Liquid carbon dioxide multistage phase change energy storage system coupled with zeolite adsorption bed

Abstract

The application discloses a liquid carbon dioxide multistage phase change energy storage system coupled with a zeolite adsorption bed, which comprises a liquid carbon dioxide storage tank, a gas suspension compressor, a liquid carbon dioxide circulating pump, a turbine generator set, a first zeolite adsorption bed, a second zeolite adsorption bed, a first multistage phase change heat storage module, a second multistage phase change heat storage module, pipelines and an intelligent valve network; the pipelines and the intelligent valve network are connected with the above components; a power generation cycle loop is formed by connecting, in sequence, one zeolite adsorption bed serving as a desorption bed, the turbine generator set and another zeolite adsorption bed serving as an adsorption bed through the pipelines, so that a closed working medium flow path is formed; the system is decoupled into an independent power generation cycle and an energy storage / energy release cycle, and the intelligent valve network is used to realize precise coupling and switching of the two cycles, so that the irreversible loss caused by frequent and severe changes of the working medium state in the traditional system is avoided.

Description

Technical Field

[0001] This invention belongs to the field of new power system energy storage technology, and in particular relates to a multi-stage phase change energy storage system for liquid carbon dioxide coupled with a zeolite adsorption bed. Background Technology

[0002] With the continuous increase in the proportion of renewable energy power generation, the demand for large-scale, long-term energy storage technologies in power systems is becoming increasingly urgent. Energy storage technologies using carbon dioxide as the working fluid have become a current research hotspot due to their advantages such as environmentally friendly working fluid, high energy density, and compact system design. Existing technological approaches mainly revolve around supercritical carbon dioxide power cycles, using electricity to drive a compressor to compress and store the working fluid, and then using the stored high-pressure working fluid to drive a turbine to generate electricity during energy release. To further improve performance, researchers are attempting to integrate high-temperature thermal storage units to recover compression heat, or to introduce adsorption to enhance the liquefaction process to reduce compression energy consumption. These explorations aim to construct a complete and efficient energy storage and conversion system.

[0003] However, the existing technical architecture still suffers from systemic bottlenecks. First, the energy storage and power generation processes are typically highly coupled within the same thermodynamic cycle, requiring the working fluid to frequently switch between different states such as compression, heat storage, expansion, and cooling. This leads to complex processes and the accumulation of irreversible losses, limiting further improvements in overall system efficiency. Second, despite the introduction of heat storage or adsorption units, there is often a lack of refined management of heat energy quality. High and low temperature heat cannot be stored in stages and precisely matched for utilization, resulting in significant waste. More critically, existing systems struggle to balance high energy density with long-term, self-sustaining operation: relying solely on physical compression for energy storage severely limits its duration due to tank volume; and achieving efficient circulation and regeneration of the working fluid within the system, avoiding dependence on external supplementation, remains a prominent challenge in engineering practice. Therefore, a new system design philosophy is urgently needed to overcome the traditional trade-offs between efficiency, duration, and operational stability. Summary of the Invention

[0004] In order to overcome the above-mentioned defects of the prior art, the present invention provides a liquid carbon dioxide multi-stage phase change energy storage system coupled with a zeolite adsorption bed, which solves the problems of efficiency bottleneck, crude thermal management and long-term energy storage in the prior art carbon dioxide energy storage technology.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A multi-stage phase change energy storage system for liquid carbon dioxide coupled with a zeolite adsorption bed includes:

[0007] Liquid carbon dioxide storage tank, air suspension compressor, liquid carbon dioxide circulating pump, turbine generator set, first zeolite adsorption bed, second zeolite adsorption bed, first multi-stage phase change thermal storage module, second multi-stage phase change thermal storage module, pipelines, and intelligent valve network;

[0008] Piping and smart valve networks connect the above components;

[0009] The intelligent valve network is configured to switch between two operating states by controlling the combination of opening and closing states of the multiple valves it contains, and to form two independent loops in either operating state, namely a power generation loop and an energy storage and release loop.

[0010] The power generation cycle loop is composed of a zeolite adsorption bed that serves as a desorption bed, a turbine generator set, and another zeolite adsorption bed that serves as an adsorption bed, connected in sequence by pipelines, forming a closed working fluid flow path.

