Classification of Energy Resources on the basis of availability:
(a) Primary energy resources:
These are obtained directly from the environment, the example includes:
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1. Fossil fuels such as coal natural gas etc.
2. Nuclear fuels such as Uranium, Thorium etc.
3. Hydro energy
4. Solar energy
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5. Wind energy
6. Geothermal energy
7. Ocean energy such as tidal energy, wave energy
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8. Biomass energy such as gobar gas
9. Hydrogen energy
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(b) Secondary energy resources:
They are derived from primary energy resources as they do not exist in nature. The examples are:
1. Petrol, diesel, kerosene oil.
2. CNG and LPG
3. Electrical energy based on coal, diesel gas.
(c) On the basis of being older and newer:
1. Conventional Energy Resources-the examples are:
1. Fossil fuel
2. Nuclear energy
3. Hydro energy
2. Non-conventional Energy Resources
For example includes-1. Solar energy, 2. Wind energy, 3. Geothermal energy,
4. Ocean energy, 5. Biomass energy, 6. H2 energy.
(d) On the basis of renewable and non-renewable energy resources
Non-renewable energy resources:
From the last few decades oils and natural gases together with hydro-electricity and natural sources occupy the first position in producing energy to mankind. The major problem, we are facing today is the fastest extinction of conventional resources of energy.
Afforestation in a large scale has caused a drastic change in the ecological pattern, flood situation and frequency of landslides.
In the near future, power generation may become cheaper option, but it would be dangerous and harmful. Excessive use of fossil fuels leads to environmental pollution, out of which C02 emission is of immense concern. Thus it is important for us to exploit fuels in a balanced way to avoid any future shortage.
Renewable energy resources:
It holds favourable future prospects not only for India but also for the whole world. These eco-friendly energy resources have the greatest potential to substitute the depleting non-renewable energy resources as alternative sources of energy in the long run. There is stress on environment friendly, decentralized energy system.
Fossil Fuel Based Energy-Coal Energy
Fossil fuels are found inside the earth’s crust where they have formed through heat and compression of forests, waste and other organic matter, which got buried due to earthquake, landslide etc. Fossil fuels are of 3 types:
(a) Solid (e.g.-coal), (b) Liquid (e.g.-petroleum) and (c) Gaseous (e.g.-Natural gas). Coal is the most abundantly found fossil fuel in the world. It contains carbon, water, sulphur and nitrogen.
Coal meets 70% of the total energy needs of the world found and 87.4% of all commercial energy. In India about 58% of commercial energy is obtained from coal and 38% from Petroleum along with natural gas.
Coal is used for cooking, heating, in industries and thermal power plants. Petroleum is useful for transportation, agricultural equipments and some industries. Natural gas is used both in cooking and in industries.
Petroleum or Crude Oil
The gaseous fuels are basically derived from petroleum. It is a natural, underground fossil energy resource. It is formed due to decomposition of micro plankton deposited upon the sea beds, lakes and rivers for million of years.
The decomposition takes place by the action of bacteria, under lack of oxygen and also by catalytic cracking. It is also called crude oil.
1. Liquid fuel is easy to transport.
2. Liquid fuel is comparatively cleaner.
3. They have made possible the introduction and development of newer means of transport.
Disadvantages
1. After extraction it causes contamination in the water when the leakage takes place.
2. Its burning produces C02 and enhances the green house effect.
3. All combustion processes produce the pollutants like NO, S02 CO, N02, C02 smog, etc.
4. Petroleum contributes to acid rain and urban pollution.
Natural Gas
After coal and petroleum, natural gas is the third major source of fossil fuel. It contributes to about 24% of the energy requirement of the world. It is fast emerging as an alternative source as it is eco-friendly in characters.
It is a mixture of hydrocarbon gases trapped beneath the earth’s surface. It is mainly consisting of methane (CHJ, propane (C3H8) and butane (C4H10). After processing it is transported to supply filling stations. Natural gas can be used in two different forms.
1. LPG (Liquefied Petroleum Gas).
2. CNG (Compressed Natural Gas).
Advantages:
1. It is a clean fuel, requiring little processing
2. It can be readily transported
3. Smog formation is less in its use
4. It is eco-friendly and causes less pollution
Disadvantages:
1. It requires both high pressure and low temperature for compression.
2. Thick walled tanks are required for storage as it is stored at a high pressure.
3. Methane is a green house gas and has a large atmospheric lifetime.
4. Leakage, in any case, is a serious threat to the environment.
Solar Energy
Sun is considered to be the king of the biosphere and our ecosystem. It is an inexhaustible source of enormous energy. It radiates its rays all round the universe in all directions. Solar energy is received in the form of cosmic radiations.
It is utilized by converting it into the following forms:
1. Thermal Conversion
2. Photo Conversion
Thermal conversion occurs by direct heating and photo conversion is an indirect conversion.
Utilization of Solar Energy
Application of Solar Energy
1. Solar water heater:
Its construction consists of a flat plate collector and a storage tank. The solar radiations fall on it are absorbed by a collector and then transferred to the circulating water. It is used in hospitals, hotels, houses and in some industries also.
2. Solar cooker:
It is comprised of an insulated metal box filled with a flat glass cover. The inner surface of the metal box is blackened. When the container is kept in the sunlight, the solar radiations are absorbed and consequentially the foods get cooked. I
3. Solar drying:
The agricultural goods are dried using solar heat by keeping them in a cabinet. It is used for drying vegetables, fruits, milk etc.
