Method and device for preheating process gas

Abstract

The invention provides an energy recovery subsystem (10) for a cryogenic energy storage system (1), comprising: an evaporator (14); a first heat exchanger (21) for transferring thermal energy from the heat transfer fluid (6) to the working fluid (5); one or more expansion stages (30) for extracting work from the working fluid (5); a regenerator (40) for transferring thermal energy from the working fluid (5) to the working fluid (5); a first conduit arrangement (100) for conveying a working fluid (5); a second conduit arrangement (200) connectable to the thermal energy storage device (TESD) (3) and to the first heat exchanger (21) for conveying a heat transfer fluid (6); the first piping arrangement (100) sequentially connects the evaporator (14), the regenerator (40), the first heat exchanger (21), and reconnects the regenerator (40) and the one or more expansion stages (30).

Description

Technical Field

[0001] This invention relates to cryogenic energy storage systems and their operating methods, and particularly to energy recovery methods and their subsystems. Background Technology

[0002] Transmission and distribution networks (or power grids) must balance generation with consumer demand. This is typically achieved by regulating the generation side (supply side) and operating some power plants at reduced loads by turning them on and off. Balancing the supply side in this way incurs efficiency losses, as most existing thermal and nuclear power plants are most efficient when operating continuously at full load. The anticipated introduction of significant amounts of intermittent renewable energy generation capacity (such as wind turbines and solar collectors) into the grid will further complicate grid balancing by introducing uncertainty into the availability of some generation sources. Effective methods for storing energy generated during periods of low demand for later use during periods of high demand or when intermittent generators are operating at low output will be highly beneficial for balancing the grid and ensuring supply security.

[0003] There are many emerging and existing energy storage methods on the market, including cryogenic storage, pumped hydro storage, compressed air storage, and chemical batteries. Such energy storage devices have three operational phases: charging, storage, and release. During periods of low demand, excess energy from the grid is used to charge the energy storage device. Energy is stored by the energy storage device in its respective medium, such as cryogenic fluids, the reservoir of a hydroelectric dam, or the internal chemical potential of a battery. During periods of high demand, this energy is released back into the grid to ensure that demand is met.

[0004] Cryogenic energy storage (CES) technology, which uses refrigerants such as liquid air, has many advantages over other available energy storage technologies. The refrigerant is a liquefied gas. Due to the physical properties of the refrigerant, CES systems are typically energy-intensive, highly locationable (because they use relatively small storage tanks and are not geographically restricted), environmentally friendly (because the working principle of CES systems does not involve the use or production of hazardous substances, such as those found in most batteries, nor does it involve the generation of carbon emissions), and relatively inexpensive (because they can utilize equipment that has been used for many years in the liquefied natural gas industry).

[0005] CES technology liquefies air or other suitable gases from the external environment and stores them at low pressure, which can then be vaporized and used to drive turbines to generate electricity. During the charging or liquefaction phase of a CES system, low-cost electricity generated during periods of low demand (off-peak) or when there is an oversupply of intermittent renewable energy is used to compress, cool, purify, and liquefy gases, such as ambient air, in units or subsystems. Two compressors are commonly used in the liquefaction process. The airflow is first compressed to approximately 15 to 20 barA in the main air compressor (MAC), then purified in an air purification unit (APU) and compressed to approximately 55 to 65 barA in a second circulating air compressor (RAC). This flow can then enter a cooling and liquefaction system, commonly referred to as a cold box. The cold box is typically implemented as an insulated (usually metal) box filled with high-performance insulation materials such as perlite. The cryogenic heat exchange process occurs within the cold box via components such as a multi-channel heat exchanger, a phase separator, and at least one expansion turbine stage and / or valves. The gas is cooled in the cold box until it essentially condenses into a liquid. Liquid products are separated from the gas and transferred from the cold box to a cryogenic storage tank, where they are stored for later use. The gas can be returned via a multi-pass heat exchanger to cool the initial incoming airflow, and then passed through to replenish the airflow upstream of the circulating air compressor for further liquefaction. Liquid products, such as liquefied air or refrigerant, are stored in the tank during the storage phase. In the energy release or recovery phase, the liquid products are released into an energy recovery unit or subsystem, where they are pressurized, vaporized, and heated to drive one or more expansion stages as part of one or more expansion turbines, thereby driving a generator and producing electricity. The energy release or recovery phase typically occurs during peak electricity prices. CES technology relies on the thermodynamic energy potential between cryogenic liquid air and gaseous air at or above ambient temperature. A CES system can perform various operations in both the charging and releasing phases simultaneously.

[0006] The pressurized gas flow to be liquefied in the liquefaction subsystem and the pressurized refrigerant or liquefied gas in the energy recovery subsystem are typically designated as the "process flow of the liquefaction subsystem" and the "working fluid of the energy recovery subsystem," respectively.

[0007] The round-trip efficiency of a CES system is simply defined as the ratio of the net electrical energy output measured during the entire discharge cycle to the net electrical energy input measured during the charging cycle. In a CES system, the heat generated by the electrical input should be captured and reused to maintain high round-trip efficiency; any uncaptured and unused heat may eventually dissipate into the environment, negatively impacting round-trip efficiency.

[0008] For example, in a liquefaction process, the process fluid is compressed, cooled, and then expanded. This process is repeated continuously, with each compression increasing the temperature of the process fluid and each cooling and expansion significantly decreasing its temperature until the process fluid is completely liquefied. The term "heat of compression" refers to the thermal energy contained within a fluid during compression. In other words, "heat of compression" refers to the temperature rise of a fluid due to compression. In this document, when heat is described as being "transferred" from one location, fluid, or component to another, it refers to the process of transferring thermal energy between two locations, fluids, or components. The methods of transfer can include any typical transfer mechanism, such as conduction, convection, or radiation, or any combination thereof, as will be apparent to those skilled in the art.

[0009] A CES system can utilize an energy capture subsystem designed to capture the heat of compression of the process fluid generated in the liquefaction subsystem during the liquefaction phase and store it in one or more thermal energy storage devices (TESDs). During the energy recovery phase, such a CES system can release the captured heat into the working fluid in the energy recovery subsystem. These subsystems are also collectively referred to as compression heat cycle systems or energy cycle subsystems.

[0010] Refrigerants such as liquid air are stored in a smaller volume than their gaseous state. In the energy recovery phase, the refrigerant is pumped from a cryogenic tank as a working fluid, then vaporized, heated, and expanded through a series of staggered or alternating heat exchangers and expansion stages. The vaporization of the working fluid produces a low-pressure gas at an extremely low temperature, with a volume much larger than the refrigerant, and it expands further during the heating process. As the working fluid is heated and expanded by the expansion turbine, it does work to drive the turbine, thereby reducing the temperature and pressure of the working fluid. The turbine can be connected to a power source such as a generator, which then generates electricity and feeds it into the grid. Increasing the temperature of the working fluid increases its pressure, thus correspondingly increasing the energy required to drive the expansion turbine. This allows the turbine to extract more energy from the hotter working fluid and rotate at a faster speed and / or with greater torque, thereby increasing the power output of the energy recovery subsystem during the energy recovery phase and improving the round-trip efficiency of the CES system. The heat of compression released during the liquefaction phase is captured by the energy capture subsystem and can be used to increase the temperature of the working fluid in the energy recovery subsystem before it expands.

