Industrial hydroelectric plants
Hydroelectricity
Hydroelectricity is electricity generated by hydropower, i.e., the production of power through use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy. Once a hydroelectric complex is constructed, the project produces no direct waste, and has a considerably lower output level of the greenhouse gas carbon dioxide (CO2) than fossil fuel powered energy plants. Worldwide, hydroelectricity supplied an estimated 715,000 MWe in 2005. This was approximately 19% of the world's electricity (up from 16% in 2003), and accounted for over 63% of electricity from renewable sources.
Electricity generation
Most hydroelectric power comes from the potential energy of dammed water driving a water turbine and generator. In this case the energy extracted from the water depends on the volume and on the difference in height between the source and the water's outflow. This height difference is called the head. The amount of potential energy in water is proportional to the head. To obtain very high head, water for a hydraulic turbine may be run through a large pipe called a penstock.
Pumped storage hydroelectricity produces electricity to supply high peak demands by moving water between reservoirs at different elevations. At times of low electrical demand, excess generation capacity is used to pump water into the higher reservoir. When there is higher demand, water is released back into the lower reservoir through a turbine. Pumped storage schemes currently provide the only commercially important means of large-scale grid energy storage and improve the daily load factor of the generation system. Hydroelectric plants with no reservoir capacity are called run-of-the-river plants. A tidal power plant makes use of the daily rise and fall of water due to tides; such sources are highly predictable, and if conditions permit construction of reservoirs, can also be dispatch able to generate power during high demand periods.
Less common types of hydro schemes use water's kinetic energy or undammed sources such as undershot waterwheels.
A simple formula for approximating electric power production at a hydroelectric plant is: P = hrgk, where P is Power in kilowatts, h is height in meters, r is flow rate in cubic meters per second, g is acceleration due to gravity of 9.8 m/s2, and k is a coefficient of efficiency ranging from 0 to 1. Efficiency is often higher with larger and more modern turbines.
Annual electric energy production depends on the available water supply. In some installations the water flow rate can vary by a factor of 10:1 over the course of a year.
Industrial hydroelectric plants
While many hydroelectric projects supply public electricity networks, some are created to serve specific industrial enterprises. Dedicated hydroelectric projects are often built to provide the substantial amounts of electricity needed for aluminium electrolytic plants. In the Scottish Highlands there are examples at Kinlochleven and Lochaber, constructed during the early years of the 20th century. The Grand Coulee Dam, long the world's largest, switched to support Alcoa aluminum in Bellingham, Washington for America's World War II airplanes before it was allowed to provide irrigation and power to citizens (in addition to aluminum power) after the war. In Suriname, the Brokopondo Reservoir was constructed to provide electricity for the Alcoa aluminium industry. New Zealand's Manapouri Power Station was constructed to supply electricity to the aluminium smelter at Tiwai Point.
Advantages
The major advantage of hydroelectricity is elimination of the cost of fuel. The cost of operating a hydroelectric plant is nearly immune to increases in the cost of fossil fuels such as oil, natural gas or coal, and no imports are needed.
Hydroelectric plants also tend to have longer economic lives than fuel-fired generation, with some plants now in service which were built 50 to 100 years ago. Operating labor cost is also usually low, as plants are automated and have few personnel on site during normal operation.
Where a dam serves multiple purposes, a hydroelectric plant may be added with relatively low construction cost, providing a useful revenue stream to offset the costs of dam operation. It has been calculated that the sale of electricity from the Three Gorges Dam will cover the construction costs after 5 to 8 years of full generation.
Related activities
Reservoirs created by hydroelectric schemes often provide facilities for water sports, and become tourist attractions in themselves. Multi-use dams installed for irrigation support agriculture with a relatively constant water supply. Large hydro dams can control floods, which would otherwise affect people living downstream of the project.
Disadvantages
Environmental damage
Hydroelectric projects can be disruptive to surrounding aquatic ecosystems both upstream and downstream of the plant site. For instance, studies have shown that dams along the Atlantic and Pacific coasts of North America have reduced salmon populations by preventing access to spawning grounds upstream, even though most dams in salmon habitat have fish ladders installed. Salmon spawn are also harmed on their migration to sea when they must pass through turbines. This has led to some areas transporting spawn downstream by barge during parts of the year. In some cases dams have been demolished (for example the Marmot Dam demolished in 2007) because of impact on fish. Turbine and power-plant designs that are easier on aquatic life are an active area of research. Mitigation measures such as fish ladders may be required at new projects or as a condition of re-licensing of existing projects.
