Optimization Method for Matching Main Unit Parameters of Compressed Air Energy Storage Power Station with Artificial Gas Storage Capacity

Abstract

This invention relates to an optimization method for matching the main unit parameters of a compressed air energy storage power station with the volume of an artificial gas storage tank. It determines the basic parameters of the main unit and the gas storage tank, calculates the required gas storage tank volume while satisfying the mass conservation equation, energy conservation equation, convective heat transfer equation, surrounding rock heat conduction equation, boundary condition equations for the surrounding rock heat conduction path, and the generalized gas state equation, and obtains the investment and construction costs of the gas storage tank and the main unit. Furthermore, it calculates the power generation efficiency of the main unit by considering the generator output of the turbine expander, the power consumption of the compressor motor, and the power consumption of auxiliary equipment during the compression process. Isolines of power generation efficiency with turbine pressure and the total investment in the gas storage tank and the main unit are plotted, resulting in the optimal solution that balances power generation efficiency and investment. This invention provides a matching scheme with high power generation efficiency and good economic efficiency, and has wider applicability.

Description

Technical Field

[0001] This invention patent belongs to the field of energy storage, and in particular relates to a method for optimizing the matching of main unit parameters of a compressed air energy storage power station with the volume of an artificial gas storage tank. Background Technology

[0002] Renewable and clean energy generation, such as wind and solar power, is subject to randomness, fluctuation, and intermittency due to weather and diurnal cycles. This disrupts the supply-demand balance of the power grid, leading to frequency fluctuations, decreased power quality, and impacts power flow distribution and voltage stability, potentially threatening grid operational safety in severe cases. Constructing large-scale, long-term energy storage systems can effectively compensate for the random and intermittent fluctuations of wind and solar power, while also playing a peak-shaving and valley-filling role, thus ensuring the safe and reliable operation of the power grid system. The proposed dual-carbon goals and the demand for new power system construction have strongly promoted the development of new energy storage technologies, and large-scale development of new energy storage is expected.

[0003] Compressed air energy storage (CASS) enables large-scale, long-term energy storage, making it a key area of ​​development in energy storage technology. While CASS projects typically require large salt caverns or mines for storage, this method is limited by available resources. However, advancements in underground space development technology have significantly reduced excavation costs, shortened construction periods, and enabled high-pressure gas underground sealing technology. This has led to the construction of artificial gas storage facilities, making artificial CASS power plants a new option. This technological development overcomes the limitations of CASS reliance on salt caverns and mines, expanding the applicability of CASS power plants.

[0004] The volume of the compressed air storage tank is closely related to the selection of the host equipment parameters. The coupling effect of the two affects the overall economics of the compressed air energy storage project. In order to obtain lower compressed air energy storage power station costs and higher benefits, it is necessary to match and optimize the selection of host equipment parameters and the volume of the artificial storage tank. Summary of the Invention

[0005] To expand the application scope of compressed air energy storage technology, overcome the limitations of resources such as salt caverns and mines, and improve the operational economy of compressed air energy storage projects, this invention provides a method for optimizing the matching of main unit parameters of a compressed air energy storage power station with the volume of an artificial gas storage facility. By using different main unit parameters and different parameter ranges to optimize the matching with the volume and scheme of the artificial gas storage facility, the cost of the energy storage power station is reduced and the economic efficiency is improved.

[0006] This invention proposes an optimization method for matching the main unit parameters of a compressed air energy storage power station with the volume of an artificial air storage tank. The method is characterized by obtaining the optimal matching scheme through the following steps:

[0007] Step 1: Determine the basic parameters of the main unit and gas storage tank, such as the pressure variation range of the main unit, the capacity range of the gas storage tank, the compressed air temperature, the energy release time, and the heat exchange medium.

[0008] Step 2: Based on the basic parameters of the host and gas storage determined in Step 1, calculate the required gas storage volume while satisfying the mass conservation equation, energy conservation equation, convective heat transfer equation, surrounding rock heat conduction equation, boundary condition equation of surrounding rock heat conduction path, and generalized gas state equation.

