Primary energy resources are those, which are mined or otherwise obtained from the environment.
(a) Fossil Fuels: Coal, Lignite, Crude Oil. Natural gas etc
(b) Nuclear Fuels: Uranium, Thorium, Deuterium, other nuclei used in fission or fusion reactions.
(c) Hydro Energy: The energy of falling water is used to turn turbines of mill wheels.
(d) Geothermal: The heat from the underground-streams or the heat stored in the hot rocks beneath the earth’s surface.
(e) Solar Energy: Electromagnetic radiation from the sun, particularly important for photosynthesis, which is the basis of all life on earth.
(f) Wind energy: The mechanical energy of moving air used by windmills.
(g) Tidal Energy: The energy associated with the rise and fall of the tidal waters.
The primary energy resources can be further classified into renewable resources and nonrenewable resources.
Renewable Resources: They are those which are not exhaustible and which can provide a continuous supply such as wood, solar and wind energy, geothermal energy.
Non-renewable Resources: These resources are finite and exhaustible such as fossil fuels and nuclear fuels.
Fossil Fuels: Coal, petroleum, natural gas etc.
Nuclear fuels: Like Uranium, Thorium, and Deuterium etc.