METHOD FOR OPERATING A STORAGE SYSTEM, STORAGE SYSTEM, CONTROL PROGRAM AND COMPUTER-READABLE MEDIUM

Description

[0001] The invention relates to a method for operating a storage system for storing electrical energy by converting it into thermal energy, in which, in a loading process via a loading side by means of a loading arrangement, a high-temperature storage device is loaded by storing energy, in particular fed-in electrical energy, in the form of thermal energy, and in a discharging process by means of a Rankine process via a discharging side, the high-temperature storage device is discharged by means of a Rankine process by means of a discharging side, the thermal energy being withdrawn from the high-temperature storage device and converted into electrical energy.

[0002] The increasing share of renewable energies, such as electricity from photovoltaic or wind power plants, requires a significant expansion of electrical storage capacity. Large-scale storage power plants and the upgrading of coal-fired power plants to thermal storage power plants are key solutions for the increasing demands for grid stability and flexibility, and state-of-the-art technology is dedicated to their development.

[0003] A method of the above-mentioned type and a storage power plant are described in EP 2 759 679 A1. This describes a thermal storage device for utilizing low-temperature heat, comprising a first heat pump and a circuit 30 configured as a Rankine cycle. A second heat pump 40 can be thermally connected upstream of the first heat pump 10.

[0004] EP 3 054 155 A1 shows a high-temperature heat storage system which is thermally coupled on both a loading side and a discharging side and serves to generate steam in a discharging process.

[0005] EP 2 101 051 A1 describes a power plant for utilizing excess capacity from a power grid, where electrical energy is stored directly in a heat storage system via a heating element. A Rankine cycle is used to discharge and reconvert the heat into electricity.

[0006] EP 2 653 668 A1 shows a method and a system for storing and releasing thermal energy based on a Rankine process which forms the basis of the discharge cycle.

[0007] WO 2021 / 026 863 A2 describes a method and a system in which a heat storage device is charged in a charging cycle designed as a heat pump process and discharged in a discharging process designed as a Rankine cycle.

[0008] WO 2015 / 131 940 A1 describes a high-temperature energy storage system with a first circuit configured as a heat pump and a fourth circuit configured as a steam power cycle. The second and third circuits are thermal coupling circuits between the first and fourth circuits, respectively, and a thermal energy storage device. A low-temperature heat source can be coupled into the first circuit and / or the fourth circuit.

[0009] EP 2 942 492 A1 discloses an electrical storage and discharge system for storing electrical energy as thermal energy. The system includes a heat pump cycle and a water-steam cycle.

[0010] WO 2017 / 065 683 A1 shows a method and a system for storing and generating electrical energy by means of heat, wherein a heat pump and at least one Rankine cycle, but no second heat pump, are present.

[0011] A key challenge to ensure competitiveness is improving the energy and cost efficiency of such storage power plants.

[0012] The present invention is based on the object of providing a method with which the overall efficiency (current-to-current efficiency) of a storage system of the type mentioned at the outset can be increased, as well as a storage system with increased overall efficiency, a corresponding control program and computer-readable medium with the control program.

[0013] The problem is solved for the method with the features of claim 1, for the storage system with the features of claim 7, for the control program with the features of claim 15 and for the computer-readable medium with the features of claim 16.

[0014] The method provides that an energy conversion arrangement present in the storage system in addition to the loading arrangement is designed as a second Joule arrangement (for carrying out a clockwise and / or counterclockwise Joule cycle), with a low-pressure side and a high-pressure side and compressor / turbine arrangements arranged therebetween - for compressing or expanding the working medium to the respective pressure level, during the loading process and / or during the discharging process of the storage system in a heat pump process (as a counterclockwise Joule cycle) and / or in a thermal power process (as a clockwise Joule cycle).

[0015] An exemplary second Joule arrangement, which is suitable for coupling under an adapted design, is specified in DE 10 2020 110 560.6, which was still unpublished at the priority date and filed with the German Patent and Trademark Office on April 17, 2020, where it can be seen as an independent thermopotential storage system, without coupling into a surrounding storage system.

[0016] The discharge process can, for example, involve a supercritical process found in modern coal-fired power plants, a conventional process involving evaporation and reheating of steam or organic working fluids, with the steam generation system designed accordingly. The water-steam process is based, in particular, on the Clausius-Rankine cycle (CRC) as a reference process. Other / further steam processes are based, in particular, on the Organic Rankine cycle (ORC).

[0017] The Rankine cycle comprises a steam turbine arrangement, a condensing arrangement, conveying devices (feedwater pumps) and a steam generation device.

[0018] A highly advantageous increase in efficiency can be achieved according to the invention by conducting the charging process via a heat pump process within the charging arrangement, wherein the charging arrangement is designed as a first Joule arrangement comprising a low-pressure side and a high-pressure side, with an intermediate compressor arrangement and turbine arrangement. Thus, the charging side is designed as a Joule arrangement. In this way, in a type of hybrid storage system, the high-temperature heat required for steam generation to charge the high-temperature storage device is generated via an efficient heat pump process using the first Joule arrangement, while the discharging process utilizes the high power density of the Rankine cycle.

