Environmental Engineering Reference
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Figure 13: Calculated extreme thrust for the 10-turbine analysis group.
particularly at the different attachment and component transitions throughout the
turbine. Goodman diagrams are used to estimate fatigue life for various stress
ratios experienced throughout the critical locations [47]. These fl uctuating loads
often dictate the fi nal sizing of structural members (beyond what is required for
extreme loads). The utility scale WT sees more fatigue load cycles than any other
manmade structure or machine - many millions of cycles over its 20-year design
life - more than automobiles, ships, aircraft or rockets.
4.3 Components
Figure 14 illustrates the top-level mass results from the value analysis program.
The extreme and time-varying loads for the 10-turbine analysis group (i.e. Table 1)
are converted into the amount of material or mass that the various components
need in order to meet the design requirements for the turbines. The results are for a
selection of component technologies that are most often used today and include:
1.
Nominal glass fi bre reinforced plastic (GFRP) blades optimized for structural
properties and lowest weight.
Nominal characteristics of a main shaft incorporating a single forward main
2.
bearing or a double-bearing design.
Nominal gearbox with the number of stages required carrying the torque for a
3.
speed-up ratio in the range of 1:100 or more.
Electrical generator spanning the range of wire wound doubly fed induction to
4.
permanent magnet full-power conversion topology.
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