A tidal current energy array site selection method based on a three-dimensional high-precision numerical model

Abstract

The present application relates to the field of ocean energy development and utilization, and particularly relates to a tidal current energy array site selection method based on a three-dimensional high-precision numerical model, comprising the following steps: (1) a macro site selection method; (2) a micro site selection method; (3) a high-precision layered three-dimensional numerical model building method; (4) a tidal current energy resource refinement evaluation method; by analyzing the model calculation results, the characteristics of the target sea area, such as the spring high-water rapid-falling rapid time, the neap high-water rapid-falling rapid time, the tidal current stability, the energy flow density, the tidal current energy resource theoretical reserves, the single-width energy flow flux, and the like, are analyzed, and the evaluation results are presented through a visual technology to guide the placement mode of the tidal current energy unit; compared with the traditional two-dimensional or simplified three-dimensional model, the evaluation accuracy is greatly improved. The tidal current characteristics at different water depths can be simulated in detail, so that the tidal current energy resource evaluation is more comprehensive and accurate.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of ocean energy development and utilization, and particularly relates to a tidal current energy array field site selection method based on a three-dimensional high-precision numerical model. BACKGROUND

[0002] With the continuous growth of global energy demand and the increasing severity of environmental problems, developing renewable energy has become an important direction of global energy strategy. Tidal current energy, as a clean, renewable and stable energy resource, has gradually become an important research object in the field of ocean energy development due to its abundant reserves and wide distribution. Tidal current energy utilization mainly relies on tidal current generators to convert the kinetic energy of seawater into electrical energy, and efficient and reasonable selection of the deployment location of the tidal current energy array field plays a key role in improving energy capture efficiency and reducing costs. Therefore, the site selection method of the tidal current energy array field is a crucial technical link in the development process of tidal current energy.

[0003] At present, most of the tidal current field site selection methods are based on two-dimensional numerical simulation or analysis of a single tidal current condition, and the complex three-dimensional flow field characteristics and their temporal and spatial variations in the tidal current field are not fully considered. Traditional methods often lack precision in tidal current resource assessment, especially in areas with complex topography and variable tidal currents, and existing technologies are difficult to accurately reflect the vertical variation and energy distribution of tidal currents. In addition, the local topographic changes of the tidal current field have a great influence on the deployment of the unit, which is difficult to accurately simulate in traditional models. These deficiencies restrict the precision of tidal current unit deployment and energy utilization, and limit the efficient development and utilization of tidal current energy.

[0004] In order to overcome the shortcomings of the prior art, there is an urgent need for a tidal current energy array field site selection method that can comprehensively consider the three-dimensional characteristics of the tidal current field and has high precision. The present application is based on a three-dimensional high-precision numerical model, which combines macro-site selection and micro-site selection to construct a three-dimensional tidal current numerical model that can truly reflect the distribution and variation of tidal current energy resources. By analyzing parameters such as the time of spring tide rise and fall, the time of neap tide rise and fall, tidal current stability, energy flow density, theoretical reserves, and single-width energy flow flux, the reserves and developability of tidal current energy resources can be finely assessed. Through this method, rapid and accurate tidal current energy resource assessment can be achieved, providing a reliable theoretical basis for the array deployment of tidal current units, responding to the development policy of "scale utilization of ocean energy", and promoting the sustainable development of ocean energy development in China. SUMMARY

[0005] The purpose of the present application is to provide a tidal current energy array field site selection method based on a three-dimensional high-precision numerical model to solve the problems of insufficient precision of the model, difficulty in capturing vertical changes of the tidal current field, and difficulty in optimizing the deployment method of the tidal current unit under complex topography and variable tidal conditions in the prior art.

[0006] The technical solutions adopted by the present application are as follows:

[0007] A tidal current energy array site selection method based on a three-dimensional high-precision numerical model, the method comprising the following steps:

[0008] (1) Macroscopic site selection method: according to historical tidal current data, seabed topography data and macroscopic distribution of energy flow density, combined with geological survey results, preliminarily determine the sea area range suitable for tidal current energy development from a macroscopic level;

[0009] (2) Microscopic site selection method: on the basis of macroscopic site selection, through local measurement and flow field analysis, considering the influence of topographic changes, tidal current conditions and shoreline morphology on the placement of tidal current energy unit, further accurately delimit the microcosmic site selection range of the array field; the contents of local measurement and flow field analysis include using a high-precision positioning system to calibrate the geographic coordinates of the sea area, using a sonar instrument to measure the water depth, and using a current profiler to monitor the sea area flow velocity and flow direction;

[0010] (3) High-precision layered three-dimensional numerical model building method: based on the geographic position, water depth data and seabed topography data of the microcosmic site, a layered three-dimensional numerical model is constructed, the model includes unstructured grid generation, dynamic boundary condition setting, tidal simulation, and calibration combined with measured and simulated data, so that the model can accurately reflect the tidal current dynamic characteristics of the target sea area;

[0011] (4) Tidal current energy resource fine evaluation method: by analyzing the model calculation results, analyzing the characteristics of the target sea area such as spring tide rise and fall, neap tide rise and fall, tidal stability, energy flow density, tidal current energy resource theoretical reserves, single-width energy flow flux, etc., and presenting the evaluation results through visualization technology to guide the placement of tidal current energy units.

[0012] The macroscopic site selection method is realized by the following steps:

[0013] a) Combined with multi-source data, including ocean hydrology, geological exploration and remote sensing satellite data, preliminarily determine the topographic profile and tidal current spatio-temporal distribution characteristics of the target sea area;

[0014] b) Multi-dimensional analysis of the interaction of tidal current, wave and wind flow in the target sea area, and selecting regions with high flow velocity, high energy flow density and good stability as candidate array field positions.

[0015] The microcosmic site selection method comprises:

[0016] a) Geographical position calibration, water depth measurement, seabed topography fine investigation and real-time tidal current field monitoring are carried out on the candidate array field positions to generate refined tidal level, flow velocity and flow direction distribution map;

[0017] b) Analyze the tidal current characteristics of the sea area based on actual data, and determine the deployment area of ​​tidal power units based on seabed topography.