[0009] Step 3: Determine the specific energy storage scheme for the gas storage facility based on the gas storage volume obtained in Step 2, and obtain the construction investment cost of the gas storage facility based on the energy storage scheme;

[0010] Step 4: Determine the construction investment cost of the host by considering the host's operating pressure, operating temperature, and host capacity;

[0011] Step 5: Calculate the generator power output of the turbine expander, the power consumption of the compressor motor, and the power consumption of the auxiliary equipment during the compression process to obtain the generator power output of the turbine expander;

[0012] Step 6: Plot the sum of the gas storage construction investment cost and the unit construction investment cost as the turbine inlet maximum pressure and pressure difference are applied, as well as the main unit power generation efficiency curve, and determine the optimal solution that balances power generation efficiency and construction investment cost.

[0013] As a preferred embodiment, the mass conservation equation, energy conservation equation, convective heat transfer equation, surrounding rock heat conduction equation, boundary condition equation for surrounding rock heat conduction path, and generalized gas state equation satisfied by calculating the gas storage volume in step two are respectively expressed by the following equations (1) to (7):

[0014]

[0015]

[0016]

[0017]

[0018]

[0019] r→∞, T R =T0 (6)

[0020] p=ZρRT (7)

[0021] In the formula, ρ is the air density inside the gas storage tank, kg / m³. 3 p is the air pressure inside the gas storage tank, Pa; T is the air temperature inside the gas storage tank, K; r is the radial distance from the center of the gas storage tank, m; RW V is the radius of the gas storage facility, in meters; V is the volume of the gas storage facility, in meters. 3 h is the enthalpy of air, J; u is the internal energy of air, J; The heat transfer rate between the air and the rock wall inside the gas storage facility, expressed in J / s; kJ / s. R t is the thermal conductivity of the rock mass, W / (m·K); t is the calculation time, s; m i (t) and m e (t) represent the inflation rate function and the deflation rate function, respectively; A c The surface area of ​​the gas storage facility is in meters. 2 c v The isochoric specific heat of air is 717 J / (mg·K); h c The heat exchange capacity between the air and the rock wall inside the gas storage facility is expressed in W / (m²). 2 ·K); R is the air constant, 286.7 J / (mg·K); T0 is the initial temperature inside the gas storage tank, K; T i The temperature of the air introduced into the gas storage tank, K; T RW Z is the temperature of the surrounding rock, in K; Z is the air compressibility coefficient; c p The isobaric specific heat of air is 1004 J / (mg·K).

[0022] As a preferred option, given the filling and pumping pressures, in solving equation (2), when the temperature of the gas storage wall is constant and the filling volume is much smaller than the gas volume inside the gas storage, for a given filling or pumping stage, equation (2) can be simplified to ordinary differential equation (8):

[0023]

[0024] Equation (8) is solved as follows:

[0025]

[0026]

[0027] Where t0 is the start time of the calculation, t1 is the end time of inflation, t2 is the start time of deflation, t3 is the end time of deflation, and t4 is the end time of the calculation.

[0028] And, in the solution of equation (8), ρ av The average air density inside the gas storage facility is expressed in kg / m³. 3 The result is obtained from equation (9):

[0029]

[0030] In the formula, ρ0 is the initial air density inside the gas storage tank, kg / m³. 3 ;

[0031] Combining equations (1) to (9), the state before the previous stage of the entire energy storage and release stage is taken as the initial condition for the next stage. After determining the charging and releasing rates and pressures, the gas storage volume V is calculated.

[0032] Preferably, the power generation efficiency of the unit can be calculated using equation (10):

[0033]

[0034] Where: η is the unit's power generation efficiency;

[0035] Tout represents the turbine expansion time, in hours.

[0036] tin represents the compressor's operating time, in hours (h).

[0037] wout represents turbine output, in kW;

[0038] wcin is the power consumption of the compressor motor, in kW;

[0039] Wain represents the power consumption of the auxiliary system during compressor operation, expressed in kW.

[0040] Preferably, in determining the pressure variation range of the host unit in step one, the highest pressure is determined to be all pressure ranges of 4MPa and above, the lowest pressure range is determined to be all pressure ranges of 1MPa and above, and the difference between the highest and lowest pressures of the host unit is determined to be all pressure ranges of 0MPa and above.

[0041] Preferably, the gas storage capacity in step one is 0.5 million standard cubic meters or more.

[0042] Preferably, the temperature of the compressed air in step one is above 80°C.

[0043] As a preferred option, the energy storage and release time in step one is 1 to 23 hours.

