After a brief consideration of the history of windmills, various models are described in detail, with discussions of their pros and cons, especially in regard to number of blades and method of orientation to the wind. Systems for transmission of power from the wind motor to a pump, generator, or cother type of equipment are described. A method for computing the tension and compression stresses on the wind motor pylon is given and the construction of pylons and water tanks is discussed. Foundation and anchoring systems are described, as are several methods for assembling and raising the wind motor on its pylon. Systems using wind motors to draw and elevate water by means of pumps and systems using wind motors in conjunction with generators, storage batteries, etc.. to generate electricity are described in detail, and efficiency tables and comparative cost price tables are provided for each of these applications.

Wind is a free form of motive power which occurs over the entire surface of the earth. Unfortunately, this power is irregular and inconstant, it sometimes becomes destructive, and it is impossible to regulate it by means of accumulating reservoirs, as can be done with waterfalls.

Although devastating hurricanes are a rare occurrence, nevertheless, due to their probability, the construction of devices using wind must be extremely solid, which greatly increases their cost price.

Despite these drawbacks, the use of wind power is to advantage, especially in countries without waterfalls, coal or oil. In Denmark, where this is the case, the importance of this problem has been understood, and in 1891, the King of Denmark assigned the French professor Paul La Cour the task of determining the optimum principles for the design and use of wind motors and their application to the production of electricity.

For this purpose, a testing station in Askov; was placed at his disposal, under a generous annual subsidy.

In 1900, Professor La'Cour had already obtained positive results. He wrote:

"The establishment of the Askov testing station is a unique phenomenom. One may find it surprising that a small country like Denmark, taking a bold step ahead of any others, is willing to devote such large sums of money to research on the use of wind power. Nothing could be more natural, however, considering that this country, which has no waterfalls or coal, is exposed to the risk of paying increasingly high rates for the purchase of fuel from foreign countries at a time when the range of uses" for machines and the cost of raw "materials are simultaneously increasing."

Mr. La Cour's main proposal was to supply energy for agricultural uses, and in Askov he gave one-week courses to farmers to familiarize them with the operation of wind motors and electrical devices.

This book will be concerned with the work of Professor La Cour.

France has a plentiful supply of waterfalls and coal, although the use of wind motors would help to conserve these resources. It is the French colonies, however, which have the greatest Interest in building windmills: there are already a great many in Algeria, Tunisia, Morocco and elsewhere. However, the number of these installations is not comparable to the number in America, where wind motor contractors are mass producing thousands of units, which are selling rapidly.

One project which should not be delayed would be to set up signaling posts, along main aircraft communication lines or desert crossings, for example; these posts would each consist of a wind motor, a generator, storage battery and a beacon which would be Illuminated automatically every night by a mechanism which would be easy to design. This would be wonderful propaganda for wind motors .

From the standpoint of supplying drinking water to cities and communities, wind motors have heavy advantages. This is due to the fact that the French government gives communities who have been wanting to set up a water supply a subsidy for the installation of machines and piping, but offers no financing for the fuel or electricity which will operate these machines.

Here the windmill would be ideal, since once it has been installed it does not consume power in any form and its annual maintenance is quite minimal. This is why a number of communities are now building these highly advantageous systems.

At any rate, it is to be regretted that the few windmill builders in France, who produce excellent systems, are not encouraged by the government or backed by a large financial outlay permitting inexpensive mass production.

From a technical standpoint, there has been no work in France which has collected all the documents and results gained in this area. This is why we have assembled and coordinated, everything we have been able to find to the best possible extent, with the hope that our book will facilitate the discovery of improved methods for capturing wind power.

Chapter 1. History

Windmills are of very ancient origin. The four-blade Dutch windmill is generally believed to be the predecessor of those currently being built , but this is in error, since windmills were known earlier still in the Orient.

In his History of the Caliphs, Washington Irving states that a certain Firus, made prisoner by the Persians in about 634 AD, complained to the caliph Omar of the heavy taxation which had been imposed upon him.

The caliph visited Firus's home and saw that the latter, who was a carpenter, had built a windmill.

Prance was the first country in Europe in which windmills were built, by one Mabillon in 1105. Prom France the windmill spread to England, and in 1332, Bartolomeo Verde introduced them in Italy.

The Dutch windmill was Invented around the year 1650, probably by a Flemish carpenter.

