Chapter I New and Renewable Energy Sources

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Chapter INew and Renewable Energy Sources

Learning ObjectivesReading this chapter would enable you to understand:

Mankind and need of energy.Various types of energy.Law of conservation of energy.Conventional and non-conventional sources of energy.Renewable sources of energy.Energy and environment.Pollution and climate change.

Contents1.1 Mankind and Need of Energy1.2 Types of Energy

1.2.1 Potential Energy1.2.2 Kinetic Energy1.2.3 Electrical Energy1.2.4 Magnetic Energy1.2.5 Radiative Energy1.2.6 Nuclear Energy1.2.7 Heat Energy1.2.8 Sound Energy1.2.9 Mass Energy1.2.10 Chemical Energy

1.3 Law of Conservation of Energy1.4 Conventional and Non-conventional Energy Sources

1.4.1 Conventional Energy Sources1.4.2 Non-conventional Energy Sources

1.5 Renewable energy Sources1.5.1 Advantages of Renewable Energy1.5.2 Obstacles to the Implementation of Renewable Energy Systems

1.6 Energy and Environment1.7 Pollution and Climate Change

1.7.1 The Greenhouse Effect1.7.2 Most Rapid Change in Last 10,000 Years1.7.3 The Impacts of Global Warming1.7.4 Action to Mitigate Climate Change1.7.5 A Challenge for Everybody1.7.6 What the Individual Can Do?

Summing UpSelf-assessmentReferences

1.1 Mankind and Need of Energy

Man has needed and used energy at an increasing rate for his sustenance.Man required energy primarily in the form of food. He derived this by eatingplants or animals, which he hunted. Subsequently he discovered fire and his

New and Renewable Energy Sources

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Renewable Sources of Energy

energy need increased as he started to make use of wood and other biomassto supply the energy need for cooking as well as keeping himself warm. Withfurther demand for energy, man began to use the wind for sailing the shipsand for driving the windmills, and force of falling water to turn water wheels.Till this time, it would not be wrong to say that the sun was supplying all theenergy needs of the man either directly or indirectly and that man was usingonly renewable sources of energy.

The Industrial Revolution that began with the discovery of the steam enginebrought about a great many changes. For the first time, man began to use anew source of energy, viz. coal. A little later, the internal combustion enginewas invented and the other fossil fuels, oil and natural gas began to be usedextensively. The fossil fuel era of using non-renewable sources had begun andenergy was now available in a concentrated form. The invention of heat enginesand the use of fossil fuels made energy portable and introduced the much-needed flexibility in man’s movement.

A new source of energy, nuclear energy, came on the scene after the, SecondWorld War. The first large nuclear power station was commissioned about 40years ago, and already, nuclear energy is providing a small but significantamount of the energy requirements of many countries.

Thus today, every country draws its energy needs, from a variety of sources.Broadly these sources can be categorised as commercial and non-commercialsources. The commercial sources include the fossil fuels (coal, oil and naturalgas), hydroelectric power and nuclear power, while the non-commercialsources include wood, animal wastes and agricultural wastes. In anindustrialised country like USA, most of the energy requirements are metfrom commercial sources, while in an industrially less developed country likeIndia, the use of commercial and non-commercial sources is about equal.

In last few years, it has become obvious that fossil fuel resources are fastdepleting and that the fossil fuel era is gradually coming to an end. This isparticularly true for oil and natural gas. It will be useful therefore to examinethe rates of consumption of the different sources of energy and to give someindications of the reserves available.

1.2 Types of Energy

Energy can be defined as anything, which makes it possible to do work. Whenone does the work there is change in energy of the system. If E1 is the energybefore doing the work and E2 is the energy after doing the work, then thework done by the system is,W = E1-E2 = ∆E (1.1)

Thus the change in energy ∆E is equal to the work done by the system. Systemwill do variety of work and so will have the variety of forms of energy. Thereare different forms of energy given as1. Potential Energy2. Kinetic Energy3. Electrical Energy4. Magnetic Energy5. Radiative Energy

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6. Nuclear Energy7. Heat Energy8. Sound Energy9. Mass Energy10. Chemical Energy

1.2.1 Potential Energy

The potential energy of the system is associated with the position of the systemrelative to earth’s surface. The gravitational force due to earth is m g. wherem is the mass of the object and g is acceleration due to gravity. Force is theentity which sets the body at rest into motion or which brings body frommotion to rest.Force = Mass x Acceleration (1.2)

Unit of force is Newton.Work is performed when a body moves in the direction of the force, which isgiven as,Work = Force x displacement (1.3)

Thus, if a mass m is lifted through height h against the gravity, then thework done (W) is stored as potential energy. HencePotential Energy (P. E.) = m g h (1.4)

Where g is acceleration due to gravity = 9.8 m s-2 or 980 cm s-2

S. I. Unit of energy is Joule (J) and in C.G.S. unit it is ergs.1 Joule = 107 ergs.

1.2.2 Kinetic energy

The kinetic energy is associated with the motion of the body. If a body of massm is moving along straight line with velocity v, then kinetic energy E is,

2

21 mvE = (1.5)

The rotational kinetic energy of body moving with angular velocity, ωωωωω alongthe arc is

2

21 ωIErot = (1.6)

Where, I is the moment of inertia of the body.

