Introduction
Hydropower is a conventional renewable source of energy, which is clean, free from pollution and generally having good environment effect.
About 30% of total power of the world is met by hydroelectric power plants. The total hydro potential of the world is about 5000 GW. In Norway the hydropower forms 90% of total power generation. In hydro power plant, output depends on the following three factors.
- Head of water. Water discharged to the turbine.
- Efficiency of the turbine
- Applications of Hydro power Plant
1) At present, hydro plant is used with thermal power plants in an interconnected system. This will result is reduction in capital cost of hydro plant as the size of the reservoir may be reduced.
2) When water flows more, the hydro plant is used as base load and steam power plant is used as peak load plant.
3) When water flows less, the hydro plant is used as peak load plant and steam power plant is used base load plant. Essential features of Hydro Power Plant
- Reservoir
- Dam
- Penstock
- Surge Tank
- Forebay
- Trash Rack
- Draft Tube
- Power House and Equipment
1) Reservoir is used to store water, which will be used to run the turbines to produce electric power. Reservoir may be natural such as lake or artificial reservoir can be built by erecting a dam across the river. Water held in upstream reservoir is called storage, whereas water behind the dam of the plant is called pondage.
2) Dam is a structure of masonry or some other material built at a suitable location across a river. The primary function of a Dam is to provide a head of water. It also creates pondage or storage.
3) Forebay In the water canal, the end is enlarged to store some water. This is called fore bay,
4) Trash Rack is provided to prevent the debris from getting entry to power house. This consists of number of steel bars and it is placed across the intake to prevent debris.
5) Penstocks are pipes made up of steel or concrete used to carry water from the dam to powerhouse.
6) Surge Tank reduces the water hammer effects on the penstock. It is located in between the dam and powerhouse on the penstock.
7) Draft Tube is an integral part of reaction turbine. Draft tube connects the runner exit to tail race. The area of the top of the draft tube is same as that of the runner to avoid shock and is circular cross section. The water after doing work on the turbine runner passes through the draft tube.
8) Power House – Turbine and generator are located in the power house
Working Principle of Hydro electric Power Plant
In a hydroelectric power plant waterpower is used for generating electricity. The water stored in a dam has potential energy on account of its position or height above the ground level. As the water falls through a certain height, it is capable of doing work. In a hydroelectric power plant, the force exerted by water is used to drive a turbine coupled to an alternator, which generates electric power.
The water collected from the catchment area is stored in a reservoir behind a dam. This catchment area gets its supply of water from rain and rivers. The water from the reservoir carried by a pressure tunnel to the surge tank. The water under pressure is supplied to the turbine by the penstock made of steel or concrete, through the inlet valve. The hydraulic turbine converts the energy of water into mechanical energy. The torque available on the turbine shaft is transferred to an alternator, which generates electricity. The voltage of the electricity is then increased by means of a step-up transformer. Now, the electricity power is distributed through distribution lines.
Dam Potential energy
↓ (Gravitational energy)
Pipes Kinetic energy
(By falling water)
↓
Turbine Mechanical energy
(By running the turbine)
↓
Alternator Electrical energy
(In the generator)
Advantages of combined cycle power plant
- Fuel economy in the secondary power production
- Thermal efficiency of the plant is more.
- Additional power production from the exhaust system of primary power plant.
Disadvantages of combined cycle power plant
- Initial investment is high.
- High maintenance cost.
- More additional equipment is required and hence more space is required.
See More: Diesel Power Plant
See More: Gas Turbine Power Plant
See More: Nuclear Power Plant
