Subcritical cycle Carnot battery with cold storage
The Carnot battery with an intermediate circuit for subcritical cycles addresses efficiency and reactivity issues, enhancing power plant flexibility and economic viability by optimizing discharge and reducing infrastructure costs.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Applications
- Current Assignee / Owner
- COMMISSARIAT A LENERGIE ATOMIQUE ET AUX ENERGIES ALTERNATIVES
- Filing Date
- 2024-12-05
- Publication Date
- 2026-06-12
AI Technical Summary
Carnot batteries operating with subcritical cycles face challenges in efficiency, economic viability, and limited reactivity due to temperature rise times, especially in grafted and coupled architectures, which require high temperatures and pressures, limiting their widespread adoption and flexibility in thermal power plants.
A Carnot battery design incorporating an intermediate circuit for transferring cold thermal energy from a thermal storage module to the power cycle, utilizing a discharge heat exchanger for indirect discharge to the engine cycle, allowing for optimal discharge and expanded operating range, particularly in subcritical cycles.
Enhances controllability and flexibility of thermal power plants, improves storage efficiency, reduces infrastructure costs, and enables load following and frequency tracking, making it economically viable for widespread adoption.
Smart Images
Figure 00000000_0000_ABST
Abstract
Description
Title of the invention: Subcritical cycle Carnot battery with cold storage. Technical field
[0001] The present invention relates to Carnot batteries and more particularly those operating with a subcritical cycle.
[0002] It belongs to the technical fields corresponding on the one hand to electricity storage technologies and on the other hand to systems increasing the flexibility of thermal power plants.
[0003] Potential applications include electricity storage linked to a thermal power plant. Another related application is the addition of a Carnot battery to a thermal power plant. STATE OF THE ART
[0004] Carnot batteries (CBs) rely on storing electricity in the form of heat. When a CB stores electricity, it converts it into heat via a charging process and then stores the heat in a thermal storage module. This charging process can typically be an electrical resistance or a heat pump (HP), both of which are electricity-to-heat converters. When the battery is required to release the electricity it has previously stored, the energy stored in the thermal storage module is discharged using a motor cycle. This motor cycle is a converter symmetrical to the charging process, which, this time, converts heat into electricity. The motor cycle can typically be an organic or non-organic Rankine cycle (ORC) or a Brayton cycle. This type of CB is referred to as an isolated or "standalone" battery in the literature.
[0005] Carnot batteries offer several advantages: firstly, they provide a solution for large-scale electricity storage. Like all electricity storage technologies, Carnot batteries can also provide services to the grid, particularly in terms of stability and flexibility. Furthermore, they have few geographical constraints, as their installation requires neither a valley nor a cavern and does not generate any particular hazards in its immediate vicinity.
[0006] However, BCs suffer from several limitations to their development: this technology has relatively modest conversion efficiencies, on the order of 30% to 60% according to the literature for isolated BCs. Related to this modest efficiency, the economic viability of projects based on BCs is not always guaranteed. Finally, isolated BCs suffer from limited reactivity, inherent to the temperature rise time of the motor cycle and the adjacent pipes during the initiation of the discharge phase.
[0007] Battery cells can be integrated through different architectures into thermal power plants. Two concepts identified to date stand out: one is called coupled batteries (CCB) and the other called grafted batteries (GBC).
[0008] The concept of coupled Carnot batteries is based on an architecture comprising a thermal power plant coupled to a Carnot battery by the charging process and by the thermal storage component. Thus, a portion of the power plant's heat flux is no longer directly converted into electricity by the engine cycle, but temporarily stored without undergoing a temperature rise. The charging cycle is used either to compensate for some of the storage losses or to increase the amount of thermal energy stored, but always at a uniform temperature between the storage and the heat source temperature of the power plant.
[0009] The main advantage of this coupling is the increased flexibility it provides to the power plant. Indeed, the plant operates continuously and, like many thermal power plants, is not easily controllable. This lack of flexibility, given the high variability of electricity demand, can cause grid stability problems. Thus, a coupled storage power plant (SPP) allows, during periods of grid tension, for a portion of the electricity production to be curtailed by diverting some of the heat flow to be stored in the storage power plant (SPP). Then, when the grid again requires increased electricity production, the SPP can be discharged via its engine cycle, which is shared with the thermal power plant. Therefore, during the discharge phase, the power plant will operate at its nominal capacity, but additional heat from the SPP will be discharged in parallel within the engine cycle.This additional heat discharge from the CCB will result in a surplus of electricity production compared to the power plant's nominal operating capacity. Thus, a CCB coupled to a power plant provides it with increased flexibility, manifesting as a better match between electricity production and demand, through demand response followed by surplus electricity production. In the case of CCBs, power modulation is therefore achieved by regulating the flow rate of the heat flux sent to the engine cycle.