Generation of hydroelectric power changes the downstream river environment. Water exiting a turbine usually contains very little suspended sediment, which can lead to scouring of river beds and loss of riverbanks. Since turbine gates are often opened intermittently, rapid or even daily fluctuations in river flow are observed. For example, in the Grand Canyon, the daily cyclic flow variation caused by Glen Canyon Dam was found to be contributing to erosion of sand bars. Dissolved oxygen content of the water may change from pre-construction conditions. Depending on the location, water exiting from turbines is typically much warmer than the pre-dam water, which can change aquatic fauna populations, including endangered species, and prevent natural freezing processes from occurring. Some hydroelectric projects also use canals to divert a river at a shallower gradient to increase the head of the scheme. In some cases, the entire river may be diverted leaving a dry riverbed. Examples include the Tekapo and Pukaki Rivers.
Population relocation
Another disadvantage of hydroelectric dams is the need to relocate the people living where the reservoirs are planned. In February 2008, it was estimated that 40-80 million people worldwide had been physically displaced as a direct result of dam construction. In many cases, no amount of compensation can replace ancestral and cultural attachments to places that have spiritual value to the displaced population. Additionally, historically and culturally important sites can be flooded and lost. Such problems have arisen at the Three Gorges Dam project in China, the Clyde Dam in New Zealand and the Ilısu Dam in Southeastern Turkey.
Dam failures
Failures of large dams, while rare, are potentially serious — the Banqiao Dam failure in Southern China resulted in the deaths of 171,000 people and left millions homeless. Dams may be subject to enemy bombardment during wartime, sabotage and terrorism. Smaller dams and micro hydro facilities are less vulnerable to these threats. The creation of a dam in a geologically inappropriate location may cause disasters like the one of the Vajont Dam in Italy, where almost 2000 people died, in 1963.
Affected by flow shortage
Changes in the amount of river flow will correlate with the amount of energy produced by a dam. Because of global warming, the volume of glaciers has decreased, such as the North Cascades glaciers, which have lost a third of their volume since 1950, resulting in stream flows that have decreased by as much as 34%. The result of diminished river flow can be power shortages in areas that depend heavily on hydroelectric power.
Isaac Newton
Isaac Newton (1643-1727) - English mathematician, engineer, astronomer and physicist, founder of classical mechanics, the term (1672) and President (since 1703) Royal Society of London. One of the founders of modern physics, formulated the basic laws of mechanics and was the actual creator of a unified program of physical descriptions of all physical phenomena on the basis of mechanics, discovered the law of universal gravitation, explained the motion of the planets around the sun and the moon around the earth and tides in the oceans, laid the foundations of continuum mechanics environments, acoustics and physical optics. Fundamental works "Mathematical Principles of Natural Philosophy" (1687) and "Optics" (1704). Newton worked out (regardless of Gottfried Leibniz) the differential and integral calculus. He opened the dispersion of light, chromatic aberration, investigated the interference and diffraction, developed the corpuscular theory of light, he hypothesized that combined corpuscular and wave representations. I built a reflecting telescope. Isaac Newton formulated the basic laws of classical mechanics. He discovered the law of universal gravitation, gave the theory of motion of celestial bodies, creating the foundations of celestial mechanics. Space and time are considered absolute. Newton's work far ahead of the overall scientific level of his time, with unclear contemporaries. He was director of the Mint, established coinage in England.
Early years
Isaac Newton was born on January 4, 1643, at Woolsthorpe near Grantema, Lincolnshire, in a small village in the family of a small farmer, who died three months before his son's birth. The baby was premature, there is a legend that it was so small that it was placed in a sheepskin mitt lying on the bench, from where he once fell and hit his head heavily on the floor. When the child was three years old, his mother remarried and left, leaving him in the care of her grandmother. Newton grew up sickly and unsocial, prone to reverie. He was attracted by poetry and painting, he is away from his peers, was making kites, he invented a windmill, a water clock, pedal cart. It was difficult for the beginning of school life of Newton. He studied bad boy was weak, and once classmates beat him until he lost consciousness. Transferring such a humiliating situation was touchy for Isaac Newton is unbearable, and there was one: to stand out success in their studies. Hard work, he has ensured that won first place in the class. Interest in the technology has forced Newton to reflect on the phenomens of nature, he was deeply involved and mathematics. This later wrote Jean Baptiste Biot: "One of his uncles, finding him once under the hedge with a book in his hands, lost in deep thought, he took the book, and found that he was busy solving mathematical problems. Struck by such a serious and active direction as a young man, he persuaded his mother not to oppose further request and send his son to continue the occupation. " After extensive training in 1660, Isaac Newton went to Cambridge as Subsizzfr'a (so-called poor students who had to serve the members of the college, which could not weigh Newton).
