Windmill
A windmill is a structure that converts wind power into rotational energy using vanes called sails or blades, by tradition specifically to mill grain (gristmills), but in some parts of the English-speaking world the term has also been extended to encompass windpumps, wind turbines, and other applications. The term wind engine is also sometimes used to describe such devices.[1][failed verification]
Windmills were used throughout the
Forerunners
One of the earliest recorded working windmill designs found was invented sometime around 700–900 AD in Persia.[11][12] This design was the panemone, with vertical lightweight wooden sails attached by horizontal struts to a central vertical shaft. It was first built to pump water, and subsequently modified to grind grain as well.[13][14]
Horizontal windmills
The first practical windmills were
Vertical-axle windmills were built, in small numbers, in Europe during the 18th and nineteenth centuries,[15] for example Fowler's Mill at Battersea in London, and Hooper's Mill at Margate in Kent. These early modern examples seem not to have been directly influenced by the vertical-axle windmills of the medieval period, but to have been independent inventions by 18th-century engineers.[23]
Vertical windmills
The horizontal-axis or vertical windmill (so called due to the plane of the movement of its sails) is a development of the 12th century, first used in northwestern Europe, in the triangle of northern
It is unclear whether the vertical windmill was influenced by the introduction of the horizontal windmill from Persia-Middle East to Southern Europe in the preceding century.[25][26]The earliest certain reference to a windmill in
Post mill
The evidence at present is that the earliest type of European windmill was the post mill, so named because of the large upright post on which the mill's main structure (the "body" or "buck") is balanced. By mounting the body this way, the mill can rotate to face the wind direction; an essential requirement for windmills to operate economically in north-western Europe, where wind directions are variable. The body contains all the milling machinery. The first post mills were of the sunken type, where the post was buried in an earth mound to support it. Later, a wooden support was developed called the trestle. This was often covered over or surrounded by a roundhouse to protect the trestle from the weather and to provide storage space. This type of windmill was the most common in Europe until the 19th century when more powerful tower and smock mills replaced them.[30]
Hollow-post mill
In a hollow-post mill, the post on which the body is mounted is hollowed out, to accommodate the drive shaft.[31] This makes it possible to drive machinery below or outside the body while still being able to rotate the body into the wind. Hollow-post mills driving scoop wheels were used in the Netherlands to drain wetlands from the 14th century onwards.[32]
Tower mill
By the end of the 13th century, the masonry tower mill, on which only the cap is rotated rather than the whole body of the mill, had been introduced. The spread of tower mills came with a growing economy that called for larger and more stable sources of power, though they were more expensive to build. In contrast to the post mill, only the cap of the tower mill needs to be turned into the wind, so the main structure can be made much taller, allowing the sails to be made longer, which enables them to provide useful work even in low winds. The cap can be turned into the wind either by winches or gearing inside the cap or from a winch on the tail pole outside the mill. A method of keeping the cap and sails into the wind automatically is by using a fantail, a small windmill mounted at right angles to the sails, at the rear of the windmill. These are also fitted to tail poles of post mills and are common in Great Britain and English-speaking countries of the former British Empire, Denmark, and Germany but rare in other places. Around some parts of the Mediterranean Sea, tower mills with fixed caps were built because the wind's direction varied little most of the time.[citation needed]
Smock mill
The smock mill is a later development of the tower mill, where the masonry tower is replaced by a wooden framework, called the "smock", which is thatched, boarded, or covered by other materials, such as
Smock windmills were introduced by the Dutch in the 17th century to overcome the limitations of tower windmills, which were expensive to build and could not be erected on wet surfaces. The lower half of the smock windmill was made of brick, while the upper half was made of wood, with a sloping tower shape that added structural strength to the design. This made them lightweight and able to be erected on unstable ground.
