Sources of Energy: Renewable and Non-renewable
a. Non-renewable energy sources.
Energy sources which cannot be replaced quickly and cannot be used forever are called non renewable sources of energy. Coal, Natural Gas, Petroleum etc are some examples. They are also called fossil energy.
b. Renewable energy sources.
The energy which are being produced continuously in natural and are inexhaustible are called renewable sources of energy. Solar energy, wind energy, hydro energy, bio gas etc are examples of renewable sources of energy.
c. Fossils Fuel/Petroleum/ Rock oil
The remaining of dead plants and animals buried under the earth’s surface millions of years ago are called fossils. Decomposition of these fossils under high temperature and pressure in absence of a oxygen results in formation of fossil fuels. Eg.; Coal, Petroleum products, natural gases etc.
Petroleum is used more than other energy sources because of following merits:
a. Easy to transport
b. Cheaply and easily available than other sources of fuel.
c. Used in factories, vehicles etc.
d. Can be used to generate electricity also.
Advantage of hydroelectricity:
a) Though initial set up of hydro electricity is expensive, it is cheap in long run.
b) It is pollution free.
c) It is renewable source of energy.
d) It is multipurpose source of energy, ie. It can be changed into any other form of energy easily.
Sources of alternative sources of energy:
i) Hydro electricity ii) Nuclear energy iii) Biomass energy
iv) Wind energy v) Tidal energy vi) Geothermal energy
# Naturally Geothermal energy can be obtained from volcanic eruption, Hot springs.
- Energy received by earth per sq. meter = 1.4 kw/m2
- Energy radiated by sun per second = 2.7×1027 j/s.
The positively charged particle whose mass is equal to the mass of electron is called positron.
Isotopes of hydrogen:
Protium – proton – 1 Neutron – 0 Atomic wt – 1
Deuterium – proton– 1 Neutron – 1 Atomic wt – 2
Tritium – proton – 1 Neutron – 2 Atomic wt – 3
Energy released when a heavier nucleus splits or lighter nuclei fuse together is called nuclear energy. Nuclear fusion and fission are of two type.
When nucleus is bombarded with slow neutrons. It split into lighter nuclei with release of large amount of energy. This process is called nuclear fission. For example: Splitting odf Uranium into Barium and Krypton as:
92U 235+0n1 ®56Ba 141 +36Kr 92+30n1+Q
Combining of two lighter nuclei to form heavier nucleas with release of enormous energy is called nuclear fusion. This process occurs in sun. Our sun is sufficiently rich in hydrogen gas. These hydrogen stoms combine together by nuclear fusion to give large amount of energy. The reaction occurs as:
1H1 +1H1 Very high temp. and pressure 1H2He0 + energy
1H2+1H1 Very high temp. and pressure 2He3+ energy
2He3 Very high temp. and pressure 2He4+1H1+1H1+ energy
Condition for nuclear fusion in sun:
i) Abundance of hydrogen gas.
ii) Extremely high temperature.
iii) Extremely high pressure.
Sun as ultimate source of energy:
All the energy sources directly or indirectly depends upon sun as their sources. For eg: water required for hydropower in rivers comes in form of rain water or snow from evaporation of oceans to cloud. Likewise wind is generated when different layer of atmosphere gets heated.
The acute scarcity of energy sources of energy due to the overuse by overpopulation, urbanization and exploitation of energy sources is called energy crisis.
Ways of Solving energy crisis:
i. Shifting our dependency of energy sources from non- renewable to renewable source of energy.
ii. Conserving existing fuels.
- Developing and using alternative source of energy.
1. Geothermal energy can be used as alternative source of energy.
Ans- Geothermal energy can be used as alternative source of energy because this energy is originated from the certain geological part of the earth’s crust.
2. Nepal has high potentiality for producing hydroelectricity however difficult to produce it.
Ans-Nepal has high potentiality for producing hydroelectricity however difficult to produce it because of lack of manpower and money.
3. The sun is the main source of energy.
Ans- The sun is the main source of energy because of the following reasons:
Ø It provides energy for all living beings on the earth directly or indirectly.
Ø Hydro-power is also the outcome of solar energy as it causes melting of ice and rainfall.
Ø Different forms of energy like wind energy, fossil energy, bio-mass etc. are derived from solar energy.