Getting creative. Optics
In six years, Isaac Newton had passed all college degree and prepared all his great discoveries further. In 1665 Newton became master of arts. In the same year, when the plague was raging in England, he decided to temporarily settle at Woolsthorpe. It was there that he began to actively engage in optics, searching for ways to eliminate chromatic aberration in the lens telescope led Newton to research what is now called the variance, t. E. Depending on the refractive index of the frequency. Many of the experiments conducted by them (and there are more than a thousand) have become classics and are repeated today in schools and institutions. The leitmotif of all the research was to understand the physical nature of light. First, Newton was inclined to think that light - is the wave of all-pervading ether, but he later abandoned the idea, thinking that the resistance of the air would have a noticeable slow down the movement of the heavenly bodies. These arguments have led Newton to the notion that light - a stream of special particles, corpuscles emitted from a source and moving in a straight line until they meet an obstacle. The corpuscular model explains not only the straightness of light, but also the law of reflection (elastic reflection), and - though not without additional assumptions - and the law of refraction. This assumption was that light corpuscles, flying to the surface of the water, for example, should be attracted by it and therefore be accelerated. According to this theory the speed of light in water should be greater than in air (which came into conflict with the later experimental data).
The laws of mechanics
The formation of the corpuscular theory of light explicitly influenced, at that time already, mainly to complete the work which was to be the main result of the great works of Newton - the creation of a unified, based on the laws of mechanics, he formulated the physical world. The basis of this idea of painting lay a material point - physically infinitesimal particles of matter and the laws governing their motion. It is a clear statement of the law and gave the mechanics of Isaac Newton fullness and completeness. The first of these laws was, in fact, the definition of inertial reference systems: in such systems have not experienced any material impact points move uniformly in a straight line. The second law of mechanics plays a central role. It states that the change in the amount of movement (the product of mass and velocity) per unit time is equal to the force acting on a material point. The weight of each of these points is a constant size. In general, all these points are not "wear out" in the words of Newton, each of them is eternal, t. E. Can neither arise nor destroyed. Material terms interact, and quantitative measure of the impact on each of them and is a force. The task of finding out what these forces is the root problem of mechanics. Finally, the third law - the law of "equality of action and reaction" to explain why the total momentum of a body does not experience external influences, remains the same, no matter how interacted its component parts.
Гидроэлектроэнергия
Гидроэлектроэнергия - электричество созданное гидроэнергетикой, то есть, энергия произведённая в результате падения или течения воды под действием сил гравитации. Это наиболее широко использованная форма возобновляемой энергии. Однажды построенный гидроэлектроэнергетический комплекс не создает никаких отходов, а также обладает более низким уровнем производства парникового газа – оксида углерода, чем при сжигании органического топлива для получения энергии на заводах. Во всем мире, гидроэлектроэнергетика произвела около 715,000 мегаватт электроэнергии в 2005. Это составило приблизительно 19% всемирного электричества (в сравнении с 16% в 2003), и составляет более 63% электроэнергии из возобновляемых источников.
Производство электроэнергии
Большая часть гидроэлектроэнергии создается за счет потенциальной энергии запруженной воды, которая приводит в действие водяную турбину и генератор. В этом случае энергия извлеченная из воды зависит от объема и разницы в высоте между источником и водостоком. Это различие высоты называется напор. Сумма потенциальной энергии воды пропорциональна напору. Чтобы получить очень высокий напор, вода для гидравлической турбины может быть пущена через большую трубу названую шлюзом.
