Energy means power for transportation for heat, light, works, manufacture of goods of all kinds. Modern society consumes energy in light, heat, electrical, mechanical, chemical and nuclear.
The rate at which energy is produced or consumed is called power. Energy and power are the master words in this century. Energy means the capacity to do work. Energy resources on earth are of following types:
1. Renewable (inexhaustible) Energy Resources:
These are biomass based and available in unlimited amount in nature because there can be renewal over relatively short period of time. E.g. Firewood, petroplasts, plant biomass, agriculture waste as biogas, animal dung, solar energy, wind energy, water energy.
2. Non-renewable or exhaustible Energy source:
These are available in limited amount and develop over longer period of time. E.g. Coal, mineral oil, natural gas and nuclear power, coal-petroleum, coal, petroleum and natural gas are common sources of energy being organic in origin. They are called on fossil fuels.
Economist and sociologist looked at energy from different angles. For ecologist, the study of energy started with sunlight, conversion by green plants into chemical energy of organic compound then transfer through food chains to animals and human populations. For economist the energy is a source of human needs, industry, transportation, agriculture and domestic needs.
The ecologist is give with sunlight to photosynthesis while economist with coal mine, oil well, power plant or nuclear reactor.
The energy utilization of human populations has increased steadily in the progression from hunter gatherer to agriculture and industrial societies. Energy utilization thus has become the modern key to human progress.
Human populate is have become predominantly dependent upon fossil fuels. In the beginning of the 21st century, the world reserve of petroleum was estimated to be 1 million barrels by the year 2001 worldwide consumption of petroleum totaled 28 billion barrels a year. The world’s natural gas was estimated to be 1500 trillion cubic metres and worldwide consumption of natural gas by 2001 totaled 2.6 trillion cubic metres.
The coal reserves were estimated to be roughly 1 trillion metric tons and by 2001 worldwide coal consumption is 5 billion metric tons in years. Total worldwide energy consumption is expected to grow 2.2 percent per year until 2015.
Plants provided energy through wood and energy plantation and as biomass energy. Biomass consists of cellulose, Hemicelluloses, lignin water, ether or alcohol.
The types of biomass are terrestrial biomass (food, vegetable, fiber, furniture), aquatic biomass (aquatic plants). Besides that some non conventional energy resources like wind energy, tidal energy, solar energy, geothermal energy and atomic Power (nuclear power), nuclear fusions and bio energy are also available.