Man has been using some form of power to supplement his own energy. Animals like cattle, horses and camels serve as draught animals for various types of works on the farm and for transport. In the developing nations of Asia and Africa, animals are still used on a large scale. Early man has also been using wind and water as sources of power. The force of falling water was harnessed by the waterwheel for grinding flour. Wood has been used for cooking and for heating homes. Though wood has ceased to be used as domestic fuel in the developed nation, wood still provides about 45% of energy needs of developing nations.
The increasing use of mineral fuels has occurred in the last one hundred years. Power resources are needed not only for industrial purposes but also for transport on land, sea and air. Power is increasingly consumed for lighting and heating homes and for the use of numerous domestic appliances, which enable us to lead a comfortable life. There is perhaps no human activity where power is not consumed. Primary industries like agriculture, fishing and forestry are consuming power for increasing production. Mechanical power has become indispensable for modern civilization.
Coal, oil and radioactive minerals like uranium and thorium are exhaustible power resource. Hydroelectric power is a renewable power resource. Other renewable power resources are solar power, wind power, tidal power, power from the biomass and geothermal power.
The known resources of oil are likely to get exhausted in a few decades at the present rate of consumption, while coal resources may last for a few centuries. It is necessary to changeover to renewable sources of energy so that coal and oil may last for a longer period.
Though the power resources are essential for satisfying all our need, these resources are very unevenly distributed. More than 90% of the coal resources are concentrated in three countries Russia, U.S.A. and China. Four regions, namely the Middle East, Russia, U.S.A. and the Caribbean have 75% of world's reserves of oil. Developed countries of Western Europe and Japan depend on imports of oil.
The disparities in economic development between the nations of the world may be explained in terms of the amount of power consumed by them. Americans and Canadians consume 11 tons of coal equivalent of power per capita per year. In the developed countries of Europe, Japan, Australia and New Zealand, the average per capita consumption is only 0.50 ton of coal per year. The developing nations do not have adequate resources of power and they cannot afford to import power due to its high cost. The solution to the problem lies in finding a process to harness solar power at a reasonable cost.
Atomic energy when available for industrial purposes will surely encourage further decentralization. Thus, man has attained a position to direct machine activity instead of functioning personally and has attained higher per capita productivity. In order to achieve further material progress and to solve social and economic problems the economy demands efficient utilization of important sources, coal, petroleum, natural gas, waterpower and perhaps, atomic energy.
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