Heat storage system, in particular cryogenic heat storage system

Abstract

The present invention relates to a heat storage system (100), in particular a cryogenic heat storage system (100), comprising at least one working fluid piping system (102) for flow with a working fluid, wherein the at least one working fluid piping system (102) comprises the following devices: - at least one high-temperature heat storage device (104) for charging and / or discharging with high-temperature heat from / on the working fluid, - at least one low-temperature heat storage device (106) for charging and / or discharging with low-temperature heat from / on the working fluid, - at least one high-temperature compression and / or expansion device (108) for compressing and / or expanding the working fluid, - at least one low-temperature compression and / or expansion device (110) for compressing and / or expanding the working fluid, and - at least one low-temperature heat exchanger device (112) for transferring low-temperature heat to the working fluid; wherein the at least one low-temperature heat exchanger device (112) is connected or connectable to a low-temperature heat source (114), in particular one positioned externally. Furthermore, the present invention relates to a method for multi-stage, in particular two-stage, thermal charging or discharging of a heat storage system.

Description

[0001] The present invention relates to a heat storage system, in particular a cryogenic heat storage system, for converting electrical energy into stored thermal energy and / or vice versa. Furthermore, the present invention relates to a method for the multi-stage, in particular two-stage, thermal loading and unloading of a heat storage system, in particular a cryogenic heat storage system, for converting electrical energy into stored thermal energy and / or vice versa.

[0002] Such heat storage systems, also known internationally as thermopotential storage or Carnot batteries (Pumped Thermal Electricity Storage, or PTES for short), represent an electrical energy storage system that combines electricity, heat, and electricity. This energy storage system can be used to store thermal energy or convert it into electrical energy on a megawatt-hour or gigawatt-hour scale, regardless of location. The operating principle of a PTES system can be described theoretically or ideally by a counterclockwise Carnot cycle for charging a high-temperature storage system and a clockwise Carnot cycle for discharging.

[0003] Pumped Cryogenic Electricity Storage (PCES) belongs to the subcategory of PTES systems and functions analogously, with the difference that the entire process on the low-temperature side takes place at temperatures well below the freezing point of water. Closed processes with air as the working medium even use low temperatures down to -192°C (below the boiling point of air) to liquefy the liquid and store it in cryogenic tanks.

[0004] Such heat storage systems are already known from the state of the art.

[0005] For example, DE 10 2020 110 560 A1 shows a method for operating a thermopotential storage system for storing electrical energy by converting it into thermal energy.

[0006] Furthermore, WO 2020239288 A1 shows a heat storage device comprising an inductor device surrounding a storage space for receiving a storage material.

[0007] EP 2 729 404 A2 shows a process for producing and / or hardening coke, in which hydrocarbons are introduced into a reaction chamber and thermally decomposed into carbon and hydrogen in the presence of a carbon-rich granulate.

[0008] US 2009 / 0282840 A1 further discloses a method for storing energy, comprising: providing a gaseous medium; generating a cryogen from the gaseous medium; storing the cryogen; expanding the cryogen; using the expanded cryogen to drive a turbine; and recovering cooling energy from the expansion of the cryogen.

[0009] To operate PCES systems, both high-temperature heat (corresponding to the heat content of a working fluid, for example, above 0°C) and low-temperature heat (corresponding to the heat content of the working fluid, for example, below 0°C) are required. A source of low-temperature heat that has not yet been used in PCES systems could be liquefied natural gas (LNG) terminals.

[0010] The supply problems triggered in 2022 led to upheavals for the European and German gas supply systems. The political shift away from pipeline gas and towards other suppliers requires the massive expansion of LNG terminals, as natural gas remains an indispensable energy source for supplying industry and households with heat and / or electricity. To ensure a secure future natural gas supply in Europe, natural gas is liquefied at temperatures below -162°C and transported as liquefied natural gas in tankers to the appropriate unloading points, so-called terminals, on the European and German coasts. There it is unloaded from the tankers via the terminal and fed into the respective natural gas grid. For this to happen, the liquefied natural gas must be regasified to its original form (under normal conditions). This process takes place by heating it to approx. 0°C to approx.20 °C through the use of treated seawater in heat exchangers, whereby the seawater serves as a heat sink for heating or gasifying the liquefied natural gas.

[0011] By using these heat exchangers when unloading the tankers, the cold or low-temperature heat (corresponding to a heat content of the liquefied natural gas, for example, below 0°C) of the liquefied natural gas from the LNG tankers has not been used so far.

[0012] In addition, the LNG terminal requires a high level of electrical energy to operate pumps, compressors, and other electrical drive components during the unloading of LNG tankers. Each site also requires additional buffer storage for temporary LNG storage. Cooling these buffer storage facilities requires additional electrical energy.

[0013] Due to the previously non-existent or insufficient use of low-temperature heat from corresponding low-temperature sources (e.g. from LNG terminals), the heat storage systems described above in the state of the art have an efficiency that can be further optimized.

[0014] The present invention is therefore based on the object of providing, in particular, a heat storage system, in particular a cryogenic heat storage system, and / or a method for multi-stage, in particular two-stage, thermal loading or unloading of a heat storage system, in particular a cryogenic heat storage system, which preferably have an improved or higher efficiency.

[0015] This object is achieved according to the invention by the features of independent claim 1. Advantageous developments of the invention are described in the dependent claims.

[0016] A heat storage system according to the invention comprises at least one working fluid line system for flowing through a working fluid, wherein the at least one working fluid line system comprises the following devices: - at least one high-temperature heat storage device for loading and / or unloading with / from high-temperature heat from / to the working fluid, - at least one low-temperature heat storage device for loading and / or unloading with / from low-temperature heat from / to the working fluid, - at least one high-temperature compression and / or expansion device for compressing and / or expanding the working fluid, - at least one low-temperature compression and / or expansion device for compressing and / or expanding the working fluid, and - at least one low-temperature heat exchanger device for transferring low-temperature heat to the working fluid; wherein the at least one low-temperature heat exchanger device is connected or connectable to a low-temperature heat source, in particular an externally positioned one.

[0017] The heat storage system can be designed to convert electrical energy into stored thermal energy.

[0018] Additionally or alternatively, the heat storage system can be designed to convert stored thermal energy into electrical energy.

[0019] The at least one working fluid line system can be understood as being able to be used for both loading and unloading.

[0020] Alternatively, the at least one working fluid line system may have only certain line sections that are used for both loading and unloading.

[0021] It is also conceivable that the at least one working fluid line system has two essentially separate working fluid line systems, one each for loading and one for unloading.

[0022] The heat storage system according to the invention can, in particular, comprise a cryogenic heat storage system. The term "cryogenic heat storage system" can be understood within the context of this invention to mean that the minimum temperature of the working fluid flowing through the working fluid line system can fall significantly below 0 °C. Depending on the working fluid used, the process control, and the low-temperature source used, the working fluid can have a temperature of, in particular, down to -192 °C. Preferably, the minimum temperature of the working fluid can be down to -164 °C.

[0023] The at least one high-temperature heat storage device is to be distinguished from the at least one low-temperature heat storage device in that the discharge or loading of high-temperature heat from / to the high-temperature heat storage device takes place at a minimum working fluid temperature of greater than 0 °C. Accordingly, the discharge or loading of low-temperature heat from / to the low-temperature heat storage device takes place at a maximum working fluid temperature of less than or equal to 0 °C.

[0024] The at least one low-temperature heat exchanger device for transferring low-temperature heat to the working fluid can be understood such that its secondary side is flowed through by a cooling fluid whose maximum inlet temperature is less than or equal to 0 °C. Accordingly, a low-temperature fluid or the cooling fluid with a maximum temperature of less than or equal to 0 °C can be provided from the low-temperature source.

[0025] Consequently, the at least one high-temperature compression and / or expansion device and the at least one low-temperature compression and / or expansion device can also be separated from one another. The at least one high-temperature compression and / or expansion device is accordingly designed to compress or expand the working fluid above a minimum working fluid temperature of greater than 0 °C. Accordingly, the low-temperature compression and / or expansion device is designed to compress or expand the working fluid below a maximum working fluid temperature of less than or equal to 0 °C.

[0026] The connection of the at least one low-temperature heat exchanger device to a low-temperature heat source can be understood in particular as an actual flow connection. The connectability, in turn, can be understood as a temporary flow connection dependent on the availability of the low-temperature source. The low-temperature heat source can preferably comprise an external low-temperature heat source, which can be positioned externally, e.g., outside the structural boundaries of the heat storage system or the working fluid piping system.

[0027] The high-temperature heat storage device may comprise a high-temperature solid heat storage device. Additionally or alternatively, the low-temperature heat storage device may comprise a solid heat storage device.

[0028] During the charging of the at least one high-temperature heat storage device and the at least one low-temperature heat storage device, the heat storage system can be operated based on a single-stage or multi-stage, in particular two-stage, heat pump process. However, during the discharging of the at least one high-temperature heat storage device and the at least one low-temperature heat storage device, the heat storage system can be operated based on a single-stage or multi-stage, in particular two-stage, Joule thermal power process.

[0029] The low-temperature heat source can, in particular, comprise a liquefied natural gas terminal. The liquefied natural gas terminal can preferably comprise a liquefied natural gas terminal. The liquefied natural gas terminal can be configured as a floating liquefied natural gas terminal or as a land-based liquefied natural gas terminal. The liquefied natural gas can preferably be liquefied natural gas.

[0030] Using the low-temperature heat exchanger device, the heat storage system can be connected to the liquefied gas terminal via connecting lines, thus utilizing the low-temperature heat of the liquefied gas as a cooling fluid. This allows the working fluid to flow through the at least one low-temperature heat exchanger device on the primary side and liquefied gas on the secondary side.

