Scientists across the world are seeking ways to turn waste heat from motor vehicles into power, to achieve lower carbon dioxide emissions and lower fuel consumption.

Researchers at the Fraunhofer Institute in Freiburg, Germany, are working on a thermoelectric generator to convertheat from car exhaust fumes into electricity. The Fraunhofer device depends on a temperature gradient: the greater the gradient, the more electricitygenerated.

Harald B?ttner, head of the thermoelectric systems department, says exhaust gas temperatures can reach more than 700?C, creating a steep gradient between gas and engine cooling fluid.

The thermoelectric convertor makes use of this differential to generate an electric current. This power source could, eventually, replace the alternator, currently responsible for a car's electrical needs. Mr B?ttnersays it could cut petrol consumption by between 5 and 7 per cent in an average car.

全球各地的科学家都在探寻将汽车尾气余热转化为电能的方法，以降低二氧化碳排放及燃料消耗。

位于德国弗赖堡(Freiburg)的弗劳恩霍夫协会(Fraunhofer Institute)的研究人员正在研制一种热电发电机，将汽车尾气中的余热转化为电能。该装置根据温度变化率工作：温度变化率越大，产生的电能就越多。

电热系统部门负责人哈拉尔德•伯特纳(Harald B?ttner)称，废气温度能达到摄氏700度以上，造成气体和发动机冷却液之间很大的温差。

热电变换器利用这种温差来产生电流。这种电源最终可能取代目前为汽车提供电能的交流发电机。伯特纳表示，这能够使一辆普通汽车节省5%至7%的油耗。
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