[0010] Another important characteristic of DCBs is that their operation is correlated with that of the thermal power plant. Indeed, for the sharing of the engine cycle between the DCB and the power plant to be realistic, the additional discharge power provided by the DCB must be small compared to the power plant's nominal output. Thus, the DCB cannot operate alone. For the BCC to be able to charge and discharge, the thermal power plant must be in operation.
[0011] The other advantages of implementing this coupling lie primarily in the sharing of the power cycle. Indeed, this sharing firstly allows for a significant reduction in the costs of a DCB compared to an isolated DCB. Secondly, this sharing also allows for a significant increase in the DCB's responsiveness. In fact, unlike isolated DCBs, where the power plant operates continuously, the power cycle is always running. Thus, since the power cycle is always at operating temperature and always running, the effects related to the inertia of starting the power cycle no longer penalize the DCB, and therefore allow for a significant gain in responsiveness. It can also be noted that DCBs, thanks to their improved responsiveness, allow for load and frequency tracking, in addition to the other classic services that storage technologies are capable of providing to the grid.
[0012] The operation and architecture of BCGs are similar to those of BCCs. Their differentiating characteristic lies in the method of utilizing the heat flow from the power plant. In the case of BCCs, the power plant's heat flow is directly integrated into the storage module, whereas for BCGs, it is utilized in the charging process.
[0013] Thus, the diverted heat from the power plant is utilized during the charging of the combined cycle heat exchanger (CCH) and is raised to a higher temperature than that of the power plant before being stored. During discharge, the heat at a higher enthalpy is used in the engine cycle and therefore increases the enthalpy of the power plant's nominal heat flow. During the discharge phase, since the engine cycle is powered by a higher enthalpy heat flow, the net output of the cycle is increased. Thus, when the grid is under load and it is necessary to store electricity, a charging phase of the CCH will be carried out, which consumes electricity. This charging phase will allow the storage of heat at a higher temperature, which will then be discharged when the grid again needs electricity, thereby increasing the net output of the power plant's engine cycle.Conversely, if the BCG has a cold storage, the temperature reached by the charging cycle will be lower than that of the cold source of the motor cycle.
[0014] Here again, the thermal power plant is in continuous operation. Thus, the major difference between BCCs and BCGs is that the production modulation of the thermal power plant is not based on a modulation of the flow rate through the engine cycle, as in the case of BCCs, but on a modulation of the temperature of the flow through the engine cycle for BCGs. This temperature-based, rather than flow-based, control strategy allows for a different constraint to be placed on the turbine, which could be interesting. Another important characteristic of BCGs is that they cannot operate independently of the power plant, as with BCCs.
[0015] The advantages of implementing a BCG are quite similar to those of a BCC. Indeed, for the same reasons as a BCC, a BCG has much better responsiveness than isolated batteries, thus enabling charge or frequency monitoring, for example. Cost reduction is also possible thanks to the sharing of the motor cycle. Finally, BCGs are capable of achieving better storage efficiencies than conventional BCs without resorting to additional external heat sources.
[0016] Patent document FR3060190B1 is also known, describing a BC architecture that increases the flexibility of a Brayton cycle. The BCG comprises a cold water storage tank supplied by a refrigeration machine. Discharge of this BCG is ensured by two heat exchangers connected directly to the working fluid circuit of the Brayton cycle.
[0017] These various solutions are well suited to operation under supercritical and transcritical cycles. However, this implies significant development and infrastructure costs to ensure that the components can be implemented in these demanding cycles, which require high temperatures and pressures.
[0018] Now, currently with the growing desire to optimize the recovery of waste heat from many industrial processes with temperatures less than or equal to 300°C, there is therefore a need to propose a solution to allow the operation of Carnot batteries and in particular Grafted Carnot Batteries (BCG) or Coupled Carnot Batteries (BCC) with subcritical cycles at low temperatures, i.e. less than or possibly equal to 300°C. SUMMARY
[0019] To achieve this objective, according to one embodiment, a Carnot battery is provided, comprising a power cycle for converting thermal energy into electricity, including an evaporator for heat exchange with a hot source, a turbine and a condenser for heat exchange with a cold source, a refrigeration machine for converting electrical energy into cold thermal energy, and a thermal energy storage module comprising a fluid for storing the cold thermal energy, characterized in that it includes an intermediate circuit for transferring the cold thermal energy from the fluid stored in the energy storage module to the power cycle; the intermediate circuit includes a discharge heat exchanger for transferring thermal energy transfer from the cold fluid to the cold source supplying the condenser of the engine cycle.
[0020] The Carnot battery according to the invention allows for the optimal discharge of stored cold in the case of subcritical cycles. Indeed, the presence of the intermediate circuit with the discharge exchanger, ensuring indirect discharge of the stored cold to the engine cycle, expands the operating range of Carnot batteries, particularly those grafted onto subcritical cycles. The Carnot battery according to the invention thus offers ease of implementation thanks to the technological maturity of the components for the low temperatures conducive to subcritical cycles. Furthermore, the infrastructure costs of grafted subcritical Carnot batteries are therefore lower, with significant potential for widespread adoption.