[0031] In other words, the low-temperature heat exchanger on the secondary side serves as an evaporator for the liquefied natural gas. In the case of natural gas, this no longer needs to be gasified via heat exchangers using seawater, but rather via the heat storage system. This means that the previously unused low-temperature heat of the liquefied natural gas can no longer be used to cool seawater, but rather to cool the working fluid, thus improving the efficiency of the heat storage system.

[0032] Additionally or alternatively, the low-temperature heat source may comprise a liquefied gas tanker. In this case, the low-temperature heat exchanger device may be connected directly to the liquefied gas tanker, i.e., in particular, without the intermediary of a liquefied gas terminal.

[0033] In addition, it is conceivable that the at least one low-temperature heat exchanger device is arranged in the at least one working fluid line system between the at least one low-temperature compression and / or expansion device and the at least one high-temperature heat storage device.

[0034] This interposition enables the working fluid to be cooled, ideally to the inlet temperature of the incoming liquefied gas (preferably liquefied natural gas), during the discharging of the heat storage system (i.e., in particular, during the discharging of the at least one high-temperature heat storage device), before the working fluid enters the at least one high-temperature heat storage device. The working fluid pre-cooled in this way can absorb more high-temperature heat, at a predetermined maximum storage temperature of the at least one high-temperature heat storage device as a reference point, than the working fluid that would be supplied to the at least one high-temperature heat storage device at ambient temperature, for example.

[0035] When loading the heat storage system, the opposite is true. The working fluid exiting the at least one high-temperature heat storage device can be cooled to ideally the inlet temperature of the incoming liquefied gas by means of the at least one low-temperature heat exchanger before entering the at least one low-temperature compression and / or expansion device, thereby transferring additional low-temperature heat to the working fluid. This additional heat can be additionally stored during loading of the at least one low-temperature heat storage device.

[0036] The heat storage system may further comprise a heating device for heating the working fluid with high-temperature heat. The heating device may comprise an electric heating device. Preferably, the heating device may comprise an inductive heating device. Additionally or alternatively, the heating device may be operable with fossil fuels (e.g., natural gas-based or petroleum-based fuels) or with hydrogen as fuel.

[0037] The heating device can be arranged, in particular, in the at least one working fluid line system between the at least one high-temperature compression and / or expansion device and the at least one high-temperature heat storage device. The working medium preheated by the heating device can increase a maximum loading inlet temperature during loading of the heat storage system, so that the at least one high-temperature heat storage device can absorb more high-temperature heat, which increases its storage density or energy density. More expansion work can thus be provided during subsequent discharging. The heating device can be provided optionally, or the operation of the heating device can be optional. The heating device can be operated, in particular, depending on the power demand and the resulting power costs.

[0038] Furthermore, it can be provided that at least one high-temperature heat exchanger device is arranged in the at least one working fluid line system between the at least one high-temperature compression and / or expansion device and the at least one low-temperature heat storage device. The at least one high-temperature heat exchanger device can preferably be or is connected to a high-temperature heat sink.

[0039] The connection of the at least one high-temperature heat exchanger device to a high-temperature heat sink can be understood in particular as a flow connection. The connectability, in turn, can be understood as a temporary flow connection dependent on the availability of the high-temperature heat source. The high-temperature heat sink can preferably have an external high-temperature heat sink, which can be positioned externally, e.g., outside the structural boundaries of the heat storage system or the working fluid piping system.

[0040] When the heat storage system is discharged, high-temperature waste heat is generated after the working fluid has been expanded (e.g., to atmospheric pressure) by means of the at least one high-temperature compression and / or expansion device. This waste heat can be reused externally, so that the working fluid is additionally cooled by the high-temperature heat sink. Therefore, the working fluid does not have to be cooled solely by the at least one low-temperature heat storage device. The additional cooling in the at least one high-temperature heat exchanger device allows the working fluid to absorb more low-temperature heat from the at least one low-temperature heat storage device, starting from a lower high temperature, which improves the overall efficiency of the heat storage system.

[0041] Additionally or alternatively, an opening point open to the atmosphere can be arranged in the at least one working fluid line system between the at least one high-temperature compression and / or expansion device and the at least one low-temperature heat storage device. Through the at least one opening point, the heat storage system can be operated as a heat storage system open to the environment with air as the working medium. Overall, this reduces the structural complexity for the at least one working fluid line system. This is because the air does not have to be transported between the at least one high-temperature compression and / or expansion device and the at least one low-temperature heat storage device for both charging and discharging, but can be released directly to the atmosphere.In addition, the opening to the atmosphere serves as a heat sink, so that a cooler can be saved.

[0042] Alternatively, the at least one working fluid line system may comprise a closed working fluid line system. In this case, the working fluid is air, nitrogen, or argon.

[0043] Furthermore, it can be provided that the high-temperature heat sink comprises a natural gas pyrolysis device, so that the at least one high-temperature heat exchanger device can be flowed through on the primary side with the working fluid and on the secondary side with gaseous natural gas and thus the gaseous natural gas can be preheated.

[0044] On the one hand, preheating the gaseous natural gas can increase the efficiency of the heat storage system, as explained above. On the other hand, preheating the gaseous natural gas can increase the efficiency of the pyrolysis plant, which has a direct impact on the future use of the LNG terminal. On the other hand, the working fluid cools, which also increases the efficiency of the heat storage system.

[0045] Substantial investments (at least in the single-digit billion euro range) are being made for the construction and operation of the LNG terminals required in Germany, although from today's perspective, these represent only a temporary solution. Natural gas is intended to be used as an energy source only temporarily until hydrogen replaces natural gas in the long term.

[0046] In other words, the LNG terminals currently being planned and built will likely no longer be used in two to three decades. Unless these sites can be used in the future to produce hydrogen from natural gas, which will require a high energy and, in particular, heat demand. There are two possibilities for this.

[0047] Either so-called "grey hydrogen" is produced using the steam reforming process (current costs of approximately €2,000 / t) with the emission of CO2, or so-called "turquoise hydrogen" is produced using the thermal process of pyrolysis of natural gas (current costs of approximately €2,600 to €3,000 / t) to produce solid carbon. Both processes have the lowest known hydrogen production costs.

[0048] The thermal pyrolysis process is more suitable from an environmental perspective because no gaseous CO2 escapes into the atmosphere and the carbon bound in solid form can be separated.

[0049] Furthermore, the at least one working fluid line system can have a loading line system for loading the at least one high-temperature heat storage device with high-temperature heat from the working fluid and for loading the at least one low-temperature heat storage device with low-temperature heat from the working fluid.

[0050] Additionally or alternatively, the heat storage system may comprise a second working fluid conduit system, which may comprise a discharge conduit system for discharging high-temperature heat from the at least one high-temperature heat storage device to the working fluid.

[0051] In addition, the second working fluid line system may be provided for discharging low-temperature heat from the at least one low-temperature heat storage device to the working fluid.

[0052] The loading line system and the discharge line system can be designed essentially separately from each other. In other words, the flow only flows through the loading line system when the heat storage system is being loaded, and the flow only flows through the discharge line system when the heat storage system is being discharged.

[0053] Alternatively, it can be provided that the loading line system and the discharge line system are each formed by the at least one working fluid line system and which, depending on the flow direction, provides the function of the loading line system or the discharge line system.

[0054] Alternatively, the at least one working fluid line system may have only certain line sections that are used for both loading and unloading.

[0055] When loading and unloading the heat storage system, the at least one high-temperature compression and / or expansion device can be configured as at least one high-temperature compression and expansion device. In other words, the at least one high-temperature compression and expansion device can comprise at least one common or integrated high-temperature device that performs the function of both a high-temperature compression device and a high-temperature expansion device.

[0056] Alternatively, it can be provided that the at least one high-temperature compression and expansion device can have at least two separate high-temperature devices. In other words, the at least one high-temperature compression and expansion device has at least one high-temperature loading compression device and at least one separate high-temperature discharging expansion device.

[0057] Accordingly, during loading and unloading of the heat storage system, the at least one low-temperature compression and / or expansion device can be configured as at least one low-temperature compression and expansion device. In other words, the at least one low-temperature compression and expansion device can comprise at least one integrated or common low-temperature device that performs the function of both a low-temperature compression device and a low-temperature expansion device.

[0058] Alternatively, it can be provided that the at least one low-temperature compression and expansion device can have at least two separate low-temperature devices. In other words, the at least one low-temperature compression and expansion device has at least one low-temperature discharge expansion device and at least one separate low-temperature discharge compression device.

[0059] To load the heat storage system, i.e. to convert electrical energy into stored thermal energy, it has at least one loading line system and can be operated as follows: First, by means of the at least one high-temperature compression device, the working fluid is compressed from a loading output pressure level (e.g. atmospheric pressure) to a first, higher pressure level, as a result of which the working fluid is heated from a first loading output high temperature (e.g. atmospheric temperature) to a first loading high temperature.

[0060] The compression work required for this is provided by an electric drive motor coupled to at least one high-temperature compression device.

[0061] Optionally, the working fluid can be heated to an even higher loading high temperature by means of the heating device at the first pressure level.

[0062] The working fluid heated in this way to the first or even higher loading high temperature now flows into the at least one high-temperature heat storage device for its loading with high-temperature heat from the working fluid (at the first pressure level).

[0063] As a result, the working fluid cools down, as the high-temperature heat is transferred to the at least one high-temperature heat storage device for charging. For this purpose, the at least one high-temperature heat storage device has a heat exchanger. The heat exchanger can be integrated into the at least one high-temperature heat storage device.

[0064] The working fluid, which has transferred the high-temperature heat to the at least one high-temperature heat storage device, now flows through the primary side of the low-temperature heat transfer device at the first pressure level, resulting in further cooling. The working fluid reaches its minimum temperature at the first pressure level.

