Source of Energy Revision Notes Class X

 

Source of Energy Revision Notes Class X Science

Introduction

Capacity of doing work is called energy. We use our muscular energy to do many works. Apart from that we use many natural sources of energy, for example burning of wax is used in candle to get light. Burning of diesel or petrol is used to run vehicles.

One form of energy can be converted into other form, for example to lit an electric torch we convert chemical energy into light energy.

There are many sources of energy we have, such as fossil fuels, wood, solar energy, wind energy, water energy, etc. which we use to make our life comfortable.

What is a Good Source of Energy?

We cannot use all sources to get energy effectively. There are some parameters which decide that which source of energy is good. These are

• Source of energy which would do a large amount of work per unit volume or mass
• Source of energy which can be easily accessible
• Source of energy which can be easy to store and transport
• Source of energy use of which is economical

Thus, source of energy which can do a large amount of work per unit volume or mass, can be easily accessible, can be stored and transported easily and is economical in use is called a good source of energy.

Conventional Sources of Energy

Fossil Fuels

Many millions of years ago living organisms, such as trees and plants, got buried. Over the time period because of anaerobic decomposition dead organisms were converted into forms sources of energies. These sources of energy are called FOSSIL FUELS.

Coal, petroleum and natural gases are example of fossil fuels. Today human depends almost completely on these fossil fuels to get energy.

Coal and petroleum is the most important and widely used fossil fuel today. Our technologies were also developed for using these energy sources, i.e. coal and petroleum.

Fossil Fuels and Non-Renewable Sources of Energy

Fossil fuels were formed over millions of years ago and there are only limited reserves of them. Since, fossil fuels take millions of years to form, thus these are called non-renewable resources of energy.

With the increase in population demand of energy is increasing. To fulfill this demand of energy we are almost completely depend on fossil fuels. If we were to continue consuming these sources at such alarming rates, we would soon run out of energy resources, i.e. out of energy. So, we must conserve these resources of energy.

Disadvantages of use of Fossil Fuels

There are many disadvantages of getting energy using of fossil fuels.

Burning of coal, petroleum and petroleum products release many harmful gases, such as oxides of carbon, nitrogen and sulphur.

These acidic oxides in the form of gases go in atmosphere and lead to acid rain. Acid rain makes our water bodies acidic which is threat to survival of aquatic organism.

Acid rain makes our soil acidic which affects yield of agriculture produces badly.

Harmful gases emit because of burning of fossil fuels make air polluted and creates many problems, such as green house effect.

Breathe in polluted air creates many health problems

Power Plant

Plants to generate electricity are generally called power plants. In a power plant, energy is used to rotate huge turbines attached to electric generator. Electric generator converts mechanical energy into electrical energy. Electricity generated by power plant is transported to different places, such as house-holds, factories, markets, etc. for further use.

The transmission of electricity is more efficient than transportation of coal, petroleum, or other resources of energy. Thus, these power plants are set up where resources of energy are available.

There are many types of power plants depend on resource of energy use in them.

Thermal Power Plant

Power plant in which coal is used to produce electricity is called THERMAL POWER PLANT. Since, in such plants fuel is burnt to produce heat energy which is converted into electrical energy, thus these are called Thermal Power Plants.

In thermal power plant coal is used to heat water, and steam so produced is used to rotate huge turbines attached to huge electric generators.

Electricity produced in thermal power plants is transmitted to different places through electric wires for further use.

Advantages of Thermal Power Plants

Coal is used in thermal power plants which is cheaper than other fuels.

Mechanism used in thermal power plant to run turbine is comparatively simple

Thermal power plants requires less space compare to hydro electric power plants

Heat produced in thermal power plants can be reused

Disadvantage of Thermal Power Plants

Thermal power plants produce huge amount of carbon dioxide which pollute atmosphere badly.

Produced carbon dioxide from thermal power plants is responsible for acid rain and green house effect.

Thermal power plants produce large amount of ash due to burning of coal, which spread surrounding area of the power plants and make agriculture land barren.

Thermal power plants are less efficient than others.

Requires huge amount of water to produce steam, thus should be set up near the river sites.

Coal is used as fuel in thermal power plants. Handling of huge amount of coal requires large space.

