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All Renewable Energy Systems

1. NONRENEWABLE
AND
RENEWABLE
RESOURCES

2. HMMMM....
What do you think
nonrenewable
resources are?
Break it down...
Nonrenewable?
Resource?

3. NONRENEWABLE RESOURCES
A nonrenewable resource is a natural
resource that cannot be re-made or
re-grown at a scale comparable to its
consumption.

4. NUCLEAR ENERGY
Nuclear fission uses
uranium to create
energy.
Nuclear energy is a
nonrenewable
resource because once
the uranium is used, it
is gone!

5. COAL, PETROLEUM, AND GAS
Coal, petroleum, and
natural gasare
considered
nonrenewable because
they can not be
replenished in a short
period of time. These
are called fossil fuels.

6. HOW IS COAL MADE ???

7. HOW ARE OIL AND GAS MADE ???

8. WHAT WAS THE DIFFERENCE
BETWEEN COAL AND OIL/GAS?

9. HMMMM....
If nonrenewable
resources are resources
that cannot be re-made
at a scale comparable
to its consumption,
what are renewable
resources?

10. RENEWABLE RESOURCES
Renewable resources are
natural resources that can be
replenished in a short period
of time.
●Solar ●Geothermal
●Wind ●Biomass
●Water

11. SOLAR
Energy from the
sun.
Why is energy
from the sun
renewable?

12. GEOTHERMAL
Energy from
Earth’s heat.
Why is energy
from the heat of
the Earth
renewable?

13. WIND
Energy from
the wind.
Why is energy
from the wind
renewable?

14. BIOMASS
Energy from
burning organic
or living matter.
Why is energy
from biomass
renewable?

15. WATER or HYDROELECTRIC
Energy from the
flow of water.
Why is energy of
flowing water
renewable?

16. SUMMARY
What are the
differences
between
nonrenewable and
renewable
resources?

17. Renewable energy resources -RES
1.Factors affecting Energy Resource
Development
Energy or Fuel Substitution
Energy Density
Power Density
Intermittency
Geographical Energy Distribution

18. 2. Energy Resources and Classifications
•PrimaryEnergyresources:arederived
directlyfromnaturalreserve.Exam-Solar,
wind,geothermal,nuclear.
•SecondaryEnergyResources:areusable
formsofenergygeneratedbysuitable
plantstoconverttheprimaryenergy.
Exam:-Electricalenergy,steampower,
hotwaterpower,hydrogenenergy.

19. Primary Energy resources Sub classified:
1.Conventionalandnonconventionalenergy
resources:
i)Conventionalenergyresources:aretheenergy
storedwithintheearthandthesea.-fossilefuels&
nuclearenergy.Alsocalledasfiniteenergy
resources.
ii)Non-conventionalenergyresources:knownas
infiniteenergyresources.Theirtechnical
knowledgeislittleknownandtheyneedfull
exploitation and improved technical
understanding.Theyareobtainedfromtheenergy
flowingthroughthenaturalenvironment.

20. 2.Renewableandnon-renewableenergy
resources.
i.Renewableenergyresources:are
continuouslyrestoredbynature.-
Exm:solar,water,wind..
ii.Nonrenewableenergyresources:arethe
reservethatisonceaccumulatedinnature
haspracticallyceasedtoformundernew
geologicalconditions.Theyarealso
knownasexpendableenergy.Exm:-coal,
oil,gas,nuclear...

21. Classification of energy Resources

23. Renewable Energy Scenario in India and around the World
–Indiaisworld's3rdlargestconsumerofelectricity
andworld's3rdlargestrenewableenergyproducer
with40%ofenergycapacityinstalledintheyear
2022(160GWof400GW)comingfromrenewable
sources.
–Ernst&Young'sGlobalLimited(EY)2021
RenewableEnergyCountryAttractivenessIndex
(RECAI)rankedIndia3rdbehindUSAandChina.
–InNovember2021,Indiahadarenewableenergy
capacityof150GWconsistingof
–Solar(48.55GW)
–Wind(40.03GW)
–Smallhydropower(4.83GW)
–Bio-mass(10.62GW)
–Largehydro(46.51GW)
–Nuclear(6.78GW)
–Indiahascommittedforagoalof500GW
renewableenergycapacityby2030.

24. Renewable Energy Scenario in India and around the World
–In2016,ParisAgreement'sIntendedNationallyDeterminedContributionstargets,India
madecommitmentofproducing50%ofitstotalelectricityfromnon-fossilfuelsources
by2030.
–In2018,India'sCentralElectricityAuthoritysetatargetofproducing50%ofthetotal
electricityfromnon-fossilfuelssourcesby2030.
–Indiahasalsosetatargetofproducing175GWby2022and500GWby2030from
renewableenergy.
–AsofSeptember2020,89.22GWsolarenergyisalreadyoperational,projectsof48.21
GWareatvariousstagesofimplementationandprojectsof25.64GWcapacityare
undervariousstagesofbidding.
–In2020,3rdoftheworld'stopand5largestsolarparkswereinIndiaincludingworld's.
–Largest2255MWBhadlaSolarParkinRajasthan
–Andworld'ssecond-largestsolarparkof2000MWPavgadaSolarParkTumkurin
Karnataka.
–And1000MWKurnoolinAndhraPradesh.
–WindpowerinIndiahasastrongmanufacturingbasewith20manufacturesof53
differentwindturbinemodelsofinternationalqualityupto3MWinsizewithexportsto
Europe,UnitedStatesandothercountries.

25. Renewable Energy Scenario in India and around the World
Largest2255MWBhadlaSolarParkinRajasthan

26. Renewable Energy Scenario in India and around the World
•Solar,windandrun-of-the-riverhydroelectricityareenvironment-friendlycheaperpower
sourcestheyareusedas"must-run"sourcesinIndiatocaterforthebaseload,andthe
pollutingandforeign-importdependentcoal-firedpowerisincreasinglybeingmovedfromthe
"must-runbaseload"powergenerationtotheloadfollowingpowergeneration(mid-priced
andmid-meriton-demandneed-basedintermittently-producedelectricity)tomeetthepeaking
demandonly.
•SomeofthedailypeakdemandinIndiaisalreadymetwiththerenewablepeakinghydro
powercapacity.
•Solarandwindpowerwith4-hourbatterystoragesystems,asasourceofdispatchable
generationcomparedwithnewcoalandnewgasplants,isalreadycost-competitiveinIndia
withoutsubsidy.
•IndiainitiatedtheInternationalSolarAlliance(ISA),anallianceof121countries.Indiawas
world'sfirstcountrytosetupaministryofnon-conventionalenergyresources(Ministryof
NewandRenewableEnergy(MNRE)inearly1980s).
•SolarEnergyCorporationofIndia(SECI),apublicsectorundertaking,isresponsibleforthe
developmentofsolarenergyindustryinIndia.
•HydroelectricityisadministeredseparatelybytheMinistryofPowerandnotincludedin
MNREtargets.

27. Renewable Energy Scenario in India and around the World
•Globalrank:
•Indiarankssecondintermsofpopulationandaccountsfor17%oftheworld’spopulation.
•Indiaisgloballyranked3rdinconsumptionofenergy.
•Intermsofinstalledcapacityandinvestmentinrenewableenergy,theEY'sRenewableEnergy
CountryAttractivenessIndex(RECAI)rankinginJuly2021isasfollows:
Global rank: Attractiveness score

28. Renewable Energy Scenario in India and around the World
•Futuretargets
Target year
Renewable energy
capacity target (GW)
Comments
2022
175
Excludes nuclear and large hydro
power.
Includes100GWsolar,60GWwind,5
smallhydro,10GWBiomasspower,
and0.168GWWaste-to-Power.
2030
500
Includesnuclearandlargehydro
power.
Setin2019atUnitedNationsClimate
Changeconferencewith15times
solarand2timeswindpowercapacity
increasecomparedtoApril2016
installedcapacity.

29. Renewable Energy Scenario in India and around the World
•Year-wiserenewableenergygenerationtrend
•YearwiserenewableenergygenerationinTWh.

30. Renewable Energy Scenario in India and around the World
•Grid-connected total
includingnon-renewable
andrenewable:
•Thefollowingtableshowsthe
breakdownofexistinginstalled
capacityinMarch2020fromall
sources,andincludes141.6GW
fromrenewablesources.
•Since2019,thehydropower
generatedbytheunderMinistry
ofPowerisalsocounted
towardsMinistryofNewand
RenewableEnergy'sRenewable
EnergyPurchaseObligation
(REPO)targets,underwhichthe
DISCOMs (Distribution
Companies)ofvariousstates
havetosourceacertain
percentageoftheirpowerfrom
Renewable EnergySources
undertwocategories,Solarand
Non-Solar.

31. Renewable Energy Scenario in India and around the World
•Off-gridrenewableenergy
installedcapacity:
•Off-gridpowerasof31July2019
(MNRE)capacity:

32. Renewable Energy Scenario in India and around the World
•ThedevelopmentofwindpowerinIndiabeganinthe1990s,andhas
significantlyincreasedinthelastfewyears.
•AlthougharelativenewcomertothewindindustrycomparedwithDenmarkor
US,domesticpolicysupportforwindpowerhasledIndiatobecomethe
countrywiththefourthlargestinstalledwindpowercapacityintheworld.
•Asof30June2018theinstalledcapacityofwindpowerinIndiawas34,293
MW,mainlyspreadacrossTamilNadu(7,269.50MW),Maharashtra(4,100.40
MW),Gujarat(3,454.30MW),Rajasthan(2,784.90MW),Karnataka(2,318.20
MW),AndhraPradesh(746.20MW)andMadhyaPradesh(423.40MW)Wind
poweraccountsfor10%ofIndia'stotalinstalledpowercapacity.
•Indiahassetanambitioustargettogenerate60,000MWofelectricityfrom
windpowerby2022.
•TheIndianGovernment'sMinistryofNewandRenewableEnergyannounceda
newwind-solarhybridpolicyinMay2018.Thismeansthatthesamepieceof
landwillbeusedtohousebothwindfarmsandsolarpanels.

33. Renewable Energy-Potentials
•Anewstudyofrenewableenergy'stechnicalpotentialfindsthateverystatein
thenationhasthespaceandresourcestogeneratecleanenergy.
•TheDepartmentofEnergy'sNationalRenewableEnergyLaboratory(NREL)
producedthestudy,U.S.RenewableEnergyTechnicalPotentials,whichlooks
ateachstate'savailablerenewableresourcesfor
•solar,
•wind,
•biopower,
•geothermal,
•andhydropowerenergy.
•Thestudyestablishesanupper-boundaryestimateofdevelopmentpotential.
•Economicormarketrestraintswouldfactorintowhatprojectsmightactually
bedeployed.

34. Renewable Energy-Potentials
•Thereportisvaluablefordecisionmakersandutilityexecutivesbecauseit
comparesestimatesacrossrenewableenergytechnologiesandunifies
assumptionsandmethods.
•Itshowstheachievableenergygenerationofaparticulartechnologygiven
resourceavailability,systemperformance,topographiclimitations,and
environmentalandland-useconstraints.
•Thestudyincludesstate-levelmapsandtablescontainingavailablelandarea
(squarekilometers),installedcapacity(gigawatts),andelectricgeneration
(gigawatt-hours)foreachtechnology.

35. Renewable Energy-Potentials

36. Renewable Energy-Potentials

37. Renewable energy In India
Sources TotalInstalled Capacity in
MW-June-2019
2022-Target in MW
Wasteto power 138 10000
Small hydropower 4604 5000
(Biomass & Gasification
and Bagasse
Cogeneration)
9806 10000
Solar power 29549 1,00,000
Wind power 36368 60000
Total 80467 175000

38. Grid connected installed capacity from all
sources as of 30 June 2019
Source Installed Capacity (MW) Share
Coal 194489.50 54.17%
Large hydro 45,399.22 12.64%
Other renewables 80467.22 22.41%
Gas 24937.22 6.9%
Diesel 637.63 0.24%
Nuclear 6,780.00 1.97%
Total 358970.78 100.00%

39. Largest wind farms in India
NO WIND FORM PRODUCER STATE CURRENT
CAPACITY
(MW)
1 Muppandal wind farm
Muppandal
Wind
Tamil Nadu 1,500
2 Jaisalmer Wind Park
Suzlon
Energy
Rajasthan 1,275
3
Brahmanvel
windfarm
ParakhAgro
Industries
Maharashtra 528
4 Dhalgaon windfarm
Gadre
Marine
Exports
Maharashtra 278
5 Chakala windfarm
Suzlon
Energy
Maharashtra 217
6
VankusawadeWind
Park
Suzlon
Energy
Maharashtra 189
7 VaspetWindfarm
ReNew
Power
Maharashtra 144

40. annual power consumption world wide

41. Annual power consumption in India

59. Solar Thermal Energy Collectors
Module2.2

60. Types of Solar collectors

62. Flat Plate Collector
•Itcaneasilyachieveatemperature60-80
o
Cabove
ambienttemperature.
•Itusesbothbeamanddiffuseradiation.0
•Doesnotrequiretracking.
•Requireslittlemaintenance.
•Efficiency:~45%at80
o
C
•Applications:airheating,waterheating,industrial
processheating,passiveairconditioning.

65. Evacuated Tubular Collector
•Itcaneasilyachieveatemperature80-120
o
Cabove
ambienttemperature.
•Itusesbothbeamanddiffuseradiation.
•Doesnotrequiretracking.
•Requireslittlemaintenance.
•Mode:Heatpipe;Utubewater;Integrated
Collector/storage
•Efficiency:~55%at80
o
C(forwaterheating)
•Applications:airheating,waterheating,industrial
processheating, passiveairconditioning.

68. Types of Concentrating Solar Collectors
Varioustypes of concentrating solar collectorsare as under:
•Parabolic trough collector.
•Power tower receiver.
•Parabolic dish collector.
•Fresnel lens collector.

70. Parabolic Trough Collector

72. Solar Tower

73. Parabolic Dish Collector

74. LinearFresnelReflector(LFR)
LinearFresnelReflector(LFR)
technologyreliesonanarrayof
linearmirrorstripswhich
concentratelightontoafixed
receivermountedonalinear
tower.
TheLFRfieldcanbeimaginedasa
brokenupparabolictrough
reflector.Butunlikeparabolic
troughs,itdoesn'thavetobeof
parabolicshape,largeabsorbers
canbeconstructedandthe
absorberdoesnothavetomove.
Linear Fresnel Reflector

75. 1. Types of Solar collectors
1.1 Flat Plate collectors:
Flat Plate Air Collectors
Flat Plate Liquid Collectors
1.2 Concentrating Collectors
Stationary Concentrating Collectors
Tracking Concentrating collectors
Comparison of collectors (Temperature Range & Concentration Ratio)

76. Flat Plate collectors
Flat plate collectors are the most common type.They are also
referred to as non-concentrating collectors and have the same
area for intercepting and absorbing solar radiation.

77. AFlatPlatecollector(Fig3.1)usuallyconsistsofthe
followingcomponents:
(i)Glazing,whichmaybeoneormoresheetsofglassorother
diathermanous(radiationtransmitting)material.
(ii)Tubes,finsorpassagesforconductingordirectingthe
heattransferfluidfromtheinlettotheoutlet.
(iii)Absorberplatewhichmaybeflat,corrugatedorgrooved
withtubes,finsorpassagesattachedtoit.
(iv)Insulationwhichminimizesheatlossfromthebackand
sidesofthecollector.
(v)Containerorcasingwhichsurroundsthevarious
componentsandprotectsthemfromdust,moistureetc.

78. Concentrating Collectors
Byusingreflectorstoconcentratesunlightontheabsorber
ofasolarcollector,thesizeoftheabsorbercanbe
dramaticallyreduced,whichreducesheatlossesand
increasesefficiencyathightemperatures.
Anotheradvantageisthatreflectorscancostsubstantially
lessperunitareathancollectors.Thisclassofcollectoris
usedforhigh-temperatureapplicationssuchassteam
productionforthegenerationofelectricityandthermal
detoxification.
Thesecollectorsarebestsuitedtoclimatesthathavean
abundanceofclearskydays,andtherefore,theyarenot
socommoninmanyregions.Stationaryconcentrating
collectorsmaybeliquid-based,air-based,orevenan
ovensuchasasolarcooker.

80. 2. Configurations of Certain Practical Solar
Thermal Collectors
2.1 Flat Plate collectors
Liquid Flat Plate Collectors
Air Flat Plate Collectors
2.2 Glazed Flat Plate Collectors
2.3 Unglazed Flat Plate Collectors
2.4 Unglazed Perforated Plate Collectors
2.5 Back pass solar collectors
2.6 Batch Flat Plate Solar Thermal Collectors
2.7 Flat Plate Collectors with Flat Reflectors
2.8Evacuted Tube Collectors

81. 3. Concentrating Collectors
3.1 Compound parabolic solar collectors
3.2 Fresnel Solar Thermal Collectors
3.3 Parabolic Trough Solar Thermal Collectors
3.4 Cylindrical Trough Solar Collectors
3.5 Parabolic Dish Systems
3.6 Heliostat Field Solar Collectors

82. 3.1 Compound parabolic solar collectors

83. 3.2 Fresnel Solar Thermal Collectors

84. 3.3 Parabolic Trough Solar Thermal Collectors

85. 3.4 Cylindrical Trough Solar Collectors

86. 3.5 Parabolic Dish Systems

87. 3.6 Heliostat Field Solar Collectors

88. Working of Practical Solar Heliostat

89. Advantages and Disadvantages of the Heliostat Solar Tower Power Plant
Afewadvantagesanddisadvantagesoftheheliostatsolartowersystemcomparedwiththeother
threeconcentratingsolarpowertechnologiesaresummarizedhere.
Advantages:
1.Althoughtheheliostatsolartowerapproachtosolarpowerproductionisnotascommercially
developedasthesolarparabolictroughsystem,itismorecommerciallydevelopedthaneitherthe
parabolicdish-Stirlingengineorlinearfresnelsystems.
2.Sincetheheliostatsolartowersystemproducessteamtogenerateelectricitywithaconventional
Rankinesteamcycle,thissystemcanbehybridized.Inotherwords,itcanbedesignedtousea
fossilfuel(mostlynaturalgas)asasupplementaryfuel,whenthesunisnotshining.
Disadvantages:
•Theheliostatsolartowersystemproducesafluidtemperaturegreaterthanthatofthesingle-axis
tracking,parabolictrough,andlinearfresnelsystem,butlessthanthatofthetwo-axistracking,
parabolicdish-Stirlingenginesystem.
•Thus,itcannotachieveefficiencyforconversionofelectricityfromthermalenergyashighasthat
ofparabolicdishstirlingenginesystem.

90. 4. MATERIAL ASPECTS OF SOLAR COLLECTORS:
Flat, corrugated, or grooved plates, to which the tubes, fins, or passages are attached.The plate
may be integrated with the tubes.
4.1 Absorber
The following are the types of solar flat plate absorbers that are most frequently used.
1.All copper plates are with integrated water passage (roll bond type).These plates can also be
made of aluminium.
2.All copper (copper sheet on copper tube).
3.copper tube or aluminumfin
4.iron or steel
5.plastic (polymers)
Absorptive Coatings: The absorptive coating of many varieties is used, ranging from flat black paint to baked
enamel.Flat black absorber coatings have high absorptivity.
The specification requirement of an absorber coating for a flat plate collector is as follows:
1.It should not degrade under ultraviolet exposure.
2.It must withstand temperature up to 200 °C.
3.It must withstand many temperature cycles over + 40 °C.
4.It must withstand many cycles of low to high relative humidity.
5.It must not chalk, fade, or chip.
6.It must not be so thick that heat conduction through the paint to the metal absorber is impeded.

91. 4.2 Glazing
one or more sheets of glass or other diathermanous (radiation transmitting) material is used as transparent
covers.
1.It must reduce convective losses from the absorber plate.
2.It must suppress radiative heat losses from the absorber plate
3.It must protect the absorber from excessive UV exposures. A glazing material must be resistant to UV
radiation.
Glass meets the overall abovementioned requirements and also the compatibility of the general requirement of
longevity.
The following are the specification requirements of glazing materials:
1.They must be reasonably impact resistant.
2.Thin or no-tempered glass panes are questionable because of the risk of damage from hail, birds, and
vandalism.
3.Low tensile strength of plastic materials (i.e., Teflon) are not advisable.
4.They must be resistant to significant temperature shock.
5.Sudden rain will cause rapid overall limb changes.A leaf on a stagnant collector can cause high localized
thermal stresses.
Thus, heat tempered glass is absolute necessity for outer collector glazing.Generally, plastic glazing can easily
withstand the temperature shocks.

92. 4.3 Insulation Shell
Asolarflatplatecollectormustbeinsulatedfromexcessiveheatlossesas
follows:
1.Backside-3.5inchoffiberglassinsulationor2inchoffoaminsulation.
2.Side-1inchoffiberglassor0.5to0.75inchoffoaminsulation.
Thefollowingarethespecificationstobemetwithinsulatingmaterials
1.Itmustwithstandthemaximumcollectorstagnationtemperaturerating(200°
C)withoutdamage.Foammaterialsshrinkduetoexcessiveheat.
2.Themaximumstagnationtemperatureshouldnotcauseevaporationor
sublimationoftheinsulatingmaterialssuchasthebinderofthefiberglass.
Specialfiberglassmaterialsareavailablethathaveaverysatisfactoryoutgassing
rate.

93. 5. PARABOLIC DISH-STIRLING ENGINE SYSTEM:
Themajorcomponentsofaparabolicdish-stirlingenginesystemareasfollows:
1.SolarDishconcentrator
2.PowerConversionunit
3.Trackingsystem

94. 6. Working of BRAYTON Heat Engine:

95. 7. Solar Collector Systems into Building Services:

96. 8. Solar Water Heating Systems
i. Active Solar water Heating Systems

97. ii. Active Solar Space Heating Systems

98. 9.Passive Solar Water Heating Systems
•Types of Passive Water Heaters
i.Batch System
ii.Thermosiphon System

99. i. Batch System

101. ii. Thermosiphon System

103. 11.Active Solar Space Cooling

104. 12. SOLAR AIR HEATING
Solar-heatedaircanbeusedfordryingmost
cropsthatrequirewarmair.Solarheatedairis
idealfordryingdelicatefoodssinceitwillnot
burnorriskpotentialdamagefromhigh
temperaturesteamheat.Solarheatisnon-
pollutingandbestofall,itincursnofuelcosts.

105. 13. SOLAR DRYERS
Solardryerscanbeutilizedforvariousdomesticpurposes.Theyalsofindnumerousapplicationsinindustriessuch
astextiles,wood,fruitandfoodprocessing,paper,pharmaceutical,andagro-industries.
Advantages
Solardryersaremoreeconomicalwhencomparedtodryersthatrunonconventionalfuelorelectricity.Thedryingprocessis
completedinthemosthygienicandeco-friendlyway.Solardryingsystemshavelowoperationandmaintenancecosts.Solar
dryerslastlonger.Atypicaldryercanlast15–20yearswithminimummaintenance.
Limitations
1. Drying can be performed only during sunny days, unless the system is integrated with a conventional energy-
based system.
2. Due to limitations of solar energy collection, the solar drying process is slow in comparison with dryers that use
conventional fuels.
3. Normally, solar dryers can be utilized only for drying at 40C–50C.

106. Solar-heated air can be used to dry
1. Crops, timber, distillers grains, and textiles. 2. Tea, coffee, beans, tobacco,
etc.
3. Food for dehydration or processing. 4. Sludge, manure, and compost

107. 14. SPACE COOLING
•Therearemanymethodsforminimizingtheheatgain.These
includesituatingabuildinginshadeornearwater,using
vegetationorlandscapingtodirectwindintothebuilding,
goodtownplanningtooptimizetheprevailingwindand
availableshade.
•Buildingscanbedesignedforagivenclimate;domedroofs
andthermallymassivestructuresinhotaridclimates,
shutteredandshadedwindowstopreventheatgain,open
structurebamboohousinginwarmandhumidareas.
•Insomecountries,dwellingsareconstructedunderground
andtakeadvantageoftherelativelylowandstable
temperatureofthesurroundingground.

108. Solarheatingbyconvectionisanaturalprocessthatinvolvestrappingairand
lettingitwarmupbeforereleasingitbackintoagivenspace.Convectionheating
isoftenusedasasolarheatingsourcebecausethetwonaturallygohandin
hand(seeFig.3.24).

110. 15. SOLAR COOKERS
Solarcookingisatechnologythathasbeengivenalotofattentioninrecentyears
indevelopingcountries.Thebasicdesignisthatofaboxwithaglasscover.The
boxislinedwithinsulationandaesurfaceisappliedtoconcentratetheheatonto
thepots.Thepotscanbepaintedblacktohelpwiththeheatabsorption.Thesolar
radiationraisesthetemperaturesufficientlytoboilthecontentsinthepots.
Cookingtimeisoftenconsiderablyslowerthanconventionalcookingstoves,but
thereisnofuelcost.
Manytypesofcookersexist.Simplesolarcookersusethefollowingbasicprinciples:
1.Concentratingsunlight:Areflectivemirrorofpolishedglass,metal,ormetalizedfilmisusedto
concentratelightandheatfromthesunintoasmallcookingarea,makingtheenergymore
concentratedandincreasingitsheatingpower.
2.Convertinglighttoheat:Ablackorlowreflectivitysurfaceonafoodcontainerortheinsideofsolarcooker
willimprovetheeffectivenessofturninglightintoheat.Lightabsorptionconvertsthesun’svisiblelightintoheat,
substantiallyimprovingtheeffectivenessofthecooker.
3.Trappingheat:Itisimportanttoreduceconvectionbyisolatingtheairinsidethecookerfromtheairoutside
thecooker.Aplasticbagortightlysealedglasscoverwilltrapthehotairinside.Thismakesitpossibletoreach
similartemperaturesoncoldandwindydaysasonhotdays.
4.Greenhouseeffect:Glasstransmitsvisiblelightbutblocksinfraredthermalradiationfromescaping.This
amplifiestheheattrappingeffect.