[0021] Storing electrical energy in the form of cold storage also reduces losses during the storage phase, thus improving the profitability of subcritical BCGs.
[0022] By introducing the intermediate circuit allowing discharge, it is possible not only to play on the degree of subcooling, but also to play on the low pressure of the engine cycle, which leads to much higher restitution ratios and suggests an economic reality for the system.
[0023] Indeed, the architectures adapted to transcritical and supercritical cycles known today in the literature do not allow a reduction in the low pressure of the engine cycle. However, in subcritical operation, the direct discharge of the BCG via a heat exchanger in series with the engine cycle evaporator leads only to an increase in subcooling.
[0024] However, an increase in subcooling does not generate any increase in turbine performance and therefore does not lead to an increase in electrical production for subcritical cycles.
[0025] The advantage of the present invention is therefore to overcome the problem of adding only subcooling to the fluid by the BCG.
[0026] The invention thus makes it possible to improve the controllability and flexibility of thermal power plants. The storage linked to the power plant provides increased stability for the grid, but also allows the operator to perform load following and frequency tracking, as well as energy arbitrage.
[0027] Following another aspect, the invention relates to a method for producing electrical energy by a Carnot battery as described above, comprising a cold thermal energy discharge stage including the removal of fluid from the thermal energy storage module, and heat exchange in the discharge heat exchanger between the fluid removed from the energy storage module thermal and a cold source to lower the temperature of the cold source, a heat exchange in the condenser of the engine cycle between the cooled cold source and an engine fluid circulating in the engine cycle allowing condensation of the engine fluid. BRIEF DESCRIPTION OF THE FIGURES
[0028] The aims, objects, features and advantages of the invention will become clearer from the detailed description of an embodiment thereof, which is illustrated by the following accompanying drawings in which:
[0029] [Fig. 1] Fig. 1 represents a schematic diagram of the Carnot battery according to the invention.
[0030] [Fig.2] Fig.2 represents a schematic diagram of the Carnot battery during of a stationary phase.
[0031] [Fig.3] Fig.3 represents a schematic diagram of the Carnot battery during of a charging phase.
[0032] [Fig.4] Fig.4 represents a schematic diagram of the Carnot battery during of a discharge phase.
[0033] [Fig.5] Fig.5 represents a schematic diagram of the Carnot battery according to a variant of [Fig.l].
[0034] The drawings are given by way of example and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate understanding of the invention and are not necessarily to scale with practical applications. DETAILED DESCRIPTION
[0035] Before proceeding to a detailed review of embodiments of the invention, optional features that may be used in combination or alternatively are listed below:
[0036] According to one example, the refrigeration machine 100 includes a condenser 102 supplied by the cold source 5, and arranged in series and upstream of the discharge heat exchanger 2.
[0037] According to one example, the motor cycle 200 includes a pump 205 arranged downstream of the condenser 204 and a recuperator 203 arranged on the motor cycle 200 to ensure heat exchange between a fluid connection linking the downstream of the turbine 201 to the upstream of the condenser 204 and a fluid connection linking the downstream of the pump 205 to the upstream of the evaporator 202.
[0038] According to one example, the cold thermal energy discharge stage includes a heat exchange in the evaporator 202 of the engine cycle 200 between a hot source 6 and the engine fluid to ensure its evaporation, and an expansion of the engine fluid. originating from the evaporator 202 in the turbine 201 of the engine cycle enabling the production of electricity by an associated generator 206.
[0039] According to one example, the electrical energy production process comprising a charging stage includes a heat exchange in the evaporator 202 of the motor cycle 200 between the hot source 6 and the motor fluid to ensure its evaporation, an expansion of the motor fluid from the evaporator 202 in the turbine 201 of the motor cycle 200 enabling the production of electricity by an associated generator 206, a heat exchange in the condenser 204 of the motor cycle 200 between the cold source 5 and the motor fluid to ensure its condensation, a production of cold thermal energy by the refrigeration machine 100 and a storage of the cold thermal energy in the thermal energy storage module 3.
[0040] According to one example, the production of cold thermal energy by the refrigeration machine 100 includes the circulation of the cold source in the condenser 102 of the refrigeration machine 100 to ensure a cooling heat transfer of a refrigerant fluid circulating in the refrigeration machine.
[0041] According to one example, the process for producing electrical energy includes a stationary operating stage comprising a heat exchange in the evaporator 202 of the motor cycle 200 between the hot source 6 and the motor fluid to ensure its evaporation, an expansion of the motor fluid from the evaporator 202 in the turbine 201 of the motor cycle 200 allowing the production of electricity by an associated generator 206, a heat exchange in the condenser 204 of the motor cycle 200 between the cold source 5 and the motor fluid to ensure its condensation.
[0042] The upstream and downstream, the inlet, the outlet, at a given point are taken in reference to the direction of fluid flow.