1.2.3 Electrical Energy

The most versatile form of energy is the electric energy. It is associated withthe flow of electrons due to potential difference between two electrodes. Ifelectron of charge e is accelerated through a potential difference of V voltsthen electrical energy is eV.e = 1.6 x 10-19 Coulomb.

The electrical energy can be transported very easily from one place to anotherand also converted into different forms of energy. The units of electrical energyare:Watt. second = Joule. (1 Watt .1second = 1 Joule)In practice we use unit as 1 kWh = 1000 Watt hour.


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Electrical generators produce electrical energy from mechanical energy.Magneto hydrodynamic generators produce electrical energy from thermalenergy. Fuel cells produce electrical energy from chemical energy. The mainadvantages of electrical energy are,

Easily obtained from various primary energy sourcesEasily and quickly transmittedEasily distributedEasily measured, controlled, monitored, and accounted.Easily converted to other forms for final energy consumption.Safe, pollution free, reliable source of energy.

1.2.4 Magnetic Energy

The magnetic field of magnet can be used as a source of energy. When weapply magnetic field B to the electron moving with velocity v then there occursthe deviation in the path of electron due to magnetic energy.

If i is the current flowing through the coil, then magnetic flux f linked withthe coil is directly proportional to current flowing through it.φ α i (1.7)φ = Li (1.8)Where, L is constant of proportionality, called as self-inductance of coil.

If there is change in flux linked with coil, then according to Faraday’s law ofelectromagnetic induction, e.m.f. e is induced in the coil which is,

dtde φ

−= (1.9)

dtdiLe −= (1.10)

The energy E stored in coil (inductor) of self inductance L, and carrying currenti is

2

21 LiE = (1.11)

1.2.5 Radiative Energy

The beam of light i.e. radiation has also energy. The light rays areelectromagnetic waves and the energy E associated with radiation ofwavelength λ and frequency ν is

eVm

hchE)(

24.1µλλ

ν === (1.12)

Where h is Planck’s constant = 6.63 x 10-34 JS and c is velocity of light= 3 x 108 m / se.g. The radiative energy associated with radiation of wavelength 4000 Å is

10

834

1040001031063.6

−

−

××××

=E Joule

E = 4.9725 x 10 - 19 Joule

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1.2.6 Nuclear Energy

This form of energy is associated with the fusion and fission reactions. Incase of fission reaction, heavy element when bombarded with a neutrino itbreaks into two small elements. In such cases the mass of basic ingredient isdifferent than that of the total mass of the final products. Hence here is lossof mass ∆m. This loss of mass in nuclear reaction is converted into thetremendous amount of energy.

2 cmE ∆= (1.13)

For example, when uranium 235 (U235) is bombarded by neutrino gives rise tofission reaction producing tremendous amount of nuclear energy.

Nuclear fusion is combining of two nuclei accompanied by release of heat.Nuclear fusion is likely to solve energy problem of the world during the 21st

century.

1.2.7 Heat Energy

It is another form of energy depending upon the temperature of the substance.That isHeat energy α Temperature TH = k T (1.14)

Where k = 0.8626 x 10-4 eV / K, is Boltzman constant.

1.2.8 Sound Energy

Sound is a mechanical wave and hence it has energy. Sound waves arelongitudinal waves. The waves that produce a sense of sound on a human earare called sound waves. Only waves with frequencies lying in the range of 20Hz to 20 KHz are audible.

The intensity of sound ‘I’ is the energy transported by sound waves in unittime across a unit area of cross section normal to the direction of propagationof wave. It is proportional to the square of the wave amplitude P. Thus,

I ∝ P2 (1.15)

BPIρ2

2

= (1.16)

Where B is bulk modulus and ρ is the density of medium. The unit of intensityof sound is W / m2

1.2.9 Mass Energy

It is known that anything that having mass is a source of energy, i.e. thematter having a mass is source of energy. The energy associated with themass m is given by well-known Einstein’s mass-energy relationE = m c2 (1.17)Where, c is velocity of light.


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1.2.10 Chemical Energy

There are two types of chemical reactions called a) Exothermic reaction andb)Endothermic reaction. Exothermic reactions release heat. Endothermicreactions absorb heat. Heat evolved in the chemical reaction is in the form ofenergy.

Chemical energy is converted into thermal energy by chemical reactions andby combustion. Chemical energy is converted into electrical energy in fuelcells, storage batteries etc. Chemical energy is an intermediate energy betweenprimary energy source and final usable energy. Petroleum resources and naturalgases are extracted from the natural reserves by means of production wells.Petrochemical sector deals with refining crude petroleum, natural gas andproducing several petroleum products used as fuels and industrial rawmaterials.

1.3 Law of Conservation of Energy

The conservation of energy can be explained on the basis of thermodynamics.Thermodynamics is the branch of science, which deals with the transfer, andtransport of heat energy. The transfer of heat from one form to other or viceversa can be explained with first law of thermodynamics and the transport ofenergy can be explained by second law of thermodynamics. Thus the law ofconservation of energy is nothing but first law of thermodynamics.

It states that, “energy can neither be created nor destroyed, the total energyof the universe is constant quantity, and only one form of energy can beconverted into other forms of energy.”

The possible ways of conversion of different forms of energy is given in figure1.1. As shown in the figure there is possible way that, electric, magnetic andelectromagnetic (Radiative) energies can be converted into heat, chemical ornuclear energy.

