Chapter 3 SOURCES OF ENERGY

The nuclear fuels like nuclear fuels are the non renewable sources of energy other than fossil fuels.

Calorific value of a fuel can be defined as the amount of heat produced by the combustion of 1 gram of that fuel completely.

Since Calorific value is the amount of heat produced by burning a unit of the fuel completely, hence, calorific value of LPG is 50kJ/gm means that if 1 gram of LPG is burnt completely, then 50kJ of heat energy will be produced.

Since LPG has a higher calorific value than coal, hence, LPG produces more heat on burning.

The lowest temperature at which a combustible substance when heated catches fire in air and continues to burn is called ignition temperature.

The ignition temperature of a fuel is 800 C means that 800C is the minimum temperature at which the particular fuel will catch fire or will ignite.

calorific value

A source of energy is one which can provide appropriate amount of energy in expedient form over a long period of time.

Two main categories of the source of energy are:

a) Renewable source of energy-source of energy that is not depleted when used. Such as wind or solar power.

b) Non- renewable source of energy-sources of energy that will run out or will not be replenished in our lifetimes or even in many, many lifetimes.

A good source of energy should have the following characteristics:

a) It should do a large amount of work per unit mass or volume that means it should have high calorific value.

b) It should be easily accessible and provide energy over a long period of time. Example: coal and petroleum.

c) Should be easy to store and transport.

d) Safe and convenient to use - energy sources should be safe as it is used by a large number of people and should be convenient.

Non-renewable source of energy is one that will run out or will not be replenished in our lifetimes—or even in many, many lifetimes. Most non-renewable energy sources are fossil fuels: coal, petroleum, and natural gas.

Renewable source of energy are those sources that generate energy from natural resources – such as sunlight, wind, rain, tides and geothermal heat – which are renewable (naturally replenished). Hence, they do not deplete with time.

Renewable energy resources: The energy resources which cannot be exhausted and can be used again and again are called renewable energy resources. For example solar energy, wind energy, tidal energy and hydroelectric etc.

Non-renewable energy resources: The energy resources which can be exhausted one day and cannot be used repeatedly are called non-renewable energy resources. The example of non-renewable energy resources are coal, petroleum, natural gases etc.

Fossil fuels are non-renewable because they take millions of years to form. Fossil fuels make up most sources of non-renewable energy, and they were created millions of years ago as a result of marine creatures decaying under immense pressure and heat.

Solar energy, wind energy, ocean energy etc., are renewable sources of energy due to the following reasons:

a) These forms of energy are available in plenty in our natural environment in the form of continuous currents of energy.

b) These energy sources will not be depleted because their supply is large and extraction of usable energy from these sources is negligible.

Two examples of non renewable sources are-

a)Coal: It is produced from dead remains of plants and animals that remain buried under the earth's crust for millions of years. It takes millions of years to produce coal. Industrialization has increased the demand of coal. However, coal cannot replenish within a short period of time. Hence, it is a non-renewable or exhaustible source of energy.

b) Wood: It is obtained from forests. Deforestation at a faster rate has caused a reduction in the number of forests on the Earth. It takes hundreds of years to grow a forest. If deforestation is continued at this rate, then there would be no wood left on the Earth. Hence, wood is an exhaustible source of energy.

Renewable source of energy - wind, tides, wood.

The above classification is based on the fact that renewable sources are inexhaustible, whereas non-renewable sources are exhaustible.

Coal is considered to be a non-renewable source of energy whereas wood is a renewable source of energy because coal is formed when dead plants got buried under the earth for a long period of time. It took millions of years to be replenished. So coal is considered to be non renewable source of energy.

A fuel is a substance which is burn to produce heat energy. Wood, Coal, LPG, Diesel are some common examples of fuel.

The characteristics of an ideal fuel are:

It must have high calorific value.

It must burn without releasing any smoke or toxic gases.

It need to have proper ignition temperature.

It should be inexpensive and easily accessible.

Fuel A:

Advantages:

No toxic gases are released.

Proper ignition temperature of around 80°C.

Disadvantages:

It has a lower calorific value of 55kJ/g.

Fuel B:

Advantages:

It has a high calorific value of 80kJ/g.

Disadvantages:

It releases toxic gases like CO and SO₂.

It has a very low ignition temperature of 10°C.

As it is prepared from the animal dung, vegetable waste, etc.

As it is a fossil fuel.

As they take millions of years to be replenished again hence, considered non-renewable source of energy.

As it is the quality of an idle fuel.

It is present as a major component in biogas.

A sapling is a tree seedling that has grown sufficiently to be planted in a Tree Patch.

Hydrogen has a calorific value of 15000Kj/kg.

Calorific value of wood in dry state 3500kj/Kg and natural state 1500kj/Kg.

As carbon has a low calorific value so it would decrease the calorific value of the fuel if present in more amount, whereas Hydrogen has high calorific value so it would increase the calorific value of the fuel if present in excess.

A Good fuel require low or at least moderate ignition temperature.

This is because Biogas isn't prepared from the remains of plants and animals whereas fossils fuels are prepared from the remains of plants and animals.

Fuel B is the most ideal fuel due to the following main reasons:

(i) As it leaves no reside on burning like the other two.

(ii) As an idle fuel it has a high calorific value of 48 KJ/g.

(iii) Moreover it does not burn explosively.

Fuel Y is a better fuel due to the following main reasons:

(i) Y has a moderate ignition temperature of 75°C

(ii) As it do not produce any harmful gas (like CO) while burning.

(i) D (calorific value of cooking gas)

(ii) E (calorific value of alcohol)

(iii) B (calorific value of wood)

(iv) C (calorific value of Hydrogen)

(v) A (calorific value of kerosene)

Hydrogen gas>Methane> Petrol > Kerosene > Biogas > Wood

Hydrogen has the highest calorific value where as wood has the lowest calorific value.

Dung cakes < Coal < Alcohol < Diesel < LPG

Dung cakes have the lowest calorific value where as LPG has the highest calorific value among them)

Hydrogen is the fuel which has a very high calorific value and do not contain any carbon)

Diesel is the product of petroleum that is used to drive heavy vehicles. It is a mixture of hydrocarbons obtained by distillation of crude oil.

LPG i.e. Liquefied petroleum fuel. LPG is prepared by refining petroleum or "wet" natural gas, and is almost entirely derived from fossil fuel sources, being manufactured during the refining of petroleum.

