Unit 11: Sources of energy - Reading

Exercise 1: ​Read the passage carefully, then choose the correct answers. The search for alternative sources of energy has led in various directions. Many communities are burning garbage and other biological waste products to produce electricity. Converting waste products to gases or oil is also an efficient way to dispose of wastes. Experimental work is being done to derive synthetic fuels from coal, oil shale, and coal tars. But to date, that process has proven expensive. Other experiments are underway to harness power with giant windmills. Geothermal power is also being tested. Some experts expect utility companies to revive hydroelectric power derived from streams and rivers. Fifty years ago hydroelectric power provided one third of the electricity used in the United States, but to day it supplies only 4 percent. The oceans are another potential source of energy. Scientists are studying ways to convert the energy of ocean currents, tides, and waves to electricity. Experiments are also underway to make use of temperature differences in ocean water to produce energy.

Exercise 2: Read the text below and decide which answer - a, b, c or d - best fits each space.  Although they are safe to use in the short term, coal, gas and oil present a long-term (7) ...... to the environment. All three types of fossil fuels produce carbon dioxide in (8) ...... greater .quantities than plants can use. The carbon dioxide then (9) ...... in the atmosphere and may even increase the earth's 'heat load' and lead to global (10) ..... in temperature. Furthermore, all three fossil 'fuels are (11) ...... forms of energy. Geothermal power is (12) ...... ever to be an energy source of major importance. It is limited and is exploitable in only a few places. Hydro-power offers a much more useful source of energy. It is also renewable but its (13) ...... is limited. Dams cannot be built in certain areas. In addition, large dams are also (14) ...... of causing changes in the world's climate. Wind power is a (15) ...... source of renewable energy but it cannot be used in many parts of the world where there is (16) ...... wind. Wave power is better source of energy in certain ways but it is clearly not practicable to build (17) ...... across every river estuary or to cover seas with expensive equipment. It is also ineffective where the sea is usually calm. Solar power is renewable, it does not cause pollution and it does not add to the earth's heat (18) ....... Unfortunately, solar power is not distributed equally, and in the northern latitudes it is difficult to (19) ...... and store. Solar power' also requires expensive equipment. Finally, nuclear power provides a very (20) ...... and renewable power source. However, not only is there a great danger of leaks or accidents but there is also the problem of the (21) ...... of radioactive waste.