4. The development of hydropower helps to reduce energy crisis further.
Ans- The development of hydropower helps to reduce energy crisis further because of the following reasons.
Ø It is a renewable source of energy which is never depleted.
Ø It does not cause any environmental pollution.
5. Renewable source can be an alternative to non-renewable sources.
Ans- If non-renewable sources of energy are exhausted, they can not be brought back to their original state and can cause energy crisis but not by renewable sources of energy so renewable source of energy can be an alternative to non-renewable sources.
6. Nowadays it is found that government has encouraged to use the bio-gas.
Ans- Nowadays it is found that government has encouraged to use the bio-gas because of the following reasons.
Ø They can never be depleted and can be used for long time again and again.
Ø The raw materials of bio-gas are also easily available locally with cheap price.
Ø Bio-gas is pollution free renewable (Alternative sources of energy).
Ø The by-producer of bio-gas is a good manure that increases the soil fertility.
7. Scientists are seen very busy to design the solar power depending equipments.
Ans- Scientists are seen very busy to design the solar power depending equipments because of the following reasons.
Ø The fossil energy are exhaustible sources of energy or non-renewable sources of energy.
Ø The solar energy is the pollution free alternative renewable sources of energy which is never finished even if it is used continuously in nature.
8. The development and use of alternative energy sources is necessary in today’s world.
Ans- Since the population is increasing day by day and the needs and demands are also increasing which directly affects the sources of energy so the development and use of alternative energy sources is necessary in today’s world.
9. The conservation of energy is necessary in today’s world.
Ans- The crisis of non-renewable sources of energy may happen in future so to save such sources the conservation of energy in necessary in today’s world.
10. Coal and petrol are called non-renewable sources of energy.
Ans- Coal and petrol are called non-renewable sources of energy because they are found in limited amount on the earth’s crust and can be exhausted and also they take a very long time period to form.
11. The use of hydropower should be increased rather than that of coal and mineral oil for getting energy.
Ans- The use of hydropower should be increased rather than that of and mineral oil for getting energy due to the following reasons.
Ø The hydropower is a renewable source of energy which is never depleted.
Ø The hydropower id clean and pollution free source of energy.
Ø Hydro-electric potential of our country is the world’s second highest 83000MW.
Ø Nepal contains large no. of fast flowing rivers from sloppy land and also has suitable location for constructions of dams and reservoirs.
Ø The rivers are perennial and the amount of water contents is never decreased.
Ø But coal and mineral oil are non-renewable sources of energy which are found in limited amount on the earth’s crust and can be exhausted and also they take a very long time period to form again.
12. The generation and use of electricity is spreading throughout the world.
Ans- due to the following reasons
Ø Electricity is one of the major sources of energy for electrical devices.
Ø It is easy to transmit and use.
Ø It is never depleted as it is a renewable source of energy.
Ø It is cheaper than other sources of energy in a long term basis.
Ø It is a pollution free source of energy.
13. Hydro-power is the renewable sources of energy that is most useful to our country.
Ans- Hydro-power is the renewable source of energy that is most useful to our country because of the following reasons:
Ø Hydor-electric potential of our country is the world’s second highest 83000MW.
Ø It doesn’t cause pollution since there is no emission of gas and dust particles.
Ø It is cheaper on a long-term basis.
14. Hydor-power is said to be an indirect source of solar energy.
Ans- Hydro power is said to be an indirect source of solar energy because it causes the melting of ice and also causes the rainfall by hydrologic (water) cyclic process.
15. Energy of fossil is also derived from the solar energy.
Ans- Energy of fossil is also derived from the solar energy because the fossil fuel is formed by the decomposition of the dead bodies of plants and animals occurs which is caused due to solar energy.
16. Government of Nepal provides loan and technical support to the farmers to establish bio-gas.
Ans-It needs very high cost to construct bio-gas plant which is beyond the reach of poor Nepalese people so government of Nepal provides loan and technical support to the farmer’s to establish bio-gas.
17. There is an acute need of the search for alternative sources of energy on the earth.
Ans- There is an acute need of the search for alternative sources of energy on the earth because of the excessive use of non-renewable source of energy by major portion of the world’s population.
18. Coal is called fossil fuel energy.
Ans- Coal is called fossil fuel energy because it is formed from the fossils of dead plants and animals.
