Introduction Hydro power refers to the energy of water. Hydel projects are a way to harness this energy t for use of mankind. In hydro projects, powerhouse of a hydroelectric development project is the place where the potential and kinetic energy of the water flowing through the water conducting system is transformed into mechanical energy of rotating turbines and which is then further converted to electrical energy by generators. Other equipments necessary are couplings to link the turbine rotation to generator and transformers and switching equipment to convey the electric power generated to the power distribution system. A control room is also essential in a powerhouse from where engineers can regulate the valves controlling water flow into the turbines or monitor the performance of each unit to the main power grid. Power houses that receive water from a reservoir through a penstock may be termed as power generating units detached from head works. Turbines are of different types like reaction or impulse-types. They may also be divided as with horizontal or vertical axes. This lesson discusses all the salient features of a hydropower generating station including the layout, structural components and mechanical parts. HydropowerHydropower is energy that comes from the force of moving water. Hydropower is a renewable energysource because it is replenished constantly by the fall and flow of snow and rainfall in the water cycle. As water flows through devices such as a water wheel or turbine, the kinetic (motion) energy of the water is converted to mechanical energy, which can be used to grind grain, drive a sawmill, pump water, or produce electricity.The primary way hydropower is used today in the United States is to produce electricity. In 1991, hydropower provided 10 percent of the nations electricity. Although a hydroelectric power plant is initially expensive to build, inthe long run, it is the cheapest way to produce electricity, primarily because the energy source, moving water, is free.Recently, many people have built smaller hydroelectric systems that produce only enough electricity to power a few homes.Renewable EnergyThere are many forms of renewable energy. Most of these renewable energies depend in one way or another on sunlight. Wind and hydroelectric power are the direct result of differential heating of the Earth's surface which leads to air moving about (wind) and precipitation forming as the air is lifted. Solar energy is the direct conversion of sunlight using panels or collectors. Biomass energy is stored sunlight contained in plants. Other renewable energies that do not depend on sunlight are geothermal energy, which is a result of radioactive decay in the crust combined with the original heat of accreting the Earth, and tidal energy, which is a conversion of gravitational energy.Hydroelectric energy.This form uses the gravitational potential of elevated water that was lifted from the oceans by sunlight. It is not strictly speaking renewable since all reservoirs eventually fill up and require very expensive excavation to become useful again. At this time, most of the available locations for hydroelectric dams are already used in the developed world. Hydroelectric PowerMoving water is a powerful entityresponsible for lighting entire cities, even countries. Thousands of years ago the Greeks used water wheels, which picked up water in buckets around a wheel. The water's weight caused the wheel to turn, converting kinetic energy into mechanical energy for grinding grain and pumping water. In the 1800s the water wheel was often used to power machines such as timber-cutting saws in European and American factories. More importantly, people realized that the force of water falling from a height would turn a turbine connected to a generator to produce electricity. Niagara Falls , a natural waterfall, powered the first hydroelectric plant in 1879.Man-made waterfallsdamswere constructedthroughout the 1900s in order to maximize this source of energy. Aside from a plant for electricity production, a hydropower facility consists of a water reservoir enclosed by a dam whose gates can open or close depending on how much water is needed to produce a particular amount of electricity. Once electricity is produced it is transported along huge transmission lines to an electric utility company. Today one-fifth of global electricity is generated by falling water.With over 2,000 facilities, the US is the second largest producer of hydropower worldwide, behind Canada . The dams that do not produce electricity are used for irrigation or flood control.There are several favorable features of hydropower.Anywhere rain falls, there will be rivers. If a particular section of river has the right terrain to form a reservoir, it may be suitable for dam construction. No fossil fuels are required to produce the electricity, and the earth's hydrologic cycle naturally replenishes the "fuel" supply.Therefore no pollution is released into the atmosphere and no waste that requires special containment is produced. Since "water is a naturally recurring domestic product and is not subject to the whims of foreign suppliers," there is no worry of unstable prices, transportation issues, production strikes, or other national security issues.Hydropower is very convenientbecause it can respond quickly to fluctuations in demand. A dam's gates can be opened or closed on command, depending on daily use or gradual economic growth in the community. The production of hydroelectricity is often slowed in the nighttime when people use less energy. When a facility is functioning, no water is wasted or released in an altered state; it simply returns unharmed to continue the hydrologic cycle. The reservoir of water resulting from dam construction, which is essentially stored energy, can support fisheries and preserves, and provide various forms of water-based recreation for locals and tourists. Land owned by the hydroelectric company is often open to the public for hiking, hunting, and skiing. Therefore, "hydropower reservoirs contribute to local economies. A study of one medium-sized hydropower project in Wisconsin showed that the recreational value to residents and visitors exceeded $6.5 million annually." Not to mention the economic stimulation provided by employment.Hydroelectric poweris also very efficient and inexpensive."Modern hydro turbines can convert as much as 90% of the available energy into electricity. The best fossil fuel plants are only about 50% efficient. In the US , hydropower is produced for an average of 0.7 cents per kilowatt-hour (kWh). This is about one-third the cost of using fossil fuel or nuclear and one-sixth the cost of using natural gas," as long as the costs for removing the dam and the silt it traps are not included. Efficiency could be further increased by refurbishing hydroelectric equipment. An improvement of only 1% would supply electricity to an additional 300,000 households.Hydropower has become"the leading source of renewable energy. It provides more than 97% of all electricity generated by renewable sources worldwide. Other sources including solar, geothermal, wind, and biomass account for less than 3% of renewable electricity production." In the US , 81% of the electricity produced by renewable sources comes from hydropower. "Worldwide, about 20% of all electricity is generated by hydropower." Some regions depend on it more than others. For example, 75% of the electricity produced in New Zealand and over 99% of the electricity produced in Norway come from hydropower. For information on making a hydro power system refer our page "Producing Hydro"The use of hydropower"prevents the burning of 22 billion gallons of oil or 120 million tons of coal each year." In other words, "the carbon emissions avoided by the nation's hydroelectric industry are the equivalent of an additional 67 million passenger cars on the road 50 percent more than there are