Volume 2 wind energy 2 03 – history of wind power

Volume 2 wind energy 2 03 – history of wind power Volume 2 wind energy 2 03 – history of wind power Volume 2 wind energy 2 03 – history of wind power Volume 2 wind energy 2 03 – history of wind power Volume 2 wind energy 2 03 – history of wind power Volume 2 wind energy 2 03 – history of wind power Volume 2 wind energy 2 03 – history of wind power

2.03.17 The Battle of the Blades: Two versus Three

2.03.18 Large Two-Bladed Wind Turbines

2.03.19 The California Wind Rush

2.03.20 Other Manufacturers

2.03.21 Large Vertical Axis Wind Turbines

2.03.22 Organizations: BWEA, EWEA, and IEA

Further Reading

2.03.1 Sails

The first engineering applications of wind in recorded history were for sailing There is evidence that ships based in the Tigris/ Euphrates Delta traded along the coast as far as Oman and Northwest India and they may have also been used upriver to carry goods between the first Mesopotamian city states of Uruk and Ur (see Figure 1)

The earliest known sailing ships, apart from logs and dugout canoes, were built before 5000 BC from reeds, bundled and lashed together to form a ‘hull’ (see Figure 2) and coated with bitumen to make them watertight Cargo and crew members were carried on top of the bundles

The pictorial record of such a sailing ship appears on a painted ceramic disc found in 2004 in Kuwait at site H3 from this early period (see Figure 3) It shows a bipod (two-footed or inverted V) mast, which is particularly well suited for reed vessel construction when the frame of the boat is not strong enough to support a single socket mast Before this recent discovery, the earliest record came from the Nile and it is probable that the stones of the great pyramids were moved from Aswan to Giza with the help of the wind The explorer Thor Heyerdahl built several reed vessels of this type during the 1970s and sailed them across the Pacific Ocean to Easter Island, proving their long-distance capabilities in ancient times but by the time that Stonehenge was built (ca 3500 years ago) far more sophisticated vessels with sails were making regular voyages around the Mediterranean Sea, and even venturing into the Atlantic Ocean as far as the British Isles in search of tin, an essential commodity for Bronze Age heroes

By the Roman era, the Chinese were building large sailing ships that could ‘point’ well into the wind So the basic idea of using a sail to capture the wind was well established The concept of lift was clearly being used practically and effectively, even if the physics

of the process was not understood

2.03.2 Early Wind Devices and Applications

There are many early land-based applications of wind power in the historical record

Wind was used in ancient times for winnowing – to separate wheat from chaff – as it still is in many parts of the world today, for example, Tibet The ears of wheat are pounded or beaten – threshed – to detach the husks from the grains of cereal and the mixture is thrown into the air The denser grains of cereal fall straight to the ground in a heap, while the wind blows away the lighter husks, the chaff Psalm 1 of the Bible, which is traditionally ascribed to King David (1000–965 BC), refers to ‘chaff that the wind blows away’,

so the practice was going strong at least 3000 years ago

Khursaniyah

Dosariyah Ain as-Sayh

It is not known when people first built wind machines to do mechanical work Man-powered and donkey-powered applications (such as the rotary donkey treadmills found in the ashes of Pompeii in AD 79) came first Water power came next (see Figures 4 and 5) but this had to be limited to riverside sites Wind power followed on, especially where no water power was available

An important use of mechanical power was for grinding corn Throughout history, with no refrigerators, it has always been a problem to preserve food and, since the invention of agriculture, cereals have been a major part of staple diets around the world, providing much of the protein for the peasantry, because they can be stored for years This was true at the time when Joseph was in charge and filled the granaries of Egypt (probably around 1700 BC) and it was still true through to the Middle Ages and beyond Porridge from oats was a major food in many regions and bread from wheat was the staple food in many others Cereals could take half of the food budget of a poor family

Apart from rice, all of these grains needed to be ground or at least crushed It has been shown that it takes 2 h a day of hard work with a manual quern to grind enough corn to produce enough flour for the bread for a single family for the day The benefits of automating the grinding process are clear and the technologies of grinding stones and gears were developed well before wind power arrived The permanent nature of the stones leaves clear archaeological evidence of the processes involved

The majority of the populations in ancient times were agricultural and grew their own corn In preference to grinding it themselves by hand, a household would take its corn along to the local mill to be ground and would collect the flour produced

