Environmental Engineering Reference
In-Depth Information
Nevertheless, the windmill persisted through the industrial revolution; it even continued
to supply essential service into the twentieth century in sparsely populated areas where
relatively small amounts of scattered power were required, and constant availability was not
essential. This was particularly true in the United States and in other countries having vast
land masses, such as the former USSR, Australia, and the Argentine. In the industrialized
regions of the world, where greater population densities and increasing manufacturing
enterprises were the rule, the windmill was becoming moribund by the end of the irst third
of the twentieth century.
Wind machines, however, were revived by the emergence and proliferation of two
major technologies: the rapid spread of electricity as a versatile transducer of energy
between the prime mover and the job, and the burgeoning of the engineering science of
aerodynamics, which was occasioned by the development of the airplane. At the end of the
last century, in the years from 1888 to 1900, experiments began in which windmills were
used to generate electricity, both in the United States and in Denmark, which has no fossil
fuels of its own.
The history of wind power in Denmark, provides a salutary example of how socio-
economic conditions can both inhibit a technology's gradual but continuous development
and rescue it from an apparently endless decline, when politics or economics intervene.
From 1900 to 1910, many Danish wind-driven electricity plants were in use, particularly
for agriculture, but diesel engines were beginning to give them some stiff competition by
1910 to 1914 because of their convenience and economy [Juul 1956, 1964]. However,
during World War I, oil supplies to the country were virtually shut off and wind power was
resurrected; many 20- to 35-kW plants were built at that time. After the war, electriication
took place throughout the country, and once more the windmill languished. In 1939, World
War II caused another cut-off in fuel supplies, and wind power was once more called upon
to the fullest extent possible. After the hostilities ended, further rapid, extensive
electriication took place, but this time the utility of wind power was not discounted;
instead, a research program was begun to consider it as a supplement to the large, central
plants.
These compelling reminders of the perils of relying on transported energy sources,
together with a degree of awareness of the eventual dissipation of these sources, prompted
some of the development of windmills into wind turbines. In the period after 1945, there
were developments not only in Denmark, but in France, Germany, and Britain as well.
These developments might have been stimulated by the 1.25-MW
Smith-Putnam turbine
in
the United States, which operated intermittently from 1941 to 1945. All these ventures
enjoyed some degree of technical success, but that was not sustained, because they were
not considered to be cost-effective. However, they did provide a useful starting point for the
renaissance of wind power in the early 1970s, which was provoked by the international oil
crisis of 1972.
In contrast to the uneven history of the windmill, the water mill has enjoyed 2,000
years of slow but continuous development up to this very day. Built in multi-megawatt
sizes, it achieves the highest eficiencies of any prime mover. The water mill has changed,
in its general physical characteristics, considerably over the centuries; the windmill, but
little (in detail, yes, but not in form). In fact, if a European miller of the thirteenth century
were given the opportunity to observe the operation loor of a modern hydroelectric plant,
he would be utterly confounded. On being taken to see a wind power station in California,
however, he might immediately express his delight in seeing so many windmills in use,
although he might also inquire as to why so many of them had lost one or two sails.
This brief review might serve to place the evolution of the windmill in its general
context. Now, however, we shall go back in time to its origins and its early development,
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