[0043] A parameter "approximately equal to / greater than / less than" or "of the order of" a given value means that this parameter is equal to / greater than / less than the given value, to within 10% or even 5% of that value.
[0044] For the purposes of this disclosure, the expression "A and / or B" means (A), (B) or (A and B). For the purposes of this disclosure, the expression "A, B and / or C" means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B and C).
[0045] By supercritical, it is understood that the Carnot battery according to the invention operates at pressure and temperature levels above the critical point of the circulating working fluid.
[0046] Transcritical means that the Carnot battery according to the invention operates at pressure and temperature levels above and below the critical point of the circulating working fluid.
[0047] By subcritical, it is understood that the Carnot battery according to the invention operates at pressure and temperature levels below the critical point of the circulating working fluid.
[0048] Fluidically connected or in fluidic connection means when a line provides a connection by or in which a fluid flows.
[0049] In this description, the expression "A fluidly connected to B" is synonymous with "A is in fluidic connection with B" and does not necessarily mean that there is no component between A and B. The expressions "arranged on" or "on" are synonymous with "fluidly connected to".
[0050] The expression "A fluidically connected to B" or "A fluidly connected to B" is synonymous with "A is in fluidic connection with B" and does not necessarily mean that there is no component between A and B. Thus, these expressions refer to a fluidic connection between two elements, this connection being either direct or indirect. This means that it is possible that between a first element and a second element that are fluidically connected, a fluid path exists through one or more conduits or connections, possibly including an additional component.
[0051] Conversely, the term "fluidically connected directly" refers to a direct fluidic connection between two elements. This means that between a first element and a second element that are fluidly connected directly, no other element is present, other than a conduit / connection / channel or several conduits / connections / channels.
[0052] Hot, cold, cooled means a relative temperature with respect to another point in the system.
[0053] The terms "first", "second" and "third", "additional" etc. are used simply as labels, and are not intended to impose numerical requirements on their objects.
[0054] The invention relates to a Carnot battery grafted onto a thermal power plant, based on an engine cycle advantageously operating in subcritical mode. The invention can also be used with an engine cycle operating in transcritical mode.
[0055] The Carnot battery according to the invention comprises a thermal power plant for generating electricity intended to convert thermal energy into electricity. In this application, the terms power plant, generating plant, and thermal power plant are used interchangeably to define the thermal power plant for generating electricity.
[0056] The thermal power plant can be of different types. The thermal power plant comprises a heat source 6 which can be of various kinds, for example, from geothermal energy, biomass, fossil fuels, solar energy, nuclear energy, etc. waste heat. The thermal power plant includes a 200-cycle engine that transforms the heat source 6 into electrical energy. For example, the heat source 6 has a temperature between 80 and 800°C.
[0057] The Carnot battery thus comprises a drive cycle 200 for converting thermal energy from a hot source 6 into electricity. The drive cycle 200 comprises at least one evaporator 202, one turbine 201 and one condenser 204.
[0058] The motor cycle 200 is for example a Brayton cycle or a Rankine cycle or an organic Rankine cycle.
[0059] The engine cycle 200 includes a fluidic circuit receiving an engine fluid and intended to connect the various components of the engine cycle 200 in fluidic connection.
[0060] The evaporator 202 is configured to ensure heat exchange between the engine cycle 200 and the hot source 6. The function of the evaporator 202 is to ensure the evaporation of the engine fluid through the supply of hot thermal energy by the hot source 6.
[0061] The turbine 201 of the engine cycle is configured to ensure the expansion of the engine fluid to drive the turbine 201. Advantageously, the turbine 201 is associated with a generator 206. The generator 206 is set in motion by the turbine 201 during the expansion of the engine fluid and thus ensures the production of electricity.
[0062] By way of example, turbine 201 is an axial turbomachine. The present invention remains functional for any type of expansion turbine, whether axial, centripetal or hybrid, a positive displacement machine of the scroll type, piston, screw, etc.
[0063] The condenser 204 of the engine cycle is configured to ensure heat exchange between the engine cycle and a cold source 5. The condenser 204 has the function of ensuring the condensation of the engine fluid through cooling achieved by the supply of cold thermal energy from the cold source 5.
[0064] Advantageously, the motor cycle includes a pump 205 intended to move the motor fluid in the fluidic circuit of the motor cycle.
[0065] According to an advantageous embodiment, the engine cycle 200 includes a first heat exchanger 203 arranged between the outlet of the turbine 201 and the outlet of the pump 205. The first heat exchanger 203 is intended to ensure heat exchange between the engine fluid at the outlet of the turbine 201 and the engine fluid at the outlet of the pump 205. The engine fluid at the outlet of the turbine 201 transfers thermal energy to the engine fluid at the outlet of the pump 205, allowing preheating of the engine fluid before its entry into the evaporator 202 and cooling of the engine fluid before its entry into the condenser 204.