Figure 3 Painted ceramic disc depicting reed-bundle boat with bipod mast The painting on the ceramic disc shows a boat with a bipod mast, which is suited to the not very rigid structure of a reed-bundle boat

Figure 4 Waterwheel machinery Typical waterwheels are horizontal axis with a gear arrangement to turn the torque through a right angle

Figure 5 An operating water mill Daniel’s Mill at Bridgnorth in Shropshire, UK, has been fully restored to its original form and it operates to produce stone-ground, wholemeal flour as the original mill would have done

to be taken home and turned into bread Waterwheels were used to power mills for grinding corn long before the arrival of windmills

The first instance of wind machines may have been in China more than 2000 years ago, but archaeologists have found no definite record of their use there, either in the form of artifacts or in writing The machinery would have been made of wood or other less permanent materials These have sometimes survived for 1000 years or so but rarely longer than that If such machines did exist

in China, they must have fallen out of use again until AD 1219, when next they are heard of in documents by the Chinese statesman Yehlu Chu Tsai

There are suggestions that wind machines were used in Mesopotamia and/or in ancient Palestine Hammurabi, king of Babylon somewhere between 1600 and 1700 BC, apparently planned to use wind pumps for his ambitious irrigation schemes, but again no detailed records have survived

Hero of Alexandria (AD 10–70) described a simple propeller-type wind turbine machine that was used to blow an organ Hero is more famous for having his name attached to an elementary steam turbine, the aeolipile This is mentioned in Vitruvius’ De Architectura some 100 years earlier than Hero lived but Hero is often mistakenly attributed to a career 200 years earlier than his actual lifetime, which is known from the dates of his publications However, the earlier invention is often called Hero’s engine As far as can be discovered, these devices were only ever used for amusement and were never put to the engineering applications that we would find so important today

The prayer wheels that can be seen today in Tibet operate as Savonius rotors, working on the same principle as the rotating advertisements that can be seen outside many garages The idea is that, with every revolution, they are taken to repeat automatically

a Buddhist prayer which is inside the central cylinder It has been claimed that these may have an ancient heritage, going back to when Buddhism was established in Tibet between AD 755 and 797 but there is no solid evidence for this Wind chimes may also have an ancient pedigree but we lack historical evidence

2.03.3 Persian Vertical Axis Designs

We can be sure that wind machines came quite early to the Muslim world History records that a carpenter ‘expert in the construction

of windmills’ was being taxed two pieces of silver a day when he murdered the second orthodox Caliph, Omar, in AD 644 in Medina Abu Lulua, the Persian technologist in question, is said to have thought he was being excessively taxed, although the authenticity of this document has been questioned on the grounds that it was dated three centuries after the event

Certainly by then, several Arabian geographers were writing about windmills in the Persian region of Seistan (a border region of modern Eastern Iran and Southwest Afghanistan) According to Al Masudi in AD 950,

Segistan is a land of winds and sand There the wind drives mills and raises water from the streams, whereby gardens are irrigated There is in the world [and God alone knows it] nowhere where more frequent use is made of the winds

Gale force winds of 20 m s−1 coming down from the Hindu Kush are not uncommon there during the four windy months of the year, so ‘a land of wind and sand’ seems a very fair description

These Persian machines were vertical axis machines with the axle fixed directly to the moving grindstone It is often claimed that

a major advantage of the vertical axis arrangement is that the mechanical drive can reach the ground and be coupled to its output without the need for gearing This could not be more directly demonstrated than in the early Persian machines

There were apparently two basic designs, one with the millstones on top of the rotor axle and one with them below The first type had tapering loopholes in the structure of the surrounding building which funneled the wind onto the sails on one side of the rotor The other type could be much higher without the need for a large supporting building It had fixed matting screens to block off the wind from one side of the rotor and to channel the wind to the sails, a panemone design In each case, the sails themselves were straw matting that formed a rotor up to 5 m in height and 3 m in diameter

There were no brakes It is suggested that screens could be moved across the loopholes or to redirect the wind as necessary, although the prospect of moving such large screens around in gale force winds is formidable It is not surprising to learn that individual mills had to be rebuilt frequently The Persian panemone design works on drag rather than lift and is inherently far less efficient than modern propeller-type designs, which is why they have prevailed elsewhere On the other hand, when there are such high wind speeds to cope with, there is a need not to capture the full force of the wind and the Persian designs were evidently in the right place at the right time