Kerosene is one of the hydrocarbon fraction obtained during the fractional distillation of petroleum and used as a domestic fuel. It is widely used as a fuel in industry and households.

Fuels that are used to generate electricity in a thermal power plant are Coal, oil and gas.

Various fractions obtained during the fractional distillation (refining) of petroleum (or crude oil). Few of them are:

Diesel, Petrol, Kerosene, Petroleum gas etc.

Liquefied Petroleum Gas (LPG) is made up of a combination of propane, butane, and trace amounts of other chemicals, including pentane. Butane comprises slightly less than 70 percent of the gas. Propane comprises nearly 29 percent of the gas, leaving just over 1 percent for the trace components.

Compressed natural gas (CNG) which is a methane stored at high pressure is being used increasingly in transport vehicles in place of gasoline (petrol), Diesel fuel and propane/LPG.

(i) LPG stands for Liquefied Petroleum Gas. They are flammable mixtures of hydrocarbon gases used as fuel.

(ii) CNG stands for Compressed Natural Gas. It is methane stored at high pressure.

(i) The main constituent of petroleum gas is butane which is often abused as an inhalant.

(ii) The main constituent of natural gas is methane. It constitutes about 75% of the mixture.

Methane is found in both natural gas and biogas. In biogas it is about 50-65% whereas in natural gas it is around 75%.

Uses of natural gas are:

i) Natural gas is a fossil fuel used as a source of energy for heating, cooking, and electricity generation.

ii) It is also used as a chemical feedstock in the manufacture of plastics and other commercially important organic chemicals.

CNG combustion produces fewer undesirable gases than other fuels. It is safer than other fuels in the event of a spill. Hence, CNG is mostly used as a fuel in transport vehicles these days.

Butane

Natural gas is primarily made of methane (the lightest hydrocarbon).It burns more cleanly than other fossil fuels, emitting lower levels of harmful emissions such as carbon monoxide, carbon dioxide and nitrous oxides. It produces less greenhouse gases than other fossil fuels do. Hence, Natural gas is considered to be a good fuel.

The conventional sources of energy are generally non-renewable sources of energy, which are being used since a long time. These sources of energy are being used extensively in such a way that their known reserves have been depleted to a great extent. Coal, oil and natural gas are a few examples of it.

In a thermal power plant, the heat that is generated by combustion of coal is used to boil water to form steam. Then, the steam, being at high temperature and pressure, rotates the turbine and its shaft, which drives the generator to produce electricity.

The disadvantages of burning fossil fuels are:

a)Fossil fuels have had a good run, but they’re on their last legs.

b)Fossil fuels release carbon dioxide when they burn, which adds to the greenhouse effect and increases global warming.

c) Combustion of fossil fuels releases acidic gases.

d)The burning of fossil fuels produce smoke and leaves behind a lot of ash.

Most fossil fuels are burned to turn into energy, and the gasses released into the air by burning, in turn causes air and water pollution. Gases released by the burning of fossil fuels include carbon monoxide, nitrogen oxides, sulfur oxides and hydrocarbons. In the air, these gases become a carcinogen, which can be inhaled and can also mix with falling rain to form acid rain.Also, burning of fossil fuels produces smoke and a lot of ash.

We can reduce pollution by fossil fuels by following ways:

● We can reduce the consumptions of fossil fuels globally, by using less energy as an individual.

● By using more efficient machines that will emit less pollutant.

● By introducing techniques of treating the pollutant before emitting in the atmosphere.

● By using alternative safer, eco- friendly technologies.

If I could use any sources of energy for heating my food, I would prefer LPG i.e. Liquefied Petroleum Gas because as an idle fuel it has a high calorific value and burns with smokeless flame.

Liquefied Petroleum Gas is considered a good fuel because of the following reasons:

a) LPG has a high calorific value. The calorific value of LPG is about 50 kj/g.

b) It is a very neat and clean domestic fuel. It burns with a smokeless flame and hence does not cause pollution.

c) It does not produce any poisonous gases on combustion.

d) LPG is easy to handle and convenient to store.

LPG is better than Coal in the following points:

a) It can be easily transported to our homes through pipelines.

b) It has a high calorific value.

c) It does not leave a solid residue and neither forms harmful gases.

d) It is easy to store.

e) It is readily available.

f) It has a low ignition point.

g) It burns at a moderate rate and its combustion is controllable using a knob.

In order to detect the leakage, a foul smelling substance called ethyl mercaptane is added to the LPG. with that strong pungent smell, we can easily know if there is a leak.

In case of LPG leakage in the kitchen, following steps must be taken:

a) The door and windows should be opened to allow the gas to escape.

b) The source of gas leakage should be checked and then set right with the help of a gas mechanic.

The fuels that are formed from the remains of dead plants and animals that lived millions of year ago are called fossil fuels. For e.g.: coal, petroleum, diesel, etc.

When the ancient plants and animals died, they decomposed and became buried under layers and layers of mud, rock, and sand. Eventually, hundreds and sometimes thousands of feet of earth covered them. In some areas, the decomposing materials were covered by ancient seas, then the seas dried up and receded. Hence, these materials away from the reach of oxygen, got converted into fossil fuels due to the chemical effects of pressure, heat and bacteria.

The sun is the ultimate source of almost all kinds of energy on earth, either directly or indirectly. Fossil fuels are the transformed forms of plants and animals which once lived on the earth and grew capturing the energy of the sun. Biomass is a product of photosynthesis where the sun has the major role. Hydro-electricity depends upon the water cycle which again is dependent on solar radiation. Similarly, wind energy, tidal power, wave power all, in some way or other, and depend on the sun.

Petroleum and natural gas are such fuels.

Coal

Petroleum gas consist mainly of butane with a very small amount of ethane and propane.

Typically if we see then natural gas consist 90% of methane.

Burning of fossil fuels release various gasses like sulphur oxide, carbon dioxide, carbon monoxide, etc.

Diesel fuel in general is any liquid fuel used in diesel engines, whose fuel ignition takes place, without any spark, as a result of compression of the inlet air mixture and then injection of fuel.

Kerosene, also known as paraffin, lamp oil and coal oil (an obsolete term), is a combustible hydrocarbon liquid which is derived from petroleum, widely used as a fuel in industry as well as households.

Since plants and animals’ existence depends on the sun directly or indirectly and fossil fuels are formed due to the remains of plants and animals hence, we can say that sun is the ultimate source of energy stored in fossil fuels.

