Offshore Wind Power Development Research Articles

Assessment of long-term offshore wind energy potential in the south and southeast coasts of China based on a 55-year dataset

In this study, based on the Japanese 55-year Reanalysis (JRA-55) dataset, the spatio-temporal variations of wind resources were analyzed in the South China Sea. An approach to determine suitable locations of offshore wind energy extraction was proposed and applied to the south and southeast coasts of China. The approach took into account various criteria, including long-term change and wave condition, with different weights. The results showed that Luzon Strait and Taiwan Strait have higher wind energy potential than other areas, while the intra-annual fluctuation in Luzon Strait is significantly high, ranging from 400 to 2500 W/m2 and thus it is not suitable to provide stable power output. The investigation of the long-term change showed that most of the South China Sea experienced a remarkable decrease in the period of 1971–1980, while the overall long-term wind energy trend during five decades was mostly even. The investigation in selected sites indicated that the most suitable location for wind power exploitation is the nearshore of Quanzhou, Fujian, near which there are wind farms under construction, already. The suggested future offshore wind power development is along the coasts of Hong Kong, with the potential of generating 35.36 MWh/y per wind turbine of type SWT-7.0-154.

Sustainable and clean oilfield development: How access to wind power can make offshore platforms more sustainable with production stability

With the continuous development of offshore wind power and clean oil fields, the introduction of wind power into the offshore oil and gas field energy system has attracted much more attention. As an oil and gas production platform with both production capacity and energy consumption, on the premise of ensuring stable production, the adoption of an economical and reasonable energy device design scheme will not only help to reduce the construction cost, but also can promote energy-saving and emission reduction. In this paper, the economic and environmental performance of the energy system for three scenarios including traditional energy system, DES without wind energy access and DES with wind energy access are simulated by building a new robust optimization model for energy system that takes the minimum annual total cost of the energy system as the objective function. The impact of wind power access platform grid on the DES is comparatively analyzed in detail. Taking an oil production platform in the Pacific as an example, the results show that, while wind power access reduces carbon emissions by approximately 39.91%, it can also reduce the total annual cost of the system by approximately 2.57%. At the same time, through sensitivity analysis, we found that there is an optimal ratio 57.04% of wind energy based on economy which is influenced by crude oil price. In addition, the effects of uncertain parameters including energy demand, associated gas production and wind power are compared and analyzed, which can provide risk mitigation support for decision makers.

Offshore Wind Power Supports China’s Energy Transition

China is rich in offshore wind power resources, and these resources can be locally consumed by the economically developed provinces located in the eastern coastal region. The development of offshore wind power can accelerate the energy transition in China and help achieve carbon peak in 2030 and carbon neutrality in 2060. In this article, we analyze the current situation, trends, and challenges of energy development in China, and propose that the development of offshore wind power is an important strategic support for the energy structure transformation in China. The key technologies of offshore wind power development in China are summarized including wind turbine, offshore power transmission, offshore engineering, and operation and maintenance technologies. In view of the bottleneck problems restricting the development of China’s offshore wind power industry, we propose some countermeasures and suggestions to promote the healthy and orderly development of China’s offshore wind power industry from five aspects: exploration and evaluation of offshore wind power resources, understanding of energy transition, overall planning and integrated planning, scientific and technological innovation, and policy support mechanism.

Research on Seismic Analysis of Converter Valve of Offshore Flexible High Voltage Direct Current Considering the Effect of Initial Displacement

Due to the acceleration of global energy transformation and the reduction of the cost of new energy, offshore wind power has been attached great importance by many countries. Therefore, offshore wind power transmission based on flexible HVDC transmission technology has become a hot issue in the development and research of offshore wind power. When the offshore platform is running for a long time, there may be extreme conditions of encountering earthquake. As the core component of flexible HVDC transmission, converter valve's structural safety research under earthquake is very necessary. Different from the onshore converter station and limited by the installation environment, the bottom support insulator of offshore converter valve tower may have initial displacement after being installed on the foundation plate of offshore platform. However, there is no literature on the effect of initial displacement on the dynamic characteristics and seismic performance of valve towers. In this paper, a practical engineering valve tower is taken as an example. Firstly, the influence of different initial displacements on the dynamic characteristics of valve tower is studied. Then, the dynamic analysis of valve tower under earthquake load is carried out by using time history integration algorithm. The influence of initial displacement on the structural safety of valve tower is studied by comparison method. The results of this paper can provide reference for similar projects.

