Email alert
RSS2023 Vol. 10, No. 4
Display Method:
2023, 10(4): 1-1.
Abstract:
Offshore wind power has the advantages of high energy density, low wind curtailment rate and small impact on the environment. It has great development potential and can provide a strong guarantee for China to achieve the goals of carbon peaking and carbon neutrality. By 2022, China's cumulative grid-connected installed capacity of offshore wind power has exceeded 30 GW, continuously ranking first in the world. In June 2022, nine departments including the National Development and Reform Commission and the National Energy Administration jointly issued the 14th Five-Year Plan for Renewable Energy Development, clearly stating that: We should optimize the layout of offshore wind power, make deep-sea offshore wind power planning, focus on building five major offshore wind power base clusters in Shandong Peninsula, Yangtze River Delta, Southern Fujian, Eastern Guangdong and Beibu Gulf, and strive to achieve a cumulative installed capacity of offshore wind power exceeding 200 GW by 2030. By promoting the innovation and demonstration application of deep-sea floating wind turbine foundation and offshore VSC-HVDC transmission technology, we are striving to commence the construction of China's first floating commercial offshore wind power project during the "14th Five-Year Plan". However, China's offshore wind power industry is still in its infancy, and there are still problems such as excessive LCOE and imperfect policy system, which seriously restrict the scale development of offshore wind power.In this context, the journal Southern Energy Construction has planned a special issue on "Offshore Wind Power Engineering Technology" in July 2023 to closely track relevant hot spots and industry trends such as offshore wind power operation and maintenance strategies, offshore wind power construction and installation technologies in China's offshore wind power industry. Front-line teachers from universities and colleges, front-line engineers from enterprises and R&D personnel were sincerely invited to share the latest research results and industry trends, including 18 high-level papers, which cover the theory, technology and application in the fields of offshore wind power installation ships, offshore wind power foundation type-selection design, offshore step-up substations, offshore wind power and offshore hydrogen production. We hope to provide useful ideas and references for the high-quality and sustainable development of China's offshore wind power industry through the burst of thinking sparks in this issue.We sincerely thank the authors, peer reviewers and readers for their support to this issue. We hope that the publication of this issue can provide reference for experts and scholars from all walks of life who are concerned about and engaged in relevant research, so as to promote the rapid development of basic theory and key application technologies in the field of offshore wind power. Introduction to Special Editors-in-Chief Shi Wei, a distinguished researcher and doctoral supervisor of Dalian University of Technology, is selected as one of the first tip-top young talents of Liaoning Province, a high-level talent of Dalian City, a talent under the "Xinghai 1000 Youth Talents Plan" of Dalian University of Technology, and an outstanding young scientific and technological talent of China Renewable Energy Society. He serves as the director of Wind Power Branch of China Steel Construction Society, an expert member of New Energy Group of China Energy Society, a Technical Program Committee (TPC) member of ISOPE (an international conference on ocean engineering), a deputy editor-in-chief of SCI Journal: Frontiers in Energy Research, an editorial board member of international journal: Journal of Modern Green Energy, and a guest editor of Frontiers in Marine Science and Journal of Marine Science and Engineering. He is mainly engaged in the research on dynamic characteristics of offshore wind turbines under complex marine environment, and has successively been responsible for more than 30 projects, including projects supported by the General Fund of National Natural Science Foundation of China (NSFC), projects supported by the Youth Fund, sub-projects of Key R&D Program of the Ministry of Science and Technology, Xingliao Talent Program, school-enterprise cooperation project. In recent years, he has published 67 SCI papers in Energy, Renewable Energy, Marine Structures, Ocean Engineering and other journals, including 4 ESI highly-cited papers and 1 ESI hot paper, as well as 45 EI papers. He has obtained 20 invention patents in China, 8 patents in the United States and more than 40 utility model patents. He has won 6 provincial and ministerial awards, including the First Prize of Marine Engineering Science and Technology Award of China Association of Oceanic Engineering, the First Prize of Electric Power Engineering Science and Technology Progress Award, and the Second Prize of Scientific and Technological Progress Award of China National Committee on Large Dams.Le Conghuan, female, is an associate researcher and master advisor at the School of Civil Engineering, Tianjin University. She is mainly engaged in the design and R&D of offshore wind power and photovoltaic support structures, offshore towage construction, and others fields. She has led seven projects, including the general project supported by the National Natural Science Foundation of China, project supported by the Youth Fund, the sub-project of the National Youth Fund, the sub-project of the National Innovative Working Methods, and project supported by Tianjin Natural Science Foundation; participated in more than 10 projects such as the one under the State High-Tech Development Plan (863 Program), project supported by International S&T Cooperation, National Ocean Demonstration Project, and projects under the National Natural Science Foundation of China and Tianjin Natural Science Foundation of China; published more than 60 SCI/EI papers; She has obtained more than 30 licensed invention patents; and won one second prize of Tianjin Science and Technology Progress Award. She serves as a guest editor of SCI Journal: Frontiers in Energy Research.