It is the excretion of a cow and not the remains of dead and decaying plants and animals.

It is a nuclear fuel used at nuclear power plants.

Liquified Petroleum Gas contains 60% of butane.

This is because it is a non-metal and it combines with oxygen and forms its gaseous non-metallic oxides.

As charcoal do not produces smoke while burning and has a low ignition temperature and high calorific value.

Acid rain is a rain or any other form of precipitation that is unusually acidic, meaning that it possesses elevated levels of hydrogen ions (low pH).

(a) X is carbon

(b) Hydrogen is another element which is usually found in combination with carbon in Fossil fuels.

Fossil fuels are obtained from remains of animals and plants under the earth over a period of millions of years these existed and grew due to sun's energy thus the ultimate source of fossil fuels can be considered to be the sun's energy.

(a) X is Ethyl mercaptan

(b) Ethyl mercaptan has a foul smell which can be detected easily at the time of leakage of LPG.

(a) Catalyltic converter- A catalytic converter is an emissions control device that converts toxic gases and pollutants in exhaust gas to less toxic pollutants by catalyzing a redox reaction (an oxidation and a reduction reaction)

(b) It helps in controlling air pollution by changing poisonous carbon monoxide into non-poisonous carbon dioxide and also converts harmful nitrogen oxides into harmless nitrogen gas.

A hydroelectric power station converts the kinetic energy of flowing or falling water into electrical energy that can be used in homes and businesses.

Kinetic energy is possessed by flowing water.

Kinetic energy of flowing water is used up by the turbine and later it it is converted into electrical energy.

Sun is the original source of wind energy. The sun’s radiation warms different parts of the earth at different rates. The result of this uneven heating is atmospheric change. Hot air rises, leaving decreased atmospheric pressure near the earth’s surface, and cool air is drawn in to replace it. The result of this air exchange is wind.

15km/hr should be the minimum wind speed for the satisfactory working of a wind- powered electric generator.

a) In the past wind energy was used in the flour mills.

b) In the present days wind energy is mainly used for generating the electricity through wind-powered generators.

The copper tube is painted black to improve their ability to absorb thermal energy. Black reflects the least amount of radiation (about 3%) of any color, and therefore absorbs almost all the radiation energy to which it is exposed.

Nuclear fusion reactions occur inside sun that produces solar energy. This reaction, converts hydrogen atoms into helium.

Solar panel, Solar charge controller, Solar inverter, Solar micro-inverter, Solar cable, Photovoltaic mounting system, etc are some of the solar energy devices.

plane mirror with high specular reflectivity is used as a reflector in box-type solar cooker to concentrate light from the sun on to a small cooking area.

The range of temperature which can be achieved in a box-type solarcooker in two to three hours is from 100°C to 140°C.

Solar cells convert sunlight into electricity. It is a form of photoelectric cell.

From the solar constant we deduce that

1.4 kW of power is incident upon every 1m2 of area.

i.e the total energy incident in 1 hr over an area of 1 m2 will be = 1.4 kW x 1 hr

(Since P=E/t or E=P x t)

Hence, energy = 1.4 kWh

Solar energy received by 1 m2 area in one hour (or 3600 s) = 1.4 x 3600 = 5040 kJ

solar energy into electrical energy.

The main difference between Thermal Power plant and Hydro Power plant are: The thermal power is produced by burning coal, petroleum or natural gas in thermal generator whereas the Hydro-electricity or Hydro power is derived from the force of running water by means of dynamo driven by hydro-turbine.

Among them, thermal power plant causes serious air pollution because it emits harmful gases like nitrogen oxide, sulphur dioxide and fly-ash into the air.

Coal and petroleum are fossil fuels they are obtained from deep under Earth’s crust. They are directly available to human beings for use. Therefore fossil fuels are the direct source of energy. But these are limited in amount also they are non-renewable.

Sun is also a direct source of energy. But it is renewable source of energy. The Sun has been shining for several years and will continue billions of years more. Solar energy is available free of cost to all in unlimited amount.

A concave mirror would be best suited for use in a solar cooker. When a concave mirror reflector is attached to a solar cooker, it converges a large amount of Sun's heat radiations at its focus due to which a high temperature is produced at the focus area.

The box is covered by a thick transparent sheet of glass. When the box is placed in the sunlight, the glass cover allows the infrared rays present in sunlight to pass into the box. Then these rays are absorbed by black surface of the box and the box becomes hot. But, after sometime when the black surface becomes hot it starts radiating out heat in the form of infrared rays. But, the glass sheet cover placed over the box does not allow the heat radiated by the black surface to go out from the box. In this way, the glass cover enables the cooker to entrap the heat inside it.

Usually, a plane mirror reflector is attached on the top of the box. This is because the plane mirror reflector increases the efficiency of solar cooker by reflecting more and more sunlight inside the box.

Advantages of using a solar cooker are:

a) There is no cost of fuel.

b) It is environment friendly and there is no residue like ash etc.

c) Cooking is hygienic and nutritious.

Disadvantages of using a solar cooker are:

a) The cooking is slow.

b) It cannot be used at all times.

c) A solar cooker can perform only limited functions.

d) Solar cookers have limited utility at the places where sunlight is less as in polar regions or where there are too much rains.

A solar cell or photovoltaic cell, is an electrical device that converts the energy of light directly into electricity by the photovoltaic effect, which is a physical and chemical phenomenon.

Silicon is usually used for making solar cells.

Uses of solar cells are:

● Solar cells are very useful in powering space vehicles such as satellites and telescopes (e.g. Hubble).

● solar cells see wide use as an off-grid energy source.

● To provide electricity to remote areas where normal electricity transmission lines do not exist.

● To provide electricity to light houses.

Advantages of using solar cells are:

●Electricity produced by solar cells is clean and silent.

●Photovoltaic systems are quiet and visually unobtrusive.

●Small-scale solar plants can take advantage of unused space on rooftops of existing buildings.

●Solar energy is a locally available renewable resource.

Disadvantage of using solar cells are:

●Some toxic chemicals, like cadmium and arsenic, are used in the PV production process.

●Solar energy is somewhat more expensive to produce.

●Solar power is a variable energy source, with energy production dependent on the sun.