[0018] c) Employ a multi-parameter evaluation model that considers topography, flow velocity, environmental factors, eddy current effects, potential obstacles, and construction feasibility to select a suitable location for the unit.

[0019] The method for building a high-precision layered three-dimensional numerical model includes:

[0020] a) A three-dimensional numerical model of the target sea area was constructed using unstructured mesh technology, and a layered processing method was adopted to simulate the changes in water velocity at different depths;

[0021] b) The model boundary conditions employ a dynamic harmonic method, combined with tidal current fractionation and large eddy simulation techniques, to handle complex tidal boundary problems, enhance the ability to capture tidal flow details, and achieve high-precision shoreline fitting.

[0022] c) Compare and optimize the model results with the measured data to ensure that the spatiotemporal accuracy of the model reaches the allowable error range for engineering.

[0023] The refined assessment method for tidal energy resources includes:

[0024] a) Based on the output of the three-dimensional model, organize the velocity and direction data of the complete tidal cycle in the target sea area to determine the moments of rapid rise and fall of spring tides and neap tides, and then determine the maximum potential of tidal energy resources in the target sea area and the tidal characteristics at moments of low energy flow density.

[0025] b) Assess the stability of the tidal currents within the region, including flow direction rotation and velocity asymmetry, using the following formula:

[0026] α θ =180°-|θ e -θ f |

[0027] α v =|1-v e / v f |

[0028] In the formula, α θ For the rotational nature of the current direction, θ f θ e These represent the principal axis directions during high and low tide, α v For the symmetry of the tidal current velocity, v f and v e These represent the average current velocity during high tide and low tide, respectively.

[0029] c) Based on the three-dimensional model of the flow rate data, the average flow rate data and the maximum flow rate data of the target sea area in a period are sorted out, and the average energy flow density and the maximum energy flow density of the tidal current energy are calculated, using the following formula:

[0030]

[0031] In the formula, P m is the average energy flow density of a complete tidal current period, ρ is the density of seawater, is the average velocity of tidal current in a complete tidal current period, P smax is the maximum energy flow density of a complete tidal current period, V smax is the maximum velocity of tidal current in a complete tidal current period.

[0032] d) According to the above tidal current energy resource reserve evaluation method, a plurality of sections with relatively rich tidal current energy resources are selected, and the theoretical reserve of tidal current energy passing through a specific waterway section in a period is calculated, using the following formula:

[0033]

[0034] In the formula, P theoretical is the theoretical reserve of tidal current energy; t is the initial time; T is the evaluation period, usually one year; L is the width of the waterway; V is the flow velocity of the tidal current.

[0035] In the actual evaluation of the theoretical reserve of tidal current energy, it is usually difficult to obtain continuous flow rate data. Relatively speaking, it is easier to obtain discrete flow rate data at a specific time and place. In order to adapt to this data availability situation, the Flux method is used to estimate the theoretical reserve of tidal current energy, and the formula is as follows:

[0036] P theoretical = P m · A

[0037] In the formula, A is the area of the waterway section.

[0038] e) Since the water depth of the target water area is deep, the waterway changes significantly with the water depth, in order to fully evaluate the tidal current energy resources of the waterway, the section with the largest theoretical reserve is selected, and the single-width energy flow flux, i.e. the energy flow flux per unit width, is further evaluated, using the following formula:

[0039]

[0040] In the formula, P is the energy flow flux, and h is the water depth.

[0041] However, since the flow velocity changes significantly with the depth, the flow velocity can be regarded as a function of the depth z, and therefore the energy flow flux can be expressed as:

[0042]

[0043] The vertical distribution of tidal current velocity generally presents the characteristics of exponential distribution, and the following several exponential distribution forms are commonly used for expression:

[0044]

[0045] In the formula, v0 is the surface flow velocity, alpha is the flow velocity profile change coefficient, which can be calculated according to the specific sea area by using the least square method, C is the residual flow velocity of the tidal current, and beta is the correction coefficient, which is used to adjust the model to better match the actual situation.

[0046] Finally, the most suitable exponential distribution form is brought into the expression of the single-width energy flow flux, that is, the following formula can be obtained:

[0047]

[0048] In the formula, h1 and h2 are the water depths of any two points (|h1|<|h2|), v exp (z) is the flow velocity at the depth z, the most suitable exponential distribution form is P u (z) is the flow velocity at the depth z, the most suitable exponential distribution form is P

[0049] f) The evaluation results of the tidal current energy resource are displayed through a visualization technology, including key indexes such as tidal current, tidal level, flow direction, flow velocity, flow direction stability and energy flow density.

[0050] The unstructured grid generation technology uses triangular or tetrahedral grid units to improve the simulation precision of complex topography in the calculation area, and improves the precision of key areas (such as areas with large fluctuations along the coast or seabed) through grid encryption processing.

[0051] The vortex and turbulent flow analysis in the evaluation method adopts the large eddy simulation technology, and the three-dimensional distribution of vortex and turbulent flow is calculated through refined grids to evaluate the influence range and degree of vortex and turbulent flow on the unit.

[0052] The method is particularly suitable for coastal sea areas with complex topography and multiple tidal currents, wave and wind flow interactions, and through three-dimensional high-precision modeling and layered data fusion, the spatial distribution characteristics of tidal current energy can be accurately reflected, and comprehensive decision support for the placement of tidal current energy units can be provided.

[0053] The innovation of the present application lies in that a high-precision layered three-dimensional numerical model is adopted, which can capture the flow velocity and energy flow density distribution of different water depth levels in detail. The layered model combines unstructured grid division and layered processing, so that the model can not only reflect the horizontal change of the tidal current, but also accurately depict the vertical direction of the tidal current dynamic.

[0054] The innovation of the present application is to propose the multi-dimensional tidal current energy resource evaluation parameters such as the rise and fall of spring and neap tides, tidal current stability, energy flow density, and single-width energy flow flux. These evaluation parameters provide a detailed and comprehensive analysis of the tidal current field, making the evaluation results more scientific and accurate. Combined with the visual technology to display the evaluation results, clear guidance is provided for the scientific placement of tidal current energy units.