2023, 10(4): 1-10.
doi: 10.16516/j.gedi.issn2095-8676.2023.04.001
Abstract:
Introduction As an important construction equipment in the development of offshore wind power, studying the bearing performance of the jack-up vessel for wind turbine installation in the in-situ state to ensure its operation safety is of great significance. Method In this paper, taking the jack-up installation vessel as the research object, the horizontal bearing performance of the jack-up installation vessel and the variation law of the surrounding earth pressure at four different penetration depths of spudcans in homogeneous sandy soil were studied by combining with the indoor model tests and finite element method. Result The results show that with the increasing of the penetration depth, the horizontal bearing capacity of the jack-up installation vessel is on an approximate linear growth trend. The penetration depth of 10 cm led to an increase of the horizontal bearing capacity by 38.02% compared with 4 cm penetration depth, and the corresponding horizontal displacement also show an increasing trend. Under the action of horizontal loads, the bearing mode of spudcans is characterized by compression of spudcans on the loading side and tension of spudcans on the non-loading-side. The pressure change law of the soil on the surface of spudcans is the same. At the penetration depth of 10 cm, the maximum variation in soil pressure at the bottom of spudcans on the loading side is 38.37 kPa, which increased by 126.2% compared to the penetration depth of 4 cm. In addition, significant variations in soil pressure are observed on the lower surface of the loading-side spudcans and the upper surface of the non-loading-side spudcans. Conclusion Under the action of horizontal load, the force mode of the jack-up installation vessel is the tension-compression mode, and increasing the penetration depth of spudcans in sandy soil can significantly enhance the horizontal bearing capacity. Therefore, in order to ensure the safety and operational capability of the wind turbine installation vessel, it is necessary to ensure sufficient penetration depth of spudcans.
2023, 10(4): 11-17.
doi: 10.16516/j.gedi.issn2095-8676.2023.04.002
Abstract:
Introduction Monopile foundation is currently the most widely used support structure for offshore wind farms. China's marine environment is mostly shallow water and medium water depth areas, which is obviously affected by nonlinear waves. Compared with the traveling wave, the focusing waves can form an impact force on the pile column in a short time, which is larger than the conventional wave force, and undermines the operational performance and fatigue life of the offshore wind turbines. Method In this paper, NREL 5 MW monopile wind turbine study was carried out according to the pool model test method at the reduced scale of 1∶80. In combination with the marine environmental conditions of China's eastern coastal wind farms, we selected three typical focusing wave models, and recorded the changes of the wave runup around the monopile and the force on the bottom under different working conditions using wave height meter and force balance. Result The results show that: the horizontal wave force on the pile foundation is significantly transient, and will suddenly increase when the focusing waves act on the monopile foundation, and the monopile foundation receives the reverse impact force at the trough of focusing wave. Conclusion This paper reveals the change law of load on monopile foundation of offshore wind turbine caused by focusing wave, confirms the important influence of nonlinear wave on the dynamic characteristics of wind turbine foundation. The results are of high theoretical value and engineering application value.
2023, 10(4): 18-31.
