WO2024076637A1

WO2024076637A1 - Thermal energy storage systems including pressure exchangers

Info

Publication number: WO2024076637A1
Application number: PCT/US2023/034471
Authority: WO
Inventors: Azam Mihir Thatte
Original assignee: Energy Recovery, Inc.
Priority date: 2022-10-05
Filing date: 2023-10-04
Publication date: 2024-04-11

Abstract

A system includes a pressure exchanger (PX) configured to receive a first fluid at a first pressure and a second fluid at a second pressure and exchange pressure between the first fluid and the second fluid. The system further includes a first heat exchanger and a second heat exchanger. The system further includes a compressor. The system further includes an electrical energy generation device. The system further includes a first valve. The system further includes a processing device operatively coupled to the first valve. The processing device is configured to provide a control signal to the first valve to cause the system to be operated in a first mode or a second mode.

Description

THERMAL ENERGY STORAGE SYSTEMS INCLUDING PRESSURE

EXCHANGERS

TECHNICAL FIELD

[0001] The present disclosure relates to energy storage systems, and more specifically, thermal energy storage systems including pressure exchangers.

BACKGROUND

[0002] Systems use fluids at different pressures. Systems use pumps or compressors to increase pressure of fluid. Systems may utilize pressure changes of a working fluid to transfer energy between various components of the system.

BRIEF DESCRIPTION OF THE DRAWINGS

[0003] The present disclosure is illustrated by way of example, and not by way of limitation in the figures of the accompanying drawings.

[0004] FIGS. 1A-B illustrate schematic diagrams of fluid handling systems including hydraulic energy transfer systems and a thermal energy storage medium, according to some embodiments.

[0005] FIGS. 2A-E are exploded perspective views of pressure exchangers (PXs), according to some embodiments.

[0006] FIG. 3A is a schematic diagram of a thermal energy storage system including a PX, according to some embodiments.

[0007] FIG. 3B is a schematic diagram of a thermal energy storage system that includes a PX, according to some embodiments.

[0008] FIG. 3C depicts a thermal energy storage system for generating a heat sink for cooling a target environment, according to some embodiments.

[0009] FIG. 4A depicts an example thermal energy storage medium management system, according to some embodiments.

[0010] FIG. 4B depicts a thermal energy storage medium reservoir, according to some embodiments.

[0011] FIG. 4C depicts a thermal energy gradient storage system, according to some embodiments.

[0012] FIG. 4D depicts a thermal energy storage medium system including a secondary energy transfer fluid, according to some embodiments. [0013] FIG. 5 is a flow diagram of a method for causing a thermal energy storage system to operate in a target mode, according to some embodiments.

[0014] FIG. 6 is a flow diagram of a method for causing a thermal energy storage system to operate in a target mode, according to some embodiments.

[0015] FIG. 7 is a block diagram illustrating a computer system, according to certain embodiments.

DETAILED DESCRIPTION OF EMBODIMENTS

[0016] Embodiments described herein are related to thermal energy storage systems that include a pressure exchanger (e.g., fluid handling systems, heat transfer systems, pressure exchanger systems, carbon dioxide (CO2) refrigeration systems, etc.).

[0017] Operations that utilize energy may be inflexible in terms of when and how they are dependent upon energy supply. For example, commercial operations may operate during conventional business hours, which may not coincide with times of energy abundance (e.g., due to wind or solar, low energy cost, or the like). Such operations may include systems that may use fluids at different pressures. These systems may include hydraulic fracturing (e.g., fracking or fracing) systems, desalinization systems, refrigeration systems, heat pump systems, energy generation systems, mud pumping systems, slurry pumping systems, industrial fluid systems, waste fluid systems, fluid transportation systems, thermal energy storage systems, etc. Pumps or compressors may be used to increase pressure of fluid to be used by systems.

[0018] Conventionally, refrigeration systems use pumps or compressors to increase the pressure of a fluid (e.g., a refrigeration fluid such as CO₂, R-744, R-134a, hydrocarbons, hydrofluorocarbons (HFCs), hydrochlorofluorocarbons (HCFCs), ammonia (NH₃), refrigerant blends, R-407A, R-404A, etc.). Conventionally, separate pumps or compressors mechanically coupled to motors are used to increase pressure of the fluid. Pumps and compressors that operate over a large pressure differential (e.g., cause a large pressure increase in the fluid) use large quantities of energy. Conventional systems thus expend large amounts of energy increasing the pressure of the fluid (via the pumps or compressors driven by the motors). Additionally, conventional heat pump systems (e.g., systems that transfer heat from one component to another via the working fluid) decrease the pressure of the fluid through expansion valves. During the process of expansion through a valve, no useful work is extracted and thus this process is one of the main reasons for energy inefficiency of conventional heat pump systems. Further, the hydrofluorocarbon (HFC) refrigerants (e.g. R- 134a, R-404a etc.) that may be used in such systems are responsible for causing global warming and are being phased out by several countries and are being replaced other refrigerants with reduced environmental impact potential, such as CO₂. However, the gas cooler / condenser pressure required for CO₂ based heat pump systems is much higher compared to that required for commonly used HFC based heat pump systems. Thus, although more climate friendly, CO₂ systems consume much more energy compared to their HFC counterparts. CO₂ system’s energy consumption further increases when the system is operated with warmer gas cooler exit temperatures (i.e. with warmer load return temperatures), since the gas cooler / condenser pressure increases as the gas cooler exit temperature increases and thus compressor needs to do more work. This is one of the key challenges associated with CO₂ heat pump systems. Such restrictions may energy used to run a conventional system (e.g., energy used to repeatedly increase the pressure of the working fluid to cause increase or decrease of temperature of the surrounding environment).

[0019] The systems, devices, and methods of the present disclosure provide thermal energy storage systems. The systems, devices, and methods of the present disclosure provide fluid handling systems (e.g., for thermal energy storage, for heat transfer systems, etc.). Thermal energy storage systems may operate to transfer heat from one medium to another, such that the media may be utilized at a later time to perform a target function. In some embodiments, thermal energy is stored in a medium by utilizing a heat pump architecture, which extracts heat from a lower temperature heat source and deposits the heat energy in a higher temperature heat sink. The stored thermal energy may later be utilized in generating electricity, e.g., via a heat engine architecture. In some embodiments, thermal energy is extracted from a low-temperature heat sink, and the low-temperature sink is later used to absorb unwanted heat, such as in a refrigeration or air conditioning system. In some embodiments, fairly low temperature waste heat (e.g., low grade waste heat from an industrial process) may be transferred to a high temperature thermal energy storage medium via a heat pump architecture. The high temperature thermal energy storage medium may be utilized to provide useful heat (e.g., high grade, high temperature heat) to the industrial process or another industrial process or as residential heat at a later time.

[0020] Thermal energy storage systems may include capability of performing operations of a charge cycle and a discharge cycle. The charge cycle may enable storage of energy and/or generation of a thermal energy storage medium in a temperature state which may later be utilized during a discharge cycle to do work, generate electricity, perform an industrial or other useful function, or the like. In some embodiments, operations of a charge cycle may be performed in response to some target condition of the thermal energy storage system. In some embodiments, operations of a discharge cycle may be performed in response to a second target condition of the thermal energy storage system. For example, operations of a charge cycle may be performed when renewable energy (e.g., solar, wind) is available, and operations of a discharge cycle may be performed when such energy sources are unavailable. Operations of the charge cycle may be performed when energy costs are low, and operations of the discharge cycle may be performed when energy costs are high. Operations of the charge cycle may be performed for an industrial process while low-grade waste heat is available, for upgrading the low-grade heat to usable heat. Operations of the corresponding discharge cycle may be performed while waste heat is not available.

[0021] In some embodiments, a system (e.g., fluid handling system, thermal energy transfer system, refrigeration system, heat pump system, heat transfer system, CO₂ refrigeration system, etc.) includes a pressure exchanger (PX) that is configured to exchange pressure between a first fluid (e.g., a high pressure portion of the refrigeration fluid in a refrigeration cycle) and a second fluid (e.g., a low pressure portion of the refrigeration fluid in the refrigeration cycle). In some embodiments, the PX may receive a first fluid (e.g., a portion of the refrigeration fluid at high pressure) via a first inlet (e.g., a high pressure inlet) and a second fluid (e.g., a portion of the refrigeration fluid at a low pressure.) via a second inlet (e.g., a low pressure inlet). When entering the PX, the first fluid may have a higher pressure than the second fluid. The PX may exchange pressure between the first fluid and the second fluid. The first fluid may exit the PX via a first outlet (e.g., a low pressure outlet) and the second fluid may exit the PX via a second outlet (e.g., a high pressure outlet). When exiting the PX, the second fluid may have a higher pressure than the first fluid (e.g., due to the pressure exchange between the first fluid and the second fluid). Aspects of the present disclosure solve challenges of utilizing CO₂ for thermal energy storage by extracting energy during expansion of the high pressure refrigerant CO₂ and using it to compress a portion of the refrigerant flow, thus reducing the energy consumption of the main compressor of the heat pump system. This makes the charge cycle of the thermal energy storage system more efficient.

[0022] In some embodiments, one or more of a heat sink and/or heat source may be an environment proximate a portion of the fluid handling system, such as an environment proximate a heat exchanger. In some embodiments, the system further includes one or more thermal energy storage mediums. For example, a first portion of the fluid handling system may bring the working fluid into thermal communication with a first thermal energy storage medium, and a second portion of the fluid handling system may bring the working fluid in thermal communication with a second thermal energy storage medium. In some embodiments, thermal energy maybe stored (e.g., transferred from a “cold” thermal medium to a “hot” thermal medium for storage) during charge cycle operations, and thermal energy may be utilized by the system to perform a useful function during a discharge cycle. In some embodiments, the thermal energy storage may include storing cold, e.g., removing thermal energy from a storage medium, during a charge cycle and providing heat to the storage medium during a discharge cycle (such as for refrigeration or air conditioning systems). Thermal energy storage mediums may include molten salt, dry ice, water, water and ice slurry, glycol, glycol/water mixtures, phase change material (e.g., paraffins such as octadecane, salt hydrates, fatty acids, esters, ionic liquids, gels, polymers, etc.), eutectic materials (e.g., mixtures of materials with a reduced melting point than other compositions of the same materials), molten metals (e.g., aluminum), molten silicon, sand, rocks, bricks, or stones, or other mediums. In some embodiments, a thermal energy storage medium may be pumped, transferred, or otherwise passed through a heat exchanger in thermal communication with a working fluid. In some embodiments, a secondary fluid may be in thermal communication with both a primary working fluid and a thermal energy storage medium. In some embodiments, a heat exchanger in thermal communication with a working fluid may be embedded in a reservoir comprising the thermal energy storage medium.

[0023] In some embodiments, the system further includes a heat exchanger (e.g., a condenser, condensing unit (CU), gas cooler, air conditioning condenser, etc.) configured to provide the first fluid to the PX (e.g., via the first inlet of the PX) and transfer corresponding thermal energy (e.g., heat) between the first fluid and a corresponding environment (e.g., a heat sink, a hot reservoir, a high temperature thermal energy storage medium, heat source, cold reservoir, ambient air, ground, etc.). In some embodiments, the first fluid (e.g., high pressure fluid) loses heat to the environment and condenses in the heat exchanger. Output of the heat exchanger (e.g., a portion of the output of the heat exchanger, first fluid, etc.) may be provided to the high pressure inlet of the PX. The heat exchanger may be upstream of the PX on a flow path of the first fluid. In some embodiments, the system further includes a second heat exchanger (e.g., an evaporator) which is configured to transfer heat from an heat source to the working fluid of the system. Input of the evaporator may be coupled to an output of the PX.

[0024] In some embodiments, the system further includes a receiver (e.g., a flash tank) to receive the first fluid output from the low pressure outlet of the PX. The receiver may form a chamber where gas and liquid of the low pressure first fluid may separate. The booster may receive a gas (e.g., gas of the high pressure first fluid) from the receiver and increase pressure of the gas to form the second fluid.

[0025] In some embodiments, the system further includes a booster that is configured to receive a gas (e.g., gas of the low pressure first fluid) from the receiver and to increase the pressure of the gas (e.g., the first portion of the first gas) to form the second fluid at a second pressure (e.g., a portion of the refrigeration fluid at a low pressure), and provide the second fluid at the second pressure to the PX via the second inlet. The booster may be a pump or a compressor and may increase pressure of the second fluid over a comparatively low pressure differential. More details regarding the pressure differential of boosters are described herein. The booster may providethe second fluid to the low pressure inlet (e.g., the second inlet) of the PX at the second pressure.

[0026] The system may further include one or more of an expansion valve and a compressor to perform a refrigeration cycle, heat transfer cycle, heat pump cycle, heat engine cycle, or the like. Working fluid may expand through the expansion valve, decreasing in pressure and temperature. The working fluid may receive thermal energy (e.g., heat) from another environment (e.g., a heat source, a cold reservoir, etc.) via another heat exchanger (e.g., an evaporator). The working fluid may be compressed in a compressor to increase pressure of the refrigeration fluid. Thermal energy may be rejected from the working fluid in the condenser, and the first fluid (e.g., at least a portion of the working fluid) may flow into the PX and exchange pressure with the second fluid as part of a heat transfer cycle.

[0027] The systems, devices, and methods of the present disclosure have advantages over conventional solutions. The systems of the present disclosure may use a reduced amount of energy (e.g., use less energy to run a heat pump cycle) compared to conventional systems. The PX may allow for the recovery of energy (e.g., pressure) that is ordinarily lost in conventional systems. This causes the systems of the present disclosure to have increased efficiency, thus using less energy and costing less over time to the end-user compared to conventional solutions. Systems of the present disclosure enable storage of thermal energy to be separated in time from utilization of the stored energy. Separation in time of energy storage and energy usage may enable taking advantage of energy availability to perform operations at a time of energy scarcity. Storing thermal energy for later usage may reduce cost of operating a system, reduce environmental impact of operating a system, etc.