[0011] In the energy recovery subsystem, heat of compression is transferred from the process fluid of the liquefaction subsystem to at least one thermal energy storage device (TESD) in the energy recovery subsystem. A heat exchanger located downstream of the compressor in the liquefaction subsystem transfers heat from the process fluid to a heat transfer fluid (HTF), which then transfers the heat to the one or more TESDs. Heat of compression is transferred from the at least one TESD to the working fluid of the energy recovery subsystem via the heat transfer fluid (HTF) or via a second separate HTF, through heat exchangers staggered with the expansion stage. The heat transfer fluid used in the TESD depends on the temperature or mass of the heat energy captured by the TESD. For example, at lower temperatures or ambient temperatures, water, water-glycol mixtures, and heat transfer oils can be used. At higher temperatures, molten salts, such as molten nitrates, can be used. Molten salts have advantages such as high heat capacity, high boiling point, good stability, low toxicity, non-flammability, and low cost. The higher the mass of the heat energy, the higher the temperature.

[0012] Energy cycle subsystems designed to store high-quality thermal energy typically use high-melting-point heat transfer fluids (HTFs) with melting points well above ambient temperature to store and / or transfer heat of compression. Some fluids can be used simultaneously as both heat transfer fluids and heat storage media within the same energy cycle subsystem. Molten salt is one such fluid. The freezing point of molten salt depends on the type and proportion of salt used. Molten salts suitable for CES systems typically freeze at around 130°C, with a safe operating temperature above approximately 150°C. The safe operating temperature refers to the temperature at which crystals will not form in the salt and includes a safety margin acceptable to operators or engineers running the CES system. The high freezing point of HTFs presents a challenge because the temperature of recently vaporized refrigerant or working fluid may be much lower than the freezing point of the HTF, which could cause the HTF to solidify or crystallize in the heat exchanger.

[0013] In a known energy recovery subsystem, a pump delivers the working fluid from a cryogenic tank through an evaporator to an expansion turbine. To increase the temperature of the working fluid and improve turbine efficiency, the working fluid can be fed into a gas-molten salt heat exchanger located between the evaporator and the expansion turbine. The working fluid exiting the evaporator is at approximately ambient temperature, or 20°C. Because the freezing point of molten salt is higher than that of the process air stream exiting the evaporator, there is a risk of molten salt solidifying in this heat exchanger over time. This risk is even higher during system startup, as the system or heat exchanger has not yet reached its operating temperature.

[0014] Molten salt solidification can lead to production losses and potentially catastrophic equipment failure. Once HTF (such as molten salt) solidifies, the entire CES system may need to be shut down for maintenance and inspection. The piping and heat exchangers through which the working fluid and HTF flow are typically under high pressure, so even minor damage can pose a safety hazard. Scale buildup in heat exchangers, common in commercial CES power plants, is difficult to remove and may necessitate complete replacement of the heat exchanger due to the challenge of assessing the extent of damage and its safety implications. Such maintenance can take weeks or even months. Summary of the Invention

[0015] Various aspects and / or embodiments of the present invention are intended to address the problem of heat transfer fluid (HTF) solidification or crystallization, thereby providing a more robust energy recovery subsystem and reducing the risk of HTF freezing or crystallization in pipes or heat exchangers along the HTF flow path.

[0016] According to a first aspect, the present invention provides an energy recovery subsystem for a cryogenic energy storage system (CES), comprising: a pump for conveying a working fluid; an evaporator; and one or more heat exchangers, including a first heat exchanger for transferring thermal energy from a heat transfer fluid to the working fluid;

[0017] One or more expansion stages for extracting work from the working fluid; a regenerator for transferring heat from the working fluid to the working fluid; a first piping arrangement for conveying the working fluid; and a second piping arrangement, which may be connected to a thermal energy storage device (TESD) and to a first heat exchanger for conveying the heat transfer fluid.

[0018] A first piping arrangement has an upstream end and a downstream end that can be connected to a working fluid source. The first piping arrangement is sequentially connected from the upstream end to an evaporator, a regenerator, a first heat exchanger, another regenerator, and one or more expansion stages.

[0019] Advantageously, the regenerator transfers the heat of the working fluid that has already flowed through the first heat exchanger to the working fluid upstream of the first heat exchanger, thereby increasing the temperature of the working fluid entering the first heat exchanger and reducing the likelihood of HTF solidification in the first heat exchanger.

[0020] Optionally, the regenerator has a first input terminal, a first output terminal, a second input terminal, and a second output terminal; wherein the first input terminal of the regenerator is connected downstream of the evaporator via a first pipe; the first output terminal of the regenerator is connected to a first heat exchanger via a first pipe; the second input terminal of the regenerator is connected to the first heat exchanger via a first pipe; and the second output terminal of the regenerator is connected upstream of one or more expansion stages via a first pipe.

[0021] Optionally, one or more heat exchangers may further include a second heat exchanger for transferring heat energy from the heat transfer fluid to the working fluid, the second heat exchanger being connected to a second piping arrangement through which the heat transfer fluid flows, and a piping arrangement connecting the heat exchanger and a first expansion stage between one or more expansion stages along the first piping arrangement for conveying the working fluid.

[0022] After passing through the first heat exchanger, the working fluid passes through a regenerator, where its temperature decreases. It then enters the second heat exchanger, where its temperature increases, before entering one or more expansion stages. These expansion stages further increase the temperature of the working fluid, thereby improving the efficiency of the first expansion stage.

[0023] Optionally, the energy recovery subsystem includes one or more expansion stages (30) comprising one or more second expansion stages for extracting work from the working fluid; and one or more heat exchangers comprising one or more third heat exchangers for transferring thermal energy from the heat transfer fluid to the working fluid. Optionally, each third heat exchanger receives working fluid from one of the one or more expansion stages located upstream along a first conduit arrangement and is connected via the first conduit arrangement to another expansion stage located downstream of the one or more third heat exchangers. The other expansion stage may be located downstream of the one or more third heat exchangers and may be located before the second expansion stages.

[0024] Passing the working fluid through a third heat exchanger before it enters one or more second expansion stages can increase the temperature of the working fluid and increase the work that can be extracted from the working fluid in each second expansion stage.

[0025] Optionally, the energy recovery subsystem further includes a final expansion stage for extracting work from the working fluid. This final expansion stage is connected downstream of all other expansion stages via a first piping arrangement, and the final expansion stage is also connected via the first piping arrangement to an outlet located at the downstream end of the first piping arrangement for discharging used working fluid from the energy recovery subsystem. Preferably, the final expansion stage or a third expansion stage is connected downstream of the preceding expansion stage without passing through any of the one or more heat exchangers.