[0019] Preferably, the loading side, in particular the first Joule arrangement, also has at least one low-temperature storage device on the low-pressure side for storing low-temperature heat, i.e., "cold," generated by the first Joule arrangement, which is thermally coupled to the discharge side, in particular to the condensation arrangement. This cold can advantageously be coupled into the discharge process, i.e., the Rankine cycle, for condensing the Rankine working fluid. This eliminates the generally required cooling environment for the Rankine cycle, which in the prior art is formed, for example, by recooling systems, which are often connected to bodies of water, with a corresponding location dependency. The presence of the first Joule arrangement with the low-temperature storage device, however, achieves advantageous location independence.This can be particularly advantageous in arid regions when combined with solar power generation, where cooling options are often scarce. Furthermore, decoupling the cooling temperature from ambient conditions creates an additional degree of freedom, allowing the cooling temperature level to be designed for low temperatures (e.g., below 0 °C, e.g., down to -100 °C). This also increases the theoretical efficiency (Carnot efficiency) of the storage system.

[0020] Particularly preferably, the second Joule arrangement is operated as a storage arrangement, wherein a high-pressure-side high-temperature storage device of the second Joule arrangement is charged in a second charging process using the heat pump process and discharged in a second discharging process using the thermal power process. Preferably, the second Joule arrangement also has a low-temperature storage device on the low-pressure side, in which the generated low-temperature heat is stored. Due to the one or two dedicated storage devices, the second Joule arrangement can be operated independently of the charging process via the first Joule arrangement and / or the discharging process via the Rankine cycle, apart from an energetic coupling between the charging side and / or the discharging side.This allows for an optimized design of the operation of the second Joule arrangement with regard to energy coupling to increase the overall efficiency of the storage system.

[0021] According to the invention, the overall efficiency is increased by transferring thermal energy between the second Joule arrangement and the discharge side during the second discharge process and / or the second charging process of the second Joule arrangement and the discharge process via the discharge side. Preferably, thermal energy can also be transferred between the second Joule arrangement and the charging side during the second discharge process and / or the second charging process of the second Joule arrangement and the charging process via the charging side.

[0022] An advantageous variant of the energy transfer consists in that during the discharge process via the discharge side, heat which arises during the operation of the second Joule arrangement, in particular during the second discharge process, is at least temporarily coupled into the Rankine cycle upstream of a steam generating device for preheating the working fluid, e.g. for high-pressure preheating, in which a higher pressure exists than in the low-pressure preheating, and / or for low-pressure preheating, in which a lower pressure exists than in the high-pressure preheating.

[0023] Advantageously, the heat from the second Joule arrangement can be extracted on the low-pressure side downstream of the compressor / turbine arrangement, in particular upstream of a low-temperature heat storage unit via a low-pressure side heat exchanger, and fed into the high-pressure preheating of the Rankine working fluid. For this purpose, the second Joule arrangement is preferably operated during the discharge process of the storage system in the second discharge process (Joule or Brayton process as a thermal power process).

[0024] Alternatively or additionally, the heat can be extracted on the high-pressure side downstream of the high-temperature storage device, upstream of the compressor / turbine arrangement, and coupled into a condenser arrangement for low-pressure preheating of the Rankine working fluid. For this purpose, the second Joule arrangement is preferably located in the second discharge process during the discharge process (Joule or Brayton cycle as a thermal power process). The coupling of heat from the second Joule arrangement into the Rankine process eliminates the need for the tapping of working fluid from the steam turbine arrangement for high-pressure preheating, which is common in the prior art. This allows the power density within the Rankine cycle to be increased along with the overall efficiency of the storage device.

[0025] Advantageously, during the discharge process, cold from a low-pressure side low-temperature storage device of the second Joule arrangement for cooling and / or condensing the working fluid can be coupled into the Rankine process downstream of a steam turbine arrangement via the discharge side, at least temporarily, wherein, for example, the cold is transferred indirectly via at least one low-pressure side low-temperature storage device of the loading side.

[0026] In a particularly advantageous embodiment of the process, a larger pressure ratio between the high-pressure and low-pressure sides is specified in the second Joule arrangement in the heat pump process than in the thermal power process. This so-called "asymmetric" pressure control results in a shift in the heat loss within the process control of the second Joule arrangement, which can be designed so that the heat loss is more advantageously utilized for the overall process, as shown below. The initial design is based on the thermodynamic equations of state of the corresponding processes.

[0027] In particular, the pressure ratio can be different in such a way that the overall efficiency of the storage system is increased compared to a process with the same pressure ratios. The efficiency of the second Joule arrangement can tend to be reduced. The asymmetry in the pressure ratios can, for example, be adjusted such that the heat loss is adapted to the heat demand for high-pressure preheating and can cover this at least partially or entirely. Additionally or alternatively, the design can, for example, aim to minimize heat loss on the high-pressure side.

[0028] For example, the pressure ratio can be different in such a way that heat loss occurring between the heat pump process and the thermal power process is matched to the need for high-pressure preheating of the Rankine working fluid and is extracted, for example, via the low-pressure side heat exchange device and / or that heat loss is minimized via a high-pressure side heat exchange device and / or that the heat loss via the high-pressure side heat exchange device is / are matched to the need for low-pressure preheating of the Rankine working fluid.

[0029] Advantageously, electrical energy can be extracted from the second Joule array during the thermal power process. This energy can be used to meet the storage system's own needs (e.g., for fans, pumps, lighting, etc.) or fed into the power grid for further use.

