Introduction - Wind Energy: Renewable Energy and the Environment - page 6

FIGURE 1.7 Diagram of different rotors.
axles of the railroad cars. In 1933, a prototype installation, which consisted of a cylinder 29 m tall
and 8.5 m in diameter mounted on a concrete base, was spun when the wind was blowing and the
force was measured. Results were inconclusive and the prospect was abandoned.
The Magnus effect has been used for ships, called Flettner rotors [12, 13], and one ship operated
using rotors for fuel savings from 1926 to 1933. In 1984 the Costeau Society had a sailing ship,
Alcyone , built that used two fixed cylinders with an aspirated turbosail [14].
In Finland, Savonius built S-shaped rotors, which were similar to two halves of a cylinder sepa-
rated by a distance smaller than the diameter. In 1927, Darrieus invented a wind machine where the
shape of the blade was similar to a jumping rope. His patent also covered straight vertical blades, a
giromill. Later the Darrieus design was reinvented by researchers in Canada [15].
In 1931 the Russians built a 100 kW wind turbine near Yalta on the Black Sea. The rotor was
30 m in diameter on a 30 m rotating tower. The rotor was kept facing into the wind by moving the
inclined supporting strut that connected the back of the turbine to a carriage on a circular track.
The blade covering was galvanized steel and the gears were of wood. The adjustable angle (pitch) of
the blades to the rotor plane controlled the rotational speed and power. Annual output was around
280,000 kWh/year.
The Smith-Putnam wind turbine ( Figure 1.8 ) was developed, fabricated, and erected in 2 years,
1939-1941 [6]. The turbine, which was located on Grandpa's Knob, Vermont, was connected to the
grid of Central Vermont Public Service. The rotor was 53 m in diameter on a 38 m tower. Blades
were stainless steel with a 3.4 m chord, and each weighed 8,700 kg. The generator was synchro-
nized with the line frequency by adjusting the pitch of the blades. At wind speeds above 35 m/s the
blades were changed to the feathered position (parallel to the wind) to shut the unit down. Rated
power output was 1,250 kW at 14 m/s. The rotor was on the downwind side of the tower and the
blades were free to move independently (teeter, perpendicular to the wind) due to wind loading.