[0044] Preferably, the heat storage and exchange medium in step one includes molten salt, heat transfer oil, and water.

[0045] As a preferred option, the energy storage scheme obtained in step three based on the volume of the gas storage facility includes the specific type of the gas storage facility. The types of gas storage facilities include artificially sealed underground chambers and linear steel tanks, as well as combinations of the two. Among them, the types of artificially sealed underground chambers include tunnel type and large tank type.

[0046] Compared with the prior art, the present invention has the following advantages:

[0047] 1. The range of main unit parameters, energy storage and release time, and artificial gas storage facility types and volume parameters is wide.

[0048] 2. This matching optimization method can yield a highly efficient and cost-effective solution.

[0049] 3. Wide applicability. Attached Figure Description

[0050] Figure 1 This is a flowchart illustrating the steps of an embodiment of the method for optimizing the matching of compressed air energy storage power station main unit parameters with artificial air storage tank volume according to the present invention.

[0051] Figure 2 This is a schematic diagram of a tunnel-type artificial underground sealed reservoir in one embodiment.

[0052] Figure 3 This is a schematic diagram of the charging and discharging gas flow rate set in one embodiment.

[0053] Figure 4 for Figure 3 The temperature change curve of the storage tank over time is shown in the example.

[0054] Figure 5 for Figure 3 The curve showing the change of pressure in the reservoir over time in the example.

[0055] Figure 6 This is a contour map of the sum of the main engine investment cost and the storage tank construction cost, as well as the main engine power generation efficiency, based on the maximum pressure and pressure difference at the turbine inlet in one embodiment.

[0056] Among them, 1 is the air extraction pipe, 2 is the vertical shaft, 3 is the storage tank, 4 is the concrete plug, and 5 is the surrounding rock. Detailed Implementation

[0057] like Figure 1 As shown, a method for optimizing the matching of main unit parameters of a compressed air energy storage power station with the volume of an artificial air storage tank is characterized by obtaining the optimal matching scheme through the following steps:

[0058] Step 1: Determine the basic parameters of the main unit and gas storage tank, such as the pressure variation range of the main unit, the capacity range of the gas storage tank, the compressed air temperature, the energy release time, and the heat exchange medium.

[0059] Step 2: Based on the basic parameters of the host and gas storage determined in Step 1, calculate the required gas storage volume while satisfying the mass conservation equation, energy conservation equation, convective heat transfer equation, surrounding rock heat conduction equation, boundary condition equation of surrounding rock heat conduction path, and generalized gas state equation.

[0060] Step 3: Determine the specific energy storage scheme (type, size, etc. of the gas storage) based on the gas storage volume obtained in Step 2, and obtain the construction investment cost of the gas storage based on the energy storage scheme.

[0061] Step 4: Determine the construction investment cost of the host by considering the host's operating pressure, operating temperature, and host capacity;

[0062] Step 5: Calculate the generator power output of the turbine expander, the power consumption of the compressor motor, and the power consumption of the auxiliary equipment during the compression process to obtain the generator power output of the turbine expander;

[0063] Step 6: Plot the sum of the gas storage construction investment cost and the unit construction investment cost as the turbine inlet maximum pressure and pressure difference are applied, as well as the main unit power generation efficiency curve, and determine the optimal solution that balances power generation efficiency and construction investment cost.

[0064] The main unit includes a compressor, turbine, heat exchanger, pump, and corresponding auxiliary and peripheral equipment.

[0065] Moreover, this method can achieve both single-variable, single-objective optimization and multi-variable, multi-objective optimization. The main variables include the main unit's maximum pressure, pressure parameter variation range, main / reheat gas temperature, storage and energy release time, installed capacity, storage heat exchange medium type, gas storage type, gas storage size, main unit investment, and gas storage investment. The optimization objectives are unit efficiency and total investment in the unit and gas storage.