[0026] Therefore, residual energy is extracted from the working fluid before it is released from the energy recovery system. The pressure of this expansion stage may be lower than that of the first and second expansion stages.

[0027] Optionally, one or more expansion stages may drive a common shaft, which may be connected to an energy receiver, such as a generator.

[0028] Optionally, the energy recovery subsystem has a second regenerator for transferring heat energy from the working fluid to the working fluid; and a fourth heat exchanger for transferring heat energy from the heat transfer fluid to the working fluid; wherein the second regenerator is connected downstream of the first regenerator via a first conduit arrangement, and the first conduit arrangement is sequentially connected to the second regenerator, the fourth heat exchanger, the second regenerator again, and upstream of one or more expansion stages.

[0029] Optionally, the second regenerator has a first input terminal, a first output terminal, a second input terminal, and a second output terminal; wherein the first input terminal of the second regenerator is connected to the first regenerator via a first pipe; the first output terminal of the second regenerator is connected to a fourth heat exchanger via a first pipe, the fourth heat exchanger is connected to the second input terminal of the second regenerator via a first pipe; and the second output terminal of the second regenerator is connected to the upstream of one or more expansion stages via a first pipe.

[0030] Optionally, both the first regenerator heat exchanger and the optional second regenerator heat exchanger are gas-to-gas heat exchangers.

[0031] Optionally, the first heat exchanger is a liquid-gas heat exchanger. Additionally, the second heat exchanger is optionally a liquid-gas heat exchanger. Optionally, the third heat exchanger is a liquid-gas heat exchanger.

[0032] Optionally, the working fluid is one or more of air, nitrogen, oxygen, hydrogen, or carbon dioxide.

[0033] Optionally, the working fluid can be sourced from a cryogenic storage tank.

[0034] Optionally, one or more heat exchangers are connected in parallel to the TESD via a second conduit. This ensures that each heat exchanger can utilize the unused high-temperature HTF.

[0035] Optionally, the second piping arrangement includes a first piping subgroup and a second piping subgroup independent of the first piping subgroup; both the first and second subgroups are used to transport heat exchange fluid and are connected to the TESD; wherein the first piping subgroup is connected to a first heat exchanger and optionally to a fourth heat exchanger so that the HTF flows through the heat exchanger; and the second subgroup is connected to a second heat exchanger and / or a third heat exchanger so that the HTF flows through the heat exchanger.

[0036] The first heat exchanger and the optional fourth heat exchanger use independent loops, meaning that the HTF flow rate in the heat exchangers associated with the regenerator can be adjusted independently of the other heat exchangers. This is particularly useful during the heating phase, as this is when solidification is most likely to occur.

[0037] Optionally, the energy recovery subsystem of the preceding claims further includes a preheater for heating the working fluid, the preheater being arranged along the first pipe upstream of the first regenerator.

[0038] Optionally, a preheater for heating the working fluid may be arranged downstream of the first heat exchanger along the first pipe.

[0039] This arrangement of placing the preheater downstream of the regenerator is particularly advantageous because it reduces the risk of molten salt solidifying in the second heat exchanger 22, since the heat from the first heat exchanger is subsequently captured by the regenerator and recovered into the air upstream of the first heat exchanger.

[0040] Optionally, a TESD is included, wherein a second piping arrangement is connected to the TESD to supply HTF therefrom.

[0041] Optionally, the second piping arrangement includes a loop for supplying heat transfer fluid to one or more heat exchangers and returning the heat transfer fluid to the TESD after use.

[0042] According to a second aspect of the present invention, a cryogenic energy storage system is provided, the system comprising the above-described energy recovery subsystem.

[0043] Optionally, the CES system includes: a liquefaction subsystem for storing energy in the form of refrigerant and connected to a cryogenic storage tank for storing and supplying refrigerant; a heat capture subsystem for capturing the heat of compression generated by the liquefaction subsystem and connected to a TESD; a TESD for storing the captured heat energy; and an energy recovery subsystem connected to the cryogenic storage tank and the TESD for releasing energy from the refrigerant.

[0044] According to another aspect of the present invention, a method for operating an energy recovery subsystem is provided. The method includes: receiving a working fluid at an upstream end of a first piping arrangement; the method further includes pumping the working fluid along the first piping arrangement sequentially through an evaporator, a regenerator, a first heat exchanger, again through the regenerator, and one or more expansion stages to recover energy from the working fluid. The method further includes: receiving a heat transfer fluid (HTF) in a second piping arrangement. The method further includes passing the heat transfer fluid along the second piping arrangement sequentially through the first heat exchanger to exchange heat energy between the working fluid and the heat transfer fluid.

[0045] Optionally, the method may further include: arranging the working fluid along a first conduit to flow through a second heat exchanger located between a regenerator and one or more expansion stages; and arranging the heat transfer fluid along a second conduit to flow through the second heat exchanger.

[0046] Optionally, the one or more expansion stages may include one or more second expansion stages, and the one or more heat exchangers may include one or more third heat exchangers. Optionally, the method may further include causing the working fluid to flow along a first conduit from one of the one or more expansion stages through one of the one or more third heat exchangers, and then through another of the one or more expansion stages.

[0047] Optionally, the method may further include: allowing the working fluid to flow along the first piping arrangement through the final expansion stage downstream of all other expansion stages, and then discharging the used working fluid from the energy recovery subsystem at the downstream end of the first piping arrangement through an outlet.

[0048] Optionally, the method may further include: causing the working fluid to flow along a first conduit through a second regenerator located downstream of the first regenerator, then through a fourth heat exchanger, then through the second regenerator again, and then upstream along the first conduit through one or more expansion stages.

[0049] Alternatively, the working fluid may also be derived from a cryogenic storage tank.

[0050] Optionally, the heat transfer fluid flows in parallel from the TESD to one or more heat exchangers along a second conduit arrangement.

[0051] Optionally, the second piping arrangement includes a first piping subgroup and a second piping subgroup separate from the first piping subgroup. Optionally, the method may further include: allowing heat exchange fluid to flow along the first piping subgroup through a first heat exchanger, and optionally through a fourth heat exchanger; and allowing heat exchange fluid to flow along the second piping subgroup through a second heat exchanger and / or a third heat exchanger. Preferably, the heat exchange fluid flowing along the first piping subgroup does not flow through the second and / or third heat exchangers. More preferably, the heat exchange fluid flowing along the second piping subgroup does not flow through the first and / or fourth heat exchangers.

[0052] Optionally, the working fluid passes through a preheater upstream of the regenerator.

[0053] Optionally, the working fluid passes through a preheater downstream of the regenerator.

[0054] Optionally, the arrangement along the second conduit forms a loop, and the method may further include allowing the heat transfer fluid to flow along the loop through one or more heat exchangers, and returning the heat transfer fluid to the TESD after use.