doi: 10.16516/j.gedi.issn2095-8676.2023.04.003
Abstract:
Introduction With the increasing demand for clean energy, the offshore wind power sector has seen a spurt of progress in recent years, and the bucket foundation has become the preferred choice for offshore wind turbines considering its good economy, convenient construction, and recyclability. Due to the widespread distribution of seismic zones in China, the seismic performance of bucket foundation is a crucial consideration for structural design. The bucket foundation is featured by high structure stiffness, so that the probability of structure damage caused by earthquake is low, and the failure under earthquake is mainly caused by the liquefaction of the foundation soil. For this purpose, the paper focuses on the seismic performance of bucket foundation in sandy soil. Method The liquefaction resistance of sandy soil for bucket foundation was analyzed by shaking table tests in this paper. The study objects included four types of bucket foundation in sandy soil, namely mono-bucket foundation (MBF), composite bucket foundation (CBF), three-bucket jacket foundation (TBJF) and four-bucket jacket foundation (FBJF). Result By carrying out shaking table tests, the excess pore pressure ratios of sandy soil for different types of bucket foundation under earthquake are obtained, and the impact mechanism of bucket foundation on the anti-liquefaction performance of sand soil is clarified. Conclusion The bucket foundation can improve the liquefaction resistance of sand, since the additional load effect of the superstructure and the hoop effect of bucket skirt weakens its shear shrinkage. The test results of MBF are compared with those of CBF, and the test results of TBJF are compared with those of FBJF. It is found that the seismic performance of CBF and FBJF is respectively superior to that of MBF and TBJF.
2023, 10(4): 32-42.
doi: 10.16516/j.gedi.issn2095-8676.2023.04.004
Abstract:
Introduction With the development of offshore wind turbine works to deep sea areas, the challenging construction environment tends to result in errors in the installation of the grouted connection for the jacket foundation. These errors can subsequently affect the axial mechanical properties of the grouted connection. Therefore, it is necessary to study the impact laws of installation errors on the axial mechanical properties of the grouted connection section. Method The study was commenced by conducting axial static loading tests on reduced-scale test piece of the grouted connection section, which was followed by simulating the axial loading process of the corresponding test piece using the finite element analysis method. The simulation results were found to align well with the experimental data, indicating a successful outcome. Result According to the research findings, the increasing in longitudinal and transverse installation errors can lead to an increase in the axial stiffness of the grouted connection section. This, in turn, further alters the longitudinal strain distribution of the casing and pile pipe. Additionally, the increase in installation errors can lead to an increase in the maximum value of the third principal stress in the grouting materials during the axial loading process, as well as changes in its distribution location. Conclusion In conclusion, the influence of installation errors on the axial mechanical properties of the grouted connection section for the jacket foundation can cause alterations in failure modes of the grouted connection section. Therefore, it is needed to consider and evaluate the harm caused by the impact laws of installation errors based on their influence rules.
2023, 10(4): 43-56.
doi: 10.16516/j.gedi.issn2095-8676.2023.04.005
Abstract:
Introduction In the context of the new power system, low-carbon maintenance of wind turbines and coordinated maintenance with conventional wind turbine generator systems (WTGS) need to be solved urgently. In this paper, taking into account the impact of multi-attribute meteorological factors and low carbon and economic needs, an optimization model for wind power, hydropower and thermal power combined low-carbon maintenance based on continuous hidden Markov model is established. Method Firstly, dynamic tracking of wind farm maintenance capacity was realized by taking rainfall, wind speed and lightning hazard degree as the observation sequence, taking maintenance capacity as hidden state sequence, and using continuous hidden Markov model (CHMM) process. Then, an optimization model for wind power, hydropower and thermal power combined low-carbon maintenance was constructed by taking the optimal maintenance capacity as the decision-making basis, taking the minimum total cost as the optimization objective, and taking the maintenance constraints and system control constraints into consideration. Finally, took the IEEE30-node system as an example. Result The results show that the proposed model has more significant economic benefits and low carbon characteristics. Conclusion The research in this paper has high theoretical value for the operation and maintenance of WTGS, and has strong engineering applicability.
2023, 10(4): 57-70.
