Development Of Offshore Wind Farms Research Articles

Case studies on suction caisson foundations in offshore wind farms in China

ABSTRACT Suction caissons are cylindrical-shaped foundation elements closed at the top and open at the bottom which are almost completely embedded with their cylindrical part in the soil. The main advantage of this foundation compared to other commonly used foundation concepts is its fast, ease, and almost noiseless installation, as well as the effortless removal at the end of the lifetime. Suction caissons supporting three- or four-legged jackets have been employed successfully in several recent offshore windfarm projects around the world. The study presented herein investigates the general suitability of suction caissons in the south china sea at three representative sites. The results show that suction caisson foundations are technically feasible. Sizes can be large and may vary between 13 m to 15 m in diameter and 10 m to 13 m in length, which, however, may reduce noticeably when considering load redistribution in the design, typically done in a FEED and detailed design. The main challenges of suction caisson application are the very soft soil conditions and possible liquefaction potential due to large earthquake events. Although technically feasible, the economic viability of suction caissons needs to be investigated on project-specific basis. For that purpose, the authors provide an overview of general aspects which need to be considered in such an evaluation. This study gives realistic case studies for research and industry in offshore wind farm development.

해상풍력단지 개발을 위한 부유식 라이다 검증

해상풍력단지 개발을 위한 부유식 라이다 검증

Numerical modelling of the migration direction of tidal sand waves over sand banks

Tidal sand waves are large-scale bed forms found in shallow sandy seas, which show a migration of several meters per year. Field data from the Dutch part of the North Sea revealed a migration pattern causing bidirectional migration of sand waves over a sand bank, resulting in sand wave migration uphill from both sides of the sand bank. In order to understand the physical mechanisms behind this migration behaviour, we study the inclusion of a sand bank under a sand wave field using the numerical model Delft3D. First, the schematized model set-up (i.e. schematized bathymetry and simple tidal forcing) showed that the alteration of the tidal flow by a sand bank resulted in tide-averaged horizontal flow towards the top of the sand bank, causing the bidirectional migration of sand waves over the sand bank. Second, a case study was performed in which a more complex model set-up was used (bathymetry and tidal forcing identical to a study site in the North Sea where an offshore wind farm is developed). Here, the model results revealed migration directions comparable to field observations. The results open opportunities to explore modelling migration patterns of sand wave fields for offshore wind farm development in areas with complex bathymetric environments.

Effects of offshore windfarms on seabird abundance: Strong effects in spring and in the breeding season

The increasing development of offshore wind farms (OWFs) worldwide leads to possible conflicts with the ecological requirements of top predators that largely depend on offshore areas. Seabird species exhibit different behavioural reactions to OWFs, ranging from avoidance resulting in habitat loss, to attraction causing an increased risk of colliding with the turbines. We investigated how OWFs affected the densities and distributions of guillemots and kittiwakes breeding in the southern North Sea and if the effects varied among seasons using a ‘before–after control impact’ (BACI) analysis approach based on a large-scale and long-term dataset covering 14 years before and 3 years after the construction of OWFs. Guillemot relative density in the OWF decreased by 63% in spring, and by 44% in the breeding season. Kittiwake relative density in the OWF decreased by 45% in the breeding season, and not significantly by 10% in spring. We furthermore estimated the response radii to the OWF for both species and seasons, finding that guillemots showed a response radius of ~9 km in spring and kittiwakes a radius of ~20 km in the breeding season. The results underline the value of large-scale and long-term assessments considering seasonal variation throughout the yearly cycle. The here provided information on the seasonally different reactions of seabirds to OWFs adds substantially to our current knowledge and provides the necessary basis for reliable estimations of OWF effects on guillemots and kittiwakes. Such evaluations are urgently needed for future planning and management recommendations to decision-makers.

Design considerations of suction caisson foundations for offshore wind turbines in Southern China

Suction caisson foundations are increasingly considered as a foundation solution for offshore wind farm development in China. This paper outlines the design considerations for developing a suction caisson supported jacket solution for an offshore wind farm in Southern China. Geotechnical analyses for four major aspects, ultimate limit state (ULS), serviceability limit state (SLS), fatigue limit state (FLS) and installation are discussed. The design challenges encountered in the project due to soft seabed and metocean characteristics (severe typhoon loading and dominant wind directions) and technical approaches adopted by the project are presented. Areas for further studies are identified and discussed. The purpose of this paper is to disseminate this knowledge and raise awareness of several important aspects.