[0066] In step two, the mass conservation equation, energy conservation equation, convective heat transfer equation, surrounding rock heat conduction equation, boundary condition equation for surrounding rock heat conduction path, and generalized gas state equation satisfied by calculating the gas storage volume are expressed by the following equations (1) to (7):

[0067]

[0068]

[0069]

[0070]

[0071]

[0072] r→∞, T R =T0 (6)

[0073] p=ZρRT (7)

[0074] In the formula, ρ is the air density inside the gas storage tank, kg / m³. 3 p is the air pressure inside the gas storage tank, Pa; T is the air temperature inside the gas storage tank, K; r is the radial distance from the center of the gas storage tank, m; R W V is the radius of the gas storage facility, in meters; V is the volume of the gas storage facility, in meters. 3 h is the enthalpy of air, J; u is the internal energy of air, J; The heat transfer rate between the air and the rock wall inside the gas storage facility, expressed in J / s; kJ / s. R t is the thermal conductivity of the rock mass, W / (m·K); t is the calculation time, s; m i (t) and m e (t) represent the inflation rate function and the deflation rate function, respectively; A c The surface area of ​​the gas storage facility is in meters. 2 c v The isochoric specific heat of air is 717 J / (mg·K); h c The heat exchange capacity between the air and the rock wall inside the gas storage facility is expressed in W / (m²). 2 ·K); R is the air constant, 286.7 J / (mg·K); T0 is the initial temperature inside the gas storage tank, K; T i The temperature of the air introduced into the gas storage tank, K; T RW Z is the temperature of the surrounding rock, in K; Z is the air compressibility coefficient; c p The isobaric specific heat of air is 1004 J / (mg·K).

[0075] Among them, under given filling and pumping pressures, in solving equation (2), when the temperature of the gas storage wall is constant and the filling volume is much smaller than the gas volume in the gas storage, for a given filling or pumping stage, equation (2) can be simplified to ordinary differential equation (8):

[0076]

[0077] Equation (8) is solved as follows:

[0078]

[0079]

[0080] Where t0 is the start time of the calculation, t1 is the end time of inflation, t2 is the start time of deflation, t3 is the end time of deflation, and t4 is the end time of the calculation.

[0081] And, in the solution of equation (8), ρ av The average air density inside the gas storage facility is expressed in kg / m³. 3 The result is obtained from equation (9):

[0082]

[0083] In the formula, ρ0 is the initial air density inside the gas storage tank, kg / m³. 3 ;

[0084] Combining equations (1) to (9), the state before the previous stage of the entire energy storage and release stage is taken as the initial condition for the next stage. After determining the charging and releasing rates and pressures, the gas storage volume V is calculated.

[0085] The power generation efficiency of the unit can be calculated using equation (10):

[0086]

[0087] Where: η is the unit's power generation efficiency;

[0088] Tout represents the turbine expansion time, in hours.

[0089] tin represents the compressor's operating time, in hours (h).

[0090] wout represents turbine output, in kW;

[0091] wcin is the power consumption of the compressor motor, in kW;

[0092] Wain represents the power consumption of the auxiliary system during compressor operation, expressed in kW.

[0093] In step one, determining the host pressure variation range defines the maximum pressure as all pressure ranges of 4 MPa and above, the minimum pressure range as all pressure ranges of 1 MPa and above, and the pressure range where the difference between the maximum and minimum host pressures is 0 MPa and above. The host pressure ranges are as follows: Figure 6 The optimal choice is to select the combination of the highest pressure and the difference between the highest and lowest pressures.

[0094] In step one, the gas storage capacity ranges from 0.5 million standard cubic meters or more; the compressed air temperature is above 80°C; the storage and release time is 1 to 23 hours and 23 to 1 hour respectively; and the heat exchange medium includes molten salt, heat transfer oil and water.

[0095] Furthermore, the energy storage scheme obtained in step three based on the volume of the gas storage facility includes the specific type of the gas storage facility. The types of the gas storage facility include artificially sealed underground chambers and linear steel tanks, as well as combinations of the two. Among them, the types of artificially sealed underground chambers include tunnel type and large tank type.

[0096] In one specific embodiment, a compressed air energy storage project with a scale of 300 MWe / 1200 MWh uses hot water as the heat exchange medium at a temperature of 175°C. The turbine inlet pressures are 9.2 MPa, 10.5 MPa, 11.0 MPa, and 14.3 MPa, and their pressure variation ranges are shown in Tables 1 to 4.

