System for energy storage and method for power generation thereof

Abstract

A system (100) for energy storage and production, comprising a primary thermal storage circuit (10) via a primary volume (12) of a high-enthalpy fluid, said circuit also comprising a primary circulation valve (17), said system comprising a secondary circuit (20) for energy production via the high-enthalpy fluid of the primary circuit, and comprising a connecting valve (27) linking the two circuits (10, 20), said system operating in two configurations: - A first configuration, with the primary circuit (10) isolated from the secondary circuit (20) by closing the valve (27), and maintaining the fluid in fixed thermodynamic conditions; - A second configuration, with the primary circuit (10) open to the secondary circuit (20) by opening the valve (27), allowing the diffusion of the fluid to drive energy production.

Description

TECHNICAL FIELD

[0001] The present invention belongs to the field of energy storage and production.

[0002] The present invention relates more particularly to an energy storage system and in particular to a method of producing electrical energy in large quantities and in a response time of less than one minute, thus being able to meet urgent electricity needs.

[0003] The present invention finds a direct application in the securing and stabilization of electrical distribution networks, acting as a power and / or frequency reserve. STATE OF THE ART

[0004] Securing electricity distribution networks is a growing concern in the context of dynamic demand and the imperatives of energy transition.

[0005] Historically, power grids were designed to adapt quantitatively to variations in consumption by relying on hydroelectric storage and power plants, adjustable according to demand. Qualitatively, the electricity in the grid must be constantly regulated in relation to electricity consumption and any potential production shortfalls in the energy network.

[0006] Today, electricity is primarily supplied by turbines. In the event of an imbalance, the grid frequency is affected such that overproduction leads to an increase in frequency, and underproduction leads to a decrease in frequency relative to a standardized frequency of 50 Hz or 60 Hz. The day-to-day management of minor variations in electricity frequency can be achieved by adjusting the inertia of rotating machines. If the deviation becomes too large, the grid is shut down.

[0007] Renewable energies exhibit seasonal, daily, hourly, or even second-level variations, and solar power does not have a rotating mass. While future power grid stabilization may be improved through additional regulation of wind turbines, the increasing integration of variable and intermittent renewable energy sources such as wind and solar presents an even greater technical challenge for power grid management.

[0008] Consequently, for the electricity grid, future energy storage solutions must meet the storage needs of surplus electricity from renewable energies, outside periods of electricity demand, as well as the quantitative and qualitative challenges of equalizing and stabilizing variations in electricity production.

[0009] More specifically, to secure the electricity grid of the future, the challenges to be met by energy storage on the scale of the ideal grid are as follows.

[0010] First, it is necessary to be able to accumulate a sufficient stock of energy, on the scale of the intermittency or absence of renewable electricity production and to compensate for increasingly frequent and critical climatic hazards, such as droughts, floods and violent winds, these hazards can also affect other electricity production systems, such as nuclear power plants during severe droughts.

[0011] Next, the production of an energy flow must have sufficient power to be able to restart an electrical network that has been taken out of service.

[0012] Finally, the energy production method must be able to meet the network's needs in a few tens of seconds and regulate the electrical frequency, thus guaranteeing the quality of the network's electricity.

[0013] Pumped storage hydroelectric plants (PSHPs), with their large-scale operating capacity and high-quality electricity production, emerged as the ideal solution. PSHPs allow for energy storage during off-peak periods and its redistribution during peak periods. These facilities offer the advantages of reversibility and longevity, which have made them the backbone of energy storage, responsible for stabilizing the electricity distribution network.

[0014] However, this technology is not without limitations. Its dependence on specific geomorphological and climatic constraints makes it a solution that cannot be generalized, thus hindering its universal implementation. Furthermore, the development of such projects can generate controversies related to water use decisions, particularly during periods of critical drought. Consequently, to anticipate the needs arising from the rapid adoption of renewable energies, a massive and further expansion of this solution is not feasible. Also, considering increasing climate risks, this energy storage solution appears increasingly risky.

[0015] Faced with these realities, alternative storage systems exploiting several physical principles, such as gravity (mass lifting towers, gravity elevators, etc.), kinetic energy (flywheels, etc.), fluid compression, electrochemical energy (batteries, etc.) and thermal energy, are gaining ground.

[0016] However, these systems can only partially address the problem of securing electricity distribution networks (energy storage capacity and / or duration of electricity supply) and / or are solutions that are difficult to deploy on a large scale, etc.

