a circumferential reinforcing element of rectangular cross-section 2r is wound around the cylindrical wall 1. Figure 3a is a half-sectional view. A gap 30 may be provided between the turns of the circumferential reinforcing elements 2r, or conversely, the gap 30 may be eliminated so that, during winding, the circumferential reinforcing element of turn n+1 is in contact with that of turn n. Thus, the sheet forms a virtually continuous surface around the cylindrical wall 1, which prevents potential pinching of the cylindrical wall 1 in the gaps 30, pinching that could generate local stress peaks and lead to premature failure of the cylindrical wall 1.Limiting the clearance between the turns of the circumferential reinforcement elements 2r prevents local buckling and excessive deformation of the cylindrical wall 1 between two consecutive sections of circumferential reinforcement elements 2r. Indeed, excessive clearance could necessitate local analyses and become a design criterion. Furthermore, this nearly continuous surface formed by the circumferential reinforcement elements 2r optimizes the transfer of compressive forces by these elements.

[0078] The rectangular section of the circumferential reinforcement elements 2r also allows for near continuity over the thickness of the elements, the thickness of these elements being defined by the difference between the outer diameter of the circumferential reinforcement elements 2r wrapped around the cylindrical wall 1 and their inner diameter.

[0079] Figure 3b illustrates, schematically and without limitation, another embodiment of the invention in which a circumferential reinforcing element of circular or substantially circular cross-section 2c is wound around the cylindrical wall 1. Figure 3b is a half-sectional view. This element could be, for example, a rope comprising one or more strands twisted together. Thus, the circumferential reinforcing elements 2c are not specific and help to limit the manufacturing cost of the tank. As in Figure 3a, the circumferential reinforcing elements 2c can be wound touching each other or, conversely, leaving a gap between each turn. When they touch, the load transfer by the circumferential reinforcing elements 2c is improved, and the deformations of the cylindrical wall 1 between the circumferential reinforcing elements 2d are reduced.

[0080] The invention is not limited to the configurations shown in Figures 3a and 3b. Within the same layer, both circumferential reinforcements with a rectangular cross-section and circumferential reinforcement elements with a circular or substantially circular cross-section may be found. When several layers are used, one of the layers may include at least one circumferential reinforcement element with a rectangular cross-section, and another layer may include at least one circumferential reinforcement element with a circular or substantially circular cross-section.

[0081] Figure 4 illustrates, schematically and without limitation, another embodiment of a pressure tank according to the invention. Figure 4 is a partial view of the tank, in which the ends are not shown. The tubular portion then comprises a cylindrical wall 1, at least one layer of circumferential reinforcing elements 2 (here of circular cross-section but could be of substantially circular or rectangular cross-section). The circumferential reinforcing elements 2 are then embedded or covered by a protective layer 3. This protective layer can then serve several functions:

[0082] Protect the circumferential reinforcement elements 2 from chemical and / or physical aggressions from the external environment such as ultraviolet radiation, external water or a fluid potentially aggressive to the material of the circumferential reinforcement elements 2.

[0083] - Participate in the resumption of pressure efforts in addition to the circumferential reinforcement elements 2.

[0084] Avoid friction between the winding turns of the circumferential reinforcement elements 2 and thus prevent their premature degradation.

[0085] - Also serves as thermal protection.

[0086] This protective layer can be, for example, a resin, such as an epoxy resin.

[0087] This protective layer can be implemented, for example, by spraying or injecting a suitable protective material.

[0088] Figure 5 schematically and non-limitingly illustrates a variant of the invention. In this variant, a layer of axial reinforcement elements 10 is shown. For clarity, the layers of circumferential reinforcement elements 2 are shown only on a portion of the cylindrical wall 1. Preferably, the layers of circumferential reinforcement elements 2 cover the entire axial length of the cylindrical wall 1. The circumferential reinforcement elements 2 are wrapped around the cylindrical wall.

[0089] The pressure tank includes two domed bottoms 25. The axial reinforcement elements 10 allow the axial forces resulting from the bottom effect to be absorbed, thus allowing the thickness of the cylindrical wall to be reduced.

[0090] The axial reinforcement elements 10 extend longitudinally along the cylindrical wall and continue into the domed ends to a zone close to the axis of the pressure vessel. For example, the axial reinforcement elements 10 can extend onto the domed ends 25, surrounding the cylindrical body 8, which has the same axis as the axis of the vessel and is located at the axial end of the domed end. Thus, in a longitudinal cross-section, the axial reinforcement element approaching the cylindrical body 8 in a direction d partially surrounds this cylindrical body 8 and then extends back in a direction d' forming an angle T with the direction d. Preferably, T is greater than or equal to 90° and preferably close to 180°. In this way, the strength of the axial reinforcement elements on the domed end is improved around the cylindrical body 8.

