Method for calculating compressed air energy storage capacity of abandoned coal mine

Abstract

The invention is suitable for the technical field of compressed air energy storage, and particularly relates to a method for calculating the compressed air energy storage capacity of an abandoned coal mine, and the method comprises the steps: obtaining the condition information of an energy storage space, and extracting the data of the energy storage space; calculating the air storage amount of a single roadway based on the energy storage space data; carrying out compression work calculation and expansion work calculation on the compressed air energy storage system to obtain a calculation result; and calculating the total energy storage capacity of the current energy storage space based on the calculation result to obtain a total energy storage value. According to the method, a set of efficient and accurate algorithm model is constructed by deeply integrating specific multi-dimensional parameters such as the roadway burial depth, the surrounding rock permeability and the air pressure working range of the abandoned coal mine, so that the complexity of a traditional evaluation process is simplified, the error rate of a calculation result is greatly reduced, and the calculation efficiency is improved. Therefore, the potential air storage capacity of the abandoned coal mine can be evaluated more quickly and accurately, and a data foundation is laid for subsequent energy development.

Description

Technical Field

[0001] The invention belongs to the technical field of compressed air energy storage, and in particular relates to a method for calculating the compressed air energy storage capacity of abandoned coal mines. Background Art

[0002] With the transformation of energy structure and the continuous increase in the proportion of renewable energy generation, the importance of energy storage technology in power systems has become increasingly prominent. Among them, compressed air energy storage (CAES) has become a highly concerned energy storage technology due to its large energy storage scale, good economy and long life. At present, many CAES projects have been put into operation or are in the development stage at home and abroad, such as the German Hunterf project and the American McIntosh project, which have been commercially operated, and the Jiangsu Jintan CAES project and the Shandong Feicheng CAES project, which are in trial operation in China. The gas storage of these CAES projects is in salt caverns. However, the distribution of these salt caverns suitable for gas storage is limited and the development cost is high. In recent years, the use of abandoned coal mines as gas storage sites for compressed air energy storage has become a research hotspot. Abandoned coal mines have the characteristics of wide geographical distribution, large space capacity and low cost, and are potential high-quality resources for gas storage construction. In the field of compressed air energy storage in abandoned coal mines, current research mainly focuses on the adaptability assessment of abandoned coal mines, the sealing transformation technology of gas storage wells, heat recovery technology, and the improvement of system comprehensive efficiency.

[0003] Current research is usually based on test scenarios or specific models, and a systematic CAES assessment method for abandoned coal mines has not yet been formed. Due to the high diversity of scale, structure and sealing conditions of abandoned coal mines, the energy storage potential of abandoned coal mines is difficult to quantify, and it is impossible to provide a clear basis for the design and planning of power stations. In addition, the geological conditions of different coal mines, such as mining depth, tunnel distribution, surrounding rock permeability and other factors, will significantly affect the performance of the energy storage system. How to scientifically and reasonably calculate and evaluate the power scale of compressed air energy storage power stations that can be supported by abandoned coal mines still lacks feasible and universal solutions. Summary of the invention

[0004] The purpose of the present invention is to provide a method for calculating the compressed air storage capacity of abandoned coal mines, aiming to solve the problem that the energy storage potential of abandoned coal mines is difficult to quantify due to the high diversity of scale, structure and sealing conditions of abandoned coal mines, and it is impossible to provide a clear basis for the design and planning of power plants.

[0005] The present invention is implemented as follows: a method for calculating the energy storage capacity of compressed air in abandoned coal mines, the method comprising:

[0006] Acquire condition information of the energy storage space and extract energy storage space data, wherein the energy storage space data includes tunnel information, weathering degree information and groundwater system information;

[0007] Calculate the storage air volume of a single lane based on the energy storage space data;

[0008] Calculate the compression work and expansion work of the compressed air energy storage system and obtain the calculation results;

[0009] Based on the calculation results, the total energy storage capacity of the current energy storage space is calculated to obtain the total energy storage value.

[0010] Preferably, the step of calculating the amount of stored air in a single lane based on the energy storage space data includes lane volume calculation, lane gas storage pressure calculation and lane gas storage mass calculation, and the lane volume is expressed as:

[0011]

[0012] Among them, a i is the starting point coordinate value of the i-th lane, S i (x) is the cross-sectional area of ​​the i-th lane at a certain coordinate value, b i is the coordinate value of the end point of the i-th lane.