2.03.4 The Introduction of Windmills into Europe

Windmills came later to Europe and were horizontal axis propeller-type designs when they arrived The winds available were not strong enough to make a practical proposition of the Persian design relying on drag

It has been suggested that Crusaders in fact introduced these so-called European mills, with sails mounted in a propeller fashion

on a horizontal axis, from Eastern Europe or the Middle East but the evidence and the timing strongly suggest that the introductions went the other way

the soul of his Father.” Evidently, this windmill was already up and running and it may well have been operating for some time before then

It is interesting to note that the monasteries, notably the recently founded Carthusians (AD 1081), were in the forefront of technology at this time The monks wanted to automate manual labor, not because they were lazy but because they wanted to devote more of their time to their devotions and to contemplation

After this first historical record, references to other windmills appear thick and fast throughout the length of England as well as in Northern France and Belgium The technology evidently spread rapidly and by AD 1200 it was well established The population was increasing and windmills may have helped to populate areas of the country where the rivers and streams were previously insufficient

to grind enough corn to support a large population

Because windmills are known to have been around in the Middle East before the Crusades, and the Crusaders are known to have used windmills, it has been claimed that it was they who introduced windmills into Europe This claim fails to explain how the complicated horizontal axis design with gears was suddenly developed from the simple vertical axis machines with direct drives that were prevalent in the region In fact the earliest known report of a Crusader’s windmill concerns one the Crusaders carried with them

to use during the siege of Acre, which ended in AD 1191 It is not known what design they brought with them but it would most likely have been the horizontal axis design prevalent in England and Northwest France In that case, the Crusaders were taking technology from Europe to the Middle East, not the other way round

Evidently wind power arose in England and spread to Northwest Europe in the first half of the twelfth century It developed rapidly thereafter For instance, the Bishopric of Ely, which had 22 watermills from AD 1086 throughout its various estates around the country, had added 4 windmills by AD 1222 but that had increased to 32 windmills by AD 1251 This rate of introduction of new wind power technology, doubling in numbers every 10 years, cannot match the rate of increase from 1990 to 2010, when wind power capacity worldwide doubled every 3 years, but it was still quite dramatic for its era

Wind power spread rapidly across the Great Plains of Northern Europe and into Scandinavia The date of the first machine in Germany has been given as 1222, Denmark 1259, Sweden 1300, and Spain, Russia, and Latvia 1330 The water flow in rivers and streams would freeze up in the middle of winter but winds would blow all the harder then In fact windmills could keep going all the year-round whenever the wind blew This gave wind power a very distinct advantage over water power in many countries Unfortunately, the wind was as variable then as it is today, so the applications had to be ones that did not need continuous power Irrigation is one such application Large areas of Britain in the fens of East Anglia were drained by the steady operation of wind pumps, whenever the wind blew The land is 3 m lower today than it was in the Middle Ages

Grinding corn was another such application If the wind did not blow today, the miller would grind your corn tomorrow and if not tomorrow, then, as long as it blew sometime before the next harvest, you would not starve

Fulling was a process of beating woolen cloth with hammers to remove grease, both that which was natural in the original fleece and any that was added to improve the spinning process The wool would come to no harm if the hammering ceased for a while when the wind dropped

2.03.5 Horizontal Axis Machines

Although a wind enthusiast will focus on the sails or the rotor as the most important feature of a windmill, from the miller’s point of view they are actually peripheral The central feature was the pair of millstones which had to be level and carefully balanced to run true and not to touch each other They had to be carefully spaced (or tentered) to control the grade of flour and they were obviously the center of the miller’s attention He had to shut down the mill and reface his millstones every couple of weeks or so Having established a satisfactory milling arrangement, driven by a waterwheel, it would have been most natural to retain that carefully developed design geometry for the most central feature of the mill when introducing a wind-driven mechanism

A waterwheel has a horizontal axis, so a 90° gearing arrangement is needed to couple it to the moving millstone That represented a considerable technical achievement in timber technology Starting from scratch, a primitive wind machine would not use such a complicated arrangement The directly coupled vertical axis Persian design is far more natural to start from and that is exactly what happened in Seistan The millers in England and Northwest Europe were not starting from scratch, however They had

developed water-driven technology in the first place and, when they came to wind technology, they were starting from a well-established milling industry based upon horizontal axis drives from waterwheels Not surprisingly, when they introduced wind power, they moved on to horizontal axis drives from wind turbines