currently." The advantages of hydropower are therefore convincing, but there are some serious drawbacks that are causing people to reconsider its overall benefit.Since the most feasible sites for damsare in hilly or mountainous areas, the faults that often created the topography pose a great danger to the dams and therefore the land below them for thousands of years after they have become useless for generating power. In fact, dam failures do occur regularly due to these terrain conditions, and the effects are devastating.When a new dam's reservoir floods the countryside,people who live in the area have to move and relinquish their former lifestyles in order to make way for the project. This is very stressful and often controversial, especially if a community has maintained a particular way of life on the same land for generations. Such is the case in Chile, where the indigenous Pehuenche "are currently fighting construction of the 570MW, US $500,000,000 Ralco Dam on the Biobo River Eight families continue to refuse to negotiate land exchanges with Endesa [the utility company], and wish to remain on their lands." If the project succeeds, a 13-square-mile reservoir would flood the land and force 600 people out of their homes, 400 of whom are Pehuenche "whose ancestral home is the upper Biobo." A total of five dams have been planned, which "would force the relocation of 1,000 Pehuenches, 20% of the survivors of this ancient culture."The construction of a damnot only affects the people nearby, it can severely alter a river's natural functions. According to American Rivers, a conservation organization, "by diverting water for power, dams remove water needed for healthy in-stream ecosystems. Stretches below dams are often completely de-watered." This may not seem like a significant problem until animal species are studied. Birds that have migrated to a specific riparian environment for generations no longer have enough insects on which to prey when the water level drops. If they have few migration alternatives, that could mean the endangerment of species that once flourished. Fish species such as salmon "depend on steady flows to flush them down river early in their life and guide them upstream years later to spawn. Stagnant reservoir pools disorient migrating fish and significantly increase the duration of their migration." Native populations of fish may decrease or disappear altogether due to temperature changes caused by dams. Slower water flow means warmer temperatures, and bottom-release of cold water means cooler temperatures. Several of hydropower's disadvantages focus on fish. It is easy to forget how important fish and other aquatic life are, some of which reside at the bottom of the food chain.The environmental changes caused by hydroelectric projectsmay be obvious to the local biologist, but elude the average person. Most people will more readily notice a smoggy haze developing in an area where a coal plant is operating than a smaller population of a particular bird species where a hydropower facility functions. Such oversights lead people to believe that nothing is wrong.Hydroelectric companies and organizationsoften emphasize their "clean" manufacture of electricity and neglect to mention the long-term environmental hazards. "Dams hold back silt, debris, and nutrients." Silt collects behind the dam on the river bottom, accumulating heavy metals and other pollutants. Eventually this renders the dam inoperable, leaving the mess for future generations, who will either have to remove the collected debris or live with a potentially catastrophic mudflow poised to inundate the area below the dam.UTILITY1 Hydroelectricity is a renewable energy source.. Hydroelectricity uses the energy of running water, without reducing its quantity, to produce electricity. Therefore, all hydroelectric developments, of small or large size, whether run of the river or of accumulated storage, fit the concept of renewable energy.2. Hydroelectricity makes it feasible to utilize other renewable sources.Hydroelectric power plants with accumulation reservoirs offer incomparable operational flexibility, since they can immediately respond to fluctuations in the demand for electricity. The flexibility and storage capacity of hydroelectric power plants make them more efficient and economical in supporting the use of intermittent sources of renewable energy, such as solar energy or Aeolian energy.3. Hydroelectricity promotes guaranteed energy and price stability.River water is a domestic resource which, contrary to fuel or natural gas, is not subject to market fluctuations. In addition to this, it is the only large renewable source of electricity and its cost-benefit ratio, efficiency, flexibility and reliability assist in optimizing the use of thermal power plants.4. Hydroelectricity contributes to the storage of drinking water.Hydroelectric power plant reservoirs collect rainwater, which can then be used for consumption or for irrigation. In storing water, they protect the water tables against depletion and reduce our vulnerability to floods and droughts.5. Hydroelectricity increases the stability and reliability of electricity systems.The operation of electricity systems depends on rapid and flexible generation sources to meet peak demands, maintain the system voltage levels, and quickly re-establish supply after a blackout. Energy generated by hydroelectric installations can be injected into the electricity system faster than that of any other energy source. The capacity of hydroelectric systems to reach maximum production from zero in a rapid and foreseeable manner makes them exceptionally appropriate for addressing alterations in the consumption and providing ancillary services to the electricity system, thus maintaining the balance between the electricity supply and demand.6. Hydroelectricity helps fight climate changes.The hydroelectric life cycle produces very small amounts of greenhouse gases (GHG). In emitting less GHG than power plants driven by gas, coal or oil, hydroelectricity can help retard global warming. Although only 33% of the available hydroelectric potential has been developed, today hydroelectricity prevents the emission of GHG corresponding to the burning of 4.4 million barrels of petroleum per day worldwide.7. Hydroelectricity improves the air we breathe.Hydroelectric power plants don't release pollutants into the air. They very frequently substitute the generation from fossil fuels, thus reducing acid rain and smog. In addition to this, hydroelectric developments don't generate toxic by-products.8. Hydroelectricity offers a significant contribution to development.Hydroelectric installations bring electricity, highways, industry and commerce to communities, thus developing the economy, expanding access to health and education, and improving the quality of life. Hydroelectricity is a technology that has been known and proven for more than a century. Its impacts are well understood and manageable through measures for mitigating and compensating the damages. It offers a vast potential and is available where development is most necessary.9. Hydroelectricity means clean and cheap energy for today and for tomorrow.With an average lifetime of 50 to 100 years, hydroelectric developments are long-term investments that can benefit various generations. They can be easily upgraded to incorporate more recent technologies and have very low operating and maintenance costs.10. Hydroelectricity is a fundamental instrument for sustainable development.Hydroelectric enterprises that are developed and operated in a manner that is economically viable, environmentally sensible and socially responsible represent the best concept of sustainable development. That means, "development that today addresses people's needs without compromising the capacity of future generations for addressing their own needs" (World Commission on the Environment and Development, 1987).

