Double membrane gasometer and energy management plant commprising said gasometer

Abstract

A double membrane gasometer (1 ) comprises: a first flexible membrane (2) defining an enclosure internally delimiting a first variable volume (3) for a gas phase working fluid; a second flexible membrane (4) open and connected to the enclosure, wherein the second flexible membrane (4) and the enclosure delimit between them a second variable volume (5) for an auxiliary fluid. A mechanical connecting device (11) is placed at an outer perimeter of the enclosure and is configured to join the second flexible membrane (4) to the enclosure. A structure (15) is constrained to the mechanical connecting device (11) and is fixed to the ground (G). The mechanical connecting device (11) comprises: a first element (13) and a second element (14) surrounding the outer perimeter of the enclosure. The first element (13) and the second element (14) are joined together and clamp between them an appendage (12) of the first flexible membrane (2) and the perimeter edge (4a) of the second flexible membrane (4).

Description

[0001] “Double membrane gasometer and energy management plant comprising said gasometer”

[0002] DESCRIPTION

[0003] Field of the invention

[0004] The present invention has as its object a double membrane gasometer. In particular, the present invention has as its object a particular structure of the double membrane gasometer designed to optimize costs and facilitate transport and assembly.

[0005] The double membrane gasometer object of the present invention can be applied for example in the field of energy management plants and processes, where by management is intended the absorption, the accumulation, the transformation, and the generation of energy, or plants capable of absorbing / using energy, keeping the stored energy over time and capable of transforming it back into available energy, for example electrical, thermal, mechanical energy.

[0006] The present invention has therefore also as its object an energy management plant comprising this double membrane gasometer.

[0007] Definitions

[0008] In the present description and in the attached claims reference will be made to the following definitions.

[0009] • Cyclic Thermodynamic Transformation (TTC): thermodynamic transformation from a point A to a point B and from a point B to a point A, without necessarily passing through the same intermediate points; the TTC works between two mass storages / accumulations, one initial and the other final, of a working fluid.

[0010] • Thermodynamic Cycle (CT): thermodynamic transformation from a point X to a point Y, wherein X coincides with Y; the thermodynamic cycle (CT) unlike the cyclic thermodynamic transformation (TTC) referred to above has no mass accumulations / storages (of the working fluid), within the cycle, significant for energy purposes.

[0011] • Closed CT and / or TTC: without mass exchange (significant for energy purposes) with the atmosphere. • Open CT and / or TTC: with mass exchange (significant for energy purposes) with the atmosphere.

[0012] • Light overpressure: pressure higher than the atmospheric pressure with a pressure difference with respect to the atmospheric pressure of a few millibars up to a few tens of millibars, for example from 3 - 4 mbar to 70 - 80 mbar.

[0013] The double-membrane gasometers are constituted by an internal membrane or gas membrane, which delimits the volume of a gas to be contained and whose upper part changes shape adapting to the volume of the contained gas, and by an outer membrane which delimits a cavity between the latter and the gas membrane. In this cavity there is air which, through a fan and valves, enters the cavity or exits the cavity to compensate for variations in the volume of the gas membrane with the aim of keeping constant the pressure in the cavity and therefore the shape of the outer membrane. The outer membrane has a hemispherical shape, as the inner one when it is completely filled with gas. Such a type of gasometer is shown for example in the public document CN113280252A.

[0014] The public document EP1338843B1 shows a cylindrical gas accumulator comprising two membranes delimiting respective chambers superimposed over the entire length of the cylinder. Membranes are constrained to hooking means anchored to the ground by means of cables.

[0015] It is furthermore known the document AT388158B that shows a digester comprising a container-shaped cement base and a balloon with an inner membrane and an outer membrane constrained to an upper edge of the cement base. The edges of the two membranes are coupled and fastened between plates by screws.

[0016] Also the document US4437987A shows a digester which comprises a cement base in the shape of a container and on the upper edge thereof two membranes are installed which delimit between them a pressurized chamber. The two membranes are fixed between them and on an upper edge of the base by means of plates and tie-rods.

[0017] The public document W02020 / 039416, in the name of the same Applicant, shows instead a process and a plant for energy storage. The plant comprises an enclosure for the storage of a working fluid other than atmospheric air, in the gas phase and in pressure equilibrium with the atmosphere; a tank for the storage of this working fluid in the liquid or super-critical phase with a temperature close to the critical temperature, wherein the critical temperature is close to the environmental temperature. The plant is configured to implement a closed cyclic thermodynamic transformation, first in one direction in an accumulation configuration and then in an opposite direction in a discharge configuration, between the casing and the tank. In the accumulation configuration the plant accumulates heat and pressure and in the discharge configuration it generates energy.

[0018] The Applicant has noted that is complex and expensive to transport and assemble on site the double-membrane gasometers of known type used in the field of energy management plants and processes, for example as the one shown in W02020 / 039416, given their considerable size.

[0019] The Applicant particularly noted that it is difficult and expensive, if not impossible, to transport such gasometers to installation sites if they are fully pre-assembled in the factory.

[0020] The Applicant also observed that transporting such gasometers in separate parts and then assembling them on site is still complex and requires long installation times and highly skilled manpower.

[0021] The Applicant therefore aimed at designing and realizing a double membrane gasometer that allows operators to install it on site within reasonable times and with relative ease.

[0022] The Applicant also aimed at realizing a double membrane gasometer that can be easily transported from the factory to the installation site.

[0023] The Applicant also aimed at realizing a double membrane gasometer that allows to reduce both production and installation costs.

[0024] The Applicant also aimed at realizing a double membrane gasometer that, once installed and operating, is reliable and secure.

[0025] The Applicant also aimed at realizing a double membrane gasometer that allows to best exploit the occupied ground, i.e. to minimize its dimensions. The Applicant has found that the above indicated objectives can be reached by adopting a double membrane gasometer formed by two main flexible membranes pre-assembled in the factory and installed in the site destined to house the gasometer by means of a peculiar mechanical connecting device that anchors it to the ground.

