In cooking (and more specifically baking ), kneading is a process in the making of bread or dough , used to mix the ingredients and add strength to the final product. It allows the process of baking to be shortened by developing the gluten more quickly than it would develop in the absence of kneading.
114-567: A watermill or water mill is a mill that uses hydropower . It is a structure that uses a water wheel or water turbine to drive a mechanical process such as milling (grinding) , rolling , or hammering . Such processes are needed in the production of many material goods, including flour , lumber , paper , textiles , and many metal products. These watermills may comprise gristmills , sawmills , paper mills , textile mills , hammermills , trip hammering mills, rolling mills , and wire drawing mills. One major way to classify watermills
228-455: A forge , fulling stocks in a fulling mill and so on. However, in corn mills rotation about a vertical axis was required to drive its stones. The horizontal rotation was converted into the vertical rotation by means of gearing, which also enabled the runner stones to turn faster than the waterwheel. The usual arrangement in British and American corn mills has been for the waterwheel to turn
342-493: A Southern Europe hydropower race. In Italy's Po Valley , the main 20th century transition was not the creation of hydropower but the transition from mechanical to electrical hydropower. 12,000 watermills churned in the Po watershed in the 1890s, but the first commercial hydroelectric plant, completed in 1898, signaled the end of the mechanical reign. These new large plants moved power away from rural mountainous areas to urban centers in
456-443: A billion tonnes of CO2 greenhouse gas a year. This occurs when organic matters accumulate at the bottom of the reservoir because of the deoxygenation of water which triggers anaerobic digestion . People who live near a hydro plant site are displaced during construction or when reservoir banks become unstable. Another potential disadvantage is cultural or religious sites may block construction. A watermill or water mill
570-436: A dam on the river above the mill and a more elaborate millpond, sluice gate, mill race and spillway or tailrace. An inherent problem in the overshot mill is that it reverses the rotation of the wheel. If a miller wishes to convert a breastshot mill to an overshot wheel all the machinery in the mill has to be rebuilt to take account of the change in rotation. An alternative solution was the pitchback or backshot wheel. A launder
684-433: A device to serve wine, and five devices to lift water from rivers or pools, where three of them are animal-powered and one can be powered by animal or water. Moreover, they included an endless belt with jugs attached, a cow-powered shadoof (a crane-like irrigation tool), and a reciprocating device with hinged valves. In the 19th century, French engineer Benoît Fourneyron developed the first hydropower turbine. This device
798-435: A distance. A hydropower resource can be evaluated by its available power . Power is a function of the hydraulic head and volumetric flow rate . The head is the energy per unit weight (or unit mass) of water. The static head is proportional to the difference in height through which the water falls. Dynamic head is related to the velocity of moving water. Each unit of water can do an amount of work equal to its weight times
912-452: A horizontal shaft on which is also mounted a large pit wheel . This meshes with the wallower , mounted on a vertical shaft, which turns the (larger) great spur wheel (mounted on the same shaft). This large face wheel , set with pegs, in turn, turned a smaller wheel (such as a lantern gear ) known as a stone nut, which was attached to the shaft that drove the runner stone. The number of runner stones that could be turned depended directly upon
1026-427: A horizontal water wheel on a vertical axle, and the other with a vertical wheel on a horizontal axle. The oldest of these were horizontal mills in which the force of the water, striking a simple paddle wheel set horizontally in line with the flow turned a runner stone balanced on the rynd which is atop a shaft leading directly up from the wheel. The bedstone does not turn. The problem with this type of mill arose from
1140-427: A low-carbon means for economic development . Since ancient times, hydropower from watermills has been used as a renewable energy source for irrigation and the operation of mechanical devices, such as gristmills , sawmills , textile mills, trip hammers , dock cranes , domestic lifts , and ore mills . A trompe , which produces compressed air from falling water, is sometimes used to power other machinery at
1254-464: A microturbine in a cylindrical housing. Electricity generated by that turbine is used to charge 12-volt batteries." The term rain power has also been applied to hydropower systems which include the process of capturing the rain. Evidence suggests that the fundamentals of hydropower date to ancient Greek civilization . Other evidence indicates that the waterwheel independently emerged in China around
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#17327835510751368-462: A more dependable source of power by smoothing seasonal changes in water flow. However, reservoirs have a significant environmental impact , as does alteration of naturally occurring streamflow. Dam design must account for the worst-case, "probable maximum flood" that can be expected at the site; a spillway is often included to route flood flows around the dam. A computer model of the hydraulic basin and rainfall and snowfall records are used to predict
1482-602: A mostly rural work process, than the ancient urban-centered literary class had been. By Carolingian times, references to watermills had become "innumerable" in Frankish records. The Domesday Book , compiled in 1086, records 5,624 watermills in England alone. Later research estimates a less conservative number of 6,082 that should be considered a minimum as the northern reaches of England were never properly recorded. In 1300, this number had risen to between 10,000 and 15,000. By
1596-490: A mutual need for hydropower could lead to cooperation between otherwise adversarial nations. Hydropower technology and attitude began to shift in the second half of the 20th century. While countries had largely abandoned their small hydropower systems by the 1930s, the smaller hydropower plants began to make a comeback in the 1970s, boosted by government subsidies and a push for more independent energy producers. Some politicians who once advocated for large hydropower projects in