Disposal of ash produced after burning of coal also requires large area

Efficiency of thermal power plants is comparatively very less, which is only about 30% to 35%.

Operation cost of thermal power plants is higher than hydro electric or nuclear power plants.

Hydro Power Plant

Kinetic energy of running water or potential energy of water at a height is another source of energy.

Hydro Power Plants convert kinetic energy of flowing water or potential energy of water at a height into mechanical energy and mechanical energy so produced in converted into electrical energy.

Electricity produced from Hydro Power Plants, big and high rise dams are constructed on the river. High rise dam store river water in reservoir by obstructs the flow of water. Because of obstruction, i.e. dam, water level rises and in this process kinetic energy of flowing water gets transformed into potential energy.

Water from high level in dam is carried to the turbine installed at the bottom of dam through pipes. Water falling from very high, makes turbine run. Electric generator attached with turbine, converts mechanical energy of turbine into electrical energy. Energy so produced is transmitted through electric wires to different places.

Water in the reservoir refilled each time when rains, thus hydro power is a renewable source of energy.

Problems associated with Hydro Electric Power

To draw hydro electricity, dam is must which can be constructed in a limited number of places. Dams are constructed preferably in hilly areas, so that hill can be act as natural boundaries for reservoir.

In the construction of dam, larges of agriculture land and human habitations are got submerged, resulting in displacement of large human population.

In the reservoir, many trees are submerged, which destroyed large eco-systems.

Vegetations submerged because of water in the dams, rot under anaerobic conditions and give rise to the large amounts of methane which make green house effect worsen.

Because of displacement and rehabilitation of people of the catchment area of dam, in recent years, Government had to face many problems while construction of Tehri Dam on the river Ganga and Sardar Sarovar project on the river of Narmada.

Advantages of Hydro Electric Power

In hydro electric power, electricity can be generated continuously once dam is constructed.

Hydro electric power does not use water at all, water returned to its origin.

Hydro electric power does not create any pollution to environment.

Dams constructed for hydro electric power station has sluice gates, which can be closed as per requirement.

After construction of dams water can be used for other purposes also, such as for irrigation, for drinking, etc. apart from production of electricity.

Hydro power plants produce clean energy.

Bio Mass

Fuels come from plant and animal produces are called Bio Mass, for example fire wood, cow dung, etc. Fire wood has been used from ancient time for getting energy along with cow dung. Even today in many areas, especially in rural areas, fire wood and cow-dung are still in use. However, burning of fire wood and cow dung do not produce much heat and these fuels produce a lot of smoke when they burn, so technologies are being improved to improve the efficiency of these fuels.

Charcoal

Charcoal is a type of fuel. Charcoal burns without flames and is comparatively smokeless and has higher heat generation efficiency. Charcoal is formed when wood is burnt in a limited supply of oxygen, water and volatile materials present in it get removed and the charcoal is left behind as the residue.

Bio Gas

Bio gas is formed by the decomposition in absence of oxygen of cow dung, various plant materials like the residue after harvesting the crops, vegetable waste and sewage, etc. Bio gas is popularly known as 'Gobar Gas' because starting material of formation of bio gas is mainly cow dung.

Bio gas is an excellent fuel. Bio gas contains up to 75% of methane. Bio gas burns without smoke and leaves no residue like ash in wood, charcoal and coal burning.

Bio-Gas Plant:

In bio gas plant, slurry of cow-dung and other waste materials of plant are put in a sealed chamber. In the sealed chamber anaerobic micro organisms that do not require oxygen decompose or break down complex compound of cow dung slurry. In few days gases like methane, carbon dioxide, hydrogen and hydrogen sulphide are produced after the completion of decomposition process. The bio gas so produced is stored in a tank and is drawn through pipes for use.

Bio gas so produced is used for lightning, cooking, etc. The slurry left behind is removed periodically. The residue, i.e. slurry left behind is rich in nitrogen and phosphorous, which is used as manure.

The large scale utilization of bio waste and sewage material provides a safe and efficient method of waste disposal besides supplying of energy and manure.

Wind Energy

Air movement and blow of wind happens because of unequal heating of land mass and water bodies. Conversion of Kinetic energy of wind into mechanical energy and finally into electrical energy is called wind energy.