Гидроаккумулирующие электростанции производят электроэнергию во время пиков нагрузки, перемещая воду между резервуарами с различными высотами. Во время низкого электропотребления, избыток энергии используется, чтобы закачать воду в более высокий резервуар. Когда появляется максимум потребления, вода снова спускается в более низкий резервуар через турбину. Гидроаккумулирующие схемы в настоящее время снабжают только важные коммерческие крупномасштабные энергосети сохраняя суточную нагрузку генерирующей системы. Гидроэлектрические заводы без возможности сохранять воду называются русловыми ГЭС. Приливная электростанция использует ежедневное повышение и падение воды из-за приливов и отливов; такие источники - очень предсказуемые, и если условия разрешают конструкцию водохранилищ, то они также могут быть использованы, чтобы генерировать мощность в течение максимумов потребления.
Менее распространенные типы гидро схем используют кинетическую энергию воды или незапруженные источники как например, колесо мельницы.
Существует простая формула, чтобы определять количество электроэнергии произведенное на гидростанции: P = hrgk, где P - мощность в киловаттах, h - напор в метрах, r - расход воды в кубических метрах в секунду, g - ускорение свободного падения 9,8 м/с2, и k - коэффициент полезного действия, колеблющийся от 0 до 1. Эффективность часто более высокая с большими и более современными турбинами.
Годовое производство электроэнергии зависит от количества поступающей воды. В некоторых системах скорость течения воды может изменяться с коэффициентом 10:1 в течение года.
Преимущества
Основное преимущество гидроэлектроэнергии является отсутствие затрат на топливо. На стоимость работы ГЭС почти не влияет увеличение стоимости ископаемого топлива, такого как нефть, природный газ или каменный уголь, а также не требуется никакого импортирования.
Гидроэлектростанции также обладают более длительным сроком службы по сравнению с генераторами, сжигающими топливо, некоторые станции, которые сейчас находятся в работе были построены от 50 до 100 лет тому назад. Обслуживающая стоимость также обычно находится на низком уровне, так как станции автоматизированы и имеют небольшое количество рабочего персонала во время нормальной работы.
В местах, где дамба служит для нескольких целей, гидроэлектростанция может быть сооружена со сравнительно низкой стоимостью, при условии, что доход будет возмещать стоимость работы дамбы. Было подсчитано, что продажа электричества с Three Gorges Dam покроет строительные затраты после 5 - 8 лет работы.
Совместная деятельность
Водохранилища, созданные гидроэлектростанциями часто обеспечивают благоприятные условия для водных видов спорта и привлекают к себе туристов. Многоцелевые дамбы используются для орошения, помогая сельскому хозяйству сравнительно постоянным водоснабжением. Большие водяные плотины могут контролировать наводнения, которые могли бы затронуть людей, живущих вниз по течению.
Недостатки
Ущерб окружающей среде
Гидроэлектростанции могут нарушать водные экосистемы как вверх по течению так и вниз по течению от места постройки станции. Например, исследования показали, что плотины вдоль побережья Атлантического и Тихого океанов у берегов Северной Америки снизили популяцию лососевых, закрыв им доступ к местам нереста, даже не смотря на то, что большинство плотин установили специальные подъёмники для рыбы. Икра лососевых также уничтожается во время миграции к морю, кода она должна пройти через турбины. Это привело к тому, что икру спускают вниз по течению на баржах в отдельное время года. В некоторых случаях плотины разрушают (например Marmot Dam разрушили в 2007) из-за влияния на рыбу. Турбины и электростанции проектируются таким образом, чтобы не создавать препятствий для водной жизни. Смягчающие меры, такие как подъёмники для рыбы обязательны на всех новых объектах, а также необходимы при релицензировании существующих объектов.
Производство гидроэлектроэнергии меняет окружающую среду вниз по течению реки. Вода выходящая из турбины обычно содержит очень маленькое количество осадков, в результате могут быть смыты дно и берега реки. Поскольку ворота турбины часто открываются нерегулярно, наблюдаются ежедневные колебания в скорости течения реки. Например, в Большом Каньоне, ежедневное циклическое изменение течения, вызванное Glen Canyon Dam, размывает песчаные отмели. Растворенный в воде кислород может повлиять на исходное состояние. В зависимости от размещения, вода, выходящая из турбины обычно теплее, чем до неё, это может повлиять на обитателей водной фауны и даже подвергнуть их опасности, а также препятствует естественному образованию льда. Некоторые гидроэлектростанции используют каналы, чтобы направлять реку на мелководье, тем самым увеличивая перепад. В некоторых случаях, целая река может быть направлена в другую строну, оставляя за собой высохшее русло. Например реки Tekapo и Pukaki.
