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

3.1.1 Tower and Foundation Design
A hub height of 70 m was achieved with a new 68-m tower designed using a new hybrid approach
utilizing a 5-m concrete pedestal and a 63-m steel tower to achieve an 80-m hub height.
Several advantages of the hybrid approach are significant. First, using concrete at the base
minimizes the diameter of the steel tower that needs to be shipped. Shortening the height of the
steel section also helps resolve buckling considerations. Finally,
access doors can be installed in the concrete much more
easily than in the welded steel construction. Studies showed,
however, that for the POC design, using more than 5 m of
concrete was not cost effective. These studies indicated, however,
that for a larger turbine, a taller concrete pedestal might
be cost effective. Figure 17 shows the tower being installed at
the test site in Tehachapi, California.
3.1.2 Drive Train Design and Testing
Figure 17. POC Tower in Tehachapi, California
Figure 18 illustrates the drive train layout. The drive train is substantially similar to that of the
GE1.5/65 turbine with the addition of the water-cooled generator (Figure 19). Figure 20 illustrates
additional components of the drive train, including the main shaft, gearbox, the high-speed
shaft, and the yaw drive. The POC 1.5-MW drive train–from the main shaft to the generator–
was delivered to the National Wind Technology Center (NWTC) at NREL in Golden, Colorado,
for comprehensive testing at their large-scale dynamometer facility. Figure 21 illustrates the test
setup at NWTC. The objectives of this testing were:
• Verify proper load transfer at the gear mesh using contact patterns test.
• Measure the efficiency of the gearbox and generator systems at different power levels using
thermal loss measurements.
45