Research on the Influence of Development Scenarios on the OLCOE of Wind Power: A Case Study of China

To achieve a high penetration of renewable energy, wind power development in China has gradually moved to diverse manifestation (e.g., centralized onshore, low wind speed, and offshore wind power). However, preexisting studies regarding wind power cost neglect to consider the respective characteristics of different development scenarios. In this paper, the overall levelized cost of energy (OLCOE) model is established for different scenarios. Taking China’s wind farm data as an example, the impact of development scenarios and wind power permeability on OLCOE and its cost components is quantitatively analysed. The results show that, (1) in the low penetration scenario, low wind speed power has the best economy and is beneficial to the conventional units; (2) the large-scale development of offshore wind power requires a reduction in the cost of offshore wind turbines and submarine cables; and (3) at present, onshore centralized wind power has economic advantages, but there is little room for its cost reduction.

Building a grey-based multi-criteria decision-making model for offshore wind farm site selection

The selection of suitable sites is a critical step for the successful development of offshore wind power. This study aims to establish an assessment framework to select the optimal alternative under multiple conflicting criteria. A hybrid model that combines the grey decision-making trial-and-evaluation laboratory-based analytic network process (grey DANP) and probability-based grey relational analysis (P-GRA) methods is proposed. Grey DANP can not only map the influential network relationship of the criteria, but also generate a set of criteria influence weights. In addition, P-GRA, which uses the concept of interval analysis, can be used to determine the gap between the alternatives and the ideal referential solution (IRS). P-GRA retains the interval value type in the calculation process to avoid the loss of potential information. The proposed model optimizes the traditional DANP and GRA methods, which improving their effectiveness and practicability for practical applications. This paper contributes to solving the problem of farm site selection based on the potential for sustainable development and the novelty of the analysis model. A case study of a Taiwan example is used to examine the feasibility of the proposed model. Finally, a sensitivity analysis was conducted to demonstrate the robustness and innovativeness of the proposed model.

Integration technology and practice for long‐distance offshore wind power in China

Offshore wind power is an important kind of clean energy and of great development potential in the future. It has advantages of high wind speed and stable wind power, and gradually exhibits large-scale, clustering, and long-distance characteristics. Key technical problems of large-capacity offshore wind power transmission over long distance must be solved in the development and utilization of offshore wind power, and will be addressed in this paper. First, this paper presents the overview of long-distance offshore wind power integration in China, and then summarizes three types of integration schemes and its applicability. Second, it analyzes the characteristics of the voltage source converter based high voltage direct current (VSC-HVDC) integration scheme and associated key technical problems in practice, and the first milestone long-distance offshore wind power integration VSC-HVDC project in China is then introduced. Finally, recommendations on long-distance offshore wind power development in China are presented based on the characteristics of long-distance offshore wind power and VSC-HVDC integration technology.

Inaugural editorial: Energy Conversion and Economics

Inaugural editorial: <i>Energy Conversion and Economics</i>

Regulation for offshore wind power development in Brazil

Offshore wind power is one of the fastest growing renewable energies and the Brazilian coastline with nearly 9650 km has a great wind potential. Even though offshore oil and gas regulation is well established, this is still unknown for offshore wind power. This article aims to propose a regulatory framework for development of offshore wind power in Brazil. A literature review and case studies were conducted on offshore wind regulation in Denmark, United Kingdom and Germany and on Brazilian offshore oil and gas. The framework involves three macro phases: Pre-development, Development and Operation and Post-Operation. As Brazil is a new market, the use of two concession regimes is proposed: open door and tender. The framework proposes a feed-in tariff contracted in the tender with readjustments by the General Index of Market Prices. The required licenses, authorized by ANEEL, IBAMA and COMAER are: area concession, simplified license for studies, marine and air collision, cable laying, construction and operation and pre-decommissioning. The research concludes that the legal framework should consider the entire life cycle of wind farm in order to avoid future regulatory problems such as those that occurred with the offshore oil and gas, which did not consider the decommissioning stage.

