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RSS2018 Vol. 5, No. 2
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2018, 5(2): 1-7.
doi: 10.16516/j.gedi.issn2095-8676.2018.02.001
Abstract:
[Introduction] With the “Guidance for bidding of the wind power farm development ” having been published, the demand of reducing the development cost is more and more urgent. Therefore, it is crucial to reduce the cost through technological innovantion. The cost of tower and foundation significantly affects the Levelized Cost of Energy(LCoE) of offshore wind and directly determines the competitiveness of offshore wind developer. [Method] This paper aims at applying an integrated Design Offshore (iDO) approach based on a digital cloud platform for an offshore wind turbine tower and foundation design in the ULS and the FLS conditions, respectively. To show the effectiveness of the iDO approach in reducing the cost of the tower and foundation, a sequentially iterated approach (SIA) was also used for a comparison using two of our offshore wind power projects. [Result] The results we obtained demonstrate that the design loads are all much smaller by using the iDO approach than the SIA approach in both ULS and FLS conditions. Our calculation results suggest that the iDO approach can significantly optimize the design process and reduce the weight and cost of the supporting structures, as well as the LCoE of offshore wind farm. [Conclusion] In the practical engineering projects of offshore wind farms, the iDO approach can significantly reduce the integrated tower & foundation cost and enhance project competitiveness. This work also provides some guidance for further study on the supporting structures design optimization by applying the iDO approach.
2018, 5(2): 8-18.
doi: 10.16516/j.gedi.issn2095-8676.2018.02.002
Abstract:
[Introduction] This paper is Part 1 of two papers, looking at applying European countries′ experience with economic regulation to one of the urgent challenges of China′s electricity systems: namely the effective connection of offshore wind. [Method] Using a methodology adapted from recent literature on comparative analysis of regulatory regimes, five components of regulatory regimes for offshore wind are defined: regulatory entity, degree of effective unbundling, connection charging method, tariff regulatory method and entity responsible for constructing/operation of the offshore connection. Regulatory regimes, including three case studies of innovative regulatory regimes, are assessed in terms of four criteria: “Price Signal” , “Cost Efficiency Incentives” , “Planning” and “Timely Connection Investment” . [Result] The paper shows that the TSO model, the generator model and the third-party model present three different, but equally successful, paths to address the challenges of offshore wind connection. [Conclusion] China′s policy-makers could learn from these experiences, both in understanding the properties of basic regulatory methods, as well as the regulatory innovations. This is further discussed in Part 2 of the paper.
2018, 5(2): 19-23.
doi: 10.16516/j.gedi.issn2095-8676.2018.02.003
Abstract:
[Introduction] Offshore wind power has become a research hotspot in the development of renewable energy in the world. Although significant achievements have been made in the early stages, it is not yet mature in terms of survey design, construction management, operation and maintenance, technological innovation, and industrial financing. In order to solve the above problems, technological innovation is particularly important. Among them, big data technology has become an important part of improving the reliability and power quality of offshore wind power and reducing the cost of transportation. [Method] Based on big data technology, the value and significance of offshore wind power data are discussed. [Result] By taking the construction of Guangdong Offshore Wind Farm Big Data Center for example, this paper puts forward the general framework of offshore wind power data, and analyzes the important tasks of marine wind power data in Guangdong Province around this framework. [Conclusion] The development of offshore wind power data has provided strong support for fully exploiting the wind energy resources in Guangdong Province, promoting the development of the marine wind power industry in Guangdong Province, and promoting the optimization and transformation of the energy structure and energy conservation and emission reduction.
2018, 5(2): 24-36.
doi: 10.16516/j.gedi.issn2095-8676.2018.02.004
Abstract:
[Introduction] Scour is a process of soil erosion, which can occur around the foundations of bridges or offshore structures through the action of flowing water; it can, therefore, reduce the capacity of the foundations and sometimes lead to the failure of structures. During an analysis of scour effects on laterally loaded piles, scour hole geometry is often ignored. Instead, scour effects are considered by simply removing the whole soil layer to the scour depth. However, a scour hole has not only depth, but also width and a slope. At present, the widely used p-y method for analyzing laterally loaded piles cannot consider three-dimensional scour hole dimensions. [Method] For this reason, a simplified method was developed herein for the analysis of laterally loaded piles in sand under a scour condition. [Result] The p-y curves in this method were based on a wedge type of failure. The effects of the scour hole dimensions on the response of laterally loaded piles in sand were evaluated using this simplified method. The computed results from the simplified method compared well with those from the three-dimensional finite-difference method. Scour depth was identified as the most influential factor on the pile response compared with scour width and scour hole angle. [Conclusion] Based on the parameters investigated, a model that removes the entire soil layer to the scour depth resulted in 49%~68% higher groundline lateral displacements of the pile than a model that incorporates the three-dimensional scour hole dimensions.
