Читать книгу Wind Energy Handbook - Michael Barton Graham - Страница 10

The second edition of the Wind Energy Handbook seeks to reflect the evolution of design rules and the principal innovations in the technology that have taken place in the 10 years since the first edition was published. A major new direction in wind energy development in this period has been the expansion offshore and so the opportunity has been taken to add a new chapter on offshore wind turbines and wind farms.

The offshore chapter begins with a survey of the present state of offshore wind farm development, before consideration of resource assessment and array losses. Then wave loading on support structures is examined in depth, including a summary of the combinations of wind and wave loading specified in the load cases of the IEC standard and descriptions of applicable wave theories. Linear (Airy) wave theory and Dean stream function theory are explained, together with their translation into wave loadings by means of Morison's equation. Diffraction and breaking wave theories are also covered.

Consideration of wave loading leads to a survey of the different types of support structure deployed to date. Monopile, gravity bases, jacket structures, tripods, and tripiles are described in turn. In view of their popularity, monopiles are accorded the most space and, after an outline of the key design considerations, monopile fatigue analysis in the frequency domain is explained.

Another major cost element offshore is the undersea cable system needed to transmit power to land. This subject is considered in depth in the section on the power collection and transmission cable network. Machine reliability is also of much greater importance offshore, so developments in turbine condition monitoring and other means of increasing reliability are discussed. The chapter is completed by sections covering the assessment of environmental impacts, maintenance and access, and optimum machine size.

The existing chapters in the first edition have all been revised and brought up to date, with the addition of new material in some areas. The main changes are as follows:

Chapter 1: Introduction This chapter has been brought up to date and expanded.

Chapter 2: The wind resource Descriptions of the high frequency asymptotic behaviour of turbulence spectra and the Mann turbulence model have been added.

Chapters 3 and 4: Aerodynamics of horizontal axis wind turbines The contents of Chapters 3 and 4 of the first edition have been rearranged so that the fundamentals are covered in Chapter 3 and more advanced subjects are explored in Chapter 4. Some material on field testing and performance measurement has been omitted to make space for a survey of wind turbine aerofoils and new sections on dynamic stall and computational fluid dynamics.

Chapter 5: Design loads for horizontal axis wind turbines The description of IEC load cases has been brought up to date and a new section on the extrapolation of extreme loads from simulations added. The size of the ‘example’ wind turbine has been doubled to 80 m, in order to be more representative of the current generation of turbines.

Chapter 6: Conceptual design of horizontal axis wind turbines The initial sections on choice of machine size, rating, and number of blades have been substantially revised, making use of the NREL cost model. Variable speed operation is considered in greater depth. The section on tower stiffness has been expanded to compare tower excitation at rotational frequency and blade passing frequency.

Chapter 7: Component design New rules for designing towers against buckling are described and a section on foundation rotational stiffness has been added.

Chapter 8: The controller Individual blade pitch control is examined in greater depth.

Chapter 9: Wind turbine installations and wind farms A survey of recent research on the impact of turbines on birds has been added.

Chapter 10: Electrical systems New sections covering (a) Grid Code requirements for the connection of large wind farms to transmission networks and (b) the impact of wind farms on generation systems have been added.