[0017] Thermal storage systems that directly or indirectly use a phase-change fluid, for example through a combined Rankine cycle, are constrained by the storage volume, which is a limiting aspect of their efficiency.

[0018] In the prior art, there are geothermal systems for storing a fluid such as carbon dioxide (CO2) or Liquefied Petroleum Gas (LPG).

[0019] However, these two examples of geothermal storage systems are also unsuitable for securing and stabilizing an electricity distribution network. In particular, geothermal energy production is generally low, constrained by an average terrestrial geothermal flux of around 60 to 100 mW / m² in deep geological reservoirs, and / or by an excessively long response time due to the thermal inertia resulting from the length of the circulation pipes in these deep systems.

[0020] Furthermore, in the case of the application using LPG, the system may present high investment and operating costs, particularly related to the management of production, reinjection and energy volumes of geothermal water, thus presenting obstacles to the development of this solution.

[0021] For energy-related issues, in France, for example, securing and stabilizing the grid requires a primary power reserve of around 570 MW, which must be available in less than thirty seconds, and a secondary power reserve of between 500 MW and 1000 MW, depending on the season, which must be available for several minutes after the primary reserve is depleted. Problems with responsiveness and production capacity arise with storage systems proposed as alternatives to pumped hydro storage (PHS), and these remain unresolved today.

[0022] Indeed, none of the current systems can simultaneously meet all the required needs, namely to offer a technique for storing electrical energy and to meet an urgent need to secure and stabilize an electrical distribution network, while maximizing its resilience to weather hazards and minimizing the ecological cost of said systems and their energy losses inherent in operating cycles. PRESENTATION OF THE INVENTION

[0023] The present invention aims to remedy, at least in part, the aforementioned disadvantages, while also leading to other advantages.

[0024] To this end, the present invention relates firstly to a system for energy storage and energy production. This system is remarkable in that it comprises a primary circuit for storing energy in thermal form and a secondary circuit for energy production. The primary circuit forms a loop comprising a primary storage volume for a high-enthalpy fluid and a primary circulation valve. The secondary circuit comprises a device for producing energy from the high-enthalpy fluid stored in the primary volume of the primary circuit, and a connecting valve linking the primary circuit to the secondary circuit. Advantageously, the system is configured to operate in two main configurations: a first configuration in which the primary circuit is disconnected from the secondary circuit by closing the connecting valve, the primary circuit including a device for maintaining the high enthalpy fluid under predetermined thermodynamic conditions; a second configuration in which the primary circuit is connected to the secondary circuit by opening the connecting valve, the primary circulation valve being closed, the high enthalpy fluid diffusing into the secondary circuit to implement the energy production device.

[0025] Thus, outside of production phases, the system maintains a high enthalpy fluid ready to be used in case of urgent need for electrical energy, and via a simple opening / closing control of valves.

[0026] According to a particular feature of the invention, the system also includes a control device for the operating configuration of said system as a function of the state of an electrical distribution network connected to said system in order to be able to switch from the first configuration to the second configuration automatically.

[0027] According to another particular feature of the invention, the primary storage volume is a deep geological storage, therefore insensitive to surface weather hazards.

[0028] Advantageously, and according to another particular characteristic, the primary storage volume is a butane tank in order to create a storage system located on the surface.

[0029] According to another particular feature of the invention, the secondary circuit also includes a secondary storage volume configured to recover the fluid after the power generation device, said fluid being called low-enthalpy fluid, the primary circuit comprising a mixing device being connected to the secondary volume, said mixing device being configured to inject the low-enthalpy fluid into the primary circuit by mixing it with the high-enthalpy fluid.

[0030] According to another particular feature of the invention, the high-enthalpy fluid and the low-enthalpy fluid are Liquefied Petroleum Gas (LPG). Since LPG is hydrophobic and lighter than water, it is stored separately in the upper part of a geological formation that naturally contains geothermal water.

[0031] Advantageously, the thermodynamic temperature T and pressure P of the high enthalpy fluid stored, for example at a depth of 3000 m, are approximately 100°C and 140 bars respectively.

[0032] According to another particular feature of the invention, the secondary circuit further comprises at least one refrigeration production system.