[0030] In a preferred embodiment, a gaseous working medium, e.g. air, argon, carbon dioxide or nitrogen, is used during the loading process and / or during the second loading process and second unloading process, i.e. within the first and / or second Joule arrangement. For this purpose, the high-temperature storage device and / or a low-temperature storage device is / are designed to transfer heat to the gaseous working medium and / or is / are integrated on the loading side so that the working medium of the heat pump process can flow through it. In order to cover the heat requirement for steam generation and superheating of the Rankine working fluid vapor, the mass flow rate of the first Joule arrangement and / or the second Joule arrangement is preferably a multiple of the mass flow rate of the working fluid (e.g. water / steam in the case of the CRC process) within the Rankine process. The factor can, for example,between 2 and 10, depending on the process design and boundary conditions such as the amount of additional heat introduced, e.g. via a heating device.

[0031] Advantageous design options for the storage system according to the invention are described, at least in part, in connection with the method. The following further descriptions of advantageous design variants of the storage system also include advantageous process variants.

[0032] To increase overall efficiency, it has proven advantageous to install a recuperator on the loading side to transfer heat between the working fluid on the high-pressure and low-pressure sides. During the loading process, the temperature within the high-temperature storage device is preferably raised to the storage temperature required to generate fresh steam (e.g., 600 °C at 270 to 300 bar). Additional heat can be introduced using the additional energy input device (e.g., a heating and / or burner device) to increase the storage density. The remaining heat is recovered by the recuperator.

[0033] An advantageous embodiment and coupling of the high-temperature storage device is expedient if a heat exchanger arrangement, in particular a heat exchanger circuit operated or operable with a gaseous heat carrier, is arranged between the high-temperature storage device and the steam generation device for their thermal coupling.

[0034] In this case, the high-temperature storage device and / or the low-temperature storage device (of the first Joule arrangement) is / are preferably designed for heat transfer to a gaseous working medium and / or integrated on the loading side so that the working medium of the heat pump process can flow through it. For example, the high-temperature storage device can be designed as an efficient high-temperature heat storage device (e.g., a regenerator storage device or molten salt storage device) and integrated directly into the heat exchange arrangement and the first Joule arrangement (i.e., so that the respective working medium can flow through it). The high-temperature storage device of the second Joule arrangement can also advantageously be designed as a high-temperature heat storage device (e.g., a regenerator storage device or molten salt storage device).

[0035] Cost advantages can be achieved if, particularly in a design for storing temperatures below 0 °C, two types of low-temperature storage devices are arranged fluidically in series on the loading side, one being designed to store heat at temperatures greater than 0 °C, in particular as a (cost-effective) hot water storage device, and one being designed to store heat at temperatures equal to or less than 0 °C, e.g. as a latent or sensible cold storage device.

[0036] The storage density in the high-temperature storage device of the first or second Joule arrangement can be further increased if the loading side and / or the second Joule arrangement has / have at least one device for coupling energy in addition to the energy required for compression, e.g., electrical energy and / or fossil energy, such as an electric heating device and / or a burner device. The device is preferably arranged upstream (with respect to the loading process) or within or thermally coupled to the high-temperature storage device.

[0037] In an advantageous embodiment, the second Joule arrangement can be designed as an open circuit, which is open to the environment via an opening downstream or upstream of the low-temperature storage device and downstream or upstream of the low-pressure side heat exchanger device (depending on the direction of the circuit). This allows the environment to be used as a heat sink during the second charging process. During the second discharging process, air from the environment can be drawn in and compressed as a working medium. In this case, ambient conditions prevail at the openings. This advantageously eliminates the need for a heat exchanger device on the high-pressure side for cooling, which reduces investment costs and system complexity.

[0038] In an advantageous embodiment of this variant, a preheating device of the Rankine cycle is arranged upstream or downstream of the opening of the low-pressure side heat exchange device, wherein the preheating device is usable or used for heat storage purposes.

[0039] The invention will be explained in more detail below using exemplary embodiments with reference to the drawings. They show: Fig. 1 a process diagram of a storage system according to the invention with a discharge side designed as a Clausius-Rankine cycle and a loading side designed as a Joule arrangement, coupled with a second Joule arrangement, Fig. 2 a Ts state diagram with an example during operation in the storage system according to Fig. 1 running Joule process (loading process) and Clausius-Rankine process (discharging process), Fig. 3 a Ts state diagram with an example during operation in the storage system according to Fig. 1 in the second Joule arrangement running Joule process during the loading process and the discharging process, and Fig. 4 a process diagram of a further example of a storage system according to the invention, with the second Joule arrangement as an open cycle process.

[0040] Fig. 1 shows a process diagram of a storage power plant designed as a storage facility 10 for storing, in particular, electrical energy by converting it into thermal energy. In this case, energy, e.g., electrically supplied, is converted into thermal energy, stored in the form of high-temperature heat, and converted back into electrical energy upon withdrawal. The energy to be stored can, in particular, be energy from renewable sources, for example, from solar power and / or wind power plants, and / or fossil sources, for example, from the conversion of a combustible energy source such as natural gas.

[0041] How Fig. 1 As shown, the storage system 10 comprises a high-temperature storage device 130 for storing the supplied energy in the form of high-temperature heat (at temperatures of, for example, more than approximately 400°C). The high-temperature storage device 130 is thermally coupled on a loading side 200 and a discharging side 100.

