A method for calculating energy stored in compressed air in abandoned coal mines

Abstract

The present application is suitable for compressed air energy storage technology field, especially relates to a kind of method for calculating abandoned coal mine compressed air energy storage quantity, the method comprises: obtaining the condition information of energy storage space, extracts energy storage space data;Based on the energy storage space data, the storage air quantity of single roadway is calculated;The compressed air energy storage system is compressed power calculation and expansion power calculation, and the calculation result is obtained;Based on the calculation result, the total energy storage capacity of current energy storage space is calculated, and the total energy storage value is obtained.The present application is deeply integrated into the multi-dimensional parameters such as the specific roadway depth, surrounding rock permeability and air pressure working range of abandoned coal mine, and a set of efficient and accurate algorithm model is constructed, which not only simplifies the complexity of traditional evaluation process, but also greatly reduces the error rate of calculation result, so that the evaluation of potential air storage capacity of abandoned coal mine is more rapid and accurate, and lays a data foundation for subsequent energy development.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of compressed air energy storage, and particularly relates to a method for calculating compressed air energy storage capacity of abandoned coal mines. BACKGROUND

[0002] With the transformation of energy structure and the continuous increase of the proportion of renewable energy power generation, the importance of energy storage technology in the power system is increasingly prominent. Among them, compressed air energy storage (CAES) has become a kind of energy storage technology that attracts much attention due to its large energy storage scale, good economy and long service life. At present, there are many CAES projects in operation or in development at home and abroad, such as the commercialized Huntorf project in Germany and the McIntosh project in the United States, the trial operation of the CAES project in Jiangsu Jintan and the CAES project in Shandong Feicheng, and the gas storage of these CAES projects is in salt caves. However, the distribution of these salt caves suitable for gas storage is limited, and the development cost is high. In recent years, using abandoned coal mines as compressed air energy storage sites 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 adaptability assessment, gas storage well sealing technology, heat recovery technology, and system comprehensive efficiency improvement.

[0003] The current research is usually based on test scenarios or specific models, and has not yet formed a systematic evaluation method for abandoned coal mine CAES. Due to the high diversity of the scale, structure and sealing conditions of abandoned coal mines, it is difficult to quantify the energy storage potential of abandoned coal mines, and it is impossible to provide clear basis for the design and planning of power stations. And different geological conditions of coal mines, such as mining depth, roadway distribution, and permeability of surrounding rock, will significantly affect the performance of the energy storage system. How to scientifically and reasonably calculate and evaluate the power scale of the compressed air energy storage power station supported by the abandoned coal mine still lacks a feasible and universal solution. SUMMARY

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

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

[0006] Obtaining condition information of the energy storage space, extracting energy storage space data, the energy storage space data including roadway information, weathering degree information and groundwater system information;

[0007] calculating the storage air mass of a single roadway based on the energy storage space data;

[0008] calculating the compression work and the expansion work of the compressed air energy storage system to obtain a calculation result;

[0009] calculating the total energy storage capacity of the current energy storage space based on the calculation result to obtain a total energy storage value.

[0010] Preferably, the step of calculating the storage air mass of a single roadway based on the energy storage space data comprises roadway volume calculation, roadway gas storage pressure calculation and roadway gas storage mass calculation, and the roadway volume is represented as:

[0011]

[0012] wherein a i is the starting point coordinate value of the i roadway, S i (x) is the cross-sectional area of a coordinate value of the i roadway, b i is the ending point coordinate value of the i roadway.

[0013] Preferably, in the step of roadway gas storage pressure calculation:

[0014] σvi=ρ i gh i ;

[0015] wherein σ vi is the ground stress received by the i roadway, with the unit of MPa, ρ i is the average density of the overlying strata of the i roadway, with the unit of kg / m 3 , g is the acceleration of gravity, with the unit of m / s 2 , and h i is the burial depth of the i roadway, with the unit of m.

[0016] Preferably, in the step of roadway gas storage mass calculation, the maximum storage air mass of the i roadway is represented as:

[0017] m max-i =n i ·M;

[0018] wherein n i is the amount of air storage material of the roadway, and M is the average molar mass of air.

[0019] Preferably, the step of calculating the compression work and the expansion work of the compressed air energy storage system comprises the steps of calculating the energy consumption of the compressor, calculating the heat exchange of the heat exchange and storage coupling system, calculating the average air retention rate of the roadway storage, and calculating the total power generation, wherein the step of calculating the energy consumption of the compressor, the outlet pressure of the i-th air compressor is:

[0020]

[0021] wherein, is the inlet pressure of the i-th compressor, π is a fixed pressure ratio, is the outlet pressure of the compressor;

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

[0023]

[0024] wherein, is the inlet temperature of the i-th 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 of air is m c , the power of the compressor is:

[0026]

[0027] wherein m c is the unit mass flow rate 1 kg / s;

[0028]

[0029] The power required for compressing the unit mass flow rate of air is P c .

[0030] Preferably, the step of calculating the heat exchange of the heat exchange and storage coupling system, the heat exchange formula is:

[0031]

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

[0033]

[0034] wherein the inlet temperature of the water flow is the ambient temperature T0.