[0033] The present invention also relates to a method of energy production implemented by means of an energy storage and energy production system as described above, said method comprising two operating phases: a first phase of energy storage comprising the following steps: preparation of a so-called high-enthalpy fluid to achieve optimal thermodynamic temperature and pressure conditions for energy production; injection of the high-enthalpy fluid into a primary storage volume of the system, by means of an injection conduit and a circulation pump of said system; recovery of the high-enthalpy fluid circulating in the primary storage volume of the system, by means of a recovery conduit and the circulation pump; a second phase of energy production comprising the following steps: production of electricity, during which the high-enthalpy fluid is converted into a low-enthalpy fluid; mixing of the low-enthalpy fluid with the high-enthalpy fluid by means of a mixing device of the system.

[0034] According to a particular characteristic, the energy production process includes a prior system initialization phase comprising an initial step of filling the system with the high enthalpy fluid.

[0035] According to a particular characteristic, the energy production process further includes, during the energy production phase, a cold production stage, said stage being carried out before, during or after the electricity production stage.

[0036] According to a particular characteristic, the energy production process further includes, during the energy production phase, a low-enthalpy fluid storage stage.

[0037] According to a particular characteristic, the energy production process further includes, during the energy production phase, a step of temporary interruption of the operation of the system.

[0038] The present invention also relates to a method for storing electrical energy in thermal form implemented by means of an energy storage and energy production system as described above, said method comprising firstly a step of monitoring the electricity sales market and, if a sales price of electricity Velec of said market is lower than a previously defined threshold value Vmax, further comprising a step of storing electrical energy in thermal form, comprising the following steps of: preparation of a so-called high-enthalpy fluid to achieve optimal thermodynamic temperature and pressure conditions for energy production; injection of the high-enthalpy fluid into a primary storage volume of the system, by means of an injection duct and a circulation pump of said system; recovery of the high-enthalpy fluid circulating in the primary storage volume of the system, by means of a recovery duct and the circulation pump;

[0039] the step of storing electrical energy in thermal form being carried out continuously or discontinuously during a storage period P during which the selling price of electricity Velec is less than the threshold value Vmax.

[0040] Finally, another object of the invention is an energy storage and energy production site characterized comprising a system for energy storage and energy production as described above.

[0041] Advantageously, the energy storage and energy production site is kept in reserve for securing the network.

[0042] Advantageously, the energy storage and production site is used to filter and correct electrical inputs originating from renewable energy sources.

[0043] The fundamental concepts of the invention having been set forth above in their most elementary form, other details and characteristics will become clearer upon reading the description that follows and in view of the attached drawings. BRIEF DESCRIPTION OF THE FIGURES

[0044] The figures are provided for illustrative purposes only to aid understanding of the invention without limiting its scope. The various elements may be represented schematically and are not necessarily to the same scale. Throughout the figures, identical or equivalent elements are identified by the same numerical reference.

[0045] This is illustrated as follows: Figure 1A : an overview of a system for storing energy in thermal form and producing energy, according to a first embodiment of the invention; Figure 1B : an overview of the system for storing energy in thermal form and producing energy, according to a second embodiment of the invention; Figure 2 : a diagram of the main steps of an energy production process, according to a first embodiment of the invention; Figure 3: a diagram of the main stages of an energy production process, according to a second embodiment of the invention; Figure 4 : a diagram of the main stages of an energy production process, according to a third embodiment of the invention; Figure 5 : a graph of the monitoring of the electricity selling price over a day; Figure 6 : a diagram of the main steps of an energy storage process, according to an embodiment of the invention. DETAILED DESCRIPTION OF IMPLEMENTATION METHODS

[0046] It should be noted that certain technical elements well known to those skilled in the art are described here to avoid any insufficiency or ambiguity in the understanding of the present invention.

[0047] In the following example, the embodiment of the invention described relates to an application implementing equipment used in the oil industry and in the geothermal industry, without this presenting a limitation.

[0048] There Figure 1A represents an overview of a 100a system for storing energy in thermal form and producing energy, particularly electrical energy, according to a first embodiment of the invention.

[0049] System 100a mainly comprises a primary circuit 10 for circulating a so-called high-enthalpy fluid and a secondary circuit 20 for producing energy, at the outlet of which circulates a so-called low-enthalpy fluid.

[0050] High enthalpy fluid means, for example, but not limited to, a liquefied gaseous hydrocarbon type fluid, such as butane or propane, or having the thermodynamic characteristic of being liquefiable at pressure and temperature values ​​below 50 bar and 150°C, which circulates continuously in the primary circuit 10 during a phase where the system 100a does not produce energy (electrical and / or thermal) and / or a liquefied gaseous hydrocarbon which is used to produce energy, by means of an energy conversion device described later.