[0026] In particular, the indicated objectives and others are substantially reached by a double membrane gasometer of the type claimed in the attached claims and / or described in the following aspects.

[0027] In a first independent aspect, the present invention relates to a double membrane gasometer, comprising: a first flexible membrane defining an enclosure internally delimiting a first variable volume for a gas phase working fluid; wherein the enclosure rests on the ground; wherein the first variable volume is connected to pipelines of a plant operating with said working fluid; a second flexible membrane open and connected to the enclosure; wherein the second flexible membrane has a perimeter edge spliced to the enclosure at an outer perimeter of the enclosure spaced from the ground; wherein the second flexible membrane and the enclosure delimit between them a second variable volume for an auxiliary fluid; a mechanical connecting device placed at the outer perimeter of the enclosure and configured to join the second flexible membrane to the enclosure; a structure constrained to the mechanical connecting device and fixed to the ground.

[0028] The enclosure rests on the ground and is defined by the first flexible membrane. The first flexible membrane, i.e. the enclosure, encloses therefore the first variable volume. Internal pressures in the first volume and second volume keep a shape of the gasometer. In particular, a lower portion of the enclosure, i.e. of the first flexible membrane, placed below the perimeter edge is self-supporting, i.e. keeps an its own shape, thanks to its internal pressure. Conversely, in documents AT388158B and US4437987A, the volume containing the gas is partly delimited by the cement base. Optionally, the mechanical connecting device may or may not comprise: a first element surrounding the outer perimeter of the enclosure; a second element surrounding the outer perimeter of the enclosure. The first element and the second element are joined together and clamp between them an appendage of the first flexible membrane and the perimeter edge of the second flexible membrane. The Applicant has verified that the double membrane gasometer according to the invention allows to achieve the above listed objectives and others.

[0029] The Applicant has first of all verified that the double membrane gasometer according to the invention allows to realize in factory finished units (i.e.: the first membrane, the second membrane, the mechanical connecting device and the ground connection structure), to transport them easily and assemble the gasometer on site within reasonable times and with relative simplicity. In fact, the different units can be individually transported. Furthermore, the first membrane defining the enclosure can be easily constrained to the second membrane by means of the mechanical connecting device. The enclosure can be entirely realized in the factory with the necessary techniques and controls so as to guarantee the tightness of the working fluid destined to be contained in the first variable volume. In particular, it is not necessary to carry out weldings between membrane parts at the installation site, which would be qualitatively lower and less repeatable with respect to weldings carried out in the factory in a controlled environment.

[0030] Conversely, the tightness of the second variable volume, however guaranteed by the mechanical connecting device, is not critical because the auxiliary fluid is not a working fluid and can also be atmospheric air.

[0031] The Applicant has also verified that the mechanical connecting device allows to join with safety between them the first and the second membrane, to create a gas tight between the first and second membrane and to safely constrain the gasometer to the ground.

[0032] The Applicant has also verified that, given its shape, the gasometer according to the invention allows to limit the surfaces of the membranes, given the same internal volumes, and therefore to reduce the costs of the material necessary for its realization.

[0033] The Applicant has also verified that the gasometer according to the invention allows to obtain greater internal volumes for each square meter of occupied ground.

[0034] In a second aspect, the present invention is related to an energy management plant, comprising: a working fluid other than atmospheric air, a double membrane gasometer in accordance with the first aspect and / or with at least one of the following aspects, wherein the gas phase working fluid stored in the first variable volume is in pressure equilibrium with the atmosphere; a mass accumulator that stores said working fluid in the liquid or supercritical phase with a temperature close to the critical temperature, wherein said critical temperature is close to ambient temperature; wherein the plant is configured to implement a closed cyclic thermodynamic transformation, first in one direction in a charging configuration and then in the opposite direction in a discharging configuration, between said gasometer and said mass accumulator; wherein in the charging configuration the plant accumulates heat and pressure and in the discharging configuration generates energy by exploiting the previously accumulated heat and pressure; wherein, both in the charging configuration and in the discharging configuration, the first variable volume varies and a first pressure in said first variable volume is kept constant.

[0035] Further aspects of the invention are listed below.

[0036] In an aspect, the second variable volume is connected to a source of the auxiliary fluid configured to keep in the second variable volume a second pressure constant as the quantity of working fluid contained in the first variable volume varies, so as to keep the first pressure in the first variable volume constant.

[0037] In an aspect, the working fluid is or comprises carbon dioxide CO2 or sulphur hexafluoride SFe or nitrogen oxide N2O.

[0038] In an aspect, the first variable volume contains up to 200000 m3, optionally up to 500000 m3, optionally up to 1000000 m3of working fluid.

[0039] In an aspect, the gasometer comprises said source of the auxiliary fluid connected to the second variable volume.

[0040] In an aspect, the source of the auxiliary fluid is the atmosphere and the auxiliary fluid is air.

[0041] In an aspect, the gasometer comprises a fan and any valves in fluid connection with the second variable volume and with the source of the auxiliary fluid, for introducing and / or extracting the auxiliary fluid into / from said second variable volume.

[0042] In an aspect, a pressure regulating device connects the first variable volume with the second variable volume and / or with the atmosphere. In an aspect, the first pressure and the second pressure are identical or substantially identical with each other.

[0043] In an aspect, the pressure regulating device comprises safety valves (PSV) which connect the first volume to the outer environment (with fixed pressure set point) or to the second volume (with variable opening pressure).

[0044] The safety valves have the function of protecting the first membrane and other elements from possible power surges.

[0045] In an aspect, the second pressure is higher than the atmospheric pressure.