[0013] Preferably, in the step of calculating the tunnel gas storage pressure:

[0014]

[0015] In the formula, σ vi is the ground stress of the ith tunnel, in MPa, and ρ is the density of the overlying rock, in kg / m 3 , g is the acceleration due to gravity, in m / s 2 ,h i is the buried depth of the i-th tunnel, in meters.

[0016] Preferably, in the step of calculating the tunnel gas storage quality, the i-th maximum air storage capacity is expressed as:

[0017] m max-i =n i M;

[0018] Where n i is the amount of air matter that can be stored in the tunnel, and M is the average molar mass of air.

[0019] Preferably, the steps of calculating the compression work and the expansion work of the compressed air energy storage system to obtain the calculation results include calculating the energy consumption of the compressor, calculating the heat exchange of the heat exchange and heat storage coupling system, calculating the average air retention rate of the tunnel storage, and calculating the total power generation power, wherein in the step of calculating the energy consumption of the compressor, the outlet pressure of the i-th stage air compressor is:

[0020]

[0021] In the formula, is the inlet pressure of the i-th stage compressor, π is the fixed pressure ratio, is the compressor outlet pressure;

[0022] The calculation formula of the compressor outlet temperature is:

[0023]

[0024] In the formula, is the inlet temperature of the i-th stage compressor, is the outlet temperature of the compressor, γ is the specific heat capacity of air, η c is the isentropic efficiency of the compressor;

[0025] When the mass flow rate is m c After the air passes through the i-th stage compressor, the power of the compressor is:

[0026]

[0027] Where m c The unit mass flow rate is 1kg / s;

[0028]

[0029] The power required to compress a unit mass flow of air is P c .

[0030] Preferably, in the step of performing heat exchange calculation on the heat exchange and heat storage coupling system, the heat exchange formula is:

[0031]

[0032] In the formula, m represents the mass flow rate, c p is the specific heat capacity, the subscript air represents air, w represents water, in represents inlet, and out represents outlet. The efficiency formula of the j-th stage heat exchanger is:

[0033]

[0034] In the formula, the inlet temperature of the water flow is is the ambient temperature T0.

[0035] Preferably, in the step of calculating the average air retention rate of the tunnel storage, the air flow velocity v is expressed as:

[0036]

[0037] In the formula, r is the distance from the center of the lining, k is the permeability of the surrounding rock or concrete lining, and P is the air pore pressure. The finite element method is used to obtain the air penetration rate through the surface of the concrete lining.

[0038] Mass leakage rate Calculated by integration:

[0039]

[0040] In the formula, ρ a is the air density, A lin is the specific surface area of ​​the roadway concrete lining;

[0041] Average air retention rate η of tunnel storage in one day s for:

[0042]

[0043] m i is the air storage capacity of the ith lane, t d The air storage time is 24h.

[0044] Preferably, in the step of calculating the total generated power, the total generated power is expressed as:

[0045]

[0046] Among them, P t,k is the power of the expander, and n is the number of expanders.

[0047] Preferably, in the step of calculating the total energy storage capacity of the current energy storage space based on the calculation result to obtain the total energy storage value, the total energy storage reservoir volume is expressed as:

[0048] Maximum storage air mass m max and the working air storage mass m are:

[0049]

[0050] When compressing air for the first time, the charging energy required for compressed air energy storage is:

[0051]

[0052] W c The unit is Wh, and t is the unit time 1s.

[0053] Preferably, after entering the stable energy supply stage, the electric energy required for charging the compressed air energy storage system once is:

[0054]

[0055] The compressed air energy storage system can release electrical energy once it is discharged:

[0056]

[0057] The method for calculating the compressed air storage capacity of abandoned coal mines provided by the present invention constructs a set of efficient and accurate algorithm models by deeply integrating multi-dimensional parameters such as tunnel burial depth, surrounding rock permeability and air pressure working range that are unique to abandoned coal mines. This not only simplifies the complexity of the traditional evaluation process, but also greatly reduces the error rate of the calculation results, making the evaluation of the potential air storage capacity of abandoned coal mines faster and more accurate, laying a data foundation for subsequent energy development. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 A flow chart of a method for calculating compressed air energy storage capacity in abandoned coal mines provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0059] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0060] It is understood that the terms "first", "second", etc. used in this application may be used herein to describe various elements, but unless otherwise specified, these elements are not limited by these terms. These terms are only used to distinguish a first element from another element. For example, without departing from the scope of this application, a first xx script may be referred to as a second xx script, and similarly, a second xx script may be referred to as a first xx script.

