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HYDRO ELECTRIC POWER PLANT
HYDRO ELECTRIC POWER PLANT
Energy is the most important thing in this world. All living plants, animals (organisms) on this earth require energy to perform any type of work. The capacity to do a work is energy. The energy may require in smaller amount or in larger amount depending upon the nature of work to be performed.
The different things from which we get the energy are called as Energy Sources. This is the simplest meaning of energy sources. There are two types of energy sources:
1. Conventional OR Non-Renewable Energy Sources
2. Non-Conventional OR Renewable Energy Sources
1. Conventional OR Non-Renewable Energy Sources:
The energy sources, which we are using from long time and which are in danger of exhausting, are called as Conventional OR Non-Renewable Energy Sources. They are not renewed by Nature and they are perishable, are going to get exhausted one day.
e. g. coal, petroleum products, nuclear fuels etc.
2. Non-Conventional OR Renewable Energy Sources:
These are the energy sources whose utilization technology is not yet fully developed. These are the sources, which can be recovered and reused. i. e. they can be used again and again to generate energy because of the renewal of their energy
We are going to consider one of the ways of generation of energy from non-conventional energy namely hydroelectric energy. As name suggest, it is the energy obtained from water.
The main principle used in this type is the kinetic energy of falling water is converted into electric energy using turbines.
History of hydro power development
The first recorded use of water power was a clock, built around 250 BC. Since that time, humans have used falling water to provide power for grain and saw mills, as well as a host of other applications. The first use of moving water to produce electricity was a waterwheel on the Fox River in Wisconsin in 1882, two years after Thomas Edison unveiled the incandescent light bulb. The first of many hydro electric power plants at Niagara Falls was completed shortly thereafter. Hydro power continued to play a major role in the expansion of electrical service early in this century, both in North America and around the world. Contemporary Hydro-electric power plants generate anywhere from a few kW, enough for a single residence, to thousands of MW, power enough to supply a large city.
Early hydro-electric power plants were much more reliable and efficient than the fossil fuel fired plants of the day. This resulted in a proliferation of small to medium sized hydro-electric generating stations distributed wherever there was an adequate supply of moving water and a need for electricity. As electricity demand soared in the middle years of this century, and the efficiency of coal and oil fueled power plants increased, small hydro plants fell out of favor. Most new hydro-electric development was focused on huge "mega-projects".
The majority of these power plants involved large dams which flooded vast areas of land to provide water storage and therefore a constant supply of electricity. In
Recent years, the environmental impacts of such large hydro projects are being identified as a cause for concern. It is becoming increasingly difficult for developers to build new dams because of opposition from environmentalists and people living on the land to be flooded. This is shown by the opposition to projects such as Great Whale (James Bay II) in Quebec and the Gabickovo-Nagymaros project on the Danube River in Czechoslovakia.
Hydropower generation is an improvarient of primitive water wheel for grinding cereals. As hydro-electric power it emerged in USA in1882, followed by sweeden and Japan. In India, hydropower plant OF 130kw installed capacity was commissioned in 1897 at sidrapong at Dargiling in West Bengal and followed by 4.5MW plant at sivsamudram in Karnataka in 1902.during period between two world wars, a number of hydro power plants such as 48MW, at Jogindernagar(H.P.),17.4MW ganga power plant(U.P.), 38.75MWpykaraand 30MWmatter(Chnnai)were commissioned,from installed capacity of 1362MW,out of which hydropower was 508 MW in 1947,the pace of growth has been rapid in post independence era. The hydal install capacity by the end 2001 is 25,574MW, out of total capacity of 102907MW.
Electricity produced from generators driven by water turbines that convert the energy in falling or fast-flowing water to mechanical energy. Water at a higher elevation flows downward through large pipes or tunnels (penstocks). The falling water rotates turbines, which drive the generators, which convert the turbines' mechanical energy into electricity. The advantages of hydroelectric power over such other sources as fossil fuels and nuclear fission are that it is continually renewable and produces no pollution. Norway, Sweden, Canada, and Switzerland rely heavily on hydroelectricity because they have industrialized areas close to mountainous regions with heavy rainfall. The U.S., Russia, China, India, and Brazil get a much smaller proportion of their electric power from hydroelectric generation. See also tidal power.
Water is needed to run a hydroelectric generating unit. It’s held in a reservoir or lake behind the dam and the force of the water being released from the reservoir through the dam spins the blades of a turbine. The turbine is connected to the generator that produces electricity. After passing through the turbine, the water reenters the river on the downstream side of the dam.