[0051] Low enthalpy fluid is understood, for example, but not limited to, a gaseous hydrocarbon which is obtained when system 100a produces energy (electrical and / or thermal) and whose thermodynamic properties and / or state differ from those of the high enthalpy fluid.

[0052] The primary circuit 10 and the secondary circuit 20 are connected by means of at least one connecting valve 27, as well as by means of at least one mixing device 14.

[0053] The primary circuit 10 also includes at least one valve 17 called primary circulation, at least one circulation pump 16 for circulating the high-enthalpy fluid in said circuit, at least one injection conduit 11 of the high-enthalpy fluid into a primary storage volume 12 and at least one recovery conduit 13 of the high-enthalpy fluid present in said volume.

[0054] The primary circuit 10 further includes at least one heat exchanger 15 for thermally recharging the high enthalpy fluid.

[0055] Preferably, the injection conduit 11 and the recovery conduit 13 are respectively an injection well and a production well such as are found in the exploitation of deposits in the petroleum industry.

[0056] In the embodiment shown in the figure 1 The primary storage volume 12 is a deep geological storage volume, comprising successively: an upper geological layer 121 forming a dome, the nature of which ensures a seal of said volume, thus blocking the upward migration of the high-enthalpy fluid; a rock layer 122 having a porosity and permeability allowing the circulation and storage of the high-enthalpy fluid; and an aquifer 123 above which the high-enthalpy fluid, being lighter than water, is under overpressure.

[0057] This type of geological structure is well known in the field of oil exploration and production. It is most often found at depths between 2000 m and 4000 m, although these depth limits are not strictly enforced.

[0058] In this example, the main characteristics of the deep geological storage volume are given, but these characteristics are subject to significant variations (thickness of the upper geological layer 121, thickness, porosity, and permeability of the rock layer 122, etc.), and can even vary at the same site, as this type of formation can extend over a large area. Furthermore, it is estimated that the storage capacity of the primary storage volume 12 can reach several hundred thousand tons of high-enthalpy fluid, resulting in the production of several GWh of electricity per day.

[0059] Valves 17 and 27 are designed to direct the high-enthalpy fluid out of the recovery duct 13: either towards the inlet of the injection conduit 11 in order to continuously circulate said fluid within the primary circuit 10, the primary circulation valve 17 being open and the connection valve 27 being closed; or towards the secondary energy production circuit 20 to produce electrical or thermal energy, the primary circulation valve 17 being closed and the connection valve 27 being open.

[0060] In a particular embodiment of the invention, the valves 17 and 27, each in the open position, are able to reinject part of the high-enthalpy fluid into the primary circuit 10, while directing the other part of the high-enthalpy fluid to the secondary circuit.

[0061] The mixing device 14 is intended to mix the high enthalpy energy production fluid, and includes valves adapted to the thermodynamic conditions of said fluids.

[0062] Advantageously, the high-enthalpy fluid, characterized in particular by a thermodynamic temperature T and a pressure P, is in a supercritical thermodynamic state when said fluid is injected into the injection conduit 10. Preferably, the high-enthalpy fluid is Liquefied Petroleum Gas (LPG) stored at an average depth of 3000 m, i.e., at a temperature T of approximately 100 °C and a pressure P of approximately 140 bar. Moreover, and compared with existing solutions, the high-enthalpy fluid is reinjected into the primary storage volume 12 without the addition of superheated water to said fluid. The high-enthalpy fluid is therefore single-phase.Since the primary storage volume 12 in this example is porous and permeable due to the presence of the rock layer 122, and said layer is entirely filled with said fluid, the single-phase flow of the high-enthalpy fluid represents advantages when reinjecting said fluid into said volume such as: . the minimization of losses related to friction due to the fact that the high enthalpy fluid, in liquid phase, has supercritical thermodynamic conditions at injection and therefore a low viscosity; the absence of surface tension problems between the high enthalpy fluid, which is by nature hydrophobic when it is a hydrocarbon for example, and water which would be present in the pores of the rock layer 122, said tensions would oppose the flow of said fluid in the primary storage volume 12, and would thus reduce the efficiency of the reinjection.