These origins of the windmill have been' outlined by the Lykkegaard Wind-Mill Manufacturing Company of Copenhagen (Denmark).

In around 1840, Berton, a mechanic in Chapelle-Saint-Denis, close to Paris, improved the blades of earlier windmills by replacing the canvas with long fir battens, parallel to the axis of the blade, which folded back on each other like a bird's feathers or the blades of a fan during hurricanes.

These battens were folded or expanded by means of a hand powered rack and pinion mechanism, and later on by an automatic system.

This windmill had four blades and the configuration of the old Dutch windmill with pivoting roofing for orientation.

On March 23, 18M2, Amedee Durand, a Parisian mechanic, presented to the Academy of Sciences a report on a wind motor mounted on a pylon made up of four wooden planks. This windmill had six sails with canvas blades which were quite similar to the so-called "brigantine" sails of ships. These blades were oriented to face into the wind, or they were allowed to float in the, direction of the wind during storms, by means of cables termed "sprits" which were automatically controlled by a counterweight. The orientation of the device was also automatic.

A description and drawings of the Berton and Durand devices may be found in the fourth volume of Cours d’agriculture [A, Course in Agriculture] by Nadault de Buffon, published in 1858 by Victor Dalmont, Paris, pages 212-222. The extensive report made to the Academy of Sciences on the Durand wind motor may also be found there.

Later on this inventor substituted wooden paddles for his canvas blades, and a large number of these motors were used to pump water.

This invention was taken up by the Americans, who made a number of Improvements and built numerous copies with a large number of sheet steel blades and automatic orientation and regulation.

The Danish built excellent models with a small number of blades per wheel (four or five).

In France, a number of constructors have undertaken the manufacture of wind turbines and have made improvements in them. These will be mentioned later on, as will be the turbines of Bollee and A. Dumont, which are based on specialized principles.

The Durand windmill, with its wooden paddles, already swiveled by means of a rudder, folded back under storm winds and was brought back Into position by springs. Thus it opened a wide field for development along these lines.

With regard to the advances made in France during the Initial use of air turbines, J. Claudel notes that Herpin had supervised the development of a four-blade windmill of the Berton system in the Indre department. Each blade was composed of 11 fir planks 1cm thick, 25 cm wide and 8m long, folding in the manner of a parallelogram.

This windmill drove three pairs of millstones, one in a sawmill, one in an oilworks, and one for a wheat thresher; it produced 2000-2500 hectoliters of ground wheat per year.

There were four windmills on exhibit at the Paris Exposition of 1867; these were discussed in a report by Mr. Lebleu, Mining Engineer 3 which may be found in Debauve's. Lepaute Mill Construction begun in 1858; two discs with veins 3m in diameter, With 16 wooden blades each. Each disc controlled; a chain pump to raise water.

Mahoudeau Mill. Wheel with six blades, each three meters long, slightly inclined into wind. Total area of blades: ten square meters. The canvas blades were supported at their free end by a flexible spring-activated blade which allowed the canvas to incline automatically when the wind became too violent. Swiveling was automatic.

Formis Mill. Invented by Dellon, Engineer of Bridges and Causeways. The canvas blades were triangular and were supported by yards which inclined when the wind was too strong, and were then returned to position by a counterweight.  There were eight blades on the wheel.

This device was used to drain marshes between Montpellier and Sete, and withstood the mistral quite satisfactorily.

Thirion Mill. Built by the Chatelineau Company. This mill had 20 wooden blades in the form of a narrow sector able to pivot on one of its radii. The regulatory system was based on centrifugal force: this consisted of counterweights which moved away from the horizontal shaft when the windmill turned too quickly, and made the blades pivot to a position parallel to the direction of the wind.

The Thirion and Formis systems were equipped with hand brakes which activated a pulley affixed to the main shaft.

Debauve also mentions the Bernard windmill, which received the wind from behind, making it swivel automatically. The weight of the wheel was equilibrated by a cast-iron counterweight and the laths on which the blades were mounted were articulated on the shafts of the blades and maintained by springs which yielded when the wind speed was too high.

The English journal Engineering gave some descriptions of English wind motors in 1903, vol. 1, pages 531, 552, and 556.

In 1890 a windmill was built at the Sainte-Adresse lighthouse in Le Havre, and in America there were a large number of small electric plants powered by wind.

England had plants of this type by about 1895, and in Germany in 1904 there was one generating 220 kW of usable power.