Novel Submodule Topology With Large Current Operation and DC-Fault Blocking Capability for MMC-HVDC

High-voltage direct-current system based on modular multilevel converter (MMC-HVDC) is widely expected to plays a significant role in promoting the development of large-scale offshore wind power. The maximum current limit of insulated-gate bipolar transistor (IGBT) is the main constrain for MMC-HVDC to operate in large current operation, while DC-fault blocking ability and economy are the two important concerns of MMC-HVDC. This paper proposes a novel parallel multiple submodule (PM-SM) topology to realize parallel output of submodule currents, which make MMC capable of large current operation and have filtering effect on high frequency harmonics. Combining with carrier phase-shift modulation or nearest level modulation, the frequency multiplication of bridge arm current of MMC can be realized to further improve the power quality of the system. Considering the demand of DC-fault blocking ability, simplified full-bridge double submodule (S-FBDSM) is also proposed as an economical option to compose PM-SM. It can provide double the reverse capacitance voltages in the arm current path regardless of a positive or negative arm fault current. The economic analysis is conducted to demonstrate the advantage of S-FBDSM. Simulation results and experiment results verify the feasibility and superiority of PM-SM composed of S-FBDSM.

SWOT Analysis of Offshore Wind Power Development in Guangdong Province

This paper starts with the current development situation of offshore wind power industry in Guangdong province, and uses SWOT analysis to explore the advantages, disadvantages, opportunities and threats of the offshore wind power industry in the Guangdong province. Based on the analysis, this paper gives some suggestions for the policy makers: firstly, it is necessary to create a proper management system for offshore wind power; secondly, Guangdong should enhance its own equipment manufacturing and scientific research capabilities which would benefit the offshore wind power industry; finally, an effective typhoon-damage prevention system is required.

A Distributed Cooperative Control Strategy of Offshore Wind Turbine Groups with Input Time Delay

With large-scale development of offshore wind power and the increasing scale of power grid interconnection, more and more attention has been drawn to the stable operation of wind power units. When the wide area measurement system (WAMS) is applied to the power system, the time delay mainly occurs in the signal measurement and transmission of the power system. When 10MW wind turbines transmit information through complex communication network, time delay often exists, which leads to the degradation of performance and instability for system. This affects the normal operation of a wind farm. Therefore, in this paper, the distributed control problem of doubly fed wind turbines with input time delay is studied based on the Hamiltonian energy theory. Firstly, the Port-controlled Hamiltonian system with Dissipation (PCH-D) model is implemented with the Hamiltonian energy method. Then, the Casimir function is introduced into the PCH-D model of the single wind turbine system to stabilize the time delay. The wind turbine group is regarded as one network and the distributed control strategy is designed, so that the whole wind turbine cluster can remain stable given a time delay occurring in the range of 30–300 ms. Finally, simulation results show that the output power of the wind turbine cluster with input delay converges to the expected value rapidly and remains stable. Additionally, the system error caused by time delay is greatly reduced. This control method can effectively solve the problem of input time delay and improve the stability of the wind turbine cluster. Moreover, the method proposed in this paper can adopt the conventional time step of dynamic simulation, which is more efficient in calculation. This method has adaptability in transient stability analysis of large-scale power system, however, the third-order mathematical model used in this paper cannot be used to analyze the internal dynamics of the whole power converter.

Numerical Analysis of Horizontal Bearing Capacity of Composite Pile Foundation for Offshore Wind Turbine

In recent years, with the rapid development of offshore wind power, the installed capacity is increasing, and the traditional single pile foundation is under heavy load. Therefore, the composite pile foundation composed of single pile foundation and bucket foundation (friction wheel) installed outside the pile body is gradually adopted to ensure the safety and stability of the fan during its service. In order to study the bearing capacity of composite pile foundation, the ABAQUS finite element software is used to study the horizontal bearing capacity of composite pile foundation, analyze its bearing capacity advantages compared with the traditional single pile foundation, and further optimize the design. The results show that: under the same load, the displacement and bending moment of composite pile foundation are greatly reduced due to the existence of friction wheel, and the horizontal bearing capacity of composite pile foundation is significantly better than that of single pile foundation; the diameter and height of friction wheel in composite pile foundation have obvious influence on its horizontal bearing capacity, but its thickness has limited influence on the horizontal bearing capacity of composite pile foundation. It can be seen that the bearing capacity of composite pile foundation is significantly better than that of single pile.