[0061] like Figure 1 As shown, it is a flow chart of a method for calculating the compressed air energy storage capacity of abandoned coal mines provided by an embodiment of the present invention, the method comprising:

[0062] The condition information of the energy storage space is obtained, and the energy storage space data is extracted, wherein the energy storage space data includes tunnel information, weathering degree information, and groundwater system information.

[0063] In this step, the energy storage space is identified. Compressed air energy storage requires good surrounding rock conditions, and the gas storage options are determined according to the following conditions: tunnels with medium or above surrounding rock stability; tunnels with low or no weathering of surrounding rocks; and the main part of the tunnel does not pass through the groundwater system.

[0064] Calculate the storage air volume of a single aisle based on the energy storage space data.

[0065] In this step, the air storage volume of a single lane is calculated.

[0066] Calculation of tunnel volume:

[0067]

[0068] a i is the starting point coordinate value S of the i-th lane i (x) is the cross-sectional area of ​​the i-th lane at a certain coordinate value, b i is the coordinate value of the end point of the ith tunnel. The data required for volume calculation can be obtained from the coal mine development design drawing.

[0069] Determination of tunnel gas storage pressure:

[0070] The minimum pressure p of compressed air stored in the i-th gas storage tunnel min-i >0.1Mpa, maximum pressure p max-i <σ vi .

[0071] Ground stressσ vi Determined by formula (2):

[0072]

[0073] In the formula, σ vi is the ground stress of the ith tunnel, in MPa, and ρ is the density of the overlying rock, in kg / m 3 , g is the acceleration due to gravity, in m / s 2 ,h i is the buried depth of the i-th tunnel, in meters.

[0074] Calculation of tunnel gas storage quality:

[0075] The maximum air storage capacity m of the ith lane can be calculated from the ideal gas equation (3) and (4): max-i ;

[0076] p i V i =n i RT0(3)

[0077] m max-i =n i ·M(4)

[0078] In actual operation, the air storage capacity of the tunnel gas storage is:

[0079]

[0080] In the formula, p i is the ground stress σ at the location of the tunnel vi ,,n iis the amount of air that can be stored in the tunnel, R is the ideal gas constant of 8.314 J / (mol·K), T0 is the tunnel temperature, and to simplify the calculation, the air storage temperature is equal to the surface ambient temperature T0. M is the average molar mass of air 0.029 kg / mol, m i is the air mass that can be stored in the i-th lane.

[0081] The compression work and expansion work of the compressed air energy storage system are calculated to obtain calculation results.

[0082] In this step, the CAES system energy storage compression work and expansion work are calculated:

[0083] Calculation of energy consumption of compressor:

[0084] The compression ratio of the multi-stage compressor is fixed, and the outlet pressure of the i-th stage air compressor is:

[0085]

[0086] In the formula is the inlet pressure of the i-th stage compressor, π is the fixed pressure ratio, is the compressor outlet pressure. The compressor outlet temperature is calculated as follows:

[0087]

[0088] In the formula, is the inlet temperature of the i-th stage compressor, is the outlet temperature of the compressor, γ is the specific heat capacity of air, η c is the isentropic efficiency of the compressor.

[0089] When the mass flow rate is m c After the air passes through the i-th stage compressor, the power of the compressor is:

[0090]

[0091] For the convenience of calculation, m c The unit mass flow rate is 1kg / s;

[0092]

[0093] The power required to compress a unit mass flow of air is Pc.

