ppt on hydropower

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1 HYDROPOWER SUSHIL KUMAR HIMANSHU DEPARTMENT OF HYDROLOGY IIT-ROORKEE

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Page 1: ppt on Hydropower

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HYDROPOWER

SUSHIL KUMAR HIMANSHUDEPARTMENT OF HYDROLOGY

IIT-ROORKEE

Page 2: ppt on Hydropower

FACTS ABOUT HYDROPOWER PLANT The World’s hydropower plants output a combined total of

675,000 megawatts, the energy equivalent of 3.6 billion barrels of oil.

worldwide, hydro powers plant produce about 24% of world’s electricity and supply more than one billion people with power.

hydropower provides about 10% of electricity in united states. India produces more than 12% of its electricity with hydropower.

Norway produces more than 99% of its electricity with hydropower. New Zealand uses hydropower for 75% of its electricity.

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World Energy Sources

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World hydro production

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Major Hydropower Producers

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HYDROPOWER PLANT A hydropower plant uses the force of falling water to make

electricity.

Flowing water creates energy that can be captured and turned into electricity. This is called hydroelectric power or hydropower.

A typical hydro plant is a system with three parts: a power plant where the electricity is produced. a dam that can be opened or closed to control water flow. a reservoir (artificial lake) where water can be stored.

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Hydropower to Electric Power

PotentialEnergy

KineticEnergy

ElectricalEnergy

MechanicalEnergy

Electricity

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THE POWER OF WATER Hydropower (from hydro meaning water) is energy that

comes from the force of moving water. The fall and movement of water is part of a continuous natural cycle called the water cycle.

The moisture eventually falls to the earth as rain or snow, replenishing the water in the oceans and rivers. Gravity drives the water, moving it from high ground to low ground. The force of moving water can be extremely powerful.

Hydropower is called a renewable energy source because the water on the earth is continuously replenished by precipitation. As long as the water cycle continues, we won’t run out of this energy source.

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Hydrologic Cycle

http://www1.eere.energy.gov/windandhydro/hydro_how.html

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CONCEPT OF HYDRO POWER PLANT Hydro system makes use of falling water in a stream or river or

storage dam between two points to generate mechanical power through a turbine which is converted into electrical power through a generator attached to turbine in a power house. Power is expressed as kw or mw depending on capacity of station.

Amount of water flow diverted from stream or river or dam called discharge (q) expressed in litres /sec or cumecs or cusecs and difference in elevation between two upstream and downstream points called gross head (h) expressed in feet or metres.

Electricity generated in alternating current (ac) mode and generating voltage expressed as volts (v) or kilo volts (kv) depending on capacity of station.

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CONCEPT OF HYDRO POWER PLANT continued……..

After flow and gross head between two points measured - hydraulic power calculated as below.

Power = qxhx9.81 watts; q in liters per second and h gross head in meters.

Net head after allowing for frictional losses in water conductor system and penstocks calculated using formulae.

In case of micro hydel projects, friction loss taken as 25% of gross head. NET HEAD (h) = GROSS HEAD – FRICTION LOSSES.

Used to calculate net hydraulic power. Mechanical power calculated using turbine efficiency. For

small shp - 65%. Useful electrical power calculated using generator efficiency -

generally 80% for small size generators (induction generators suitable for direct drive).

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COMPONENT OF HYDRO POWER PLANT

In general, larger the scale of a system, more the number of components.

Intake: water from the river/spring/dam/irrigation channel is diverted from its main course. Generally weir used to divert water through intake into open channel.

Water conductor system : leads water from intake to head of penstock.

De-silting basin with spillway : small tank designed to desilt water. Provide spillway - a flow regulator for the channel. Combined with control gates to provide means of emptying channel. Spill flow fed back to river.

Forebay tank: at head of penstock. Serves as buffer to control sudden flow and pressure variations. 12

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COMPONENT OF HYDRO POWER PLANT continued……..

Penstock: pipeline supplying water from forebay to turbine. Mild steel, upvc and hdpe - most commonly used materials.

Power house: houses turbine – generator with mechanical control valves and electrical control panels. Switch yard and connection to distribution system.

Tail race channel: leads water from turbines(s) back into stream/river/irrigation channel.

Turbine and generator: hydro power in jet at end of penstock transmitted to turbine runner - changes to mechanical power.

Governor: ensures that generator is not affected when load on it changes. Hydraulic, or electronic. Depends on the generator.

Generator: electricity generated when turbine drives generator -most common type of generator produces alternative current and known as alternator.