Additionally, the systems of the present disclosure reduce wear on components (e.g., pumps, compressors) compared to conventional systems because the pumps or compressors of the systems disclosed herein are allowed to run more efficiently compared to conventional systems (e.g., the PX performs a portion of the increasing of pressure of the fluid to decrease the load of the pumps and/or compressors). Additionally, some systems described herein reduce the number of moving components (e.g., some systems use ejectors in lieu of boosters). This also allows systems of the present disclosure to have increased reliability, less maintenance, increased service life of components, decreased downtime of the system, and increased yield (e.g., of refrigeration, cooling, heating, etc.). The systems of the present disclosure may use a pressure exchanger that allows for longer life of components of the system, that increases system efficiency, allows end users to select from a larger range of pumps and/or compressors, reduces maintenance and downtime to service pumps and/or compressors, and allows for new instrumentation and control devices.

[0028] Although some embodiments of the present disclosure are described in relation to pressure exchangers, energy recovery devices, and hydraulic energy transfer systems, the current disclosure can be applied to other systems and devices (e.g., pressure exchanger that is not isobaric, rotating components that are not a pressure exchanger, a pressure exchanger that is not rotary, systems that do not include pressure exchangers, etc.).

[0029] Although some embodiments of the present disclosure are described in relation to exchanging pressure between fluid used in, heat pump systems, and/or refrigeration systems, the present disclosure can be applied to other types of systems. Fluids can refer to liquid, gas, transcritical fluid, supercritical fluid, subcritical fluid, and/or combinations thereof.

[0030] In some aspects of the present disclosure, a system includes a pressure exchanger (PX) configured to receive a first fluid at a first pressure and a second fluid at a second pressure and exchange pressure between the first fluid and the second fluid. The system further includes a first heat exchanger and a second heat exchanger. The system further includes a compressor. The system further includes an electrical energy generation device. The system further includes a first valve. The system further includes a processing device operatively coupled to the first valve. The processing device is configured to provide a control signal to the first valve to cause the system to be operated in a first mode or a second mode. Operation in the first mode includes providing fluid flow to the PX, the first heat exchanger, the second heat exchanger, and the compressor. Operation in the second mode comprises providing fluid flow to the first heat exchanger, the second heat exchanger, and the electrical energy generation device.

[0031] In other aspects of the present disclosure, a system includes a PX configured to receive a first fluid, receive a second fluid, and exchange pressure between the first fluid and the second fluid. The system further includes a heat exchanger configured to receive the first fluid from the PX and to exchange heat between the first fluid and a third fluid. The system further includes a thermal storage medium in thermal communication with the third fluid. The system further includes a cooling coil, configured to exchange thermal energy between the third fluid and an environment proximate the cooling coil. The system further includes a pump configured to circulate the third fluid between the thermal storage medium, the cooling coil, and the heat exchanger.

[0032] In other aspects of the disclosure, a system includes a PX configured to receive a first fluid, receive a second fluid, and exchange pressure between the first fluid and the second fluid. The system further includes a first heat exchanger configured to provide the first fluid to the PX. The first heat exchanger is in thermal communication with a thermal storage medium. The system further includes a second heat exchanger configured to receive the first fluid from the PX. The second heat exchanger is in thermal communication with a heat source. The system further includes a heat sink in thermal communication with the thermal storage medium. The system further includes a processing device, configured to provide a control signal causing the system to operate in a first mode or a second mode. [0033] FIG. 1A illustrates a schematic diagram of a fluid handling system 100A that includes a hydraulic energy transfer system 110 and a thermal energy storage medium 180, according to certain embodiments.

[0034] In some embodiments, a hydraulic energy transfer system 110 includes a pressure exchanger (e.g., PX). The hydraulic energy transfer system 110 (e.g., PX) receives low pressure (LP) fluid in 120 (e.g., via a low-pressure inlet) from an LP in system 122. The hydraulic energy transfer system 110 also receives high pressure (HP) fluid in 130 (e.g., via a high-pressure inlet) from HP in system 132. The hydraulic energy transfer system 110 (e.g., PX) exchanges pressure between the HP fluid in 130 and the LP fluid in 120 to provide LP fluid out 140 (e.g., via low-pressure outlet) to LP fluid out system 142 and to provide HP fluid out 150 (e.g., via high-pressure outlet) to HP fluid out system 152. A controller may cause an adjustment of flowrates of HP fluid in 130 and LP fluid out 140 by one or more flow valves, pumps, and/or compressors (not illustrated). Fluid handling system 100A includes one or more thermal energy storage mediums 180. Thermal energy storage medium 180 may provide a heat sink, e.g., a material utilized by fluid handling system 100A to absorb and retain heat. Thermal energy storage medium 180 may provide a heat source, e.g., a material utilized by fluid handling system 100 A to provide heat and maintain a low temperature to later absorb heat. [0035] In some embodiments, the hydraulic energy transfer system 110 includes a PX to exchange pressure between the HP fluid in 130 and the LP fluid in 120. In some embodiments, the PX is substantially or partially isobaric (e.g., an isobaric pressure exchanger (IPX)). The PX may be a device that transfers fluid pressure between HP fluid in 130 and LP fluid in 120 at efficiencies (e.g., pressure transfer efficiencies, substantially isobaric) in excess of approximately 50%, 60%, 70%, 80%, 90%, or greater (e.g., without utilizing centrifugal technology). High pressure (e.g., HP fluid in 130, HP fluid out 150) refers to pressures greater than the low pressure (e.g., LP fluid in 120, LP fluid out 140). LP fluid in 120 of the PX may be pressurized and exit the PX at high pressure (e.g., HP fluid out 150, at a pressure greater than that of LP fluid in 120), and HP fluid in 130 may be at least partially depressurized and exit the PX at low pressure (e.g., LP fluid out 140, at a pressure less than that of the HP fluid in 130). The PX may operate with the HP fluid in 130 directly applying a force to pressurize the LP fluid in 120, with or without a fluid separator between the fluids. Examples of fluid separators that may be used with the PX include, but are not limited to, pistons, bladders, diaphragms, and/or the like. In some embodiments, PXs may be rotary devices. Rotary PXs, such as those manufactured by Energy Recovery, Inc. of San Leandro, Calif., may not have any separate valves, since the effective valving action is accomplished internal to the device via the relative motion of a rotor with respect to end covers. In some embodiments, rotary PXs operate with internal pistons to isolate fluids and transfer pressure with relatively little mixing of the inlet fluid streams. In some embodiments, rotary PXs operate without internal pistons between the fluids. Reciprocating PXs may include a piston moving back and forth in a cylinder for transferring pressure between the fluid streams. Any PX or multiple PXs may be used in the present disclosure, such as, but not limited to, rotary PXs, reciprocating PXs, or any combination thereof. In addition, the PX may be disposed on a skid separate from the other components of a fluid handling system 100 A (e.g., in situations in which the PX is added to an existing fluid handling system). In some examples, the PX may be fastened to a structure that can be moved from one site to another. The PX may be coupled to a system (e.g., pipes of a system, etc.) that has been built on-site. The structure to which the PX is fastened may be referred to as a ‘skid.’

[0036] In some embodiments, a motor 160 is coupled to hydraulic energy transfer system 110 (e.g., to a PX). In some embodiments, the motor 160 controls the speed of a rotor of the hydraulic energy transfer system 110 (e.g., to increase pressure of HP fluid out 150, to decrease pressure of HP fluid out 150, etc.). In some embodiments, motor 160 generates energy (e.g., acts as a generator) based on pressure exchanging in hydraulic energy transfer system 110.

[0037] The hydraulic energy transfer system 110 may include a hydraulic turbocharger or hydraulic pressure exchanger, such as a rotating PX. The PX may include one or more chambers and/or channels (e.g., 1 to 100) to facilitate pressure transfer between first and second fluids (e.g., gas, liquid, multi-phase fluid). In some embodiments, the PX may transfer pressure between a first fluid (e.g., pressure exchange fluid, such as a proppant free fluid, substantially proppant free fluid, high density fluid, lower viscosity fluid, fluid that has lower than a threshold amount of certain chemicals, etc.) and a second fluid that may have a higher viscosity (e.g., be highly viscous), have a lower density, include more than a threshold amount of certain chemicals, and/or contain solid particles (e.g., frac fluid and/or fluid containing sand, proppant, powders, debris, ceramics, contaminants, particles from welded or soldered joints, etc.).

[0038] In some embodiments, LP in system 122 includes a booster (e.g., a pump and/or a compressor) to increase pressure of fluid to form LP fluid in 120. In some embodiments, LP in system 122 includes an ejector to increase pressure of fluid to form LP fluid in 120. In some embodiments, LP in system 122 receives a gas from LP out system 142. In some embodiments, LP in system 122 receives fluid from a receiver (e.g., a flash tank, etc.). The receiver may receive LP fluid out 140 output from hydraulic energy transfer system 110. [0039] Fluid handling system 100 A may additionally include one or more sensors to provide sensor data (e.g., flowrate data, pressure data, velocity data, etc.) associated with the fluids of fluid handling system 100A. One or more controllers may control one or more flow rates of fluid handling system 100A based on the sensor data. In some embodiments, controllers cause one or more flow valves to actuate based on sensor data received.

[0040] One or more components of the hydraulic energy transfer system 110 may be used in different types of systems, such as thermal energy storage systems, fracing systems, desalination systems, refrigeration and heat pump systems (e.g., FIG. IB), slurry pumping systems, industrial fluid systems, waste fluid systems, fluid transportation systems, heat transfer systems, etc.

[0041] FIG. IB illustrates a schematic diagram of a fluid handling system 100B including a hydraulic energy transfer system 110 and thermal energy storage medium 180, according to certain embodiments. Fluid handling system 100B may be a thermal energy storage system, a refrigeration system, and/or a heat pump system. In some embodiments, fluid handling system 100B is a thermal energy (e.g., heat) transport system (e.g., heat transport system, thermal transport system). Fluid handling system 100B may be configured to store thermal energy for later use. Fluid handling system 100B may be configured to upgrade thermal energy from a low-grade (e.g., low temperature) to a high-grade (e.g., high-temperature) heat. Fluid handling system 100B may be configured to maintain one or more thermal energy storage mediums at temperatures different from environmental temperatures, equilibrium temperatures, or the like, and to use the storage mediums to perform one or more functions at a later time. Fluid handling system 100B may be configured to cool and/or heat an environment (e.g., an indoor space, a refrigerator, a freezer, etc.). In some embodiments, fluid handling system 100B includes more components, less components, same routing, different routing, and/or the like than that shown in FIG. IB. Some of the features in FIG. IB that have similar reference numbers as those in FIG. lA may have similar properties, functions, and/or structures as those in FIG. 1 A.

[0042] Hydraulic energy transfer system 110 (e.g., PX) may receive LP fluid in 120 from LP in system 122 (e.g., low pressure lift device 128, low pressure fluid pump, low pressure booster, low pressure compressor, low pressure ejector, etc.) andHP fluid in 130 from HP in system 132 (e.g., first heat exchanger (HX) 138, condenser, gas cooler, heat exchanger, etc.). The first heat exchanger 138 may be thermally coupled to thermal energy storage medium 180 A. The first heat exchanger 138 may be embedded in thermal energy storage medium 180A, may be in thermal contact with a secondary fluid for providing transfer of heat between first heat exchanger 138 and thermal energy storage medium 180 A, etc. Various fluid handling systems represented by fluid handling system 100B may include one or more thermal energy storage mediums, e.g., thermal energy storage medium 180A coupled to first heat exchanger 138, thermal energy storage medium 180B coupled to second heat exchanger 144, etc. The hydraulic energy transfer system 110 (e.g., PX) may exchange pressure between the LP fluid in 120 and HP fluid in 130 to provide HP fluid out 150 to HP out system 152 (e.g., high pressure lift device 159, high pressure fluid pump, high pressure booster, high pressure compressor, high pressure ejector, etc.) and to provide LP fluid out 140 to LP out system 142 (e.g., evaporator, second heat exchanger 144, heat exchanger, receiver 113, etc.). The LP out system 142 (e.g., second heat exchanger 144, receiver 113) may provide the fluid to compressor 178 and low pressure lift device 128. The second heat exchanger 144 may provide the fluid to compressor 178 and the receiver 113 (e.g., flash tank) may provide fluid to the low pressure lift device 128. Receiver 113 may form a chamber to collect and/or contain fluid. Receiver 113 may receive the fluid in a two-phase state (e.g., liquid and gas). Receiver 113 may separate phases of the fluid. Receiver 113 may enable gas and liquid to be provided separately to other components, e.g., to control fluid density, to ensure a target phase reaches a target component, or the like. The first heat exchanger 138 may receive fluid from compressor 178 and high pressure lift device 159. One or more controllers may control one or more components of fluid handling system 100B. High pressure lift device 159 may be a high pressure booster and low pressure lift device 128 may be a low pressure booster.

[0043] The fluid handling system 100B may be a closed system. LP fluid in 120, HP fluid in 130, LP fluid out 140, andHP fluid out 150 may all be a fluid (e.g., refrigerant, the same fluid, a working fluid) that is circulated in the closed system of fluid handling system 100B. [0044] Fluid handling system 100B may additionally include one or more sensors configured to provide sensor data associated with the fluid. One or more flow valves may control flowrates of the fluid based on sensor data received from the one or more sensors. In some embodiments, a controller causes one or more flow valves (not illustrated) to actuate based on sensor data received.

[0045] FIGS. 2A-E are exploded perspective views a rotary PX 40 (e.g., rotary pressure exchanger, rotary liquid piston compressor (LPC)), thermally coupled to a thermal energy storage medium 180, according to certain embodiments. Some of the features in one or more of FIGS. 2A-E may have similar properties, functions, and/or structures as those in one or more of FIGS. 1 A-B.