doi: 10.16516/j.gedi.issn2095-8676.2023.04.006
Abstract:
Introduction Speeding up the offshore wind power construction and development is of great significance to promoting the adjustment of China's energy structure. China is accelerating the process of its wind power development in the entire offshore area, and the geological survey is a vital foundation and key technology of offshore wind power development. Method By studying the marine geological survey technologies at home and abroad and combining years of experience in different sea areas, this paper proposed a new technology of engineering geological modeling for offshore wind power development based on the principle of consistency. Firstly, the survey equipment selection and survey line layout started from a three-dimensional initial model to evaluate the impact of geological changes and geohazards on the offshore wind power engineering construction and took into full account the ship selection, field in situ and laboratory tests, and correlation of geophysical prospecting and geotechnical data. Then, with abundant and continuous data obtained from the boreholes and the whole wind farm during the feasibility study and detailed survey, the methods of combination of indoor geotechnical tests with the in-situ tests, the combination of multiple geophysical prospecting devices and the combination of geotechnical and geophysical prospecting methods were used to conduct a consistency analysis of various data, manage the geological survey data platform, update the model and build the final model, and the engineering geological model was continuously optimized and iterated in the subsequent stages. The engineering geological model provided comprehensive engineering geological information for the entire life cycle of offshore wind farm design, installation, operation, maintenance and decommissioning. Result The research results and offshore wind power geological survey examples show that by conducting consistent comprehensive layout and data analysis, effectively connecting geotechnical investigation with engineering geophysical prospecting and constructing a three-dimensional crossing engineering geological model, it can effectively solve the problem of "ambiguities of geological survey data" and improve the reliability, accuracy and application of geological survey data. Conclusion The new method proposed is one of the effective methods to reduce cost and increase efficiency in offshore engineering as well as the embryonic form of digital twin of offshore wind power geological survey and the foundation for the construction of a geological survey big data base.
2023, 10(4): 71-81.
doi: 10.16516/j.gedi.issn2095-8676.2023.04.007
Abstract:
Introduction With the development of wind power generation technology, the unit capacity of permanent magnet wind generator is increasing, and the heating power is also increasing. The heat dissipation of generator is facing unprecedented challenges. How to effectively solve the problem of generator temperature rise and heat dissipation difficulty has been the focus of our study. Method Based on the STAR-CCM+ software platform, an integrated numerical simulation method for generator heat dissipation and cooling was proposed in this paper. The reliability of the numerical calculation method was verified by comparing the calculated values with the experimental values. On this basis, a study was conducted on the internal temperature distribution law and the factors influencing the cooling system heat dissipation performance of the high power permanent magnet wind generator. Result Under the rated power, the highest temperature of the winding and stator core appear in the middle area. If the process conditions allow, the cooling water pipe should be as close to the winding as possible to take away more heat. The stator core temperature and winding temperature can be reduced significantly by increasing the total intake air volume of the generator. The intake air temperature has a linear relationship with the maximum temperature of the winding and stator core. For every 5℃ decrease in the intake air temperature, the maximum temperature will be reduced by about 1.4℃. Reducing the intake air temperature can improve the heat dissipation performance of the generator to a certain extent. The intake water temperature has a linear relationship with the maximum temperature of the winding and stator core. For every 5℃ decrease in the intake water temperature, the maximum temperature will be reduced by about 3.3℃. Reducing the intake water temperature can greatly improve the heat dissipation performance of the generator. In addition, the gap between the cooling water pipe and the stator core greatly hinders the heat transfer of the cooling water pipe. Filling the gap with materials with good thermal conductivity can effectively improve the heat dissipation performance of the generator. Conclusion The conclusions drawn in this paper can effectively guide the heat dissipation design of permanent magnet wind generator and ensure the safe operation of wind turbines in normal work.
2023, 10(4): 82-90.
doi: 10.16516/j.gedi.issn2095-8676.2023.04.008
Abstract:
Introduction Large-scale connection of wind power to the power grid poses great challenges to the stability (especially frequency stability) of grid operation.In order to solve the problem of inadequate frequency regulation capability caused by large-scale connection of wind power to the power grid and improve the frequency adaptability of wind power grid connection, wind turbines need to have frequency regulation function and response timeliness. Method This paper adopted a frequency regulation system scheme based on rotor kinetic energy and pitch angle reserve, which could provide active support for the power grid quickly and accurately during the power grid frequency change. Firstly, the main control algorithm was designed based on the theoretical analysis of inertia response and primary frequency regulation algorithm logic. Then, the functional verification was carried out on the co-simulation platform. Finally, the actual test was carried out in a project. Result The simulation and test results showed that the frequency regulation system scheme based on rotor kinetic energy and pitch angle reserve could cope with a variety of grid frequency changes and quickly provided active support. Conclusion The frequency regulation system scheme of wind turbines can perform a fast inertia response (with the response time less than 500 ms) and primary frequency regulation response (with the response time less than 5 s) under various frequency change conditions and provide active support for the power grid, which can help recover the grid frequency and effectively improve the frequency adaptability of wind turbines.
