A deep geothermal energy storage comprehensive evaluation method based on variable weight multi-factor fusion

Abstract

The application discloses a kind of deep energy storage comprehensive evaluation methods based on variable weight multi-factor fusion, first carry out the hierarchical cyclic loading and unloading test of simulated deep energy storage working condition, four kinds of core evaluation parameters such as surrounding rock stability, sealing, energy storage efficiency, environmental safety are synchronously collected;Second, the single cycle evaluation quantity and cumulative evaluation quantity of each dimension are calculated;Further introduce variable weight theory, determine the basic weight by analytic hierarchy process, construct state adjustment function to realize weight dynamic adjustment, and calculate the deep energy storage comprehensive evaluation index;Finally, according to the value of comprehensive index, the whole cycle operation stage is divided, and the corresponding hierarchical early warning and operation and maintenance strategy is matched.The application solves the problem that the existing deep energy storage evaluation dimension is single, the weight is fixed and the engineering guidance is insufficient, and the evaluation result is consistent with the cycle degradation law of energy storage system, which can provide quantitative decision basis for the safe operation and risk control of various deep energy storage projects such as compressed air energy storage, hydrogen energy storage and pumped storage.

Description

Technical Field

[0001] This invention relates to the field of deep underground energy storage safety evaluation technology, and in particular to a comprehensive evaluation method for deep underground energy storage based on variable weight multi-factor fusion, which is applicable to the full-cycle safety assessment and operation and maintenance decision-making of various deep underground energy storage projects such as compressed air energy storage, hydrogen (ammonia) energy storage, and pumped hydro storage. Background Technology

[0002] Deep-ground energy storage has rapidly developed as a core technology for large-scale, long-cycle energy storage, and is a crucial infrastructure supporting renewable energy consumption and ensuring stable grid operation. Under the long-term "energy storage-release" cycle load, deep-ground energy storage systems face multiple challenges, including accumulated surrounding rock damage, deterioration of sealing performance, decline in energy storage efficiency, and increased environmental risks. Establishing a scientific, comprehensive, and dynamic evaluation method is a core prerequisite for ensuring the safe and efficient operation of these projects.

[0003] Current methods for assessing the safety of deep underground energy storage mainly suffer from the following technical deficiencies: 1. Single evaluation dimension and lack of multi-dimensional collaborative system: Existing evaluations mostly focus on single-factor analysis of surrounding rock structure stability or medium sealing, without systematically integrating dimensions such as energy storage efficiency and environmental safety. This makes it impossible to fully reflect the real operating status of the energy storage system and to support the coordinated management of safety and economy.

[0004] 2. The fixed weight model is not dynamic enough: Traditional evaluation methods often use fixed weight allocation, which cannot adapt to the dynamic changes in the importance of various factors at different stages of the entire deep underground energy storage cycle. The sensitivity to identify weak links in the system is insufficient, and the evaluation results do not fit well with the actual deterioration patterns of the project.

[0005] 3. Lack of quantitative correlation between operating parameters and surrounding rock response: Existing methods are mostly based on static evaluation of fixed operating parameters, and have not established a quantitative mapping between operating parameters such as energy storage cycle number and pressure level and the multi-physics field response of surrounding rock, making it difficult to support dynamic optimization and adjustment of operating parameters.

[0006] 4. Lack of a corresponding mechanism for graded early warning and operation and maintenance decision-making: Existing evaluation results are mostly qualitative or semi-quantitative conclusions, and there is no direct mapping between evaluation results and engineering operation and maintenance strategies, so the engineering guidance value of the evaluation results is limited.

[0007] Therefore, there is an urgent need to develop a comprehensive evaluation method for deep-earth energy storage that can integrate multi-dimensional factors, dynamically adjust weights, and match graded early warnings to fill the existing technological gap. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a comprehensive evaluation method for deep underground energy storage based on variable weight multi-factor fusion. This method integrates four core dimensions: surrounding rock stability, sealing performance, energy storage efficiency, and environmental safety. It introduces variable weight theory to achieve dynamic adaptive adjustment of weights and establishes a full-cycle stage division and hierarchical early warning system, providing quantitative decision-making basis for the safe and efficient operation of deep underground energy storage projects.