[0011] The energy storage and release loop is connected in sequence by pipelines to a liquid carbon dioxide storage tank and a multi-stage phase change thermal energy storage module. It can also be connected to an air suspension compressor or a liquid carbon dioxide circulation pump depending on the working mode, thus forming another closed working fluid flow path.

[0012] During system operation, the energy storage and release loop is regulated by an intelligent valve network to achieve fluid communication and heat exchange with the zeolite adsorption bed, which serves as the desorption bed in the power generation loop.

[0013] Preferably, the first multi-stage phase change thermal energy storage module includes a first latent heat phase change heat exchanger and a first sensible heat phase change heat exchanger connected in series.

[0014] The second multi-stage phase change thermal energy storage module includes a second latent heat phase change heat exchanger and a second sensible heat phase change heat exchanger connected in series.

[0015] Preferably, both the first sensible heat phase change heat exchanger and the second sensible heat phase change heat exchanger have at least two independent heat exchange units integrated inside.

[0016] Each heat exchange unit contains a phase change material with a specific melting point, and the melting points of the phase change materials in different heat exchange units are different.

[0017] Preferably, the phase change material includes a first phase change material and a second phase change material;

[0018] The melting point range of the first phase change material is 120°C to 180°C;

[0019] The melting point of the second phase change material is above 300℃.

[0020] Preferably, the adsorbent filled in the first zeolite adsorption bed and the second zeolite adsorption bed is zeolite molecular sieve.

[0021] Zeolite molecular sieves have selective adsorption capacity for carbon dioxide, and their crystal structure type is at least one of X-type, A-type or Y-type.

[0022] Preferably, medium-temperature thermochemical thermal storage refers to the thermal storage and release process achieved through the adsorption and desorption reactions of carbon dioxide in a zeolite adsorption bed.

[0023] The temperature range of the heat source required to drive the zeolite adsorption bed to complete the desorption reaction is 150℃ to 400℃.

[0024] Preferably, the two operating states achieved by the intelligent valve network are:

[0025] First working state: The first zeolite adsorption bed acts as a desorption bed and is fluidly connected to the energy storage and release circulation loop to receive the heat source; the second zeolite adsorption bed acts as an adsorption bed.

[0026] Second working state: The second zeolite adsorption bed acts as a desorption bed and is fluidly connected to the energy storage and release circulation loop to receive the heat source; the first zeolite adsorption bed acts as an adsorption bed.

[0027] Preferably, in the first working state, the high-pressure carbon dioxide desorbed from the first zeolite adsorption bed drives the turbine generator set to do work and generate electricity, and the low-pressure carbon dioxide after doing work is adsorbed by the second zeolite adsorption bed.

[0028] In the second operating state, the high-pressure carbon dioxide desorbed from the second zeolite adsorption bed drives the turbine generator set to do work and generate electricity, and the low-pressure carbon dioxide after doing work is adsorbed by the first zeolite adsorption bed.

[0029] Preferably, it also includes: an external circulating heat exchange system;

[0030] The external circulating heat exchange system is connected to the liquid carbon dioxide storage tank to exchange heat with the liquid carbon dioxide in the tank during system operation in order to maintain the working fluid balance.

[0031] Preferably, the energy storage and release loop has two operating modes, which are switched by an intelligent valve network;

[0032] In energy storage mode, the air suspension compressor is connected to the loop to drive the carbon dioxide working fluid circulation and store the high-temperature heat energy generated during the compression process in the multi-stage phase change thermal energy storage module currently connected to it;

[0033] In the energy release mode, a liquid carbon dioxide circulation pump is connected to the loop to drive the carbon dioxide working fluid to circulate, so that it absorbs heat from the multi-stage phase change thermal storage module that has stored heat and vaporizes it, and then provides desorption heat to the zeolite adsorption bed that is currently connected to it.

[0034] The technical effects and advantages of the multi-stage phase change energy storage system for liquid carbon dioxide coupled with a zeolite adsorption bed according to the present invention are as follows:

[0035] 1. This invention fundamentally avoids the irreversible losses caused by frequent and drastic changes in the working fluid state in traditional systems by decoupling the system into independent power generation and energy storage / release cycles, and by utilizing an intelligent valve network to achieve precise coupling and switching between the two. The power generation cycle focuses on efficient heat-work conversion, and its closed-loop operation and the alternating operation of the two zeolite adsorption beds ensure continuous and stable self-sustaining power generation capabilities.