[0066] According to a preferred possibility, the fluidic circuit of the motor cycle 200 ensures the successive fluidic connection of the evaporator 202 connected fluidly, preferably directly, to the turbine 201, then the turbine 201 is connected fluidly to the condenser 204, preferably via the first recuperator 203, then the condenser 204 is connected fluidly, preferably directly, to the pump 205, then the pump 205 is connected fluidly to the evaporator 202, preferably via the first recuperator of 203.
[0067] According to the illustrated embodiment, the engine cycle 200 is an organic Rankine cycle. As such, the engine fluid circulating in the engine cycle 200 is an organic fluid such as Novec649.
[0068] According to the invention, the Carnot battery includes a refrigeration machine 100 intended to convert electrical energy into cold thermal energy.
[0069] By way of example, the refrigeration machine 100 includes a refrigeration circuit designed to receive a refrigerant fluid and ensuring the fluidic connection of the components of the refrigeration machine. The refrigeration machine 100 includes a compressor 101, an evaporator 104, an expansion valve 103 and a condenser 102. The compressor 101 is fluidly connected, preferably directly, to the condenser 102, then the condenser 102 is fluidly connected, preferably directly, to the expansion valve 103, then the expansion valve 103 is fluidly connected, preferably directly, to the evaporator 104, and finally the evaporator 104 to the compressor 101.
[0070] The condenser 102 is intended to ensure a heat exchange between a cold source 5, 105 and the refrigerant fluid so as to condense the refrigerant fluid.
[0071] The cold source 5,105 is, for example, water from a water network, water from a river, etc. Preferably, the temperature of the cold source is between -50°C and 50°C.
[0072] According to a first possibility, the condenser 102 of the refrigeration machine 100 is supplied by a cold source 105 different from the cold source 5 supplying the condenser 204 of the motor cycle 200. The cold source 105 is, for example, ambient air.
[0073] According to another possibility, the condenser 102 of the refrigeration machine 100 is supplied by the cold source 5 supplying the condenser 204 of the motor cycle 200. According to this possibility, the cold source 5 successively supplies, according to the flow of the cold source 5, the condenser 102 of the refrigeration machine, then the discharge heat exchanger 2 of the intermediate circuit 1, then the condenser 204 of the motor cycle 200.
[0074] The refrigeration machine 100 is a thermodynamic machine that is more efficient the smaller the temperature difference between its cold and hot sources. Thus, rather than the condenser 102 of the refrigeration machine 100 using the ambient temperature, connecting it to the heat flow of the cold source 5 of the engine cycle 200, which is at a lower temperature than the ambient temperature, optimizes the operation of the refrigeration machine 100. The refrigeration machine 100 releases heat to the cold source 5, which supplies the condenser 204 of the engine cycle 200. This operation, which consumes electricity, does not reduce electricity production during the BCG load, provided that the cold source 5 has a sufficient flow rate.
[0075] Preferably, the cold source 5 is an infinite flow source allowing the storage module load to be decoupled from the operation of the engine cycle 200, considering that the condenser 204 is supplied by a cold source at a constant temperature independent of the load
[0076] According to the invention, the Carnot battery comprises a thermal storage module 3 including a fluid for storing cold thermal energy, advantageously produced by the refrigeration machine. The thermal storage module 3 is, for example, a fluid reservoir, advantageously thermally insulated from the environment.
[0077] As a preferred example, the fluid is glycol water. As an example, the fluid stored in the thermal storage module is at a temperature between -50 and 50°C.
[0078] The evaporator 104 of the refrigeration machine 100 is intended to ensure a heat exchange between the refrigerant fluid of the refrigeration machine 100 and the fluid of the thermal storage module 3 so as to ensure the evaporation of the refrigerant fluid and to cool the fluid of the thermal storage module 3.
[0079] By way of example, the refrigeration machine 100 operates according to a subcritical cycle. The cycle of the refrigeration machine 100 can also be transcritical or supercritical depending on the heat transfer fluid considered and the desired temperature levels. By way of example, the refrigerant is an organic fluid such as R 134a.
[0080] According to the invention, the Carnot battery includes an intermediate circuit 1 ensuring the heat transfer of cold thermal energy from the fluid stored in the energy storage module 3 to the engine cycle 200. The intermediate circuit 1, called the intermediate discharge circuit, includes a discharge heat exchanger 2 ensuring the heat transfer between the fluid and a cold source 5 supplying the condenser 204 of the engine cycle 200.
[0081] Preferably, the intermediate circuit 1 includes a pump 4 for circulating the fluid between the storage module 3 and the discharge heat exchanger 2.
[0082] The architecture of the Carnot battery according to the invention makes it possible to optimize the discharge phase. Indeed, after having been previously charged via the refrigeration machine 100, the storage module 3 is discharged via the intermediate circuit 1 on the circuit of the cold source 5.
[0083] Indeed, the presence of intermediate circuit 1 ensures optimal discharge of the Carnot battery, particularly for subcritical cycles.
