User:Kawther.H/Hydropower

Hydropower or water power (from ὕδωρ, "water") is a process that involves forms of energy transformation in which kinetic energy of falling or fast-running water is converted to electrical or mechanical energy to be utilized for human benefits. Hydropower is classified to be one of few technologies that produce green energy.

Since ancient times, hydropower from many kinds of watermills has been used a number of times as a renewable energy source for irrigation and the operation of different  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 a distance.

The use water power has several benefits such as the generation of electricity, and powering machines. However, by extension hydropower has other environmental benefits such as the reduction of fossil fuels, and improve climate conditions. On the other hand, there are multiple economic, sociological, and even some environmental downside.

International institutions such as the World Bank view hydropower as a means for economic development without adding substantial amounts of carbon to the atmosphere,

= History = There are many evidence suggesting that the fundamentals of hydropower date back to ancient Greek civilization. According to separate evidence, the waterwheel emerged in China around the same period independently from the Greeks. Other evidence suggest that earliest evidence of water wheels and watermills date back to the ancient Near East in the 4th century BC. Moreover, evidence of the utilization of hydropower for human benefits using irrigation machines dates back to ancient civilizations such as Sumer and Babylonia in the region of Mesopotamia. 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 the first century BC. The Barbegal mill had sixteen 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 which drove two crank-and-connecting rods to power two saws. It also appears in two 6th century Eastern Roman saw mills excavated at Ephesus and Gerasa respectively. The crank and connecting rod mechanism of these Roman watermills converted the rotary motion of the waterwheel into the linear movement of the saw blades.

The 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. There are many texts that describe 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 the 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. Another example of early utilizations of hydropower is seen in hushing. Hushing is the use of the power of a wave of water released from a tank in the extraction of metal ores. The method was first used at the Dolaucothi Gold Mines in Wales from 75 AD onwards. However, this method was further developed in Spain in mines such as Las Médulas. Hushing was also widely used in Britain in the Medieval and later periods to extract lead and tin ores. It later evolved into hydraulic mining when used during the California Gold Rush.

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 utilized and developed and early uses of tidal power emerged along with large hydraulic factory complexes. There was a wide range of water-powered industrial mills used in 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, employed gears in watermills and water-raising machines, and pioneered the use of dams as a source of water power, used to provide additional power to watermills and water-raising machines. 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, 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, and a reciprocating device with hinged valves.

In the 19th century the Fourneyron turbine was developed by Benoit Fourneyron which was the first device using hydropower turbine. This device was implemented in the commercial plant of Niagara Falls and it is still operating today. In the early 20th century specifically 1978, the English Engineer William Armstrong made a significant achievement in the development of hydropower when he built and operated the first private electrical power station which was located in his house in Cragside in Northumberland, England. Early Hydraulic power networks used pipes to carry pressurized water and transmit mechanical power from the source to end users. The power source was normally a head of water which was sometimes assisted by a pump. This type of hydraulic power network were extensively in Victorian cities in the United Kingdom. A hydraulic power network was also developed in Geneva, Switzerland. The world-famous Jet d'Eau was originally designed as the over-pressure relief valve for the network

Although the use of 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 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.

 Hydroelectricity  Hydropower is currently the world's first renewable energy source of electricity since it generates about 15% of the global electricity. Furthermore, hydroelectricity is the number one application of hydropower. The generation of electricity through hydropower starts with the process of converting either the potential energy of water that is present due to the site's elevation or the kinetic energy of falling water into electrical energy.

There are a few types of Hydroelectric power plants in terms of the way the water is harvested and used to generate energy. One of these types is one involving building a dam and a reservoir that collects a certain amount of water. In this case the water in the reservoir will be available upon demand and it will be used to generate electricity by passing through specialty channels that connect the dam to the reservoir. This is then passed to turbines that derive a generator which as the name implies generates electricity. The other type of hydroelectric power plants is called the run-of-river project. In this case, to control the flow of water a barrage is built and instead of collecting water in a reservoir. Also, the kinetic energy of flowing water is the main source of energy that is converted to electrical energy.

Both of these types of hydroelectricity plants designs have some limitations. For example, the construction of dams can be very loud and will result in discomfort to the people living around it, also the presence of the dam and reservoirs will occupy a relatively large amount of space which is not usually favoured by communities living in the area. Moreover, the reduction of the amount of water of the downstream due to presence of a reservoir can potentially have major environmental consequences such as harming habitats living in the downstream of the site. On the other hand, the limitation of the run-of-river project is the decreased efficiency of electricity generation because the process depends on the speed of the river flow which is seasonal. This means that when the rainy season begins in the area, electricity generation will be maximized while it will decrease during the dry season.

The size of hydroelectricity water plants can vary small community sized plants called micro hydro, to very large plants supplying power to a whole country. As of 2019, the five largest power stations in 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 hydroelectricity. 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.

Disadvantages and Limitations of Hydropower:
Refer to greenhouse gases for more information regarding greenhouse gasses impacts

There are a few disadvantages of hydropower that have been identified in the past years. Those disadvantages vary in severity and impact with some being outweighed by the benefits. One of the most prominent sociological disadvantages is the displacement of people that live in the areas surrounding a a hydro plant construction site, or when the reservoir banks become unstable. Another identified sociological disadvantage of hydropower constructions is the occasional requirement to demolish cultural or religious sites. This has been identified as a reason for hydropower projects to be refused. This is since the extend of the impact of demolishing such important sites is deemed to be unethical by international standards, like that published by WCD and will result in a public outrage. Furthermore, the resettlement of the displaced communities needs to be factored into the cost of hydropower projects. Writers note that some companies understate the cost of resettlements in project assessments to cut on costs. Furthermore, the presence of large dams in an area poses as a major hazard for people living in the communities surrounding it. There are several reason that correspond to this hazard, one of which being floods during rainy seasons due to dams overflow.

As per the impact on the ecosystem, it was found that dams and reservoirs have major negative impacts on river ecosystems. 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 gas which is a greenhouse gas. This occurs when organic matters accumulate at the bottom of the reservoir because of the deoxygenation of water which triggers anaerobic digestion. Furthermore, studies found that the construction of dams and reservoirs can result in habitat loss for some aquatic species.