Non Conventional Source Of Energy
The sources of energy which are being produced continuously in nature and are in exhaustible are called nonconventional energy (or) renewable sources of energy
The Sun has been radiating an enormous amount of energy. Small part of solar energy reaches the outer layer of the earth’s atmosphere is absorbed while passing through the atmosphere and the rest reaches the earth’s surface.
A black surface absorbs more heat as compared to a white or a reflecting surface under identical conditions. Solar cookers and solar water heaters use this property in their working. Some solar cookers achieve a higher temperature by using mirrors to focus the rays of the Sun. Solar cookers are covered with a glass plate.
Solar cells convert solar energy into electricity. A typical cell develops a voltage of 0.5–1 V and can produce about 0.7 W of electricity when exposed to the Sun. A large number of solar cells are, combined in an arrangement called solar cell panel that can deliver enough electricity for practical use.The principal advantages associated with solar cells are that they have no moving parts, require little maintenance and work quite satisfactorily without the use of any focusing device. Another advantage is that they can be set up in remote and inaccessible hamlets or very sparsely inhabited areas in which laying of a power transmission line may be expensive and not commercially viable. Silicon, which is used for making solar cells, is abundant in nature but availability of the special grade silicon for making solar cells is limited. The entire process of manufacture is still very expensive, silver used for interconnection of the cells in the panel further adds to the cost. In spite of the high cost and low efficiency, solar cells are used for many scientific and technological applications. Artificial satellites and space probes like Mars orbiters use solar cells as the main source of energy.
Energy from sea
Due to the gravitational pull of mainly the moon on the spinning earth, the level of water in the sea rises and falls.This phenomenon is called high and low tides and the difference in sea-levels gives us tidal energy. Tidal energy is harnessed by constructing a dam across a narrow opening to the sea. A turbine fixed at the opening of the dam converts tidal energy to electricity.
the kinetic energy possessed by huge waves near the seashore can be trapped in a similar manner to generate electricity.The waves are generated by strong winds blowing across the sea. Wave energy would be a viable proposition only where waves are very strong. A wide variety of devices have been developed to trap wave energy for rotation of turbine and production of electricity.
Ocean Thermal Energy
The water at the surface of the sea or ocean is heated by the Sun while the water in deeper sections is relatively cold. This difference in temperature is exploited to obtain energy in ocean-thermal-energy conversion plants. These plants can operate if the temperature difference between the water at the surface and water at depths up to 2 km is 293 K (20°C) or more. The warm surface-water is used to boil a volatile liquid like ammonia. The vapours of the liquid are then used to run the turbine of generator. The cold water from the depth of the ocean is pumped up and condense vapour again to liquid.The energy potential from the sea (tidal energy, wave energy and ocean thermal energy) is quite large, but efficient commercial exploitation is difficult.
Geo thermal energy
Due to geological changes, molten rocks formed in the deeper hot regions of earth’s crust are pushed upward and trapped in certain regions called ‘hot spots’. When underground water comes in contact with the hot spot, steam is generated. Sometimes hot water from that region finds outlets at the surface. Such outlets are known as hot springs.
The steam trapped in rocks is routed through a pipe to a turbine and used to generate electricity. The cost of production would not be much, but there are very few commercially viable sites where such energy can be exploited. There are number of power plants based on geothermal energy operational in New Zealand and United States of America.
The process of splitting of a heavy nucleus into two lighter nuclei of comparable masses (after bombardment with a energetic particle) with liberation of energy is called nuclear fission.
Fission reaction of U235
92U235 + 0n1 → 92U236 →
56Ba141 + 36Kr92 + 30n1 + Q
The energy released in U235 fission is about 200MeV or 0.8 MeV per nucleon.
Fission of U235 occurs by slow neutrons only (of energy about 1 eV) or even by thermal neutrons (of energy about 0.025 eV).
The neutrons released during the fission process are called prompt neutrons.
Most of energy released appears in the form of kinetic energy of fission fragments.
It has been observed that under special conditions, it is possible for the nuclei of light elements to combine and form a nucleus of a high atomic number. When two or more light nuclei moving at very high speed are fused together to form a heavy nucleus, then the process is known as nuclear fusion.
The mass of the product nucleus is smaller than the sum of the masses of the nuclei which were fused. The lost mass is converted into energy which is released in the process.
Deuteron Deuteron Triton Proton Energy
The triton so formed can further fuse with a third deuteron to form an a–particle (Helium–nucleus).
Difference (Table) :
|S.No||NUCLEAR FISSION||NUCLEAR FUSION|
|1||A heavy nucleus disintegrates to give lighter nuclei with the release of energy.||Two or more light nuclei join together to form a heavy nucleus with the release of energy|
|2||Nuclear fission is a chain reaction-the fission of one nucleus leading to the production of neutrons, which cause more nuclei to disintegrate.||Nuclear fusion is not a chain reaction.|
|3||Nuclear fission requires thermal neutrons neutronswith sufficient energy to split a nucleus. But it does not require very high temp.||Nuclear fusion requires high temperatures in the range of 106K.|
|4||Fission process can be carried out in a reactor.||Fusion cannot be carried out in any container, as the temperature is very high. Scientists hope to contain matter in a magnetic field|
|5||Controlled nuclear fission is possible and takes place in a nuclear reactor.||Controlled nuclear fusion has so far not been achieved. Only uncontrolled fusion reactions in the thermonuclear devices such as the hydrogen bomb have been achieved.|
|6||Nuclear fission produces radioactive wastes, which pose the problem of waste disposal.||Nuclear fusion does not produce radioactive wastes and, therefore, does not cause pollution.|