[0036] 2. This invention innovatively employs a composite energy storage mechanism combining "zeolite adsorption chemical energy storage" and "multi-stage phase change thermal energy storage." Energy is stored not only in the form of high-density chemical potential energy in the zeolite adsorption bed, but also in the form of latent heat in the phase change material in stages. This dual high-density storage mode makes the system's energy storage capacity easily expandable through modularization, making it naturally suitable for large-scale, long-term energy storage applications.

[0037] 3. This invention integrates heat storage modules made of phase change materials with different melting points, enabling graded and lossless storage of compression heat and potentially integrated external heat energy based on temperature grade. During energy release, the heat at the required temperature can be precisely extracted through the sequential heat absorption of the low-temperature working fluid, providing the optimal heat source for zeolite desorption. This "heat bank" style management achieves full heat recovery and on-demand matching within the system, greatly improving efficiency.

[0038] 4. The system architecture of this invention is highly flexible. The energy storage / release cycle can operate independently and is compatible with charging using grid power and renewable energy. Simultaneously, its design easily integrates medium-temperature heat sources such as industrial waste heat and solar thermal energy within the range of 150℃ to 400℃, organically combining electrical energy storage and waste heat recovery to improve overall energy input density and economy. The diverse configurations of the external circulation heat exchange system also enhance the system's adaptability to different environmental conditions.

[0039] 5. The core process of this invention's entire system involves physical adsorption and phase change, without violent chemical reactions, resulting in mild operation. The working fluid is carbon dioxide, which is non-toxic, non-flammable, and widely available. The system's closed-loop design avoids working fluid emissions, making it environmentally friendly. Core components such as zeolite and phase change materials have long lifespans, low maintenance requirements, and high overall system safety and reliability. Attached Figure Description

[0040] Figure 1 This is a system block diagram of a multi-stage phase change energy storage system for liquid carbon dioxide coupled with a zeolite adsorption bed proposed in this invention. Detailed Implementation

[0041] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0042] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include," "contain," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "includes..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0043] refer to Figure 1 This invention discloses a multi-stage phase change energy storage system for liquid carbon dioxide coupled with a zeolite adsorption bed. Its core lies in providing a system architecture that efficiently decouples and coordinates energy storage, release, and power generation processes. The system includes a liquid carbon dioxide storage tank, two zeolite adsorption beds, a turbine generator set, two sets of multi-stage phase change thermal storage modules, an air-suspended compressor, a liquid carbon dioxide circulating pump, and an intelligent valve network. The intelligent valve network controls the opening and closing combinations of valves to create two independent circulation loops: one is a closed-loop power generation loop consisting of the zeolite adsorption bed and the turbine generator set, used for self-sustaining power generation; the other is an energy storage / release loop consisting of the storage tank, thermal storage modules, and a compressor or circulating pump, specifically responsible for energy storage and transportation. Through precise valve switching, the energy storage / release loop can selectively provide a precisely matched desorption heat source to the zeolite adsorption bed, which acts as the desorption bed in the power generation loop. This system innovatively combines zeolite adsorption chemical energy storage with multi-stage phase change thermal energy storage technology. Through a dual-cycle decoupling design, it effectively solves the problems of large energy loss, extensive thermal management, and difficulty in achieving long-term self-sustaining cycles caused by frequent changes in the working fluid state of traditional systems. As a result, it achieves the beneficial effects of tiered utilization of energy quality, high efficiency, easy expansion of energy storage time, and stable operation.

[0044] Example 1

[0045] This embodiment provides a multi-stage phase change energy storage system for liquid carbon dioxide coupled with a zeolite adsorption bed, used for basic system configuration and full-cycle demonstration. Specific implementation details include:

[0046] Purpose of implementation: To demonstrate the core architecture of the system and a typical, continuous "energy storage-energy release-power generation" working cycle, and to verify the basic functions of the dual-cycle decoupling design.