111. Types of Solar Cookers
All the solar cookers are subdivided into four configurations:
1.Solar cooking boxes
2.Reflector cookers
3.Solar steam and convection cookers
4.Heat Storage Solar Cookers

112. Advantages
Solar energy cooking has a variety of advantages, out of which the most important are as follows:
•1. Cooking with solar energy saves fuel wood and/or chemical fuels.
•2. Cooking with solar energy is clean and healthy and reduces health problems related to
kitchen smoke.
•3. Solar cooking enables individual families to do without commercial fuels, and thus, money
can be saved.
•4. Solar cooking saves time and effort that would otherwise be spent in collecting fuel wood.
•5. Food cooked in box-type solar cookers cannot burn and does not have to be stirred or watched.
•6. Food cooked in box-type solar cooker is cooked gently so that more of the nutrients and
flavour of the food are conserved than when cooking on the fire.

113. Disadvantages
The followingare some disadvantages related to the principle of solar cooking.
•1. Solar cooking requires good weather with relatively steady sunshine.
•2. Solar cooking cannot completely replace the conventional wood, gas, or kerosene fire.
•3. Solar cooking is only possible during the daytime and not in the mornings and evenings
(except with storage-type solar cookers).
•4. Most types of solar cookers require industrially manufactured components. These can easily
be destroyed, and it is difficult or impossible to repair or replace them with local material.
•5. Some solar cooking boxes do not attain high temperatures. This requires long cooking time.
•6. Boiling, roasting, and grilling require high temperatures, and thus, it is only possible in a few
types of solar cookers
•7. Some reflector-type solar cookers demand understanding, skill, and almost constant attention
when handling and cooking with them.
•8. The person doing the cooking has to stay out in the sun to avoid the risks of being dazzled or
burnt.
•9. Generally, families that need solar cookers mostly cannot afford them.

114. 16.SOLAR POND

120. Components of a Solar Cell System
Theseincludesolarcellpanels,oneormorebatteries,achargeregulatoror
controllerforastandalonesystem,aninverterforautilitygrid-connected
system,requirementofalternatingcurrent(AC)ratherthandirectcurrent(DC),
wiring,andmountinghardwareoraframework.

121. Elements of Silicon Solar Cell
1.Substrate:
Itisanunpolishedp-typewaferreferredtoasp-regionbasematerial.
Theimportantparameterstobekeptinmindwhilechoosingawaferforsolarcells
areitsorientation,resistivity,thickness,anddoping.
Typicalthicknessofwafersusedforsolarcellsis180–300µm.
Thetypicalresistivityvaluesarein1–2Ωcm.Thedopingshouldbecloseto5×
1015/cm3to1×1016/cm3.
Thewafercanbesinglecrystallineormulti-crystalline.

122. Elements of Silicon Solar Cell
2.Emitter:
Theemitterformationinvolvesthedopingofsiliconwithpentavalentimpurities
suchasphosphorus,arsenic,andantimony.
However,forsolarcellapplications,phosphorusisthewidelyusedimpurity.The
dopingisdonebytheprocessofdiffusion.
Thebasicideaistointroducethewaferinanenvironmentrichinphosphorusat
hightemperatures.
Thephosphorusdiffusesin,duetotheconcentrationgradient,anditcanbe
controlledbyvaryingthetimeandtemperatureoftheprocess.
CommonlyuseddiffusiontechniquemakesuseofPOCl3asthephosphorussource.
Theprocessisdoneattemperaturesof850°Cto1,000°C.
Thetypicaldopingconcentrationwillbeoftheorderof1×1019/cm3.Thejunction
depthsareintherangeof0.2–1µm.
Thisisalsocommonlyknownasn-regiondiffusedlayers

123. Elements of Silicon Solar Cell
3.Electricalcontacts:
Theseareessentialtoaphotovoltaiccellsince
theybridgetheconnectionbetweenthe
semiconductormaterialandtheexternal
electricalload.Itincludes
(a)Backcontact:Itisametallicconductor
completelycoveringback.Thebackcontactofa
cellislocatedonthesideawayfromthe
incomingsunlightandisrelativelysimple.It
usuallyconsistsofalayerofaluminiumor
molybdenummetal.
(b)Frontcontact:Currentcollectiongridof
metallicfingertypeisarrangedinsuchaway
thatphotonenergyfallsonn-regiondiffused
layers.Thefrontcontactislocatedontheside
facingthelightsourceandismorecomplicated.
Whenlightfallsonthesolarcell,

124. Fundamentals of Solar Photo Voltaic Conversion
Whenlightshinesonaphotovoltaic(PV)cell–alsocalledasolarcell–thatlight
maybereflected,absorbed,orpassrightthroughthecell.
ThePVcelliscomposedofsemiconductormaterial;the“semi”meansthatit
canconductelectricitybetterthananinsulatorbutnotaswellasagood
conductorlikeametal.
ThereareseveraldifferentsemiconductormaterialsusedinPVcells.
Whenthesemiconductorisexposedtolight,itabsorbsthelight’senergyand
transfersittonegativelychargedparticlesinthematerialcalledelectrons.
Thisextraenergyallowstheelectronstoflowthroughthematerialasan
electricalcurrent.
Thiscurrentisextractedthroughconductivemetalcontacts–thegrid-likelines
onasolarcells–andcanthenbeusedtopoweryourhomeandtherestofthe
electricgrid.

125. Fundamentals of Solar Photo Voltaic Conversion
TheefficiencyofaPVcellissimplytheamountofelectricalpowercomingout
ofthecellcomparedtotheenergyfromthelightshiningonit,whichindicates
howeffectivethecellisatconvertingenergyfromoneformtotheother.
TheamountofelectricityproducedfromPVcellsdependsonthe
characteristics(suchasintensityandwavelengths)ofthelightavailableand
multipleperformanceattributesofthecell.
AnimportantpropertyofPVsemiconductorsisthebandgap,whichindicates
whatwavelengthsoflightthematerialcanabsorbandconverttoelectrical
energy.
Ifthesemiconductor’sbandgapmatchesthewavelengthsoflightshiningonthe
PVcell,thenthatcellcanefficientlymakeuseofalltheavailableenergy.
Learnmorebelowaboutthemostcommonly-usedsemiconductormaterialsfor
PVcells.

126. Fundamentals of Solar Photo Voltaic Conversion

137. Solar PV Power Generation
Photovoltaictechnologyhelpstomitigateclimatechangebecauseitemitsmuchlesscarbondioxidethan
fossilfuels.
SolarPVhasspecificadvantagesasanenergysource:onceinstalled,itsoperationgeneratesnopollution
andnogreenhousegasemissions,itshowsscalabilityinrespectofpowerneedsandsiliconhaslarge
availabilityintheEarth'scrust,althoughothermaterialsrequiredinPVsystemmanufacturesuchassilver
mayconstrainfurthergrowthinthetechnology.
Othermajorconstraintsidentifiedarecompetitionforlanduse.
TheuseofPVasamainsourcerequiresenergystoragesystemsorglobaldistributionbyhigh-voltagedirect
currentpowerlinescausingadditionalcosts,andalsohasanumberofotherspecificdisadvantagessuchas
variablepowergenerationwhichhavetobebalanced.
Productionandinstallationdoescausesomepollutionandgreenhousegasemissions,thoughonlyafraction
oftheemissionscausedbyfossilfuels.

138. Solar PV Power Generation
Photovoltaicsystemshavelongbeenusedinspecializedapplicationsasstand-aloneinstallations
andgrid-connectedPVsystemshavebeeninusesincethe1990s.
Photovoltaicmoduleswerefirstmass-producedin2000,whentheGermangovernmentfundeda
onehundredthousandroofprogram.
DecreasingcostshasallowedPVtogrowasanenergysource.
ThishasbeenpartiallydrivenbymassiveChinesegovernmentinvestmentindevelopingsolar
productioncapacitysince2000,andachievingeconomiesofscale.Improvementsin
manufacturingtechnologyandefficiencyhavealsoledtodecreasingcosts.
Netmeteringandfinancialincentives,suchaspreferentialfeed-intariffsforsolar-generated
electricity,havesupportedsolarPVinstallationsinmanycountries.
Panelpricesdroppedbyafactorof4between2004and2011.Modulepricesdroppedbyabout
90%overthe2010s.

139. Solar PV Power Generation
In2019,worldwideinstalledPVcapacityincreasedtomorethan635gigawatts(GW)coveringapproximately
twopercentofglobalelectricitydemand.
Afterhydroandwindpowers,PVisthethirdrenewableenergysourceintermsofglobalcapacity.
In2019theInternationalEnergyAgencyexpectedagrowthby700–880GWfrom2019to2024.
Insomeinstances,PVhasofferedthecheapestsourceofelectricalpowerinregionswithahighsolar
potential,withabidforpricingaslowas0.01567US$/kWhinQatarin2020.
In2020theInternationalEnergyAgencystatedinitsWorldEnergyOutlookthat‘[f]orprojectswithlowcost
financingthattaphighqualityresources,solarPVisnowthecheapestsourceofelectricityinhistory.

140. Solar PV Applications
Photovoltaicsystemshavelongbeenusedinspecializedapplicationsasstand-aloneinstallations
andgrid-connectedPV.
GridInteractivePVPowerGeneration
WaterPumping
Lighting
MedicalRefrigeration
VillagePower
TelecommunicationandSignaling
PVwithBatteryStorage
PVwithBackupGeneratorPower
PVConnectedtotheLocalUtility
Utility-ScalePowerProduction
HybridPowerSystems

141. 1
Alternative Sources of Energy

142. Ken Youssefi
Engineering 10, SJSU 2
Wind Turbine Energy

143. 3
Wind Turbine
Wind energy is created when the atmosphere is heated
unevenly by the Sun, some patches of air become
warmer than others. These warm patches of air rise,
other air rushes in to replace them – thus, wind blows.
A wind turbine extracts energy from moving air by
slowing the wind down, and transferring this energy into
a spinning shaft, which usually turns a generator to
produce electricity. The power in the wind that’s
available for harvest depends on both the wind speed
and the area that’s swept by the turbine blades.

144. 4
Two types of turbine design are possible – Horizontal axis and
Vertical axis. In horizontal axis turbine, it is possible to catch more
wind and so the power output can be higher than that of vertical axis.
But in horizontal axis design, the tower is higher and more blade
design parameters have to be defined. In vertical axis turbine, no yaw
system is required and there is no cyclic load on the blade, thus it is
easier to design. Maintenance is easier in vertical axis turbine
whereas horizontal axis turbine offers better performance.
Wind Turbine Design
Horizontal axis
Turbine
Vertical axis
Turbine

145. 5
Main components of a Horizontal Axis Wind
Turbine
Gear box: Wind turbines rotate typically between 40 rpm and 400
rpm. Generators typically rotates at 1,200 to 1,800 rpm.
Most wind turbines require a step-up gear-box for efficient
generator operation (electricity production).
Blades and rotor: Converts the wind power to a rotational mechanical power.
Generator: Converts the rotational mechanical power to electrical power.

146. 6
Main components of a Wind Turbine
Rotor
The portion of the wind turbine that collects energy from the wind is called the
rotor. The rotor usually consists of two or more wooden, fiberglass or metal
blades (new design) which rotate about an axis (horizontal or vertical) at a
rate determined by the wind speed and the shape of the blades. The blades
are attached to the hub, which in turn is attached to the main shaft.
Rotor

147. 7
Conduct an internet search to obtain enough
information to help you decide on the number and
profile of the blades.
Blade Length
Blade Number
Blade Pitch
Blade Shape
Blade Materials
Blade Weight
Rotor Blade Variables
What should be the angle of attack?
What should be the blade profile?
How many blades to use?

148. 8
Wind Turbine
For the drag design, the wind literally
pushes the blades out of the way.
Drag powered wind turbines are
characterized by slower rotational
speeds and high torque capabilities.
They are useful for the pumping,
sawing or grinding work that Dutch,
farm and similar "work-horse"
windmills perform. For example, a
farm-type windmill must develop high
torque at start-up in order to pump,
or lift, water from a deep well.
Drag Design
Blade designs operate on either the principle of drag or lift.

149. Wind Turbine Design using Drag Principle
9

150. 10
Wind Turbine
The lift blade design employs the same principle that enables airplanes, kites and birds
to fly. The blade is essentially an airfoil, or wing. When air flows past the blade, a wind
speed and pressure differential is created between the upper and lower blade surfaces.
The pressure at the lower surface is greater and thus acts to "lift" the blade. When
blades are attached to a central axis, like a wind turbine rotor, the lift is translated into
rotational motion. Lift-powered wind turbines have much higher rotational speeds than
drag types and therefore are well suited for electricity generation.
Lift Design

151. 11

The angle between the chord line of the airfoil and the flight direction
is called the angle of attack. Angle of attack has a large effect on the
lift generated by an airfoil. This is the propeller efficiency. Typically,
numbers here can range from 1.0 to 15.0 degrees.
Angle of attack (blade angle)
Wind Turbine – Blade Design

152. Ken Youssefi 12
Angle of attack

153. 13
Increasing the number of blades from one to two
yields a 6% increase in efficiency, whereas
increasing the blade count from two to three yields
only an additional 3% in efficiency. Further increasing
the blade count yields minimal improvements in
aerodynamic efficiency and sacrifices too much in
blade stiffness as the blades become thinner.
Wind Turbine – Blade Design
One blade rotor
Blade Number
The determination of the number of blades involves design considerations
of aerodynamic efficiency, component costs, system reliability, and
aesthetics..
Aerodynamic efficiency increases with the
number of blades but with diminishing return.
Generally, the fewer the number of blades, the lower the
material and manufacturing costs will be. Higher rotational
speed reduces the torques in the drive train, resulting in
lower gearbox and generator costs.

154. 14
Wind Turbine – Blade Design
The ideal wind turbine rotor has an infinite number of infinitely thin
blades. In the real world, more blades give more torque, but slower
speed, and most alternators need fairly good speed to cut in.
Wind turbines are built to catch the wind's kinetic (motion) energy.
You may therefore wonder why modern wind turbines are not built
with a lot of rotor blades, like the old "American" windmills you have
seen in the Western movies and still being used in many farms.
Turbines with many blades or very wide blades will be subject to
very large forces, when the wind blows at a hurricane speed.
The ideal wind turbine design is not dictated by technology alone, but
by a combination of technology and economics: Wind turbine
manufacturers wish to optimize their machines, so that they deliver
electricity at the lowest possible cost per kilowatt hour (kWh) of
energy.

155. 15
Wind Turbine – Blade Design
A rotor with an even number of blades will cause stability
problems for a wind turbine. The reason is that at the very
moment when the uppermost blade bends backwards,
because it gets the maximum power from the wind, the
lower most blade passes into the wind shade in front of
the tower. This produces uneven forces on the rotor shaft
and rotor blade.
Even or Odd Number of Blades

156. 16
Wind Turbine – Blade Design (Shape)
To study how the wind moves relative to the rotor
blades of a wind turbine, attach red ribbons to the
tip of the rotor blades and yellow ribbons about 1/4
of the way out from the hub.
Since most wind turbines have constant rotational
speed, the speed with which the tip of the rotor blade
moves through the air (the tip speed) is typically
some 64 m/s, while at the centre of the hub it is zero.
1/4 out from the hub, the speed will then be some 16
m/s.

The yellow ribbons close to the hub of the rotor will
be blown more towards the back of the turbine than
the red ribbons at the tips of the blades. This is
because, at the tip of the blades, the speed is some 8
times higher than the speed of the wind hitting the
front of the turbine.
V = Rω
ω
R

157. 17
Wind Turbine – Blade Design (Shape)
Rotor blades for wind turbines are always twisted.
Seen from the rotor blade, the wind will be coming from a
much steeper angle (more from the general wind direction in
the landscape), as you move towards the root of the blade,
and the center of the rotor. A rotor blade will stop giving lift
(stall), if the blade is hit at an angle of attack which is too
steep.
Therefore, the rotor blade has to be twisted, so as to achieve
an optimal angle of attack throughout the length of the blade.

158. Engineering 10, SJSU 18
5-station design as seen from the tip
Wind Turbine – Blade Design
Blade size and shape
Last profile next
to the hub
First profile at
the tip

159. 19
Power Generated by Wind Turbine
Swept area
Diameter
Elevation
There are about 4,800 wind turbines in California at Altamont Pass
(between Tracy and Livermore). The capacity is 580 MW, enough to serve
180,000 homes. In the past, Altamont generated 822x10
6
kW hours,
enough to provide power for 126,000 homes (6500 Kwh per house)

160. 20
0 ~ 10 mph --- Wind speed is too low for generating power. Turbine is not
operational. Rotor is locked.

10 ~ 25 mph --- 10 mph is the minimum operational speed. It is called “Cut-in
speed”. In 10 ~ 25 mph wind, generated power increases
with the wind speed.

25 ~ 50 mph --- Typical wind turbines reach the rated power (maximum
operating power) at wind speed of 25mph (called Rated
wind speed). Further increase in wind speed will not result in
substantially higher generated power by design. This is
accomplished by, for example, pitching the blade angle to
reduce the turbine efficiency.

> 50 mph --- Turbine is shut down when wind speed is higher than 50mph
(called “Cut-out” speed) to prevent structure failure.



Typical Wind Turbine Operation

161. 21
Theoretical Power Generated by Wind Turbine
Power = ½ (ρ)(A)(V)
3

A = swept area = π(radius)
2
, m
2

V = Wind Velocity, m/sec.
ρ = 1.16 kg/m
3
at Altamont pass, at 1010 feet elevation and average wind
velocity of 7m/s (15.6 mph) at 50m tower height (turbines need a minimum of
14 mph, 6.25 m/s, wind velocity to generate power).
ρ = 1.16 kg/m
3
, at 1000 feet elevation
ρ = 1.00 kg/m
3
, at 5000 feet elevation
ρ = 1.203 kg/m
3
at San Jose, at 85 feet elevation. The average
wind velocity is 5 mph at 50m tower height
ρ = Density of air = 1.2 kg/m
3
(.0745 lb/ft
3
), at sea level, 20
o
C and dry air
A

162. 22
Wind Turbine Efficiency, η
It is the flow of air over the blades and through the rotor area
that makes a wind turbine function. The wind turbine
extracts energy by slowing the wind down. The theoretical
maximum amount of energy in the wind that can be
collected by a wind turbine's rotor is approximately 59.3%.
This value is known as the Betz limit. If the blades were
100% efficient, a wind turbine would not work because the
air, having given up all its energy, would entirely stop. In
practice, the collection efficiency of a rotor is not as high as
59%. A more typical efficiency is 35% to 45%. A complete
wind energy system, including rotor, transmission,
generator, storage and other devices, which all have less
than perfect efficiencies, will deliver between 10% and 30%
of the original energy available in the wind.
Betz Limit

163. 23
Power Generated by HWind Turbine
Air density is lower at higher elevation. For 1000 feet above sea
level, ρ is about 1.16 kg/m
3


Power = ½ (ρ)(A)(V)
3
(η)
= 0.5(1.16)(π50
2
)(12)
3
(0.4)
= 3.15 x 10
6
Watt
= 3.15 MW



where we assumed the turbine efficiency is 40%.


How much power a wind turbine with 50 meters long blade can
generate with a wind speed of 12 m/s? The site of the
installation is about 1000 feet above sea level. Assume 40%
efficiency (η).

164. 24

The number of blades and the total area they cover affect
wind turbine performance. For a lift-type rotor to function
effectively, the wind must flow smoothly over the blades. To
avoid turbulence, spacing between blades should be great
enough so that one blade will not encounter the disturbed,
weaker air flow caused by the blade which passed before it.
Wind Turbine
Tip Speed Ratio
The tip-speed ratio is the ratio of the rotational speed of the
blade to the wind speed. The larger this ratio, the faster the
rotation of the wind turbine rotor at a given wind speed.
Electricity generation requires high rotational speeds.
Lift-type wind turbines have maximum tip-speed ratios of
around 10, while drag-type ratios are approximately 1. Given
the high rotational speed requirements of electrical
generators, it is clear that the lift-type wind turbine is the
most practical for this application.

165. 25
Inside this component, coils of wire are rotated in a magnetic field to produce electricity.
Different generator designs produce either alternating current (AC) or direct current
(DC), available in a large range of output power ratings.
Most home and office appliances operate on 120 volt (or 240 volt), 60 cycle AC. Some
appliances can operate on either AC or DC, such as light bulbs and resistance heaters,
and many others can be adapted to run on DC. Storage systems using batteries store
DC and usually are configured at voltages of between 12 volts and 120 volts.
Generators that produce AC are generally equipped with features to produce the correct
voltage (120 or 240 V) and constant frequency (60 cycles) of electricity, even when the
wind speed is fluctuating.
Wind Turbine
The Generator
The generator converts the mechanical energy
of the turbine to electrical energy (electricity).

166. 26
Wind Turbine
The number of revolutions per minute (rpm) of a wind turbine rotor can range
between 40 rpm and 400 rpm, depending on the model and the wind speed.
Generators typically require rpm's of 1,200 to 1,800. As a result, Some
DC-type wind turbines do not use transmissions. Instead, they have a direct
link between the rotor and generator. These are known as direct drive
systems. Without a transmission, wind turbine complexity and maintenance
requirements are reduced, but a much larger generator is required to deliver
the same power output as the AC-type wind turbines.
Transmission
Most wind turbines require a gear-box
transmission to increase the rotation of the
generator to the speeds necessary for efficient
electricity production.

167. 27
Cut-in speed is the minimum wind speed at which the wind turbine
will generate usable power. This wind speed is typically between 7
and 15 mph.
Wind Turbine
Cut-in Speed
Rated Speed
The rated speed is the minimum wind speed at which the wind turbine will
generate its designated rated power. For example, a "10 kilowatt" wind
turbine may not generate 10 kilowatts until wind speeds reach 25 mph.
Rated speed for most machines is in the range of 25 to 35 mph. At wind
speeds between cut-in and rated, the power output from a wind turbine
increases as the wind increases. The output of most machines levels off
above the rated speed. Most manufacturers provide graphs, called
"power curves," showing how their wind turbine output varies with wind
speed.

168. 28
Wind Turbine
At very high wind speeds, typically between 45 and 80 mph, most wind
turbines cease power generation and shut down. The wind speed at which
shut down occurs is called the cut-out speed. Having a cut-out speed is a
safety feature which protects the wind turbine from damage. Shut down may
occur in one of several ways. In some machines an automatic brake is
activated by a wind speed sensor. Some machines twist or "pitch" the blades
to spill the wind. Still others use "spoilers," drag flaps mounted on the blades
or the hub which are automatically activated by high rotor rpm's, or
mechanically activated by a spring loaded device which turns the machine
sideways to the wind stream. Normal wind turbine operation usually resumes
when the wind drops back to a safe level.
Cut-out Speed

169. 29
Power Generated by Wind Turbine
Wind turbines with rotors (turbine blades and hub) that are about 8 feet in diameter
(50 square feet of swept area) may peak at about 1,000 watts (1 kilowatt; kW), and
generate about 75 kilowatt-hours (kWh) per month with a 10 mph average wind
speed. Turbines smaller than this may be appropriate for sailboats, cabins, or other
applications that require only a small amount of electricity. [Small Wind]
For wind turbine farms, it’s reasonable to use turbines with rotors up to 56 feet in
diameter (2,500 square feet of swept area). These turbines may peak at about
90,000 watts (90 kW), and generate 3,000 to 5,000 kWh per month at a 10 mph
average wind speed, enough to supply 200 homes with electricity.
Homes typically use 500-1,500 kilowatt-hours of electricity per month. Depending upon
the average wind speed in the area this will require a wind turbine rated in the range
5-15 kilowatts, which translates into a rotor diameter of 14 to 26 feet.

170. 30
Bergey wind turbines operate at variable speed to
optimize performance and reduce structural loads.
Power is generated in a direct drive, low speed,
permanent magnet alternator. The output is a
3-phase power that varies in both voltage and
frequency with wind speed. This variable power
(wild AC) is not compatible with the utility grid. To
make it compatible, the wind power is converted
into grid-quality 240 VAC, single phase, 60 hertz
power in an IGBT-type synchronous inverter, the
GridTek Power Processor. The output from the
GridTek can be directly connected to the home or
business circuit breaker panel. Operation of the
system is fully automatic. It has a rotor diameter of
23 feet and is typically installed on 80 or 100 foot
towers.
10kW Turbine $27,900
100 ft.Tower Kit $9,200
Tower Wiring Kit $1,000
Total Cost: $38,100
Example Residential Wind Turbine

171. 31
Doubling the tower height increases the expected wind speeds by 10% and the
expected power by 34%. Doubling the tower height generally requires doubling
the diameter as well, increasing the amount of material by a factor of eight.

At night time, or when the atmosphere becomes stable, wind speed close to
the ground usually subsides whereas at turbine altitude, it does not decrease
that much or may even increase. As a result, the wind speed is higher and a
turbine will produce more power than expected - doubling the altitude may
increase wind speed by 20% to 60%.
Wind Turbine
Tower heights approximately two to three times the blade
length have been found to balance material costs of the tower
against better utilization of the more expensive active
components.

