Assessment of Research Needs for Wind Turbine Rotor Materials Technology (1991) / Chapter Skim
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1 INTRODUCTION
1 INTRODUCTION
Pages 5-24
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From page 5... ...
A major area of potential improvement, and the focus of this report, is the need for improved knowledge of materials properties and advanced, economical, high-volume manufacturing processes. This chapter traces the evolution of wind power systems in this country, identifies the principal components of ~ powes-generating wind turbine, presents a simplified description of the relationship between the power in the wind and the power flow through the turbine drive train, and describe" the characteristics of the wind environment that impact both the short- and the long-term structural integrity of wind turbines.
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From page 6... ...
i:: ~ if: : : : ~:: : : : ~: : : :: :::: : ~:~::~ :: a: :~. i:: ~ ~ : FIGURE 1-1 Wine power plant in Altamont Pass, California.
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From page 7... ...
However, an the systems improved in performance and began to produce large amounts of energy, these accusations were replaced by a growing appreciation of the environmental benefits and advantage" offered by this renewable power generation technology. The advantages and benefits include the following: Environmentally Benign: Wind power systems are environmentally benign.
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From page 8... ...
Wear MATERIALS KNOWLEDGE IS CRITICAL From an engineering perspective, the early structural failures and continuing rinks had their genesis in an early lack of understanding of the wind forces acting on these large structure". This included not only the effects of the steady -- tate component of the incident wind flow field, but
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From page 9... ...
The California installations are Situated principally in the Altamont Pa=" Legion, about 60 miles east of San Francisco near Livermore; the Tehachapi region, about 100 miles northwest of Los Angeles near Mojave; and the San Gorgonio Pass region, about 100 mile" southeast of Los Angele" near Palm Springs. The wind power plants in northern California (about half of the total)
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From page 10... ...
60 ~ 398 ] : 5 n 154 150 1 _ 134 r _ 81 82 83 84 85 86 87 88 89 90 1 800 ~ 1600 1400 ~ 1200 1 000 800 -600 -400 ~ 200 o FIGURE 1-3 Growth of generating capacity for the California wind power plants.
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From page 11... ...
The first thing to notice about the information in Figure 1-3 i" the current rated capacity of the wind power plants. For a power generation technology that has evolved over the recent decade, the nearly 1500 MW of installed capacity is substantial.
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From page 12... ...
While this is economically competitive in the context of the most attractive power purchase contracts currently in place, and is competitive with some conventional means of energy generation, the full potential of wind power as a large-scale
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From page 13... ...
This range will make wind power systems competitive not only with nuclear but also with new coal-fired installations. At the same time, the performance characteristics will be improved to the extent that wind turbine installations can be economically productive over a broader class of wind regimes and geographical regions.
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From page 14... ...
The aerodynamic characteristic" of the blade airfoils, the rotor diameter, and the range of operating wind speeds determine the optimum rotor speed. For wind turbines having power ratings in the range of 100 to 600 kW, the range of current interest and emphasis, the corresponding rotor speed range would be approximately 35 to 70 rpm.
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From page 15... ...
~ y H'~ ~ ~ These values define the wind turbine Eswe£_cy~, a graph of the electrical power output as a function of wind speed. The general features of a wind turbine power curve are depicted in Figure 1-6.
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From page 16... ...
POWER CONVERSION EQUATTON8 Illustrated in Figure 1-7 are the principal loads, torques, and moments resulting from an incident wind flow field. The relationship between the power in the wind and the resulting power flow through the drive train can be described by simplified analytic expressions.
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From page 17... ...
This relationship indicate" that the output power an well as the power flowing through the drive train in proportional to the cube of the wind speed, to the area of the rotor, and to the power conversion efficiency of the rotor. Under the idealized assumptions of thin model, the maximum value achievable by the rotor power conversion coefficient is 16/27, the Bet z limit:
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From page 18... ...
The problem is that the power in the wind flow field increases as V3' since the rotor area is fixed in practically all designs. Thus, over the 10 to 50 mph operating range cited earlier, the incident wind power increases by a factor of 125.
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From page 19... ...
These include vertical wind shear, temporal and spatial turbulence, gravity, and interaction of the rotor with the tower. These sources are discussed next in the context of a more realistic description of the wind flow field.
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From page 20... ...
Second, the center of the wind turbine rotor, the hub, nits not at a 10 m height but more typically at two to three times that height. Because wind speeds increase with height in the earth's boundary layer where wind turbines operate, wind speeds are typically higher at the hub height relative to a 10-m height.
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From page 21... ...
; and is the number of cyclic events accumulated (pure number) during the elapsed calendar time t as a function of the operating hours per year Hop, the low-"peed shaft rotational speed a, and the number of cyclic events per revolution k, where N = Nt t | a, k, Hop )
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From page 22... ...
, the cumulative number of fatigue cycles lies in the range of 10 to 10 . This extreme accumulation of fatigue cycles with such a large amplitude range is unequaled by practically any other mechanical or structural system.
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From page 23... ...
Paul Gipe & Associates, Tehachapi, California, May. (A fairly complete, rational summary of the evolution and performance of the large-mcale California wind power stations, including comparisons with other countries and potential.)
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From page 24... ...
California Energy Commission, Sacramento, California, August. (One of a eerie" of quarterly and annual reports that track the energy production performance of the California wind power stations.)
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