[0055] The present application has the following outstanding and beneficial technical effects compared with the prior art:

[0056] 1. The present application adopts a high-precision layered three-dimensional numerical model, which can accurately capture the flow velocity changes of the tidal current field in the vertical and horizontal directions, especially in complex terrain and variable tidal current conditions. Compared with traditional two-dimensional or simplified three-dimensional models, the evaluation accuracy is greatly improved. The model can simulate the tidal current characteristics at different water depths through unstructured grid division and layering, making the tidal current energy resource evaluation more comprehensive and accurate.

[0057] 2. The present application combines macro and micro site selection methods, from preliminary site selection in a large area to local precise site selection, providing a combination of global and local refinement. Macro site selection quickly locks in high-quality sea areas for tidal current energy development, and micro site selection conducts in-depth analysis of local characteristics, avoiding the uncertainty of single-scale evaluation in the prior art, greatly improving the placement efficiency and resource utilization rate of tidal current energy units.

[0058] 3. The present application proposes multiple evaluation dimensions such as the rise and fall of spring and neap tides, tidal current stability, energy flow density, and single-width energy flow flux, and comprehensively analyzes the complex characteristics of the tidal current field to ensure the reliability of the tidal current energy resource evaluation results. Compared with the relatively single evaluation method in the prior art, the present application has significantly improved in evaluation dimension and depth, and the evaluation results are more scientific and accurate, providing rich reference for the placement of tidal current array fields.

[0059] 4. The comprehensive evaluation process of the present application realizes fast and efficient resource evaluation from macro to micro, significantly shortening the time of tidal current energy development in the early stage of site selection. Compared with the traditional method of relying on a large number of field measurements and evaluations, the present application greatly improves the efficiency of resource evaluation through automated evaluation of numerical models, providing strong support for the rapid advancement of projects. BRIEF DESCRIPTION OF DRAWINGS

[0060] Figure 1 is the overall flow chart of a tidal current array field site selection method based on a three-dimensional high-precision numerical model of the present application.

[0061] Figure 2 is the macro site selection flow chart of the tidal current array field of the present application.

[0062] Figure 3The tide energy array field micro field site selection flow chart of the present application.

[0063] Figure 4 The high-precision layering three-dimensional numerical model building process flow chart of the present application.

[0064] Figure 5 The tide energy resource fine evaluation flow chart of the present application.

[0065] Figure 6 The research area range of the present application.

[0066] Figure 7 The grid building range of the research area of the present application.

[0067] Figure 8 The water depth distribution map of the entire Zhoushan sea area of the present application.

[0068] Figure 9 The water depth distribution map of the research area of the present application.

[0069] Figure 10 The tide level comparison chart of the research area of the present application in different periods.

[0070] Figure 11 The flow velocity and flow direction rose diagram of the research area of the present application.

[0071] Figure 12 The average energy flow density distribution map of the research area of the present application.

[0072] Figure 13 The maximum energy flow density distribution map of the research area of the present application.

[0073] Figure 14 The four control surface selection schematic diagram of the research area of the present application.

[0074] Figure 15 The fitting process schematic diagram of the flow velocity along the depth direction at the section C of the research area of the present application. DETAILED DESCRIPTION

[0075] As Figures 1-15As shown, the application provides a tidal current energy array field site selection method based on a three-dimensional high-precision numerical model, which can quickly and accurately select suitable tidal current energy array fields and provide reliable theoretical basis for array placement of tidal current energy units. The method includes macro-siting, micro-siting, high-precision layered three-dimensional numerical model building, and fine evaluation of tidal current energy resources. The macro-siting of the tidal current energy array field is to select a sea area with relatively rich tidal current energy resources and relatively flat seabed topography from a large sea area according to existing survey data. The micro-siting of the tidal current energy array field is to further accurately demarcate the micro-target sea area of the array field through water depth measurement and flow field analysis of a small range of sea area based on the selection of the macro-siting. The building of the high-precision layered three-dimensional numerical model is to comprehensively consider the geographic information, water depth data and seabed topography data of the target sea area determined in the early stage, construct a layered three-dimensional numerical model of the target sea area, and calibrate the model to accurately reflect the tidal current dynamic characteristics of the target sea area. The fine evaluation of tidal current energy resources is to analyze the tidal current characteristic parameters of the target sea area, including the spring tide rise and fall time, neap tide rise and fall time, tidal current stability, energy flow density, tidal current energy resource theoretical reserve, single-width energy flow flux, etc., and then present the evaluation results through visualization technology to guide the placement of the tidal current energy unit.

[0076] The research area of the embodiment is a waterway between Zhuchunshan Island and Xiaozhuchunshan Island in Zhoushan City, with geographic coordinates of 122°074'~122°078' east longitude and 29°955'~29°96' north latitude. Due to the large number of islands in Zhoushan sea area and the complex and variable seabed topography, in order to reduce the influence of small model boundary and better reflect the tidal current characteristics of the research area, the simulation range is expanded to the entire Zhoushan sea area, which is a rectangular area with geographic coordinates of 29°955'~29°96' east longitude and 29°955'~29°96' north latitude. The research area is as shown in Figure 6

[0077] The specific method of the macro-siting of the tidal current energy array field is as follows:

[0078] ​Firstly, based on multi-source data such as ocean hydrology, geological exploration and remote sensing satellites, the target sea area is preliminarily evaluated. Ocean hydrology data includes tidal level, flow velocity, flow direction, tidal flow period and spatio-temporal distribution characteristics. These data can be obtained through long-term on-site monitoring, ocean data platform and remote sensing data. Geological exploration data are mainly used to reflect the topographic profile of the target sea area, especially the topographic relief and sediment layer thickness of the seabed. Geological exploration data are derived from sonar mapping, depth detection and marine geological survey reports, which can reflect the complexity and local changes of the seabed topography in detail. Remote sensing satellite data provide a global perspective of sea surface changes, which can assist in analyzing the dynamic characteristics of tidal flow in the nearshore area. Through data fusion processing, the basic flow field characteristics of the target sea area and the accurate description of the seabed topography can be obtained.

