As a student of wind energy in all its far-flung arcana, I felt this information should be brought back into the light so others might be able to refer to it in their own work.
The following is a portion of Chapter 5 from my 1995 opus, Wind Energy Comes of Age that introduces the concept of Windmill Liberation. Keep in mind that this was written nearly three decades ago.
“Ech kier die Nuet/On schaff och Bruet (Ich wende die Not/und schaffe euch Brot).Inscription in dialect on beard of windmill in northern Germany: “I turn away need and furnish your bread.”
Inventive minds have long sought to harness the wind. Weary Egyptians may have been the first, when they sailed up the Nile against the current. Crude vertical axis panemones have ground grain in the Afghan highlands since the 7th century. By the 17th century windmills were such a commonplace technology that Cervantes’ fictional Don Quixote was tilting at them near Consuegra on the plains of La Mancha. According to French historians, as many as 500,000 windmills were being used in China by the 1800s and possibly an equal number were scattered across Europe.
A European Tradition
Traditionally, the history of Western wind technology begins with the first documented appearance of the European or “Dutch” windmill in Normandy in the year 1180. Presumably, the vertical axis windmills of Persia spread from the Middle East across the Mediterranean to Europe, and in so doing evolved into horizontal axis windmills. From France, the technology spread across the channel to southern England (1191), into nearby Flanders (1190), then on into Germany (1222), and subsequently north to Denmark (1259). Finally “Dutch” windmills reached Poland in the 14th century. For a more detailed account see Dennis Shepherd’s chapter on the “Historical Development of the Windmill” in Wind Turbine Technology.
In Harvesting the Air: Windmill Pioneers in Twelfth-Century England, historian Edward Kealey threw the preceding scenario on its head with his controversial thesis that the technology is indigenous to Europe, originating in southern England. According to Kealey, the English post mill predates the mills in Normandy–possibly by as much as a century–and originated in England, not in the Orient. He cites records documenting the operation of post mills during the mid 12th century, long before the first mention of windmills on the continent. And probably most heretically of all, Kealey argues that the European windmill arose independently of the vertical axis mills used in Persia, suggesting that the European post mill is technologically unique and not a derivative of those in the East.
English Post Mill
Kealey ventures further out on the academic limb to propose that the direction of technology transfer was the reverse of that commonly believed, and that crusaders took windmills to the Holy Land in 1191. Historians commonly cite a reference to German knights building the first windmill in Syria during the Third Crusade. Kealey suggests that the Germans could originally have been Saxons, who as Norsemen had previously”settled” in England. Though this academic debate is of interest solely to historians and students of technological dissemination, a lesser-known theme of Kealey’s is pertinent to modern wind turbines and their technology.
For many of the alternative energy and environmental activists of the 1970s, wind turbines were more than mere machines; they were vehicles of social change. Wind turbines offered these idealists a means for building a more sustainable society, a mechanism for living within natural bounds instead of outside them. Few then knew that there was a strong historical case for such a vision.
Kealey, and French historians as well, have found that windmills have at various times fueled great social upheavals. According to Kealey’s research, many early English windmill pioneers were progressive citizens with reputations for what we would today call social activism. The development of the English post mill occurred during a period of social and agricultural modernization and was a product, as well as a cause, of these changes.
Just as the sail liberated slaves from Mediterranean galleys, the proliferation of post mills across the English countryside in the 12th century put power into the hands of those who were previously powerless, and liberated women from grinding grain by hand. “The windmill was an instrument of social progress,” says Kealey. “It enlarged the community of skilled mechanics and lightened the daily work load of countless women.” Kealey lovingly describes the English post mill as “appealing, productive, and even mysterious,” but the “windmill was above all a triumph of ingenuity over toil.
The challenge to the growth of wind energy in the 12th century was, as it is today, not due to the technology’s limitations, but rather to resistance from those with the most to lose. The land, the forests, and the water: all were part of the feudal estate. The wind, however, was not. Church and feudal lords feared losing their lucrative milling rights to commoners who harnessed the free power of the wind.
According to these historians, the windmill provided a technology for the “liberation theology” of the era and devotees went forth spreading the word. Early wind advocates, including an obscure cleric, “broadcast an invention,” says Kealey, “that challenged the foundations of medieval society.” Their proselytizing spread windmills across central England.
The technology took root at a time of rebellion against the tyranny of feudal monopolies. Often windmills were built in direct opposition to the feudal lord who controlled the nearby water mills. Water power was never free from conflicting claims, even at the time of the Magna Carta, which gave the rights of passage and other uses of stream courses to the nobility, but limited its right to build structures in waterways.
