Shivajirao Jondhale College Ofengineering (Dombivali)
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Shivajirao Jondhale College OfEngineering (Dombivali) BE Mechanical VII Semester Power Plant Engineering Case Study title: Hydroelectric Power Generation Group members: Name Roll No. 1. Nishikant V. Kulkarni 25 2. Rahul A. Mane 30 What is hydroelectric power generation? Hydroelectric power generation is the term referring to generation of electricityby hydropower i.e. the production of electrical power through the use of the gravitational force of falling or flowing water.Most hydroelectric stations use either the natural drop of a river, such as a waterfall or rapids, or a dam is built across a river to raise the water level, and provide the drop needed to create a driving force. It is the most widely used form of renewable energy, accounting for 16 percent of global electricity generation – 3,427 terawatt-hours of electricity production in 2010 and is expected to increase about 3.1% each year for the next 25 years. Hydropower is produced in 150 countries, with the Asia-Pacific region generating 32 percent of global hydropower in 2010. China is the largest hydroelectricity producer, with 721 terawatt-hours of production in 2010, representing around 17 percent of domestic electricity use. History of hydroelectric power generation: Hydropower has been used since ancient times to grind flour and perform other tasks. In 1878 the world's first hydroelectric power scheme was developed at Cragside in Northumberland, England by William George Armstrong. It was used to power a single arc lamp in his art gallery. The old Schoelkopf Power Station No. 1 near Niagara Falls in the U.S. side began to produce electricity in 1881. The firstEdison hydroelectric power plant, the Vulcan Street Plant, began operating September 30, 1882, in Appleton, Wisconsin, with an output of about 12.5 kilowatts. At the beginning of the 20th century, many small hydroelectric power plants were being constructed by commercial companies in mountains near metropolitan areas. Hydroelectric power plants continued to become larger throughout the 20th century. The Three Gorges Dam in China produces 22,500 MW. The United States currently has over 2,000 hydroelectric power plants that supply 6.4% of its total electrical production output, which is 49% of its renewable electricity. Components of Hydropower plant: 1. Intake Arrangement- Storage Reservoir Spillway Forebay Trash Rack Gates 2. Water Conductor System - Power Channel/Duct Water Tunnel Surge Tank Drop Shaft Pressure Shaft Penstock with Penstock Protection Valve (Butterfly Valve) 3. Power House - A. Mechanical Component: Distributor / Spiral Casing Spherical Valve or Main Inlet Valve Turbine B. Electrical Component: Generator Transformer Switchyard Transmission Line C. Powerhouse Auxiliaries: Cooling water system Compressed Air System De-watering System Drainage System Air Conditioning System Control & Monitoring System Fire Protection System Of these the major components are described below: 1. Reservoir: A reservoir is a natural or artificial lake, storage pond or impoundment from a dam which is used to store water. Reservoirs may be created in river valleys by the construction of a dam or may be built by excavation in the ground or by conventional construction techniques such as brickwork or cast concrete. 2. Spillway: A spillway is a structure used to provide the controlled release of flows from a dam or levee into a downstream area, typically being the river that was dammed. Spillways release floods so that the water does not overtop and damage or even destroy the dam. 3. Forebay: A forebay is an artificial pool of water in front of a larger body of water. They are used in flood control to act as a buffer during flooding or storm surges, impounding water and releasing in a controlled way into the larger water body. 4. Trash rack: A trash rack is a wooden or metal structure, frequently supported by masonry that prevents water-borne debris from entering the intake of a dam. This protects water wheels, penstocks, and sluice gates from destruction during floods. 5. Water tunnel: It is a tunnel which supplies water to penstock. It is either circular or horseshoe shaped in construction. 6. Surge tank: A surge tank (or surge drum) is a standpipe or storage reservoir at the downstream end of a closed aqueduct or feeder or a dam or barrage pipe to absorb sudden rises of pressure, as well as to quickly provide extra water during a brief drop in pressure. 7. Penstock: A penstock is a sluice or gate or intake structure that controls water flow, or an enclosed pipe that delivers water to hydraulic turbines and sewerage systems. 