In 1903 the Askov installation in Denmark, which Professor La Cour had been perfecting since 1891, was powering 450 incandescent lamps, 2 arc lamps and 2 electric motors. The cost price per kilowatt-hour was barely seven centimes (gold francs ), or approximately 85 centimes in new francs, a cost much lower than that of public utilities.

The drawing on the May 1931 issue of the Russian journal Electrichestvo, La Technique Moderne, in its issue of November 1, 1931, notes that a wind motor installation generating 150 hp per hour under a 10-meter-per-second wind had just been put into operation in Sevastopol, in the Crimea.

The wheel of this windmill was 30 m in diameter and rotated at 30 rpm with variations of ±4 %, which was quite minimal.

This high regularity made it possible to connect this wind; turbine to an asynchronous generator supplying 220 volts, stepped up to 6600 volts by means of a static converter to power the high- tension network of the Sebastopol docks.

The experiments of Coulomb (1720) in Prance and Smeaton (1755) in England, followed by those of Rankine, heavily contributed to the establishment of theory and practical data for the construction of modern windmills. Here is the description of Dutch and Flemish windmills given in about 1830 by Maison Rustique du XIXe siecle [The 19th Century Rustic Home]:

"Everyone knows what a windmill looks like. The usual receiving device for a windmill consists of blades or vanes affixed perpendicular to the end of a horizontal shaft and uniformly distributed around it. Generally four blades are used; these are rectangular in shape and their dimensions in the vicinity of Paris are about 12 m long and about 2 m wide. In the Northern Department, the length of the blade is 38 and sometimes 13-14 m against a width of 2 m. Here is the description of the characteristic appearance of windmills in the vicinity of Lille given by Coulomb.

"1m 67mm of the width of the blade consists of canvas attached to a frame, with the root resting on an extremely light plank. The joint line between the plank and the canvas, on the side struck by the wind, forms an appreciably concave angle at the beginning of the blade which progressively diminishes and disappears at the tip of the blade. The piece of wood which forms the arm is located behind this concave angle. The surface of the canvas forms a curved surface composed of straight lines perpendicular to the arm of the blade and coinciding at their ends, with the concave angle formed by the joint between the canvas and the plank. The rotating shaft to which the blades are attached is inclined 8-15° to the horizon."

Vertical windmills occur in various forms. Fig. 3. shows a wooden cage with its inside frame-work, the entire structure rotating at will or with the wind, by means of a rudder to which a swivel and line have been adapted; this is what is termed "orienting" the windmill.

"Sometimes the windmill is constructed in such a way that it is able to orient itself; in these cases it is somewhat more complicated. Experience has shown that this procedure does not offer sufficient advantages to compensate for a structure which is more costly and more subject to repair.

"The considerable irregularity and the violence of the wind frequently make it necessary to modify its force, either to regulate it or to prevent the windmill from being damaged or overturned. In this case the vanes are "stripped" to a given extent by folding back the canvases or blades. A wooden brake which drags on the inside of the wheel is used to stop the windmill.

This operation may be performed from the outside by means of a line connected to the spring which sets this brake in motion.

"In general, when wind is used as motive power it acts- on vertical vanes; although horizontal windmills have frequently been tested, they are not being used. The advantage offered by this type of windmill at first glance is the ability to turn under any wind without the necessity for orientation; however, it has the disadvantage of presenting no more than one blade at a time to the wind, while in ordinary windmills, the wind acts on all four vane's at the same time.

Fig. 5 shows the details of construction of a Dutch windmill used to drain a swamp, with a paddle wheel operating in a masonry mill-race."

In the museum of the National Conservatory of Arts and Crafts in Paris there is a collection of small-scale models and drawings of wind-mills and "pananemones."

These models are master-pieces of precision and workmanship; however, the models exhibited are quite old, and it is extremely unfortunate that the designers of wind motors did not consider it apropos to offer this wonderful museum small-scale models of their current Inventions and designs. There is a regretable gap in this area. As a result, young engineers who come to the museum to learn are unable to find any up-to-date examples of advances in the industrial use of wind power. For the following list of exhibits I am extremely indebted to Mr. Landiais, curator of the museum, who was kind enough to go with me to the glass cases containing the wind motors. This is a quite valuable list, even though it is somewhat outdated, since it can still serve as a source of information to modern designers in regard to the inclination of the shaft to the horizon and that of the blade surfaces to the plane of the wheel.


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