Cable Installation and Burial: Practical Considerations

AbstractThis Technical Note provides a practical background to the commonly used burial techniques for protecting power cables, with an emphasis on cable linking offshore wind turbines (commonly known as inter-array cables). Common definitions and abbreviations are discussed, and typical approaches undertaken are outlined. Installation aspects are also touched upon, with differences between typical oil and gas and renewables projects highlighted. Finally, CTC’s vision for the future, namely the installation of inter-turbine cables with no requirement to transfer personnel to the turbine foundation, is outlined.

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Demonstration of the Intelligent Mooring System for Floating Offshore Wind Turbines

ASME 2019 2nd International Offshore Wind Technical Conference ◽

10.1115/iowtc2019-7544 ◽

2019 ◽

Cited By ~ 1

Author(s):

Magnus J. Harrold ◽

Philipp R. Thies ◽

Peter Halswell ◽

Lars Johanning ◽

David Newsam ◽

...

Keyword(s):

Wind Turbines ◽

Oil And Gas ◽

Oil And Gas Industry ◽

Offshore Wind ◽

Mooring System ◽

Gas Industry ◽

Offshore Wind Turbines ◽

Floating Offshore Wind Turbines ◽

Physical Testing ◽

Line Loads

Abstract Existing mooring systems for floating offshore wind turbines are largely based on designs from the oil and gas industry. Even though these can ensure the safe station keeping of the floating wind platform, the design of the mooring system is currently largely conservative, leading to additional expense in an industry striving to achieve cost reduction. Recent interest in the usage of mooring materials with non-linear stiffness has shown that they have the potential to reduce peak line loads, ultimately reducing cost. This paper reports on the combined physical testing and numerical modeling of a hydraulic-based mooring component with these characteristics. The results suggest that the inclusion of the component as part of the OC4 semi-submersible platform can reduce the peak line loads by 10%. The paper also discusses a number of challenges associated with modeling and testing dynamic mooring materials.

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WindFloat: A Floating Foundation for Offshore Wind Turbines—Part I: Design Basis and Qualification Process

Volume 4: Ocean Engineering; Ocean Renewable Energy; Ocean Space Utilization, Parts A and B ◽

10.1115/omae2009-79229 ◽

2009 ◽

Cited By ~ 22

Author(s):

Dominique Roddier ◽

Christian Cermelli ◽

Alla Weinstein

Keyword(s):

Wind Turbine ◽

Wind Turbines ◽

Oil And Gas ◽

Large Diameter ◽

Offshore Wind ◽

Site Location ◽

Offshore Wind Turbines ◽

Design Basis ◽

Floating Foundation ◽

Visual Impacts

This paper and the corresponding hydrodynamic and structural study paper (also in these proceedings) summarize the feasibility study conducted for the WindFloat technology. The WindFloat is a 3-legged floating foundation for very large offshore wind turbines. It is designed to accommodate a wind turbine, 5 MW or larger, on one of the columns of the hull with minimal modifications to the tower, nacelle and turbine. Technologies for floating foundations for offshore wind turbines are evolving. It is agreed by most experts that the offshore wind industry will see a significant increase in activity in the near future. Fixed offshore turbines are limited in water depth to approximately 30∼50m. Market transition to deeper waters is inevitable, provided suitable technologies can be developed. Despite the increase in complexity, a floating foundation offers distinct advantages: • Flexibility in site location. • Access to superior wind resources further offshore. • Ability to locate in coastal regions with limited shallow continental shelf. • Ability to locate further offshore to eliminate visual impacts. • An integrated structure, without a need to redesign the mast foundation connection for every project. • Simplified offshore installation procedures. Anchors are significantly cheaper to install than fixed foundations and large diameter towers. This paper focuses on the design basis for wind turbine floating foundations, and explores the requirements that must be addressed by design teams in this new field. It shows that the design of the hull for a large wind turbine must draw on the synergies with oil and gas offshore platform technology, while accounting for the different design requirements and functionality of the wind turbine.

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New Design Proposal for the TLP Type Offshore Wind Turbines

Volume 3: Materials Technology; Ocean Space Utilization ◽

10.1115/omae2013-11263 ◽

2013 ◽

Author(s):

Yasunori Nihei ◽

Midori Matsuura ◽

Motohiko Murai ◽

Kazuhiro Iijima ◽

Tomoki Ikoma

Keyword(s):

Wind Turbines ◽

Oil And Gas ◽

Design Method ◽

Offshore Wind ◽

Wave Forces ◽

Oil And Gas Development ◽

Offshore Wind Turbines ◽

Motion Characteristics ◽

Set Up ◽

High Set

In this paper, we will show a new proposal to design a Tension Leg Platform (TLP) type offshore wind turbines. Generally, TLPs are used in deepwater oil and gas development fields due to their favorable motion characteristics. In this field, they have high set up costs. An upper structure of 5MW wind turbine, however, is only 450tons at its total weight, which is much lighter than that of oil and gas platforms. Therefore the displacement and water plane area of the platform might be smaller. As a result, wave forces could decrease and it could lead initial tensions to be lower. This idea that leads to low set up costs was discussed in our previous paper. Principal particulars of TLP prototypes was proposed and a tank test with both waves and wind that used 1/100 scale models was examined in the previous paper. Capsizing could be observed based on the conventional design method. So we reason why and how this capsizing occured in this paper. Also we propose new design process and new TLP prototypes based on this process.