172. 32
(1)High Annual average wind speed
(2)Availability of anemometry data
(3) Availability of wind V curve at the proposed site
(4)Wind structure at the proposed site
(5)Altitude of the proposed site
(6)Terrain and its aerodynamic
(7)Local Ecology
(8)Distance to roads or railways
(9)Nearness of site to local centre/users
(10)Nature of ground
(11)Favourable land cost


Wind Site Selection

173. 33
❖Hill Effect
❖Roughness or the amount of friction that earth’s surface
exerts on wind.
❖Tunnel effect
❖Turbulence: Rapid changes in the speed and direction of the
wind, often caused by the wind blowing over natural or
artificial barriers are called turbulence.
❖Variations in wind speed
❖Wake: the abrupt change in the speed makes the wind
turbulent, a phenomenon called wake.
❖Wind obstacles
❖Wind shear



Wind Site Selection

174. 34
❖Hill Effect
❖Roughness or the amount of friction that earth’s surface
exerts on wind.
❖Tunnel effect
❖Turbulence: Rapid changes in the speed and direction of the
wind, often caused by the wind blowing over natural or
artificial barriers are called turbulence.
❖Variations in wind speed
❖Wake: the abrupt change in the speed makes the wind
turbulent, a phenomenon called wake.
❖Wind obstacles
❖Wind shear



Wind Site Selection

175. 35



Maximum Power of Wind Turbine

176. 36



Maximum Power of Wind Turbine

177. 37



Maximum Power of Wind Turbine

178. 38



Maximum Power of Wind Turbine

179. 39



Maximum Power of Wind Turbine

180. 40



Maximum Power of Wind Turbine

181. 41



Maximum Power of Wind Turbine

182. Module 3
Hydrogen Energy:

208. PROBLEMS ASSOCIATED WITH HYDROGEN ENERGY
Theseriousproblemsthatareaffectingthedevelopmentofhydrogenforhouseholdandtransport
applicationsareasfollows:
1.Hydrogenstorage:Theconcernssurroundingthestorageofhydrogenareamajorissue.Itmust
bestoredatextremelylowtemperaturesandhighpressure.Acontainercapableofwithstanding
thesespecificationsislargerthanastandardgastank.Hydrogenstoragecouldbeviewedasa
problembyconsumers.
2.Highreactivityofhydrogen:Hydrogenisextremelyreactive.Itiscombustibleandflammable.The
Hindenburgdisaster,whereahydrogen-filledblimpexplodedandmanypeopledied,hascauseda
fearofhydrogen
3.Costandmethodsofhydrogenfuelproduction:Currentproductionofhydrogentakesalotof
energy.Ifonehastoburnfossilfuelstomakehydrogen,whathasreallybeengained?New,clean
energytechnologyorhydrogenproductionmethodswillneedtobedevelopedforhydrogen
vehiclestomakesense.
4.Consumerdemand:Anotherproblemforhydrogenfuelisconsumerdemandandthecostto
changeallgasolinefillingstationsandvehicleproductionlinesintohydrogen.Themajortransport
companieswillnotstarttoproducehydrogenvehiclesuntilthereisconsumerdemand.Why
wouldapersonpayforanexpensivehydrogenvehicle?
5.Costofchangingtheinfrastructure:Toaccommodatehydrogenequipmentandappliances.

209. GEOTHERMAL ENERGY
Trapping the Earth’s Internal Heat

210. What is Geothermal Energy?
•Geo (Greek for earth)
Thermal (heat)
•Temp. of Shallow
Crust (upper 10 ft.)
Constant 55-75°F
(13-24°C)
•Up to 14,400°F
(8,000°C) at Molten
Core (approx. 4,000
mi. to center of core)

211. How is Geothermal Energy Generated?
•Temperatures hotter than the sun’s surface are
continuously produced inside the earth by a slow
decay of radioactive particles
•The most common method that scientists use to find
geothermal reservoirs is drilling a deep well and
testing the temperature deep underground.
•Steam or very hot water from deep within the earth
is piped to the surface and used as a heat source or
to produce electricity.
•Earth’s kinetic energy is converted into electricity.

212. Energy Efficient and Cost Effective
•According to the
EPA, geothermal are
the most energy
efficient, cost
effective, and
environmentally
clean systems for
temperature control

213. Geothermal Energy and Geothermics
•Geothermal energy is that part of the total heat energy stored
within the Earth’s interior that is available for human use. That
means practically that it is related to the heat energy stored in the
upper layers (crust) of the earth.
•Although the earth’s stored heat is theoretically finite, its large
amount (12.6 x 10
24
MJ) makes geothermal energy practically a
renewable energy that can theoretically sustain the energy needs
of mankind many times.
•Geothermicsis the science that deals with the theoretical studdy
of the thermal regime of the earth as well as the engineering
aspects to use the earth’s heat for heating / cooling and electric
power generations.

214. Uses and Goals
•Heat pumps –heat and cool building; melt snow
from roads and sidewalks
•Direct use applications –greenhouses, heat water
for fish farming, pasteurize milk, food
dehydration, gold mining
•Power plants –produce electricity
•Help mitigate global warming

215. 1 Origins of geothermal energy
–1. Left-over heat from the
time of the accretion of the
earth (4.6 By BC) (30%)
–2. heat generated by the
decay of the long-lived
radioactive isotopes of
uranium (U238, U235),
thorium (Th232) and
potassium (K40) (70%).

216. 1 Origins of geothermal energy
Temperature distribution in the earth
Temperatures in the earth Geothermal gradient in the upper 150km
dT/dz ~ 30
o
C/km

217. 2. Classification of geothermal systems
2.1 Deep geothermal energy reservoirs
Classification of geothermal reservoirs in relation to the temperature
o
C

218. 2. Classification of geothermal systems
2.1 Deep geothermal energy reservoirs
2.1.1 High enthalpy reservoirs
Characterization of high enthalpy-systems
Mostly in regions with vulkanic activity
Use for generation of electricity (flash-method)
and of process heat
Temperature range: 90 –300°C
Depending on pressure reservoirs have more
steam or water
Steam is reinjected
no negativ environmental impact
higher productivity

219. 2. Classification of geothermal systems
2.1 Deep geothermal energy reservoirs
2.1.1 High enthalpy reservoirs

220. 2. Classification of geothermal systems
2.1 Deep geothermal energy reservoirs
2.1.1 High enthalpy reservoirs/ Examples
Laradello
geothermal
power plant
The Geysers
geothermal field,
California
http://geothermal.marin.org/GEOpresentation/sld036.htm

221. 2. Classification of geothermal systems
2.1 Deep geothermal energy reservoirs
2.1.2 Low enthalpy reservoirs
2.1.2.1 Hydrothermal systems
http://www.unendlich-viel-
energie.de/uploads/media/
Hydrothermale_Geothermi
e.pdf
Thermal power extraction
P
therm= ρc
p Q
flow ΔT
ρ= density of water
c
p= specific heat
Q
flow= flow rate
ΔT = T
hot-T
cold

222. How is Geothermal Energy Generated?
•Temperatures hotter than the sun’s surface
are continuously produced inside the earth by
a slow decay of radioactive particles
•People around the world use geothermal
energy to produce electricity and heat their
homes by digging deep wells and pumping the
heated water or steam to the surface

223. Where is Geothermal Energy Found?
•Found along major
plate boundaries where
earthquakes and
volcanoes are
concentrated
–Geysers
–Hot springs
–Fumaroles
–Geothermal reservoirs

224. The Ring of Fire

225. The US and Geothermal Energy
•Most of the geothermal reservoirs in the U.S. are
located in the western states, Alaska and Hawaii.
•California generates the most electricity from
geothermal energy.
•"The Geysers" dry steam reservoir in northern
California is the largest known dry steam field in
the world and has been producing electricity
since 1960.
•7 states have geothermal power plants
•In 2008 U.S. geothermal power plants produced
0.4% of total electricity in the United States.

226. Geothermal Energy is the U.S.

227. Iceland
•Iceland plans to run
its entire economy
on renewable
hydropower,
geothermal energy,
and wind; and use
these sources to
produce hydrogen
gas for running all
of its motor
vehicles and ships
by the year 2050.

228. 2. Classification of geothermal systems
2.2 Surficial geothermal energy use with heat pumps
Open dublett system horizontal ground loops vertical U-tube loop
(most common)
In 2009 in Germany 330.000 ground source heat pumps(GSHP) installed
with 51.000 new installations in 2010

229. 2. Classification of geothermal systems
2.2 Surficial geothermal energy use with heat pumps/Principle
Heat Pump:
Coefficient of Performance
COP= Q
th/ W
el~ 4-5
with
Q
th= output heat rate
=Q
in+ W
el
W
el= electric power input

230. 2. Classification of geothermal systems
2.5Geothermal energy use for seasonal storage

231. 3. Use of geothermal energy
3.1 Direct use
http://geothermal.marin.org/
GEOpresentation/sld072.htm

232. 3. Use of geothermal energy
3.2 Heating and cooling
http://geothermal.marin.org/
GEOpresentation/sld089.htm

233. 3. Use of geothermal energy
3.3 Electric power generation
http://geothermal.marin.org/GEOpresentation/sld036.htm
Carnot thermodynamic efficiency
η= W/Q
therm= 1 -T
cold/T
hot

234. Geothermal Power Plants
•Require high
temperatures (300 F –
700 F) hydrothermal
resources that may either
come from dry steam
wells or hot water wells
•There are three types of
geothermal power plants:
dry steam plants, flash
steam plants, and binary
cycle power plants

235. Direct District Heating System
•Use hot water from
springs or reservoirs near
the surface.
•Hot water near the
earth's surface can be
piped directly into
buildings and industries
for heat.

237. Dry Steam Plants
•Use steam piped
directly from a
geothermal
reservoir to turn
the turbo
generator

238. Dry Steam Geothermal Plants Cont’d
•The “Geysers” in CA
–Opened in 1960
•After 30 yrs. –temp. remains constant; pressure
drop from 3.3 to 2.3 MPa near wells
•Output–2700 MW; enough for San Francisco (pop.
780,000)
1

239. Electricity Generation
•Dry Steam Power Plant: Uses the
superheated, pressurized steam (180°-
350°C)

240. Why Haven’t We Built More Dry Steam
Geothermal Plants?
•Pro:
–Lowest Technology Required –Lowest
Capital Costs
•Con:
–Ideal Conditions Required
•Few Sites Available (Very Rare) in U.S.

241. Flash Steam Plants
•Takes high pressure hot
water from deep inside
the earth and converts it
to steam to drive the
generator turbines
•When the steam cools it
condenses into water and
is injected into the earth
to be used over and over
again.
•Most geothermal plants
are flash steam plants

242. Electricity Generation
•Flash Steam Power Plant: use hot water
above 182°C (360°F) from geothermal
reservoirs.

243. FlashSteamPowerPlantsarethemostcommonformofgeothermalpower
plant.Thehotwaterispumpedundergreatpressuretothesurface.Whenit
reachesthesurfacethepressureisreducedandasaresultsomeofthewater
changestosteam.Thisproducesa‘blast’ofsteam.Thecooledwateris
returnedtothereservoirtobeheatedbygeothermalrocksagain.

244. Electricity Generation
•Binary Cycle Power Plant:
–Insufficiently hot resource to efficiently produce steam
–Too many chemical impurities to allow flashing.

245. Binary Cycle Power Plants
•Transfers the heat from
geothermal hot water
to another liquid.
•The heat causes the
second liquid to turn to
steam which is used to
drive a generator
turbine.

246. Geothermal Power Plant Piping

247. Geothermal Power Plants and the
Environment
•Geothermal power plants
do not burn fuel to generate
electricity so their emission
levels are very low
•Release less that 1% of
carbon dioxide emissions of
a fossil fuel plant
•Use scrubber systems to
clean the air of hydrogen
sulfide
•Emits 97% less acid rain-
causing sulfur compounds
than fossil fuel plants

248. Advantages
•Very high efficiency/high net yield
•Very reliable (runs 24 hrs. a day)
•Very clean –no air pollution or GHGs
•Renewable and sustainable
•Conserves fossil fuels
•Can help decrease dependence of foreign oil
•No transportation involved

249. Disadvantages
•Can’t provide our current energy needs
•Can only be used in certain geologically active
areas
•Water contains minerals that can be corrosive
and difficult to dispose of safely
•Harmful gases can escape from deep within the
earth
•Piping system requires large areas of land
•Initial costs can be high

250. ASSOCIATED PROBLEMS
•Amajorproblemofgeothermalpoweristheestimationof
thepowerlifeofthereservoirtomakeareasonably
accuratedecisiononthesizeofstationtobebuilt.
•Thefinanciallifeofsuchastationshouldbesufficiently
longinwhichtheborrowedmoneymethodshavebeen
developedforpredictingthereservoirwithunique
features,andthepredictionoflifeofreservoirisonly
determinedonthebasisofhistoricaldevelopment;thus,
theassessmentoffieldliferemainsasubjectofcurrent
interest.
•Thesecondproblemisassociatedwiththeseparationof
steamfromthesteam-watermixturesatthewellheads
andtransmissionofsteamonlythroughalongpipelineto
thepowerhouse.

251. ASSOCIATED PROBLEMS
•Inspiteoflargeandextensivecommercialdevelopmentat
LarderelloandGeysers,theoriginandnatureofthe
geothermalsystemsthatyielddrysteamandwhythey
differfromtheabundanthotwatersystemsareyet
unknown.
•Anotherimportantproblemistheselectionofmaterials
thataresuitableforgeothermalsystemsandplants.
•Materialsshouldhavelargeresistancetocorrosionforthe
gaseousproductsandpropertiestofulfilthe
electromechanicalandotherrequirements.
•Astheautomatic-startcontrolisratherexpensive,manual-
startcontrolisused.Thus,anoperatingconditionserious
enoughtotriptheunitrequiresinvestigationattheplant
beforetheunitisrestarted.

252. ENVIRONMENTAL EFFECTS
•Considerableattentionhasbeenmadethatcanhaverelatively
smalleffectontheenvironment.
•Althoughenvironmentalistshavereasonstobelievethat
geothermalenergymayprovetobethecleanestsourceof
convertiblepowerreadilyavailable,certainundesirableeffectscan
extendforseveralkilometresfromthegeothermalfielditself;thus,
theyintroduceenvironmentalproblemsintothesurrounding
regions.
•Thesedamagestoenvironmentthatareinherentingeothermal
developmentneedcarefulstudyandsolutionsmustbefoundto
controlthematreasonablecosts.
•Thepotentialeffectsontheenvironmentofmostimmediate
concernaregaseousandparticulateemission,landpollution,
subsidencepotential,andseismicconsideration,biological,and
socialeffects.
•Researchshouldbedirectedtowardsaccuratedeterminationand
evaluationoftheircharacteristicsandmagnitudeinvestigationat
theplantbeforetheunitisrestarted.

253. ENVIRONMENTAL EFFECTS
•GaseousandParticulateEmission
•Fluidsdrawnfromthedeepearthcarryamixtureofgases,notably
carbondioxide(CO2),hydrogen
•sulphide(H2S),methane(CH4),andammonia(NH3).These
pollutantscontributetoglobalwarming,acidrain,andnoxious
smellsifreleased.Existinggeothermalelectricplantsemitan
averageof122kgofCO2permegawatt-hour(MWh)ofelectricity
andasmallfractionoftheemissionintensityofconventionalfossil
fuelplants.Plantsthatexperiencehighlevelsofacidsandvolatile
chemicalsareusuallyequippedwithemission-controlsystemsto
reducetheexhaustemissions.
•Inadditiontothedissolvedgases,hotwaterfromgeothermal
sourcesmayholdinsolutiontraceamountsoftoxicchemicalssuch
asmercury,arsenic,boron,andantimony.
•Thesechemicalsprecipitateasthewatercoolsandcancause
environmentaldamage,ifreleased.Themodernpracticeof
injectingcooledgeothermalfluidsintotheearthtostimulate
productionhasanadditionalbenefitofreducingthisenvironmental
risk.

254. ENVIRONMENTAL EFFECTS
•GaseousandParticulateEmission
•Someofthenoxiousmaterialscreatingairpollutionfromthe
existinggeothermalsteampowerplantsarehydrogensulphides,
mercuriccompounds,radioactivematerialssuchaslead210and
radon222.
•Researchmustbeappliedtoidentifythechemicalcompositionof
thenoncondensablegasderivedfromgeothermalreservoirsandto
quantitypermissibleexposurelimit.
•Basedonthesefindings,methodsforcontainmentandsafe
disposalofthesematerialsmustbedeveloped.Concomitantwith
theseresearchefforts,thereisaneedtodeveloptheanalytical
techniquesandinstrumentationtomonitorandcontrolthe
dischargeofthesematerials.
•Similarresearchmustbedirectedtowardstheemissionof
particulatematter.Particulateemissionfromanoperating
geothermalpowerplantmaynotreadilyappear,butitcanoccur.
•Thebasicneedsofresearcharethustoidentify,quantity,and
regulatethedisposalofgaseousandparticulatematterfrom
geothermalresources.

255. ENVIRONMENTAL EFFECTS
•LandPollution
•Inrelationtotheproblemoflandsurfacepollution,researchisto
bedirectedtowardspreventingthedegradationofusablesoiland
towardsthecontrolofon-sitesurfacedispositionofpollutantthat
maybetransportedsubsequentlyfromthesiteofproductiontothe
surroundingenvironment.
•Typesofthegeothermalfieldcomplicatetheseproblems.With
regardtovapour-dominatedsystem,researchisneededtoidentify
andquantifyallpollutants(suchasHg,As,Se,andPb210)inthe
vapourphaseofageothermalsourceandateachsiteproposedfor
development.
•Inconnectionwiththewater-dominatedgeothermalsystem,the
effectsofaccidentalrunoffofgeothermalfluidsfromthe
productionsitetosurroundinglandareasneedtobeassessedwith
anidentificationofsurface-depositedmaterialthatmayharmplant,
soilsterility,orbesubjectstobiologicalmagnificationandentrance
intofoodchains.
•Blowoutcontingencyplanstominimizelandpollutionbychemical
depositionandtocontrolpossibleerosionareneededateach
developedsite.

256. ENVIRONMENTAL EFFECTS
•SubsidenceEffect
•Ithasbeeninvestigatedthatsubsidenceoccursin
someareaswhenafluidisremovedfromthe
ground,whileinotherareas,theremovalof
equalquantitiesoffluidproducednomeasurable
subsidence.
•Subsidenceeffectsarebetterunderstoodfrom
studiesofboothpetroleumandgroundwater
reservoir;however,verylittlehasbeengathered
fromtheproductionofgeothermalfluids.
•Thetoolsandtechniquesforthesestudiesare
presentlyavailable.

257. ENVIRONMENTAL EFFECTS
•SeismicHazards
•Mostly,thegeothermalresourceareasareclosely
associatedwiththeregionsofhighgeologicactivity,
whichismanifestedmostcommonlyasearthquakes.
•Studieshaveshownthatiffluidpressuresarechanged
inregionsoftectonicsstresses,fluidpressuresarealso
changedinregionsofearthquakeactivity.
•Presentresearchisbeingdirectedtowardsresolving
manyquestionsregardingseismicactivitiesandsome
oftheinformationcanbeappliedtogeothermalfield.
•However,seismicmonitoringstationsshouldbe
establishednearproductivegeothermalareasto
determineifpatternsemerge;thesepatternsappearto
berelatedtotheremovalorinjectionoffluidsfrom
geothermalreservoirs.

258. ENVIRONMENTAL EFFECTS
•WaterPollution
•WaterPollutionApossibleriskassociatedwiththe
developmentandutilizationofgeothermalresourcesisthe
contaminationofsurfaceandgroundwaterbygeothermal
fluids.
•Althoughearliertoolsandtechniquesdevelopedcanbe
applied,butspecificresearchisrequiredtoidentifythose
chemicalconstituents,whichmayhaveadetrimental
effect.
•Samplecollection,analysis,andproceduresshouldbe
developedwheretheyarepresentlylackingoraretoo
expensiveforwidespreadfieldapplicationwithparticular
referencetoinjectionofgeothermalfluids.
•Chemicalandisotopicstudiesshouldbeundertakento
determineifgeothermalfluidswillreturntothereservoir
fromwhichtheyareproducedoriftheymigrateintoother
reservoirs.

259. ENVIRONMENTAL EFFECTS
•BiologicalEffects
•Numerousunknowneffectsexistregardingtheimpactof
geothermaloperationuponthebionaturetoprospective
resourceareaaswellasareaspresentlyunderexplorationor
development.
•Giventhedelicatebalanceofnaturalenvironment,damage
tomanyspeciesofplantandanimallifecantakeplace
throughchangesofchemicalbalanceinsoilandwater,the
useoftoxicsubstancesinindustrialapplication,the
destructionofsuchspecializedhabitantsasthermalpools
alpinemeadow,theinterruptionofmigratorypatterns,long
termalterationinhumidity,andtheintroductionofhuman
presence,andactivityintoformerlyunaffectedregions.
•Theseandotherfactorsneedcriticalstudyin
representativelyselectedgeothermalresourceareasto
determinenecessaryproceduresfortheadequateprotection
ofplantsandanimallifeinregionsofdevelopment.

260. ENVIRONMENTAL EFFECTS
•SocialEffects
•Serioussocialeffectsarisingfromgeothermal
resourcedevelopment,whichneedresearch,
involveproblemsofnoiseandlanduse.
•Sociological,economical,andplanningstudiesare
greatlyneededtodeterminepublicpolicyforthe
equitableresolutionofconflictsoflandusearising
inthesecases.

261. Module4
:Biomass
Energy
•Solarenergybymeansofphotosynthesisstoresenergyintrees
andplantsthatcanbeconvertedintoliquidfuelssuitablefor
internalcombustionengines.
•Similarly,ethanolcouldbeproducedfromcelluloseonlarge
scale.
•Thereisnodoubtthatrisingenergycostswillleadtomore
concentratedresearchofsuchbiologicalsystem;suchthat,
energygainsmadeviaplantphotosynthesisusingintensive
systemsaresubsequentlymorethanthatlostintheconversionof
biomassenergycontentintostorablehighenergyfuels(i.e.,
ethanolormethane).
•Thegrowthofsugarcaneanditsfermentationtoethanolmaybe
consideredtobethemostfavourableforthemarginalnetenergy
productionprocess,whichissuitableforIndianclimatic
conditions.
•Biomassisusedforheating,electricpowergeneration,and
combinedheatandpower.
•Severalmethodsareusedfortheconversionofbiomassinto
usefulenergy,suchaselectricitygenerationbydirectburningof
biomass,synthesisgasproductionbygasification,andmethane
gasproductionbyanaerobicdigestion.

262. Module4
:Biomass
Energy
•However,followingissuesmaybethoroughlyinvestigated
forimplementingbiomassproductionscheme:
1.Thetypesofvegetationbestsuitedforanintensiveenergy
plantationandbiogenerationselectioncriteria.
2.Thetypeandavailabilityoflandforgrowingenergycrops
andplantmaterialproductions.
3.Harvestingforconceptualplantation.
4.Techno-economiccomparisonoffiringcropsdirectlyfor
electricpowergenerationwithconversiontocleanfuelgas
(methaneorlowBTUgas)eitheratthefarmsiteoratthe
selectedmarket.

263. BIOMASS
PRODUCTION
•Sunistheprimarysourceofallkindsofavailablerawenergyresourcesincluding
biomass.
•Thesunlightenergyistransferredtobiospherebythephotosynthesisprocess
thatoccursinplants,algae,andsometypesofbacteria.
•Plantmattercreatedbytheprocessofphotosynthesisiscalledbiomass.
Photosynthesisisanaturalradiation.
•Initssimplestform,thefinalreactionofthisprocesscanberepresentedas
follows:
•6HO22CO61262++solarlightenergy→+CHOCO
•Itisseenthatintheprocess,waterandcarbondioxideareconvertedinto
organicmaterial.
•Thetermbiomassreferstothoseorganicmattersthatarestoredinplantand
treesintheformofcarbohydrate(sugar).
•Itisthentransferredthroughfoodchainsinhumans,animals,andotherliving
creaturesandtheirwastes.
•Thetermbiomassincludesallplantlife:trees,agriculturalplants,bush,grass
andalgae,andtheirresiduesafterprocessing.Biomassmaybeobtainedfrom
forestswoods,agriculturallands,aridlands,andevenwastelands.
•Itmaybeobtainedinaplannedorunplannedmanner.Thetermisalsogenerally
understoodtoincludeanimalandhumanwaste.Biomasshastheadvantageof
controllabilityandavailabilitywhencomparedtomanyotherrenewableenergy
options.
•Thereareavarietyofwaysofobtainingenergyfrombiomass.Thesemaybe
broadlyclassifiedasdirectmethodsandindirectmethods.

264. BIOMASS
PRODUCTION
1.Direct
Methods
•Rawmaterialsthatcanbeusedtoproducebiomassenergyareavailable
throughouttheworldinthefollowingforms:
1.Forestwoodandwastes
2.Agriculturalcropsandresidues
3.Residentialfoodwastes
4.Industrialwastes
5.Humanandanimalwastes
6.Energycrops
•Properlymanagedforestswillalwayshavemoretrees,andagriculturaland
energycropsmanagementwillalwayshavecrops;further,theresidualbiological
matteraretakenfromthosecrops.
•Rawbiomasshasalowenergydensitybasedontheirphysicalformsand
moisturecontentsandtheirdirectuseareburningthemtoproduceheatfor
cooking.
•Thetwinproblemsoftraditionalbiomassuseforcookingandheatingarethe
energyinefficiencyandexcessivepollution.
•Inefficientwayofdirectcookingapplications,inconvenientandinefficient
methodsofrawbiomasstransportationandstorageandhighenvironmental
pollutionproblemsmadethemunsuitableforefficientandeffectiveuse.
•Thisnecessitatedsomekindofpre-processingandconversiontechnologyfor
enhancingtheusefulnessofbiomass

265. BIOMASS
PRODUCTION
2. Indirect
Methods
•Biomasscanalsobeusedindirectlybyconvertingiteitherintoelectricityand
heatorintoaconvenientusablefuelinsolid,liquid,orgaseousform.
•Theefficientconversionprocessesareasfollows:
•1.Thermo-electricalconversion:Thedirectcombustionofbiomassmaterialin
theboilerproducessteamthatisusedeithertodriveaturbinecoupledwithan
electricalgeneratortoproduceelectricityortoprovideheatforresidentialand
industrialsystem.
•However,theboilerequipmentareveryexpensiveandenergyrecoveryislow.
Fortunately,improvedpollutioncontrolsandcombustionengineeringhave
advancedtothepointthatanyemissionsfromburningbiomassinindustrial
facilitiesaregenerallylesswhencomparedtotheemissionsproducedwhen
usingfossilfuels(coal,naturalgas,andoil).
•2.Biomassconversiontofuel:Underpresentconditions,economicfactorsseem
toprovidethestrongestargumentofconsideringbiomassconversiontofuel
suchasfermentationandgasification.
•Inmanysituations,wherethepriceofpetroleumfuelsishighorwheresupplies
areunreliable,thebiomassgasificationcanprovideaneconomicallyviable
system,providedthesuitablebiomassfeedstockiseasilyavailable.