2018, 5(2): 37-46.
doi: 10.16516/j.gedi.issn2095-8676.2018.02.005
Abstract:
[Introduction] In the geotechnical investigation of offshore projects, the drilling disturbance of the soil sample may be very large, which may lead to the unreliability of laboratory tests. As one of the most important method of in-situ tests offshore, piezocone penetration (CPTU) test has been more and more used in China and abroad. [Method] Therefore, the strata classification and soil parameters analysis methods based on CPTU are summarized and analyzed.On this basis, the analysis methods are applied to offshore wind farm in China, and the applicability of current soil parameters interpretation methods are further evaluated. [Result] The results show that the experience parameters which adopted in abroad may overestimate the soil parameters. It is recommended to calibrate the experience parameters of interpretation formulae in combination with the characteristic of offshore strata in China. [Conclusion] Based on the experiment test and in-situ test data of regional soil in seabed of Jiangsu, Zhejiang and Fujian, we demonstrate that it is workable to improve and calibrate the parameter of empirical formula. This work can provide some guidances for further study on offshore wind farm design.
2018, 5(2): 47-59.
doi: 10.16516/j.gedi.issn2095-8676.2018.02.006
Abstract:
[Introduction] Wind energy is one type of rapidly-developing renewable clean energy. The number of installed wind turbines (WTs) has increased significantly over the past 20 years. The offshore WTs are typically exposed to a harsh sea environment and prone to natural hazards. Failure analyses for WTs are systematically reviewed in this paper. [Method] The actual damage incidents during historical typhoons are summarized. Waves and earthquakes are another two types of potential hazards for offshore WTs that require serious consideration, although a limited number of WT structure failure induced by earthquakes was reported. A variety of load modeling and simulation methods, which are the prerequisite for WT structural failure analysis, have been developed for different types of loads. [Result] Accordingly, different finite element methods, dynamic simulation methods, and failure criteria have been studied and adopted in the failure analysis. The past results obtained show that extreme wind load governs structural failure of WTs. Meanwhile, structural health monitoring (SHM) techniques have seen increasing applications in civil and mechanical structures. The state-of-the-practice for SHM in civil infrastructure is introduced. Similar SHM concept has recently been applied in WT industry. [Conclusion] This review presents the principles and applications of SHM in WT. The valuable information derived from SHM systems can not only help to prevent potential structural failure, but also improve and optimize the current WT design. However, only a narrow range of WT SHM is covered in this paper. In-service long term monitoring for WT is a critical research area that needs significant research effort in future.
2018, 5(2): 60-64.
doi: 10.16516/j.gedi.issn2095-8676.2018.02.007
Abstract:
[Introduction] In order to research the possibility and feasibility of the combination of wave energy generation, ocean current energy generation and offshore wind power generation, [Method] the paper presented the combination of three common power generation by analyzing wave energy and the equipment type and technology level of current energy generation. By analyzing the natural conditions of wind energy, wave energy and ocean current energy in Fujian province, combined with the unique geographical location of offshore wind power project. [Result] This paper combed out offshore wind power project which is easy to combine with wave energy and ocean current energy generation, and put forward some problems needed attention in the next stage. [Conclusion] This paper puts forward a new way to develop marine energy and improve the efficiency of sea-use, which becomes a new research direction for the development of marine energy in the future.
2018, 5(2): 67-70.
doi: 10.16516/j.gedi.issn2095-8676.2018.02.009
Abstract:
[Introduction] The development and construction management of the montanic wind power differs significantly from the management of the traditional thermal power projects, this requires a wind power adapted constructing mode, which can reduce the risks during the wind power project and lubricate its construction process. [Method] This discussion pointed out the difficulties and the key points in the construcion of montanic wind power, and discussed its development and management works. [Result] The results indicate that the refined management measures direct to the montanic wind power construction are necessary. The measures include the staged objectives such as anemometry, the wind resource evaluation, the selection of wind turbine, micro-sitting selection and road design. Besides, the management of the building process, including QS, safety standards, duration of the project and daily communication, is also of the essence for the montanic wind power project. [Conclusion] The results contribute to the wind power plants that build and operate in mountainous areas, and may be insrtuctive to the healthy development of wind power in China.
