HydroElectric Power Station

Energy is required for the overall progress. The natural resources of any country may be large but they can only be turn into wealth  if they are developed, used and exchanged for other goods. This cannot be achieved without energy. The hydro sources are used to generate electrical energy where water resources are available in large quantity.

Adam Beck Complex

A generating station which utilizes  the potential energy of water at a high level for the generation of electrical energy is known as hydroelectric power station. The energy of water utilized for hydroelectric power generation may be kinetic or potential. Kinetic energy of water is its energy in motion and is a function of mass and velocity while potential energy is a function of the difference in level of water is between two points. In either case the availability of water is a basic requirement. For this purpose water collected in natural lakes and reservoirs at high altitudes may be made use of or water may be artificially stored by constructing dams across flowing streams. Hydro power is considered to be a renewable energy source because it uses the continuous flow of water to rotate the turbine. 

Working 

Layout of Hydroelectric Power Station

In hydroelectric power generation, the water either stored in dam or flowing is made to fall on the turbine blades. The kinetic or potential energy of water rotates the turbine blade. The turbine is coupled with alternator or DC generator. The kinetic or potential energy of water is converted into mechanical energy. We know the basic law that mechanical energy can be converted into electrical energy. Implicating this law the mechanical energy from turbine is converted into electrical energy by the alternator. The generated electrical energy is fed to the transformer and busbar section of the power plant. Then this is stepped up and transmitted to substations via transmission lines. This is the most basic( conversion of some form of energy into mechanical energy and then its converted into electrical energy by alternator/generator) of any power plant either its nuclear/thermal or hydro, etc.

Main function or selection criterion for erecting hydroelectric power plant

1. Quantity of water available :- Water is the primary requirement of hydroelectric power plant and the availability of huge amounts of water has the most important and greater impact in the generation of electric power. The availability of water can be estimated by using various method, for example by measuring the stream flow over a period as long as possible. By collecting and analysing the previous records of rainfall and minimum and maximum quantity of water available during the year. The losses which may occur  due to evaporation and percolation  is calculated and the net volume of water available for power generation can be determined.
2. Storage of Water :- We know that the rain does not fall all the time throughout the year (fun fact). So its necessary to store the water by building a dam in order to ensure the availability of water throughout the year for power generation.Storing water has many advantages. The storage helps in equalizing the flow of water so that any excess quantity of water at a certain period of the year can be made available in times of very low flow in the river.
3. Head of Water :-Availability of head of water has considerable effect on the cost and economy of the power generation. The topography of the area selected for installing the power station is responsible for the available water head.
4. Cost and type of land :- The bearing capacity of the ground should be adequate to withstand the weight of heavy equipment to be installed. The cost of land available for power plant must be available at reasonable cost. And last but not least the selected should be away from earthquake centers.
5. Near to load centers :- Owing to minimize the transmission cost the site selected for hydroelectric power station should be located near to load centers. 
6. Transportation facility :- For the transportation of machinery and equipments the power station should be efficiently connected with rail and road. 

Major Components of Hydroelectric Power Station 

Reservoir , Dam, trash rack, forebay, surge tank, penstock, spillway are some some of the important component of hydroelectric power station. The power house itself has prime movers and generators in addition to the above mentioned components.

1. Reservoir :- The purpose of reservoir is to store water which may be utilized to run the prime mover to produce electrical power. It is the basic requirement of hydroelectric power station. A reservoir store water during the rainy season and supplies the same during dry season.

   

   Reservoir - Taum Sauk Hydroelectric Power Station

2. Dam :- A dam may be considered as a large storage bay where water is stored to provide water head. Dam is a barrier; it is built of concrete or earth or rock fill.  

   

   Upper Wardha Dam

3. Trash Rack :- The purpose of trash rack is to prevent entry of debris or material which might damage the wicket gates and the turbine runners or mean checking of nozzles of impulse turbine.

   

   Trash Rack

4. Forebay :- The forebay is similar to reservoir but it is built in small manner. It serves as a regulating reservoir storing water temporarily when load on the plant is increased or reduced. In short it may be considered as the enlarged body of the water just before the intake. 
   
5. Surge Tank :- To protect the penstock from abnormal pressure surge tank is open at the top and is located near the beginning of the penstock. When the load is steady on the alternator, turbine run swiftly and there is no surge in the flow water through penstock. It can be understood by considering that, when the load is steady the quantity of water flowing through the penstock is sufficient to drive the turbine and meet the load demand. However when the load on the alternator increases or decreases suddenly the governor has to close the gates of the turbine to reduce or increase water supply to the turbine but due to certain time lag the water pressure in the penstock increases or decreases, this may damage the penstock. For avoiding this abnormal condition the surge tank is provided to maintain the flow of water and the pressure in the penstock by increasing or decreasing the water level.



Surge Tank and Penstock

6. Penstock :- It is a conduit system which controls the flow of water and for taking water from the intake and forebay to the turbine. The penstock pipes are generally of steel for high and medium head plants, they may be of concrete in low head plants. The diameter and cross sectional area of penstock pipe is dependent on the velocity of water and pressure of water. It is a gate or an enclosed pipe which delivers water from valve house to power house ( hydro turbines ).