Primary, Secondary and Supplementary Sources of Energy
The energy sources available in the world can be divided into the following categories :
(a) Primary energy sources.
(b) Secondary energy sources.
(c) Supplementary sources.
(a) Primary energy sources : These are the energy sources which provide a net supply of energy. Coal, oil, gas, uranium etc. are the examples of this type. The energy required to obtain these fuels is much less than what they can produce by combustion or nuclear reaction etc. The primary fuels only can accelerate growth, but their supply is limited. These fuels are the main source of energy production, hence they contribute considerably to the energy supply.
(b) Secondary energy sources : Secondary fuels produce no net energy. Intensive agriculture is an example, where the yield is less in comparison to the energy input.
(c) Supplementary sources : They are defined as those, whose net energy yield is zero and those requiring highest investment in terms of energy. Thermal Insulation is an example of this source.
Coal, natural gas, oil and nuclear energy using breeder reactor are net energy yielding sources and are the primary sources of energy. Secondary sources are solar energy, wind energy, water energy etc. Solar energy can be used through plants, solar cells, solar heaters etc. Solar tower is another emerging technology. Solar drying and solar heating are applications which cost less. Other better sources are wind, tide, wave and hydro electric applications. Geothermal and ocean thermal are another sources which will provide worthwhile. It is necessary in future to develop the secondary sources like solar energy and wind energy.