Unit 6
Electricity generation
Tuning-in
Generating electricity is a miracle of modern technology. Acting more or less like a force field, electric current is comprised of protons and electrons that become charged when induced by friction or chemical changes. Most power plants burn fuel - coal, oil, natural gas, biomass - which creates steam to drive a turbine that generates electricity. Sometimes nuclear or solar energy creates the steam to drive the turbine. Other technologies - such as solar photovoltaics or fuel cells - rely upon chemical reactions to generate electricity.
Task 1. List the different ways in which electricity can be generated
Reading
Task 2. Study the diagram below of a portable generator. Answer these questions using the diagram and your own knowledge of engineering.
1) What are its main parts?
2) What does the engine run on?
3) What are the four strokes called?
4) What is the function of a crankshaft?
5) What do both stator and rotor have?
6) What is the difference between stator and rotor?
A portable generator can provide electricity to power lights and other appliances no matter how far you are from the mains. It works by turning the movement of a piston into electrical energy.
Task 3. Read the text to check as many of the answers as you can. You will not find complete answers to all the questions.
Active vocabulary
alternator - генератор переменного тока |
to power - приводить в действие или движение |
cord - шнур |
power - сила (физическая) , мощность, энергия, |
compressor stroke - такт сжатия |
производительность |
Exhaust valve - выпускной клапан |
to wind – wound - обматывать |
crankshaft - коленчатый вал |
winding – обмотка, намотка |
set – комплект, набор; установка, агрегат |
to ignite - возгорать(ся) |
Socket – гнездо, розетка |
to descend - спускать(ся); снижать(ся) |
appliance - аппарат, прибор, устройство |
to feed – fed - подавать; питать; снабжать; подводить |
armature - якорь |
to spin - быстро вращаться; вертеть(ся); крутиться |
Portable generator
Although most electricity comes from power stations, power can also be generated by far smaller means. Nowadays, electricity generators can be small enough to hold in the hand.
Portable generators are made up of two main parts: an engine, which powers the equipment, and an alternator, which converts motion into electricity. The engine shown (Fig.1) runs on petrol. It is started by pulling a cord. This creates a spark inside which ignites a fuel mixture.
In a typical four-stroke engine, when the piston descends, the air inlet valve opens and a mixture of air and petrol is sucked in through a carburetor. The valve closes, the piston rises on the compressor stroke and a spark within the upper chamber ignites the mixture. This mini-explosion pushes the piston back down, and as it rises again the fumes formed by the ignition are forced out through the exhaust valve. This cycle is repeated many times per second. The moving piston makes the crankshaft rotate at great speed.
The crankshaft extends directly to an alternator, which consists of two main sets of windings – coils of insulated copper wire wound closely around an iron core. One set, called stator windings, is in a fixed position and shaped like a broad ring. The other set, the armature windings, is wound on the rotor which is fixed to the rotating crankshaft. The motor makes about 3,000 revolutions per minute.
The rotor is magnetized and it spins round, electricity is generated in the stator windings through the process of electromagnetic induction. The electric current is fed to the output terminals or sockets.
This type of generator can produce a 700 watt output, enough to operate lights, television, and some domestic appliances. Larger versions provide emergency power to hospitals and factories.
Task 4. Study this text on the four-stroke cycle. Name the cycles.
In the four-stroke cycle, the piston descends on the intake stroke, during which the inlet valve is open. The piston ascends on the compression stroke with both valves closed and ignition takes place at the top of the stroke. The power or expansion stroke follows. The gas generated by the burning fuel expands rapidly, driving the piston down, both valves remaining closed. The cycle is completed by the exhaust stroke, as the piston ascends once more, forcing the products of combustion out through the exhaust valve. The cycle then repeats itself.
Listening
Task 5
Listen to the text and answer the questions. Speak on the electricity generation using questions as a plan.
Electricity generation
electric utilities – электростанция общего пользования
harness – перекрытие
landfill gas - газ из органических отходов
Electricity generation is the process of converting non-electrical energy to electricity. For electric utilities, it is the first process in the delivery of electricity to consumers. The other processes, electric power transmission and electricity distribution, are normally carried out by the electrical power industry.
Electricity has been generated at central stations since 1881. The first power plants were run on water power or coal, and today we rely mainly on coal, nuclear, natural gas, hydroelectric, and petroleum with a small amount from solar energy, tidal harnesses, wind generators, and geothermal sources.
The demand for electricity is met in several ways. Large centralized generators have been the primary method thus far.
Distributed generation uses a larger number of smaller generators throughout the electricity network. Some use waste heat from industrial processes; others use fuels that would otherwise be wasted, such as landfill gas. Wind and solar generation tend to be distributed because of the low density of the natural energy they collect.
1) Name the processes in the delivery of electricity to consumers.
2) Since when has electricity been generated at central stations?
3) What sources are power plants run on?
4) What can smaller generators use?
5) What is the advantage of wind and solar generation?
Word Building
Task 6
Translate the following derivative words:
noun + -ous, -ious, -eous → adjective
autonomy – autonomous, prestige – prestigious, right – righteous, religion – religious, glory – glorious, ambition – ambitious, fame – famous, industry – industrious, victory – victorious
verb + -er/-or → noun
to provide – provider, to educate – educator, to separate – separator, to examine – examiner, to demonstrate – demonstrator, to investigate – investigator, to govern - governor
verb + -tion, -ion, -ation → noun
to educate – education, to compete – competition, to combine – combination, to separate – separation, to administer - administration
Task7.
Suffixes -ize/-ise
Study the statement:
The rotor is magnetized.
What does it mean? We can rewrite this statement as:
The rotor is made magnetic.
Verbs ending in -ize/-ise have a meaning of make + adjective.
Rewrite these sentences replacing the phrases in italics with appropriate -ize/-ise verbs.
(as a rule, -ize is American variant, -ise is mostly British; to be sure, look up the word in a dictionary).
Some cars are fitted with a security device which makes the engine immobile.
In areas where the power supply fluctuates, for sensitive equipment a device to make the voltage stable is required.
Manufacturers seek to keep costs to a minimum and profits to a maximum.
Most companies have installed computers to control their production line.
Companies may make their operation more rational by reducing the variety of products they make.
Technical Reading
Task 8
Read and translate the text.
FUTURE POWER SOURCES
Introduction
Scientists and engineers are devoting an increasing amount of attention to what are commonly called "new" or "unconventional" power sources. The impetus for this development effort stems from many things. In a general way, the continually increasing demand for electric power, and the eventual inability of present energy sources to supply our needs are the dominant factors. However, there are others — the need for specialized power plants to serve in space or in remote land areas, to name one.
Four of the most promising of the "new" power sources - thermoelectric, thermionic and magnetohydrodynamic generators, and fuel cells — are discussed in the following pages. As most readers will recognize, none of these power generation methods are new in principle. The concept of thermoelectric devices dates back to 1822; the thermionic principle to 1878; magnetohydrodynamics to about 1835, and, the fuel cell to 1802. However, only recently have these principles come in for serious attention as the basis for large-scale power generators. The present interest stems largely from a better understanding of the physics and chemistry involved, and our ability to develop new materials to meet the unusual requirements.
In these articles no particular attempt has been made to evaluate each new generating method fully. At this stage of development, any general evaluation would be impractical, because much remains to be learned about each method.