266. BIOMASS
PRODUCTION
2. Indirect
Methods
•Biomassconversionprocessescanbeclassifiedundertwomaintypes:
•(a)Thermo-chemicalconversionincludesprocessessuchasdestructive
distillation,pyrolysis,andgasification.
•(b)Biologicalconversionincludesprocessessuchasfermentationand
anaerobicdigestion.
•Gasificationproducesasynthesisgaswithusableenergycontentby
heatingthebiomasswithlessoxygenthanneededforcomplete
combustion.
•Pyrolysisyieldsbio-oilbyrapidlyheatingthebiomassintheabsenceof
oxygen.
•Anaerobicdigestionproducesarenewablenaturalgas(methanegas)
whenorganicmatterisdecomposedbybacteriaintheabsenceof
oxygen.
•Asaresult,itisoftenadvantageoustoconvertthiswasteintomore
readilyusablefuelformlikeproducergas.
•Hence,itistheattractivenessofgasification.Theefficiencyofadirect
combustionorbiomassgasificationsystemisinfluencedbyanumberof
factorssuchasincludingbiomassmoisturecontent,combustionair
distributionandamounts(excessair),operatingtemperatureand
pressure,andfluegas(exhaust)temperature.

267. ENERGY
PLANTATION
•Aninterestingapproachforthelarge-scaleplanneduseof
woodisthe‘energyplantation’approach.
•Inthisscheme,selectedspeciesoftreesareplantedand
harvestedoverregularintervalsoftimeinaphasedmanner
sothatwoodiscontinuouslyavailableforcookingorallied
purposes.
•Energyplantationsinclude,amongstothers,pine,
cottonwood,hybridpoplar,sweetgum,andeucalyptus.
•Muchoftheemphasishasbeenonhardwoodplantations
duetotheirabilitytocoppice,continuedgenetic
improvementprogramsaswellastheopportunityto
combinefastgrowthandwood.
•SomeimportanttreesgrowninIndiaforthispurposeare
eucalyptus,babool,andcasuarinas.
•Arichexperienceofcommercialenergyplantations
managementsysteminvariedclimaticconditionshas
emergedduringthepast4–5decades.

268. ENERGY
PLANTATION
•Improvementsinsoilpreparation,planting,cultivationmethods,
speciesmatching,biogeneticsandpest,diseaseandfirecontrol
haveledtoenhancedyields.
•Ithasbeensuggestedthatelectricalpowerbeproducedbythe
energyplantationapproach,thewoodgrowninthismanner
beingusedasafuelfortheboilersofaconventionalpowerplant.
•Thetechnologyofbiomass-basedelectricpowerplantsiswell
establishedintheUSAandEuropeandthereareover500such
plantsusewood,woodwaste,andvarioustypesofagricultural
waste.
•Whenaphotosyntheticconversionefficiencyofaround1%is
assumed,itisestimatedthata1,000MWpowerplantmay
requireanareaofabout1,000km2fortheenergyplantation.
•Althoughthisisalargearea,itshouldnotbedifficulttoprovidein
mostcountriessincethelandrequiredneednotdisplace
agriculturalland.However,carehasbeentakensothatthereisno
dangerofmonocultureweakeningtheecologicalsystem.

269. BIOMASS GASIFICATION
•Biomassgasificationisaprocessofpartialcombustioninwhichsolid
biomassusuallyintheformofpiecesofwoodoragriculturalresidueis
convertedintoacombustiblegasmixture.
•Gasification,whichisincompletecombustionofcarbonaceousfuels,
canberepresentedwiththefollowingsub-stoichiometricequation.
Biomass+air→carbonmonoxide(CO)+carbondioxide(CO2)+
methane(CH4)+hydrogen(H2)+nitrogen(N2)+watervapour.
•Gasificationproducesasynthesisgaswithusableenergycontentis
producedbygasificationinwhichbiomassisheatedwithlessoxygen
thanthatneededforcompletecombustion.
•Asaresult,agaseousmixtureofcarbonmonoxide(CO),carbondioxide
(CO2),methane(CH4),hydrogen(H2),andnitrogen(N2)called
producergasisobtained.
•Producergascanbeused
•1.toruninternalcombustionengines(bothcompressionandspark
ignition)
•2.assubstituteforfurnaceoilindirectheatapplicationsand
•3.toproduce,inaneconomicallyviableway,methanol

270. BIOMASS GASIFICATION
•Methanolisanextremelyattractivechemicalthatisusefulbothasfuel
forheatenginesaswellaschemicalfeedstockforindustries.
•Sinceanybiomassmaterialcanundergogasification,thisprocessis
muchmoreattractivethanethanolproductionorbiogaswhereonly
selectedbiomassmaterialscanproducethefuel.
•Gasificationprocessesinvolvedwithbiomassareasfollows:
•1.Dryingoffuels:Itistheprocessofdryingbiomassbeforeitisfed
intogasifier.
•2.Pyrolysis:Itisaprocessofbreakingdownbiomassintocharcoalby
applyingheattobiomassintheabsenceofoxygen.
•3.Combustion:Alltheheatrequiredfordifferentprocessesof
gasificationaremadeavailablefromcombustions.
•4.Cracking:Inthisprocess,breakingdownoflargecomplexmolecules
(suchastar)takesplacewhenheatedintolightergases.
•5.Reduction:Oxygenatomsareremovedinthisprocessfromthe
combustionproducts(hydrocarbon)moleculesandreturningthemto
combustibleformagain.

271. BIOMASS GASIFICATION
1.LowTemperatureGasification
•Whengasificationofbiomassiscarriedoutat750°Cto1,100°C,itis
referredtoaslowtemperaturegasification.
•Thegasproducedhasrelativelyhighlevelofhydrocarbons.Itisused
directlytoeitherburnforsteamproductionandgenerationof
electricityorcleanedandusedininternalcombustionengineor
combinedheatpower(CHP).
•Theproducergasisamixtureofcarbonmonoxide(CO),carbondioxide
(CO2),hydrogen(H2),methane(CH4),andnitrogenfromair.Thegas
mixturecompositiondependsongasifiers.
•2.HighTemperatureGasification
•Itiscarriedoutintemperaturerangeof1,200°C–1,600°Candgas
productisreferredtoassynthesisgas(Syngas).
•ItcontainshighproportionofCOandH2andisconvertibletohigh
qualitysyntheticdieselbiofuelcompatibleforuseindieselengines

272. BIOMASS GASIFICATION
3.CompositionandPropertiesofProducerGas
•Theproducergasisaffectedbyvariousprocessesasabovementioned,
andhenceonecanexpectvariationsinthegasproducedfromvarious
biomasssources.
•Thecompositionofproducergasishighlydependentupontheinputs
tothegasifierandgasifierdesign.Table9.1liststhecompositionof
gasproducedfromvarioussources.
•Nitrogenaffectsthemaximumdilutionofgasandalmost50%–60%of
gasiscomposedofnoncombustiblenitrogen.
•Theuseofoxygeninsteadofairwillbebeneficialforgasificationwith
dueregardstothecostsofoxygen.
•Nevertheless,productionofahighenergyqualitymethanolmay
justifythecostofoxygen.
•Onanaverage,1kgofbiomassproducesabout2.5m3ofproducer
gasatS.T.Pandconsumesabout1.5m3ofairforcombustion.
•Forcompletecombustionofwood,about4.5m3ofairisrequired.

273. BIOMASS GASIFICATION

274. BIOMASS GASIFICATION
4. Temperature of Gas
•Theaveragegastemperatureproducedbygasifierisabout300°C–400°Cand
itmayevenattainahighertemperatureofapproximately500°C,ifpartial
combustionofgasistakingplace.
•Partialcombustionofbiomasscanbeeliminatedbyincreasingairflowrate
higherthanthedesignvalue

275. THEORY OF GASIFICATION
•Gasificationmaybeconsideredasaspecialcaseofpyrolysiswheredestructive
decompositionofbiomass(woodwastes)byheatisconvertedintocharcoal,
oils,tars,andcombustiblegas.
•Itisreferredtoasthepartialcombustionofsolidfuel(biomass)andtakes
placeattemperaturesofabout1,000°C.
•Thereactorusedforgasificationiscalledagasifier.Thecompletecombustion
ofbiomassproducesbiomassgassesthatgenerallycontainnitrogen,water
vapour,carbondioxide,andsurplusofoxygen.
•However,ingasification(withincompletecombustion),asshowninFigure9.1,
productgascontainsgasessuchascarbonmonooxide(CO),hydrogen(H2),
andtracesofmethaneandnon-usefulproductssuchastaranddust.
•Theproductionofthesegasesisobtainedbythereactionofwatervapourand
carbondioxidethroughaglowinglayerofcharcoal.Thus,thekeytogasifier
designistocreateconditionssuchthat

276. THEORY OF GASIFICATION

277. GASIFIER AND THEIR CLASSIFICATIONS
•Biomass gasifier may be considered as a chemical reactor
in which biomass goes through several complex physical
and chemical processes and producer or syngas is
produced and recovered.
•There are two distinct types of gasifier:
•1. Fixed bed gasifier: In this gasifier, biomass fuels move
either countercurrent or concurrent to the flow of
gasification medium (steam, air, or oxygen) as the fuel is
converted to fuel gas.
•They are relatively simple to operate and have reduced
erosion. Since there is an interaction of air or oxygen and
biomass in the gasifier, they are classified according to the
way air or oxygen is introduced in it.

278. GASIFIER AND THEIR CLASSIFICATIONS

279. GASIFIER AND THEIR CLASSIFICATIONS
•There are three types of gasifier as shown in Figure 9.2.

280. GASIFIER AND THEIR CLASSIFICATIONS
•(a)Updraftgasifiers:
•Updraftgasifierhasairpassingthroughthebiomassfrombottomandthe
combustiblegasescomeoutfromthetopofthegasifier.

281. GASIFIER AND THEIR CLASSIFICATIONS
•(b)Downdraftgasifiers:
•Inthedowndraftgasifier,theairispassedfromthelayersinthedowndraft
direction.Singlethroatgasifiersaremainlyusedforstationaryapplications,
whereasdoublethroatgasifierisusedforvaryingloadsaswellasautomotive
purposes.

282. GASIFIER AND THEIR CLASSIFICATIONS
•(c)Crossdraftgasifiers:
•Itisaverysimplegasifierandishighlysuitableforsmalloutputs.Withslight
variation,almostallthegasifiersfallintheabovementionedcategories.
•Thechoiceofonetypeofgasifieroverotherisdictatedbythefuel,itsfinal
availableform,itssize,moisturecontent,andashcontent.
•2.Fluidizedbedgasifier:Influidizedbedgasifier,aninertmaterial(suchas
sand,ash,orchar)isutilizedtomakebedandthatactsasaheattransfer
medium

283. Advantages and Disadvantages of Fixed Bed Gasifiers

284. CHEMISTRY OF REACTION PROCESS IN GASIFICATION
•Fourdistinctprocessestakeplaceinagasifierwhenfuelmakesitswayto
gasification:
1.Dryingzoneoffuel:Inthiszone,themoisturecontentofbiomassisremovedto
obtainthedrybiomass.Someorganicacidsalsocomeoutduringthedrying
process.Theseacidsgiverisetocorrosionofgasifiers.
2.Pyrolysiszone:Inthiszone,thetarandothervolatilesaredrivenoff.The
productsdependupontemperature,pressure,residencetime,andheatlosses.
However,followinggeneralremarkscanbemadeaboutthem.
(a)Uptothetemperatureof200°C,onlywaterisdrivenoff.
(b)Between200°Cand280°Ccarbondioxide,aceticacid,andwateraregivenoff.
(c)Therealpyrolysis,whichtakesplacebetween280°Cand500°C,produceslarge
quantitiesoftarandgasescontainingcarbondioxide.Besideslighttars,some
methylalcoholisalsoformed.
(d)Between500°Cand700°C,thegasproductionissmallandcontainshydrogen.
3.Combustion(oxidation)zone:Inthiszone,carbonfromthefuelcombustand
formscarbondioxidewiththeoxygenintheairbythereaction:
C + O2 → CO2 + Heat
Becauseoftheheatemittedduringthereaction,thetemperaturerisesuntila
balancebetweenheatsupplyandheatlossoccurs

285. CHEMISTRY OF REACTION PROCESS IN GASIFICATION
•4.Reductionzone:Thehotgaspassesthroughthereductionzoneafterthe
combustionzone.
•Asthereisnofreeoxygeninthiszonethatcausesinflammablecarbondioxide
gastoreactwiththecarboninthefuelandformsflammablecarbonmonoxide
gas.
•Thisreactionisendothermic(demandsheat)andoccursattemperature
exceedingabout1,000°C.
•Carbonmonoxideisthemostimportantflammableelementsintheproduced
gasobtainedfromthereductionreactionas
•C + CO2 + heat → 2CO (9.3)
•Anotherimportantendothermicreactioninthereductionzoneisthewater–gas
shiftreaction.
•Itisthereactionofwatervapourandcarbontogivecarbonmonoxideand
hydrogen
•C + H2O + Heat → CO + H2 (9.4)
•Bothgassesareflammable,andtheheatingvalueofthegasisincreased.If
thereisstillsurplusofwaterinthereductionzone,thencarbonmonoxidemay
reactwithwatervapourandformcarbondioxideandhydrogen.
•Thisreactionisexothermic(emitsheat)anddecreasestheheatingvalueofthe
producedgas.ThereactionisCO+H2O−Heat→CO2+H2(9.5)
•Equations(9.3)and(9.4)aremainreductionreactionsandbeingendothermic
havethecapabilityofreducinggastemperature.Consequently,the
temperaturesinthereductionzonearenormally800°C–1,000°C.Thelowerthe
reductionzonetemperature(~700°C–800°C),loweristhecalorificvalueofgas

286. CHEMISTRY OF REACTION PROCESS IN GASIFICATION
•Equations(9.3)and(9.4)aremainreductionreactionsandbeingendothermic
havethecapabilityofreducinggastemperature.
•Consequently,thetemperaturesinthereductionzonearenormally800°C–
1,000°C.Thelowerthereductionzonetemperature(~700°C–800°C),loweristhe
calorificvalueofgas.
•Thegasalsocontainsmeasurableamountsofparticulatematerialandtar.
•Theheatingvalueofthegasrangesfrom4,000to5,000kJ/m3,whichisa
relativelylowvaluewhencomparedtotheheatingvalueofothergaseousfuels
likenaturalgas.
•Theconversionefficiencyofagasifierisdefinedastheratiooftheheatcontent
intheproducergastotheheatcontentinthebiomasssuppliedandisusually
around75%.
•Althoughthereisaconsiderableoverlapoftheprocesses,eachcanbeassumed
tooccupyaseparatezonewherefundamentallydifferentchemicalandthermal
reactionstakeplace.

287. UPDRAFT GASIFIERS
•Theoldestandsimplesttypeofgasifieristhecountercurrentorupdraftgasifier
shownschematicallyinFigure9.3.Theairintakeisatthebottomandgasleaves
atthetop(thecountercurrentflow).
•Thereactiveagentisinjectedatthebottomofthereactorandascendstothe
top,whilethefuelisintroducedatthetopanddescendstothebottom.
•Thecombustionreactionsoccurnearthegrateatthebottomthatarefollowed
byreductionreactionssomewhathigherupinthegasifier.
•Intheupperpartofthegasifier,heatingandpyrolysisofthefeedstockoccurasa
resultofheattransferbyforcedconvectionandradiationfromthelowerzones.
Gases,tar,andothervolatilecompoundsaredispersedatthetopofthereactor,
whileashisremovedatthebottom.
•Thesyngastypicallycontainshighlevelsoftar,whichmustberemovedor
furtherconvertedtosyngasforuseinapplicationsotherthandirectheating.
•Updraftgasifiersarewidelyusedtogasifybiomassresourcesandgenerallyuse
steamasthereactiveagent,butslaggingcanbesevereifhighashfuelsare
used.Theyareunsuitableforusewithfluffy,low-densityfuels.
•Thesegasifiersarebestsuitedforapplicationswheremoderateamountsofdust
inthefuelgasareacceptableandahighflametemperatureisrequired.
•Typicalapplicationswheretheupdraftgasifiershavebeensuccessfullyusedare
asfollows:
•1.Packagedboilers2.Thermalfluidheaters3.Aluminiummelting/annealing
furnaces4.Allkindsoffryerroaster

288. DOWNDRAFT GASIFIER
•Inthisgasifiers,theprimarygasificationairisintroducedatorabovethe
oxidationzoneinthegasifierandtheproducergasisremovedatthebottomof
theapparatus,sothatfuelandgasmoveinthesamedirection,asschematically
showninFigure9.4.
•Thebiomassfeed(suchaswoodwaste)anditsgasificationairbothflowinthe
samedownwarddirectionthroughthegasifiers’fuelbed.
•Thebiomassfeedisadmittedatthetopsimilartotheupdraftgasifier.Asthe
feedprogressesdownthroughthegasifier,itdriesanditsvolatilesarepyrolysed.
•Thecharisdirectedintoareduceddiametercylindricalthroatsectionatthe
bottomofthegasifier.Gasificationairisinjectedintothethroatthrough
openingsinthethroatwall.
•Duetothehightemperaturesexistingatthethroatsection,tarsandoilscould
becracked,whichtendtoforminproducergas,particularlywhenthebiomassis
wetterthanabout20%moisturecontent(wetbasis).Theproducergasleavesat
thebottomofthegasifier.
•Thestart-uptimeofabout5–10minisnecessarytoigniteandbringplantto
workingtemperaturewithgoodgasqualityisshorterthanupdraftgasproducer.
•Downdraftgasifiersarewidelyusedinthefollowingapplications:
•1.Continuousbakingovens(bread,biscuits,andpaint)2.Batchtypebaking
oven(rotaryovenforbread)3.Dryersandcuring(tea,coffee,mosquitocoil,and
paperdrying)4.Boilers5.Thermalfluidheaters.6.Annealingfurnaces7.Direct
firedrotarykilns8.Internalcombustionengines

289. CROSS-DRAFT GASIFIER
•Unlikedowndraftandupdraftgasifiers,theash
bin,fire,andreductionzoneincross-draft
gasifiersareseparated.
•Thesedesigncharacteristicslimitthetypeof
fuelforoperationtolowashfuelssuchas
wood,charcoal,andcoke.
•Therelativelyhightemperatureincross-draft
gasproducerhasanobviouseffectongas
compositionsuchashighcarbonmonoxide,
andlowhydrogenandmethanecontentwhen
dryfuellikecharcoalisused.
•Cross-draftgasifieroperateswellondryair
blastanddryfuel.Typically,thegasifierisa
verticalcylindricalvesselofvaryingcross
section.
•Thebiomassisfedinatthetopatregular
intervalsoftimeandisconvertedthrougha
seriesofprocessesintoproducergasandash,
asitmovesdownslowlythroughvariouszones
ofthegasifier.

290. Advantages and Benefits
•Thefluidizedbedgasificationprocessoffersseveralsubstantialbenefitswhen
comparedtosimpleburningprocessesandotherformsofgasification.
•Advantages
•1.Reducedcostofboilerordryerorkilnoperationbyusingwoodand/orbark
wastesratherthangasoroil
•2.Reducedcostforadditionalsteamingcapacitywhencomparedtonewwood
andorbarkfiredboilers.
•3.Reduceddependencyonexternalfuelsourcesforpropane,naturalgas,and
oil.
•Benefits
•1.Highoverallefficiency:Highefficiencyintherangeof70%–90%canbe
achieved.Moisturecontentsandtheashcontentsreducedtheoverallthermal
efficiencyoffluidizedbedgasifier
•2.Fuelflexibility:Thefluidizedbedgasifiershavefuelflexibilityandoperate
satisfactorilywithhighlyvariablefeedmaterials.Rangingfromcoal,shredded
woodandbarktosawdustfines,orlumpwoodwithparticlesizesoflessthan
4–6cm.Thus,thevarioustypesoffuelsgenerallyavailablearoundlumbermills
canbeusedinfluidbedgasifierswithgoodresults.
•3.Highlyreliable:Thefluidizedbedgasifierneitherhavemovinggratesnor
othermovingpartsinthehightemperatureregionsofthebedandhencethey
arehighlyreliable.

291. Advantages and Benefits
•4.Lowpurchaseandinstallationcosts:
•Airflowusedinthegasifiersiscomparativelylow,andhencesizeofgasifieris
smallandcompact.Thesepermitsystemstobecompletelyshopfabricatedand
assembledonskids,therebyreducingpurchasepriceandinstalledcosts.
•5.Flexibleoperations:Fuelgasproductoffluidizedbedgasifieriseasilyapplied
toavarietyofindustrialprocessesincludingboilers,drykilns,veneerdryers,or
severalpiecesofequipmentatonce.Thus,theyprovideflexibleoperations.
•6.Lowemissions:Theyareverylowemissiongasifiersanddonotrequire
exhaustcleanupdevices
USE OF BIOMASS GASIFIER
•Theoutputofabiomassgasifiercanbeusedforavarietyofdirectthermal
applicationssuchascooking,drying,heatingwater,andgeneratingsteam.
•Itcanalsobeusedasafuelforinternalcombustionenginestoobtain
mechanicalshaftpowerorelectricalpower.Ifusedasafuelforinternal
combustionengines,ithastobecleanedfirstforcompleteremovalof
particulatematerialandtar.
•Acleaningsystemconsistingofcyclone,ascrubber,andafilterisusedforthe
purpose.Iftheengineisaspark-ignitionengine,itcanoperatewithproducer
gasalone.
•Thegasissuckedfromthegasifierandcleanerunitbytheenginesuctionalong
withaproportionateamountofair.

292. USE OF BIOMASS GASIFIER
•Itisthencompression-ignitionengine,asitoperatesinthe‘dual-fuel’mode.
Here,theenginesucksinamixturethatiscompressedandasmallamountof
dieselsprayedin.
•Combustioninitiateswiththedieseldropletsandthenspreadstothemixtureof
thegaseousfuelandair.
•Thephrase‘dual-fuel’impliesthatbothdieselandproducergasare
simultaneouslyused.
•Indiaisoneoftheleadingcountriesintheworldinthefieldofbiomass
gasification.
•Biomassgasifiersystemsareavailableinawiderangeofcapacitiesandstandard
facilitiesfortestingandevaluatinggasifiershavebeensetup.Forthermal
applications,systemswithoutputsrangingfrom60,000to5×106kJ/hare
available,whileforelectricalpowergeneration,systemswithoutputsranging
from3to500kWarealsoavailable.
•Thelargestbiomassgasificationsystemproduces5×106kJ/h(1,450kW)
outputinthethermalmodeand500kWintheelectricpowergenerationmode.
•Itusesbiomassintheformofwoodblocks(25to100mmlongandupto70
mmindiameter)attherateof500kg/handproduces1,250m3/hofgas.The
internalcombustionengineisacompressionignitionengineoperatinginthe
dual-fuelmode.Itusesonly25%ofthedieselnormallyrequiredbytheengineif
operatingwithdieselalone.

293. Liquid Fuels
•Whencomparedtogaseousfuelssuchasproducergasorbiogas,liquidfuels
aresomewhathardertoobtainfrombiomasssources.
•Oneofthemethodsistheproductionofmethanolfromwoodorstraw.The
processinvolvesthegasificationofplantmatterfollowedbychemicalsynthesis.
•Anothermethodistheconversionofcertainfoodgrainsandcropssuchas
sugarcane,maize,cassavaandtapiocabyfermentationintoethanol.
•Whenblendedwithpetrol,ethanolisgoodalternatefuelforautomotive
engines.
•Thisfacthasreceivedconsiderableattentionasameansofovercomingtheoil
crisis.
•However,ifoneexaminestherequirementoflandforgrowingtheagricultural
productsconcerned,itisobviousthatthemethodcanbeofsubstantialbenefit
onlytoacountryhavingalargesurplusofland.
•Forthisreason,Brazilhasadoptedthismethodonalargescaleandproduces
significantamountsofethanolforuseasanalternatefuel.However,the
positioninIndiaisquitedifferentsincetheavailabilityoflandislimited.
•Inplants,algaeandcertaintypesofbacteria,thephotosyntheticprocessresults
inthereleaseofmolecularoxygenandtheremovalofcarbondioxidefromthe
atmospherethatisusedtosynthesizecarbohydrates(oxygenicphotosynthesis).
•Othertypesofbacteriauselightenergytocreateorganiccompoundsbutdo
notproduceoxygen(anoxygenicphotosynthesis).

