In many countries, people produce power from coal, but it is very dirty and causes acid rain.
在很多国家，人们都用煤发电，但是这污染很大，还会导致酸雨。
Some countries use nuclear energy to produce power.
有些国家利用核能来发电。
However, nuclear power can be very dangerous.
但是，核能非常危险。
To solve the energy problem, people all over the world are looking for new ways to produce power.
为了解决能源问题，全世界的人们都在寻找新办法来发电。
China is one of the first countries in the world to use biogas technology.
中国是世界上最早使用沼气技术的国家之一。
Farmers recycle straw, grass and animal waste to make biogas.
农民们回收稻草、杂草和动物粪便来产生沼气。
This renewable energy is used in people's everyday lives.
人们日常生活中每天都会用到这种可再生能源。
Its key disadvantage is that the process requires a long time (up to 30 days) and the cost is high.
它最主要的缺陷就是整个过程需要很长时间（长达30天），而且花费很多。
Electric vehicles were developed in the 1990s.
20世纪90年代出现了电动车。
On April 11, 2010 a new kind of electric vehicle named "Yezi" was shown in the 2010 Shanghai World Expo.
2010年4月，一种名为Yezi的新型电动车在2010上海世博会上展出。
It produces electricity from the sun, the wind and CO2.
它靠太阳能、风能和二氧化碳发电。
It can not only protect the environment but also save energy.
它不仅能保护环境，还能节省能源。
It's too small to hold many people, but larger models will be developed in the near future.
它体型较小，无法承载太多人，不过更大的车型很快就会开发出来。
In China, the best-known maglev train is the German-built one in Shanghai.
在中国，最出名的磁悬浮列车是上海的一辆德国制造列车。
It takes people just 7 minutes to go the airport 30 km away.
只用7分钟，人们就能到达30千米外的机场。
The train can reach a top speed of 431 km per hour. It is quiet and quick.
这辆列车最快的速度能达到431千米每小时。它又安静速度又快。
There is no wheel noise, because there are no wheels.
没有车轮噪音，因为根本就没有车轮。
Maglev trains are very energy efficient and do not pollute the air.
磁悬浮列车非常节能，而且不会污染空气。
However, maglev guide paths are much more expensive than traditional steel railways.
但是，磁悬浮列车比传统铁轨昂贵许多。
