Sources Of Energy

What are the Sources of Energy?

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What are the Sources of Energy?

If energy can neither be created nor destroyed, we should have no worries! We should be able to perform endless activities without thinking about energy resources then why we speak to save energy ?
Its because energy from the usable form, is dissipated to the surroundings in less usable forms. Hence, any source of energy we use, to do work, is consumed and cannot be used again.

Good Sources of Energy

A good source of energy would be one

  • Which would do a large amount of work per unit volume or mass,
  • Be easily accessible,
  • Be easy to store and transport, and
  • Economical.

Renewable and Non- Renewable Resources

Natural resources can be classified into the renewable resources and non-renewable resources.
The resources which have the capacity or ability to reproduce or renew quickly are called renewable resources. They include solar and wind energy, water, soil, forests, etc. Some of the renewable resources can be destroyed due to careless use.
The non-renewable resources are limited in reserves and it may take thousands of years to renew them. For example, coal or petroleum if taken out completely, may take millions of years to produce them.

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Sun “The Ultimate Source Of Energy”

The source of the large amount of solar energy is due to fusion of lighter nuclei. About 90 percent of the solar mass is composed of hydrogen and helium and rest 10 percent contains other elements. The temperature of the interior of the sun is estimated to be about 2 × 107 K.
The nuclei of hydrogen fuse together in the sun’s interior to produce helium and a huge amount of energy is released. It is estimated that 1g of hydrogen produces 620,000 million joules of energy.
The fusion process in the sun can be described by the equation.
\(4_{1}^{1}H\text{ }\to \text{  }_{2}^{4}He\text{   +   2 }_{+1}^{0}e\text{   +  Energy}\)

  • The sun can provide us with inexhaustible solar energy that comes from nuclear fusion occurring inside the sun.
  • The energy radiated from the sun’s surface in one year is equivalent to 250 thousand million million million tonnes of petroleum. If we could harness the solar energy on earth, we would have solved our energy problem.
  • However, we make very little direct use of solar energy. This is because technology has not yet provided an economical method of transforming solar radiation into usable energy.
  • Solar cells are still very expensive and inefficient. Furthermore, sunlight is intermittent and unreliable in many areas. The development in the storage of solar energy may help us solve the problem.
  • The knowledge of thermochemistry can help us store solar energy.
    (a) Ionic hydrates such as hydrated sodium sulphate, [Na2SO4.10H2O(s)] can be used to store solar energy.
    (b) When the hydrates are warmed by sunlight to over 32°C, the three moles of ions dissolve in the ten moles of water in an endothermic process.
    What are the Sources of Energy 1
    (c) When cooled below 32°C after sunset, the solution recrystallises, releasing the absorbed energy.
    What are the Sources of Energy 2

Fossil fuels

  • Fossil fuels are most widely used because they are very convenient to use and have relatively high fuel values. But they are non-renewable and can cause environmental problems like the greenhouse effect and acid rain.
  • We can use generators and engines to harness heat energy from fossil fuels.
  • It is estimated that fossil fuels will be depleted in another 10 years. Thus, we need to find alternative energy sources.

Water

  • With the use of hydroelectric power stations, we can harness hydroelectric energy from water.
  • Hydroelectric energy is clean, renewable, convenient and economical to use.
  • Unfortunately, hydroelectric energy is limited in its location. It needs high cost of construction at the beginning stages and sometimes vast areas of land are needed, and thus might cause destruction of the surrounding environment.

Biomass

  • By using generators and engines we can harness biomass energy.
  • We can obtain biomass energy from either plants or droppings of animals. Palm oil, for example, is used to make biodiesel which can be used to power cars and generators.
  • Biomass energy, however, needs large areas of land to grow plants and may also cause environmental problems like the disposal of waste.

Radioactive substances

  • By using nuclear fission and nuclear fusion, we could obtain enormous supply of nuclear energy from radioactive substances like uranium and plutonium.
  • The heat given out during controlled nuclear fission and fusion can be used to generate electricity.
  • Nuclear energy is non-renewable and is very destructive if a nuclear accident occurs. Furthermore, we will face problems of disposing the nuclear wastes.

Other energy sources

  • Other energy sources that we can use are wind, tidal, geothermal, chemical fuel cells and hydrogen from the electrolysis of sea water.
  • Scientists and engineers are actively seeking new energy sources as the earth has only a limited supply of fossil fuels which will run out soon.
  • We must learn to use and conserve our finite energy resources more wisely and more efficiently.

