Now listen to part of lecture on the topic you just read about.
现在来听一段有关你刚刚读到的话题的演讲。
The reading is correct in pointing out the problems associated with oil-powered cars.
阅读文章在指出与燃油汽车有关的问题时是对的。
Yes, oil is a finite resource, and yes, burning oil harms the environment.
是的，石油是有限的资源，而且，燃烧石油有害环境。
However, the reading is way too optimistic in its assessment of hydrogen-based fuel-cell engines.
然而，阅读部分对于氢动力燃料电池发动机的评价却过于乐观。
Hydrogen is not the solution to these problems.
氢不是解决这些问题的方法。
First, hydrogen is not as easily available as the passage indicates.
首先，氢不像文章中提到的那样容易获得。
Although it's present in common substances like water, it's not directly useable in that form.
尽管它呈现在像水这样的平常物质中，但它在那个状态下不是直接可用的。
For using a fuel-cell engine, hydrogen must first be obtained in a pure liquid state.
使用燃料电池发动机，首先必须要获得纯液态氢。
This pure liquid hydrogen is a highly artificial substance.
这种纯的液体氢是高度人工的物质。
It's technologically very difficult to produce and store liquid hydrogen.
生产和储存液氢技术上来说非常困难。
For example, it must be kept very very cold at minus 253 degrees Celsius.
比如，它必须被储存在非常非常冷的温度，零下253摄氏度。
Imagine the elaborate cooling technology that's required for that!
试想一下那个需要的精密制冷技术。
So hydrogen is not such a practical and easily available substance, is it?
所以氢不是一种现实的容易获得的物质，是吗？
Second, using hydrogen would not solve the pollution problems associated with cars.
第二，使用氢不能解决汽车所带来的污染问题。
Why? Producing pure hydrogen creates a lot of pollution.
为什么？生产纯氢会产生很多污染。
To get pure hydrogen from water or natural gas,
要从水或者天然气中获得氢，
you have to use a purification process that requires lots of energy that's obtained by burning coal or oil.
必须使用纯化工序，这个工序需要大量的通过燃烧煤炭和石油获得热量。
And burning coal and oil creates lots of pollution.
燃烧煤炭和石油会造成很多污染。
So although the cars would not pollute, the factories that generated the hydrogen for the cars would pollute.
所以，尽管汽车不会污染，但是生产汽车所用的氢的工厂会污染。
Third, there won't necessarily be any cost savings when you consider how expensive it is to manufacture the fuel-cell engine.
第三，未必能节约成本，如果你考虑一下生产燃料电池发动机有多贵的话。
That's because fuel-cell engines require components made of platinum, a very rare and expensive metal.
那是因为燃料电池发动机需要铂金制成的零部件，铂金是一种稀有而贵重的金属。
Without the platinum components in the engine,
发动机里没有铂金部件的话，
the hydrogen doesn't undergo the chemical reaction that produces the electricity to power the automobile.
氢不会进行化学反应来发电以供汽车动力。
All the efforts to replace platinum with a cheaper material have so far been unsuccessful.
目前所有用便宜一点的材料来替换铂金的努力都不成功。