[0055] Optionally, the heat transfer fluid comes from a thermal energy storage device (TESD). Attached Figure Description

[0056] The embodiments will be described below by way of example only and in conjunction with the accompanying drawings, wherein the same reference numerals denote the same parts, wherein:

[0057] Figure 1 A cryogenic energy storage system according to the present invention is shown, which includes an energy recovery subsystem;

[0058] Figure 2 It shows Figure 1 The system shown is a variant in which the energy recovery subsystem further includes a second regenerator and its associated heat exchanger;

[0059] Figure 3 It shows Figure 1 A variant of the system shown, wherein the energy recovery subsystem includes multiple independent pipe subgroups, one group of which transports heat exchange fluid from the thermal energy storage device to the heat exchanger associated with the second regenerator, and another group of which transports heat exchange fluid to the remaining heat exchangers. Figure 4A It shows Figure 1 A variant of the system shown, in which a preheater is added upstream of the flow path of the working fluid toward the regenerator;

[0060] Figure 4B It shows Figure 1 A variation of the system shown, in which a preheater is added downstream of the flow path of the working fluid toward the regenerator; and

[0061] Figure 5 It shows Figure 1 A variation of the system shown, in which there is no heat exchanger between the regenerator and the first expansion stage in the process flow of the working fluid. Detailed Implementation

[0062] refer to Figure 1 The first embodiment will now be described. Figure 1 The image shows a cryogenic energy storage (CES) system 1, which includes an energy capture subsystem 2, a liquefaction subsystem 4, and an energy recovery subsystem 10.

[0063] The liquefaction subsystem 4 is used to store energy as potential energy in the form of a cryogenic gas. The liquefaction subsystem 4 receives air or other suitable gas and compresses and cools it to convert it into a cryogenic liquid (referred to as a refrigerant), which is then transported to a cryogenic gas storage device 8a, such as a cryogenic tank 8b. The CES system 1 and / or any subsystems 2, 4, 10 described herein can use any suitable gas suitable for liquefaction and use as a refrigerant for energy storage. For example, the working fluid 5 can be one or more of air, nitrogen, oxygen, hydrogen, or carbon dioxide. The CES system 1 and / or any subsystems 2, 4, 10 can also use combinations of the above gases, and therefore may include necessary gas separation devices 80 and / or liquid separation devices 82, as well as separate storage devices for using and handling different gases or liquids.

[0064] Energy capture subsystem 2 is used to capture the heat of compression released by liquefaction subsystem 4 during liquefaction. Energy capture subsystem 2 transfers the heat recovered from liquefaction subsystem 4 to thermal energy storage device 3 (TESD) via heat transfer fluid 6. Heat transfer fluid 6 can also be referred to as heat transfer fluid 6 (HTF).

[0065] CES system 1 also includes an energy recovery subsystem 10 for recovering energy stored in a refrigerant, which is used as the working fluid 5 in the energy recovery subsystem 10. The energy recovery subsystem 10 includes a first piping arrangement 100 for conveying the working fluid 5; and a second piping arrangement 200, which is connectable to the thermal energy storage device (TESD) 3 and for conveying the heat transfer fluid (HTF) 6. An upstream end 120 of the first piping arrangement 100 is fluidly connected to a downstream end 121 to allow the working fluid 5 to flow therebetween. The downstream end 121 of the first piping arrangement 100 is connected to an outlet 70 for discharging waste working fluid 5 from the energy recovery subsystem 10. This outlet 70 may be connected to the atmosphere or another system that can capture the working fluid 5 and / or use it for other purposes. The working fluid 5 used by the energy recovery subsystem 10 originates from a working fluid source 8. The working fluid source may be a cryogenic gas storage device 8a supplied by the aforementioned liquefaction subsystem 4.

[0066] The energy recovery subsystem 10 also includes: a pump 12 for conveying working fluid 5 along the first piping arrangement 100; an evaporator 14 for evaporating liquid working fluid 5; a regenerator 40 for transferring thermal energy of working fluid 5 between different locations along the first piping arrangement 100; one or more heat exchangers 20 for transferring thermal energy between heat transfer fluid 6 and working fluid 5; and one or more expansion stages 30 for extracting energy from working fluid 5.

[0067] One or more expansion stages 30 are connected to an output shaft 36, which is connected to an energy receiver 60, such as a generator 61. If there are multiple expansion stages 30, they can share the output shaft 36. The energy receiver 60 can be a generator 61 or other machine that requires a rotating power source 62.

[0068] Evaporator 14, regenerator 40, first heat exchanger 21 of one or more heat exchangers 20, regenerator 40 (again), and one or more expansion turbines 30 are sequentially fluidly connected via a first piping arrangement 100, through which working fluid flows sequentially from the first piping arrangement 100 through these components. The regenerator heat exchanger 40 includes a first inlet 42, a first outlet 44, a second inlet 46, and a second outlet 48. The first inlet is connected to the evaporator 14 via the first piping arrangement 100 to receive working fluid from the evaporator 14; the first outlet 44 is connected to the first heat exchanger 21 via the first piping arrangement 100 to deliver working fluid to the first heat exchanger 21; the second inlet 46 is connected via the first piping arrangement 100 to receive working fluid 5 from the first heat exchanger 21; and the second outlet 48 is connected to the first piping arrangement located upstream of one or more heat exchangers 20. Figure 1 In the illustrated embodiment, the second output terminal 48 is connected to the second heat exchanger 22 to deliver the working fluid to the second heat exchanger 22.

[0069] Pump 12 is also connected to piping system 100 for conveying working fluid 5. For example... Figure 1 As shown, pump 12 is connected between the upstream end 120 of the first piping arrangement 100 and the evaporator 14. It should be noted that pump 12 can be located anywhere suitable for delivering the working fluid 5 along the first piping arrangement 100.

[0070] Figure 1 A second heat exchanger 22 is shown in a first piping arrangement between a regenerator 40 and one or more expansion stages 30. The second heat exchanger 22 raises the temperature of the working fluid 5 again after it has been cooled by the regenerator 40, thereby improving the efficiency of the first expansion stage 31 of the one or more expansion stages 30.

[0071] While a single expansion stage 30 can be set, it is preferable to set multiple expansion stages 30. Figure 1 It includes multiple expansion stages 30, including a first expansion stage 31 connected downstream of a regenerator 40 for receiving working fluid 5 from the regenerator 40; and two second expansion stages 32 and a third expansion stage 33, which are sequentially connected downstream of the first expansion stage 31 via a first conduit arrangement 100.

[0072] One or more second expansion stages 32 receive working fluid from a third heat exchanger 23, which is connected between the second expansion stage 32 and the next expansion stage 30 upstream of the first conduit arrangement 100 along the first conduit arrangement 100. Figure 1Two second expansion stages 32 supplied by two third heat exchangers 23 are shown, but it should be understood that one or more second expansion stages 32 and / or third heat exchangers 23 may be included in the energy recovery subsystem 10, wherein the second expansion stages 32 and the third heat exchangers 23 are arranged alternately along the first conduit arrangement 100.

