Hydroelectric Power Plant
Hydroelectric power Plant involves the storage of a water, conversion of the potential energy of the water into mechanical (kinetic) energy through turbine, and conversion of the mechanical energy to electrical energy through electric generator.
Hydro-electric Generating stations are generally located in hilly areas where dams can be built conveniently and large water reservoirs can be obtained. In a hydro-electric generating station, water head is created by constructing a dam across a river or lake. Water stored in a dam possesses potential energy. From the dam, water is led to fall on turbine blades, turbine starts to rotate.in this way water turbine converts the potential energy of water into mechanical energy. The turbine in turn drives the alternator (generator) which converts mechanical energy into electrical energy. The total energy produced in hydro – electric power plant is
P=9.81Q\rho hKW\\or \\P = 9.81Qh\eta\\where\\P = Power produced\\\rho = density of water = 1000Kg/m3 \\h = head in meters\\\eta = efficiency
Classification of Hydro-electric power plants on basis of Head
On the basis of availability of head hydro – electric power plants are classified into three categories
1. High head Hydro – Electric generating station.
2. Medium head Hydro – Electric generating station
3. Low head hydro – Electric generating station
High Head hydro – Electric Power Plant:
These type of power stations have head ranging from 100m to 500m. in these plants water is carried from main reservoir by a tunnel up-to the surge tank and then from the surge tank to power house through pen stock. The Pelton wheel is the common turbine used in these power stations.
Medium Head hydro – Electric Power Plant:
These type of power stations have head ranging from 30m to 100m. In these type of power stations uses Francis turbines. The forebay provided at the beginning of the pen stock serves as water reservoir. The water is carried out from main reservoir to forebay through open channels and then to power house through pen stock.
Low Head hydro – Electric Power Plant:
In such power plant the head of dam is below 30m. No surge tank is required. Excess of water is allowed to fall over the dam. In these plants Francis or Kaplan Turbine is used.
Advantages
1. It requires no fuel as water is used for generating electric power which is naturally available.\\2. Hydro- Electric generating station uses water as fuel, so it’s a clean fuel source, meaning it won’t pollute the air like power plants that burn fossil fuels, such as coal or natural gas.\\3. It requires very small running charges because water is the source of energy which is available free of cost.\\4. In addition to a sustainable fuel source, hydro-electric generating stations efforts produce a number of benefits, such as flood control, irrigation, and water supply.
5. It is comparatively simple in construction and requires less maintenance.\\6. Hydroelectric power is a domestic source of energy, allowing each state to produce their own energy without being reliant on international fuel sources.\\7. Hydro-electric power is completely renewable, which means it will never run out unless the water stops flowing. As a result, hydro plants are built to last. In some cases, equipment that was built to last 25 years is still operational after double the amount of time has passed.
Disadvantages
1. The capital cost of the hydro – electric generating station is high due to construction of Dam.\\2. There is uncertainty about the availability of huge amount of water due to dependence on weather conditions.\\3. It is challenging to find a suitable spot that has a large year-round water supply, with the right amount of water and is close enough to existing power lines.\\It is also a delicate balancing act to keeping enough river water wild (meaning without dams), versus damming up many rivers for power.
4. It requires high cost of transmission lines as the plant is located in hilly areas which are quite away from the consumers.\\5. Flood Risk: When dams are built at higher elevations, they pose a serious risk to any town nearby that is below it. While these dams are built very strong, there are still risks. The biggest dam failure in history is the Banqiao Dam failure. Due to excess rainfall from a typhoon, the dam collapsed. This resulted in the deaths of 171,000 people.
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