Solar panels are devices that convert light into electricity. They are called "solar" panels because most of the time, the most powerful source of light available is the Sun, called Sol by astronomers. Two main advantages of using solar panels are:

a) It provides much more electric power than a single solar cell.

b) It is used to provide electricity in remote and inaccessible rural areas.

Solar constant is the rate at which energy reaches the earth's surface from the sun, usually taken to be 1,388 watts per square metre.

Its value is 1.4kJ/s/m².

Area, A=5 m²

Time, t=10 min

=600sec

E=4200 kJ

Solar constant =E/(A x t)

=4200/(5x600)

=1.4 kJ/s/m²

Traditionally, waterfalls were used as a source of potential energy in which water is allowed to fall on the blades of the turbine where the rotatory motion of the blades of the turbine is converted into electrical energy. But waterfalls are few in number therefore water dams have been constructed. Nowadays, hydro-electric power stations are used in order to harness potential energy of stored water.

Earlier, the windmills were used to harness wind energy to do mechanical work such as lifting or drawing water from a well. But now a day’s windmills are used to generate electricity. In windmills the rotatory motion of the blades turns the blades of turbine to generate electricity.

As the name indicates hydroelectricity is the electricity that is produced through water. Conservation of energy is the basic principle that is used for the generation of hydroelectricity which is explained in the following diagram:

The two advantages of using hydroelectricity are:

i) Hydropower is fueled by water, so it's a clean fuel source, meaning it won't pollute the air like power plants that burn fossil fuels.

ii) Hydroelectric power is a domestic source of energy, allowing each state to produce their own energy without being reliant on international fuel sources.

Disadvantages:

i) Hydroelectricity plants are very expensive.

ii) The building of dams for hydroelectric power can also cause a lot of water access problems.

Solar cookers vary in design, but many feature a chamber lined with reflective surfaces, such as aluminum foil and a clear, plastic or glass window, through which the sunlight enters. When sunlight passes through plastic or glass, its spectrum shifts, and much of the ultraviolet radiation is filtered out. However, this filtered light transforms into heat, which raises the temperature inside the solar cooker.

As we know that dark colors are a good conductor of heat. Therefore to absorb a large amount of heat solar cookers are painted black.

When sunlight falls over the solar cooker top, the sun rays pass through the glass sheet cover and get absorbed inside the cooker box.

This glass sheet covers does not allow the solar energy to flow out in the form of radiant heat. Thus it traps more and more heat rays of the sun thereby producing greenhouse effect. That is why glass lid is used in the solar cooker.

Wind is moving air and is caused by differences in air pressure within our atmosphere. Wind possesses a form of energy referred to as kinetic energy. Kinetic energy is energy of motion i.e. energy that a body possesses because it is in motion.

Wind turbines convert the kinetic energy in the wind into mechanical power. This mechanical power can be used for specific tasks (such as grinding grain or pumping water) or a generator can convert this mechanical power into electricity.

Advantages of using wind energy for generating electricity are:

(i)Wind energy itself is both renewable and sustainable. The wind will never run out.

(ii)Wind turbines have a relatively small land footprint.

Limitations of wind energy are

(i) Wind energy has a similar drawback to solar energy in that it is not a constant energy source.

(ii) Although costs are reducing over time, the installation of a wind turbine is considered expensive.

At it won't get the sufficient sunlight to create greenhouse effect.

A hydro power plant is a complex of installations and equipment that is used to convert the energy of a stream of water into electrical energy.

As it traps the absorbed radiations inside traping more and more heat.

Because in semiconductors, the energy band gap is quite less. The photons can easily eject the electrons out of it provided the energy of the electrons is more than the threshold energy required.

The solar constant, is the conventional name for the mean solar electromagnetic radiation (the solar irradiance) per unit area that would be incident on a plane perpendicular to the rays, at a distance of one astronomical unit (AU) from the Sun (roughly the mean distance from the Sun to the Earth).

Infrared radiation, or simply infrared or IR, is electromagnetic radiation (EMR) with longer wavelengths than those of visible light, and is therefore invisible.

As it do not allows the absorbed radiations to pass out hence, traping out more and more heat.

A wind turbine is a device that converts the wind's kinetic energy into electrical power.

From the solar constant we deduce that

1.4 kW of power is incident upon every 1m² of area.

i.e. the total energy incident in 1 hr over an area of 1 m² will be

= 1.4 kW x 1 hr

(Since P=E/t or E=P x t)

Hence, energy = 1.4 kWh

Converting into Kj we get 5040 Kj)

Glass sheet covers does not allow the solar energy to flow out in the form of radiant heat. Thus it traps more and more heat rays of the sun thereby producing green house effect. That is why glass lid are closed in the solar cooker in order to trap more and more heat.

(a) Electrical energy produced by coal-fired plant,

= 2000MW

= 2000x106W

Electrical energy produced by wind turbine

= 300kW

= 300x103W

No. of wind turbine required,

= 2000x106/300x103 = 6666.6

Hence, 6667 wind turbines would be needed to replace the power station.

(b) In actual practice, this no. of wind turbines could not replace the coal-fired power plant because the efficiency of wind turbines keeps changing due to changes in wind speed but the efficiency of steam turbines used in coal-fired power stations remains the same.

In a solar water heater, the storage tank placed at a higher level than the solar panel containing coils because hot water, being lighter and less denser, rises to the top.

The electricity that is produced by the solar cells during the day time is stored in the rechargeable batteries so that the produced electricity can be used later on, for instance, at night.

At first, with the help of solar cells, solar energy is converted into electrical energy. Then, while charging the batteries this electrical energy gets converted into chemical energy.

Later, while using the batteries, chemical energy again gets converted into the electrical energy and then the electric motor converts electrical energy into kinetic energy.

(i) Due to the large amount of solar energy, batteries of the car gets charged quickly.

(ii) As on a cloudy day less amount of sunlight is present therefore batteries charge up very slowly.

(iii) Due to the absence of light batteries do not charge up a tall.

Charcoal is obtained as a residue when wood is burned in a limited supply of air.

Geothermal energy is neither derived from the sun directly or indirectly. It is the heat present inside the earth.

Geothermal energy is the heat energy obtained from hot rocks inside the earth. It's clean and sustainable. Resources of geothermal energy range from the shallow ground to hot water and hot rock found a few miles beneath the Earth's surface, and down even deeper to the extremely high temperatures of molten rock called magma.

Anaerobic bacteria decomposes animal dung into biogas. It digests the animal dung into a closed system and produces the biogas.

