Developing a Hydroelectric Power Plant

Developing A Hydroelectric Power Plant

Prepared for

Mohammad Mussa

Instructor, ART 203

Md Abdur Rashid

ID # 07305012

BSEEE

08 July 2011

Letter of Transmittal

Mohammad Musa

Faculty, ART 203

IUBAT-InternationalUniversity of Business Agriculture and Technology

4, Embankment Drive Road, UttaraModelTown,

Sector 10, Dhaka 1230, Bangladesh.

Subject: Request for the Proposal.

Dear Sir,

With due respect, I would like to submit this Report as partial fulfillment of the course ART 203, the topic of “Developing A Hydro-electric Power Plant”.It was a great opportunity for us to work on this topic to actualize our theoretical knowledge in the

Practical area and to have an real experience on Electricity GenerationSystem.

Now I am looking forward for your kind assessment regarding this proposal. I would be very grateful to you, if you please take the trouble of going through the proposal and evaluate our performance regarding this proposal

Sincerely Yours

……………………..

Md. Abdur Rashid

Table of Contents

Title Page ………………………………………………………………1

Letter of Transmittal……………………………………………………2

Table of contents……………………………………………………….3

Executive Summary…………………………………………………….4

Introduction………………………………………………………....5
Background…………………………………………………………6
Sources………………………………………………………………7
Benefits of Hydropower…………………………………………….8
Electrical System Benefits…………………………………………..9
How Hydro Power Works………………………………………… 10
The different parts of a hydroelectric power plant………………...11
Turbines…………………………………………………………….13
Low-head Hydropower…………………………………………….14
A simple formula…………………………………………………..15
Load factor, Load control governors………………………………16
Environmental impacts…………………………………………….17
Karnafuli Hydro Power Station……………………………………18
Conclusion………………………………………………………….20
Work Cited………………………………………………………….21

Figure :Hydro-electric Power Station………………………………….7

Figure : Hydro-electric Dam………..………………………………….11

Figure : Turbine……………………..………………………………….13

EXECUTIVE SUMMARY

Hydroelectric power plants are the most efficient means of producing electric energy. Since water is the most abundant resource in the world, the most efficient way to harness the power of water is to collect the potential energy. This is done by damming up a body of flowing water. A dam is an object that restricts the flow of water. In today’s hydroelectric dams, the restricted water is diverted to a turbine using a penstock and exits the turbine through the tailrace. The turbine is made up of a shaft with blades attached. As a fluid flows through the blades a rotational force is created. This force causes a torque on the shaft. The turbine shaft is coupled to a generator, where electricity is produced. The backbone of most power generation system is the generator. An electric generator is “any machine that converts mechanical energy into electricity for transmission and distribution.” The generator works by spinning a rotor that is turned by a turbine. The rotor is a shaft that has field windings. These windings are supplied with an excitation current or voltage. As the rotor turns, the excitation current creates a magnetically induced current onto a stator. The stator is a cylindrical ring made of iron that is incased by another set of field windings and is separated from the rotor by a small air gap. Hydroelectric generations can vary from 1 watt to 100’s mega-watts. With today’s technology it is possible to generate power with small scale parameters with low flow.

Introduction

Hydropower, hydraulic power or water power is power that is derived from the force or energy of moving water, which may be harnessed for useful purposes. Prior to the development of electric power, hydropower was used for irrigation, and operation of various machines, such as watermills, textile machines, sawmills, dock cranes, and domestic lifts.Another method used a trompe to produce compressed air from falling water, which could then be used to power other machinery at a distance from the water.

In hydrology, hydropower is manifested in the force of the water on the riverbed and banks of a river. It is particularly powerful when the river is in flood. The force of the water results in the removal of sediment and other materials from the riverbed and banks of the river, causing erosion and other alterations.

Water power can be harnessed in many ways; tidal flows can be utilised to produce power by building a barrage across an estuary and releasing water in a controlled manner through a turbine; large dams hold water which can be used to provide large quantities of electricity; wave power is also harnessed in various ways. It is a technology that has been utilised throughout the world, by a diverse range of societies and cultures, for many centuries. Water can be harnessed on a large or a small scale - Table 1, below outlines the categories used to define the power output form hydropower. Micro-hydro power is the small-scale harnessing of energy from falling water; for example, harnessing enough water from a local river to power a small factory or village. This fact sheet will concentrate mainly at micro-hydro power.

Large- hydro More than 100 MW and usually 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

(kW (kilowatt) - 1000 Watts; MW (megawatt) - 1 000 000 Watts or 1000 kW)

Background

In the UK, water mills are known to have been in use 900 years ago. Their numbers grew steadily and by the 19th century, there were over 20,000 in operation in England alone. In Europe, Asia and parts of Africa, water wheels were used to drive a variety of industrial machinery, such as mills and pumps. The first effective water turbines appeared in the mid 19th century and it was not long before they were replacing water wheels in many applications. In contrast to water wheels and the early turbines, modern turbines are compact, highly efficient and capable of turning at very high speed. Hydropower is a well-proven technology, relying on a non-polluting, renewable and indigenous resource, which can integrate easily with irrigation and water supply projects. China alone has more than 85,000 small-scale, electricity producing, hydropower plants.

