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 10 other power source Primary energy sources used in electrical power generation 15 20 25 30 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 20052006 37 35 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 40 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 45 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 Rephrasing Rewrite the following sentences, replacing the words in italics with expressions from the passage which have similar meanings: Small mobile generators are often driven by diesel motors, especially on ships, remote building sites or for emergency standby The world depends mainly on coal and natural gas for power Tidal harnesses use the force of the moon on bodies of water to turn a turbine Pumped-storage hydroelectricity is used to level needs on the power grid 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 Contextual reference What the words in italics in these sentences refer to? 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 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 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 Checking facts and ideas 38 Decide if these statements are true or false Quote from the passage to support your decisions Steam, water, wind are used as an intermediate energy carrier to drive turbines The world relies only on coal and natural gas for power In hydroelectric power plants, water flows directly through the turbines to power the generators Thermonuclear fusion has been used to generate electricity Power generation by thermonuclear fusion has great potential because it might provide a relatively clean and safe source of electrical power As estimated, the construction of a large experimental reactor will commence in 20052006 Co-generation plants achieve efficiencies as high as 80% Heated steam only used to turn turbines 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 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: It is used for measuring voltage It is used to measure voltage We measure voltage with an ammeter We measure current using an ammeter Now describe the purpose of these instruments and facilities using of the structures presented above A battery charger A megohmmeter A radiator A waveform display equipment A signal generator A turbine A current transformer 39 A protective relay A full cell 10 Pumped-storage hydroelectricity Task Relative clauses 2: making definitions Study these two sentences: The insulators are deteriorated The insulators are contaminated We can link them in two ways using a relative clause: The insulators WHICH ARE CONTAMINATED are deteriorated The insulators, WHICH ARE CONTAMINATED, are deteriorated Sentence 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 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: (a) An electric motor (b) a machine is which (c) converts electrical energy into mechanical energy 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 a particular job Machine a piece of equipment with moving parts that is designed to 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 40 (a) Porcelain A radiator A transducer A circuit breaker Thermo tracer A transformer A generator A miliammeter A governor Copper III (b) (c) 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 INFORMATION TRANSFER Task Describing component values Study this table: Prefix Symbol Multiple Example Giga G 109 GHz Gigahertz Mega M 106 MBar Megabars kilo k 103 kA Kiloamps deci d 10-1 dB Decibels milli m 10-3 mV Millivolts micro µ 10-6 µs Microsecs nano n 10-9 nF Nanofarads pico p 10-12 pF picofarads 41 Identify the components in the following circuit and write out their value in full: F 1.25A 1.4mH 1000µF 16V L1 R4 C2 25V 100µF R1 22kΩ C4 68nF 39kΩ R6 C6 1kΩ +14V BC328 BC148 C1 2.2µF 63V R2 C5 15nF 82kΩ R5 C3 BD433 R7 R8 100Ω 100Ω BC148 1kΩ 470µF 10V BD434 C7 100µF 16V R9 R3 120Ω RL 3.3Ω 1/2W 2Ω or 4Ω 42 IV GUIDED WRITING Task 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 when Electricity is generated A loop of conducting wire rotates in a magnetic field 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 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 which Geothermal power generation is an environmentally friendly power generation method Geothermal power generation produces only 1/20th of CO emissions per a unit of electricity generated compared with thermal power generation before The connection between magnetism and electricity was discovered Generators used electrostatic principles because Copper is used in many wires Copper has a lower resistance than many other metals after, that Electricity is produced at power plants Electricity has to get to the customers The customers use the electricity although Nuclear power stations have a good safety record There have been some well-known accidents such as Chernobyl 43 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) 44 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 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 or no 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 m 3) The heavier no "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 45 How does a fossil fuel power plant work? What does a battery convert into electricity for temporary or intermittent use? 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? What are swiveling couplers for? What is stored in vertical cylindrical steel tanks as large as 90,000 barrels (14,000 m3)? 46 ... 1.4mH 1000µF 16V L1 R4 C2 25V 100µF R1 22kΩ C4 68 nF 39kΩ R6 C6 1kΩ +14V BC328 BC148 C1 2.2µF 63 V R2 C5 15nF 82kΩ R5 C3 BD433 R7 R8 100Ω 100Ω BC148 1kΩ 470µF 10V BD434 C7 100µF 16V R9 R3 120Ω... 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... sites or for emergency standby The world depends mainly on coal and natural gas for power Tidal harnesses use the force of the moon on bodies of water to turn a turbine Pumped-storage hydroelectricity