19. We might face energy crisis in near future, Why?
Ans- In present day’s world, about 80% of energy demand is being full-filled by petroleum, coal and natural gas. The stock of these fuels in the mines is limited and they are non-renewable sources of energy. According to research by 2.3% per year. If the demand of energy increases in this rate, it is likely that the stock of fossils fuel will be exhausted by 2037 A.D. Due to this there will arise a big energy crisis in the near future if the alternative sources of energy are not developed and used.
20. Nuclear energy is most efficient but dangerous.
Ans- Nuclear energy is extremely efficient in addition to being cleaner, more reliable and more cost effective then fossil fuels. One small amount of nuclear fuel can produce the large amount of energy for which a large amount of fossil fuel is required. On the other hand, it is the process in which the energy is released by controlled nuclear fission reaction. During this process a large amount of harmful radiations are emitted which directly harm the living organism. Also, the nuclear wastes are also the main problem. So, nuclear energy is most efficient but dangerous.
Why Conservation of Energy?
Energy and its sources
- Energy is the ability to do work or the total power derived from our natural resources. The energy exists in many forms and can be converted from one form of energy into another. Energy in usable form is dissipated to the surroundings as less usable form.
- Energy is mainly derived from natural sources like the sun, oceans, fossil fuels, wind etc and is converted into electrical energy that we consume for our daily needs and benefits.
What Is a Good Fuel?
A good source of energy
- Sources can be classified as renewable and nonrenewable sources of energy.
- Any source of energy that does not get depleted or gets exhausted is considered a good source of energy and are usually called as renewable.
A good source of energy/fuel should be:
- Easily available
- Easy to store and transport
- Able to perform large amounts of work per unit mass and volume
Fossil Fuels and Thermal Energy
Conventional sources of energy
- Sources of energy that have been in use for a very long time or have been used extensively worldwide are known as conventional sources. Eg: wood as a common source of heat energy or the usage of coal after the Industrial Revolution.
- Examples: Fossil Fuels, Hydro Power
- Fossil fuels are formed due to compression of dead organic matter over millions of years, buried deep under the earth. Eg. coal or natural gas.
- We rely heavily on fossil fuels for most of our work.
- Fossil Fuels are non-renewable sources of energy as they have limited reserves and hence finding alternative sources is essential to avoid an energy crisis.
Disadvantages of burning fossil fuels
- Fossil fuels also produce byproducts due to combustion which causes air pollution.
- Burning coal and petroleum produces harmful oxides of carbon, nitrogen, and sulphur which pollute the air leading to acid rain and greenhouse effect.
- Gases emitted by the combustion of fossil fuels are the main contributor to global warming.
Thermal power plants
- Thermal power plants use steam produced by burning fossil fuels (mainly coal) to move the turbines to generate electricity.
- The burning of coal heats up the water and forms steam that is used to run the turbine.
- Usually, Thermal power plants are located near coal or oil fields as it is easier to transmit electricity than transport coal.
- A turbine is a rotatory mechanical device that extracts kinetic energy in various forms and converts it into useful work. It uses a dynamo to convert this mechanical energy into electrical energy.
- Various uses of this have been implemented in power plants where the shaft of the dynamo is made to rotate by mechanical means.
- Another traditional source of energy is from the kinetic energy of flowing water or harnessing potential energy of water falling from a height.
- The falling/flowing water moves the turbine, which with the help of a dynamo converts mechanical energy into electrical energy.
- Hydropower plants are usually constructed near dams or waterfalls.
A dam is a barrier that impounds water or underground streams. The water is ejected upon requirement by the power plant to generate hydroelectricity.
- Biomass is the source of energy derived from living things (organic matter). For a long time, we relied on wood for the source of heat energy. In India, we make fuel out of biowaste such as cow dung due to the availability of a thriving population of livestock.
- When wood is burnt in a limited supply of oxygen and water until volatile materials are removed, the residue left behind is charcoal. Charcoal has good heat generating efficiency. It also burns without flames.
- In India cow dung, sewage waste, plant matter are decomposed in absence of oxygen to produce biogas. Since it has cow dung it is often termed as gobar gas.
- A biogas plant is a dome-like structure built with bricks where cow dung and other biowaste are mixed with water to form a slurry and put into a digester.
- The digester is a sealed chamber with anaerobic bacteria which breaks down the slurry.
- This decomposition process releases gases like methane, CO2, hydrogen sulfide and hydrogen.