[0094] Heat exchange and heat storage coupling system:

[0095] The heat exchange and heat storage coupling system is divided into a heat exchange system and a reheat system. The function of the heat exchange system is to cool the air passing through the compressor and recover the heat energy. The function of the reheat system is to use the recovered heat energy to heat the air before entering the expander. The intercooler and reheater of the heat exchange system have the same structure. In the heat exchange calculation of the entire compressed air energy storage system, water is used as the cooling medium. The heat absorbed by the circulating water is equal to the heat lost by the air. The heat exchange formula is:

[0096]

[0097] In the formula, m represents the mass flow rate, c p is the specific heat capacity, the subscript air represents air, w represents water, in represents inlet, and out represents outlet. The efficiency formula of the j-stage heat exchanger is:

[0098]

[0099] In the formula, the inlet temperature of the water flow is is the ambient temperature T0.

[0100] The reheater and the intercooler have the same structure, so in the subsequent power generation process of compressed air, the calculation of the reheater system efficiency is the same as that of the intercooler, which will not be repeated here.

[0101] Lane storage:

[0102] There is a certain amount of air leakage in the tunnel during the gas storage process. Assuming that the leakage airflow passes through the lining and surrounding rock at a slow speed and follows Darcy's law, the airflow velocity v is determined by the following formula:

[0103]

[0104] Where r is the distance from the center of the lining, k is the permeability of the surrounding rock or concrete lining, and P is the air pore pressure. Using the finite element method, the air penetration rate through the concrete lining surface can be obtained.

[0105] Mass leakage rate It can be calculated by integration:

[0106]

[0107] In the formula, ρ a is the air density, A lin is the specific surface area of ​​the tunnel concrete lining.

[0108] Average air retention rate η of tunnel storage in one day s for:

[0109]

[0110] mi is the air storage capacity of the ith lane, t d The air storage time is 24h.

[0111] turbine:

[0112] After being heated by the j-th stage reheater, the air enters the k-th stage turbine to drive the turbine to generate electricity. The pressure change of the high-pressure gas after passing through the turbine is:

[0113]

[0114] In the formula is the inlet pressure of the kth compressor, β is the fixed expansion ratio, is the compressor outlet pressure. The calculation formula for the outlet temperature is as follows:

[0115]

[0116] In the formula, is the inlet temperature of the kth expander, is the outlet temperature of the expander, γ is the specific heat capacity of air, η t is the isentropic efficiency of the compressor.

[0117] Assuming that the air charging and discharging time is the same, the compressor air flow mc and the expander mt have the following relationship:

[0118] m t =ηm c (17)

[0119] After the air of the air flow passes through the kth expander, the power of the expander is:

[0120]

[0121] The total power generation of the energy storage system is:

[0122]

[0123] In this part of the calculation, the i in the i-th lane is the lane count, which can range from dozens to hundreds depending on the development design of the coal mine. The compressor, heat exchange system, and expander have the same number of stages, which are counted as i, j, and k respectively.

[0124] Based on the calculation results, the total energy storage capacity of the current energy storage space is calculated to obtain the total energy storage value.

[0125] In this step, the total energy storage capacity of abandoned coal mines is calculated:

[0126] (1) Calculation of total energy storage volume:

[0127]

[0128] (2) Maximum storage air mass m max and the working air storage mass m are:

[0129]

[0130] (3) Calculation of compressed air energy storage capacity in abandoned coal mines:

[0131] When air is compressed for the first time, the air storage space needs to be completely filled with air, so the charging energy required for coal mine compressed air energy storage is:

[0132]

[0133] Wc is represented by Wh, and t is the unit time of 1s.

[0134] After entering the stable energy supply stage, the power required for a coal mine CAES charge is:

[0135]

[0136] The electrical energy released by coal mine CAES discharge once is:

[0137]

[0138] 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 and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for calculating the compressed air energy storage capacity of abandoned coal mines, characterized in that: The method comprises: Acquire condition information of the energy storage space and extract energy storage space data, wherein the energy storage space data includes tunnel information, weathering degree information and groundwater system information; Calculate the storage air volume of a single lane based on the energy storage space data; Calculate the compression work and expansion work of the compressed air energy storage system and obtain the calculation results; Based on the calculation results, the total energy storage capacity of the current energy storage space is calculated to obtain the total energy storage value.