OFFSHORE WIND ENERGY RESOURCE ASSESSMENT IN MALAYSIA WITH SATELLITE ALTIMETRY

Realistic view on the potential of offshore wind farm development in Malaysia is necessary and requires accurate and wide coverage of wind speed data. Long term global datasets of satellite altimetry of wind speed provide a potentially valuable resource to identify the potential of offshore wind energy in Malaysia. This paper presents three different assessments of offshore wind energy resources in Malaysia using satellite altimetry. The wind speed data obtained from Radar Altimeter Database System (RADS) were validated and identified to be in agreement with previous studies. The resources were then assessed at three different levels; theoretical, technical and practical offshore wind energy potential. The technical resource potential was assessed by taking into consideration the available offshore wind turbine technology. Conflicting uses and environmental constraints that define the practical offshore wind energy resources are plotted on the maps to present a practicality of offshore wind farm development in Malaysian sea. The study concluded that, in theoretical view, Malaysia does have potential of offshore wind energy resource especially in Borneo Water with average annual wind energy density above 500 kWh/m2. However, the development of offshore wind farm in Malaysia will be difficult taking into consideration the technical and practical challenge.

How to model social-ecological systems? – A case study on the effects of a future offshore wind farm on the local society and ecosystem, and whether social compensation matters

Models of social-ecological systems (SES) are acknowledged as an important tool to understand human-nature relations. However, many SES models fail to integrate adequate information from both the human and ecological subsystems. With an example model of a future Offshore Wind Farm development and its effects on both the ecosystem and local human population, we illustrate a method facilitating a “balanced” SES model, in terms of including information from both subsystems. We use qualitative mathematical modeling, which allows to quickly analyze the structure and dynamics of a system without including quantitative data, and therefore to compare alternative system structures based on different understandings of how the system works. By including similar number of system variables in the two subsystems, we balanced the complexity between them. Our analyses show that this complexity is important in order to predict indirect and sometimes counterintuitive effects. We also highlight some conceptually important questions concerning social compensations during developmental projects in general, and wind farms in particular. Our results suggest that the more project holders get involved in various manner in the local socio-ecological system, the more society will benefit as a whole. Increased involvement through e.g. new projects or job-opportunities around the windfarm has the capacity to offset the negative effects of the windfarm on the local community. These benefits are enhanced when there is an overall acceptance and appropriation of the project. We suggest this method as a tool to support the decision-making process and to facilitate discussions between stakeholders, especially among local communities.

Model Tests on the Penetration Resistance of Bucket Foundations for Offshore Wind Turbines in Sand

Driven by the rapid development of offshore wind farms, bucket foundations have come to constitute a very promising form of foundation for offshore wind turbines, mainly owing to their efficient construction. However, the penetration resistance of the suction penetration of a bucket foundation, when calculated inaccurately, may lead to installation failure of the foundation. In this study, model tests were performed on the suction penetration of a mono-bucket mono-compartment foundation and a mono-bucket multi-compartment foundation in saturated fine marine sand, aiming to compare their penetration resistances and critical suctions, and the development of a soil plug in the two models was analyzed. The results will provide a design reference for the penetration construction of bucket foundations for offshore wind turbines.

Spatial energy planning of offshore wind farms in Greece using GIS and a hybrid MCDM methodological approach

The present paper focuses on the efficient development of offshore wind farms in shallow waters in Greece. An integrated spatial energy planning approach is introduced. The proposed methodology is implemented using geographic information system and Statistical Design Institute software and applied at the national spatial planning scale. It consists of four distinct stages: (1) identifying appropriate areas to site offshore wind farms (the macro-siting configuration), (2) determining the principal technical specifications of the offshore wind turbines as well as the micro-siting configurations of offshore wind projects, (3) estimating the total investment cost of each potential offshore wind project, and (4) prioritizing the most suitable potential sites for offshore wind farms based on specific assessment criteria. The final outcomes of the proposed methodology are the development of a marine site suitability index and an assessment of the effects of different policy orientations for offshore wind farm siting on that index. Four ‘what-if’ critical scenarios are applied to test the robustness of the overall suitability index to the subjectivity of expert judgments of potential sites and thus assess the reliability of the proposed methodology. The implementation of the proposed methodology could facilitate the fulfillment of national targets for the energy sector and encourage energy interdependence among many geographic areas in Greece, since the total estimated production capacity of all the proposed offshore wind projects is expected to reach 1,185 MW.

