Modeling and simulation method for volume linear variable process in pressure building and energy storage stages of energy storage container

Abstract

The invention provides an energy storage container pressure building and energy storage stage volume linear variable process modeling and simulation method. The method comprises the steps that a pressure-time mathematical model in a container in the energy storage process of a hydraulic compressed air system is established; initial pressure building and energy storage are divided into four sub-steps, liquid is alternately pumped into two acting containers, pressurized gas is pushed to enter an energy storage container, and multiple times of inflation are completed in a circulating mode; based on 12 thermodynamic assumptions (such as temperature uniformity, ideal gas state, quasi-steady state process and the like), deriving functions of pressure and gas volume changing along with time; and a pressure change curve is obtained through simulation calculation. According to the method, the dynamic characteristics of the energy storage process can be accurately described, the change relation between physical quantities is reflected, a theoretical basis is provided for system working condition analysis, parameter matching and optimization design, meanwhile, an ideal mathematical model is established by simplifying coupling factors, and a target is provided for calculation of the maximum energy storage capacity of the system.

Description

Technical Field

[0001] This invention relates to the field of hydraulic compression energy storage technology, specifically to a method for modeling and simulating the linearly variable volume process during the pressurization stage of an energy storage container. Background Technology

[0002] With the increasing global demand for clean energy, energy storage technology has received widespread attention as a key means to address the intermittency and volatility of renewable energy. Hydraulic compressed air energy storage technology, as a novel large-scale energy storage technology, boasts advantages such as large storage capacity, low cost, and long lifespan, and is considered one of the most promising energy storage methods.

[0003] In hydraulic compressed air energy storage systems, the matching and optimization of parameters such as unit parameters, container parameters, and power generation duration is one of the core aspects of system design, directly affecting the energy storage efficiency and economics of the entire system. However, current research in this field faces numerous challenges. Energy storage systems exhibit strong coupling characteristics between multiple physical fields, including water, air, mechanical, electrical, and thermal fields. The container walls also exchange heat with the external environment, enhancing the system's time-varying nonlinearity. Traditional models often fail to consider all factors, resulting in low accuracy and reliability. Furthermore, the models are extremely complex, making it difficult to reveal the relationships between different parameters, thus unsuitable for rapid system selection and design requirements.

[0004] On the other hand, most existing research focuses on analysis under steady-state conditions, lacking sufficient ability to simulate and predict ideal dynamic processes. For example, in practical engineering applications, it is difficult to provide an analytical function expression for the theoretical pressure change curve within the energy storage container during ideal isothermal compression, and existing technologies struggle to provide decisive improvement directions and solutions for optimizing actual pressure changes.

[0005] In summary, existing technologies are insufficient in terms of model building and dynamic response characteristic analysis of hydraulic compressed air energy storage devices. They are unable to meet the needs of rapid system selection and design, and efficient and stable operation prediction in practical engineering. There is an urgent need for a model building and simulation method that can highlight the main contradictions in system operation and predict and analyze dynamic characteristics in combination with system operation mode. Summary of the Invention

[0006] The present invention aims to at least solve one of the technical problems existing in the prior art, and provides a method for modeling and simulating the linearly variable volume process of the energy storage container during the pressurization stage.

