Overall energy efficiency analysis and calculation method for vertical shaft type gravity energy storage system

Abstract

The invention relates to the technical field of vertical shaft type gravity energy storage systems, in particular to a vertical shaft type gravity energy storage system overall energy efficiency analysis and calculation method which comprises the steps that the complete charging and discharging circulation of a vertical shaft type gravity energy storage system is divided into a plurality of stages according to the movement path of a gravity medium; aiming at the charging state, establishing a kinetic equation and an energy conversion equation of the gravity medium in the horizontal transportation and vertical lifting process, solving to obtain an energy change value of each stage, and obtaining the total energy of the charging process; aiming at the discharge state, establishing a kinetic equation and an energy conversion equation of the gravity medium in the horizontal transportation and vertical descending processes, solving to obtain an energy change value of each stage, and obtaining the total energy of the discharge process; and obtaining the overall energy conversion efficiency of the system based on the total energy of the discharging process and the total energy of the charging process. The calculation method provided by the invention realizes the quantitative analysis of the whole process of the vertical shaft type gravity energy storage system from the power grid side input energy to the power grid side output energy.

Description

Technical Field

[0001] This invention relates to the field of vertical shaft gravity energy storage system technology, and in particular to a method for overall energy efficiency analysis and calculation of vertical shaft gravity energy storage system. Background Technology

[0002] Gravity energy storage, as a novel physical energy storage technology, operates on the principle of using a height difference to raise and lower the energy storage medium, thereby enabling the charging and discharging process of the energy storage system. It features flexible site selection, large capacity, long storage time, long system lifespan, and safety and environmental friendliness. Compared to pumped hydro storage, gravity energy storage is not limited by water resources and can utilize solid heavy materials as the energy storage medium. Among these technologies, shaft-based gravity energy storage utilizes the space resources of abandoned mines to construct gravity energy storage systems, achieving the reuse of abandoned mine resources and demonstrating broad development prospects.

[0003] With the development of gravity energy storage technology, scholars and enterprises both domestically and internationally have conducted extensive research on shaft-type gravity energy storage systems. This research primarily focuses on system architecture design, operation control strategies, and equipment selection and configuration, aiming to improve system performance and economic efficiency. However, accurately assessing the overall energy conversion efficiency of the system remains a critical issue during the feasibility study phase of engineering projects. The lack of quantitative analysis methods for the complete charge-discharge cycle process limits the further promotion and application of shaft-type gravity energy storage technology.

[0004] Chinese patent application CN117886198A discloses a vertical shaft gravity energy storage system and its operation and design methods. This patent utilizes at least two gravity turbine systems, employing the coordinated operation of a first gravity turbine sheave, a second gravity turbine sheave, and a gravity turbine friction wheel to achieve the lifting and lowering of the gravity medium within the shaft. Continuous discharge of the system is achieved through a lifting container connected by wire ropes and an equal-weight tail rope. This technical solution focuses on optimizing the system architecture and improving the operation control method to enhance the system's conversion efficiency and achieve continuous discharge. However, the lack of quantitative analysis of the overall energy conversion efficiency of the system creates a deficiency in the feasibility study of vertical shaft gravity energy storage systems, thus limiting the further development of the gravity energy storage market. Summary of the Invention

[0005] In view of this, the present invention proposes an overall energy efficiency analysis and calculation method for a vertical shaft gravity energy storage system. Based on the dynamic equations of the gravity medium under various operating conditions of the vertical shaft gravity energy storage system and the energy loss generated in the process, the energy conversion efficiency of the system in a single charge-discharge cycle on the grid side is calculated, providing guidance for the design of the main technical parameters of the subsequent vertical shaft gravity energy storage system.

[0006] The technical solution of this invention is implemented as follows: This invention provides a method for overall energy efficiency analysis and calculation of a vertical shaft gravity energy storage system, including the following steps: S1. The complete charge and discharge cycle of the vertical shaft gravity energy storage system is divided into multiple stages according to the movement path of the gravity medium. The stages include the process of the gravity medium moving from the lower chamber through the bottom of the shaft to the shaft opening and then to the upper chamber in the charging state, and the process of the gravity medium moving from the upper chamber through the shaft opening to the bottom of the shaft and then to the lower chamber in the discharging state. S2. For each stage of the charging state, establish the dynamic equations and energy conversion equations for the gravity medium in the horizontal transportation and vertical lifting process. By solving the dynamic equations and energy conversion equations, obtain the energy change value of each stage. Accumulate the energy change values ​​of each stage of the charging state and combine them with the system efficiency parameters to calculate the total energy input from the grid side during the charging process. S3. For each stage of the discharge state, establish the dynamic equations and energy conversion equations for the gravity medium during horizontal transport and vertical descent. Solve the dynamic equations and energy conversion equations to obtain the energy change values ​​for each stage. Accumulate the energy change values ​​for each stage of the discharge state and combine them with the system efficiency parameters to calculate the total energy output to the grid side during the discharge process. S4. Calculate the ratio of the total energy output to the grid side during the discharge process to the total energy input to the grid side during the charging process to obtain the overall energy conversion efficiency of the system.