[0073] A third expansion stage 33 is connected to a first piping arrangement 100 located downstream of one or more expansion stages 30, through which the working fluid does not flow in a heat exchanger 20. One or more third expansion stages 33 may be included. Figure 1 A third expansion stage, namely the final expansion stage 33, is shown, which is connected downstream of all other one or more expansion stages 30 via a first piping arrangement 100. The final expansion stage 33 is also connected via the first piping arrangement 100 to an outlet 70 for releasing the working fluid 5 used in the energy recovery subsystem 10 at a downstream end 121 of the first piping arrangement 100.

[0074] The third expansion stage 33 is connected downstream of all other one or more expansion stages 30 via the first piping arrangement 100, and preferably receives the working fluid 5 from the last expansion stage of the second expansion stage 32 without passing through the heat exchanger 20. Alternatively, the last expansion stage of one or more expansion stages 30 may also be connected via the first piping arrangement 100 to an outlet 70 for releasing the used working fluid 5 from the energy recovery subsystem 10 at the downstream end of the first piping arrangement 100.

[0075] The second piping arrangement 200 may be connected to the thermal energy storage device 3 and is used to transport the heat transfer fluid 6 from the thermal energy storage device 3 to one or more heat exchangers 20 to heat the working fluid 5. Figure 1 A second piping arrangement 200 is shown, including a supply pipe 202 connectable to TESD 3 and to one or more heat exchangers 20 for supplying HTF 6 thereto; and a return pipe 204 for receiving HTF 6 after passing through one or more heat exchangers 20. One or more heat exchangers 20 are connected in parallel between the supply pipe 202 and the return pipe 204 via the second piping arrangement 200. Figure 1 A second piping arrangement 200 is shown as a loop that carries HTF 6 from TESD 3 through each of one or more heat exchangers 20 and returns HTF 6 to TESD 3.

[0076] In the figure, TESD 3 is shown as a separate module, but it should be understood that TESD 3 may include one or more hot tanks 3a for high-energy HTF 6 connected to supply line 202, and one or more cold tanks 3b for conveying used HTF 6 through return line 204.

[0077] like Figure 1 As shown, the first piping arrangement 100 includes: a first pipe 101, which is connectable to the working fluid source 8 and extends between the upstream end 120 of the first piping arrangement 100 and the pump 12; a second pipe 102, which extends between the pump 12 and the evaporator 14; a third pipe 103, which extends between the evaporator 14 and the first input end 42 of the regenerator 40; a fourth pipe 104, which extends between the first output end 44 of the regenerator 40 and the first heat exchanger 21; a fifth pipe 105, which extends between the first heat exchanger 21 and the second input end 46 of the regenerator 40; a sixth pipe 106, which extends between the second output end 48 of the regenerator 40 and the second heat exchanger 22; and a seventh pipe 107, which extends between the second heat exchanger 22 and the first expansion stage. Between 31; the eighth conduit 108, which extends between the first expansion stage 31 and the first of the third heat exchanger 23; the ninth conduit 109, which extends between the first of the third heat exchanger 23 and the first of the second expansion stage 32; the tenth conduit 110, which extends between the second expansion stage 32 and the second of the third heat exchanger; the eleventh conduit 111, which extends between the second of the third heat exchanger 23 and the second of the second expansion stage 32; the twelfth conduit 112, which extends between the second (and last) of the second expansion stage 32 and the third expansion stage 33; the thirteenth conduit 113, which extends between the third expansion stage and the downstream end 121 of the first conduit arrangement 100, which includes an outlet 70 for conveying the working fluid 5.

[0078] Figure 2 It shows Figure 1 The CES system variant shown includes, with Figure 1 The same features, and using the same reference numerals, are used, but with the addition of a second regenerator 50 and a fourth heat exchanger 24, which are arranged along the first conduit 100, located between the heat exchangers downstream of the first regenerator 40 and upstream of one or more expansion stages 30. The first regenerator 40, the second regenerator 50, the fourth heat exchanger 24, and the recurring second regenerator 50 are connected along the first conduit 100 in the order described above to transport the working fluid 5 therein.

[0079] The second regenerator 50 includes a first input terminal 52, a first output terminal 54, a second input terminal 56, and a second output terminal 58. The first input terminal 52 can be connected downstream of the first regenerator 40 via a first piping arrangement 100; the first output terminal 54 can be connected to a fourth heat exchanger 24 via the first piping arrangement 100 to deliver working fluid to the fourth heat exchanger 24; the second input terminal 56 can be connected to the fourth heat exchanger 24 via the first piping arrangement 100 to receive working fluid from the fourth heat exchanger 24; and the second output terminal 58 is connected to the first piping arrangement 100 located upstream of one or more heat exchangers 30. Figure 2 In the illustrated embodiment, the second output terminal 58 is connected to the second heat exchanger 22 to deliver the working fluid to the second heat exchanger 22.

[0080] exist Figure 2 In the embodiment shown, Figure 1 In the illustrated embodiment, the sixth pipe 106 in the first piping arrangement 100 is replaced by the following pipes: a fourteenth pipe 114 extending between the second output end 48 of the first regenerator 40 and the first input end 52 of the second regenerator 50; a fifteenth pipe 115 extending between the first output end 54 of the second regenerator 50 and the fourth heat exchanger 24; a sixteenth pipe 116 extending between the fourth heat exchanger 24 and the second input end 56 of the second regenerator 50; and a seventeenth pipe 117 extending between the second output end 58 of the second regenerator 50 and the second heat exchanger 22, for conveying working fluid 5 therebetween. The second piping arrangement 200 is connected to the fourth heat exchanger 24 for supplying HTF 6 thereto.

[0081] Figure 3 It shows Figure 1 The variations of the CES system shown include those with... Figure 1 They have the same features and the same reference numerals. Figure 3 The layout and Figure 1 The illustrated arrangement differs in that the second piping arrangement 200 includes a first piping sub-group 210 and a second piping sub-group 220. Both the first piping sub-group 210 and the second piping sub-group 220 have supply pipes 202, 212, 222 and return pipes 204, 214, 224. The first piping sub-group 210 can be connected to the TESD 3 and to the first heat exchanger 21 to supply it with HTF 6. This allows for independent control of the flow rate of HTF 6 supplied to the first heat exchanger 21 by the regenerator 40. This is particularly useful during the start-up phase of the energy recovery system 10. The second piping sub-group 220 can be connected to the TESD 3 and to the second heat exchanger 22 and / or one or more third heat exchangers 23. Preferably, the second heat exchanger 22 and / or one or more third heat exchangers 23 are connected in parallel.

[0082] Figure 3 Only one regenerator 40 associated with the first heat exchanger is shown. It should be understood that, as Figure 2 As shown, the first piping sub-assembly 210 can also supply HTF 50 associated with the fourth heat exchanger 24. Preferably, in this arrangement, the first heat exchanger 21 and the fourth heat exchanger 24 are connected in parallel via the first piping sub-assembly 210 and are supplied with HTF 6 by it.