[0079] On this basis, the spatio-temporal distribution characteristics of tidal flow in the target sea area are analyzed. Using tidal flow observation data, the spatial distribution of tidal flow velocity in the sea area is preliminarily evaluated, especially the seasonal variation of tidal flow velocity and the periodic variation of tidal flow direction. Through time series analysis of tidal flow, the area with relatively stable flow velocity is determined, and the candidate area suitable for tidal current energy development is preliminarily selected. In addition, based on the long-term observation data of tidal flow velocity, the energy flow density of the area is calculated to evaluate the theoretical reserves of tidal current energy resources. Generally speaking, the area with higher energy flow density has higher development value, so energy flow density is one of the most important evaluation parameters in the micro-site selection process.

[0080] Secondly, in the preliminarily determined target sea area, the interaction of tidal flow, wave and wind flow is analyzed in multiple dimensions. Tidal flow is the main energy source, but the coupling effect of wave and wind flow may disturb the tidal flow field, especially in shallow sea and coastal areas, the influence of wave on tidal flow is particularly significant. Through numerical simulation, the influence of wave and wind flow on tidal flow under different seasons and weather conditions is evaluated in detail, especially the disturbance degree of wave and wind flow on tidal flow velocity and direction. With the aid of large eddy simulation model, the local influence of eddy current and turbulent flow on the flow field is further studied to ensure that the selected candidate area not only has high flow velocity but also has stable energy flow density, which is suitable for the placement of tidal current energy units.

[0081] After multi-dimensional analysis, the area that meets the following conditions is finally selected as the candidate tidal current energy array field: high flow velocity, high energy flow density, good tidal flow stability, less influence of eddy current and turbulent flow, gentle seabed topography, and suitable for the placement and construction of tidal current energy units. In this process, special attention should be paid to the long-term stability of tidal current energy development to ensure that the energy output change range of tidal current energy resources during spring tide and neap tide is controllable, and the long-term operation safety of equipment is considered.

[0082] The specific method of micro-site selection of the tidal current energy array field is as follows:

[0083] First, fine geographic positioning, water depth measurement, seabed topography investigation, and real-time tidal current field monitoring are implemented for the candidate array field area. In this stage, high-precision satellite positioning systems such as DGPS are used for geographic positioning of the target sea area to ensure the accuracy and rationality of spatial layout of the selected area. At the same time, multi-beam echo sounder instruments are used to accurately measure the water depth of the target sea area, generating a water depth profile. This step is particularly important because the installation of tidal current energy units needs to fully consider the water depth to ensure that the units can maintain normal operation under different tidal current conditions. Next, fine investigation of seabed topography is implemented, using side-scan sonar and geological exploration instruments to scan the seabed and record the ups and downs of the seabed, sediment distribution, and the presence of underwater obstacles. Seabed investigation not only serves to confirm the stability of the foundation during unit placement, but also provides key data for subsequent construction. In terms of tidal current field monitoring, Doppler acoustic current profiler is used to monitor the tidal current velocity and direction in the area in real time, record the changes of tidal level, velocity and direction in different tidal stages, and generate a detailed tidal current field distribution map. These data can help further analyze the distribution and stability of tidal current energy resources.

[0084] After completing the above data collection, the tidal current characteristic analysis stage is entered. In this stage, the tidal current change characteristics of the target sea area need to be analyzed based on the monitoring data of tidal level, velocity and direction, especially the velocity characteristics during spring tide and neap tide and the periodic fluctuations of tidal current. At the same time, based on the investigation data of seabed topography, the interaction between seabed topography and tidal current is analyzed in depth. Seabed undulations may cause local tidal current velocity to increase or decrease, thereby affecting the power generation efficiency of the unit, so the disturbance effect of seabed topography on tidal current velocity and direction must be evaluated in detail. Through the detailed analysis of tidal current flow field, the preliminary areas for tidal current energy unit placement are determined, which need to have high and stable tidal current velocity, suitable water depth and smooth seabed topography, laying a foundation for subsequent evaluation.

[0085] Next, a multi-parameter comprehensive evaluation model is used to conduct in-depth evaluation on the determined tidal current energy unit placement position. The model combines seabed topographic features, vortex effect, potential obstacles, and construction feasibility and other key factors for comprehensive analysis. First, the seabed topographic features are analyzed, including the influence of seabed undulations on tidal current velocity, seabed slope, and local topography on the formation of turbulence. The height difference of the seabed can cause changes in local tidal current velocity, especially when there are obvious highlands or gullies on the seabed, the tidal current will speed up or slow down in these areas, forming local high-velocity or low-velocity areas. This phenomenon can cause the tidal current energy unit to be unable to fully utilize tidal current energy in some positions, or cause structural fatigue risk due to excessive local flow velocity. If there is a large change in seabed slope, it can cause deflection of the tidal current direction, especially in areas with sharp changes in water depth, the tidal current can change greatly in flow direction with the seabed slope. This not only affects the capture efficiency of the tidal current energy unit, but also can cause uneven stress during installation of the unit, affecting the structural stability. The complexity of the seabed topography can also cause vortexes in the tidal current field, especially in areas where the seabed topography changes suddenly (such as seabed mountains, gullies, or seabed uplifts). These vortexes can cause energy loss downstream of the unit, reducing the power generation efficiency of subsequent units. In addition, the pressure fluctuations and unstable flow in the vortex area can cause additional stress on the structure of the unit, so these areas must be avoided. Then, the influence of vortex effect on unit placement is evaluated, especially when multiple units are placed in an array, the mutual interference between units can form vortexes, reducing the power generation efficiency of downstream units. By introducing large eddy simulation technology, the vortex distribution and its influence range are analyzed in detail, and the unit placement position is optimized to ensure the maximum efficiency of each unit in the array. Second, potential seabed obstacles such as sunken ships, rocks, sediment protrusions, etc. are checked to ensure the safety and stability of the unit placement. On this basis, the construction feasibility of the placement area is analyzed, including seabed bearing capacity, complexity of geological structure, and installation and maintenance conditions of construction equipment, to ensure that the unit can be safely and stably placed and operated for a long time.