Figure 1.1 Energy conversion chart

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The internal energy is associated with the internal changes within the solid.e.g. the vibrations of lattice called phonons. Like that mass energy can beconverted into nuclear energy and vice versa. The mass energy can be convertedinto kinetic energy, E = m c2 or

2

21 mvE = . The law of conservation of energy can be explained by considering

the mechanical energy, which involves potential energy (P. E.) and kineticenergy (K. E.). Consider a closed space with the boundary such that energyis not allowed to come in or go out from the closed space. Let us consider ata moment t = t1 a small stone of mass m is held at height h within the closedspace. At t = t1, Ein = 0 and Eout = 0, the energy of the system is Potential energyV = m g h and total energy of the system is potential energy.

Figure 1.2 Law of conservation of energy

At the next moment t = t2, the stone is allowed to fall down and it is just aboutto touch the border of the wall, at this moment also, Ein = 0 and Eout = 0.However it has kinetic energy and total energy of the system is kinetic energy.Thus from figure 1.2, since energy is not allowed to enter or to go out, thetotal energy of the system is conserved.

The law of conservation of energy can also be explained by considering theelectromagnetic source. For example, the generation of radio waves orgeneration of microwave signals of mobile. The pointing vector S gives theamount of energy flowing out due to electromagnetic waves,

)(4

HEcS ×=π (1.18)

Where, E and H are electric and magnetic field components. The physicalsignificance of the Pointing vector S is the total normal outward electric fieldflux flowing through unit area in unit time.

1.4 Conventional and Non-conventional Energy Sources

The variety of energy sources can be broadly categorised as conventional andnon-conventional energy sources. The conventional energy sources includethe fossil fuels (coal, oil and natural gas), hydroelectric power and nuclearpower, while non-conventional energy sources include wood, animal wasteand agricultural wastes.


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1.4.1 Conventional energy sources

Major conventional sources of energy include:

1. Fossil fuels i.e. solid fuels like coal, liquid and gaseous fuels includingpetroleum and its derivatives and natural gas.

2. Water power or energy stored in water.3. Energy of nuclear fusion.

The percentage use of various energy sources for the total energy consumptionin the world is given in the table 1.1 below.

Coal 32.5%Oil 38.3%Gas 19.0%Uranium 0.13%Hydro 2.0%Wood 6.6%Dung 1.2%Waste 1.3%

Table 1.1. The percentage use of various energy sources forthe total energy consumption in the world

Fossil fuels: Looking at the percentage distribution one finds that world’senergy supply comes mainly from fossil fuels.

Coal: Since the advent of industrialisation, coal has been the most commonsource of energy. In last few decades, the world switched over from coal to oilas a major source of energy because it is simpler and cleaner to obtain usefulenergy from oil.

According to estimates, coal is abundant. It is enough for last 200 years.However, it is low in calorific value and its shipping is expensive. Coal ispollutant and when burnt it produces CO2 and CO. Extensive use of coal as asource of energy is likely to disturb the ecological balance of CO2 sincevegetation in the world would not be capable of absorbing such largeproportions of carbon dioxide produced by burning large quantities of coal.

Oil: Almost 40% of the energy needs of the world are fed by oil. The risingprices of oil have brought a considerable strain on the economy of the world.With today’s rate of consumption and a resource amount of 250,000 milliontones of oil, it would suffice for about 100 years unless more oil is discovered.The question is whether an alternative to oil would then be available; theworld must start thinking of a change from a world economy dominated byoil.

Gas: Gas is incompletely utilised at present and huge quantities are burnt offin the oil production process because of the non-availability of ready market.The reason may be high transportation cost of the gas. To transport gas iscostlier than transporting oil. Large reserves are estimated to be located ininaccessible areas.

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Gaseous fuels can be classified as:1. Gases of fixed composition such as acetylene, ethylene, methane etc.2. Composite industrial gases such as producer gas, coke oven gas, water

gas, blast furnace gas etc.

Water Power: Water power is developed by allowing water to fall under theforce of gravity. It is used most exclusively for electric power generation. Infact, the generation of water power on a large scale became possible aroundthe beginning of the twentieth century only with development of the electricalpower transmission. Prior to that, water power plants (hydroelectric plants)were usually of small capacities, less than 100 kW.

Potential energy of water is converted into mechanical energy by using primemoves known as hydraulic turbines. Water power is quite cheap where wateris available in abundance. Hydroelectric power is one of the indirect ways inwhich solar energy is being used. Thus, the main factor in its favour is that itis the only renewable non-depleting source of the present commercial sourcesof energy. In addition it does not create any pollution problem. The developmentrate of hydropower is still low, due the following problems.1. In a developing project, it will take about 6-10 years time for planning,

investing and construction.2. High capital investment is needed, and some parts of the investment

have to derive from foreign sources.3. The growing problems on relocation of villages involved, compensation

of damage, selecting suitable resettlement area and environmentalimpact.

Nuclear Power: According to modern theories of atomic structure, matterconsists of minute particles known as atoms. These atoms represent enormousconcentration of binding energy. Controlled fission of heavier unstable atomssuch as U235, Th232 liberate large amount of heat energy. This enormous releaseof energy from a relatively small mass of nuclear fuels makes this source ofenergy of great importance. The energy released by the complete fission ofone kg of U235, is equal to the heat energy obtained by burning 4500 tons ofhigh-grade coal or 2200 tons of oil. The heat produced by nuclear fission ofthe atoms of fissionable material is utilised in special heat exchangers for theproduction of the steam which is then used to drive turbo generators as inthe conventional power plants.