[0083] Figure 4A It shows Figure 1 The variant of CES system 1 shown includes, with Figure 1 They have the same features and the same reference numerals. Figure 4A The layout and Figure 1 The arrangement shown differs in that the first piping arrangement 100 of the energy recovery subsystem 10 includes a preheater 16 located along the first piping arrangement 100 between the evaporator 14 and the regenerator 40. Specifically, the preheater 16 is located between the evaporator 14 upstream of the first piping arrangement 100 and the first input terminal 42 of the regenerator 40 downstream of the first piping arrangement 100. Figure 1 In this embodiment, the third pipe 103 is replaced by the eighteenth pipe 118 extending between the evaporator 14 and the preheater 16 and the nineteenth pipe 119 extending between the preheater 16 and the regenerator 40, for conveying the working fluid 5.

[0084] Figure 4B It also shows Figure 1 The variant of CES system 1 shown includes, with Figure 1 They share the same features and have the same reference numerals. For example... Figure 4A similar, Figure 4B A first piping arrangement 100 of an energy recovery subsystem 10 is shown, which includes a preheater 16 located on the first piping arrangement. Figure 4A The difference is that the preheater 16 is arranged along the first pipeline, between the second output end 48 of the regenerator 40 located upstream along the first pipeline and the second heat exchanger 22 located downstream along the first pipeline. Figure 1 In this embodiment, the sixth pipe 106 is replaced by the twentieth pipe 106a extending between the second output end 48 of the regenerator 40 and the preheater 16, and the twenty-first pipe 106b extending between the preheater 16 and the second heat exchanger 22, for conveying the working fluid 5.

[0085] This arrangement, placing the preheater 16 downstream of the regenerator 40, helps reduce the risk of molten salt solidifying in the second heat exchanger 22. When air flows through the first heat exchanger 21, it is heated by the molten salt, but this heat is subsequently captured by the regenerator 40 and recovered into the air upstream of the first heat exchanger 21. This lowers the temperature of the air leaving the regenerator and entering the second heat exchanger 22, thereby increasing the risk of molten salt solidifying in the second heat exchanger 22. As described in other parts of this disclosure, molten salt freezing can lead to production losses and potentially catastrophic equipment failure, especially during system startup.

[0086] The preheater 16 is supplied with heat by a heat source 18, which may be different from the TESD 3 connected to the second piping arrangement 200, and the preheater is used to raise the temperature of the working fluid 5 before it enters the first heat exchanger 21. The heat source 18 may be located inside or outside the preheater 16. If the heat source 18 is located outside the preheater 16, a second heat transfer fluid (HTF) can be used to transfer heat from the heat source 18 to the preheater 16. The second heat transfer fluid (HTF) may be different from the first heat transfer fluid (HTF 6) used in the second piping arrangement 200 and / or have a lower freezing point or crystallization temperature. The preheater 16 may be an electric heater 16a or a combustion heater 16b, or it may receive waste heat from a source outside the energy recovery subsystem 10 (e.g., waste heat from an adjacent industrial system). Preferably, the preheater 16 is used during the start-up phase of the energy recovery subsystem 10, when the temperature of the HTF 6 reaching the first heat exchanger 21 may be relatively low.

[0087] Figure 5 It shows Figure 1 A variation of the CES system 1 shown, wherein one or more heat exchangers 20 of the energy recovery subsystem 10 do not include a second heat exchanger 22. The first piping arrangement 100 includes a twentieth pipe 122 extending between the regenerator 40 and one or more expansion stages 30 for conveying working fluid 5 therebetween, replacing... Figure 1 The sixth pipe 106 and the seventh pipe 107 are shown in the arrangement. This arrangement requires fewer heat exchangers 20, which may have the advantage of reducing the number of components and eliminating the pressure drop on the second heat exchanger 22, which may offset the disadvantage of reduced efficiency caused by supplying colder working fluid 5 to the first expansion stage 31.

[0088] It should be understood that although the energy recovery subsystem 10 is shown as part of the CES system 1 in the figure, the energy recovery subsystem 10 can be supplied by any working fluid source 8 and achieve the claimed advantages of the energy recovery subsystem 10. It should also be understood that... Figure 1 Various variations, such as Figures 2 to 5 As shown in the embodiments and arrangements, they can be combined in any combination.

[0089] Regenerators 40 and 50 may be gas-to-gas regenerators for transferring the heat energy of the working fluid 5 between different locations along the first conduit arrangement 100. Each of one or more heat exchangers 20 may be a liquid-to-gas heat exchanger for transferring heat energy between the HTF6 and the working fluid 5.

[0090] One or more expansion stages 30 may be arranged as a single turbine with multiple expansion stages, or as multiple turbines, each turbine may contain any combination of one or more expansion stages 30. The one or more expansion stages 30 shown in the figures include a first expansion stage 31, one or more second expansion stages 32, and a third expansion stage 33. Those skilled in the art will understand that the one or more expansion stages 30 may include one or more of the first expansion stage 31, the second expansion stage 32, and / or the third expansion stage 33.

[0091] During operation, the energy recovery system 10 receives working fluid 5 from the working fluid source 8 located at the upstream end 120 of the first piping arrangement 100. Figures 1 to 5In the CES system 1 shown, the working fluid 5 is a refrigerant provided by the energy capture subsystem 2, which includes a liquefaction subsystem 4 for generating the refrigerant. Pump 12 delivers the working fluid 5 along a first conduit arrangement 100, causing it to flow through an evaporator 14, where the liquid cryogenic working fluid 5 evaporates into a gas. The working fluid 5 then optionally flows along the first conduit arrangement 100 through a preheater 16, then through a regenerator 40, then into a first heat exchanger 21, and finally returns to the regenerator 40. The regenerator 40 transfers the heat from the working fluid 5 heated by the first heat exchanger 21 to the working fluid 5 located upstream of the first heat exchanger 21 along the first conduit arrangement 5. This increases the temperature of the working fluid 5 before it enters the first heat exchanger 21 and reduces the likelihood of crystal formation or condensation of HTF 6 in the first heat exchanger 21. The optional preheater 16 can further increase the temperature of the working fluid 5 before it enters the first heat exchanger 21. The working fluid 5 flows downstream of the first piping arrangement 100 through one or more expansion stages 30 to extract work. The working fluid 5 exits the regenerator 40 at a lower temperature than it exits the first heat exchanger 21 or the regenerative heat exchanger 21. Optionally, the first piping arrangement 100 feeds the working fluid 5 into a second heat exchanger 22 or a booster heat exchanger 22 to increase the temperature of the working fluid 5 before entering one or more expansion stages 30, thereby increasing the efficiency and / or output rate of the first expansion stage 31 in one or more expansion stages 30. If one or more expansion stages 30 comprise two or more expansion stages 30, the first piping arrangement may allow the working fluid 5 to pass through one or more third heat exchangers 23 or interstage heat exchangers 23 before passing through another expansion stage located downstream of the third heat exchanger 23. Each third heat exchanger 23 increases the temperature of the working fluid 5 before entering the next expansion stage along the first piping arrangement 100, thereby increasing the pressure of the working fluid 5, and the work extracted from the working fluid can improve the efficiency of the second expansion stage 32. The first piping arrangement 100 allows the working fluid 5 to pass directly through the third expansion stage 33 or the final expansion stage 33 without passing through the third heat exchanger 23. This third expansion stage, which may be referred to as the final expansion stage 33, functions to extract residual work from the working fluid 5 before it is released from the energy recovery system 10 located at the downstream end 121 of the first piping arrangement 100. One or more heat exchangers 30 are supplied with HTF 6 by the second piping arrangement 200 for heating the working fluid 5. The one or more heat exchangers 20 are preferably connected in parallel such that each heat exchanger receives heated HTF 6 from the TESD 3.

