If by "world" you mean "planet Earth", that would be the Sun.
Sunlight
fossil fuels
Most of the world's high energy resources are from the conversion of the sun's rays to other energy. Without it, all living things will die.
The source of energy for most organisms is chemical energy and sunlight.
fule fossile is the most used energy source
Mechanical and Electrical
The world countries that uses nuclear power as a source of Energy are United States, France, Japan
Solar energy is the most abundant alternative energy source, as the sun provides more energy in one hour than the entire world consumes in a year. Solar panels can harness this energy and convert it into electricity for various applications.
Coal is the most used source for electricity in the US. World wide, other countries, I don't know.
Nuclear energy that is the source of sun energy which in turn is the source of fossil and renewable energies.
The sun is the main source of energy on earth.
Glucose is the most common energy source in cellular respiration.