To capture the energy in the wind, it was not sufficient to replace the waterwheel with some form of wind wheel An additional problem had to be overcome Water flow is always in the same direction determined by the stream or river but, to quote the Christian Gospel according to St John, “The wind bloweth where it listeth, and thou hearest the sound thereof, but canst not tell whence it cometh, and whither it goeth.” It is the exception rather than the rule, certainly throughout Europe, for the wind to have a strongly prevailing direction A windmill needs to be able to capture the wind coming from any direction A vertical axis Savonius rotor can do that but a horizontal axis (propeller-type) wind rotor needs to turn to face into the wind

2.03.6 Post and Tower Mills

The most obvious development was to mount the whole mill on a large post about which it could pivot and this produced the post mill, the type of windmill that is shown in medieval manuscripts To support the whole of the milling machinery and the cladding which protected it from the weather needed a massive post of timber with an elaborate framework to support it and to provide bearings which would allow it to rotate but would withstand the sideways thrust It was then the miller’s main job to push the whole structure round to face into the wind

It was not very convenient to have the whole of the space inside the mill rotatable to turn into the wind – or out of the wind when it needed to stop A subsequent development placed only the essential parts that needed to rotate – the sails and the shaft – in

a rotatable cap at the top of the structure, with the rest of the machinery in a fixed tower as the lower part of the structure (Figure 6)

Figure 6 Post mill In a post mill, the whole of the machinery was supported by and turned together with a central post so that the rotor could face the wind All early windmills in Europe were post mills but this one incorporates advanced technology (after 1600) with the spars nearer the leading edges of the blade

The prospect of doing this reefing in a strong wind, quite possibly in rain and sleet, handling soaking wet and even freezing canvas, is not attractive Modern health and safety regulations would make the miller’s job extremely difficult today! In parts of Northern Europe, wooden boards could be used instead of canvas, fixed in place with wooden dowels passed through staples (Figure 8)

Figure 8 Tower mill A tower mill worked in the same way as a smock mill but the cladding was more substantial, often brick or stone This picture by Ramelli published in 1588 shows many detailed features, but note that the blade spars are central along the blades unlike the later design shown in Figure 6

Figure 9 Don Quixote’s windmills These tower mills at Campo de Criptana are typical of the ones that were to be found in Central Spain in the early part

of the seventeenth century when ‘The Ingenious Gentleman Don Quixote of La Mancha’ invented by author Miguel Cervantes mistook them for knights-errant and famously proposed to tilt at them

Figure 10 Brueghel’s painting of a landscape with windmills Oil painting by Jan the Elder Brueghel (1568–1625) of a village entrance with windmill The windmill blades are tapered and twisted representing the latest technological developments at the time

Figure 11 Brueghel’s painting of a village entrance with a windmill Oil painting by Jan The Elder Brueghel (1568–1625) of a village entrance with windmill The miller can be seen turning his windmill into the wind

Many other technological improvements were introduced from time to time over the next few centuries Leonardo da Vinci (1452–1519) sketched a windmill with six sails rather than four, but it did not catch on (Figure 10)

A brake was a rather vital component which is not mentioned in the literature until 1588 and windmills were still being built without a brake as late as 1756 However, the brake was a rather dangerous contraption If a windmill accelerated in a gust of wind despite the brake being on, the brake could become red hot and the wooden mechanism could burst into flame With inflammable powder from the flour, an explosion could occur Many windmills came to a fiery end and burnt down

Twisted blades were thought to improve performance and Cornelis Dircksz Muys, an engineer of Delft, took out letters patent on sails with double curvature in 1589, which duly appeared in paintings by Brueghel around 1614 (Figure 11)

The fantail, which automatically turns a windmill to face into the wind, was not patented until 1745 A secondary rotor mounted

at right angles to the main rotor axis can drive the main rotor round until it is exactly sideways to the wind and the main rotor axis is aligned to the wind Figure 17 shows a typical example of a fantail on a more modern machine

2.03.8 Theory and Experiment: The Early Science

Simon Stevin was able to show in 1607 that the power of one of his mills was about 10 hp by working backward from how fast it pumped water and how high it raised the water As he had no way of measuring wind speeds, he was not able to develop any theory Many books of the period show how to build windmills but none is able to give any theory