8. Hydraulic turbine: A water turbine is a rotary engine that takes energy from moving water. It makes use of water’s kinetic energy or pressure energy or both to generate power. Various turbines working under a wide range of heads with different disposition of shafts are available. 9. Electric generator: An electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric current to flow through an external circuit. Working of hydroelectric power plant: The dam stores a lot of water behind it in the reservoir. This storage of water has tremendous potential energy. 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 carries electricity to industrial and residential areas. The water continues past the propeller through the tailrace into the river past the dam. A hydraulic turbine converts the energy of flowing water into mechanical energy. A hydroelectric generator converts this mechanical energy into electricity. The operation of a generator is based on the principles discovered by Faraday. He found that when a magnet is moved past a conductor, it causes electricity to flow. In a large generator, electromagnets are made by circulating direct current through loops of wire wound around stacks of magnetic steel laminations. These are called field poles, and are mounted on the perimeter of the rotor. The rotor is attached to the turbine shaft, and rotates at a fixed speed. When the rotor turns, it causes the field poles (the electromagnets) to move past the conductors mounted in the stator. This, in turn, causes electricity to flow and a voltage to develop at the generator output terminals. The electricity produced is transmitted to residential and industrial areas through transmission lines. Case study on hydroelectric power plant Koynahydrolelectric power plant The Koyna Hydroelectric Project is the largest completed hydroelectric power plant of India. It is a complex project consisting of total four dams with the largest Dam built on Koyna River known as Koyna Dam hence the name Koyna Hydroelectric project. The project uses potential of water from Koyna River. The project site is situated in Satara district near Patan. The village Helwak near the dam was later known as Koynanagar. The total Installed capacity of the project is 1,960 MW. The project consists of 4 stages of power generation. All the generators are located in the underground Powerhouses excavated deep inside the surrounding mountains of the Western Ghats. A dam foot powerhouse also contributes to the electricity generation. Due to the project's electricity generating potential the Koyna River is considered as thelife line of Maharashtra The project gets advantage of the height of Western Ghats also known asSahyadri. Thus very large hydraulic head is available in a very short distance toward the Arabian Sea. History: The Koyna River’s hydro-electric potential was understood in a general survey of hydro- electric possibilities in India in the first decade of 20th century. After the first World War, a hydro-electric project on the Koyna river was investigated by the Tata Group. The 1928 financial crisis caused the project to shelve. However after the independence of India, it was taken over by Government of Maharashtra. Then In 1951 Koyna dam division was started to look into the project. The project got approved in 1953 and work commenced in early 1954. The Project: The project is composed of four dams with major contributors Koyna Dam andKolkewadi Dam. The water from Shivasagar reservoir formed by Koyna dam is used for electricity generation in 1st, 2nd and 4th stages. This water is drawn from head race tunnels situated underground below the reservoir. Then it travels through vertical pressure shafts to the Underground Powerhouses. The discharged water from these stages is collected and stored in Kolkewadi Dam situated near villageAlore at a lower level than Koyna dam. The water is drawn from penstocks of Kolkewadi dam to an underground power station in the 3rd stage and then discharged to the Arabian sea. The electricity generated in all the stages is delivered to the main electrical grid. The project is run by Maharashtra State Electricity Board. Stage Installed capacity 1st stage 4 x 70 MW = 280 MW Stage Installed capacity 2nd stage 4 x 80 MW = 320 MW Dam foot Powerhouse 2 x 20 MW = 40 MW 3rd stage 4 x 80 MW = 320 MW 4th stage 4 x 250 MW = 1,000 MW Total 1,960 MW Stage I and II The first stage of the project was approved in late 1953 and construction began in early 1954. Initially a two-stage construction was conceived. But the total generation capacity of the two stages was too large for load forecasts of that time. So a time lag of more than 10 years was proposed between the two stages. Within two years thereafter, it came to be noticed that the 10 years time tag between these two stages will not be affordable and to cope up with the power requirements, the two stages should be merged and both the stages should be constructed simultaneously.