However, there are some limitations in the use of nuclear energy namely highcapital cost of nuclear power plants, limited availability of raw materials,difficulties associated with disposal of radioactive waste and shortage of well-trained personnel to handle the nuclear power plants.

1.4.2 Non-conventional Energy Sources

While fossil fuels will be the main fuels for thermal power, there is fear thatthey will get exhausted eventually in coming years. Therefore other systemsbased on non-conventional and renewable sources are being tried by manycountries. These are solar, wind, sea, geothermal and biomass.

Solar Energy: Solar energy can be a major source for power. Its potential is178 billion MW which is about 20,000 times the world’s demand. Bur so far it


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could not be developed on a large scale. Sun’s energy can be utilised as thermaland photovoltaics. The former is currently being used for steam and hot waterproduction.

Energy comes to the earth from the sun. This energy keeps the temperatureof the earth, above that in colder space, causes current in the atmosphereand in the ocean, causes the water cycle and generates photosynthesis inplants.

The solar power where sun hits atmosphere is 107 watts, whereas the solarpower on earth’s surface is 106 watts. The total worldwide power demand ofall need of civilisation is 1013 watts. Therefore, the sun gives us 1000 timesmore power than we need. If we can use 5% of this energy, it will be 50 timeswhat the world would require. The energy radiated by the sun on a brightsunny day is approximately 1 kW/m2. Attempts have been made to make useof this energy in raising steam, which may be used to generate electricity.

The applications of solar energy which are enjoying most success today are:

1. Heating and cooling of residential building.2. Solar water heating.3. Solar drying of agricultural and animal products.4. Solar distillation on a small community scale.5. Salt production by evaporation of seawater or inland brines.6. Solar cookers.7. Solar engines for water pumping.8. Food refrigeration.9. Bioconversion and wind energy, which are indirect sources of solar

energy.10. Solar furnaces.11. Solar electric power generation by-

i) Solar pondsii) Steam generators heated by rotating reflectors (heliostat mirrors).iii) Cylindrical parabolic reflectors.

12. Solar photovoltaic cells, which can be used for conversion of solar energydirectly into electricity or for water pumping in rural agriculturalpurposes.

Wind energy: Wind energy uses high wind velocity available in certain parts.Wind energy is used for pumping the water or power generation. About 1million wind pumps are in operation in different countries. A minimum windspeed of 3 m/s is needed. Coastal, hilly and valley areas are suitable for thisprocess. Potential in India is estimated between 20,000 and 25,000 MW. Coastalareas of Gujarat, Maharashtra and Tamil Nadu are considered as favourable.

Energy of wind can be economically used for the generation of electrical energy.Winds are caused from two main factors:

1. Heating and cooling of the atmosphere, which generates convectioncurrents. Heating is caused by the absorption of solar energy on theearth’s surface and in the atmosphere.

2. The rotation of the earth with respect to the atmosphere, and its motionaround the sun.

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Many types of windmills have been designed and developed. However, only afew have been found to be practically suitable and useful. Some of these are:1. Multiblade type windmill.2. Sail type windmill.3. Propeller type windmill.4. Savonius type windmill.5. Darrieus type windmill.

The first three are the examples of horizontal axis windmills, while last twohave a vertical axis.

Some characteristics of wind energy are stated below:i. It is a renewable source of energy.ii. Like all forms of solar energy, wind power systems are non-polluting,

so it has no adverse influence on the environment.iii. Wind energy systems avoid fuel provision and transport.iv. On a small scale, upto a few kilowatt system, is less costly. On a large

scale, costs be competitive with conventional electricity and lower costscould be achieved by mass production.

But with wind energy following problems are associated.

1. Wind energy available is dilute and fluctuating in nature. Because ofdilute form, conversion machines have to be necessarily large.

2. Unlike water energy, wind energy need storage means because of itsirregularity.

3. Wind energy systems are noisy in operation; a large unit can be heardmany kilometers away.

4. Large areas are needed to install wind farms for electrical powergeneration.

Energy from Biomass and Bio-gas:

Biomass is another renewable source of energy in the form of wood,agricultural residues, etc. the potential for application of bio-mass as analternate source of energy in India is very great. We have plenty of agriculturaland forest resources for production of bio-mass. Bio-mass is produced in naturethrough photosynthesis achieved by solar energy conversion. As the wordclearly signifies, Bio-mass means organic matter. In the simplest form thereaction is the process of photosynthesis in the presence of solar radiation,can be represented as follows

H2O + CO2 CH2O + O2 (1.19)

In the reaction, water and carbon dioxide are converted into organic materiali.e. CH2O, which is the basic molecule of forming carbohydrates stable at lowtemperature, it breaks at high temperature, releasing an amount of heat equalto 112,000 cal/mol (469 kJ/mole).

CH2O + O2 CO2 + H2O + 112 kcal/mol. (1.20)

The bio-mass is used directly by burning or is further processed to producemore convenient liquid and gaseous fuel.

solar energy


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Bio-mass resources fall into three categories:1. Bio-mass in its traditional solid mass (wood and agricultural residue).2. Bio-mass in non-traditional form (converted into liquid fuels).

