Innovation in Wind Turbine Design

Peter Jamieson

• Publisher: Wiley
• Year: 2018
• Print ISBN: 9781119137900
• eBook ISBN: 9781119137948
• Edition: 2
• Topic: Technology & Engineering
• Subtopic: Mechanical Engineering
• Index: Technology & Engineering

An updated and expanded new edition of this comprehensive guide to innovation in wind turbine design

Innovation in Wind Turbine Design, Second Edition comprehensively covers the fundamentals of design, explains the reasons behind design choices, and describes the methodology for evaluating innovative systems and components.

This second edition has been substantially expanded and generally updated.  New content includes elementary actuator disc theory of the low induction rotor concept, much expanded discussion of offshore issues and of airborne wind energy systems, updated drive train information with basic theory of the epicyclic gears and differential drives, a clarified presentation of the basic theory of energy in the wind and fallacies about ducted rotor design related to theory, lab testing and field testing of the Katru and Wind Lens ducted rotor systems, a short review of LiDAR, latest developments of the multi-rotor concept including the Vestas 4 rotor system and a new chapter on the innovative DeepWind VAWT.

The bookis divided into four main sections covering design background, technology evaluation, design themes and innovative technology examples.

Key features:

• Expanded substantially with new content.

• Comprehensively covers the fundamentals of design, explains the reasons behind design choices, and describes the methodology for evaluating innovative systems and components.
• Includes innovative examples from working experiences for commercial clients.
• Updated to cover recent developments in the field. 

The book is a must-have reference for professional wind engineers, power engineers and turbine designers, as well as consultants, researchers and graduate students.

Part I
Design Background

Chapter 1
Rotor Aerodynamic Theory

1.1 Introduction

Theoretical background in energy extraction generalities and, more specifically, rotor aerodynamics of horizontal axis wind turbines (HAWTs) is developed in this chapter. Some prior knowledge of fluid dynamics in general and as applied to the analysis of wind turbine systems is assumed, in particular basic expressions for energy in a fluid flow, Bernoulli's equation, definitions of lift and drag, some appreciation of stall as an aerodynamic phenomenon and blade element momentum (BEM) theory in its conventional form as applied to HAWTs. Nevertheless, some of this basic knowledge is also reviewed, more or less from first principles. The aim is to express particular insights that will assist the further discussion of issues in optimisation of rotor design and also aid evaluation of various types of innovative systems, for example, those that exploit flow concentration.

Why focus much at all on theory in a book about innovative technology? Theory is often buried in more or less opaque computer code, which may generate loads of information that engineers can use in design. However, as is amplified in the following chapters, theory is in itself:

• Food for innovation and suggestive of methods of performance enhancement or alternative concepts;
• A basis for understanding what is possible and providing an overview appraisal of innovative concepts;
• A source of analytic relationships that can guide early design at a stage where many key parameters remain to be determined and there are too many options to subject each to detailed evaluation.

Prior to discussions of actuator disc theory and the BEM theory that has underpinned most practical engineering calculations for rotor aerodynamic design and determination of wind turbine loads, some discussion of aerodynamic lift is presented. This is intended particularly to highlight a few specific insights which can guide design and evaluation of wind energy systems. In general, a much more detailed understanding of basic aerodynamics is required in wind turbine design. This must cover a wide range of topics, 2D and 3D flow effects in relation to aerofoil performance, stall behaviour, aeroelastic behaviour, unsteady effects including stall hysteresis and induction lag, determination of suitable aerofoil data for wide ranges in angle of attack, and so on. References [1–10] are a sample from extensive published work covering some of these issues.

1.2 Aerodynamic Lift

The earliest wind turbines tended to use the more obvious drag forces [11] experienced by anyone exposed to wind on a windy day, and use of the potentially more powerful lift forces was almost accidental. Exploitation of the aerodynamic lift force is at the heart of efficient modern wind turbines, but surprisingly the explanation of lift has been quite contentious. Before entering that territory, consider first Bernoulli's equation which is derived in many standard sources on fluid mechanics. Ignoring gravitational, thermal and other energy sources and considering only pressure and kinetic energy, this equation becomes:

, where p is static pressure in a fluid element moving with a velocity of magnitude U, ρ is fluid density and p₀ is the total pressure which, in the absence of energy extraction, is constant along any streamline in the flow field.

Bernoulli's equation is essentially an energy equation expressed dimensionally in units of pressure and can be viewed as conservation of energy per unit volume of the fluid. In that connection, pressure can be regarded as the source potential energy (per unit volume) that drives fluid flow. This interpretation is discussed subsequently and is seen to be crucial to a clear understanding of how a wind turbine rotor works.

Returning to the issue of aerodynamic lift, one view of the explanation of the lift force has been that the fluid, should it have a longer path to traverse on one side of an aerofoil, will travel faster in order to meet the fluid flowing past the other side at the trailing edge of the aerofoil. With increase in velocity, the associated static pressure in that region will reduce in consequence of Bernoulli's equation. The pressure deficit on the side of the plate with the longer flow path is then considered the source of the lift force.

There are various problems with this as an explanation of the lift force. Firstly, a thin plate set at an angle in a uniform flow field will...

Table of contents

• Cover
• Title Page
• Copyright
• Table of Contents
• Dedication
• Foreword
• Preface
• Acknowledgement
• Introduction
• Part I: Design Background
• Part II: Technology Evaluation
• Part III: Design Themes
• Part IV: Innovative Technology Examples
• Index
• End User License Agreement