2023, 10(4): 91-102.
doi: 10.16516/j.gedi.issn2095-8676.2023.04.009
Abstract:
Introduction With the steady progress of the carbon peaking and carbon neutrality goals, more and more distributed renewable energy is connected to the power grid. Among them, in economically developed coastal areas with heavy power load, vigorously developing offshore wind power has become a hot point of wide concern for scholars at home and abroad. However, the inherent intermittency of wind power generation, especially when the offshore wind farm is actively disconnected from the main grid during typhoons, can adversely affect the receiving-end grid. Method In order to realize the friendly access of offshore wind power during typhoon, considering the advantages of hydrogen energy storage such as high storage efficiency, low emission and wide application, this paper proposed a collaborative control method between offshore wind farm and hydrogen management system (HMS). On the one hand, during the period of typhoon approaching, this method could maximize the use of wind energy for power generation under normal operation. On the other hand, when the typhoon passed through and the offshore wind farm was gradually disconnected from the grid, the hydrogen energy system released electric energy to alleviate the active power drop of the wind farm and solve the problems such as the ramp rate in the operation of the traditional wind turbine generator systems, so as to reduce its adverse impact on the receiving-end grid and effectively smooth the volatility of the offshore wind power output. This paper firstly introduced the physical modeling method and control model of offshore wind farm and hydrogen energy system in detail, and explained the collaborative control strategy between them according to the typhoon period. Result Finally, simulation results show that the proposed method enables the offshore wind farms to be more flexible and friendly to meet the grid-connected operation during typhoons. In addition, the hydrogen energy storage system can maximize the use of wind energy for power generation under normal operation. Conclusion Control the hydrogen energy system to release electric energy during typhoons can solve the problems such as the ramp rate of the traditional wind turbine generator systems, so as to reduce its adverse impact on the receiving-end grid.
2023, 10(4): 103-112.
doi: 10.16516/j.gedi.issn2095-8676.2023.04.010
Abstract:
Introduction Under the trend of accelerating the clean transformation of coastal energy and adjusting the industrial structure, offshore wind power will become an important support for the safe, clean and efficient transformation of power energy in coastal provinces due to its rich wind resources, high number of utilization hours and convenient consumption. Method In this paper, the current situation and future development prospect of offshore wind power industry were analyzed, and the comprehensive cost reduction trend of shallow-water and far-reaching deep-sea offshore wind industry was predicted. Result The results show that whether the Guangdong sea area can realize connection to grid at a fair price during the 14th Five-Year Plan period is dependent on the average annual comprehensive cost reduction rate; Some far-reaching deep-sea projects in Guangdong can achieve connection to grid at a fair price by the end of the 14th Five Year Plan period, and there is still room for cost reduction under the scale effect. Conclusion Offshore wind power industry chain of our country has been improved gradually, but there are still many key components and core technologies relying on imports, so it is necessary to carry out continuous localization research to effectively reduce the industrial costs.
2023, 10(4): 113-121.
doi: 10.16516/j.gedi.issn2095-8676.2023.04.011
Abstract:
Introduction The growth of wind power industry is accelerating faster than ever worldwide, at the same time, the waste generation from end-of-life wind turbine blades is expected to peak in recent years. Efficient recycling of end-of-life wind turbine blades has become a key issue affecting the sustainable development of the wind power industry and its low-carbon-footprint target. Method Traditionally, majority of the end-of-life blades were either buried or incinerated after being dismantled, causing resources wasting and severe environmental problems. In this context, this paper reviewed the mainstream domestic and international recycling processes of end-of-life wind turbine blades such as mechanical recycling, pyrolysis, chemical recycling and comprehensive recycling, and analyzed their corresponding advantages and disadvantages. Result By summarizing the industrial recycling application scenarios, this paper provides suggestions and prospects for the prospective recycling market of the end-of-life wind turbine blades. Conclusion Wind power industry plays an important role in realizing the "carbon-peaking and carbon-neutrality" goals through assisting in implementation of the energy-conservation and emission-reduction strategy. However, the wind turbine blade recycling market is currently in the exploratory stage with medium and small-size, there is an urgent need for policies, standards and technology development to help with its large scale industrialization. This paper illustrates current status and development trend of domestic and international recycling technology and application scenarios of end-of-life wind turbine blades, and aims to provide the scientific references for the sustainable and low-carbon development of the wind power industry.