[0046] In an aspect, the second pressure has a pressure difference with respect to atmospheric pressure from a few millibars to a few tens of millibars, optionally from 3 - 4 mbar up to a 70 - 80 mbar.

[0047] The Applicant has verified that the second pressure and consequently, the first pressure higher than the atmospheric pressure, even if only slightly, allow to keep stable a shape of the gasometer.

[0048] In an aspect, the appendage of the first flexible membrane and the perimeter edge of the second flexible membrane are clamped between the first element and the second element.

[0049] In an aspect, the first element and the second element are shaped as plates.

[0050] In an aspect, the first element comprises a plurality of plates connected to each other to surround the outer perimeter of the enclosure.

[0051] In an aspect, the second element comprises a plurality of plates connected to each other to surround the outer perimeter of the enclosure.

[0052] In an aspect, the mechanical connecting device comprises removable couplings, optionally screws or bolts, coupled to the first element and to the second element to join between them said first element and second element.

[0053] In an aspect, the removable couplings are configured to compress the appendage of the first flexible membrane and the perimeter edge of the second flexible membrane between the first element and the second element.

[0054] In an aspect, the appendage of the first flexible membrane and the perimeter edge of the second flexible membrane placed between the first element and the second element are arranged in vertical planes side by side.

[0055] In an aspect, the appendage of the first flexible membrane extends continuously all around the enclosure. In an aspect, the second flexible membrane is located above the enclosure.

[0056] In an aspect, the appendage of the first flexible membrane divides the enclosure in a lower part and in an upper part, wherein the upper part defines a separation septum between the first variable volume and the second variable volume.

[0057] In an aspect, when the first variable volume is maximum, the upper part is placed next to an inner surface of the second flexible membrane.

[0058] In an aspect, the second variable volume is delimited by the second flexible membrane, by the upper part of the enclosure and by a portion of the appendage.

[0059] In an aspect, the structure comprises a plurality of tie-rods presenting upper ends constrained to the mechanical connecting device and lower ends fixed to the ground.

[0060] In an aspect, the tie-rods are preloaded.

[0061] In an aspect, the tie-rods are crossed with each other.

[0062] In an aspect, the tie-rods form a grid arranged around a lower portion of the enclosure.

[0063] In an aspect, an embankment, optionally in concrete or in earth, surrounds the enclosure.

[0064] In an aspect, the lower ends of the tie-rods are fixed to said embankment.

[0065] In an aspect, an excavation is made in the ground and a base surface of the enclosure is placed in the excavation.

[0066] In an aspect, the earth removed from the excavation is used to build the embankment.

[0067] The Applicant has verified that the excavation and / or the embankment allow to repair the gasometer from the wind in areas usually subject to the highest positive pressure.

[0068] In an aspect, an overall outer surface of the gasometer is shaped as a cylinder with a circular cross-section or as a sphere.

[0069] In an aspect, the cylinder with a circular cross-section has opposite convex ends.

[0070] In an aspect, the opposite convex ends are shaped as spherical sectors, optionally as hemispheres.

[0071] In an aspect, an outer surface of the second membrane is shaped as a semi-cylinder with opposite convex ends, optionally as quarters of a sphere.

[0072] In an aspect, an outer surface of the second membrane is shaped as a hemisphere. In an aspect, the enclosure is provided with a flattened portion resting on the ground. In an aspect, the flattened portion is base surface of the enclosure placed in excavation.

[0073] In an aspect, the preload of the tie rods is such as to keep the enclosure pressed to the ground with said flattened portion.

[0074] In an aspect, said outer perimeter of the enclosure is spaced from the ground of a first height between 0.2 and 0.8 times a diameter of the cylinder with a circular crosssection or of the sphere.

[0075] In an aspect, a second height of a longitudinal axis “X-X” of the cylinder with a circular cross-section or of a center of the sphere from the ground is between 0.3 and 0.5 times the diameter of said cylinder with a circular cross-section or of said sphere.

[0076] In an aspect, the preload of the tie-rods is such as to keep said first height and / or said second height from the ground.

[0077] The Applicant has verified that the above indicated shapes of the gasometer allow to limit the surfaces of the membranes and therefore dimensions and costs, given the same delimited volumes.

[0078] The Applicant has also verified that the enclosure which contains the working fluid is resistant and reliable because it has no structural role. In fact, the upper part of the enclosure is in pressure equilibrium between inside (first variable volume with the working fluid) and outside (second variable volume with the auxiliary fluid). The lower part of the enclosure is subject to the ambient pressure and therefore to a pressure difference but the generated forces are discharged to ground. As a result, the first membrane is stress-free as long as the pressure of the working fluid in the first variable volume is less than or equal to the pressure of the auxiliary fluid in the second variable volume. The second membrane instead is under tension due to the pressure of the auxiliary fluid in the second variable volume and due to phenomena of the outer environment.

[0079] Furthermore, the preload of the tie-rods allows to unload the lower surface of the first membrane and to increase the stability of the structure to outer forces, such as the wind.

[0080] In an aspect, a plurality of cables, each straddling an outer surface of the second flexible membrane, has opposite ends fixed to the ground. The Applicant has verified that the cables allow to better ensure and stabilize the gasometer.

[0081] In an aspect, panels are leaning against sides of an overall outer surface of the gasometer to deflect the wind.

[0082] In an aspect, said panels are inclined.

[0083] In an aspect, the panels are located at zones of the gasometer subjected to a positive wind pressure.

[0084] The Applicant has verified that the panels allow to deflect the wind and to reduce the outside pressure generated by it. In this way, it is not necessary to increase the second internal pressure in the second volume and, consequently, the load on the membranes and on the tie rods, which would force to oversize these elements with an increase in costs.

[0085] In an aspect, the first flexible membrane is realized in a gas impermeable material. In an aspect, the first flexible membrane comprises polyester and / or PVC and / or PVDC and / or HDPE and / or LDPE and / or aluminum, optionally polyester coated with PVC or PVDC.