294. Liquid Fuels
•Photosynthesisprovidestheenergyandreducedcarbonrequiredforthe
survivalofvirtuallyalllifeonourplanet,aswellasthemolecularoxygen
necessaryforthesurvivalofoxygenconsumingorganism.
•Inaddition,thefossilfuels,currentlybeingburnedtoprovideenergyforhuman
activity,wereproducedbyancientphotosyntheticorganisms.
•GASIFIERBIOMASSFEEDCHARACTERISTICS
•Mostofgasifiermanufacturersclaimthatagasifierisavailableandcangasify
anybiomassfeed.However,thereisnosuchthingasauniversalgasifier.
•Agasifierisinrealsenseverymuchbiomassfeedspecificanditistailored
accordingly.
•Followingbiomassfeedcharacteristicsorparametersdictatethequalityand
classificationofgasifiers:
•1.Energycontentofthefuel
•2.Bulkdensity
•3.Moisturecontent
•4.Dustcontent
•5.Tarcontent
•6.Ashandsloggingcharacteristic

295. GASIFIER BIOMASS FEED CHARACTERISTICS
•EnergyContentandBulkDensityofFuel
•Thehighertheenergycontentandbulkdensityoffuel,thesimilaristhegasifier
volume;asforonebiomassfuelcharge,powercanbeobtainedforlongertime
duration.
•MoistureContent
•Moisturecontentisverytrivialcomponentsofbiomassfuelsanditis
determinedbythetypeoffuel,itsorigin,andtreatment.
•Itisdesirabletousefuelwithlowmoisturecontenttominimizeheatlossdueto
itsevaporation.Besidesimpairingthegasifierheatbudget,highmoisture
contentalsoputsloadoncoolingandfilteringequipmentbyincreasingthe
pressuredropacrosstheseunitsbecauseofcondensingliquid.
•Thus,inordertoreducethemoisturecontentoffuel,somepre-treatmentof
fuelisrequired.Generally,desirablemoisturecontentforfuelshouldbeless
than20%.
•DustContent
•Allgasifierfuelsproduceundesirabledustthatcanclogtheinternalcombustion
engineandhenceithastoberemoved.
•Thegasifierdesignshouldbesuchthatitshouldnotproducedustbeyond
specifiedlimits.
•Thehigherthedustproduced,moreistheloadputonfiltersnecessitatingtheir
frequentflushingandincreasedmaintenance.

296. GASIFIER BIOMASS FEED CHARACTERISTICS
•TarContent
•Tarisoneofthemostunpleasantconstituentsofthegasasittendstodeposit
inthecarburettorandintakevalvescausingstickingandtroublesome
operations.
•Itisaproductofhighlyirreversibleprocesstakingplaceinthepyrolysiszone.
•Thereareapproximately200chemicalconstituentsthathavebeenidentifiedin
tarsofar.Verylittleresearchworkhasbeendoneintheareaofremovingor
burningtarinthegasifiersothatrelativelytarfreegascomesout.
•Thus,themajorefforthasbeendevotedtocleaningthistarbyfiltersand
coolers.
•AshandSlaggingCharacteristics
•Themineralcontentinthefuelthatremainsinoxidizedformaftercomplete
combustionisusuallycalledash.Theashcontentofafuelandtheash
compositionhasamajorimpactontroublefreeoperationofgasifier.
•Ashbasicallyinterfereswiththegasificationprocessintwoways:
•1.Itfusestogethertoformslagandthisclinkerstopsorinhibitsthedownward
flowofbiomassfeed.
•2.Evenifitdoesnotfusetogether,itsheltersthepointsinfuelwhereignitionis
initiated,andthuslowersthefuel’sreactionresponse.

297. GASIFIER BIOMASS FEED CHARACTERISTICS
•Ashandtarremovalarethetwomostimportantprocessesingasification
systemforitssmoothrunning.However,slaggingcanbeovercomebytwotypes
ofoperationofgasifier:
•1.Lowtemperatureoperationthatkeepsthetemperaturewellbelowtheflow
temperatureoftheash.
•2.Hightemperatureoperationthatkeepsthetemperatureabovethemelting
pointofash.
•Thefirstmethodisusuallyaccomplishedbysteamorwaterinjection,whilethe
lattermethodrequiresprovisionsfortappingthemoltenslagoutofthe
oxidationzone.
•Eachmethodhasitsadvantagesanddisadvantagesanddependsonspecificfuel
andgasifierdesign.Keepinginmindtheabovementionedcharacteristicsoffuel,
onlytwofuelshavebeenthoroughlytestedandproventobereliable.
•Theyarecharcoalandwood.Ascharcoalistarfreeandhasrelativelylowash
contentproperty,itwasthepreferredfuelduringWorldWarIIandstillremains
so.However,thereisamajordisadvantageofcharcoalintermsofenergy.
•Charcoalismostlyproducedfromwoodandintheconversionofwoodto
charcoal,about50%oforiginalenergyislost

298. GASIFIER BIOMASS FEED CHARACTERISTICS
•BiomassFeed(Fuel)
•Themajorbiomasssourcespresentlyusedareasfollows:
•1.Sugarcaneandcorn,wheat,sugarbeet,sweetsorghum,andcassavato
producebioethanol.
•2.Rapeseed,sunflowerseeds,soybean,canola,peanuts,jatropha,coconut,and
palmoilforbiodieselproduction.
•3.Widerangeofcellulosicmaterials(suchasgrassycrops,woodyplants,by-
productsfromtheforestryandagriculturalsectorincludingwoodresidues,
stems,andstalksandmunicipalwastesconstitutetheso-calledsecond
generationoffeedstock).
•4.Wastesandresiduesconstitutealargesourceofbiomass.Theseincludesolid
andliquidmunicipalwastes,manure,lumberandpulpmillwastes,andforest
andagriculturalresidues.
•Lowwatercontent(dried)biomassfeedstockisburnttogenerateheatand
electricity.Woodwastesinthepaperandpulpindustriesandbagassefromthe
sugarcaneindustryareusedinethanolfermentation.
•Avarietyofrawmaterialsthatincludeagriculturalwastes,municipalsolid
wastes,marketgarbage,andwaste,waterfromfoodandfermentation
industries(allorganicmaterialscontainingcarbohydrates,lipids,andproteins)
arefeedstockforanaerobicdigesterformethaneproduction.

299. APPLICATIONS OF BIOMASS GASIFIERS
•Themainapplicationsofbiomassgasifierproductsareasfollows:
•1.Motivepower:Gasifierproductsareusedtoprovideshaftpowertoindustrial
andagriculturalequipmentandmachinerysuchas
•(a)Dieselengineoperationondualor100%modes.
•(b)Waterpumps
•(c)Tractors,harvesters,etc.
•(d)RunningofhighefficiencyStirlingengines.
•2.Directheatapplications:Gasifiersheathasdirectheatapplicationssuchas
•(a)Dryingofagriculturalcropandfoodproductssuchaslargecardamom,
ginger,rubber,andteaatlowtemperaturerangeofabout85°C–125°C.
•(b)Bakingoftilesandpotteriesinthemoderatetemperaturerangeofabout
800°C–900°C.
•(c)Formeltingmetalsandalloysinnon-ferrousinthetemperaturerangeof
700°C–1,000°C.
•(d)Asboilerfuelsprovidesteamorhotwaterforprocessindustriessuchassilk
reeling,dyeing,turmericboiling,cooking,jiggerymaking,etc.
•3.Electricalpowergeneration:Electricpowergenerationfromfewkilowattsto
hundredsofkilowattseitherforlocalconsumptionorforgridpowerisbeing
installedbasedongasifierproducts.Small-scaleelectricitygenerationsystems
alsoprovideanattractivealternativetoelectricsupplycompany.
•4.Chemicalproduction:Productionofchemicalssuchasmethanolandformic
acidfromproducergas.

300. COOLING AND CLEANING OF GAS
•Forefficientandeffectiveuseofgasfornumerous
applications,itshouldbecleanedoftaranddust,freefrom
moisturecontentandcooled.
•Therefore,coolingandcleaningofthegasisoneofthemost
importantprocessesinthewholegasificationsystem.
•Thefailureorthesuccessofproducergasunitsdepends
completelyontheirabilitytoprovideacleanandcoolgasto
theenginesorforburners.Thetemperatureofgascoming
outofgeneratorisnormallybetween300°Cand500°C.
•Theenergydensityofgascanbeincreasedtoalargeextent
bycoolingit.Mostcoolersaregastoairheatexchangers
wherethecoolingisdonebyfreeconvectionofaironthe
outsidesurfaceofheatexchanger.
•Someheatexchangersprovidepartialscrubbingofgasforthe
removalofmoistureandtarcontents.
•Thus,ideally,thegasgoingtoaninternalcombustionengine
shouldbecooledtonearlyambienttemperatureandshallbe
freefromtarandmoisturecontents.Normally,thereare
threetypesoffiltersusedforcleaningofgas,asshownin
Figure9.7,whichisschematicallyadowndraftgasification
systemwithcleaningandcoolingtrain.

301. COOLING AND CLEANING OF GAS
•Theyareclassifiedasdry,moist,andwet.
•1.Cyclonefilters:
•Theyaredesignedaccordingtotherateofgasproductionandits
dustcontent.
•Theyareusefulforparticlesizeof5µmandgreater.Since60%–
65%oftheproducergascontainsparticlesabove60µminsize,
thecyclonefilterisanexcellentcleaningdevice.
•2.Wetscrubber:
•Evenaftercyclonefiltering,thegasstillcontainsfinedust,
particles,andtar.
•Itisfurthercleanedbypassingthroughawetscrubberwhere
gasiswashedbywaterincountercurrentmode.
•Thescrubberalsoactslikeacooler,fromwherethegasgoesto
clothorcorkfilterforfinalcleaning.
•3.Clothfilters:
•Itisafinefilter.Anycondensationofwateronitstopsthegas
flowbecauseofanincreaseinpressuredropacrossit.
•Thus,inquiteanumberofgasificationsystems,thehotgasesare
passedthroughtheclothfilter,andthenonlydotheygotothe
cooler.
•Sincethegasesarestillabovethedewpoint,nocondensation
takesplaceinfilter.

302. Biogas Energy
•Biogasisamixtureofdifferentgases,suchasmethane,carbondioxide,
hydrogen,etc.,producedbythebiologicalbreakdownoforganicmatterinthe
absenceofoxygen.
•Itisarenewableenergysource,andinmanycases,itexertsaverysmallcarbon
footprint.
•Biogascanbeproducedbyeitheranaerobicdigestionwithanaerobicbacteria,
whichdigestmaterialinsideaclosedsystem,orfermentationofbiodegradable
materials.Itisprimarilymethane,carbondioxide,smallamountsofhydrogen
sulphide,moisture,andsiloxanes.
•Anaerobicdigestionisaprocessthatbreaksdownorganicmatterintosimpler
chemicalcomponentsintheabsenceofoxygen.
•Thisprocesshasprovedtobeveryeffectivetotreatorganicwastesfor
minimizingenvironmentalpollution.
•Thecommonorganicwastesarelistedasfollows:
•1.Sewagesludge
•2.Organicfarmwastes
•3.Municipalsolidwastes
•4.Organicindustrialandcommercialwastes
•5.Forestsandagriculturalwastes
•Thedigestionprocessitselftakesplaceindigester,whichisclassifiedinterms
oftemperature,watercontentoffeedstockandthenumberofstages(single
ormulti-stage).Theby-productsofanaerobicdigestion,namelybiogasand
digestate,canbeusedtocreateasourceofincome.

303. Biogas Energy
•INTRODUCTION
•Inananaerobicdigestionprocess,organicmattersarebroken
downintosimplerchemicalcomponentsintheabsenceof
oxygen,andthisprocesshasprovedtobeveryusefulfor
organicwastestreatmentinordertominimizeenvironmental
pollution.
•Inthisprocess,breakingdownoforganicmatterstakesplace
inanaerobicdigestersthatareclassifiedbasedonfeedstock,
watercontent,temperature,andnumberofstages.
•Thecommonorganicwastesfeedforanaerobicdigesters
includehumanandanimalexcreta,forestsandagricultural
wastes,sewagesludge,organicfarmwastes,municipalsolid
wastes,organicindustrialandcommercialwastes.
•Biogasandmanurearetheby-productsofanaerobicdigestion
thatprovidesenergyandorganicfertilizersforimproving
comfortsandincome.
•Anaerobicdigestionisalsousedforwastemanagementin
industrialanddomesticsectors.

304. BIOGASAND ITS COMPOSITION
•Biogasisaclean,non-polluting,andlow-costfuel.
•Itcontainsabout50%–70%methane,whichisinflammable.Amethane
gasmoleculehasoneatomofcarbonandfouratomsofhydrogen
(CH4)andisthemainconstituentofpopularlyknownbiogas.
•Acolourless,odourless,inflammablegasalsobeenreferredtoas
seweragegas,cleargas,marshgas,refuse-derivedfuel(RDF),sludge
gas,gobargas(cowdunggas),andbioenergy.
•Itproducesabout9,000kcalofheatenergypercubicmetresofgas
burntandspecificallyusedforcooking,heating,andlighting.
•ThecompositionofbiogasisshowninTable10.1,whichmainly
composedof50%to70%methane(CH4),30%to40%carbondioxide
(CO2),andtracesofothergases.
•Biogasislighterthanairbyabout20%andhasanignitiontemperature
intherangeof650°Cto750°Cburnswithclearblueflamesimilarto
thatofliquefiedpetroleumgas(LPG)andburnswith60%efficiencyin
aconventionalbiogasstove.
•Itscalorificvalueis20MJ/m3.Itsequivalencewithotherenergyand
fuelsareasfollows:

305. BIOGASAND ITS COMPOSITION
•A1,000cubicfeetofprocessedbiogasisequivalenttoabout
•600cubicfeetofnaturalgas
•4.6gallonsofdieseloil
•5.2gallonsofgasoline
•6.4gallonsofbutane
•Itisalsoestimatedthatforasimplefamilysizeoffivepersonsand
fourcowsandbuffaloes,animaldung(leavingtheuseofhuman
excretaforsocialproblems)willproduceabout175cubicfeetof
biogasperdaywhichwillbesufficientforfamilyrequirementsof
cookingandlighting.
•Inaddition,ruralhousewivesusingthebiofuelaresparedtheirritating
smokecomingoutoftraditionalcookingonrawbiomassmaterialand
reducedlabourrequiredforcleaningthecookingequipmentsand
utensils.Thedigestedmaterial,whichcomesoutoftheplant,is
enrichedmanure.

306. ANAEROBIC DIGESTION
•Itisabiologicalprocessthatproducesagas(commonly
knownasbiogas)intheabsenceofoxygenandhasmajor
componentsofmethane(CH4)andcarbondioxide(CO2).
•Anaerobicdigestionofmethanegasproductionisaseries
ofprocessesinwhichmicroorganismbreakdown
biodegradablematerialintheabsenceofoxygenwhich
completesthroughfollowingsteps:
•1.Inthefirststep,theorganicmatter(e.g.plantsresidues,
humanandanimalwastesandresidues)isdecomposed
(hydrolysis)tobreakdowntheorganicmaterialinto
usable-sizedmoleculessuchassugar.
•2.Conversionofdecomposedmatterintoorganicacidsis
thesecondstep.
•3.Finally,organicacidsareconvertedtobiogas(methane
gas).

307. ANAEROBIC DIGESTION
•ProcessStagesofAnaerobicDigestion
•Thebiologicalandchemicalstagesofanaerobicdigestionareshownin
Figure10.1.
•Thesearedividedintothefollowingfourmainstages:
•1.Hydrolysis
•2.Acidogenesis
•3.Acetogenesis
•4.Methanogenesis

308. ANAEROBIC DIGESTION
1.Hydrolysis
Theprocessofbreakinglargebiomassorganicchainsintotheir
smallerconstituentpartssuchassugar,fattyacids,andamino
acidsanddissolvingthesmallermoleculesintosolutioniscalled
hydrolysis.
Thisprocessassistsbacteriainanaerobicdigesterstoaccessthe
energypotentialofthematerial.
Hydrolysisofthesehigh-molecular-weightpolymeric
componentsofbiomasscompletesthefirststepinanaerobic
digestion.
Hydrogenandacetateproductsoffirststagearedirectlyusedby
methanogens.
Othermoleculeswithachainlengthlargerthanthatofacetate
(e.g.volatilefattyacids)mustfirstbecatabolizedinto
compoundsandthenusedbymethanogens.
2.Acidogenesis
Acidogenesisisthebiologicalprocessinwhichtheremaining
componentsarebrokendownbyacidogenetic(fermentative)
bacteria.
Itcreatesvoltaicfattyacidstogetherwithammonia,carbon
dioxide,andhydrogensulphide,andotherby-products.

309. ANAEROBIC DIGESTION
3.Acetogenesis
Inthisstageofanaerobicdigestion,simplemolecules
createdthroughtheacidogenesisphasearefurther
digestedtoproducemoreaceticacid,carbondioxide,
andhydrogen.
4.Methanogenesis
Finally,theprocessofbiogasproductioniscompleted
bymethanogenesis.
Inthisstageofanaerobicdigestion,themethanogens
useintermediateproductsoftheprecedingstagesand
convertthemintomethane,carbondioxide,andwater
whichmakesthemajorityofthebiogasemittedfrom
thesystem.
MethanogenesisissensitivetobothhighandlowpH
values.
Asimplifiedgenericchemicalequationfortheoverall
processesoutlinedearlierisasfollows:
C6H12O6 → 3CO2 + 3CH4
Theremainingindigestiblematerialcannotbeusedby
microbesandanydeadbacterialremainsconstitute
thedigestate.

310. BIOGAS PRODUCTION
•Asalreadydiscussed,biogasoriginatesfrombacteriainthe
processofbiodegradationoforganicmaterialunderanaerobic
(intheabsenceofoxygen)conditions.
•Anaerobicprocesseseitheroccurnaturallyorcreatedina
controlledenvironment,namelyabiogasplantinwhichorganic
wastesareputinanairtightcontainercalleddigestertoperform
anaerobicdigestionprocess.
•ConstructionPartsofBiogasPlantsFigure10.2showsvarious
partsoftypicalbiogasplant.Itisabrickandcementstructure
havingthefollowingfivesections:
•1.Mixingtank
•2.Digestertank
•3.Domeorgasholder
•4.Inletchamber
•5.Outletchamber
•1.MixingTank
•Itisthefirstpartofbiogasplantslocatedabovethegroundlevel
inwhichthewaterandcowdungaremixedtogetherinequal
proportions(theratioof1:1)toformtheslurrythatisfedinto
theinletchamber.

311. BIOGAS PRODUCTION
•2.DigesterTank
•Itisadeepundergroundwell-likestructureandisdividedintotwo
chambersbyapartitionwallinbetween.
•Itisthemostimportantpartofthecowdungbiogasplantswhereall
theimportantchemicalprocessesorfermentationofcowdungand
productionofbiogastakesplace.
•Thedigesterisalsocalledasfermentationtank.Itiscylindricalin
shapeandmadeupofbricks,sand,andcementbuiltunderground
overthesolidfoundation.
•Twoopeningsareprovidedontheoppositesidesandatthespecified
heightofdigesterforinflowoffreshcowdungslurryandoutflowof
usedslurryasmanure.
•Thetwolongcementpipesareusedasfollows:
•1.Inletpipeopeningintotheinletchamberforinputtingtheslurryin
digestertank.
•2.Outletpipeopeningintotheoverflowtank(outletchamber)forthe
removalofspentslurryfromthedigestertank.
•Aseparatorisalsoplacedinthemiddleofdigestertanktoimprove
effectivefermentationsoffeedstock.

312. BIOGAS PRODUCTION
•3.DomeorGasHolder
•Thehemisphericaltopportionofthedigesteriscalleddome.Ithas
fixedheightinwhichallthegasgeneratedwithinthedigesteris
collected.
•Thegascollectedinthedomeexertspressureontheslurryinthe
digester.
•Thedomeorgasholderismadeeitherfixeddomeorfloatingdome
type.
•Cementandbricksareusedintheconstructionoffixeddome,andit
isconstructedusingapproximatelyatthegroundsurface.
•Floatingdometypeisaninvertedsteeldrumrestingonthedigester
abovethegroundsurface.
•Thedrumfloatsoverthedigesterandmovesupanddownwith
biogaspressure.
•4.InletChamber
•Thecowdungslurryissuppliedtothedigesterofthebiogasplant
viainletchamber,whichismadeatthegroundlevelsothatthe
slurrycanbepouredeasily.Ithasbellmouthsortofshapeandis
madeupofbricks,cement,andsand.Theoutletwalloftheinlet
chamberismadeinclinedsothattheslurryeasilyflowsintothe
digester.

313. BIOGAS PRODUCTION
•5.OutletChamber
•Thedigestedslurryfromthebiogasplantsisremovedthroughthe
outletchamber.
•Theopeningoftheoutletchamberisalsoatthegroundlevel.The
slurryfromtheoutletchamberflowstothepitmadeespeciallyfor
thispurpose.
•6.GasOutletPipeandValve
•Thegasholderhasanoutletatthetopwhichcouldbeconnectedto
gasstovesforcookingorgas-lightingequipmentsoranyother
purpose.
•Flowofthegasfromthedomeviagaspipecanbecontrolledby
valve.Thegastakenfromthepipecanbetransferredtothepointof
use.
•7.Foundation
•Thefoundationformsthebaseofthedigesterwherethemost
importantprocessesofbiogasplantoccur.
•Itismadeupofcement,concrete,andbricksstrongenoughsothatit
shouldbeabletoprovidestablefoundationforthedigesterwallsand
beabletosustainthefullloadofslurryfilledinit.
•Thefoundationshouldbewaterproofsothatthereisnopercolation
andleakageofwater.

314. BIOGAS PRODUCTION
•WorkingofBiogasPlant
•TheworkingprincipleofbiogasplantcanbeexplainedinFigure10.2.
•Thevariousstepsofworkingprincipleofbiogasplantsareasfollows:
•1.Cattledungandwateraremixedtogetherthoroughlyinequal
proportion(intheratioof1:1)toformtheslurryinthemixingtank.
•Then,thisslurryispouredintothedigesterviainletchamberupto
thecylindricalportionlevelofthedigester.
•2.Thefermentationofslurrystartsinthedigestertank,andafter
completionofdifferentanaerobicdigestionprocesses,biogasis
formed.
•3.Thegascontinuouslyproducedindigestertankisaccumulatedat
thetopofthedigesterinthedomeorgasholder.
•Normally,theoutletgasvalveremainsclosed,andhence,the
accumulatedbiogasinthedomeexertspressureontheslurrywhich
startsmovingintheinletandoutletchamberduetowhichthelevelof
slurrydropsindigesterandincreasesintheoutletchamber.
•Thisprocesscontinuestilltheslurryreachestohighestpossiblelevel
intheinletandoutletchamberbecauseofincreasedgaspressure.

315. BIOGAS PRODUCTION
•4.Ifthegasvalveisstillkeptclosedthebiogaswillfurtherget
accumulatedinthedomeanddevelophighpressureenoughinthe
gastostartescapingthroughtheinletandoutletchamberstothe
atmosphere.
•Thebiogascreatesbubblesintheslurryininletandoutletchambers
duringitsescape,andfrothisalsoformed.
•5.Anincreaseinthevolumeofslurryintheinletandoutletchambers
helpstocalculatetheamountofbiogasgeneratedwithinthedigester.
•6.Gaspipevalvecanbeopenedpartlyorfullytoprovidebiogasfor
differentapplications.Underthissituation,slurrylevelinthedigester
increaseswhilethelevelininletandoutletchambersreduces.
•7.Whenthegasisbeingtakenoutfromthegasoutletatthetopof
thedome,theslurryfromtheoutletchamberisremovedand
equivalentamountoffreshslurryisinductedintothedigesterto
continuetheprocessoffermentationandtheformationofthebiogas.
•Therefore,moreisthebiogasrequired,morecontinuouswillbethe
freshslurryofcowdungandwaterrequired.
•Thesizeofthedigestertankalsodecidestheamountofthegasthat
canbegeneratedbythebiogasplant.

316. Types of Biogas Plants
•Fixeddomeandfloatingdomeconstructionarethetwotypesof
biogasplants.
•Basedonthesetypes,severalbiogasplantmodelsaredeveloped.
•1.FixedDomeType:(Janatamodel)
•SchematicofafixeddomebiogasplantisgiveninFigure10.3.It
consistsoffollowingparts.
•1.Mixingtank:Inmixingtank,thewaterandcattledungaremixed
togetherthoroughlyintheratioof1:1toformtheslurry.
•2.Inletchamber:Themixingtankopensundergroundintoasloping
inletchamber.
•3.Digester:Digesterisahugetankwithadometypeceiling.
•Theceilingofthedigesterhasanoutletwithavalveforthesupplyof
biogas.
•Theinletchamberopensfrombelowintothedigestertank.
•Thedigesteropensfrombelowintoanoutletchamberwhichis
openedfromthetopintoasmalloverflowtank.

317. Types of Biogas Plants
•WorkingPrinciple
•Thevariousformsoforganicbiodegradablebiomassarecollectedand
mixedwithequalamountofwaterproperlyinthemixingtanktoform
slurry.
•Theslurryisfedintothedigestertankthroughinletchamberand
pipe,andthedigesterispartiallyfilledbyabouthalfofitsheight.
•Thefeedingofslurryisthendiscontinuedforabout60dayswhen
anaerobicbacteriapresentintheslurrydecomposesorfermentsthe
biomassinthepresenceofwater.
•Biogasisthenformedandstartsaccumulatingintheupperdomearea
ofthebiogasplants,andthepressureisexertedonthespentslurryto
forceitflowintotheoutletchamber.
•Finally,thespentslurryoverflowsintotheoverflowtankfromwhereit
ismanuallyremovedandusedasmanureforagriculturalcropsand
plants.
•Gascontrolvalveatthetopofdomeisopenedpartiallyorfullyto
supplyrequiredgasforparticularapplications.
•Afunctioningplantisfedcontinuouslywiththepreparedslurryto
obtainacontinuoussupplyofbiogas.

318. Types of Biogas Plants
•Advantages
•Advantagesoffixeddome-typebiogasplantareasfollows:
•1.Thecostsofafixeddomebiogasplantarerelativelylowas
comparedtofloatingdometype.
•2.Itissimpleinconstructionasnomovabledomeexists.
•3.Itismadeupofconcrete,bricks,andcementsandlonglifeofthe
plant(20yearsormore)canbeexpected.
•4.Undergroundandalmostgroundsurfacedomeconstructionsaves
spaceandprotectfromphysicaldamagetotheplant.
•5.Theanaerobicdigestionprocessesinthedigesterarelittle
influencedbytemperaturefluctuationindayandnight.
•Disadvantages
•Disadvantagesofbiogasplantareasfollows:
•1.Porosityandcracksinplantwallsisthemajordrawbacks.
•2.Maintenanceisratherdifficult.