[0065] The working fluid then flows through at least one low-temperature loading expansion device and is expanded by the first to the pressure outlet level, where the working fluid reaches the lowest loading temperature in absolute terms.

[0066] After leaving the at least one low-temperature loading expansion device, the working fluid now flows into the at least one low-temperature heat storage device for its loading with low-temperature heat (at the first loading outlet pressure level).

[0067] As a result, the working fluid heats up, as the low-temperature heat is transferred to the at least one low-temperature heat storage device for charging. For this purpose, the at least one low-temperature heat storage device has an additional heat exchanger. The latter can be integrated into the at least one low-temperature heat storage device.

[0068] After flowing through the heat exchanger of the at least one low-temperature heat storage device at the loading outlet pressure level (e.g. atmospheric pressure), the working fluid is heated to the first loading high temperature (e.g. atmospheric temperature), from where the operation of the heat storage system was started (as described above) and can now be cyclically restarted or continued.

[0069] In addition, the heat storage system may have at least one discharge line system for its discharge (i.e. for the conversion of stored thermal energy into electrical energy) and may be operated as follows: First, the working fluid flows through the heat exchanger of the at least one low-temperature heat storage device to discharge low-temperature heat to the working fluid at the discharge outlet pressure level (e.g. atmospheric pressure).

[0070] At the inlet of this heat exchanger, the working fluid has a first discharge exit high temperature (e.g., atmospheric temperature). As a result, the flow through the working fluid causes it to cool to a first discharge low temperature. This is because the stored low-temperature heat is transferred from the at least one low-temperature heat storage device to the working fluid for discharge. At the first discharge low temperature, the working fluid has its lowest discharge temperature in absolute terms.

[0071] For this purpose, the at least one low-temperature heat storage device has its own heat exchanger. The latter can be integrated into the at least one low-temperature heat storage device.

[0072] The working fluid then flows through the at least one low-temperature discharge compression device and is compressed from the discharge outlet pressure level to a first, higher discharge pressure level, where the working fluid reaches a second, higher discharge low temperature.

[0073] The working fluid, which has absorbed the low-temperature heat from the at least one low-temperature heat storage device, now flows through the primary side of the low-temperature heat transfer device at the first discharge pressure level. As a result, further cooling occurs at the first discharge pressure level to a third discharge low temperature, which lies between the first and second discharge low temperatures.

[0074] The working fluid thus cooled to the third low discharge temperature now flows into the at least one high-temperature heat storage device for discharging high-temperature heat to the working fluid (at the first pressure level).

[0075] As a result, the working fluid is heated to a second high-temperature discharge temperature. This is because the high-temperature heat is transferred from the at least one high-temperature heat storage device to the working fluid for its discharge. For this purpose, the at least one high-temperature heat storage device has a heat exchanger, which can be integrated into the at least one high-temperature heat storage device.

[0076] After leaving the at least one high-temperature heat storage device, the working fluid can optionally flow through the heating device, whereby the working fluid is heated to a maximum discharge high temperature.

[0077] After flowing through the at least one high-temperature heat storage device and / or the heating device, the working fluid is introduced into the high-temperature discharge expansion device at the first discharge pressure level and the second discharge high temperature or the maximum discharge high temperature. There, the working fluid is expanded back to the discharge outlet pressure level, where, after expansion, it can again assume the first discharge high temperature.

[0078] Optionally, the working fluid can additionally flow through the at least one high-temperature heat exchanger device following the high-temperature discharge expansion device (in particular after prior heating to the maximum discharge high temperature) and thus be cooled to the first discharge high temperature by releasing high-temperature waste heat at the discharge outlet pressure level.

[0079] At the first high discharge temperature, the discharge operation of the heat storage system was started (as described above) and can now be restarted cyclically.

[0080] The expansion energy converted during expansion is converted into usable electrical energy by an electrical generator coupled to at least one high-temperature expansion device. This electrical energy can partially or completely cover the power requirements of an LNG terminal. This enables efficient and economical site operation for Germany's future LNG supply.

[0081] The operating modes of the heat storage system described above are based on a single-stage loading and unloading process. The single-stage loading process involves compressing the working fluid from a loading outlet pressure level to a first loading pressure level and then releasing it back to the loading outlet pressure level.

[0082] The single-stage unloading process involves compressing the working fluid from a discharge outlet pressure level to a first discharge pressure level and then releasing it back to the discharge outlet pressure level. The two aforementioned pressure levels for loading and unloading each form a pressure stage.

[0083] Alternatively, a heat storage system that can be operated or operated in two stages can be provided for loading.

[0084] In this regard, a heat storage system can be provided whose loading line system includes the following devices: - the at least one high-temperature compression device for compressing the working fluid from a loading initial pressure level to a first, higher loading pressure level, - the at least one high-temperature heat storage device for loading with high-temperature heat from the working fluid at the first loading pressure level, - a second high-temperature compression device for compressing the working fluid from the first to a second, higher loading pressure level, - a second high-temperature heat storage device for loading with high-temperature heat from the working fluid at the second loading pressure level, - at least one low-temperature / high-temperature heat storage device for providing low-temperature heat to the working fluid at the second loading pressure level, - the at least one low-temperature expansion device for expanding the working fluid from the second loading pressure level to the loading outlet pressure level, and - the at least one low-temperature heat storage device for loading with low-temperature heat from the working fluid at the loading output pressure level.

[0085] The heat storage system, which can be operated or operated in two stages with regard to loading, can contribute in particular to increasing the energy density and overall efficiency. This allows the working fluid to be compressed to the second loading pressure level. Starting from the second loading pressure level, the working fluid (e.g., air) can be expanded to the initial loading pressure level in its wet steam region.

[0086] This liquefies the working fluid, allowing it to be stored in cryogenic tanks. This enables a compact heat storage system that can be installed at LNG terminals even when space is limited. Furthermore, the cryogenic technology used at the LNG terminal can be utilized with the appropriate infrastructure.

[0087] The heat storage system may further comprise a pre-heat exchanger, the primary side of which is arranged in the loading line system between the second high-temperature compression device and the at least one low-temperature expansion device.

[0088] Its secondary side can be arranged in the loading line system between the at least one high-temperature compression device and the at least one low-temperature heat storage device for preheating the working fluid on the secondary side by means of the working fluid on the primary side.

[0089] This pre-heat exchanger has the special feature that it can be flowed through by the working fluid on both the primary and secondary sides. Its arrangement takes advantage of the fact that its primary side is located between the second high-temperature compression device and the at least one low-temperature expansion device, so that high-temperature heat can be easily extracted at this point and fed upstream to the at least one high-temperature compression device. The pre-heat exchanger can thus preferably be designed as a recuperator.

[0090] Furthermore, it can be provided that the heat storage system has an ambient air heat exchanger, the primary side of which is arranged in the loading line system between the at least one low-temperature expansion device and the at least one low-temperature heat storage device.

[0091] Ambient air can flow through its secondary side to preheat the working fluid.

[0092] The ambient air heat exchanger provides an optional way to heat the working fluid before it enters the at least one low-temperature heat storage device. This heating can be particularly advantageous when not all of the low-temperature heat is required for charging.

[0093] Furthermore, a heat storage system that can be operated or operated in two stages can also be provided for discharge.

[0094] In this regard, a heat storage system may be provided whose discharge pipe system includes the following devices: - the at least one low-temperature heat storage device for discharging low-temperature heat to the working fluid at a discharge outlet pressure level, - the at least one low-temperature compression device for compressing the working fluid from the discharge outlet pressure level to a first, higher discharge pressure level, - a second low-temperature heat exchanger device for transferring low-temperature heat to the working fluid at the first discharge pressure level; - a second low-temperature compression device for compressing the working fluid from the first discharge pressure level to a second, higher discharge pressure level, - a second high-temperature heat storage device for discharging high-temperature heat to the working fluid at the second discharge pressure level, - a second high-temperature expansion device for expanding the working fluid from the second discharge pressure level to the first discharge pressure level, - the at least one high-temperature heat storage device for discharging high-temperature heat to the working fluid at the first discharge pressure level, and - the at least one high-temperature expansion device for expanding the working fluid from the first discharge pressure level to the discharge outlet pressure level.

[0095] All structural and functional features associated with the previously described two-stage heat storage system and its embodiments can also be included in the single-stage heat storage system, either alone or in combination, and the associated properties, configurations, and advantages can also be included and achieved accordingly.

[0096] The previously described single-stage heat storage system is preferably used in the megawatt power range.

[0097] Furthermore, the two-stage heat storage system described above is preferably used in the megawatt power range.

[0098] The at least one high-temperature compression and / or expansion device for compressing and / or expanding the working fluid, which is / are used in the previously described single-stage operable or operating heat storage system, can preferably be designed as a piston machine or piston machines.

[0099] The at least one low-temperature compression and / or expansion device for compressing and / or expanding the working fluid, which is / are used in the previously described single-stage operable or operating heat storage system, can preferably be designed as a piston machine or piston machines.

[0100] The at least one high-temperature compression and / or expansion device for compressing and / or expanding the working fluid, which is / are used in the previously described two-stage operable or operating heat storage system, can preferably be designed as a turbomachine or turbomachines.

[0101] The at least one low-temperature compression and / or expansion device for compressing and / or expanding the working fluid, which is / are used in the previously described two-stage operable or operating heat storage system, can preferably be designed as a turbomachine or turbomachines.

[0102] Furthermore, the present invention relates to a method for multi-stage, in particular two-stage, thermal loading of a heat storage system, in particular a cryogenic heat storage system, for converting electrical energy into stored thermal energy and / or for converting stored thermal energy into electrical energy.