[0007] This invention provides a method for modeling and simulating the linearly variable volume process during the pressurization stage of an energy storage container, comprising the following steps: Step S1: Based on the pressure-time relationship inside the container, establish a mathematical model of the container during the energy storage process of the hydraulic compressed air system; Step S2, the initial pressure build-up and energy storage stage, is divided into four sub-steps. Sub-step 1 uses a pump to fill liquid into the working container 1 until the air pressure reaches the same level as the energy storage container. Sub-step 2 involves the pressurized gas in the working container 1 being expelled by the liquid in the pump and entering the energy storage container. Sub-step 3 involves the pump filling liquid into the working container 2 again until the air pressure reaches the same level as the energy storage container. Sub-step 4 involves the pressurized gas in the working container 2 being expelled by the liquid in the pump and entering the energy storage container. In sub-steps 3 and 4, the liquid in the working container 1 flows back to the water tank under atmospheric pressure, completing one inflation cycle. After multiple repeated inflation cycles, the pressure inside the energy storage container rises to the set value, completing the initial pressure build-up and energy storage process. Step S3: The following assumptions are made during the modeling process: Assumption (1): The temperature inside the control body is uniformly distributed and there is no temperature gradient; Assumption (2): The ambient temperature remains constant; Assumption (3): The thermophysical properties of the container wall material are constant; Assumption (4): Heat exchange between the two control bodies is ignored; Assumption (5): All processes are quasi-steady-state processes; Assumption (6): The gas inside the container satisfies the ideal gas law; Assumption (7): The temperature of the liquid inside the container remains constant; Assumption (8): After the work container is filled with liquid, there is no energy loss when the gas is discharged into the energy storage container, and the liquid inside the work container does not affect the next pump operation; Assumption (9): The liquid in the work container flows back to the water tank naturally under atmospheric pressure without the need for external energy supply; Assumption (10): The heat transfer characteristics of the container wall are ignored; Assumption (11): The air inside the energy storage container and the work container satisfies a polytropic process during the energy storage process; Assumption (12): The energy loss of the water pump and motor is ignored, and the gas volume inside the work container changes continuously. Step S4: Combining steps S2 and S3, based on the laws of thermodynamic processes, derive the pressure-time variation function and the gas volume-time variation function for the initial pressure build-up and energy storage stages. Step S5: Based on the mathematical model in step S4, multi-condition simulation is performed by setting different combinations of air volume reduction slope, work container volume, and energy storage container volume parameters to obtain pressure-time dynamic response curves. Then, the synergistic influence of gas compression rate and container geometry on system energy storage capacity, pressure evolution characteristics, and effective volume change is analyzed.

[0008] In some possible embodiments, the rate of change of gas compression work in the work container during the initial pressure build-up and energy storage stage sub-step 1 of step S5 is equal to the external electrical power:

[0009] in, P For input power, p The air pressure inside the work container. The negative sign indicates that the volume of air inside the container is gradually decreasing.

[0010] In some possible embodiments, the gas volume change in the work container of sub-step 1 of the initial pressure build-up and energy storage stage in step S5 satisfies the following equation;

[0011] in, The initial air volume inside the work container. This represents the initial air pressure inside the container. For input electrical power, The slope representing the decrease in air volume. Indicates time.

[0012] In some possible embodiments, the gas pressure change in the work container of sub-step 1 of the initial pressure build-up and energy storage stage in step S5 satisfies the following equation;

[0013] in, The initial air volume inside the work container. This represents the initial air pressure inside the container. For input electrical power, The slope representing the decrease in air volume. Indicates time.

[0014] In some possible embodiments, the gas volume changes in the work container and energy storage container in the initial pressure build-up and energy storage stage sub-step 2 of step S5 satisfy the following equation;

[0015] in, The sum of the volume of the work container and the volume of the energy storage container at the end of sub-step 1. This indicates the air pressure inside the container at the end of sub-step 1. For input electrical power, Indicates a volatile index. Indicates time, The slope is reduced to decrease the air volume.

[0016] In some possible embodiments, the gas pressure change in the work container of sub-step 2 of the initial pressure build-up and energy storage stage in step S5 satisfies the following equation;

[0017] in, The sum of the volume of the work container and the volume of the energy storage container at the end of sub-step 1. This indicates the air pressure inside the container at the end of sub-step 1. For input electrical power, Indicates a volatile index. Indicates time, The slope is reduced to decrease the air volume.