1710-535: A remote sensor." Villazon suggested a better application would be to collect the water from fallen rain and use it to drive a turbine, with an estimated energy generation of 3 kWh of energy per year for a 185 m roof. A microturbine-based system created by three students from the Technological University of Mexico has been used to generate electricity. The Pluvia system "uses the stream of rainwater runoff from houses' rooftop rain gutters to spin
1824-463: A shaft with a horizontal axis to one with a vertical axis. Although to date only a few dozen Roman mills are archaeologically traced, the widespread use of aqueducts in the period suggests that many remain to be discovered. Recent excavations in Roman London, for example, have uncovered what appears to be a tide mill together with a possible sequence of mills worked by an aqueduct running along
1938-418: A single waterwheel driving more than one set of stones was drawn by Henry Beighton in 1723 and published in 1744 by J. T. Desaguliers . The overshot wheel was a later innovation in waterwheels and was around two and a half times more efficient than the undershot. The undershot wheel, in which the main water wheel is simply set into the flow of the mill race, suffers from an inherent inefficiency stemming from
2052-475: A source of water, used to provide additional power to watermills and water-raising machines. Fulling mills, and steel mills may have spread from Al-Andalus to Christian Spain in the 12th century. Industrial watermills were also employed in large factory complexes built in al-Andalus between the 11th and 13th centuries. The engineers of the Islamic world used several solutions to achieve the maximum output from
2166-687: A tool to interfere in the economic development of African countries, such as the World Bank with the Kariba and Akosombo Dams , and the Soviet Union with the Aswan Dam . The Nile River especially has borne the consequences of countries both along the Nile and distant foreign actors using the river to expand their economic power or national force. After the British occupation of Egypt in 1882,
2280-485: A turbine with 90% efficiency. He applied scientific principles and testing methods to the problem of turbine design. His mathematical and graphical calculation methods allowed the confident design of high-efficiency turbines to exactly match a site's specific flow conditions. The Francis reaction turbine is still in use. In the 1870s, deriving from uses in the California mining industry, Lester Allan Pelton developed
2394-408: A vertical-waterwheel via a gear mechanism, and the other equipped with a horizontal-waterwheel without such a mechanism. The former type can be further divided, depending on where the water hits the wheel paddles, into undershot, overshot, breastshot and reverse shot waterwheel mills. The Greeks invented the two main components of watermills, the waterwheel and toothed gearing, and used, along with
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#17327835510752508-577: A water-powered grain-mill to have existed near the palace of king Mithradates VI Eupator at Cabira , Asia Minor , before 71 BC. The Roman engineer Vitruvius has the first technical description of a watermill, dated to 40/10 BC; the device is fitted with an undershot wheel and power is transmitted via a gearing mechanism . He also seems to indicate the existence of water-powered kneading machines. The Greek epigrammatist Antipater of Thessalonica tells of an advanced overshot wheel mill around 20 BC/10 AD. He praised for its use in grinding grain and
2622-701: A watermill by 748 AD which employed five waterwheels that ground 300 bushels of wheat a day. By 610 or 670 AD, the watermill was introduced to Japan via Korean Peninsula . It also became known in Tibet by at least 641 AD. According to Greek historical tradition, India received water-mills from the Roman Empire in the early 4th century AD when a certain Metrodoros introduced "water-mills and baths, unknown among them [the Brahmans] till then". Engineers under
2736-499: A watermill. One solution was to mount them to piers of bridges to take advantage of the increased flow. Another solution was the ship mill, a type of watermill powered by water wheels mounted on the sides of ships moored in midstream . This technique was employed along the Tigris and Euphrates rivers in 10th-century Iraq , where large ship mills made of teak and iron could produce 10 tons of flour from corn every day for
2850-535: Is a mill that uses hydropower. It is a structure that uses a water wheel or water turbine to drive a mechanical process such as milling (grinding) , rolling , or hammering . Such processes are needed in the production of many material goods, including flour , lumber , paper , textiles , and many metal products. These watermills may comprise gristmills , sawmills , paper mills , textile mills , hammermills , trip hammering mills, rolling mills , and wire drawing mills. One major way to classify watermills
2964-423: Is an attractive alternative to fossil fuels as it does not directly produce carbon dioxide or other atmospheric pollutants and it provides a relatively consistent source of power. Nonetheless, it has economic, sociological, and environmental downsides and requires a sufficiently energetic source of water, such as a river or elevated lake . International institutions such as the World Bank view hydropower as
3078-501: Is available on demand to be used to generate electricity by passing through channels that connect the dam to the reservoir. The water spins a turbine, which is connected to the generator that produces electricity. The other type is called a run-of-river plant. In this case, a barrage is built to control the flow of water, absent a reservoir . The run-of river power plant needs continuous water flow and therefore has less ability to provide power on demand. The kinetic energy of flowing water
3192-400: Is by an essential trait about their location: tide mills use the movement of the tide; ship mills are water mills onboard (and constituting) a ship. A plentiful head of water can be made to generate compressed air directly without moving parts. In these designs, a falling column of water is deliberately mixed with air bubbles generated through turbulence or a venturi pressure reducer at
3306-650: Is by an essential trait about their location: tide mills use the movement of the tide; ship mills are water mills onboard (and constituting) a ship. Watermills impact the river dynamics of the watercourses where they are installed. During the time watermills operate channels tend to sedimentate , particularly backwater . Also in the backwater area, inundation events and sedimentation of adjacent floodplains increase. Over time however these effects are cancelled by river banks becoming higher. Where mills have been removed, river incision increases and channels deepen. There are two basic types of watermills, one powered by