[0047] System Implementation: The system comprises a liquid carbon dioxide composite energy storage system coupled with medium-temperature thermochemical thermal storage, including a liquid carbon dioxide storage tank, an air-suspension compressor, a liquid carbon dioxide circulation pump, a turbine generator set, a first zeolite adsorption bed, a second zeolite adsorption bed, a first multi-stage phase change thermal storage module, a second multi-stage phase change thermal storage module, pipelines, and an intelligent valve network. The intelligent valve network, by controlling the combination of valve opening and closing states, enables the system to form two independent loops: a power generation cycle and an energy storage and release cycle, and allows selective fluid connectivity between the two loops.

[0048] Implementation steps:

[0049] Initial state settings: The first zeolite adsorption bed is saturated with carbon dioxide and is in a "waiting to desorb" state; the second zeolite adsorption bed is an empty bed and is in a "waiting to adsorb" state. The first multi-stage phase change thermal storage module is in a cold state (solid state), and the second multi-stage phase change thermal storage module is in a hot state (liquid state, thermal storage has been completed).

[0050] Phase 1 Energy Release and Power Generation:

[0051] The intelligent valve network switching brings the system into its "first working state." Specifically, the second zeolite adsorption bed is connected to the energy storage and release cycle loop as a desorption bed, while the first zeolite adsorption bed is connected to the power generation cycle loop as an adsorption bed.

[0052] Start the liquid carbon dioxide circulation pump. Liquid carbon dioxide is pumped out from the storage tank, flows through the second multi-stage phase change thermal storage module, absorbs heat, and vaporizes into high-temperature and high-pressure gas.

[0053] The high-temperature gas flows into the second zeolite adsorption bed, providing it with the heat required for desorption.

[0054] High-pressure carbon dioxide desorbed from the second zeolite bed enters the turbine generator set, expands, and performs work to drive the generator to generate electricity.

[0055] The low-pressure exhaust gas after work is introduced into the first zeolite adsorption bed and adsorbed.

[0056] The working fluid, after providing heat to the second zeolite bed, flows through the cold first multi-stage phase change thermal storage module to release residual heat, and then returns to the storage tank after condensation.

[0057] Phase 1 synchronous energy storage:

[0058] During or between power generation, the intelligent valve network switches paths to start the air suspension compressor.

[0059] The carbon dioxide working fluid flows out of the storage tank, is pre-cooled by the first multi-stage phase change thermal energy storage module, and is compressed into a high-temperature and high-pressure gas by the compressor.

[0060] The high-temperature gas flows through the second multi-stage phase change thermal storage module, where its heat of compression is stored in stages within the phase change material of the module. The working fluid itself condenses and returns to the storage tank. This process stores heat for the next working cycle.

[0061] State transition and second phase:

[0062] When the desorption of the second zeolite bed is nearing completion and the adsorption of the first zeolite bed is nearing saturation, the intelligent valve network switches to the "second working state". At this time, the first zeolite adsorption bed becomes a desorption bed, and the second zeolite adsorption bed becomes an adsorption bed; the first multi-stage phase change thermal storage module becomes a heat source end, and the second multi-stage phase change thermal storage module becomes a thermal storage end.

[0063] Repeat steps 2 and 3 for energy release, power generation, and energy storage, but with the roles of heat source and adsorption bed reversed to achieve continuous operation.

[0064] Implementation Results: The system successfully achieved a self-sustaining power generation cycle without relying on continuous external replenishment of working fluid. The energy storage process converts electrical energy (driving the compressor) into stored thermal energy; the energy release process precisely uses the stored thermal energy to drive zeolite desorption, which is then converted into electrical energy. The two cycles operate independently yet are precisely coordinated through a valve network, verifying the feasibility and stability of the system design.

[0065] Example 2

[0066] This embodiment provides a multi-stage phase change energy storage system for liquid carbon dioxide coupled with a zeolite adsorption bed, used for system operation employing type A zeolite adsorbent. Specific implementation details include:

[0067] Objective: To verify the applicability of zeolite molecular sieves with different crystal structures as adsorbents in this system.

[0068] System implementation: The system architecture is the same as in Example 1. The key change is that the adsorbent filled in both zeolite adsorption beds is 5A type zeolite molecular sieve.

[0069] Implementation steps: The operation process, steps and valve switching logic are exactly the same as in Example 1.