[0007] Based on the above technical solutions, preferably, the efficiency parameters of the system include the efficiency of the transmission mechanism, the efficiency of the energy conversion device, and the efficiency of the electrical energy conversion device.

[0008] Based on the above technical solutions, preferably, the charging state includes the stage from the lower chamber to the bottom of the well, the stage from the bottom of the well to the wellhead, and the stage from the wellhead to the upper chamber; the discharging state includes the stage from the upper chamber to the wellhead, the stage from the wellhead to the bottom of the well, and the stage from the bottom of the well to the lower chamber.

[0009] Based on the above technical solutions, preferably, step S2 specifically includes: S21. For the stage from the lower chamber to the bottom of the wellbore during the charging state, considering the traction force, frictional resistance and kinetic energy change of the gravity medium during the movement from the storage point in the lower chamber to the bottom of the wellbore, establish the dynamic equation and energy conversion equation for the first stage, and calculate the first energy change value. S22. For the stage from the bottom of the well to the top of the well in the charging state, considering the gravity, wind resistance and kinetic energy changes experienced by the gravitational medium during the movement from the bottom of the well to the top of the well, establish the dynamic equation and energy conversion equation for the second stage, and calculate the second energy change value. S23. For the stage from the wellhead to the upper chamber in the charging state, considering the traction force, frictional resistance and kinetic energy change during horizontal displacement, as well as the energy loss generated during the vertical hoisting process, establish the dynamic equation and energy conversion equation for the third stage, and calculate the third energy change value. S24. Calculate the total energy input from the grid side during the charging process by taking the first energy change value, the second energy change value, the third energy change value, and the system efficiency parameters.

[0010] Based on the above technical solutions, the preferred formula for calculating the first energy change value includes: In the formula, The traction force experienced by the gravity medium during its transport at the bottom of the well. It is the coefficient of static friction between the gravity medium and the conveyor belt during belt transportation. For the mass of the gravitational medium, It is the acceleration due to gravity. The instantaneous velocity of the gravitational medium. The initial velocity of the motion in the gravitational medium. The velocity at the end of the motion in the gravitational medium. This is the first energy change value. This is the time required for the gravitational medium to move from the lower chamber to the center of the bottom of the wellbore. This refers to the equivalent distance of the gravity medium distributed in the bottom tunnels relative to the center of the shaft bottom. The inclination angle of the tunnel at the bottom of the well; The formula for calculating the second energy change value includes: In the formula, This refers to the traction force experienced by the gravity medium during its vertical lifting within the wellbore. This is the drag coefficient. air density, This refers to the cross-sectional area of ​​the transport car. This is the second energy change value. This is the time required for the gravitational medium to move from the bottom of the wellbore to the wellhead. This refers to the height of the wellbore. The formula for calculating the third energy change value includes: In the formula, This refers to the traction force experienced by a gravitational medium during ground transportation. This refers to the static friction coefficient of the transportation system during ground transfer. This is the third energy change value. This is the time required for the gravity medium to move horizontally from the wellhead to the center of the upper storage stack. The energy consumed in hoisting gravity-fed media stored and stacked in the upper warehouse. The horizontal equivalent distance of the gravity medium distributed within the upper storage stack relative to the center of the wellhead. The vertical equivalent height of the gravity medium within the upper warehouse stack relative to the ground.

[0011] Based on the above technical solutions, preferably, if the upper warehouse storage stacking adopts a square or circular arrangement, then The distance from the geometric center of the upper storage stack to the shaft opening along the transport path can be measured. If the upper storage stack is arranged in n layers, the vertical equivalent height of the gravity medium within the upper storage stack relative to the ground can be calculated using the following formula: In the formula, The height of a single gravitational medium.

[0012] Based on the above technical solutions, the preferred formula for calculating the total energy input from the grid side during the charging process is: in, The transmission efficiency of the gearbox in a gravity energy storage system. The energy conversion efficiency of the electric generator in the gravity energy storage system. The AC / DC power conversion efficiency of the converter in the gravity energy storage system; This is the first energy change value; This is the second energy change value. This is the third energy change value.

