Energy efficient process converts up to 80% of the expended energy into useful heat to save costs.

能量的有效转换过程中，高达80%的能源转化成为有用热，以节省成本。

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When the magnesium is mixed with water, it produces heat, boiling the water to produce steam, which can then drive a turbine and do useful work.

当镁与水混合在一起时，它就会产生热量，让水沸腾产生蒸汽，而产生的蒸汽然后就可以驱动涡轮机，而且也可用来做些有用的工作。

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In practice, not enough heat is generated to make a useful amount of electricity.

实际上，产生的热量并不足以用来发电。

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What does come out, which is very useful is, if you do run the reaction, here's how much heat comes out.

能得到的结果是，如果我们进行这个化学反应，有多少热量放出，当然这也是很重要的。

麻省理工公开课 - 热力学与动力学课程节选

Research suggests that up between 20 and 30 gigawatt-hours (GWh) of electric energy could be stored as useful heat in hot water.

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But heat is useful in its own right.

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Some of the heat is useful.

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