[0070] Implementation Results: The 5A type zeolite molecular sieve exhibited excellent adsorption and desorption performance for carbon dioxide. The system operated stably and was able to complete the full adsorption-desorption cycle. Due to the differences in adsorption isotherms and desorption kinetics between the 5A type zeolite and the 13X type (hypothetical in Example 1), the system also achieved efficient continuous power generation and energy storage by monitoring bed pressure and temperature with sensors and fine-tuning the valve switching sequence. This indicates that the system has a certain degree of tolerance for different types of zeolite adsorbents.

[0071] Example 3

[0072] This embodiment provides a multi-stage phase change energy storage system for liquid carbon dioxide coupled with a zeolite adsorption bed, used to adjust the system performance of the phase change material melting point parameter. Specific implementation details include:

[0073] Objective: To investigate the impact of varying melting points of phase change materials within a specific range on system thermal management and operational efficiency.

[0074] Implementation System: The system architecture is the same as in Implementation Example 1. The key changes are: in the sensible heat phase change heat exchangers of the first and second multi-stage phase change thermal storage modules, the first-stage phase change material is replaced with an organic material with a melting point of 135°C, and the second-stage phase change material is replaced with a high-temperature molten salt with a melting point of 380°C.

[0075] Implementation steps: The basic operating logic is the same as in Example 1. In energy release mode, the flow rate of the liquid circulation pump needs to be optimized according to the new phase change temperature to ensure that the temperature of the outflowing carbon dioxide gas can still meet the heat requirements of zeolite desorption (>150℃). In energy storage mode, the compressor operating parameters are also adjusted accordingly to match the heat storage characteristics of the phase change material.

[0076] Implementation Results: The system is operating successfully. Using a combination of phase change materials at 135℃ and 380℃, the system still achieves effective staged heat storage and release. Although the working fluid heating curve changed, the desorption and power generation processes were not significantly affected by adjusting the operating parameters. This demonstrates the system's good adaptability within the phase change temperature range.

[0077] Example 4

[0078] This embodiment provides a multi-stage phase change energy storage system for liquid carbon dioxide coupled with a zeolite adsorption bed, used for enhanced applications of systems integrating industrial waste heat recovery. Specific implementation details include:

[0079] Purpose of implementation: To demonstrate the system's ability as a multi-energy flow integrated platform to efficiently recover and utilize external medium-temperature waste heat.

[0080] Implementation System: Based on the system in Example 1, an industrial flue gas waste heat exchanger is connected in parallel to the pipeline between the outlet of the air-suspension compressor and the inlet of the second multi-stage phase change thermal storage module in the energy storage and release loop. This heat exchanger can be used to supply industrial waste gas at 300-350°C.

[0081] Implementation steps:

[0082] When the system executes the energy storage process, the intelligent valve network guides the high-temperature carbon dioxide working fluid from the compressor to flow through the industrial flue gas waste heat exchanger, absorbing the waste heat in the flue gas and further increasing the temperature.

[0083] Subsequently, this high-grade thermal energy, carrying both "electrical energy conversion heat" and "industrial waste heat," flows into a multi-stage phase change thermal energy storage module for storage.

[0084] The energy release and power generation process is the same as in Example 1, but the heat released this time includes two parts of energy, resulting in a significant increase in power generation.

[0085] Implementation Results: The system successfully integrates industrial waste heat with electrical energy storage. Compared to pure electric energy storage, the overall energy input density is significantly increased, and more electricity can be generated with the same heat storage volume, significantly improving the system's economic efficiency and overall energy utilization efficiency.

[0086] Example 5

[0087] This embodiment provides a multi-stage phase change energy storage system for liquid carbon dioxide coupled with a zeolite adsorption bed, used in a system employing a ground source heat pump as an external heat exchange system. Specific implementation details include:

[0088] Purpose of implementation: To verify the effectiveness of different types of external heat exchange systems in maintaining the basic thermal balance of the system.

[0089] System implementation: The system architecture is the same as in Implementation Example 1. The key change is that the external circulating heat exchange system is replaced by a ground source heat pump system instead of a cooling tower.

[0090] Implementation steps: The system operation process is the same as in Example 1. The ground source heat pump system continuously exchanges heat with the liquid carbon dioxide storage tank, utilizing the stable temperature of the underground soil to provide or remove heat from the working fluid inside the tank.

