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increasingly advanced developments as they became available. The plan also assumed that
three cycles or “generations” of experimental turbines would be required. First-generation
turbines would be necessary merely to develop an understanding of design issues and to
obtain basic data. The second generation was needed to put new developments into
practice. Finally, a third generation of wind turbines would be required to reach a level of
performance and reliability that could be cost effective on a broad scale. This series of
wind turbines was designed to prove the technology and to reduce technical risk to the
point where signiicant private capital could be attracted for continued development and
commercial production.
Since the role of turbine size in the economics of the wind machine market was not
understood at the time (and, to some extent, is still not clearly deined) a second major
feature of the federal plan was that it supported the parallel development of prototypes in
three sizes: Small-scale turbines (1 kW to 99 kW) for rural and remote use; medium-scale
turbines (100 kW to 999 kW) for a remote community or industrial market; and large-scale
systems (1 MW to 5 MW), primarily for the electric utility market.
NASA/DOE Mod-0 100-kW Experimental HAWT:
1975 to 1987
One of the irst activities under the Federal Wind Energy Program was the design and
construction of an experimental, medium-scale HAWT to serve as a test bed. This size was
clearly needed in order to reach reasonable risk levels before proceeding to large-scale
turbines. Conversely, many of the test results from a medium-scale turbine could well be
applied to small-scale systems. This new research wind turbine was designated the
Mod-0
to emphasize its role as a test bed. It was designed and built for NSF by an engineering
and fabrication team at the NASA Lewis Research Center [Puthoff and Sirocky 1974].
Installed in 1975 at NASA's Plum Brook Test Station near Sandusky, Ohio, it became a
mainstay of experimental work on HAWTs in the U.S. for the next dozen years.
Original Mod-0 Coniguration
The diameter of the Mod-0 rotor was selected to be 38.1 m, and a very low rated
power of 100 kW (at a rated wind speed of 8.0 m/s at hub elevation) was chosen. This low
rating was determined to be suitable for such a large rotor because of the modest wind
speeds in the Sandusky area. Available running time for experimental work was a much
higher priority than cost optimization at that time.
As shown in Figure 3-9, a two-bladed rotor located downwind of the tower was
selected, following the examples of the Smith-Putnam and Hütter turbines and in accordance
with economic studies that indicated a third blade was not cost-effective in large-scale
systems. The Mod-0 rotor and power train were located in a streamlined
nacelle
atop a
stiff, four-legged truss tower, with the rotor axis at an elevation of 30.5 m. Its original set
of blades were of aluminum rib/spar/skin construction, following airplane wing design.
While quite expensive, they were very light in weight (9,000 N each), which was considered
a necessity because of the many unknowns in the structural dynamic behavior of the system.
Details of the Mod-0 power train and yaw drive subsystems are illustrated in Figure
3-10. The rotor drove the
turbine shaft
at 40 rpm which, through a
parallel-shaft step-
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