The capability to produce and deliver electricity for widespread consumption was one of the most important factors in the surge of American economic influence and wealth in the late nineteenth and early twentieth centuries. Hydroelectric power, among the first and simplest of the technologies that generated electricity, was initially developed using low dams of rock, timber, or granite block construction to collect water from rainfall and surface runoff into a reservoir. The water was funneled into a pipe (or pen-stock) and directed to a waterwheel (or turbine) where the force of the falling water on the turbine blades rotated the turbine and its main shaft. This shaft was connected to a generator, and the rotating generator produced electricity. One gallon (about 3.8 liters) of water falling 100 feet (about 30 meters) each second produced slightly more than 1,000 watts (or one kilowatt) of electricity, enough to power ten 100-watt light bulbs or a typical hairdryer.
There are now three types of hydroelectric installations: storage, run-of-river, and pumped-storage facilities. Storage facilities use a dam to capture water in a reservoir. This stored water is released from the reservoir through turbines at the rate required to meet changing electricity needs or other needs such as flood control, fish passage, irrigation, navigation, and recreation. Run-of-river facilities use only the natural flow of the river to operate the turbine. If the conditions are right, this type of project can be constructed without a dam or with a low diversion structure to direct water from the stream channel into a penstock. Pumped-storage facilities, an innovation of the 1950s, have specially designed turbines. These turbines have the ability to generate electricity the conventional way when water is delivered through penstocks to the turbines from a reservoir. They can also be reversed and used as pumps to lift water from the powerhouse back up into the reservoir where the water is stored for later use. During the daytime when electricity demand suddenly increases, the gates of the pumped-storage facility are opened and stored water is released from the reservoir to generate and quickly deliver electricity to meet the demand. At night when electricity demand is lowest and there is excess electricity available from coal or nuclear electricity generating facilities the turbines are reversed and pump water back into the reservoir. Operating in this manner, a pumped-storage facility improves the operating efficiency of all power plants within an electric system. Hydroelectric developments provide unique benefits not available with other electricity generating technologies. They do not contribute to air pollution, acid rain, or ozone depletion, and do not produce toxic wastes. As a part of normal operations many hydroelectric facilities also provide flood control, water supply for drinking and irrigation, and recreational opportunities such as fishing, swimming, water-skiing, picnicking, camping, rafting, boating, and sightseeing.
Hydro electric power plant
Installations (e.g. Dams) to a large extent. Manufacturers have Been quick enough to develop package designs for small units. These are also called as Small Scale Hydroelectric Power Plants. These facilities can supply in principle significant amounts of electricity for irrigation, or potable water pumping lighting or health or educational purpose. The total potential amount of such a resources is poorly documented but is apt to be large.
Up to 1972, hydro engineers concentrated on developing the larger sites, where the economy of scale enabled the production of energy at a cost low enough to compete thermal power etc. But the shortage of fuel, high cost of fuels needed for many of the other plants made the engineers to pay attention to the naturally occurring renewable sources which can be efficiently used as energy sources. Moreover, the remarkable advancement in the technology of development of turbines suitable for utilizing small falls and small discharges from RIVERS increased the chances of development of small hydral For many small hydro plants of less than 500 kW capacity, electronic load controllers have been developed to replace the governor. These controllers maintain a constant load on the turbine and hence constant flow, surplus power is diverted to a resistor and either wasted or used to heat water.
The advantage of Hydro Power Plants operation in hilly areas and remote areas and the elimination of long transmission system, & lesser gestation periods have lent added attraction. It has little or no adverse environmental impact, effects on stream ecology.
In India, the potential of small hydropower is estimated to be 5000
MW at present, while further investigations and surveys are expected to indicate
a higher potential. Small Hydropower is covered in renewable programme. The alternate hydro-energy center at Roorki works on the development of solar hydropower system as well as Hybrid Hydro systems. If small hydropower stations are set up all over the country, decentralized availability of power will become possible.
Many countries now have active small hydro development and rural electrification programmes, due to the several advantages offered by these plants.