[0042] For charging the high-temperature storage device 130, the storage system 10 has the charging side 200, which is designed as a heat pump arrangement, here in particular as a first Joule arrangement 201, for efficient charging. The Joule arrangement 201 comprises a circuit for carrying out a Joule process, with a high-pressure side 205 and a low-pressure side 209.

[0043] On the high-pressure side 205, the high-temperature storage device 130 is arranged or integrated on the loading side. On the low-pressure side 209, two low-temperature storage devices 210, 212 are arranged, as an example, in this case. At least one of the low-temperature storage devices, here the low-temperature storage device 212, can be assigned an additional (feedwater) cooling system 214. By using the storage devices 130, 210, 212 on the high-pressure and low-pressure sides, the loading process can be temporally decoupled from the discharging process.

[0044] A turbine arrangement 208 for expansion and a compressor arrangement 204 for compression of the circulating working fluid are arranged between the high-pressure side 205 and the low-pressure side 209. Energy to be stored can be coupled into the compressor arrangement 204 during the charging process of the storage system 10.

[0045] Furthermore, the Joule arrangement 201 has at least one device for additional isobaric introduction of (electrical and / or fossil) energy, for example, a heating device 206 in the form of a flow heater and / or a burner device, on the high-pressure side 205 upstream of, or alternatively within, the high-pressure storage device 130. This allows the storage density within the high-pressure storage device 130 to be increased.

[0046] To increase the inlet temperature in the high-pressure storage device 130, the loading side 200 of the storage system 10 also includes a recuperator 202, which is arranged on the high-pressure side downstream of the high-pressure storage device 130 and on the low-pressure side upstream of the compressor arrangement 204. Optionally, an additional heat exchanger device 220 can be integrated on the loading side 200 upstream of the recuperator 202 (and downstream of the low-temperature storage device 212), which allows additional heat (environmental heat and / or generated process waste heat) to be incorporated into the process in order to increase overall efficiency and reduce the temperature requirements of the recuperator.

[0047] During operation, the heat required for steam generation is stored in the high-pressure storage device 130. The excess heat can be recovered to preheat the working fluid to be compressed.

[0048] The Joule arrangement 200 uses a gaseous working medium, such as air, nitrogen, argon, or carbon dioxide, during operation. To enable direct integration of the storage devices 130, 210, 212 into the circuit, they are preferably designed for heat transfer to the gaseous working medium, for example, as solid-state storage devices.

[0049] For discharging during the discharging process, the storage system 10 has the discharge side 100, which is designed as a Rankine cycle 101, for operating with, for example, water or steam as the working medium. The Clausius-Rankine cycle 101 comprises, as core components, a steam generator 108 and a steam turbine arrangement 110, which, during operation, drives a generator 118 for extracting electrical energy. The steam turbine arrangement 110, in the present example, has a high-pressure turbine stage 112, a medium-pressure turbine stage 114, and a low-pressure turbine stage 116.

[0050] Downstream of the steam turbine assembly 110 is a condensation assembly 119, which, in this example, has two condensation stages 120, 122. Downstream of the condensation assembly 119, means for preheating the Rankine working fluid before steam generation are arranged, here, for example, a heat exchanger device 104 for low-pressure preheating, a tank device 106, and a heat exchanger device 402 for high-pressure preheating. A conveying device 102 conveys the working fluid in the circuit during operation.

[0051] The steam generating device 108 serves to generate steam by coupling heat from the high-temperature storage device 130 during the discharge process. Heat transfer from the high-temperature storage device 130 to the steam generating device 108 takes place, for example, via a heat exchange arrangement 124 in the form of a heat exchanger circuit, which includes a conveying device 126 and, for precise control and regulation, a bypass 132 with a valve means 128. A gas, for example, air, is preferably used as the heat transfer medium. In this way, the high-temperature storage device 130, which may be designed as a solid-state storage device, can advantageously be directly flowed through by the working medium of the heat exchange arrangement 124.Alternatively, the high-temperature storage device 130 may comprise a high-temperature storage component and a heat exchange device by means of which high-temperature heat is transferred between the working medium and the high-temperature storage component during operation.

[0052] According to the invention, the storage system 10 comprises a further circuit in the form of a second Joule arrangement 400, which can be operated during the charging and / or discharging process of the storage system 10. The operation of the second Joule arrangement 400 can take place both in a heat pump process (charging the second Joule arrangement 400, hereinafter also referred to as the "second charging process") and in a thermal power process (discharging the second Joule arrangement 400, hereinafter also referred to as the "second discharging process"). The second Joule arrangement 400 is energetically coupled into the storage system 10.

[0053] The second Joule arrangement 400 comprises a high-pressure side 405 and a low-pressure side 409, as well as compressor / turbine arrangements 404, 414 arranged therebetween. A second high-temperature storage device 410 is arranged on the high-pressure side 405, and a second low-temperature storage device 416 is arranged on the low-pressure side 409. For coupling out irreversibly generated heat, the second Joule arrangement 400 has a heat exchange device 412 on the high-pressure side 405 and / or a heat exchange device 402 on the low-pressure side 409. Furthermore, the second Joule arrangement 400 can comprise a heating device 408 for the isobaric coupling of electrical and / or fossil energy or heat.

