The revised and expanded section on blade design necessitated the gathering of much new material. In this context, Tony Burton would like to thank Mark Hancock for sharing his insights into the practicalities of blade design, Daniel Samborsky for shedding light on the lessons from laminate fatigue testing, and Tomas Vronsky for hosting an informative visit to the Vestas blade testing facility on the Isle of Wight.
The new section on monopile geotechnical design focuses on the more sophisticated design methods made possible by the PISA joint industry research project. Tony Burton would like to thank two lead participants in the project, Byron Byrne and Guy Houlsby of Oxford University, for hosting a tutorial on the project findings, and their research student, Toby Balaam, for his part in arranging it.
Tony Burton would also like to record his gratitude to those who have taken on the chore of reviewing parts of the text. Amongst these are Mark Hancock, Daniel Samborsky, and Samuel Scott, who have reviewed different parts of the blade design section; Byron Byrne, who checked the section on monopile geotechnical design; and James Nicholls and Kevin Drake, who critiqued the floating support structures section. However, responsibility for any errors in these sections remains with the author.
Nick Jenkins would like to express his thanks to Alan Harris of ReSoft for his advice and the use of images from the Windfarm design tool. He would also like to acknowledge and thank Prof. Janaka Ekanayake of Peradeniya University for his contributions to and scrutiny of Chapter 11.
A workspace free from interruptions and distractions is vital for any author. Tony Burton would like to thank former colleague Richard Stonor for providing a quiet and congenial place of work in his home, until evacuation was mandated by Covid‐19 guidelines in March 2020.
We have made extensive use of publications by NREL, Sandia Laboratories, Montana State University, DNV GL, and Danish Technical University and record our thanks to these organisations for making documents available to us free of charge and sanctioning the reproduction of some of the material therein. Thanks are also due to Georgios Deskos (Imperial College London and now at National Renewable Energy Laboratory, CO. USA) for the cover design taken from his numerical simulation of flow through a wind farm.
List of Symbols
Note: This list is not exhaustive and omits many symbols that are unique to particular chapters
tangential flow induction factor at the blade tipatwo‐dimensional lift curve slope, (dC1/dα)a1constant defining magnitude of structural dampingA, ADrotor swept areaA∞, Awupstream and downstream streamtube cross‐sectional areasAcCharnock's constantbface width of gear teeth; eccentricity of bolt to tower wall in bolted flange joint; wake widthbrunbiased estimator of βrBnumber of bladescblade chord; Weibull scale parameter; dispersion of distribution; flat plate half width; half of cylinder immersed widthc*half of cylinder immersed width at time t*
damping coefficient per unit lengthcigeneralised damping coefficient with respect to the ith modeCdecay constant; wave celerity, L/T; constrained wave crest elevationC(v), C(k)Theodorsen's function, where v or k is the reduced frequency: C(v) = F(v) + iG(v)Cdsectional drag coefficientCDdrag coefficient in Morison's equationCDSsteady flow drag coefficient in Morison's equationCfsectional force coefficient (i.e. Cd or C1 as appropriate)C1, CLsectional lift coefficientCMinertia coefficient in Morison's equation; moment coefficient (Section 4.6)
coefficient of a Kinner pressure distributionCNnormal force coefficient (Section 4.6)Cppressure coefficientCPpower coefficient or coefficient of performanceCQtorque coefficientCTthrust coefficient; total cost of wind turbineCTBtotal cost of baseline wind turbineCxcoefficient of sectional blade element force normal to the rotor planeCycoefficient of sectional blade element force parallel to the rotor planeC(Δr, n)coherence – i.e. normalised cross‐spectrum – for wind speed fluctuations at points separated by distance s measured in the across wind directionCjk(n)coherence – i.e. normalised cross‐spectrum – for longitudinal wind speed fluctuations at points j and kdstreamwise distance between vortex sheets in a wake; water depth; floating support structure draftd1pitch diameter of pinion geardPLpitch diameter of planet gearDdrag force; tower diameter; rotor diameter; flexural rigidity of plate; constrained wave trough elevationEenergy capture, i.e. energy generated by turbine over defined time period; modulus of elasticityE1longitudinal elastic modulus of uniaxial composite plyE2transverse elastic modulus of uniaxial composite plyE{}time averaged value of expression within brackets
expected value of significant wave height conditional on a hub‐height mean wind speed
ftip‐loss factor; Coriolis parameter; wave frequency; source intensityf( )probability density functionf1(t)support structure first mode hub displacementfj(t)blade tip displacement in jth modefin(t)blade tip displacement in ith mode at the end of the nth timestepfJ(t)blade j first mode tip displacementfpwave frequency corresponding to peak spectral densityfT(t)hub displacement for tower first modeFforce; force per unit lengthFxload in x (downwind) directionFYload in y directionFtforce between gear teeth at right angles to the line joining the gear centresF(μ)flow expansion function determining the radial distribution of the radial component of induced velocity normal to the wake axisF( )cumulative probability distribution functionF(x|Uk)cumulative probability distribution function for variable x conditional on U = Ukgacceleration due to gravity; vortex sheet strength; peak factor, defined as the number of standard deviations of a variable to be added to the mean to obtain the extreme value in a particular exposure period, for zero up‐crossing frequency, vgpeak factor as above, but for zero up‐crossing frequency nGgeostrophic wind speed; shear modulus; gearbox ratioG12shear modulus of composite plyG(f)transfer function divided by dynamic magnification ratioG(t)t second gust factorhheight of atmospheric boundary layer; duration of timestep; thickness of thin‐walled panel; maximum height of single gear tooth contact above critical root section; height of centre of buoyancy above centre of gravity for a spar buoyh(ψ)root vortex influence functionHhub height; wave height; hub height above mean sea levelH11 year extreme wave heightH5050 year extreme wave heightHjkelements of transformational matrix, H, used in wind simulationHi(n)complex frequency response function for the ith modeH(f)frequency‐dependent transfer functionHssignificant wave heightHs11 year extreme significant wave height based on 3 hour reference periodHs5050 year extreme significant wave height based on 3 hour reference periodHBbreaking wave heightIturbulence intensity; second moment of area; moment of inertia; electrical current (shown in bold when complex)Iambient turbulence intensityI+added turbulence intensityI++added turbulence intensity above hub heightIbblade inertia about rootIrinertia of rotor about horizontal axis in its planeIrefreference turbulence intensity, defined as expected value of hub‐height turbulence intensity at reference mean wind speed of 15 m/sIulongitudinal turbulence intensityIvlateral turbulence intensityIwvertical turbulence intensityIwaketotal wake turbulence intensityi, j
kshape parameter for Weibull function; shape parameter for GEV distribution; integer; reduced frequency, (ωc/2W); wave
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