Advanced Wind Turbine Program Next Generation Turbine ... - NREL

Figure 5. Fatigue Damage Equivalent von Mises Stress Distribution
for “Optimized” Cylindrical Steel Nacelle
2.1.4 Summary of Drive Train Concepts
The result of all of the electromechanical concept studies is that no concept produces a significant
improvement in the COE delivered by wind power. Only two concepts–the medium-speed
wound rotor induction generator operating in VSCF mode and the medium-speed wound rotor
synchronous generator operating in fixed-speed mode–showed any improvement at all in COE,
and even then the estimated improvement was less than $0.01/kWh, probably within the uncertainty
range of these analyses. The remainder of the concepts produced no improvement or increase
in COE.
As a result, GE decided that none of the concepts investigated showed potential for improving
COE. The only one that has piqued some enduring interest is the medium-speed wound-rotor
induction generator. This concept clearly allows for the elimination of all but the first stage of
the gearbox, thereby guaranteeing some cost savings. However, the costs saved by eliminating
the second and third stages of the gearbox are not overwhelming and may not justify the risk associated
with development of a 40-pole generator.
Significant improvements in COE must be identified elsewhere, as noted in the subsequent sections.
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