[...]... performance and cut-in speed—the lowest wind speed at which power is extracted Both of these are more important for small machines because: • Small wind turbines are often located where the power is required or adjacent to the owner’s home which may not be the windiest location, whereas wind farms containing large turbines are deliberately sited in windy areas • The generators of small turbines often... section and its influence on blade aerodynamics is a major topic of Chaps 4 and 5 Low values of Re mean, in practice, that small wind turbines bear greater similarity to model, rather than full-sized, aircraft, and hummingbirds rather than eagles The later discussion of airfoil lift and drag and blade performance calculations identifies many features particular to small turbines • Large wind turbines. .. the Proven and the Skystream being downwind machines Most upwind small turbines have a tail fin which keeps the blades pointing into the wind The tail fin is designed to minimize h, the yaw angle of the turbine 1.2 Examples of Wind Turbines 5 Fig 1.2 A range of small wind turbines Clockwise from top left the Aerogenesis 5 kW turbine, a remote power turbine in Nepal (photo Peter Feere), the Rutland 913 (http://www.marlec.co.uk/),... the wind speed? Answer 1 3 PD ¼ qU0 2 so that U0 ¼ ð2 Â 100=1:2Þ1=3 ¼ 5:5 m=s: 1.2 Examples of Wind Turbines Wind turbines range in power output from a few Watts to tens of megawatts The IEC safety standard for small wind turbines, IEC 61400-2, defines a small turbine as having a rotor swept area less than 200 m2, which corresponds roughly to P \ 50 kW The precise definition of the boundary between small. .. extraction (Chaps 5 and 7) and starting performance, Chaps 6 and 7 Small blade manufacture and testing is covered in Chap 7 1.3 Wind Turbine Noise In siting a wind turbine, the first and often far from trivial task is to determine the wind resource, which may vary significantly over short distances because of the surface roughness, the topography, and proximity to buildings, trees and the like These issues... aspects of wind turbine performance and design, covered in Chap 5 Most large turbines have three blades, partly because this number is held to be visually more appealing than the main alternative of two blades Large blades can be over 60 m long and weigh over 20 tonnes The small wind turbines in Fig 1.2 have between two and seven blades The choice of blade number is a recurrent theme of this book and is... and permanent magnet generators (PMGs), e.g Burton et al [2] and Bianchi et al [3] DFIGs require a gearbox and are rarely used on small turbines, but PMGs do not They and the less-used induction generators (IGs) are described in Sect 1.8 and Chap 11 There is a much greater diversity of small turbine types as seen in Fig 1.2 with the number of blades varying from two to seven, and the most popular turbines, ... area, DA, and length normal to the disk, dx, so its mass is qDAdx D Wood, Small Wind Turbines, Green Energy and Technology, DOI: 10.1007/978-1-84996-175-2_1, Ó Springer-Verlag London Limited 2011 1 2 Fig 1.1 Wind flow past a circular disk representing the blades 1 Introduction to Wind Turbine Technology δx U0 U0 Elemental volume of length δx and area δA about to cross disk Circular disk of area A 2 and its... nearly all large turbines but rarely for small ones, there is also a ‘‘cut-out’’ wind speed at which the turbine is shut down for safety reasons This is 25 m/s for the V80 (not shown in Fig 1.5) At this speed, the brake is activated, and not released until the wind has died down At high wind speeds, smaller turbines such as the Bergey 10 kW, are often ‘‘furled’’, that is turned out of the wind direction... (squares) 17 0.15 0.1 0.05 0 0 5 10 Wind speed (m/s) 15 20 favourable locations around the world, and much higher at the Australian Antarctic Base at Mawson where the 10 m average wind speed is 14 m/s Small wind turbines tend to have much lower capacity factors, and a value of 0.20 is usually regarded as ‘‘high’’ Figure 1.8 also shows another important general fact of wind turbines: the greatest contribution . Energy and Technology For further volumes: http://www.springer.com/series/8059 David Wood Small Wind Turbines Analysis, Design, and Application 123 Dr. David Wood Department of Mechanical and Manufacturing. which, like the Standard, covers only horizontal-axis wind turbines. Until the beginning of the twentieth century, all wind turbines were small, at least in terms of power output, and were used for. 1, 7 and 11. Detailed dynamics analysis based on ‘‘aero-elastic’’ modeling is still an immature subject for small wind turbines but will undoubtedly develop as more small turbines are built and