Source Of Energy

Large scale nuclear energy is prohibitive because:

(a) The waste material produced by the fission at the nuclear power plants are radioactive and hence are very harmful to all the living beings. It is difficult to dispose off the nuclear waste safely.

(b) The installation cost of nuclear power plant is also very high and the limited availability of uranium fuel makes the large scale use of nuclear energy prohibitive.

Thermal power plants are set up near coal and oil fields because it is easier and convenient to transmit electricity over large distances than to carry coal (oil or gas) over the same distance.

The process of decomposition in the biogas plant is carried out by the microorganisms called the anaerobic bacteria. The decomposition takes place in absence of oxygen and is thus called anaerobic degradation. Anaerobic bacteria does not require oxygen to decompose complex organic compounds present in cow dung and any other plant waste.

We could minimize the environmental pollution caused by burning of fossil fuels by:

(a) Fitting catalytic convertors in the vehicles. The catalytic convertor is a device which changes the harmful gases coming from the engine of car to harmless gasses before releasing them in the air

(b) Installing electrostatic precipitators in the chimneys of thermal power plants and factories. By using this we can control the pollution caused by the burning of fossil fuel.

The unburnt carbon particles and fly ash particles present in the smoke keep on depositing on the walls of chimney and don’t go to the air.

The huge waves near the sea shore possess the kinetic energy in them. Due to the blowing of wind on the surface of sea, very fast sea waves moves on its surface. The kinetic energy of the sea waves can be used to generate electricity.

The solar cooker made by the student does not function well because he used transparent plastic sheet to cover the open face of the box. The transparent plastic sheet is not much effective in trapping the sunlight to heat up the cooker. Instead of plastic sheet, he should have used a transparent glass sheet to cover the open face of the box.

This is because glass sheet can trap the heat rays of sun very effectively by producing the greenhouse effect.

Black colour is very good absorber of heat. So, painting the inner and outer surface of the cooker along with the cooking vessels with black will enhance the absorption of the heat rays of the sun.

Disadvantages of constructing of big dams across the river are:

(a) A vast variety of flora and fauna (plants and animals), large areas of agricultural lands and human settlements get submerged in the water of reservoir formed by the dam.

(b) The construction of dams disturbs the ecological balance in downstream area of ricer by decreasing the fertility of soil in the downstream area. This leads in decrease in crop yields.

(c) The fish in downstream area don’t get sufficient nutrients and fish production also decreases.

(d) Production of greenhouse gasses: The vegetation which is submerged under water at the dam rots under anaerobic condition and produces large amount of methane, which is a greenhouse gas.

The three advantages of solar cell are:

(a) Solar cells can be set up in remote, inaccessible and sparsely inhabited areas where laying of usual power transmission lines are difficult and expensive.

(b) They require very less maintenance

(c) They have no moving parts and work satisfactorily without the use of any focussing device to focus light.

First of all we need to understand the sources of conventional and non-conventional sources of energy.

The sources of energy which are familiar to most of the people are called conventional sources of energy. For example, coal, coke, diesel, kerosene, petrol, fuel oil, etc.

The sources of energy that are not based on burning of fossil fuels or splitting of atoms of nuclear fuels are called alternative sources of energy or the non-conventional sources of energy. For example, solar energy, wind energy, etc.

Reasons for the need of harvesting non-conventional sources of energy are:

(a) The fossil fuel (conventional sources) are limited and non-renewable. So, if we keep on using them at the present rate, then they will not last longer. By using non-conventional we can help conserve fossil fuels.

(b) By using alternative sources of energy, the pollution caused by the burning of fossil fuels can be controlled.

The waste material produced by the fission of Uranium-235 during the generation of electricity at the nuclear power plant are called nuclear waste.

● The nuclear waste is radioactive and hence is extremely harmful to all the living beings. The improper disposal of nuclear waste may lead to contamination of radioactive material. Long-term effects of radiation can even cause cancer.

● Since the nuclear waste is highly radioactive, so it is disposed of off with very carefully. The nuclear waste is usually put in storage containers made of steel that is further placed in a concrete container so as to prevent harmful radiations from coming out and harming the environment.

The sun produces the large energy from the fusion of hydrogen nuclei into helium nuclei.

The fusion of 4 hydrogen atom nuclei to form a bigger nucleus of helium atom releases the tremendous amount of energy in the sun.

We need to look for alternative sources of energy because:

(a) The conventional sources such as fossil fuels like coal, petrol, diesel etc. are non-renewable and are limited in nature. If we continue to use them at the present rate, then they won’t last long.

(b) The burning of fossil fuels pollutes the environment by releasing harmful gasses in the environment which can lead to health hazards.

(c) The major gas released is carbon dioxide which is responsible for the greenhouse effect. This leads to global warming which itself is one of the main environmental issues.

(d) The alternative sources like the solar energy, hydroelectric energy, wind energy etc. use the renewable source of energy and also do not cause the pollution.

The use of alternative sources of energy has manifold advantages over the usage of fossil fuels.

The wind and water energy were traditionally used to pump water (lift water) from a well and to grind wheat into flour.

The traditional use of wind and water energy has now been modified by the improvement of technology to generate electricity through the wing powered generators and hydroelectric power plants respectively.

Wind Power Generators: A wind generator is used to generate electricity by using wind energy. When a fast moving wind strikes the blades of the wind turbine, the wind turbine rotates continuously. The shaft of a wind turbine is connected to a small generator. When the turbine rotates, the shaft also rotates to drive the generator and produce electricity.