There is no formal definition of a small hydro plant but this may generally be taken as power station or plant having output up to 5000 kW. Some associate the concept of small hydro with low head say up to 15 m. This may not generally be true as there is no restriction on head for these power plants. Stations up to output 1000 kW are called micro and up to 5000 kW as mini power plants. Conceptually these power plants can be categorized into two types:
1) One utilizing small discharges but having high head
2) One utilizing large discharges but having comparatively smaller head. Hydro-electric power plants convert the kinetic energy contained in falling water into electricity. The energy in flowing water is ultimately derived from the sun, and is therefore constantly being renewed. Energy contained in sunlight evaporates water from the oceans and deposits it on land in the form of rain. Differences in land elevation result in rainfall runoff, and allow some of the original solar energy to be captured as hydro-electric power.
Hydro power is currently the world's largest renewable source of electricity, accounting for 6% of worldwide energy supply or about 15% of the world's electricity. In Canada, hydroelectric power is abundant and supplies 60% of our electrical needs. Traditionally thought of as a cheap and clean source of electricity, most large hydro-electric schemes being planned today are coming up against a great deal of opposition from environmental groups and native people.
Hydro-electric Power Plants
Hydroelectric energy is produced by the force of falling water. The capacity to produce this energy is dependent on both the available flow and the height from which it falls. Building up behind a high dam, water accumulates potential energy. This is transformed into mechanical energy when the water rushes down the sluice and strikes the rotary blades of turbine. The turbine's rotation spins electromagnets which generate current in stationary coils of wire. Finally, the current is put through a transformer where the voltage is increased for long distance transmission over power lines.
Hydro-electric power plants capture the energy released by water falling through a vertical distance, and transform this energy into useful electricity. In general, falling water is channeled through a turbine which converts the water's energy into mechanical power. The rotation of the water turbines is transferred to a generator which produces electricity. The amount of electricity which can be generated at a hydro-electric plant is dependant upon two factors. These factors are (1) the vertical distance through which the water falls, called the "head", and (2) the flow rate, measured as volume per unit time. The electricity produced is proportional to the product of the head and the rate of flow. The following is an equation which may be used to roughly determine the amount of electricity which can be generated by a potential hydro-electric power site:
POWER (kW) = 5.9 x FLOW x HEAD
In this equation, FLOW is measured in cubic meters per second and HEAD is measured in meters.
Based on the facts presented above, hydroelectric power plants can generally be divided into two categories. "High head" power plants are the most common and generally utilize a dam to store water at an increased elevation. The use of a dam to impound water also provides the capability of storing water during rainy periods and releasing it during dry periods. This results in the consistent and reliable production of
Electricity, able to meet demand. Heads for this type of power plant may be greater than 1000 m. Most large hydroelectric facilities are of the high head variety. High head plants with storage are very valuable to electric utilities because they can be quickly adjusted to meet the electrical demand on a distribution system.
Hydroelectric power for the Nation
Although most energy in the United States is produced by fossil fuel and nuclear power plants, hydroelectricity is still important to the Nation, as about 10 percent of total power is produced by hydroelectric plants. Nowadays, huge power generators are placed inside dams. Water flowing through the dams spin turbine blades (made out of metal instead of leaves) which are connected to generators. Power is produced and is sent to homes and businesses. Producing electricity using hydroelectric power has some advantages over other power producing methods. Let's do a quick comparison:
Reservoir construction is "drying up"
Gosh, hydroelectric power sounds great -- so why don't we use it to produce all of our power? Mainly because you need lots of water and a lot of land where you can build a dam and reservoir, which all takes a LOT of money, time, and construction. In fact, most of the good spots to locate hydro plants have already been taken. In the early part of the century hydroelectric plants supplied a bit less than one-half of the nation's power, but the number is down to about 10 percent today. The trend for the future will probably be to build small-scale hydro plants that can generate electricity for a single community.
As this chart shows, the construction of surface reservoirs has slowed considerably in recent years. In the middle of the 20th Century, when urbanization was occurring at a rapid rate, many reservoirs were constructed to serve peoples' rising demand for water and power. Since about 1980, the rate of reservoir construction has slowed considerably.
Hydro-electric power plants have many environmental impacts, some of which are just beginning to be understood. These impacts, however, must be weighed against the environmental impacts of alternative sources of electricity. Until recently there was an almost universal belief that hydro power was a clean and environmentally safe method of producing electricity. Hydro-electric power plants do not emit any of the standard atmospheric pollutants such as carbon dioxide or sulfur dioxide given off by fossil fuel fired power plants. In this respect, hydro power is better than burning coal, oil or natural gas to produce electricity, as it does not contribute to global warming or acid rain. Similarly, hydro-electric power plants do not result in the risks of radioactive contamination associated with nuclear power plants.