[0103] This procedure includes the following steps: - compressing a working fluid from a loading initial pressure level to a first, higher loading pressure level by means of at least one high-temperature compression device; - loading at least one high-temperature heat storage device with high-temperature heat from the working fluid at the first loading pressure level; - compressing the working fluid from the first loading pressure level to a second, higher loading pressure level by means of a second high-temperature compression device; - loading a second high-temperature heat storage device with high-temperature heat from the working fluid at the second loading pressure level; - expanding the working fluid from the second loading pressure level to the loading outlet pressure level, in particular in the wet steam region of the working fluid, by means of at least one low-temperature expansion device; and - Loading at least one low-temperature heat storage device with low-temperature heat from the working fluid at the loading output pressure level.

[0104] All structural and functional features associated with the previously described heat storage system and its embodiments can also be included in the loading method according to the invention, either alone or in combination, and the associated properties, configurations and advantages can also be included and achieved accordingly.

[0105] In addition, the heat storage system described above may be configured to carry out the loading method described herein, and the loading method described herein may be designed to be executable by means of the heat storage system described above.

[0106] Furthermore, it can be provided that the method comprises a step such that after the compression of the working fluid from the first loading pressure level to the second loading pressure level, the working fluid is cooled by providing, in particular external, low-temperature heat to the working fluid at the second loading pressure level by at least one low-temperature / high-temperature heat storage device.

[0107] The external low-temperature heat can be provided, in particular, by the previously described LNG terminal. The low-temperature heat exchanger device can be integrated into the at least one low-temperature / high-temperature heat storage device and serve as an evaporator for the liquefied gas, in particular liquefied natural gas.

[0108] This means that this gas no longer needs to be gasified via heat exchangers using seawater, but rather using the process described above to operate the heat storage system. The previously unused low-temperature heat of the liquefied natural gas is no longer used to cool seawater, but rather to cool the working fluid, which improves the efficiency and utilization of the process.

[0109] Furthermore, it can be provided that the method comprises a step in which, after the compression of the working fluid from the initial loading pressure level to the first loading pressure level, the working fluid is heated by means of a heating device to the first loading pressure level.

[0110] The heating device can, as described above, comprise, for example, an electrical, in particular inductive, heating device.

[0111] The working medium heated by the heating device to the first loading pressure level can increase a maximum loading inlet temperature before loading the at least one high-temperature heat storage device.

[0112] This allows the at least one high-temperature heat storage device to absorb more high-temperature heat, increasing its storage capacity. The heating device can be optionally provided, or its operation can be optional. The heating device can be operated, in particular, depending on the electricity demand and the resulting electricity costs, for example, on the German electricity market.

[0113] Furthermore, the present invention relates to a method for multi-stage, in particular two-stage, thermal discharging of a heat storage system, in particular a cryogenic heat storage system, for converting electrical energy into stored thermal energy and / or for converting stored thermal energy into electrical energy.

[0114] This process includes the following steps: - discharging low-temperature heat from at least one low-temperature heat storage device to a working fluid at a discharge outlet pressure level; - compressing the working fluid from the discharge outlet pressure level to a first, higher discharge pressure level by means of at least one low-temperature compression device; - providing low-temperature heat from a second low-temperature-high-temperature heat storage device to the working fluid at the first discharge pressure level; - compressing the working fluid from the first discharge pressure level to a second, higher discharge pressure level by means of a second low-temperature compression device; - discharging high-temperature heat from a second high-temperature heat storage device to the working fluid at the second discharge pressure level; - expanding the working fluid from the second discharge pressure level to the first discharge pressure level by means of a second high-temperature expansion device; - discharging high-temperature heat from at least one high-temperature heat storage device to the working fluid at the first discharge pressure level; and - Relaxing the working fluid from the first discharge pressure level to the discharge outlet pressure level by means of at least one high-temperature expansion device

[0115] All structural and functional features associated with the previously described heat storage system and / or the loading method and their embodiments can also be included in the unloading method according to the invention, either alone or in combination, and the associated properties, configurations and advantages can also be included and achieved accordingly.

[0116] Furthermore, the heat storage system described above may be configured to carry out the discharge method described herein, and the discharge method described herein may be designed to be executable by means of the heat storage system described above.

[0117] Further preferred features and / or advantages of the present invention are the subject of the following description and the drawings of exemplary embodiments.

[0118] The drawings show: Fig. 1 a schematic representation of a heat storage system according to an exemplary embodiment of the prior art; Fig. 2 a schematic representation of a method for operating the heat storage system according to Fig. 1; Fig. 3 a schematic representation of a heat storage system, in particular a cryogenic heat storage system, according to an exemplary embodiment of the present invention; Fig. 4 a schematic representation of a method in a Ts diagram according to an exemplary embodiment of the present invention for operating the heat storage system according to Fig. 3; Fig. 5 is a schematic representation of a heat storage system, in particular a cryogenic heat storage system, according to another exemplary embodiment of the present invention; and Fig. 6 a schematic representation of a method in a Ts diagram according to another exemplary embodiment of the present invention for operating the heat storage system according to Fig. 5.

[0119] Identical or functionally equivalent elements or devices are provided with the same reference numerals in all figures.

[0120] Fig. 1 shows a schematic representation of a heat storage system 100 from the prior art.

[0121] The heat storage system 100 is configured and set up to convert electrical energy into stored thermal energy and to convert stored thermal energy into electrical energy.

[0122] The heat storage system 100 comprises a working fluid line system 102, a first heat storage device 104, a second heat storage device 106, and a first compression and / or expansion device 108 and a second compression and / or expansion device 110.

[0123] The first and second compression and / or expansion devices 108 are each coupled to an electric generator or drive motor 132.

[0124] Fig. 2 shows a schematic representation of a method for operating the heat storage system 100 from the prior art according to Fig. 1.

[0125] The heat storage system 100 from Fig. 1 can be operated and loaded with heat by means of a counterclockwise heat pump cycle along the states 1'' - 2 - 3 - 4 - 1'' of the working fluid in the Ts diagram.

[0126] In this case, the working fluid is compressed from atmospheric pressure (1 bar) from point 4 to point 3 to approximately 13 bar by means of the first compression and / or expansion device 108. The resulting compression heat (at over 800 °C) can be stored in the first heat storage device 104 or the first heat storage device 104 can be charged in this way.

[0127] The necessary compaction work can be provided by the electric drive motor 132.

[0128] In the opposite case, the heat storage system 100 can be Fig. 1 can be operated by means of a clockwise Joule-based heat process along the states 1' - 2' - 3' - 4' - 1' of the working fluid in the Ts diagram.

[0129] In this case, the heat stored in the first heat storage device 104 (previously by loading) (e.g. at over 800 °C) can be expanded from the pressure level of approximately 13 bar to 1 bar atmospheric pressure by means of the first compression and / or expansion device 108.

[0130] The expansion work converted in this way can be converted into electrical energy by the generator 132.

[0131] Fig. 3 shows a schematic representation of a heat storage system 100 according to an exemplary embodiment of the present invention.

[0132] The heat storage system 100 is configured and set up to convert electrical energy into stored thermal energy and to convert stored thermal energy into electrical energy.

[0133] The heat storage system 100 comprises a cryogenic heat storage system 100.

[0134] The cryogenic heat storage system 100 can be understood in such a way that the minimum temperature of the working fluid on the low-temperature side falls significantly below 0 °C.

[0135] Depending on the working fluid and the heat storage system 100 or low-temperature source used, the working fluid can have a temperature of, in particular, up to -192 °C. Preferably, the minimum temperature of the working fluid can be up to -164 °C.

[0136] The preferred working fluid is air, nitrogen or argon.

[0137] The heat storage system 100 comprises a working fluid line system 102 for flowing through a working fluid, wherein the working fluid line system 102 comprises a plurality of devices or a plurality of devices are arranged in the working fluid line system 102, as described below.

[0138] According to Fig. 3, the working fluid line system 102 comprises a high-temperature heat storage device 104 for loading with high-temperature heat from the working fluid.

[0139] Furthermore, the high-temperature heat storage device 104 is arranged or configured to discharge high-temperature heat to the working fluid.

[0140] The loading and unloading of the high-temperature heat takes place via a storage heat exchanger 128 coupled to the high-temperature heat storage device 104.

[0141] This storage heat exchanger 128 can be integrated into the high-temperature heat storage device 104.

[0142] In addition, the working fluid line system 102 comprises a low-temperature heat storage device 106 for loading with low-temperature heat from the working fluid.

[0143] Furthermore, the low-temperature heat storage device 106 is configured to discharge low-temperature heat to the working fluid.

[0144] The loading and unloading of the low-temperature heat takes place via a storage heat exchanger 130 connected to the low-temperature heat storage device 106.

[0145] This storage heat exchanger 130 can be integrated into the low-temperature heat storage device 106.

[0146] The high-temperature heat storage device 104 is to be distinguished from the low-temperature heat storage device 106 in that the discharge or loading of / with high-temperature heat takes place at a minimum working fluid temperature of greater than 0 °C.

[0147] Accordingly, the discharge or loading of / with low-temperature heat takes place at a maximum working fluid temperature of less than or equal to 0 °C.

[0148] The high-temperature heat storage device 104 may comprise a high-temperature solid heat storage device. Accordingly, the low-temperature heat storage device 106 may also comprise a solid heat storage device.

[0149] The working fluid line system 102 further comprises a high-temperature compression and expansion device 108 for compressing and expanding the working fluid at high temperature.

[0150] According to Fig. 3, the high-temperature compression and expansion device 108 is shown as a common or integral functional device 108 which performs both the compression and the expansion of the working fluid at high temperature.

[0151] Preferably, however, the high-temperature compression and expansion device 108 comprises a high-temperature compression device 108 and a separate high-temperature expansion device 108.

[0152] In the megawatt power range, the at least one high-temperature compression device 108 and the at least one high-temperature expansion device 108 can each have a piston engine.