[0013] Based on the above technical solutions, preferably, step S3 specifically includes: S31. For the stage from the upper chamber to the wellhead in the discharge state, considering the traction force, frictional resistance and kinetic energy change of the gravity medium during horizontal displacement, as well as the energy loss generated during the vertical hoisting process, establish the dynamic equation and energy conversion equation for the fourth stage, and calculate the fourth energy change value. S32. For the stage from the wellhead to the bottom of the well in the discharge state, considering the gravity, wind resistance and kinetic energy changes experienced by the gravitational medium during the movement from the wellhead to the bottom of the well, establish the dynamic equation and energy conversion equation for the fifth stage, and calculate the fifth energy change value. S33. For the stage from the bottom of the well to the lower chamber in the discharge state, considering the traction force, frictional resistance and kinetic energy change of the gravity medium during the movement from the bottom of the well to the storage point in the lower chamber, establish the dynamic equation and energy conversion equation for the sixth stage, and calculate the sixth energy change value. S34. Based on the fourth, fifth, and sixth energy change values, and combined with the system's efficiency parameters, the total energy output to the grid side during the discharge process is calculated.

[0014] Based on the above technical solutions, the preferred formula for calculating the fourth energy change value includes: In the formula, This refers to the traction force experienced by a gravitational medium during ground transportation. This refers to the static friction coefficient of the transportation system during ground transfer. This is the fourth energy change value. This is the time required for the gravity medium to move horizontally from the center of the upper storage stack to the wellhead; The formula for calculating the fifth energy change value includes: In the formula, This refers to the traction force experienced by the gravitational medium as it descends vertically within the wellbore. This is the fifth energy change value. This is the time required for the gravity medium to move from the wellhead to the bottom of the well. Since the system only connects to the grid when power output is stable... This is the effective height corresponding to the uniform motion state during the descent of the gravitational medium; The formula for calculating the sixth energy change value includes: In the formula, This refers to the traction force experienced by the gravity medium during its transport at the bottom of the well. It is the coefficient of static friction between the gravity medium and the conveyor belt during belt transportation. This is the sixth energy change value. The time required for the gravitational medium to move from the bottom of the wellbore to the equivalent geometric center point of the lower chamber.

[0015] Based on the above technical solutions, the preferred formula for calculating the total energy output to the grid side during the discharge process is as follows: in, The transmission efficiency of the gearbox in a gravity energy storage system. The energy conversion efficiency of the electric generator in the gravity energy storage system. The AC / DC power conversion efficiency of the converter in the gravity energy storage system; This is the fifth energy change value. This is the fourth energy change value. This is the sixth energy change value.

[0016] The overall energy efficiency analysis and calculation method for the vertical shaft gravity energy storage system of the present invention has the following advantages over the prior art: The present invention provides a method for overall energy efficiency analysis and calculation of a shaft-type gravity energy storage system. This method divides the complete charge-discharge cycle into multiple stages according to the motion path of the gravity medium, establishes dynamic equations and energy conversion equations for each stage, and comprehensively considers various physical factors such as traction force, frictional resistance, gravity, wind resistance, and kinetic energy changes. It also incorporates system efficiency parameters such as the efficiency of the transmission mechanism, energy conversion device, and power conversion device, enabling quantitative analysis of the entire process of energy input and output from the grid side of the shaft-type gravity energy storage system. This method provides a theoretical basis for the design optimization, equipment selection, and economic evaluation of shaft-type gravity energy storage systems. It can calculate the system scale, output power, energy conversion efficiency, and other key technical indicators of shaft-type gravity energy storage power stations under specific constraints, guiding engineering design. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart of the overall energy efficiency analysis and calculation method for the vertical shaft gravity energy storage system of the present invention; Figure 2 This is a schematic diagram of the vertical shaft gravity energy storage system of the present invention; Figure 3 This is a top view of the shaft bottom tunnel in an embodiment of the present invention. Explanation of reference numerals in the attached figures