The smock windmill design included a small turbine in the back that helped the main mill to face the direction of the wind.[33]
Mechanics
Sails
Common sails consist of a lattice framework on which the sailcloth is spread. The miller can adjust the amount of cloth spread according to the wind and the power needed. In medieval mills, the sailcloth was wound in and out of a ladder-type arrangement of sails. Later mill sails had a lattice framework over which the sailcloth was spread, while in colder climates, the cloth was replaced by wooden slats, which were easier to handle in freezing conditions.[34] The jib sail is commonly found in Mediterranean countries and consists of a simple triangle of cloth wound round a spar.[35]
In all cases, the mill needs to be stopped to adjust the sails. Inventions in Great Britain in the late eighteenth and nineteenth centuries led to sails that automatically adjust to the wind speed without the need for the miller to intervene, culminating in patent sails invented by William Cubitt in 1807. In these sails, the cloth is replaced by a mechanism of connected shutters.[citation needed]
In France, Pierre-Théophile Berton invented a system consisting of longitudinal wooden slats connected by a mechanism that lets the miller open them while the mill is turning. In the twentieth century, increased knowledge of aerodynamics from the development of the airplane led to further improvements in efficiency by German engineer Bilau and several Dutch millwrights.[citation needed] The majority of windmills have four sails. Multiple-sailed mills, with five, six, or eight sails, were built in Great Britain (especially in and around the counties of Lincolnshire and Yorkshire), Germany, and less commonly elsewhere.[citation needed] Earlier multiple-sailed mills are found in Spain, Portugal, Greece, parts of Romania, Bulgaria, and Russia.[36] A mill with an even number of sails has the advantage of being able to run with a damaged sail by removing both the damaged sail and the one opposite, which does not unbalance the mill.[citation needed]
In the Netherlands, the stationary position of the sails, i.e. when the mill is not working, has long been used to give signals. If the blades are stopped in a "+" sign (3-6-9-12 o'clock), the windmill is open for business. When the blades are stopped in an "X" configuration, the windmill is closed or not functional. A slight tilt of the sails (top blade at 1 o'clock) signals joy, such as the birth of a healthy baby. A tilt of the blades to 11-2-5-8 o'clock signals mourning, or warning. It was used to signal the local region during Nazi operations in World War II, such as searches for Jews. Across the Netherlands, windmills were placed in mourning positions in honor of the Dutch victims of the 2014
Machinery
Gears inside a windmill convey power from the rotary motion of the sails to a mechanical device. The sails are carried on the horizontal windshaft. Windshafts can be wholly made of wood, wood with a cast iron pole end (where the sails are mounted), or entirely of cast iron. The brake wheel is fitted onto the windshaft between the front and rear bearings. It has the brake around the outside of the rim and teeth in the side of the rim which drives the horizontal gearwheel called wallower on the top end of the vertical upright shaft. In
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An isometric drawing of the machinery of the Beebe Windmill
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Cross section of a post mill
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Windshaft, brake wheel, and brake blocks in smock mill d'Admiraal in Amsterdam
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Interior view, Pantigo windmill,Historic American Buildings Survey
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Technical drawing of a 1793 Dutch smock mill for land drainage
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1813 technical drawing
Spread and decline
In the 14th century, windmills became popular in Europe; the total number of wind-powered mills is estimated to have been around 200,000 at the peak in 1850, which is close to half of the some 500,000
Of the 10,000 windmills in use in the Netherlands around 1850,[40] about 1,000 are still standing. Most of these are being run by volunteers, though some grist mills are still operating commercially. Many of the drainage mills have been appointed as a backup to the modern pumping stations. The Zaan district has been said to have been the first industrialized region of the world with around 600 operating wind-powered industries by the end of the eighteenth century.[40] Economic fluctuations and the industrial revolution had a much greater impact on these industries than on grain and drainage mills, so only very few are left.
Construction of mills spread to the
Wind turbines
A
Forerunners of modern horizontal-axis utility-scale wind generators were the WIME-3D in service in
As the 21st century began, rising concerns over
Materials
In an attempt to make wind turbines more efficient and increase their energy output, they are being built bigger, with taller towers and longer blades, and being increasingly deployed in offshore locations.[48][49] While such changes increase their power output, they subject the components of the windmills to stronger forces and consequently put them at a greater risk of failure. Taller towers and longer blades suffer from higher fatigue, and offshore windfarms are subject to greater forces due to winds of higher wind speeds and accelerated corrosion due to the proximity to seawater. To ensure a long enough lifetime to make the return on the investment viable, the materials for the components must be chosen appropriately.