- These gases are drawn via pipes which are transmitted to a turbine for the production of electricity.
- Environment-friendly efficient source of energy.
- Wind is the natural phenomenon caused by pressure differentials due to unequal heating of land and water masses on the surface of the earth. It is harnessed in the form of kinetic energy.
- Wind Energy is harnessed by rotatory structures known as windmills.
- They have huge blades or fans attached very high on a rigid support that is attached to turbines that rotate due to high speeds of wind and generate electricity.
- A single windmill has a low output and therefore, the wind farms are built that comprises of several windmills.
Advantages and limitations of wind energy
Advantages: Environment-friendly, efficient, renewable source, with no recurring cost for production of electricity.
- Wind speeds should be constant and > 15 km/h.
- Must have back up storage facilities like cells.
- Requires large land area.
- High initial cost and regular maintenance are required.
- Light energy and heat energy from the sun are known as solar energy.
- Sun has been radiating energy from the past 5 billion years and will continue to do so at the same rate for another 5 billion years or more.
- We must find ways to harness the energy with maximum efficiency, although only a small fraction of the solar energy reaches the earth’s surface.
- Solar cookers and water heaters use solar energy to operate.
- Black surfaces absorb more energy than other surfaces and solar cookers use this property by coating their insides black.
- They use reflecting surfaces like mirrors to focus the sun’s rays.
- The device is covered with a glass plate thereby establishing the greenhouse effect by trapping heat inside the cooker.
- A device that converts solar energy into electricity is known as a solar cell.
- A typical solar cell produces a voltage of 0.5 1 V and 0.7 W of electrical power. A large number of such cells can combine to form a solar panel which can generate power large enough for practical uses.
- Advantages: (i) no moving parts (ii) require little maintenance (iii) can be set up in remote areas without the hassle and expenses of transmission lines.
- Disadvantages: (i) Requires a special grade silicon which is not easily available (ii) Usage of silver for interconnections makes it expensive.
- Uses: traffic signals, calculators, artificial satellites and space probes.
Energy From the Sea
Energy from sea
The seas and oceans and other water bodies are a source of kinetic and potential energy due to the immense volume of water and the motion of waves.
- Tides are variations in the level of water due to the gravitational pull of the moon.
- The phenomenon of rise and fall of water level or high and low tide gives tidal energy.
- Tidal energy is obtained by constructing dams near the narrow openings of the sea. When the tide sets in, it moves the turbine which directly produces electricity.
- It is limited to places near the sea.
- Waves possess a lot of kinetic energy that can be harnessed to produce electricity.
- Waves are produced by strong winds blowing over the sea.
- Limited to places with strong winds. Devices have been designed to capture this energy.
Ocean thermal energy
- The difference in surface temperatures of water and water at a certain depth in oceans is exploited to harness this form of energy.
- Temperature difference must be 20∘ between the surface and water up to depths of 2 km.
- Warm water is used to boil volatile ammonia to form vapours that move the turbine. Cold water is used to condense the vapour back to liquid.
- There is a huge amount of heat trapped inside the earth. Molten rocks from Earth’s core sometimes come up due to geological changes and get trapped in hotspots. Harnessing this heat energy is called geothermal energy.
- Any underground water present gets heated due to the hotspots and gets converted to steam which escapes from the surface of the earth as hot springs.
- This steam is used to rotate turbines and generate electricity.
- Nuclear energy can be used to generate electricity by means of nuclear fission.
- In a nuclear reactor, the nuclear fuel is used to carry out sustained fission chain reaction to produce electricity at a controlled rate.
Nuclear fission is the process where a heavy atom (uranium or plutonium) is bombarded with neutrons that split the atom to give lighter nuclei. This process releases tremendous amounts of energy. For example, Fission of 1 atom of uranium gives 10 million times the energy of combustion of 1 atom of carbon from coal.
Disadvantages of using nuclear energy
- Nuclear waste is hazardous as heavy atoms decay into harmful subatomic particles.
- High setup and maintenance cost
- Limited availability of uranium
- Can be used for destructive purposes
- Fusion means combining lighter nuclei to produce a heavier nucleus, usually hydrogen or hydrogen isotopes to create helium.
- It releases a huge amount of energy. The mass deficit between the product and reactants are given by Einstein’s equation. E=mc2