[0019] 1. Heavy block; 2. Upper warehouse stack; 3. Shaft; 4. Shaft bottom tunnel; 5. Conveyor belt; 6. Transport car; 7. Head sheave; 8. Friction wheel; 9. Motor; 10. Converter; 11. Power grid. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] like Figure 1 As shown, this invention provides a method for overall energy efficiency analysis and calculation of a vertical shaft gravity energy storage system, including the following steps: S1. The complete charge and discharge cycle of the vertical shaft gravity energy storage system is divided into multiple stages according to the movement path of the gravity medium. The stages include the process of the gravity medium moving from the lower chamber through the bottom of the shaft to the shaft opening and then to the upper chamber in the charging state, and the process of the gravity medium moving from the upper chamber through the shaft opening to the bottom of the shaft and then to the lower chamber in the discharging state. S2. For each stage of the charging state, establish the dynamic equations and energy conversion equations for the gravity medium in the horizontal transportation and vertical lifting process. By solving the dynamic equations and energy conversion equations, obtain the energy change value of each stage. Accumulate the energy change values ​​of each stage of the charging state and combine them with the system efficiency parameters to calculate the total energy input from the grid side during the charging process. S3. For each stage of the discharge state, establish the dynamic equations and energy conversion equations for the gravity medium during horizontal transport and vertical descent. Solve the dynamic equations and energy conversion equations to obtain the energy change values ​​for each stage. Accumulate the energy change values ​​for each stage of the discharge state and combine them with the system efficiency parameters to calculate the total energy output to the grid side during the discharge process. S4. Calculate the ratio of the total energy output to the grid side during the discharge process to the total energy input to the grid side during the charging process to obtain the overall energy conversion efficiency of the system.

[0022] In one embodiment of the present invention, step S1 specifically includes: dividing the vertical shaft gravity energy storage system into two states according to its operation mode: charging and discharging, and defining a complete charging and discharging process as the standard cycle for system energy efficiency calculation. In the charging state, the system is specifically divided into three stages according to the movement position of the gravity medium: the stage from the lower chamber to the bottom of the shaft, the stage from the bottom of the shaft to the top of the shaft, and the stage from the top of the shaft to the upper chamber. In the discharging state, the system is specifically divided into three stages according to the movement position of the gravity medium: the stage from the upper chamber to the top of the shaft, the stage from the top of the shaft to the bottom of the shaft, and the stage from the bottom of the shaft to the lower chamber.

[0023] like Figure 2As shown, the vertical shaft gravity energy storage system mainly includes an upper chamber, a shaft hoisting system, and a lower chamber. The shaft hoisting system consists of components such as a sheave 7, a friction wheel 8, hoisting ropes, a transport car 6, an electric generator 9, and a converter 10, and is connected to the power grid 11. The lower chamber system includes a conveyor belt 5 and a shaft bottom tunnel 4. The sheave 7 and the friction wheel 8 together form a gearbox, i.e., a transmission mechanism. During the charging process, the heavy block 1 (i.e., the gravity medium) is transported from the bottom of the shaft 4 through the bottom of the shaft 3 to the shaft 3 via the conveyor belt 5. It is then vertically lifted to the shaft 3 opening by the transport car 6 via the hoisting rope and the sheave system. It is then sent to the upper storage stack 2 for stacking and storage via the ground transfer system. The electrical energy provided by the power grid is converted into mechanical energy by the converter 10, the electric generator 9, the sheave 7, and the friction wheel 8 to drive the system. During the discharging process, the heavy block 1 is transported from the upper storage stack 2 to the shaft 3 opening via the ground transfer system. It is then lowered along the shaft 3 to the bottom of the shaft 3 by the transport car 6 under the action of gravity. It is then sent to the lower storage stack via the bottom conveyor system. The gravitational potential energy released during the descent is converted into electrical energy by the sheave 7, the friction wheel 8, the electric generator 9, and the converter 10 and sent to the power grid 11. In the diagram, A, B, C, and D represent the critical positions of the gravity medium at the upper storage platform, shaft opening, shaft bottom, and lower storage tunnel, respectively. In the charging state, the gravity medium moves sequentially from D to C, C to B, and B to A. In the discharging state, the gravity medium moves sequentially from A to B, B to C, and C to D.

[0024] In one embodiment of the present invention, step S2 specifically includes: S21. For the stage from the lower chamber to the bottom of the wellbore during the charging state, considering the traction force, frictional resistance and kinetic energy change of the gravity medium during the movement from the lower chamber storage point to the bottom of the wellbore, establish the dynamic equation and energy conversion equation for the first stage, and calculate the first energy change value.