[0153] According to Fig. 3, the high-temperature compression and expansion device 108 is mechanically coupled to an electric drive or generator device 132. During loading, the electric drive or generator device 132 serves as an electric drive motor, providing the necessary compressor work.

[0154] Accordingly, in the case of discharge, the electrical drive or generator device 132 serves as an electrical generator which converts the relaxation work into usable electrical energy.

[0155] This usable electrical energy can partially or completely cover the power requirements of the LNG terminal. This enables efficient and cost-effective site operation for the future supply of LNG.

[0156] The working fluid line system 102 also includes a low-temperature compression and expansion device 110 for compressing and expanding the working fluid at low temperature.

[0157] According to Fig. 3, the low-temperature compression and expansion device 110 is shown as a common or integral functional device 110 which performs both the compression and the expansion of the working fluid at low temperature.

[0158] Preferably, the low-temperature compression and expansion device 110 also comprises a low-temperature compression device 110 and a separate low-temperature expansion device 110.

[0159] In the megawatt power range, the at least one low-temperature compression device 110 and the at least one low-temperature expansion device 110 can each have a piston engine.

[0160] The high-temperature compression and expansion device 108 is designed to compress or expand the working fluid above a minimum working fluid temperature of greater than 0 °C.

[0161] Accordingly, the low-temperature compression and expansion device is designed to compress or expand the working fluid below a maximum working fluid temperature of less than or equal to 0 °C.

[0162] The working fluid line system 102 further comprises a low-temperature heat exchanger device 112 for transferring low-temperature heat to the working fluid.

[0163] The low-temperature heat exchanger device 112 is connected to an externally positioned low-temperature heat source 114.

[0164] The externally positioned low-temperature heat source 114 is positioned externally, e.g. outside the structural boundary of the heat storage system 100 or the working fluid piping system 102.

[0165] The low-temperature heat source 114 preferably comprises a liquid gas terminal.

[0166] The liquefied natural gas terminal preferably comprises a liquefied natural gas terminal for supplying liquefied natural gas from a liquefied natural gas tanker.

[0167] The connection of the low-temperature heat exchanger device 112 to the low-temperature heat source is a flow connection.

[0168] Thus, the low-temperature heat exchanger device 112 can be flowed through on the primary side with the working fluid and on the secondary side with liquefied gas, preferably with liquefied natural gas.

[0169] Additionally or alternatively, the low-temperature source may comprise a liquefied gas tanker.

[0170] The low-temperature heat exchanger device 112 is according to Fig. 3 is arranged in the working fluid line system 102 between the low-temperature compression and expansion device 110 and the high-temperature heat storage device 104.

[0171] The heat storage system 100 further comprises a heating device 116 for heating the working fluid with high-temperature heat.

[0172] The heating device 116 can preferably be designed as an electrical heating device 116.

[0173] The electrical heating device 116 can further preferably be designed as an inductive heating device 116.

[0174] Additionally or alternatively, the heating device 116 can be operated with fossil fuels (e.g. natural gas-based or petroleum-based fuels) or with hydrogen as fuel.

[0175] The heating device 116 is arranged in the working fluid line system 102 between the high-temperature compression and expansion device 108 and the high-temperature heat storage device 104.

[0176] In the working fluid line system 102, a high-temperature heat exchanger device 118 can be arranged between the high-temperature compression and expansion device 108 and the low-temperature heat storage device 106.

[0177] The latter can be connected to a high-temperature heat sink 120, which is also positioned externally.

[0178] The high-temperature heat sink 120 comprises a natural gas pyrolysis device, so that the high-temperature heat exchanger device 118 can be flowed through on the primary side with the working fluid and on the secondary side with gaseous natural gas, thereby preheating the gaseous natural gas.

[0179] Additionally or alternatively, an opening point 122 which is open to the atmosphere is arranged in the working fluid line system 102 between the high-temperature compression and expansion device 108 and the low-temperature heat storage device 106.

[0180] If the working fluid line system 102 has the opening point 122, this line system 122 is a so-called open line system, which is preferably operable by means of the working fluid air due to the atmospheric opening.

[0181] As an alternative to the high-temperature heat exchanger device 118, in an open line system 102, a connecting line (not shown) can be provided between the high-temperature compression and expansion device 108 and the low-temperature heat storage device 106. Fig. 3) and be connected directly to the external natural gas pyrolysis device 120.

[0182] If, however, the opening 122 is missing, this working fluid line system 102 is a so-called closed line system, which is separated from the atmosphere during normal operation. In this case, air, nitrogen, or argon can preferably be used as the working fluid.

[0183] The working fluid line system 102 has a loading line system 124 for loading the high-temperature heat storage device 104 with high-temperature heat from the working fluid and for loading the low-temperature heat storage device 106 with low-temperature heat from the working fluid.

[0184] Furthermore, the heat storage system 100 has a second working fluid line system 126, which has a discharge line system 126 for discharging high-temperature heat from the high-temperature heat storage device 104 to the working fluid and for discharging low-temperature heat from the low-temperature heat storage device 106 to the working fluid.

[0185] According to Fig. 3, the loading line system 124 and the unloading line system 126 are shown as a common working fluid line system 102.

[0186] Only the flow direction (represented by the arrows with dashed or solid lines) characterizes whether the working fluid line system 102 is configured as the loading line system 124 or the unloading line system 126.

[0187] Alternatively, it can be provided that the loading line system 124 and the discharging line system 126 are designed as separate or at least partially separate line systems.

[0188] The function of the heat storage system 100 will now be explained using the method according to the invention for operating the heat storage system 100 according to Fig. 4 explained in a Ts diagram.

[0189] Fig. 4 shows a schematic representation of a method according to an exemplary embodiment of the present invention for operating the heat storage system 100 according to Fig. 3.

[0190] The operation of the heat storage system 100 according to Fig. 3 includes the loading and unloading of the high-temperature heat storage device 104 and the low-temperature heat storage device 106, respectively.

[0191] The loading of the heat storage system 100 is based on a heat pump process, which is carried out in the Fig. 4 shown Ts diagram is shown by the enclosed dotted area in the Ts diagram.

[0192] To load the heat storage system 100, ie to convert electrical energy into stored thermal energy, the working fluid is compressed from a loading initial pressure level p1 (e.g. atmospheric pressure at 1 bar) to a first, higher loading pressure level p2 (at 15 bar) by means of the high-temperature compression device 108, starting from point 4.

[0193] As a result, the working fluid heats up from a first loading high temperature T4 (e.g. atmospheric temperature) to a second, higher loading high temperature T3, which is the maximum loading high temperature at over 300 °C.

[0194] The compression work required for this is provided by an electric drive motor 132 coupled to the high-temperature compression device 108.

[0195] Optionally, the working fluid can be heated by means of the heating device 116 at the first loading pressure level p2 to an even greater loading high temperature, so that more loading high temperature heat can be provided for storage.

[0196] The working fluid heated in this way to the second loading high temperature T3 (or the even higher loading high temperature) now flows into the high-temperature heat storage device 104 for its loading with high-temperature heat from the working fluid (at the first loading pressure level p2).

[0197] As a result, the working fluid cools down to the first loading pressure level p2, since the high-temperature heat is transferred to the high-temperature heat storage device 104 for its loading.

[0198] For this purpose, the high-temperature heat storage device 104 has a heat exchanger 128, which can be integrated into the high-temperature heat storage device 104.

[0199] The working fluid, which has transferred the high-temperature heat to the high-temperature heat storage device 104, now flows through the primary side of the low-temperature heat transfer device 112 at the first loading pressure level p2. As a result, further cooling occurs.

[0200] If cooling during loading is not desired, the low-temperature heat transfer device 112 can be bypassed via a bypass line. The working fluid now reaches its minimum temperature at the first loading pressure level p2.

[0201] The working fluid then flows through the low-temperature expansion device 110 and is expanded from the first loading pressure level p2 to the loading outlet pressure level p1, where the working fluid reaches the lowest loading temperature in absolute terms.

[0202] After leaving the low-temperature expansion device 110, the working fluid now flows into the low-temperature heat storage device 106 for its loading with low-temperature heat starting from the working fluid (at the loading outlet pressure level p1).

[0203] As a result, the working fluid is heated to the loading outlet pressure level p1, since the low-temperature heat is transferred to the low-temperature heat storage device 106 for its loading.

[0204] For this purpose, the low-temperature heat storage device 106 has a further heat exchanger 130, which can be integrated into the low-temperature heat storage device 106.

[0205] As a result of the flow through the additional heat exchanger 130 of the low-temperature heat storage device 106 at the loading outlet pressure level p1 (e.g., atmospheric pressure at 1 bar), the working fluid is heated to the first high-loading temperature T4 (e.g., atmospheric temperature). From there, the loading operation of the heat storage system 100 was started (as described above) and can now be cyclically restarted or continued.

[0206] The discharge of the heat storage system 100 is based on a Joule-based thermal power process, which is carried out in the Fig. 4 shown Ts diagram based on the corner points 1 - 2 - 2 cool- 3 - 0. The discharge process is represented by the enclosed hatched area in the Ts diagram.

[0207] To discharge the heat storage system 100, ie to convert stored thermal energy into electrical energy, the working fluid flows from point 0 through the heat exchanger 130 of the low-temperature heat storage device 106. Here, the low-temperature heat is discharged to the working fluid at a discharge output pressure level p1 (e.g. atmospheric pressure at 1 bar).

[0208] At the inlet of the heat exchanger 130, the working fluid has a first discharge high temperature T0 (e.g., atmospheric temperature).

[0209] As a result of the flow through the heat exchanger 130, the working fluid is cooled to a first discharge low temperature T1, since the stored low-temperature heat is released from the low-temperature heat storage device 106 to the working fluid for its discharge.

[0210] At the first low discharge temperature T1, the working fluid has the lowest discharge temperature in absolute terms.