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

[0036]

[0037] wherein r is the distance from the center of the lining, k is the permeability of the surrounding rock or the concrete lining, P is the air pore pressure, and the permeation velocity of the air through the surface of the concrete lining is obtained by using the finite element method,

[0038] Mass leakage rate The mass leakage rate is calculated by integration:

[0039]

[0040] wherein p a is the air density, A lin is the specific surface area of the concrete lining of the roadway;

[0041] The average air retention rate of the roadway reservoir in one day is denoted as s :

[0042]

[0043] m i is the stored air mass of the i-th roadway, t d is the air storage time of 24 h.

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

[0045]

[0046] wherein 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 results to obtain the total energy storage value, the total energy storage volume is expressed as:

[0048] The maximum stored air mass m max and the working stored air mass m are respectively:

[0049]

[0050] The charging electric energy required for compressed air energy storage when the compressed air is first compressed is:

[0051]

[0052] W c Unit kWh, t is the unit time 1s.

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

[0054]

[0055] The compressed air energy storage system can release electric energy once:

[0056]

[0057] The method for calculating the compressed air energy storage capacity of the abandoned coal mine provided by the present application simplifies the complexity of the traditional evaluation process, greatly reduces the error rate of the calculation results, and makes the evaluation of the potential air storage capacity of the abandoned coal mine more rapid and accurate, thereby laying a data foundation for subsequent energy development. BRIEF DESCRIPTION OF DRAWINGS

[0058] Figure 1 The flowchart of the method for calculating the compressed air energy storage capacity of the abandoned coal mine provided by the present application is shown in the figure. DETAILED DESCRIPTION

[0059] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0060] It can be understood that the terms "first", "second" and the like used in the present application can be used herein to describe various elements, but unless specifically stated, these elements are not limited by these terms. These terms are only used to distinguish the first element from another element. For example, without departing from the scope of the present application, the first xx script can be referred to as the second xx script, and similarly, the second xx script can be referred to as the first xx script.

[0061] As shown in the figure, the flowchart of the method for calculating the compressed air energy storage capacity of the abandoned coal mine provided by the present application, the method comprises: Figure 1

[0062] Obtain the condition information of the energy storage space, extract the energy storage space data, and the energy storage space data includes roadway 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. The following conditions are used to determine the gas storage options: roadway with medium or above stability of surrounding rock; roadway with low or no weathering of surrounding rock; main part of roadway not passing through groundwater system.

[0064] The storage air quality of a single roadway is calculated based on the energy storage space data.

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

[0066] Roadway volume calculation:

[0067]

[0068] a i S i is the starting point coordinate value of the ith roadway, b i is the ending point coordinate value of the ith roadway. The data required for volume calculation can be obtained from the coal mine development design map.

[0069] Roadway gas storage pressure determination:

[0070] The minimum pressure p min-i of the ith gas storage roadway for compressed air storage is greater than 0.1 MPa, and the maximum pressure p max-i <σ vi .

[0071] The ground stress σ vi is determined by formula (2):

[0072]

[0073] In the formula, σ vi is the ground stress received by the ith roadway, with units of MPa, ρ i is the average density of the overburden of the ith roadway, with units of kg / m 3 , g is the acceleration of gravity, with units of m / s 2 , h i is the burial depth of the ith roadway, with units of m.

[0074] Roadway gas storage quality calculation:

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

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

[0077] m max-i= n i • M(4)

[0078] In actual operation, the storage air mass of the roadway gas storage is:

[0079]

[0080] In the formula, p i is the ground stress σ vi , n i is the mass of the air stored in the roadway, R is the ideal gas constant 8.314 J / (mol·K), T0 is the temperature of the roadway, for the sake of simplifying the calculation, the air storage temperature is equal to the surface environment 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 roadway.

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

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

[0083] Energy consumption calculation of the compressor:

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

[0085]

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

[0087]

[0088] In the formula, T is the inlet temperature of the i-th 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 of air is m c , the power of the i-th compressor is:

[0090]

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

[0092]

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

[0094] The 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 reheating system. The function of the heat exchange system is to cool the air after the compressor and recover the heat energy. The function of the reheating system is to heat the air before entering the expander. The intercooler and the reheater of the heat exchange system have the same structure. In the heat exchange calculation of the whole compressed air energy storage system, water is used as the cooling medium. The heat absorbed by the circulating water is equal to the heat dissipated 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 the inlet, and out represents the outlet. The efficiency formula of the jth heat exchanger is:

[0098]

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

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

[0101] Roadway storage:

[0102] The roadway has a certain amount of air leakage during the air storage process. It is assumed that the leakage air flow passes through the lining and surrounding rock at a slow speed and follows Darcy's law. The air flow velocity v is determined by the following formula:

[0103]

[0104] 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 permeation velocity of air through the surface of the concrete lining can be obtained by using the finite element method.

[0105] The mass leakage rate 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 roadway concrete lining.

[0108] Average air retention rate of roadway storage η s is:

[0109]

[0110] m i is the storage air mass of the ith roadway, t d is the air storage time 24h.