319. Types of Biogas Plants
•FloatingType(KVIC:KhadiandVillageIndustriesCommission)
•ThefloatinggasholdertypeofbiogasplantisshowninFigure10.4.
•Theconstructionandworkingprincipleofthisbiogasplantsissimilar
tofixeddometypeexceptthatgasholdertankismadeupofsteeland
placedonthetopofdigestercirculartankandismovableupand
downalsoshowninFigure10.4.
•Advantages
•Floatingdome-typebiogasplanthasthefollowingadvantages:
•1.Veryefficient
•2.Simplemaintenanceschedulingpossible
•Disadvantages
•Floatingdome-typebiogasplanthasthefollowingdisadvantages:
•1.Expensive
•2.Steeldrummayrust
•3.Requiresregularmaintenance

320. Types of Biogas Plants
•DifferentModelsofBiogasPlants
•Severaltypesofbiogasplantsareavailableinsizesandthecapacities
rangingfromabout2to180m3gasoutputperday.
•Therearehardlythreemillionbiogasplantsofsmallcapacitiesare
installedinIndiabecauseofsocialacceptabilityandotherproblems.
•ThedesignmodelasshowninFigures10.2and10.4iscalledKVIC
(KhadiandVillageIndustriesCommission)model.
•Aunitofthistypewithagascapacityof2m3/daycostsapproximately
`15000.
•Anumberofotherdesignsrangingincostfrom`10000to25000for
thesamecapacityhavealsobeendeveloped.
•Large-sizedcommunitybiogasplantisencouragedtoassurebetter
andeconomicalutilizationofanimalandhumanwastesControlof
severaloperatingparameters,suchastemperatureandalkalinityof
theslurry,sludgeliquidityandbuild-upofscumonthesurfaceofthe
slurry,givesgoodperformance.
•Suchcontrolisobviouslyeasiertoachieveincommunity-sizedplants.

321. Types of Biogas Plants
•TypesofFixedDomeBiogasPlants
•Differenttypesoffixeddomebiogasplantsareasfollows:
•1.Chinesefixeddometype:Ithasarch-typefixeddomeasshownin
Figure10.3.
•Thedigesterconsistsofacylinderwithroundbottomandtop.Several
millionsofsuchbiogasplantshavebeenconstructedinChina.
•2.Janatamodel:InresponsetotheChinesefixeddomeplant,Janata
modelwasthefirstfixeddomedesignconstructedinIndia.
•Itisnotconstructedanymore.
•Themodeofconstructionleadstocracksandgasleakageinthegas
holder,andhence,thismodelhasnosocialacceptability.
•3.Deenbandhumodel:ItisthesuccessoroftheJanataplantinIndia,
withimprovedcrackproofdesign,whichconsumeslessbuildingmaterial
thantheJanataplantwithahemispheredigester.
•4.CAMARTECmodel:Ithasasimplifiedstructureofahemispherical
domeshellbasedonarigidfoundationringonlyandwasdevelopedin
Tanzania.

322. Types of Biogas Plants
•TypesofFloatingDrumPlants
•Therearedifferenttypesoffloatingdrumplantsandareasfollows:
•1.KVICmodelistheoldestandmostwidespreadfloatingdrumbiogas
plantfromIndia.
•2.Pragatimodelisdevelopedwithahemispheredigester.
•3.Ganeshmodelisconstructedwithangularsteelandplasticfoil.
•4.Aratibiogasmodelhaslow-costfloatingdrumplantsmadeofplastic
watercontainersorfiberglassdrums.
•5.BORDAmodelcombinesthestaticadvantagesofhemispherical
digesterwiththeprocessstabilityofthefloatingdrumandthelonger
lifespanofawaterjacketplant.

323. BENEFITS OF BIOGAS
•Abiogasenergysystemhaswholerangeofbenefitsforthe
users,thesociety,andtheenvironment.
•Itincludesthefollowing:
•1.Productionofenergy(heat,light,andelectricity):Thecalorific
valueofbiogasisabout6kWh/m3,whichisequivalentto
abouthalfaliterofdieseloil.
•Thenetcalorificvaluedependsontheefficiencyoftheburners
orappliances.
•Itreplacestheconventionalandtraditionalcookingandheating
fuelsandthereforepermitstheconservationsofenergyand
fuels.
•Thesmall-andmedium-sizedunits(upto6m3)aregenerally
usedforprovidinggasforcookingandlightingpurposes.
•Largeunits(orcommunalunits)producethisgasinlarge
quantitiesandcanbeusedtopowerenginesandgeneratorsfor
mechanicalworkorpowergeneration.

324. BENEFITS OF BIOGAS
•2.Transformationoforganicwastesintohigh-qualityorganicfertilizer:
Thebiogasplantisconsideredasaperfectfertilizer-makingmachine.
•Thereisnobetterwaytodigestorcompostmanureandotherorganic
materialthaninabiogasplant.
•Outputfromthedigester(digestedmanure)isactuallyahigh-quality
organicfertilizer.
•Ithasbeenanalysedthatthefertilizer,whichcomesfromabiogas
plant,containsthreetimesmorenitrogenthanthebestcompostmade
throughopenairdigestion.
•Thisnitrogenisalreadypresentinthemanure.Thenitrogenis
preservedwhenwasteisdigestedinanenclosedbiogasplant,whereas
thesamenitrogenevaporatesawayasammoniaduringopenair
composting.
•Thebiogasplantdoesnotmakeextranitrogen,itdoesnotcreate
nitrogen,anditmerelypreservesthenitrogenthatisalreadythere.
•3.Healthbenefitsofbiogasandtheimprovementofhygienic
conditions(reductionofpathogens,wormeggs,andflies):
•Significanthealthbenefitsareachievedbytheuseofpurebiogas.
•Ithasbeenfoundthatnon-biogasusershavemorerespiratorydiseases
thanthosewhousebiogasplants.

325. BENEFITS OF BIOGAS
•Respiratoryillness,eyeinfection,asthma,andlungproblemshave
largelydecreasedinthefamilyhavinginstallingabiogasplantfor
heating,cooking,andotherwork.
•Theimprovementinhygieniccookingonbiogasalsohaseconomic
benefits.Theprincipaldiseasespreadingorganisms,suchastyphoid,
paratyphoid,choleraanddysenterybacteria,hookworm,bilharzias
tapeworm,androundworm,arekilledinbiogasplants.
•Cookingonbiogascanhaveeffectsonnutritionalpatternstoo.It
increasescookedfooddigestibility.
•4.Reductionofworkload,mainlyforwomen,infirewoodcollection
andcooking:
•Timeandhumanlabourenergyisgreatlyreducedinsearching,
collecting,andcarryingthefirewoodhomefromlongdistanceplaces
andcleaningofcookingequipmentsandutensils.
•Biogasplantsalsoimprovehealthconditionsinthehomes.
•Homeremainsfreefromsmokesanddust,andmorehygienic
conditionsaremaintained,andthespacerequiredforkeeping
firewoodmaterialsisalsominimized.

326. BENEFITS OF BIOGAS
•5.Environmentaladvantagesthroughprotectionofforests,soil,water,
andair:Abiogasplantdirectlysavestheuseofforestwoodandforest
residuesandhelpsindeforestation.
•Thewidespreadproductionandutilizationofbiogasisexpectedtomake
asubstantialcontributiontosoilprotectionandamelioration.
•First,biogascouldincreasinglyreplacefirewoodasasourceofenergy.
Second,biogassystemsyieldmoreandbetterfertilizer.Asaresult,more
fodderbecomesavailablefordomesticanimals.
•This,inturn,canlessenthedangerofsoilerosionattributableto
overgrazing.
•6.Globalenvironmentalbenefitsofbiogastechnology:Biogasisa
renewablesourceofenergywhichhasimportantclimaticeffects.
•Asthedemandforfossilfuelrequiredforheatingandcookingisreduced
bytheuseofbiogas,emissionsofcarbondioxidearealsolargely
reduced.
•Also,capturing-uncontrolledmethaneemissionsignificantlyreducesthe
globalwarming.

327. FACTORS AFFECTING THE SELECTION OF A PARTICULAR MODEL
OF A BIOGAS PLAN
Variousfactorsaffectingtheselectionofaparticularmodelofabiogasplantare
explainedasfollows:
1.Cost:Theprincipalandmaintenancecostsofbiogasplansshouldbeaslowas
possible(intermsoftheproductioncostperunitvolumeofbiogas)bothtothe
userandtothesociety
2.Simplicityindesign:Thedesignshouldbesimplenotonlyforconstruction
purposesbutalsoforoperationandmaintenance.Thisisanimportant
considerationespeciallyincountrieswheretherateofliteracyislowandthe
availabilityofskilledhumanresourceisscarce.
3.Durability:Longerlifespanofbiogasplantsisessentialinsituationswhere
peopleareyettobemotivatedfortheadoptionofthistechnology,andthe
necessaryskillandmaterialsarenotreadilyavailable,anditisnecessaryto
constructplantsthataremoredurable,althoughthismayrequireahigherinitial
investment.
4.Suitabilityforusewithavailablerawinputs:Thedesignshouldbecompatible
withthetypeofinputsthatwouldbeused.Ifplantmaterialssuchasricestraw,
maizestraw,orsimilaragriculturalwastesaretobeused,thenthebatchfeeding
designordiscontinuoussystemshouldbeusedinsteadofadesignforcontinuous
orsemi-continuousfeeding.
5.Inputsandoutputsusefrequency:Frequencyofutilizationofbiogasand
feedstockinputtinginbiogasplants,influencetheselectionofaparticulardesign,
andthesizeofvariouscomponentsofbiogasplants.

328. BIOGAS PLANT FEEDS AND THEIR CHARACTERISTIC
•Anybiodegradableorganicmaterialcanbeusedasinputsforprocessinginside
thebiodigester.However,foreconomicandtechnicalreasons,somematerials
aremorepreferredasinputsthanothers.
•Iftheinputsarecostlyorhavetobepurchased,thentheeconomicbenefitsof
outputssuchasgasandslurrywillbecomelow.
•Economicvalueofbiogasanditsslurryandreducedenvironmentalcostof
biodegradablewastesdisposalinlandfillarethetwobenefitsofbiogasenergy.
•Oneofthemainattractionsofbiogastechnologyisitsabilitytogenerate
biogasoutoforganicwastesthatareinabundanceandfreelyavailable.
•Cattledungismostcommonlyusedasaninputmainlybecauseofits
availability.Thepotentialgasproductionfromsomeanimaldungisgivenin
Table10.2.
•Inadditiontotheanimalandhumanwastes,plantmaterialsarealsousedto
producebiogasandbiomanure.
•Sincedifferentorganicmaterialshavedifferentbiochemicalcharacteristics,
theirpotentialforgasproductionalsovaries.Basicrequirementsforgas
productionorfornormalgrowthofmethanogensareachievedbymixingtwo
ormoreofdifferentorganicmaterialsandfeedingtothebiogasplantscanbe
usedtogetherprovidedthatsomearemet.
•Somecharacteristicsoftheseraworganicinputsmaterialshavingsignificant
impactonthelevelofgasproductionaredescribedbelow.

329. BIOGAS PLANT FEEDS AND THEIR CHARACTERISTIC
•Carbon/Nitrogen(C/N)Ratio
•Therelationshipbetweenamountofcarbonandnitrogenpresentinorganic
materialsisexpressedintermsofthecarbon/nitrogen(C/N)ratio.
•AC/Nratiorangingfrom20to30isconsideredoptimumforanaerobic
digestion.
•FororganicmaterialswithveryhighC/Nratio,thenitrogenwillbeconsumed
rapidlybymethanogensformeetingtheirproteinrequirementsandleftover
carboncontentofthematerialwillnothaveanyreactionprocess.
•Thiswillreducethebiogasproduction.ForverylowC/N,nitrogenwillbe
liberatedandaccumulatedintheformofammonia(NH4)whichwillincrease
thepHvalueofthecontentinthedigester.
•ApHvalueshigherthan8.5willstartshowingtoxiceffectonmethanogens
population.
•C/NratioofafewcommonlyusedmaterialsarepresentedinTable10.3.
•AsevidentfromTable10.3animalwaste,particularlycattledunghasan
averageC/Nratioofabout24.Theplantmaterials,suchasstrawandsawdust,
containahigherpercentageofcarbon/nitrogenratiowhereasthehuman
excretahaveaC/Nratioaslowas8.
•Inordertobringtheaverageratioofthecompositeinputtoadesirablelevel
materialswithhighC/NratiocouldbemixedwiththoseoflowC/Nratio.
•InChina,itiscustomarytoloadricestrawatthebottomofthedigesterupon
whichlatrinewasteisdischargedasameanstobalanceC/Nratio.

330. BIOGAS PLANT FEEDS AND THEIR CHARACTERISTIC
•Advantages
•Itincludesthefollowing:
•1.Cleanfuelofhighcalorificvalueandhasaconvenientignitiontemperature.
2.Noresidue,smoke,anddustproduced.
•3.Non-polluting.Significanthealthbenefitsareachievedbytheuseofclean
biogas.
•4.Economicalbenefitsofbiogasandhigh-qualitymanure.
•5.Providesnutrientrich(NandP)manureforplants.
•Limitations
•Thelimitationsareasfollows:
•1.Initialcostofinstallationoftheplantishigh.
•2.Inadequacyoforganicrawmaterialsanditscontinuityofsupply.
•3.Socialacceptability.
•4.Maintenanceandrepairofbiogasplants.
•Uses
•1.Itisusedasadomesticfuel.
•2.Itisusedasafuelformotivepower.
•3.Itisusedforelectricitygeneration.

331. Tidal Energy
•Tides are periodic rises and falls of large bodies of water.
•Gravity is one major force that creates tides. In 1687, Sir Isaac Newton explained
that ocean tides result from the gravitational attraction of the sun and moon on
the oceans of the earth.
•Spring tides are especially strong tides that occur when the earth, the sun, and
the moon are in a line.
•The gravitational forces of the moon and the sun both contribute to the tides.
Spring tides occur during the full moon and the new moon.
•Neap tides are especially weak tides. They occur when the gravitational forces of
the moon and the sun are perpendicular to one another with respect to the
earth.
•Neap tides occur during quarter moons. Tidal energy is a form of hydropower that
converts the energy of the tides into electricity or other useful forms of power.
•The tide is created by the gravitational effect of the sun and the moon on the
earth causing cyclical movement of the seas.
•Therefore, tidal energy is an entirely predictable form of renewable energy.
•Until recently, the common plant for tidal power facilities involved erecting a tidal
dam, or barrage, with a sluice across a narrow bay or estuary.
•As the tide flows in or out, creating uneven water levels on either side of the
barrage, the sluice is opened and water flows through low-head hydro turbines to
generate electricity.
•For a tidal barrage to be feasible, the difference between high and low tides must
be at least 5 m.

332. Tidal Energy
•GENERAL
•Energynaturallypresentinoceanwaterbodiesorintheir
movementcanbeusedforthegenerationofelectricity.Thisis
achievedbroadlyinthefollowingways:
•1.Tidalenergy:Duringtherisingperiodoftides,waterisstored
inawaterreservoirconstructedbehinddamsonshore.The
potentialenergyofstoredwaterbodyisusedtogenerate
electricalenergysimilartothatinaconventionalhydropower
plant.Forthetidalenergymethodtoworkeffectively,thetidal
difference(differenceintheheightofthehighandlowtides)
shouldbeatleast4m.Wediscusstidalenergyinthischapter.
•2.Waveenergy:Usingthekinetic(dynamic)energyofthe
ocean,wavesisutilizedtorotateanunderwaterpowerturbine
andgenerateelectricitythereonasanunderwaterwindfarm.
•3.Oceanthermalenergy:focussesonthetemperature
differencebetweenwarmoceansurfacewateranddeepsea
coldwaterisusedtogenerateelectricity.Thisissimilarto
geothermalpowergenerationwhereheattrappedintheearth
surfaceisconvertedintoelectricalenergy.

333. TIDAL ENERGY RESOURCE
•Tidesarethewavescausedduetothegravitationalpullofthemoon
andalsothesun(althoughitspullisverylow).
•Theriseofseawateriscalledhightideandfallinseawateriscalledlow
tideandthisprocessofrisingandrecedingofwaterwaveshappen
twiceadayandcauseenormousmovementofwater.
•Thus,enormousrisingandfallingmovementofwateriscalledtidal
energy,whichisalargesourceofenergyandcanbeharnessedin
manycoastalareasoftheworld.
•Tidaldamsarebuiltnearshoresforthispurposeinwhichwaterflows
duringhightideandwaterflowsoutofdamduringlowtides.Thus,
theheadcreatedresultsinturningtheturbinecoupledtoelectrical
generator.
•Tidalenergyhasbeendevelopedonacommercialscaleamongthe
variousformsofenergycontainedintheoceans.
•Whenthemoon,theearth,andthesunarepositionedclosetoa
straightline,thehighesttidescalledspringtidesoccur.Whenthe
earth,moon,andsunareatrightanglestoeachother(moon
quadrature),thelowesttidescalledneaptidesoccur.
•Thewatermassmovedbythemoon’sgravitationalpullwhenmoonis
veryclosetooceanandresultsindramaticrisesofthewaterlevel
(tidecycle).
•Thetidestartsrecedingasthemooncontinuesitstravelfurtherover
theland,awayfromtheocean,reducingitsgravitationalinfluenceon
theoceanwaters(ebbcycle).

334. TIDAL ENERGY AVAILABILITY
•Gravitationalforcesbetweenthemoon,thesun,andtheearthcause
therhythmicriseandfallofoceanwatersthroughouttheworld.Those
resultintidewaves.
•Themoonexertsmorethantwiceasgreataforceonthetidesasthe
sunduetoitsmuchcloserpositiontotheearth.
•Asaresult,thetidecloselyfollowsthemoonduringitsrotation
aroundtheearth,creatingdiurnaltideandebbcyclesatanyparticular
oceansurface.
•Theamplitudeorheightofthetidewaveisverysmallintheopen
oceanwhereitmeasuresseveralcentimetresinthecentreofthewave
distributedoverhundredsofkilometres.
•However,thetidecanincreasedramaticallywhenitreaches
continentalshelves,bringinghugemassesofwaterintonarrowbays,
andriverestuariesalongacoastline.
•Forinstance,thetidesintheBayofFundyinCanadaarethegreatest
intheworld,withamplitudebetween16and17mnearshore.
•Hightidesclosetothesefigurescanbeobservedatmanyothersites
worldwide,suchastheBristolChannelinEngland,theKimberlycoast
ofAustralia,andtheOkhotskSeaofRussia.
•Table11.1givesrangesofamplitudeforsomelocationswithlarge
tides.

335. TIDAL ENERGY
AVAILABILITY
•Tidalenergyprojectsareextremelysitespecific.Thequalityofthetopographyofthe
basinalsoneedstofacilitatecivilconstructionofthepowerplant.Itisacleanmechanism
anddoesnotinvolvetheuseoffossilfuels.However,environmentalconcernsexist
mainlytodowithhighsiltformationattheshore(duetopreventingtidesfromreaching
theshoreandwashingawaysilt)anddisruptiontomarinelifenearthetidalbasin.
•Waveenergyprojectshavelesserecologicalimpactthantidalwaveenergyprojects.In
termsofreliability,tidalenergyprojectsarebelievedtobemorepredictablethanthose
harnessingsolarorwindenergy,sinceoccurrencesoftidesarefullypredictable.Table
11.2providesglimpsesoffewpotentialsitesfortidalpowergeneration

336. TIDAL ENERGY AVAILABILITY

337. TIDAL POWER GENERATION IN
INDIA
•Long coastline with the estuaries and gulfs in India has a strong tidal range and height to move
turbines for electrical power generation. Important site location and estimated power potential of a
few Indian tidal energy plant is given in Table 11.3.
•Many organizations and government agencies are busy in the construction of tidal power plants on
all those location and harnessing tidal energy at full capacity.
•There is an ample prospect for tidal power development in India. It has been investigated that Gulf
of Cambay may prove the biggest tidal energy reservoir for India.
•Extensive exploration on the western coast in Gulf of Kutch (at Mandva), Gulf of Combay(at Hazira),
Maharashtra (at Janjiraand Dharmata) and also in Hoogali, Chhatarpur, and Puri on Eastern coast
may be worth attempting.
•Nevertheless, the possibility of developing tidal power scheme in India may be examined in the
following all aspects:
•1. Economic aspects of tidal power schemes when compared to the conventional schemes.
•2. Problems associated with the construction and operation of plant.
•3. Problems related to the hydraulic balance of the system in order to minimize the fluctuation in
the power output.
•4. Environmental effects of the schemes.

338. LEADING COUNTRY IN TIDAL
POWER PLANT INSTALLATION

339. ENERGY AVAILABILITY IN TIDES
•Potentialenergyandkineticenergyarethetwo
energycomponentsofenergyofthetidewaves.
•Thepotentialenergyistheworkdoneinlifting
themassofwaterabovetheoceansurface.This
energycanbecalculatedas

340. ENERGY AVAILABILITY IN TIDES
•Thetotalenergyoftidewavesequalsthesumofitspotentialandkinetic
energycomponents.
•Estimationandunderstandingofthepotentialenergyavailabilityofthe
tidesarekeyfordesigningconventionaltidalpowerplantsusingwater
damsforcreatingartificialupstreamwaterheads.
•Suchpowerplantsexploitthepotentialenergyofverticalriseandfallof
thewater.
•Thekineticenergyofthetidehastobeknownfordesigningothertypes
oftidalpowerplants(likeSoating),whichharnessenergyfromtidal
currentsorhorizontalwater.Theydonotinvolvetheinstallationof
waterdams.

341. Calculation of Tidal Power
•Potentialtidalpowercanbereckonedbasedonamathematical
calculation.
•Letusassumethatthesurfaceareaofthereservoirasstablebetween
thefullstoredwaterlevelandtheemptiedfloor,theenergyproduced
bytheebbingwatercouldbeexpressedas

342. Tidal Stream Generator
•Itisoftenreferredtoasatidalenergyconverter(TEC).
•Itisamachinethatextractskineticenergyfrommovingmassesofwater
inparticulartides.
•ATECdeviceextractsenergyfromatidalflowmuchinthesameway
thatawindmillextractsenergyfromthewind.
•Thefollowingequationcanbeusedtocalculatethepoweroutputof
eitherdevices

343. TIDAL POWER BASIN
•Thebasinsystemisthemostpracticalmethodof
harnessingtidalenergy.Itiscreatedbyenclosingaportion
ofseabehinderecteddams.
•Thedamincludesasluicethatisopenedtoallowthetide
toflowintothebasinduringtideriseperiodsandthe
sluiceisthenclosed.
•Whenthesealeveldrops,traditionalhydropower
technologies(waterisallowedtorunthroughhydro
turbines)areusedtogenerateelectricityfromthe
elevatedwaterinthebasin.
•FromEquation11.7,wecanobservethatthetidalpower
variesasthesquareoftheheadandsincetheheadvaries
withthetidalrange,thepoweravailableatdifferentsites
showsverywidevariation.
•Inordertoovercomethiswidevariationinavailabilityof
tidalpower,varioustidalbasinsystemshave,therefore,
beendeveloped.
•Theyarediscussedinthefollowingsections.

344. Single-basin System
•Thisisthesimplestwayofpowergenerationandthesimplest
schemefordevelopingtidalpoweristhesingle-basinarrangement
asshowninFigure.
•Singlewaterreservoirisclosedoffbyconstructingdamorbarrage.
•Sluice(gate),largeenoughtoadmitthewaterduringtidesothat
thelossofheadissmall,isprovidedinthedam.
•Thesingle-basinsystemhastwoconfigurations,namely:
•1.One-waysingle-basinsystem:Thebasinisfilledbyseawater
passingthroughthesluicegateduringthehightideperiod.When
thewaterlevelinthebasinishigherthanthesealevelatlowtide
period,thenpowerisgeneratedbyemptyingthebasinwater
throughturbinegenerators.Thistypeofsystemscanallowpower
generationonlyforabout5handisfollowedbytherefillingofthe
basin.Powerisgeneratedtilltheleveloffallingtidescoincideswith
thelevelofthenextrisingtide.
•2.Two-waysinglebasin:Thissystemallowspowergenerationfrom
thewatermovingfromtheseatothebasin,andthen,atlowtide,
movingbacktothesea.Thisprocessrequiresbiggerandmore
expensiveturbine.Single-basinsystemhasthedrawbacksof
intermittentpowersupplyandharnessingofonlyabout50%of
availabletidalenergy

345. Single-basin System

346. Two-basin Systems
•Animprovementoverthesingle-basinsystemisthetwo-basinsystem.
•Inthissystem,aconstantandcontinuousoutputismaintainedby
suitableadjustmentoftheturbinevalvestosuittheheadunderwhich
theseturbinesareoperating.
•Atwo-basinsystemregulatespoweroutputofanindividualtide,butit
cannottakecareofthegreatdifferenceinoutputsbetweenspringand
neaptides.
•Therefore,thissystemprovidesapartialsolutiontotheproblemof
gettingasteadyoutputofpowerfromatidalscheme.
•Thisdisadvantagecanbeovercomebythejointoperationoftidalpower
andpumpedstorageplant.
•Duringtheperiod,whenthetidalpowerplantisproducingmoreenergy
thanrequired,thepumpedstorageplantutilizesthesurpluspowerfor
pumpingwatertotheupperreservoir.
•Whentheoutputofthetidalpowerplantislow,thepumpedstorage
plantgenerateselectricpowerandfeedsittothesystem.
•Thisarrangement,eventhoughtechnicallyfeasible,ismuchmore
expensive,asitcallsforhighinstalledcapacityformeetingaparticular
load.
•Thisbasicprincipleofjointoperationoftidalpowerwithsteamplantis
alsopossiblewhenitisconnectedtoagrid.Inthiscase,whenevertidal
powerisavailable,theoutputofthesteam

347. Two-basin Systems
•plantwillbereducedbythatextentthatleadstosavingin
fuelandreducedwearandtearofsteamplant.
•Thisoperationrequiresthecapacityofsteampowerplant
tobeequaltothatoftidalpowerplantandmakesthe
overallcostofpowerobtainedfromsuchacombined
schemeveryhigh.
•InthesystemshowninFigure11.2,thetwobasinscloseto
eachother,operatealternatively.Onebasingenerates
powerwhenthetideisrising(basingettingfilledup)and
theotherbasingeneratespowerwhilethetideisfalling
(basingettingemptied).
•Thetwobasinsmayhaveacommonpowerhouseormay
haveseparatepowerhouseforeachbasin.Inboththe
cases,thepowercanbegeneratedcontinuously.
•Thesystemcouldbethoughtofasacombinationoftwo
single-basinsystems,inwhichoneisgeneratingpower
duringtidingcycle,andtheotherisgeneratingpower
duringemptying.