[0025] Specifically, the gravity medium is horizontally transported within the bottom tunnel via a belt conveyor system, and the formula for calculating the first energy change value includes: In the formula, This refers to the traction force experienced by the gravity medium during its transport at the bottom of the well. It is the coefficient of static friction between the gravity medium and the conveyor belt during belt transportation. For the mass of the gravitational medium, It is the acceleration due to gravity. The instantaneous velocity of the gravitational medium. is the initial velocity of the motion in the gravitational medium, and is the final velocity of the motion in the gravitational medium. This represents the first energy change value, i.e., the energy consumed by the system during the movement of the gravitational medium from the lower chamber to the center of the bottom of the wellbore. This is the time required for the gravitational medium to move from the lower chamber to the center of the bottom of the wellbore. This refers to the equivalent distance of the gravity medium distributed in the bottom tunnels relative to the center of the shaft bottom. The angle of inclination of the tunnel at the bottom of the well.

[0026] Furthermore, assuming that the gravity medium storage chamber is located from the bottom of the wellbore along... n The alleyways are arranged as follows: Figure 3 As shown, then The following formula can be used for calculation: In the formula, For the first n The distance between the gravity medium at the very end of the tunnel and the center of the bottom of the shaft.

[0027] S22. For the stage from the bottom of the well to the top of the well in the charging state, considering the gravity, wind resistance and kinetic energy changes experienced by the gravitational medium during its movement from the bottom of the well to the top of the well, establish the dynamic equation and energy conversion equation for the second stage, and calculate the second energy change value.

[0028] Specifically, the gravitational medium is vertically lifted inside the shaft by a transport car, which is connected to a gearbox on the ground via ropes. The formula for calculating the second energy change value includes: In the formula, This refers to the traction force experienced by the gravity medium during its vertical lifting within the wellbore. This is the drag coefficient. air density, This refers to the cross-sectional area of ​​the transport car. This is the second energy change value, which represents the energy consumed by the system during the movement of the gravitational medium from the bottom to the top of the wellbore. This is the time required for the gravitational medium to move from the bottom of the wellbore to the wellhead. This represents the height of the wellbore.

[0029] S23. For the stage from the wellhead to the upper chamber in the charging state, considering the traction force, frictional resistance and kinetic energy change during horizontal displacement, as well as the energy loss generated during the vertical hoisting process, establish the dynamic equation and energy conversion equation for the third stage, and calculate the third energy change value.

[0030] Specifically, the formula for calculating the third energy change value, obtained by horizontally transporting the gravitational medium on the ground via a transfer system, includes: In the formula, This refers to the traction force experienced by a gravitational medium during ground transportation. This refers to the static friction coefficient of the transportation system during ground transfer. This is the third energy change value, which represents the energy consumed by the system during the movement of the gravitational medium from the wellhead to the center of the upper storage stack. This is the time required for the gravity medium to move horizontally from the wellhead to the center of the upper storage stack. The energy consumed in hoisting gravity-fed media stored and stacked in the upper warehouse. The horizontal equivalent distance of the gravity medium distributed within the upper storage stack relative to the center of the wellhead. The vertical equivalent height of the gravity medium within the upper warehouse stack relative to the ground.

[0031] Furthermore, if the upper warehouse storage stacks are arranged in a square or circular pattern, then It can be determined by measuring the distance from the geometric center of the upper storage stack along the transportation path to the wellhead.

[0032] Furthermore, if the upper warehouse storage stacking adopts n For a layered layout, the equivalent vertical height of the gravity medium within the upper storage stack relative to the ground can be calculated using the following formula: In the formula The height of a single gravitational medium.

[0033] S24. Calculate the total energy input from the grid side during the charging process by taking the first energy change value, the second energy change value, the third energy change value, and the system efficiency parameters.

[0034] Specifically, the system efficiency parameters include the efficiency of the transmission mechanism, the efficiency of the energy conversion device, and the efficiency of the power conversion device. More preferably, the transmission mechanism is a gearbox, the energy conversion device is an electric generator, and the power conversion device is a converter. When the gravity medium moves vertically within the wellbore, the transport car is connected to the gearbox on the ground via ropes. The gearbox converts mechanical energy into electrical energy through the electric generator and a four-quadrant converter, enabling interaction with the power grid. Based on the analysis of the above motion process, the formula for calculating the total energy input from the power grid during the charging process is: in, The transmission efficiency of the gearbox in a gravity energy storage system. The energy conversion efficiency of the electric generator in the gravity energy storage system. The AC / DC power conversion efficiency of the converter in the gravity energy storage system.