[0097]

[0098] Table 1

[0099]

[0100] Table 2

[0101]

[0102] Table 3

[0103]

[0104]

[0105] Table 4

[0106] During the operation of this embodiment, the gas storage tank undergoes a constant-volume, variable-pressure process. For different pressure changes, the total amount of compressed air consumed by the turbine is obtained by integrating the following equation (11) based on the consumption curve provided by the manufacturer:

[0107]

[0108] Among them, M Gen m represents the total amount of compressed air consumed during the energy release period. T This represents the air consumption per unit time. The total compressed air consumption is calculated to obtain the compressed air volume per unit time and the compressed air consumption of the turbine per unit time. For this embodiment, the energy storage time is 8 hours, the energy release time is 4 hours, and the compressed air volume per unit time and the turbine air consumption per unit time are shown in Tables 1 to 4 above.

[0109] In one specific embodiment,

[0110] like Figure 2 As shown in section a, a tunnel-type compressed air energy storage sealed silo is presented. Considering its stress characteristics, its cross-section is generally circular, such as... Figure 2 As shown in section b. Due to the inflation and deflation process of the compressed air energy storage sealed silo, the internal pressure changes, which in turn cause changes in the air temperature inside the silo. The air and the silo wall will also generate convective heat transfer, and the silo wall rock mass will also generate heat conduction. Under the set inflation and deflation pressure conditions, the volume of the silo can be solved by combining the above equations (1) to (9).

[0111] like Figures 3-5 As shown, combining equations (1) to (9) above, taking the artificially sealed gas storage tank as an example, assuming the tank filling time is 8 hours, the high-pressure storage time is 6 hours, the venting time is 4 hours, the low-pressure storage time is 6 hours, and the filling and venting rates are 364 kg / s and 728 kg / s respectively, as follows: Figure 4 As shown, the inflation temperature is 40℃. Figure 5As shown, the inflation pressure is 8.2 MPa to 10.2 MPa, the deflation pressure is 10.0 MPa to 8.0 MPa, the diameter of the cave is 8 m, and the heat transfer power h between the air and the rock wall inside the cave is... c Take 30W / (m 2 ·K), then through trial calculations, the required cavern volume is found to be 500,000 m³. 3 .

[0112] As can be seen from the specific embodiments above, given the installed capacity and energy storage power generation time of an energy storage power station, different unit parameters, such as the maximum turbine pressure and pressure variation range, can be used to determine the unit's power generation efficiency and investment cost. By matching the tank volume with the unit parameters, different tank volumes can be obtained, thus determining the tank's construction cost. Using the sum of the unit investment cost and the tank construction cost as the optimization objective, combined with the unit's power generation efficiency, optimal unit parameters and tank volume can be obtained.

[0113] Regarding the above Figures 3-5 The illustrated embodiment can be drawn as follows Figure 6 The diagram shows contour lines representing the sum of the unit investment cost and the tunnel construction cost as a function of the maximum turbine inlet pressure and pressure difference, as well as the unit power generation efficiency as a function of the maximum turbine inlet pressure and pressure difference. Solid lines represent the contour lines of the sum of the underground sealed tunnel construction investment and the unit investment, while dotted lines represent the unit efficiency contour lines. Based on the determined unit efficiency, the optimal maximum turbine inlet pressure and pressure difference are obtained by minimizing the sum of the unit investment cost and the tunnel construction cost. For example, for a unit efficiency of 0.665, the optimal point is found at boundary point A, corresponding to a maximum turbine inlet pressure of 9.2 MPa and a pressure difference of 6.6 MPa. For a unit efficiency of 0.654, the optimal point is found at boundary point B, corresponding to a maximum turbine inlet pressure of 10.9 MPa and a pressure difference of 8.0 MPa.