[0091] Thus, the various axial reinforcement elements 10 arriving at and departing from the cylindrical body 8 located at the axial end of the domed bottom 25 form a star E with an even number of points (here, an 8-pointed star). Figure 6 schematically and non-limitingly illustrates another variant of a pressure tank according to the invention, comprising a layer of axial reinforcement elements 10a with two flat bottoms 5. The axial reinforcement elements 10a are located inside the pressure tank. The mounting diameter of these axial reinforcement elements 10a is therefore smaller than the internal diameter of the cylindrical wall. Advantageously, these axial reinforcement elements 10a are evenly distributed around the circumference of the pressure tank so as to distribute the axial tensile forces equally among the various axial reinforcement elements 10a.Furthermore, an axial reinforcement element 10a can be provided at the center of the pressure tank (i.e., coinciding with the axis of the pressure tank). This distribution also prevents tank deflection that could be caused by an improper circumferential distribution.

[0092] These axial reinforcement elements 10a can have a circular or substantially circular cross-section, for example, ropes with one or more strands twisted together. Ropes offer a good strength-to-mass ratio. Alternatively, other cross-sections could be considered.

[0093] The material of these axial reinforcement elements 10a can advantageously be the same as that of the circumferential reinforcements.

[0094] This configuration allows for good absorption of axial forces.

[0095] Figure 7 schematically and non-limitingly illustrates another variant of a pressure tank according to the invention, comprising a layer of axial reinforcement elements 10b with two flat ends 5. The axial reinforcement elements 10b are located outside the pressure tank. The mounting diameter of these axial reinforcement elements 10b is therefore greater than the outside diameter of the tubular section. Advantageously, these axial reinforcement elements 10b are evenly distributed around the circumference of the pressure tank so as to absorb the axial tensile forces equally among the different axial reinforcement elements 10b. This distribution also prevents tank deflection that could be caused by an uneven circumferential distribution.

[0096] These axial reinforcement elements 10b can have a circular or nearly circular cross-section, for example, ropes with one or more strands twisted together. Ropes offer a good strength-to-weight ratio. Alternatively, other cross-sections could be considered.

[0097] The material of these axial reinforcement elements 10b can advantageously be the same as that of the circumferential reinforcements.

[0098] Placing the axial reinforcement elements 10b outside the pressure tank has the advantage of not hindering tank inspection, particularly for periodic service checks. Furthermore, it also eliminates the need for the axial reinforcement elements 10b to pass through the tank body at the bottom 5, thus avoiding the associated risk of leakage.

[0099] Figure 8 illustrates, schematically and without limitation, a fourth variant of the pressure tank with axial reinforcements. In this variant, the pressure tank comprises two layers of axial reinforcement elements 10a and 10b with two flat ends 5. The layer of axial reinforcement elements 10b is located outside the pressure tank (as in Figure 7) while the layer of axial reinforcement elements 10a is located inside the pressure tank (as in Figure 6).

[0100] The axial reinforcement elements 10a and 10b may have a circular, substantially circular, cross-section, for example, ropes with one or more strands twisted together. Alternatively, other cross-sections could be considered.

[0101] The material of these axial reinforcement elements 10a and 10b can advantageously be the same as that of the circumferential reinforcements.

[0102] This configuration allows for a superior recovery of tensile forces.

[0103] Figures 9 to 13 illustrate, schematically and without limitation, embodiments of pressure tank including, in addition, at least one sliding connection J between one of the bottoms 5, 5a or 5b and the tubular part of the pressure tank.

[0104] The sliding connection J allows relative axial movement between a bottom 5, 5a, or 5b and the tubular section. As a result, the bottom effect induced by pressure on the bottom 5, 5a, or 5b is only partially, or even completely, transferred to the tubular section. This allows for a reduction in both the mass and cost of the tubular section.

[0105] The sliding connection J may include, in particular, elastomer seals or a projection of a polymer-based product.

[0106] In these figures, references 5, 5a and 5b relate respectively to a bottom in a generic way, to a bottom connected by a sliding connection to the tubular part and to a bottom rigidly fixed to the tubular part.

[0107] In Figures 9 to 11, the tubular section comprises a cylindrical wall 1 and a layer of circumferential reinforcing elements 2. The axial reinforcing elements 10a are located inside the pressure tank; the axial reinforcing elements 10b are located outside the pressure tank. The axial reinforcing elements 10a and 10b extend longitudinally along the axis of the pressure tank. However, the design of the sliding connections is independent of the use or absence of axial reinforcing elements, and their locations. In Figure 9, a sliding connection J is located between each of the two flat ends 5 and the tubular section. Furthermore, each of these sliding connections J is positioned between the outer diameter of the cylindrical wall 1 and the inner diameter of the flat end 5. Consequently, the axial force experienced by the cylindrical wall is a compressive force.

[0108] The axial reinforcement elements 10a and 10b of the two internal and external layers of the pressure tank allow the bottoms to be held by the absorption of bottom effects.

[0109] In Figure 10, a sliding connection J is located between each of the two flat ends 5 and the tubular section. Furthermore, each of these sliding connections J is positioned between the inner diameter of the cylindrical wall 1 and the outer diameter of the flat end 5. Consequently, the bottom effect due to pressure on the ends is not transmitted to the tubular section. Moreover, the tubular section experiences no axial stress, which is a particularly advantageous configuration.

