What is renewable energy?

We need energy for homes, schools, factories and transport. Much of it comes from fossil fuels: coal, oil and natural gas. These formed from ancient plants and animals over millions of years, so once we use them, they are gone. Burning them also releases carbon dioxide, a gas that traps heat in the atmosphere and is the main cause of global warming. They are called non-renewable.

Renewable sources keep refilling.

• Solar power: solar panels turn sunlight into electricity. They can also heat water.
• Wind power: the wind turns the blades of a turbine, which spins a generator. Wind farms work best in windy places such as coasts and hills.
• Hydroelectric power: a dam holds back water. When it is released, it flows through turbines. Many countries use it. Norway gets almost all of its electricity from water power, Brazil gets more than half, and Nigeria has dams such as Kainji.
• Geothermal energy: heat from deep underground makes steam to turn turbines. It works well in volcanic regions like Iceland.
• Biomass: fuel from plants and waste, such as wood or biogas. It can be renewable if new plants are grown to replace what is burned.
• Tidal and wave power: the movement of the sea drives generators.

Each has advantages and drawbacks. Renewables make little or no pollution while running, and the fuel is free. But the Sun does not always shine and the wind does not always blow, so electricity grids use batteries, other sources and clever planning to keep the lights on. Building the equipment needs materials and space.

Nuclear power stations use uranium, which is not renewable, but they release almost no carbon dioxide. Many countries are using more renewables each year. Everyone can help by saving energy at home, such as switching off lights. See energy and electricity.