[0035] The energy efficiency analysis method for the charging process described above systematically considers the dynamic characteristics and energy loss mechanisms of the gravity medium during the three stages of transport in the shaft bottom tunnel, vertical hoisting of the shaft, and surface transfer, establishing a complete energy consumption calculation model. This method comprehensively considers various physical factors such as frictional resistance, wind resistance, work done by gravity, and changes in kinetic energy. It also introduces the concepts of equivalent distance and equivalent height to simplify complex spatial layout calculations. Furthermore, it incorporates the efficiencies of the transmission mechanism, energy conversion device, and electrical energy conversion device into the overall energy calculation framework, achieving precise quantification of energy flow during the charging process.

[0036] In one embodiment of the present invention, step S3 specifically includes: S31. For the stage from the upper chamber to the wellhead in the discharge state, considering the traction force, frictional resistance and kinetic energy change of the gravity medium during horizontal displacement, as well as the energy loss generated during the vertical hoisting process, establish the dynamic equation and energy conversion equation for the fourth stage, and calculate the fourth energy change value.

[0037] Specifically, the motion process in this stage is the opposite of the motion process from the wellhead to the upper chamber in the charging state, and the calculation formula for the fourth energy change value includes: In the formula, This refers to the traction force experienced by a gravitational medium during ground transportation. This refers to the static friction coefficient of the transportation system during ground transfer. This is the fourth energy change value, which represents the energy consumed by the system during the movement of the gravitational medium from the center of the upper storage stack to the wellhead. This is the time required for the gravity medium to move horizontally from the center of the upper storage stack to the wellhead.

[0038] S32. For the stage from the wellhead to the bottom of the well in the discharge state, considering the gravity, wind resistance and kinetic energy changes experienced by the gravitational medium during its movement from the wellhead to the bottom of the well, establish the dynamic equation and energy conversion equation for the fifth stage, and calculate the fifth energy change value.

[0039] Specifically, the formula for calculating the fifth energy change value is as follows: The gravity medium descends vertically through the transport car within the shaft. In the formula, This refers to the traction force experienced by the gravitational medium as it descends vertically within the wellbore. This is the fifth energy change value, which represents the energy output by the system during the process of the gravitational medium moving from the wellhead to the bottom of the well. This is the time required for the gravity medium to move from the wellhead to the bottom of the well. Since the system only connects to the grid when power output is stable... This represents the effective height when the medium is in a state of uniform motion during its descent under gravity.

[0040] S33. For the stage from the bottom of the well to the lower chamber during the discharge state, considering the traction force, frictional resistance and kinetic energy change of the gravitational medium during its movement from the bottom of the well to the storage point in the lower chamber, establish the dynamic equation and energy conversion equation for the sixth stage, and calculate the sixth energy change value.

[0041] Specifically, the motion process in this stage is the opposite of the motion process from the lower chamber to the bottom of the wellbore under charging conditions. The formula for calculating the sixth energy change value includes: In the formula, This refers to the traction force experienced by the gravity medium during its transport at the bottom of the well. It is the coefficient of static friction between the gravity medium and the conveyor belt during belt transportation. The sixth energy change value is the energy consumed by the system during the process of the gravitational medium moving from the bottom of the well to the equivalent geometric center point of the lower chamber. This is the time required for the gravitational medium to move from the bottom of the wellbore to the equivalent geometric center point of the lower chamber.

[0042] S34. Based on the fourth, fifth, and sixth energy change values, and combined with the system's efficiency parameters, the total energy output to the grid side during the discharge process is calculated.

[0043] The formula for calculating the total energy output to the grid during the discharge process is: in, The transmission efficiency of the gearbox in a gravity energy storage system. The energy conversion efficiency of the electric generator in the gravity energy storage system. The AC / DC power conversion efficiency of the converter in the gravity energy storage system.

[0044] The energy efficiency analysis method for the above-mentioned discharge process conducts an in-depth analysis of the mechanism by which gravitational potential energy is converted into electrical energy during the descent of the gravitational medium. It focuses on the main energy output during the vertical descent phase within the wellbore, as well as the energy consumption during the surface transfer and wellbore transport phases. By introducing the concept of effective height, the method accurately captures the energy conversion characteristics of the system during the stable power output phase, avoiding interference from acceleration / deceleration transition phases on the overall energy efficiency assessment and improving the engineering applicability of the calculation results.

[0045] In one embodiment of the present invention, step S4 specifically includes: considering the system architecture of the shaft-type gravity energy storage system, the overall system efficiency of the shaft-type gravity energy storage system for a complete charge-discharge cycle can be expressed as: The above-mentioned complete charge-discharge cycle energy efficiency analysis and calculation method can quantitatively evaluate the overall energy conversion efficiency of vertical shaft gravity energy storage systems under specific technical parameters and operating conditions, providing a theoretical basis for system scale design, equipment selection and economic evaluation.