348. Co-operating Two-basin Systems
•Thisschemeconsistsoftwobasinsatdifferentelevation
connectedthroughtheturbine.
•Thesluicesinthehigh-andlow-levelbasincommunicatewith
seawaterdirectly,asshowninFigure11.3.
•Thehigh-levelbasinsluicesarecalledtheinletsluicesandthelow
levelasoutletsluices.
•Thebasicoperationoftheschemeisasfollows:
•1.Therisingtidefillsthehigh-levelbasinthroughthesluiceways.
•2.Whenthefallingseawaterlevelisequaltothewaterlevelin
thehigh-levelbasin,thesluicewaysareclosedtopreventthe
outflowinghigh-levelbasinwaterbacktothesea.
•3.Thewaterfromhigh-levelbasinisthenallowedtoflowthrough
theturbinegeneratorstothelow-levelbasin.
•4.Whenthefallingseawaterlevelbecomeslowerthantherising
waterlevelinthelow-levelbasin,thesluicewaysareopenedto
allowwatertoflowintotheseafromthelow-levelbasin.
•Thisprocesscontinuesuntilthewaterlevelinthelow-levelbasin
equalstotherisingsealevel.Then,thesluicewaysareclosedto
preventthefillingoflow-levelbasinfromtheseawater.

349. Co-operating Two-basin Systems
•5.Whentheseawateragainrisesduringthenextrisingtide
equalstolowlevelofhigh-levelbasin,sluicesofhigh-level
basinisagainopenforfillingofwaterinhigh-level
basin.Thus,thecycleisrepeated.
•Figure11.4givesanotherschematicdiagramofco-
coordinatingtwo-basintidalpowerstations.
•Withtwobasins,oneisfilledathightideandtheotheris
emptiedatlowtide.
•Turbinesareplacedbetweenthebasinsandbetweenthe
basinandthesea.
•Thistwobasinsystemsallowcontinuouspowergeneration.
•However,theyareveryexpensivetoconstructduetothe
costoftheextralength.

350. TURBINES FOR TIDAL POWER
•Tidalpowerplantsoperateusingarapidlyvaryingheadof
water,andtherefore,theirturbinesmusthavehigh
efficiencyatvaryinghead.
•Theseareasfollows:
•1.TheKaplantypeofwaterturbineoperatesquite
favourablyundertheseconditions.
•2.Thepropellertypeofturbineisalsosuitablebecausethe
angleofthebladescanbealteredtoobtainmaximum
efficiencywhilewaterisfalling.
•3.Acompactreversiblehorizontalturbine(bulb-type
turbine)hasbeendevelopedbyFrenchEngineeranditacts
withequalefficiencybothasapumpandasaturbine.

351. Bulb-type turbine
•Thebulb-typeturbineshowninFigure11.5consistsofa
steelshellcompletelyenclosingthegeneratorthatis
coupledtotheturbinerunner.
•Theturbineismountedinatubewithinthestructureofthe
barrage,andthewholemachinebeingsubmergedatall
times.
•Whenthepowerdemandonthesystemislowduringthe
risingtides,theunitoperatesasapumptotransferwater
fromseatothebasin.
•Whentheloadonthissystemishigh,theunitwillworkasa
generator,anddeliverthestoredenergythatisavaluable
additionalinputtothesystem.
•Bulbturbinesincorporatedthegenerator–motorunitinthe
flowpassageofthewater.TheseturbinesareusedattheLa
RancepowerstationinFrance.
•Themaindrawbackisthatwaterflowsaroundtheturbine,
makingmaintenancedifficult.

352. ADVANTAGESOF TIDAL POWER
•Thefollowingaretheadvantagesoftidalpower:
•1.Abouttwo-thirdofearth’ssurfaceiscoveredbywater,thereis
scopetogeneratetidalenergyonlargescale.
•2.Techniquestopredicttheriseandfalloftidesastheyfollow
cyclicfashionandpredictionofenergyavailabilityiswell
established.
•3.Theenergydensityoftidalenergyisrelativelyhigherthanother
renewableenergysources.
•4.Tidalenergyisacleansourceofenergyanddoesnotrequire
muchlandorotherresourcesasinharnessingenergyfromother
sources.
•5.Itisaninexhaustiblesourceofenergy.
•6.Itisanenvironmentfriendlyenergyanddoesnotproduce
greenhouseeffects.
•7.Efficiencyoftidalpowergenerationisfargreaterwhencompared
tocoal,solar,orwindenergy.Itsefficiencyisaround80%.
•8.Despitethefactthatcapitalinvestmentofconstructionoftidal
powerishigh,runningandmaintenancecostsarerelativelylow.9.
Thelifeoftidalenergypowerplantisverylong.

353. DISADVANTAGESOF TIDAL POWER
•Thefollowingarethedisadvantagesoftidalpower:
•1.Capitalinvestmentforconstructionoftidalpowerplantishigh.
•2.Onlyaveryfewideallocationsforconstructionofplantare
availableandtheytooarelocalizedtocoastalregions.
•3.Unpredictableintensityofseawavescancausedamagetopower
generatingunits.
•4.Aquaticlifeisinfluencedadverselyandcandisruptthemigration
offish.
•5.Theenergygeneratedisnotmuchashighandlowtidesoccur
onlytwiceadayandcontinuousenergyproductionisnotpossible.
•6.Theactualgenerationisforashortperiodoftime.Thetidesonly
happentwiceadaysoelectricitycanbeproducedonlyforthat
time,approximatelyfor12hand25min.
•7.Thistechnologyisstillnotcosteffectiveandmoretechnological
advancementsarerequiredtomakeitcommerciallyviable

354. PROBLEMS FACED IN EXPLOITING TIDAL ENERGY
•1.Usuallytheplaceswheretidalenergyisproducedarefarawayfromthe
placeswhereitisconsumed.Thistransmissionisexpensiveanddifficult.
•2.Intermittentsupply:Costandenvironmentalproblems,particularly
barragesystemsarelessattractivethansomeotherformsofrenewable
energy.
•3.Cost:Thedisadvantagesofusingtidalandwaveenergymustbe
consideredbeforejumpingtoconclusionthatthisrenewable,cleanresource
istheanswertoallourproblems.Themaindetrimentisthecostofthose
plants.
•4.Alteringtheecosystematthebay:Damagessuchasreducedflushing,
wintericing,anderosioncanchangethevegetationoftheareaanddisrupt
thebalance.Similartootheroceanenergies,tidalenergyhasseveral
prerequisitesthatmakeitonlyavailableinasmallnumberofregions.
•Foratidalpowerplanttoproduceelectricityeffectively(about85%effi
ciency),itrequiresabasinoragulfthathasameantidalamplitude(the
differencesbetweenspringandneaptide)of7mormore.
•Itisalsodesirabletohavesemi-diurnaltideswheretherearetwohighand
lowtideseveryday.
•Abarrageacrossanestuaryisveryexpensivetobuildandaffectsaverywide
area—theenvironmentischangedformanymilesupstreamand
downstream.
•Manybirdsrelyonthetideuncoveringthemudflatssothattheycanfeed.
Therearefewsuitablesitesfortidalbarrages.

355. PROBLEMS FACED IN EXPLOITING TIDAL ENERGY
•1.Onlyprovidespowerforaround10heachday,whenthetideisactually
movinginorout.
•2.Presentdesignsdonotproducealotofelectricity,andbarragesacross
riverestuariescanchangetheflowofwater,andconsequently,thehabitat
forbirdsandotherwildlife.
•3.Expensivetoconstruct.
•4.Powerisoftengeneratedwhenthereislittledemandforelectricity.
•5.Limitedconstructionlocations.
•6.Barragesmayblockoutletstoopenwater.Althoughlockscanbeinstalled,
thisisoftenaslowandexpensiveprocess.
•7.Barragesaffectfishmigrationandotherwildlife;manyfishlikesalmon
swimuptothebarragesandarekilledbythespinningturbines.
•8.Fishladdersmaybeusedtoallowpassageforthefish,buttheseare
never100%effective.
•9.Barragesmayalsodestroythehabitatofthewildlifelivingnearit.
•10.Barragesmayaffectthetidallevel—thechangeintidallevelmayaffect
navigation,recreation,causefloodingoftheshoreline,andaffectlocal
marinelife.
•11.Tidalplantsareexpensivetobuild.
•12.Theycanonlybebuiltonoceancoastlines;thismeanthatfor
communitiesthatarefarawayfromthesea,itisuseless

356. Ocean Thermal Energy Conversion
•Oceanthermalenergyconversion(OTEC)isamethodtoproduceelectricityby
usingthetemperaturedifferencesbetweenwarmoceansurfaceandcooldeep
oceanwatertorunaheatengine.
•Iftemperaturedifferenceisgreater,thenmoreenergywillbeproduced.About
70%oftheearth’ssurfaceiscoveredbyoceans,whicharecontinuouslyheated
bythesun.
•Extractingthesolarenergystoredinanoceaniscarriedoutbyexploitingthe
temperaturedifferencebetweenwarmsurfacewaterandcolddeepseawater.
Low-gradeheatfromrenewableenergysourcesisconsideredtobeagood
candidatetogenerateelectricity.
•Amongthosesources,OTECandsolarenergyaretypicallyutilizedinconverting
low-gradeheatintopowergenerationandotherapplications.

357. Ocean Thermal Energy Conversion
•OTECsystemsusetheocean’snaturalthermalgradienttodriveapower-
producingcycle.
•Aslongasthetemperaturedifferencebetweenwarmsurfacewaterandcold
deepseawaterisgreaterthanabout20°C,anOTECsystemcanproducea
significantamountofpower.
•SuitablelocationsforOTECsystemsintheworldhavebeenidentified.Itwas
foundthatnaturaloceanthermalgradientsnecessaryforOTECoperation
generallyexistbetweenlatitudes200°Nand200°S.
•OTECcan,therefore,besitedanywhereacrossabout60millionsquare
kilometresoftropicaloceansanywherethereisdeepcoldwaterlyingunder
warmsurfacewater.
•ThisgenerallymeansbetweentheTropicofCancerandtheTropicofCapricorn.
Surfacewaterintheseregions,warmedbythesun,generallystaysat25°Cor
above.Oceanwatermorethan1,000metresbelowthesurfaceisgenerallyat
about5°C.

358. Ocean Thermal Energy Conversion
•INTRODUCTION
•Low-temperatureheatobtainedfromrenewableenergyresources,suchassolar
thermal,geothermal,oceanthermal,etc.ispresentlyconvertedintoelectricityand
utilizedfordirectheatingapplications.
•About70%ofearth’ssurfaceiscoveredbyoceanwhichiscontinuouslyheatedby
solarheat.Solarheatisstoredasunevendistributionofheatbetweenwarmsurface
waterandcolddeepoceanwater(calledgradient)fromwhereitisharnessedas
oceanthermalenergy.
•OTECsitesthatarelocatedbetweentheTropicofCancerandTropicofCapricorn
(23.5°Nand23.5°Sofequator)foundtobebestlocations.Oceanwaterwith
temperaturegradientof5°Candmoreisknownasoceanthermalenergy.
•However,significantamountofelectricpowercanbegeneratedinthelocationwhere
atemperaturedifferenceof20°Candaboveexistsbetweenwarmsurfacewaterand
colddeepwater.Inmanyregions,oceansurfacewaterisgenerallymaintainedat25°C
oraboveandmorethan1,000metresbelowthesurfaceisgenerallyatabout5°C.
SinceaveragetemperatureinBalticSeaisabout10°C,settingupofOTECelectrical
powerplantisnotprofitable

359. Ocean Thermal Energy Conversion
•INTRODUCTION
•Therefore,OTECisanenergytechnologythatconvertssolarradiationtoelectric
powerthroughheatofoceanwater.Thesesystemsuseocean’snaturalthermal
gradient.Aslongasthetemperaturedifferencebetweenthewarmsurface
waterandthecolddeepwaterbelow600metresbyabout20°C,anOTEC
systemcanproduceasignificantamountofpower.Thus,oceansarevast
renewableresourceswiththepotentialtoproducethousandsofkWofelectric
power.ThecolddeepseawaterusedintheOTECsystemisalsorichin
nutrients,anditcanbeusedtocultivateplantandmarineorganismnearthe
shoreoronland.

360. PRINCIPLE OF OCEAN THERMAL ENERGY CONVERSION
•Thebasicprincipleofoceanthermalenergyconversion(OTEC)isexplainedasfollows:The
warmwaterfromtheoceansurfaceiscollectedandpumpedthroughtheheatexchangerto
heatandvapourizeaworkingfluid,anditdevelopspressureinasecondarycycle.
•Then,thevapourizedworkingfluidexpandsthroughaheatengine(similartoaturbine)
coupledtoanelectricgeneratorthatgenerateselectricalpower.
•Workingfluidvapourcomingoutofheatengineiscondensedbackintoliquidbyacondenser.
Colddeepoceanwaterispumpedthroughcondenserwherethevapouriscooledandreturns
toliquidstate.
•Theliquid(workingfluid)ispumpedagainthroughheatexchangerandcyclerepeats.Itis
knownasclosed-cycleOTEC.Ifoceansurfacewaterishigh,enoughpropaneorsimilar
materialisusedasworkingfluid;otherwise,forlow-temperaturesurfacewater,fluidsuchas
ammoniawithlowboilingpointisused.
•Inanopen-cycleOETC,warmoceansurfacewaterispumpedintoalow-pressureboilertoboil
andproducesteam.Then,thesteamisusedinsteamturbinetodriveanelectricalgenerator
forproducingelectricalpower.
•Thecolddeepseawaterisusedincondensertocondensesteam.Somefractionsofelectrical
powergeneratedbyOTECplantsareusedforoperatingandcontrollingequipmentsinvolved
inpowerplants,andhighelectricalpowerisusedforfeedingtoseveralotherenergy
consumers.

361. PRINCIPLE OF OCEAN THERMAL ENERGY CONVERSION
•TherearetwodifferentkindsofOTECpowerplants,
namelyland-basedpowerplantandfloatingpower
plant.
•Land-basedPowerPlant
•Theland-basedpowerplantwillconsistofabuilding
asshowninFigure13.1.Itisconstructedonshore
andaccommodatesallpartsofOTECplants.
•Itrequireslayingdownlongpipesfromplantsiteon
shoretotwoextremepointsofnecessary
temperaturegradient.Onepipeisusedtocollect
warmoceansurfacewaterthroughscreened
enclosureneartheshore.
•Anotherlongpipelaydownontheslopedeepinto
theoceantocollectcoldwater.Athirdpipeisusedas
outlettodischargeusedwateragaininoceanvia
marineculturepondsdeepdowntheocean.
•Costofpipeinstallationandmaintenanceisvery
expensive,andlandbasedplantisalsovery
expensive.Sincelargeelectricityisusedtopump
waterthroughlongpipes,thenetelectricityreduces
considerably.
•Land-basedOTECplanthastheadvantageofsavings
onelectricaltransmissionlineandconnectivityto
electricalpowergrid.

362. PRINCIPLE OF OCEAN THERMAL ENERGY CONVERSION
•FloatingPowerPlant
•Floatingpowerplantisbuiltonaship
platformexactlywhererequired
temperaturegradientsufficientforOTEC
plantisavailable.
•Theworkingprincipleofoceanthermal
energyconversion(OTEC)issameasthat
ofland-basedpowerplant.
•Undoubtedly,thecostsavingsexiston
pipingsystem,butlongtransmissionline
isrequiredtotransmitelectricalpower
fromplanttoseashore.
•Owingtohighinstallationcostoflong
underwaterpowercablesandits
inefficiencyandmanyotherassociated
problems,floatingOTECplantsare
consideredfortheproductionoffuels,
suchashydrogen,ontheplatformitself
bytheelectrolysisofwater.

363. PRINCIPLE OF OCEAN THERMAL ENERGY CONVERSION
•FloatingPowerPlant
•Coldwaterpipeisthelargestsingle
itemintheland-basedplantdesign,as
theslopesareseldomlargerthan15°
ormore.
•If1,000-metres-longverticalpipewith
10to15mdiameterusedinfloating
plant,thelengthofland-basedplant
consideringslopewillbeaboutthree
times.

364. BASIC RANKINE CYCLE AND ITSWORKING
•ThebasicRankinecycleshownin
Figure13.3consistsofthefollowing:
1.Anevaporator
•2.Aturbineexpander
•3.Acondenser
•4.Apump
•5.Aworkingfluid
•Inopen-cycleOTEC,warmseawateris
usedasworkingfluid,whereasin
closed-cycletype,low-boilingpoint
ammoniaorpropaneisused.

365. BASIC RANKINE CYCLE AND ITSWORKING
•Warmoceansurfacewaterflowsintothe
evaporatorwhichisthehigh-temperature
heatsource.
•Afluidpumpisutilizedtoforcethefluidina
heatevaporatorwhereliquidfluid
vapourizes.
•Then,thevapourofboilingfluidentersthe
turbineexpandercoupledwithanelectrical
generatortogenerateelectricalpower.
•Thevapourreleasedfromtheturbineenters
intocondenserwhereitcondenses.Thecold
deepseawaterispumpedthroughthe
condenserforheatrejectionfromvapour
fluidandcondensesitasliquidfluid.
•Theliquidfluidisagainpumpedthrough
evaporatorandcyclerepeats.
•Astemperaturedifferencebetweenhigh-
andlow-temperatureendsislargeenough,
thecyclewillcontinuetooperateand
generatepower.

366. BASIC RANKINE CYCLE AND ITSWORKING
•SelectionofWorkingFluids
•ThesteamRankinecycleandorganicRankinecyclearethetwomaintypesused
inOTECsystems,andthechoiceofworkingfluidsplaysanimportantrolein
designandperformanceofOTEC.
•WateristheonlyworkingfluidforsteamRankinecycle,butalargenumberof
workingfluidisavailablefororganicRankinecycle.Theworkingfluidhasthe
followingproperties:
•1.Chemicalstabilityandcompatibility:Certainorganicfluidsaremoreproneto
decomposewhensubjectedtohighpressureandtemperaturewhichresultsin
materialcorrosionofdifferentpartsofplants,explosionetc.Thus,workingfluid
shouldbechemicallystableandcompatiblewithmaterialsandstructuresof
OTECplants.
•2.Heattransfercoefficient:Low-thermalresistanceofworkingfluidsimproves
heattransfer.

367. BASIC RANKINE CYCLE AND ITSWORKING
•SelectionofWorkingFluids
•3.Flashpoint:Aworkingfluidwithahighflashpointshouldbeusedinorderto
reduceflammability.
•4.Specificheat:Aworkingfluidwithalowspecificheatshouldbeusedto
reduceloadonthecondenser.
•5.Latentheat:Aworkingfluidwithahighlatentheatshouldbeusedinorder
toraisetheefficiencyofheatrecovery.
•6.Safety:Workingfluidshouldbenon-corrosive,non-toxic,andnon-
inflammablehavingmaximumallowableconcentrationandexplosionlimitfor
safeandefficientoperationofOTECplants.
•7.Environmentalacceptability:Low-toxicityworkingfluidminimizeswater
contamination.TheenvironmentalriskofOTECplantislow.
•8.Costandavailability:Theeaseofavailabilityandlowcostofworkingfluidis
alsoimportant.

368. CLOSED CYCLE, OPEN CYCLE, AND HYBRID CYCLE
•TherearethreetypesofOTECcycledesigns,namelyopencycle,closedcycle,and
hybridcycle.
•1.Inanopencycle,warmseawaterispumpedintoaflashevaporatorasworkingfluid
whereitboilsatlowpressureandconvertsintosteam.Thissteamexpandsthrough
low-pressureturbinewhichdrivesanelectricalgeneratorandgenerateselectricity.
Thesteamreleasedfromturbinecondensedinacondenserbydeepseacoldwateras
non-salinewater.Whennon-condensablegasesareseparatedandexhausted,the
non-salinewateriseitherpumpedinmarineculturepondsforfreshwaterapplications
orfinallydischargedinseasurfacewater.
•2.Inclosedcycle,organicfluidflowsinaseparateclosed-cycleloopcalledorganic
Rankinecycle.Warmseasurfacewaterpumpedthroughanotherpipevapourizes
workingfluidinheatexchangerstodriveturbinegenerator,Thefluidvapour
condensesintoliquidformbydeepseawaterpumpedincondenserbyaseparate
pumpingsystem,Theprocessofpumpingliquidfluidinanevaporatorcycleis
repeated.
•3.Ahybridcycleisacombinationofbothclosedandopencycle.

369. CLOSED CYCLE, OPEN CYCLE, AND HYBRID CYCLE
•Anopen-cycleOTECusesthewarmocean
surfacewaterasworkingfluid.Itisanon-
toxicandenvironmentfriendlyfluid.
•Themajorcomponentsofthissystemare
showninFigure13.4.Itconsistsof
evaporator,low-pressureturbinecoupled
withelectricalgenerator,condenser,
marinecultureponds,non-condensable
gasexhaust,andpumps.
•Evaporatorusedinanopen-cyclesystem
isaflashevaporatorinwhichwarmsea
waterinstantlyboilsorflashinthe
chamberthathasreducedpressurethan
atmosphereorvacuum.

370. CLOSED CYCLE, OPEN CYCLE, AND HYBRID CYCLE
•Itresultsinreducedvapourizationpressureofwarm
seawater.
•Alargeturbineisrequiredtoaccommodatelarge
volumetricflowratesoflow-pressuresteam,whichis
neededtogenerateelectricalpower,andisusedwith
otherplantcomponentsinasimilarmanner.
•Duringvapourizationprocessinanevaporator,oxygen,
nitrogen,andcarbondioxidedissolvedinseawaterare
separatedandarenon-condensable.
•Theyareexhaustedbynon-condensablegasexhaust
system.Condenserisusedtocondensevapour
orsteamreleasedfromsteamturbineiscondensedby
colddeepseawaterandreturnedbacktosea.
•Ifasurfacecondenserisused,condensedsteam
(desalinatedwater)remainsseparatedfromcoldsea
waterandispumpedintomarinecultureponds.
•Toavoidleakageofairinatmosphereandtoprevent
abnormaloperationofplants,perfectsealingofall
componentsandpipingsystemsisessential.

371. CLOSED CYCLE, OPEN CYCLE, AND HYBRID CYCLE
•Theworkingprinciplesofopen-cycleOTECplantsare
explainedasfollowswiththehelpofFigure13.4.
•1.Thewarmoceansurfacewaterispumpedintoflash
evaporatorwhereitispartiallyflashedintosteamata
verylowpressure.Theremainingwarmseawateris
dischargedintothesea.
•2.Thelow-pressurevapour(steam)expandsinturbineto
driveacoupledelectricalgeneratortoproduceelectricity.
Aportionofelectricitygeneratedisconsumedinplantsto
runpumpsandforotherwork,andtheremaininglarge
amountofelectricityisstoredasnetelectricalpower.
•3.Thesteamwithmanygases(suchasoxygen,nitrogen,
andcarbondioxide)releasedfromtheturbineseparated
fromseawaterinanevaporatorispumpedinto
condenser.Thesteamiscooledinacondenserbycold
deepseawater.
•4.Thecondensednon-salinewaterisdischargedeither
directlyindeepseacoldwaterorthroughthemarine
culturepond.
•5.Thenon-condensablegasesarecompressedtopressure
andexhaustedsimultaneously.
•6.Thewarmoceansurfacewateriscontinuouslypumped
intoevaporatorandcyclerepeats

372. CLOSED CYCLE, OPEN CYCLE, AND HYBRID CYCLE
•Closed-cycleOTEC
•Theschematicofclosed-cycleOTECisshowninFigure
13.5.
•Ithasdifferentarrangementwhencomparedtoopen-
cycleOTEC.Organicfluidwithlowboilingpointisused
asworkingfluid.
•Ammonialiquidisthemostwidelyusedworkingfluid.
Workingfluidflowsinaclosedloopandperfectly
sealedpipingsystem.Workingfluidcirculatesaround
theloopcontinuously.
•Warmoceansurfacewaterflowsthroughcompletely
separatepipingsystemanddischargesinuppersurface
ofocean.Warmsurfaceseawaterandworkingfluid
pipingareplacedverycloselytoeachotherinaheat
exchangertotransferwarmseawaterheatinto
workingfluid.
•Thecolddeepseawaterpipingsystemisincontact
withworkingfluidpipingsysteminacondenserwhere
workingfluidcondensestoitsliquidstate.
•Othercomponentsofbothopen-andclosed-cycle
OTECsaresimilar.Workingprinciplesofclosed-cycle
OTECareasfollows:

373. CLOSED CYCLE, OPEN CYCLE, AND HYBRID CYCLE
•Closed-cycleOTEC
•1.Workingfluidispumpedthroughheatexchangersin
aclosedloopcyclewhichisperfectlyleakageproof.
•2.Warmseasurfacewaterispumpedthroughseparate
pipeinheatexchangerinclosecontactwithfluidclosed
loopcycle
•3.Warmseawatertransferitsheatenergytoworking
fluidinheatexchangerandworkingfluidvapourizes.
•4.Thefluidvapourmakestheturbinetorotateand
driveanelectricalgeneratortoproduceelectricity.
•5.Fluidvapourleavingtheturbineiscooledand
condensedasliquidfluidandispumpedagaintorepeat
cycle.
•6.Colddeepseawaterispumpedthroughaseparate
pipeincondenserforprovidingefficientcoolingof
workingfluid

374. CLOSED CYCLE, OPEN CYCLE, AND HYBRID CYCLE
•OTECHybridCycle
•AsshowninFigure13.6,ahybridcyclecombines
thefeaturesofbothclosed-cycleandopen-cycle
systems.
•Warmseawaterispumpedintoavacuum
chamberwhereitisusedtoflashandproduces
steam.
•Workingfluidinanotherclosedcycleloopis
evaporatedandvapourizedbysteaminvacuum
chamber.
•Thefluidvapourrotatestheturbineanddrivean
electricgeneratortoproduceelectricity.