[0018] The gas equation in the work container in sub-step 3 is consistent with the equation in sub-step 1. The gas equation in the work container in sub-step 4 is consistent with the equation in sub-step 2. The gas equation in the energy storage container is consistent with the equation in sub-step 2. The simulation results include the pressure in the energy storage container and the pressure in the work container changing with time during the energy storage process.

[0019] Compared with existing technologies, the modeling and simulation method for the linearly variable volume process of the pressurized energy storage stage of the energy storage container provided by this invention can use a time-varying function to describe the dynamic characteristics of the gas storage container in the hydraulic compression energy storage system during the energy storage process. It can clearly reflect the dynamic relationship between various physical quantities, providing a method for quickly analyzing the response mechanism of the gas storage container under different operating conditions and the matching relationship between different parameters. This is of great value for system analysis, calculation, and design. At the same time, it simplifies the complex coupling factors of the energy storage process and provides a mathematical model of the maximum energy storage capacity of the system under ideal conditions, providing a theoretical target for system optimization design. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of a hydraulic compressed air energy storage system. Figure 2 This is a flowchart illustrating the modeling and simulation method for the linearly variable volume process of the energy storage container during the pressurization and energy storage stage, according to an embodiment of the present invention. Detailed Implementation

[0022] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0023] Unless otherwise specifically stated, the technical or scientific terms used in the embodiments of this invention should be understood in their ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains. The terms "comprising" or "including," as used in the embodiments of this invention, do not limit the shapes, numbers, steps, actions, operations, components, elements, and / or groups thereof mentioned, nor do they exclude the appearance or addition of one or more other different shapes, numbers, steps, actions, operations, components, elements, and / or groups thereof, or the inclusion of these.

[0024] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale, and techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail; however, where appropriate, the illustrated techniques, methods, and apparatus should be considered part of the specification. In all the examples shown and discussed herein, any other specific example may have different values. It should be noted that similar symbols and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0025] In the description of the embodiments of the present invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In the embodiments of the present invention, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in the embodiments of the present invention, as well as the features of different embodiments or examples.

[0026] Hereinafter, exemplary embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments of the present invention. It should be understood that the present invention is not limited to the exemplary embodiments described herein.

[0027] refer to Figure 1 and Figure 2The hydraulic compression energy storage system of the present invention includes a water turbine, a water turbine generator, an energy storage pump, an energy storage pump motor, a makeup water pump, a makeup water pump motor, a working container 1, a working container 2, an energy storage container, a water storage tank, and valves 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0028] The work container 1 and the energy storage container 2 are connected by a pipeline. Valves 2 and 4 are installed on the pipeline. The main purpose of the pipeline is to store the compressed high-pressure air in the work containers 1 and 2 in the energy storage container during the energy storage stage. Valves 2 and 4 are installed on the pipeline to ensure that the gas pressure in the work containers 1 and 2 remains constant during the discharge process.

[0029] The system starts operating, initially entering the pressure build-up and energy storage phase. The working container 1 is connected to atmospheric pressure. All valves except the one connecting the working container to the energy storage pump are closed. Motor 1 drives the energy storage pump to fill the working container 1 with water. The pressure inside both the working container and the energy storage container continuously increases. At this time, the pressure inside both the energy storage container and the working container increases synchronously over time. Once the liquid level in the working container reaches its maximum value, the connecting valve between the energy storage container and the working container 1 is closed.

[0030] During the energy storage process of working container 1, working container 2 absorbs air from the atmosphere and closes valve 3, severing the connection with the atmosphere. The water pump fills working container 2 with water, increasing the pressure inside working container 2. When the pressure inside working container 2 reaches the air pressure value in the energy storage container, valve 4 is opened, connecting the energy storage container and working container 2. The water pump continuously injects water into working container 2 to pressurize it, and the air pressure in the energy storage container and working container 2 rises synchronously. After the liquid level in the working container reaches its maximum value, the connecting valve between the energy storage container and working container 2 is closed.