Environmental Consequences

Exploiting any source of energy disturbs the environment in some way or the other. In any given situation, the source we would choose depends on factors such as the ease of extracting energy from that source, the economics of extracting energy from the source, the efficiency of the technology available and the environmental damage that will be caused by using that source. Research continues in these areas to produce longer lasting devices that will cause less damage throughout their life.

Saving Energy Resources

we cannot depend on the fossil fuels for much longer. Such sources that will get depleted some day are said to be exhaustible sources or non-renewable sources of energy. On the other hand, if we manage bio-mass by replacing the trees we cut down for fire-wood, we can be assured of a constant supply of energy at a particular rate. Such energy sources that can be regenerated are called renewable sources of energy.
Renewable energy is available in our natural environment, in the form of some continuing or repetitive currents of energy, or is stored in such large underground reservoirs that the rate of depletion of the reservoir because of extraction of usable energy is practically negligible.

What are the Non Conventional Energy Resources?

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What are the Non Conventional Energy Resources?

  1. Electrical energy cannot be created. It must be transformed from other forms of energy.
  2. The resources of energy to generate electricity can be classified as:
    (a) Renewable energy resource or Non conventional energy resource
    An energy resource that is continually replaced and will not run out.
    (b) Non-renewable energy resource  or Conventional energy resource
    An energy resource that effectively cannot be replaced once it has been used.
  3. Oil, diesel, natural gas and coal are fossil fuels. They have been formed in the ground from dead vegetation and creatures by a very slow process that takes many years.
  4. Nuclear energy is released during the fission of a heavy nucleus or fusion of light nuclei.

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Why do we need to use more renewable energy?

The Importance of Renewable Energy:

  1. At present our main energy resource is non-renewable energy from fossil fuels such as oil, coal and natural gas. The rapid growth in the world population and the high rate of use of electrical energy have raised concerns that the resources of non-renewable energy will run out one day.
  2. The burning of fossil fuels has harmful effects on the environment. Carbon dioxide, released into the atmosphere by the burning of fossil fuels, traps the Sun’s heat and causes global warming. This is called the greenhouse effect and causes changes in the world’s climate.
  3. The burning of oil and coal also release sulphur dioxide gas into the atmosphere where it combines with water to form acid rain. Acid rain damages plants and buildings.
  4. The mining of fossil fuels often damages the environment and upsets the balance of the ecosystem.
  5. The depletion and negative effects of non-renewable energy have made the use of renewable energy become increasingly more important. These resources do not run out as they are continually replaced by natural processes.
  6. Renewable energy resources are cleaner to use. In most cases, renewable energy resources are used to drive turbines of power generators directly. They do not involve processes that will discharge harmful gases into the atmosphere. For example, in the hydroelectric power stations the kinetic energy of the water is utilised directly to drive turbines.
  7. The use of renewable energy resources do not cause much harm to the environment.

How do solar panels convert the sun’s energy into electricity?

Solar 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.
(i) Solar cooker:
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-cooker (ii) Solar cell:
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 focussing 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.

(B) Energy From Sea

(i) What is the tidal energy?
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.
(ii) What is the wave energy?
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.
(iii) What is 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.

(C) What is the geothermal 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.

(D)  How the electricity is generated from water?

Hydro power plant:
Hydro power plants convert the potential energy of falling water into electricity. Since there are very few water-falls which could be used as a source of potential energy, hydro power plants are associated with dams.
What are the Non Conventional Energy Resources 1In order to produce hydel electricity, high-rise dams are constructed on the river to obstruct the flow of water and thereby collect water in larger reservoirs. The water level rises and in this process the kinetic energy of flowing water gets transformed into potential energy. The water from the high level in the dam is carried through pipes, to the turbine, at the bottom of the dam .
Since the water in the reservoir would be refilled each time it rains (hydro power is a renewable source of energy) we would not have to worry about hydro electricity sources getting used up the way fossil fuels would get finished one day.
Limitation: constructions of big dams have certain problems associated with it. The dams can be constructed only in a limited number of places, preferably in hilly terrains. Large areas of agricultural land and human habitation are to be sacrificed as they get submerged.
Large eco-systems are destroyed when submerged under the water in dams.
The vegetation which is submerged rots under anaerobic conditions and gives rise to large amounts of methane which is also a green-house gas. It creates the problem of satisfactory rehabilitation of displaced people. Opposition to the construction of Tehri Dam on the river Ganga and Sardar Sarovar project on the river Narmada are due to such problems.