Francis Bacon wrote in 1622

There is nothing very intricate in the motion of windmills but yet it is not generally demonstrated or explained… The wind rushing against the machine

is compressed by the four sails and compelled to make a passage through the four openings between them But this confinement it does not willingly submit to; so that it begins as it were to joy [sic] the sides of the sails and turn them round as children’s toys are set in motion and turned by the finger If the sails were stretched out equally it would be uncertain to which side they would incline As, however, the side which meets the wind throws off the

impulse [that which is made in the front] but from the lateral impulse after compression has taken place

Bacon’s best attempt to provide himself with an open-ended wind tunnel used bellows His models had paper sails of various shapes but he advised, “If these experiments be put into practice in windmills, the whole machine, especially its foundations, should

be strengthened.”

Antoine Parent published Recherches de Mathématiques et de Physique in 1713, 3 years before he died, which included a proof that the wind force on the sails was proportional to the square of its speed and the square of the sine of the angle of incidence, from which he deduced the optimum should be 54°44′

Those calculations stood for 50 years until in 1754 William Emerson published The Principles of Mechanics in which he explained that Parent had ignored the effect of rotation on the angle of incidence, so the calculation was only correct with the rotor at rest, as it

is when starting He said that the optimum

would always be so, if the wind struck them when moving as when at rest But by reason of the swift motion of the sails, especially near the end [the tip], the wind strikes them under a far less angle; and not only so, but as the motion of the end is so swift, it may strike them on the backside Therefore it will

be more advantageous to make the angle of incidence greater, and so much more as it is further from [the axis]

These qualitative observations were being developed quantitatively in France by two outstanding mathematicians, Leonhard Euler and Jean-Baptiste le Rond d’Alembert, but John Smeaton, FRS, was ahead of them He won the Copley Medal of the Royal Society in 1759 for his work on waterwheels and windmills, while at the same time famously working on plans for the Eddystone lighthouse He was a brilliant mechanical engineer but he is also regarded as the ‘father of civil engineering’ having invented the forerunner of portland cement For his paper ‘An experimental enquiry concerning the natural powers of water and wind to turn mills and other machines depending on circular motion’, Smeaton had built a hydraulic test rig to compare different types of waterwheels For a wind test rig, he noted that “the wind itself is too uncertain to answer the purpose, we must therefore have recourse to an artificial wind” and he fixed his test devices on the end of a 1.54 m long arm that could be rotated in a horizontal circle, keeping time with a swinging pendulum

He found that with fixed pitch blades, the velocity of the sail varied as the wind velocity, V The force varied as the velocity of the wind times the velocity of the sail, that is, as V2 Finally, the ‘effect’ (or power output) was proportional to V3 “The effects of the sails at

a maximum are nearly, but somewhat less than, as the cubes of the velocity of the wind.” These findings pretty well summarize the basic science of wind turbines as we know them today and Smeaton’s work on many other details was regarded as definitive for the next century or more (Figure 12)

Figure 12 John Smeaton’s test apparatus (1759) The apparatus was rotated by hand (Z) pulling on a rope wound round the axle (H) Rotations were timed by synchronizing with the balanced pendulum (V–X) The work done by the rotor on the end of the arm was measured by raising weights in the pan P

Figure 13 Hammers for pressing oil These hammers are for pressing oil from rapeseed or olives Coulomb was able to measure accurately the rate of work done by such a machine as each of the hammers is lifted a fixed distance before being allowed to drop

Another scientist and engineer who made careful measurements of the performances of working windmills (pressing oil from rapeseed near Lille in 1781) was Charles Coulomb, who is better remembered for his work on electrostatics (Figure 13) (The unit of electrical charge is named after him.)

