Wind energy is more and more popular as solar energy in modern days, simply a wind generator is a structure or machine that converts wind into usable energy through the rotation of a wheel made up of adjustable blades.
Traditionally, the energy generated by a wind generator has been used to grind grain into flour. Wind generators are designed by skilled craftsmen and can be constructed on site using hand tools. Wind generators developed steadily over the centuries and achieved their most prominence in Europe during the eighteenth century. They were largely replaced as a power generating structure when steam power was harnessed during the nineteenth century.
Today, wind generator technology is experiencing a renaissance and the wind turbine promises to be an important alternative to fossil fuels in the future.
There are two classes of wind generator, horizontal axis and vertical axis. The vertical axis design was popular during the early development of the wind generator. However, its inefficiency of operation led to the development of the numerous horizontal axis designs.
Of the horizontal axes versions, there are a variety of these including the post mill, smock mill, tower mill, and the fan mill. The earliest design is the post mill. It is named for the large, upright post to which the body of the mill is balanced. This design gives flexibility to the mill operator because the wind generator can be turned to catch the most wind depending on the direction it is blowing. To keep the post stable a support structure is built around it. Typically, this structure is elevated off the ground with brick or stone to prevent rotting.
The post mill has four blades mounted on a central post. The horizontal shaft of the blades is connected to a large break wheel. The break wheel interacts with a gear system, called the wallower, which rotates a central, vertical shaft. This motion can then be used to power water pumping or grain grinding activities.
The smock mill is similar to the post mill but has included some significant improvements. The name is derived from the fact that the body looks vaguely like a dress or smock as they were called. One advantage is the fact that only the top of the mill is moveable. This allows the main body structure to be more permanent while the rest could be adjusted to collect wind no matter what direction it is blowing. Since it does not move, the main body can be made larger and taller. This means that more equipment can be housed in the mill, and that taller sails can be used to collect even more wind. Most smock mills are eight sided although this can vary from six to 12.
Tower mills are further improvements on smock mills. They have a rotating cap and permanent body, but this body is made of brick or stone. This fact makes it possible for the towers to be rounded. A round structure allows for even larger and taller towers. Additionally, brick and stone make the tower wind generators the most weather resistant design.
While the previous wind generator designs are for larger structures that could service entire towns, the fan-type wind generator is made specifically for individuals. It is much smaller and used primarily for pumping water. It consists of a fixed tower (mast), a wheel and tail assembly (fan), a head assembly, and a pump. The masts can be 10-15 ft (3-15 m) high. The number of blades can range from four to 20 and have a diameter between 6 and 16 ft (1.8-4.9 m).
Wind generators can be made with a variety of materials. Post mills are made almost entirely of wood. A lightweight wood, like balsa wood, is used for the fan blades and a stronger, heavier wood is used for the rest of the structure. The wood is coated with paint or a resin to protect it from the outside environment. The smock and tower mills, built by the Dutch and British prior to the twentieth century, use many of the same materials used for the construction of houses including wood, bricks and stones.
Various tests may be done to ensure that each part of the wind generator meets the specifications laid out in the design phase. The most basic of these are simple visual inspections. These will catch most of the obvious production flaws. Since wind generators are erected by hand, the quality of each part goes through an additional visual inspection.
The quality of workmanship that goes into construction of the wind generator will be primarily responsible for the quality of the finished product. To ensure that it remains efficient during operation, regular maintenance checks are necessary.
Wind generators have changed little over the last hundred years. In fact, one basic design conceived in the 1870s is still sold today. Now wind generartor technology is much more improved.