Using Artificial-Reef Knowledge to Enhance the Ecological Function of Offshore Wind Turbine Foundations: Implications for Fish Abundance and Diversity

As the development of large-scale offshore wind farms (OWFs) amplifies due to technological progress and a growing demand for renewable energy, associated footprints on the seabed are becoming increasingly common within soft-bottom environments. A large part of the footprint is the scour protection, often consisting of rocks that are positioned on the seabed to prevent erosion. As such, scour protection may resemble a marine rocky reef and could have important ecosystem functions. While acknowledging that OWFs disrupt the marine environment, the aim of this systematic review was to examine the effects of scour protection on fish assemblages, relate them to the effects of designated artificial reefs (ARs) and, ultimately, reveal how future scour protection may be tailored to support abundance and diversity of marine species. The results revealed frequent increases in abundances of species associated with hard substrata after the establishment of artificial structures (i.e., both OWFs and ARs) in the marine environment. Literature indicated that scour protection meets the requirements to function as an AR, often providing shelter, nursery, reproduction, and/or feeding opportunities. Using knowledge from AR models, this review suggests methodology for ecological improvements of future scour protections, aiming towards a more successful integration into the marine environment.

Interval type-2 fuzzy sets based multi-criteria decision-making model for offshore wind farm development in Ireland

Offshore wind energy takes up an important place in Ireland’s renewable generation portfolio thanks to its abundant offshore wind resource. Optimal offshore site selection and developing site-specific energy policy instruments are of key importance to the success of offshore wind energy investments. In this respect, this study aims at developing a multi-criteria decision-making (MCDM) model considering technical, economic, environmental and social criteria to assess Ireland’s most promising offshore wind sites in terms of their sustainable development. An interval type-2 fuzzy sets based MCDM model is developed that integrates the score function with positive and negative solutions to achieve better results. Moreover, advanced energy economic metrics such as levelized cost of electricity with higher resolution are integrated into the decision-making process to make more precise decisions. Case studies are conducted for the five of the offshore sites in development pipeline. Results are compared to those of other state-of-the-art MCDM methods. It is found that Arklow Bank-2 is the most favorable site while Sceirde is the least site. The ranking of other sites is found to be Oriel>Dublin Array>Codling Park. It is shown that the proposed approach is superior in terms of stability and implementation as compared to its counterparts.

Overplanting in offshore wind power plants in different regulatory regimes

AbstractThe development of offshore wind farms depends on many technical and economic parameters, which requires an integrated planning approach. Some parameters can be controlled by the wind farm developer, and some are determined by the regulatory authorities. Others can be outside control of both. One aspect of optimizing wind farm development is overplanting, which represents the capacity optimization between installed generation capacity and transmission capacity, which allows for a minor share of energy curtailment to increase the overall value of the farm. Quantifying this value also depends on the regulatory framework, which is analyzed here by comparing United Kingdom and Danish conditions. Using a discounted cash flow model, we find that UK conditions are favorable to overplanting from the developer perspective, where the benefit of using the transmission cable more efficiently supports overplanting. In the Danish case, the private‐economic incentive to overplant is minor due to the constraint of linking subsidies to a certain energy output. On the other hand, when the cost of turbines declines relative to transmission system costs, overplanting tends to become more attractive. This is mostly the case when installing wind farms further offshore compared to projects closer to the coast, which has been exerted more and more exerted in the recent years. In a socioeconomic perspective, overplanting is also a viable method to optimize the wind farm technically and economically, if the cost of the additional turbines is less than the value of the additional generation that can be fed into the grid by the transmission line.This article is categorized under:Wind Power > Economics and PolicyWind Power > Systems and Infrastructure

