Unit 6 methods for generating electricity

The most common usage is by steam in fossil fuel power plants or nuclear power plants, and by water in hydroelectric dams.. Fuel cells produce electricity using a variety of chemicals an

Unit 6: Methods for generating

electricity

I READING AND COMPREHENSION

METHODS OF GENERATING ELECTRICITY

Methods for transforming other power into electrical power

Rotating turbines attached to electrical generators produce most commercially available electricity Turbines may be driven by using steam, water, wind or other fluids as an intermediate energy carrier The most common usage is by steam in fossil fuel power plants or nuclear power plants, and by water in hydroelectric dams Small mobile generators are often driven by diesel engines, especially on ships, remote building sites or for emergency standby Fuel cells produce electricity using a variety of chemicals and are seen by some people to be the most likely source of power in the long term, especially if hydrogen can be used as the feedstock However, hydrogen is usually only an energy carrier, and must be formed by some other power source

Primary energy sources used in electrical power generation

The world relies mainly on coal and natural gas for power

The high capital requirements of nuclear power and the fear of its dangers have prevented the ordering of new nuclear

power plants in North America since the 1970s

Steam turbines can be powered using steam produced from

geothermal sources, solar energy, or nuclear reactors, which

use the energy created by the fission of radioactive

plutonium or uranium to generate heat Nuclear power

plants often use a primary and secondary steam circuit to

add an additional layer of protection between the location

of the nuclear fuel and the generator room

Hydroelectric power plants use water flowing directly

through the turbines to power the generators Tidal harnesses

use the force of the moon on bodies of water to spin a

turbine Wind turbines use wind to turn turbines that are

hooked up to a generator Pumped-storage hydroelectricity is

used to level demands on the power grid

Power generation by thermonuclear fusion has been suggested as a possible way of generating electricity; currently a number of technical obstacles and environmental concerns stand in the way, but if realized fusion might provide a relatively clean and safe source of electrical power The construction of a large experimental reactor (ITER) is expected to commence in 2005-2006

5

10

15

20

25

30

Improving efficiency

Co-generation (combined heat and power) plants combine the generation of electricity and heat using solar power, fossil fuels, syngas, biomass, or biogas as a fuel source These plants can achieve efficiencies as high as 80%, but many of these plants being built today only expect to achieve stated maximum 55% efficiency Heated steam turns a turbine, and then excess heat is distributed for space heating in buildings, industrial processes or green house heating Whole communities can benefit from heat distributed through a district heating scheme

The ability to achieve tri-generation using fossil fuels or solar energy to generate heat, electricity and evaporative cooling exists These combined power plants have the best energy conversion ratio after hydroelectric plants Small photovoltaic arrays, windmills and bicycles hooked up to a turbine can all be used to generate mobile electricity

Task 1 Rephrasing

Rewrite the following sentences, replacing the words in italics with expressions

from the passage which have similar meanings:

1 Small mobile generators are often driven by diesel motors, especially on ships, remote

building sites or for emergency standby

2 The world depends mainly on coal and natural gas for power.

3 Tidal harnesses use the force of the moon on bodies of water to turn a turbine.

4 Pumped-storage hydroelectricity is used to level needs on the power grid

5 Co-generation (combined heat and power) plants integrate the generation of electricity

and heat using solar power, fossil fuels, syngas, biomass, or biogas as a fuel source

Task 2 Contextual reference

What do the words in italics in these sentences refer to?