[0046] PX 40 is configured to transfer pressure and/or work between a first fluid (e.g., high-pressure working fluid, refrigerant, , supercritical carbon dioxide, HP fluid in 130) and a second fluid (e.g., low-pressure working fluid, refrigerant, superheated gaseous carbon dioxide, LP fluid in 120) with minimal mixing of the fluids. The rotary PX 40 may include a generally cylindrical body portion 42 that includes a sleeve 44 (e.g., rotor sleeve) and a rotor 46. The rotary PX 40 may also include two end caps 48 and 50 that include manifolds 52 and 54, respectively. Manifold 52 includes respective inlet port 56 and outlet port 58, while manifold 54 includes respective inlet port 60 and outlet port 62. In operation, these inlet ports 56, 60 enable the first and second fluids to enter the rotary PX 40 to exchange pressure, while the outlet ports 58, 62 enable the first and second fluids to then exit the rotary PX 40. In operation, the inlet port 56 may receive a high-pressure first fluid (e.g., HP fluid in 130) output from a condenser or gas cooler, and after exchanging pressure, the outlet port 58 may be used to route a low-pressure first fluid (e.g., LP fluid out 140) out of the rotary PX 40 to a receiver (e.g., flash tank) configured to receive the first fluid from the rotary PX 40. The receiver may form a chamber configured to separate the fluid into a gas and a liquid. Similarly, the inlet port 60 may receive a low-pressure second fluid (e.g., LP fluid in 120) from a booster configured to receive a portion of the gas from the receiver and increase pressure of the gas, and the outlet port 62 maybe used to route a high-pressure second fluid (e.g., HP fluid out 150) out of the rotary PX 40. The end caps 48 and 50 include respective end covers 64 and 66 (e.g., end plates) disposed within respective manifolds 52 and 54 that enable fluid sealing contact with the rotor 46.

[0047] One or more components of the PX 40, such as the rotor 46, the end cover 64, and/or the end cover 66, may be constructed from a wear-resistant material (e.g., carbide, cemented carbide, silicon carbide, tungsten carbide, etc.) with a hardness greater than a predetermined threshold (e.g., a Vickers hardness number that is at least 1000, 1250, 1500, 1750, 2000, 2250, or more). In some examples, tungsten carbide may be more durable and may provide improved wear resistance to abrasive fluids as compared to other materials, such as alumina ceramics. Additionally, in some embodiments, one or more components of the PX 40, such as the rotor 46, the end cover 64, the end cover 66, and/or other sealing surfaces of the PX 40, may include an insert. In some embodiments, the inserts may be constructed from one or more wear-resistant materials (e.g., carbide, cemented carbide, silicon carbide, tungsten carbide, etc.) with a hardness greater than a predetermined threshold (e.g., a Vickers hardness number that is at least 1000, 1250, 1500, 1750, 2000, 2250, or more) to provide improved wear resistance.

[0048] The rotor 46 may be cylindrical and disposed in the sleeve 44, which enables the rotor 46 to rotate about the axis 68. The rotor 46 may have a plurality of channels 70 (e.g., ducts, rotor ducts) extending substantially longitudinally through the rotor 46 with openings 72 and 74 (e.g., rotor ports) at each end arranged symmetrically about the longitudinal axis 68. The openings 72 and 74 of the rotor 46 are arranged for hydraulic communication with inlet and outlet apertures 76 and 78 (e.g., end cover inlet port and end cover outlet port) and 80 and 82 (e.g., end cover inlet port and end cover outlet port) in the end covers 64 and 66, in such a manner that during rotation the channels 70 are exposed to fluid at high-pressure and fluid at low-pressure. As illustrated, the inlet and outlet apertures 76 and 78 and 80 and 82 may be designed in the form of arcs or segments of a circle (e.g., C-shaped).

[0049] In some embodiments, a controller using sensor data (e.g., revolutions per minute measured through a tachometer or optical encoder, volumetric flow rate measured through flowmeter, etc.) may control the extent of mixing between the first and second fluids in the rotary PX 40, which may be used to improve the operability of the fluid handling system (e.g., fluid handling systems 100A-B of FIGS. 1A-B). In some examples, varying the volumetric flow rates of the first and/or second fluids entering the rotary PX 40 allows the operator (e.g., system operator, plant operator) to control the amount of fluid mixing within the PX 40. In addition, varying the rotational speed of the rotor 46 (e.g., via a motor) also allows the operator to control mixing. Three characteristics of the rotary PX 40 that affect mixing are: (1) the aspect ratio of the rotor channels 70; (2) the duration of exposure between the first and second fluids; and (3) the creation of a barrier (e.g., fluid barrier, piston, interface) between the first and second fluids within the rotor channels 70. First, the rotor channels 70 (e.g., ducts) are generally long and narrow, which stabilizes the flow within the rotary PX 40. In addition, the first and second fluids may move through the channels 70 in a plug flow regime with minimal axial mixing. Second, in certain embodiments, the speed of the rotor 46 reduces contact between the first and second fluids. In some examples, the speed of the rotor 46 (e.g., rotor speed of approximately 1200 revolutions per minute (RPM)) may reduce contact times between the first and second fluids to less than approximately 0.15 seconds, 0.10 seconds, or 0.05 seconds. Third, the rotor channel 70 (e.g., a small portion of the rotor channel 70) is used for the exchange of pressure between the first and second fluids. [0050] In a thermal energy storage system, operations of the PX 40 may proceed as described below: low pressure gaseous CO₂ flow provided to a low-pressure inlet (LP-in) of the PX 40 enters the duct and is sealed in the duct as duct rotates past the LP-in port. Then as this duct becomes exposed to high-pressure outlet, a pressure wave may be generated that compresses this low pressure gaseous CO₂ to high pressure, in the process also increasing its temperature. Thus the low pressure gaseous CO₂ gets converted to high pressure, high temperature supercritical CO₂ state. This high pressure high temperature supercritical CO₂ is then ejected out through an high-pressure outlet (HP-out) port as the high pressure, medium temperature supercritical CO₂ enters the duct from opposite end (e.g., HP-in port) and pushes the now compressed portion of fluid out of the HP-out port. The HP-in fluid portion then becomes sealed in the duct as the duct continues its rotation past the HP-in port. Subsequently, this duct is exposed to the LP-out port, an expansion wave may propagate through the duct and converts high-pressure moderate-temperature supercritical CO₂ into a low-pressure low-temperature two-phase liquid gas mixture which is then ejected out of the LP-out port.

[0051] In some embodiments, a volume of fluid remains in the channel 70 as a barrier between the first and second fluids. All these mechanisms may limit mixing within the rotary PX 40. Moreover, in some embodiments, the rotary PX 40 may be designed to operate with internal pistons or other barriers, either complete or partial, that isolate the first and second fluids while enabling pressure transfer. [0052] PX 40 may be in a system (e.g., thermal energy storage system) that also includes thermal energy storage medium 180. The thermal energy storage medium may provide heat to the working fluid of PX 40. The thermal energy storage medium may receive heat from the working fluid of PX 40. The thermal energy storage medium may be in thermal communication with the working fluid of PX 40. The thermal energy storage medium may be in thermal communication via one or more other components of subsystems, such as one or more heat exchangers, a secondary heat transfer fluid, or the like. A fluid handling system may have one thermal energy storage system, e.g., for storing heat to later be provided to a target area or process, for later receiving heat to cool a target area or component, or the like. A fluid handling system may have multiple thermal energy storage systems, e.g., for passing heat between the storage systems. As an example, a fluid handling system including PX 40 may include a first “hot” thermal energy storage medium 180 maintained at a high temperature (compared to an ambient temperature, a second energy storage medium, or the like), and a second “cold” thermal energy storage medium 180 maintained at a low temperature. The fluid handling system may be operated in cycles, e.g., a charge cycle (e.g., in which work is performed on the working fluid to act as a heat pump) and a discharge cycle (e.g., in which a stored state of a thermal energy storage medium 180 is utilized to perform a target function). In some embodiments, a charge cycle may store thermal energy and a discharge cycle may extract energy from the thermal energy storage medium 180, e.g., via an electric generator of a heat engine system. In some embodiments, a charge cycle may generate a cold thermal energy storage medium 180, and a discharge cycle may use the thermal energy storage medium 180 as a heat sink to cool a target location, component, material, or the like. In some embodiments, a charge cycle may increase the temperature of a thermal energy storage medium 180 (e.g., by transferring heat from a lower temperature heat source), and a discharge cycle may utilize the high temperature heat for a target process (e.g., an industrial process). In some embodiments, PX 40 may be utilized for one cycle of a fluid handling system and not another cycle. For example, PX 40 may be utilized during a charge cycle and not be utilized during a discharge cycle. Fluid handling systems may include multiple architectures, e.g., to accommodate the charge and discharge cycles. Fluid handling system architectures may have some overlap of components (e.g., thermal energy storge medium 180) and may have some exclusive components (e.g., PX 40, a main working fluid compressor, an electric generator, etc.).

[0053] FIGS. 2B-2E are exploded views of an embodiment of the rotary PX 40 illustrating the sequence of positions of a single rotor channel 70 in the rotor 46 as the channel 70 rotates through a complete cycle. It is noted that FIGS. 2B-2E are simplifications of the rotary PX 40 showing one rotor channel 70, and the channel 70 is shown as having a circular cross- sectional shape. In other embodiments, the rotary PX 40 may include a plurality of channels 70 with the same or different cross-sectional shapes (e.g., circular, oval, square, rectangular, polygonal, etc.). Thus, FIGS. 2B-2E are simplifications for purposes of illustration, and other embodiments of the rotary PX 40 may have configurations different from those shown in FIGS. 2A-2E. As described in detail below, the rotary PX 40 facilitates pressure exchange between first and second fluids (e.g., a higher pressure refrigerant and lower pressure refrigerant, etc.) by enabling the first and second fluids to briefly contact each other within the rotor 46. In some embodiments, the PX facilitates pressure exchange between first and second fluids by enabling the first and second fluids to contact opposing sides of a barrier (e.g., a reciprocating barrier, a piston, not shown). In some embodiments, this exchange happens at speeds that result in limited mixing of the first and second fluids. The speed of the pressure wave traveling through the rotor channel 70 (as soon as the channel is exposed to the aperture 76), the diffusion speeds of the fluids, and/or the rotational speed of rotor 46 may dictate whether any mixing occurs and to what extent. PX 40 may be included in a thermal energy storage system, e.g., a system further including thermal energy storage medium 180. [0054] FIG. 2B is an exploded perspective view of an embodiment of a rotary PX 40 (e.g., rotary LPC), according to certain embodiments. In FIG. 2B, the channel opening 72 is in a first position. In the first position, the channel opening 72 is in fluid communication with the aperture 78 in end cover 64 and therefore with the manifold 52, while the opposing channel opening 74 is in hydraulic communication with the aperture 82 in end cover 66 and by extension with the manifold 54. The rotor 46 may rotate in the clockwise direction indicated by arrow 84. In operation, low-pressure second fluid 86 (e.g., low pressure slurry fluid) passes through end cover 66 and enters the channel 70, where it contacts the first fluid 88 at a dynamic fluid interface 90. The second fluid 86 then drives the first fluid 88 out of the channel 70, through end cover 64, and out of the rotary PX 40. However, because of the short duration of contact, there is minimal mixing between the second fluid 86 (e.g., slurry fluid) and the first fluid 88 (e.g., particulate-free fluid). In some embodiments, low pressure second fluid 86 contacts a first side of a barrier (e.g., a piston, not shown) disposed in channel 70 that is in contact (e.g., on an opposing side of the barrier) by first fluid 88. The second fluid 86 drives the barrier which pushes first fluid 88 out of the channel 70. In such embodiments, there is negligible mixing between the second fluid 86 and the first fluid 88. [0055] FIG. 2C is an exploded perspective view of an embodiment of a rotary PX 40 (e.g., rotary LPC), according to certain embodiments. In FIG. 2C, the channel 70 has rotated clockwise through an arc of approximately 90 degrees. In this position, the opening 74 (e.g., outlet) is no longer in fluid communication with the apertures 80 and 82 of end cover 66, and the opening 72 is no longer in fluid communication with the apertures 76 and 78 of end cover 64. Accordingly, the low-pressure second fluid 86 is temporarily contained within the channel 70.

[0056] FIG. 2D is an exploded perspective view of an embodiment of a rotary PX 40 (e.g., rotary LPC), according to certain embodiments. In FIG. 2D, the channel 70 has rotated through approximately 60 degrees of arc from the position shown in FIG. 2B. The opening 74 is now in fluid communication with aperture 80 in end cover 66, and the opening 72 of the channel 70 is now in fluid communication with aperture 76 of the end cover 64. In this position, high-pressure first fluid 88 enters and pressurizes the low-pressure second fluid 86, driving the second fluid 86 out of the rotor channel 70 and through the aperture 80.

[0057] FIG. 2E is an exploded perspective view of an embodiment of a rotary PX 40 (e.g., rotary LPC), according to certain embodiments. In FIG. 2E, the channel 70 has rotated through approximately 270 degrees of arc from the position shown in FIG. 2B. In this position, the opening 74 is no longer in fluid communication with the apertures 80 and 82 of end cover 66, and the opening 72 is no longer in fluid communication with the apertures 76 and 78 of end cover 64. Accordingly, the first fluid 88 is no longer pressurized and is temporarily contained within the channel 70 until the rotor 46 rotates another 90 degrees, starting the cycle over again.

[0058] FIGS. 3A-C are schematic diagrams of thermal energy storage systems 300A-C (e.g., refrigeration systems, heat pump systems, power generation systems, energy transfer systems, energy storage systems, etc.) including PXs, according to some embodiments. Some of the components of one or more of FIGS. 3A-C may share one or more features, properties, functions, or structures as components of FIGS. 1 A-B and/or FIGS. 2A-E. Systems of one or more of FIGS. 3A-C and/or FIGS. 3A-C may be used to perform operations of methods 500 and/or 600, described in FIGS. 5-6.