2023, 10(4): 122-130.
doi: 10.16516/j.gedi.issn2095-8676.2023.04.012
Abstract:
Introduction In order to guarantee urban power supply and offshore wind power utilization without building new power lines, the paper aims to establish a electricity transmission strategy based on wind-coal-battery- hydrogen -CCUS multi energy coupling and bundling system, which is analyzed theoretically and verified by simulation. Method To verify the effectiveness of the strategy, four experimental schemes (separate transmission of wind and coal power, bundled transmission of wind and coal power without operation coupling, bundled transmission of wind and coal power with operation coupling, and wind-coal-battery-hydrogen-CCUS coupled transmission) were set up, and based on the HOMER software environment and particle swarm optimization algorithm, the system operation simulation and index calculation of the test scheme are carried out. Result According to the simulation results, compared with normal separate transmission strategy, power transmission line capacity of system applying wind-coal bundled transmission strategy can be decreased by 2.2 GW, with an average utilization rate of 59%, i.e. 21%~23% higher. In the case that the wind power and coal power share the same transmission line without coordinated operation, the wind power curtailment is 164 GWh in total. System applying wind-coal-battery–hydrogen-CCUS bundled transmission strategy could avoid wind power curtailment and reduce carbon emission from unit power supply by about 30~33g/MWh. Conclusion In conclusion, the electricity transmission strategy established by this paper is supposed to be feasible and effective and contributing to planning and construction of offshore wind power project.
2023, 10(4): 131-137.
doi: 10.16516/j.gedi.issn2095-8676.2023.04.013
Abstract:
Introduction At present in China, the ships near offshore wind power platforms are mainly monitored by means of the ship AIS system and remote cameras. Such means lacking information technology often require a lot of manpower and material resources. In order to effectively warn the ships near the offshore wind power platform, this paper analyzes the urgent problems to be solved that are encountered in the current offshore ship identification, and proposes an offshore ship fusion recognition algorithm that combines the improved Faster-RCNN network and ship AIS system. Method Firstly, improvement suggestions were proposed for three aspects of the Fast-RCNN model, and the structures such as the backbone network and the loss function were adjusted. Secondly, the ships in the pictures taken by the remote cameras were detected by the improved Faster-RCNN network, and the results were supplemented and corrected in combination with the relevant information from the ship AIS system. Finally, the verification sets were tested according to the optimal model saved in the model training process, and each model was evaluated using the indicators of precision, recall and average precision. Result The Faster-RCNN model inference speed and accuracy for different feature extraction networks and classification loss functions are improved greatly. The ability of offshore wind power platforms to monitor ships is improved. The offshore ship information was processed and the navigation trajectory was obtained in combination with the ship AIS system, realizing the detection of the ships in the pictures taken by the remote cameras. Conclusion Experiments show that the feature extraction network and the replacement of the classification loss function of the traditional Faster-RCNN can effectively improve the detection accuracy of the network in the ship recognition task and the ship trajectory can be effectively obtained by integrating the ship AIS system.
2023, 10(4): 138-147.
doi: 10.16516/j.gedi.issn2095-8676.2023.04.014
Abstract:
Introduction This article aims to study the optimal planned capacity setting of large-scale offshore wind farm. Method A series of numerical experiments were conducted on a single planned site with a capacity of 1 GW using three models with different unit capacities and three offshore wind farm wake models, combined with an offshore wind resource atlas, to gradually expand it to 2 GW. Power generation, wake effects and marginal utility of the whole site were analyzed. Result The results show that employing the wind turbine with larger single-unit capacity, the higher gaining of the power generation and slower growth of wake loss appear during the capacity expansion. Meanwhile, the larger effective expansion range which taking into account the safety of the wind turbine and the marginal utility exists. However, evaluation of effective expansion range may be affected by wake model selection. Conclusion This article shows that the optimal planned capacity of a single offshore wind farm can be slightly higher than the existing benchmark when multiple constraints, such as utilization of sea area, wind turbine safety and economical efficiency are met. Individual site needs to be subdivided scientifically and the optimal planned capacity should be reasonably set in the future planning of offshore wind farm bases with capacities in the tens of millions of kilowatts.