[0046] The above description is only a preferred embodiment of the present invention and is 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 method for overall energy efficiency analysis and calculation of a vertical shaft gravity energy storage system, characterized in that: Includes the following steps: S1. The complete charge and discharge cycle of the vertical shaft gravity energy storage system is divided into multiple stages according to the movement path of the gravity medium. The stages include the process of the gravity medium moving from the lower chamber through the bottom of the shaft to the shaft opening and then to the upper chamber in the charging state, and the process of the gravity medium moving from the upper chamber through the shaft opening to the bottom of the shaft and then to the lower chamber in the discharging state. S2. For each stage of the charging state, establish the dynamic equations and energy conversion equations of the gravity medium in the horizontal transportation and vertical lifting process, and obtain the energy change value of each stage by solving the dynamic equations and energy conversion equations. The energy change values ​​at each stage of the charging process are summed up, and combined with the system's efficiency parameters, the total energy input from the grid side during the charging process is calculated. S3. For each stage of the discharge state, establish the dynamic equations and energy conversion equations for the gravity medium during horizontal transport and vertical descent, and obtain the energy change values ​​for each stage by solving the dynamic equations and energy conversion equations. The energy changes at each stage of the discharge process are summed up, and combined with the system's efficiency parameters, the total energy output to the grid during the discharge process is calculated. S4. Calculate the ratio of the total energy output to the grid side during the discharge process to the total energy input to the grid side during the charging process to obtain the overall energy conversion efficiency of the system.

2. The method for overall energy efficiency analysis and calculation of a vertical shaft gravity energy storage system as described in claim 1, characterized in that: The system's efficiency parameters include the efficiency of the transmission mechanism, the efficiency of the energy conversion device, and the efficiency of the electrical energy conversion device.

3. The method for overall energy efficiency analysis and calculation of a vertical shaft gravity energy storage system as described in claim 2, characterized in that: The charging state includes the stages from the lower chamber to the bottom of the well, the stage from the bottom of the well to the top of the well, and the stage from the top of the well to the upper chamber; the discharging state includes the stages from the upper chamber to the top of the well, the stage from the top of the well to the bottom of the well, and the stage from the bottom of the well to the lower chamber.

4. The method for overall energy efficiency analysis and calculation of a vertical shaft gravity energy storage system as described in claim 3, characterized in that: Step S2 specifically includes: S21. For the stage from the lower chamber to the bottom of the wellbore during the charging state, considering the traction force, frictional resistance and kinetic energy change of the gravity medium during the movement from the storage point in the lower chamber to the bottom of the wellbore, establish the dynamic equation and energy conversion equation for the first stage, and calculate the first energy change value. S22. For the stage from the bottom of the well to the top of the well in the charging state, considering the gravity, wind resistance and kinetic energy changes experienced by the gravitational medium during the movement from the bottom of the well to the top of the well, establish the dynamic equation and energy conversion equation for the second stage, and calculate the second energy change value. S23. For the stage from the wellhead to the upper chamber in the charging state, considering the traction force, frictional resistance and kinetic energy change during horizontal displacement, as well as the energy loss generated during the vertical hoisting process, establish the dynamic equation and energy conversion equation for the third stage, and calculate the third energy change value. S24. Calculate the total energy input from the grid side during the charging process by taking the first energy change value, the second energy change value, the third energy change value, and the system efficiency parameters.

5. The method for overall energy efficiency analysis and calculation of a vertical shaft gravity energy storage system as described in claim 4, characterized in that: The formula for calculating the first energy change value includes: In the formula, This refers to the traction force experienced by the gravity medium during its transport at the bottom of the well. It is the coefficient of static friction between the gravity medium and the conveyor belt during belt transportation. For the mass of the gravitational medium, It is the acceleration due to gravity. The instantaneous velocity of the gravitational medium. The initial velocity of the motion in the gravitational medium. The velocity at the end of the motion in the gravitational medium. This is the first energy change value. This is the time required for the gravitational medium to move from the lower chamber to the center of the bottom of the wellbore. This refers to the equivalent distance of the gravity medium distributed in the bottom tunnels relative to the center of the shaft bottom. The angle of inclination of the tunnel at the bottom of the well; The formula for calculating the second energy change value includes: In the formula, This refers to the traction force experienced by the gravity medium during its vertical lifting within the wellbore. This is the drag coefficient. air density, This refers to the cross-sectional area of ​​the transport car. This is the second energy change value. This is the time required for the gravitational medium to move from the bottom of the wellbore to the wellhead. This refers to the height of the wellbore. The formula for calculating the third energy change value includes: In the formula, This refers to the traction force experienced by a gravitational medium during ground transportation. This refers to the static friction coefficient of the transportation system during ground transfer. This is the third energy change value. This is the time required for the gravity medium to move horizontally from the wellhead to the center of the upper storage stack. The energy consumed in hoisting gravity-fed media stored and stacked in the upper warehouse. The horizontal equivalent distance of the gravity medium distributed within the upper storage stack relative to the center of the wellhead. The vertical equivalent height of the gravity medium within the upper warehouse stack relative to the ground.