Biogas contains 54-70% of methane which is used as a fuel.

The constituents of biogas are mentioned below along with their % Constitution:

Methane: 54 – 70%

Carbon dioxide: 27 – 45%

Nitrogen: 0.5 – 3%

Hydrogen: 1 – 10%

Carbon monoxide: 0.1%

Oxygen: 0.1%

Hydrogen sulfide: traces.

Water is required in the formation of biogas from cow-dung. And biogas is produced in the absence of oxygen in a closed system.

Biogas is the cleanest fuel that can be obtained from cow-dung. It typically refers to a mixture of different gases produced by the breakdown of organic matter in the absence of oxygen.

Apart from cattle dung, human excreta, agriculture wastes, vegetable wastes, poultry droppings, paper scrap etc. can also be added to a biogas plant. A biogas plant is an anaerobic digester that produces biogas.

the three forms of energy are:

(i) Tidal energy

It is a form of hydropower that converts the energy obtained from tides into useful forms of power, mainly electricity.

(ii) Wave energy

It describes the process by which wind is used to generate electricity.

(iii) Ocean thermal energy

It is a process that can produce electricity by using the temperature difference between deep cold ocean water and warm tropical surface waters.

Sea-waves energy and Ocean thermal energy manifests itself in sea.

OTE stands for Ocean Thermal Energy. Ocean thermal energy is derived from the solar energy that is absorbed by the oceans.

Anaerobic bacteria help in the degradation of cow-dung in the presence of water but in the absence of oxygen and hence produces biogas. The most of the important bacteria involved in biogas production process are anaerobes.

False- Sea-waves energy and Ocean thermal energy are the forms of energy which solar energy manifests itself in oceans.

(a) solar (b) twice

Biomass is fuel that is developed from organic materials, a renewable and sustainable source of energy used to create electricity or other forms of power. Examples of biomass include landfill gas, wood, crops, garbage and alcohol fuels.

Wood is still widely used as a source of heat energy in many households of country.

Two ways in which cow-dung can be used as a fuel are:

a) In the form of cow-dung cakes, which can be used directly as a fuel.

b) By preparing biogas from cow-dung.

Charcoal is a lightweight, black residue, consisting of carbon and any remaining ash, obtained by removing water and other volatile constituents from animal and vegetation substances. Charcoal is usually produced by slow process-the heating of wood in the absence of oxygen.

Charcoal is better fuel than wood because: When the same amount of charcoal and wood are burnt, charcoal produces almost twice the heat produced by wood. Charcoal produces much less smoke than wood. Charcoal is a compact fuel that is more convenient to handle than wood.

Bio-mass is renewable sources of energy. It mass is derived from dead plants and animal wastes. Therefore it is naturally replenished. Wood, gobar gas etc. are some of the examples of bio-mass.

Hydro-electricity is also renewable sources of energy. But it is obtained from the potential energy stored in water at a height. Energy from it can be produced again and again.

Biogas is considered as an ideal fuel due to the following reasons:

a) It has an appropriate calorific value.

b) It is easy to store, handle and transport.

c) It is easily processed from cow dung and other waste materials.

d) It has also an appropriate ignition temperature.

e) It is also environment friendly and don't cause much harm to the environment.

f) It burns smoothly and does not leave behind much residue. Infact it contains negligible non-volatile material.

During high tide, when the level of water in the sea is high, sea-water flows into the reservoir of the barrage and turns the turbines. The turbines then turn the generator and the electricity is produced. And during the low tide, when the level of sea-water is low, the sea-water stored in the barrage reservoir is allowed to flow out into the sea. This flowing water also turns the turbines and generates electricity.

The tidal energy is not likely to be a potential source of energy because:

(i) The rise and fall of sea-water during high and low tide is not so high to generate electricity on a large-scale.
(ii) There are very few sites in the sea around the world that are suitable to build dams.
(iii) Start up cost to build a tidal energy plant is high.

Sea-waves energy can be harnessed by the following ways:

a) By setting up floating generators in the sea. They would move up and down with the sea-waves and their movement would drive the generators to generate electricity.

b) By letting the sea-waves move up and down inside large tubes so that when the waves move up, the air in the tubes is compressed and this compressed air can then be used to turn a turbine of a generator to produce electricity.

The energy present due to the difference in the temperature of water at the upper surface and the deeper layers of ocean is known as ocean thermal energy.

Ocean thermal energy is used to produce electricity in an Ocean Thermal Energy Conversion power plant. A temperature difference of 20°C or more between the surface water and deeper water is needed for the working of these plants. The warm surface water of ocean is used to boil a liquid like ammonia or chlorofluorocarbon. The high pressure of liquid vapors is used to turn the turbine of a generator and produce electricity.

There are certain limitations to harness energy from the sea. Those limitations are

a) High dams are required to be built to convert tidal energy into electricity which incurs lot of cost.

b) Very strong waves are required, which are not possible all the time.

c) Tidal energy depends on the relative positioning of the Earth, moon, and the Sun.

d) To harness ocean thermal energy the difference in the temperature of surface hot water and the cold water at depth must be 20°C or more.

Biogas is a safe and efficient method for the disposal of bio wastes and sewage materials. In a biogas plant all the organic wastes such as cow dunk, plant wastes or the residue of any crop is used as a fuel for the production of biogas. Other waste products such as kitchen waste is also used. Hence, all waste is being disposed and converted into biogas.

Following sources of energy are not derived from the sun:

● Geothermal energy-The heat present within the Earth.

● Nuclear fuels-The energy related to radioactive material.

● Tidal energy-The energy generated using the potential energy of water.

Biogas typically refers to a mixture of different gases produced by the breakdown of organic matter in the absence of oxygen. Methane is the major component of biogas constituting about 60%.

Biogas is produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste or food waste.

Manure and dung are also fed into the biogas plant. In the fermenter, heated to approx. 38-40 °C, the substrate is decomposed by the micro-organisms under exclusion of light and oxygen. The final product of this fermentation process is biogas with methane as the main ingredient.

Uses of biogas:

• It can be used for any heating purpose, such as cooking.

• It can also be used in a gas engine to convert the energy in the gas into electricity and heat.

Advantages and Benefits of Biogas:

• Provides a non-polluting and renewable source of energy.

• Efficient way of energy conversion (saves fuel wood ).

