Classification of Energy Sources (1) By production process ① Primary energy: a type of energy that can be gained directly from nature, such as solar heat, tidal power, wave power, hydraulic power, geothermal heat, coal, petroleum, and natural gas. ② Secondary energy: a type of energy that is processed from primary energy and converted into a form that can be used in daily life or industry such as electric power, city gas, petroleum products, and coke.
(2) By form
① Mechanical energy: the type of energy that indicates the potential energy and kinetic energy of an object. It creates electric energy by spinning a wheel, windmill, steam turbine, etc. ② Electric energy: the type of energy an object with an electric charge or live lead wire has. It can be used after being converted into mechanical energy. ③ Chemical energy: the type of energy generated in the form of heat or electric power through chemical reactions such as oxidation and reduction. ④ Thermal energy: the type of energy generated in the form of heat. Modern day energy is mostly converted from thermal energy. ⑤ Light energy: a type of energy essential for organisms to survive. Plants that have chlorophyll photosynthesize substances needed for growth using light energy. Light energy radiated from the sun is a source of all types of energy of the earth. ⑥ Atomic energy: an alternative energy resource of fossil fuel. It is divided into nuclear fission energy and nuclear fusion energy.