[0111] Turbo:

[0112] After the air is heated by the jth reheater, it enters the kth turbine to drive the turbine generator. The pressure change of the high-pressure gas after passing through the turbine is:

[0113]

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

[0115]

[0116] where, 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 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, i in the ith roadway is the roadway count, which is dozens to hundreds according to the design of the coal mine development. 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 the abandoned coal mine is calculated:

[0126] (1) The calculation of the total energy storage library volume:

[0127]

[0128] (2) The maximum storage air mass m max And the working storage air mass m respectively:

[0129]

[0130] (3) The calculation of the compressed air energy storage capacity of the abandoned coal mine:

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

[0132]

[0133] Wc is in units of kWh, and t is in units of 1s.

[0134] After entering the stable energy supply stage, the electric energy required for the coal mine CAES charging once is:

[0135]

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

[0137]

[0138] The above only describes the preferred embodiments of the present application and is not used to limit the present application, any modification, equivalent replacement and improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for calculating the energy storage capacity of compressed air in abandoned coal mines, characterized in that, The method includes: Obtain condition information of the energy storage space and extract energy storage space data, including tunnel information, weathering degree information and groundwater system information; Calculate the stored air quality of a single tunnel based on energy storage space data; The compression work and expansion work of the compressed air energy storage system are calculated, and the calculation results are obtained. 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; Calculation of gas storage mass in tunnels: The maximum air storage mass m of the i-th tunnel can be calculated from the ideal gas equation (3) and equation (4). max-i ; p i V i =n i RT0(3) m max-i =n i ·M(4) In actual operation, the air quality stored in the tunnel gas storage facility is as follows: In the formula, p i The ground stress σ at the location of the tunnel vi n i Let R be the amount of air that can be stored in the tunnel, R be the ideal gas constant of 8.314 J / (mol·K), T0 be the tunnel temperature (for simplicity, the air storage temperature is equal to the surface ambient temperature T0), M be the average molar mass of air of 0.029 kg / mol, and m be the average molar mass of air. i Let P be the air quality that can be stored in the i-th tunnel. maxi The upper limit pressure of the air stored in the i-th tunnel, P min i Let be the lower limit pressure for storing air in the i-th tunnel.

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

3. The method for calculating the energy storage of compressed air in abandoned coal mines according to claim 2, characterized in that, In the steps of calculating the gas storage pressure in the tunnel, σvi=ρ i gh i In the formula, σ vi ρ represents the in-situ stress experienced by the i-th tunnel, expressed in MPa. i The density of the overlying rock strata of the i-th tunnel is expressed in kg / m³. 3 g is the acceleration due to gravity, with units of m / s². 2 h i The depth of the i-th tunnel is expressed in meters (m).

4. The method for calculating the energy storage of compressed air in abandoned coal mines according to claim 2, characterized in that, In the steps of calculating the gas storage mass in the tunnel, the maximum stored air mass m of the i-th tunnel... max-i Represented as: m max-i =n i ·M; In the formula, n i Let M be the amount of air that can be stored in the tunnel, and M be the average molar mass of air.

5. The method for calculating the energy storage of compressed air in abandoned coal mines according to claim 1, characterized in that, The steps for calculating the compression work and 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 storage coupling system, calculating the average air retention rate of the tunnel storage tank, 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, Let π be the inlet pressure of the i-th stage compressor, and π be the constant pressure ratio. This refers to the compressor's outlet pressure. The formula for calculating the compressor outlet temperature is: In the formula, Let be the inlet temperature of the i-th stage compressor. η is the outlet temperature of the compressor, γ is the specific heat capacity of air, and η is the specific heat capacity of air. c 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 compressor's power is: In the formula m c The unit mass flow rate is 1 kg / s; The power required to compress a unit mass flow rate of air is P. c .

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

7. The method for calculating the energy storage of compressed air in abandoned coal mines according to claim 5, characterized in that, In the step of calculating the average air retention rate of the tunnel storage tank, the airflow 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 permeation velocity of air through the surface of the concrete lining is obtained using the finite element method. mass leakage rate It can be calculated by integration: In the formula, ρ a For air density, A lin Specific surface area of ​​the concrete lining of the tunnel; Average air retention rate η of the tunnel storage warehouse within one day s for: m i Let t be the stored air quality of the i-th tunnel. d Air storage time is 24 hours.

8. The method for calculating the energy storage of compressed air in abandoned coal mines according to claim 5, characterized in that, In the step of calculating the total power generation, the total power generation 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 energy storage of compressed air in abandoned coal mines according to claim 1, characterized in that, In the step of calculating the total energy storage capacity of the current energy storage space based on the calculation results, the total energy storage volume is expressed as: Maximum stored air mass m max The working and storage air masses m are respectively: The electrical energy required for charging the compressed air during the initial air compression is: W c The unit is kWh, and t is the unit of time, 1 second.

10. The method for calculating the energy storage of compressed air in abandoned coal mines according to claim 9, characterized in that, After entering the stable power supply phase, the electrical energy required for the compressed air energy storage system to charge once is: The electrical energy that a compressed air energy storage system can release in a single discharge is:

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