The first category is to burn the bio-mass directly and get the energy.In the second category, the bio-mass is converted into ethanol andmethanol to be used as liquid fuels in engines.

3. The third category is to ferment the bio-mass anaerobically to obtaingaseous fuel called bio-gas (bio-gas- 55 to 65% methane, 30 to 40% CO2

and rest impurities i.e. H2, H2S and some N2.).

Bio-mass resources include the following:1. Concentrated waste-municipal solids, sewage wood products, industrial

waste.2. Dispersed waste residue-crop residue, legging residue, disposed manure.3. Harvested bio-mass, standby bio-mass, bio-mass energy plantation.

Bio-gas: The main source for production of bio-gas is wet cow dung or wetlivestock (and even human) waste, to produce bio-gas. The bio-gas productionis of particular significance for India because of its large cattle population.The total cattle population in country is about 250 million. Some of the othersources of bio-gas are:(i) Sewage, (ii) crop residue, (iii) vegetable wastes, (iv) water hyacinth, (v)poultry droppings, (vi) pig-manures, (vii) Algae, (viii) Ocean-kelp.

In the rural sector, bio-gas finds great applications in cooking, lighting,mechanical power and generation of small electricity. The gas can also beused with advantage to improve sanitary conditions and also to checkenvironmental pollution. Bio-gas can be used solely or with diesel in I.C.engines, for production of power.

Ocean thermal energy conversion: This is also an indirect method ofutilising solar energy. A large amount of solar energy is collected and storedin tropical oceans. The surface of water acts as the collector for solar heat,while the upper layer of the sea constitutes infinite heat storage reservoir.Thus the heat contained in the oceans, could be converted into electricity byutilising fact that the temperature difference between warm surface waters ofthe tropical oceans and the colder water in the depths about 20-25 o K.Utilisation of this energy, with its associated temperature difference and itsconversion into work, forms the basis of ocean thermal energy conversion(OTEC) systems. The surface water, which is at higher temperature could beused to heat some low boiling organic fluid, the vapours of which would runa heat engine. The exit vapour would be condensed by pumping cold waterfrom the deeper regions. The amount of energy available for ocean thermalpower generation is enormous, and is replenished continuously.

All the systems for OTEC method work on a closed Rankine cycle and uselow boiling organic fluids like ammonia, propane, R-12, R-22 etc.

Tidal energy: The tides in the sea are the result of the universal gravitationaleffect of heavenly bodies like sun and moon on the earth. Due to fluidity ofwater mass, the effect of this force becomes apparent in the motion of water,which shows periodic rise and fall in level which is in rhythms with dailycycle of rising and setting of sun and moon. This periodic rise and fall of the

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water level of sea is called tide. These tides can be used to produce electricalpower, which is known as tidal power. When water is above the mean sealevel, it is called flood tide and when the level is below the mean sea level, it iscalled ebb tide.

Geothermal energy: This is the energy, which lies embedded within theearth. According to various theories the earth has a molten core. The factthat volcanic action takes place in many places on the surface of the earth,supports these theories. The steam and hot water comes naturally to thesurface of the earth in some locations of the earth. For large-scale use boreholes are normally sunk with depth up to 1000 m, releasing steam and waterat temperatures upto 200 or 300oC and pressures upto 3000 kgN/m2. Twoways of electric power production from geothermal energy has been suggested.In one of this heat energy is transferred to a working fluid, which operatesthe power cycle. This may be particularly useful at places of fresh volcanicactivity. Where the molten interior mass of earth vents to the surface throughfissures and substantially high temperatures, such as between 450 to 550oCcan be found. By embedding coil of pipes and sending water through themcan be raised. In the other, the hot geothermal water and/or steam is used tooperate the turbines directly. From the wellhead the steam is transmitted bypipelines up to 1 m in diameter over distances upto about 3 km to the powerstation. Water separators are usually required to separate moisture and solidparticles from steam.

At present only steam coming out of the ground is used to generate electricity,the hot water is discarded because it contains as much as 30% dissolved saltsand minerals, and these cause serious rust damage to the turbine. The waterhowever contains more than 1/3 of the available thermal energy.

Hydrogen energy: Hydrogen as an energy can play an important role as analternative to conventional fuels. For that technical problem of production,storage and transportation can be resolved satisfactorily and the cost couldbe brought down to acceptable limits. One of he most attractive features ofhydrogen as an energy carrier is that it can be produced from water which isabundantly available in nature. Hydrogen has the highest energy content perunit of mass than any chemical fuel and can be substituted for hydrocarbonsin a broad range of applications. Its burning process is non-polluting and itcan be used in fuel cells to produce both electricity and useful heat.

Fuel cells: It may be defined as an electrochemical device for the continuousconversion of the free energy change in a chemical reaction to electrical energy.It is distinguished from a batter y in that it operates with continuousreplenishment of the fuel and the oxidant at active electrode area and doesnot require recharging.Main components of fuel cell are (i) a fuel electrode, (ii) an oxidant or electrodeand (iii) an electrolyte.

Some of the advantages of fuel cells are:1. It is a direct conversion process and does not involve a thermal process,

so it has high operating efficiency.2. The unit is lighter, smaller and needs less maintenance.3. Fuel power plants may further cut generation costs by reducing

transmission losses.


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4. Little pollution, little noise, so that it can be readily acceptable inresidential areas.