[0110] The transfer of the background effect is achieved here by the internal layer of axial reinforcement elements 10a. The transfer of the background effect is facilitated in this configuration compared to that of Figure 9.

[0111] Figure 11 shows a configuration where one of the bottoms 5b is rigidly fixed to the tubular section. The other bottom 5a is connected to the tubular section via a sliding connection J. The sliding connection J is positioned between the outer diameter of the cylindrical wall 1 and the inner diameter of the flat bottom 5a. Thus, the cylindrical wall 1 experiences a compressive force induced by the pressure on its cross-section, which is relatively small compared to the tensile force due to the bottom effect induced by the pressure on the entire surface of the flat bottom 5a / 5b.

[0112] The background effect is taken up by the axial reinforcement elements 10a and 10b of the two layers.

[0113] Figure 12 presents a variant of Figure 11 where the sliding connection J is positioned between the outer diameter of the bottom 5a and the inner diameter of the cylindrical wall 1. In this configuration, the cylindrical wall 1, and more generally the tubular part, is not subjected to any tensile / compressive force.

[0114] The background effects are taken up by the axial reinforcement elements 10a of the internal layer.

[0115] Figure 13 illustrates a variant in which the tank comprises a bottom 5b fixed to the tubular section and a bottom 5a connected to the tubular section via a sliding connection J. In this variant, the axial reinforcement elements include the embedding of the pressure tank in the ground 20. More precisely, the two flat bottoms 5a and 5b are embedded in the ground 20, and the ground can then act as a stop against the axial displacement of at least one of the two bottoms: the ground thus limits the axial displacement of at least one of the two bottoms. Alternatively, the bottoms could not be flat but, for example, convex. This embedding in the ground 20 acts as axial reinforcement elements by directly counteracting the bottom effects represented by the arrows L.

[0116] The tank can also be totally buried, that is to say not only buried at the bottom but totally covered on its external surface by the soil 20.

Claims

Demands 1. Pressure tank, comprising a tubular part and two bottoms (5), said two bottoms (5) being positioned at the ends of said tubular part, said tubular part comprising a cylindrical wall (1) and at least a first layer of circumferential reinforcement elements (2), said first layer of circumferential reinforcement elements (2) being wrapped around said cylindrical wall (1), characterized in that the modulus of elasticity of the material of the cylindrical wall (1) is less than the modulus of elasticity of the material of said first layer of circumferential reinforcement elements (2).

2. Tank according to claim 1, for which the modulus of elasticity of the material of the cylindrical wall (1) is less than at least 10%, preferably at least 30%, than the modulus of elasticity of the material of said first layer of circumferential reinforcement elements (2).

3. Tank according to any one of the preceding claims, wherein at least one of said two bottoms (5) is a domed bottom, preferably spherical or hemispherical.

4. Tank according to any one of the preceding claims, wherein the tank comprises at least a second layer of axial reinforcement elements (10), said axial reinforcement elements (10) extending in the axial direction and / or said axial reinforcement elements (10) comprising a burial in the ground of said pressure tank.

5. Tank according to claims 3 and 4, wherein said axial reinforcement elements (10) of said second layer continue at the level of the domed bottom towards the axial end of said domed bottom (25), forming a star on said domed bottom.

6. Tank according to claim 4, wherein at least a second layer of axial reinforcement elements (10a) is positioned inside the inner cylinder defined by said cylindrical wall, said axial reinforcement elements (10a) of said second layer being regularly distributed over the circumference of said cylindrical wall.

7. Tank according to claim 4 or 6, wherein at least a second layer of axial reinforcement elements (10b) is positioned outside said tubular part, said axial reinforcement elements (10b) of said second layer being regularly distributed over the circumference of said tubular part.

8. Tank according to any one of the preceding claims, wherein the material of said circumferential reinforcement elements (2) of said first layer is a polymer, preferably an aramid fiber, a polyamide nylon, a polypropylene, or a polyethylene, and even more preferably a high-strength polyethylene.

9. Tank according to any one of the preceding claims, wherein the material of said cylindrical wall (1) is a metallic material, preferably a steel, or a polymer.

10. Tank according to any one of the preceding claims, wherein said circumferential reinforcement elements (2) of said first layer are embedded in a protective layer (3). 1 1. Tank according to any one of the preceding claims, wherein said circumferential reinforcement elements (2) of said first layer and / or said axial reinforcement elements (10) of said second layer have a circular, substantially circular (2c) or rectangular (2r) cross-section.

12. Tank according to any one of the preceding claims, wherein the tank comprises at least one sliding connection (J) between said cylindrical wall (1) and at least one of said two bottoms (5).

13. Tank according to claim 12, wherein said sliding connection (J) is positioned between the outer diameter of said cylindrical wall (1) and the inner diameter of said bottom (5).

14. Tank according to claim 12, wherein said sliding connection (J) is positioned between the outer diameter of said bottom (5) and the inner diameter of said cylindrical wall (1).

15. Tank according to any one of the preceding claims, wherein at least one of said two bottoms (5) is embedded in the ground.

16. Energy storage and recovery system comprising at least one compression means, at least one expansion means, at least one heat storage means and at least one compressed air tank according to one of the preceding claims.