Academic Reading
Wind Power in the US
Prompted by the oil crises of the 1970s, a wind-power industry flourished briefly in the United States. But then world oil prices dropped, and funding for research into renewable energy was cut. By the mid 1980s US interest in wind energy as a large-scale source of energy had almost disappeared. The development of wind power at this time suffered not only from badly designed equipment, but also from poor long-term planning, economic projections that were too optimistic and the difficulty of finding suitable locations for the wind turbines.
Only now are technological advances beginning to offer hope that wind power will come to be accepted as a reliable and important source of electricity. There have been significant successes in California, in particular, where wind farms now have a capacity of 1500 megawatts, comparable to a large nuclear or fossil-fuelled power station, and produce 1.5 per cent of the states electricity.
Nevertheless, in the US, the image of wind power is still distorted by early failures. One of the most persistent criticisms is that wind power is not a significant energy resource. Researchers at the Battelle Northwest Laboratory, however, estimate that today wind turbine technology could supply 20 per cent of the electrical power the country needs. As a local resource, wind power has even greater potential. Minnesotas energy commission calculates that a wind farm on one of the states south western ridges could supply almost all that states electricity. North Dakota alone has enough sites suitable for wind farms to supply more than a third of all electricity consumed in the continental US.
The prevailing notion that wind power is too costly results largely from early research which focused on turbines with huge blades that stood hundreds of metres tall. These machines were not designed for ease of production or maintenance, and they were enormously expensive. Because the major factors influencing the overall cost of wind power are the cost of the turbine and its supporting systems, including land, as well as operating and maintenance costs, it is hardly surprising that it was thought at the time that wind energy could not be supplied at a commercially competitive price.
More recent developments such as those seen on California wind farms have dramatically changed the economic picture for wind energy. These systems, like installations in Hawaii and several European countries, have benefited from the economies of scale that come through standardised manufacturing and purchasing. The result has been a dramatic drop in capital costs: the installed cost of new wind turbines stood at $1000 per kilowatt in 1993, down from about $4000 per kilowatt in 1980, and continues to fall.
Design improvements and more efficient maintenance programs for large numbers of turbines have reduced operating costs as well. The cost of electricity delivered by wind farm turbines has decreased from about 30 cents per kilowatt-hour to between 7 and 9 cents, which is generally less than the cost of electricity from conventional power stations. Reliability has also improved dramatically. The latest turbines run more than 95 per cent of the time, compared with around 60 per cent in the early 1980s.
中考英语词汇“for短语”全攻略
初中英语 词缀记忆法
2009中考英语词汇表 系列H
英乐时空Here I Am
中考英语词汇--“美味水果”大聚会
2009中考英语词汇表 系列T
09年中考英语总复习经典习题讲解3一冠词
为英语写作”画龙点睛“的24句谚语
初中英语常用词组2 介词短语词组
2009中考英语词汇短语集锦 (2)
09年中考英语总复习经典习题讲解4一数词
十个窍门积累英语词汇
2009中考英语词汇表 系列PQ
2010年中考英语词汇熟词新义:start
张惠妹《排山倒海》英文版
“爱”成中学生作文出现频率最高词汇
高中英语词汇:80后“A到Z”生存法则
初中英语常用词组3 量词词组
初中英语短语汇总 A- Y
2009中考英语词汇表 系列R
常用英语词语辨析105组(4)
2009中考英语词汇表 系列W
初中英语常用词组复习1
词汇笔记 五种词汇的学习方法 超强
09年中考英语总复习经典习题讲解5一代词
2009中考英语词汇表 系列S
09年英语短语集中联想记忆110条
初中英语常用词组复习2
从奥巴马演讲词看英语写作词汇的应用
2009中考英语词汇表 系列M
不限 |
英语教案 |
英语课件 |
英语试题 |
不限 |
不限 |
上册 |
下册 |
不限 |