4. Solar furnace:
The temperature in a furnace is very high as solar radiation is concentrated using lenses in the furnace.
5. Solar greenhouse:
A green house is a closed chamber covered by transparent glass or plastic. It acts as a solar radiation collector to utilize solar energy for growing plants.
Solar Energy and Environment (Advantages and Limitations)
Advantages:
(i) Its use is eco-friendly as it never creates pollution.
(ii) The equipments do not require any attention during their working e.g solar cooker.
(iii) The food cooked with the help of solar energy remains nutritional.
(iv) The maintenance cost remains negligible in most of the equipments.
(v) Containers to store fuel are not required and its initial cost remains cheaper.
(vi) In lieu of storage vessels, it requires less space on the floor.
(vii) It has a noiseless operation.
Limitations:
(i) It does not work during night and during cloudy days and becomes useless in the rainy seasons.
(ii) All sort of food cannot be cooked in the solar cooker.
(iii) Solar cooking takes more time. It does not help when food is required urgently.
Nuclear Energy
It can be considered a renewable energy resource. It presents nuclear power; it is a highly developed alternative for energy production in place of coal. Nuclear energy can be derived by two methods-nuclear fission and nuclear fusion.
In nuclear fission, the heavy nucleus splits into lighter nuclei with a huge release of energy. But in nuclear fusion two light nuclei of hydrogen fuse to form a helium nucleus with a release of enormous amount of energy. One a.m.u (atomic mass unit) of Uranium-235 yield energy equal to burning of 15 metric tones of coal.
Nuclear reactors are the devices need to liberate energy from nuclear fuels, under controlled conditions. The output of these reactors is in the form of a high temperature fluid. This can be used in the generation of electricity or as a direct source of heat for intensive industries.
However civilian uses of nuclear energy are currently restricted to the production of electricity. As most of the industries that require high energy are located in the areas of high population and locating a nuclear reactor in such places would be of greater risks.
Nowadays the interaction and over exploitation of fuels and other resources are causing more pollution. Thus we need to think of more and more eco-friendly renewable energy resources.
Biomass Energy
Biomass energy or bioconversion refers to the direct burning of wood, agricultural waste manure, waste paper and converting them to a fuel.
Certain of them produce either alcohol or methane gas, when they digest biomass in absence of air which themselves give energy on combustion. As biomass energy is obtained through the process of photosynthesis it is considered to be the indirect form of solar energy.
Plantation of more trees and other crops should be considered important to get biomass energy either for direct burning or for conversion to alcohol or methane. Moreover, to prevent soil erosion and fulfill the requirements of fertilizer.
Biomass energy should be preferred wherever energy can be produced as a byproduct of waste disposal in countries like USA.
Use of alcohol as fuel is being promoted, in the grain growing regions. Alcohol is produced by fermentation of grains. Wood and farm wastes are renewable natural resources.
An aerobic digestion of sewage sludge and animals manure is a biomass utilizing method and produces nutrient rich compost which is a good organic fertilizer, which can be used for growing forage for animals and do not cause any adverse environmental consequence.
The burning of dung destroys essential nutrients like N and P. It is therefore, more useful to convert biomass into biogas and biofuels.
Biofuels: How Biogas is generated
Floating gas holder type of plant. The diagram below shows the details of floating gas holder type of biogas plant.
B iogas
Biogas is mixture of following gases-
(a) CH4(40%), (b) C02, (c) H2, (d) N2,
Biogas plants are of mainly following types-
(a) Floating gas holder type
(b) Fixed dome type
(c) KVIC type
Advantages of using Biogas-
(i) It provides eco-friendly clean fuel
(ii) Without storage tank, it can be supplied directly to the homes from plant.
(iii) Pathogens and parasites cannot come in contact of faecal material as the degestion of waste takes place in closed chamber.
(iv) It is a good substitute of chemical fertilizers as per year its production is around 200 million tonnes.
Hydrogen as a Fuel for Future
As hydrogen burns in air, it combines with oxygen to form water and a large amount of energy (150 kilojoules per gm.) is released. Due to its highest calorific value, hydrogen serves as an excellent fuel. Moreover it is non-polluting.
It can be easily produced. Its production becomes possible by thermal dissociation, photolysis or electrolysis of water.
1. By thermal, dissociation of H20, H2 is produced.
2. Thermo chemically, H2 is produced by chemical reaction of H20 with some other chemicals in 2-3 cycles.
3. Electrolytic method dissociates water into hydrogen & oxygen by making a current flow through it.
4. Photolysis of H20 involves breakdown of H20 in sunlight to release hydrogen. Green plants also have photolysis of water during photosynthesis. Efforts are underway to trap hydrogen molecules which are produced during photosynthesis.
However, H2 is highly inflammable and explosive in nature. Hence, it requires safe handling when used as a fuel. It is also difficult to be stored & transported as is being very light; it has to be stored in bulks.
Hydro Electric Energy
Hydro power is the cleanest, cheapest & best source of electricity generation. It falls under the conventional energy resource. Energy is derived from fast flowing water.
Hydropower converts power of the falling water to electric power which can be transmitted to long distances through wires & cables.
It can be stored for future use also. Hydropower is generated by using hydraulic machine, called turbines. Now high dams are built to obtain a substantial amount of hydrostatic pressure.