[0059] FIG. 3A is a schematic diagram of a thermal energy storage system 300A including a PX 310, according to some embodiments. In some embodiments, thermal energy storage system 300 A is a thermal energy transport system and/or a fluid handling system. Thermal energy storage system 300 A may circulate a working fluid for performing energy storage operations, e.g., a refrigerant, propane, ammonia, CO₂ etc. Thermal energy storage system 300 A include a first architecture 302 and a second architecture 304. First architecture 302 may be configured to perform operations of a charge cycle. Second architecture 304 may be configured to perform operations of a discharge cycle. The charge cycle may be a heat pump cycle. The charge cycle may transfer heat from an area of lower temperature (e.g., low temperature heat exchanger 318) to an area of higher temperature (e.g., high temperature heat exchanger 329. Transferring heat from a lower temperature region to a higher temperature region may be performed at the cost of energy to perform work on the system, e.g., performed by compressor 322. PX 310 may reduce the energy requirements of the system by reducing an amount of working fluid that must be compressed by compressor 322, by performing more efficient forms of compression and/or expansion of the working fluid, etc. PX 310 performs expansion work recovery, e.g., it recovers the pressure energy from the high pressure refrigerant fluid exiting the high temperature heat exchanger 329 and uses it to compress a portion of the low pressure refrigerant vapor exiting the low temperature heat exchanger 318. Without the PX 310 this pressure energy would have been lost through expansion across a high pressure valve in a standard heat pump system. Thus PX 310 reduces the amount of low-pressure working fluid that needs to be compressed by compressor 322 and thus reduces energy consumption of the compressor 322. This causes a charge cycle utilizing architecture 302 of thermal energy storage system 300 A to be more efficient. The discharge cycle may transfer thermal energy from a region of higher temperature to a region of lower temperature. The discharge cycle may be used (e.g., as a heat engine) to generate energy for use or storage (e.g., electricity) for use.

[0060] PX 310 may be included in a first architecture (e.g., may be utilized in a charge cycle of thermal energy storage system 100A). PX 310 may be a rotary pressure exchanger. In some embodiments, PX 310 is an isobaric or substantially isobaric pressure exchanger. PX 310 may be configured to exchange pressure between a first fluid and a second fluid. PX 310 may be configured to receive a first fluid at a high pressure via a high-pressure inlet (HP in) and a second fluid at a low pressure via a low-pressure inlet (LP in). PX 310 may be configured to exchange pressure between the high-pressure fluid and the low-pressure fluid. PX 310 may be configured to provide the first fluid at a low pressure via a low-pressure outlet (LP out) and the second fluid at a high pressure via a high-pressure outlet (HP out). In some embodiments, PX 310 is coupled to a motor (e.g., rotation of a rotor of PX 310 is controlled by the motor). In some embodiments, the motor controls the rotational speed of the PX 310. Mass flow (e.g., of the first fluid and/or of the second fluid) through the PX 310 may be related to the rotational speed of the PX 310. In some embodiments, the pressure of the fluid (e.g., the first fluid) in one or more other components (e.g., high temperature heat exchanger 329, low temperature heat exchanger 318, etc.) may be related to the rotational speed of the PX 310. In some embodiments, a controller receives sensor data from one or more sensors of motor thermal energy storage system 300 A.

[0061] In some embodiments, PX 310 is to receive the first fluid at a high pressure (e.g., HP fluid in 130 of FIGS. 1A-B) via a high pressure inlet. In some embodiments, PX 310 is to receive the second fluid at a low pressure (e.g., LP fluid in 120 of FIGS. 1A-B) via a low pressure inlet. Although there is a reference to “high pressure” and “low pressure,” “high pressure” and “low pressure” may be relative to one another and may not connote certain pressure values (e.g., the pressure of the HP fluid in 130 is higher than the pressure of LP fluid in 120). PX 310 may exchange pressure between the first fluid and the second fluid. PX 310 may provide the first fluid via a low pressure outlet (e.g., LP fluid out 140) and may provide the second fluid via a high pressure outlet (e.g., HP fluid out 150). In some embodiments, the first fluid provided via the low pressure outlet is at a low pressure and the second fluid provided via the high pressure outlet is at a high pressure.

[0062] In some embodiments, fluid handling system 300A includes a high temperature heat exchanger 329 (e.g., a gas cooler, condenser), a lowtemperatureheat exchanger 318 (e.g., an evaporator), and a compressor 322. In some embodiments, fluid handling system 300A is a thermal energy storage system. In some embodiments, the high temperature heat exchanger 329 is a heat exchanger that provides the heat from the working fluid (e.g., the first fluid, refrigerant, CO₂) to an environment. In some embodiments, the high temperature heat exchanger 329 may be coupled to a thermal energy storage medium. Heat may be rejected from the working fluid in high temperature heat exchanger 329 to be absorbed by the thermal energy storage medium. Heat rejected by the thermal energy storage medium may be absorbed by the working fluid in high temperature heat exchanger 329. Some variations of thermal energy storage media are discussed in connection with FIGS. 4A-D.

[0063] In some embodiments, high temperature heat exchanger 329 may act as a condenser that condenses fluid flowing through the high temperature heat exchanger 329 (e.g., while cooling the fluid). For example, high temperature heat exchanger 329 may cool a working fluid of thermal energy storage system 300A during a charge cycle, while first architecture 302 is in operation, or the like. The phase of the working fluid may change from gas to liquid (e.g., condense) within the high temperature heat exchanger 329.

[0064] In some embodiments, high temperature heat exchanger 329 is a heat exchanger that does not condense fluid flowing through the high temperature heat exchanger 329 (e.g., cools the fluid without condensing the fluid). For example, during a charge cycle, high temperature heat exchanger 329 may cool the working fluid of thermal energy storage system 300A without condensing the fluid. In some embodiments, the pressure of the fluid within the high temperature heat exchanger 329 is above the critical pressure of the fluid. In some embodiments, the high temperature heat exchanger 329 is a gas cooler and does not condense the fluid (e.g., in a gaseous state). The high temperature heat exchanger 329 may provide the heat from the fluid (e.g., gas) to a corresponding environment. In some embodiments, the temperature of the fluid in the high temperature heat exchanger 329 may be lowered, but the fluid may not condense (e.g., the fluid does not change phase from gas to liquid). In some embodiments, above the critical pressure of the fluid (e.g., of the refrigerant), the thermodynamic distinction between liquid and gas phases of the fluid within the high temperature heat exchanger 329 disappears and there is only a single state of fluid called the supercritical state.

[0065] In some embodiments, high temperature heat exchanger 329 may provide heatto the working fluid of thermal energy storage system 300A (e.g., during a discharge cycle). High temperature heat exchanger 329 may act as an evaporator, e.g., the working fluid may experience a phase change to gas based on the absorbed heat. High temperature heat exchanger 329 may, in some embodiments, not act as an evaporator during a discharge cycle (e.g., a working fluid may not experience a phase change in high temperature heat exchanger 329 during a discharge cycle).

[0066] Thermal energy storage system 300A includes low temperature heat exchanger 318 (e.g., in thermal communication with a thermal energy storage medium or environment that is maintained at a lower range of temperatures than the environment or thermal energy storage medium associated with high temperature heat exchanger 329). Low temperature heat exchanger 318 may provide heat absorbed by system 300A from a heat source (e.g., a cold reservoir) to the working fluid during a charge cycle. The heat may be rejected to a heat sink (e.g., a hot reservoir) via the high temperature heat exchanger 329 (e.g., while thermal energy storage system 300 A is acting as a heat pump, during a charge cycle, while the system is operating in a first mode, or the like). In some embodiments, the working fluid facilitates heat transfer from an environment associated with an evaporator to an environment associated with a condenser during a charge cycle. In some embodiments, the working fluid facilitates heat transfer from an environment or thermal energy storage medium associated with the low temperature heat exchanger 318 to an environment or thermal energy storage medium associated with high temperature heat exchanger 329 during a charge cycle. Compressor 322 of thermal energy storage system 300A may increase corresponding pressure of the working fluid along a flow path between the low temperature heat exchanger 318 and the high temperature heat exchanger 329. Compressor 322 may be active during a charge cycle. Compressor 322 may further be utilized during a discharge cycle, or another device (e.g., a pump 323) may be utilized during a discharge cycle. In some embodiments, different components (e.g., compressors, pumps, etc.) may be available for different operating modes, operating conditions, or the like. For example, during a charge cycle, a compressor may be utilized (e.g., for supercritical and/or gaseous working fluid) and during a discharge cycle, a pump may be utilized (e.g., for liquid working fluid). In some embodiments, the working fluid is CO2 or another refrigeration fluid. The working fluid may flow substantially in a cycle (e.g., from high temperature heat exchanger 329 to PX 310 to low temperature heat exchanger 318 to compressor 322 to high temperature heat exchanger 329, etc.). In some embodiments, the cycle may be associated with operation in a first mode, such as a charge cycle, and a different cycle (e.g., a different collection of components, a different flow path, a different architecture, etc.) may be utilized for a second mode. First architecture 302 may be associated with a first mode (e.g., a charge mode or charge cycle) and second architecture 304 may be associated with operation in a second mode (e.g., a discharge mode or discharge cycle).

[0067] Thermal energy storage system 300A may include a turbine 324 for operation during a discharge cycle. During a discharge cycle, heat may be transferred from high temperature heat exchanger 329 (or an associated environment, thermal energy storage medium, or the like) to low temperature heat exchanger 318. Energy may be extracted from the flow of heat, e.g., thermal energy storage system 300A may be operated as a heat engine (e.g., in a heat engine mode, in a discharge mode, in a discharge cycle, or the like). Turbine 324 may be coupled to a generator 325 for producing electricity, or another component for extracting energy, work, or the like from the thermal energy storage system 300 A. Turbine 324 may be configured to convert energy of the working fluid to electrical energy.

[0068] In some embodiments, fluid handling system 300A includes a low-pressure booster and/or a high-pressure booster (not shown). Both a low-pressure booster and a high-pressure booster may be configured to increase (e.g., “boost”) pressure of the working fluid, e.g., before providing the fluid to the LP in and HP in ports of the PX 310, respectively. For instance, a low-pressure booster may increase pressure of the working fluid output from low temperature heat exchanger 318 (e.g., received from the PX 310). A high-pressure booster may increase pressure of the working fluid output by the PX 310. The working fluid may be provided (e.g., by the high-pressure booster) to combine with fluid output from the compressor 322 (e.g., upstream of an inlet of the high temperature heat exchanger 329) to be provided to the high temperature heat exchanger 329. The low-pressure booster may increase pressure less than a threshold amount (e.g., may operate over a pressure differential that is less than a threshold amount). In some examples, a low-pressure booster may increase pressure of the working fluid approximately 10 to 60 psi. The working fluid may experience pressure loss (e.g., due to fluid friction loss in piping) as the second fluid flows from the low pressure booster to the LP-in inlet of the PX 310. A high-pressure booster may increase pressure of the working fluid between the second outlet of the PX 310 and an inlet of the high temperature heat exchanger 329. The high-pressure booster may increase pressure less than a threshold amount (e.g., may operate over a pressure differential that is less than a threshold amount). In some examples, a high-pressure booster may increase pressure of the second fluid approximately 10 to 60 psi. A high-pressure booster may increase pressure of the working fluid to a pressure that substantially matches the pressure of fluid output from the compressor 322 (e.g., the pressure of high temperature heat exchanger 329). In contrast to any boosters, the compressor 322 may increase pressure of fluid more than a threshold amount (e.g., compressor 322 may operate over a pressure differential that is greater than a threshold amount). In some examples, the compressor 322 may increase pressure of the fluid greater than approximately 200 psi. In some embodiments, one or more controllers control a flowrate of fluid through the PX 310 by controlling a flowrate of booster pumps, such as a low-pressure booster.

[0069] In some embodiments, low temperature heat exchanger 318 is a heat exchanger to exchange (e.g., provide) corresponding thermal energy from an environment (e.g., a medium of an environment) to a working fluid during a charge cycle. In some examples, low temperature heat exchanger 318 may receive heat (e.g., thermal energy) from air of the environment and provide the heat to the working fluid. In some embodiments, during a charge cycle, low temperature heat exchanger 318 may receive heat from a thermal energy storage medium and provide the heat to the working fluid. In some embodiments, low temperature heat exchanger 318 may provide opposite functions during a discharge cycle. For example, during a discharge cycle, low temperature heat exchanger 318 may provide thermal energy from the working fluid to an environment, to a thermal energy storage medium, or the like. In some embodiments, the environment is a refrigerated space such as the inside of a refrigerator or freezer, an interior space (e.g., of a building or vehicle), or any other space that is to be kept cool. In some examples, the environment can be the interior of a freezer or refrigeration section at a supermarket or warehouse. In some embodiments, the environment is a thermal energy storage medium, either configured to provide heat to the high temperature heat exchanger 329 for storage and later use, to act as a later heat sink to absorb heat from a target material or environment to be kept cool, or the like.

[0070] In some embodiments, the high temperature heat exchanger 329 is a heat exchanger to transfer corresponding thermal energy (e.g., heat) between working fluid and an environment. In some embodiments, during operation in a first mode (e.g., a charge cycle), high temperature heat exchanger 329 may provide heat to an environment or thermal energy storage medium from a working fluid of thermal energy storage system 300 A, and during operation in a second mode (e.g., a discharge cycle), high temperature heat exchanger 329 may absorb heat from the environment or thermal energy storage medium and provide the heat to the working fluid of thermal energy storage system 300A.

[0071] Thermal energy storage system 300 A may include one or more controllers.

Controllers may control the boosters, various valves, and/or compressors of system 300A. Controllers may receive sensor data from one or more sensors of system 300 A. The sensors may include pressure sensors, flowrate sensors, and/or temperature sensors. Controllers of thermal energy storage system 300A may perform operations to determine whether thermal energy storage system 300A is operated in a first mode (e.g., a charge mode) or a second mode (e.g., a discharge mode). Determinations of which mode to operate in may be based on a number of factors. For example, thermal energy may be stored while electricity to operate compressor 322 is abundant (e.g., above a threshold amount), and thermal energy may be expended to generate electricity via generator 325 while electricity is scarce (e.g., below a threshold amount). Time of day, price of power, availability of renewable energy, etc., may contribute to a determination of whether to operate thermal energy storage system 300A in a first mode or a second mode. Further, conditions of the thermal energy storage mediums (e.g., temperature, percent of material in a target phase, etc.) may be utilized in determining whether to operate in a first or second mode. Further, requirements of a process (e.g., heat requirements of an industrial process, cooling or heating requirements of a heating venting and air conditioning system, or the like) may be used in determining whether to operate in a first mode or a second mode.

