Energy Conversion processes
Almost 90 per cent of the world’s current energy supply is based on fossil or mineral sources, oil, coal, gas and uranium.
Only 10 per cent comes from renewable sources, especially hydro-power and biomass, while the share of solar and wind energy is below 1 per cent.
The following table indicates the pattern of primary consumption in the world:
Table 3.1 Primary energy consumption in the world:
|Energy source||World-wide consumption||Percentage|
|Solar||0.1 TWH||1.10 3|
|Geo-thermal energy||76 TWH||0.1|
It is undisputed that this structure of supply involves three problems: if consumption rates do not change, reserves of non-renewable energy will largely run out in one or two generations; the waste products caused by consumption in the water, the earth and in the atmosphere threaten mankind and the environment; and finally the cost of this shortage and the effects on consumption will be too much.
The use of energy is increasing day by day and according to an estimate oil and gas will be in shortage after 2050 AD and coal reserves will also fall short after 2200 AD. Even today, there are problems in coal mining. The world supply of natural gas is also limited.
Nuclear power, which amounted to over 5 per cent of global energy production accounts for very limited use and after the Chernobyl accident more technological precautions are needed. At present, there is a need for adopting methods for conservation of energy resources and also to develop and use more and more renewable energy sources.
The conservation methods should be applied for coal, petroleum and natural gas in order to preserve these resources, so that their use may be possible for a longer period and their environmental effects can be minimised. The coal mines have become deeper in most of the countries; therefore, new techniques should be applied.
The new methods like gasification may help in deeper mining operations. The coal should be classified and cleared at production centres itself. The use of secondary coal products like coal tar, ammonium sulphate, gas, light oil, benzol, sulphur, etc., should be made. A better transportation and marketing system as well as research in use and mining of coal should be applied.
The conservation of petroleum or mineral oil is the need of the time because the availability of petro-reserves is limited and the use of oil is increasing day by day especially in the field of transportation.
The following steps may help in conservation of petroleum:
(i) Reduction of the consumption of petroleum,
(ii) Development of such engines which consume lesser petroleum,
(iii) Intensive survey for new resources,
(iv) Exploitation of oil resources from ocean floors,
(v) Correct estimation of available resources,
(vi) New techniques for oil drilling and refining should be developed,
(vii) To reduce petroleum consumption in certain areas such as for military purposes,
(viii) To develop alternative source of energy for automobiles, etc.,
(ix) International cooperation in reduction of the consumption of petro-products, and
(x) Research institutes working in this field should intensify their work.
The energy crisis can be solved to some extent by proper use of renewable sources of energy. The renewable energy sources include solar energy, wind energy, tidal energy hydro-power, ocean energy and geo-thermal energy. Renewable energies are also called the energies of the future, because in principle they are inexhaustible and neutral in terms of CO2.
The renewable energy sources utilised by man come from three primary sources:
i. Isotopic disintegration in the earth’s interior,
ii. Thermo-nuclear conversion (fusion) in the sun, and
iii. The movement of planets, combined with mass attraction.
The greatest of the renewable energy sources is the solar energy or solar radiation reaching the earth’s atmosphere year after year. Every 29 seconds the solar energy that falls on our planet is equivalent to human energy needs for one day at the 1980 consumption level.
In case of solar-thermal utilisation, the solar energy is converted to heat through absorption. This can occur through passive systems, i.e., through constructional measures for collecting, storing and distributing solar energy which renounce thermal installations to a considerable degree or through active system, i.e., collectors or absorbers.
The advantages of using solar energy are – limitless supply, no air pollution, no water pollution, no harmful wastes, and no possibility of a large-scale explosion or disaster. There is a need to evolve cheaper technology to harvest solar energy. At least for tropical regions it is the greatest source of energy.
There is no need to stress the importance of water energy or hydro-power. Water energy is already in use in developed countries, but in developing countries vast energy potentials exist.
There is enough wind energy available to supply the world’s energy needs, and it is technically feasible to build windmills capable of producing electricity. These can be built either as small home-sized units or as large central generators. Besides the conversion of rotation energy into electrical energy, the conversion of rotation energy into mechanical energy also finds application in pumping of water, etc.
Ocean energy refers to a number of different renewable energy sources – tidal energy, wave energy, ocean currents and ocean heat.
Today, the significant attempts at harnessing the energy of the ocean have been related to tidal power. In many coastal regions, the flow of the tide naturally funnels through narrow entrances into bays and estuaries, and strong currents can be used to generate power.
Energy derived from the heat of the earth’s crust is called geo-thermal energy. In various places on the globe, hot springs, geysers and underground steam are available, which can be used for power generation.
Bio-energy can be produced by organic compounds through chemical and biological processes. The combustion, gasification and liquefaction helps in production of gas which can be used as a source of energy. The bio-gas plant has now become a common feature in rural India.
Viewed in the long-term perspective utilisation of renewable energy sources is of major significance, in terms of both the conservation of the reserves of fossil fuels and the reduction of pollutant emissions caused by the conversion of energy from coal, oil and gas. The renewable energy sources have good chances for the future energy supply. How large their contribution will be, depends upon the question of how safe, economical and environmentally friendly each particular ‘new’ energy is.