[0086] The specific method for building the high-precision layered three-dimensional numerical model of tidal current energy is as follows:

[0087] First, according to the target sea area of micro-siting, the geographical coordinate information and water depth point data of the sea area are sorted, and a one-to-one correspondence between the two is established, that is, each geographical coordinate information point has a water depth point corresponding to it, and then the water depth distribution of the target sea area is calculated by using the Kriging interpolation method, which can be expressed by the following formula:

[0088]

[0089] In the formula, C(x i -x j ) represents the covariance function; λ iThe weight is represented by μ, which is the Lagrange multiplier used to ensure that the sum of the weights equals 1. The water depth data of the Zhoushan sea area mainly comes from the paper nautical charts published by the China Maritime Safety Administration with the numbers 13300, 13310, 13359, 13361, 13391 and 13519.

[0090] like Figure 8 As shown in the figure, this embodiment plots a water depth distribution map of the entire Zhoushan sea area based on the interpolation results. Figure 9 As shown, to better understand the water depth and seabed topography of the Zhairuoshan Channel, water depth data for the study area were further extracted, and a more detailed three-dimensional water depth map was created using this data. The slope of the study area shows significant spatial variation, with the water depth distribution characterized by deeper depths at the eastern and western ends and shallower depths in the middle. Specifically, the western side is deeper than the eastern side. In the western region, the slope is steeper, and the water depth changes rapidly, reaching a maximum depth of approximately 55 meters. In contrast, the slopes in the central and eastern regions are relatively gentler, and the water depth typically remains between 20 and 25 meters.

[0091] Secondly, the model is constructed using unstructured mesh technology. To adapt to the complex topography and tidal current characteristics of the target sea area, unstructured meshes are used for three-dimensional numerical simulation. This technology, through flexible mesh generation, especially in areas near the shoreline and areas with significant seabed undulations, enables high-precision topographic fitting and detailed characterization of the tidal field. During model construction, detailed data on water depth, shoreline, and topography of the target sea area are first collected. Based on this data, the mesh density is locally refined according to the complexity of the topography, particularly in areas such as the shoreline, islands, and shoals, to improve the simulation accuracy of these key areas. To further improve the vertical analytical accuracy of the model, a layered processing technique is employed, dividing the water body into multiple water layers and setting different velocity variation zones from the surface to the seabed based on water depth changes. This layered processing method effectively captures the vertical velocity gradient changes of the tidal current, especially at the boundary between deep and shallow water areas, where the model can accurately simulate subtle changes in the tidal field, ensuring a precise assessment of the distribution of tidal energy resources. Based on the above construction of unstructured grids, stratification of water bodies, and fine-grained delineation of shorelines, a stratified numerical model based on the target sea area can be built.

[0092] Then, in terms of boundary condition setting, the present application adopts a dynamic reconciliation method to ensure that the complex boundary problems of the tidal current field can be effectively handled during the simulation process. The boundary conditions simulate the periodic changes of the tidal current by combining the main tidal components of the tidal current. These components are input into the model after accurate reconciliation analysis, providing a basis for the dynamic changes of the boundary conditions of the tidal current field. In order to further improve the simulation accuracy, the large eddy simulation technique is used to finely process the turbulence and vortex flow in the tidal current field. The large eddy simulation can capture the transient changes of large-scale turbulence in the tidal current field, especially in the local vortex flow area formed when the tidal current flows through complex topography or encounters seabed obstacles. Through this technique, the model can accurately simulate the influence of vortex flow on tidal current energy resource distribution, ensuring high accuracy in tidal current energy resource assessment under complex boundary conditions. Based on the above, through dynamic reconciliation analysis of the tidal current boundary, input of tidal current components, and fine processing of turbulence and vortex flow using large eddy simulation, a high-precision stratified three-dimensional numerical model based on the target sea area is established.

[0093] After the model is built, the simulation results are compared with the measured data and error analysis is performed to ensure that the accuracy of the model meets the engineering requirements. In this stage, multiple key parameters such as tidal level, flow velocity, flow direction, etc. are selected for verification, and the measured data mainly comes from the field tidal observation system (such as ADCP) and historical data. Multiple statistical error analysis indicators are introduced, including mean absolute error, mean relative error, root mean square error, correlation coefficient and technical score, etc. By comparing the simulation results and measured data in different time periods, the spatio-temporal error distribution of the model is determined, the error sources are analyzed and optimized.

[0094] To ensure the accuracy of the hydrodynamic model used in this study, the model was calibrated using the observation data from Station 1, as shown in Figure 6 During the calibration of the model, special attention was paid to the two key parameters of bed friction and vortex viscosity. Bed friction directly affects the degree of flow velocity reduction in the model, while vortex viscosity affects the turbulence characteristics and mixing effect of the fluid. By repeatedly adjusting key parameters such as bed friction and vortex viscosity, the difference between the model simulation values (tidal level, flow velocity and flow direction) and the measured values is minimized.

[0095] Figure 10 The comparison between the tidal level simulation results obtained by the three-dimensional model during spring tide, medium tide and neap tide and the measured results is shown. It can be seen that the simulation results of the model in amplitude and phase show good consistency with the measured results.

[0096] If the error exceeds the engineering allowable range, the initial conditions, boundary conditions and grid density of the model are adjusted using optimization algorithms until the error is controlled within the requirements of engineering design. During the optimization adjustment process, special attention is paid to the changes of tidal current velocity under different tidal conditions and the disturbance effect of eddy current on tidal current field, to ensure the prediction accuracy of the model in different time scales and spatial scales. Finally, a high-precision stratified three-dimensional numerical model that meets the characteristics of tidal current in the target sea area is obtained.

[0097] Mean relative error:

[0098] Mean relative error:

[0099] Root mean square error:

[0100] Correlation coefficient:

[0101]

[0102] In the formula, mod is the simulation value, obs is the observed value, N is the time series, is the average value of the simulation value, is the average value of the observed value. The closer the values of mean relative error, mean absolute error and root mean square error to 0, the better the calculation effect of the model; the closer the correlation coefficient and the technical score to 1, the closer the simulation value to the observed value.