[0086] In an aspect, the first flexible membrane comprises a plurality of layers.

[0087] In an aspect, the first membrane comprises a film of aluminum.

[0088] In an aspect, the first membrane comprises a joining film between PVC and aluminum, optionally of polyethylene or HDPE or LDPE.

[0089] In an aspect, the aluminum is coated with polyethylene terephthalate PET to make it more resistant.

[0090] In an aspect, the first flexible membrane comprises a plurality of pieces joined together gas-tight.

[0091] In an aspect, the pieces are joined by weldings, optionally hot air or high frequency ones.

[0092] In an aspect, the second flexible membrane is realized in polyester and / or PVC and / or PVDC and / or HDPE and / or LDPE and / or aluminum, optionally polyester coated with PVC or PVDC.

[0093] In an aspect, the second membrane comprises a film of aluminum optionally coated with polyethylene terephthalate PET or HDPE or LDPE.

[0094] In an aspect, the first flexible membrane is defined by a plurality of enclosures defining respective first variable volumes for the gas phase working fluid. In an aspect, the first variable volume is divided into a plurality of first variable volumes by septa inside the first flexible membrane.

[0095] In an aspect, the enclosures are welded together.

[0096] In an aspect, the first variable volumes are in fluid connection among them.

[0097] In an aspect, the septa have openings to put in fluid communication between them the first variable volumes.

[0098] In an aspect, the first variable volumes are connected among them through the first pipelines.

[0099] The Applicant has verified that the division into several enclosures allows to transport the individual components more easily and to weld them at the installation site and therefore to realize longer gasometers.

[0100] In an aspect, the energy management plant comprises: a compressor in fluid connection with the gasometer; an expander in fluid connection with the gasometer; a thermal accumulator in fluid connection with the compressor and with the expander and configured to exchange heat with the working fluid; pipelines and control devices configured to operate the plant in the charging configuration and in the discharging configuration; wherein, in the charging configuration, the working fluid transits from the gasometer to the mass accumulator through the compressor, the thermal accumulator and is stored in the mass accumulator; wherein, in the discharging configuration, the working fluid transits from the mass accumulator, to the gasometer through the thermal accumulator and the expander and is again stored in the gasometer.

[0101] In an aspect, the plant comprises a plurality of double-membrane gasometers side by side to form a series.

[0102] In an aspect, said double-membrane gasometers are side by side with their longitudinal axes arranged parallel to each other.

[0103] In an aspect, each of two gasometers places at opposite ends of the series comprises the panels leaning against one side.

[0104] The Applicant has verified that the lateral gasometers are protected from the wind through the panels and the remaining gasometers are protected by the gasometers that they have next to them.

[0105] In use, a change of the quantity of the working fluid in the first volume, inside the enclosure, causes a deformation of said enclosure, in particular of the upper part (separation septum) of the enclosure whereas the shape of the second membrane remains unchanged thanks to the compensation generated by the introduction or by the extraction of the auxiliary fluid in / from the second volume.

[0106] Further features and advantages will be clearer from the detailed description of preferred, but not exclusive embodiments of a double membrane gasometer according to the present invention.

[0107] This description will be shown below with reference to the attached drawings, provided for illustrative purposes only and, therefore, not limiting thereto, in which:

[0108] ■ figure 1 shows an energy management plant comprising a double membrane gasometer according to the present invention;

[0109] ■ figure 2 shows the double membrane gasometer of figure 1 ;

[0110] ■ figure 3 is a lateral view of the double membrane gasometer of figure 2;

[0111] ■ figure 4 shows some elements of the double membrane gasometer of the preceding figures;

[0112] ■ figure 5 shows a variant of the double membrane gasometer of figure 2;

[0113] ■ figure 6 shows an assembly of double-membrane gasometers according to the present invention;

[0114] ■ figure 7 shows a further variant of the double membrane gasometer of figure 2;

[0115] ■ figure 8 shows an assembly comprising double-membrane gasometers each one realized as in figure 7;

[0116] ■ figures 9 and 10 show further variants of the gasometer according to the invention.

[0117] Detailed description

[0118] With reference to the attached figures, with the reference number 1 it has been overall indicated a double membrane gasometer according to the present invention. In figure 1 , the double membrane gasometer 1 is part of an energy management plant 200. This plant 200 can be one of the embodiments described in the public documents WO2021191786A1 and WO2021255578A1 in the name of the same Applicant. The shown plant 200 operates with a working fluid other than atmospheric air, for example chosen in the group comprising: carbon dioxide CO2, sulphur hexafluoride SFe, nitrogen oxide N2O. The plant 200 is configured to implement a closed thermodynamic cyclic transformation (TTC), first in one direction in a charging configuration / step and then in the opposite direction in a discharging configuration / step, wherein in the charging configuration the plant 200 accumulates heat and pressure and in the discharging configuration the plant 200 generates electric energy.

[0119] With reference to figure 1 , the plant 200 comprises an expander 202, for example a turbine, and a compressor 203 mechanically connected to a shaft of a moto- generator 204.

[0120] The plant 200 comprises furthermore the double membrane gasometer 1 which will be described in more detail below.

[0121] First pipelines 206 develop between the double membrane gasometer 1 and an inlet 203a of the compressor 203 and between the double membrane gasometer 1 and an outlet 202b of the turbine 202 to put in fluid communication the double membrane gasometer 1 with said compressor 203 and turbine 202.

[0122] A valve or a system of valves, not shown, may be operatively located on the first pipelines 206 to alternatively put in fluid communication the double membrane gasometer 1 with the inlet 203a of the compressor 203 or the outlet 202b of the turbine 202 with the double membrane gasometer 1 .