Technical and economic demands of HVDC submarine cable technology for Global Energy Interconnection

Power transmission across the sea is an important part of global energy interconnection (GEI). To support the construction of GEI and to serve the needs of future clean energy trans-sea transportation and offshore wind power development, this study a) analyzes the requirements of the GEI backbone network pertaining to direct current (DC) submarine cable technology, and b) defines the key technical and economic indices of ultrahigh-voltage direct current (UHVDC) submarine cable based on theoretical computations. The research is based on the thermoelectric coupling model and the finite element method. It is shown that the dielectric strength of the insulating materials of the ±800 kV~±1100 kV/ 4000 MW~12000 MW UHVDC submarine cable (extrusion insulation) should be not less than 43~65 kV/mm, while the heat resistance is not less than 110 °C. As the cost of submarine cable is 5~10 times higher than that of the overhead line, the project investment need to be decreased to a level within the economical carrying capacity to guarantee extensive applicability of the HVDC submarine cable technology.

Optimization modelling of HCMC-STATCOMs for offshore wind power based on PSCAD

Under normal circumstances, the voltage fluctuation of the wind farm’s grid connection point is mainly caused by the volatility of wind power output. In recent years, with the clustering development of offshore wind power, the voltage fluctuation brought by the output fluctuation of wind power is becoming more and more notable. The main method of improving the reactive voltage problem of wind farms is to add more static and dynamic reactive power compensation devices. Hybrid cascaded multilevel converter STATCOMs (HCMC-STATCOMs) don’t need transformers to increase the device capacity and decrease the harmonics on the output voltage, which is effective in reducing the device cost and volume. This paper firstly introduces the topology and operation principles of an HCMC-STATCOM and then carries out a comparative study on HCMC-STATCOMs and traditional cascaded STATCOMs. Finally PSCAD/EMTDC is applied to model and simulate HCMC-STATCOMs. The simulation result shows that the reactive power of HCMC-STATCOMs can accurately vary according to the system’s demand on reactive power. This means that HCMC-STATCOMs have good dynamic performance and the harmonic contents in the output phase voltage and AC current are quite small. As a dynamic reactive power compensation device, HCMC-STATCOM can be adjusted in real time according to the system’s reactive power requirements, and has the advantages of small volume and low cost. The simulation results show that the properties of HCMC-STATCOMs are advantageous for the operation and control of the system and applicable for the dynamic reactive power configuration of offshore wind power.

Immune response of mollusk Onchidium struma to extremely low-frequency electromagnetic fields (ELF-EMF, 50 Hz) exposure based on immune-related enzyme activity and De novo transcriptome analysis

Along with rapid offshore and onshore wind power development in modern society, extremely low frequency electromagnetic fields (ELF-EMF) is produced extensively in the habits of aquatic organisms. However, the biological effects of ELF-EMF on aquatic organisms are almost sparse. In this study, Onchidium struma without shell was chosen to aim whether ELF-EMF can elicit immune response of mollusk based on immune-related enzyme activities and gene expression through high-throughput transcriptome sequencing. Three experimental groups, i.e. ELF-EMF unexposed control group (C), ELF-EMF (50 Hz, 100 μT) exposed E1 group, and ELF-EMF (50 Hz, 500 μT) exposed E2 group, were set, and coelomocytes were collected to analyze. The results showed that total coelomocyte and spherulocyte density in E1 group increased significantly compared to groups C and E2 (P < 0.05). There were no significant differences on amoebocyte and chromatocyte density among groups C, E1 and E2. ELF-EMF exposure could significantly increase immune-related enzyme activities in coelomic fluid of O. struma, including acidic phosphatase, alkaline phosphatase, antioxidative capacity, catalase, superoxide dismutase, and polyphenol oxidase (P < 0.05). A total of 54.32 Mb and 55.27 Mb raw reads with average length of 1520 bp were obtained from coelomocytes of O. struma in unexposed and exposed groups, respectively. There were 341 differentially expressed genes (DGEs) between unexposed and exposed groups, including 209 up-regulated and 132 down-regulated unigenes. All the DGEs were allocated to 14 Kyoto Encyclopedia of Genes and Genomes pathways, and five pathways were associated with immune response, including TLR/TNF/NOD-like receptor/MAPK/Fc epsilon RI signaling pathways. Altogether, short-term (to one week) exposure of O. struma to lower luxy density ELF-EMF (<500 μT) could elicit the immune response, and antioxidant system is recommended as indicators of immunological effects. Hopefully, this study will further provide insights into exploring biomarker for evaluation of the effect of ELF-EMF exposure on aquatic organisms regarding to field density, frequency and exposure duration, and provide good guidance for exploitation and utilization of renewable energy.

