Hydroelectric power is rare in the Middle East, excepting in Turkey, where it is substantially used.
Hydroelectric power generation takes advantage of the effect of gravity on water; as it flows downwards. Hydroelectric power plants harness the energy to generate electricity. Th It is currently the biggest source of renewable energy, providing about 6 percent of world energy, and 14 percent of the world’s electricity.
Essentially, the power is harnessed by using the motion of the water to turn a wheel. This movement is used to generate electricity.
Water was first used to generate electricity in 1882 in the United States. Today, hydroelectric power plants come in an enormous range of sizes. Micro-installations becoming popular options to provide power for small communities in mountainous areas in less developed countries. In contrast are the massive, many thousand-megawatt installations, such as the Hoover dam on the Colorado River, the massive Three Gorges Dam in China and the Ataturk Dam in Turkey.
The amount of electricity that flowing water can generate depends on two factors; its volume and its kinetic energy. The greater either is, the more energy can be extracted from the water. The amount of kinetic energy is determined by the amount of potential energy and the rate at which it is released.
The potential energy is determined by the difference in height between the point of origin and the power plant. The shorter the distance to the plant relative to the height it originated, the greater the kinetic energy.
The transfer of the energy of water to mechanical movement retains the same principle as the water wheel, but has become more refined. A waterwheel of the past is now a turbine. This is a much more sophisticated and efficient version of a waterwheel, many of which have variable pitch blades, in order to keep the rate of rotation constant. It fed by a tube called a penstock whose rate of supply is controlled by a series of sluices.
Probably the most popular image of hydropower is the dam. The purpose of a dam is to create a reservoir. Reservoirs may have any of a number of ultimate purposes, but the main one is to reduce variability of flow to the generation plant. This was the purpose of the millponds of yore. Fluctuations caused by bouts of heavy rainfall or dry periods are evened out. The generator would otherwise be over powered by floodwaters and would be well below capacity during drought periods.
Dams may also serve to increase the potential energy of the water in the reservoir. The enormous height of some modern dams makes the pressure of the water trying to escape extraordinarily high. Furthermore, in many cases, the actual generating facility is not at the base of the dam, but at the base of the mountainous area in which the dam is located. The water is fed through steep pipes down the mountain to the generators. This further increases the head (the height of the reservoir above the turbine), and therefore the potential power output. In many cases. This might be as much as 1,000 m.
A further use for reservoirs is as a store of energy, which might not be needed immediately. A number of hydroelectric installations pump water into higher elevation reservoirs when their energy generation exceeds demand. Then when there is a surge in demand, this stored water can be released. Such storage is even more valuable if intermittent sources of electricity such as solar or wind is hooked into the system.
·Like any activity, hydroelectric power generation has both advantages and disadvantages. For a long time it was perceived as a very attractive option, but as the industry has matured and more of the potential of hydroelectricity has been exploited, some of its shortcomings have been noticed.
·Hydroelectricity is a non-thermal electricity generation process, so the only heat loss is through friction generated in the mechanical operating equipment. Also, by avoiding combustion, the process releases no pollutants.
In principle, a source of water is never ending and non-polluting. This means that the life of a power plant should be as long as its parts last. Dams typically have very long planned life expectancies, in excess of 100 or even 200 years.
The relatively simple nature of the technology means that maintenance is low and therefore inexpensive. This means that after construction, overheads are low. Once a dam is built, the only major costs are routine maintenance and supervision staff.
Small scale installations can easily be built at relatively low cost (financial and environmental) to power the needs of small communities in remote areas. A dam can be used to control the rate that water flows in a river, helping to manage rivers in times of flood. It can therefore prevent potentially dangerous surges and flooding downstream.·Reservoirs produced by the dams allows provide recreational areas for boating or swimming. And the dam itself can also become a tourist attraction.
The cost of constructing a dam plus the cost of purchasing the land that will be affected by the reservoir, means that up-front costs are high.
Hydroelectric schemes can have a major local environmental impact. The reservoir created by a dam floods land causing major changes in the landscape. This makes the siting of large dams difficult due to objections from environmentalists and others. An examples was the massive opposition to the Bakun dam in Malaysia (now indefinitely postponed) and the strong ongoing opposition to the Three Gorges dam (for a range of environmental, social and economic reasons).
Hydropower is vulnerable to drought. If a reservoir becomes depleted, the amount of power a dam can generate is reduced. This is a particularly problem when the dry season coincides with winter, when power demand is the greatest.
Dams can interfere with the wildlife living in a river by blocking migration routes. For example, salmon depend on travelling up river to spawn. Large dams make this impossible.
Dams interfere with the rate of silt deposition, with two main effects. Areas downstream of the dam receive much less silt.
Silt is a source of nutrition for land around the river, and also helps in maintaining its shape. Also, accumulation of silt behind the dam can seriously threaten its operating efficacy by blocking the ·sluice gates and/or filling up the reservoir. For example, after only four years of operation, the Sanmen George dam on the Yellow River, China lost 41 percent of its water storage capacity and ·75 percent of its 1,000 MW maximum power capacity to sedimentation. Power plants can thus ·have their projected lifespans dramatically shortened.
The potential of dam failure is something of a specter to communities living downstream of large dams. Failures have occurred with loss of life, but the security of dam building technology improves apace.
Some studies have actually suggested that the biodegradation of vegetation submerged by large dams actually releases so much methane that it burdens large reservoirs with a very large greenhouse gas potential. This has not yet been conclusively shown, but would be a blow to protagonists of hydropower who espouse its lack of greenhouse gas emissions.
AlBawaba--MEBG.
