Hydropower

WHAT IS HYDROPOWER• Hydropower is the electricity or power that is generated from

the energy of moving water. Hydro means “water.”• It is a renewable source of energy. It is constantly being

refilled by the water cycle, specifically precipitation.

HISTORY OF HYDROPOWER• Ancient Greek farmers have used water wheels to grind wheat

into flour.• In the early 1800’s, American and European factories made use

of the water wheel to run machines.• In the late 19th century, hydropower was used for generating

electricity.• Waterwheels and mills were used for irrigation and mining.• Hydropower was the foremost source of energy for new

inventions

HISTORY OF HYDROPOWER• In the 1830’s, hydropower provided the energy for transportation

up and down steep hills.• In 1848, the turbine was created, improving the waterwheels

and mills which were bulky and slow. Turbines are specific to each site.

• The first hydroelectric power plant was built at the Niagara Falls in 1879.

• In the late 1940’s, big dams for hydropower had been built.

CLASSIFICATION OF HYDROPOWER PLANTS : Classification of hydropower plants

According to Capacity

Large

Medium

Small

Mini

Micro

Pico

According to head

High

Medium

Low

According to purpose

Single purpose

Multi purpose

According to facility types

Run-of-River

Reservoirs

In-stream

Pumped storage

According to hydrological

relation

Single

Cascade

According to transmission

system

Isolated

Connected to grid

CLASSIFICATION ACCORDING TO CAPACITY:

LARGE: >100 MWMEDIUM: 25 – 100 MWSMALL: 1-25 MWMINI: 100 KW - 1MWMICRO: 5 – 100 KW PICO: < 5 KW

CLASSIFICATION ACCORDING TO HEADLOW HEAD: Low head hydro power applications use river current or tidal flows of 30 meters or less to produce energy.These applications do not need to dam or retain water to create hydraulic head, the head is only a few meters.Using the current of a river or the naturally occurring tidal flow to create electricity may provide a renewable energy source that will have a minimal impact on the environment.

Figure-sectional view of low head hydropower plant

CLASSIFICATION ACCORDING TO HEAD

MEDIUM HEAD: A power station operating under heads from 30m to 300m.

Figure- sectional view of medium head hydropower plant

CLASSIFICATION ACCORDING TO HEADHIGH HEAD:

A power station operating under heads above about 300m.A head of 200m/250m is considered as the limit between medium and high head power stations.

Figure- high head hydropower plant

Figure-(a) single stage hydropower development scheme (b) cascade or multistage hydropower system

CLASSIFICATION ACCORDING TO HDROLOGICAL RELATION

SINGLE STAGE-When the run off from a single hydropower plant is diverted back into river or for any other purpose other than power generation, the setup is known as Single Stage.

CASCADE SYSTEM-When two or more hydropower plants are used in series such that the run off discharge of one hydro power plant is used as the is a intake discharge of the second hydro power plant such a system is known as CASCADE hydropower plant.

CLASSIFICATION ACCORDING TO PURPOSE:

SINGLE PURPOSE: When the whole soul purpose of a project is to produce electricity then such a project is known as a Single Purpose Hydro Power Project.

MULTIPURPOSE : When the water used in hydropower project is to be used for other purposes like irrigation, flood control or fisheries then such a project is known as Multi Purpose Hydro Power Project.

These are hydro power plants that utilize the stream flow as it comes , without any storage being provided.

CLASSIFICATION ACCORDING TO FACILITY TYPE

RUN-OF-RIVER TYPE

Figure-Run-of-River hydropower plant

Hydropower plants can be classified in three categories according to operation and type of flow

Hydropower plants with storage are supplied with water from large storage reservoir that have been developed by constructing dams across rivers. Assured flow for hydro power generation is more certain for the storage schemes than the run-of-river schemes.

STORAGE (RESERVOIR) TYPE

Figure-pumped storage hydropower plant

CLASSIFICATION ACCORDING TO FACILITY TYPE

PUMPED STORAGE TYPE

Figure-pumped storage hydropower plant

Pumped storage type hydropower plants are those which utilize the flow of water from a reservoir at higher potential to one at lower potential.During off-peak hours, the reversible units are supplied with the excess electricity available in the power grid which then pumps part of the water of the tail-water pond back into the head-water pond.

CLASSIFICATION ACCORDING TO FACILITY TYPE

IN-STREAM

When the velocity of water i.e kinetic energy flowing in the stream is used for conversion into electrical power, then the system is known as In-stream.

CLASSIFICATION ACCORDING TO FACILITY TYPE

Photograph of In-stream hydro power system

CLASSIFICATION ACCORDING TO TRANSMISSION SYSTEM:

ISOLATED: Whenever a hydropower plant is set up in a remote area in order to meet the local demands then such a hydropower plant is known as Isolated System.

CONNECTED TO GRID: Whenever the hydropower plant is set up to meet the demands of areas which are at a fair distance from the plant, then the transmission of power takes through the grid system. Such a setup is referred to as Connected to grid.

COMPONENTS

1. Dam and Reservoir2. Spillway3. Penstock4. Turbine5. Generator ,Transformer7-power lines

DAM AND RESERVOIR

An open-air storage area usually formed by masonry or earthwork where water is collected and kept in quantity so that it may be drawn off for use.

The water reservoir is the place behind the dam where water is stored. The water in the reservoir is located higher than the rest of the dam

structure. The height of water in the reservoir decides how much potential energy

the water The higher the height of water, the more its potential energy. The high position of water in the reservoir also enables it to move downwards effortlessly.