[0009] To achieve the above objectives, the technical solution adopted by this invention is: a comprehensive evaluation method for deep underground energy storage based on variable weight multi-factor fusion, comprising the following steps: S1. Conduct graded cyclic loading-unloading tests simulating deep underground energy storage conditions, and simultaneously collect evaluation parameters in four dimensions: surrounding rock stability, sealing performance, energy storage efficiency, and environmental safety.

[0010] S2. Based on the collected parameters, calculate the single-cycle evaluation value and the total cumulative evaluation value for each dimension.

[0011] S3. Standardize the various cumulative evaluation quantities, construct a multi-factor fusion evaluation model in combination with variable weight theory, and calculate the comprehensive evaluation index of deep underground energy storage.

[0012] S4. Based on the range of values ​​for the comprehensive evaluation index of deep underground energy storage, divide the entire life cycle of deep underground energy storage into different stages and match them with corresponding hierarchical early warning rules and operation and maintenance management strategies.

[0013] S5. Verify the effectiveness of the method using indoor test data or on-site engineering monitoring data.

[0014] Further, step S1 recreates the real service environment of deep-ground energy storage through indoor rock mechanics tests. The confining pressure and temperature are set according to the target project's burial depth and geothermal conditions. The axial pressure is applied in stages to simulate the energy storage and release process. The four types of parameters correspond to the four core evaluation dimensions of structural safety, medium safety, economic efficiency, and environmental risk, all of which can be obtained through conventional testing equipment and monitoring methods. Specifically, rock samples taken from the target deep-ground energy storage chamber are subjected to confining pressure corresponding to the burial depth to simulate deep geostress conditions, and a temperature field is applied to simulate high geothermal temperatures and temperature fluctuations during the energy storage process. The axial pressure is gradually increased according to the actual operating pressure of the energy storage chamber and then unloaded to the initial load. The loading is cyclically applied until the sample suffers macroscopic failure to simulate the "energy storage-release" cycle. Within each loading-unloading cycle, the four types of evaluation parameters are collected simultaneously. (1) Surrounding rock stability parameters: residual strain after unloading to the initial load .

[0015] (2) Sealing parameters: Permeability at the start of loading Permeability at the end of unloading The difference .

[0016] (3) Energy storage efficiency parameters: energy dissipation in a single cycle It is obtained by integral calculation from the load-displacement curve.

[0017] (4) Environmental safety parameters: acoustic emission ring count within a single cycle .

[0018] Furthermore, step S2 quantifies the evolutionary patterns of each dimension from two aspects: the degradation rate in a single cycle and the cumulative degradation degree over the entire cycle. The cumulative evaluation value can intuitively reflect the current degradation level of each dimension, providing a unified quantitative basis for multi-factor fusion. The calculation methods for the single-cycle evaluation value and cumulative evaluation value of the four dimensions are as follows: (1) Surrounding rock stability dimension: Single cycle evaluation quantity: Cumulative number of reviews: (2) Sealing dimension: Single cycle evaluation quantity: Cumulative number of reviews: (3) Energy storage efficiency dimension: Single cycle evaluation quantity: Cumulative number of reviews: (4) Environmental safety dimension: Single cycle evaluation quantity: Cumulative number of reviews: Where i is the current loop count and j is the loop number; , , , These are the total residual strain, total permeability change, total dissipated energy, and total acoustic emission ring count for all cycles before the rock sample fails.

[0019] Furthermore, step S3 employs the analytic hierarchy process (AHP) to determine the basic weights under normal operating conditions, ensuring the rationality of the evaluation system. It introduces variable weight theory to construct a state adjustment function, automatically amplifying the weight of a certain dimension index when it significantly deteriorates, highlighting the system's "weakest link effect," and improving the sensitivity of the evaluation results to safety risks. Specifically, this includes: S31. Standardization of Indicators: The extreme value normalization method is used to uniformly map the four types of cumulative evaluation quantities to the [0,1] interval to obtain standardized indicators. j=1, 2, 3, 4 correspond to the dimensions of surrounding rock stability, sealing performance, energy storage efficiency, and environmental safety, respectively.