[0084] According to one aspect, the Carnot battery comprises a control module including a plurality of valves for controlling the circulation of the working fluid in the fluid circuits and a plurality of sensors for measuring predefined parameters on the fluid circuits. The operation of the Carnot battery includes measuring predefined parameters on the fluid circuits using sensors, comparing the measurements with predefined values, and activating the different operating phases of the battery.
[0085] The architecture of a Carnot battery according to an example of the invention as illustrated in [Fig.1] is detailed below.
[0086] At the engine cycle 200, the hot source 6 is fluidically connected to the evaporator 202 of the engine cycle 200. The hot source 6 is fluidly connected, preferably directly, to the inlet of the hot source of the evaporator 202 by a fluid connection F. An outlet of the hot source of the evaporator 202 is fluidly connected to the outlet of the hot source 6 by a fluid connection G. Advantageously, the pump 11 is arranged on the fluid connection G.
[0087] At the engine cycle 200, the evaporator 202 includes an inlet and an outlet of the engine fluid. The engine fluid outlet of the evaporator 202 is fluidically connected, preferably directly, to the inlet of the turbine 201 by a fluid connection H. The engine fluid inlet of the evaporator 202 is fluidly connected to a second outlet of the recuperator 203, if present, by the fluid connection L, otherwise to the pump 5, otherwise to the condenser 204.
[0088] The turbine 201 includes an inlet and an outlet of motive fluid. The outlet of motive fluid of the turbine 201 is fluidically connected to the inlet of the condenser 204, preferably the outlet of the turbine 201 is fluidically connected directly to a first inlet of the recuperator 203 by the fluidic connection I, a first outlet of the recuperator 203 being fluidically connected directly to the inlet of motive fluid of the condenser 204 by the fluidic connection J.
[0089] The condenser 204 includes an inlet and an outlet for the motive fluid. The motive fluid outlet of the condenser 204 is fluidically connected to a second inlet of the recuperator 203 by the fluid connection K. Advantageously, the pump 205 is arranged on the fluid connection K, advantageously downstream of the condenser 204 and upstream of the recuperator 203, if it is present, or otherwise upstream of the evaporator 202.
[0090] The condenser 204 includes a cold source inlet 5 fluidically connected to the cold source inlet in the Carnot battery.
[0091] At the intermediate circuit 1, the discharge heat exchanger 2 includes a cold source inlet and outlet 5, the cold source inlet of the discharge exchanger 2 is connected to the fluidic connection C allowing the arrival of the cold source in the Carnot battery, the cold source outlet of the discharge exchanger 2 is fluidically connected to the cold source inlet of the condenser 204 by the fluidic connection D, preferably directly.
[0092] The condenser 204 includes a cold source outlet fluidly connected to the cold source outlet out of the Carnot battery by the fluidic connection E.
[0093] The storage module 3 includes a stored fluid outlet fluidically connected to the fluid inlet of the discharge heat exchanger 2 by the fluidic connection A. Advantageously, a pump 4 is arranged on the fluidic connection A. The discharge heat exchanger 2 includes a fluid outlet fluidly connected to the inlet of the storage module 3 by the fluidic connection B.
[0094] The Carnot battery according to the invention operates in 3 phases, including a stationary phase corresponding to the operation of transforming thermal energy into electrical energy, a charging phase corresponding to the operation of storing thermal energy and a discharging phase corresponding to the operation of releasing thermal energy.
[0095] In stationary phase, the Carnot battery according to the invention operates as illustrated in [Fig.2] detailed below.
[0096] The hot source 6, the motor cycle 100, and the cold source supply to the condenser 204 are active in the steady-state phase. Active means that fluid circulation is occurring. In the steady-state phase, the refrigeration machine 100 and the intermediate circuit 1, which provides heat exchange between the storage module 3 and the motor cycle 200, are not active; that is, there is no fluid circulation.
[0097] The stationary phase will be described below from an operational point of view.
[0098] The hot source 6 supplies the evaporator 202 of the engine cycle 200.
[0099] The hot source 6 enters the evaporator 202 at a higher temperature at its temperature at the outlet of evaporator 202. The hot source 6 transfers its thermal energy to the engine cycle 200 through the evaporator 202. The engine cycle 200 enables the production of electrical energy by its associated turbine 201 to generator 206. Condenser 204 is supplied by the cold source 5 from the environment, which is neither supplied nor cooled by the storage module. Refrigeration unit 100 is not operating; there is no cold production or cold storage in storage module 3. There is no cold release from the storage module. The stationary phase is an operating mode corresponding to a simple energy conversion.
[0100] The charging phase of the Carnot battery is intended for the conversion of electricity from a cold source 5 via the refrigeration machine 100.
[0101] During the charging phase, the Carnot battery according to the invention is illustrated in [Fig.3] detailed below.
