Design of Foundations for Offshore Wind Turbines

Subhamoy Bhattacharya

• Publisher: Wiley
• Year: 2019
• ISBN:
  9781119128144
• Edition: 1
• Topic: Technologie et ingénierie
• Subtopic: Génie mécanique

Comprehensive reference covering the design of foundations for offshore wind turbines

As the demand for "green" energy increases the offshore wind power industry is expanding at a rapid pace around the world.

Design of Foundations for Offshore Wind Turbines is a comprehensive reference which covers the design of foundations for offshore wind turbines, and includes examples and case studies. It provides an overview of a wind farm and a wind turbine structure, and examines the different types of loads on the offshore wind turbine structure. Foundation design considerations and the necessary calculations are also covered. The geotechnical site investigation and soil behavior/soil structure interaction are discussed, and the final chapter takes a case study of a wind turbine and demonstrates how to carry out step by step calculations.

Key features:

• New, important subject to the industry.
• Includes calculations and case studies.
• Accompanied by a website hosting software and data files.

Design of Foundations for Offshore Wind Turbines is a must have reference for engineers within the renewable energy industry and is also a useful guide for graduate students in this area.

1
Overview of a Wind Farm and Wind Turbine Structure

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Learning Objectives

The aim of this chapter is to provide an overview of the power generation from wind and features of a wind turbine structure. The overall layout of a wind farm is also discussed to appreciate the multidisciplinary nature of the subject. The fundamental concepts and understanding of other disciplines and fields not directly related to foundations but are necessary to carry out the foundation design are also described with references for further study. The chapter also provides description of different types of foundations that are being used and planned to be used.

After you read this chapter, you will be able to: (i) appreciate the complexity and multidisciplinary nature of the design; (ii) get an overview of the subject; (iii) differentiate between oil and gas (O&G) structure and offshore wind turbine structure.

The chapters of the book are arranged in the following way: It starts with a system‐level understanding (overall wind farm – Chapter 1) and then to component level (foundations design – Chapters 2 and 3) and finally to the element level (soil behaviour, provided in Chapter 4). Chapter 5 discusses the different methods of analyses and Chapter 6 provides some example applications.

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1.1 Harvesting Wind Energy

Offshore wind power generation has established itself as a source of reliable energy rather than a symbolism of sustainability. It has been reported by National Grid of the United Kingdom (UK) that on 19 October 2014, 24% of the electricity supply in the United Kingdom was provided by offshore wind farms due to an unexpected fire in Didcot power station and when few of the nuclear power stations were offline due to maintenance and technical issues. Furthermore, National Grid also reported that on 21 October 2014, UK wind farms generated 14.2% of the electricity, which is more than the electricity generated by its nuclear power station (13.2%) for a 24‐hour period.

Before the details of engineering of these systems are discussed, it is considered useful to discuss the sustainability of wind resources as it is often noted that wind doesn't blow all the time. Wind, essentially atmospheric air in motion, is a secondary source of energy and is dependent on the sun. The electromagnetic radiation of the Sun unevenly heats the Earth's surface and creates a temperature gradient in the air, thereby also developing a density and pressure difference. The disparity in differential heating of the surface of the Earth is also a result of specific heat and absorption capacity of sand, clay, intermediate and mixed soils, rocks, water, and other materials. This also results in differential heating of air in different regions and at different rates. The physical process or mechanism that governs the air flow is convection. Common examples are land and sea breezes in coastal regions. The direction and velocity of wind are partly influenced by the rotation of the Earth and topography of the Earth's surface, and thus coastal areas are attractive locations for harvesting wind power. This above discussion shows the sustainability of the wind resource as it is related to the Sun and Earth's motion.

In 2017, Europe was the global leader for offshore wind energy, with the United Kingdom leading the field. This is partially due to the aspirations and policies of the European Union to reduce its greenhouse emissions from the 1990 levels by 20% by the year 2020 and then a further reduction of 80–95% by 2050. There is also an initiative in Europe to make its energy system clean, secure, and efficient.

Offshore wind farming is considered to be one of the most reliable ways to produce clean green energy for five reasons:

1. The average wind speed over sea is generally higher and more consistent than onshore, making the offshore wind farming more efficient.
2. The noise and vibrations from the wind turbines will have minimum impact on human beings due to their distance from land.
3. Large capacity can be installed offshore in comparison to an equivalent onshore wind farm. The reasons are that heavier wind turbine generators (WTGs) or towers can be easily transported and installed using sea routes. In contrast, transporting these large and heavy structures/components during construction will substantially disrupt the daily ...

Table of contents

• Cover
• Table of Contents
• Preface
• About the Companion Website
• 1 Overview of a Wind Farm and Wind Turbine Structure
• 2 Loads on the Foundations
• 3 Considerations for Foundation Design and the Necessary Calculations
• 4 Geotechnical Site Investigation and Soil Behaviour under Cyclic Loading
• 5 Soil–Structure Interaction (SSI)
• 6 Simplified Hand Calculations
• Appendix A: Natural Frequency of a Cantilever Beam with Variable Cross Section
• Appendix B: Euler‐Bernoulli Beam Equation
• Appendix C: Tower Idealisation
• Appendix D: Guidance on Estimating the Vertical Stiffness of Foundations
• Appendix E: Lateral Stiffness KL of Piles
• Appendix F: Lateral Stiffness KL of Suction Caissons
• Bibliography
• Index
• End User License Agreement