2018, 5(2): 71-76.
doi: 10.16516/j.gedi.issn2095-8676.2018.02.010
Abstract:
[Introduction] Due to the intermittent, random and anti-peaking characteristics of wind power output, large-scale renewable energy wind power grid integration has made serious problem of wind power curtailment in winter heating period within Beijing-Tianjin-Tangshan region. [Method] To make quantitative research of the influence on wind power curtailment when power-peaking, tie-line delivery changes and accurately measure the accommodation capacity of wind power under different scenarios, the wind power curtailment evaluation method is established from the perspective of system peak-load regulation and subject to the balance of electric load, heating load and generator output constraints. [Result] The results show that the deeper depth of conventional peak-load regulation and the smaller depth of outside system delivery is, the large space of wind power accommodation capacity is accepted; while rapid growth of wind power installed capacity and higher rate of thermal power unit heating will inhibit wind power output, resulting in wind power curtailment. [Conclusion] So the ability of wind power accommodation capacity can be improved by activating the system peak-load regulation, controlling the liaison lines peak-to-valley difference and reduce the output range of the thermal power unit. While selecting a certain proportion of wind power installed capacity growth rate can control the amount of wind power to be rejected within a certain level.
2018, 5(2): 77-85.
doi: 10.16516/j.gedi.issn2095-8676.2018.02.011
Abstract:
[Introduction] Guangdong province is a typhoon-prone area, but neither the international offshore wind engineering design standards nor the Chinese design codes which to be issued consider the influence of typhoon. The objective reliability index (failure probability) remains unknown. Moreover, the partial safety factors (PSFs) for different loads in Chinese design codes are different, which will be an obstacle for the integrated design of offshore wind turbines. [Method] In this study, the authors compared the Chinese design codes with the international standards and calculated the objective reliability index of the codes and the corresponding modified PSFs under different coefficients of variance, ratios and correlation coefficients of load effects. And the authors also gave the method to obtain the equivalent unified PSF. [Result] The results show that using the same PSFs and combination factors, the reliability index will decreases by 0.5~1.0 when the coefficient of variation of loads increases from 0.2 to 0.6. [Conclusion] The authors suggests the reliability index of 3.2 and the PSFs and combination factor are determined by the site condition.
2018, 5(2): 86-92.
doi: 10.16516/j.gedi.issn2095-8676.2018.02.012
Abstract:
[Introduction] In offshore wind power project, it is necessary to test the pile at sea, which can further optimize the design of pile foundation and provide construction parameters for large scale pile sinking. In recent years, with the increasing capacity of the offshore wind turbine assembly machine, and the sea wind field site continues to move towards the deep water area, in order to meet the bearing requirements, the length of the steel pipe pile in the foundation of the offshore wind power is increasing. Compared with the ordinary test pile, there are many differences in the test pile of super long steel pipe pile. To ensure the offshore super long steel pipe pile is to achieve the desired goal, [Method] the key technology of offshore pile test was discussed in depth. The paper first discussed the setting of test items for super long steel pipe pile test, [Result] and determined the reasonable sequence of test piles. Then the paper analyzed the key technologies of super long steel pipe pile test pile, such as datum pile setting, counterforce device, pile driving construction, scour monitoring, pile protection and sensor protection for pile body, [Conclusion] which has guiding significance to the offshore super long steel pipe pile test project in the future; Finally, the future development and prospect of offshore pile testing project is summarized in this paper.
2018, 5(2): 93-98.
doi: 10.16516/j.gedi.issn2095-8676.2018.02.013
Abstract:
[Introduction] Offshore wind farm has been gradually developed with the strong support of China goverment. As the most important structure of offshore wind farm, offshore substations should be paid attention. Due to the wide range adaptability to water depth, most of the foundation of offshore substations has been currently used as jacket. According to the different connection between the jacket and pile, it was divided into skirt pile jacket and conventional jacket. [Method] Based on past experience, the skirt pile jacket was generally used in the deep water area (more than 40 m). In this paper, based on the construction and design of skirt pile jacket, the author compared the design with the conventional jacket under the regional geological conditions of one project. [Result] The results show that compared with the conventional jacket, the skirt pile jacket of offshore substation can reduce the length of the pile and the section of the jacket bar, thus the steel material is reduced and the cost is saved. [Conclusion] The research results have much significance in modularization development of offshore substation.