[0103] The accuracy of the model tidal level is evaluated by using five statistical indicators of mean relative error, mean absolute error, root mean square error, correlation coefficient and technical score, and the calculation results are shown in Table 1. From the data in the table, it can be seen that the model simulated tidal level has high consistency with the measured results, the error level is low, and the correlation is significant.

[0104] Table 1 Calculation results of tidal level statistical indicators

[0105]

[0106] The specific method of the tidal current energy resource fine evaluation is as follows:

[0107] Firstly, based on the output results of the three-dimensional numerical model, the system organizes the flow velocity and direction data within a complete tidal cycle in the target sea area. The three-dimensional numerical model can output the tidal current field at different time periods, including the temporal and spatial variations of flow velocity and direction. Through these data, the change of tidal current direction is analyzed, and then the time of flood, ebb and slack during spring tide and neap tide is determined. During spring tide, the change of flow velocity and direction is relatively severe, usually showing high flow velocity and rapid adjustment of tidal current direction, which represents the maximum potential time of tidal current energy resources. By accurately analyzing the time nodes of flood, ebb and slack, the peak value of tidal current energy resources can be determined; during neap tide, the change of flow velocity and direction is relatively slow, and the flow velocity is low, which represents a period of low energy flow density, which is crucial for the selection of tidal current energy units. When analyzing the flow velocity changes during spring tide and neap tide, not only the extreme points of tidal current should be concerned, but also the duration and frequency of tidal current change should be considered, so as to more comprehensively evaluate the spatial and temporal distribution characteristics of tidal current energy resources.

[0108] Then, the stability of tidal current in the region is evaluated. The stability of tidal current directly affects the power generation efficiency of the unit and the reliability of equipment operation, especially in the sea area where the flow velocity has obvious asymmetry and the flow direction has significant rotation, which will interfere with the effect of tidal current energy capture.

[0109] This embodiment extracts the flow velocity and direction data of No. 1 station from the model, and draws the flow velocity and direction rose diagram of the station, as shown in Figure 11 During spring tide, the flow velocity distribution extends to both ends, and part of the area exceeds 2 m / s, indicating that there may be intermittent strong current in this area. During neap tide, the flow velocity changes slightly, and the overall flow velocity slows down, and no particularly high or low flow velocity is observed. During neap tide, the flow velocity is mainly concentrated around 1 m / s, with a small change range, indicating that the flow velocity in this area is relatively stable during neap tide, and the flow direction is also relatively consistent. Overall, the flow velocity and direction of the study area remain relatively stable.

[0110] In order to accurately quantify the stability of tidal current, the present application adopts two indexes of flow velocity asymmetry and flow direction rotation to evaluate the stability of tidal current, and the formulas are as follows:

[0111] α θ =180°-|θ e -θ f |

[0112] α v =|1-v e / v f |

[0113] In the formula, α θ is the rotation of tidal current direction, θ f is the main axis direction during flood tide, and θ eis the direction of the principal axis during ebb tide, a v is the symmetry of tidal current velocity, v f is the average velocity during flood tide, v e is the average velocity during ebb tide. This formula can effectively evaluate the flow direction rotation (i.e. the degree of flow direction deflection) and the asymmetry of flow velocity (i.e. the difference in flow velocity between flood tide and ebb tide) by analyzing the time series of flow velocity and flow direction. When the flow direction deflection is large or the flow velocity asymmetry is significant, the energy capture efficiency of the unit may be affected, so the tidal current stability evaluation is crucial for optimizing the placement of the unit. By calculating the tidal current stability index in different time periods, we can identify areas suitable for long-term stable power generation. Table 2 below shows the calculation results of tidal current stability in the study area.

[0114] Table 2 Tidal current characteristics calculation results

[0115] Tidal current characteristic parameters Values Tidal current energy characteristic parameters Values Mean current velocity (m / s) 1.51 Maximum current velocity (m / s) 3.83 Mean channel depth (m) 21.15 Maximum channel depth (m) 35.44 Mean current velocity during flood (m / s) 1.83 Mean current velocity during ebb (m / s) 1.37 Principal axis direction during flood (°) 243.7 Principal axis direction during ebb (°) 66.9 Standard deviation of current direction during flood (°) 2.93 Standard deviation of current direction during flood and ebb (°) 5.16 Symmetry of current velocity 0.2514 Rotation of current direction (°) 3.3

[0116] After completing the tidal current stability evaluation, based on the flow velocity data of the three-dimensional model, the average flow velocity data and the maximum flow velocity data in the complete tidal cycle in the target sea area are sorted out. The average flow velocity reflects the stable output level of tidal current energy in the entire tidal cycle, while the maximum flow velocity represents the extreme state that the tidal current may reach in a certain period of time. Based on these flow velocity data, the average energy flux density and the maximum energy flux density of tidal current energy are further calculated using the following formulas:

[0117]

[0118] where P m is the average energy flux density of a complete tidal cycle, p is the density of seawater, is the average velocity of tidal current in a complete tidal cycle, P smax is the maximum energy flux density of a complete tidal cycle, V smax is the maximum velocity of tidal current in a complete tidal cycle. Through these two formulas, the energy output potential of tidal current energy at different flow velocities can be calculated, especially under the condition of maximum flow velocity, the peak energy flux density of tidal current energy resources can be evaluated. The average energy flux density represents the long-term stable output capacity of tidal current energy resources, which is of great significance for the economic evaluation of the unit. By extracting the flow velocity data of the study area, it is found that the area with flow velocity exceeding 2.2 m / s is relatively wide, especially in the eastern channel, the flow velocity is significantly higher than in the west. The average energy flux density P m of the entire study area is calculated, and the average energy flux density distribution map of P Figure 12 is drawn. The average energy flux density of this channel is between 0.4 kW / m 2 and 2.8 kW / m 2The maximum tidal flow density in the study area is significantly higher than that of surrounding waterways, highlighting the potential for tidal energy development in this region. The maximum energy flow density of the study area was calculated, and the results were plotted. Figure 13 The peak energy flux density distribution is shown in the figure. It can be seen from the figure that the maximum energy flux density in most areas reaches 3.2 kW / m². 2 The above values ​​are also found in a wide range of areas.

