hydraulic power plant

POOJA S NATHANS1 BT

Energy

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WHAT IS RENEWABLE ENERGY?

Renewable energy is energy generated from natural resources—such as sunlight, wind, rain, tides and geothermal heat—which are renewable (naturally replenished). Renewable energy technologies range from solar power, wind power, hydroelectricity/micro hydro, biomass and biofuels for transportation.

Introduction • Hydroelectric power (hydropower) systems

convert the kinetic energy in flowing water into electric energy.

• Falling or flowing water turns a propeller like piece called a turbine.

• The turbine turns a metal shaft in an electric generator which produces electricity.

Selection of site• The site for Hydraulic power plant is selected

considering the following factors Water available. Storage of water. Head of water. Distance from load center. Accessibility of the site. The land of site should be cheap and rocky.

Components of hydel schemeThe principal components are:

1.Forebay2.Intake structure3.Penstocks4.Surge tank5.Turbines6.Power house7.Draft tube8.Tail race

Dams• A Dam is a structure of masonry built at a

suitable location across a river.

• The primary function of the dam is to provider the head of water.

• Dams are classified based on Function Shape Construction materials Design

• Dams - Classification

DAM

Functions

Shape

Constructionmaterial

Design

Storage Dams

Diversion Dams

Arch Dam

Trapezoidal

Stone masonry

RCC

Structural

HydraulicOverflow

Non-overflow

Buttress

Earth

Rock fill

Arch

Gravity

Forebay

• Forebay acts as a regulating reservoir temporarily

• The forebay has the following parts Entrance bay Spillway Flushing sluice Screens Valve chamber Penstock inlet

Forebay

• Enlarged body of water provided in front of penstock.

• Provided in case of run off river plants and storage plants.

• Main function to store water which is rejected by plant.

• Power house located closed to dam penstock directly take water from reservoir, reservoir act as forebay.

Intake structure• Water conveyed from forebay to

penstocks through intake structures.• Main components are trash rack and

gate.• Trash rack prevent entry of debris.

Trash rack• It is provided for preventing the debris from

getting into the intakes from dam or from the forebay

• Trash rack is made up of steel bars

• The spacing of bars depends upon the following factors

Type of turbine Size of floating material Velocity of flow through trash rack.

Waterway• A waterway is used to carry water from the dam to

powerhouse.

• It includes canal, penstock and tunnel

• Tunnel is the passage by cutting mountain to reduce the length of waterway to reservoir and the power house.

• The tunnel is either circular or horse shoe shaped.

• A canal is an open structure constructed on earth or rock.

• The canal should be located on the economically short route. ……….

• Penstock is a pipe which carry the water from reservoir to turbine house.

• Penstock is made up of steel or reinforced concrete or wood.

• Penstock should be sloping towards the powerhouse.

• Sharp bends should be avoided and require special anchorages .

• The intake of the penstock should be at a low level to provide adequate water seal under all conditions

Surge tank • additional storage for near to turbine,

usually provided in high head plants.• located near the beginning of the

penstock.• As the load on the turbine decreases

or during load rejection by the turbine the surge tank provides space for holding water.

• surge tank over comes the abnormal pressure 

in the conduit when load on the turbine falls and acts as a reservoir during increase of load

on the turbine.

Turbines

• turbines are used to convert the energy water of falling water into mechanical energy.

• water turbine is a rotary engine that takes energy from moving water. 

• flowing water is directed on to the blades of a turbine runner, creating a force on the blades.

• Since the runner is spinning, the force acts through a distance n this way, energy is transferred from the water flow to the turbine. 

• The principal types of turbines are:1)    Impulse turbine2)    Reaction Turbine

Draft tube• A Draft tube connects the

runner exit to tail race.• Draft tube provides a

negative head at the runner outlet by which it is possible to attach a turbine above the tail race.

• The outlet velocity of water is reduced and a gain in pressure head i.e. the net working head of turbine is increased.

Power house

• Power house contains the electro mechanical equipment i.e. hydro power turbine, Generator, excitation system, main inlet valves, transformers, Switchyard, DC systems, governor, bus duct, step up transformers, step down transformers, high voltages switch gears, control metering for protection of systems.

Tail race• tail race tunnel or channel are provided

to direct the used water coming out of draft tube back to the river.

• important criteria of designing the tail race is kind of draft tube, the gross head and geographical situation of the area.

• Tail race is designed in such a way that water hammer is minimizes when water leaves the draft tube.

The amount of electricity that can be generated by a hydropower plant depends on two factors:• flow rate - the quantity of water flowing in a given time; and• head - the height from which the water falls.The greater the flow and head, the more electricity produced.