[0031] During energy storage, when the pressure reaches the set value, the gas pressure in the working container still needs to be discharged into the energy storage container before the operation of the energy storage pump can be stopped.

[0032] In step S5, during the initial pressure build-up and energy storage stage, the rate of change of gas compression work inside the work container in sub-step 1 is equal to the external electrical power.

[0033] in, P For input power, p The air pressure inside the work container. The negative sign indicates that the volume of air inside the container is gradually decreasing.

[0034] The gas volume change in the work container during the initial pressure build-up and energy storage stage in step S5 satisfies the following equation;

[0035] in, The initial air volume inside the work container. This represents the initial air pressure inside the container. For input electrical power, The slope representing the decrease in air volume. Indicates time.

[0036] The gas pressure change in the work container of sub-step 1 in the initial pressure building and energy storage stage of step S5 satisfies the following equation;

[0037] in, The initial air volume inside the work container. This represents the initial air pressure inside the container. For input electrical power, The slope representing the decrease in air volume. Indicates time.

[0038] In step S5, the gas volume changes in the work container and energy storage container during the initial pressure build-up and energy storage stage sub-step 2 satisfy the following equation;

[0039] in, The sum of the volume of the work container and the volume of the energy storage container at the end of sub-step 1. This indicates the air pressure inside the container at the end of sub-step 1. For input electrical power, Indicates a volatile index. Indicates time, The slope is reduced to decrease the air volume.

[0040] The gas pressure change in the work container during the initial pressure build-up and energy storage stage in step S5 satisfies the following equation;

[0041] in, The sum of the volume of the work container and the volume of the energy storage container at the end of sub-step 1. This indicates the air pressure inside the container at the end of sub-step 1. For input electrical power, Indicates a volatile index. Indicates time, The slope is reduced to decrease the air volume.

[0042] In sub-step S4, the gas equation inside the work container is consistent with the equation in sub-step S5, and the gas equation inside the energy storage container is consistent with the equation in sub-step S6. The simulation results include the pressure curves inside the energy storage container and the pressure curves inside the work container as a function of time during the energy storage process. Furthermore, based on the mathematical model in step S4, multi-condition simulations are performed by setting different combinations of air volume reduction slopes, work container volume, and energy storage container volume parameters to obtain pressure-time dynamic response curves. This allows for the analysis of the synergistic influence of gas compression rate and container geometry on the system's energy storage capacity, pressure evolution characteristics, and effective volume change.

[0043] The method for modeling and simulating the linearly variable volumetric process of the pressurization stage of an energy storage container provided in this invention can describe the dynamic characteristics of the gas storage container in a hydraulic compression energy storage system during the energy storage process using a time-varying function. It clearly reflects the dynamic relationships between various physical quantities, providing a method for rapidly analyzing the response mechanism of the gas storage container under different operating conditions and the matching relationships between different parameters. This is of significant value for system analysis, calculation, and design. Simultaneously, it simplifies the complex coupling factors of the energy storage process and provides a mathematical model of the maximum energy storage capacity of the system under ideal conditions, providing a theoretical target for system optimization design.