The primary drawbacks of fuel cells are, their low voltage, high initial costsand low service life.

Magneto hydro-dynamics generator: The principle of MagnetoHydrodynamics (MHD) power generation enables direct conversion of thermalenergy to electrical energy. MHD power generation works on the principlethat described by Faraday: When an electric conductor moves across amagnetic field, a voltage is induced in it, which produces an electric current.In MHD generators, the solid conductors are replaced by a fluid, which iselectrically conducting. The working fluid may be either ionised gas or liquidmetal. The hot, partially ionised and compressed gas is expanded in a duct,and forced through a strong magnetic field; electrical potential is generatedin the gas. Electrodes placed on the side of the duct pick up potential generatedin the gas. In this manner, direct current is obtained which can be convertedinto AC with the aid of an inverter.

1.5 Renewable Energy Sources

Renewable energy sources include both ‘direct’ solar radiation intercepted bycollectors and indirect solar energy such as wind, hydropower, ocean energyand bio-mass resources that can be managed in sustainable manner.Geothermal fields tapped with present drilling technologies have a finite lifebut are sometimes considered renewable for planning purposes. Traditionalmethods of using biomass and derivatives such as wood and charcoal arehighly inefficient.

If broadly interpreted, the definition of renewable resources also includes thechemical energy stored in food and non-fuel plant products and even the energyin the air used to dry material or to cool and heat the interiors of the buildings.From a operative view point, the correct way to treat renewable energy is asa means to reduce the demand for conventional energy forms. Thus, inperforming economic and financial analysis, there is no real distinction betweenrenewable energy technologies and those designed to improve the efficiencyof conventional energy use.

A further point is that cost-effective approaches to energy efficiency rangingfrom no or low cost measures. (e.g. reducing excess air in the boilers, shuttingdown equipments when not needed) to systems requiring moderate capitalinvestment. Improvements in the efficiency of the energy use can be teamedwith a variety of energy supply technologies, and this fact must be recognisedwhen assessing the relative economics of renewable and conventional energysystems.

Three independent primary sources provide energy to the earth: the sun,geothermal forces and planetary motion in the solar system. In particular,direct solar radiation represents an enormous resource for a moderntechnological civilisation. However, human capacity to harness these giganticnatural flows of energy to perform useful work depends largely on the economicfeasibility of the required conversion in comparison with fossil fuel optionsand the extent to which large scale applications affect food production, climateand ecology.

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1.5.1 Advantages of Renewable Energy

Even though renewable options are not likely to supply a substantial amountof energy to developing countries over the short term, they do have followingadvantages.1. Renewable energy is indigenous resource available in considerable

quantities to all developing nations. It has significant local, regional ornational economic impact. The use of renewable energy could help toconserve foreign exchange and generate local employment if conservationtechnologies are designed, manufactured, assembled and installed locally.

2. Several renewable options are financially and economically competitivefor certain applications, such as in remote locations, where the costs oftransmitting electrical power or transporting conventional fuels are high,or in those well endowed with bio-mass, hydro or geothermal resources.

3. Because conversion technology tends to be flexible and modular, it canusually be rapidly deployed. Other advantages of modular over very largeindividual units include easy in adding new capacity, less risk incomparison with ‘lumpy’ investments, lower interest on borrowed capitalbecause of shorter lead times and reduced transmission and distributioncosts for dispersed rural locations.

4. Rapid scientific and technological advantages are expected to expandthe economic range of renewable energy applications over the next 8-10years, making it imperative for international decision makers andplanners to keep abreast of these developments.

1.5.2 Obstacles to the Implementation of Renewable Energy Systems

Experience with renewable energy projects in the developing countriesindicates that there are a number of barriers to the effective development andwidespread diffusion of the systems. Among these are:1. Inadequate documentation and evaluation of past experience, a paucity

of validated field performance data and a lack of clear priorities for futurework.

2. Weak or non-existent institutions and policies to finance andcommercialise renewable energy systems. With regard to energyplanting, separate and completely uncoordinated organisations are oftenresponsible for petroleum, electricity, coal, forestry, fuel wood, renewableresources and conservation.

3. Technical and economic uncertainties in many renewable energy systems,high economic and financial costs for some systems in comparison withconventional supply options and energy efficiency measures.

4. Skeptical attitudes towards renewable energy systems on the part ofthe energy planners and a lack of qualified personnel to design,manufacture, market, operate and maintain such systems.

5. Inadequate donor coordination in renewable assistance activities, withlittle or no information exchange on successful and unsuccessful projects.

1.6 Energy and Environment

Energy and environment are two sides of a coin. One thing to be noted is that,while man’s large-scale use of commercial energy has lead to a better qualityof life, it has also created many problems. The most serious of these is theharmful effect on the environment. The combustion of fossil fuels has caused


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serious air pollution problems. It has also resulted in the phenomenon of theglobal warming which now a matter of great concern. Similarly, the release oflarge amount of heat from power plants has caused thermal pollution in lakesand rivers leading to the destruction of many forms of plants and animal life.In the case of nuclear power plants, there is also concern over the possibilityof radioactivity being released into the atmospheres. The gravity of most ofthese environmental problems had not really been foreseen. Now, however,as a man embarks on the search for alternative sources of energy, it is clearthat he would do well to keep the environment clean.