[0092] The HTF 6 used in the second piping arrangement 200 has a freezing point above ambient temperature. The use of molten salt as HTF 6, in particular, has proven to be highly efficient in transferring and storing thermal energy. As mentioned above, this presents a problem: if the energy recovery system 10 allows the HTF 6 to cool below its initial solidification temperature (referred to as the crystallization temperature, the temperature at which salt crystals begin to appear in the molten fluid), issues arise. When the energy recovery subsystem 10 is operational, especially during system startup, there is a risk of HTF 6 crystallizing or completely solidifying. At this time, the working fluid enters the upstream end of the first piping arrangement 100 as a cryogenic liquid, at an extremely low temperature, which can easily cause the HTF 6 within the first (or most upstream) heat exchanger of one or more heat exchangers 20 in the energy recovery subsystem 10 to solidify.

[0093] The first piping arrangement 100 and the second piping arrangement 200 fluidly connect the various components to which they are connected. Unless otherwise stated, "sequential" connection means that the listed components pass through the working fluid in a given order, or that the piping arrangements 100 and 200 are connected to each other relative to the first set of piping arrangements 100 and 200. This does not mean that the components are directly connected upstream or downstream to each other. Other components such as valves, sensors, connectors, or other components may be connected between the various components along piping arrangements 100 and 200 in a specific order.

[0094] The second piping arrangement 200 and its respective piping subgroups 210 and 220 each include supply pipes 202, 212, and 222, and return pipes 204, 214, and 224. One or more heat exchangers 20 are connected between the supply pipe 202 and the return pipe 204, respectively for supplying heat exchange fluid 6 and discharging used heat exchange fluid 6. If the TESD 3 includes a single storage tank for storing HTF 6, the first piping arrangement 200 may form one or more loops. However, the TESD 3 preferably includes a hot tank 3a for storing hot HTF 6 and a cold tank 3b for storing used HTF 6. It should be noted that even in the cold tank, the temperature of the heat exchange fluid 6 is maintained at a safe operating temperature well above its freezing point.

[0095] Any system feature described herein can also be provided as a method feature, and vice versa. As used herein, method features and functional features can also be represented by their corresponding structures.

[0096] Features of any aspect, variation, or embodiment may be applied to other aspects, variations, or embodiments in any suitable combination. In particular, method aspects may be applied to system aspects, and vice versa. Furthermore, any, part, and / or all features of any aspect may be applied to any, part, and / or all features of any other aspect in any suitable combination.

[0097] It should also be understood that any particular combination of the various features described and defined in any respect may be implemented and / or provided and / or used independently.

Claims

1. An energy recovery subsystem (10) for a cryogenic energy storage system (CES) (1), comprising: Pump (12) for conveying working fluid (5); Evaporator (14); One or more heat exchangers (20) including a first heat exchanger (21) for transferring thermal energy from the heat transfer fluid (6) to the working fluid (5); One or more expansion stages (30) for extracting work from the working fluid (5); A regenerator (40) is used to transfer heat energy from the working fluid (5) to the working fluid (5); The first piping arrangement (100) is used to transport the working fluid (5); A second piping arrangement (200) is provided, which can be connected to a thermal energy storage device (TESD) (3) and to a first heat exchanger (21) to transport heat transfer fluid (6) therebetween; The first piping arrangement (100) has an upstream end (120) connected to the working fluid source (8) and a downstream end (121), and from the upstream end (120) are sequentially connected an evaporator (14), a regenerator (40), a first heat exchanger (21), a regenerator (40) again, and one or more expansion stages (30).

2. The energy recovery subsystem (10) according to claim 1, wherein, The regenerator (40) has a first input terminal (42), a first output terminal (44), a second input terminal (46), and a second output terminal (48); The first input end (42) of the regenerator (40) is connected to the downstream of the evaporator (14) via a first pipe arrangement (100); The first output end (44) of the regenerator (14) is connected to the first heat exchanger (21) via a first piping arrangement (100), and the second input end (46) of the regenerator (14) is connected to the first heat exchanger (21) via the first piping arrangement (100); and The second output (48) of the regenerator (40) is connected upstream of one or more expansion stages (30) via a first piping arrangement (100).

3. The energy recovery subsystem (10) according to claim 1 or 2, wherein one or more heat exchangers (20) further comprises a second heat exchanger (22) for transferring thermal energy from the heat transfer fluid (6) to the working fluid (5), the second heat exchanger (22) being connected to a second piping arrangement (200) for allowing the heat transfer fluid (6) to flow therethrough and connected along a first piping arrangement (100) between the regenerator (40) and a first expansion stage (31) of one or more expansion stages (30) for conveying the working fluid (4) therethrough.

4. The energy recovery subsystem (10) according to any one of the preceding claims, wherein, The one or more expansion stages (30) include one or more second expansion stages (32) for extracting work from the working fluid (5); and the one or more heat exchangers (20) include one or more third heat exchangers (23) for transferring thermal energy from the heat transfer fluid (6) to the working fluid (5); Each third heat exchanger (23) receives working fluid (5) from one of one or more expansion stages (30) located upstream of the first piping arrangement (100) and is connected via the first piping arrangement (100) to another expansion stage (30) located downstream of each of the one or more third heat exchangers (23).

5. The energy recovery subsystem (10) according to any one of the preceding claims further includes a final expansion stage (33) for extracting work from the working fluid (5), and the final expansion stage is connected downstream of all other expansion stages (31, 32) via a first piping arrangement (100), and wherein the final expansion stage (33) is also connected via the first piping arrangement (100) to an outlet (70) for discharging used working fluid (5) from the energy recovery subsystem (10) at a downstream end (121) of the first piping arrangement (100).

6. The energy recovery subsystem (10) according to any one of the preceding claims, wherein one or more expansion stages (30) drive a common shaft that can be connected to an energy receiver (60) such as a generator (61).

7. The energy recovery subsystem (10) according to any one of the preceding claims, comprising: The second regenerator (50) is used to transfer thermal energy from the working fluid (5) to the working fluid (5); And a fourth heat exchanger (24), which is used to transfer heat energy from the heat transfer fluid (6) to the working fluid (5); The second regenerator (50) is connected downstream of the first regenerator (40) via a first piping arrangement (100), and the first piping arrangement sequentially connects the second regenerator (50), the fourth heat exchanger (24), and the second regenerator (50) again, and is connected upstream of the first piping arrangement (100) to one or more expansion stages (30).