[0072] The direction of transfer of thermal energy (e.g., heat transfer) of the system 300A may be reversible in some embodiments. For example, in refrigeration / air-conditioning / air cooling implementations of system 300A, the high temperature heat exchanger 329 placed outdoors rejects heat (e.g., provide corresponding thermal energy from the refrigeration fluid to the corresponding environment) and the low temperature heat exchanger 318 absorbs heat (e.g., provide corresponding thermal energy from the corresponding environment to the refrigeration fluid). While in heat pump implementation of system 300A, the high temperature heat exchanger 329 placed indoors rejects heat to its indoor environment and low temperature heat exchanger 318 absorbs heat from its outdoor environment. In some embodiments, system 300A includes one or more valves (e.g., a reversing valve, diversion valve(s), etc.) to reverse the function of system 300A (e.g., reverse the flow of thermal energy facilitated by system 300 A). In some embodiments, one or more flows of working may be reversed and/or diverted. In some examples, one or more reversing or diversion valves included in system 300A in some embodiments can direct fluid from the compressor 322 toward the outdoor unit. Similar valves may direct fluid from the compressor 322 to the indoor unit.

[0073] Thermal energy storage system 300A may be utilized in a first mode (e.g., using components of first architecture 302) or a second mode (e.g., using components of second architecture 304). Operations of a first mode (e.g., charge cycle) may include utilizing abundant power to store thermal energy. Storing of thermal energy may include providing heat via high temperature heat exchanger 329 to a thermal energy storage medium. [0074] In operation of the first mode, abundant power may be utilized to operate compressor 322. In the process of compression, the temperature of the working fluid may be increased. A portion of working fluid that is not provided to compressor 322 may be provided to a low-pressure inlet of PX 310, to be brought to a higher pressure via pressure exchange with another fluid stream of PX 310. The temperature of the fluid compressed in PX 310 may also increase.

[0075] In operation in the first mode, output fluid of compressor 322 and high-pressure output fluid of PX 310 may be provided to high temperature heat exchanger 329. The high temperature working fluid (e.g., gas, supercritical fluid, etc.) rejects heat to a lower temperature thermal energy storage medium. The thermal energy storage medium may store the heat by increasing in temperature and/or performing a phase change, depending on temperature, the storage medium, etc.

[0076] In operation in the first mode, after rejecting heat to the thermal energy storage medium, the working fluid has lost heat energy, and may have a reduced temperature as well. In the first mode, output of the high temperature heat exchanger 329 may be provided to a high-pressure inlet of PX 310, for exchanging pressure with a low-pressure fluid stream of PX 310. The working fluid exists a low-pressure outlet of PX 310. [0077] In operation in the first mode, fluid output by the low-pressure outlet of PX 310 may be provided to low temperature heat exchanger 318. The low pressure fluid (e.g., two phase gas-liquid mixture) may absorb heat from a thermal energy storage medium in thermal communication with the low temperature heat exchanger 318. The working fluid may be vaporized in the low temperature heat exchanger 318, e.g., may become a working gas. A first portion of the low pressure, low temperature gas may be provided to compressor 322, and a second portion of the low pressure, low temperature gas may be provided to a low- pressure inlet of PX 310. In some embodiments, a temperature difference between a thermal energy storage medium in communication with high temperature heat exchanger 329 (e.g., a high temperature thermal energy storage medium) and a thermal energy storage medium in communication with low temperature heat exchanger 318 (e.g., a low temperature thermal energy storage medium) may be large. Efficiency of operation in a second mode may be dependent on a temperature difference between two thermal energy storage mediums. [0078] Operation in a first mode of system 300 A may comprise operation of a charge cycle. During a charge cycle, a system may receive the low-pressure low temperature refrigerant (e.g., working fluid, CO₂, etc.) vapor from the exit of low temperature heat exchanger 318 and compresses it to high pressure, in the process increasing its temperature. The high- pressure refrigerant thus produced can be in the subcritical vapor state (pressure below the critical pressure of refrigerant) or in supercritical state (pressure and temperature above the critical point of the refrigerant). The high pressure, high temperature vapor thus produced may exchange heat with the thermal energy storage medium (e.g., as depicted in any one or more of FIGS. 4A-D) via high temperature heat exchanger 329. A thermal energy storage medium configured to be in thermal communication with high temperature heat exchanger 329 can store this high temperature heat either as sensible heat ( i.e. via temperature increase) or as latent heat ( i.e. via phase change from solid to liquid or from liquid to gas). After rejecting heat to the thermal storage medium, the high pressure refrigerant vapor may cool down and either condense into a liquid state ( if subcritical) or remains in supercritical state (if supercritical) but at lower temperature. This colder high-pressure refrigerant may then enter PX 310 through HP-in port and expands to low pressure. As it expands, temperature of the working fluid may drop and changes the phase to two phase liquid-gas mixture. This cold two phase liquid-gas mixture may exit the LP-out port of PX 310 and enters the low temperature heat exchanger 318 and absorbs heat from the low temperature thermal storage medium in thermal communication with low temperature heat exchanger 318, e.g., water or water/ice slurry, which may take a form represented by any one or more of FIGS. 4A-D. As the refrigerant absorbs the heat from low temperature storage medium, the low temperature medium can change its phase (e.g., liquid becomes progressively more and more ice slurry with increasing ice fraction by mass). After absorbing heat, the refrigerant liquid vaporizes and may become pure vapor at the exit of low temperature heat exchanger 318. This refrigerant vapor then may exit the low temperature heat exchanger and be split into two streams. One stream may enter the LP-in port of the PX 310 and other stream may enter the inlet of compressor 322. PX 310 compresses the portion of the low-pressure low-temperature refrigerant vapor entering LP-in port of PX 310 and converts it into high-pressure high- temperature vapor or supercritical fluid. Compressor 322 compresses the remaining portion of the refrigerant vapor to high pressure, high temperature vapor or supercritical fluid. The two high pressure high temperature streams (one from PX 310 and the other from compressor 322) merge and proceed to reject heat to a high temperature thermal energy storage medium via high temperature heat exchanger 329. The cycle may then repeat to continue charging thermal energy storage.

[0079] Thermal energy storage system 300A may further be operated in a second mode. In the second mode, a temperature difference between a hot reservoir (e.g., hot thermal energy storage associated with high temperature heat exchanger 329) and a cold reservoir (e.g., low temperature thermal energy storage associated with low temperature heat exchanger 318) may be utilized to extract energy from the system, to do work, to perform a target function, or the like.

[0080] In some embodiments, when power (e.g., electricity) is scarce, thermal energy storage system 300A may be operated in a second mode. The second mode may discharge thermal energy storage for performance of one or more target functions.

[0081] During operation in a second mode, low pressure working fluid which may be a gas, liquid, or a supercritical fluid may be compressed or pumped to high pressure, e.g., by pump 323. The working fluid may then be provided to high temperature heat exchanger 329.

[0082] During operation in a second mode, the working fluid may absorb heat from a high temperature thermal energy storage medium in high temperature heat exchanger 329. The temperature of the working fluid may increase. Enthalpy of the working fluid may increase. [0083] The high pressure and temperature working fluid may be provided to turbine 324. At the turbine, the high pressure and temperature working fluid may expand over the turbine and decrease in pressure. Turbine 324 may extract mechanical work from the working fluid through this process. The work extracted may cause a rotor of the turbine to spin, and a target function may be performed, such as using the motion of the rotor to drive generator 325 to generate electricity. In some embodiments, more electricity may be generated by generator 325 than is consumed by pump 323, leading to a net increase in stored electricity or produced electricity during operation in the second mode (e.g., during a discharge cycle).

[0084] During operation in the second mode, working fluid that exits the turbine may be of a higher temperature than a cold/low temperature thermal energy storage medium in connection with low temperature heat exchanger 318. Working fluid may reject heat to the thermal energy storage medium as the working fluid passes through low temperature heat exchanger 318. In some embodiments, working fluid may condense to a liquid state. Determining whether to operate at a temperature that working fluid condenses may be in view of target performance of the thermal energy storage system 300A, e.g., target efficiency, target level of cycle optimization, or the like. The size (e.g., thermodynamic energy capacity) of one or more thermal energy storage mediums may be determined based on a target electricity generation goal, target electricity generation time span, or the like. In some embodiments the high temperature heat exchanger 329 may represent more than one physical heat exchanger, where a different heat exchanger is used during discharge cycle than that used during charge cycle. Similarly in some embodiments the low temperature heat exchanger 318 may represent more than one physical heat exchanger. This configuration allows using two different working fluids (e.g., refrigerants) during a charge cycle and a discharge cycle. In some embodiments, both charge and discharge cycle may use CO₂ as the working fluid while in other embodiments, charge cycle may use CO₂ as the working fluid and a discharge cycle may use air or organic Rankine fluids ( e.g. Butane, Pentane, Hexane, silicon oils etc.) as working fluids.

[0085] FIG. 3B is a schematic diagram of a thermal energy storage system 300B that includes a pressure exchanger (PX), according to some embodiments. In some embodiments, thermal energy storage system 300B is a thermal energy transport system and/or a fluid handling system. In some embodiments, features that have reference numbers that are similar to reference numbers in other figures include similar properties, structures, and/or functionality as those described in other figures. In some examples, features of thermal energy storage system 300B may have similar properties, structures, and/or functionality as features of thermal energy storage system 300 A of FIG. 3A.

[0086] Thermal energy storage system 300B may include capability to operate in a first operational mode 301 and a second operational mode 303 (e.g., a charge mode and a discharge mode). The first operational mode 301 may correspond in one or more functions to first architecture 302 of FIG. 3A. The second operational mode 303 may share one or more features with second architecture 304 of FIG. 3A.

[0087] Thermal energy storage system 300B includes a controller 326, a three-way valve 328, and a flow control valve 330. Controller 326 may receive input. The input may include sensor data, user input, time data, or the like. For example, controller 326 may be coupled to a device that accepts user input for determining whether to operate thermal energy storage system 300B in a first mode or a second mode. Controller 326 may receive sensor data (e.g., associated with conditions of one or more thermal energy storage mediums, associated with energy availability/scarcity, etc.) and determine, based on the input data, whether to operate thermal energy storage system 300B in a first mode or a second mode.

[0088] Upon determining that thermal energy storage system 300B is to be operated in a first mode, controller 326 may provide one or more components with a control signal. For example, three-way valve 328 and/or flow control valve 330 may be operatively coupled to controller 326, to actuate based on control signals received from controller 326.

[0089] To operate thermal energy storage system 300B in a first mode, controller 326 may cause three-way valve 328 to actuate to enable flow from high temperature heat exchanger 329 to PX 310, and disable flow from high temperature heat exchanger 329 to turbine 324 (e.g., during a charge cycle, as shown by the dashed fluid flow path). During operation in a first mode, energy may be input into thermal energy storage system 300B (e.g., via compressor 322) rather than extracted via turbine 324. To operate thermal energy storage system 300B in the first mode, controller 326 may further provide a control signal to flow control valve 330. The signal provided to flow control valve 330 may determine a portion of fluid output by low temperature heat exchanger 318 that is provided to PX 310, and a portion that is provided to compressor 322. Determination of portions of fluid flow provided to compressor 322 and PX 310 during operation in the first mode may be determined by capability and/or capacity of the PX 310, capability of compressor 322, fluid system conditions (e.g., temperature and pressure), heat source and/or sink conditions (e.g., temperatures, masses, heat absorption, etc., of various thermal energy storage mediums), ambident conditions, optimizing energy efficiency or heat transfer rate or other parameters of interest. A portion of fluid output by low temperature heat exchanger 318 may be compressed to a higher pressure by compressor 322, while a portion of fluid output by low temperature heat exchanger 318 may be compressed by exchanging pressure with another fluid stream in PX 310. [0090] Upon determining that thermal energy storage system 300B is to be operated in a second mode, controller 326 may provide one or more components with a further control signal. Three-way valve 328, flow control vale 330, and other components of thermal energy storage system 300B may be provided with control signals by controller 326.

[0091] To operate thermal energy storage system 300B in a second mode, three-way valve 328 may be caused by controller 326 to be actuated such that flowis provided to turbine 324, and flow to PX 310 is disabled (as depicted by dashed working fluid flow paths in FIG. 3B). Working fluid may be allowed to flow to turbine 324, which may cause turbine 324 to rotate to perform a target function (e.g., electricity generation). In a second mode, thermal energy may be expended from storage (e.g., via a thermal energy storage medium in thermal communication with high temperature heat exchanger 329) to perform a target function, such as causing rotation of the turbine 324. To operate thermal energy storage system 300B in the second mode, flow control valve 330 may be cause by controller 326 to be actuated to disable fluid flow to PX 310. Workingfluid may be compressed by compressor 322 (or a different device than is utilized in the first mode, as depicted in FIG. 3A). The compressed working fluid is then provided to high temperature heat exchanger 329 during operation in the second operating mode of thermal energy storage system 300B.