In ancient times also, Kinetic Energy of wind was harnessed by windmills, such as in water lifting pump, in grinding of grains, etc.

Today, wind mills are used to generate electricity. A windmill has structure similar to a large electric fan that erected at some height on a rigid support.

In wind mills the rotary motion of blades is used to turn the turbine of the electric generator. But, output of one windmill is very small and cannot use for commercial purpose, so a series of windmills are established to coupled together to get electricity at commercial scale.

Wind energy is an environment friendly and efficient source of renewable energy as it requires no expense on fuel to produce electricity.

Limitation or Disadvantage of Wind Energy

To established wind energy farms, only those places are required where wind blows for greater part of the year.

Wind speed should also be more than 15 km/h to maintain the required speed of turbine to generate electricity.

Back up facilities should be required to conserve electricity produced for use when there is no required wind.

For generation of 1 MW of electricity, about 2 hectares of land is required, this make the cost of establishment very high.

Tower and blades are exposed the vagaries of nature, like rain, sun, storm and cyclone, etc. thus it needs a high level of maintenance.

Country of Winds: Denmark

In the country of Denmark about more than 25% of required electricity is generated by wind energy farms. So, Denmark is known as Country of Winds. India lies at fifth rank in the world in terms of wind energy production.

Alternate & Non-Conventional Sources of Energy

Sources of Energy on which we depend today are non-renewable and getting consumed with alarming rate, this compels us to see and discover alternative or non-conventional sources of energy.

Solar Energy

Heat energy we get from sun is called Solar Energy. This heat energy can be used by developing special devices.

Solar Cooker and Solar Heater

Solar cookers and Solar water heater is used to cook food and to heat water respectively. Body of Solar cooker is made of black material as black material absorbs more heat as compared to a white or a reflecting surface under identical conditions. A mirror is fitted with the lid of solar cooker that reflects the sun rays to the cooker.

Some solar cookers are made of parabolic surface fitted with mirror, which concentrates sunlight and concentrates heat of sunlight to cook food. Heat can be reached upto 4000C in a parabolic solar cooker.

But solar cooker like devices are useful only at certain times during the day.

Solar Cells

Solar cells are device which convert solar energy into electrical energy. Solar cells are called photovoltaic cells also. A large number solar cells connected together form a solar panel that can deliver electricity for practical use.

A typical solar cell develops a voltage of 0.5 V to 1 V and can produce about 0.7W of electricity when exposed to the Sun.

Advantage of solar energy

Solar cells have no moving parts and hence required little maintenance and work quite satisfactorily without use of any focusing device.

Solar panels can be set up in remote and inaccessible hamlets or very sparsely inhabited areas in which laying of power transmission line may be expensive and not commercially viable.

Solar energy produce nothing as residue and hence is very good green energy.

Sun shines need no fuel and hence no cost for production.

Disadvantages of Solar Energy

Silicon, which used for making solar cells, is abundant in nature but availability of special grade silicon form making solar cells is limited.

The process of manufacturing of solar cells is very expensive as silver metal is used for interconnection of cells in the panel further adds the cost.

Since, sun shines only in day time, hence to use of solar energy while night or in rainy seasons when sun does shines or shines very less, energy produced by solar panel is to be conserved using electric cells.

Other uses of solar energy

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.

Radio or wireless transmission systems or TV relay stations in remote locations use solar cell panels.

Traffic signals, calculators and many toys are fitted with solar cells.

Today cars are also made to use solar energy.

In recent days a plane name Solar Impulse 2 completed its 40000 km travel for 500 hours. It has successfully completed the first fuel-free flight around the world.

These days use of solar cells is increasing inspite of its high cost.

Energy From the Sea

Phenomenon of High tides and low tides take place at regular interval in oceans and seas. This is rise and fall of water and conserves potential energy. This energy can be converted into electrical energy.

When there is high tide, water is trapped into dams made nearby. And in the case of low tide, kinetic energy of flow of water from narrow openings of these dams is converted into electrical energy. This method harnessed energy using similar method to hydro electric energy.

However, location where such dams can be built are limited, instead of that there is potency to harness energy by this method.

