HYDRO ELECTRIC POWER PLANT

Water power – Hydrological cycle / flow measurement – drainage area characteristics – Hydrographs – storage and pondage – classification of dams and spill ways.

HYDRO PROJECTS AND PLANT

Classification – Typical layouts – plant auxiliaries – plant operation pumped storage plants

Unit 5

Hydrological Cycle

Hydrological Cycle

Evaporation

Precipitation

Condensation

Hydrological Cycle

Exchange of heat energyIn evaporation heat is absorbed and in

condensation heat is released

Water power

Concept The power is generated by the energy of water which moves

turbines, which runs the electric generator, as a resultPower

When rain water falls over the earth’s surface, it possesses potential energy relative to sea or ocean towards which it flows.

If at a certain point, the water falls through an appreciable vertical height, this energy can be converted into shaft work.

As the water falls through a certain height, its potential energy is converted into kinetic energy and this kinetic energy is converted to the mechanical energy by allowing the water to flow through the hydraulic turbine runner.

This mechanical energy is utilized to run an electric generator which is coupled to the turbine shaft.

Power generated

Power = W.Q.H.η watts

where W = Specific weight of waterQ = Rate of water flowH = Height of fall or headη = Efficiency of conversion of potential energy

into mechanical energy

Hydrograph

A hydrograph is a graph showing the rate of flow (discharge) versus time past a specific point in a river, or channel carrying flow

Hydrograph (example)

Features of HPP

The essential features of a water power plant are as below:

Catchment areaReservoirDam and intake houseInlet water wayPower houseTail race or outlet water way

Features

Catchment Area

The catchment area of a hydro plant is the whole area behind the dam, draining into a stream or river across which the dam has been built at a suitable place

Reservoir

Whole of the water available from the catchment area is collected in a reservoir behind the dam.

The purpose of the storing of water in the reservoir is to get a uniform power output throughout the year.

A reservoir can be either natural or artificial. A natural reservoir is a lake in high

mountains and an artificial reservoir is made by constructing a dam across the river

Dam

A dam is built across a river for two functions: to impound the river water for storage and to create the head of water.

A barrier to confine or raise water for storage or diversion to create a hydraulic head

Types of Dams

Dams

Fill Dams

Earth Dams

Rock-fill Dams

Masonry Dams

Solid Gravity Dams

Buttress Dams

Arc Dams

Timber Dams

Fill Dams

Earth Fill Dam - Tarbela Dam, Pakistan

Rock Fill Dam - New Melones Dam, California

Masonry Dams

Solid Gravity Dam -  Grand Coulee Dam

Arch Dam – Gordon Dam, Tasmania

Types of Spillways

Over-fall spillway or solid gravity spillwayChute or through spillwaySide channel spillway Saddle spillway Shaft or glory hole spillway Siphon spillway Emergency spillway

Hydro Projects and Plant

Hydropower (hydro means water) is energy that comes from the force of moving water.

Classification

The hydro-power plants can be classified as below:

l. Storage plant(a) High head plants(b) Low head plants(c) Medium head plants.

2. Run-of-river power plants(a) With pondage(b) Without pondage.

3. Pumped storage power Plants

High head plants

The water is taken from the reservoir through tunnels which distribute the water to penstock through which the water is conveyed to the turbines

The water from the reservoir can be taken to a smaller storage known as a fore-bay. The fore-bays help to regulate the demand for water according to the load on the turbines

The function of the surge tank is to prevent a sudden pressure rise in the penstock when the load on the turbines decreases and the inlet valves to the turbines are suddenly closed

Example: Pelton Wheel

High head plants

Pelton Wheel

Medium Head Plants

If the head of water available is more than 50 m., then the water from the fore-bay is conveyed to the turbines through pen-stocks

The river water is usually tapped off to a fore-bay on one bank of the river

From the fore-bay, the water is then led to the turbines through penstocks

Example: Francis Turbine

Medium Head Plants

Francis Turbine

Low Head Power Plants

These power plants are also known as Canal power plants

A dam is built on the river and the water is diverted into a canal which conveys the water into a fore-bay from where the water is allowed to flow through turbines

Example: Kaplan Turbine

Low Head Power Plants

Kaplan Turbine

Pumped Storage Power Plants

These plants supply the peak load for the base load power plants and pump all or a portion of their own water supply

The usual construction would be a tail water pond and a head water pond connected through a penstock

During off peak hours, some of the surplus electric energy being generated by the base load plant, is utilized to pump the water from tail water pond into the head water pond and this energy will be stored there

During times of peak load, this energy will be released by allowing the water to flow from the head water pond through the water turbine of the pumped storage plant

When the water flows through it from the head water pond it will act as a turbine and rotate the generator. When rotated in the reverse direction by means of an electric motor, it will act as a pump to shunt the water from the tail water pond to the head water pond

Pumped Storage Power Plants

Sources

WikipediaPPE by RajputPPE by Dwivedi

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