Collection and distribution system of waterIntakes / Intake StructuresIt is the structure built in the body of water to draw water from the source.Source may be canal, river, dam. It is built as an integral part of the source.Function of Intakes The main function of intakes is to provide highest quality of water from source. To protect pipes and pumps from damaging or clogging by wave action, floating bodies and submerged marine.The intakes consists of opening, strainer or grating through which water enters and conduit conveying the water usually by gravity to a well.Designing of intake structuresThe following points must be considered while designing and locating the intake structures. The source of supply must be considered including the wide fluctuation in water level. Intake surroundings should be considered. For example depth of water around intake. Characteristics of bottom, navigation requirements, the effect of floods and storm to the structure and scouring in the bottom are also considered. The location with respect to the sources of pollution is also considered. The frequency of floating materials such as ice, vegetation is considered. Intake capacity must be large enough to meet the requirement of design discharge.CLASSIFICATION (TYPES) OF DAMSBASED ON PURPOSE1. STORAGE DAM OR IMPOUNDING DAM2. DETENTION DAM3. DIVERSION DAM4. COFFER DAM5. DEBRIS DAM1.STORAGE DAM OR IMPOUNDING DAMIt is constructed to create a reservoir to store water during periods when there is huge flow in the river (in excess of demand) for utilisation later during periods of low flow (demand exceeds flow in the river). Water stored in the reservoir is used for irrigation, power generation, water supply etc. By suitable operation, it can also serve as a detention dam.2.DETENTION DAMIt is primarily constructed to temporarily detain all or part of the flood water in a river and to gradually release the stored water later at controlled rates so that the entire region on the downstream side of the dam is protected from possible damage due to floods. It may also be used as a storage dam.3. DIVERSION DAMIt is constructed to divert part of or all the water from a river into a conduit or a channel. For diverting water from a river into an irrigation canal, mostly a diversion weir is constructed across the river.4. COFFER DAMIt is a temporary dam constructed to exclude water from a specific area. It is constructed on the u/s side of the site where a dam is to be constructed so that the site is dry. In this case, it behaves like a diversion dam.5.DEBRIS DAMIt is constructed to catch and retain debris flowing in a river.

