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.
According to the author, the impracticability of using coal, oil shale and coal tars as sources of energy is due to ___________ .
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Lời giải:
Báo saikiến thức: đọc
Giải thích: 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, heat from the earth, is also being tested.
Dịch: Công việc thí nghiệm đang được thực hiện để lấy nhiên liệu tổng hợp từ than đá, đá phiến dầu và than đá. Nhưng đến nay, quá trình đó đã được chứng minh là tốn kém. Các thí nghiệm khác đang được tiến hành để khai thác - sức mạnh với cối xay gió khổng lồ. Năng lượng địa nhiệt, nhiệt từ trái đất, cũng đang được thử nghiệm