Hydro power plant

HYDRO ELECTRIC POWER PLANT

WHAT IS HYDRO POWER?

The objective of a hydropower scheme is to convert the

potential energy of water, flowing in a stream with a certain fall to the turbine (termed the "head"), into electric

energy at the lower end of the scheme, where the powerhouse

is located. The power output from the scheme is proportional

to the flow and to the head.

HYDRO-POWER PLANT

• It plays very important role in the development of country.

• It provides power at cheapest rate.

• About 20% of the total world power is generated using hydro power plants.

4% of the total hydel energy potential in world is in India.

In India 25.32% of total electricity generation capacity is produced by hydel power plant.

As per records of March-2000 23,816 MW electricity was generated by hydel power plant.

It is increasing day by day because of the institutes like National Hydro Power Corporation Limited(NHPCL).

HYDRO-POWER PLANTHYDRO-POWER PLANT

DAM TURBINE

POWER HOUSE

INTAKE

GENERATOR

PENSTOCKRE

SEVO

IR

POWER LINE

TRANSFORMER

HOW A HYDROELECTRIC POWER SYSTEM WORKS

Flowing water is directed at a turbine (remember turbines are just advanced waterwheels). The flowing water causes the turbine to rotate, converting the water’s kinetic energy into mechanical energy.A control mechanism to provide stable electrical power. It is called governor.

The mechanical energy produced by the turbine is converted into electric energy using a turbine generator. Inside the generator, the shaft of the turbine spins a magnet inside coils of copper wire. It is a fact of nature that moving a magnet near a conductor causes an electric current.

HOW A HYDROELECTRIC POWER SYSTEM WORKS

SIZES OF HYDROPOWER PLANTS• Pico hydroelectric plant.

– Up to 10kW, remote areas, away from the grid.• Micro hydroelectric plant

– Capacity 10kW to 300kW, usually provided power for small community or rural industry in remote areas away from the grid.

• Small hydroelectric plant. – Capacity 300kW to 1MW

• Mini hydroelectric plant. – Capacity above 1MW

• Medium hydroelectric plant.– 15 - 100 MW usually feeding a grid.

• Large hydroelectric plant.– More than 100 MW feeding into a large electricity grid.

Classification of Hydro electric power station.

• CLASSIFICATION BASED ON HEAD.

A. High head plant ( < 300 m.)

B. Medium head plant. (60m to 300 m.)

C. Low head plant. ( > 60m.)

• CLASSIFICATION BASED ON WATER CONDITION.

A. Flow of water plant.

B. Storage of water plant.

C. Pump storage water plant.

Micro Hydropower Systems

• Many creeks and rivers are permanent, they never dry up, and these are the most suitable for micro-hydro power production.

• Micro hydro turbine could be a water-wheel turbine, Pelton wheel. (most common turbine).

• Others : Turgo, Cross-flow and various axial flow turbines.

HYDRO POWER PLANT

• Head – Water must fall from a higher elevation to a lower one to

release its stored energy. – The difference between these elevations (the water levels in

the forebay and the tailbay) is called head.• Dams: Are of three categories.

– high-head (800 or more feet)– medium-head (100 to 800 feet)– low-head (less than 100 feet)

• Power is proportional to the product of head x flow

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Element of Hydro power station,

1. Reservoir.

2. Catchments area.

3. Dam.

• (a) Earthen dam.

• (b) Masonry dam.

• (c) Concrete dam.

• 4. Spill ways.

• 5. Screen.

• 6. Fore bay or Intake.

Element of Hydro power station,

• 7. Tunnel.

• 8. Penstock or pipe line.

• 9. Surge tank.

• 10. Draft tube.

• 11. Tail race.

• 12. Fish passes.

• 13. Turbine.

Different type of turbine use in hydro power station

• 1.High head schemes. (Impulse turbine, pelton wheel)

• 2.Medium head schemes. (reaction turbine )

• 3.Low head schemes. (propeller turbine )

Micro Hydro Example

Used in remote locations in northern Canada

Pumped Storage Schematic

Cabin Creek Pumped Hydro

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• base load capacity– Water flows downhill during day/peak periods

• Typical efficiency of 70 – 85%Completed 1967• Capacity – 324 MW

– Two 162 MW units.• Purpose – energy storage

– Water pumped uphill at night• Low usage – excess

ADVANTAGES OF PUMPED STORAGE PLANT

• There is substantial increase in peak load capacity of plant at comparatively low capital cost.

• There is an improvement in the load factor of plant.

• Load on hydro-electrical plant remains uniform.

FIRST ELEMENT :-

DAMSDAM TYPES

1. Arch2. Gravity3. Buttress4. Embankment or

Earth

1.Arch Dams

• Arch shape gives strength

• Less material (cheaper)• Narrow sites• Need strong abutments

2.Concrete Gravity Dams

• Weight holds dam in place.

• Lots of concrete. (expensive)

3.Buttress Dams

• Face is held up by a series of supports.

• Flat or curved face.