Figure: Dam ConstructionBASED ON HYDRAULIC DESIGN1. OVERFLOW DAM OR OVERFALL DAMIt is constructed with a crest to permit overflow of surplus water that cannot be retained in the reservoir. Generally dams are not designed as overflow dams for its entire length. Diversion weirs of small height may be designed to permit overflow over its entire length.2.NON-OVERFLOW DAMIt is constructed such that water is not allowed to overflow over its crest.In most cases, dams are so designed that part of its length is designed as an overflow dam (this part is called the spillway) while the rest of its length is designed as a non-overflow dam. In some cases, these two sections are not combined.BASED ON MATERIAL OF CONSTRUCTION1. RIGID DAMIt is constructed with rigid material such as stone, masonry, concrete, steel, or timber. Steel dams (steel plates supported on inclined struts) and timber dams (wooden planks supported on a wooden framework) are constructed only for small heights (rarely).2.NON-RIGID DAM (EMBANKMENT DAMS)It is constructed with non-rigid material such as earth, tailings, rockfill etc. Earthen dam gravel, sand, silt, clay etc Tailings dam waste or refuse obtained from mines Rockfill dam rock material supporting a water tight material on the u/s face Rockfill composite dam Rockfill on the d/s side and earth fill on the u/s side Earthen dams are provided with a stone masonry or concrete overflow (spillway) section. Such dams are called composite dams. In some cases, part of the length of the dam is constructed as earth dam and the rest (excluding the spillway) as a masonry dam. Such dams are called masonry cum earthen dams.BASED ON STRUCTURAL BEHAVIOUR GRAVITY DAM ARCH DAM BUTTRESS DAM EMBANKMENT DAMGRAVITY DAMIt is a masonry or concrete dam which resists the forces acting on it by its own weight. Its c/s is approximately triangular in shape.Straight gravity dam A gravity dam that is straight in plan.Curved gravity plan A gravity dam that is curved in plan.Curved gravity dam (Arch gravity dam) It resists the forces acting on it by combined gravity action (its own weight) and arch action.Solid gravity dam Its body consists of a solid mass of masonry or concreteHollow gravity dam It has hollow spaces within its body.Most gravity dams are straight solid gravity dams.Concrete Gravity Dams Weight holds dam in place Lots of concrete (expensive)