These are the gates built on the inside of the dam. The water from reservoir is released and controlled through these gates.

These are called inlet gates because water enters the power generation unit through these gates.

When the control gates are opened the water flows due to gravity through the penstock and towards the turbines.

The water flowing through the gates possesses potential as well as kinetic energy.

PENSTOCK

The penstock is the long pipe or the shaft that carries the water flowing from the reservoir towards the power generation unit, comprised of the turbines and generator. The water in the penstock possesses kinetic energy due to its motion and potential energy due to its height.

Hydro Turbines is a rotary machine that converts kinetic and potential energy of water into mechanical work.

Turbine :

Pelton Wheel Turbine:This type Turbine is used for high Head and lowDischarge (Head above 180 meters.)

Francis turbine (used at RBPH): This type turbine is used for medium head andmedium discharge (head 40 to 400 meters.)

Kaplan Turbine (used at CHPH): This type Turbine is used for low Head and high Discharge (Head 40 to 60 Meters.)

Types of Turbine used :

Generator ,Transformer

• As the water rushes through the turbine, it spins the turbine shaft, which is coupled to the electric generator. The generator has a rotating electromagnet called a rotor and a stationary part called a stator. The rotor creates a magnetic field that produces an electric charge in the stator. The charge is transmitted as electricity. The step-up transformer increases the voltage of the current coming from the stator.

SITE SELECTION FOR HYDROPOWER PLANTS

• Water Storage for water Availability of Water:Run-off data for many years availability throughout the year

• Head of Water most economic head, possibility of constructing a dam to get required head

• Geological Investigations strong foundation, earthquake frequency is less

• Water Pollution excessive corrosion and damage to metallic structures

SITE SELECTION FOR HYDROPOWER PLANTS

• Social and Environmental Effects submergence of areas, effect on biodiversity (e.g. western ghat), cultural and historic aspects

• Access to Site for transportation of construction material and heavy machinery new railway lines or roads may be needed

• Multipurpose: power generation, irrigation, flood control, navigation, recreation; because initial cost of power

plant is high because of civil engineering construction work

• Water is a renewable energy source.• Maintenance and operation charges are very low.• The efficiency of the plant does not change with age.• In addition to power generation, hydro-electric power plants are also useful for

flood control, irrigation purposes, fishery and recreation.• Have a longer life(100 to 125 years) as they operate at atmospheric temperature.• Water stored in the hydro-electric power plants can also be used for domestic

water supply.• Since hydro-electric power plants run at low speeds(300 to 400 rpm) there is no

requirement of special alloy steel construction materials or specialised mechanical maintenance.

• Advantages of hydro power plant :

• The initial cost of the plant is very high.• Since they are located far away from the load centre, cost of

transmission lines and transmission losses will be more.• During drought season the power production may be reduced or

even stopped due to insufficient water in the reservoir.• Water in the reservoir is lost by evaporation.

• Disadvantages of hydro power plant :

FUTURE OF HYDROPOWERAfrica’s hydropower future

Energy poverty is rife in Africa. Of the more than one billion people living in its 54 countries, over half lack access to electricity.

In global debates on renewable energy and the drive to find cleaner, greener alternatives to fossil fuels, wind and solar power usually grab the headlines.

But the data shows a different picture. Hydropower produces more than three-quarters of the world’s renewable energy output each year. And its carbon emissions — over the entire lifecycle of construction, operation and decommissioning — are often far lower than those from all other renewable sources, including wind and solar.Across Africa, hydropower is responsible for 84 per cent of all non-fossil fuel energy use. But in a continent rich in lakes and rivers, the opportunities for expanding hydropower are huge.

THE NILE IS THE WORLD’S LONGEST RIVER, MAKING IT ONE OF AFRICA’S GREATEST POTENTIAL SOURCES OF HYDROPOWER.

THE GERD IS BEING BUILT IN THE BENISHANGUL-GUMUZ REGION OF ETHIOPIA, JUST UPSTREAM FROM THE SUDANESE BORDER. ON COMPLETION IN 2017, IT IS

PLANNED TO BE 145 METRES HIGH — NEARLY ONE-AND-A-HALF TIMES THE HEIGHT OF VICTORIA FALLS — MAKING IT THE HIGHEST DAM IN AFRICA. ITS

RESERVOIR IS SET TO CONTAIN 74 BILLION CUBIC METRES OF WATER, ROUGHLY THE SAME AS 13 TIMES ETHIOPIA’S TOTAL ANNUAL WATER CONSUMPTION. THE ETHIOPIAN GOVERNMENT EXPECTS THE DAM TO PRODUCE SIX GIGAWATTS OF ENERGY AT PEAK OUTPUT. THIS WILL ALMOST TRIPLE ETHIOPIA’S ELECTRICITY PRODUCTION, WHICH CURRENTLY STANDS AT LESS THAN THREE GIGAWATTS.

HYDROPOWER PROJECTS OFTEN SPLIT OPINION. THEY CAN PROVIDE ABUNDANT CLEAN ENERGY FOR AROUND 50 YEARS WITHOUT MAJOR MAINTENANCE AND,

UNLIKE OTHER RENEWABLES SUCH AS SOLAR OR WIND, THEY PRODUCE CONTINUOUS POWER.

Future European hydro power

Global potential for small-scale hydro power

Pumping power increases system reliability