Isotopic analyses, a good tool to validate models in the context of Marine Renewable Energy development and cumulative impacts

As part of the energy transition, the French government is planning Offshore Wind Farm (OWF) constructions in the next decades. An integrated ecosystem approach of two future OWF sites of the Eastern English Channel (Courseulles-sur-mer and Dieppe-Le Tréport) was developed to model the marine ecosystems before the OWF implementation. Such ecosystem models allow simulating the possible reef and reserve effects associated to the presence of the farm, and to character the overall changes in the food-web functioning. This holistic view of OWF effects could be replicated on other sites and form the basis of an ecosystem based management of marine renewable energies. However, to use these models for management purpose, they need to be validated. In order to do so, stable isotope ratios of nitrogen were used for determining the accuracy of the effective trophic levels computed in these two models. Results showed that trophic levels estimated by the two models were consistent with the trophic levels estimated by the independent isotopic data. In the context of OWF development and cumulative impacts analysis, this step of validation of the models is essential for developing their use by management actors and policy makers.

Public acceptance of and heterogeneity in behavioral beach trip responses to offshore wind farm development in Catalonia (Spain)

A combined travel cost – contingent behaviour survey of residents and tourists in Catalonia is conducted on-site to examine the effects on beach recreational demand of developing an offshore wind farm (OWF) project. The survey considers four potential OWF scenarios with different degrees of visual impact. We allow for heterogeneity in trip preferences among individuals and control for on-site sampling through the use of a random parameters negative binomial (RPNB) model and a Multivariate Poisson log-normal (MPLN) model, respectively. The welfare measures derived from the RPNB model relate to the current beach users only, whereas those from the MPLN model refer to the general population of residents and tourists in Catalonia. The results show the importance of the specific place of location of the OWF project and how the installation of wind turbines would significantly decrease the demand for trips, depending on their degree of visual impacts, leading to a substantial welfare loss. However, the results also show that the project mainly would cause a displacement of trips to other beaches within Catalonia rather than outside Catalonia and that the welfare per trip measures generated by the RPNB and MPLN models substantially differ. Policy implications of these findings are discussed.

Assessment on liquefaction potential of seabed soil in Chang-Bin Offshore wind farm considering parametric uncertainty of standard penetration tests

Liquefaction potential analysis is a required task in the foundation design process of offshore wind turbine in Taiwan. The standard penetration test (SPT) is mostly used in the preliminary soil investigation of the pilot offshore wind farm in Chang-Bin, Taiwan. Due to the different experimental conditions and operating conditions, the N value (SPT-N) of SPT varies greatly. This study applies statistical methods in conjunction with the New Japan Road Association simplified-empirical method (NJRA method) to incorporate the uncertainty of SPT-N values into the offshore liquefaction potential assessment to quantify the risk of seabed liquefaction. The study statistics the field experimental geotechnical parameters SPT-N and determines the probability density function of the SPT-N distribution of each layer of soil in the offshore wind farm. In order to quantify the risk of seabed soil liquefaction potential, the Monte Carlo random sampling method is used, and by the NJRA method to carry out the seabed liquefaction potential in Changhua, Taiwan. After comparing, the results obtained by the current SPT-based soil liquefaction potential assessment by deterministic approach are conservative. In the ground investigation of offshore wind farm development, the method proposed in this paper can access the thickness of liquefiable soil layers under any given probability for optimizing offshore wind turbine foundation design.

Progress of NEDO project Bottom fixed offshore wind farm development support project (Establishment of offshore wind resource assessment method)

Progress of NEDO project Bottom fixed offshore wind farm development support project (Establishment of offshore wind resource assessment method)

Current status and perspectives on offshore wind farms development in the United Kingdom

AbstractThe purpose of the article is to present perspectives for the development of offshore wind farms in the leading, in this respect, country in the EU and in the world – Great Britain. Wind power plays a remarkable role in the process of ensuring energy security for Europe since in 2016 the produced wind energy met 10.4% of the European electricity demand while in 2017 it was already around 11.6%. The article analyses the capacity of wind farms, support systems offered by this country and the criteria related to the location of offshore wind farms. The research has been based on the analysis of legal acts, regulations, literature on the subject, information from websites. The article shows that in recent years, the production of energy at sea has been developing very rapidly, and the leading, in this matter, British offshore energy sector is characterised by strong governmental support.