[0091] Implementation Results: In environments with significant temperature fluctuations, the ground source heat pump system can more stably maintain the temperature of the liquid carbon dioxide storage tank, effectively preventing dry ice blockage that may occur due to excessively low temperatures caused by flash evaporation or throttling during carbon dioxide circulation. The system operates more smoothly and reliably, making it particularly suitable for areas with large diurnal or seasonal temperature differences.

[0092] Comparative Example 1

[0093] This comparative example provides a traditional supercritical carbon dioxide battery energy storage system, specifically including:

[0094] Purpose of implementation: To highlight the advantages of this invention in terms of cycle efficiency, energy storage duration, and thermal management by comparing it with existing technologies.

[0095] System Implementation: A typical supercritical carbon dioxide energy storage system is employed. The system includes a compressor, a high-pressure storage tank, a turbine generator set, a regenerator, a cooler, and a low-pressure storage tank. During energy storage, the electrically driven compressor compresses carbon dioxide to a supercritical state and stores it in the high-pressure tank. During energy release, the high-pressure carbon dioxide absorbs heat through the regenerator and then drives the turbine to generate electricity; the exhaust gas is cooled, liquefied, and stored in the low-pressure tank. The system does not integrate zeolite adsorption and multi-stage phase change thermal storage; the energy storage and power generation processes are tightly coupled.

[0096] Comparative analysis:

[0097] Efficiency: In comparative systems, turbine back pressure is limited by ambient temperature, resulting in a limited expansion ratio. Furthermore, the heat of compression and liquefaction cooling are difficult to fully recover, with a typical round-trip efficiency of approximately 50-60%. The system of this invention maintains extremely low turbine back pressure through zeolite adsorption, achieving an extremely high expansion ratio. It also utilizes multi-stage phase change heat storage to recover almost all heat, with simulated round-trip efficiency exceeding 70%.

[0098] Energy storage duration and self-sufficiency: The power generation duration of comparative power generation is strictly limited by the volume of the high-pressure storage tank, which cannot be expanded, and a closed-loop self-sufficient cycle of the working fluid cannot be achieved. The energy of this invention is stored in high-density form in the form of chemical energy and latent heat energy, which can be easily expanded in duration, and a truly closed-loop self-sufficient cycle is achieved through the alternation of two beds.

[0099] Thermal Management: Comparative systems rely on a single heat source, resulting in inefficient heat utilization. This invention achieves multi-grade, precise heat transfer and matching from the compression end to the desorption end, significantly improving thermal management efficiency.

[0100] Implementation Results (Comparative Conclusions): The dual-cycle decoupling design of this invention, combined with zeolite adsorption and multi-stage phase change thermal storage, fundamentally solves the problems of efficiency bottlenecks, limited energy storage time, and crude thermal management in traditional systems, demonstrating significant comprehensive performance advantages.

[0101] Comparing Examples 1-5 with Comparative Example 1, the systematic comparison of Examples 1-5 with Comparative Example 1 clearly reveals the fundamental breakthrough and comprehensive advantages of the liquid carbon dioxide composite energy storage system of the present invention compared to traditional architectures. In summary:

[0102] Cyclic Architecture and Efficiency: Comparative Example 1 represents the traditional approach, where energy storage and power generation are completed in a single, tightly coupled thermodynamic cycle. This binding results in turbine back pressure being limited by ambient temperature and cooling capacity, an upper limit to the expansion ratio, and difficulty in fully recovering compression heat and liquefaction cooling during frequent state switching, typically limiting the system's round-trip efficiency to below 60%. In contrast, Embodiments 1-5 of this invention are revolutionary due to their "dual-cycle decoupling" architecture. The power generation cycle (zeolite bed-turbine-zeolite bed) focuses on efficient heat-work conversion, while the energy storage / release cycle independently handles energy "transportation" and grade regulation. More importantly, by introducing a zeolite adsorption bed, the system actively creates an extremely low turbine back pressure close to vacuum, breaking through the expansion ratio limit of traditional cycles; through multi-stage phase change heat storage, high-grade, lossless storage and precise release of compression heat are achieved. The operation of Embodiments 1 and 3 verifies that this design can improve the overall system efficiency to over 70%, achieving a leap in energy efficiency.