[0102] The hot source 6, the motor cycle 200, the refrigeration machine 100, and the cold source supply to the condenser 204 are active during the charging phase. Active means that fluid circulation is occurring. The intermediate circuit 1, which provides heat exchange between the storage module 3 and the motor cycle 200, is not active; that is, there is no fluid circulation.
[0103] During the charging phase, the operation of the Carnot battery according to the invention is identical to its operation during the stationary phase, with the addition of the operation of the refrigeration machine 100, which allows the storage of electrical energy in the form of cold thermal energy. This charging phase is implemented when there is a surplus of electrical energy relative to the demand on the grid. The Carnot battery according to the invention thus allows the storage of surplus electrical energy in the form of cold thermal energy.
[0104] The discharge phase of the Carnot battery is intended for the transmission of the previously stored cold to the engine cycle.
[0105] In discharge phase, the Carnot battery according to the invention is illustrated in [Fig.4] detailed below.
[0106] The hot source 6, the motor cycle 200, the intermediate circuit 1, and the cold source supply to the condenser 204 are active during the discharge phase. Active means that fluid circulation is occurring. The refrigeration machine 100 is not active; that is, there is no fluid circulation.
[0107] In discharge phase, the operation of the Carnot battery according to the invention is identical to the operation in stationary phase with the addition of the operation of the intermediate circuit 1 which allows the release of the cold thermal energy stored in the storage module 3 to the motor cycle 200.
[0108] The fluid stored in the storage module 3 is discharged to the heat exchanger 2, which transfers the thermal energy of the stored fluid to the cold source 5, which then supplies the condenser 204 of the engine cycle. 200. The fluid returns to storage module 3 at a higher temperature than when it left.
[0109] Thus, the discharge exchanger 2, via sensible heat transfer only, lowers the temperature of the cold source 5 of the engine cycle 200. The cold source 5 therefore enters the condenser 204 of the engine cycle at a lower temperature than during the stationary, also called nominal, operation of the Carnot battery. The temperature of the cold source 5 entering the condenser 204 results from the supply of cooling from the storage module 3 at the nominal heat flux of the cold source 5. Thus, since the profile of the cold source 5 at the condenser 204 is lower, this allows for a lower condensing pressure of the engine fluid than during the nominal operation of the Carnot battery. This reduction in low pressure resulting from the discharge of the storage module 3 is advantageous because the better the pressure ratio between the upstream and downstream sides of the turbine 201, the better its performance.Thus, the lowering of the low pressure due to the discharge of the storage module 3 allows a notable increase in the electrical production of the motor cycle 200, which is therefore sought in the context of the operation of a Carnot battery according to the invention. Examples
[0110] A Carnot battery according to the invention was simulated using EES (Engineering Equations Solver) software.
[0111] Regarding the hot source 6, its nature, flow rate, and temperature can be arbitrary; however, typical temperature and power assumptions have been adopted. Thus, the hot source 6 of the power plant has been modeled as a heat source 6 at a constant temperature of 130°C, delivering a maximum power of 80 kW, also constant over time. The profile of this hot source 6 is left as a degree of freedom. The cold source 5 is considered to have a constant temperature of 13°C, but with infinite power and flow rate. The profile of this source 5 is also a degree of freedom. The assumption of infinite power and flow rate models a Carnot battery whose cold source 5 would be provided by a stream or reservoir with a limited and constant temperature, but with an available flow rate of a much greater order of magnitude than the power plant's requirements.
[0112] The component efficiencies were assumed to be constant and are taken from the literature. The adopted efficiency values are given below: Isentropic turbine 201: 0.75; Generator 206: 0.95; Pumps 4, 205, 11: 0.5; Isentropic compressor 101: 0.9
[0113] Losses during storage were neglected and a constant pinch was adopted for the various exchangers of the BCG.
[0114] Data on the performance of the Carnot battery according to the invention are given below:
[0115] Grafting degree: 10%
[0116] Charge / discharge ratio: 100%
[0117] Motor cycle efficiency during the stationary phase: 9.8%
[0118] Motor cycle efficiency during the charging phase: 9.8%
[0119] Motor cycle efficiency during the discharge phase: 10.7%
[0120] BCG Return Report: 76.8%
[0121] The degree of integration is an indicator used to obtain information about the battery size. The battery size is considered here in relation to the services it can provide to the grid in terms of power modulation of the thermal power plant's output. Here, the simulated Carnot battery has a degree of integration of approximately 10%, meaning that it will be able to modulate the engine cycle power, during discharge, by 10% of the nominal output. The simulated Carnot battery here is therefore of sufficient size to provide services to the grid.
[0122] The charge / discharge ratio is set to 100%, meaning that the charge phase is of the same duration as the discharge phase.
[0123] The Carnot battery restitution ratio here is 76.8%, which means that 76.8% of the electricity that was consumed during charging (i.e. stored in the Carnot battery) was returned during the discharge of the Carnot battery.
[0124] The invention is not limited to the embodiments previously described and extends to all embodiments covered by the invention.