Applicability of Low Frequency Transmission Technology in Offshore Wind Power Transmission Scene

This paper investigates the worldwide development status of wind power and the main opinions and advantages of offshore wind power development in the industry, and summarizes that the development of offshore wind power will be in the direction of large capacity and distant sea area. At the same time, the distribution of wind energy resources in China’s coastal areas is investigated, and combined with the constraints of offshore wind energy development in China, it is concluded that offshore wind power development in China will also develop to distant sea areas. Secondly, three transmission modes including power frequency AC, flexible HVDC and low frequency AC are briefly described, and the technical economy of the three modes is analyzed with typical cases. In addition, the technical feasibility of 400 MW offshore wind power Grid-connected through low-frequency transmission technology is verified by system model building and simulation. Thirdly, combined with the development trend of offshore wind power, current research and manufacturing level, the opportunities and challenges of the application of low frequency transmission technology are analyzed. Finally, the main points of this paper are summarized. It is preliminarily clear that the low-frequency transmission mode has better technical and economic performance within a certain transmission distance, and can be used as a beneficial supplement to the conventional power frequency and flexible HVDC transmission mode.

L2 Disturbance Suppression Controller Design for Multiple Time Delays Offshore Wind Turbines

With the large-scale development of offshore wind power and the rapid development of smart grid, more and more attention has been paid to the stable operation of wind turbines under various conditions. In the actual operation process of wind turbines, there are inevitably many kinds of uncertain time delays, and also external or parameter disturbances, which affect the stable operation of wind turbines and make the system deviate from the original stable state. Based on Hamiltonian energy theory, the disturbance rejection of doubly fed wind turbines with multiple time delays is studied in this paper. Firstly, the doubly fed wind turbine is Hamiltonian realized to obtain its port controlled Hamiltonian with dissipation(PCH-D) model. Then, aiming at the PCH-D model, a multiple time delays controller is designed based on Casimir function, which can make wind turbines run stably under multiple time delays. Furthermore, based on the passive control theory, L2 gain disturbance rejection control technology is introduced to eliminate the steady-state error caused by external disturbance and improve the stability of wind turbines. Finally, the simulation results show that the proposed controller can effectively solve the multiple time delays and disturbance problems in the system, and improve the stability and anti-interference of wind turbines.

A decision framework of offshore wind power station site selection using a PROMETHEE method under intuitionistic fuzzy environment: A case in China

Multi-criteria decision-making (MCDM) method has a widely application in management and energy field. Considering the broad development prospects of offshore wind power and deficiency of integrated coastal management, a decision framework combining triangular intuitionistic fuzzy numbers (TIFNs), Analytic Network Process (ANP) and Preference Ranking Organization Method for Enrichment Evaluations (PROMETHEE) is proposed and applied in site selection of offshore wind power station (OWPS). The aim of this study is to provide theoretical and methodological support for the site selection decision-making of coastal wind power projects and to improve the benefits of integrated coastal management. Taking six criteria (wind resources, construction, economic, environment, society, risk) and the related sub-criteria into consideration, an evaluation system of OWPS site selection is established. The optimal location scheme is determined by the decision framework in current paper. After a sensitivity analysis and a comparative analysis, the result shows that decision framework has strong robustness and feasibility. Thus, the evaluation criteria and methodology in this paper can provide a theoretical reference for the development of coastal management and offshore wind power.

유럽 주요국과 한국의 해상풍력개발정부 정책 비교연구

유럽 주요국과 한국의 해상풍력개발정부 정책 비교연구