Coal-fired Power Plants
The invention of the incandescent light bulb by Thomas A. Edison in 1879 created a demand for a cheap, readily available fuel with which to generate large amounts of electric power. Coal seemed to fit the bill, and it fueled the earliest power stations . As more power plants were constructed throughout the country, the reliance on coal increased. Since the First World War, coal-fired power plants have accounted for about half of the electricity produced in the United States each year. In 1986 such plants had a combined generating capacity of 289, 000 megawatts and consumed 83 percent of the nearly 900 million tons of coal mined in the country that year. Given the uncertainty in the future growth of nuclear power and in the supply of oil and natural gas, coal-fired power plants could well provide up to 70 percent of the electric power in the United States by the end of the century. Yet, in spite of the fact that coal has long been a source of electricity and may remain one for many years , it has actually never been the most desirable fossil fuel for power plants. Coal contains less energy per unit of weight than natural gas or oil; it is difficult to transport, and it is associated with a host of environmental issues, among them acid rain. Since the late 1960s problems of emission control and waste disposal have sharply reduced the appeal of coal-fired power plants. The cost of ameliorating these environmental problems along with the rising cost of building a facility as large and complex as a coal-fired power plant, have also made such plants less attractive from a purely economic perspective. Changes in the technological base of coal-fired power plants could restore their attractiveness, however. Whereas some of these changes are evolutionary and are intended mainly to increase the productivity of existing plants, completely new technologies for burning coal cleanly are also being developed.
过去进行时语法知识要点
形容词和副词速记口诀
many,old 和 far的区别
英语语法:every , no, all, both, neither, nor的区别
助动词be的用法
英语语法:many,much的区别
英语语法:代词比较辩异 one,that 和it
英语语法:the + 最高级 + 比较范围
助动词should,would的用法
短语动词的用法
英语语法:关系代词
英语语法:不定冠词的用法
接不定式作宾语的动词速记口诀
英语语法:both, either, neither, all, any, none的区别
英语语法:数词的应用
英语语法:anyone/any one;no one/none;every/each的区别
英语语法:物主代词
以-ly结尾的形容词
接动名词作宾语的动词速记口诀
冠词用法的速记口诀
英语语法:反身代词
英语语法:冠词与形容词+名词结构
多个形容词修饰名词的顺序
英语语法:代词的指代问题
英语语法:one/another/the other的区别
英语中可修饰比较级的词有哪些
和more有关的词组语法讲解
助动词shall和will的用法
英语语法:冠词的位置
助动词have的用法
不限 |
英语教案 |
英语课件 |
英语试题 |
不限 |
不限 |
上册 |
下册 |
不限 |