[0125] List of references 1. Intermediate circuit 2. Discharge exchanger 3. Storage Module 4. Discharge pump 5. Cold source 6. Hot spring 11. Hot spring pump 100. Refrigeration machine 101. Compressor 102. Condenser 103. Pressure relief valve 104. Evaporator 105. Cold source of the refrigeration machine 200. Engine cycle 201. Turbine 202. Evaporator 203. Recovery 204. Condenser 205. Pump 206. Generator A. Fluidic connection between the outlet of the cold storage module and the inlet of the discharge exchanger of the intermediate circuit B. Fluidic connection between the outlet of the intermediate circuit discharge exchanger and the inlet of the cold storage module C. line of supply from a first cold source of the engine cycle feeding the discharge exchanger of the intermediate circuit D. Fluidic connection between the discharge exchanger and the engine cycle condenser E. Return line from the cold source of the motor cycle out of the condenser F. Fluidic connection between the hot source and the evaporator of the engine cycle G. Fluidic connection between the engine cycle evaporator and the hot source H. Fluidic connection between the engine cycle evaporator and the turbine I. Fluidic connection between the turbine and the engine cycle recuperator J. Fluidic connection between the engine cycle recuperator and the engine cycle condenser K. Fluidic connection between the engine cycle condenser and the engine cycle recuperator L. Fluidic connection between the engine cycle recuperator and the engine cycle evaporator
Claims
Demands
1. Carnot battery comprising a power cycle (200) for converting thermal energy into electricity, including an evaporator (202) providing heat exchange with a hot source (6), a turbine (201) and a condenser (204) providing heat exchange with a cold source (5), a refrigeration machine (100) for converting electrical energy into cold thermal energy, and a thermal energy storage module (3) comprising a fluid for storing cold thermal energy, characterized in that it comprises an intermediate circuit (1) providing heat transfer of cold thermal energy from the fluid stored in the energy storage module (3) to the power cycle (200), the intermediate circuit (1) comprising a discharge heat exchanger (2) providing heat transfer of cold thermal energy from the fluid to the cold source (5) supplying the condenser (204) of the power cycle (200).
2. Carnot battery according to the preceding claim in which the refrigeration machine (100) comprises a condenser (102) supplied by the cold source (5), and arranged in series and upstream of the discharge heat exchanger (2).
3. Carnot battery according to any one of the preceding claims wherein the engine cycle (200) comprises a pump (205) arranged downstream of the condenser (204) and a recuperator (203) arranged on the engine cycle (200) to ensure heat exchange between a fluid connection linking the downstream of the turbine (201) to the upstream of the condenser (204) and a fluid connection linking the downstream of the pump (205) to the upstream of the evaporator (202).
4. A method for producing electrical energy by a Carnot battery according to any one of the preceding claims, comprising a cold thermal energy discharge stage including, a removal of the fluid from the thermal energy storage module (3), a heat exchange in the discharge heat exchanger (2) between the fluid removed from the thermal energy storage module (3) and a cold source (5) to lower the temperature of the cold source (5), a heat exchange in the condenser (204) of the engine cycle (200) between the cooled cold source (5) and an engine fluid circulating in the engine cycle (200) allowing condensation of the engine fluid.
5. Method of producing electrical energy according to the preceding claim wherein the cold thermal energy discharge step includes a heat exchange in the evaporator (202) of the engine cycle (200) between the heat source (6) and an engine fluid circulating in the engine cycle (200) to ensure the evaporation of the engine fluid, an expansion of the engine fluid from the evaporator (202) in the turbine (201) of the engine cycle enabling the production of electricity by an associated generator (206).
6. A method for producing electrical energy according to any one of the two preceding claims comprising a charging stage including heat exchange in the evaporator (202) of the engine cycle (200) between the hot source (6) and the engine fluid to ensure evaporation of the engine fluid, expansion of the engine fluid from the evaporator (202) in the turbine (201) of the engine cycle (200) enabling the production of electricity by an associated generator (206), heat exchange in the condenser (204) of the engine cycle (200) between the cold source (5) and the engine fluid to ensure condensation of the engine fluid, production of cold thermal energy by the refrigeration machine (100) and storage of the cold thermal energy in the thermal energy storage module (3).
7. Method of producing electrical energy according to the preceding claim wherein the production of cold thermal energy by the refrigeration machine (100) comprises the circulation of the cold source in the condenser (102) of the refrigeration machine (100).
8. A method for producing electrical energy according to any one of the four preceding claims, comprising a stationary operating stage comprising a heat exchange in the evaporator (202) of the engine cycle (200) between the hot source (6) and the engine fluid to ensure the evaporation of the engine fluid, an expansion of the working fluid from the evaporator (202) in the turbine (201) of the engine cycle (200) enabling the production of electricity by an associated generator (206), a heat exchange in the condenser (204) of the engine cycle (200) between the cold source (5) and the engine fluid to ensure the condensation of the engine fluid.