[0211] The working fluid then flows through the low-temperature discharge compression device 110 and is compressed from the discharge outlet pressure level p1 to a first, higher discharge pressure level p2, where the working fluid reaches a second discharge low temperature T2.

[0212] The working fluid, which has absorbed the low-temperature heat from the low-temperature heat storage device 106, now flows through the primary side of the low-temperature heat transfer device 112 at the first discharge pressure level p2. As a result, further cooling occurs at the first discharge pressure level p2 to a low-discharge temperature T2. cooı which lies between the first and second discharge low temperatures T1, T2.

[0213] This is so high at the discharge temperature T2 cooı cooled working fluid now flows into the high-temperature heat storage device 104 for the discharge of high-temperature heat to the working fluid (at the first discharge pressure level p2).

[0214] As a result, the working fluid heats up to a second discharge high temperature T3 because the high temperature heat is transferred from the high temperature heat storage device 104 to the working fluid for its discharge.

[0215] For this purpose, the high-temperature heat storage device 104 has a heat exchanger 128, which can be integrated into the high-temperature heat storage device 104.

[0216] After leaving the high-temperature heat storage device 104, the working fluid can optionally flow through the heating device 116, whereby the working fluid can be heated to a maximum discharge high temperature. Alternatively, the heating device 116 can be bypassed by a bypass line if additional heating is not desired.

[0217] After flowing through the high-temperature heat storage device 104 or the heating device 116, the working fluid is introduced into the high-temperature discharge expansion device 108 at the first discharge pressure level p2 and the second discharge high temperature T3 or the maximum discharge high temperature. Therein, the working fluid is expanded back to the discharge outlet pressure level p1, where, after expansion, it again assumes the first discharge high temperature T0.

[0218] Optionally, the working fluid downstream of the high-temperature discharge expansion device 108 can additionally flow through the high-temperature heat exchanger device 118 (in particular if previously heated to the maximum discharge high temperature) and thus be cooled to the first discharge high temperature T0 by releasing high-temperature waste heat at the discharge outlet pressure level p1.

[0219] At the first high discharge temperature T0, the discharge operation of the heat storage system 100 was started (as described above) and can now be cyclically restarted or continued to operate.

[0220] The expansion work converted during the expansion is converted into usable electrical energy by an electrical generator 132 coupled to the high-temperature discharge expansion device.

[0221] Fig. 5 shows a schematic representation of a heat storage system 200 according to another exemplary embodiment of the present invention.

[0222] The heat storage system 200 according to Fig. 5 basically has the same or equivalent or corresponding structural and / or functional features as the heat storage system 100 according to Fig. 3 on.

[0223] However, heat storage system 100 is configured for single-stage operation, whereas heat storage system 200 is configured for two-stage operation. Additional equipment is required for this two-stage operation, which is described below.

[0224] The heat storage system 200 for operation using a two-stage process control is particularly advantageous in the megawatt power range.

[0225] In the megawatt power range, the at least one high-temperature compression device 108 and the at least one high-temperature expansion device 108 can each comprise a turbo and / or piston machine.

[0226] In the megawatt power range, the at least one low-temperature compression device 110 and the at least one low-temperature expansion device 110 can each comprise a turbo and / or piston machine.

[0227] How heat storage system includes according to Fig. 5 the loading line system 124, which in turn comprises the high-temperature compression device 108 for compressing the working fluid from a loading initial pressure level to a first, higher loading pressure level.

[0228] Furthermore, the loading line system 124 comprises the high-temperature heat storage device 104 for loading with high-temperature heat from the working fluid at the first loading pressure level.

[0229] The heating device 116 is also arranged between the high-temperature heat storage device 104 and the high-temperature compression device 108.

[0230] Furthermore, the loading line system 124 comprises a second high-temperature compression device 202 for compressing the working fluid from the first to a second, higher loading pressure level.

[0231] In addition, the loading line system 124 comprises a second high-temperature heat storage device 204 for loading with high-temperature heat from the working fluid at the second loading pressure level.

[0232] The second high-temperature heat storage device 204 preferably comprises a heat storage device for storing sensible heat.

[0233] Additionally or alternatively, the second high-temperature heat storage device 204 could also be designed as a latent heat storage device.

[0234] The second high-temperature heat storage device 204 comprises a first heat exchanger 218 for sensible heat transfer, a first salt heat storage device 220 and a first piping system 222 with an integrated pump 224.

[0235] Furthermore, the loading line system 124 comprises a low-temperature-high-temperature heat storage device 206 for providing low-temperature heat to the working fluid at the second loading pressure level.

[0236] The low-temperature / high-temperature heat storage device 206 comprises a high-temperature heat exchanger 226, a high-temperature heat storage 228, a low-temperature heat storage 230, and a low-temperature heat exchanger 232, which is arranged on the primary side in the loading line system 124.

[0237] In addition, this low-temperature heat exchanger 232 can be connected to the externally positioned low-temperature heat source 114 as described in Fig. 3 explained.

[0238] Through this connection, additional low-temperature heat provided by the external low-temperature source can be transferred to the working fluid via the low-temperature heat exchanger 232 for cooling purposes.

[0239] In addition, the loading line system 124 includes the low-temperature expansion device 110 for expanding the working fluid from the second loading pressure level to the loading outlet pressure level.

[0240] Furthermore, the loading line system 124 comprises the low-temperature heat storage device 106 for loading with low-temperature heat from the working fluid at the loading output pressure level.

[0241] The heat storage system 200 further comprises a pre-heat exchanger 208, the primary side of which is arranged in the loading line system 124 between the second high-temperature compression device 202 and the low-temperature expansion device 110.

[0242] Its secondary side, in turn, is arranged in the loading line system 124 between the high-temperature compression device 108 and the low-temperature heat storage device 106 for preheating the working fluid on the secondary side by means of the working fluid on the primary side.

[0243] The heat storage system 200 or the charging line system 124 further comprises an ambient air heat exchanger 210, the primary side of which is arranged in the charging line system 124 between the low-temperature expansion device 110 and the low-temperature heat storage device 106. Ambient air can flow through its secondary side to preheat the working fluid.

[0244] A second low-temperature / high-temperature heat storage device 212 is arranged between the low-temperature expansion device 110 and the ambient air heat exchanger 210.

[0245] The latter comprises a high-temperature heat exchanger 236, a high-temperature heat accumulator 238, a low-temperature heat accumulator 240 and a low-temperature heat exchanger 242.

[0246] The high-temperature heat exchanger 236 is arranged on the primary side in the loading line system 124 between the low-temperature expansion device 110 and the ambient air heat exchanger 210.

[0247] On the secondary side, the high-temperature heat exchanger 236 is fluidly connected to the high-temperature heat storage 238 and the low-temperature heat storage 240.

[0248] Between the low-temperature expansion device 110 and the second low-temperature-high-temperature heat storage device 212, a so-called cryogenic tank 244 is arranged for storing the (partially) liquid working fluid under cryogenic conditions.

[0249] A feed pump 246 is arranged between the cryogenic tank 244 and the second low-temperature-high-temperature heat storage device 212.

[0250] As mentioned above (e.g. in the description of Fig. 3), the heat storage system 200 has, in addition to the loading line system 124, also the discharge line system 126.

[0251] The discharge line system 126 is separate from the loading line system 124.

[0252] However, the discharge line system 126 is coupled to at least the loading line system 124 for mutual heat exchange with the following devices: high-temperature heat storage device 104, second high-temperature heat storage device 204, low-temperature high-temperature heat storage device 206, and second low-temperature high-temperature heat storage device 212.

[0253] The discharge line system 126 comprises according to Fig. 5 the low-temperature heat storage device 106 for discharging low-temperature heat to the working fluid at a discharge outlet pressure level.

[0254] Furthermore, the discharge line system 126 comprises the low-temperature compression device 110 for compressing the working fluid from the discharge outlet pressure level to a first, higher discharge pressure level.

[0255] Furthermore, the discharge line system 126 comprises the second low-temperature-high-temperature heat storage device 212 for providing or transferring low-temperature heat to the working fluid at the first discharge pressure level.

[0256] The low-temperature heat exchanger 242 is arranged on the primary side in the discharge line system 126 between the low-temperature compression device 110 and the low-temperature-high-temperature heat storage device 206.

[0257] On the secondary side, the low-temperature heat exchanger 242 is fluidly connected to the high-temperature heat storage 238 and the low-temperature heat storage 240.

[0258] In addition, the discharge line system 126 includes a second low-temperature compression device 214 for compressing the working fluid from the first discharge pressure level to a second, higher discharge pressure level.

[0259] Furthermore, the discharge line system 126 also partially comprises the second high-temperature heat storage device 204 for discharging high-temperature heat to the working fluid at the second discharge pressure level.

[0260] The second high-temperature heat storage device 204 comprises a second heat exchanger 248 for sensible heat transfer, a second salt heat storage device 250 and a second pipe system 252 with an integrated pump 254.

[0261] The second high-temperature heat storage device 204 is according to Fig. 5 both a partial component of the discharge line system 126 (by means of its second heat exchanger 248 for sensible heat transfer) and a partial component of the loading line system 124 (by means of its first heat exchanger 218 for sensible heat transfer).

[0262] Furthermore, the discharge line system 126 comprises a second high-temperature expansion device 216 for expanding the working fluid from the second discharge pressure level to the first discharge pressure level.

[0263] The second high-temperature expansion device 216 is mechanically coupled to the low-temperature compression device 110 via a shaft 234 and serves to drive it.

[0264] In addition, the discharge line system 126 includes the high-temperature heat storage device 104 for discharging high-temperature heat to the working fluid at the first discharge pressure level.

[0265] In addition, the discharge line system 126 includes the high-temperature expansion device 108 for expanding the working fluid from the first discharge pressure level to the discharge outlet pressure level.