6. The method for overall energy efficiency analysis and calculation of a vertical shaft gravity energy storage system as described in claim 5, characterized in that: If the upper warehouse storage stacks are arranged in a square or circular pattern, then The distance from the geometric center of the upper storage stack to the shaft opening along the transport path can be measured. If the upper storage stack is arranged in n layers, the vertical equivalent height of the gravity medium within the upper storage stack relative to the ground can be calculated using the following formula: In the formula, The height of a single gravitational medium.

7. The method for overall energy efficiency analysis and calculation of a vertical shaft gravity energy storage system as described in claim 5, characterized in that: The formula for calculating the total energy input from the grid during the charging process is: in, The transmission efficiency of the gearbox in a gravity energy storage system. The energy conversion efficiency of the electric generator in the gravity energy storage system. The AC / DC power conversion efficiency of the converter in the gravity energy storage system; This is the first energy change value; This is the second energy change value. This is the third energy change value.

8. The method for overall energy efficiency analysis and calculation of a vertical shaft gravity energy storage system as described in claim 3, characterized in that: Step S3 specifically includes: S31. For the stage from the upper chamber to the wellhead in the discharge state, considering the traction force, frictional resistance and kinetic energy change of the gravity medium during horizontal displacement, as well as the energy loss generated during the vertical hoisting process, establish the dynamic equation and energy conversion equation for the fourth stage, and calculate the fourth energy change value. S32. For the stage from the wellhead to the bottom of the well in the discharge state, considering the gravity, wind resistance and kinetic energy changes experienced by the gravitational medium during the movement of the gravitational medium from the wellhead to the bottom of the well, establish the dynamic equation and energy conversion equation for the fifth stage, and calculate the fifth energy change value. S33. For the stage from the bottom of the well to the lower chamber in the discharge state, considering the traction force, frictional resistance and kinetic energy change of the gravity medium during the movement from the bottom of the well to the storage point in the lower chamber, establish the dynamic equation and energy conversion equation for the sixth stage, and calculate the sixth energy change value. S34. Based on the fourth, fifth, and sixth energy change values, and combined with the system's efficiency parameters, the total energy output to the grid side during the discharge process is calculated.

9. The method for overall energy efficiency analysis and calculation of a vertical shaft gravity energy storage system as described in claim 8, characterized in that: The formula for calculating the fourth energy change value includes: In the formula, This refers to the traction force experienced by a gravitational medium during ground transportation. This refers to the static friction coefficient of the transportation system during ground transfer. This is the fourth energy change value. This is the time required for the gravity medium to move horizontally from the center of the upper storage stack to the wellhead; The formula for calculating the fifth energy change value includes: In the formula, This refers to the traction force experienced by the gravitational medium as it descends vertically within the wellbore. This is the fifth energy change value. This is the time required for the gravity medium to move from the wellhead to the bottom of the well. Since the system only connects to the grid when power output is stable... This is the effective height corresponding to the uniform motion state during the descent of the gravitational medium; The formula for calculating the sixth energy change value includes: In the formula, This refers to the traction force experienced by the gravity medium during its transport at the bottom of the well. It is the coefficient of static friction between the gravity medium and the conveyor belt during belt transportation. This is the sixth energy change value. This is the time required for the gravitational medium to move from the bottom of the wellbore to the equivalent geometric center point of the lower chamber.

10. The method for overall energy efficiency analysis and calculation of a vertical shaft gravity energy storage system as described in claim 9, characterized in that: The formula for calculating the total energy output to the grid during the discharge process is: in, The transmission efficiency of the gearbox in a gravity energy storage system. The energy conversion efficiency of the electric generator in the gravity energy storage system. The AC / DC power conversion efficiency of the converter in the gravity energy storage system; This is the fifth energy change value. This is the fourth energy change value. This is the sixth energy change value.

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