2.03.9 The End of Windmills

Just as understanding was developing of how the large post and tower windmills worked, James Watt was pursuing the development that would eclipse them almost completely

Hero’s engine and other steam devices, such as those described by Taqi al-Din in 1551 and Giovanni Branca in 1629, were turbine devices with little practical use Thomas Savery and many others worked on steam engines during the 1600s but it was Thomas Newcomen who built, in 1712, the first truly useful steam engine that could pump water out of mine workings from a hitherto impossible depth

Newcomen’s steam engine was not very efficient, probably much less than 1%, but James Watt made many improvements, especially that of building a separate condenser, and by 1776 he was installing steam engines in various commercial enterprises, mainly for pumping water out of mines in Cornwall

From then on, the days of the windmill were numbered No longer would the miller be at the mercy of the wind

2.03.10 The American Wind Pump

When steam took over the role of wind in Europe, wind pumps for water still flourished in the Great Plains of America Any enthusiast of cowboy movies will be familiar with two very characteristic scenes The first is the cows, as far as the eye can see, tens of thousands of cows, which gave the cowboys their raison d’être The next shot is of the desert – as far as the eye can see, dry dusty desert It is obvious with a little thought that there must be some third shot, just out of these two frames, which explains how these two scenes can come within a hundred miles of each other In dry, dusty desert, cows will die without water

Well the water was there all right Across the Great Plains, the proverbial dust bowl, groundwater is only a few meters below the dry, dusty surface All the rancher running the herd had to do to find water was to dig down He then had the problem of raising the water to the surface and for that the American wind pump was ideally suited

The American wind pump was a multiblade machine of typically less than 1 hp mechanical output and, between 1850 and 1970, over six million of these small wind machines were installed in the United States alone

The primary use was water pumping and the main applications were stock watering and farm home water needs Very large wind pumps, with rotors up to 18 m in diameter, were used to pump water for the steam railroad trains that provided the primary source

of commercial transportation in areas where there were no navigable rivers

The most important refinement of the American fan-type windmill was the development of steel blades in 1870 (Figure 5) Steel blades could be made lighter and worked into more efficient shapes They worked so well, in fact, that their high speed required a reduction (slowdown) gear to turn the standard reciprocating pumps at the required speed (Figure 14)

Most of these wind pumps had tails to orient them into the wind but some had downwind rotors coned to allow the wind itself

to steer them directly Some designs controlled their speed by hinging sections of blades to fold back like an umbrella in high winds, reducing the rotor capture area

The simplex ‘geared’ wind engine

Suitable for driving deep well pumps, farm machinery,

Made of the best materials and workmanship wood sawing

draining, irrigating, electric lighting

Advantages cheap power without the expenses of fuel, haulage, and attention

Engines of this class are capable

of application to nearly all purposes for which a stationary steam, gas, or oil engine can

be used;

are very reliable in action; and the cost of attention and repairs

is very small

Illustrations given as a general guide, but are not binding as to detail

Figure 14 American multiblade wind pump Thousands of American wind pumps like this one advertised in a 1905 catalog were sold to drive reciprocating pumps The shutters could be feathered and a fantail keeps the main rotor facing into the wind

It is not too much to claim that it was the American wind pump that opened up the American West, at least as far as the Rockies

A similar situation is found in Australia where the arid central region of semidesert covers water courses and underground aquifers that are fed from the tropical jungles of New Guinea

American wind pumps disappeared almost overnight in the 1920s The coming of the great dams and cheap electricity, starting with the Hoover Dam, meant that, when a wind pump broke down, it was cheaper to install a small electric motor than to mend the rotor and its couplings

2.03.11 Electrical Power from the Wind

In 1821, Michael Faraday at the Royal Institution demonstrated the first electrical motor, a small DC homopolar unit Ten years later, he had discovered electrical induction (although others, including the American Joseph Henry, could claim to have done so independently) Within 10 more years, he had built a dynamo

There is no argument that the first public power supply was water-driven to light the streets of Godalming in Surrey, England, in

1881 Steam power followed rapidly in 1882 when Thomas Edison opened a power plant at Holborn Viaduct in London and, later

in the year, he opened one at Pearl Street in Manhattan By 1887, there were 121 Edison power stations in the United States delivering DC electricity to customers The new electrical technology was advancing at a cracking pace

It was perhaps natural to think of driving an electrical dynamo from a wind machine to produce wind power generation and several people can claim to have been among the first (Figure 15)

Figure 15 Blyth’s wind generator Prof James Blyth from a forerunner of University of Strathclyde can claim to be the first to have generated electrical power from the wind His first experiments in 1887 used a smock mill design (horizontal axis) but this 10 m diameter vertical axis machine was built at Marykirk, Scotland, in 1891 and continued to operate until 1914 Each semicylindrical box is 1.8 � 1.8 m and the lady standing at the door of the electrical enclosure gives the scale A railway embankment and bridge over the North Esk River are in the background