Claims

1. A method for optimizing the matching of main unit parameters of a compressed air energy storage power station with the volume of an artificial air storage tank, characterized in that, The optimal matching scheme is obtained through the following steps: Step 1: Determine the parameters of the basic host and gas storage tank; the parameters of the basic host and gas storage tank include the host pressure variation range, the gas storage tank capacity range, the compressed air temperature, the energy release time, and the heat exchange medium. Step 2: Based on the basic parameters of the host and gas storage determined in Step 1, calculate the required gas storage volume while satisfying the mass conservation equation, energy conservation equation, convective heat transfer equation, surrounding rock heat conduction equation, boundary condition equation of surrounding rock heat conduction path, and generalized gas state equation. Step 3: Determine the specific energy storage scheme for the gas storage facility based on the gas storage volume obtained in Step 2, and obtain the construction investment cost of the gas storage facility based on the energy storage scheme; Step 4: Determine the construction investment cost of the host by considering the host's operating pressure, operating temperature, and host capacity; Step 5: Calculate the generator power output of the turbine expander, the power consumption of the compressor motor, and the power consumption of the auxiliary equipment during the compression process to obtain the generator power output of the turbine expander; Step 6: Plot the sum of the gas storage construction investment cost and the unit construction investment cost as the maximum pressure and pressure difference at the turbine inlet, as well as the main generator power generation efficiency curve, and determine the optimal scheme that balances power generation efficiency and construction investment cost. Based on the determined power generation efficiency, the optimal maximum turbine inlet pressure and pressure difference can be obtained by minimizing the sum of the gas storage construction investment cost and the unit construction investment cost. In determining the pressure variation range of the main unit in step one, the highest pressure is defined as all pressure ranges of 4MPa and above, the lowest pressure range is defined as all pressure ranges of 1MPa and above, and the difference between the highest and lowest pressures of the main unit is defined as all pressure ranges of 0MPa and above; the gas storage capacity range in step one is 0.5 million standard cubic meters and above; the compressed air temperature in step one is 80℃ and above; the storage and release times in step one are both 1 to 23 hours. In step two, the mass conservation equation, energy conservation equation, convective heat transfer equation, surrounding rock heat conduction equation, boundary condition equation for surrounding rock heat conduction path, and generalized gas state equation satisfied by the calculation of the gas storage volume are expressed by the following equations (1) to (7): (1) (2) (3) (4) (5) (6) (7) In the formula, The density of air inside the gas storage facility is expressed in kg / m³. is the air pressure inside the gas storage tank, Pa; T is the air temperature inside the gas storage tank, K; r is the radial distance from the center of the gas storage tank, m; V is the radius of the gas storage facility, in meters; V is the volume of the gas storage facility, in cubic meters (m³); h is the enthalpy of air, in kilometres (J); u is the internal energy of air, in kilometres (J). The heat exchange rate between the air and the rock wall inside the gas storage tank is expressed in J / s. The thermal conductivity of the rock mass ; t is the calculation time, in seconds; and These are the inflation rate function and the deflation rate function, respectively; The surface area of ​​the gas storage facility is in m2; For the isochoric specific heat of air, 717 ; This refers to the heat exchange capacity between the air and the rock wall inside the gas storage facility. R is the air constant, 286.

7. ; The initial temperature inside the gas storage tank, in K; The temperature of the air introduced into the gas storage tank, K; Z is the temperature of the surrounding rock, in K; Z is the air compressibility coefficient. The isobaric specific heat of air, 1004 ; The energy storage scheme obtained in step three based on the volume of the gas storage facility includes the specific type of the gas storage facility. The types of gas storage facilities include artificial sealed underground chambers and linear steel tanks, as well as combinations of the two. Among them, the types of artificial underground sealed chambers include tunnel type and large tank type. In step five, the power generation efficiency is calculated using equation (10): （10） Where: η is the generator efficiency; tout is the turbine expansion time, h; tin is the compressor working time, h; wout is the turbine output, kw; wcin is the power consumption of the compressor motor, kw; wain is the power consumption of the auxiliary system during compressor operation, kw; Under given charging and pumping pressures, in the solution of equation (2), when the temperature of the gas storage wall is constant and the charging volume is much smaller than the gas volume in the gas storage, for a given charging stage or pumping stage, equation (2) can be simplified to ordinary differential equation (8): （8） Equation (8) is solved as follows: Where t0 is the start time of the calculation, t1 is the end time of inflation, t2 is the start time of deflation, t3 is the end time of deflation, and t4 is the end time of the calculation. And, in solving equation (8) The average air density inside the gas storage tank, kg / m3, is calculated using equation (9): (9) In the formula, The initial density of air inside the gas storage facility is expressed in kg / m³. Combining equations (1) to (9), the state before the previous stage of the entire energy storage and release phase is taken as the initial condition for the next stage. After determining the charging and releasing rates and pressures, the gas storage volume V is calculated.

2. The method for optimizing the matching of compressed air energy storage power station main unit parameters with artificial air storage tank volume according to claim 1, characterized in that, The heat exchange medium in step one includes molten salt, heat transfer oil, and water.

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