[0123] The plant 200 comprises a primary heat exchanger 100 which may be put in fluid communication alternatively with an outlet 203b of the compressor 203 or with an inlet 202a of the turbine 202. To this end, second pipelines 208 develop between the inlet 202a of the turbine 202 and the primary heat exchanger 100 and between the outlet 203b of the compressor 203 and the primary heat exchanger 100. The primary heat exchanger 100 is a thermal accumulator defined for example by a Thermal Energy Storage (TES) provided with a thermal mass configured to accumulate heat.

[0124] A valve, or a valve system, not shown, is operatively located on the second pipelines 208 to alternatively put in fluid communication the primary heat exchanger 100 with the inlet 202a of the turbine 202 or the outlet 203b of the compressor 203 with the primary heat exchanger 100. A mass accumulator defined by a tank 209 is in fluid communication with the primary heat exchanger 100 and is configured to accumulate the working fluid in the liquid or supercritical phase at a temperature close to the critical temperature. The critical temperature of the working fluid is close to the ambient temperature and is for example between 0°C and 100°C.

[0125] A secondary heat exchanger 210 is operatively active upwards of the tank 209 and is configured to operate on the working fluid in the charging step in the tank 209. Third pipelines 212 develop between the primary heat exchanger 100 and the tank 209 to put in fluid communication said primary heat exchanger 100 with said tank 209 and with said secondary heat exchanger 210.

[0126] In the example representation of figure 1 , the plant 200 comprises furthermore an additional heat exchanger 213 operatively interposed between the double membrane gasometer 1 and the compressor 202 and between the double membrane gasometer 1 and the turbine 202.

[0127] A basin 2000 with a liquid, typically water, is connected with the secondary heat exchanger 210 and with the additional heat exchanger 213 and is coupled to a radiator 223 provided with a fan 224.

[0128] The primary 100, secondary 210 and additional 213 heat exchangers are configured to store thermal energy released by the working fluid in the thermal mass of the TES and in the liquid of the basin 2000 or to release thermal energy, previously stored in thermal mass of the TES and in the liquid of the basin 2000, to the working fluid.

[0129] The plant 200 is configured to implement a closed cyclic thermodynamic transformation, first in one direction in a charging configuration and then in the opposite direction in a discharging configuration, between said double membrane gasometer 1 and said tank 209, for example according to what is described in the public documents WO2021191786A1 and WO2021255578A1 .

[0130] In the charging configuration, the plant 200 accumulates energy (coming for example from the electric grid or wind generators) in the form of heat and pressure. In the discharging configuration, the plant 200 generates mechanical energy and transforms it eventually into electrical energy by exploiting the previously accumulated heat and pressure.

[0131] In the charging configuration, the working fluid coming from the double membrane gasometer 1 is compressed in the compressor 203, operated by the moto-generator 204 which works as an electric motor powered for example by the electric grid or wind generators, and heats up. The working fluid flows therefore through the primary heat exchanger 100 (TES) that works as a cooler to remove heat from the compressed working fluid, cool it and accumulate the thermal energy removed from said working fluid as heat in the thermal mass. The working fluid transfers then heat to the liquid of the basin 2000 at the secondary heat exchanger 210, condenses and is stored in the tank 209.

[0132] In the discharging configuration, the working fluid coming from the tank 209 and already warmed by the secondary heat exchanger 210, through the heat transferred from the water in the basin 2000, passes through the primary heat exchanger 100 that now works as a heater and transfers additional heat, previously accumulated in the thermal mass, to the working fluid and heats it to then be introduced in the turbine 202. In the turbine 202, the working fluid expands and rotates the turbine 202 that generates electric energy through the moto-generator 204 that works as an electric generator. The expanded working fluid is then again accumulated in the double membrane gasometer 1 , ready for a new cycle.

[0133] Both in the charging configuration / step and the discharging configuration / step, the double membrane gasometer 1 keeps the gas phase working fluid in the gasometer

[0134] 1 itself and incoming or outgoing from / in the double membrane gasometer 1 at a substantially constant pressure, close to the atmospheric pressure and in pressure equilibrium with the atmosphere.

[0135] To this end, the double membrane gasometer 1 comprises a first flexible membrane

[0136] 2 that defines an enclosure, which internally delimits a first variable volume 3 for the aforementioned gas phase working fluid which is kept at a first pressure “P1”.

[0137] A second flexible membrane 4 is shaped as an open sheet and is placed above the enclosure. A perimeter edge 4a of the second flexible membrane 4 is spliced to the enclosure at an outer perimeter of the enclosure itself. The second flexible membrane 4 and the first flexible membrane 2 (enclosure) delimit between them a second variable volume 5 for an auxiliary fluid.

[0138] The first flexible membrane 2 is gas impermeable. The first flexible membrane 2 can be realized in multiple layers and comprises, for example, a layer in polyester coated with PVC, a joining film of aluminum and a film in polyethylene, between PVC and aluminum. The film of aluminum can be between a thin layer of PE and one of PET, the first allows to adhere better to PVC through a glue, the second makes the aluminum more resistant. The first flexible membrane 2 is realized in factory and comprises a plurality of pieces gas-tight joined together through hot air or high frequency weldings. The second flexible membrane 4 can be realized with the same materials used for the first flexible membrane 2.

[0139] As can be seen by observing the attached figures, the first flexible membrane 2 (enclosure) is functionally separated in a lower part 2a and in an upper part 2b by the aforementioned outer perimeter joined to the perimeter edge 4a of the second flexible membrane 4. The upper part 2b defines a separation septum between the first variable volume 3 and the second variable volume 5 and remains inside and protected by the second flexible membrane 4. The lower part 2a remains exposed to the atmospheric environment and rests on the ground “G”. The second variable volume 5 is therefore delimited by the second flexible membrane 4 and by the upper part 2b of the enclosure.