Flow Rate = the quantity of water flowing Head = the height from which water falls

Power generation

Power = the electric power in kilowatts or kW

Head = the distance the water falls (measured in feet)

Flow = the amount of water flowing (measured in cubic feet per second or cfs)

Efficiency = How well the turbine and generator convert the power of falling water into electric power. This can range from 60% (0.60) for older, poorly maintained hydroplants to 90% (0.90) for newer, well maintained plants.

11.8 = Index that converts units of feet and seconds into kilowatts

A standard equation for calculating energy production:

Power = (Head) x (Flow) x (Efficiency)

11.8

Hydroelectric power (often called hydropower)is considered a renewable energy source. A renewable energy source is one that is not depleted (used up) in the production of energy. Through hydropower, the energy in falling water is converted into electricity without “using up” the water.

Hydropower energy is ultimately derived from the sun, which drives the water cycle. In the water cycle, rivers are recharged in a continuous cycle. Because of the force of gravity, water flows from high points to low points. There is kinetic energy embodied in the flow of water.

Kinetic energy is the energy of motion. Any moving

object has kinetic energy.

Humans first learned to harness the kinetic energy in water by using waterwheels.A waterwheel is a revolving wheel fitted with blades, buckets, or vanes.Waterwheels convert the kinetic energy of flowing water to mechanical energy.

Mechanical energy is a form of kinetic energy, such as in a machine. Mechanical energy has the ability to do work. Any object that is able to do work has mechanical energy.

Hydroelectric power (hydropower) systems convert the kinetic energy in flowing water into electric energy.

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.

How a Hydroelectric Power System Works - Part 1

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 – Part 2

Advantages1. Once a dam is constructed, electricity can be produced

at a constant rate.2. If electricity is not needed, the sluice gates can be shut,

stopping electricity generation. The water can be saved for use another time when electricity demand is high.

3. Dams are designed to last many decades and so can contribute to the generation of electricity for many years / decades.

4. The lake that forms behind the dam can be used for water sports and leisure / pleasure activities. Often large dams become tourist attractions in their own right.

5. The lake's water can be used for irrigation purposes.

Disadvantages1. Dams are extremely expensive to build and must be built

to a very high standard.2. The high cost of dam construction means that they must

operate for many decades to become profitable.3. The flooding of large areas of land means that the

natural environment is destroyed.4. People living in villages and towns that are in the valley

to be flooded, must move out. This means that they lose their farms and businesses. In some countries, people are forcibly removed so that hydro-power schemes can go ahead.

5. The building of large dams can cause serious geological damage. For example, the building of the Hoover Dam in the USA triggered a number of earth quakes and has depressed the earth’s surface at its location.

SIGNIFICANCE Hydropower stands as the most significant

renewable energy source. It uses the single but very powerful energy force of moving water. By some comparison, it competes with the energy produced by fossil fuels and nuclear power, but is considered much cleaner and more simplistic. Hydropower remains popular even in third-world countries, which do not have the resources to build expensive nuclear generating stations. Hydropower does not pollute the atmosphere or environment. 

Facts• Hydropower uses the energy of moving water for a

variety of useful applications.• Hydroelectricity generates electricity by harnessing the

gravitational force of falling water.• In 2006, hydroelectricity supplied around 20% of the

world’s electricity.• Most hydroelectric power stations use water held in

dams to drive turbines and generators which turn mechanical energy into electrical energy.

• The largest hydroelectric power station in the world is the Three Gorges Dam in China.

Environmental Impacts • Hydroelectric power includes both massive

hydroelectric dams and small run-of-the-river plants. Large-scale hydroelectric dams continue to be built in many parts of the world (including China and Brazil), but it is unlikely that new facilities will be added to the existing U.S. fleet in the future.

• Instead, the future of hydroelectric power in the United States will likely involve increased capacity at current dams and new run-of-the-river projects. There are environmental impacts at both types of plants. 

• The IHA (International Hydropower Association) Working Group on Environmental Impact Assessment (EIA) calls for impact assessment to be an integral part of the multidisciplinary planning approach, and to include a strong element of public consultation. EIAs should cover both positive and negative impacts both upstream and downstream of a proposed project.

Economic Impacts

Large dams have long been promoted as providing "cheap" hydropower and water supply. Today, we know better. The  costs and poor performance of large dams were in the past largely concealed by the public agencies that built and operated the projects. Dams consistently cost more and take longer to build than projected. In general, the larger a hydro project is, the larger its construction cost overrun in percentage terms.

SOCIAL ISSUES

• Relocating people from the reservoir area is the most challenging social aspect of hydropower, leading to significant concerns regarding local culture, religious beliefs, and effects associated with inundating burial sites. While there can never be a 100 percent satisfactory solution to involuntary resettlement, enormous progress has been made in the way the problem is handled.