These dams are heavy and massive wall-like structures of concrete in which the whole weight acts vertically downwards

As the entire load is transmitted on the small area of foundation, such dams are constructed where rocks are competent and stable. Bhakra Damis the highest Concrete Gravity dam in Asia and the second highest in the world. Bhakra Damis across river Sutlej in Himachal Pradesh The construction of this project was started in the year 1948 and was completed in 1963 . It is 740 ft. high above the deepest foundation as straight concrete dam being more than three times the height of QutabMinar. Length at top 518.16m (1700 feet); width at base 190.5m (625 feet), and at the top is 9.14m (30 feet) Bhakra Dam is the highest Concrete Gravity damin Asia and Second Highest in the world.

2. ARCH DAMIt is a curved masonry or concrete dam, convex upstream, which resists the forces acting on it by arch action.The only arch dam in India Idukki dam (double curvature in plan) concrete arch damArch Dams Arch shape gives strength Less material (cheaper) Narrow sites Need strong abutments

These type of dams are concrete or masonry dams which are curved or convex upstream in plan This shape helps to transmit the major part of the water load to the abutments Arch dams are built across narrow, deep river gorges, but now in recent years they have been considered even for little wider valleys.

Good for narrow, rocky locations. They are curved and the natural shape of the arch holds back the water in the reservoir. Arch dams, like the El Atazar Dam in Spain, are thin and require less material than any other type of dam.

3. BUTTRESS DAMIt consists of water retaining sloping membrane or deck on the u/s which is supported by a series of buttresses. These buttresses are in the form of equally spaced triangular masonry or reinforced concrete walls or counterforts. The sloping membrane is usually a reinforced concrete slab. In some cases, the u/s slab is replaced by multiple arches supported on buttresses (multiple arch buttress dam) or by flaring the u/s edge of the buttresses to span the distance between the buttresses (bulkhead buttress dam or massive head buttress dam). In general, the structural behaviour of a buttress dam is similar to that of a gravity dam.Buttress Dams Face is held up by a series of supports Flat or curved face

Buttress Dam Is a gravity dam reinforced by structural supports Buttress a support that transmits a force from a roof or wall to another supporting structure This type of structure can be considered even if the foundation rocks are little weaker.

4. EMBANKMENT DAMIt is a non-rigid dam which resists the forces acting on it by its shear strength and to some extent also by its own weight (gravity). Its structural behaviour is in many ways different from that of a gravity dam. Earth or rock Weight resists flow of water

Earth Dams They are trapezoidal in shape. Earth dams are constructed where the foundation or the underlying material or rocks are weak to support the masonry dam or where the suitable competent rocks are at greater depth. Earthen dams are relatively smaller in height and broad at the base. They are mainly built with clay, sand and gravel, hence they are also known as Earth fill dam or Rock fill dam.HEADRACE TUNNEL (HRT)There are different definitions for headrace tunnel (HRT) used at different scenarios.Headrace tunnel takes water from connecting channels and convey it to the fore bay or directly to the penstock provided with surge shaftdepending upon the project and site requirements some times also known as power tunnels. OrA tunnel provided betweenDe-silting chamber or Fore-bay to the Surge ShaftorA structure that carries water from intake to the power house for power generation

Types on the basis of flowOn the basis of flow headrace tunnels can be divided into the following main types Pressure flow tunnels Gravity flow tunnels

Types on the basis of shapeOn the basis of shape tunnels can be divided in to the following main types Semicircular Circular Elliptical Horseshoe and Square with an arched ceilingNow a days horseshoe tunnels are widely used for hydropower project because of its efficiency and easy construction.