2018, 5(2): 99-108.
doi: 10.16516/j.gedi.issn2095-8676.2018.02.014
Abstract:
[Introduction] With the expansion of the offshore wind farm projects, new power transmission technologies have been widely applicated into the power transfer of the offshore wind farm. The offshore wind farm faces an new challenge which is different from the mature mode of inland power grid, then the different power transmission technologies and development prospect should be further defined. [Method] This paper summarizes the technical characteristics and development prospect of the four kinds of transmission methods including the offshore wind farm, namely, the high voltage AC submarine cable, the flexible DC transmission technology, the high pressure gas insulated pipe bus (GIL) and the hybrid DC transmission mode; meanwhile, the detailed cost structure analysis and calculation of the various transmission modes are proposed; Finally, economic comparison of different transmission distance from different transmission capacity of the transmission mode is made. [Result] The results we obtained demonstrate that the current high-voltage AC and DC transmission technology is more mature, and the transmission mode is affected by the transmission distance. The transmission distance is about 52 km as the critical point. AC transmission has economic advantages as the transmission distance is less than 52 km, the cost of AC transmission is equal to DC transmission as the transmission distance is about 52 km, and the cost of AC transmission is less than DC transmission as the transmission distance is more than 52 km, but the transmission capacity has no significant influence on the transmission mode. [Conclusion] With the different power transmission of the offshore wind farm, AC and DC transmission technology are respectively adoptd from shelf to offshore waters.
2018, 5(2): 109-114.
doi: 10.16516/j.gedi.issn2095-8676.2018.02.015
Abstract:
[Introduction] The power grid is usually formed in the type of distribution. This type of grid has high cost and poor economic effect. The VSC-HVDC technology does not require alternating phase current in the AC power grid, and the VSC-HVDC has the ability to control both active and reactive power. Besides, there is no need to configure a large amount of compensation equipment. So it can solve the problems for offshore platform. [Method] Based on the characteristics of VSC-HVDC technology and connection type, this article studied the DC control configuration, analyzed common DC fault characteristics and the DC protection configuration. [Result] The configuration principle and scheme of DC control system, the configuration principle and scheme of DC protection is given. [Conclusion] This work provides some guidance for the application of the technology in the related engineering.
2018, 5(2): 115-120,114.
doi: 10.16516/j.gedi.issn2095-8676.2018.02.016
Abstract:
[Introduction] Offshore platforms generally use self-powered offshore solutions. The power supply has a single power source, poor scalability, weak impact resistance, and low reliability and reliability of power supply. At the same time, the space of the offshore platform is very limited, and the investment in building a self-powered power supply is relatively high. [Method] Based on a comparative study of the advantages and disadvantages of shoreline AC power transmission and DC power transmission schemes, this paper proposes a hybrid HVDC transmission scheme for a technically feasible and economical offshore platform. On this basis, this paper establishes the mathematical model of the conventional direct current and offshore platform side flexible DC on the land network. Combining the typical control method of the traditional HVDC converter and the typical control method of the flexible DC converter, a hybrid HVDC control strategy is proposed. [Result] An electromagnetic transient simulation model of a hybrid flexible HVDC transmission system is established on PSCAD/EMTDC, including simulation system models of near area AC grid, hybrid HVDC system and offshore platform system. Carry out modeling and simulation analysis and analysis. [Conclusion] The research results are very important to solve the safety and reliable power supply of offshore platform.
2018, 5(2): 121-125.
doi: 10.16516/j.gedi.issn2095-8676.2018.02.017
Abstract:
[Introduction] Protection of submarine power cables is an important part of offshore wind farms construction. The largest insurance claims in offshore wind power are due to cable damages. As the cable routing is long, it will pass through different regions. Therefore, the protection schemes in each area are different. [Method] In this paper, the basic situation of submarine power cable protection is briefly introduced, and then the submarine cable landing scheme is described in detail. Then, the protection scheme of the submarine power cable over other cables or pipes and besides cable tube is described. Finally, the protection schemes of submarine power cable in offshore wind farm is summarized. [Result] For the landing section of submarine cables, casing protection, cable trenches and horizontal directional drilling schemes are mostly used; for the cross-section of submarine cables, cushion block solution is adopted at the crossover point; for the submarine cable near the foundation, J-tube with a bend restrictor is mainly used. [Conclusion] No matter which method is adopted, the protection of submarine cables in offshore wind farms should be highly valued to ensure the safety of submarine cables during operation.