A few recent studies of large reservoirs created behind hydro dams have suggested that decaying vegetation, submerged by flooding, may give off quantities of greenhouse gases equivalent to those from other sources of electricity. If this turns out to be true, hydro-electric facilities such as the James Bay project in Quebec that flood large areas of land might be significant contributors to global warming. Run of the river hydro plants without dams and reservoirs would not be a source of these greenhouse gases.
The most obvious impact of hydro-electric dams is the flooding of vast areas of land, much of it previously forested or used for agriculture. The size of reservoirs created can be extremely large. The La Grande project in the James Bay region of Quebec has already submerged over 10,000 square kilometers of land; and if future plans are carried out, the eventual area of flooding in northern Quebec will be larger than the country of Switzerland. Reservoirs can be used for ensuring adequate water supplies, providing irrigation, and recreation; but in several cases they have flooded the homelands of native peoples, whose way of life has then been destroyed. Many rare ecosystems are also threatened by hydro-electric development.
Large dams and reservoirs can have other impacts on a watershed. Damming a river can alter the amount and quality of water in the river downstream of the dam, as well as preventing fish from migrating upstream to spawn. These impacts can be reduced by requiring minimum flows downstream of a dam, and by creating fish ladders which allow fish to move upstream past the dam. Silt, normally carried downstream to the lower reaches of a river, is trapped by a dam and deposited on the bed of the reservoir. This silt can slowly fill up a reservoir, decreasing the amount of water which can be stored and used for electrical generation. The river downstream of the dam is also deprived of silt which fertilizes the river's flood-plain during high water periods.
Bacteria present in decaying vegetation can also change mercury, present in rocks underlying a reservoir, into a form which is soluble in water. The mercury accumulates in the bodies of fish and poses a health hazard to those who depend on these fish for food. The water quality of many reservoirs also poses a health hazard due to new forms of bacteria which grow in many of the hydro rivers. Therefore, run of the river type hydro plants generally have a smaller impact on the environment.
Different classifications of Hydroelectric power plants:
1) Depending upon Capacity to generate power:
Size unit size Installation
Micro upto 100 kW 100 kW
Mini 101 to 1000 kW 2000 kW
Small 1001 to 6000 kW 15000 kW
2) Depending on head:
Ultra low head: Below3 meters,
Low head : Less than 30 meters,
Medium head: Between 30 to 75 meters,
High head : Above 75 meters,
Selection of site for Hydro Power Plants:
1. Large quantity of water at a reasonable head should be available
2. The site should provide strong and high mountains on the two sides of the river reservoir with minimum gap for economical dam construction.
3. The rainfall should be sufficient to maintain desired water level in the reservoir throughout the year.
4. The catchments area for the reservoir to collect rainwater should be large.
5. There should not be any possibility of leakage of water in future.
6. The site should have firm rock for foundation.
Basic components of a hydroelectric power plant:
The basic and common components of a hydroelectric power plant are given below:
a) Diversion and intake
b) Desilting chamber
c) Water conducting system
d) Balancing reservoir
e) Surge tank (if necessary)
g) Power house: turbine, generator, protection and control equipment, dewatering, drainage system, auxiliary, power system, grounding, emergency and standby power system, lighting and ventilation
Tail race channel.
• Diversion structure:
The diversion structure provided should be simple in construction as well as economical. It should involve minimum maintenance. Depending upon the type of river bed the diversion structure may be of two-type viz. Boulder weir and Trench type weir. It is usually constructed in re-enforced concrete or masonry.
• Water conductor system:
Water conducting system is the very important component of hydro-power plant. The type of water conductor system depends on the site conditions and the materials available. The design of the water conduction system should ensure minimum head loss, adequate velocity of flow so that silt does not settle down. The material of construction should be such that loss due to seepage is also minimized. The most commonly used channel section is trapezoidal.
• Desalting tank :
Desilting tank is provided usually in the initial reaches of water conductor to trap the suspended silt load and pebbles etc ; so as to minimize the erosion damages to the turbine runner. The size of silt particles to be trapped for medium head power stations is from 0.2 to 0.5 mm and for high head it is from 0.1 to 0.2 mm. The depth of tank may be kept between 1.5 to 4 m. The horizontal flow velocity should not exceed 0.4 to 0.6 m/s.
Layout of hydro power plants:
The layout of hydro power plants envisages positioning of the various components of the plant to insure optimum use of available space for its efficient and convenient erection, operation and maintenance.