(E) How does biomass power plants work?

Biomass power plant:
Plant and animal products are said to be bio-mass. These fuels, however, do not produce much heat on burning and a lot of smoke is given out when they are burnt. Therefore, technological inputs to improve the efficiency of these fuels are necessary.
When wood is burnt in a limited supply of oxygen, water and volatile materials present in it get removed and charcoal is left behind as the residue. Charcoal burns without flames, is comparatively smokeless and has a higher heat generation efficiency.
Similarly, cow-dung, various plant materials like the residue after harvesting the crops, vegetable waste and sewage are decomposed in the absence of oxygen to give bio-gas. Since the starting material is mainly cow-dung, it is popularly known as ‘gobar-gas’
What are the Non Conventional Energy Resources 2Structure:
The plant has a dome-like structure built with bricks. A slurry of cow-dung and water is made in the mixing tank from where it is fed into the digester.
The digester is a sealed chamber in which there is no oxygen. Anaerobic micro-organisms that do not require oxygen decompose or break down complex compounds of the cow-dung slurry.
It takes a few days for the decomposition process to be complete and generate gases like methane, carbon dioxide, hydrogen and hydrogen sulphide.
The bio-gas is stored in the gas tank above the digester from which they are drawn through pipes for use. Bio-gas is an excellent fuel as it contains up to 75% methane. It burns without smoke, leaves no residue like ash in wood, charcoal and coal burning. Its heating capacity is high. Bio-gas is also used for lighting. The slurry left behind is removed periodically and used as excellent manure, rich in nitrogen and phosphorous.

(F) How do we generate energy from wind?

Wind energy:
Heating of the landmass and water bodies by solar radiation generates air movement and causes winds to blow. This kinetic energy of the wind can be used to do work. This energy was harnessed by windmills in the past to do mechanical work.
For example, in a water-lifting pump, the rotatory motion of windmill is utilised to lift water from a well. Today, wind energy is also used to generate electricity.
To generate electricity, the rotatory motion of the windmill is used to turn the turbine of the electric generator. The output of a single windmill is quite small and cannot be used for commercial purposes. Therefore, a number of windmills are erected over a large area, which is known as wind energy farm.
What are the Non Conventional Energy Resources 3Advantage:
Wind energy is an environment-friendly and efficient source of renewable energy. It requires no recurring expenses for the production of electricity.
limitations: Wind energy farms can be established only at those places where wind blows for the greater part of a year. The wind speed should also be higher than 15 km/h to maintain the required speed of the turbine. Furthermore, there should be some back-up facilities (like storage cells) to take care of the energy needs during a period when there is no wind.
Establishment of wind energy farms requires large area of land. For a 1 MW generator, the farm needs about 2 hectares of land. The initial cost of establishment of the farm is quite high. Moreover, since the tower and blades are exposed to the vagaries of nature like rain, Sun, storm and cyclone, they need a high level of maintenance.

What are the Conventional Energy Resources?

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What are the Conventional Energy Resources?

  1. The demand for energy is always increasing as the human population grows and our lives become more and more sophisticated. A large portion of the energy we use is in the form of electricity.
  2. Electricity is needed for a wide range of uses such as heating, lighting, motion and processing.
  3. Non-renewable energy resource or Conventional energy resource: An energy resource that effectively cannot be replaced once it has been used.
  4. The non-renewable resources are limited in reserves and it may take thousands of years to renew them. For example, coal or petroleum if taken out completely, may take millions of years to produce them.

(A) Why fossil fuels are so important?

Fossil Fuels:
Millions of years ago, the remains of plants and animals were buried under the earth by the forces of nature. The large amount of heat and pressure inside the earth converted these remains in fossil fuels, such as coal, petroleum and natural gas. These are the main sources of conventional energy.
The reserves of the fossil fuels are finite and limited. Their consumption is rapidly increasing in the modern world than their rate of formation. Thus one day or the other, the fossil fuels are likely to be exhausted.
They cannot be replenished like commodities derived from plant and animal kingdoms. Thus, we must develop alternative sources of power

(B) Thermal power plant:

Large amount of fossil fuels are burnt every day in power stations to heat up water to produce steam which further runs the turbine to generate electricity.
The transmission of electricity is more efficient than transporting coal or petroleum over the same distance. Therefore, many thermal power plants are set up near coal or oil fields. Here fuel is burnt to produce heat energy which is converted into electrical energy.

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