夏日的风可以带来凉意，冬日的风可以吹起漫天的雪花，此外，风还有什么作用呢？
The production tax credit for renewable forms of energy was supposed to end this December. But Congress has extended it through 2008. Other reasons for the expansion include improved turbine technology and lower production costs. They also include policies that make it easier for wind power producer…