[0054] Optionally, an additional heat exchange device 424 can be integrated between the low-temperature storage device 416 and the heat exchange device 402, which incorporates additional heat (environmental heat or process waste heat) into the process in order to increase the overall efficiency.

[0055] An example of the operation of the storage system 10 is explained below. The thermodynamic states of the working media during the process are shown in the Fig. 2 and Fig. 3 shown temperature (T)-entropy (s) phase diagrams 300 and 500. In the phase diagrams 300, 500, the temperatures in [°C] 302, 502 are plotted against the specific entropy s in [kJ / kgK] 304, 504. The states 1A - 7A (regarding the loading process via the heat pump process 314) and 1 - 9 (regarding the discharging process via the Clausius-Rankine process 312) shown in the state diagram 300 as well as states 1B - 6B (regarding operation of the second Joule arrangement 400 in the heat pump process 508) and 1B' - 6B' (regarding operation of the second Joule arrangement 400 in the thermal power process 510) shown in the state diagram 500 are shown at the corresponding procedural point in Fig. 1 specified.

[0056] Fig. 2 includes the states during the loading process of the storage system 10, ie during the heat pump process 314 within the first Joule arrangement 201, and during the unloading process of the storage system 10, ie during the Rankine process 312 within the Rankine cycle 101. As an exemplary Rankine process 312, a supercritical water-steam process is shown, as it is operated, for example, in modern coal-fired power plants.

[0057] Fig. 3 includes the states within the second Joule array 400, which is operated as a storage array in the second charging process, the heat pump process 508, for charging the high-temperature storage device 410, and a second discharging process, the thermal power process 510, for discharging the high-temperature storage device 410. The illustrated processes 508, 510 include real effects such as heat loss due to irreversibility.

[0058] In the Fig. 2 In the heat pump process 314 shown, an isobaric heating 1A-2A of approximately 20 °C to just under 200 °C takes place from state 1A by means of the recuperator 202. Optionally, the additional heat exchange device 220 can be integrated at point 1A-2A (cf. Fig. 1 ), which incorporates additional heat (environmental heat or accumulating process waste heat) at a temperature level between, for example, 60 °C and 100 °C into the process in order to increase overall efficiency and to reduce the temperature requirements of the recuperator. After subsequent polytropic compression (state change 2A-3A) via the compressor arrangement 204 to a pressure of, for example, 12 bar, additional energy can be supplied, for example, via the heating device 206 (not shown here), to increase the power density. In an isobaric state change 3A-4A, generated high-temperature heat required for steam generation, in this case approximately 650 °C, is transferred to the high-temperature storage device 130, where it is stored until it is withdrawn via the withdrawal process. Further heat is transferred to the low-pressure side working medium (4A - 5A) via the recuperator 202.In state 5A, the temperature of the working medium is approximately 60 °C.

[0059] The low-temperature heat, i.e., "cold," subsequently generated by polytropic expansion (5A-6A) via the turbine arrangement 208 to a temperature of, for example, -100°C is temporarily stored in the low-temperature storage devices 210, 212 for use during the discharge process (6A-7A, 7A-1A). Particularly when expanding to temperatures below 0°C, as in the present case, the storage device 210 can be configured as a latent or sensible cold storage device for temperatures less than or equal to 0°C, and the second storage device 212 can be configured, for example, as a cost-effective hot water storage device for temperatures greater than 0°C.

[0060] The low-temperature storage devices 210, 212 are thermally coupled to the loading side 200 via two heat exchanger circuits 217, 219, each of which has conveying devices 216, 218.

[0061] During the discharge process, the heat stored in the high-temperature storage device is used to generate fresh steam, at, for example, 600 °C and 270 bar to 300 bar. The corresponding Rankine process 312 is shown in relation to a bell-shaped curve 308 representing the characteristic behavior of the working fluid water for the change of state of water above the wet steam region 310. According to the Rankine process 312, which is based on the Clausius-Rankine process as a comparison process, in state changes 1-2 and 2-3, the pressure of the working medium—in this state, the working fluid in liquid form—is increased via the conveying devices 102 and / or 103. The working fluid is then preheated via the condensation arrangement 119 in state changes 2-3 (low-pressure preheating) and 3-4 (high-pressure preheating).The heat required for this purpose is provided in particular at least largely by means of the second Joule arrangement 400, as described in connection with . Fig. 3 explained. The heated working fluid enters the steam generation device 108. In the steam generation device 108, heat from the high-temperature storage device 130 is supplied via the heat exchange arrangement 124 for evaporation and superheating to approximately 600 °C and 270 bar to 300 bar in state changes 4-5. The generated superheated steam is then expanded via the steam turbine arrangement 110 in the individual stages (state changes 5 - 9). As shown here, intermediate superheating can advantageously occur between the high-pressure turbine stage 112 and the medium-pressure turbine stage 114 via further supply of heat from the high-temperature storage device 130, Q 130 . The generated electrical power is coupled out via the generator 118.

[0062] Condensation then completes the cycle (state change 9-1). The cooling required for this is coupled into the cycle from the low-temperature storage devices 210, 212.

[0063] A significant increase in current-to-current efficiency from, for example, 60% to 70% can be achieved by energetically coupling the loading side 200 and / or discharging side 100 of the storage system 10 with the second Joule arrangement 400, as described below.

