Wave Power

25% of the world's electricity already comes from dams and rivers. Now, scientists are learning how to use the sea's power, too. What they're doing is collecting the energy contained in waves. Here's how it works. First, water enters a special wave machine. This pushes all the air inside the machine up to the top. Then the water leaves again and pulls the air back down. This pushing and pulling makes enough energy to work an electric motor. At the moment wave machines are small and expensive. They don't produce much electricity, either. But in the future they will be bigger and cheaper. One day scientists think they will produce between 25% and 30% of our electricity.

Geo-Thermal Power

As well as solar, wind and wave power, there are other kinds of natural energy, too. One is from the hot rocks and water at the centre of the Earth. This kind of “geo-thermal” energy already heats thousands of buildings in Iceland, Hungary, Japan and New Zealand. (In fact, 60% of Iceland's energy comes from under the ground.)