Energy flow in ecosystem
Facts about Energy flow in ecosystem
A source of energy provides energy in a convenient form over a long period of time.
Sources of energy can be classified as renewable and non-renewable sources.
Solar energy is the main source of energy on the earth.
Solar cookers, solar water heaters and solar concentrators are some devices used for harnessing solar energy.
Solar cells are devices that convert solar energy directly into electricity.
Solar energy also manifests itself in nature as the energy of winds, water flowing through rivers, ocean waves, besides ocean thermal energy.
Energy harnessed through wind energy devices is utilized either to do mechanical work, or to produce electricity.
Energy derived from the hot spots beneath the earth is called geothermal energy.
Green plants convert solar energy into chemical energy through the process of photosynthesis. This energy is known as bio-energy.
Biomass is utilized to produce heat by burning it or to produce biogas through its anaerobic decomposition in a biogas plant.
Hydrogen and alcohol could be a source of energy in future.
Fossil fuels like coal, petroleum and natural gas are a mixture of hydrocarbons. These are fossil remains produced by the decay of plants and marine animals that were buried in the earth millions of years ago.
Fuels like coal, petroleum and natural gas are being utilized at very high rates, resulting in fast depletion of their known reserves. Fossil fuels may not be available in future, as these are not being formed now.
Fuels are characterized by their calorific value and ignition temperature, besides the nature of product produced by their combustion.
The three conditions essential for combustion are attainment of ignition temperature, presence of oxygen and a combustible material.
The factors that help to choose a good fuel for a given purpose are its availability, cost, its characteristic and physical properties, besides considerations of the effects of its by-products on environment.
Type of Energy flow in ecosystem
1. Wind Energy: The energy possessed due to moving air is called wind energy.
(i) It does not cause any pollution.
(ii) The source of wind energy is air. (Renewable Energy)
(iii) It is available free of cost.
2. Water Energy: The energy possessed due to flowing of water is called the water energy.
Water Wheel: The device used for obtaining energy from flowing water is called water wheel. The basic principle of water wheel is that the moving water rotates the water wheel and this water wheel can be made to turn machines, which do work for us.
3. Electric Power Plants: The set-up, which can produce large quantity of electricity, from a few kilowatts to a few hundred megawatts, are called power plants. There are three types of power stations (plants). These are:
(a) Hydroelectric power stations;
(b) Thermal power stations;
(c) Nuclear (or atomic power stations)
Principle of hydroelectric power: The potential energy of the water stored at great heights in the dams is converted into kinetic energy by flowing water to flow at high speeds due to which electricity is generated. The electric power so generated is called hydroelectric power.
4. Solar Energy: The energy obtained from the sun is called solar energy.
Advantages of Solar Energy
(i) It is inexhaustible source of energy.
(ii) It does not cause pollution.
(iii) It is available free of cost.
Disadvantages of Solar Energy:
(i) It is not available all the time.
(ii) It is very much diffused and scattered.
5. Tidal Energy: The energy obtained from tides is called tidal Energy.
Merits of tidal energy
• It is an inexhaustible source of energy.
• It is independent of uncertainty of rainfall.
• It is a pollution free source of energy.
• It does not require large area of valuable land.
Demerits of tidal energy
• Power generation is intermittent due to variation in tidal range.
• The most difficult problem in the use of tidal power are the barrage construction in areas of high tidal flow and corrosion of barrage.
6. Merits of wave energy
• It is a renewable and pollution free source of energy.
• It does not require large land areas.
Demerits of wave energy
• The power supply is variable in nature due to variability in wave formation.
• It is expensive.
• Marine life could be affected due to wave energy harnessing structures.
7. Merits of OTEC
• The electric power produced is continuous, renewable and pollution free.
• OTEC system eriches the fishing grounds by transferring nutrients from the unproductive deep waters to the warmer surface.
• OTEC system does not have daily or seasonal variations in their output as in case with the solar energy devices.
Demerits of OTEC
• OTEC system requires a lot of capital investment.
• The conversion efficiency is low as there is small temperature difference between the surface water and the deep water.
8. Merits of geothermal energy
• It is the most versatile and least polluting renewable source of energy.
• It is relatively inexpensive and power generation level is higher as compared to solar energy and wind energy.
Demerits of geothermal energy
• Though geothermal energy is inexhaustible, a single bore has a limited life span of about 10 years.
• Geothermal hot spots are scattered.
• Noise pollution is caused by drilling operations at geothermal sites.
9. Advantages of nuclear fusion over nuclear fission
Energy released in fusion reaction is much greater than energy released in fission reaction. The products of fusion are not radioactive whereas it is radioactive in case of nuclear fission and require careful disposal.
Hazards of nuclear power generation and safety measures
The major hazards of nuclear power generation are:
• Storage and disposal of spent or used nuclear fuels as they continue to decay into harmful subatomic particles (radiations). This would lead to environmental contamination.
• There is a risk of accidental leakage of nuclear radiation.
• It has high cost of installation of a nuclear power plant.
Types of Nuclear Reactions:
(i) Nuclear Fusion Reaction: The process in which two or more nuclei of lighter atoms combine to form a heavy nucleus with the liberation of a large amount of energy is called fusion reaction. For example:
(ii) Nuclear Fission Reactions: The process of splitting of a nucleus of a heavy atom into a number of nuclei of smaller mass with the liberation of large amount of energy is called nuclear fission. For example
Cause of tremendous Amount of Energy: The cause of tremendous amount of energy during the nuclear fission is the loss of mass. The loss of mass is also called mass defect.
Where m = The mass lost or mass defect. c = the velocity of light. E = amount of energy.
Chain Reaction: A reaction in which the number of neutrons goes on increasing during fission till whole of the fissionable material is disintegrated.
Nuclear Reactor: It is a device, which is used for carrying out fission reaction at a controlled rate. It is used to generate electricity.
Nuclear fuel: The fissionable material used in the nuclear reactor is called nuclear fuel.
For ex., U235, Pu239.