[0140] As can be seen by observing figures 1 , 2 and 3, the first pipelines 206 are connected to the first variable volume 3. The second variable volume 5 is instead connected to a source of the auxiliary fluid configured to keep in the second variable volume 5 a second pressure “P2”.

[0141] In the embodiment of figure 3, the auxiliary fluid is atmospheric air and the gasometer 1 comprises a fan 6 placed on an inlet duct and a discharging valve 7 placed on an extraction duct. The introduction and extraction ducts are in fluid connection with the second variable volume 5 and with the atmosphere. The fan 6 and the discharging valve 7 allow to introduce and / or extract the air into / from the second variable volume 5.

[0142] The fan 6 and the discharging valve 7 are controlled so as to keep the second pressure “P2” constant as the quantity of the working fluid contained in the first variable volume 3 varies and slightly higher than the atmospheric pressure. The second pressure “P2” has a pressure difference with respect to the atmospheric pressure “Patm” from a few millibars to a few tens of millibars, for example from 3 - 4 mbar to a 70 - 80 mbar.

[0143] This allows to keep constant or substantially constant the first pressure “P1” both in the charging configuration and in the discharging configuration during the operative steps of the plant 200 as the quantity of the working fluid in the first variable volume 3 varies, i.e. as the filling of said first variable volume 3 varies. The first pressure “P1” and the second pressure “P2” are equal or substantially equal to each other.

[0144] The first pressure “P1” and the second pressure “P2” confer to an overall outer surface of the gasometer 1 , formed by the lower part 2a of the first flexible membrane 2 and by the second flexible membrane 4, a stable shape. In the embodiment shown in figures 1 , 2 and 3, the overall outer surface of the gasometer 1 is a cylinder with a circular cross-section with opposite ends shaped like hemispheres. In other embodiments and depending on the required volume, the gasometer 1 may have a spherical shape.

[0145] Instead, during the operative steps of the plant 200, the upper part 2b of the first flexible membrane 2 (separation septum) moves and / or deforms making the first variable volume 3 and the second variable volume 5 vary. When the first variable volume 3 is maximum, the upper part 2b is placed next to an internal surface of the second flexible membrane 4. For example, the first variable volume can contain up to 200000 m3or up to 500000 m3or up to 1000000 m3of working fluid, depending on the size of the plant 200.

[0146] Furthermore, as shown in figure 2, a pressure regulating device 8 connects the first variable volume 3 with the second variable volume 5 and / or with the atmosphere and is configured to safeguard the enclosure from any power surges. The pressure regulating device 8 of figure 3 comprises a first duct that connects the first variable volume 3 to the outer environment and is provided with a first safety valve 9 (with fixed pressure set point) and comprises a second duct that connects the first variable volume 3 to the second variable volume 5 and is provided with a second safety valve 10 (with variable opening pressure).

[0147] The junction of the perimeter edge 4a of the second flexible membrane 4 to the outer perimeter of the enclosure is carried out by means of mechanical connecting device 11 which extends throughout around the gasometer 1.

[0148] The enclosure comprises an appendage 12 of the first flexible membrane 2 that is visible in figure 4. The appendage 12 extends continuously all around the enclosure and towards the outer environment.

[0149] The mechanical connecting device 11 comprises a first element 13 and a second element 14 surrounding the outer perimeter of the enclosure. The first element 13 and the second element 14 are joined together the one to the other and clamp between them the aforementioned appendage 12 and the perimeter edge 4a of the second flexible membrane 4 (figure 4).

[0150] In the non-limiting shown embodiment, the first element 13 comprises a plurality of plates (one of which is visible in section in figure 4) connected to each other to surround the outer perimeter of the enclosure. Similarly, the second element 14 comprises a plurality of plates (one of which is visible in section in figure 4) connected to each other to surround the outer perimeter of the enclosure. The first element 13 and the second element 14 are arranged in vertical planes and the appendage 12 and the perimeter edge 4a are arranged in vertical planes side by side.

[0151] The first element 13 is placed between the enclosure and the second element 14. The appendage 12 and the perimeter edge 4a of the second flexible membrane 4 are clamped between the first element 13 and the second element 14 and said appendage 12 is interposed between the perimeter edge 4a and the first element 13.

[0152] Removable connections, as not shown screws or bolts, are coupled to the first element 13 and to the second element 14 to join them among them and are configured to compress the appendage 12 of the first flexible membrane 2 and the perimeter edge 4a of the second flexible membrane 4 between the first element 13 and the second element 14.

[0153] As shown in figure 4, the second variable volume 5 is partly delimited also by a portion of the appendage 12.

[0154] The double membrane gasometer 1 comprises furthermore a structure 15 constrained to the mechanical connecting device 11 and fixed to the ground “G” to anchor the enclosure and the second flexible membrane 4.

[0155] In the shown embodiment, the structure 15 comprises a plurality of tie-rods 16 presenting upper ends constrained to the mechanical connecting device 11 and lower ends fixed to the ground “G”. In figure 4, the tie-rods 16 are constrained to the first element 13. In figure 3, the tie-rods 16 are crossed with each other to form a grid that is arranged around the lower part 2a of the first flexible membrane 2.

[0156] In figures from 4 to 8, the tie-rods 16 are preloaded so as to keep the second membrane 2 and therefore the whole gasometer 1 pressed on the ground “G”. The enclosure is then provided with a flattened portion 17 that rests on the ground “G”. The outer perimeter of the enclosure is spaced from the ground of a first height “H1” about 0.35 times a diameter “D” of the cylinder with a circular cross-section. In the shown embodiment, such first height “H1” coincides with the height of the longitudinal axis “X-X” of the cylinder from the ground “G” (second height “H2”). In fact, the perimeter edge lies in a horizontal plane in which also said longitudinal axis “X-X” lies (figure 5).