Different types of surge tanks used in hydro power plantsA surge tank is a small reservoir or tank in which the water level rises or falls to reduce the pressure swing at the turbine inlet which are transmitted in a fully closed circuit. In a summarized way the surge tank in hydro power plant serves the following purposes. The main purpose to reduce the distance between surface and turbine thereby reducing the water hamming effect on penstock and also to protect the upstream tunnel from the high pressure rises. It serves as a supply tank to the turbine when the water in the pipe is accelerating during increased load conditions and as a storage tank when the water is decelerating during load rejections or reduced load conditions.Types of surge tanks used in hydro power plants:The following are the general types of surge tanks: Simple surge tankInclined surge tankGallery type surge tankRestricted orifice surge tankDifferential surge tank

Powerhouse1. The main powerhouse structure, housing the generating units and having either separate or combined generator and turbine room,2. Erection bay, and3. Service areas.

1. Main powerhouse structureThegenerator roomis the main feature of the powerhouse about which other areas are grouped.It is divided intobaysorblockswith one generating unit normally located in each block. The width (upstream-downstream dimensions) of thegeneratorroom for the indoor type should provide for a passageway or aisle with a minimum width of 10 feet between the generators and one powerhouse wall.Waddamana Power Station A generator room

Theheight of the generator roomis governed by the maximum clearance height required for dismantling and/or moving major items of equipment, such as parts of generators and turbines; location of the crane rails due to erection bay requirements; the crane clearance requirements; and the type of roof framing.All clearances should be adequateto provide convenient working spacebut should not be excessive.The elevation of the turbine room floor should be established so as to provide a minimum requirement of 3 feet of concrete over a steel spiral case, or a minimum roof thickness of4 feetfor a semi spiral concrete case.In establishing thedistance betweenthe generator and turbine room floors, if they are notcombined, the size of equipment to be handled in the turbine room, the head room between platforms in theturbine pit, and the generator room floor constructionshould be considered.2. Erection bayIn general,the erection bayshould be located atthe end of the generator room, preferably at the same floor elevation and with a length equal to at least one generator bay.The above length should be increased sufficientlyto provide adequate working roomif railroad access is provided into the erection bay at right angles to the axis of the powerhouse.However, no additional space should be required if the access railroad enters from the end of the powerhouse.Elevation of the crane rail in hydropwer plant

3. Service areaService areas include:offices, control and testing rooms, storage rooms, maintenance shop, auxiliary equipment rooms, and other rooms for specialuses.Ontario Hydro Niagara Falls Power Plant Control Room

Tail Race and Draft TubeThe channel into which the turbine discharges in case of impulse wheel and through draft tube in case of reaction turbine is called a tail race. The suction pipe or draft tube is nothing but an airtight tube fitted to all reaction turbines on the outlet side. It extends from the discharge end of the turbine runner to about 0.5 metres below the surface of the tail water level. The straight draft tube is generally given a flare of 4 to 6 degrees to gradually reduce the velocity of water.The suction action of the water in this tube has same effect on the runner as an equivalent head so that the turbine develops the same power as if it were placed at the surface of the tail water. The tail race of the impulse wheel is commonly an approximately rectangular passage, running from a point under the wheel to a point outside the power house foundations where it enters the exit channel or the river. Because of the small discharge of the impulse wheel, as well as higher allowable velocity, the tail race passage is much smaller than that of the reaction turbine.