3420-445: Is by using hybrid solar panels called "all-weather solar panels" that can generate electricity from both the sun and the rain. According to zoologist and science and technology educator, Luis Villazon, "A 2008 French study estimated that you could use piezoelectric devices, which generate power when they move, to extract 12 milliwatts from a raindrop. Over a year, this would amount to less than 0.001kWh per square metre – enough to power
3534-420: Is by wheel orientation (vertical or horizontal), one powered by a vertical waterwheel through a gear mechanism, and the other equipped with a horizontal waterwheel without such a mechanism. The former type can be further subdivided, depending on where the water hits the wheel paddles, into undershot, overshot, breastshot and pitchback (backshot or reverse shot) waterwheel mills. Another way to classify water mills
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3648-420: Is by wheel orientation (vertical or horizontal), one powered by a vertical waterwheel through a gear mechanism, and the other equipped with a horizontal waterwheel without such a mechanism. The former type can be further subdivided, depending on where the water hits the wheel paddles, into undershot, overshot, breastshot and pitchback (backshot or reverse shot) waterwheel mills. Another way to classify water mills
3762-801: Is carried out in the UK at Daniels Mill , Little Salkeld Mill and Redbournbury Mill . This was boosted to overcome flour shortages during the Covid pandemic. Some old mills are being upgraded with modern hydropower technology, such as those worked on by the South Somerset Hydropower Group in the UK. In some developing countries, watermills are still widely used for processing grain. For example, there are thought to be 25,000 operating in Nepal, and 200,000 in India. Many of these are still of
3876-439: Is lost from erosion. Furthermore, studies found that the construction of dams and reservoirs can result in habitat loss for some aquatic species. Large and deep dam and reservoir plants cover large areas of land which causes greenhouse gas emissions from underwater rotting vegetation. Furthermore, although at lower levels than other renewable energy sources, it was found that hydropower produces methane equivalent to almost
3990-428: Is the tide mill . This mill might be of any kind, undershot, overshot or horizontal but it does not employ a river for its power source. Instead a mole or causeway is built across the mouth of a small bay. At low tide, gates in the mole are opened allowing the bay to fill with the incoming tide. At high tide the gates are closed, trapping the water inside. At a certain point a sluice gate in the mole can be opened allowing
4104-403: Is the decreased efficiency of electricity generation because the process depends on the speed of the seasonal river flow. This means that the rainy season increases electricity generation compared to the dry season. The size of hydroelectric plants can vary from small plants called micro hydro , to large plants that supply power to a whole country. As of 2019, the five largest power stations in
4218-423: Is the main source of energy. Both designs have limitations. For example, dam construction can result in discomfort to nearby residents. The dam and reservoirs occupy a relatively large amount of space that may be opposed by nearby communities. Moreover, reservoirs can potentially have major environmental consequences such as harming downstream habitats. On the other hand, the limitation of the run-of-river project
4332-461: Is the use of falling or fast-running water to produce electricity or to power machines. This is achieved by converting the gravitational potential or kinetic energy of a water source to produce power. Hydropower is a method of sustainable energy production. Hydropower is now used principally for hydroelectric power generation , and is also applied as one half of an energy storage system known as pumped-storage hydroelectricity . Hydropower
4446-472: The Aurelian walls in the late 3rd century. A breastshot wheel mill dating to the late 2nd century AD was excavated at Les Martres-de-Veyre , France. The 3rd century AD Hierapolis water-powered stone sawmill is the earliest known machine to incorporate the mechanism of a crank and connecting rod . Further sawmills, also powered by crank and connecting rod mechanisms, are archaeologically attested for
4560-662: The Caliphates adopted watermill technology from former provinces of the Byzantine Empire , having been applied for centuries in those provinces prior to the Muslim conquests , including modern-day Syria , Jordan , Israel , Algeria , Tunisia , Morocco , and Spain (see List of ancient watermills ). The industrial uses of watermills in the Islamic world date back to the 7th century, while horizontal-wheeled and vertical-wheeled watermills were both in widespread use by
4674-924: The Columbia River and its tributaries. The Bureau of Reclamation built the Hoover Dam in 1931, symbolically linking the job creation and economic growth priorities of the New Deal . The federal government quickly followed Hoover with the Shasta Dam and Grand Coulee Dam . Power demand in Oregon did not justify damming the Columbia until WWI revealed the weaknesses of a coal-based energy economy. The federal government then began prioritizing interconnected power—and lots of it. Electricity from all three dams poured into war production during WWII . After
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4788-656: The Democratic Republic of the Congo and Ghana , frequently sell excess power to neighboring countries. Foreign actors such as Chinese hydropower companies have proposed a significant amount of new hydropower projects in Africa, and already funded and consulted on many others in countries like Mozambique and Ghana. Small hydropower also played an important role in early 20th century electrification across Africa. In South Africa, small turbines powered gold mines and
4902-602: The Industrial Revolution would drive development as well. At the beginning of the Industrial Revolution in Britain, water was the main power source for new inventions such as Richard Arkwright 's water frame . Although water power gave way to steam power in many of the larger mills and factories, it was still used during the 18th and 19th centuries for many smaller operations, such as driving
