Design of Wind Turbines - Wind Energy: Renewable Energy and the Environment - page 123

A table of wind energy systems larger than 500 kW through 1993 lists information on thirty-five
units [7, Table 3-2]. Divone describes the evolution of modern wind turbines from 1970 through
1990, with emphasis on description and operational notes of large units [7, Chapter 3].
The other end was the design and construction of wind turbines from 20 to 100 kW for the
commercial market. All sorts of different designs were built and sold. In the United States there
were two blades, fixed pitch, with teetered hubs, downwind; three blades, fixed pitch, downwind;
and three blades, variable pitch, downwind, of which U.S. Windpower installed over 4,000 units
in California. In Europe the three-bladed, upwind, constant-rpm, stall control units predominated.
The different designs and their evolution through the mid-1980s are clearly shown by data sheets
of wind turbines in Europe [46]. The technical data on wind turbines in commercial operation in
the United States [7, Appendix C], also through the mid-1980s, include the total number of units
installed of a given configuration. With the wind farm market in California and afterwards the wind
market in the 1990s in Europe, there was the continuing evolution toward larger wind turbines,
and by 2008, the predominant wind turbines were megawatt size, three blades, rigid hub, variable
pitch (full-span control), variable- and constant-rpm operation, upwind. So in the evolution of wind
turbines, the manufacturers of small wind turbines became the winners over the large prototypes.
Surprisingly, U.S. Windpower, the early leader in number of units installed, also built over 300
larger units (300 kW), but was unable to continue in business.
A Vestas, 90 m diameter, 3 MW wind turbine was installed near Gruver, Texas, during the winter
(Figure 6.23). For installation, an 800-metric-ton crane was needed, and it took twenty trucks to
haul the crane to the site and another ten trucks for the turbine and tower. The weight of the main
FIGURE 6.23 Photos showing different stages of erection of 3 MW wind turbine.