Fundamentals of wind energy - Wind Power Generation and Wind Turbine Design - page 8

The double acting piston bellows was invented in China and was widely used
in metallurgy in the fourth century BC [11]. It was the capacity of this type of
bellows to deliver continuous blasts of air into furnaces to raise high enough tem-
peratures for smelting iron. In such a way, ancient Chinese could once cast several
tons of iron.
3.3 Windmills
China has long history of using windmills. The unearthed mural paintings from the
tombs of the late Eastern Han Dynasty (25-220 AD) at Sandaohao, Liaoyang City,
have shown the exquisite images of windmills, evidencing the use of windmills in
China for at least approximately 1800 years [12].
The practical vertical axis windmills were built in Sistan (eastern Persia) for
grain grinding and water pumping, as recorded by a Persian geographer in the
ninth century [13].
The horizontal axis windmills were invented in northwestern Europe in 1180s
[14]. The earlier windmills typically featured four blades and mounted on central
posts - known as Post mill. Later, several types of windmills, e.g. Smock mill,
Dutch mill, and Fan mill, had been developed in the Netherlands and Denmark,
based on the improvements on Post mill.
The horizontal axis windmills have become dominant in Europe and North
America for many centuries due to their higher operation effi ciency and technical
advantages over vertical axis windmills.
3.4 Wind turbines
Unlike windmills which are used directly to do work such as water pumping or
grain grinding, wind turbines are used to convert wind energy to electricity. The
fi rst automatically operated wind turbine in the world was designed and built by
Charles Brush in 1888. This wind turbine was equipped with 144 cedar blades
having a rotating diameter of 17 m. It generated a peak power of 12 kW to charge
batteries that supply DC current to lamps and electric motors [5].
As a pioneering design for modern wind turbines, the Gedser wind turbine was
built in Denmark in the mid 1950s [15]. Today, modern wind turbines in wind
farms have typically three blades, operating at relative high wind speeds for the
power output up to several megawatts.
3.5 Kites
Kites were invented in China as early as the fi fth or fourth centuries BC [11]. A
famous Chinese ancient legalist Han Fei-Zi (280-232 BC) mentioned in his topic
that an ancient philosopher Mo Ze (479-381 BC) spent three years to make a kite
with wood but failed after one-day fl ight [ 16 ].