[0064] Fig. 3 shows in the state diagram 500 the sequence of the second charging process (heat pump process 508) and the second discharging process (thermal power process 510), which are initially described separately from the first charging process and discharging process of the storage system 10. The types of state changes via states 1B - 6B in the second charging process for charging the high-temperature storage device 410 and the low-temperature storage device 416 correspond in principle to those of the first Joule arrangement 201. In the illustrated heat pump process 508, an isobaric heating 1B-2B takes place from state 1B by means of the low-temperature storage device 416. Optionally, the additional heat exchanger device 424 can be integrated at point 1B-2B downstream of the low-temperature storage device 416, which exchanges additional heat (environmental heat or accumulating process waste heat) with a temperature level between, for example,60 °C and 100 °C are incorporated into the process in order to increase overall efficiency and to reduce the temperature requirements of the recuperator. The compression 2B - 3B, here polytropic, takes place to a pressure of 13 bar and a temperature between 400 °C and 600 °C. Finally, an optional isobaric heating via the heating device 480 to a state 3b takes place. This high-temperature heat is temporarily stored in the high-temperature storage device 410. The heat exchanger device 412 offers the option of extracting waste heat Q 412 (state change 4B-5B), which is not used here, however. In state 6B = 1B, the temperature is between -100 °C and -20 °C and the pressure is 1 bar.

[0065] In the second discharging process, the high-temperature storage device 410 and the low-temperature storage device 416 are discharged via the thermal power process 510 in the opposite direction to the second charging process via the states 1B' to 6B'. Starting from the state 1B' = 6B, the working medium is brought to high pressure in state 2B' with a pressure of, for example, 9 bar by means of the compressor / turbine arrangement 414 with the supply of energy or compressor work, which is preferably at least partially decoupled as turbine energy from the compressor / turbine arrangement 404. Subsequently, high-temperature heat is extracted from the high-temperature storage device 410 by means of the working medium in an isobaric change of state 2B' - 3B', wherein the working medium has a temperature of between 500 °C and 700 °C. In a polytropic expansion orExpansion 3B' - 4B' by means of the first compressor / turbine arrangement 404, useful electrical energy can be released from the storage system 10 under the action of the motor / generator arrangement 406.

[0066] In the present example, there is an energetic coupling of the second Joule arrangement 400 with the Rankine cycle 101 via the heat generated during the change of state 4B'-5B'. Heat loss 512, generated due to real effects or irreversibility, which must be dissipated from the second Joule arrangement 400, is coupled into the Rankine cycle 101 for high-pressure preheating 3 - 4 of the working fluid via the heat exchanger device 402 (see also Fig. 1 , Fig. 2 and Fig. 4 ).

[0067] The low-temperature heat carried in the working medium is then stored in the low-temperature storage device 416 (5B' - 1B').

[0068] In contrast to the first Joule arrangement 201, which is operated only in the charging process, in the heat pump process 314, with the discharging process taking place via the Rankine cycle 312, the second Joule arrangement 400 is operated both in the second charging process, the heat pump process 508, for charging the high-temperature storage device 410, and in the second discharging process, the thermal power process 510, for discharging the high-temperature storage device 410. Thus, the second Joule arrangement 400, apart from the energetic coupling, can operate independently of the Rankine cycle 101. The execution of the second charging and discharging processes is preferably coordinated with the operation of the first Joule arrangement 201 (charging process) and / or the Rankine cycle 101 (discharging process), e.g., as described below. In this way, an optimized energy coupling can be achieved, accompanied by an increase in the overall efficiency of the storage system 10.

[0069] The adjustment of the operation for coupling thermal energy from the second Joule arrangement 400 can be achieved via different (alternative or complementary) mechanisms. Fig. 1 , 2 and 3 In the exemplary coupling of the processes shown, the thermal energy from the second Joule arrangement 400, as described, is extracted in the form of heat loss 512 (4B' - 5B') on the low-pressure side 409 and coupled into the Rankine cycle 101 on the discharge side 100. There, it serves for the high-pressure preheating of the working fluid upstream of the steam generating device 108. In this variant, the second discharge process of the Joule arrangement 400 preferably runs parallel to the discharge process via the Rankine cycle 101. Intermediate storage of the heat loss 512 would also be conceivable.

[0070] Alternatively or additionally, in an embodiment not shown here, heat loss from the second Joule arrangement 400 on the high-pressure side 405 downstream of the high-temperature storage device 410 and upstream of the turbine / compressor arrangement 414 can be extracted via the heat exchange device 412 (4B - 5B) and used for low-pressure preheating of the working fluid ( Fig. 2 : State change 2-3), e.g., via the heat exchanger device 104. In this case, the waste heat is compression waste heat from the compressor, which may therefore have a lower efficiency. In this variant, the second discharge process of the Joule arrangement 400 preferably runs parallel to the discharge process via the Rankine cycle 100. Intermediate storage of the waste heat would also be conceivable.

[0071] Due to the heat coupling from the second Joule arrangement 400, tapping from the steam turbine arrangement 110 for preheating the working fluid before evaporation, as is common in the prior art, can advantageously be dispensed with. This allows the highest possible power density to be achieved during the discharge process via the Rankine cycle 101.

