Wind Mill Power

There were two ancient types of windmills. The first, created by Persians in the 9th Century, used a vertical axis with attached sails. The latter, and more complex, used a rotating horizontal axis that faced the wind and used tapered blades to be very efficient in changing winds. Both were used initially to grind grain, though some later uses included transporting water, a crucial innovation that allowed America to irrigate vast amounts of farmland. Modern windmills transform wind energy into electricity, and these are more commonly referred to as wind turbines. They hold great promise for the future, as they are a clean energy source.

The first practical windmills were engineered by the Persians in the 9th Century. These windmills had a vertical axis (imagine your weather vane) and were used to grind corn and other foodstuffs. The more prevalent type of windmill, the horizontal windmill, was created by the French in the late 12th Century. This windmill has blades that face the wind, and, similar to the Persians, the French used it to grind cereals.

Since then, windmills have undergone immense innovations. These include getting windmills to transport water, which was influential in irrigation of vast American plains, and recently integrating windmills to harness wind energy into the electric grid. The engineering behind windmills is now considered simple; though back when they were first created they were major technological feats. This began with the vertical-axis windmills.

A simple construction is as follows: Get a vertical axis, and attach a number of arms to said axis. Then, the engineers attached cloth sails to the end of each arm. This is quite similar to a watermill, except with the axis rotated ninety degrees so that the shaft is vertical. The end-result, incoming wind would push against the vertical sails on one end of the windmill, in which case the other end would have to be covered, or the sails would be skewed so as to create more wind torque in one radial direction. The rotating axis would be used to grind grain and cereals.

A more complex windmill was created with the invention of the horizontal-axis windmill, the form most prevalent today. This windmill idea presented a challenge; how does one get a horizontal axis to spin when the blades are facing the wind? The problem was solved in a two-fold manner. First, the axis was not perfectly horizontal; it was manufactured so that the upper end would be further back. And second, the blades were skewed. If the blades have the bulk of the area facing the wind, or their sides facing the wind, they would not rotate. The only way to get these blades to rotate when hit by an oncoming wind was to curve the blades so that they tapered off near the end. Another problem was also solved; these windmills used intricate gears to turn rotation in the horizontal axis into rotation in the vertical axis, an engineering feat that is now common in the transmissions of cars.

Though more complicated then the vertical-axis forms, these windmills were a breakthrough in Europe, since frequent wind changes required the mill to be able to operate under changing wind vectors, which it accomplished by having the blades and axis rotate to face the oncoming wind. Although now these wooden windmills are not practical, the Western world has seen a rebirth in windmill technology in the form of wind turbines, or windmills that create electrical energy. These turbines convert the kinetic energy of the wind into mechanical energy which is then transformed into electricity at a very efficient rate. The power that is transferred to the wind turbine is proportional to the radius swept out by the blades squared times the velocity cubed.

Like their ancient predecessors, there are two forms, horizontal and vertical axis wind turbines. The horizontal-axis wind turbines (the more common of the two) are 200 % more efficient, but they are far larger and more expensive than their vertical counterparts.

What do wind turbines hold for the future? That is still to be decided. Although they are a zero-carbon energy source, they are still impractical on a large scale. To be fully integrated, there still has to be improvements in reducing the cost and increasing the efficiency of these behemoths. The only certainty is that progress will happen, as demonstrated by the development of windmills from simple rotating sails more than a thousand years ago to complex engineering feats today.


For more information about wind mill power:

Advantages and Disadvantages of Wind Energy