Sources of energy
Energy sources are categorized as renewable or non-renewable.
- Renewable energy. A source of energy is considered renewable if it comes from natural sources or processes that are constantly replenished. Examples are solar (from the sun), wind, water, geothermal (from the earth) and biomass (from organic materials).
- Non-renewable energy sources don’t replenish. They were formed when prehistoric plants and animals died and were gradually buried by layers of soil rock. The kind of fuel that was created varies depending on whether it came from plants or animals, how long it was buried, at what temperature and under what pressure. Types of non-renewable energy are natural gas, coal and oil.
Types of energy
- Chemical energy – stored within bonds between molecules. Sources include natural gas, gasoline, coal and batteries. Even the food we eat is considered chemical energy.
- Electrical energy – comes from tiny charged particles called electrons. A lightning bolt is one form of electrical energy. The electricity in our homes is made by humans.
- Gravitational energy – associated with a gravitational field, like the one that surrounds the Earth. If you’ve ever fallen down, you’ve experienced the power of gravitational energy. Gravitational energy is the reason why riding your bike downhill is faster than riding your bike uphill.
- Kinetic energy – anything that moves is using this kind of energy. Examples include running, cycling, climbing – even swiping your finger across your smart phone! Wind turbines capture the kinetic energy in wind and transform it into mechanical energy.
- Mechanical energy – stored in objects by tension. When the tension is released, motion occurs. A compressed spring contains mechanical energy as does a stretched rubber band.
- Nuclear energy – stored inside tiny atoms that are invisible, but make up the elements of the entire universe. Nuclear energy is released when atoms join together (fusion) or split (fission). The fusion reaction in the sun provides warmth and light, while the fission reaction at a nuclear power plant creates enough energy to power large cities.
- Solar (radiant) energy – energy that comes from the movement of light.
- Sound energy – produced when an object is made to vibrate producing a sound. Your voice and musical instruments use sound energy.
- Thermal (heat) energy – created from moving molecules. The energy that comes from a fire is thermal energy.