[0020] S32. Determining Basic Weights: A judgment matrix is ​​constructed using the analytic hierarchy process (AHP) to calculate the basic weights for each dimension. .

[0021] S33. Variable Weight State Adjustment: Constructing the State Adjustment Function The actual weights are dynamically adjusted based on the degree of degradation of each dimension indicator; the expression of the state adjustment function is:

[0022] in, The degradation sensitivity coefficient is 3 for the sealing performance dimension and the surrounding rock stability dimension, and 2 for the energy storage efficiency dimension and the environmental safety dimension.

[0023] S34. Calculation of Comprehensive Evaluation Index: Combining basic weights, state adjustment function, and standardized indicators, a weighted comprehensive evaluation index for deep underground energy storage is obtained. The calculation formula is:

[0024] The comprehensive evaluation index ranges from [0,1]. The larger the value, the higher the overall deterioration of the deep-earth energy storage system and the greater the safety risk.

[0025] Furthermore, step S4 divides the entire lifecycle of deep underground energy storage into three stages based on a comprehensive evaluation index, matching different monitoring and operation and maintenance strategies for each stage. This enables the direct transformation of evaluation results into engineering decisions, enhancing the engineering application value of the method. Specifically, the full lifecycle operation stages and tiered operation and maintenance strategies for deep underground energy storage are as follows: when When the energy storage is in a stable operation phase, regular monitoring will be performed to maintain normal energy storage and release operations.

[0026] when When the energy storage performance is in a decay phase, the monitoring frequency should be increased, the charging and discharging pressure and rate should be appropriately reduced, the evolution trend of sealing performance should be assessed, and reinforcement and maintenance measures should be taken if necessary.

[0027] when If the situation is determined to be a risky stage for the energy storage system, the energy storage operation should be immediately stopped, a comprehensive safety assessment should be conducted, the emergency plan should be activated, and reinforcement and remediation measures should be taken.

[0028] Compared with the prior art, the present invention has the following advantages: 1. This invention is the first to systematically integrate four core dimensions: surrounding rock stability, sealing performance, energy storage efficiency, and environmental safety. It comprehensively covers the structural safety, medium safety, economic efficiency, and environmental risks of deep-earth energy storage, solving the problem of the one-sidedness of single-factor evaluation and truly reflecting the overall operating status of the energy storage system.

[0029] 2. This invention breaks through the limitations of traditional fixed weights and constructs a dynamic adaptive variable weight evaluation model. Through a state adjustment function, the weights are dynamically adjusted according to the degree of degradation. It automatically identifies and amplifies the weight contribution of weak links in the system. The evaluation results are more in line with the actual law of deep underground energy storage cycle degradation, and significantly improve the accuracy and adaptability of the evaluation.

[0030] 3. This invention conducts a collaborative evaluation of energy storage efficiency and safety dimensions, establishes a quantitative correlation between operating parameters and surrounding rock response, and can dynamically optimize energy storage operating parameters based on the evaluation results, thereby improving the economic benefits of the energy storage system while ensuring safety.

[0031] 4. This invention forms a three-level mapping mechanism of "evaluation index - operation phase - operation and maintenance strategy". The evaluation results directly correspond to graded early warning and control measures, which can be widely applied to the full life cycle safety assessment and risk management of various deep earth energy storage projects.

[0032] 5. The parameters required by the method of this invention can all be obtained through conventional rock mechanics tests and engineering monitoring methods. The calculation process is clear and the physical meaning is well-defined. The weighting coefficients and stage thresholds can be flexibly calibrated according to the surrounding rock type, energy storage medium and operating conditions of different projects, making it highly adaptable. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the overall process of the method of the present invention.

[0034] Figure 2 This is a schematic diagram of the variable weight multi-factor fusion calculation process of the present invention.

[0035] Figure 3 This is a schematic diagram illustrating the operational phase division and hierarchical early warning mapping of deep underground energy storage according to the present invention. Detailed Implementation

[0036] The present invention will be further described below.

