Date post: | 14-Apr-2018 |
Category: |
Documents |
Upload: | nijaz-lukovac |
View: | 229 times |
Download: | 2 times |
of 120
7/30/2019 Lecturenote Micro hydropower development
1/120
EU DELEGATION TO PAKISTAN
LectureNotesonMHPDevelopment
SRSP2012ByNijazLukovac
V.1.0
June,2012
Funded by
the European Union
Member of the COWIConsortium
7/30/2019 Lecturenote Micro hydropower development
2/120
TableofContents:
Coursecurriculum......................................................................................................................................9
Introduction.............................................................................................................................................10
1. Datacollectionandacquisition...................................................................................................11
1.1. Survey.......................................................................................................................................11
1.1.1. Overview..................................................................................................................................11
1.1.2. MultiplefrequencyGPS............................................................................................................12
1.1.3. TraditionalmethodsofquickSurvey.................................................................................12
1.2. Hydrology.................................................................................................................................16
1.2.1. Overview..................................................................................................................................16
1.2.2. Analyses....................................................................................................................................17
a) Availabledischarge.....................................................................................................................17
b) Flooddischarge...........................................................................................................................20
1.2.3. Measurements.........................................................................................................................24
c) Measuringweirs..........................................................................................................................25
d) Stagedischargemethod.............................................................................................................25
e) 'Saltgulp'method.......................................................................................................................26
f) Bucketmethod............................................................................................................................27
g) Floatmethod...............................................................................................................................27
h) Currentmeters............................................................................................................................28
i) Automatedmeasurements.........................................................................................................28
1.3. GeologyandGeomechanics.....................................................................................................29
1.3.1. Overview..................................................................................................................................29
2. Basicsofhydraulics.....................................................................................................................33
2.1. Overview.....................................................................................................................................33
2.2. Pipelines......................................................................................................................................33
2.3. Canals..........................................................................................................................................41
2.4. Tyroleanintake............................................................................................................................43
2.4.1. Intake........................................................................................................................................44
2.4.2. Collectioncanal........................................................................................................................46
2.4.3. Spillwayonthesill(Q1/100)........................................................................................................47
7/30/2019 Lecturenote Micro hydropower development
3/120
2.4.4. Stillingbasin(Q1/100).................................................................................................................48
2.4.5. Settlingbasin(Qi).....................................................................................................................50
2.4.1. Siltoutlet(Qout).........................................................................................................................52
2.4.2. Spillwayfromsettlingbasin(Qmax)...........................................................................................54
2.4.3. Dutyflowoutlet(Qmin).............................................................................................................54
3. HydropowerbasicsandHydraulicstructures.............................................................................56
3.1. General........................................................................................................................................56
3.2. History.........................................................................................................................................56
3.3. Advantagesanddisadvantages...................................................................................................56
3.4. StreamorCatchmentDevelopment...........................................................................................57
3.5. CostoftheMHP..........................................................................................................................60
3.6. FromwatertoWatts(again).......................................................................................................60
3.7. Differentsizeshydropowerinstallations....................................................................................63
3.8. Smallhydropower.......................................................................................................................64
3.9. Energyuses.................................................................................................................................64
3.10. Componentsofascheme............................................................................................................65
3.10.1. Weirandintake........................................................................................................................66
a) Sideintakewithoutweir.............................................................................................................68
b) Sideintakewithweir...................................................................................................................68
c) Bottomintake.............................................................................................................................71
3.10.2. Channels...................................................................................................................................72
3.10.3. Settlingbasin/Sandtrap..........................................................................................................73
3.10.4. Spillways...................................................................................................................................75
3.10.5. Forebaytank.............................................................................................................................75
3.10.6. PenstockMaterials...................................................................................................................77
3.10.7. Penstock...................................................................................................................................78
d) Penstockjointing.........................................................................................................................84
e) Buryingorsupportingthepenstock............................................................................................84
f) PenstockAnchorBlocksdimensions...........................................................................................85
g) Waterhammer.............................................................................................................................87
3.10.8. Powerhouse..............................................................................................................................89
4. Equipment...................................................................................................................................94
4.1. Hydromechanicalequipment....................................................................................................94
7/30/2019 Lecturenote Micro hydropower development
4/120
4.1.1. Trashracks................................................................................................................................94
4.1.2. Rakes........................................................................................................................................95
4.1.3. StoplogsandGates..................................................................................................................96
4.1.4. Valves.......................................................................................................................................97
4.1.5. Airvents...................................................................................................................................98
4.1.6. Airvessels.................................................................................................................................99
4.2. Electromechanicalequipment.................................................................................................100
4.2.1. TurbineSelection....................................................................................................................100
4.2.2. Turbinediameter....................................................................................................................103
4.2.3. Suctionheadforreactiveturbines.........................................................................................104
4.2.1. Pumpsasturbines..................................................................................................................104
4.3. Electricalequipment.................................................................................................................107
4.3.1. Generators/alternators..........................................................................................................107