8. The energy recovery subsystem (10) according to claim 7, wherein, The second regenerator (50) has a first input terminal (52), a first output terminal (54), a second input terminal (56), and a second output terminal (58); The first input end (52) of the second regenerator (50) is connected to the first regenerator (40) through the first pipe arrangement (100); The first output terminal (54) of the second regenerator (50) is connected to the fourth heat exchanger (24) via a first piping arrangement (100), and the fourth heat exchanger (24) is connected to the second input terminal (56) of the second regenerator (50) via the first piping arrangement (100); and The second output (58) of the second regenerator (50) is connected to the upstream of one or more expansion stages (30) via a first piping arrangement (100).

9. The energy recovery subsystem (10) according to any one of the preceding claims, wherein the first regenerator (40) and optionally, in claim 7 or claim 8, the second regenerator (50) are gas-to-gas heat exchangers.

10. The energy recovery subsystem (10) according to any one of the preceding claims, wherein one or more heat exchangers (20) are liquid-gas heat exchangers.

11. The energy recovery subsystem (10) according to any one of the preceding claims, wherein the working fluid (5) is one or more of air, nitrogen, oxygen, hydrogen or carbon dioxide.

12. The energy recovery subsystem (10) according to any one of the preceding claims, wherein the working fluid source (8) is a cryogenic storage tank (8a).

13. The energy recovery subsystem (10) according to any one of the preceding claims, wherein one or more heat exchangers 20 are connected in parallel to the thermal energy storage device (3) via a second piping arrangement (200).

14. The energy recovery subsystem (10) according to any one of claims 3 to 13, wherein, The second piping arrangement (200) includes a first piping subgroup (210) and a second piping subgroup (220), the second piping subgroup being separate from the first piping subgroup (210); both the first piping subgroup (210) and the second piping subgroup (220) are used to transport heat exchange fluid (6) and can be connected to a thermal energy storage device (3); The first pipe sub-assembly (210) is connected to the first heat exchanger (21) and optionally carries heat exchange fluid (6) therebetween via a fourth heat exchanger (24), and the second pipe sub-assembly (220) is connected to the second heat exchanger (22) and / or the third heat exchanger (23).

15. The energy recovery subsystem (10) according to any one of the preceding claims further includes a preheater (16) for heating the working fluid (5) and is arranged along the first conduit (100) upstream of the first regenerator (40).

16. The energy recovery subsystem (10) according to any one of claims 1 to 14 further includes a preheater (16) for heating the working fluid (5), which is arranged along the first conduit (100) downstream of the first regenerator (40).

17. The energy recovery subsystem (10) according to any one of the preceding claims includes a thermal energy storage device (3), wherein a second piping arrangement (200) is connected to the thermal energy storage device (3) to supply heat transfer fluid 6 therefrom.

18. The energy recovery subsystem (10) according to claim 17, wherein the second piping arrangement (200) includes a loop for supplying heat transfer fluid (6) to one or more heat exchangers (20) and returning the heat transfer fluid (6) to the thermal energy storage device (3) after use.

19. A cryogenic energy storage system (1) comprising an energy recovery subsystem (10) according to any one of claims 1 to 18.

20. The cryogenic energy storage system (1) according to claim 19, comprising: The liquefaction subsystem (4), which is used to store energy in the form of refrigerant, is connected to, A cryogenic storage tank (8a) for storing and supplying the refrigerant; An energy capture subsystem (2), which is used to capture the heat of compression generated by the liquefaction subsystem (4) and is connected to, Thermal energy storage device (3) for storing the captured thermal energy; as well as An energy recovery subsystem (10) is connected to the cryogenic storage tank (8a) and the thermal energy storage device (3) for releasing energy from the refrigerant.

21. A method of operating an energy recovery subsystem (10), wherein the method comprises: The working fluid (8) is received at the upstream end (120) of the first pipeline arrangement (100); The working fluid (8) is pumped (12) through a first conduit arrangement (100) to flow through an evaporator (14), then through a regenerator (40), then through a first heat exchanger (21), then through the regenerator (40) again, and then through one or more expansion stages (30) to recover energy from the working fluid (8); The heat transfer fluid (6) is received in the second pipe arrangement (200); as well as The heat transfer fluid (6) is arranged along the second pipe (200) and flows through the first heat exchanger (21) to exchange heat energy between the working fluid (8) and the heat transfer fluid (6).

22. The method of claim 21, wherein the method further comprises: The working fluid is arranged along the first conduit (100) and flows through the second heat exchanger (22) located between the regenerator (40) and the first expansion stage (31) of one or more expansion stages; as well as The heat transfer fluid (6) is arranged along the second pipe (200) and flows through the second heat exchanger (22).

23. The method according to claim 21 or 22, wherein, The one or more expansion stages (30) include one or more second expansion stages (32), the one or more heat exchangers (20) include one or more third heat exchangers (23), and the method further includes: The working fluid (8) is arranged along a first conduit (100) from one of the one or more expansion stages (30) through one of the one or more third heat exchangers (23), and then through one of the one or more expansion stages (30).

24. The method according to any one of claims 21 to 23, wherein the method further comprises: The working fluid is allowed to flow along the first piping arrangement (100) through the final expansion stage (33) downstream of all other expansion stages (31, 32), and then the used working fluid (5) is discharged from the energy recovery subsystem (10) through the outlet (70) at the downstream end (121) of the first piping arrangement (100).

25. The method according to any one of claims 21 to 24, wherein the method further comprises: The working fluid is made to flow along the first piping arrangement (100) through the second heat exchanger (50) located downstream of the first heat exchanger (40), then through the fourth heat exchanger (24), then through the second heat exchanger (50) again, and upstream along the first piping arrangement (100) to one or more expansion stages (30).

26. The method according to any one of claims 21 to 25, wherein, The working fluid comes from a cryogenic storage tank.

27. The method according to any one of claims 21 to 26, wherein, The heat transfer fluid is arranged along the second conduit (200) and flows in parallel from the thermal energy storage device (3) to each of one or more heat exchangers (20).

28. The method according to any one of claims 21 to 27, wherein, The second piping arrangement (200) includes a first piping subgroup (210) and a second piping subgroup (220) separate from the first piping subgroup (210), and the method includes: The heat exchange fluid flows along the first pipe sub-group (210) through the first heat exchanger (21) and optionally through the fourth heat exchanger (24); and The heat exchange fluid is made to flow along the second pipe sub-group (220) through the second heat exchanger (22) and / or the third heat exchanger (23).

29. The method according to any one of claims 21 to 28, wherein, The working fluid (8) flows upstream of the regenerator (40) through the preheater (16).

30. The method according to any one of claims 21 to 28, wherein, The working fluid (8) flows downstream of the regenerator (40) through the preheater (16).

31. The method according to any one of claims 21 to 30, wherein, The second piping arrangement (200) includes a loop, and the method further includes: The heat transfer fluid (6) is allowed to flow through one or more heat exchangers (20) along the loop, and after use, the heat transfer fluid (6) is returned to the thermal energy storage device (3).

32. The method according to any one of claims 21 to 31, wherein, The heat transfer fluid (6) comes from the thermal energy storage device (TESD) (3).

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