202 Useful Exercises for IELTS Side2-01-AudioTrack01

　　 Narrator: Exercise 3.9. Lecture 3:

       Electric cars? Solar-powered buses? When most people imagine solutions to the problems of city air pollution they probably think of electricity and solar power. But the problem with an electric car is that the electrical energystored within the batteries has to be first produced by conventional means such as burning coal, which creates thevery problem the car is supposedly designed to avoid. Even the battery disposal is an environmental hazard. Asfor solar power, at present the solar panels that catch the sunlight are twice as big as the cars they power. Andspeeds of ten kilometres an hour are hardly practical. What is required is a safe, cheap and highly efficient enginethat produces fewer major air pollutants 1 and only in small quantities. You may be surprised that the answer hasbeen with us for quite some time.

The probable solution to city air pollution is a concept for an engine that was first proposed by a French scientistin 1824 and later designed and patented by a German refrigeration engineer in 1892, whose name was RudolphDiesel. His design for an engine that would produce more energy output but burn less fuel became known as thediesel engine. Most people think of diesel 2 engines as being efficient and cheaper to run but smelly and rather noisy.

It is true that the black soot 3 emitted from the exhausts of diesel lorries does not naturally lead us to conclude thatthe diesel engine can eradicate 4 air pollution, but, contrary to popular belief, they emit far fewer of all the majorair pollutants than petrol-driven engines, except for nitrogen oxides and black soot. However, soot can be trapped,and already new diesel engines are under development, being redesigned to burn diesel fuel in such a way thatthe nitrogen oxide 5 gases are released into the air as harmless nitrogen and oxygen.

In fact, if all cars were running on diesel fuel, air pollution in major cities would disappear overnight. Why thenhas it taken this long to do something about it? The problem is that the disadvantages of diesel engines, whichinclude greater noise and vibration 6 as well as taking longer to start up, have meant that car manufacturers havebeen reluctant to invest in production of more expensive diesel-powered cars - afraid that customers would notpurchase their products. Fortunately, new technology is ensuring that diesel-powered engines become lean, cleanand mean. It might not be long before city smog is but a distant memory.