[0266] The high-temperature expansion device 108 is according to Fig. 5 is coupled to the electrical generator 132, which converts the relaxation work into usable electrical energy.

[0267] This electrical energy can partially or completely cover the power requirements of the LNG terminal. This will enable efficient and cost-effective site operation for the future supply of LNG.

[0268] Fig. 6 shows a schematic representation of a method in a Ts diagram according to another exemplary embodiment of the present invention for operating the heat storage system according to Fig. 5.

[0269] The operation of the heat storage system 200 according to Fig. 5 includes the loading and unloading of, in particular, the high-temperature heat storage device 104 and the low-temperature heat storage device 106.

[0270] The loading of the heat storage system 200 is based on a two-stage heat pump process, which is carried out in the Fig. 6 shown Ts diagram using the enclosed dotted area.

[0271] To load the heat storage system 200, i.e. to convert electrical energy into stored thermal energy, the working fluid is compressed from a loading initial pressure level p1 (1 bar) to a first, higher loading pressure level p2 (10 bar) by means of the high-temperature compression device 108.

[0272] After compressing the working fluid from the loading initial pressure level p1 to the first loading pressure level p2, the working fluid can optionally be heated to the first loading pressure level p2 by means of the heating device 116.

[0273] In a further step, the high-temperature heat storage device 104 is loaded with high-temperature heat starting from the working fluid at the first loading pressure level p2.

[0274] In a further step, the working fluid is compressed from the first loading pressure level p2 to a second, higher loading pressure level p4 (80 bar) by means of the second high-temperature compression device 202.

[0275] In a further step, the second high-temperature heat storage device 204 is loaded with high-temperature heat starting from the working fluid at the second loading pressure level p4.

[0276] Here, the working fluid flows into the first heat exchanger 218 for sensible heat transfer, so that the second salt heat storage unit 250 (secondary side) is loaded with high-temperature heat starting from the working fluid at the third loading pressure level p4 (primary side).

[0277] The working fluid then flows into the pre-heat exchanger 208, whereby high-temperature heat is transferred to its secondary side and serves to heat the working fluid before it enters the high-temperature compression device 108.

[0278] Downstream of the pre-heat exchanger 208, the first low-temperature-high-temperature heat storage device 206 is arranged, the low-temperature heat exchanger 232 of which transfers low-temperature heat from the low-temperature heat storage device 230 to the working fluid for its further cooling.

[0279] The pre-heat exchanger 208 is preferably designed as a recuperator.

[0280] By means of the low-temperature heat exchanger 232, after compressing the working fluid from the first loading pressure level p2 to the second loading pressure level p4, the working fluid can optionally be cooled by transferring external low-temperature heat (from the LNG terminal) to the working fluid at the second loading pressure level p4.

[0281] In a further step, the working fluid is expanded from the second loading pressure level p4 to the loading outlet pressure level p1 in the wet steam region of the working fluid by means of the low-temperature expansion device 110.

[0282] The working medium liquefied in this way is then temporarily stored in a cryogenic tank 244 arranged downstream of the low-temperature expansion device 110 and is then sucked in by a feed pump 246 and fed to the second low-temperature / high-temperature heat storage device 212.

[0283] As a result of the flow through its high-temperature heat exchanger 236, a high-temperature heat transfer to the working fluid takes place to heat it to the loading outlet pressure level p1.

[0284] Since the working fluid is still in the partially liquid phase, this heating occurs at constant temperature by absorbing heat of vaporization with increasing specific entropy (see horizontal curve in the Ts diagram).

[0285] The working fluid then optionally flows through an ambient air heat exchanger 210, which is used when not all of the low-temperature heat still available is needed to charge the low-temperature heat storage device 106.

[0286] Accordingly, in a next step, the low-temperature heat storage device 106 is loaded with low-temperature heat starting from the working fluid at the loading initial pressure level p1.

[0287] After the low-temperature heat storage device 106 has been loaded with low-temperature heat, the working fluid has returned to the starting point (e.g., atmospheric temperature at 1 bar atmospheric pressure) at which the loading operation of the heat storage system 200 (as described above) was started and can now be cyclically restarted or continued to operate.

[0288] The discharge of the heat storage system 200 is based on a two-stage Joule thermal power process, which is carried out in the Fig. 6 shown Ts diagram is shown by the enclosed hatched area.

[0289] To discharge the heat storage system 200, i.e., to convert stored thermal energy into electrical energy, the method first comprises discharging low-temperature heat from the low-temperature heat storage device 106 to a working fluid at a discharge outlet pressure level p1 (1 bar).

[0290] In a further step, the working fluid is compressed from the discharge outlet pressure level p1 to a first, higher discharge pressure level p3 (20 bar) by means of the low-temperature compression device 110.

[0291] In a further step, low-temperature heat is provided from the second low-temperature / high-temperature heat storage device 212 to the working fluid at the first discharge pressure level p3. For this purpose, the working fluid flows through the low-temperature heat exchanger 242.

[0292] As a result of the flow through the low-temperature heat exchanger 242, low-temperature heat is transferred or provided to the working fluid for cooling it to the first discharge pressure level p3.

[0293] Since the working fluid is still in the partially liquid phase, this cooling occurs at constant temperature (within the wet steam region) by absorbing condensation heat with decreasing specific entropy.

[0294] In a further step, the working fluid is compressed from the first discharge pressure level p3 to a second, higher discharge pressure level p5 (100 bar) by means of a second low-temperature compression device 214 (also referred to as a cryo-pump).

[0295] Further downstream, the working fluid then flows through the high-temperature heat exchanger 226 of the first high-temperature-low-temperature heat storage device 206.

[0296] As a result of the flow through the high-temperature heat exchanger 226, a high-temperature heat transfer to the working fluid takes place to heat it to the second discharge pressure level p5.

[0297] In a further step, high-temperature heat is discharged from the second high-temperature heat storage device 204 to the working fluid at the second discharge pressure level p5.

[0298] Here, the working fluid flows through the second heat exchanger 248 for sensible heat transfer of the second high-temperature heat storage device 204, so that high-temperature heat is discharged from the second salt heat storage device 250 to the working fluid at the second discharge pressure level p5. As a result, the working fluid reaches its highest temperature at the second discharge pressure level p5.

[0299] This highest temperature is preferably in a range of approximately 500 °C to approximately 600 °C.

[0300] After leaving the second heat exchanger 248 for sensible heat transfer, the cooled liquid salt now flows back into the first salt heat storage unit 220, from where the liquid salt is fed to the first heat exchanger 218 for sensible heat transfer for recharging.

[0301] In a further step, the working fluid is then expanded from the second discharge pressure level p5 to the first discharge pressure level p3 by means of a second high-temperature expansion device 216.

[0302] In a further step, high-temperature heat is discharged from the high-temperature heat storage device 104 to the working fluid at the first discharge pressure level p3. After this discharge, the working fluid reaches its absolute maximum discharge temperature, which can be greater than approximately 500°C to approximately 600°C without the optional heating device 116 and approximately 700°C to approximately 1000°C with heating by the heating device 116.

[0303] In a further step, the working fluid is now expanded from the first discharge pressure level p3 to the discharge outlet pressure level p1 by means of the high-temperature expansion device 108.

[0304] The high-temperature expansion device 108 is mechanically or rotationally fixedly coupled to the generator 132.

[0305] Accordingly, the electrical generator 132 serves to convert the relaxation work into usable electrical energy.

[0306] Downstream of the high-temperature expansion device 108, the discharge line system 126 may optionally have an opening point 122.

[0307] As a result, the residual heat contained in the working fluid after expansion to the discharge outlet pressure level p1 (depending on the process control, the working fluid can still have a temperature of approximately 100 to approximately 200 °C without the use of an optional heating device 116 and approximately 300 °C to approximately 800 °C with heating by the heating device 116) can be fed either via a corresponding line to an external pyrolysis device.

[0308] Alternatively, the discharge line system 126 can be a closed line system, so that instead of the opening point, the high-temperature heat exchanger device 118 (cf. Fig. 3) is arranged between the low-temperature heat storage device 106 and the high-temperature expansion device 108.

[0309] In this case, the high-temperature heat exchanger device 118 provides high-temperature residual heat for the external pyrolysis device.

[0310] The opening to the atmosphere has the fundamental advantage that it serves as a heat sink, so that a heat exchanger for process cooling is not required at this point.

[0311] Since the production of so-called turquoise hydrogen requires heat, this heat can be provided from the heat storage system 200 in the form of waste or residual heat in order to increase the overall efficiency (utilization rate) of both the heat storage process described above for operating the heat storage system 200 and the hydrogen production process by means of pyrolysis.

[0312] Thereafter, the working fluid is fed back to the low-temperature heat storage device 106 and the previously described discharge process begins again.

[0313] It is understood that all structural and functional features associated with the heat storage systems 100, 200 of Fig. 3 and Fig. 5, also in the proceedings under Fig. 4 and Fig. 6 may be included either alone or in combination and the associated features, characteristics and advantages may also be included and achieved accordingly.