[0037] Example 1: Indoor graded cycle test verification (granite compressed air energy storage) This embodiment uses a deep-ground compressed air energy storage chamber with a burial depth of 1000m as the engineering background. A graded cyclic loading and unloading test was conducted on granite samples taken from the target stratum of the chamber to verify the effectiveness of the method of the present invention. The specific implementation process is as follows: (1) Setting up experimental conditions (step S1) The specimen was a standard cylindrical granite specimen with dimensions of φ50mm×100mm; the in-situ stress was calculated based on the burial depth, and the confining pressure was set to 25MPa; the test temperature was set to 60℃ to simulate the deep geothermal environment.

[0038] The axial pressure was applied using a progressively increasing cyclic loading method: the initial axial pressure was 10 MPa, and the maximum axial pressure increased by 5 MPa in each cycle. Each cycle completed one loading-unloading cycle. After unloading to the initial axial pressure of 10 MPa, the cycle continued until the sample underwent macroscopic failure. A total of 12 cycles were completed to fully simulate the cyclic load condition of deep-earth energy storage’s “energy storage-energy release”.

[0039] After each iteration, four types of evaluation parameters were collected simultaneously. The experimental data are as follows: ① Surrounding rock stability parameters (residual strain) ): 0.002‰, 0.005‰, 0.009‰, 0.014‰, 0.021‰, 0.030‰, 0.042‰, 0.058‰, 0.080‰, 0.110‰, 0.152‰, 0.210‰; Total residual strain =0.733‰.

[0040] ② Sealing parameters (change in permeability) ): 0.03×10 -18 m 2 0.07×10 -18 m 2 0.12×10 - 18 m 2 0.19×10 -18 m 2 0.28×10 -18 m 2 0.40×10 -18 m 2 0.55×10 -18 m 2 0.75×10 -18 m 2 1.02×10 - 18 m 2 1.38×10 -18 m 2 1.85×10 -18 m 2 2.47×10 -18 m 2 Change in total penetration rate =9.11×10 -18 m 2 .

[0041] ③ Energy storage efficiency parameters (energy dissipation in a single cycle) ): 1.2J, 2.5J, 4.1J, 6.0J, 8.3J, 11.0J, 14.2J, 18.1J, 22.8J, 28.5J, 35.4J, 43.8J; Total energy dissipation =195.9J.

[0042] ④ Environmental safety parameters (acoustic emission ring count) ): 12 times, 28 times, 45 times, 65 times, 90 times, 120 times, 158 times, 205 times, 265 times, 342 times, 442 times, 572 times; Total ring count =2344 times.

[0043] (2) Calculation of single and cumulative evaluation scores (step S2) Taking the 6th level cycle as an example, calculate the single and cumulative evaluation scores for each dimension: ① Surrounding rock stability dimension: The total residual strain of the first 6 stages = 0.002 + 0.005 + 0.009 + 0.014 + 0.021 + 0.030 = 0.081‰ Single cycle evaluation quantity Cumulative ratings ②Sealing dimension: The total change in permeability for the first six stages = 0.03 + 0.07 + 0.12 + 0.19 + 0.28 + 0.40 = 1.09 × 10⁻⁶ -18 m 2 Single cycle evaluation quantity Cumulative ratings ③ Energy storage efficiency dimension: The total energy dissipated by the first 6 stages = 1.2 + 2.5 + 4.1 + 6.0 + 8.3 + 11.0 = 33.1 J Single cycle evaluation quantity Cumulative ratings ④ Environmental safety dimension: The total number of ring counts for the first 6 levels = 12 + 28 + 45 + 65 + 90 + 120 = 360 times Single cycle evaluation quantity Cumulative ratings By calculating the cumulative evaluation value of all 12 cycles using the same method, the degradation evolution curves for each dimension can be obtained.

[0044] (3) Multi-factor fusion and comprehensive evaluation index calculation (step S3) ①Indicator Standardization: In this embodiment, the cumulative evaluation quantity has been mapped to the [0,1] interval through total normalization and is directly used as the standardized indicator. .

[0045] ②Basic weights: A judgment matrix is ​​constructed using the analytic hierarchy process (AHP) to calculate the basic weights for rock stability. airtightness Energy storage efficiency Environmental safety .