375. CARNOT CYCLE
•TheCarnotcycleisthemostefficient
thermodynamicalcyclebyexploitingthewarm
seasurfacewaterandcolddeepseawaterLetW
betheworkdonebythesystem(energyexiting
thesystemaswork),QHbetheheatputintothe
system(heatenergyenteringthesystem),

376. APPLICATION OF OTEC IN ADDITION TO
PRODUCEELECTRICITY OTEC
•schematicdiagramandapplicationsare
showninFigure13.8.Oceanthermal
convertingplantsprovideseveralproducts
forusebymankind.Theseareexplainedas
follows:
•1.Electricity:Electricalenergyistheprimary
productofOTECplants.Layingdownlong
transmissionanddistributioncablesupto
theseashorefordomesticandindustrial
applicationsisnotpracticalfromeconomic
viewpoint.OTECplantsare,therefore,
consideredforotherproductsand
applications.
•2.Hydrogenproduction:Electricityproduced
fromOTECplantsisusedforseparatingwater
inhydrogenandoxygenbythemethodof
electrolysisofwater.Hydrogenis
consideredasthesecondbestusableformof
energyafterelectricity.Useofdeepseacold
waterandOTECelectricityforhydrogen
productionsignifiestheimportant
applicationsofOTECplants.

377. APPLICATION OF OTEC IN ADDITION TO
PRODUCEELECTRICITY OTEC
•3.Ammoniaandmethanolproduction:OTEC
electricitycanbeusedtoobtainby-products,suchas
ammoniaandmethanol,thatcanbetransported
eitherbytankersorthroughpipelinestoonshore
applications
•4.Desalinatedwater:Desalinatedwaterisproduced
inanopen-cycleandhybrid-typeOTECplants
throughsurfacecondenser.Itisfreshwaterand
widelyusedaswaterresourcefordrinking,
agriculture,andindustry.
•5.Aquaculture:Nutrient-richcolddeepseawater
providessufficientenvironmentforfishfarming
whichmaycreateaprofitablebusinessactivities.
•6.Chilledsoilagriculture:Chilledsoilagricultureis
anotherapplicationofOTECplants.Colddeepsea
waterflowingthroughundergroundpipeschillsthe
surroundingsoil.Thetemperaturedifferenceis
maintainedbetweenplantrootsinthecoolsoiland
plantleavesinthewarmair,andthus,thetreeand
plantsgrows.Theamountoffoodthatcanbe
producedinthiswayisverylarge,largerinmarket
valuethantheelectricpowerproducedbytheplant.
•7.Airconditioning:Becausethetemperatureisonly
afewdegrees,coldwatercanbeusedasafluidinair
conditionsystems.

378. ADVANTAGES, DISADVANTAGES AND BENEFITS OF OTEC
•Advantages
•1.Oceanthermalenergyisarenewable,cleannaturalresourceavailableinabundance.
•2.Itispollution-freeandhasnogreenhouseeffects.
•3.Itisagoodsourceoffreshwaterandportablewater.
•Disadvantages
•1.Highcost:ElectricitygeneratedbyOTECplantsismoreexpensivethanelectricityproducedby
chemicalandnuclearfuels.
•2.Complexity:OTECplantsmustbelocatedwhereadifferenceofabout20°Coccursyearround.
Oceandepthsmustbeavailablefairlyclosetoshore-basedfacilitiesforeconomicoperation.
Floatingplantshipscouldprovidemoreflexibility.
•3.Acceptability:Forthelarge-scaleproductionofelectricityandotherproducts,OTECplantsare
poorlyacceptableduetotheirhighcosts.
•4.Ecosystemdamage:ItisobviousbysettingOTECplants.
•5.Lowerefficiency:Ahighertemperaturedifferencebetweenoceansurfacewarmwaterand
colddeepoceanwaterisrequiredforhighlyefficientoperationofplant

379. Benefits as a Measure of the Value of OTEC
•EconomicandotherbenefitsarethevalueofOTECplants.
•Theseincludethefollowing:
•1.Itisaclean,renewablenaturalresourceavailableinplenty.
•2.Ithasnoenvironmentalproblemsandgreenhouseeffects.
•3.Itisasourceofbaseloadelectricityandfuelssuchashydrogen,methanol,andammonia.
•4.Itprovidesfreshwaterfordrinking,agriculture,andindustry.5.Itencourageschilledagriculture
andaquaculture.
•6.Self-sufficiency,noenvironmentaleffects,andimprovedsanitationandnutritionaretheadded
benefitsforisland.

380. Module 5
SEA WAVE ENERGY
•The energy in ocean waves mainly comes in an irregular and oscillating form at all times of the day and night.
•Solar energy causes winds to blow over vast ocean areas, which in turn cause waves to form, gather, and travel huge
distances to the shoreline of continents.
•The wave height, period, and direction are primarily dependent on the wind properties (speed, direction, and duration)
and also the geometry of the sea (fetch length and depth).
•There is surprisingly little loss of energy in deep-water ocean waves, so as they travel to distant shores they continue to
collect more and more wind energy.
•However, as waves approach relatively shallow water, their energy is greatly dissipated due to ground effects and this
causes the dynamic, chaotic, and highly variable environment known as wave breaking close to shore.
•Kinetic energy, the energy of motion, in waves is tremendous. An average 4-foot, 10-s wave striking a coast puts out more
than 35,000 horsepower per mile of coast.
•Waves get their energy from the wind. Wind comes from solar energy. Waves gather, store, and transmit this energy
thousands of miles with little loss.
•As long as the sun shines, wave energy will never be depleted. It varies in intensity, but it is available all the times.

381. SEA WAVE
ENERGY
•GENERAL
•Waves get their energy from the solar energy through the wind. Wave
energy will never be depleted as long as the sun shines.
•Energy intensity may, however, have variation but it is available 24 h a day
in the entire year.
•They are caused by the wind blowing over the surface of the oceanwith
enough consistency and force in many areas of the world to provide
continuous waves along the shore line.
•It contains tremendous energy potential and wave power devices extract
energy from either the surface motion of ocean waves or from pressure
fluctuations below the surface.
•The movement of the ocean water and the changing water wave heights
and speed of the swells are the main sources of wave energy.
•Kinetic energy in the wave motion is tremendous that can be extracted
by the wave power devices from either the surface motion of ocean
waves or from pressure fluctuations below the ocean surface.

382. MOTION IN
THE SEA WAVES
•When the wind blows across smooth water surface, air
particles from the wind grab the water molecules they touch.
Stretching of the water surface by the force or friction between
the air and the water creates capillary waves (small wave
ripples).
•Surface tension acts on these ripples to restore the smooth
surface, and thereby, waves are formed.
•Thecombinationofforcesduetothegravity,seasurface
tension,andwindintensityarethemainfactorsoforiginofsea
wavesasshowninFigure12.1,whichillustratestheformation
ofseawavesbyastorm.
•Wavesizeisdeterminedbywindspeedandfetches(definedas
thedistanceoverwhichthewindexcitesthewaves)andbythe
depthandtopographyoftheseabed(whichcanfocusor
dispersetheenergyofthewaves).
•Seawaveshavearegularshapeatfardistancefromthefetch
andthisphenomenoniscalledswell.Waveformationmakes
thewatersurfacefurtherroughandthewindcontinuouslygrips
theroughenedwatersurface,andthus,wavesareintensified.

383. MOTION IN
THE SEA WAVES
•Awaveisaforwardmotionofenergyandnotthewaterindeepsea.In
truesense,theseawaterdoesnotmoveforwardwithawave.Wavesare
characterizedbythefollowingparameters,asshowninFigure12.2.
•1.Crest:Thepeakpoint(themaximumheight)onthewaveiscalledthe
crest.
•2.Trough:Thevalleypoint(thelowestpoint)onthewaveiscalledthe
trough.
•3.Waveheight(H):Waveheightisaverticaldistancebetweenthewave
crestandthenexttrough(m).
•4.Amplitude(a):ItisdefinedasH/2(m).
•5.Wavelength(l):Itisthehorizontaldistanceeitherbetweenthetwo
successivecrestsortroughsoftheoceanwaves(m).
•6.Wavepropagationvelocity(v):Themotionofseawaterinadirection
(m/s).
•7.Waveperiod(T):Itmeasuresthesizeofthewaveintime(s).Itisthe
timerequiredfortwosuccessivecrestsortwosuccessivetroughstopass
apointinspace.
•8.Frequency(f):Thenumberofpeaks(ortroughs)thatpassafixedpoint
persecondisdefinedasthefrequencyofwaveandisgivenbyf=1/T
(cycle/s).

384. POWER
ASSOCIATED WITH
SEA WAVES
•Ithasbeenconcludedbyresearchersthroughlinearwavemotiontheory
thatthekineticandpotentialenergy(E)ofawavepermeterofcrestand
unitofsurfacecanbeapproximatedas

385. POWER
ASSOCIATED WITH
SEA WAVES

386. Another Wave
Power Formula

387. WAVE ENERGY
AVAILABILITY
•Thedensityofwaterisabout800timeshigherthanair,andtherefore,the
energydensityofoceanwavesaresignificantlyseveraltimesmorethanair.
•Theamountofenergyavailableinoceanwavesistremendouslyhigh,and
hence,itisconsideredasarenewable,zeroemissionsourceofpower.
Estimatesoftheglobaloceanwaveenergyaremorethan2TW(whichmeans
17,500TWh/year)accordingtotheWorldEnergyCouncil.
•IthasbeenreportedthatthetotalavailableUSwaveenergyresourceis23
GW,whichismorethantwiceasmuchasJapan,andnearlyfivetimesasmuch
asGreatBritain.
•TheWestCoastofUSisthemostpromisingareawithwaveenergydensitiesin
therangeof25–40kW/m.
•TheoceanwavealongthewesterncoastofEuropeischaracterizedby
particularlyhighenergy.IthasoverhalfthewaveenergypotentialofEurope
andhaspoweruptoextentof75kW/moffthecoastalareaofIrelandand
Scotland.
•Wavepowerisdistinctfromthediurnalfluxoftidalpowerandthesteadygyre
ofoceancurrents.
•Thishugeamountofrenewableandenvironmentallyacceptablewaveenergy,
ifextractedandutilized,hascompetitivenesswithfossilandnuclearfuels.
•Generally,extremelatitudesandwestcoastsofcontinentsarethebestwave
location.
•Aviewofglobalwaveatlas(basedonsatellitedata)andanotherworldwave
mapareshowninFigure12.3.

388. WAVE ENERGY
AVAILABILITY
•Waveenergyisconvertedintoelectricitybyplacingwaveenergy
converteronthesurfaceoftheocean.Theelectricalenergygeneratedis
themostoftenusedindesalinationplants,powersupplytoelectrical
consumers,andenergizingwaterpumps.
•Theyaremostlyusingthefirstgenerationoscillatingwatercolumns
(OWS)converters.OthertechnologiessuchastheJapanesePendulorand
theTapchancanalsobefitinthiscategory.
•Theseoceanwaveenergytechnologiesrelyontheup-and-downmotion
ofwavestogenerateelectricity.Severalinstallationshavebeenbuiltin
Scotland,Portugal,Norway,theUSA,China,Japan,Australia,andIndia.
•Thenextgenerationofdevicescomprisesnew,modularfloatingdevices,
buttheserequirefurtherresearchand/ordemonstration.
•Afewinstallationofwavepowerconvertsareasfollows:
•1.Thefirstwave-powerpatentwasfora1799proposalbyaParisian
namedMonsieurGirardandhissongotpatentedthefirstwavepower
converterin1979tousedirectmechanicalactiontodrivepumps,saws,
mills,orotherheavymachinery.
•2.Duringthefirstdecadesofthe19thcentury,adevicewasputin
operationinAlgeriathatcapturedwaveoscillationandtransformedit
intousableformbyusingasystemofcamsandgears.
•3.A10-kWcomplaintflappilotplantwasinstalledintheBalticseain
1917andlaterondismantle.

389. WAVE ENERGY
AVAILABILITY
•4.Pelamisbecametheworld’sfirstoffshorewavemachineto
generateelectricityandfedintothegrid,whenitwasfirst
connectedtotheUKgridin2004.
•5.SalterDuckwaveconverterwasdevelopedaround1980inUK.
•6.A120kW(Oscillatingwavecolumn)prototype(TheMighty
Whale)with3OWCsinarowhasbeenoperatingsince1998(1.5
kmoffNanseiTown,Japan)at40mdepth
•7.A2MW(AWS)systemoffthecoastofPortugal.
•8.Theprototype(WaveDragon)isdeployedinNissumBredning,
aninletinthenorthernpartofDenmark.
•9.A40mlongprototype(McCabeWavePump)wasdeployedin
1996offthecoastofKilbaha,CountyClare,Ireland
•10.Atypical30MW(Pelamis)installationwouldoccupyasquare
kilometreofoceanandprovidessufficientelectricityfor20,000
homes.
•11.A750kWproject(Pelamis)offIslay,Scotland.
•12.A2MW(Pelamis)projectoffthecoastofVancouverIsland,
Canada.
•13.A5MW(perhapstheworld’sfirstcommercialwaveenergy
plant)developedbyWaveGenislocatedinIsleofIslay,Scotland.

390. Wave Energy
Availability in
India
•ThecoastalareaofMaharashtrahasanannualwavepotential
rangingbetween4kW/mand8kW/mwavefront,whichisquite
highas12–20kW/mduringthemonsoon.
•Thewaveenergypotentialofthemostfeasiblesitesin
MaharashtraisgiveninTable12.1foroffshorelocation.
•TheVengurlaandMalvanrocksandRediareonthetopamongthe
offshorelocations.Inthecoastallocation,however,Pawaand
RatnagiritopthelistfollowedbyGiryeandMiyetpoint.
•Vizhinjamfishingharbour,Kerala,isthesiteofaunique
demonstrationplantthatconvertsseawaveenergytoelectricity
andisgiventothelocalgrid.Thisplanthasoscillatingwater
column(OWC)converterin1990.

391. Wave Energy
Availability in
India

392. DEVICES FOR
HARNESSING WAVE
ENERGY
•Therearethreebasictechnologiesforconvertingwaveenergyto
electricity.Theyareasfollows:
•1.Terminatordevices:Itisawaveenergydeviceoriented
perpendiculartothedirectionofthewaveandhasonestationaryand
onemovingpart.
•Themovingpartmovesupanddownlikeacarpistoninresponseto
oceanwavesandpressurizesairoroiltodriveaturbine.
•Anoscillatingwatercolumn(OWC)converterisanexampleof
terminatordevice.Thesedevicesgenerallyhavepowerratingsof500
kWto2MW,dependingonthewaveparametersandthedevice
dimensions.
•2.Attenuatordevices:Thesedevicesareorientedparalleltothe
directionofthewavesandarelongmulti-segmentfloating
structures.
•Ithasaseriesoflongcylindricalfloatingdevicesconnectedtoeach
otherwithhingesandanchoredtotheseabed.
•Theyridethewaveslikeaship,extractingenergybyusingrestraints
atthebowofthedeviceandalongitslength.
•Thesegmentsareconnectedtohydraulicpumpsorotherconverters
togeneratepowerasthewavesmoveacross.Pelamiswaveenergy
converterisoneoftheknownexamplesofattenuatordevices.

393. DEVICES FOR
HARNESSING WAVE
ENERGY
•3.Pointabsorber:Itisafloatingstructurewithpartsmovingrelative
toeachotherowingtowaveactionbutithasnoorientationinany
definedwaytowardsthewavesinsteadabsorbsthewaveenergy
comingfromanydirection.
•Itutilizestheriseandfallofthewaveheightatasinglepointfor
energyconversion.
•Thepressurizedwatercreatesupanddownbobbintypemotionand
drivesabuilt-inturbinegeneratorsystemtogenerateelectricity.
•AquaBuOYWECisanexampleofpointabsorberdevices.
•4.Overtoppingdevices:Thesedeviceshavereservoirslikeadamthat
arefilledbyincomingwaves,causingaslightbuild-upofwater
pressure.
•Gravitycausesreleasedwaterfromreservoirtoflowbackintothe
oceanthroughturbinecoupledtoanelectricalgenerator.SalterDuck
WECistheexampleofovertoppingdevices.

394. Float or Buoy
Devices
•ThissystemisshowninFigure12.4.
•Aseriesofanchoredbuoysriseandfallwiththewavethatcreates
mechanicalenergytodriveelectricalgeneratorforgenerationof
electricity,whichistransmittedtooceanshorebyunderground
cables.

395. Oscillating Water
Column Devices
•Anoscillatingwatercolumndevice(OWCdevice)isshowninFigure
12.5.
•Itisaformofterminatorinwhichwaterentersthroughasubsurface
openingintoachamber,trappingairabove.
•Thewaveactioncausesthecapturedwatercolumntomoveupand
downlikeapiston,forcingtheairthoughanopeningconnectedtoa
turbinetogeneratepower.
•Itisashoreline-basedoscillatingwatercolumn(OWC)buildinUK.
Further,itisinstalledatIslay.
•Itisaconcretestructurepartiallysubmergedinseawaterand
enclosesacolumnofairontopofacolumnofwater.
•Thewatercolumnsinpartiallysubmergedchamberriseandfall,
whenseawavesimpingeonthedevice.
•Thiswaveactionalternativelycompressesanddepressurizestheair
column,whichisallowedtoflowtoandfromtheatmosphereviaa
turbine.

396. Oscillating Water
Column Devices
•Theenergycanthenbeextractedfromthesystemandusedto
generateelectricity.Wells’turbinesasshowninFigure12.6areused
toextractenergyfromthereversingairflow.
•Ithasthepropertyofrotatinginthesamedirectionregardlessofthe
directiontotheairflow

397. Pendulum
System
•Thependulumsystemisashorelinedevicethatconsistsofa
parallelepipedconcretebox,whichisopentotheseaatoneend,
asshowninFigure12.7.A
•pendulumflapishingedoverthisopening,whichswingsbackand
forthbytheactionsofthewaves.Thebackandforthmotionof
pendulumisthenusedtopowerahydraulicpumpandanelectric
generator.

398. TAPCHAN
(Tapered Channel)
•TheschematicarrangementofTAPCHANdevice(aNorwegian
system)isshowninFigure12.8.
•Ithasataperedchannelconnectedtoareservoirconstructed
abovethesealevelataheightof3–5m.
•Theyarerelativelylowpoweroutputdevicesandsuitablefordeep-
watershorelineandlowtidalrange.
•Itisaverysimpledevice.Wavescollectintoachannel,which
tapersintoalargereservoir.
•Asthewavewidthdecreases,thewaveamplitudeincreases
accordingtotheprinciplesofconservationofenergyandthis
enablesthewavestotraveluparampandpourintothereservoir
asshowninFigure12.8.
•Thepotentialenergyofwaterstoredinthereservoirisextractedby
releasingthereservoirwaterbacktotheseathroughalowhead
Kaplanturbinecoupledtoanelectricalgenerator.

399. Salter’s Duck
System
•SalterDuckWECistheexampleofovertoppingdevices.Itwas
inventedinScotlandin1970toextractmechanicalenergyfromthe
oceanwaves.
•TheschematiccrosssectionofSalterDuckisgiveninFigure12.9.
•Itisanegg-shapeddevicethatmoveswiththemotionofthe
waves.
•Theshapeofleadingedgeoftheduckisinsuchawaythatthe
approachingseawavepressureisexertedontheduck.
•Itforcestheducktorotateaboutacentralaxisandthetipofthe
cambobsupanddowninthewater.
•AstheSalterDuckmoves(orbobsorrocks)upanddownonthe
seawaves,pendulumconnectedtoelectricalgeneratorswings
forwardandbackwardtogenerateelectricity.
•Twosetsofcablesareattachedtothedevice,onetoapendulum
insidethedeviceandtheothertoafixedarmoutsidethedevice.
•Thecablesattachedtotheinternalpendulumcontainhydraulics
thatpumpsasthedevicemovesbackandforthwiththewaves.
•Thismovementofthepressurizedoilpumpedintohydraulic
machinethatdriveselectricgenerators.

400. Offshore Wave
Dragon System
•Thewavedragonisanovertoppingdevicethatelevatesocean
wavestoareservoirabovesealevelasshowninFigure12.10.
•Waterisletoutthroughanumberofturbines,andinthisway,itis
transformedintoelectricity.
•Thebasicideaofthissystemconsistsoftwolarge‘arms’thatfocus
wavesuparampintoareservoir.
•Thewaterreturnstotheoceanbytheforceofgravityviaalow
headhydroturbinethatdrivesanelectricgenerator.

401. Bristol Cylinder
•TheBristolcylinderoperatesunderthesealevel,asshownin
Figure12.11.
•Itconsistsofafloatingcylinderthatcollectedthewave’s
movement.
•Thecylinderismechanicallyconnectedtotheenergyunitby
flexiblejointsandrods.
•Therodsaremovingslowlywithcylinderandthereciprocating
motionistransferredtotheaxelsinconverterunit.
•Whentransferringconvertermovementswithmechanicalarmsand
rotationtothegenerator,theefficiencyshouldbekeptashighas
possible.

402. Archimedes Wave
Swing Devices
•TheArchimedeswaveswingdevice(showninFig.12.12)isan
underwaterbuoyofwhichtheupperpart(floater)movesupand
downinthewave,whilethelowerpartstaysinposition.
•Thefloater(air-filledchamber)ispusheddownunderawavecrest
(top)andmovesupunderawavetrough(valley).
•Theinteriorofthesystemispressurizedwithairandservesasan
airspring.Themechanicalpowerisconvertedintoelectricalpower
bymeansofapowertake-offsystem(PTO).
•ThePTOconsistsofalinearelectricalgeneratorandanitrogen
filleddampingcylinder.
•Ithastheadvantageofbeinga‘point’absorberthatabsorbspower
fromwavestravellinginalldirections,andextractsabout50%of
theincidentwavepowerinadditiontotheadvantageofbeingable
tosurvivedespiteroughseaconditionsonthesurface.

403. ADVANTAGES AND
DISADVANTAGES
OF WAVE POWER
•Advantages
•1.Seawaveshavehighenergydensitiesandprovideaconsistent
streamofelectricitygenerationcapacity.
•2.Waveenergyiscleansourceofrenewableenergywithlimited
negativeenvironmentalimpacts.
•3.Ithasnogreenhousegasemissionsorwaterpollutants.
•4.Operatingcostislowandoperatingefficiencyisoptimal.
•5.Damagetooceanshorelineisreduced.
•Disadvantages
•1.Highconstructioncosts.
•2.Marinelifeisdisruptedanddisplaced.
•3.Damagetothedevicesfromstrongstormsandcorrosioncreate
problems.
•4.Waveenergydevicescouldhaveaneffectonmarineand
recreationenvironment.

404. RES Question Bank -3
Module 4
Biomass Energy
1. Write the applications of biomass gasifiers.
2. State and explain processes of biomass gasification and stages of anaerobic digestion.
3. Draw the schematic representation of either of the following gasifiers. Further, explain their working
and application areas. (a) Updraft gasifier (b) Downdraft gasifier (c) Cross-draft gasifier (d) Fluidized
bed gasifier.
4. State and explain processes of biomass gasification. Further, define average energy conversion
efficiency of gasifiers.
5. What is the meaning of biomass? Further, discuss its multipurpose utilization.
6. Classify and explain methods of obtaining energy from biomass.
7. Describe the advantages and benefits of fluidized bed gasifier?
Biogas Energy
1. Explain the meaning of anaerobic digestion and discuss processes involved during anaerobic digestion.
2. Describe the construction and working of a biogas plant, its material aspects, and utilization of plant
products.
3. What is biogas? Discuss its composition and property.
4. Explain the constructional details and working of KVIC digester.
5. Explain advantages and uses of biogas.
6. Explain advantages and limitations of biogas plants.
Tidal Energy
1. Explain the ‘single-basin’ and ‘two-basin’ systems of tidal power harnessing. Further, discuss their
advantages and limitations.
2. Explain the working principle of Bulb-type turbine.
3. What are the special problems in the construction of barrage for tidal scheme?
4. Discuss the relative merits and limitations of tidal power.
5. What are the difficulties in tidal power developments?
6. State the types of tidal energy conversion schemes.
Module-5
Sea Wave Energy
1. Discuss the principle and working of sea wave energy conversion system.
2. Discuss the performance and limitations of sea wave energy conversion plants.
3. Describe principle of oscillating water column devices ocean wave machine and Salter’s Duck
System.
4. Discuss limitations of ocean wave energy.
5. Advantages and disadvantages of ocean wave energy.
Ocean Thermal Energy Conversion
1. With a suitable diagram, explain the Open cycle OTEC for Ocean Thermal energy.
2. Describe the closed cycle OTEC system, with its advantages over open –cycle system.
3. Write the advantages, disadvantages and benefits of OTEC system.
4. What are the main types of OTEC power plants? Describe their working principle in brief.
5. What is the limitation of open-cycle OTEC systems?
6. Explain Carnot efficiency for an OTEC plant with the help of a thermodynamic cycle on a T–S plane.