5016-697: The Mauryan , Gupta and Chola empires. Another example of the early use of hydropower is seen in hushing , a historic method of mining that uses flood or torrent of water to reveal mineral veins. The method was first used at the Dolaucothi Gold Mines in Wales from 75 AD onwards. This method was further developed in Spain in mines such as Las Médulas . Hushing was also widely used in Britain in
5130-891: The Medieval and later periods to extract lead and tin ores. It later evolved into hydraulic mining when used during the California Gold Rush in the 19th century. The Islamic Empire spanned a large region, mainly in Asia and Africa, along with other surrounding areas. During the Islamic Golden Age and the Arab Agricultural Revolution (8th–13th centuries), hydropower was widely used and developed. Early uses of tidal power emerged along with large hydraulic factory complexes. A wide range of water-powered industrial mills were used in
5244-473: The Roman Empire . So-called 'Greek Mills' used water wheels with a horizontal wheel (and vertical shaft). A "Roman Mill" features a vertical wheel (on a horizontal shaft). Greek style mills are the older and simpler of the two designs, but only operate well with high water velocities and with small diameter millstones. Roman style mills are more complicated as they require gears to transmit the power from
5358-595: The Romans , undershot, overshot and breastshot waterwheel mills. The earliest evidence of a water-driven wheel appears in the technical treatises Pneumatica and Parasceuastica of the Greek engineer Philo of Byzantium (ca. 280−220 BC). The British historian of technology M.J.T. Lewis has shown that those portions of Philo of Byzantium's mechanical treatise which describe water wheels and which have been previously regarded as later Arabic interpolations, actually date back to
5472-510: The ancient world ". It featured 16 overshot waterwheels to power an equal number of flour mills. The capacity of the mills has been estimated at 4.5 tons of flour per day, sufficient to supply enough bread for the 12,500 inhabitants occupying the town of Arelate at that time. A similar mill complex existed on the Janiculum hill, whose supply of flour for Rome 's population was judged by emperor Aurelian important enough to be included in
5586-429: The gliadin and glutenin proteins in the flour expand and form strands of gluten , which gives bread its texture . (To aid gluten production, many recipes use bread flour , which is higher in protein than all-purpose flour.) The kneading process warms and stretches these gluten strands, eventually creating a springy and elastic dough. If bread dough does not develop these gluten strands, it will not be able to hold
5700-629: The granary in Baghdad . More than 300 watermills were at work in Iran till 1960. Now only a few are still working. One of the famous ones is the water mill of Askzar and the water mill of the Yazd city, still producing flour. Typically, water is diverted from a river or impoundment or mill pond to a turbine or water wheel, along a channel or pipe (variously known as a flume , head race, mill race , leat , leet, lade (Scots) or penstock ). The force of
5814-496: The 1st century AD, there is no sufficient literary evidence for it until the 5th century AD. In 488 AD, the mathematician and engineer Zu Chongzhi had a watermill erected which was inspected by Emperor Wu of Southern Qi (r. 482–493 AD). The engineer Yang Su of the Sui dynasty (581–618 AD) was said to operate hundreds of them by the beginning of the 6th century. A source written in 612 AD mentions Buddhist monks arguing over
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#17327835510755928-433: The 4th century BC refer to the term cakkavattaka (turning wheel), which commentaries explain as arahatta-ghati-yanta (machine with wheel-pots attached), however whether this is water or hand powered is disputed by scholars India received Roman water mills and baths in the early 4th century AD when a certain according to Greek sources. Dams, spillways, reservoirs, channels, and water balance would develop in India during
6042-545: The 6th century AD water-powered stone sawmills at Gerasa and Ephesus . Literary references to water-powered marble saws in what is now Germany can be found in Ausonius 4th century AD poem Mosella . They also seem to be indicated about the same time by the Christian saint Gregory of Nyssa from Anatolia , demonstrating a diversified use of water-power in many parts of the Roman Empire . The earliest turbine mill
6156-612: The 9th century. A variety of industrial watermills were used in the Islamic world, including gristmills , hullers , sawmills , ship mills, stamp mills , steel mills , sugar mills , and tide mills . By the 11th century, every province throughout the Islamic world had these industrial watermills in operation, from al-Andalus and North Africa to the Middle East and Central Asia . Muslim and Middle Eastern Christian engineers also used crankshafts and water turbines , gears in watermills and water-raising machines , and dams as
6270-836: The American West, organized opposition to hydroelectric dams sparked up in the 1950s and 60s based on environmental concerns. Environmental movements successfully shut down proposed hydropower dams in Dinosaur National Monument and the Grand Canyon , and gained more hydropower-fighting tools with 1970s environmental legislation. As nuclear and fossil fuels grew in the 70s and 80s and environmental activists push for river restoration, hydropower gradually faded in American importance. Foreign powers and IGOs have frequently used hydropower projects in Africa as
6384-679: The British worked with Egypt to construct the first Aswan Dam, which they heightened in 1912 and 1934 to try to hold back the Nile floods. Egyptian engineer Adriano Daninos developed a plan for the Aswan High Dam, inspired by the Tennessee Valley Authority's multipurpose dam. When Gamal Abdel Nasser took power in the 1950s, his government decided to undertake the High Dam project, publicizing it as an economic development project. After American refusal to help fund
6498-697: The Grand Coulee to build a nuclear site placed on the banks of the Columbia. The nuclear site leaked radioactive matter into the river, contaminating the entire area. Post-WWII Americans, especially engineers from the Tennessee Valley Authority , refocused from simply building domestic dams to promoting hydropower abroad. While domestic dam building continued well into the 1970s, with the Reclamation Bureau and Army Corps of Engineers building more than 150 new dams across
