Windmills - Windmill Farms

The wind has played a long and important role in the history of human civilization. The first known use of wind dates back 5,000 years to Egypt, where boats used sails to travel from shore to shore. The first true windmill, a machine with vanes attached to an axis to produce circular motion, may have been built as early as 2000 B.C. in ancient Babylon. By the 10th century A.D., windmills with wind-catching surfaces as long as 16 feet and as high as 30 feet were grinding grain in the area now known as eastern Iran and Afghanistan.

The western world discovered the windmill much later. The earliest written references to working wind machines date from the 12th century. These too were used for milling grain. It was not until a few hundred years later that windmills were modified to pump water and reclaim much of Holland from the sea.

The familiar multi-vane "farm windmill" of the American Midwest and West was invented in the United States during the latter half of the l9th century. In 1889 there were 77 windmill factories in the United States, and by the turn of the century, windmills had become a major American export. Until the diesel engine came along, many transcontinental rail routes in the U.S. depended on large multi-vane windmills to pump water for steam locomotives.

Farm windmills are still being produced and used, though in reduced numbers, and show no sign of becoming obsolete. They are best suited for pumping ground water in small quantities to livestock water tanks. Without the water supplied by the multi-vane windmill, beef production over large areas of the West would not be possible.

In the 1930s and 1940s, hundreds of thousands of electricity producing wind turbines were built in the U.S. They had two or three thin blades which rotated at high speeds to drive electrical generators. These wind turbines provided electricity to farms beyond the reach of power lines and were typically used to charge storage batteries, operate radio receivers and power a light bulb or two. By the early 1950s, however, the extension of the central power grid to nearly every American household, via the Rural Electrification Administration, eliminated the market for these machines. Wind turbine development lay nearly dormant for the next 20 years.

Following the OPEC Oil Embargo of 1973, interest in wind energy resurfaced in response to climbing energy prices and questionable availability of conventional fuels. Federal and state tax incentives and aggressive government research programs triggered the development and use of many new wind turbine designs. Some experimental models were very large. With a blade diameter of 300 feet, a single machine was able to supply enough electricity for 700 homes. A wide variety of small-scale models also became available for home, farm and remote uses.

In the 1970s there were nearly 50 domestic wind turbine manufacturers. Since then, the wind industry has undergone massive consolidation, resulting in less than a dozen domestic manufacturers in 1997. Roughly half of these deal exclusively with small-scale models. This consolidation followed the expiration of the tax incentives in the mid-1980s and the easing of the energy crisis, both of which reduced market demand. A competitive marketplace to weed out inferior products further contributed to consolidation.

Meanwhile, a new market for wind systems, "wind farms," began in the early 1980s. This market evolved thanks in part to a new Federal law, the Public Utility Regulatory Policies Act of 1978. This legislation requires utilities to buy electricity from private, non-utility individuals and developers. California has been home to most wind farm development due to very attractive electricity buy-back rates and the availability of windy, sparsely populated mountain passes. As of 1997, nearly 2% of California's electricity is generated by the wind. As the cost of the technology has continued to decline, other areas of the country, namely the Great Plains, Pacific Northwest and Northeast, are now beginning to see greater wind farm development.

The windmill was introduced into England in the 12th century - probably by Crusaders returning from the wars in the Holy Land. These early Mills were quite small and we can glimpse some of their details from mediaeval manuscripts, stained glass and carved representations.

Wind power had been used to move ships long before it was applied to grinding corn.

To be effective the mill needed the wind to blow toward the sails. As the wind often changes direction it was necessary to be able to face the sails into the wind so that the mill could work. To make this possible the mill body was made to rest upon an upright post. A long lever projecting from the rear of the mill body allowed it to be turned around. Mills of this type are called post mills.

The earliest post mills were small and their trestles were not protected from the weather. As the drawing shows the work of putting the heavy timbers in place was not easy. Ropes, pulleys and levers were the chief mechanical aids.

The 14th and 15th centuries provide evidence of what the early mills looked like, with illustrations occuring in diverse media such as memorial brasses, stained glass, and wood carvings, as well as the expected manuscript records.

The pinnacles of windmill design include those built by the Dutch (who used windmills extensively to pump water as well grind flour) and the British, who developed many advanced "automatic control" mechanisms over the centuries.

As steam power developed, the uncertain power of the wind became less and less economic, and we are left today with a tiny fraction of the elegant structures that once extracted power from the wind. These remaining windmills, scattered throughout the world, are a historic, and certainly very photogenic, reminder of a past technological age.

However the promise of power from the wind lives on, both in the form of wind turbines producing electricity, and in the form of small scale windpumps (often largely low-tech "appropriate technology" installations) still used extensively in world agriculture.

Millers who used common sails had to stop the mill working if the strength of the wind altered, so that the canvas could be adjusted. In 1772 a Scottish engineer, Andrew Meikle, invented a new type of sail. It was made from a series of shutters which could be opened or closed by a system of levers. This idea made it easier to change a sail's wind resistance but the mill had to be stopped to alter each sail. The design was improved in 1807 when William Cubbit invented his Patent Sails. These could be adjusted without stopping the mill. All the sails could be changed by the movement of the striking rod.

To make the sails face the wind the entire post mill had to be turned. This was a cumbersome and time consuming task. Eventually a better way was found to achieve to same end. Masonry towers were constructed and the sails were placed in a cap which could be turned 360 degrees. We do not know who invented the cap but it seems to have been in use by the fourteenth century. Many small drawings appear in manuscripts of that time and examples can be found in stained glass. These drawings show how mills appeared to mediaeval artists. They may not have known how a mill worked but some drawings do provide technical evidence.

Wind power was also used to raise water. The earliest water-raising mills operated scoop wheels. A Scoop-wheel had a lift which was less than its radius. Many mills of this kind were used by the Dutch engineers Nicholas Vermuyden when he drained the Fens in the C17. There were hundreds of drainage mills in various parts of England but most were in Suffolk or Norfolk. Wooden scoop wheels were placed in narrow brick channels and as the wheel turned it pushed water uphill and across the threshold. This then ran off into a higher channel. On a steep slope several wind pumps were used close together.

The use of wind energy has been re-valued in recent years. Wind power can be used to generate electricity. Even traditional mills can be constructed to provide power. This Cretan form of mill is one of many to be seen at the Centre for Alternative Technology, Machynlleth. It is simple to build and does not require elaborate tools.

- John Vance

Our energy future is in the wind July 13, 2002 - Boston Daily Globe

Satellite Sees Double Zones of Converging Tropical Winds   July 2002 - Cosmiverse

'Windiest' farm is now open in Britain  BBC - July 8, 2002

Wind Energy in California

What is a wind tunnel and what does it do?

Don Quixote - Chasing after  Windmills  CBS
  Don Quixote 17th-century Spanish tale about a madcap knight, 
  written by Miguel de Cervantes