Turbine Ranges of Application

24Boyle, Renewable Energy, 2nd edition, Oxford University Press, 2003

Turbine Design Recommendations

Head Pressure

High Medium Low

Impulse PeltonTurgo

Multi-jet Pelton

CrossflowTurgo

Multi-jet Pelton

Crossflow

Reaction   FrancisPump-as-Turbine

PropellerKaplan

Turbine Classified

Turbine Design Ranges

• Kaplan• Francis• Pelton• Turgo

2 < H < 40 10 < H < 350 50 < H < 1300 50 < H < 250

(where H = head in meters)

LIST OF VARIOUS FACTORS WHICH DESCRIBE THE SELECTION OF TURBINE

• Specific speed; high specific speed is essential where head is low.

• Rotational speed; • Efficiency;• Part of load operation;• Cavitations;• Disposition of turbine shaft;• Head;

Types of Hydropower Turbines

• REACTION TURBINES– Derive power from pressure drop across turbine.– Totally immersed in water.– Angular & linear motion converted to shaft power.– Propeller, Francis, and Kaplan turbines

• IMPULSE TURBINES– Convert kinetic energy of water jet hitting buckets.– No pressure drop across turbines.– Pelton, Turgo, and crossflow turbines

Impulse Turbines

• Uses the velocity of the water to move the runner and discharges to atmospheric pressure.

• The water stream hits each bucket on the runner. • No suction downside, water flows out through turbine

housing after hitting.• High head, low flow applications. • Types : Pelton wheel, Cross Flow

Reaction Turbines

• Combined action of pressure and moving water.

• Runner placed directly in the water stream flowing over the blades rather than striking each individually.

• Lower head and higher flows than compared with the impulse turbines.

Chain Turbine

Advantages of Chain Turbine

• It is run-of-river power plant.• Do not worry about the turbidity of water.• There is no danger of cavitations.• It is simple to construct, repaired and

maintenance.

Disadvantages of Chain Turbine

• The slow rotation of chain turbine leads to high speed ratios when connect to generator at 600 rpm – 1500 rpm.

• This chain turbine operation is very noisy.• Structure of turbine is very big.

Pelton Wheel Turbine

Pelton Wheels• Nozzles direct forceful

streams of water against a series of spoon-shaped buckets mounted around the edge of a wheel.

• Each bucket reverses the flow of water and this impulse spins the turbine.

Pelton Wheels

• Suited for high head, low flow sites.

• The largest units can be up to 200 MW.

• Can operate with heads as small as 15 meters and as high as 1,800 meters.

Francis Turbine Cross-Section

Kaplan Turbine Schematic

View of penstock &draft tube in Hydro power plant.

“used for conveying water from the intake to the power house”.

The water in the reservoir is considered as stored energy.

When the gate opens, the water flowing through the

penstock strikes the turbine.

PENSTOCK

Function of surge tank

• Its function is to prevent sudden increase of pressure in the supply line or in the penstock. It is placed as near as possible to the turbine.

• Water hammer• Due to the variation in the demand of water supply according

to load, the turbine gates get closed suddenly which cause increase in pressure. This is known as water hammer.

TRASH RACK

Almost all small hydroelectric plants have a trash rackcleaning machine, which removes all material from water in order to avoid entering in plants intake water.

After passing through the turbine the water returns to the river trough a short canal called a tailrace.

Tailraces:-Tailraces:-

Function of spillway is to discharge the excess amount of water during floods and keep the level of water to the head of reservoir.

During the lifetime of a dam different flow conditions will be experienced and a dam must be able to safely accommodate high floods that can exceed normal flow conditions in the river. For this reason, carefully passages are corporated in the dams as a part of structure. These passages are known as spillways.

What is the function of Spill ways?What is the function of Spill ways?

Advantage of Hydro power station.

1. The plant is simple in construction ,robust and required low maintenance.

2. It can be put in the service instantly.

3. It can respond to changing loads without any difficulty.

4. There are no stand by losses.

5. The running charges are very small.

6. No fuels is burnt.

7. The plant is quite neat and clean.

8. The water after running the turbine can be used for irrigation and other purpose.

Disadvantage of Hydro power station.

1. The capital cost of generators, civil engineering work etc is high.

2. High cost of transmission lines.

3. Long dry seasons may effect the delivery of power.

Selection of site for Hydro electric power station.

1. sufficient quantity of water at a reasonable head should be available.

2. The site should allow for strong foundations with minimum cost.

3. There should be no possibility of future source of leakage of water.

4. The selected site should be accessible easily.5. There should be possibility of stream diversion during

construction period.6. The reservoir to be constructed should have large catchments

area, so that the water in it should never fall below the minimum level.

Benefits…

• Environmental Benefits of Hydro power plant.• No operational greenhouse gas emissions.

Non-environmental benefits– flood control, irrigation, transportation, fisheries and tourism.

Hydropower Calculations

HQPHQgP

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• P = power in kilowatts (kW)• g = gravitational acceleration (9.81 m/s2)• = turbo-generator efficiency (0<n<1)• Q = quantity of water flowing (m3/sec)• H = effective head (m)