6612-536: The Greek 3rd century BC original. The sakia gear is, already fully developed, for the first time attested in a 2nd-century BC Hellenistic wall painting in Ptolemaic Egypt . Lewis assigns the date of the invention of the horizontal-wheeled mill to the Greek colony of Byzantium in the first half of the 3rd century BC, and that of the vertical-wheeled mill to Ptolemaic Alexandria around 240 BC. The Greek geographer Strabo reports in his Geography
6726-612: The Hun waterwheel; some of the earliest ones are the Jijiupian dictionary of 40 BC, Yang Xiong 's text known as the Fangyan of 15 BC, as well as Xin Lun, written by Huan Tan about 20 AD. It was also during this time that the engineer Du Shi (c. AD 31) applied the power of waterwheels to piston - bellows in forging cast iron. Ancient Indian texts dating back to
6840-639: The Nile, hydroelectric projects cover the rivers and lakes of Africa. The Inga powerplant on the Congo River had been discussed since Belgian colonization in the late 19th century, and was successfully built after independence. Mobutu's government failed to regularly maintain the plants and their capacity declined until the 1995 formation of the Southern African Power Pool created a multi-national power grid and plant maintenance program. States with an abundance of hydropower, such as
6954-1276: The United States' hydroelectric plants in Niagara Falls and the Sierra Nevada inspired bigger and bolder creations across the globe. American and USSR financers and hydropower experts also spread the gospel of dams and hydroelectricity across the globe during the Cold War , contributing to projects such as the Three Gorges Dam and the Aswan High Dam . Feeding desire for large scale electrification with water inherently required large dams across powerful rivers, which impacted public and private interests downstream and in flood zones. Inevitably smaller communities and marginalized groups suffered. They were unable to successfully resist companies flooding them out of their homes or blocking traditional salmon passages. The stagnant water created by hydroelectric dams provides breeding ground for pests and pathogens , leading to local epidemics . However, in some cases,
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#17327835510757068-635: The bellows in small blast furnaces (e.g. the Dyfi Furnace ) and gristmills , such as those built at Saint Anthony Falls , which uses the 50-foot (15 m) drop in the Mississippi River . Technological advances moved the open water wheel into an enclosed turbine or water motor . In 1848, the British-American engineer James B. Francis , head engineer of Lowell's Locks and Canals company, improved on these designs to create
7182-416: The buckets fill, the weight of the water starts to turn the wheel. The water spills out of the bucket on the down side into a spillway leading back to river. Since the wheel itself is set above the spillway, the water never impedes the speed of the wheel. The impulse of the water on the wheel is also harnessed in addition to the weight of the water once in the buckets. Overshot wheels require the construction of
7296-440: The cost of building new hydroelectric dams increased 4% annually between 1965 and 1990, due both to the increasing costs of construction and to the decrease in high quality building sites. In the 1990s, only 18% of the world's electricity came from hydropower. Tidal power production also emerged in the 1960s as a burgeoning alternative hydropower system, though still has not taken hold as a strong energy contender. Especially at
7410-673: The dam, and anti-British sentiment in Egypt and British interests in neighboring Sudan combined to make the United Kingdom pull out as well, the Soviet Union funded the Aswan High Dam. Between 1977 and 1990 the dam's turbines generated one third of Egypt's electricity. The building of the Aswan Dam triggered a dispute between Sudan and Egypt over the sharing of the Nile, especially since the dam flooded part of Sudan and decreased
7524-699: The date of the earliest tide mills, all of which were discovered on the Irish coast: A 6th century vertical-wheeled tide mill was located at Killoteran near Waterford . A twin flume horizontal-wheeled tide mill dating to c. 630 was excavated on Little Island . Alongside it, another tide mill was found which was powered by a vertical undershot wheel. The Nendrum Monastery mill from 787 was situated on an island in Strangford Lough in Northern Ireland . Its millstones are 830 mm in diameter and
7638-506: The dearth of studies of the subject in several other countries. The waterwheel was found in China from 30 AD onwards, when it was used to power trip hammers , the bellows in smelting iron , and in one case, to mechanically rotate an armillary sphere for astronomical observation (see Zhang Heng ). Although the British chemist and sinologist Joseph Needham speculates that the water-powered millstone could have existed in Han China by
7752-411: The dough is elastic and smooth. The dough can then be allowed to rise or " prove ". Similar to kneading is knocking back or punching down , which is done to the dough after proving. The dough is punched once or twice, after which it is kneaded gently for a short time. The aim of this is to remove any large gas pockets which have formed in the dough, create an even texture in the bread, and redistribute
7866-535: The draining water to drive a mill wheel or wheels. This is particularly effective in places where the tidal differential is very great, such as the Bay of Fundy in Canada where the tides can rise fifty feet, or the now derelict village of Tide Mills, East Sussex . The last two examples in the United Kingdom which are restored to working conditions can be visited at Eling , Hampshire and at Woodbridge , Suffolk . Run of
7980-619: The early 20th century, two major factors motivated the expansion of hydropower in Europe: in the northern countries of Norway and Sweden high rainfall and mountains proved exceptional resources for abundant hydropower, and in the south coal shortages pushed governments and utility companies to seek alternative power sources. Early on, Switzerland dammed the Alpine rivers and the Swiss Rhine , creating, along with Italy and Scandinavia ,
8094-402: The early 7th century, watermills were also well established in Ireland . A century later they began to spread across the former Roman Rhine and Danube frontier into the other parts of Germany . Ship mills and tide mills , both of which yet unattested for the ancient period, were introduced in the 6th century. In recent years, a number of new archaeological finds has consecutively pushed back