• Provides a source for decentralized power generation.

Geothermal energy is the heat from the Earth. It's clean and sustainable. Resources of geothermal energy range from the shallow ground to hot water and hot rock found a few miles beneath the Earth's surface, and down even deeper to the extremely high temperatures of molten rock called magma.

Hot rocks present inside the earth are the source of heat contained in geothermal energy.

Extremely hot rocks present below the surface of earth heat the underground water converting it into steam. When more and more steam is formed between the rocks, it gets compressed to high pressures. This high pressure steam is brought up through pipes and is used to run the turbine of a generator to produce electricity.

Advantages of geothermal energy

i. It is a renewable source of energy.

ii. By far, it is non-polluting and environment friendly.

iii. There is no wastage or generation of by-products.

Disadvantage of geothermal energy:

i. Only few sites have the potential of Geothermal Energy.

ii. Most of the sites, where geothermal energy is produced, are far from markets or cities, where it needs to be consumed.

iii. Total generation potential of this source is too small.

It is a energy carried by atoms.

It is the energy present inside the earth.

Biogas constitutes methane gas about 60% within it.

Biogas contains around 60% of the methane.

It is a smokeless fuel with high calorific value.

nuclear powerplants usually use a very rare type of uranium, U-235 as a fuel hence categorizing it as a non-renewable source.

It is caused by the attractive forces of the Moon and Sun’s gravitational fields as well as the centrifugal force due to the Earth’s spin.

As biogas can be prepared only in the absence of oxygen.

Coke is derived from destructive distillation of low-ash, low-sulfur bituminous coal.

Natural gas is a fossil fuel which is a non-renewable source.

Geothermal energy is heat energy generated and stored in the Earth. The geothermal energy of the Earth's crust originates from the original formation of the planet and from radioactive decay of materials.

Construction of dams require a large amount of area.

The cost of hydroelectricity is relatively low, making it a competitive source of renewable electricity. The hydro station consumes no water, unlike coal or gas plants.

(a) Ocean thermal energy is the energy generated due to the difference in the temperature of water at the surface of the ocean and its deeper levels.

(b)No this Energy isn't derived from the sun.

(c) Ocean thermal energy is used to generate electricity in an Ocean Thermal Energy Conversion power plant also called as OTEC power plant. A temperature difference of 20°C or more between the surface water and deeper water is needed for the operation of these plants. The warm surface water of ocean is used to boil a liquid like ammonia or chlorofluorocarbon. The high pressure of the vapors of liquid is used to turn the turbine of a generator and produce electricity.

(d)20°C is the minimum temperature difference in water at the surface of ocean and its deeper level which is required to operate power plants based on this energy.

(a) The condition when the sea water rises is termed as high tide.

(b)When the rised water of the sea resides, the situation is termed as low tide.

(c)Tidal Energy (Tidal energy is a form of hydropower that converts the energy obtained from tides into useful forms of power, mainly electricity)

(d)At high tide, water flows from sea into reservoir and turns the turbine.

At low tide, stored water flows out from reservoir into sea and turns the turbine.

A is coal; It is mainly made up of 65-95% carbon and also contains hydrogen, sulphur, oxygen and nitrogen.

B is coke; Coke is a fuel with few impurities and a high carbon content, usually made from coal.

C is wood;

D is charcoal; Charcoal is a lightweight, black residue, consisting of carbon and any remaining ash, obtained by removing water and other volatile constituents from animal and vegetation substances.

Geothermal Energy is the form of energy which is not sourced directly or indirectly from the sun.

a) Nuclear fission-Nuclear fission is a process where the nucleus of an atom is split into two or more smaller nuclei, known as fission products.

b) Nuclear fusion-nuclear fusion is a reaction in which two or more atomic nuclei come close enough to form one or more different atomic nuclei and subatomic particles.

neutrons of uranium-235 are utilized to cause further fission of its nuclei. A uranium-235 atom absorbs a neutron and fissions into two new atoms (fission fragments), releasing three new neutrons and some binding energy.

Neutrons bring about the fission of uranium-235.

The fission of uranium-235 is caused by low energy neutrons because a fast neutron will not be captured, so neutrons must be slowed down by moderation to increase their capture probability in fission reactors.

a) Nuclear fusion-It's a mixture of deuterium and tritium (both of them rare forms of hydrogen) for nuclear fusion.

b) Nuclear fission-It's either uranium or plutonium for fission bombs.

Commonly used moderators include regular (light) water (roughly 75% of the world's reactors), solid graphite (20% of reactors) and heavy water (5% of reactors).

Control rods of a nuclear reactor are made of boron. Control rods are used in nuclear reactors to control the fission rate of uranium and plutonium.

Nuclear reaction produces heavy hazardous radiations in the nuclear power plants. Hence, thick concrete chamber is required to prevent the radioactive rays to travel outside.

Uranium is used up in the reactors in a nuclear power station.

Nuclear fission is used to generate electricity, for the destructive component of nuclear weapons and to break down radioactive elements into other elements.

Million electron volt (MeV) is used for expressing the energy released in nuclear reactions.

1 atomic mass unit=931 MeV, where MeV stands for Million electron Volt.

(a) Nuclear fission

(b) Neutrons; nuclear fission

(c) Fission

(d) Reactor

Nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts (lighter nuclei).The fission process often produces free neutrons and photons (in the form of gamma rays), and releases a large amount of energy.

E.g., When uranium-235 atoms are bombarded with slow moving neutrons, the heavy uranium nucleus breaks up to produce two medium-weighted atoms and 3 neutrons, with the emission of tremendous amount of energy.

The process that fuels our sun and allows it to give off that much energy is called nuclear fusion. Nuclear fusion is a reaction where two atomic nuclei fuse together to create a larger nucleus and in the process release energy.

When deuterium atoms are heated to an extremely high temperature under extremely high pressure, then two deuterium nuclei combine together to form a heavy nucleus of helium, and a neutron is emitted. A tremendous amount of energy is liberated in the process.

For a nuclear fusion reaction to occur, it is necessary to bring two nuclei so close that nuclear forces become active and glue the nuclei together. This is the reason why nuclear fusion reactions occur mostly in high density, high temperature environment.

Hydrogen gas is the nuclear fuel in the sun. The sun can be assumed as a huge thermonuclear furnace where hydrogen atoms continuously get fused into helium atoms. Hence, the mass during these fusion reactions gets lost and as a product energy is being produced.

