Environmental Engineering Reference
In-Depth Information
The last wind turbine discussed in this review is the product of a landmark achievement
in wind power. This work was conceived and led by Palmer C. Putnam, a brilliant, forceful
American engineer who for many years contended that large wind turbines should be
utilized to supplement central power plants. In the late 1930s, Putnam interested the S.
Morgan Smith Company of York, Pennsylvania, in his plan to build a prototype of a
megawatt-scale
wind turbine generator using the latest technology. The Smith Company,
experienced in the construction of hydroelectric turbines and electrical power equipment,
agreed to provide inancing and manage all phases of the engineering, construction, and
operation. The result of this collaboration was the construction in 1941 of the largest wind
turbine up to that time and for almost 40 years afterward.
The
Smith-Putnam wind turbine
,
shown in Figure 1-22 [Voaden 1943; Putnam 1948;
Koeppl 1982], had a two-bladed rotor that swept an area 53.3 m in diameter. It had a truss-
type tower and a rotor axis 33.5 m above grade. The rotor powered a 1.25-MW
synchro-
nous generator
through a geared step-up transmission. This coniguration was chosen to
meet Putnam's goal of producing energy at the lowest possible unit cost and in large
enough quantities to be useful to electric utilities. The preliminary design effort was led
by Putnam, who recruited a nationwide team of consultants for assistance, including
aerodynamicists such as Theodore von Karman at the California Institute of Technology,
engineering faculty members at the Massachusetts Institute of Technology, and staff
engineers at the General Electric Company.
Technological innovations in the Smith-Putnam wind turbine included
full-span active
control
of blade pitch; the use of individual
lapping hinges
on the blades to reduce
gyroscopic loads on the shaft (a generic problem with two-bladed rotors on rigid hubs that
the Jacobs brothers had experienced earlier); and
active yaw control
by means of a
servo-
motor
turning a pinion meshing with a large
bull gear
between the machinery house or
nacelle
and the tower.
The Smith Company organized an experienced industrial team for the inal design
work, which began in 1939, and for the fabrication of parts, which began in 1940. Blades
were built by the Budd Company of Philadelphia with stainless steel skins to resist
corrosion, applying a technology they developed for railway passenger cars. After shop
assembly and system tests by the Wellman Engineering Company in Cleveland, the
machinery and blades were shipped to the site — a hill in Vermont called “Grandpa's
Knob.” On October 10, 1941, electricity lowed for the irst time from “the windmill on
Grandpa's Knob” into the network of the Central Vermont Public Service Corporation.
Several hundred hours of testing proved that the system could operate satisfactorily as
a utility power plant. However, a bearing failure in 1943 caused operations to be delayed
for two years, because of wartime supply dificulties. It was also discovered that the blade
spars were under-designed at the root, and so reinforcing doublar plates were welded in
place. The rotor was then locked in place for the duration of the war, to endure winter
storms with little or no maintenance. When operations recommenced in 1945, cracks were
discovered in a blade root at a repair weld. Unable to obtain funding for a replacement
rotor, the project managers took the risk that the test program could be completed
successfully before the cracks propagated to failure. The turbine was run continuously for
several weeks with excellent power production, but the risk was too high. In the early
hours of March 26, 1945, the faulty blade spar separated at the repair weld. Unfortunately,
the S. Morgan Smith company could not afford to continue the work.
As we close this review of the technological development of windmills and early wind
turbines — an evolution that stretches back to ancient Persia — we should note that the
Smith-Putnam team made two other signiicant contributions to the technology: They were
pioneers in organizing a wind turbine research and development project along the lines of
a modern industry/university partnership, and they served as an inspiration for the eventual
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