What is the concept and characteristics of energy

1. Primary energy refers to the energy existing in nature, that is, the energy obtained directly from nature, without changing its basic form.

2, the primary energy source, no matter how many times after the conversion of another energy source, are called secondary energy.

3, renewable energy - that is, can be recycled, constantly replenished primary energy, such as: water energy, solar energy, wind energy, ocean energy, geothermal energy and so on.

4, oil and natural gas are fluids, easy to extract, transport, use, high calorific value, basically ashless fuel, is a high-quality energy.

5. Hydroelectric energy is a renewable energy source and can be utilized sustainably to generate electricity.