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By
Mary
Bellis
Lester Pelton invented a type of free-jet
water turbine called the Pelton Wheel or Pelton turbine. Lester Pelton was
born in 1829 in Vermillion, Ohio. In 1850, he immigrated to California during
the time of the gold rush. Pelton made his living as a carpenter and a
millwright. At that time there was a great demand for new power sources to run
the machinery and mills necessary for the expanding gold mines. Many mines
depended on steam engines, however those required exhaustible supplies of wood
or coal. What was abundant was water power from the fast running mountain
creeks and waterfalls. Waterwheels
that had been used to power flour mills, worked best on larger rivers and did
not work well in the faster moving and less voluminous mountain creeks and
waterfalls. What did work was the newer water turbines that used wheels with
cups rather than flat panels. A landmark design in water turbines was the
highly efficient Pelton Wheel.
David P. Stern writes in his NASA article
"From Stargazers to Starships":
According to a 1939 article by W. F. Durand
of Stanford University in Mechanical Engineering, Pelton´s invention
started from an accidental observation, some time in the 1870s. Pelton was
watching a spinning water turbine when the key holding its wheel onto its
shaft slipped, causing it to become misaligned. Instead of the jet hitting
the cups in their middle, the slippage made it hit near the edge (drawing);
rather than the water flow being stopped, it was now deflected into a
half-circle, coming out again with reversed direction. Surprisingly, the
turbine now moved faster. That was Pelton´s great discovery. In other
turbines the jet hit the middle of the cup and the splash of the impacting
water wasted energy.
Lester Pelton developed his
design, settling in the end on a double cup with a wedge-shaped divider in
the middle, splitting the jet--half to the left, half to the right. In the
winters of 1877 and 1878 he tested turbines of different sizes, including a
small one for running his landlady's sewing machine (it worked, but he was
not happy with the design). In 1880, he also obtained his first patent for a
water turbine.
 To
the left, you can view the patent drawing for a 1889 patent issued to Lester
Pelton for an improved water wheel.
In 1883, the Pelton turbine won a competition
for the most efficient water wheel turbine held by the Idaho Mining Company of
Grass Valley, California. Pelton´s turbine proved to be 90.2% efficient, and
the turbine of his closest competitor was only 76.5% efficient. In
1888, Lester Pelton formed the Pelton Water Wheel Company in San Francisco,
and began to mass manufacture his new water turbine.
The Pelton water wheel turbine set the
standard, until the Turgo impulse wheel was invented by Eric Crewdson in 1920.
However, the Turgo impulse wheel was an improved design based on the Pelton
turbine. The Turgo was smaller than the Pelton and cheaper to manufacture. Two
other important hydropower systems include the Tyson turbine, and the Banki
turbine (also called the Michell turbine).
Hydroelectricity
Hydropower converts the energy of flowing
water into electricity or hydroelectricity. The amount of electricity
generated is determined by the volume of water and the amount of
"head" (the height from the turbines in the powerplant to the water
surface) created by the dam. The greater the flow and head, the more
electricity is produced.
The mechanical power of falling water is an
age-old tool. Of all the renewable energy sources that generate electricity,
hydropower is the most often used. It is one of the oldest sources of energy
and was used thousands of years ago to turn a paddle wheel for purposes such
as grinding grain. In the 1700's, mechanical hydropower was used extensively
for milling and pumping.
The first industrial use of hydropower to
generate electricity occurred in 1880, when 16 brush-arc lamps were powered
using a water turbine at the Wolverine Chair Factory in Grand Rapids,
Michigan. The first U.S. hydroelectric power plant opened on the Fox River
near Appleton, Wisconsin, on September 30, 1882. Until that time, coal was the
only fuel used to produce electricity. The early hydroelectric plants were
direct current stations built to power arc and incandescent lighting during
the period from about 1880 to 1895. Because the source of hydropower is water,
hydroelectric power plants must be located on a water source. Therefore, it
wasn’t until the technology to transmit electricity over long distances was
developed that hydropower became widely used. By the early 1900's,
hydroelectric power accounted for more than 40 percent of the United States'
supply of electricity. The years 1895 through 1915 saw rapid changes occur in
hydroelectric design and a wide variety of plant styles built. Hydroelectric
plant design became fairly well standardized after World War I with most
development in the 1920's and 1930's being related to thermal plants and
transmission and distribution.
Next
page > How
are Turbines Used to Generate Electricity?
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