2023, 10(4): 148-157.
doi: 10.16516/j.gedi.issn2095-8676.2023.04.015
Abstract:
Introduction The top grouting jacket pile foundation is a new type of foundation application for offshore wind power jackets on clay seabed. Since the grouting section can bear some loads, its stress and deformation mechanism is significantly different from that of conventional tubular piles. The existing design often ignores the bearing capacity sharing of each part of the foundation, and only treats the grouting section as a hollow tubular pile, ignoring the bearing capacity of the grouting section. Method This paper firstly compared the bearing capacity calculation formulas of existing ocean pile foundations and mesoscale foundations, and analyzed the applicability of various calculation formulas to top grouting jacket pile foundations. Then, a numerical model for top grouting pile foundation on clay seabed was established using the finite element method. The validity of the numerical model was verified by comparing with the field test and centrifugal model test results. Finally, based on the finite element results, the vertical bearing capacity calculation formula suitable for the top grouting pile foundation was analyzed. Effects of various soil strength distributions and length-diameter ratios on the foundation bearing characteristics and bearing proportion were explored. Result Results show that for the soil layers with linearly increasing strength and under various surface strengths, with the increase of the surface strength, the bearing capacity of the grouting section increases, but the bearing proportion of the grouting section gradually decreases. For the same soil layer, the bearing proportion of the grouting section gradually decreases with the increase of the buried depth of pile foundation (length-diameter ratio). Conclusion The bear loads of the grouting section can increase the vertical bearing capacity of jacket pile foundation, which is of great significance for the optimization of jacket pile foundation engineering.
2023, 10(4): 158-165.
doi: 10.16516/j.gedi.issn2095-8676.2023.04.016
Abstract:
Introduction The objective is to solve the injury and destruction of the wind turbine equipment caused by the common mode interference current and avoid the long-term operation of the wind turbine with faults and the damage to the large components of the wind turbine, which will lead to the decrease of the availability of wind turbines, wind abandonment phenomenon and loss of power generation. Method The article elaborated on the interference signal phenomenon from common mode current, on-site equipment damage, misoperation signal fault, overheating of the current output cable and transformer of the wind turbine caused by faults, equipment misoperation protection, abnormal vibration of the generator set, and other phenomena of a wind turbine in a certain wind farm in southern China. Taking the # 11 wind turbine in the wind farm as the detection point, on-site machine position experiment detection was conducted, and a systematic theoretical analysis of the problem was conducted combined with on-site measurement data and pictures. Result The existence of common mode interference current generated by the conversion system is confirmed, which causes a series of problems such as overheating of current output cable, overheating of transformer, misoperation of protective equipment and abnormal vibration of generator set. As the wind farm project is an online power generation project that has been put into operation for many years, the equipment and cable layout have been in place and fixed, which is difficult to change or disassemble. In order to avoid affecting the normal operation of the generator set, the solution of installing anti-interference coil CoolBLUE® series on the generating busbar of the generator set is adopted without affecting the current situation of the original line. Conclusion The practice shows that this improvement scheme is effective and feasible, it can provide suggestions and ideas for the prevention and improvement of such faults in the future, avoid the similar faults of the wind turbine again, increase the availability of wind power generator sets, and it can be popularized and applied.
2023, 10(4): 166-173.
doi: 10.16516/j.gedi.issn2095-8676.2023.04.017
Abstract:
Introduction From 2022, the state subsidies for offshore wind power has been fully withdrawn. The foundation of offshore wind turbines is the supporting structure of wind turbines and plays a crucial role in the safe operation of offshore wind farms. Reasonable selection and design of the offshore wind turbine foundation is an effective way to reduce costs and increase efficiency of offshore wind farms under the guidance of such policies as the "30·60" dual-carbon target and the national "14th Five-Year Plan" energy plan. Method The article took the selection and design of a wind turbine foundation for a certain offshore wind farm as an example, and combined the construction experience of domestic offshore wind farms to compare and select the foundation types; firstly, preliminary selection was made among three foundation types, namely monopile foundation, jacket foundation and high pile cap foundation; then, combined with the marine hydrological and geological conditions of the offshore wind farm, the applicable water depths and advantages and disadvantages of different wind turbine foundation types were analyzed, and a comprehensive comparison was conducted from the aspects of structural safety, construction feasibility, duration and engineering economy. Result Research has shown that the selection of wind turbine foundation type is related to several factors such as water depth, soil geological conditions, natural frequency of wind turbines, capacity of construction and equipment installation, construction duration, and engineering cost. The monopile foundation has excellent structural type, construction feasibility, the shortest construction duration and the best economy. Conclusion The monopile foundation is recommended for the wind turbine foundation of this offshore wind farm.
