PROMISING SOURCES OF POWER
The large quantities of electric power generated at present mostly depend on various sources of mechanical power. It is obvious that production of so much power by existing means only could not last for ever since the earth's available supply of coal, wood and oil will be completely used up some day.
Apart from the main sources of power, that is, fuel and water power which meet most of the present-day power requirements of mankind and also apart from atomic power, there are several other sources as well.
It is with one of these so-called "new sources of power" that we shall deal below.
Wind-Driven Power Plant. It is calculated that the annual power available in the winds over the earth's surface exceeds millions of millions of kilowatt hours. Nevertheless, only a comparatively negligible part of that value finds an efficient application under our present conditions.
It would be hard to say exactly when windmills were first harnessed as a source of mechanical power. The Dutch, at least, are said to have used them for centuries in order to perform certain kinds of mechanical work. Old Egyptian writings tell us that wind power had already been used a thousand and more years before our times. However, wind power has been able to meet but small local needs for mechanical power.
Today scientists, designers, and inventors are turning their attention to another purpose, namely, that of electricity generation. Generally speaking, electric windmills are in production or operation in a number of countries, the Russian Federation, the United States, England and France being among them. We should like to point out here that in 1931 a large turbine-powered by the wind was built for electricity generation in Yalta, the Crimea. The electric generator of that equipment was housed in an installation raised on a high tower.
Windmills may in theory obtain perhaps about 60 per cent of the wind power but in practice losses in the rotor and in the whole equipment as well as considerable electrical losses are supposed to reduce the efficiency to some 40 per cent or even less. The basic elements defining and influencing the obtainable power are the velocity and strength of the wind.
So far nothing was said about the principal disadvantage distinguishing wind power from some of the other sources of power. Sometimes there is no wind at all and even when it blows, its strength and direction may change at any moment. In short, we cannot expect the wind to blow when, where and as long as we should like it.
Whatever may be its exact form, purpose, or maintenance, a wind power plant must consist of the following main parts:
1. A rotor which is turned round by the wind. It goes without saying that a wind-driven rotor must obviously be designed in such a manner that the wind blowing upon it causes it to rotate.
2. A tower to raise the rotor well above the earth's surface so that it can circulate freely without any danger or damage to people. The tower should be as high as possible because then the rotor intercepts wind moving at a greater and steadier rate than that over the earth's surface.
3. The electric generator to be driven by the rotor and to produce power.
The three parts mentioned above form the wind-driven power plant.
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