Clean energy is the term used to describe sources of energy that are considered to be environmentally friendly and non-polluting, such as:
Solar energy is energy from the sun. It can be used for heat and electricity.
Wind energy is the kinetic energy that is present in moving air.
Biogas is a mixture comprising mainly of methane and carbon dioxide. It is produced when organic matter decomposes in the absence of oxygen (anaerobic digestion).
A fuel cell is a device that generates electricity by a chemical reaction.
Environment: That which environs or surrounds; surrounding conditions, influences, or forces, by which living forms are influenced and modified in their growth and development. Fresh air and its various components and energy sources, rivers, lakes, and oceans, and soil and living of humans and animals and plants . . . all of these elements together are the components of the environment.
Energy: ability to do things, energy cannot be created nor destroyed. The only thing that can happen with energy in a closed system is that it can change form, for instance kinetic energy can become electrical energy.