The power is positioned at the toe of the concrete masonry dam where the suitable rock to lay foundation is available each turbine is fed by a separate penstock which is embedded inside the non-overflow section of the dam. The power house separated from the dam expansion joints. With a view to minimize the fluctuations in the tail water level. Especially due to ski jump trajectory, the power go use maybe located further downstream and fed through a tunnel branching into individual penstocks near the powerhouse.
The powerhouse may be located at the underground, led through pressure shafts or pressure tunnels with surge tank. The power house may be located below the ski jump bucket itself. In the case of earth and rock fill dams, the power house is separated from the dam founded on suitable location and fed by penstock s generally taken out from a tunnel earlier used as diversion tunnel. Sometimes penstock may be laid in trench excavated below the dam buried in concrete.
Types of powerhouses:
Surfaces power house:
It is the best choice when sufficient area is available to accommodate the powerhouse within economical and convenient excavation. The there are three types of surface powerhouse depending on superstructure are outdoor, semi out door, indoor types
Semi-underground power house
The surface with setting of turbines below the minimum tail water level may involve substantial excavation and then backfilling with concrete to facilitate construction of high retaining walls for protections against floods. In this type vertical shafts are driven in rock for housing part of draft tube, spiral casings turbines and generators.
In this type of power plant which is incorporated in the body of spillway beneath the crest. The head water elevation is incorporated in the body of spillway beneath the crest. The head water elevation is maintained with the help of vertical lift crest gates. It has advantages of economy because separate powerhouse structure is avoided in this arrangement.
Hydroelectric power: How it works
So just how do we get electricity from water? Actually, hydroelectric and coal-fired power plants produce electricity in a similar way. In both cases a power source is used to turn a propeller-like piece called a turbine, which then turns a metal shaft in an electric generator which is the motor that produces electricity. A coal-fired power plant uses steam to turn the turbine blades; whereas a hydroelectric plant uses falling water to turn the turbine. The results are the same.
Take a look at this diagram (courtesy of the Tennessee Valley Authority) of a hydroelectric power plant to see the details:
The theory is to build a dam on a large river that has a large drop in elevation (there are not many hydroelectric plants in Kansas or Florida). The dam stores lots of water behind it in the reservoir. Near the bottom of the dam wall there is the water intake. Gravity causes it to fall through the penstock inside the dam. At the end of the penstock there is a turbine propeller, which is turned by the moving water. The shaft from the turbine goes up into the generator, which produces the power.
Power lines are connected to the generator that carry electricity to your home and mine. The water continues past the propeller through the tailrace into the river past the dam. By the way, it is not a good idea to be playing in the water right below a dam when water is released!
Impulse Turbines: The Pelton Wheel
The impulse turbine is very easy to understand. A nozzle transforms water under a high head into a powerful jet. The momentum of this jet is destroyed by striking the runner, which absorbs the resulting force. If the velocity of the water leaving the runner is nearly zero, all of the kinetic energy of the jet has been transformed into mechanical energy, so the efficiency is high.
A practical impulse turbine was invented by Lester A. Pelton (1829-1908) in California around 1870. There were high-pressure jets there used in placer mining, and a primitive turbine called the hurdy-gurdy, a mere rotating platform with vanes, had been used since the '60's, driven by such jets. Pelton also invented the split bucket, now universally used, in 1880. Pelton is a trade name for the products of the company he originated, but the term is now used generically for all similar impulse turbines.
Reaction Turbines: The Lawn Sprinkler
By contrast with the impulse turbine, reaction turbines are difficult to understand and analyze, especially the ones usually met with in practice. The modest lawn sprinkler comes to our aid, since it is both a reaction turbine, and easy to understand. It will be our introduction to reaction turbines. In the impulse turbine, the pressure change occurred in the nozzle, where pressure head was converted into kinetic energy. There was no pressure change in the runner, which had the sole duty of turning momentum change into torque. In the reaction turbine, the pressure change occurs in the runner itself at the same time that the force is exerted. The force still comes from rate of change of momentum, but not as obviously as in the impulse turbine.