1 The high capital requirements of nuclear power and the fear of its dangers have prevented

the ordering of new nuclear power plants in North America since the 1970s (line 15) (a) The high capital requirement’s

(b) Nuclear power’s

(c) New nuclear power plant’s

2 Steam turbines can be powered using steam produced from geothermal sources, solar

energy, or nuclear reactors, which use the energy created by the fission of radioactive

plutonium or uranium to generate heat (line 19)

(a) Steam turbines

(b) Geothermal sources

(c) Nuclear reactors

3 Wind turbines use wind to turn turbines that are hooked up to a generator (line 27)

(a) Steam turbines

(b) Wind turbines

(c) Turbines

Task 3 Checking facts and ideas

35

40

45

Decide if these statements are true or false Quote from the passage to support your decisions

1 Steam, water, wind are used as an intermediate energy carrier to drive turbines

2 The world relies only on coal and natural gas for power

3 In hydroelectric power plants, water flows directly through the turbines to power the generators

4 Thermonuclear fusion has been used to generate electricity

5 Power generation by thermonuclear fusion has great potential because it might provide a relatively clean and safe source of electrical power

6 As estimated, the construction of a large experimental reactor will commence in 2005-2006

7 Co-generation plants achieve efficiencies as high as 80%

8 Heated steam only used to turn turbines

9 Tri-generation power plants have the best energy conversion ratio after hydroelectric plants

10 Small photovoltaic arrays, windmills and bicycles can all be used to generate mobile electricity

II USE OF LANGUAGE

Task 4 Describing purpose

When we answer the question What is X for?, we describe the purpose of X.

EXAMPLE

What is a voltmeter for?

We can use the following ways to describe the purpose of a voltmeter:

1 It is used for measuring voltage

2 It is used to measure voltage

3 We measure voltage with an ammeter

4 We measure current using an ammeter

Now describe the purpose of these instruments and facilities using of the structures presented above

1 A battery charger

2 A megohmmeter

3 A radiator

4 A waveform display equipment

5 A signal generator

6 A turbine

7 A current transformer

8 A protective relay

9 A full cell

10 Pumped-storage hydroelectricity

Task 5 Relative clauses 2: making definitions

Study these two sentences:

1 The insulators are deteriorated

2 The insulators are contaminated

We can link them in two ways using a relative clause:

1 The insulators WHICH ARE CONTAMINATED are deteriorated

2 The insulators, WHICH ARE CONTAMINATED, are deteriorated

Sentence 1 means that only the contaminated insulators are deteriorated Other

insulators such as silicon coated insulators are not deteriorated The relative clause is a defining one It defines the type of insulators which are contaminated It carries essential information.

Sentence 2 means that all the insulators are deteriorated and all the insulators are

contaminated The relative clause is a non-defining one It adds some extra information to the sentence but it is not essential We can remove it from the sentence and the sentence still makes good sense It is separated from the rest of the sentence by commas.

One use of defining relative clauses is to make definitions Study this diagram:

Now make ten definitions using the information in the following table You must decide on the correct combinations of (a), (b), and (c)

Apparatus the tools or other pieces of equipment that are needed for a particular

activity or task

Device an object or a piece of equipment that has been designed to do a

particular job

Machine a piece of equipment with moving parts that is designed to do a

particular job

Instrument A tool or device used for measuring speed, distance, temperature, etc

in a vehicle or on a piece of machinery

Equipment the things that are needed for a particular purpose or activity

(a) An electric motor

(c) converts electrical energy into mechanical energy

(b) a machine

is

which

(a) (b) (c)

Porcelain

A radiator

A transducer

A circuit breaker

Thermo tracer

A transformer

A generator

A miliammeter

A governor

Copper

an instrument

a device

an equipment

a machine

an apparatus

a material

controls the rotational speed of turbines converts mechanical energy into electrical energy

changes the magnitude of an ac voltage measures small currents

dismisses heat from equipment does not readily release electrons provide an easy path for an electric current

converts changes in the physical variable into electrical signals

protects power system from excessive currents

measures temperature using infrared rays

III INFORMATION TRANSFER

Task 6 Describing component values

Study this table:

Identify the components in the following circuit and write out their value in full:

C1

C2

100 25V F

R4 22k

R1

39k

63V

2.2 F

R2

82k

R3

3.3

10V

470 F

C3

R5 1k

C5 15nF

C4

R7

100

R8

100

16V

1000 F

C6

16V

100 F

C7

R9

120

1/2W

F 1.25A

R L

L 1

2  or 4

BC148

BC328

BC148

BD433

BD434

1.4mH

+14V

IV GUIDED WRITING

Task 7 Sentence building

Join the following groups of sentences to make the longer sentences Use the words

printed in italics at the beginning of each group You may omit words and make

whatever changes you think are necessary in the word order and punctuation of the sentences