Over the last few decades, there has been a growing realisation in developing countries that micro-hydro schemes have an important role to play in the economic development of remote rural areas, especially mountainous ones. Micro-hydro schemes can provide power for industrial, agricultural and domestic uses through direct mechanical power or by the coupling of the turbine to a generator to produce electricity.

Sources

In 2005, more than 3/4 of total world energy consumption was through the use of fossil

fuels.” With the current state of the environment, it is essential to explore all the

possibilities for renewable energy. The main forms of renewable energy are wind, solar,

biomass, and hydroelectric . “Hydroelectric power plants are the most efficient means

of producing electric energy.”

Since water is the most abundant resource in the world, it is important to utilize the

power of flowing water. The most efficient way to harness the power of water is to

collect the potential energy. This is done by damming up a body of flowing water. A dam

is an object that restricts the flow of water. In today’s hydroelectric dams, the restricted

water is diverted to a turbine using a penstock and exits the turbine through the tailrace.

The turbine is made up of a shaft with blades attached. As a fluid flows through the

blades a rotational force is created. This force causes a torque on the shaft. The turbine

shaft is coupled to a generator, where electricity is produced.

The backbone of most power generation system is the generator. An electric generator is

“any machine that converts mechanical energy into electricity for transmission and

distribution.” The generator works by spinning a rotor that is turned by a turbine. The

rotor is a shaft that has field windings. These windings are supplied with an excitation

current or voltage. As the rotor turns, the excitation current creates a magnetically

induced current onto a stator. The stator is a cylindrical ring made of iron that is incased

by another set of field windings and is separated from the rotor by a small air gap.

Hydroelectric generations can vary from 1 watt to 100’s mega-watts. With today’s

technology it is possible to generate power with small scale parameters. With low flowand low head parameters a micro generator can be used to produce electric power. Fromthe source of the flowing water, a weir, small scale dam, can be used to restrict the flowof water. From this the water can be piped to a turbine. Since the turbine is coupled to thegenerator, a micro generator can generate about 1 watt to 100 kilowatts. This

generator can be used to power residential loads

Benefits of Hydropower

Hydropower is one of the three principal sources of energy used to generate electricity, the other two being fossil fuels and nuclear fuels. Hydroelectricity has certain advantages over these other sources: it is continually renewable thanks to the recurring nature of the water cycle, and causes no pollution. Also, it is one of the cheapest sources of electrical energy. Hydropower provides unique benefits, rarely found in other sources of energy. These benefits can beattributed to the electricity itself, or to side-benefits, often associated with reservoir development.Despite the recent debates, few would disclaim that the net environmental benefits of hydropower are farsuperior to fossil-based generation. In 1997, for example, it has been calculated that hydropower saved GHGemissions equivalent to all the cars on the planet (in terms of avoided fossil fuel generation).While development of all the remaining hydroelectric potential could not hope to cover total future worlddemand for electricity, implementation of even half of this potential could thus have enormousenvironmental benefits in terms of avoided generation by fossil fuels.

Carefully planned hydropower development can also make a vast contribution to improving living stands inthe developing world (Asia, Africa, Latin America), where the greatest potential still exists. Approximately2 billion people in rural areas of developing countries are still without an electricity supply.As the most important of the clean, renewable energy options, hydropower is often one of a number ofbenefits of a multipurpose water resources development project. As hydro schemes are generally integratedwithin multipurpose development schemes, they can often help to subsidize other vital functions of aproject. Typically, construction of a dam and its associated reservoir results in a number of benefits

associated with human well-being, such as secure water supply, irrigation for food production and floodcontrol, and societal benefits such as increased recreational opportunities, improved navigation, thedevelopment of fisheries, cottage industries, etc. This is not the case for any other source of energy.

Electrical System Benefits

Hydropower, as an energy supply, also provides unique benefits to an electrical system. First, when stored inlarge quantities in the reservoir behind a dam, it is immediately available for use when required. Second, theenergy source can be rapidly adjusted to meet demand instantaneously. These benefits are part of a largefamily of benefits, known as ancillary services. They include:

Spinning reserve - the ability to run at a zero load while synchronized to the electric system. When loadsincrease, additional power can be loaded rapidly into the system to meet demand. Hydropower canprovide this service while not consuming additional fuel, thereby assuring minimal emissions.

Non-spinning reserve - the ability to enter load into an electrical system from a source not on line. Whileother energy sources can also provide non-spinning reserve, hydropower's quick start capability isunparalleled, taking just a few minutes, compared with as much as 30 minutes for other turbines and

hours for steam generation.