The duty of the lawn sprinkler is to spread water; its energy output as a turbine serves only to move the sprinkler head. It is a descendant of Hero's aeolipile, the rotating globe with two bent jets that was quite a sensation in ancient times, though this worked with steam, not water. The lawn sprinkler seems directly descended from Rev. Robert Barker's proposed mill of 1740. He used two jets at right angles to the radius. A later improvement fed water from below to balance the weight of the runner and reduce friction. Barker's mills only appeared as models, and were never commercially offered. The flow of water in a lawn sprinkler is radially outward. Water under pressure is introduced at the centre, and jets of water that can cover the area necessary issue from the ends of the arms at zero gauge pressure. The pressure decrease occurs in the sprinkler arms. Though the water is projected at an angle to the radius, the water from an operating sprinkler moves almost along a radius. If you have such a sprinkler, by all means observe it in action. The jets do not impinge on a runner; in fact, they are leaving the runner, so their momentum is not converted into force as in the impulse turbine. The force on the runner must act in reaction to the creation of the momentum instead, which is, of course, the origin of the name of the reaction turbine.
Total annual cost of hydro power project:
Total annual cost of hydro power project consists of three elements:
1. Fixed charges it includes fixed charges on plant interest taxes insurances depreciation and obsolescence
2. Operation and maintenance cost
It includes operating cost, fuel cost, supervisory, labor maintenance, repair and miscellaneous expenses .the annual operation and maintenance cost is roughly proportional to the capacity of plant and the number of unit installed. The annual maintenance cost is usually taken as 1.5% of capital cost.
3. Transmission cost
It covers the cost of transmission facilities to connect the power generated to the system load.
"Low head" hydroelectric plants are power plants which generally utilize heads of only a few meters or less. Power plants of this type may utilize a low dam or weir to channel water, or no dam and simply use the "run of the river". Run of the river generating stations cannot store water, thus their electric output varies with seasonal flows of water in a river. A large volume of water must pass through a low head hydro plant's turbines in order to produce a useful amount of power. Hydro-electric facilities with a capacity of less than about 25 MW (1 MW = 1,000,000 Watts) are generally referred to as "small hydro", although hydro-electric technology is basically the same regardless of generating capacity.
"Pumped Storage" is another form of hydro-electric power. Pumped storage facilities use excess electrical system capacity, generally available at night, to pump water from one reservoir to another reservoir at a higher elevation. During periods of
Peak electrical demand, water from the higher reservoir is released through turbines to the lower reservoir, and electricity is produced (Figure 2). Although pumped storage sites are not net producers of electricity - it actually takes more electricity to pump the water up than is recovered when it is released - they are a valuable addition to electricity supply systems. Their value is in their ability to store electricity for use at a later time when peak demands are occurring. Storage is even more valuable if intermittent sources of electricity such as solar or wind are hooked into a system.
GE has a strong background in building large slow-speed horizontal synchronous machines of this type. In such applications, our experience focuses on air-gap stability, distortion control, unbalanced magnetic pull, ventilation, frame stiffness and seal design.
Designed for all types of vertical axis applications, conventional generators are installed in locations having a variety of head and flow conditions.
Straflo (Rim-Type) Generators
These types of generators are designed for straight-flow turbine system applications to harness tidal flow effectively for the production of electric power as well as for low head applications.
Motors for Pumped Storage
Many utilities lower system costs by adding pumped storage capacity. In addition to supplying low cost peaking capacity, pumped storage provides spinning reserve to the system. GE has supplied more than 50 units with a total capacity of over 7,400,000 kVA (7,000,000 kW).
Future Directions for the Hydroelectric Industry
The hydroelectric industry has been termed "mature" by some who charge that the technical and operational aspects of the industry have changed little in the past 60 years. Recent research initiatives counter this label by establishing new concepts for design and operation that show promise for the industry. A multi-year research project is presently testing new turbine designs and will recommend a final turbine blade configuration that will allow safe passage of more than 98 percent of the fish that are directed through the turbine. The DOE also recently identified more than 30 million kilowatts of untapped hydroelectric capacity that could be constructed with minimal environmental effects at existing dams that presently have no hydroelectric generating facilities, at existing hydroelectric projects with unused potential, and even at a number of sites without dams. Follow-up studies will assess the economic issues associated with this untapped hydroelectric resource. In addition, studies to estimate the hydroelectric potential of undeveloped, small capacity, dispersed sites that could supply electricity to adjacent areas without connecting to a regional electric transmission distribution system are proceeding. Preliminary results from these efforts have improved the visibility of hydroelectric power and provide indications that the hydroelectric power industry will be vibrant and important to the country throughout the next century.