[0103] Energy Storage Duration and Operating Mode: Comparative Example 1 is essentially a "gas battery," whose discharge duration is strictly limited by the physical volume of the high-pressure storage tank, making it uneconomical to extend to long-term energy storage (e.g., exceeding 10 hours). Furthermore, each cycle requires repeated conversion of the working fluid between gas and liquid phases, making it unsustainable. This invention, however, utilizes a composite energy storage mechanism combining chemical adsorption (zeolite) and latent heat (phase change material) to store energy in a high-density form. As shown in Examples 1 and 2, the alternating operation of the two zeolite adsorption beds enables the carbon dioxide working fluid to achieve a near-closed-loop cycle within the system, requiring no external replenishment and theoretically allowing for unlimited self-sustaining power generation. The energy storage duration is determined solely by the scale of the thermal storage module and the capacity of the zeolite bed, facilitating modular expansion and perfectly meeting long-term energy storage requirements.

[0104] Refined Thermal Management and Energy Integration Capabilities: Comparative Example 1 demonstrates relatively crude thermal management, with high- and low-grade heat easily mixed, making tiered utilization difficult. Examples 3, 4, and 5 of this invention fully showcase its precise thermal management and powerful multi-energy flow integration capabilities. The multi-stage phase change thermal storage module (such as the 135℃ / 380℃ combination in Example 3) acts like a "thermal energy battery pack," capable of classifying and storing heat of different grades (compressor-generated heat, external waste heat) and releasing it on demand and sequentially during energy release, perfectly matching the heat requirements of zeolite desorption and achieving "maximum utilization of heat." Example 4 further demonstrates that the system can serve as an open platform, efficiently integrating external medium-temperature heat sources (150-400℃) such as industrial waste heat, upgrading a single "electricity storage" system into a comprehensive unit of "electricity-heat synergistic storage and conversion," significantly improving economic efficiency.

[0105] System adaptability and environmental friendliness: The performance of Comparative Example 1 is sensitive to ambient temperature; low temperatures may affect liquefaction efficiency, while high temperatures limit turbine output. Example 5 of this invention demonstrates that by adapting to different external heat exchange systems (such as ground source heat pumps), the system can better adapt to various climatic conditions and maintain stable operation. Simultaneously, the entire cycle is primarily based on physical adsorption and phase change, with carbon dioxide as the working fluid, making it environmentally friendly and highly safe.

[0106] Compared to traditional supercritical carbon dioxide energy storage systems (Comparative Example 1), this invention systematically solves fundamental problems such as efficiency bottlenecks, storage duration limitations, and inefficient thermal management through the synergistic effect of three core innovations: decoupling design of power generation and energy storage release cycles, low back pressure cycle created by zeolite adsorption, and precise energy management of multi-stage phase change thermal storage. Examples 1-5 verify from different perspectives that this system is not only a more efficient energy storage device, but also a sustainable energy conversion and circulation system capable of long-term operation, flexible integration of multiple energy sources, and strong environmental adaptability, representing an important development direction for next-generation large-scale long-term energy storage technology.

[0107] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of protection of the claims.

[0108] In conclusion, the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A multi-stage phase change energy storage system for liquid carbon dioxide coupled with a zeolite adsorption bed, characterized in that, include: Liquid carbon dioxide storage tank, air suspension compressor, liquid carbon dioxide circulating pump, turbine generator set, first zeolite adsorption bed, second zeolite adsorption bed, first multi-stage phase change thermal storage module, second multi-stage phase change thermal storage module, pipelines, and intelligent valve network; Piping and smart valve networks connect the above components; The intelligent valve network is configured to switch between two operating states by controlling the combination of opening and closing states of the multiple valves it contains, and to form two independent loops in either operating state, namely a power generation loop and an energy storage and release loop. The power generation cycle loop is composed of a zeolite adsorption bed that serves as a desorption bed, a turbine generator set, and another zeolite adsorption bed that serves as an adsorption bed, connected in sequence by pipelines, forming a closed working fluid flow path. The energy storage and release loop is connected in sequence by pipelines to a liquid carbon dioxide storage tank and a multi-stage phase change thermal energy storage module. It can also be connected to an air suspension compressor or a liquid carbon dioxide circulation pump depending on the working mode, thus forming another closed working fluid flow path. During system operation, the energy storage and release loop is regulated by an intelligent valve network to achieve fluid communication and heat exchange with the zeolite adsorption bed, which serves as the desorption bed in the power generation loop.