[0119] Next, based on the assessment method for tidal energy resource reserves, several sections with relatively abundant tidal energy resources were selected from the target sea area, and the theoretical tidal energy reserves in these sections were further calculated. The formula is as follows:

[0120]

[0121] In the formula, P theoretical t is the theoretical potential of tidal energy; t is the initial moment; T is the evaluation period, usually one year; L is the width of the channel; V is the tidal velocity.

[0122] In practical engineering, obtaining continuous tidal flow velocity data is often challenging, while discrete velocity data at specific times and locations is usually easier to obtain. To overcome this problem, this invention employs the Flux method to process discrete velocity data and then estimate the theoretical potential of tidal energy. The calculation formula for the Flux method is as follows:

[0123] P theoretical =P m ·A

[0124] In the formula, A is the area of ​​the waterway cross section.

[0125] The Flux method can effectively integrate discrete flow velocity data to calculate the tidal energy reserves at different cross sections, ensuring accurate estimation of tidal energy potential even when data is scarce.

[0126] like Figure 14 As shown, when assessing the tidal energy resources of the study area, the spatial distribution of water depth and average energy flux density were comprehensively considered, and four key control surfaces were identified accordingly. During the selection of control surfaces, intersections with the southern and northern coastlines were deliberately avoided. The main reason for this selection is that the complex seabed topography and steep slope in this area pose difficulties for equipment installation and maintenance, and may also affect the long-term operational efficiency and safety of the equipment, making it unsuitable for deploying tidal power units. To further evaluate the tidal energy potential of the selected control surfaces, detailed calculations were performed on the main characteristic parameters of the control surfaces, including cross-sectional water depth, cross-sectional length, cross-sectional area, and theoretical tidal resources. The calculation results are shown in Table 3.

[0127] Table 3 Calculation results of cross-sectional characteristic parameters

[0128]

[0129] In the study area, Figure 14 The tidal current energy theoretical reserves of the four sections A, B, C and D in the waterway are between 2.4 MW and 9.98 MW. This change reflects the trend that the tidal current energy resources gradually increase from the west to the east of the waterway, reach a peak, and then gradually decrease, showing a significant change in resource quantity.

[0130] Since the target water area is deep, the topography of the waterway changes significantly with water depth, therefore, in order to fully evaluate the tidal current energy resources in the waterway, the present application further selects the section with the largest theoretical reserves to calculate the energy flux per unit width (energy flux per unit width). This index reflects the energy flow density per unit width through the section, and is calculated using the following formula:

[0131]

[0132] In the formula, P is the energy flux, and h is the water depth.

[0133] However, since the tidal current velocity changes greatly with water depth, under normal circumstances, the velocity distribution can be regarded as a function of water depth. In the actual tidal current field, the vertical distribution of velocity usually presents an exponential distribution characteristic, and the commonly used expression form is:

[0134]

[0135] In the formula, v0 is the surface velocity, α is the velocity profile change coefficient, which can be calculated according to the specific sea area by the least square method, C is the residual velocity of the tidal current, and β is the correction coefficient, which is used to adjust the model to better match the actual situation. As shown in Figure 15 , the actual velocity data is brought into the nonlinear fitting, and the correlation coefficient (R 2 ) is used to measure the fitting effect of the exponential distribution. The correlation coefficient R 2 of the quadratic exponential distribution is 0.98, which is closest to 1, indicating that the exponential distribution is very close to the measured data, and the actual situation of the change of velocity with water depth can be accurately described by the model.

[0136] By bringing the exponential distribution of velocity into the calculation formula of energy flux per unit width, the more accurate distribution characteristics of tidal current energy resources in the section can be obtained, and the calculation formula is as follows:

[0137]

[0138] In the formula, h1 and h2 are the water depths of any two points (|h1|<|h2|), v exp (z) is the velocity at depth z, which is the most suitable exponential distribution form, and P uThe single-width energy flux is the energy flux per unit width. This method can effectively capture the nonlinear characteristics of the flow rate change with water depth, ensuring the accuracy of the energy flux calculation.

[0139] Finally, the evaluation results of tidal current energy resources are presented through visualization techniques. The visualization results include key indicators such as tidal level changes, flow velocity distribution, flow direction distribution, energy flux density, and tidal current stability. These results can present the spatial distribution of tidal current energy resources in the target sea area in an intuitive way, providing key references for decision-making of tidal current energy development. Engineers can understand the tidal current energy potential and stability in different regions through these visualization results, thereby optimizing the placement scheme of the unit and ensuring efficient use of resources.

[0140] The innovation of the present application lies in the use of a high-precision layered three-dimensional numerical model, which can capture the flow velocity and energy flux density distribution of different water depth levels in detail. This layered model combines unstructured grid division and layering processing, so that the model can not only reflect the horizontal changes of tidal current, but also accurately depict the vertical direction of tidal current dynamics.

[0141] The innovation of the present application lies in the proposal of multi-dimensional tidal current energy resource evaluation parameters such as spring tide and neap tide rise and fall, tidal current stability, energy flux density, and single-width energy flux. These evaluation parameters provide a detailed and comprehensive analysis of the tidal current field, making the evaluation results more scientific and accurate. Combined with visualization techniques to display the evaluation results, it provides clear guidance for the scientific placement of tidal current units.

[0142] The above embodiments are only preferred embodiments of the present application, and do not limit the protection scope of the present application, therefore: any equivalent changes made according to the structure, shape, principle of the present application should be covered within the protection scope of the present application.

[0143] The basic principles and main features of the technical solution and the advantages of the technical solution are shown and described above. Those skilled in the art should understand that the technical solution is not limited by the above embodiments, and the above embodiments and descriptions in the specification are only to illustrate the principles of the technical solution. Without departing from the spirit and scope of the technical solution, the technical solution can be variously changed and improved, and these changes and improvements all fall within the scope of the claimed technical solution.