[0157] In other embodiments, not shown, the perimeter edge 14 of the second membrane 4 is spliced to the enclosure at a horizontal plane that is spaced from the longitudinal axis “X-X”, therefore the first height “H1” and the second height “H2” are different from each other.

[0158] Referring now to figure 4:

[0159] 1 ) F3 = F1 - F2 wherein:

[0160] F1 : force due to the pressure difference between the second pressure “P2” and the atmospheric pressure “Patm” of the outer environment acting on the second membrane 4;

[0161] F2: preload of cables 16;

[0162] F3: force acting on the lower portion 2a of the first membrane 2 due to the pressure difference between the first pressure “P1” and the atmospheric pressure of the outer environment.

[0163] The second membrane 4 always works under pressure (force “F3”) since the second pressure “P2” is slightly higher than the atmospheric pressure “Patm”.

[0164] Since the first pressure “P1” and the second pressure “P2” are kept equal, the upper part 2b of the first membrane 2 does not have a structural role as it is not under tension.

[0165] The flattened portion 17 of the lower part 2a of the first membrane 2 lean against the ground “G”.

[0166] Furthermore, by adjusting the preload “F2” of cables 16, it is possible to reduce or eliminate tension “F3” in the lower part 2a of the first membrane 2 comprised between the ground “G” and the mechanical connecting device 11 . The gasometer 1 of the embodiment of figure 5 comprises furthermore a plurality of cables 18, of which only one is visible. Each one of the cables 18 is straddling the gasometer 1 , in particular an outer surface of the second flexible membrane 4, and has opposite ends attached to the ground. The cables 18 are used to better stabilize the gasometer 1. Furthermore, the gasometer 1 of the embodiment of figure 5 comprises two panels 19, each one inclined and leaning against a side of the gasometer to deflect the wind.

[0167] Figure 6 shows a series or battery of gasometers 1 as the one of figure 5 side by side and with their longitudinal axes arranged parallel. Cables 18 extend from one side of the series to the other and above all the gasometers 1. Furthermore, each one of two gasometers 1 placed at two opposite ends of the series comprises the panels 19 leaning against a respective side.

[0168] In the embodiment variant of figure 7, the gasometer 1 is placed in an excavation made in the ground “G”. In particular, the base surface 17 of the enclosure is positioned resting on a bottom of the excavation. Furthermore, with the earth of excavation and / or with concrete, is realized an embankment 20 surrounding the enclosure and the lower ends of the tie-rods 18 are fixed to the embankment 20.

[0169] Figure 8 shows a series or battery of gasometers 1 as the one of figure 6, located in respective excavations, side by side and with their longitudinal axes arranged parallel. Above the gasometers 1 of the series, for example above the cables 18, can furthermore be installed photovoltaic panels, not shown.

[0170] Figures 9 and 10 show further variants of the gasometer 1. The first flexible membrane 2 is defined by three enclosures welded together and defining respective first variable volumes 3’, 3”, 3”’ for the gas phase working fluid. The first variable volume 3 is thus divided into the three aforementioned first variable volumes 3’, 3”, 3”’ by septa 21 internal to the first flexible membrane 2. The first variable volumes 3’, 3”, 3”’ are in fluid connection among them to keep the same first pressure “P1”. In the figure 9, the septa 21 have openings to put in fluid communication among them the first variable volumes. In figure 10, the first variable volumes 3’, 3”, 3”’ are connected among them through the first pipelines 206. In figures 9 and 10 the first pipeline 206 is just one and alternatively allows the inlet or the outlet of the working fluid in / from the gasometer 1. List of elements

[0171] 1 double membrane gasometer

[0172] 2 first flexible membrane

[0173] 2a lower part

[0174] 2b upper part

[0175] 3, 3’, 3”, 3”’ first variable volume

[0176] 4 second flexible membrane

[0177] 4a perimeter edge

[0178] 5 second variable volume

[0179] 6 fan

[0180] 7 discharging valve

[0181] 8 pressure regulating device

[0182] 9 first safety valve

[0183] 10 second safety valve

[0184] 11 mechanical connecting device

[0185] 12 appendage

[0186] 13 first element

[0187] 14 second element

[0188] 15 structure

[0189] 16 tie-rods

[0190] 17 flattened portion

[0191] 18 cable

[0192] 19 panel

[0193] 20 embankment

[0194] 21 septa

[0195] 100 primary heat exchanger

[0196] 200 energy management plant

[0197] 202 expander / turbine

[0198] 202a inlet of the turbine

[0199] 202b outlet of the turbine

[0200] 203 compressor

[0201] 203a inlet of the compressor

[0202] 203b outlet of the compressor 204 moto-generator

[0203] 206 first pipelines

[0204] 208 second pipelines

[0205] 209 tank 210 secondary heat exchanger

[0206] 212 third pipelines

[0207] 213 additional heat exchanger

[0208] 223 radiator

[0209] 224 fan

[0210] 2000 basin

Claims

CLAIMS1. Double membrane gasometer, comprising: a first flexible membrane (2) defining an enclosure internally delimiting a first variable volume (3) for a working fluid in the gas phase; wherein the enclosure rests on the ground; wherein the first variable volume (3) is connected to pipelines of a plant (200) operating with said working fluid; a second flexible membrane (4) open and connected to the enclosure; wherein the second flexible membrane (4) has a perimeter edge (4a) spliced to the enclosure at an outer perimeter of the enclosure spaced from the ground (G); wherein the second flexible membrane (4) and the enclosure delimit a second variable volume (5) for an auxiliary fluid between them; a mechanical connecting device (11 ) placed at the outer perimeter of the enclosure and configured to join the second flexible membrane (4) to the enclosure; a structure (15) constrained to the mechanical connecting device (11 ) and fixed to the ground (G); wherein the mechanical connecting device (11 ) comprises:■ a first element (13) surrounding the outer perimeter of the enclosure;■ a second element (14) surrounding the outer perimeter of the enclosure; wherein the first element (13) and the second element (14) are joined together and clamp an appendage (12) of the first flexible membrane (2) and the perimeter edge (4a) of the second flexible membrane (4).