Hydro Power Generator: A hydro power generator is used to generate electricity using the potential energy of the water stored in a dam. Water falling down from a height flows very fast and pushes the blades of the turbine to rotate continuously. The shaft connected to the turbine also rotates and drives the generator to produce electricity in the powerhouse.

Biomass is the organic matter such as dead parts of plants, trees and waste materials of animals which are used as a fuel to produce energy. Biomass contains chemical energy in the form of carbon compounds.

Bioenergy is the energy produced from the biological sources like biomass. To obtain bioenergy from biomass, one method is Biogas Plant.

In the Biogas Plant, biogas which is a mixture of methane, carbon dioxide, hydrogen, and hydrogen sulphide is obtained by an anaerobic degradation of biomass. The anaerobic degradation is carried out by the anaerobic bacteria (which do not require oxygen to decompose complex organic compounds).

Wood is also a biomass and energy is produced by directly burning it, though the better way is to produce charcoal first and then use it for bioenergy to reduce smoke.

Nuclear power is an excellent non-conventional source of energy still it is not used commonly for power generation because:

(a) In the old nuclear reactors, there is a risk of accidents due to the leakage of radioactive material which can cause serious damage to the living beings and the environment.

(b) The nuclear waste produced in the nuclear power plants are radioactive and are very harmful to the living beings. If it is not disposed of properly, it may lead to contamination and a longer exposure can lead to cancer.

(c) The nuclear plants are very expensive to install and the limited availability of uranium fuel makes the large scale use of nuclear energy prohibitive.

Nuclear energy is obtained from two types of nuclear reactions:

(i) Nuclear fission

(ii) Nuclear fusion

Nuclear Fission: The process in which heavy nucleus of radioactive atoms (such as uranium, thorium or plutonium) splits up into smaller nuclei when bombarded with low energy neutrons, is called nuclear fission.

Nuclear Fusion: The process in which two nuclei of light elements (such as Hydrogen) combine to form a heavy nucleus (such as Helium) is called nuclear fusion.

In both the cases, the tremendous amount of nuclear energy is released due to the small loss of mass.

Nuclear Fission Reaction:

Nuclear Fusion Reaction:

Nuclear energy is used to generate electricity. Nuclear power plants use controlled fission reaction to generate it.

(a) Geothermal Energy:

Geothermal Energy is the heat energy from hot rocks present inside the earth. The heat can be used as a source of energy to produce electricity.

At some places, rocks at some depth close to earth’s surface are very hot. These are known as hot spots and are sources of geothermal energy.

The hot rocks heat the underground water to produce steam. A hole is dug and the pipe is put in it. The steam present around the rocks come up at high pressure, which turns the turbine of the generator to produce electricity.

(b) Advantages of Wind Energy:

(a) It does not cause any pollution

(b) The wind energy is a renewable source of energy and never gets exhausted

Increased use of wind energy to generate electricity helps in conserving fossil fuels like coal, petroleum and natural gas.

We cannot make use of solar cells to meet all our energy needs since:

(a) Solar cells have very low efficiency. At present, the best designed solar cells can generate 240 Wm^-1 in bright sunlight with a maximum efficiency of 25%. So, they can convert 25 percent of the light falling on them into electricity.

(b) Solar cells are very expensive. The special grade silicon needed for making solar cells is expensive. The silver wires used to interconnect the solar cells is also very expensive. So, the extensive use of solar cells in generating power is limited due to their high cost.

(c) Solar cells can only be used during daylight. During night or during cloudy days, the solar cells are unable to produce electricity.

The various forms in which energy is available from the sea are:

(a) Tidal Energy: The enormous movement of water between the high tides and low tides provides a very large source of energy in coastal areas of the world. The tidal energy can be harnessed by constructing a tidal barrage or tidal dam or tidal dam across the narrow opening to the sea.

(b) Wave Energy: Due to the high speed, sea waves have a lot of kinetic energy in them. The energy of moving sea waves can be used to generate electricity.

(c) Ocean Thermal Energy: The energy availability due to the difference in temperature of water at the surface of the ocean and at deeper levels is called ocean thermal energy. The device used to harness ocean thermal energy is called Ocean Thermal Energy Conversion Power Plant (OTEC power plant).

Limitations of Harnessing:

Tidal Energy:

There are very few sites around the world which are suitable for building tidal barrages or tidal dams.

Rise and fall of sea water during high and low tides is not enough to generate electricity on high scale.

Wave Energy:

The harnessing of sea wave energy would be a viable proposition only in those places where sea waves are very strong.

The factors that must be kept in mind before choosing a source of energy are:

(a) Ease of extraction: While selecting or choosing a source of energy we must always keep in mind the process involved in the production of the energy from that source. One must also keep in mind the calorific value of the source (in case of fuel). One should also keep in mind the abundance of source in the nature, which implies whether the source is renewable or non-renewable.

(b) The cost of extracting energy from the source is also an important factor in choosing a source. The source may be renewable or physically abundant but the cost of installation may be very high. Hence the expense is also an important factor.

(c) The damage to the environment that the source will cause in the process of extracting energy from it is also an important factor in deciding or choosing the source of energy. The source should cause least pollution, release least harmful gasses and should not harm the environment.

By considering these issues, one should decide what source of energy should be chosen over what.