8208-490: The earth, we taste again the golden age . The Roman encyclopedist Pliny mentions in his Naturalis Historia of around 70 AD water-powered trip hammers operating in the greater part of Italy. There is evidence of a fulling mill in 73/74 AD in Antioch , Roman Syria . The 2nd century AD multiple mill complex of Barbegal in southern France has been described as "the greatest known concentration of mechanical power in
8322-421: The fact that the wheel itself, entering the water behind the main thrust of the flow driving the wheel, followed by the lift of the wheel out of the water ahead of the main thrust, actually impedes its own operation. The overshot wheel solves this problem by bringing the water flow to the top of the wheel. The water fills buckets built into the wheel, rather than the simple paddle wheel design of undershot wheels. As
8436-570: The falls far enough away to actually reach enough people and justify installation. The project succeeded in large part due to Nikola Tesla's invention of the alternating current motor . On the other side of the country, San Francisco engineers, the Sierra Club , and the federal government fought over acceptable use of the Hetch Hetchy Valley . Despite ostensible protection within a national park, city engineers successfully won
8550-590: The first century BC. The Barbegal mill , located in modern-day France, had 16 water wheels processing up to 28 tons of grain per day. Roman waterwheels were also used for sawing marble such as the Hierapolis sawmill of the late 3rd century AD. Such sawmills had a waterwheel that drove two crank-and-connecting rods to power two saws. It also appears in two 6th century Eastern Roman sawmills excavated at Ephesus and Gerasa respectively. The crank and connecting rod mechanism of these Roman watermills converted
8664-446: The first electric railway in the 1890s, and Zimbabwean farmers installed small hydropower stations in the 1930s. While interest faded as national grids improved in the second half of the century, 21st century national governments in countries including South Africa and Mozambique, as well as NGOs serving countries like Zimbabwe, have begun re-exploring small-scale hydropower to diversify power sources and improve rural electrification. In
8778-403: The first half of the 20th century began to speak out against them, and citizen groups organizing against dam projects increased. In the 1980s and 90s the international anti-dam movement had made finding government or private investors for new large hydropower projects incredibly difficult, and given rise to NGOs devoted to fighting dams. Additionally, while the cost of other energy sources fell,
8892-453: The flow of a body of water without necessarily changing its height. In this case, the available power is the kinetic energy of the flowing water. Over-shot water wheels can efficiently capture both types of energy. The flow in a stream can vary widely from season to season. The development of a hydropower site requires analysis of flow records , sometimes spanning decades, to assess the reliable annual energy supply. Dams and reservoirs provide
9006-502: The head lost due to flow friction in the power canal or penstock, rise in tailwater level due to flow, the location of the station and effect of varying gravity, the air temperature and barometric pressure, the density of the water at ambient temperature, and the relative altitudes of the forebay and tailbay. For precise calculations, errors due to rounding and the number of significant digits of constants must be considered. Some hydropower systems such as water wheels can draw power from
9120-419: The head. The power available from falling water can be calculated from the flow rate and density of water, the height of fall, and the local acceleration due to gravity: To illustrate, the power output of a turbine that is 85% efficient, with a flow rate of 80 cubic metres per second (2800 cubic feet per second) and a head of 145 metres (476 feet), is 97 megawatts: Operators of hydroelectric stations compare
9234-460: The high-efficiency Pelton wheel impulse turbine , which used hydropower from the high head streams characteristic of the Sierra Nevada . The modern history of hydropower begins in the 1900s, with large dams built not simply to power neighboring mills or factories but provide extensive electricity for increasingly distant groups of people. Competition drove much of the global hydroelectric craze: Europe competed amongst itself to electrify first, and
9348-400: The high-level intake. This allows it to fall down a shaft into a subterranean, high-roofed chamber where the now-compressed air separates from the water and becomes trapped. The height of the falling water column maintains compression of the air in the top of the chamber, while an outlet, submerged below the water level in the chamber allows water to flow back to the surface at a lower level than
9462-401: The highest among all renewable energy technologies. Hydroelectricity generation starts with converting either the potential energy of water that is present due to the site's elevation or the kinetic energy of moving water into electrical energy. Hydroelectric power plants vary in terms of the way they harvest energy. One type involves a dam and a reservoir . The water in the reservoir
9576-512: The horizontal wheel is estimated to have developed 7 ⁄ 8 horsepower (650 W) at its peak. Remains of an earlier mill dated at 619 were also found at the site. In a 2005 survey the scholar Adam Lucas identified the following first appearances of various industrial mill types in Western Europe. Noticeable is the preeminent role of France in the introduction of new innovative uses of waterpower. However, he has drawn attention to
9690-598: The intake. A separate outlet in the roof of the chamber supplies the compressed air. A facility on this principle was built on the Montreal River at Ragged Shutes near Cobalt, Ontario , in 1910 and supplied 5,000 horsepower to nearby mines. Hydroelectricity is the biggest hydropower application. Hydroelectricity generates about 15% of global electricity and provides at least 50% of the total electricity supply for more than 35 countries. In 2021, global installed hydropower electrical capacity reached almost 1400 GW,
9804-412: The lack of gearing; the speed of the water directly set the maximum speed of the runner stone which, in turn, set the rate of milling. Most watermills in Britain and the United States of America had a vertical waterwheel, one of four kinds: undershot, breast-shot, overshot and pitchback wheels. This vertical produced rotary motion around a horizontal axis, which could be used (with cams) to lift hammers in