To an entrepreneur, wind was advantageous on several counts. There were more sites available for windmills than there were for water mills. And users were not tied to the river courses where most prime sites had already been developed. The lower cost of windmills over water mills encouraged their proliferation at a time when a growing urban population needed a new energy source. Wind filled the void. The advent of the windmill and the growth of cities simultaneously breached the hold of feudal lords.
Feudalism eventually adapted to the threat. During the period 1162-1180, for example, the archbishop of southern France regulated windmills by demanding 5% of the grain ground there. In England, lords sometimes destroyed windmills that commercially threatened their water mills, or seized a windmill on a pretext. Yet despite the setbacks to their owners, the modest English post mill flowered, jumped the Channel and grew into the towering windmills of the lowlands.
According to Jaap de Blecourt, the millwright who reassembled the De Zwaan windmill in Holland, Michigan, wind’s heyday in the Netherlands contributed to the country’s golden age. Windmills “fit” the rural Dutch landscape because they were the available power source during the 17th century. Blecourt’s comment reflects a common perception among the Dutch. “Windmills belong to the Dutch landscape, to such an extent, that we cannot imagine this landscape without them,” said Frederick Stokhuyzen in his book on The Dutch Windmill.
Only by tapping the wind could Jan Leegwater (literally “empty water”), and the engineers that followed him, drain the polders and make the Netherlands what it is today.As late as 1850, 90% of the power used in Dutch industry came from the wind. Steam supplied the rest. The 700 windmills in the Zaan district north of Amsterdam formed the core of what would become the center of Dutch manufacturing.
Only in the late 19th century did the use of wind wane. Yet in 1904, wind still provided 11% of Dutch industrial energy. The switch from wind to steam was based on more than cost; reasons included changes in social conditions, agricultural practices, and the mood of the rural populace. This could be a harbinger of why wind’s star may be in the ascendancy now that it has become economic once again. Wind offers other attributes now considered important, such as its ability to generate electricity renewably, without combustion or the creation of radioactive wastes.
In 1896, at the height of the Industrial Revolution, wind still pumped 41% of the polders in the Netherlands. Only after cheap coal became available from the nearby Ruhr did steam-pumping erode wind’s dominance. Even then, steam was not clearly superior. Steam required larger polders to perform optimally, and individual polder mills were cheaper to operate than equivalent steam pumps through the turn of the century.
Just as is the case today, the capital costs of wind were higher than those of coal. Though the wind was free, capital was not. And much like it is today, the coal was cheap, once publicly constructed canals linked the Netherlands with the Rhine and the Ruhr. Steam also required less than one-third the labor used by wind to drain a large polder such as the Haarlemmermeer where Amsterdam’s Schipohl airport now sits. Steam also was available upon demand; wind was not. A long lull could delay spring planting until the windmill pumped the polder dry. The steam engine put control over drainage into the hands of the community. For the first time, farmers could manage the water level to maximize crop yields, something not possible with the polder mill. (Fortunately, today’s large interconnected electrical networks have allayed concern about wind’s intermittency.) And steam engines could be placed wherever they were needed. Polder mills needed well-exposed sites. For these reasons, the European windmill began a long decline which was only arrested in the 1970s by preservation societies and industrial archeologists.
Windmill performance increased greatly between the 12th and 19th centuries with the introduction of metal parts. In the 17th century, these parts were some of the first examples of the standardization that eventually led to mass production. By the time the “Dutch” or European windmill began to fall out of favor at the turn of the century, the typical machine used a rotor spanning 25 meters (80 feet). The stocks on some reached 30 meters (100 feet) in length, the height of the tallest tree that could be shipped. Curiously, one of the largest ever built was erected in San Francisco’s Golden Gate Park in the early 1900s. With a diameter of 114 feet (35 meters), this giant could pump 40,000 gallons (150 cubic meters) per hour. Most mills were capable of producing the equivalent of 25-30 kW in a mechanical form suitable for grinding grain, shredding tobacco, sawing timber, milling flax, pressing oil, or pumping water for polder drainage.
Later innovations included automatic fan tails for pointing the rotor into the wind, automatic movable louvers instead of sails, air brakes, and airfoil-shaped leading edges that pointed the way toward modern wind turbines. At their height, there were some 1,500 MW of European windmills in documented use, a level not seen again until 1988. And it was only in the late 1980s that wind turbines of equivalent size were once again plentiful. Modern airfoils and materials enable today’s machines to extract 10 times more power from the wind than the European windmill 100 years earlier.