[0046] ③ State adjustment function: adopts Among them, the degradation sensitivity coefficient is the surrounding rock stability. airtightness Energy storage efficiency Environmental safety .

[0047] ④ Comprehensive evaluation index: according to the formula calculate.

[0048] Example of a level 6 loop calculation: , , , , molecule = Denominator = It has been determined that the energy storage is in a stable operation phase.

[0049] Example of a level 9 loop calculation: Cumulative evaluation scores for each dimension: , , , State adjustment function: , , , Calculated , in The interval is determined to be the stage of energy storage performance degradation.

[0050] Cycle 12 (before specimen failure): The cumulative evaluation scores for each dimension approach 1, and the calculated scores are... It was determined to be in the risk stage of the energy storage system.

[0051] (4) Verification of method validity (step S5) In this embodiment, the comprehensive evaluation index exhibits a clear three-stage evolution characteristic of "slow growth - accelerated growth - rapid growth" with the number of cycles, which is completely consistent with the damage evolution law of the granite sample: The first to sixth cycle stages correspond to the initial compaction and stable deformation stages, with the comprehensive index increasing slowly, which is consistent with the characteristics of the initial stable operation of the energy storage system. Cycle levels 7-10 correspond to the stable development stage of damage, with the comprehensive index increasing rapidly, corresponding to the mid-term stage of gradual performance degradation of the energy storage system. Cycle levels 11-12 correspond to the stage of accelerated damage penetration, with a sharp increase in the comprehensive index, representing the later stage of high risk for the energy storage system.

[0052] Compared with single-factor evaluation, the comprehensive evaluation index of this invention has a smoother transition, can take into account both safety and efficiency dimensions, and is more sensitive to the deterioration of key safety factors such as sealing performance and surrounding rock stability. It effectively avoids evaluation misjudgment caused by fluctuations of a single factor, and verifies the accuracy and effectiveness of the method.

[0053] Example 2: Field Engineering Application (Salt Cavern Hydrogen Energy Storage Chamber) This embodiment applies the method to the operation monitoring of a deep underground hydrogen energy storage chamber in a salt cavern. The chamber is buried at a depth of 800m, with a designed working pressure of 12MPa. It has been in operation for 3 years and has completed a total of 120 energy storage and release cycles.

[0054] By using the surrounding rock convergence deformation sensor, gas leakage rate monitoring system, circulating energy metering system and microseismic monitoring system installed in the chamber, four types of parameters are collected in real time: surrounding rock convergence deformation, gas leakage rate, circulating energy efficiency ratio and microseismic event frequency. These parameters correspond to the four evaluation dimensions of the present invention: surrounding rock stability, sealing performance, energy storage efficiency and environmental safety.

[0055] Substituting the monitoring data into the evaluation model of this invention, the current comprehensive evaluation index of the chamber is calculated. The system is currently in a stable energy storage operation phase, with all performance indicators in good condition, and can maintain normal operation. Meanwhile, based on the dynamic changes in weights identified by the variable weight model, the actual weight of the sealing dimension has increased by approximately 4.2% compared to the base weight, suggesting that the evolution trend of gas sealing performance should be closely monitored in subsequent operations, and sealing inspections and maintenance should be arranged in advance.

[0056] This embodiment verifies that the method can be directly connected to the engineering site monitoring system to realize real-time dynamic evaluation and risk warning of deep underground energy storage systems, and has good engineering applicability and promotion value.

[0057] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A comprehensive evaluation method for deep underground energy storage based on variable weight multi-factor fusion, characterized in that, Includes the following steps: S1. Conduct graded cyclic loading-unloading tests simulating deep underground energy storage conditions, and simultaneously collect evaluation parameters in four dimensions: surrounding rock stability, sealing performance, energy storage efficiency, and environmental safety. S2. Based on the collected parameters, calculate the single-cycle evaluation value and the total cumulative evaluation value for each dimension. S3. Standardize the various cumulative evaluation quantities, and construct a multi-factor fusion evaluation model in combination with the variable weight theory to calculate the comprehensive evaluation index of deep earth energy storage. S4. Based on the value range of the deep underground energy storage comprehensive evaluation index, divide the entire life cycle operation stage of deep underground energy storage, and match the corresponding hierarchical early warning rules and operation and maintenance management strategies to achieve comprehensive evaluation of deep underground energy storage.