Endangered Atlantic Sturgeon in the New York Wind Energy Area: implications of future development in an offshore wind energy site

Imminent development of offshore wind farms on the outer continental shelf of the United States has led to significant concerns for marine wildlife. The scarcity of empirical data regarding fish species that may utilize development sites, further compounded by the novelty of the technology and inherent difficulty of conducting offshore research, make identification and assessment of potential stressors to species of concern problematic. However, there is broad potential to mitigate putatively negative impacts to seasonal migrants during the exploration and construction phases. The goal of this study was to establish baseline information on endangered Atlantic Sturgeon in the New York Wind Energy Area (NY WEA), a future offshore development site. Passive acoustic transceivers equipped with acoustic release mechanisms were used to monitor the movements of tagged fish in the NY WEA from November 2016 through February 2018 and resulted in detections of 181 unique individuals throughout the site. Detections were highly seasonal and peaked from November through January. Conversely, fish were relatively uncommon or entirely absent during the summer months (July–September). Generalized additive models indicated that predictable transitions between coastal and offshore habitat were associated with long-term environmental cues and localized estuarine conditions, specifically the interaction between photoperiod and river temperature. These insights into the ecology of marine-resident Atlantic Sturgeon are crucial for both defining monitoring parameters and guiding threat assessments in offshore waters and represent an important initial step towards quantitatively evaluating Atlantic Sturgeon at a scale relevant to future development.

Placing Green Energy in the Sea: Offshore Wind Farms, Dolphins, Oysters, and the Territorial Politics of the Intertidal Zone in Taiwan

The development of offshore wind farms has been a way for the state to repackage national development projects using green energy discourses. In Taiwan, where the further development of nuclear power is suspended due to public antinuclear sentiment, offshore wind farms have been heavily promoted as a way of meeting electricity demand. The planned site for offshore wind farms, mainly the intertidal zone along the coast of Changhua County, overlaps with both oyster farms and the habitat of Taiwanese humpbacked dolphins, categorized as a critically endangered species by the International Union for Conservation of Nature. This has resulted in a clash between conserving the oyster farming landscape, protecting an endangered species, and developing green energy. Facing this dilemma, pro–wind farm discourses that highlight concerns about global climate change have gradually supplanted those stressing the welfare of oysters and dolphins, even though the latter have been used successfully as local icons by movements opposing previous development projects on the intertidal zone. This article reconsiders the politics of territorialization implied by the “green” label affixed to offshore wind farm projects and other forms of green energy in general. As such, the meaning of offshore wind farms, as a newly discovered energy resource, is intertwined with the changing meanings of both dolphins and oyster farms, as rival nonhuman objects of resource exploitation and natural conservation. The territorialization of such resources in the emerging discursive space of green energy has proceeded via relational placemaking with nonlinear connections among multiple human and nonhuman elements. Key Words: conservation, intertidal zone, landscape, renewable resources, resource frontier.

Using the Cloud-Bayesian Network in Environmental Assessment of Offshore Wind-Farm Siting

Offshore wind energy has become the fastest growing form of renewable energy for the last few years. And the development of offshore wind farms (OWFs) is now characterized by a boom. OWF siting is crucial in the success of wind energy projects. Therefore, this paper aims to introduce intelligent algorithms to improve the siting assessment under conditions of multisource and uncertain information. An optimization macrositing model based on Cloud-Bayesian Network (Cloud-BN) is put forward. We introduce the cloud model and adaptive Gaussian cloud transformation (A-GCT) algorithm to grade indicators and apply BN to achieve nonlinear integration and inference of multi-indicators. Combined with the fuzzy representation of the cloud model and probabilistic reasoning of BN, the proposed model can investigate the most efficient siting areas of OWFs in the North Sea of Europe. The experimental results indicate that the siting accuracy is up to 86.67% with reference to the actual OWF location.