In areas where the wind dies down, backup electricity from a utility company or from an energy storage system becomes necessary.

在风能不稳定的一些地区，需要供电事业公司或者能量储存系统来提供备用电能。

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But when the wind dies down, the surface of the water settles down. And soon the water is still again.

风停了，水面也慢慢稳下来，不久水面又静止了。

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The wind often dies down at sunset.

风往往在日落前停息。

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To that end, green fuels require back-up generation that kicks in when the wind dies down or the sun ceases to shine.

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And skeptics are also saying that wind energy is an intermittent fuel that must always be backed up by a power source that can begin generating when the wind dies down, making it expensive to operate.

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The company would like to see a fraction of the credit go to utilities to compensate them for having to reserve space on their transmission systems and for having to run the back-up systems when the wind dies down.

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