Man’s Quest to Harness the  Wind

BY AWAKE! WRITER IN SPAIN

WHAT do you think of when you look at the windmill on the following page? Are you reminded of a Dutch landscape? Or do you call to mind Don Quixote, a fictional Spanish nobleman who imagined windmills to be dangerous giants? Perhaps the picture makes you think of a restored windmill that is now a local landmark.

Although windmills still dot the countryside in many parts of the world, they may seem little more than quaint reminders of a bygone age. For centuries, however, windmills were at the cutting edge of technology. And recently, after decades of neglect, the windmill concept has enjoyed a revival that is benefiting people everywhere. You are invited to follow the history of the windmill as it has been adapted to changing winds and changing needs.

Grinding Without the Grind

It all started with the basic need for bread. To obtain flour for bread, ancient peoples, such as the Israelites, ground edible grains by using “hand mills.” (Numbers 11:7, 8) Grinding with one heavy stone above another by hand was an arduous task. In time, heavier millstones “turned by an ass” or some other draft animal became popular. (Matthew 18:6) But even animal-driven mills had their drawbacks.

Man had already learned to harness water power with the waterwheel and wind power with the sailboat. Possibly somewhere in the arid steppes of Asia or the Middle East about the seventh century C.E., the two concepts were combined to get the wind to turn a grindstone. The wind-driven sails of this new invention turned a vertical axle that was attached to a millstone. a This type of rudimentary windmill served to grind wheat or barley as well as to pump underground water. How true that necessity is the mother of invention!

Changing the Design to Catch the Wind

The early mills, with their sails revolving around a vertical axle, were not very efficient. But their efficiency greatly improved when it was discovered that more power could be produced when the sails or blades were attached to a horizontal shaft that jutted out of a tower. To turn the millstone below, the rotation of the horizontal shaft was transmitted to a vertical shaft through a series of gears. This modification enabled windmills to take greater advantage of the wind’s energy. These new mills had enough power to drive heavy machinery, such as circular saws.

Whatever the task, however, windmills needed a constant energy supply. And wind has the inconvenient habit of changing direction frequently. How could the windmill’s sails keep aligned with the wind? An early solution was the invention of a swiveling windmill, or post-mill. The mill was pivoted on a post, which permitted the whole structure, along with the main sails, to swivel directly into the wind.

 Since such swiveling windmills had, of necessity, size limitations, other millwrights decided to keep the tower fixed and instead have a revolving roof. In these windmills the main axle protrudes from the roof, enabling roof and sails to face the wind irrespective of its direction. How could a miller move a roof complete with axle, sails, and a brake system? Take another look at the photograph on page 23 of a windmill in Cartagena, Spain. You will notice a beam that slides out of the roof behind the windmill and reaches down to the ground. Although it may look like a support post, it is actually a leverage arm. This pole can be pushed or pulled by human or animal power, turning the roof until the mill’s blades face the wind.

Other windmills have what looks like a small propeller, or fantail, set behind the main sails. This fantail is designed to move the sails automatically in the right direction. How does it work? Imagine that the main sails of the windmill are facing the wind and revolving at full speed. Suddenly the wind shifts direction, and the sails slow down. The fantail, located at a right angle to the sails, now catches the wind and begins to spin. This motion turns a set of gears that automatically turn the roof and the sails back into alignment with the ever-shifting wind.

From Sails to Slats

Another factor that makes harnessing the wind difficult is its constant change of strength. Early windmills, which had sails similar to those of a sailboat, could not easily adapt to variable wind speeds. If brakes were applied, the resulting heat produced by the friction could start a fire. And strong gusts of wind could cause sails to crash into each other or into the mill itself, causing untold damage. In some cases, when the brakes slipped while the miller was on a blade folding up the sails, he was flung into the air!

In 1772 this problem was overcome when a Scottish millwright replaced the sails with shutters that automatically opened and closed, somewhat resembling venetian blinds. The book Windmills explains: “When a strong gust comes, the pressure on the shutters overcomes the tension of the spring and the shutters open, spilling wind and slowing the sail. As the wind dies away, the tension of the spring overcomes the pressure of the wind and the shutters close, presenting a greater surface to the wind and maintaining the speed of the sail.”

With rotating roofs and self-adjusting sails, windmills reached their zenith by the late 19th century, when it was estimated that European mills were churning out some 1,500 megawatts of power. b But then the winds of technological change brought electricity, steam turbines, and the internal-combustion engine. Windmills could not compete with  the efficiency and mobility of the new machines, and it seemed that the wind had been blown out of their sails forever. Then an unexpected need arose.

Modern Successors to the Ancient Windmills

The fuel crisis of the 1970’s led to the investigation of alternative energy not dependent on fossil fuels. At approximately the same time, a growing concern arose about emissions from fossil-based fuels polluting the atmosphere. The search began for “clean” energy. Suddenly, the windmill concept became an attractive option and wind turbines became a developing technology.

Modern “windmills” are much slimmer than their predecessors. This is because, unlike the traditional windmill, modern wind turbines do not normally drive a machine housed within the mill structure. Each turbine converts wind power into electrical energy, which often passes to the local electricity grid. By 1988 these new “windmills” were producing 1,500 megawatts of power in Europe, just as their predecessors had done a century earlier.

Looking like a line of huge, frost-covered trees on the crests of prominent hills, modern wind farms have begun to change the face of rural landscapes. Although these wind turbines may not look beautiful, most people feel that any negative visual impact is a small price to pay for the tens of thousands of megawatts of clean power that the wind turbines produce globally. These modern windmills make a significant contribution to the worldwide effort to reduce greenhouse gases, something that benefits everyone.

However, neither the traditional windmill nor the modern wind turbine could function if it were not for that never-ending supply of “clean” energy​—the wind. How grateful we can be to “the Creator of the wind”!​—Amos 4:13.

[Footnotes]

[Picture on page 23]

Spanish windmill with eight sails, named El Molino Zabala

[Picture on page 24, 25]

Modern wind turbines, Cádiz, Spain

[Pictures on page 25]

1. Consuegra, Spain

2. Majorca, Spain

3. Aruba, Lesser Antilles

[Credit Lines]

Godo-Foto

Godo-Foto