2. The method for calculating the compressed air energy storage capacity of abandoned coal mines according to claim 1, characterized in that: The step of calculating the storage air volume of a single lane based on the energy storage space data includes lane volume calculation, lane gas storage pressure calculation and lane gas storage mass calculation. The lane volume is expressed as: Among them, a i is the starting point coordinate value of the i-th lane, S i (x) is the cross-sectional area of ​​the i-th lane at a certain coordinate value, b i is the coordinate value of the end point of the i-th lane.

3. The method for calculating the compressed air energy storage capacity of abandoned coal mines according to claim 2, characterized in that: In the steps of calculating the tunnel gas storage pressure, In the formula, σ vi is the ground stress of the ith tunnel, in MPa, and ρ is the density of the overlying rock, in kg / m 3 , g is the acceleration due to gravity, unit is m / s 2 ,h i is the buried depth of the i-th tunnel, in meters.

4. The method for calculating the compressed air energy storage capacity of abandoned coal mines according to claim 2, characterized in that: In the step of calculating the air storage quality of the roadway, the maximum air storage volume m of the i-th roadway is max-i It is expressed as: m max-i =n i ·M; Where n i is the amount of air matter that can be stored in the tunnel, and M is the average molar mass of air.

5. The method for calculating the compressed air energy storage capacity of abandoned coal mines according to claim 1, characterized in that: The steps of calculating the compression work and the expansion work of the compressed air energy storage system to obtain the calculation results include calculating the energy consumption of the compressor, calculating the heat exchange of the heat exchange and heat storage coupling system, calculating the average air retention rate of the tunnel storage, and calculating the total power generation. In the step of calculating the energy consumption of the compressor, the outlet pressure of the i-th stage air compressor is: In the formula, is the inlet pressure of the i-th stage compressor, π is the fixed pressure ratio, is the compressor outlet pressure; The calculation formula of the compressor outlet temperature is: In the formula, is the inlet temperature of the i-th stage compressor, is the outlet temperature of the compressor, γ is the specific heat capacity of air, η c is the isentropic efficiency of the compressor; When the mass flow rate is m c After the air passes through the i-th stage compressor, the power of the compressor is: Where m c The unit mass flow rate is 1kg / s; The power required to compress a unit mass flow of air is P c .

6. The method for calculating the compressed air energy storage capacity of abandoned coal mines according to claim 5, characterized in that: In the step of heat exchange calculation for the heat exchange and heat storage coupling system, the heat exchange formula is: Where m represents mass flow rate, c p is the specific heat capacity, the subscript air represents air, w represents water, in represents inlet, and out represents outlet. The efficiency formula of the j-th stage heat exchanger is: In the formula, the inlet temperature of the water flow is is the ambient temperature T0.

7. The method for calculating the compressed air energy storage capacity of abandoned coal mines according to claim 5, characterized in that: In the step of calculating the average air retention rate of the tunnel storage, the air flow velocity v is expressed as: In the formula, r is the distance from the center of the lining, k is the permeability of the surrounding rock or concrete lining, and P is the air pore pressure. The finite element method is used to obtain the air penetration rate through the surface of the concrete lining. Mass leakage rate It can be calculated by integration: In the formula, ρ a is the air density, A lin is the specific surface area of ​​the roadway concrete lining; Average air retention rate η of tunnel storage in one day s for: m i is the air storage capacity of the ith lane, t d The air storage time is 24h.

8. The method for calculating the compressed air energy storage capacity of abandoned coal mines according to claim 5, characterized in that: In the step of calculating the total generated power, the total generated power is expressed as: Among them, P t,k is the power of the expander, and n is the number of expanders.

9. The method for calculating the compressed air energy storage capacity of abandoned coal mines according to claim 1, characterized in that: Based on the calculation results, the total energy storage capacity of the current energy storage space is calculated to obtain the total energy storage value. The total energy storage volume is expressed as: Maximum storage air mass m max and the working air storage mass m are: When compressing air for the first time, the charging energy required for compressed air energy storage is: W c The unit is Wh, and t is the unit time 1s.

10. The method for calculating the compressed air energy storage capacity of abandoned coal mines according to claim 9, characterized in that: After entering the stable energy supply stage, the power required for charging the compressed air energy storage system once is: The compressed air energy storage system can release electrical energy once it is discharged:

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