Nuclear reaction:

4¹₁H ⁴₂He + 2₊₁⁰e + tremendous amount of energy

Einstein's mass-energy equation is, E=mc²,

The equation is derived directly from Einstein’s Special Theory of Relativity

Each of the letters of E = mc² stands for a particular physical quantity. Writing them out in full we get:

E = energy (measured in joules, J)

m = mass (measured in kilograms, kg)

c = the speed of light (measured in meter per second, ms^-1)

As,

1 atomic mass unit = 931 MeV

25 atomic mass unit

= 931 x 25 MeV

= 23275 MeV

Hence, 23275 MeV of energy is released.

The source of energy of this sun and other stars is nuclear fusion reactions of hydrogen. The net process is the fusion of four Hydrogen nuclei to make one helium nucleus plus some energy. The balance between gravity compression and outward thermal pressure controls the rate of the nuclear fusion reactions.

The hydrogen bomb consists of heavy isotopes of hydrogen called deuterium and tritium along with lithium-6. Atom bomb is used for the explosion of hydrogen bomb. While the atom bomb is exploded, since its fission reaction a lot of heat is produced which raises the temperature of deuterium and tritium to 107°C in a few microseconds. Then fusion reactions of deuterium and tritium take place which produces a tremendous amount of energy. This explodes the hydrogen bomb. Lithium-6 is used to produce more tritium needed for fusion.

The source of energy is same for both the sun and the hydrogen atom, that is nuclear fusion.

When slow moving neutrons are made to strike the atoms of a heavy element uranium-235, the heavy uranium nucleus breaks up to produce two medium-weighted atoms and 3 neutrons, with the emission of tremendous amount of energy. This process is called nuclear fission..

At nuclear power station such process are utilized.

advantages of nuclear energy are as follows:

1. Expense

Less uranium is needed to produce the same amount of energy as coal or oil, which lowers the cost of producing the same amount of energy.

2. Reliability

When a nuclear power plant is functioning properly, it can run uninterrupted for up to 540 days.

3. No Greenhouse Gases

While nuclear energy does have some emissions, the plant itself does not give off greenhouse gasses.

Disadvantages of nuclear energy are as follows:

1.Raw Material

Since, uranium is naturally unstable therefore special precautions must be taken during the mining, transporting and storing of the uranium.

2.Water Pollutant

The water that is pumped outside into nearby wetlands contains immense heat that can be damaging to eco systems located nearby the reactor.

3. If it has structural flaws or are improperly installed, a nuclear reactor could release harmful amounts of radiation into the environment during the process of regular use.

a) Uranium-235 produces the energy in the fuel rods

b) No they won't last forever.

c) Energy is produced by nuclear fission.

d) In a nuclear reactor, a moderator is mixed with the uranium fuel to slow down the fast neutrons to the speed of thermal neutrons, which enables fission to occur in a controlled nuclear chain reaction.

e) Boron rods are used in nuclear reactors to control the fission rate of uranium and plutonium.

f) Liquid sodium or carbon dioxide gas is used as a 'coolant' to transfer the heat produced to heat exchanger for converting water into steam.

(a) Graphite is used as a moderator.

(b) Concrete are used to absorb the radiations

(c) U-235 is used in control rods

(d) Boron can be used as control rods

(e) Liquid sodium is used to carry away heat.

a) In Nuclear reactors control rods are stick down into the fuel to absorb neutrons, to slow the reaction down, or withdraw to speed the reaction up.

b) Heat is removed from the nuclear reactor core with the help of liquid sodium. It absorbs the heat and transfers it to the heat exchanger. Then, this heat is used for converting water into steam in the heat exchanger, which is later used to produce electricity by rotating a turbine and its shaft which is connected to a generator.

On inserting the control rods in the graphite core, the rods begin absorbing the excess neutrons and maintain the rate of reaction as it is required . We can raise or lower the rods in the reactor from outside as per our requirement. The part which is present inside the reactor absorbs neutrons.

Advantages of nuclear energy:

i) It produces a large amount of useful energy from a very small amount of a nuclear fuel.

ii) Once the nuclear fuel is loaded into the reactor, the nuclear power plant can go on producing electricity for two to three years at a stretch. There is no need of feeding the fuel again and again.

iii) It does not produce gases like CO₂ or SO₂.

Disadvantages of nuclear energy:

i) The waste products of nuclear fission reactions are radioactive which keep on emitting harmful radiations for thousands of years and are difficult to store or dispose safely.

ii) Very high cost of installation is required.

iii) There is a limited availability of uranium fuel.

A nuclear reactor, formerly known as an atomic pile, is a device used to initiate and control a sustained nuclear chain reaction. Nuclear reactors are used at nuclear power plants for electricity generation and in propulsion of ships. U-235 is the fuel used in a nuclear reactor.

In a nuclear power plant, the fission of uranium-235 is carried out in a reactor R. Uranium-235 rods are inserted in a graphite core which acts as a moderator to slow down the neutrons. Boron rods B absorb excess neutrons and controls the rate of reaction. Liquid sodium or carbon dioxide gas, which is pumped continuously through pipes embedded in reactor by using a pump P, is used as a 'coolant' to transfer the heat produced to heat exchanger for converting water into steam. The hot steam at high pressure goes into a turbine chamber and makes the turbine rotate. The shaft of the generator also rotates and drives a generator connected to it.

The working nuclear reactor of a power plant can be shut down in an emergency by inserting the control rods of Boron completely. They absorb all the neutrons, shutting down the reactor.

Five places in India where nuclear powerplants are located are:

(i) Tarapur

(ii) Kalpakkam

(iii) Narora

(iv) Kaprapur

(vi) kaiga

Both fission and fusion are nuclear reactions that produce energy, but the applications are not the same. Fissions the splitting of a heavy, unstable nucleus into two lighter nuclei, and fusion is the process where two light nuclei combine together releasing vast amounts of energy.

(i) nuclear fission

(ii) nuclear fusion

Among both the process nuclear fusion produces more energy

Mass of material,

m = 5g = 0.005kg,

Speed of light, c = 3 x 10⁸m/s

We know that, E = mc²

E = 0.005 x (3 x 10⁸)²

E = 4.5 x 10¹⁴J

Hence, energy released= 4.5 × 10¹⁴J

The energy in MeV is given by:

(Since 1 MeV = 1.6 × 10^–13 J)

= 2.8 × 10²⁷ MeV

Graphite is a crystalline form of carbon, a semimetal, a native element mineral, and one of the allotropes of carbon. Graphite is the most stable form of carbon under standard conditions.