[0092] Controller 326 may further provide additional control signals to additional components. For example, in some embodiments compressor 322 may be operated at a different speed or otherwise differently in the first mode and the second mode. Controller 326 may provide one or more control signals to adjust operation of compressor 322. In some embodiments, operations of compressor 322 may in practice be performed by a number of devices, e.g., a set of compressors, pumps, etc., and different devices may be utilized for different operating conditions, different target working fluid conditions, different target applications, different operating modes, or the like. Controller 326 may provide control signals to any of these devices, as well as any valves for adjusting flow paths to and/or from such devices, as a part of operating in the first or second operational mode. In some embodiments, additional components may be included in a thermal energy storage system, with additional control provided by controller 326. It will be understood that controller 326 may represent a single device or multiple devices, each performing a single function, or a combination of these descriptions. Controller 326 may be a purpose-built device, a general computing system, a microcontroller, a processing device coupled to memory, or any other device capable of providing control signals to one or more components based on receiving one or more inputs. [0093] Controller 326 may further provide control signals to one or more thermal energy storage medium systems. For example, in some embodiments, a thermal energy storage medium or associated heat transfer fluid of hot thermal energy storage system 380 may be pumped through high temperature heat exchanger 329 to be in thermal contact with the working fluid of thermal energy storage system 300B. A thermal energy storage medium or associated heat transfer fluid of cold thermal energy storage system 381 may be pumped through low temperature heat exchanger 318 to be in thermal contact with the working fluid of thermal energy storage system 300B. Controller 326 may provide control signals to the thermal energy storage medium systems for determining speed, direction, etc., of transport of thermal energy storage media (e.g., between a hot reservoir and a cold reservoir). Examples of thermal energy storage medium systems are described in connection with FIGS. 4A-D. In some embodiments, a separate high temperature heat exchanger 329 and/or low temperature heat exchanger 318 may be utilized for operation in a charge and discharge mode. In some embodiments, a separate charge and discharge architecture may be included in a system such as thermal energy storage system 300B, with a thermal energy storage medium in thermal communication with first heat exchangers associated with the charge architecture and second heat exchangers associated with the discharge architecture.

[0094] FIG. 3C depicts a thermal energy storage system 300C for generating a heat sink for cooling a target environment, according to some embodiments. Thermal energy storage system 300C may share one or more features with thermal energy storage systems 300 A and/or 300B. For example, components labeled with the same reference number may perform similar functions, share similar features, etc.

[0095] Thermal energy storage system 300C includes several optional components that may also be included in other thermal energy storage systems. For example, thermal energy storage system 300C may include a flash tank 313 (e.g., receiver). In some embodiments, flash tank 313 is a receiver configured to receive a flow of fluid (e.g., first fluid) output from the low pressure outlet of the PX 310. Flash tank 313 may form a chamber to collect the first fluid from the first outlet of the PX 310. Flash tank 313 may receive the first fluid in a two- phase state (e.g., liquid and gas). In some embodiments, flash tank 313 is a tank constructed of welded sheet metal. Flash tank 313 may be made of steel (e.g., steel sheet metal, steel plates, etc.). The first fluid (at a low pressure) may separate into gas and liquid inside the flash tank 313. The liquid of the first fluid may settle at the bottom of the flash tank 313 while the gas of the first fluid may rise to the top of the flash tank 313. The liquid may flow from the flash tank 313 towards the low temperature heat exchanger 318 (e.g., via expansion valve 316). The chamber of flash tank 313 maybe maintained at a set pressure. The pressure may be set by a user (e.g., an operator, a technician, an engineer, etc.) and/or by a controller (e.g., controller 380). In some embodiments, the pressure of the flash tank 313 is controlled by one or more valves (e.g., flash gas valve 320, a pressure regulator valve, a safety valve, etc.). In some embodiments, the flash tank 313 includes at least one pressure sensor (e.g., pressure transducer).

[0096] Thermal energy storage system 300B may include an expansion valve 316. In some embodiments, expansion valve 316 is disposed along a flow path between flash tank 313 and low temperature heat exchanger 318. Expansion valve 316 may be an adjustable valve (e.g., an electronic expansion valve, a thermostatic expansion valve, a ball valve, a gate valve, a poppet valve, etc.). Expansion valve 316 may be controllable by a user (e.g., a technician, an operator, an engineer, etc.) or by controller 380. In some embodiments, the expansion valve 316 is caused to actuate by controller 380 based on sensor data (e.g., pressure sensor data, flowrate sensor data, temperature sensor data, etc.). In some embodiments, expansion valve 316 is a thermal expansion valve. Expansion valve 316 may actuate (e.g., open and/or close) based on temperature data associated with the low temperature heat exchanger 318 (e.g., temperature data of the working fluid exiting the evaporator). In some examples, a sensing bulb (e.g., a temperature sensor, a pressure sensor dependent upon temperature, etc.) of the expansion valve 316 may increase or decrease pressure on a diaphragm of the expansion valve 316, causing a poppet valve coupled to the diaphragm to open or close, thus causing more or less flow of fluid to the low temperature heat exchanger 318, thereby causing more or less expansion of the fluid. The sensing bulb of the expansion valve may be positioned proximate to the downstream end of the low temperature heat exchanger 318 (e.g., proximate the fluid outlet of the low temperature heat exchanger 318) and may be fluidly coupled to the diaphragm via a sensing capillary (e.g., a conduit between the sensing bulb and the low temperature heat exchanger valve 316). In some embodiments, expansion valve 316 is controlled and actuated entirely based on electronic commands (e.g., from controller 380). [0097] Thermal energy storage system 300B may include a flash gas valve 320 to regulate a flow of gas on a flash gas bypass flow path. In some embodiments, flash gas valve 320 is a bypass valve that regulates a flow of gas from a gas outlet of the flash tank 313 to be combined with output of the low temperature heat exchanger 318. In some embodiments, the flow of gas from the flash tank 313 flows along the flash gas bypass flow path to bypass the low temperature heat exchanger 318. In some embodiments, the flash gas flow path is between flash tank 313 and a location downstream of an outlet of the low temperature heat exchanger 318. The gas flowing along the flash gas bypass flow path may be combined with output of the low temperature heat exchanger 318. The flash gas valve 320 may cause gas collected in the flash tank 313 to expand (e.g., decrease in pressure) as the gas flows toward the compressor 322. The flash gas valve 320 may, in some embodiments, be an adjustable valve. In some embodiments, the flash gas valve 320 is caused to actuate by controller 380 based on sensor data, time/date data, user input, energy availability data, environmental data, or the like.

[0098] In some embodiments, such as illustrated in FIG. 3C, LP booster 314 receives a flow of fluid from flash tank 313. In some embodiments, LP booster 314 receives a flow of gas from flash tank 313. In some examples, LP booster 314 receives a portion of the gas flowing along the flash gas bypass flow path between flash tank 313 and the flash gas valve 320. In some embodiments, the LP booster 314 receives the fluid and increases pressure of the fluid to form the second fluid (e.g., at the second pressure). The fluid is provided at the increased pressure (e.g., second pressure) to the second inlet of the PX 310 as the second fluid. In some embodiments, LP booster 314 is a compressor or pump that operates over a low pressure differential to “boost” the pressure of the gas received from flash tank 313. In some embodiments, the HP booster 385 is a compressor or pump that operates over a low pressure differential to “boost” the pressure of the fluid (e.g., second fluid) received from the second outlet of the PX. In some embodiments, a compressor is configured to increase pressure of a fluid substantially made up of gas, while a pump is configured to increase pressure of a fluid substantially made up of liquid.

[0099] Thermal energy storage system 300C further includes a secondary loop of components in thermal communication with the primary working fluid loop via low temperature heat exchanger 318. Thermal energy storage system 300C may be configured to remove heat from storage medium 342 (e.g., in a first operating mode, in a time of energy abundance, in a charge cycle, etc.) and deposit the heat at high temperature heat exchanger 329 (e.g., a gas cooler or condenser in an outdoor environment for rejecting heat from storage medium 342). The secondary loop may include a second energy transfer fluid, which may be the same or different from the fluid utilized in the loop including PX 310. For example, the secondary working fluid may be CO₂, glycol, a water/glycol mixture, or another fluid for transfer of heat energy between low temperature heat exchanger 318 and storage medium 342.

[00100] While operating in a second mode, thermal energy storage system 300C may be configured to utilize the heat sink generated during operation in the first mode at storage medium 342 to remove thermal energy from a target location. In some embodiments, a cooling coil 344 in connection with a fan 350 may be utilized to provide cool air flow during operation in a second mode, e.g., for cooling of a building or other interior space. In some embodiments, operations of a charge cycle may occur at a first time (e.g., when exterior temperatures around high temperature heat exchanger 329 are low, when energy costs are low, when a target area to be cooled is unoccupied, etc.), and a discharge cycle may occur during a second time (e.g., when energy costs are high, when the target area is occupied, etc.).

[00101] Storage medium 342 may provide a manner for exchanging heat between the secondary working fluid of the secondary loop and the storage medium 342. For example, a reservoir containing storage medium 342 may include one or more channels through the reservoir through which the secondary working fluid flows, for exchanging thermal energy with the storage medium 342. In some embodiments, the storage medium may be a phasechange material. The storage medium may be water, ice, and ice/water mixture or slurry, or another type of thermal energy storage medium.

[00102] One or more valves may be included in thermal energy storage system 300C, such as a temperature modulating valve 348, one or more three way valves 346, etc. During operation in a first mode (e.g., a charge mode, an ice-making mode, etc.), flow of the secondary working fluid may be directed through storage medium 342, e.g., to maximize energy transfer between the secondary working fluid and storage medium 342. During operation in a first mode, flowbypassing storage medium 342 may be restricted or disabled, e.g., by actuation of temperature modulating valve 348. During operation in the first mode, an air handling unit, air conditioning unit, cooling unit, or the like (e.g., cooling coil 344) may be bypassed. During operation in the first mode, cooling coil 344 may be bypassed by actuation of three way valve 346.

[00103] During operation in a second mode (e.g., discharge mode, air conditioning mode, air cooling mode, etc.), three way valve 346 may be operated to provide flow of secondary working fluid to cooling coil 344. In some embodiments, three way valve 346 may be replaced with a flow control valve, e.g., to provide control of a flow rate of fluid through cooling coil 344. During operation in the second mode, temperature modulating valve 348 may be operated. Temperature modulating valve 348 may be operated to provide a target mixing of secondary working fluid that has and has not been passed through storage medium 342. Temperature modulating valve 348 may be operated to provide secondary working fluid to cooling coil 344 at a target temperature, e.g., for improving operation of an air conditioning or cooling function of thermal energy storage system 300C.

[00104] Controller 380 may provide control signals to one or more components of thermal energy storage system 300C. Controller 380 may provide control signals to components of thermal energy storage system 300C to determine a mode of operation of the system. In some embodiments, the primary loop including the PX 310 may only be operated in a first mode, in a charge cycle, or the like. In some embodiments, pump 340 may circulate the secondary working fluid in both a charge mode and a discharge mode. In some embodiments, colling coil 344 and/or fan 350 may only operate in a discharge mode.

[00105] To operate in a first mode, controller 380 may provide a control signal to temperature modulating valve 348 to cause secondary working fluid to flow through storage medium 342, for transferring heat from storage medium 342 to the secondary working fluid. To operate in the first mode, controller 380 may provide a control signal to three way valve 346 to bypass cooling coil 344. Controller 380 may further provide control signals to cause operations of HP booster 385, compressor 322, LP booster 314, flash gas valve 320, expansions valve 316, etc., to operate in the first mode. For example, these components may operate to perform various functions to the primary working fluid during operation in the first mode. Adjustment of operation of one or more components may be performed by providing a control signal via controller 380 to the components, e.g., based on input data to controller 380.

[00106] To operate in a second mode, controller 380 may provide a control signal to temperature modulating valve 348 to cause a portion of the secondary working fluid to flow through storage medium 342 and a portion to bypass storage medium 342. The portion may be determined based on data generated by a temperature sensor, provided as input to controller 380. The portion may be determined to maintain a temperature of fluid exiting temperature modulating valve 348, entering cooling coil 344, or the like. To operate in the second mode, controller 380 may provide a control signal to three way valve 346, e.g., to provide flow of the secondary working fluid to cooling coil 344. To operate in the second mode, controller 380 may provide a control signal to fan 350, e.g., to provide increased transfer of heat between an environment proximate cooling coil 344 and the secondary working fluid of cooling coil 344. Controller 380 may further provide control signals to pump 340 (e.g., based on target energy transfer characteristics) to adjust operation of pump 340. [00107] FIGS. 4A-D depict systems for managing thermal energy storage mediums, according to some embodiments. The systems depicted in FIGS. 4A-D may be associated with a high temperature thermal energy storage system. The systems depicted in FIGS. 4A-D may be associated with a low temperature thermal energy storage system. Any of the systems depicted in FIGS. 3A-C may include one or more of the thermal energy storage medium systems depicted in FIGS. 4A-D. Any of the thermal energy storage solutions depicted in FIGS. 4A-D may be in thermal communication with any of the high temperature or low temperature heat exchangers depicted in FIGS. 3A-C.

[00108] FIG. 4 A depicts an example thermal energy storage medium management system 400A, according to some embodiments. The thermal energy storage medium management system 400A may include multiple reservoirs, e.g., high temperature storage 402 and low temperature storage 404. Thermal energy storage system400Amay be configured to bring a thermal energy storage medium into thermal contact with heat exchanger 406, e.g., for exchanging energy with a working fluid of a thermal energy storage system including a PX, such as those depicted in FIGS. 3A-C. Thermal energy storage system 400A may be in thermal communication with a high temperature heat exchanger 329, a low temperature heat exchanger 318, etc.

[00109] Thermal energy storage management system 400A may include one or more pumps (e.g., pump 408) for transferring a thermal energy storage medium between reservoirs. In some embodiments, multiple pumps may be utilized, multiple flow paths may be utilized, etc., for facilitating transfer between reservoirs in multiple directions. In some embodiments, more than two reservoirs may be included, e.g., any number of high temperature storage reservoirs and low temperature storage reservoirs may be included. Pumps, valves, etc., which determine flow path of thermal energy storage material between reservoirs may be controlled based on control signals provided by one or more controllers (e.g., controller 380 of FIG. 3C)

[00110] During operation in a mode when the thermal energy storage medium is to absorb heat from a working fluid, pump 408 may cause the storage medium to be transferred from the low temperature storage 404 to the high temperature storage 402. Use of “high” and “low” temperature in the context of thermal energy storage systems is relative, e.g., the entire storage system may be maintained above or below some temperature such as ambient conditions, target temperature of a system, or the like, with the low temperature storage 404 being at a lower temperature than the high temperature storage 402. During operation in a mode when thermal energy is to be transferred from the storage medium to a working fluid via heat exchanger 406, pump 408 may cause a thermal energy medium to be transferred from high temperature storage 402 to low temperature storage 404 via heat exchanger 406, transf erring heat to the working fluid in heat exchanger 406 and reducing temperature of the thermal energy storage medium. Pump 408 may be included in a fluid transfer system, fluidized sand transfer system, etc.