[0072] Alternatively or additionally, "cold," ie, low-temperature heat, can be extracted from the second Joule arrangement 400 and coupled into the Rankine cycle 312 downstream of the steam turbine arrangement 110 for cooling and / or condensing working fluid. The cold is extracted from the low-temperature storage device 416. The low-temperature storage device 416 is preferably, as in Fig. 1 shown, thermally coupled to the low-temperature storage device 210 of the first Joule arrangement 201. Thus, the cold from the second Joule arrangement 400 can be indirectly coupled into the Rankine cycle 312 via the low-temperature storage device 210 on the loading side 200.

[0073] The advantageous effect of the thermal coupling of the different processes can be optimized by specifying a larger pressure ratio between the pressure on the high-pressure side 405 and the low-pressure side 409 in the second Joule arrangement 400 during the heat pump process 508 than in the thermal power process 510. This pressure control, also referred to as "asymmetrical," leads to a shift of the heat loss, in this case, for example, from the high-pressure side 405 in the second loading process (state change 4B-5B) to the low-pressure side 409 in the second discharging process (state change 4B'-5B').

[0074] The goal of asymmetric pressure control is to increase the overall efficiency of the storage system 10. The efficiency of the second Joule arrangement 400 can tend to be reduced. In this case, the pressure ratio within the heat pump process 508 is 13 and within the thermal power process 510 is 9. The asymmetry in the pressure ratios of 13 / 9 in this case is designed, for example, such that the heat loss 512 is adapted to the heat demand for high-pressure preheating and can cover this. Another important aspect is the inlet temperature of the Rankine working fluid into the steam generation device 108. This should be selected between 200 °C and 350 °C to reduce thermal stresses in the steam generation device. Additionally or alternatively, the design can aim, for example, to minimize heat loss on the high-pressure side.The design is based on the thermodynamic equations of state of the corresponding processes.

[0075] Fig. 4 shows a further advantageous variant of the storage system 10 or the method for its operation. The second Joule arrangement is designed as an open circuit. The circuit between the heat exchanger device 402 and the low-temperature storage device 416 is open to the environment via openings 420, 422. The environment is used as a heat sink during the second loading process. During the second discharging process, air can be sucked in from the environment as a working medium and compressed. In this case, ambient conditions (pu , T u ) are present at the openings 420, 422. Advantageously, the heat exchanger device 412 on the high-pressure side for cooling can be dispensed with (in Fig. 4symbolized by the cross-connection of the heat exchanger device 412), which in turn is accompanied by a reduction in investment costs and system complexity. The container device 106, if present, can be used for temperature storage purposes.

[0076] In summary, the described method and the storage device 10 shown serve to provide efficient and / or location-independent storage power plants for storing electrical energy.

Claims

1. Method for operating a storage system (10) for storing electrical energy by conversion into thermal energy, in which - in a charging process via a charging side (200), by means of a charging arrangement, a high-temperature storage device (130) is charged by storing energy, in particular fed-in electrical energy, in the form of thermal energy, wherein the charging process takes place via a heat pump process (314) within the charging assembly, which is designed as a first Joule arrangement (201) comprising a low-pressure side (205) and a high-pressure side (209), with an interposed compressor assembly (204) and turbine assembly (208), and - in a discharging process, by means of a Rankine process (312), the high-temperature storage device (130) is discharged via a discharging side (100) with the thermal energy being released from the high-temperature storage device (130) and converted into electrical energy, wherein an energy conversion arrangement provided in the storage system (10), in addition to the charging arrangement, in the form of a second Joule arrangement (400), comprising a low-pressure side (405) and a high-pressure side (409) and compressor / turbine assemblies (406, 414) arranged therebetween, is operated during the charging process and / or during the discharging process of the storage system (10) in a heat pump process (508) and / or in a thermal power process (510), wherein in particular during the second discharging process and / or the second charging process of the second Joule arrangement (400) and the charging process via the charging side (200), thermal energy is transferred between the second Joule arrangement (200) and the charging side (200), characterized in that, during the second discharging process and / or the second charging process of the second Joule arrangement (400) and the discharging process via the discharging side (100), thermal energy is transferred between the second Joule arrangement (200) and the discharging side (100).

2. Method according to claim 1, characterized in that the second Joule arrangement (400) is operated as a storage arrangement, wherein a high-pressure-side high-temperature storage device (410) of the second Joule arrangement (400) is charged in a second charging process by means of the heat pump process (508) and is discharged in a second discharging process by means of the thermal power process (510).

3. Method according to claim 1 or 2, characterized in that during the discharging process via the discharging side (100), heat which is generated during operation of the second Joule arrangement (400), in particular in the second discharging process, is at least temporarily coupled into the Rankine process (312) upstream of a steam generating device (108) for preheating working fluid.

4. Method according to claim 3, characterized in that the heat from the second Joule arrangement (400) is decoupled on the low-pressure side (405) downstream of the compressor / turbine assembly (404), in particular upstream of a low-temperature storage device (416) via a low-pressure-side heat exchanger device (402), and is coupled in for high-pressure preheating of the working fluid and / or is decoupled on the high-pressure side (409) downstream of the high-temperature storage device (410), upstream of the compressor / turbine assembly (414), and is coupled in downstream of a condensation arrangement (119) for low-pressure preheating of the working fluid.