2. Gasometer according to claim 1 , wherein the first element (13) and the second element (14) are shaped as plates.

3. Gasometer according to claim 1 or 2, wherein the mechanical connecting device (11 ) comprises removable couplings, optionally screws or bolts, coupled to the first element (12) and second element (14) to join said first element (13) and second element (14) together.

4. Gasometer according to one of claims 1 to 3, wherein the structure (15) comprises a plurality of tie-rods (16) presenting upper ends constrained to the mechanical connecting device (11 ) and lower ends attached to the ground (G).

5. Gasometer according to claim 4, wherein the tie-rods (16) are preloaded.

6. Gasometer according to claim 4 or 5, wherein the tie-rods (16) are crossed with each other.

7. Gasometer according to one of claims 4 to 6, wherein the tie-rods (16) form a grid arranged around a lower portion of the enclosure.

8. Gasometer according to one of claims 4 to 7, comprising an embankment (20), optionally of concrete or earth, surrounding the enclosure; wherein the lower ends of the tie-rods (16) are attached to said embankment (20).

9. Gasometer according to one of claims 1 to 8, wherein the appendage (12) of the first flexible membrane (2) extends continuously all around the enclosure.

10. Gasometer according to one of claims 1 to 9, wherein an overall outer surface of the gasometer (1 ) is shaped as a cylinder with a circular cross-section or as a sphere, optionally provided with a flattened portion (17) resting on the ground (G).

11. Gasometer according to claim 10, wherein the cylinder with circular crosssection has opposite convex ends, optionally shaped as spherical sectors.

12. Gasometer according to claim 10 or 11 , wherein said outer perimeter of the enclosure is spaced from the ground (G) by a first height (H1 ) between 0.2 and 0.8 times a diameter (D) of the circular-section cylinder or sphere.

13. Gasometer according to claim 12, wherein a second height (H2) of a longitudinal axis (X-X) of the circular-section cylinder or a center of the sphere fromthe ground (G) is between 0.3 and 0.5 times the diameter (D) of said circular-section cylinder or said sphere.

14. Gasometer according to one of claims 1 to 13, wherein the first flexible membrane (2) is made of a gas impermeable material, optionally including a plurality of layers.

15. Gasometer according to claim 14, wherein the first flexible membrane (2) comprises a plurality of pieces joined together gas-tight.

16. Gasometer according to one of claims 1 to 15, wherein the second flexible membrane (3) is made of PVC coated polyester.

17. Gasometer according to one of claims 1 to 16, comprising a plurality of cables (18), each straddling an outer surface of the second flexible membrane (4) and presenting opposite ends attached to the ground (G).

18. Gasometer according to one of claims 1 to 17, comprising panels (19) leaning against sides of an overall outer surface of the gasometer (1 ) and inclined to deflect the wind.

19. Gasometer according to one of claims 1 to 18, comprising an excavation made in the ground (G), wherein a base surface (17) of the enclosure is placed in the excavation.

20. Gasometer according to one of claims 1 to 19, wherein a source of the auxiliary fluid is the atmosphere and the auxiliary fluid is air, wherein the gasometer (1 ) comprises a fan (6) and valves (7) in fluid connection with the second variable volume (5) and with the atmosphere, for introducing and / or extracting air into / from said second variable volume (5).

21. Gasometer according to one of claims 1 to 20, comprising a pressure regulating device (8) connecting the first variable volume (3) with the second variable volume (5) and / or with the atmosphere.

22. Gasometer according to one of claims 1 to 21 , wherein the first flexible membrane (2) is defined by a plurality of enclosures defining respective first variable volumes (3', 3", 3") for the gas phase working fluid or wherein the first variable volume (3) is divided into a plurality of first variable volumes (3', 3", 3") by septa (21 ) internal to the first flexible membrane (2).

23. Energy management plant, comprising: a working fluid other than atmospheric air, optionally carbon dioxide; a double membrane gasometer (1 ) in accordance with at least one of the previous claims, wherein the gas phase working fluid stored in the first variable volume (3) is in pressure equilibrium with the atmosphere; a mass accumulator (209) that stores said working fluid in the liquid or supercritical phase with a temperature close to the critical temperature, wherein said critical temperature is close to ambient temperature; wherein the plant (200) is configured to implement a closed thermodynamic cyclic transformation (TTC), first in one direction in a charging configuration and then in the opposite direction in a discharging configuration, between said gasometer (1 ) and said mass accumulator (209); wherein in the charging configuration the plant (200) accumulates heat and pressure and in the discharging configuration it generates energy by exploiting the previously accumulated heat and pressure; wherein, in both the charging and discharging configurations, the first variable volume (3) varies and a first pressure (P1 ) in said first variable volume (3) is kept constant.

24. Plant according to claim 23, comprising: a compressor (203) in fluid connection with the gasometer (1 ); an expander (202) in fluid connection with the gasometer (1 ); a thermal accumulator (100) in fluid connection with the compressor (203) and the expander (202) and configured to exchange heat with the working fluid;pipelines and control devices configured to operate the plant (200) in the charging configuration and in the discharging configuration; wherein, in the charging configuration, the working fluid transits from the gasometer (1 ) to the mass accumulator (209) through the compressor (203), the thermal accumulator (100) and is stored in the mass accumulator (209); wherein, in the discharge configuration, the working fluid transits from the mass accumulator (209), to the gasometer (1 ) through the thermal accumulator (100) and the expander (202) and is again stored in the gasometer (1 ).

25. Plant according to claim 23 or 24, comprising a plurality of double membrane gasometers (1) side by side to form a series.

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