1 when

Electricity is generated

A loop of conducting wire rotates in a magnetic field

2 however

Fuel cells produce electricity using a variety of chemicals and are seen by some people to be the most likely source of power in the long term, especially if hydrogen can be used as the feedstock

Hydrogen is usually only an energy carrier, and must be formed by some other power source

3 as

Co-generation gas turbines (COGT) offer efficiencies of up to 60%

They generate power both directly by combustion of natural gas and also use residual heat to generate electricity from steam

4 which

Geothermal power generation is an environmentally friendly power generation method

Geothermal power generation produces only 1/20th of CO2 emissions per a unit of electricity generated compared with thermal power generation

5 before

The connection between magnetism and electricity was discovered

Generators used electrostatic principles

6 because

Copper is used in many wires

Copper has a lower resistance than many other metals

7 after, that

Electricity is produced at power plants

Electricity has to get to the customers

The customers use the electricity

8 although

Nuclear power stations have a good safety record

There have been some well-known accidents such as Chernobyl

9 while

In the 21st century, nations must optimize use of low-quality fossil fuels and sustainable-source energy

Nations must give equal consideration to resource depletion, environment protection, and the varying economic considerations affecting all nations

10 whether

Regardless of the prime mover we can interface a control system to fit your specification

It is a standard application or a custom designed control system

V READING AND SUMMARIZING

Study this passage carefully and answer the questions which follow:

FOSSIL FUEL POWER PLANT

A fossil fuel power plant (FFPP) (also known as steam electric power plant in the

US, thermal power plant in Asia, or power station in the UK) is an energy

conversion center designed on a large scale for continuous operation Just as a battery converts relatively small amounts of chemical energy into electricity for temporary or intermittent use, the FFPP converts the energy stored in fossil fuels such as coal, oil, or natural gas successively into thermal energy, mechanical energy, and finally electric energy for continuous use and distribution across a wide geographic area Each FFPP

is a highly complex, custom-designed system Present construction costs (as of 2004)

run to $1300/kW, or $650 million USD for a 500 MWe unit Multiple generating units may be built at a single site for more efficient use of land, resources, and labor The operational descriptions below are typical for a large plant and will vary from one plant to the next

Fuel transport and delivery

Coal may be delivered by transport truck or railroad cars A large coal train may be nearly a mile long, containing 100 cars, each with 100 tons of coal, for a total load of 10,000 tons Modern unloaders use rotary dump devices The unloader includes a train positioner arm that moves the entire train to position a car over a coal hopper The dumper clamps an individual car against a platform, which swivels the car upside down to dump the coal Swiveling couplers enable the entire operation to occur while the cars are still coupled together Unloading a train takes about three hours Older unloaders may still use bottom dump rail cars Generating stations adjacent to a mine sometimes haul coal with massive diesel-electric drive trucks with 140 ton capacity Trucks this large typically have 8 ft (2.5 m) diameter tires, too big and heavy to be licensed for highway use

For startup or auxiliary purposes, the plant may use no 2 or no 5 fuel oil as well, Fuel oil may be delivered by tanker truck or train car It is stored in vertical cylindrical steel tanks as large as 90,000 barrels (14,000 m3) The heavier no 5 "bunker" fuel must be steam heated before pumping in cold climates

Natural-gas fuelled plants are usually built adjacent to gas transport pipelines or have dedicated gas pipelines extended to them

1 How does a fossil fuel power plant work?

2 What does a battery convert into electricity for temporary or intermittent use?

3 Can the FFPP can either converts the energy stored in fossil fuels such as coal, oil,

or natural gas successively orr elatively small amounts of chemical energy into thermal energy, mechanical energy? Why?

4 What are swiveling couplers for?

5 What is stored in vertical cylindrical steel tanks as large as 90,000 barrels (14,000

m3)?