2. The method according to claim 1, characterized in that, Step S1 specifically includes: Rock samples taken from the target deep-ground energy storage chamber were subjected to confining pressure at the corresponding burial depth to simulate deep geostress conditions, and a temperature field was applied to simulate high deep geothermal temperatures and temperature fluctuations during the energy storage process. The axial pressure was gradually increased according to the actual operating pressure of the energy storage chamber and then unloaded to the initial load. The load was cyclically applied until the sample underwent macroscopic failure to simulate the "energy storage-release" cycle. Within each load-unload loop, four types of evaluation parameters are collected synchronously: (1) Surrounding rock stability parameters: residual strain after unloading to the initial load ; (2) Sealing parameters: Permeability at the start of loading Permeability at the end of unloading The difference ; (3) Energy storage efficiency parameters: energy dissipation in a single cycle It is obtained by integrating the load-displacement curve; (4) Environmental safety parameters: acoustic emission ring count within a single cycle .

3. The method according to claim 1, characterized in that, In step S2, the calculation methods for the single-cycle evaluation and cumulative evaluation of the four dimensions are as follows: (1) Surrounding rock stability dimension: Evaluation quantity per cycle: Cumulative number of reviews: (2) Sealing dimension: Evaluation quantity per cycle: Cumulative number of reviews: (3) Energy storage efficiency dimension: Evaluation quantity per cycle: Cumulative number of reviews: (4) Environmental safety dimension: Evaluation quantity per cycle: Cumulative number of reviews: Where i is the current loop count and j is the loop number; , , , These are the total residual strain, total permeability change, total dissipated energy, and total acoustic emission ring count for all cycles before the rock sample fails.

4. The method according to claim 1, characterized in that, Step S3 specifically includes: S31. Standardization of Indicators: The extreme value normalization method is used to uniformly map the four types of cumulative evaluation quantities to the [0,1] interval to obtain standardized indicators. j=1, 2, 3, 4 correspond to the dimensions of surrounding rock stability, sealing performance, energy storage efficiency, and environmental safety, respectively; S32. Determining Basic Weights: A judgment matrix is ​​constructed using the analytic hierarchy process (AHP) to calculate the basic weights for each dimension. ; S33. Variable Weight State Adjustment: Constructing the State Adjustment Function The actual weights are dynamically adjusted based on the degree of degradation of each dimension indicator. S34. Calculation of Comprehensive Evaluation Index: Combining basic weights, state adjustment function, and standardized indicators, a weighted comprehensive evaluation index for deep underground energy storage is obtained. .

5. The method according to claim 4, characterized in that, In step S32, the basic weight allocation ratio is as follows: sealing performance 35%, surrounding rock stability 30%, energy storage efficiency 20%, and environmental safety 15%.

6. The method according to claim 4, characterized in that, The expression for the state adjustment function is: in, The degradation sensitivity coefficient is 3 for the sealing performance dimension and the surrounding rock stability dimension, and 2 for the energy storage efficiency dimension and the environmental safety dimension.

7. The method according to claim 4, characterized in that, The formula for calculating the comprehensive evaluation index of deep underground energy storage is as follows: The comprehensive evaluation index ranges from [0,1]. The larger the value, the higher the overall deterioration of the deep-earth energy storage system and the greater the safety risk.

8. The method according to claim 4, characterized in that, In step S4, the specific details of the full-cycle operation phase and hierarchical operation and maintenance strategy for deep underground energy storage are as follows: when When the energy storage is deemed to be in a stable operation phase, routine monitoring will be conducted to maintain normal energy storage and release operations. when When the energy storage performance is in a deterioration phase, the monitoring frequency should be increased, the charging and discharging pressure and rate should be appropriately reduced, the evolution trend of sealing performance should be assessed, and reinforcement and maintenance measures should be taken if necessary. when If the situation is determined to be a risky stage for the energy storage system, the energy storage operation should be immediately stopped, a comprehensive safety assessment should be conducted, the emergency plan should be activated, and reinforcement and remediation measures should be taken.

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