The theoretical size of the worldwide hydro power is about four times greater than that which has been exploited at this time. The actual amount of electricity which will ever be generated by hydro power will be much less than the theoretical potential. This is due to the environmental concerns outlined above, and economic constraints. Much of the remaining hydro potential in the world exists in the developing countries of Africa and Asia. Harnessing this resource would require billions of dollars, because hydro-electric facilities generally have very high construction costs. In the past, the World Bank has spent billions of foreign aid dollars on huge hydro-electric projects in the third world. Opposition to hydro power from environmentalists and native people, as well as new environmental assessments at the World Bank will restrict the amount of money spent on hydro-electric power construction in the developing countries of the world.
In North-America and Europe, a large percentage of hydro power potential has already been developed. Public opposition to large hydro schemes will probably result in very little new development of big dams and reservoirs. Small scale and low head hydro capacity will probably increase in the future as research on low head turbines, and standardized turbine production, lowers the costs of hydro-electric power at sites with Companies have to dig up the Earth or drill wells to get the coal, oil, and gas
for nuclear power plants there are waste-disposal problems
Low heads. New computerized control systems and improved turbines may allow more electricity to be generated from existing facilities in the future. As well, many small hydro electric sites were abandoned in the 1950's and 60's when the price of oil and coal was very low, and their environmental impacts unrealized. Increased fuel prices in the future could result in these facilities being refurbished.
1. Renewable source of energy thereby saves scares fuel reserves.
2. Economical source of power.
3. Non-polluting and hence environment friendly.
4. Reliable energy source with approximately 90% availability.
5. Low generation cost compared with other energy sources.
6. Indigenous, inexhaustible, perpetual and renewable energy source.
7. Low operation and maintenance cost.
8. Possible to build power plant of high capacity.
9. Plant equipment is simple.
10. Socio-economic benefits being located usually remote areas.
11. Higher efficiency, 95%to98%.
12. Fuel is not burned so there is minimal pollution
13. Water to run the power plant is provided free by nature
14.It's renewable - rainfall renews the water in the reservoir, so the fuel is almost always there.
1. Susceptible to vagaries of nature such as draught.
2. Longer construction period and high initial cost.
3. Loss of large land due to reservoir.
4. Non-availability of suitable sites for the construction of dam.
5. Displacement of large population from reservoir area and rehabilitation.
6. Environmental aspect reservoirs verses river ecology.
7. High cost of transmission system for remote sites.
8. They use up valuable and limited natural resources
9. They can produce a lot of pollution
10.Companies have to dig up the Earth or drill wells to get the coal, oil, and gas
11.For nuclear power plants there are waste-disposal problems
CASE STUDY EXAMPLE
KOYNA DAM, KOYNA NAGAR.
Koyna Dam is one of the largest dams in Maharashtra, India. It is located in Koyna Nagar, nestled in the Western Ghats on the state highway between Chiplun and Karad, Maharashtra. The dam supplies water to western Maharashtra as well as cheap hydroelectric power to the neighbouring areas with a capacity of 1,920 MW. The Koyna project is actually composed of four dams, with the Koyna dam having the largest catchment area.
The catchment area dams the Koyna River and forms a huge lake — the Shivsagar Lake whose length is 50 kilometres. Completed in 1963, it is one of the largest civil engineering projects commissioned after Indian independence. The Koyna electricity project is run by the Maharashtra State Electricity Board. Most of the generators are located in excavated caves a kilometre deep, inside the heart of the surrounding hills.
The dam is blamed for the spate of earthquakes in the recent past. In 1967 a devastating earthquake almost razed the dam, with the dam developing major cracks. Geologists are still uncertain if the Koyna Dam is responsible for the spate in seismic activity.
Koyna Dam is one of the largest damsinMaharashtra,India. It is located in Koyna Nagar, nestled in the Western Ghats on the state highway between Chiplun and Karad,Maharashtra. The dam supplies water to western Maharashtra as well as cheap Hydro electric power to the neighbouring areas with a capacity of 1,920 MW. The Koyna project is actually composed of four dams, with the Koyna dam having the largest catchment area.
The catchment area dams the Koyna River and forms a huge lake — the Shivsagar Lake whose length is 50 kilometres. Completed in 1963, it is one of the largest civil engineering projects commissioned after Indian independence. The Koyna electricity project is run by theMaharashtra State Electricity Board. Most of the generators are located in excavated cavesa kilometre deep, inside the heart of the surrounding hills.