Переселение населения
Другой недостаток гидроэлектростанций является необходимость переселения людей, живущих в зоне планируемого водохранилища. В Феврале 2008, было подсчитано, что 40-80 миллионов людей во всем мире были переселены непосредственно из-за строительства плотины. Во многих случаях, никакая сумма компенсации не может заменить потомственную и культурную привязанность к местам, откуда их пересилили. Кроме того, исторически и культурно важные места могут быть затоплены и потеряны. Подобные проблемы возникли в при строительстве Three Gorges Dam в Китае, Clyde Dam в Новой Зеландии и Ilısu Dam в Юго-восточной Турции.
Разрушившиеся плотины
Разрушение больших плотин, пока явление редкое, но потенциально опасное - разрушение Banqiao Dam в Южном Китае закончилось смертью 171,000 людей и появлением миллионов бездомных. Плотины могут подвергнуться бомбардировке в военное время, диверсии или террористическому акту. Маленькие плотины и микро ГЭС менее уязвимы к таким опасностям. Создание плотины в геологически неподходящем месте может вызвать бедствие подобно Vajont Dam в Италии, где погибло почти 2000 людей в 1963.
Влияние нехватки течения
Изменения в величине течения реки изменяет суммарную энергию произведенную плотиной. Из-за глобального потепления, уменьшаются объемы ледников, как например ледники North Cascades, которые потеряли трети их объема с 1950, результатом стало уменьшение потока на 34%. Результатом этого уменьшения стал дефицит мощности в области, сильно зависящей от гидроэлектрической энергии.
Hydroelectricity
Hydroelectricity is electricity generated by hydropower, i.e., the production of power through use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy. Once a hydroelectric complex is constructed, the project produces no direct waste, and has a considerably lower output level of the greenhouse gas carbon dioxide (CO2) than fossil fuel powered energy plants. Worldwide, hydroelectricity supplied an estimated 715,000 MWe in 2005. This was approximately 19% of the world's electricity (up from 16% in 2003), and accounted for over 63% of electricity from renewable sources.
Electricity generation
Most hydroelectric power comes from the potential energy of dammed water driving a water turbine and generator. In this case the energy extracted from the water depends on the volume and on the difference in height between the source and the water's outflow. This height difference is called the head. The amount of potential energy in water is proportional to the head. To obtain very high head, water for a hydraulic turbine may be run through a large pipe called a penstock.
Pumped storage hydroelectricity produces electricity to supply high peak demands by moving water between reservoirs at different elevations. At times of low electrical demand, excess generation capacity is used to pump water into the higher reservoir. When there is higher demand, water is released back into the lower reservoir through a turbine. Pumped storage schemes currently provide the only commercially important means of large-scale grid energy storage and improve the daily load factor of the generation system. Hydroelectric plants with no reservoir capacity are called run-of-the-river plants. A tidal power plant makes use of the daily rise and fall of water due to tides; such sources are highly predictable, and if conditions permit construction of reservoirs, can also be dispatch able to generate power during high demand periods.
Less common types of hydro schemes use water's kinetic energy or undammed sources such as undershot waterwheels.
A simple formula for approximating electric power production at a hydroelectric plant is: P = hrgk, where P is Power in kilowatts, h is height in meters, r is flow rate in cubic meters per second, g is acceleration due to gravity of 9.8 m/s2, and k is a coefficient of efficiency ranging from 0 to 1. Efficiency is often higher with larger and more modern turbines.
Annual electric energy production depends on the available water supply. In some installations the water flow rate can vary by a factor of 10:1 over the course of a year.
Industrial hydroelectric plants
While many hydroelectric projects supply public electricity networks, some are created to serve specific industrial enterprises. Dedicated hydroelectric projects are often built to provide the substantial amounts of electricity needed for aluminium electrolytic plants. In the Scottish Highlands there are examples at Kinlochleven and Lochaber, constructed during the early years of the 20th century. The Grand Coulee Dam, long the world's largest, switched to support Alcoa aluminum in Bellingham, Washington for America's World War II airplanes before it was allowed to provide irrigation and power to citizens (in addition to aluminum power) after the war. In Suriname, the Brokopondo Reservoir was constructed to provide electricity for the Alcoa aluminium industry. New Zealand's Manapouri Power Station was constructed to supply electricity to the aluminium smelter at Tiwai Point.