[00111] In some embodiments, heat exchanger 406 may be a high temperature heat exchanger, e.g., high temperature heat exchanger 329. During operation in a first mode (e.g., charge mode), pump 408 may cause thermal energy storage medium to be transferred from low temperature storage 404 to high temperature storage 402, increasing temperature of the thermal energy storage medium via thermal communication with the working fluid of a thermal energy storage system in heat exchanger 406. If heat exchanger 406 is a high temperature heat exchanger, during operation in a second mode (e.g., discharge mode) pump 408 may cause a thermal energy storage medium to be transferred from high temperature storage 402 to low temperature storage 404, increasing temperature of the working fluid via thermal interaction in heat exchanger 406.

[00112] In some embodiments, heat exchanger 406 may be a low temperature heat exchanger, e.g., low temperature heat exchanger 318. During operation in a first mode (e.g., a charge cycle), pump 408 may cause a thermal storage medium to be transferred from high temperature storage 402 to low temperature storage 404, providing heat to a working fluid in heat exchanger 406. If heat exchanger 406 is a low temperature heat exchanger, during operation in a second mode (e.g., a discharge cycle), pump 480 may cause a thermal energy storage medium to be transferred from low temperature storage 404 to high temperature storage 402, absorbing heat from a working fluid in heat exchanger 406.

[00113] Various thermal energy storage mediums may be utilized in connection with systems such as thermal energy storage management system 400A. The thermal energy storage medium may include molten salt (e.g., a mixture of sodium nitrate and potassium nitrate). Molten salt may be maintained in low temperature storage 404 at least the melting temperature of the salt (e.g., around220 °C). The thermal energy storage medium may be or include sand. Pump 408 may be replaced, augmented, or the like with a pneumatic sand transfer system. Heat exchanger 406 may be configured to support fluidized sand transport, heat exchange between fluidized sand and the working fluid, etc.

[00114] FIG. 4B depicts a thermal energy storage medium reservoir 400B, according to some embodiments. In some embodiments, a heat exchanger 410 (e.g., high temperature heat exchanger 329, low temperature heat exchanger 318) may be embedded in a thermal energy storage medium 412. The thermal energy storage medium 412 may include one or more materials for storing heat, for generating a heat sink, or the like. By bringing the working fluid in contact with the heat exchanger embedded in the thermal energy storage medium 412, heat may be transferred between the working fluid and the thermal energy storage medium. In some embodiments, the heat exchanger may be a pillow plate embedded in a tank including a thermal energy storage medium 412, e.g., water. The working fluid may be fluidly coupled to a system such as systems depicted in FIGS. 3A-C, e.g., a thermal energy transfer system including a PX.

[00115] Thermal energy storage medium 412 may be any material that stores heat or from which heat can be extracted (e.g., “stores cold” or generates a heat sink). In some embodiments, thermal energy storage medium 412 may be a material that changes phase during a target temperature transition for heat storage. For example, thermal energy storage medium 412 may be water (e.g., a mixture of water and ice, water/ice slurry, or the like), for example surrounding a low temperature heat exchanger. Thermal energy storage medium 412 may be a high temperature phase change material (e.g., paraffins, octadecane, salt hydrates, fatty acids, esters, ionic liquids, etc.), for example surrounding a high temperature heat exchanger. Thermal energy storage medium 412 may be or include a phase change thermal storage medium. Use of a high temperature phase change material may be utilized for upgrading industrial waste heat to high temperature (e.g., high grade) heat stored in thermal energy storage medium 412. The high temperature heat stored in thermal energy storage medium 412 may be transferred via a heat transfer system to a target process (e.g., high temperature industrial process) for usage of the high temperature heat in the process.

[00116] FIG. 4C depicts a thermal energy gradient storage system 400C, according to some embodiments. Thermal energy gradient storage system 400C includes temperature gradient storage 414. Temperature gradient storage 414 may include or contain a thermal energy storage medium (e.g., either solid or liquid) that is capable of maintaining a temperature gradient, e.g., from top to bottom of the storage reservoir. As an example, temperature gradient storage 414 may include sand at different temperatures dependent upon height in the reservoir. Hot and cold regions of the storage medium are separated by a thermocline, e.g., temperature gradient. In case of liquid based storage medium, the density difference between hot and cold parts of the storage medium creates thermal layers in the fluid within the storage tank and helps stabilize and maintain the thermocline. Thermal energy gradient storage system 400C may be configured to bring a thermal energy storage medium into thermal communication with heat exchanger 416, which may also be in thermal communication with a working fluid of a thermal energy transfer system including a PX, such as those depicted in FIGS. 3A-C [00117] In a first mode, cold thermal storage medium may be provided to heat exchanger 416 to absorb heat from a working fluid also provided to heat exchanger 416. For example, during a charge cycle, cold thermal storage may be brought into thermal communication with a working fluid to increase temperature of the storage medium. In a second mode, hot storage medium may be provided to heat exchanger 416 to provide heat to a working fluid in heat exchanger 416. For example, during a discharge cycle, hot thermal storage may be brought into thermal communication with a working fluid in heat exchanger 416 to increase temperature of the working fluid.

[00118] In some embodiments, a pump 418 (e.g., pneumatic pump for transferring fluidized sand) may provide transport of a thermal energy storage medium from the bottom of temperature gradient storage 414 to the top of temperature gradient storage 414. Temperature gradient storage 414 may be gravity-fed, e.g., position of the thermal storage medium in the reservoir may be adjusted by gravity. Pump 418 may be replaced or augmented with a conveyor belt, or other mechanical device to transferring the thermal energy storage medium to the top of the reservoir. Pump 418 may be included in a fluid transfer system, fluidized sand transfer system, etc.

[00119] In some embodiments, temperature gradient storage 414 may be filled or substantially filled with low temperature thermal storage medium. The storage medium may be provided to heat exchanger 416 from the bottom of temperature gradient storage 414. The temperature of the storage medium may be increased by interaction in the heat exchanger 416 with working fluid (e.g., during a charge cycle). The high temperature storage medium may then be replaced in the top of temperature gradient storage 414. This process may continue until temperature gradient storage 414 is filled or substantially filled with hot thermal energy storage medium, e.g., for storing the thermal energy. During operation in a second mode, the hot thermal energy storage medium filling or substantially filling temperature gradient storage 414 may be provided to heat exchanger 416. The hot thermal energy storage medium may interact with a working fluid in heat exchanger 416, transferring heat to the working fluid (e.g., during a discharge cycle). The cold thermal energy storage medium may then be replaced at the top of the temperature gradient storage 414. This process may continue until temperature gradient storage 414 is filled or substantially filled with cold thermal energy storage medium.

[00120] FIG. 4D depicts a thermal energy storage medium system 400D including a secondary energy transfer fluid, according to some embodiments. Thermal energy storage medium reservoir 420 may include a storage medium that a secondary heat transfer fluid is passed through, e.g., by pump 424. Thermal energy storage medium system 400D may be configured to bring the secondary heat transfer fluid into thermal communication with heat exchanger 422. Heat exchanger 422 may further be in thermal communication with a working fluid of a system for transferring and/or storing thermal energy including a PX, e.g., one of the systems depicted in FIGS. 3A-C. Thermal energy storage medium reservoir 420 may include a solid phase thermal energy storage medium. For example, thermal energy storage medium reservoir may include natural stone (e.g., high heat capacity rock, lava rock, extrusive igneous rock, volcanic cinders, etc.), artificial stone (e.g., bricks, concrete), sand, or the like.

[00121] Thermal energy storage medium system 400D includes a pump 424 for transferring a secondary heat transfer fluid through the thermal energy storage medium reservoir 420 to bring the secondary heat transfer fluid into thermal communication with the thermal energy storage medium. The secondary heat transfer fluid may be provided to heat exchanger 422, where it may exchange thermal energy with a primary working fluid of a thermal energy storage system. Pump 424 may be included in a fluid transfer system, fluidized sand transfer system, etc.

[00122] In a mode where temperature of the thermal energy storage medium reservoir 420 is to be increased (e.g., a charge cycle if heat exchanger 422 is a high temperature heat exchanger, or a discharge cycle if heat exchanger 422 is a low temperature heat exchanger), the secondary fluid may be cycled through the thermal energy storage medium reservoir 420, brought into thermal contact with high temperature working fluid in heat exchanger 422, and returned to thermal energy storage medium reservoir 420 to transfer heat to the thermal energy storage medium, increasing the temperature of the storage medium. In a mode where temperature of thermal energy storage medium reservoir 420 is to be decreased (e.g., a charge cycle if heat exchanger 422 is a low temperature heat exchanger, or a discharge cycle if heat exchanger 422 is a high temperature heat exchanger), the hot secondary fluid may be provided from the thermal energy storage medium reservoir 420 to heat exchanger 422 to provide thermal energy to a working fluid, and the cooled secondary fluid may then be provided via pump 424 to the thermal energy storage medium reservoir 420, decreasing a temperature of thermal energy storage medium reservoir 420. The secondary heat transfer fluid may be any fluid that can exchange heat with the thermal energy storage medium. The secondary heat transfer fluid may be selected to optimize cost, heat exchange with the thermal energy storage medium in the target temperature range, or the like. The secondary heat transfer fluid may be liquid, gas, supercritical fluid, mixtures, etc. The secondary heat transfer fluid may be air or water in some embodiments.

[00123] In some systems, high temperature heat transfer fluid may flow into the top of the thermocline and exit through the bottom. This moves the thermocline (e.g., temperature boundary, temperature gradient, etc.) downward and stores thermal energy in the storage medium. During a discharge cycle, cold fluid may flow into the cold bottom of the thermocline and exits from the hot top, thus gaining heat from the thermocline and moving thermocline upward.

[00124] FIGS. 5-6 are flow diagrams of methods 500 and 600 associated with controlling thermal energy storage systems, according to some embodiments. Methods 500 and 600 may be performed by processing logic that may include hardware (e.g., circuitry, dedicated logic, programmable logic, microcode, processing device, etc.), software (such as instructions run on a processing device, a general purpose computer system, or a dedicated machine), firmware, microcode, or a combination thereof. In some embodiments, methods 500 and 600 may be performed, at least in part, by a controller, such as controller 326, controller 380, or one or more other controllers. In some embodiments, a non-transitory machine-readable storage medium stores instructions that when executed by a processing device cause the processing device to perform one or more of methods 500 and/or 600.

[00125] For simplicity of explanation, methods 500 and 600 are depicted and described as a series of operations. However, operations in accordance with this disclosure can occur in various orders and/or concurrently and with other operations not presented and described herein. Furthermore, not all illustrated operations may be performed to implement methods 500 and/or 600 in accordance with the disclosed subject matter. In addition, those skilled in the art will understand and appreciate that methods 500 and 600 could alternatively be represented as a series of interrelated states via a state diagram or events.

[00126] FIG. 5 is a flow diagram of a method 500 for causing a thermal energy storage system to operate in a target mode, according to some embodiments. The target mode may be a charge mode, a charge cycle, a heat pump mode, an energy storage mode, a heat sink generation mode, or the like. The target mode may be a discharge mode, a discharge cycle, a heat engine mode, an energy expending mode, an environment cooling mode, or the like. Operating in a target mode may include performing operations to configure a system operating in a different mode to change to operating in the target mode.

[00127] At block 502, processing logic (e.g., of a controller) receives input indicative that a thermal energy storage system is to be operated in the target mode. The input may include sensor data. The input may include time/date data. The input may include an indication of user input.

[00128] At block 504, processing logic generates a control signal. The control signal may be based on the input, the target mode, operations in the target mode, etc.

[00129] At block 506, processing logic causes a valve of the thermal energy storage system to actuate. The valve may be an on-off valve. The valve may be a control valve. The valve may be a valve that controls split of a fluid flow between multiple flow paths. Causing the valve to actuate includes providing the control signal to the valve. Causing the valve to actuate includes configuring the thermal energy storage system for operation in the target mode. Causing the valve to actuate may include configuring the thermal energy storage system to no longer operate in a second mode.

[00130] As an example, a system such as the system depicted in FIG. 3A may be operated in a first mode or a second mode, a charge mode or a discharge mode, or the like. Operation in the first mode may include providing working fluid to components included in first architecture 302. Operation in the second mode may include providing working fluid to components included in second architecture 304. To transition a system such as system 300 A from a discharge mode to a charge mode, a control signal may be generated and provided to one or more components to transition flow from second architecture 304 to first architecture 302. To transition system 300A from operating in a discharge mode to operating in a charge mode, one or more valves may be actuated to direct flow through PX 310 and compressor 322, and to direct flow away from turbine 324. To transition a system such as system 300A from a charge mode to a discharge mode, one or more valves may be actuated to direct flow away from PX 310 and through turbine 324.

[00131] As a further example, a system such as the system depicted in FIG. 3B may be operated in a first mode or a second mode, a charge mode or a discharge model, etc. Operation in the charge mode may include actuating one or more valves (e.g., three-way valve 328, flow control valve 330) to direct working fluid flow through components including PX 310. Operation in the discharge mode may include actuating one or more valves of system 300B to direct working fluid flow through components including turbine 324. [00132] FIG. 6 is a flow diagram of a method 600 for causing a thermal energy storage system to operate in a target mode, according to some embodiments. At block 610, processing logic (e.g., of a controller) receives input indicative that a thermal energy storage system is to be operated in a target mode. The input may share one or more features with the input associated with block 502 of FIG. 5. [00133] At block 612, processing logic generates one or more control signals. The control signals may be for controlling various components of the thermal energy storage system, e.g., components that operate based on a mode of operation of the thermal energy storage system. [00134] At block 614, processing logic provides the one or more control signals to one or more components of the thermal energy storage system. The one or more components may include any components that operate differently in a first mode than in a second mode (e.g., in the target mode than in another operational mode) of the thermal energy storage system. The one or more components may include one or more valves. Flow of a working fluid may be directed to a different set of components based on actuation of one or more valves. The one or more components may include one or more pumps or compressors, that may activate, deactivate, or change an operating speed based on a transition to the first operating mode of the thermal energy transfer system. The one or more components may include a motor operatively coupled to a PX. The one or more components may include pumps, compressors, or other transfer devices of secondary heat transfer mediums, such as thermal energy storage mediums (e.g., molten salt, fluidized sand, etc.), secondary heat transfer fluids (e.g., glycol, glycol/water mixture, air, water, etc.), or the like. The one or more components are configured to cause operation of the thermal energy storage system in the first mode responsive to receiving the one or more control signals.