Wave Energy

Due strong winds blowing across the sea, strong waves are caused in seas and oceans. Because of waves, there is continuous and rhythmic rise and fall in seas and ocean water.

Special devices are made, similar to leg operating sewing machines, to harness the energy possessed by rhythmic rise and falls of seas and ocean waves. Energy trapped in rhythmic rise and fall of water waves make the rotation of turbines attached to special devices and produce electrical energy.

Many countries, such as China, USA, etc. generate a good amount of electrical energy from wave energy.

Ocean Thermal Energy

Surface water of seas and oceans get heated due to Sun shines while water in deeper section is relatively cold. This difference of heat is harnessed into electrical energy using ocean thermal energy conversion plants.

Ammonia is a liquid which boils at low temperature. Ammonia vapour forms due to temperature difference in seas or  ocean water is used to run the turbine of electric generator. The cold water from the lower part of sea water is then pumped to cool down the ammonia vapour again into liquid. This process continues and produces electricity.

Ocean thermal energy plant operates if the temperature difference between the water at the surface and water at the depth upto 2km is 200 or more.

Ocean thermal energy is very large, but efficient commercial exploitation is difficult

Geothermal Energy

Hot spots are the region of earth's crust where molten rocks are pushed upward and get trapped because of geological changes. Sometimes hot water comes in contact with those hot spots while finding outlet and are called hot springs.

Underground water gets heated and form steam when come in contact with such hot spots. The steam produced by the underground water and hot spots get trapped in rocks which is brought to turbines of electric generator is exploited to electricity.

However the cost of production of electricity using geothermal energy is too much, instead of that it is clean energy and can be exploited without burning any fuels.

Many countries like New Zealand and USA set up many number of power plants to generate electricity using geothermal energy.

Nuclear Energy

The main concept to produces electricity is to run turbines of electric generators. Nuclear fission is a process in which nucleus of radioactive elements is broken down by bombardment with low energy neutrons. In the breaking down of nucleus of radioactive elements, huge amount of energy is produced.

Heat energy produced by breaking of nucleus of radioactive elements is used to produce steam which runs the turbines of electric generator to produce electricity.

To do nuclear fission is similar to explode an atom bomb.

Disadvantage of Nuclear Energy

Cost of set up of Nuclear Power Plant is very high.

Fatal health problems may arise due any leak in power plants.

Limit availability of radioactive elements.

Advantage of Nuclear Energy

Once power plant set up, energy produced from this cost very less.

Nuclear energy power plant can produce enough amount of electric energy to feed the increasing demand.

In India, and around the world, there are many Nuclear Power Plants in operation. Such as Kakrapar Atomic Power Station located in the state of Gujarat, Kundankulam Nuclear Power Plant, in Tamil Nadu, Madras Atomic Power Station in Kalpakkam, Tamil Nadu, Narora Atomic Power Station in Uttar Pradesh, etc. are some of the Nuclear Power Plants are in operation in India.

Environmental Consequences

Energy makes our life comfortable. We use various sources to get energy. Getting energy from different sources has their own merits and demerits. Some sources give us energy at the cost of more damaging of environment while some gives at the cost of less environmental damage. Although energy from some sources of energy are termed is termed as clean energy, but we could not develop devices to get clean energy so far. With increase in population demand of energy is increasing with leaps and bound while sources of energy are getting exhausted with alarming rate as sources on which we depend for energy today are non-renewable and limited. Scientists are trying their best to develop devices to get energy from renewable sources and alternate and new sources of energy are being discovered.

We should rethink while exploiting sources of energy as these has other dark aspects.

How Long Will an Energy Source Last Us?

Today most of our needs depend on fossil fuels, which is a non renewable energy and has limited stock as it takes millions of years to replenishment of fossil fuels. On the other hand getting energy from fossil fuels cause many problems to environment, green house effect is one of them.

Bio mass, which is also a source of energy can be replenished by planting more and more tree, so that we would never out of run of source of energy, thus bio mass is one of the alternative today. But still better and efficient devices yet to be discovered and manufactured.

We should see towards alternate and non conventional sources of energy, such as tidal energy, solar energy, etc.

If we keep our eyes open and keep developing new devices, we would never out of energy.