[0314] In addition, it should be understood that the heat storage system 100 according to Fig. 3 can be configured to Fig. 4 described procedures or that the heat storage system 200 is in accordance with Fig. 5 can be configured to Fig. 6 described procedures and that the procedures described herein in accordance Fig. 4 and Fig. 6 can be designed to be executable by means of the heat storage system 100 and / or heat storage system 200. List of reference symbols 100 heat storage system 102 Working fluid line system 104 High-temperature heat storage device 106 Low-temperature heat storage device 108 High-temperature compression and / or expansion device 110 Low-temperature compression and / or expansion device 112 Low-temperature heat exchanger device 114 Low-temperature heat source 116 Heating device 118 High-temperature heat exchanger device 120 high-temperature heat sink 122 opening point 124 Loading line system 126 Discharge line system 128 heat exchangers 130 heat exchangers 132 electrical drive or generator device 200 heat storage system 202 second high-temperature compression device 204 second high-temperature heat storage device 206 Low-temperature-high-temperature heat storage device 208 Pre-heat exchanger 210 Ambient air heat exchanger 212 second low-temperature-high-temperature heat storage device 214 second low-temperature compression device 216 second high-temperature expansion device 218 first heat exchanger for sensible heat transfer 220 first salt heat storage 222 first pipeline system 224 integrated pump 226 high-temperature heat exchangers 228 high-temperature heat storage 230 low-temperature heat storage units 232 low-temperature heat exchangers 234 Wave 236 high-temperature heat exchangers 238 high-temperature heat storage 240 low-temperature heat storage units 242 low-temperature heat exchangers 244 Cryotank 246 Feed pump 248 second heat exchanger for sensible heat transfer 250 second salt heat storage 252 second pipeline system 254 integrated pump QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2020 110 560 A1

[0005] WO 2020239288 A1

[0006] EP 2 729 404 A2

[0007] US 2009 / 0282840 A1

[0008]

Claims

[1] Heat storage system (100), in particular a cryogenic heat storage system (100), for converting electrical energy into stored thermal energy and / or for converting stored thermal energy into electrical energy, comprising at least one working fluid line system (102) for the flow of a working fluid, wherein the at least one working fluid line system (102) comprises the following devices: - at least one high-temperature heat storage device (104) for loading and / or discharging high-temperature heat from / to the working fluid, - at least one low-temperature heat storage device (106) for loading and / or unloading with / from low-temperature heat from / to the working fluid, - at least one high-temperature compression and / or expansion device (108) for compressing and / or expanding the working fluid, - at least one low-temperature compression and / or expansion device (110) for compressing and / or expanding the working fluid, and - at least one low-temperature heat exchanger device (112) for transferring low-temperature heat to the working fluid; wherein the at least one low-temperature heat exchanger device (112) is connected or connectable to a low-temperature heat source (114), in particular an externally positioned one. [2] Heat storage system (100) according to claim 1, characterized by in that the low-temperature heat source (114) comprises a liquefied gas terminal and / or a liquefied gas tanker, so that the at least one low-temperature heat exchanger device (112) can be flowed through on the primary side with the working fluid and on the secondary side with liquefied gas. [3] Heat storage system (100) according to claim 1 or claim 2, characterized bythat the at least one low-temperature heat exchanger device (112) is arranged in the at least one working fluid line system (102) between the at least one low-temperature compression and / or expansion device (110) and the at least one high-temperature heat storage device (104). [4] Heat storage system (100) according to one of claims 1 to 3, characterized by that the heat storage system (100) comprises a heating device (116), in particular an electric one, for heating the working fluid with high-temperature heat, which is arranged in particular in the at least one working fluid line system (102) between the at least one high-temperature compression and / or expansion device (108) and the at least one high-temperature heat storage device (104). [5] Heat storage system (100) according to one of the preceding claims, characterized byin that in the at least one working fluid line system (102) between the at least one high-temperature compression and / or expansion device (108) and the at least one low-temperature heat storage device (106) at least one high-temperature heat exchanger device (118) is arranged, which is connected or connectable to a, in particular externally positioned, high-temperature heat sink (120), and / or wherein in the at least one working fluid line system (102) between the at least one high-temperature compression and / or expansion device (108) and the at least one low-temperature heat storage device (106) an opening point (122) is arranged, which is open to the atmosphere. [6] Heat storage system (100) according to claim 5, characterized byin that the high-temperature heat sink (120) comprises a natural gas pyrolysis device, so that the at least one high-temperature heat exchanger device (118) can be flowed through on the primary side with the working fluid and on the secondary side with gaseous natural gas and thus the gaseous natural gas can be preheated. [7] Heat storage system (100) according to one of the preceding claims, characterized byin that the at least one working fluid line system (102) has a loading line system (124) for loading the at least one high-temperature heat storage device (104) with high-temperature heat from the working fluid and for loading the at least one low-temperature heat storage device (106) with low-temperature heat from the working fluid, and / or wherein the heat storage system (100) has a second working fluid line system (126) which has a discharge line system (126) for discharging high-temperature heat from the at least one high-temperature heat storage device (104) to the working fluid and for discharging low-temperature heat from the at least one low-temperature heat storage device (106) to the working fluid. [8] Heat storage system (200) according to claim 7, characterized by that the loading line system (124) comprises the following devices: - the at least one high-temperature compression device (108) for compressing the working fluid from a loading initial pressure level to a first, higher loading pressure level, - the at least one high-temperature heat storage device (104) for loading with high-temperature heat from the working fluid at the first loading pressure level, - a second high-temperature compression device (202) for compressing the working fluid from the first to a second, higher loading pressure level, - a second high-temperature heat storage device (204) for loading with high-temperature heat from the working fluid at the second loading pressure level, - at least one low-temperature / high-temperature heat storage device (206) for providing low-temperature heat to the working fluid at the second loading pressure level, - the at least one low-temperature expansion device (110) for expanding the working fluid from the second loading pressure level to the loading output pressure level, and - the at least one low-temperature heat storage device (106) for loading with low-temperature heat from the working fluid at the loading output pressure level. [9] Heat storage system (200) according to claim 7 or claim 8, characterized byin that the heat storage system (200) has a pre-heat exchanger (208), the primary side of which is arranged in the loading line system (124) between the second high-temperature compression device (202) and the at least one low-temperature expansion device (110), and the secondary side of which is arranged in the loading line system (124) between the at least one high-temperature compression device (108) and the at least one low-temperature heat storage device (106) for preheating the working fluid on the secondary side by means of the working fluid on the primary side. [10] Heat storage system (200) according to claim 8 or claim 9, characterized byin that the heat storage system (200) has an ambient air heat exchanger (210), the primary side of which is arranged in the loading line system (124) between the at least one low-temperature expansion device (110) and the at least one low-temperature heat storage device (106), and wherein the secondary side of which can be flowed through by ambient air for preheating the working fluid. [11] Heat storage system (200) according to claim 7, characterized by that the discharge line system (126) comprises the following devices: - the at least one low-temperature heat storage device (106) for discharging low-temperature heat to the working fluid at a discharge outlet pressure level, - the at least one low-temperature compression device (110) for compressing the working fluid from the discharge outlet pressure level to a first, higher discharge pressure level, - a second low-temperature-high-temperature heat storage device (212) for providing low-temperature heat to the working fluid at the first discharge pressure level; - a second low-temperature compression device (214) for compressing the working fluid from the first discharge pressure level to a second, higher discharge pressure level, - a second high-temperature heat storage device (204) for discharging high-temperature heat to the working fluid at the second discharge pressure level, - a second high-temperature expansion device (216) for expanding the working fluid from the second discharge pressure level to the first discharge pressure level, - the at least one high-temperature heat storage device (104) for discharging high-temperature heat to the working fluid at the first discharge pressure level, and - the at least one high-temperature expansion device (108) for expanding the working fluid from the first discharge pressure level to the discharge output pressure level. [12] Method for multi-stage, in particular two-stage, thermal loading of a heat storage system (200), in particular a cryogenic heat storage system (200), for converting electrical energy into stored thermal energy and / or for converting stored thermal energy into electrical energy, comprising the following steps: - compressing a working fluid from a loading initial pressure level to a first, higher loading pressure level by means of at least one high-temperature compression device (108); - loading at least one high-temperature heat storage device (104) with high-temperature heat from the working fluid at the first loading pressure level; - compressing the working fluid from the first loading pressure level to a second, higher loading pressure level by means of a second high-temperature compression device (202); - loading a second high-temperature heat storage device (204) with high-temperature heat from the working fluid at the second loading pressure level; - expanding the working fluid from the second loading pressure level to the loading outlet pressure level, in particular in the wet steam region of the working fluid, by means of at least one low-temperature expansion device (110); and - loading at least one low-temperature heat storage device (106) with low-temperature heat from the working fluid at the loading output pressure level. [13] Method according to claim 12, characterized bythat after the compression of the working fluid from the first loading pressure level to the second loading pressure level, the working fluid is cooled by providing, in particular external, low-temperature heat to the working fluid at the second loading pressure level by at least one low-temperature / high-temperature heat storage device (206). [14] Method according to claim 12 or claim 13, characterized by that after the compression of the working fluid from the initial loading pressure level to the first loading pressure level, the working fluid is heated to the first loading pressure level by means of a heating device (116), in particular an electric one. [15] Method for multi-stage, in particular two-stage, thermal discharge of a heat storage system (200), in particular a cryogenic heat storage system (200), for converting electrical energy into stored thermal energy and / or for converting stored thermal energy into electrical energy, comprising the following steps: - discharging low-temperature heat from at least one low-temperature heat storage device (106) to a working fluid at a discharge outlet pressure level; - compressing the working fluid from the discharge outlet pressure level to a first, higher discharge pressure level by means of at least one low-temperature compression device (110); - providing low-temperature heat from a second low-temperature-high-temperature heat storage device (212) to the working fluid at the first discharge pressure level; - compressing the working fluid from the first discharge pressure level to a second, higher discharge pressure level by means of a second low-temperature compression device (214); - discharging high-temperature heat from a second high-temperature heat storage device (204) to the working fluid at the second discharge pressure level; - expanding the working fluid from the second discharge pressure level to the first discharge pressure level by means of a second high-temperature expansion device (216); - discharging high-temperature heat from at least one high-temperature heat storage device (104) to the working fluid at the first discharge pressure level; and - Relaxing the working fluid from the first discharge pressure level to the discharge outlet pressure level by means of at least one high-temperature expansion device (108).

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