The dam is blamed for the spate of earthquake in the recent past. In 1967 a devastating earthquake almost razed the dam, with the dam developing major cracks. Geologists are still uncertain if the Koyna Dam is responsible for the spate in seismic activity.
o Gross storage: 98.78 TMC
o Live: 93.65 TMC
o Dead: 5.125 TMC
• Length: 1807.22 m
• Height: 85.35 m
• Year of completion: 1963
The Koyna Dam in Maharashtra
The resovoir behind the dam is 50 km in length.
Gravitational potential energy is stored in the water above the dam. Because of the great height of the water, it will arrive at the turbines at high pressure, which means that we can extract a great deal of energy from it. The water then flows away downriver as normal.
In mountainous countries such as Switzerland and New Zealand, hydro-electric power provides more than half of the country's energy needs.
An alternative is to build the station next to a fast-flowing river. However with this arrangement the flow of the water cannot be controlled, and water cannot be stored for later use.
Hydro-electric power stations can produce a great deal of power very cheaply.
When it was first built, the huge "Hoover Dam", on the Colorado river, supplied much of the electricity for the city of Las Vegas; however now Las Vegas has grown so much, the city gets most of its energy from other sources.
There's a good explanation of how hydro power works at
Although there are many suitable sites around the world, hydro-electric dams are very expensive to build. However, once the station is built, the water comes free of charge, and there is no waste or pollution.
1962 - 1963
Height of dam: 103 meters
Water storage: 2,797.400 km³
Volume of dam: 1,555.000 m³
Width of dam: 808 m
Slope at water side: 24:1
Length of 60 km
Lake tapping at Koyna
In a major technological breakthrough, the engineers of Koyna hydroelectric project today successfully performed the `lake tapping' operations at Shivaji Sagar reservoir of the dam. This operation or `lake tapping' using Norwegian technology will pave the way for the commissioning of the 1,000 MW stage four of the Koyna hydroelectric project, which would take total generation capacity to 1,920 MW by this year end.
Enthusiasm reigned on the banks of Shivaji Sagar reservoir, as people from neighbouring villages flocked the lake to witness the `lake tapping', the first of its kind in Asia.
Standing on the hilly terrain of the Koyna backwater, people were all ears to the announcements made by Shrikant Huddar, chief engineer of the Koyna Hydel project. And as Huddar instructed his subordinates to switch on the Konsbergs underwater cameras, the countdown for the million dollar blast had begun.
Beginning from 10, Huddar launched his countdown and just after he had announcedzero, within a fraction of a second after Chief Minister Narayan Rane had switched knobs activating the blastings, hundreds of people felt waves of tremors passing under their feet. Suddenly, a mushroom flower-like cloud of water erupted from Shivaji Sagar reservoir, and ripples after ripples hit the banks. Soon after the ripples hit the banks, villagers standing on the banks lifted the water from the reservoir and gently applied it to their foreheads. No one could hear the sound of the blasts, but they had certainly felt it deep inside their hearts. Certainly it was a moment to cherish.
Planned for 1000 MW power generation, the fourth stage of Koyna hydro electric project, envisages that the water will be tapped by piercing the Koyna reservoir, following which it will be carried through a 4.25 km-long head race tunnel into the underground power house. The water will be finally released in Kolkewadi Lake of stage III.
Speaking on the occasion after the blasts had been conducted, ministers Eknath Khadase,Anna Dange, Harshvardhan Patil, Deputy Chief Minister Gopinath Munde and Chief Minister Narayan Rane were all praise for the State irrigation department. While Irrigation Minister Khadse said such blasts could be replicated in future to generate more power, Rural Development Minister Anna Dange actually coined a couplet describing the event.Munde, who also holds the energy portfolio, expressed his gratitude to irrigation department for inviting him to witness the `lake tapping'. He also said the `event' was a major leap towards the State Government's dream to be self-sufficient in power generation.
``At present there is a shortage of nearly 1000-1500 MW of power in the State. This difference will be reduced after the Koyna fourth stage starts generating 1000 MW power,'' he said. Chief Minister was also all praise for the irrigation department and said this development would go a long way in providing excess power for the State.
The Koyana dam is at Koynanagar in Patan tehsil of Satara district in theSahyadaris. Its Shivaji Sagar reservoir has a capacity of 2,797 million cubic metres of water. The Rs 1,300 crore stage-four project is a World Bank funded project having commenced in 1992.
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|Author: Shyni 31 May 2008||Member Level: Gold Points : 2|
|Very Nice Information|
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