2. The liquid carbon dioxide multi-stage phase change energy storage system coupled with a zeolite adsorption bed as described in claim 1, characterized in that, The first multi-stage phase change thermal energy storage module includes a first latent heat phase change heat exchanger and a first sensible heat phase change heat exchanger connected in series. The second multi-stage phase change thermal energy storage module includes a second latent heat phase change heat exchanger and a second sensible heat phase change heat exchanger connected in series.

3. A multi-stage phase change energy storage system for liquid carbon dioxide coupled with a zeolite adsorption bed as described in claim 2, characterized in that, Both the first and second sensible heat phase change heat exchangers have at least two independent heat exchange units integrated inside. Each heat exchange unit contains a phase change material with a specific melting point, and the melting points of the phase change materials in different heat exchange units are different.

4. A multi-stage phase change energy storage system for liquid carbon dioxide coupled with a zeolite adsorption bed as described in claim 3, characterized in that, Phase change materials include first phase change materials and second phase change materials; The melting point range of the first phase change material is 120°C to 180°C; The melting point of the second phase change material is above 300℃.

5. A multi-stage phase change energy storage system for liquid carbon dioxide coupled with a zeolite adsorption bed as described in claim 1, characterized in that, The adsorbents filled in the first and second zeolite adsorption beds are zeolite molecular sieves. Zeolite molecular sieves have selective adsorption capacity for carbon dioxide, and their crystal structure type is at least one of X-type, A-type or Y-type.

6. A multi-stage phase change energy storage system for liquid carbon dioxide coupled with a zeolite adsorption bed as described in claim 1, characterized in that, Medium-temperature thermochemical thermal storage refers to the process of storing and releasing heat through the adsorption and desorption reactions of carbon dioxide in a zeolite adsorption bed. The temperature range of the heat source required to drive the zeolite adsorption bed to complete the desorption reaction is 150℃ to 400℃.

7. A multi-stage phase change energy storage system for liquid carbon dioxide coupled with a zeolite adsorption bed as described in claim 1, characterized in that, The two operating states achieved by the intelligent valve network are: First working state: The first zeolite adsorption bed acts as a desorption bed and is fluidly connected to the energy storage and release circulation loop to receive the heat source; the second zeolite adsorption bed acts as an adsorption bed. Second working state: The second zeolite adsorption bed acts as a desorption bed and is fluidly connected to the energy storage and release circulation loop to receive the heat source; the first zeolite adsorption bed acts as an adsorption bed.

8. A multi-stage phase change energy storage system for liquid carbon dioxide coupled with a zeolite adsorption bed as described in claim 7, characterized in that, In the first working state, the high-pressure carbon dioxide desorbed from the first zeolite adsorption bed drives the turbine generator set to do work and generate electricity, and the low-pressure carbon dioxide after doing work is adsorbed by the second zeolite adsorption bed. In the second operating state, the high-pressure carbon dioxide desorbed from the second zeolite adsorption bed drives the turbine generator set to do work and generate electricity, and the low-pressure carbon dioxide after doing work is adsorbed by the first zeolite adsorption bed.

9. A multi-stage phase change energy storage system for liquid carbon dioxide coupled with a zeolite adsorption bed as described in claim 1, characterized in that, Also includes: External circulation heat exchange system; The external circulating heat exchange system is connected to the liquid carbon dioxide storage tank to exchange heat with the liquid carbon dioxide in the tank during system operation in order to maintain the working fluid balance.

10. A multi-stage phase change energy storage system for liquid carbon dioxide coupled with a zeolite adsorption bed as described in claim 1, characterized in that, The energy storage and release loop has two operating modes, which are switched by an intelligent valve network; In energy storage mode, the air suspension compressor is connected to the loop to drive the carbon dioxide working fluid circulation and store the high-temperature heat energy generated during the compression process in the multi-stage phase change thermal energy storage module currently connected to it; In the energy release mode, a liquid carbon dioxide circulation pump is connected to the loop to drive the carbon dioxide working fluid to circulate, so that it absorbs heat from the multi-stage phase change thermal storage module that has stored heat and vaporizes it, and then provides desorption heat to the zeolite adsorption bed that is currently connected to it.

Images