What is Hydroelectric Power Station & How it Works?
As we know that hydro means water, So the generating station where the water potential energy is utilized at a high level for the generation of electrical power is known as a hydroelectric power station. Hydro-electric power stations are usually built on the hilly location where the dams can be built easily and a large amount of water can be stored. In a hydroelectric power station, water head is created by constructed a dam across a lake or river. Hydro-electric power station popularity is increasing day by day due to the reserves of fuel (coal and oil) are depleting gradually. Hydro-electric power station added importance for flood control, storage of water for irrigation and water for drinking purposes.
Site selection and Factors Affecting the Location of Dam of Hydroelectric Power Plants
Before discussing the hydro-electric power stations we need to know the where we should locate our hydro-electric power station. What factors we should keep in our mind while building a hydro-electric power station. So we going to discuss few factors which are considered the most important.
Availability of water:
Since water is the primary requirement of the hydro-electric power station. Water availability must be in huge quantity. Such power plants must be built at a place where the water is available in a huge amount at a good head as well.
Storage of water:
There is wide variation in water availability from rivers throughout the year. This makes it necessary to store the available water. In order to store water for constant generation of electrical power, we must build dams. In certain days of the year, the water quantity decreases up to a low level which can affect the generation of electrical power as well.
Cost and type of land:
Another most important point is the initial cost and type of land. The land on which the powerhouse is going to be built must be at a reasonable price and secondly the bearing capacity of the land. The ground should be good to withstand the weight of heavy types of equipment.
The site selected for the hydro-electric plant must be accessible on transport facility. So that heavy machinery could be easily transported to the station.
Constituents of a hydro-electric plant
The constituents of hydro-electric power station can be divided mainly into three categories 1) hydraulic structure 2) water turbines 3) electrical equipment. We are going to discuss each item in turn.
Hydraulic structure of hydro-electric power station includes a dam, spillways, head works, surge tank, and penstock.
- Dam: The place where the water can be store and creates water head. Dams are mostly built of concrete or stone masonry, the type and arrangement depend on the location of the site. The type of dam also depends on the foundation condition, local material, and transportation available. The dam should not be very expensive.
- Spillways: There are times when the water head exceeds the storage capacity of the reservoir. Such situation can affect the whole process. In order to discharge the surplus water from the storage area into the river downstream. A concrete path constructed alongside the dam called spillways is used to drain the excess water.
- Headworks: The headworks consist of the diversion structures at the head of an intake. it controls the flow of water into and through headworks should be as smooth as possible to avoid heat loss.
- Surge tank: When the open conduit is used to carry water to the turbine it requires no protection but when the closed conduit is used it needs protection to limit the pressure in the conduit. For this reason, a surge tank is used for closed conduit. The surge tank is a small reservoir or tank in which water level rises or falls to reduce the pressure.
5) Penstock: Penstocks are open or closed conduits which carry water to the turbines. They are mostly made of reinforced concrete or steel.
- Water turbines: Those devices which convert water’s kinetic energy into mechanical energy are called water turbines. There are so many turbines used to generate mechanical effort.1) impulse turbines 2) reaction turbines. Reaction turbine has two types 1) Francis turbines 2) Kaplan turbines
- Electrical equipment: Every power station consists of different electrical types of equipment. There are so many types of equipment can be used for example alternator, exciter, Dc batteries, relays, circuit breakers, measuring devices, controlling devices, electrical motors etc.
A schematic arrangement of hydro-electric power station & its operation:
Although a hydro-electric power station simple involves the conservation of hydraulic energy into electrical energy. So it needs the equipment and constituents must be in proper order and working efficiently. The dam is constructed across the river where the catchment area stores the water to provide a sufficient water head. The penstock is connected to the dam for carrying the water. Turbine is connected at the far end of the penstock. The turbine shaft is coupled with alternator shaft which moves at synchronized speed after the waterfall on the turbine.
When a certain of water head is available on the dam. That water with some potential energy is carried through the penstock to the blades of turbines. Where the kinetic energy of the water is utilized and converted into the mechanical energy by the movement of the shaft. The turbine shaft is coupled with the alternator shaft both moves at synchronized speed. The alternator shaft moves in the magnetic field where the magnetic flux is linked with the stationary coils and induced EMF is produced. Here the mechanical energy is converted into electrical energy.