Claims

1. A method for site selection of tidal energy array fields based on a three-dimensional high-precision numerical model, characterized in that, The method includes the following steps: (1) Macro-site selection method: Based on historical tidal data, seabed topographic data and macro-distribution of energy flow density, combined with geological survey results, the marine area suitable for tidal energy development is initially determined from a macro-level perspective. (2) Micro-site selection method: Based on macro-site selection, the micro-site selection range of the array field is further precisely delineated by considering the influence of topographic changes, tidal current conditions and shoreline morphology on the deployment of tidal power units through local measurement and flow field analysis; the local measurement and flow field analysis includes using a high-precision positioning system to calibrate the geographic coordinates of the sea area, using sonar instruments to measure the water depth, and using a current profiler to monitor the sea area current velocity and direction; (3) High-precision layered three-dimensional numerical model construction method: Based on the geographical location, water depth data and seabed topography data of the micro-site selection range, a layered three-dimensional numerical model is constructed. The model includes unstructured mesh generation, dynamic harmonic boundary condition setting, tidal simulation, and is calibrated by combining measured and simulated data so that the model can accurately reflect the tidal dynamic characteristics of the target sea area. (4) Refined assessment method of tidal energy resources: By analyzing the model calculation results, the timing of rapid rise and fall of spring tides, the timing of rapid rise and fall of neap tides, tidal stability, energy flow density, theoretical reserves of tidal energy resources, unit width energy flow and tidal properties of the target sea area are analyzed, and the assessment results are presented through visualization technology to guide the deployment of tidal energy units. The refined assessment method for tidal energy resources includes: a) Based on the output of the three-dimensional model, organize the velocity and direction data of the complete tidal cycle in the target sea area, determine the moments of rapid rise and fall of spring tides and neap tides, and then determine the maximum potential of tidal energy resources in the target sea area and the tidal characteristics at moments of low energy flow density. b) Assess the stability of the tidal currents within the region, including flow direction rotation and velocity asymmetry, using the following formula: a θ =180°-|θ e -θ f | α v =|1-v e / v f | In the formula, α θ For the rotational nature of the current direction, θ f θ represents the principal axis direction during high tide. e α represents the principal axis direction during low tide. v For the symmetry of the tidal current velocity, v f v is the average current velocity during high tide. e The average current velocity during low tide; c) Based on the current velocity data from the 3D model, the average and maximum current velocity data for the target sea area over one period are compiled, and then the average and maximum tidal energy flux densities are calculated using the following formulas: In the formula, P m Let ρ be the average energy flux density over a complete tidal cycle, and ρ be the density of seawater. P is the average tidal velocity over a complete tidal cycle. smax The maximum energy flux density for a complete tidal cycle, V smax The maximum velocity of a tidal current for a complete tidal current cycle; d) Based on the above methods for assessing tidal energy reserves, select several sections with relatively abundant tidal energy resources and calculate the theoretical tidal energy reserves passing through a specific waterway section over a period of time using the following formula: In the formula, P theoretical t is the theoretical potential of tidal energy; t is the initial moment; T is the evaluation period, usually one year; L is the width of the channel; V is the tidal velocity; h is the water depth. The Flux method was used to estimate the theoretical potential of tidal energy, and the formula is as follows: P theoretical =P m ·A In the formula, A is the area of ​​the waterway cross section; e) Select the section with the largest theoretical potential of the waterway and evaluate the energy flux per unit width; the energy flux per unit width is the energy flux flowing through the waterway, and is calculated using the following formula: In the formula, P represents the energy flux; Treating the flow velocity as a function of depth z, the energy flux can therefore be expressed as: The vertical distribution of tidal current velocity generally exhibits the characteristics of an exponential distribution, and is commonly expressed in the following forms of exponential distribution: In the formula, v0 is the surface velocity; α is the velocity profile variation coefficient, which is calculated based on the specific sea area using the least squares method; C is the residual velocity of the tidal current; β is the correction coefficient, used to adjust the model to better match the actual situation; Finally, substituting the most suitable exponential distribution form into the expression for the energy flux of a single width, we obtain: In the formula, h1 and h2 are the water depths at any two points (|h1| < |h2|), v exp (z) represents the flow velocity at depth z, which is the most suitable exponential distribution form, P u This is the unit width energy flux; f) Visualize the assessment results of tidal energy resources using visualization technology, including key indicators such as tidal level, velocity, direction, direction stability, and energy flow density.

2. The method for site selection of tidal energy array field according to claim 1, characterized in that, The macroscopic site selection method is implemented through the following steps: a) By combining multi-source data, including marine hydrological, geological exploration and remote sensing satellite data, the topographic contours and temporal and spatial distribution characteristics of tidal currents in the target sea area are preliminarily determined; b) Conduct multidimensional analysis of the interaction between tidal currents, waves, and wind currents in the target sea area, and select areas with high flow velocity, high energy flux density, and good stability as candidate array field locations.

3. The method for site selection of tidal energy array field according to claim 1, characterized in that, The micro-site selection method includes: a) Geographic location calibration, water depth measurement, detailed seabed topography survey, and real-time monitoring of tidal current field are performed on the candidate array field locations to generate detailed tidal level, current velocity, and current direction distribution maps; b) Analyze the tidal current characteristics of the sea area based on actual data, and determine the deployment area of ​​tidal power units based on seabed topography. c) Use a parameter evaluation model based on topography, flow velocity, and environmental factors, combined with eddy current effects, potential obstacles, and construction feasibility, to select a suitable location for the unit.

4. The tidal energy array field site selection method according to claim 1, characterized in that, The method for building a high-precision layered three-dimensional numerical model includes: a) A three-dimensional numerical model of the target sea area was constructed using unstructured mesh technology, and a layered processing method was adopted to simulate the changes in water velocity at different depths; b) The model boundary conditions adopt the dynamic harmonic method, combined with tidal current division and large eddy simulation technology, to handle complex tidal boundary problems, enhance the ability to capture the details of tidal flow, and achieve high-precision fitting of the shoreline. c) Compare and optimize the model results with the measured data to ensure that the spatiotemporal accuracy of the model reaches the allowable error range for engineering.

5. The tidal energy array field site selection method according to claim 4, characterized in that, The unstructured mesh generation technique uses triangular or tetrahedral mesh cells to improve the simulation accuracy of complex terrain in the computational area, and improves the accuracy of key areas through mesh refinement.

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