5. Method according to any of claims 2 to 4, characterized in that during the discharging process via the discharging side (100), cold from a low-pressure-side low-temperature storage device (416) of the second Joule arrangement (400) is at least temporarily coupled into the Rankine process (312) downstream of a steam turbine assembly (110) for cooling and / or condensation of working fluid, wherein, for example, the cold is transferred indirectly via at least one low-pressure-side low-temperature storage device (210) of the charging side (200).

6. Method according to any of the preceding claims, characterized in that in the second Joule arrangement (400) during the heat pump process (508), a larger pressure ratio is set between the high pressure side (405) and the low pressure side (409) than in the thermal power process (510), wherein in particular the pressure ratio is different such that the overall efficiency of the storage system (10) is increased compared to a process with the same pressure ratios,wherein in particular - heat loss (512) occurring between the heat pump process (508) and the thermal power process (510) is adapted to the requirement for high-pressure preheating of the working fluid and is decoupled, for example, via the low-pressure-side heat exchanger device (402), and / or - heat loss is minimized via a high-pressure-side heat exchanger device (412) and / or - heat loss is adapted to the requirement for low-pressure preheating of the working fluid via the high-pressure-side heat exchanger device (412).

7. Storage system (10) for storing electrical energy by converting it into thermal energy, which is designed in particular for carrying out a method according to any of the preceding claims, comprising - a high-temperature storage device (130), - a charging side (200) for charging the high-temperature storage device (130) in a charging process by storing energy, in particular fed-in electrical energy, in the form of thermal energy, with a charging arrangement which is designed as a first Joule arrangement (201), comprising a low-pressure side (205) and a high-pressure side (209), with an interposed compressor assembly (204) and turbine assembly (208), - a discharging side (100) which is designed to discharge the high-temperature storage device (130) by releasing the thermal energy and converting it into electrical energy in a Rankine process (312), wherein the discharging side (100) is designed as a Rankine cycle (101) comprising a steam turbine assembly (110), a condensation arrangement (119), conveying devices (102, 103) and a steam generating device (108), wherein a second Joule arrangement (400) is arranged within the storage system (10) so as to be coupled in terms of energy, in particular thermally coupled, to the charging side (200) and / or the discharging side (100) for operation during the charging process and / or during the discharging process as a heat pump process and / or as a thermal power process, characterized in that the second Joule arrangement (400) is thermally coupled to the discharging side (100) for transferring thermal energy between the second Joule arrangement (200) and the discharging side (100) during the second discharging process and / or the second charging process and the discharging process via the discharging side (100).

8. Storage system (10) according to claim 7, characterized in that a recuperator (202) is arranged on the charging side (200) for heat transfer between the working medium located on the high pressure side (205) and the low pressure side (209).

9. Storage system (10) according to either of claims 7 or 8, characterized in that a heat exchanger arrangement (124), in particular a heat exchanger circuit operated or operable with a gaseous heat transfer medium, is arranged between the high-temperature storage device (130) and the steam generating device (108) for thermal coupling thereof.

10. Storage system (10) according to any of claims 7 to 9, characterized in that on the charging side (200), two types of low-temperature storage devices (210, 212) are arranged fluidically in series, wherein one is designed to store heat at temperatures greater than 0°C, in particular as hot water storage, and one is designed to store heat at temperatures equal to or less than 0°C, e.g. as a latent or sensitive cold storage.

11. Storage system (10) according to any of claims 7 to 10, characterized in that the second Joule arrangement (400) and / or the charging side (200) has / have at least one device for coupling in energy in addition to the energy required for compression, e.g. electrical energy and / or fossil energy, e.g. an electrical heating device (206) and / or a burner device (408).

12. Storage system (10) according to any of claims 7 to 11, characterized in that the second Joule arrangement (400) has a low-temperature storage device (416) on the low-pressure side (405), wherein in particular the low-temperature storage device (416) of the second Joule arrangement (400) is thermally coupled to the discharging side (100) for cooling the working fluid vapor downstream of the steam turbine assembly (110), in particular via thermal coupling with the at least one low-temperature storage device (210, 212) on the charging side (200).

13. Storage device (10) according to any of claims 7 to 12, characterized in that the second Joule arrangement (400) is thermally coupled to the discharging side (100) for preheating the working fluid upstream of the steam generating device (108), in particular via a heat exchange device (402), e.g. for high-pressure preheating of the working fluid, and / or via a heat exchange device (412, 104), e.g. for low-pressure preheating of the working fluid.

14. Storage system (10) according to any of claims 7 to 13, characterized in that the second Joule arrangement (400) is designed as an open circuit which is open to the surroundings downstream or upstream of the low-temperature storage device (416) and upstream or downstream of the low-pressure-side heat exchange device (402), in each case via an opening (420, 422), wherein in particular the one container device (106) of the Rankine cycle (101) is connected upstream or downstream of the opening (420) upstream or downstream of the low-pressure-side heat exchange device (402), wherein the container device (106) is usable or used for heat storage purposes.

15. Control program for a control device, comprising functions which cause a control device to control a storage system according to any of claims 7 to 14 in an open-loop and / or closed loop manner in such a way that a method according to any of claims 1 to 6 is carried out.

16. A computer-readable medium on which a control program according to claim 15 is stored.