1.7 Pollution and Climate Change

Man extracts energy from the nature in the form of raw energy (primaryenergy sources). The primary energy sources are processed and transformedto intermediate and finally useable energy forms. The energy conversionprocesses are accompanied with pollution problems.

A major portion of energy is transformed to electrical form by power plants.Coal fired power plants emit solid particles, SOx, NOx, CO, CO2 and wasteheat and chemicals, etc. into the environment. Pollution of the environmentdisturbs the ecological balance, which leads to global warming and climatechange. The world’s annual energy consumption rate is increasing at a rate oftwo to four percent. Nuclear power plants, thermal power plants, chemicalconversion plants etc. are emitting solid, liquid and gaseous pollutants in theenvironment. Gaseous pollution is causing green house effect and globalwarming.

1.7.1 The Greenhouse Effect

The Earth absorbs the heat energy of sunshine mainly at the surface. Tomaintain a steady temperature, a balancing amount of energy is then radiatedupwards from the surface at longer, infrared, wavelengths. Some of the gasesin the atmosphere, which are present naturally, particularly water vapour,carbon dioxide and methane, absorb some of this infrared radiations so actingas ‘blankets’ over the surface. Close control is thereby kept on globaltemperature; with the earth’s surface nearly 300C warmer providing an averageclimate for the earth, which is suitable for human life.

Increases in the amount of gases such as carbon dioxide in the atmosphereare occurring because of emissions from human activities such as the burningof fossil fuels (coal, oil and gas) or through deforestation. These increasesare sufficient to lead on average to substantially increased warming. It is calledthe ‘greenhouse effect’ because the glass in a greenhouse possesses similarproperties to the atmosphere.

1.7.2 Most Rapid Change in Last 10,000 Years

The climate record over many thousands of years can be built up by analysingthe composition of the ice, and the air trapped in the ice, obtained from differentdepths from cores drilled from the Antarctic or Greenland ice caps.

The earth’s climate is in a long-term warm phase that began when the last iceage ended about 20,000 years ago; the last warm period was about 120,000

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years ago. The main triggers for ice ages have been the small regular variationsin the geometry of the Earth’s orbit about the sun, which affect the distributionof solar radiation at the earth’s surface. The next ice age is expected to beginin about 50,000 years time.

Figure 1.3 is a record of the change in temperature at which ice was laid down(the change in global average temperature is about half the change at thepoles) and of the atmospheric carbon dioxide content over the last 160,000years.

A strong correlation exists between atmospheric temperature and carbondioxide content. This is partly because the amount of carbon dioxide in theatmosphere is dependent on factors strongly connected to the averagetemperature. Also, the carbon dioxide content in its turn influences thetemperature through the greenhouse effect

Over the past 200 years human activities have increased the amount of carbondioxide in the atmosphere by over 30% - well beyond the range of its naturalvariation during the last million years or more. If the increase continues andif adequate action is not taken to stem it, the atmospheric carbon dioxidecontent will reach double its pre-industrial value during the 21st century.

Figure 1.3 Record from an antarctic ice core of temperature andcarbon dioxide concentration

As a result the average rate of warming of the climate is expected to be greaterthan at any time during the last 10,000 years. This is not necessarily bad;some communities may experience a net benefit. But many ecosystems andhumans will find it difficult to adjust to this rapid rate of change.


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1.7.3 The Impacts of Global Warming

In some locations, the impacts of global warming may be positive. For somecrops, increased carbon dioxide aids growth and at high northern latitudeswinters will be less cold and the growing season longer. However, becausehumans and ecosystems have adapted closely to the current climate, mostclimate change, especially if the change is fast, is likely to have negativeimpacts. The main impacts are likely to be changes in sea level, rainfall, andtemperature extremes.

First, largely because of thermal expansion of ocean water and acceleratedmelting of glaciers, sea level is likely to rise by about half a meter by 2100. Seadefenses in many coastal regions will need to be improved, albeit atconsiderable cost. However, such adaptation is not possible for countries withlarge river deltas such as Bangladesh, Southern China and Egypt and formany islands in the Pacific and Indian Oceans.

A second major impact of global warming is likely to be on water supplies.Warming of the earth’s surface means greater evaporation and, on average, ahigher water vapour content in the atmosphere. Because the latent heat ofcondensation is the main energy source for the atmosphere’s circulation thisleads to a more vigorous hydrological cycle. In many areas, heavy rainfallmay become heavier while semi-arid areas may receive less rainfall. Therewill be more frequent and more intense floods or droughts, especially in sub-tropical areas, which are vulnerable to such events. In many places, water israpidly becoming a critical resource; a former Secretary General of the UnitedNations said that he expected the next war to be about water not oil!Floods and droughts already cause more deaths, misery and economic damagethan any other type of disasters. Any increase in their frequency or intensitycould be the most damaging impacts of global climate change.

Studies of food supplies in a globally warmed world suggest that the worldwidequantity of available food supply might not be greatly affected. Some regionsmight be able to grow more while others grow less. However, the distributionof food production will change, not least because of changed water availability.The regions likely to be adversely affected are those in developing countriesin the sub-tropics. Here there are rapidly increasing populations andagricultural production will become inadequate to meet local needs.Considering food supplies, sea level rise and the incidence of floods anddroughts, a recent carefully researched study has estimated that there maybe 150 million environmental refugees by 2050.