[0063] Thus, in addition to the advantages listed above, continuous circulation within the primary circuit 10 of system 100a, when the system is waiting to produce electrical or thermal energy, allows for overall energy efficiency that is beneficial for industrial-scale operation. The injection of the high-enthalpy fluid requires less use of circulation pumps 16, and therefore results in energy savings. Advantageously, the continuous circulation of the high-enthalpy fluid facilitates its recompression and liquefaction when it is in the gaseous phase.To maintain the thermodynamic conditions of the high-enthalpy fluid at optimal levels for continuous circulation in the primary circuit 10, the fluid passes through the heat exchanger 15 before being reinjected into the injection duct 11, which then adjusts the thermal energy supplied to the fluid to achieve these conditions. The heat exchanger 15 is an external thermal energy source or a high-temperature heat pump. In the embodiment where the heat exchanger 15 is a high-temperature heat pump, it is adapted to the flow rates and temperature specifications required for the optimal circulation of the high-enthalpy fluid.When a demand for electrical energy is signaled to system 100a, the system configures itself in production mode: valves 17 and 27 open or close automatically to circulate the high-enthalpy fluid from the outlet of the recovery line 13 to the secondary production circuit 20. The opening and closing of valves 17 and 27 is controlled by a control device 19 that determines the operating configuration of system 100a. The control device 19 operates based on the state of an electrical distribution network 300 connected to system 100a. The electrical distribution network 300 includes, in particular, renewable electrical energy sources such as solar panels 32 and wind turbines 31, these sources being by definition intermittent due to day-night cycles and weather conditions (cloud cover, wind speed, etc.).In the preferred embodiment of the invention, the high-enthalpy fluid circulates exclusively in the secondary circuit 20 when the system 100a produces energy. In another embodiment, the high-enthalpy fluid circulates simultaneously in the primary circuit 10 and the secondary circuit 20.

[0064] The secondary power generation circuit 20 comprises at least one set of power ducts 201, said circuit comprising, for the purpose of power generation, at least one power generation device such as a thermodynamic machine 22, said machine being coupled to an electric generator 23 to convert the mechanical energy produced as a result of the transformation of the enthalpy of the high-enthalpy fluid by means of said machine. The thermodynamic machine 22 is, for example, an expansion turbine sized according to the thermodynamic characteristics corresponding to a steady-state power generation regime.

[0065] In a particular embodiment of the invention, the secondary circuit 20 further comprises at least one cooling production system 21, such as an evaporator.

[0066] In another embodiment, the secondary circuit 20 further includes at least one capacitor positioned at the output of the thermodynamic machine 22. Thus, a system manager 100a is able to size and adapt said system, and to operate all or part of the thermodynamic machines 22 and the refrigeration production systems 21, to optimally meet energy needs.

[0067] Advantageously, and due to its response time of significantly less than thirty seconds, as generally recommended by the main electricity grid operators, the 100a system is capable of producing electricity by responding instantly to the needs of the 300 electrical grid. This system thus contributes to the security and stability of said grid (power and frequency). Indeed, the continuous circulation of the high-enthalpy fluid in the primary circuit 10, with the fluid maintained at optimal thermodynamic characteristics, allows for the immediate availability of a fluid ready to be driven by the turbine. Simple opening and closing of valves 17 and 27 directs this fluid into the secondary production circuit 20.Thus, the 100a system has a response time that is similar to that of Pumped Storage Power Plants (PSPPs), without presenting the disadvantages of this type of installation (environmental and social impact of artificial water reservoirs, water resource management during drought episodes, etc.).

[0068] This embodiment has an electrical energy production capacity that can range from several hundred MWh to several GWh per day, and which is notably a function of the capacity of the primary storage volume 12 and the daily duration of energy production stored each day.

[0069] There figure 1 B represents an overview of a 100b system for energy storage, according to a second embodiment of the invention, which consists of constructing a thermal battery known as a "surface battery". This particular embodiment differs from that shown in the figure 1 , by the primary storage volume 12 which is then located at the surface, and no longer at depth. In this new example, the primary storage volume 12 is a fluid reservoir, such as a butane tanker 18 or a set of tanks.

[0070] Regarding the other elements of system 100b, these are similar to those of the embodiment shown in the figure 1 .

[0071] This alternative embodiment is possible due to the simplification of the energy storage and production process, which does not require mixing the high-enthalpy fluid with superheated water. This allows for the operation of a miniaturized system essentially based on the exclusive storage of the high-enthalpy fluid in the butane tank 18 and / or a set of thermally insulated tanks. In this example, the butane tank 18 has a total storage capacity of several tens of tons of the fluid, with the high-enthalpy fluid having a thermodynamic temperature T maintained at a maximum of 150°C and a pressure P between 10 and 60 bar. Furthermore, this type of installation has an electrical energy production capacity exceeding 1 MWh per day.