[0044] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for modeling and simulating the linearly variable volume process during the pressurization stage of an energy storage container, characterized in that, Includes the following steps: Step S1: Based on the pressure-time relationship inside the container, establish a mathematical model of the container during the energy storage process of the hydraulic compressed air system; Step S2, the initial pressure build-up and energy storage stage, is divided into four sub-steps. Sub-step 1 uses a pump to fill liquid into the working container 1 until the air pressure reaches the same level as the energy storage container. Sub-step 2 involves the pressurized gas in the working container 1 being expelled by the liquid in the pump and entering the energy storage container. Sub-step 3 involves the pump filling liquid into the working container 2 again until the air pressure reaches the same level as the energy storage container. Sub-step 4 involves the pressurized gas in the working container 2 being expelled by the liquid in the pump and entering the energy storage container. In sub-steps 3 and 4, the liquid in the working container 1 flows back to the water tank under atmospheric pressure, completing one inflation cycle. After multiple repeated inflation cycles, the pressure inside the energy storage container rises to the set value, completing the initial pressure build-up and energy storage process. Step S3: The following assumptions are made during the modeling process: Assumption (1): The temperature inside the control body is uniformly distributed and there is no temperature gradient; Assumption (2): The ambient temperature remains constant; Assumption (3): The thermophysical properties of the container wall material are constant; Assumption (4): Heat exchange between the two control bodies is ignored; Assumption (5): All processes are quasi-steady-state processes; Assumption (6): The gas inside the container satisfies the ideal gas law; Assumption (7): The temperature of the liquid inside the container remains constant; Assumption (8): After the work container is filled with liquid, there is no energy loss when the gas is discharged into the energy storage container, and the liquid inside the work container does not affect the next pump operation; Assumption (9): The liquid in the work container flows back to the water tank naturally under atmospheric pressure without the need for external energy supply; Assumption (10): The heat transfer characteristics of the container wall are ignored; Assumption (11): The air inside the energy storage container and the work container satisfies a polytropic process during the energy storage process; Assumption (12): The energy loss of the water pump and motor is ignored, and the gas volume inside the work container changes continuously. Step S4: Combining steps S2 and S3, based on the laws of thermodynamic processes, derive the pressure-time variation function and the gas volume-time variation function for the initial pressure build-up and energy storage stages. Step S5: Based on the mathematical model in step S4, multi-condition simulation is performed by setting different combinations of air volume reduction slope, work container volume, and energy storage container volume parameters to obtain pressure-time dynamic response curves. Then, the synergistic influence of gas compression rate and container geometry on system energy storage capacity, pressure evolution characteristics, and effective volume change is analyzed.

2. The method according to claim 1, characterized in that, In step S5, during the initial pressure build-up and energy storage stage, the rate of change of gas compression work inside the work container in sub-step 1 is equal to the external electrical power. in, P For input power, p The air pressure inside the work container. The negative sign indicates that the volume of air inside the container is gradually decreasing.

3. The method according to claim 2, characterized in that, The gas volume change in the work container during the initial pressure build-up and energy storage stage in step S5 satisfies the following equation; in, The initial air volume inside the work container. This represents the initial air pressure inside the container. For input electrical power, The slope representing the decrease in air volume. Indicates time.

4. The method according to claim 3, characterized in that, The gas pressure change in the work container of sub-step 1 in the initial pressure building and energy storage stage of step S5 satisfies the following equation; in, The initial air volume inside the work container. This represents the initial air pressure inside the container. For input electrical power, The slope representing the decrease in air volume. Indicates time.

5. The method according to claim 4, characterized in that, In step S5, the gas volume changes in the work container and energy storage container during the initial pressure build-up and energy storage stage sub-step 2 satisfy the following equation; in, The sum of the volume of the work container and the volume of the energy storage container at the end of sub-step 1. This indicates the air pressure inside the container at the end of sub-step 1. For input electrical power, Indicates a volatile index. Indicates time, The slope is reduced to decrease the air volume.

6. The method according to claim 5, characterized in that, The gas pressure change in the work container during the initial pressure build-up and energy storage stage in step S5 satisfies the following equation; in, The sum of the volume of the work container and the volume of the energy storage container at the end of sub-step 1. This indicates the air pressure inside the container at the end of sub-step 1. For input electrical power, Indicates a volatile index. Indicates time, The slope is reduced to decrease the air volume.

7. The method according to any one of claims 1 to 6, characterized in that, The gas equation in the work container in sub-step 3 is consistent with the equation in sub-step 1. The gas equation in the work container in sub-step 4 is consistent with the equation in sub-step 2. The gas equation in the energy storage container is consistent with the equation in sub-step 2. The simulation results include the pressure in the energy storage container and the pressure in the work container changing with time during the energy storage process.

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