Figure 1.4 Global carbon emissions from fossil fuel use(from 1850-1990 and as projected to 2100 - in billions of tones of carbon (GtC)

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Region A shows the range of likely emissions under ‘business as usual’ andcur ve B an emission scenario that would lead to stabilisation of theatmospheric carbon dioxide concentration. Other likely impacts are on humanhealth (increased heat stress and more widespread vector borne diseasessuch as malaria) and on the health of some ecosystems (e.g. forests), whichwill not be able to adapt rapidly enough to match the rate of climate change.

Studies show that the necessary action to achieve a scenario of carbon dioxideemissions such as B in figure 1.4, if carefully planned and phased, is likely tocost less than 1% of the Global World Product, much less than the likely costof damage and adaptation would be if there were no action at all.

The achievement of scenario B in figure 1.4 will require rapid developmentand deployment of appropriate technology and a great deal of determinationon the part of the world community.

1.7.4 Action to Mitigate Climate Change

To mitigate the effects of global climate change, action is required to reducethe human-induced emissions of carbon dioxide. This has large implications,for the energy sector in particular. Technology is already available for muchof what is required, for instance to generate and use energy much moreefficiently and to develop renewable energy sources such as solar, wind, water,biomass and others, which are not dependent on fossil fuels.

Action can also be taken to increase the sinks, which remove carbon dioxidefrom the atmosphere (e. g. by reducing deforestation and increasing forestationor by direct sequestration of carbon dioxide) and to reduce methane emissionsfrom, for example, leakage from mines and landfill sites. The main role ofgovernments and world agencies will be to stimulate markets, to encouragethe development and use of the most appropriate clean technologies.

1.7.5 A Challenge for Everybody

For scientists, to provide better information about likely climate changeand its various local impactsFor governments, to set the necessary frameworkFor business and industry, to seize the opportunities for innovation anduse of ‘clean’ technologiesFor all communities and individuals in the world, to support the actionbeing taken and contribute to it

1.7.6 What the Individual Can Do?

Ensure maximum energy ef ficiency in the home (over 25% of CO2emissions are from domestic energy use) through good heat insulationand through the use of high efficiency appliances (e.g. low energy lightbulbs, Grade A or B appliances).Ensure maximum energy saving - do not overheat rooms and turn offlights when not required.Support, where possible, the provision of energy from renewable sources;e.g. purchase ‘green’ electricity now that this option is available.


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Use public transport, and walk and cycle where possible, and use a fuel-efficient car (over 25% of CO2 emissions come from transport).Consider the environment when shopping; e.g. buy goods producedwith low energy use and products that originate from renewable sources.Through the democratic process, encourage local and nationalgovernment to deliver policies that properly take the environment intoaccount.

Summing Up

The chapter is of general introductory nature concerned with the variousforms of energy. It gives basic and fundamental information about conventionaland non-conventional energy sources. The effect on environment due to releaseof waste heat from power plants, leading to global warming and climate changeis also described.

Self-assessment

a) Select correct alternative

1. S. I. Unit of energy is ———————a) Wattb) Joulec) Newton

2. First law of thermodynamics is nothing but law of conservation of ————a) Energyb) Massc) Momentum

3. Which of the following is the conventional source of energy?a) Solarb) Windc) Oil

4. Which of the following is non-conventional source of energy?a) Oilb) Natural gasc) Wind

5. In solar cell ———— energy is converted into electrical energy.a) Heatb) Solarc) mechanical

6. Tides in the sea are the result of the ———— effect of the sun or moonon the earth.a) Magneticb) Nuclearc) Gravitational

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7. An electrochemical device in which chemical energy of fuel is convertedinto electrical energy, is called as———————————a) Fuel cellb) Battery cellc) Solar cell

8. Force x Displacement = ——————————a) Workb) Energyc) Power

9. 1 Joule = —————— ergs.a) 105

b) 106

c) 107

10. Heavy element when bombarded with a neutrino breaks into two lightelements, releasing large amount of energy. This process is called as————a) Fusionb) Fissionc) Radioactivity

11. The chemical reaction in which heat is released is called as—————a) Endothermicb) Exothermicc) Electrochemical

12. The potential energy of mass lifted to height h, is equal to—————a) m g hb) m g / hc) m /g h

13. An electron of charge e, accelerated through potential difference of Vvolts has energy equal to ————a) 2 e Vb) e Vc) e V2

14. Einstein’s mass energy relation is———--a) E = m g hb) E = m c2

c) E = 21

m v2

15. Potential energy of a substance of 1 kg mass lifted at a height of 1 meteris————a) 98 Jb) 980 Jc) 9.8 J


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References

1. Solar Energy, Principles of Thermal Collection and Storage,S.P.Sukhatme. second editin.2000, Tata Mc Graw Hil Publishing CompanyLimited, New Delhi.

2. Energy technology, Non-conventional renewable and conventional,S. Rao, B. B. Parulekar, Khanna Publishers, Delhi.

3. Non-conventional Energy Sources, G. D. Rai, fourth edition, KhannaPublishers, Delhi.4. 4. Energy, Science and Environment, David Elliot,1997, Routledge, London and New York.

5. Solid State Energy Conversion, Edited by S. H. Pawar, C. H. Bhosale,R. N. Patil, 1985, Shivaji University, Kolhapur.

Documents

Chapter I New and Renewable Energy Sources