[0072] There figure 2represents the diagram of the main steps 500 of an energy production process according to a first embodiment of the invention.

[0073] First, process 500 includes, during an initialization phase, a step 501 of filling the geological structure during which system 100 is charged with the high-enthalpy fluid. This phase prepares system 100 for continuous and optimized operation.

[0074] Then, during an operational phase, the preferred embodiment of process 500 mainly comprises: a step 511 of preparation of the high enthalpy fluid; a step 512 of injection of the high enthalpy fluid; a step 513 of recovery of the high enthalpy fluid; These three steps being implemented continuously, and when an energy requirement is signaled to system 100, said process further includes: a step 514 of modifying the circulation of the high enthalpy fluid; a step 521 of producing electricity; a step 523 of storing the low enthalpy fluid; a step 524 of temporarily interrupting the operation of system 100; and a step 525 of mixing the low enthalpy fluid with the high enthalpy fluid.

[0075] On the figure 2 , a pre-production frame 510 represents the repetitive steps of the cycle in the absence of energy demand, i.e. steps 511 to 513, and a production frame 520 represents the steps of the cycle during energy production, i.e. steps 521 to 525.

[0076] During step 511 of preparation of the high enthalpy fluid, said fluid is thermally recharged by means of the heat exchanger 15 to maintain the thermodynamic temperature substantially at 100°C, for a pressure substantially of 140 bars.

[0077] During step 512 of high enthalpy fluid injection, said fluid is injected into the primary storage volume 12 via the injection conduit 11, said fluid being subsequently recovered via the recovery conduit 13.

[0078] If no energy demand is indicated to system 100, the high enthalpy fluid returns to the primary circuit 10 to complete the cycle defined by the steps described above.

[0079] In the event that an energy demand is signaled to system 100, the high-enthalpy fluid is directed to the secondary energy production circuit 20 by opening or closing valves 17 and 27. This occurs during step 514, which modifies the circulation of said fluid. Advantageously, this step is carried out in a very short time, corresponding to the time required to open or close valves 17 and 27, i.e., a time on the order of one second.

[0080] During the electricity production step 521, electrical energy is generated by means of the thermodynamic machine 22 coupled to an electric generator 23, and this energy is then fed into the electrical distribution network 300. The output of the thermodynamic machine 22 is a low-enthalpy fluid, whose thermodynamic temperature and pressure differ from those of the high-enthalpy fluid. Furthermore, the low-enthalpy fluid is in a gaseous phase, while the high-enthalpy fluid is in a liquid phase. In the preferred embodiment of the invention, the low-enthalpy fluid is stored in the secondary volume 25 during the fluid storage step 523. Once the system 100 has met the energy demand, the temporary interruption of the system's operation is carried out in step 524.During this stage, there is therefore no energy production via the secondary circuit 20, nor is the high-enthalpy fluid injected into the primary volume 12 via the primary circuit 10. Stage 524, the temporary interruption of system 100's operation, is intended to allow time for optimal conditions to restart system 100 in order to once again reach the nominal thermodynamic conditions of the high-enthalpy fluid. Optimal conditions for restarting system 100 include, for example, periods during which electricity is inexpensive, or even negatively priced, as is the case during periods of abundant renewable energy production and low demand.A well-known example of such periods is the peak in electricity production from solar panels, energy that then needs to be stored because production is very often uncorrelated with consumption, or certain periods corresponding to non-working days (Saturdays, Sundays, public holidays, etc.). Advantageously, these periods can be anticipated, and it is therefore possible to plan the operating and production phases of system 100. Once one of these periods is reached, system 100 can then be restarted at low cost. This operating method is similar to that used for pumped hydro storage: when electricity is cheap, energy is stored as potential energy, which is then used in the event of subsequent high demand.An example of these periods and the main stages of an energy storage process according to one embodiment are presented respectively in the . figure 5 and to the figure 6 .

[0081] When a period of low cost or negative price electricity occurs, step 524 of temporary interruption of the operation of system 100 ends so that step 525 of mixing the low enthalpy fluid with the high enthalpy fluid can then be carried out.