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Concrete is the Future for Offshore Foundations

Wind Engineering ◽

10.1260/030952405776234571 ◽

2005 ◽

Vol 29 (6) ◽

pp. 531-563 ◽

Cited By ~ 10

Author(s):

Per Vølund

Keyword(s):

Wind Turbines ◽

Lower Cost ◽

Low Cost ◽

Extra Cost ◽

Offshore Wind ◽

Light Weight ◽

Conceptual Foundation ◽

Offshore Wind Turbines ◽

The Future ◽

Main Construction

This paper compares the costs of using concrete foundations against steel monopile foundations for offshore wind turbines, and argues that concrete foundations will be cheaper. Most offshore windfarms have steel monopile foundations, but in Denmark concrete gravity foundations have been used with success. Two projects have tendered for steel monopiles and for concrete foundations and have implemented the concrete foundations that proved cheaper. No project has tendered for both foundation concepts and chosen steel monopiles. Nysted Offshore Windfarm with concrete foundations has the cheapest foundations of any offshore windfarm so far. A conceptual foundation study carried out for the London Array West Offshore Windfarm indicates that the same method and very low-cost foundations as for Nysted can be used. Optimised design of light-weight concrete constructions is the key to low-cost installation. Cheap manufacture can be carried out near the site or at even lower cost in Eastern Europa from where it can be shipped at little extra cost. The main construction of steel monopile foundations will become twice as costly as of concrete gravity foundations, and though installation is more costly for the gravity foundations it seems most likely that tendering between steel monopile and concrete gravity for London Array West will prove concrete considerably cheaper. It is argued that these considerations are to a wide extent generally valid, and also for very large turbines in deeper water. Concrete foundations will in 2006 be installed at Lillegrunden Offshore Windfarm in Sweden, and at Belgian Thornton Bank in 2006–7. So indications are strong that concrete is the future for offshore foundations.

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Femtosecond laser-inscribed fiber Bragg gratings for strain monitoring in power cables of offshore wind turbines

Applied Optics ◽

10.1364/ao.50.001868 ◽

2011 ◽

Vol 50 (13) ◽

pp. 1868 ◽

Cited By ~ 8

Author(s):

Jörg Burgmeier ◽

Wolfgang Schippers ◽

Nico Emde ◽

Peter Funken ◽

Wolfgang Schade

Keyword(s):

Femtosecond Laser ◽

Wind Turbines ◽

Fiber Bragg Gratings ◽

Bragg Gratings ◽

Offshore Wind ◽

Power Cables ◽

Offshore Wind Turbines ◽

Strain Monitoring

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Damage detection in grouted connections using electromechanical impedance spectroscopy

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406218764226 ◽

2018 ◽

Vol 233 (3) ◽

pp. 947-950 ◽

Cited By ~ 5

Author(s):

Jochen Moll

Keyword(s):

Impedance Spectroscopy ◽

Damage Detection ◽

Wind Turbine ◽

Wind Turbines ◽

Oil And Gas ◽

Offshore Wind ◽

Wind Loading ◽

Offshore Wind Turbine ◽

Offshore Wind Turbines ◽

Electromechanical Impedance

Grouted connections are structural joints formed by a cementitious grout cast between two concentric circular tubes. They are widely used in the offshore construction of oil and gas platforms, and for offshore wind turbines (monopiles and jackets). However, their application in offshore wind turbine installations can be critical due to the high bending moments coming from wind loading. Recently, it was found that grouted connections show limited performance in offshore wind turbine installations leading to settlements between the steel tubes and steel/grout debonding. Hence, structural health monitoring techniques for grouted connections are needed that ensure a safe and reliable operation of offshore wind turbines. This short communication describes the successful application of electromechanical impedance spectroscopy for damage detection in grouted connections.

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Designing Process and Motion Characteristics of Spar Type Offshore Wind Turbines

Volume 3: Materials Technology; Ocean Space Utilization ◽

10.1115/omae2013-11262 ◽

2013 ◽

Cited By ~ 2

Author(s):

Yasunori Nihei ◽

Tomoki Ikoma ◽

Minori Kozen ◽

Fumiya Sato ◽

Motohiko Murai ◽

...

Keyword(s):

Wind Turbine ◽

Wind Turbines ◽

Oil And Gas ◽

Type Structure ◽

Offshore Wind ◽

Scale Model ◽

Offshore Wind Turbine ◽

Offshore Wind Turbines ◽

Motion Characteristics

In this paper, we will discuss about the designing process and the motion characteristics of the spar type offshore wind turbines. When considering a spar type structure for offshore wind turbines, it is important to take a lot of elements into consideration which have not yet been considered in the case of oil and gas platforms. In this research, we used the following standards to conduct our tests. The limit of the heel angle was 5 degrees when the wind turbines are generating in the rated state. When designing the substructure for this research we have decided to go with a substructure that operates in depth of 100m or more. Following the conditions above we have designed the spar type offshore wind turbine used for this research. In order to compare the simulated result we have created a scale model and performed tank tests under various conditions. Also we observed unexpected motion characteristics in certain mooring arrangement. So we will touch these subjects in this paper.

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