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HYDROPOWER PLANT

Tail water

Draft tube gate

Draft tube

TurbineMain valve

Penstock

Air inletInlet gate

Surge shaft

TunnelSand trap

Trash rack

Self closing valve

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HOW A HYDROPLANT WORKS To generate electricity, a dam opens its gates to allow water

from the reservoir above to flow down through large tubes called penstocks.

At the bottom of the penstocks, the fast-moving water spins the blades of turbines.

The turbines are connected to generators to produce electricity.

The electricity is then transported via huge transmission lines to a local utility company.

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STORING ENERGY One of the biggest advantages of a hydropower plant is its

ability to store energy. The water in a reservoir is, after all, stored energy. Water can be stored in a reservoir and released when needed for electricity production.

During the day when people use more electricity, water can flow through a plant to generate electricity. Then, during the night when people use less electricity, water can be held back in the reservoir.

Storage also makes it possible to save water from winter rains for summer generating power, or to save water from wet years for generating electricity during dry years.

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hydrodams A dam serves two purposes at a hydro plant. First, a dam

increases the head or height of the water. Second, it controls the flow of water. Dams release water when it is needed for electricity production. Special gates called spillway gates release excess water from the reservoir during heavy rainfalls.

Dams are built on rivers where the terrain will produce an artificial lake or reservoir above the dam. Most dams are built for flood control and irrigation, not electric power generation.

It’s easier to build a hydro plant where there is a natural waterfall. Dams, which are artificial waterfalls, are the next best way.

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Conventional Impoundment Dam

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Schematic of Impound Hydropower

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Terminology 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: 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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Scale of Hydropower Projects Large-hydro

More than 100 MW feeding into a large electricity grid Medium-hydro

15 - 100 MW usually feeding a grid Small-hydro

1 - 15 MW - usually feeding into a grid Mini-hydro

Above 100 kW, but below 1 MW Either stand alone schemes or more often feeding into the grid

Micro-hydro From 5kW up to 100 kW Usually provided power for a small community or rural industry

in remote areas away from the grid. Pico-hydro

From a few hundred watts up to 5kW Remote areas away from the grid.

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Ecological Impacts Loss of forests, wildlife habitat, species. Degradation of upstream catchment areas due to inundation of

reservoir area. Rotting vegetation also emits greenhouse gases. Loss of aquatic biodiversity, fisheries, other downstream

services. Cumulative impacts on water quality, natural flooding. Disrupt transfer of energy, sediment, nutrients. Sedimentation reduces reservoir life, erodes turbines

Creation of new wetland habitat Fishing and recreational opportunities provided by new

reservoirs

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Environmental and Social Issues Land use – inundation and displacement of people Impacts on natural hydrology

Increase evaporative losses Altering river flows and natural flooding cycles Sedimentation/silting

Impacts on biodiversity Aquatic ecology, fish, plants, mammals

Water chemistry changes Mercury, nitrates, oxygen Bacterial and viral infection

Seismic Risks Structural dam failure risks

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Impacts of Hydroelectric Dams

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ADVANTAGES Hydropower’s fuel supply (flowing water) is clean and is

renewed yearly by snow and rainfall. hydro plants do not emit pollutants into the air because they

burn no fuel. With growing concern over greenhouse gas emissions and

increased demand for electricity, hydropower may become more important in the future.

Hydropower facilities offer a range of additional benefits. Many dams are used to control flooding and regulate water supply, and reservoirs provide lakes for recreational purposes, such as boating and fishing.

Low operating and maintenance cost.

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DISADVANTAGES

Damming rivers may permanently alter river systems and wildlife habitats. Fish, for one, may no longer be able to swim upstream.

Hydro plant operations may also affect water quality by churning up dissolved metals that may have been deposited by industry long ago.

Hydropower operations may increase silting, change water temperatures, and lower the levels of dissolved oxygen.

Degradation of upstream catchment areas due to inundation of reservoir area.

High initial capital cost.

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Efficiency of Hydropower Plants

Hydropower is very efficient Efficiency = (electrical power delivered ÷ (potential energy

of head water)

Typical losses are due to Frictional drag and turbulence of flow Friction and magnetic losses in turbine & generator

Overall efficiency ranges from 75-95%.

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Hydropower Calculations

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)

HQP

HQgP

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Calculation of head loss

g2

c

D

Lfh

2

f

Where: hf = Head loss [m]

f = Friction factor [ - ] L = Length of pipe[m] D = Diameter of the pipe [m] c = Water velocity[m/s] g = Gravity [m/s2]

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