[0082] During step 525 of mixing the low enthalpy fluid with the high enthalpy fluid, the low enthalpy fluid previously stored in the secondary volume 25 is then mixed with the high enthalpy fluid contained in the primary circuit 10, by means of the mixing device 14. The fluid mixture, which is in liquid phase, is then thermally recharged by means of the heat exchanger 15.

[0083] The steps described in pre-production box 510 then follow again.

[0084] As an example, the daily period of energy production has a duration of between five and ten hours, a period which can be continuous or discontinuous.

[0085] There figure 3 This diagram represents the main steps of the energy production process 500 according to a second embodiment of the invention. This second embodiment differs from the first embodiment in that it further includes a cooling production step 522, which is carried out by means of the cooling production system 21. The cooling production step 522 may be carried out before, at the same time as, or after the electricity production step 521.

[0086] Advantageously, we exploit the possibility of combining electricity production with cold production by means of a single system 100.

[0087] Stage 522 of the cooling production process at a site equipped with system 100 is a modular stage, adaptable to local needs. The characteristic of the thermal system as described in this stage is net cooling production, as the resulting waste heat is recovered and stored in the working fluid. However, these hot fluid discharges, if released into the environment, can be considered thermal pollution, particularly in hot countries or during periods of intense heat in temperate latitudes. Thermal applications associated with this co-production of cooling include supplying a local air conditioning network, industrial uses (for example, in the food industry), or providing power to data centers. data centers ) heavy consumers of refrigeration and electricity.

[0088] There figure 4Figure 500 represents the diagram of the main steps of the energy production process according to a third embodiment of the invention. This third embodiment differs from the first and second embodiments in that the circulation of the high-enthalpy fluid is not interrupted during energy production, but continues in parallel. In other words, the low-enthalpy fluid is not stored in the secondary volume 25 but is directly mixed with the high-enthalpy fluid. Furthermore, this third embodiment does not include a step 514 for modifying the circulation of the high-enthalpy fluid, nor a step 524 for temporarily interrupting the operation of the system 100; the high-enthalpy and low-enthalpy fluids circulate continuously in the system 100.

[0089] There figure 5Figure 900 represents a graph tracking the selling price of Velec electricity over a day. In this example, taken for illustrative purposes only and whose values ​​are not to be considered strictly, the selling price of Velec electricity varies between -20€ / MWh and 40€ / MWh over 24 hours, and during a period around 4pm, represented by a hatched area, said selling price is negative.

[0090] Thus, and depending in particular on economic criteria and the operating costs of system 100 on an installation site, an operator is able to define a threshold value Vmax below which it is economically interesting to store energy in said system during a storage period P.

[0091] There figure 6 represents a diagram of the main steps of an energy storage process 600, according to an embodiment of the invention.

[0092] The 600 energy storage process mainly comprises: a step 610 of monitoring the electricity sales market; a step 620 of storing electrical energy in thermal form.

[0093] During step 610 of the electricity sales market monitoring, system 100 monitors the electricity selling price Velec and compares it to the threshold value Vmax in order to identify the economically advantageous storage period P. This monitoring can be performed automatically using a control unit (not shown here) such as a server or computer, or manually by the operator, based on forecasts or real-time data.

[0094] In the event that the selling price of Velec electricity is higher than the Vmax value, the 100 system does not trigger the storage of electrical energy in thermal form.

[0095] In the event that the selling price of Velec electricity is lower than the Vmax value, system 100 implements stage 620 of electrical energy storage in thermal form, which mainly comprises: a step 621 of preparation of the high enthalpy fluid; a step 622 of injection of the high enthalpy fluid; a step 623 of recovery of the high enthalpy fluid; these three steps are implemented continuously.

[0096] During the 620 stage of storing electrical energy in thermal form, the electrical energy consumed to power the mixing device 14, the heat exchanger 15 and the circulation pump 16 being at low cost or at a negative price, the storage of energy in thermal form in the system 100 therefore becomes economically viable when reselling the electricity produced by said system when the selling price of electricity is high.

[0097] It should be noted that each step could be adapted with alternative technologies or methods, such as the use of different fluids or varied storage systems, to adapt to local conditions or technological innovations.