The blade of a wind turbine consists of 4 main elements: the root, spar, aerodynamic fairing, and surfacing. The fairing is composed of two shells (one on the pressure side, and one on the suction side), connected by one or more webs linking the upper and lower shells. The webs connect to the spar laminates, which are enclosed within the skins (surfacing) of the blade, and together, the system of the webs and spars resist the flapwise loading. Flapwise loading, one of the two different types of loading that blades are subject to, is caused by the wind pressure, and edgewise loading (the second type of loading), is caused by the gravitational force and torque load. The former loading subjects the spar laminate on the pressure (upwind) side of the blade to cyclic tension-tension loading, while the suction (downwind) side of the blade is subject to cyclic compression-compression loading. Edgewise bending subjects the leading edge to a tensile load, and the trailing edge to a compressive load. The remainder of the shell, not supported by the spars or laminated at the leading and trailing edges, is designed as a sandwiched structure, consisting of multiple layers to prevent elastic buckling.[50]
In addition to meeting the stiffness, strength, and toughness requirements determined by the loading, the blade needs to be lightweight, and the weight of the blade scales with the cube of its radius. To determine which materials fit the criteria described above, a parameter known as the beam merit index is defined: Mb = E^1/2 / rho,
Recycling and waste problems with polymers blades
When the Vindeby Offshore Wind Farm was taken down in Denmark in 2017, 99% of the not-degradable fiberglass from 33 wind turbine blades ended as cut up at the Rærup Controlled Landfill near Aalborg, and in 2020 with considerably larger fiberglass quantities, even though it is the least environmentally friendly way of handling waste.[citation needed] Scrapped wind turbine blades are set to become a huge waste problem in Denmark and countries Denmark, to a greater and greater extent, export its many produced wind turbines.[53][54][55]
"The reason why many wings end up in landfill is that they are incredibly difficult to separate from each other, which you will have to do if you hope to be able to recycle the fiberglass", says Lykke Margot Ricard, Associate Professor in Innovation and Technological Foresight and education leader for civil engineering in Product Development and Innovation at the University of Southern Denmark (SDU). According to Dakofa, the Danish Competence Center for Waste and Resources, there is nothing specific in the Danish waste order about how to handle discarded fiberglass.[53][56]
Several
Since 1996, according to an estimate made by Lykke Margot Ricard (SDU) in 2020, at least 8,810 tonnes of the wing scrap have been disposed of in Denmark, and the waste problem will grow significantly in the coming years when more and more wind turbines have reached their end of life. According to the SDU lecturer's calculations, the waste sector in Denmark will have to receive 46,400 tonnes of fiberglass from wind turbine blades over the next 20–25 years.[58]
As so, at the island, Lolland, in Denmark, 250 tonnes of fiberglass from wind turbine waste also pours up on a landfill at Gerringe in the middle of Lolland in 2020.[57][59]
In the United States, a scrap of, and worn-out wind turbine blades made of fiberglass, go to the handful of landfills that accept them, like in Lake Mills, Iowa; Sioux Falls, South Dakota; and Casper.[60]
Windpumps
Windpumps were used to pump water since at least the 9th century in what is now Afghanistan, Iran and Pakistan.[19] The use of wind pumps became widespread across the Muslim world and later spread to East Asia (China) and South Asia (India).[61] Windmills were later used extensively in Europe, particularly in the Netherlands and the East Anglia area of Great Britain, from the late Middle Ages onwards, to drain land for agricultural or building purposes.
The "American windmill", or "wind engine", was invented by
In Australia, the Griffiths Brothers at
See also
- Don Quixote
- Éolienne Bollée
- History of wind power
- Horse mill
- List of windmills
- Mill (heraldry)
- Molinology
- Sustainable energy
- Sustainable living
- Tide mill
- Watermill
References
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- ^ Geography, Landscape and Mills. Pennsylvania State University.
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- ^ A.G. Drachmann, "Hero's Windmill", Centaurus, 7 (1961), pp. 145–151
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- ^ Needham, Joseph (1986). Science and Civilization in China: Volume 4, Physics and Physical Technology, Part 2, Mechanical Engineering. Taipei: Caves Books Ltd., p. 560.
- ^ Hills, R L. Power from Wind: A History of Windmill Technology Cambridge University Press 1993
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- ^ a b c "Wind powered factories: history (and future) of industrial windmills". Low-tech Magazine. 8 October 2009. Retrieved 15 August 2013.
- ^ "Windmill Sail - Different Types of Windmill Sails". www.historyofwindmills.com. Retrieved 2022-02-21.
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- ^ The Return of Windpower to Grandpa's Knob and Rutland County Archived 28 August 2008 at the Wayback Machine, Noble Environmental Power, LLC, 12 November 2007. Retrieved from Noblepower.com website 10 January 2010. Comment: this is the real name for the mountain the turbine was built, in case you wondered.
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{{cite web}}
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- Donald Routledge Hill, Mechanical Engineering)
- ^ a b Clements, Elizabeth (2003-02-14). "Historic Turns in The Windmill City". Ferimi News. Office of Science/US Dept of Energy. Retrieved 2015-01-25.
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- ^ Millet, Bruce (1984). "Triumph of the Griffiths Family". Retrieved 2013-12-10.
Further reading
- R. Gregory, The Industrial Windmill in Britain. Phillimore, 2005
- Mishmastnehi, Moslem (2021). "Technological Heritage of Persian Windmills". Iran: Journal of the British Institute of Persian Studies: 1–17. S2CID 238712550.
- Vowles, Hugh Pembroke: "An Enquiry into Origins of the Windmill", Journal of the Newcomen Society, Vol. 11 (1930–31)
External links
- Architecture: Windmills at Curlie
- Earth Science Australia, Wind Power and Windmills
- The International Molinological Society
- Windmills at Windmill World
- Mill Database, Belgium and Netherlands Archived 2009-11-19 at the Wayback Machine
- A Geograph article and photo-record of Windmills in Great Britain
- The Mills Archive
- Wind and watermill collections at the University of Kent