William Thomson, later to become Lord Kelvin, can probably claim to be the first to propose it seriously in his 1881 address to the British Association ‘On the sources of energy in nature available to man for the production of mechanical effect’

Prof James Blyth was appointed professor of Natural Philosophy in Anderson’s College, Glasgow, and, shortly after the College became Glasgow and West of Scotland Technical College in 1886 (which in due course became University of Strathclyde in 1964),

he was experimenting with a wind-to-electricity machine His first generation was recorded in July 1887 and that seems to be the first electrical power from the wind, although Blyth did not patent his vertical axis wind turbine for generating electricity until 1891

On a much grander scale, Charles Brush in the United States first generated power from the wind in the winter of 1887 and he is often credited with the leading role His huge wind turbine generator gave his home the first electricity supply in Cleveland, Ohio, in

1888 and it is claimed that “Over its 20 year life, the turbine never failed to keep the home continuously powered.” As an inventor and industrialist he had made a fortune selling arc lighting systems across America from New York to San Francisco and he set up what became Brush Electrical Engineering in Loughborough, England (Figure 16) He sold his American company off to General Electric (GE)

Figure 16 Brush’s wind generator American inventor and industrialist Charles Brush was one of the first to generate electrical power from the wind and

he built a huge wind turbine generator 17 m in diameter with 144 blades to power his home in Cleveland, Ohio, throughout the 1890s

Figure 17 Poul La Cour’s experimental station Wind turbine generators built at La Cour’s experimental station at Askov, Denmark, in 1891 and 1897 La Cour is regarded in Denmark as the father of wind power

Poul La Cour was also active in the field and he may also have generated electricity from the wind around the same time in 1887 Certainly by 1891 La Cour was the director of a windmill experimental station established by the Danish government at Askov near Esbjerg and his work provided a lasting foundation for later wind power developments in Denmark

After the Wright Brothers’ successful powered flight in 1903, aeronautical developments proceeded rapidly, for instance with the founding of the Royal Aircraft Establishment at Farnborough, UK, as a center of expertise in 1909 Betz, at Göttingen in Germany, pointed out in 1920 that his theory of propellers to drive aeroplanes, with simple reversal of the flow, established the limit of 16/27ths for the extraction of power from the wind with a propeller type of rotor Frederick Lanchester in England in fact deserves priority because he had already derived the same expression which is valid for incompressible flow but he published his result in

1915 in the Proceedings of the Institution of Naval Architects because he was interested in ships propellers Joukowski had also discovered the limit independently in 1920 but he published his result in Russian For the aerodynamics community, both these contributions were published in unfamiliar places and Betz’ name was firmly associated with the 16/27 limit before either of his competitors for priority was properly recognized (Figure 17)

Many small wind turbine generators were developed for sites remote from electrical supplies, which were commonplace in the late 1800s and early 1900s, including ones on sailing ships The range of machines in widespread use was considerable and around

1930 a team from Oxford University set up a test site near Harpenden, 25 miles north of London, where they operated a range of different types of wind turbine, nine in all The machines varied from slow-turning multiblade American designs to ones with aerofoil blades Rotor diameters ranged from 2.4 to 9 m and annual electrical generation was from 83.5 to 199 kWh m−2 (from 10 to

25 W year-round average per square meter)

This was the era of small machines and by 1947 the market in America alone was more than 10 000 per year for wind turbines generating less than 1 kW and at the 1954 World Power Conference in Brazil, Russia claimed to have nearly 30 000 wind power plants averaging around 4 kW each

2.03.12 Large Machines

Interest in large machines to supply electrical power systems was sporadic until the 1980s The individual machines that were built were designed by different enthusiasts and teams with no connections or access to the details of what had gone before and most of the expertise was from other fields of mechanical and aeronautical engineering

In 1925, Flettner crossed the Atlantic in a ship powered by two vertical electrically driven rotating rotors using the Magnus effect and the following year he built a four-bladed propeller rotor with each blade consisting of an electrically driven rotating cylinder The Magnus effect excites interest because it provides the means to avoid the Betz limit of 16/27 or 59% A rotor cannot extract all the kinetic energy in the wind If it did, it would bring the air to rest and the incoming flow would be diverted round the obstruction The best that can be done is to reduce the wind speed to one-third and therefore the kinetic energy of the air that goes through the rotor to one-ninth, but the slowed air then pushes one-third of the air flow aside from the rotor, so the rotor only captures two-thirds of eight-ninths of the incoming energy or 16/27ths (Figure 18)