Claims

1. System (100) for energy storage and energy production, characterized in thatit comprises a primary circuit (10) for storing energy in thermal form and a secondary circuit (20) for producing energy, the primary circuit (10) forming a loop comprising a primary volume (12) for storing a fluid called high enthalpy and a valve (17) called primary circulation, the secondary circuit (20) comprising a device for producing energy from the high enthalpy fluid stored in the primary volume (12) of the primary circuit (10), a valve (27) called connecting linking the primary circuit (10) to the secondary circuit (20), the system (100) being configured to operate in two main configurations: a. A first configuration in which the primary circuit (10) is disconnected from the secondary circuit (12) by closing the connecting valve (27), the primary circuit (10) comprising a device for maintaining the high enthalpy fluid under predetermined thermodynamic conditions; b.A second configuration in which the primary circuit (10) is connected to the secondary circuit (12) by opening the connecting valve (27), the primary circulation valve (17) being closed, the high enthalpy fluid diffusing into the secondary circuit (12) to implement the energy production device.

2. System (100) according to claim 1, wherein said system also includes a control device (19) for the operating configuration of said system (100) as a function of a state of an electrical distribution network (300) connected to said system (100).

3. System (100) according to claim 1 or claim 2, wherein the primary storage volume (12) is a deep geological storage.

4. System (100 according to claim 1 or claim 2, wherein the primary storage volume (12) is a butane tank.

5. A system (100) according to any one of the preceding claims, wherein the secondary circuit (20) also comprises a secondary storage volume (25) configured to recover the fluid after the power generation device, said fluid being referred to as the low-enthalpy fluid, the primary circuit (10) comprising a mixing device (14) being connected to the secondary volume (25), said mixing device (14) being configured to inject the low-enthalpy fluid into the primary circuit (10) by mixing it with the high-enthalpy fluid.

6. System (100) according to any one of the preceding claims, wherein the high-enthalpy fluid and the low-enthalpy fluid are Liquefied Petroleum Gas (LPG).

7. System (100) according to claim 6, wherein the thermodynamic temperature T and the pressure P of the high enthalpy fluid are substantially 100°C and 140 bars respectively.

8. System (100) according to any one of the preceding claims, wherein the secondary circuit (20) further comprises at least one refrigeration production system (21).

9. A method (500) for energy production implemented by means of an energy storage and energy production system (100) according to any one of the preceding claims, characterized in thatThe process comprises two operating phases: - a first energy storage phase comprising the following steps: - (511) preparation of a so-called high-enthalpy fluid to achieve optimal thermodynamic temperature and pressure conditions for energy production; - (512) injection of the high-enthalpy fluid into a primary storage volume (12) of the system (100), by means of an injection conduit (11) and a circulation pump (16) of said system; - (513) recovery of the high-enthalpy fluid circulating in the primary storage volume (12) of the system (100), by means of a recovery conduit (13) and the circulation pump (16); - a second energy production phase comprising the following steps: - (521) electricity production, during which the high-enthalpy fluid is converted into a low-enthalpy fluid;- (525) mixing of the low enthalpy fluid with the high enthalpy fluid by means of a mixing device (14) of the system (100).; 10. Method (500) according to claim 9, said method comprising a preliminary phase of initializing the system 100 including an initial step (501) of filling the system (100) with the high enthalpy fluid.

11. Method (500) according to claim 9 or claim 10, said method further comprising, during the energy production phase, a cold production step (522), said step being carried out before, during or after the electricity production step (521).

12. A method (500) according to any one of claims 8 to 10, said method further comprising, during the energy production phase, a step (523) of storing the low-enthalpy fluid.

13. Method (500) according to claim 12, said method further comprising during the energy production phase a step (524) of temporary interruption of the operation of the system (100).

14. A method (600) for storing electrical energy in thermal form implemented by means of an energy storage and energy production system (100) according to any one of claims 1 to 8, characterized in thatThe process first includes a step (610) of monitoring the electricity sales market and, if a Velec electricity sales price of said market is less than a previously defined threshold value Vmax, further includes a step (620) of storing electrical energy in thermal form, comprising the following steps of: - (621) preparing a so-called high-enthalpy fluid to achieve optimal thermodynamic temperature and pressure conditions for energy production; - (622) injecting the high-enthalpy fluid into a primary storage volume (12) of the system (100), by means of an injection conduit (11) and a circulation pump (16) of said system; - (623) recovering the high-enthalpy fluid circulating in the primary storage volume (12) of the system (100), by means of a recovery conduit (13) and the circulation pump (16);The step (620) of storing electrical energy in thermal form being carried out continuously or discontinuously during a storage period P during which the selling price of electricity Velec is less than the threshold value Vmax.; 15. Energy storage and energy production site characterized in that it includes a system (100) for energy storage and energy production according to any one of claims 1 to 8.

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