Реферат: Wind Power Essay Research Paper The wind

the pumping windmill was 20-50 feet high with a 6-16 foot wheel diameter”

(45)]. With 10-mph wind speed, a 6 foot-diameter wheel, a 2-foot diameter

pump cylinder, a windmill-pump could lift 52 gallons per hour to a

height of 38 feet. A 12-foot in diameter wheel could lift 80 gallons per

hour to a height of 120 feet. (Naar, p. 46).

The growth of wind-electricity in America was greatly stunned in 1937 with

the Rural Electrification Act, which made low-cost electricity more

available. However, in the 1970’s, due to oil shortages, earlier

prototypes of high-speed horizontal-axis windm ills were developed.

High-speed horizontal-axis types are used for many purposes, come in many

sizes. These include the typical windmills on a California windmill farm

and other windmill farms, and any other wind turbines in which the shaft

turned by th e aerofoils is horizontal. High-speed horizontal types may

have 1, 2, 3, 4, or many aerofoils. Low-speed types such as European ones

have much larger aerofoils in relation to their height above the ground.

Low speed types such as American Midwest ones are usually a pinwheel, with

many small blades encircled with an outer frame like a wheel.

Vertical-axis windmills were first developed in the Persians in

1500 BCE to mill corn. Sails were mounted on a boom, which was attached

to a shaft that turned vertically. By 500 BCE, the technology had spread

to Northern Africa and Spain. Low-speed ve rtical-axis windmills are

popular in Finland. They are about 150 years old. They consist of a

55-gallon oil drum split in half. They are used to pump water and aerate

land. They are inefficient. High-speed vertical-axis windmills include

the Darrieus

models. These have long, thin, curved outer blades, which rotate at 3 to

4 times the wind speed. They have a low starting torque and a high

tip-speed ratio. They are inexpensive and are used for electricity

generation and irrigation. There are three types, the delta, chi, and