9918-497: The last unexploited energy sources in nature. When it rains, billions of litres of water can fall, which have an enormous electric potential if used in the right way." Research is being done into the different methods of generating power from rain, such as by using the energy in the impact of raindrops. This is in its very early stages with new and emerging technologies being tested, prototyped and created. Such power has been called rain power. One method in which this has been attempted
10032-408: The lower plain. Italy prioritized early near-nationwide electrification, almost entirely from hydropower, which powered their rise as a dominant European and imperial force. However, they failed to reach any conclusive standard for determining water rights before WWI. Kneading Kneading's importance lies in the mixing of flour with water; when these two ingredients are combined and kneaded,
10146-500: The maximum flood. Some disadvantages of hydropower have been identified. Dam failures can have catastrophic effects, including loss of life, property and pollution of land. Dams and reservoirs can have major negative impacts on river ecosystems such as preventing some animals traveling upstream, cooling and de-oxygenating of water released downstream, and loss of nutrients due to settling of particulates. River sediment builds river deltas and dams prevent them from restoring what
10260-412: The nutrients for the yeast, thus allowing fermentation to continue. The dough can then be proofed a second time. Another method of knocking back (also known as "folding") is to gently stretch and pat out the proved dough before folding the sides in towards the centre. In bread baking, kneading can be substituted by allowing a relatively wet, low-yeast dough to ferment for more than 12 hours, which allows
10374-626: The power available for British grain milling. By the early 20th century, availability of cheap electrical energy made the watermill obsolete in developed countries although some smaller rural mills continued to operate commercially later throughout the century. A few historic mills such as the Water Mill , Newlin Mill and Yates Mill in the US and The Darley Mill Centre in the UK still operate for demonstration purposes. Small-scale commercial production
10488-608: The power from a toothed annular ring that is mounted near the outer edge of the wheel. This drives the machinery using a spur gear mounted on a shaft rather than taking power from the central axle . However, the basic mode of operation remains the same; gravity drives machinery through the motion of flowing water . Toward the end of the 19th century, the invention of the Pelton wheel encouraged some mill owners to replace over- and undershot wheels with Pelton wheel turbines driven through penstocks . A different type of watermill
10602-463: The reduction of human labour: Hold back your hand from the mill, you grinding girls; even if the cockcrow heralds the dawn, sleep on. For Demeter has imposed the labours of your hands on the nymphs , who leaping down upon the topmost part of the wheel, rotate its axle; with encircling cogs, it turns the hollow weight of the Nisyrian millstones . If we learn to feast toil-free on the fruits of
10716-547: The region including fulling mills, gristmills , paper mills , hullers , sawmills , ship mills , stamp mills , steel mills , sugar mills , and tide mills . By the 11th century, every province throughout the Islamic Empire had these industrial mills in operation, from Al-Andalus and North Africa to the Middle East and Central Asia . Muslim engineers also used water turbines while employing gears in watermills and water-raising machines. They also pioneered
10830-687: The revenues gained from watermills. The Tang dynasty (618–907 AD) 'Ordinances of the Department of Waterways' written in 737 AD stated that watermills should not interrupt riverine transport and in some cases were restricted to use in certain seasons of the year. From other Tang-era sources of the 8th century, it is known that these ordinances were taken very seriously, as the government demolished many watermills owned by great families, merchants, and Buddhist abbeys that failed to acknowledge ordinances or meet government regulations. A eunuch serving Emperor Xuanzong of Tang (r. 712–756 AD) owned
10944-477: The rights to both water and power in the Hetch Hetchy Valley in 1913. After their victory they delivered Hetch Hetchy hydropower and water to San Francisco a decade later and at twice the promised cost, selling power to PG&E which resold to San Francisco residents at a profit. The American West, with its mountain rivers and lack of coal, turned to hydropower early and often, especially along
11058-447: The river schemes do not divert water at all and usually involve undershot wheels the mills are mostly on the banks of sizeable rivers or fast flowing streams. Other watermills were set beneath large bridges where the flow of water between the stanchions was faster. At one point London bridge had so many water wheels beneath it that bargemen complained that passage through the bridge was impaired. In 1870 watermills still produced 2/3 of
11172-514: The rotary motion of the waterwheel into the linear movement of the saw blades. Water-powered trip hammers and bellows in China, during the Han dynasty (202 BC – 220 AD), were initially thought to be powered by water scoops . However, some historians suggested that they were powered by waterwheels. This is since it was theorized that water scoops would not have had the motive force to operate their blast furnace bellows. Many texts describe
11286-453: The same period. Evidence of water wheels and watermills date to the ancient Near East in the 4th century BC. Moreover, evidence indicates the use of hydropower using irrigation machines to ancient civilizations such as Sumer and Babylonia . Studies suggest that the water wheel was the initial form of water power and it was driven by either humans or animals. In the Roman Empire , water-powered mills were described by Vitruvius by
11400-631: The side of the River Fleet . In 537 AD, ship mills were ingeniously used by the East Roman general Belisarius , when the besieging Goths cut off the water supply for those mills. These floating mills had a wheel that was attached to a boat moored in a fast flowing river. The surviving evidence for watermills sharply increases with the emergence of documentary genres such as monastic charters , Christian hagiography and Germanic legal codes . These were more inclined to address watermilling,