[00135] As an example, a system such as the system depicted in FIG. 3C may be operated in a first mode or a second mode, a charge mode or a discharge mode, or the like. Upon determining that the system is to be operated in a charge mode, one or more valves may be actuated (e.g., temperature modulating valve 348, three-way valve 346, etc.). Upon determining that the system is to be operated in a charge mode, fluid flow may be directed away from cooling coil 344 by providing a control signal to three-way valve 346. Upon determining that the system is to be operated in a charge mode, fluid flow may be directed through storage medium 342 by actuation of temperature modulating valve 348. Upon determining that the system is to be operated in a charge mode, other components may be provided with control signals, including pump 340, compressor 322, a motor of PX 310, HP booster 385, LP booster 314, flash gas valve 320, fan 350, etc. Upon determining that the system is to be operated in a discharge mode, temperature modulating valve 348 may be provided one or more control signals for mixing different temperature fluids to achieve target performance. Three-way valve 346 maybe actuated to provide fluid flow to cooling coil 344. Upon determining that the system is to be operated in a discharge mode, fan 350 may be provided with one or more control signals to enable air flow through cooling coil 344. [00136] FIG. 7 is a block diagram illustrating a computer system 700, according to certain embodiments. In some embodiments, the computer system 700 is a client device. In some embodiments, the computer system 700 is a controller device (e.g., server, controller 326 of FIG. 3B, controller 380 of FIG. 3C).

[00137] In some embodiments, computer system 700 is connected (e.g., via a network, such as a Local Area Network (LAN), an intranet, an extranet, or the Internet) to other computer systems. Computer system 700 operates in the capacity of a server or a client computer in a client-server environment, or as a peer computer in a peer-to-peer or distributed network environment. In some embodiments, computer system 700 is provided by a personal computer (PC), a tablet PC, a Set-Top Box (STB), a Personal Digital Assistant (PDA), a cellular telephone, a web appliance, a server, a network router, switch or bridge, or any device capable of executing a set of instructions (sequential or otherwise) that specify actions to be taken by that device. Further, the term "computer" shall include any collection of computers that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methods described herein.

[00138] In some embodiments, the computer system 700 includes a processing device 702, a volatile memory 704 (e.g., Random Access Memory (RAM)), a non-volatile memory 706 (e.g., Read-Only Memory (ROM) or Electrically-Erasable Programmable ROM (EEPROM)), and/or a data storage device 716, which communicates with each other via a bus 708.

[00139] In some embodiments, processing device 702 is provided by one or more processors such as a general purpose processor (such as, in some examples, a Complex Instruction Set Computing (CISC) microprocessor, a Reduced Instruction Set Computing (RISC) microprocessor, a Very Long Instruction Word (VLIW) microprocessor, a microprocessor implementing other types of instruction sets, or a microprocessor implementing a combination of types of instruction sets) or a specialized processor (such as, in some examples, an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), a Digital Signal Processor (DSP), or a network processor). In some embodiments, processing device 702 is provided by one or more of a single processor, multiple processors, a single processor having multiple processing cores, and/or the like.

[00140] In some embodiments, computer system 700 further includes a network interface device 722 (e.g., coupled to network 774). In some embodiments, the computer system 700 includes one or more input/output (I/O) devices. In some embodiments, computer system 700 also includes a video display unit 710 (e.g., a liquid crystal display (LCD)), an alphanumeric input device 712 (e.g., a keyboard), a cursor control device 714 (e.g., a mouse), and/or a signal generation device 720. Computer system 700 may be a controller, and may utilize signal generation device 720 to deliver control signals to components of a thermal energy storage system, in accordance with embodiments described herein.

[00141] In some implementations, data storage device 718 (e.g., disk drive storage, fixed and/or removable storage devices, fixed disk drive, removable memory card, optical storage, network attached storage (NAS), and/or storage area-network (SAN)) includes a non- transitory computer-readable storage medium 724 on which stores instructions 726 encoding any one or more of the methods or functions described herein, and for implementing methods described herein. Methods of functions described in connection with FIGS. 5-6, for example, may be stored as instructions 726.

[00142] In some embodiments, instructions 726 also reside, completely or partially, within volatile memory 704 and/or within processing device 702 during execution thereof by computer system 700, hence, volatile memory 704 and processing device 702 also constitute machine-readable storage media, in some embodiments.

[00143] While computer-readable storage medium 724 is shown in the illustrative examples as a single medium, the term "computer-readable storage medium" shall include a single medium or multiple media (e.g., a centralized or distributed database, and/or associated caches and servers) that store the one or more sets of executable instructions. The term "computer-readable storage medium" shall also include any tangible medium that is capable of storing or encoding a set of instructions for execution by a computer that cause the computer to perform any one or more of the methods described herein. The term "computer- readable storage medium" shall include, but not be limited to, solid-state memories, optical media, and magnetic media.

[00144] The methods, components, and features described herein may be implemented by discrete hardware components or may be integrated in the functionality of other hardware components such as ASICS, FPGAs, DSPs or similar devices. In addition, the methods, components, and features may be implemented by firmware modules or functional circuitry within hardware devices. Further, the methods, components, and features may be implemented in any combination of hardware devicesand computer program components, or in computer programs.

[00145] Unless specifically stated otherwise, terms such as “actuating,” “adjusting,” “causing,” “controlling,” “determining,” “identifying,” “providing,” “receiving,” “regulating,” or the like, refer to actions and processes performed or implemented by computer systems that manipulates and transforms data represented as physical (electronic) quantities within the computer system registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices. Also, the terms "first," "second," "third," "fourth," etc. as used herein are meant as labels to distinguish among different elements and may not have an ordinal meaning according to their numerical designation. [00146] Examples described herein also relate to an apparatus for performing the methods described herein. This apparatus may be specially constructed for performing the methods described herein, or it may include a general purpose computer system selectively programmed by a computer program stored in the computer system. Such a computer program may be stored in a computer-readable tangible storage medium.

[00147] The methods and illustrative examples described herein are not inherently related to any particular computer or other apparatus. Various general purpose systems may be used in accordance with the teachings described herein, or it may prove convenient to construct more specialized apparatus to perform methods described herein and/or each of their individual functions, routines, subroutines, or operations. Examples of the structure for a variety of these systems are set forth in the description above.

[00148] The preceding description sets forth numerous specific details, such as examples of specific systems, components, methods, and so forth, in order to provide a good understanding of several embodiments of the present disclosure. It will be apparent to one skilled in the art, however, that at least some embodiments of the present disclosure may be practiced without these specific details. In other instances, well-known components or methods are not described in detail or are presented in simple block diagram format in order to avoid unnecessarily obscuringthe present disclosure. Thus, the specific details set forth are merely exemplary. Particular implementations may vary from these exemplary details and still be contemplated to be within the scope of the present disclosure.

[00149] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrase “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. In addition, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or.” When the term “about,” “substantially,” or “approximately” is used herein, this is intended to mean that the nominal value presented is precise within ±10%. Also, the terms "first," "second," "third," "fourth," etc. as used herein are meant as labels to distinguish among different elements and can not necessarily have an ordinal meaning according to their numerical designation.

[00150] The terms “over,” “under,” “between,” “disposed on,” and “on” as used herein refer to a relative position of one material layer or component with respect to other layers or components. In some examples, one layer disposed on, over, or under another layer may be directly in contact with the other layer or may have one or more intervening layers. Moreover, one layer disposed between two layers may be directly in contact with the two layers or may have one or more intervening layers. Similarly, unless explicitly stated otherwise, one feature disposed between two features may be in direct contact with the adjacent features or may have one or more intervening layers.

[00151] Although the operations of the methods herein are shown and described in a particular order, the order of the operations of each method may be altered so that certain operations may be performed in an inverse order or so that certain operation may be performed, at least in part, concurrently with other operations. In another embodiment, instructions or sub-operations of distinct operations may be in an intermittent and/or alternating manner. In one embodiment, multiple metal bonding operations are performed as a single step.

[00152] It is to be understood that the above description is intended to be illustrative, and not restrictive. Many other embodiments will be apparent to those of skill in the art upon reading and understanding the above description. The scope of the disclosure should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which each claim is entitled.

Claims

CLAIMS What is claimed is:

1. A system comprising: a pressure exchanger (PX) configured to receive a first fluid, receive a second fluid, and exchange pressure between the first fluid and the second fluid; a first heat exchanger configured to provide the first fluid to the PX; a second heat exchanger configured to receive the first fluid from the PX; a compressor configured to compress at least a portion of the first fluid output by the second heat exchanger; an electrical energy generation device, configured to convert energy of the first fluid output by the first heat exchanger to electrical energy; a first valve; and a processing device, operatively coupled to the first valve, wherein the processing device is configured to: responsive to determining that the system is to be operated in a first mode, cause the first valve to provide fluid flow to the PX, the first heat exchanger, the second heat exchanger, and the compressor; and responsive to determining that the system is to be operated in a second mode, cause the first valve to provide fluid flow to the first heat exchanger, the second heat exchanger, and the electrical energy generation device.

2. The system of claim 1 , further comprising a thermal energy storage medium that is in thermal communication with the first heat exchanger or the second heat exchanger.

3. The system of claim 2, wherein the thermal energy storage medium comprises one or more of: molten salt; sand; natural or artificial rock; silicon; aluminum; a phase change material; or a eutectic material.

4. The system of claim 3, further comprising; a first reservoir comprising a first portion of the thermal energy storage medium at a first temperature; a second reservoir comprising a second portion of the thermal energy storage medium at a second temperature that is less than the first temperature; and a transfer system configured to transfer the second portion of the thermal energy storage medium from the second reservoir to the first reservoir, wherein the thermal energy storage medium is in thermal communication with the first heat exchanger while the second portion of the thermal energy storage medium is being transferred via the transfer system.

5. The system of claim 3, further comprising: a reservoir comprising the thermal energy storage medium; a fluid transfer system comprising a third fluid, wherein the fluid transfer system is configured to transfer heat between the first heat exchanger and the reservoir via the third fluid.

6. The system of claim 2, wherein the thermal energy storage medium comprises one or more of: carbon dioxide; water; or a phase change material.

7. The system of claim 6, further comprising: a first reservoir comprising a first portion of the thermal energy storage medium at a first temperature; a second reservoir comprising a second portion of the thermal energy storage medium at a second temperature that is less than the first temperature; and a transfer system configured to transfer the first portion of the thermal energy storage medium from the first reservoir to the second reservoir, wherein the thermal energy storage medium is in thermal communication with the second heat exchanger while the first portion of the thermal energy storage medium is being transferred via the transfer system.

8. The system of claim 1, wherein: the system in the first mode is to operate as a heat pump; and the system in the second mode is to operate as a heat engine.

9. A system comprising: a pressure exchanger (PX) configured to receive a first fluid, receive a second fluid, and exchange pressure between the first fluid and the second fluid; a heat exchanger configured to receive the first fluid from the PX, and to exchange heat between the first fluid and a third fluid; a thermal storage medium in thermal communication with the third fluid; a cooling coil, configured to exchange thermal energy between the third fluid and an environment proximate the cooling coil; and a pump configured to circulate the third fluid between the thermal storage medium, the cooling coil, and the heat exchanger.

10. The system of claim 9, further comprising a gas cooler that is in thermal communication with the first fluid, wherein the system is configured to transfer heat from the thermal storage medium to an environment proximate the gas cooler while operated in a first mode.

11. The system of claim 9, wherein the thermal storage medium comprises a reservoir of water.

12. The system of claim 9, further comprising a temperature sensor, wherein the system is configured to selectively operate the system in a first mode, comprising operation of the PX, ora second mode, comprising operation of the cooling coil, based on data generated by the temperature sensor.

13. The system of claim 12, wherein operation in the first mode comprises actuation of a valve to provide flow of the third fluid to bypass the cooling coil.

14. The system of claim 9, further comprising a temperature modulating valve, wherein operation in a second mode comprises actuation of the temperature modulating valve to determine a first portion of the third fluid that exchanges thermal energy with the thermal storage medium.

15. The system of claim 9, wherein operation of the system in a first mode comprises a charge cycle that reduces a temperature of the thermal storage medium, and wherein operation of the system in a second mode comprises a discharge cycle that transfers heat from the environment proximate the cooling coil to the thermal storage medium.

16. The system of claim 9, wherein the third fluid comprises a water-glycol mixture.

17. A system comprising; a pressure exchanger (PX) configured to receive a first fluid, receive a second fluid, and exchange pressure between the first fluid and the second fluid; a first heat exchanger configured to provide the first fluid to the PX, wherein the first heat exchanger is in thermal communication with a thermal storage medium; a second heat exchanger configured to receive the first fluid from the PX, wherein the second heat exchanger is in thermal communication with a heat source; a heat sink in thermal communication with the thermal storage medium; and a processing device, configured to provide a control signal causing the system to operate in a first mode or a second mode.

18. The system of claim 17, wherein operation in the first mode comprises a charge cycle that transfers heat from the heat source to the thermal storage medium, and operation in the second mode comprise a discharge cycle that transfers heat from the thermal storage medium to the heat sink.

19. The system of claim 17, wherein the thermal storage medium comprises a phase change thermal storage medium.

20. The system of claim 17, wherein the operation in the second mode comprises circulating a heat transfer fluid to transfer heat from the thermal storage medium to the heat sink.