Regulation and frequency response - the ability to meet moment-to-moment fluctuations in systempower requirements. When a system is unable to respond properly to load changes its frequencychanges, resulting not just in a loss of power, but potential damage to electrical equipment connected tothe system, especially computer systems. Hydropower's fast response characteristic makes it especiallyvaluable in providing regulation and frequency response.

Voltage support - the ability to control reactive power, thereby assuring that power will flow fromgeneration to load.

Black start capability - the ability to start generation without an outside source of power. This serviceallows system operators to provide auxiliary power to more complex generation sources that could takehours or even days to restart. Systems having available hydroelectric generation are able to restoreservice more rapidly than those dependent solely on thermal generation.

HOW HYDROPOWER WORKS

Hydroelectric power plants convert the hydraulic potential energy from water into electricalenergy. Such plants are suitable were water with suitable head are available. The layoutcovered in this article is just a simple one and only cover the important parts of hydroelectricplant.

Most hydroelectric stations use either the natural drop of a river, such as a waterfall or rapids, or a dam is built across a river to raise the water level, and provide the drop needed to create a driving force.

Water at the higher level is collected in the forebay. It flows through the station's intake into a pipe, called a penstock, which carries it down to a turbine. The turbine is a type of water wheel that is connected to a generator. As the water flows down the penstock the water pressure increases. It is this pressure and flow that causes the turbine to revolve which in turn spins a generator.

Inside the generator are large electromagnets attached to a rotor that is located within a coil of copper wires called the stator. As the generator rotor spins the magnets a flow of electrons is created in the coils of the stator.

This produces electricity that can be stepped up in voltage through the station’s transformers and sent across transmissions lines. The falling water, having served its purpose, exits the generating station through what is called the tailrace, where it rejoins the main stream of the river.

The different parts of a hydroelectric power plant

(1) Dam

Dams are structures built over rivers to stop the water flow and form a reservoir.The

reservoir stores the water flowing down the river. This water is diverted to turbines in power stations. The dams collect water during the rainy season and stores it, thus allowing for a steady flow through the turbines throughout the year. Dams are also used for controlling floods and irrigation. The dams should be water-tight and should be able to withstand the pressure exerted by the water on it. There are different types of dams such as arch dams, gravity dams and buttress dams. The height of water in the dam is called head race.

(2) Spillway

A spillway as the name suggests could be called as a way for spilling of water from dams. It is used to provide for the release of flood water from a dam. It is used to prevent over toping of the dams which could result in damage or failure of dams. Spillways could be controlled type or uncontrolled type. The uncontrolled types start releasing water upon water rising above a particular level. But in case of the controlled type, regulation of flow is possible.

(3) Penstock and Tunnel

Penstocks are pipes which carry water from the reservoir to the turbines inside power station. They are usually made of steel and are equipped with gate systems.Water under high pressure flows through the penstock. A tunnel serves the same purpose as a penstock. It is used when an obstruction is present between the dam and power station such as a mountain.

(4) Surge Tank

Surge tanks are tanks connected to the water conductor system. It serves the purpose of reducing water hammering in pipes which can cause damage to pipes. The sudden surges of water in penstock is taken by the surge tank, and when the water requirements increase, it supplies the collected water thereby regulating water flow and pressure inside the penstock.

(5) Power Station

Power station contains a turbine coupled to a generator. The water brought to the power station rotates the vanes of the turbine producing torque and rotation of turbine shaft. This rotational torque is transfered to the generator and is converted into electricity. The used water is released through the tail race. The difference between head race and tail race is called gross head and by subtracting the frictional losses we get the net head available to the turbine for generation of electricity.

Turbines

A turbine converts the energy in falling water into shaft power. There are various types of turbine which can be categorised in one of several ways. The choice of turbine will depend mainly on the pressure head available and the design flow for the proposed hydropower installation. As shown in table 2 below, turbines are broadly divided into three groups; high, medium and low head, and into two categories: impulse and reaction.

Head pressure
Turbine Runner / High / Medium / Low
Impulse / Pelton TurgoMulti-jet Pelton / Crossflow
Turgo
Multi-jet Pelton / Crossflow
Reaction / Francis
Pump-as-turbine (PAT) / Propeller
Kaplan

Table 1: Classification of turbine types.

Source: Micro-hydro Design Manual, IT Publications, 1993

The difference between impulse and reaction can be explained simply by stating that the impulse turbines convert the kinetic energy of a jet of water in air into movement by striking turbine buckets or blades - there is no pressure reduction as the water pressure is atmospheric on both sides of the impeller. The blades of a reaction turbine, on the other hand, are totally immersed in the flow of water, and the angular as well as linear momentum of the water is converted into shaft power - the pressure of water leaving the runner is reduced to atmospheric or lower.