11514-489: The start of the American hydropower experiment, engineers and politicians began major hydroelectricity projects to solve a problem of 'wasted potential' rather than to power a population that needed the electricity. When the Niagara Falls Power Company began looking into damming Niagara, the first major hydroelectric project in the United States, in the 1890s they struggled to transport electricity from
11628-405: The supply of water available. As waterwheel technology improved mills became more efficient, and by the 19th century, it was common for the great spur wheel to drive several stone nuts, so that a single water wheel could drive as many as four stones. Each step in the process increased the gear ratio which increased the maximum speed of the runner stone. Adjusting the sluice gate and thus the flow of
11742-478: The tiny pockets of gas ( carbon dioxide ) created by the leavening agent (such as yeast or baking powder ), and will collapse, leaving a heavy and dense loaf. Kneading can be performed by hand (the traditional way), with a mixer equipped with a dough hook, or with a bread machine . In hand kneading, the dough is put on a floured surface, pressed and stretched with the heel of the hand, folded over, and rotated through 90° repeatedly. This process continues until
11856-423: The total electrical energy produced with the theoretical potential energy of the water passing through the turbine to calculate efficiency. Procedures and definitions for calculation of efficiency are given in test codes such as ASME PTC 18 and IEC 60041. Field testing of turbines is used to validate the manufacturer's efficiency guarantee. Detailed calculation of the efficiency of a hydropower turbine accounts for
11970-664: The traditional style, but some have been upgraded by replacing wooden parts with better-designed metal ones to improve the efficiency. For example, the Centre for Rural Technology in Nepal upgraded 2,400 mills between 2003 and 2007. This is also the period when water-mills started to spread outside the former Empire. According to Cedrenus (Historiarum compendium), a certain Metrodoros who went to India in c. AD 325 "constructed water-mills and baths, unknown among them [the Brahmans] till then". Hydropower Hydropower (from Ancient Greek ὑδρο -, "water"), also known as water power ,
12084-721: The use of dams as a source of water power, used to provide additional power to watermills and water-raising machines. Islamic irriguation techniques including Persian Wheels would be introduced to India, and would be combined with local methods, during the Delhi Sultanate and the Mughal Empire . Furthermore, in his book, The Book of Knowledge of Ingenious Mechanical Devices , the Muslim mechanical engineer, Al-Jazari (1136–1206) described designs for 50 devices. Many of these devices were water-powered, including clocks,
12198-563: The volume of water available to them. Ethiopia , also located on the Nile, took advantage of the Cold War tensions to request assistance from the United States for their own irrigation and hydropower investments in the 1960s. While progress stalled due to the coup d'état of 1974 and following 17-year-long Ethiopian Civil War Ethiopia began construction on the Grand Ethiopian Renaissance Dam in 2011. Beyond
12312-481: The war, the Grand Coulee Dam and accompanying hydroelectric projects electrified almost all of the rural Columbia Basin , but failed to improve the lives of those living and farming there the way its boosters had promised and also damaged the river ecosystem and migrating salmon populations. In the 1940s as well, the federal government took advantage of the sheer amount of unused power and flowing water from
12426-486: The water past the main wheel allowed the miller to compensate for seasonal variations in the water supply. Finer speed adjustment was made during the milling process by tentering , that is, adjusting the gap between the stones according to the water flow, the type of grain being milled, and the grade of flour required. In many mills (including the earliest) the great spur wheel turned only one stone, but there might be several mills under one roof. The earliest illustration of
12540-596: The water's movement drives the blades of a wheel or turbine, which in turn rotates an axle that drives the mill's other machinery. Water leaving the wheel or turbine is drained through a tail race, but this channel may also be the head race of yet another wheel, turbine or mill. The passage of water is controlled by sluice gates that allow maintenance and some measure of flood control; large mill complexes may have dozens of sluices controlling complicated interconnected races that feed multiple buildings and industrial processes. Watermills can be divided into two kinds, one with
12654-618: The world are conventional hydroelectric power stations with dams. Hydroelectricity can also be used to store energy in the form of potential energy between two reservoirs at different heights with pumped-storage . Water is pumped uphill into reservoirs during periods of low demand to be released for generation when demand is high or system generation is low. Other forms of electricity generation with hydropower include tidal stream generators using energy from tidal power generated from oceans, rivers, and human-made canal systems to generating electricity. Rain has been referred to as "one of
12768-558: Was found in Chemtou and Testour , Roman North Africa , dating to the late 3rd or early 4th century AD. A possible water-powered furnace has been identified at Marseille , France. Mills were commonly used for grinding grain into flour (attested by Pliny the Elder ), but industrial uses as fulling and sawing marble were also applied. The Romans used both fixed and floating water wheels and introduced water power to other provinces of
12882-668: Was implemented in the commercial plant of Niagara Falls in 1895 and it is still operating. In the early 20th century, English engineer William Armstrong built and operated the first private electrical power station which was located in his house in Cragside in Northumberland , England. In 1753, the French engineer Bernard Forest de Bélidor published his book, Architecture Hydraulique , which described vertical-axis and horizontal-axis hydraulic machines. The growing demand for
12996-435: Was placed at the end of the flume on the headrace, this turned the direction of the water without much loss of energy, and the direction of rotation was maintained. Daniels Mill near Bewdley , Worcestershire is an example of a flour mill that originally used a breastshot wheel, but was converted to use a pitchback wheel. Today it operates as a breastshot mill. Larger water wheels (usually overshot steel wheels) transmit
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