Betz’s theory was for irrotational and incompressible flow through a rotor such as a propeller A rotating cylinder creates a vortex which extends to a far greater radius than the central cylinder which constitutes the rotor and it can capture energy from the wind over a much broader area

Mádaras proposed to take this principle to a grand scale He proposed to mount rotating cylinders on a train of flat railway trucks

on a circular track (which would reverse the direction of thrust twice in each circuit round the track) and in 1933 he built and tested

a full-scale single-cylinder demonstration unit, which was 27.5 m in height and 8.5 m in diameter, at Burlington, New Jersey Demonstrably the principle works, but, despite these successes, Magnus effect machines have not gained favor

Figure 18 Flettner rotors’ trans-Atlantic crossing Flettner’s ship the Baden Baden was fitted with two electrically driven rotating cylinders which used the Magnus effect to sail successfully across the Atlantic in 1925

In 1929, Darrieus designed a very elegant propeller machine with a two-blade, 20 m diameter rotor, which was built on the French side of the English Channel at Le Bourget However, he is better known for his vertical axis wind turbines with troposkein blades that took the shape of a skipping rope or ‘egg whisk’ under centrifugal forces He patented his design in 1931 but little work was done on it until it was taken up by the Canadians 40 years later

Balaclava in the Crimea is famous for the heroic (and useless) Charge of the Light Brigade in 1854 Seventy-seven years later, in

1931, at a site overlooking the Black Sea (which is repeatedly and erroneously in the literature referred to as the Caspian Sea), the Central Wind Power Institute of Russia built a 30 m diameter, two-blade propeller-type wind turbine, which reached its rated power

of 100 kW at a wind speed of 11 m s−1 An aerodynamically shaped nacelle sat on a 30 m tower and was supported against the force

of the wind by an angled strut, the bottom end of which moved around a circular track on the ground (Figure 19)

Figure 19 Darrieus’ two-blade, 20 m diameter wind turbine This wind turbine was erected at Le Bourget in France in 1929

Figure 20 Russian two-blade, 30 m diameter, 100 kW wind turbine The first machine to feed AC into a local grid was built at Balaclava in 1931 It ran successfully for 10 years

This was the first wind turbine generator to feed AC into the local electricity network and it was maintained in service for 10 years, until it was damaged by World War II The reported performance as a generator was somewhat ambiguous When it had operated for more than 2 years feeding power into the local 6.3 kV power distribution network, it was claimed to have generated

200 000 kWh That would correspond to an average load factor of less than 12%, although an annual load factor of 32% was optimistically claimed Nevertheless, it represented a noteworthy achievement (Figure 20)

2.03.13 The Smith-Putnam Machine

Palmer Cosslett Putnam served in the British Royal Air Force toward the end of the first world war He graduated from MIT (Massachusetts Institute of Technology) with a degree in geology in 1924 and was chairman of the Putnam family publishing house from 1930 to 1932 He developed an interest in power from the wind after reading about the Balaclava machine and experiencing high winds at the holiday home he built for himself at Cape Cod in 1934

Putnam put together proposals to build and operate a large 1.5 MW wind turbine He had a wide range of contacts in Cambridge (Massachusetts) and by 1937 he had gained the interest and support of the dean of engineering at MIT The dean introduced him to

a vice president of GE, who provided him with office space and agreed to supply the generator The engineers at GE introduced him

to the president and the chief engineer of the New England Public Service Corporation, who arranged that a subsidiary, the Central Vermont Public Service Corporation, would integrate the wind turbine into their local system (Figure 21)

In 1939, he found the S Morgan Smith Company, a prosperous family business, which was prepared to undertake the construction of the 1.5 MW wind turbine and to provide most of the necessary finance entirely from its own private resources, which were substantial The company appointed Putnam as project manager By the end of the project, the company had spent more than US$1.25 million on the prototype turbine, US$19 million in today’s money The whole of the project is described in great detail by Putnam in his 1948 book Power from the Wind

The huge Smith-Putnam project brings us full cycle from the introduction of horizontal axis wind turbines into Europe when wind machines were developed from waterwheels This was what happened inside the S Morgan Smith Company The company’s main business was to build variable-pitch hydraulic turbines to generate water power They thought that wind