Because boron is capable of absorbing many neutrons without itself fissioning.

A nuclear reactor, formerly known as an atomic pile, is a device used to initiate and control a sustained nuclear chain reaction.

A nuclear reactor coolant is a coolant in a nuclear reactor used to remove heat from the nuclear reactor core and transfer it to electrical generators and the environment.

Nuclear power is the use of nuclear reactions that release nuclear energy to generate heat, which most frequently is then used in steam turbines to produce electricity in a nuclear power plant

1 a.m.u is defined as 1/12th of the mass of an atom of 6C¹² isotope. Hence a change in mass of 1a.m.u (called mass defect) releases an energy equal to 931 MeV.1 amu = 931 MeV is used as a standard conversion.

In nuclear physics and nuclear chemistry, nuclear fission is either a nuclear reaction or a radioactive decay process in which the nucleus of an atom splits into smaller parts (lighter nuclei).

(W = qV )

= (1.6 x 10-19 C) x (1 J/C)

= 1.6 x 10-19 J)

Nuclear Fusion and nuclear fission are similar in that they both release large amounts of energy.

Nuclear fusion is sun's source of energy.

Nuclear fuel is a substance that is used in nuclear power stations to produce heat to power turbines. Heat is created when nuclear fuel undergoes nuclear fission.

Nuclear fusion converts Hydrogen gas into helium producing tremendous amount of energy.

An atom bomb, known as the A-bomb for short, is a bomb that creates its devastating explosive force by the splitting of atoms' nuclei through a process known as nuclear fission.s

Nuclear energy is the energy obtained by manipulating the internal structure of atoms.

nuclear fusion is a reaction in which two or more atomic nuclei come close enough to form one or more different atomic nuclei and subatomic particles.

Nuclear Waste is radioactive and that is the primary cause of the negative effects on human health and bodies.

Energy is released from fission and fusion because breaking and formation of bond takes place.

Deuterium (symbol D or 2H, also known as heavy hydrogen) is one of two stable isotopes of hydrogen.

(a) Nuclear fission in which large nucleus splits into two smaller nuclei with the release of energy, brought about by the absorption of a neutron.

(b) Particle c is neutron; x = 3

(c) E represents the Energy liberated

(d) The reaction is utilized in Nuclear Power Station

(e) Atom bomb is based on similar type of reaction called nuclear fusion.

(a) Nuclear fusion in which two smaller nuclei combine in order to form a bigger nucleus with the release of energy, brought about under the conditions of high temperature and pressure.

(b) Particle c is neutron; x = 1

(c) E is the Energy liberated

(d) Such reactions takes place user the two following conditions:

• Millions of degrees of temperature and

• Millions of pascals of pressure

(e) Hydrogen bomb is based on similar reaction.

(i)D with a Mass number of 235

(ii) A with a Mass number of 2

If the reactor core all of a sudden gets too hot then it indicates that the rate of nuclear fission is intensified excessively so in order to reduce the rate of nuclear fission process insert the control rods of boron a little more into the reactor and hence the reactor would start working normally.

If such circumstances happens then we would withdraw the control rods a little more from inside the reactor. Doing this will increase the rate of nuclear fission process and hence would produce more heat .

In a nuclear reactor, the chain reaction stops if the control rods are fully inserted into the graphite because the control rods absorb all the neutrons, and hence stopping the nuclear chain reaction.

Hydrogen fuel is cleaner than CNG. CNG contains hydrocarbons. Therefore, it has carbon contents. Carbon is a form of pollutant present in CNG. On the other hand, hydrogen is waste-free. The fusion of hydrogen does not produce any waste. Hence, hydrogen is cleaner than CNG.

CFLs are more energy efficient as they last from 8-10 times longer, use about 75% less energy, and produce 90% less heat while delivering more light per Watt.

Coal is expected to last for about 200 years,

Petroleum is expected to last for 40 years and

Natural Gas may last for 60 years

Solar cooker and pressure cooker can be utilized for the cooking of food so as to save fuel as they use less energy to cook food in comparison of others.

Factors which we should keep in mind while choosing a source of energy are:

It should do a large amount of work per unit mass or volume - it means that the output energy must be more than the input energy. It should have high calorific value.

It should be easily accessible - the energy source should be able to provide energy over a long period of time. Example: coal and petroleum.

Should be easy to store and transport - most common sources of energy such as coal, petrol and LPG need to be transported to users from their points of production. They also need proper storage. Thus it is important to store and transport these sources safely and economically.

Safe and convenient to use - energy sources should be safe as it is used by a large number of people and should be convenient.

No source of energy can be pollution-free. It is considered that solar cells are pollution-free. However, even their making causes environmental damage indirectly.

Also, in the case of nuclear energy, there is no waste produced after the fusion reactions. However, it is not totally pollution-free. To start the fusion reactions, approximately 107 K temperature is required, which is provided by fission reactions. The wastes released from fission reactions are very hazardous. Hence, no source of energy is pollution-free.

The increasing demand for energy is largely being met by the use of fossil fuel - coal and petroleum. But these fuels are exhaustible and non-renewable sources of energy. Moreover, burning of fossil fuels causes air pollution. Release of acidic oxides leading to acid rain affects our water and soil resources. These gases also produce greenhouse effect leading to rise in temperature. Then, there is a problem of disposal of ash produced due to burning of coal. Thus, our environment is being degraded.

To reduce energy consumption:

● we should lead a simple and a natural life. As an example, instead of using an air conditioner in a closed room we should live in an airy room having appropriate number of windows.

● Turn your monitor off at night and ditch the screensaver.

● Use LED bulbs as LED bulbs use 75% less electricity than incandescent bulbs.

Gases released by the burning and combustion of fossil fuels include carbon monoxide, nitrogen oxides, sulfur oxides and hydrocarbons. In the air, these gases become a carcinogen, which can be inhaled and can also mix with falling rain to form acid rain.

Ultimate reserves designates all the coal that can eventually be mined in a given zone (that can be the whole planet).

Petroleum is a naturally occurring, yellow-to-black liquid found in geological formations beneath the Earth's surface, which is commonly refined into various types of fuels.

CFLs use much less energy than incandescent lamps