2018, 5(2): 126-132.
doi: 10.16516/j.gedi.issn2095-8676.2018.02.018
Abstract:
[Introduction] Due to the jacket multi-pile structure-foundation has not been widely used in our country up to now, there is no mature technology for using. In order to solve the difficult problem of jack four-pile foundation positioning accuracy control and tilt control for Zhuhai Gui Shan Offshore Wind Power Engineering, we explored a new technology, which fills a domestic gap. [Method] According to carefully analyzed the special hydrology、geology、wind、waves and other sea conditions, combined with international cases, repeated investigation and research, and invite expert argumentation, We finally proposed a new method to control the positional accuracy and tilt accuracy of multi-pile connection, and designed a set equipment to assist jacket installation. [Result] The set of techniques′ function include double-deck guide frame for accurate positioning and leveling、lower guide frame for limiting pile inserting、double hydraulic jack is used to adjust the inclination of steel pile、RTK GPS total station real-time tracking and guide jacket connect to multi-pile underwater. The method was successfully used in Zhuhai Gui Shan Offshore Wind Power Engineering, it optimized the design process, made the jacket four-pile foundation installation project completed efficiently、high quality and accurately. The application in the ZhuHai project saved much valuable time, it made a good preparation for wind-turbine installation, sea cable laying and combining to grid. [Conclusion] The application of the techniques promoted the jacket multi-pile theoretical research to engineering practice, solved the difficult problem of jacket multi-pile installation accuracy controlling for offshore wind powering engineering, made a good technical reserve for wide use of jacket multi-pile platform in offshore wind powering engineering.
2018, 5(2): 133-137.
doi: 10.16516/j.gedi.issn2095-8676.2018.02.019
Abstract:
[Introduction] With the rapid development of offshore wind turbine installed capacity, the owner attaches more and more importance to safe operation of offshore wind turbines, and imposes more stringent requirements for reliability. The traditional after-fault trouble-shooting pattern cannot ensure reliability of offshore wind power equipment. Moreover, as the accessibility of the offshore wind power equipment is unfavorable, the passive trouble-shooting pattern leads to huge loss of outgoing power, which fails to meet the latest requirements of the modern offshore wind farm. The intelligent fault warning system can predict the abnormal conditions of equipment and eliminate the hidden danger at its very beginning stage, preventing it from further deterioration. [Method] The forecast of critical faults, such as generator temperature abnormal, generator bearing abnormal and gear box heat dissipation abnormal and cog belt rupture, can be achieved in advance, by collecting the data of wind turbine unit critical components, summing up the fault characteristics from historical data and employing the big data algorithm including neural network. [Result] In accordance with early warning of equipment faults, active and preventive maintenance strategy can be practiced in a planned manner, in combination with the OWF maintenance characteristics of meteorology, typhoon, oceanic and maritime conditions. Thus, large component faults and wind turbine unit failures can be effectively prevented. [Conclusion] The research results could enhance the wind turbine unit reliability and ensure the overall gains of the offshore wind farm.
2018, 5(2): 138-142.
doi: 10.16516/j.gedi.issn2095-8676.2018.02.020
Abstract:
[Introduction] Ultra-short baseline positioning is an important underwater acoustic positioning method, the paper mainly solves the disadvantages that remote positioning of ultra-short baseline positioning spread fast and is not high accurate. [Method] The paper introduced the principle of ultra-short baseline positioning system, analyzed the various factors which cause ultra-short baseline positioning error, and aimed at these factors, proposed the corresponding processing strategy. [Result] Combined with practical application of Hainan Island Power Grid Interconnection Project submarine cable testing, validated the effectiveness that processing strategy of ultra-short baseline positioning overcome the disadvantages remote positioning of ultra-short baseline positioning spread fast and is not high accurate. [Conclusion] Hainan Island Power Grid Interconnection Project submarine cable testing in practical application proves that the processing strategy in high accurate positioning at the bottom of sea direct at the disadvantages remote positioning of ultra-short baseline positioning spread fast and have low accuracy is effective.
2018, 5(2): 143-148.
doi: 10.16516/j.gedi.issn2095-8676.2018.02.021
Abstract:
[Introduction] China′s offshore wind power industry has entered a period of rapid development. How to innovate project development and management models and effectively deal with issues such as high cost, multiple interfaces, and long construction schedules to achieve cost reduction and efficiency enhancement are important for promoting the healthy and rapid development of the offshore wind power industry. [Method] This paper applies the concept of ecosystem to offshore wind farm project development to construct an offshore wind power project ecosystem whose core is building a wind farm neural network, improve the overall associated efficiency, and achieve the goal of optimal development of offshore wind farms. Using the AHP to quantitatively analyze the weight of the system′s impact factors. [Result] Through the construction of an offshore wind farm ecosystem, offshore wind farms have the ability to quickly collect, store, share, analyze information and perform feedback regulation, reduce costs and increase efficiency, and enhance the stability of wind farms. [Conclusion] The introduction of the ecosystem has provided new ideas for the development and management of offshore wind farm projects. With the help of cutting-edge technologies such as artificial intelligence, offshore wind farm ecosystems will be continuously improved and widely used.