2023, 10(4): 174-183.
doi: 10.16516/j.gedi.issn2095-8676.2023.04.018
Abstract:
Introduction The topside module of an offshore step-up station usually has numerous tube-I section joints with complicated structure, which cannot be checked by general structural design software. Hence, a feasible checking design method and refinement of stiffener schemes are in need. Method A simplified model based on typical tube-I section joints of the topside module of an offshore step-up station was established, and five stiffener schemes were designed for it. Based on the finite element software simulation method, three typical displacement loading conditions, i.e., axial compression displacement, in-plane rotation, and out-of-plane rotation, were applied to analyze the plastic zone development and failure modes of the five stiffener schemes. For the longitudinal stiffener scheme selected, the effective stress section of the stiffener was assumed based on existing codes, and a simplified calculation method for stiffener stress check under complicated loads was proposed. The results were examined using the finite element method. Result The results show that the unstiffened tube-I section joint cannot satisfy the design principle of "strong joint and weak member", and it is necessary to take stiffening measures such as stiffeners. The longitudinal stiffener scheme performs better in terms of bearing capacity and economical efficiency. Longitudinal stiffeners are essential for the shearing capacity of beam webs, while the transverse stiffeners cannot enhance shearing capacity. Finite element analysis indicates that the stress distribution is consistent with the assumption of the simplified calculation method, and the simplified calculation method predicts higher stress levels than the finite element results, which means the proposed simplified calculation method is feasible and safer. Conclusion The longitudinal stiffener scheme is a better stiffening scheme for the joint. The proposed simplified calculation method can be adopted to check the longitudinal stiffener scheme efficiently.
2023, 10(4): 184-192.
doi: 10.16516/j.gedi.issn2095-8676.2023.04.019
Abstract:
Introduction Under the guidance of energy policy with the goal of "double carbon", offshore wind power generation, as a new energy technology, has been widely applied and rapidly developed in China. Monopile foundation is the most economical and widely used foundation in offshore wind power. In order to solve the problem of deformation and erosion protection of monopile foundation, a foundation reinforcement technology is proposed, and the reinforcement technology is studied and analyzed, and the basis of reinforcement method is given. Method Researched and demonstrated the method of pile foundation reinforcement technology, selected a foundation reinforcement technology suitable for offshore construction through research on the technology roadmap and process of reinforcement, and used numerical analysis method to conduct a detailed analysis of the reinforcement effect and reinforcement influence range. Result The results show that under 1.15 times of load, the horizontal bearing capacity of monopile foundation strengthened by foundation can be increased by more than 15%, and it can be applied to larger capacity models through foundation reinforcement. In this analysis case, when the depth and horizontal range of foundation reinforcement reach 8 m, the benefits obtained from the soil in the direction of reinforcement depth are greater than those in the direction of reinforcement plane. Conclusion The technical scheme of using cement soil reinforcement has been verified to be reliable through numerical analysis, significantly improving the bearing capacity of monopile, and the reinforcement range is reasonable and economical. It can provide reference for the application of monopile foundation reinforcement technology in subsequent offshore wind power engineering.
2023, 10(4): 193-199.
doi: 10.16516/j.gedi.issn2095-8676.2023.04.020
Abstract:
Introduction At present, in China's offshore wind power projects, with the gradual development of the far-reaching sea, the most commonly used foundation structure of wind turbine is the pile foundation, and the most commonly used superstructure is the jacket structure. The combination of the two constitutes the basic support system of wind turbine. In some shallow cover areas of deep water, the application demand of large diameter jacket foundation is particularly strong, and the design of the lower pile foundation directly determines the feasibility of the scheme and the safety of the structure. In order to verify the bearing capacity of the large diameter short pile foundation of the jacket, the calculation method of CPTU is proposed. Method Through the UWA-05 method recommended in the CPTU calculation method of API specification, the bearing capacity was calculated, and the actual measurement of high strain data of a wind field in Guangdong and the formula calculation results were further analyzed, and the parameters of the end resistance of the formula itself were quite different. Result The results show that the CPTU method is used to fit the side resistance with the measured data. It is difficult to form an effective soil plug for the large diameter short pile of the jacket. When calculating the end resistance by using the CPTU method, it is recommended to consider only the end ring area. Conclusion Therefore, it is a reliable method to calculate the bearing capacity of large diameter short pile in jacket, but it is suggested to compare and verify the data of test pile, so as to provide reference for the subsequent application of large diameter short pile in far-reaching sea breeze field.
