But batteries and fuelcells have only recently become light enough to open up a large market.
但干电池和燃料电池技术直到最近才取得突破——其重量大大减轻,从而打开了市场的大门。
2
But while batteries store all the chemicals needed for the necessary chemical reactions in a sealed package, fuelcells use an external fuel source and air from the atmosphere.
电池是在密封容器存贮化学反应必需的化学品,但燃料电池却使用外部燃料和大气。
3
The technology is finally becoming practical, from tiny fuelcells to replace batteries in portable devices to large ones that can power buildings.