Future electric cars will not need to get electricity from anywhere. People are developing new batteries which use a metal called zinc. When zinc mixes with oxygen from the a chemical process makes electricity When the battery i finished, the zinc can easily be recycled and used again. Hydrogen The cleanest fuel is hydrogen. When hydrogen burns, it just makes water. We already have cars and even helicopters that use hydrogen, but this gas is difficult to produce. Today, most hydrogen is made from fossil fuels, and this produces pollution. About 4 per cent of hydrogen is made from water, but this process uses a lot of electricity and can be dangerous. In 2010, engineers invented a machine which uses energy from the sun to make hydrogen. Other people are trying to use bacteri to make it. These 'clean' ways of mak hydrogen are still very new. If they become cheaper, we may ll drive hydrogen cars in the future entis are developing lots of new fuels, but it will be a long time before most of us can use them. The biggest problem is finding the money to make the necessary changes to things like cars and petrol stations, For example, there are about 140.000 petrol stations in the USA today but only 2,800 of them sell bioethanol. Renewable energy is energy which comes from things that go on and on, like the sun or the wind. Some the fuels in this chapter are renewable, and some are not. Biofuels are renewable because we can grow them again every year. Hydrogen is a renewable fucl when we make it water but not when we make it from fossil fuels. some o her types of the next few chapters, we wi look renewable energy