ABSTRACT
Humans need energy to live. This is provided by food. The basal metabolism of a human being requires about 2.7 kWh/day. Human beings need also energy to produce work, to manufacture objects, to move from one place to the other with vehicles, to produce light when it is dark, to cook food, etc. This energy is provided by various sources such as oil, natural gas, coal, biomass, hydroelectric power, solar power, wind power etc.
