风一向多变，因此它永远比不上廉价又脏兮兮的煤，后者产出了美国半数电力。
Wind is inherently variable, so it can never compete with the cheap and dirty coal that generates half of America's electricity.
他们认为可再生能源是多变的、唾手可得的，刮风、晴天就有，而风停、阴天则无。
Renewable power is fickle, available when the wind blows or the sun shines but absent when it does not.
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