4.3.2. TransformersandSwitchgears...............................................................................................108
4.3.3. Automationequipment..........................................................................................................109
4.3.4. Localillumination/lighting....................................................................................................110
4.3.5. AntiThunderGrounding........................................................................................................111
5. DesigntoolsandDrawings........................................................................................................112
5.1. Designtools...............................................................................................................................112
5.2. Designphases............................................................................................................................112
5.3. Drawings....................................................................................................................................113
6. Monitoring................................................................................................................................114
7. Practicalexercise.......................................................................................................................118
8. Trainingevaluation....................................................................................................................119
9. Literature...................................................................................................................................120
Figures:
Figure1UsingGPSinthefield...............................................................................................................12
Figure2Measuringheadinsteps.........................................................................................................14
Figure3Measuringheadinstepsusingspiritlevelmeter....................................................................14
Figure4Measuringheadinstepsusingpocketsightinglevel..............................................................15
Figure5Measuringheadinstepsusingclinometermethod................................................................15
Figure6Hydrologic
cycle.......................................................................................................................16
7/30/2019 Lecturenote Micro hydropower development
5/120
Figure7ExampleofqspAC(=Fsl)..........................................................................................................18
Figure8ExampletypicalMHPFDC.......................................................................................................18
Figure9Catchmentareaboundaries....................................................................................................19
Figure10
Catchment
area
boundaries
(3D)..........................................................................................19
Figure11ExampleofMHPcatchmentshownon1:25000...................................................................20
Figure12ExampleofintensitycurvesforvariousreturnperiodsforSarajevo.................................22
Figure13Exampleofafloodhydrograph.............................................................................................24
Figure14Flowmeasurementsusingweir.............................................................................................25
Figure15Flowmeasurementsusingfloat............................................................................................26
Figure16Flowmeasurementsusingdilution........................................................................................27
Figure17Flowmeasurementsusingcurrentmeters............................................................................28
Figure18RiverCATinaction................................................................................................................28
Figure19ExampleoftheuseofGoogleEarthinanalysingthearea....................................................29
Figure20Exampleofthegeologicalprofiletakenfromthegeologicalbasemap1:100000..............30
Figure21Exampleofthegeologicalbasemap1:100000....................................................................30
Figure22Landslides..............................................................................................................................30
Figure23Screes.....................................................................................................................................31
Figure24Slopestabilityresults.............................................................................................................31
Figure253Dsitegeologicalpresentation.............................................................................................32
Figure26n=f(R)relationshipintransitionalflowzone.......................................................................35
Figure27 Typicalcanalsection..............................................................................................................41
Figure28 Typicalcanalsectionwithlateralgroundslope.....................................................................41
Figure29Criticaldepthandflowregimes.............................................................................................42
Figure30Typicalchangesofflowregimes...........................................................................................43
Figure31Tyroleanintake......................................................................................................................44
Figure32Waterprofileontheintake..................................................................................................45
Figure
33
Water
profile
on
the
collection
canal...................................................................................47
7/30/2019 Lecturenote Micro hydropower development
6/120
Figure34WaterprofilealongSB..........................................................................................................49
Figure35WaterprofilealongSBanddownstream..............................................................................50
Figure36Tyroleanintake drawing.....................................................................................................55
Figure37
Example
of
stream
power
capacity
calculation.....................................................................59
Figure38Typicalarrangementofmicrohydroscheme........................................................................60
Figure39Flowdurationcurve...............................................................................................................61
Figure40Netheaddurationcurve........................................................................................................62
Figure41Powerdurationcurve............................................................................................................62
Figure42Majorcomponentsofamicrohydroscheme........................................................................65
Figure43Examplesoftemporaryintakes..........................................................................................67
Figure44TheexampleofpermanentMHPconcreteintake.............................................................67
Figure45Uncontrolledintake............................................................................................................68
Figure46Examplesideintake...............................................................................................................69
Figure47Overviewofthesideintake...................................................................................................69
Figure48Exampleofgabionsillintake.................................................................................................70
Figure49Examplesideintake...............................................................................................................71
Figure50ExampleofTyrolean(bottomwithdrawal)intake................................................................72
Figure51Typicalheadracecanalsections............................................................................................73
Figure52Typicalsandtrap/settlingbasin..........................................................................................74
Figure53Typicalsandtrap/settlingbasinelevationsketch...............................................................74
Figure54Exampleofcanalsiltation.....................................................................................................75
Figure55Typicalforebaytankdesigndrawing..................................................................................76
Figure56Typicalforebaytankoverview...............................................................................................76
Figure57Comparisonofpipematerials...............................................................................................78
Figure58Penstockalignmentdesigndrawing...................................................................................79
Figure59PenstockAnchorBlocks(ThrustBlocks)................................................................................79
Figure
60
Penstock
Anchor
Blocks
at
Powerhouse................................................................................80
7/30/2019 Lecturenote Micro hydropower development
7/120
Figure61PenstockExpansionJoints.....................................................................................................80
Figure62PenstockSupportsspacing...................................................................................................81
Figure63PenstockAlignmentproblems...............................................................................................81
Figure64
Plastic
pipe
laid
on
ground....................................................................................................81
Figure65Plasticpipeburiedinthetrench............................................................................................82
Figure66Penstockplacements.............................................................................................................83
Figure67Penstockdiameteroptimisation............................................................................................84
Figure68Penstocksupports..................................................................................................................85
Figure69Waterhammerschematicsforsuddenclosure......................................................................88
Figure70ResultofwaterhammercomputationforalongMHPpenstock...........................................88
Figure71ExamplesofsimpleMHPPowerhouses.................................................................................89
Figure72TypicalMHPPowerhouse......................................................................................................89
Figure73FrontfaadeofaMHPPowerhouse......................................................................................90
Figure74MHPPowerhouseTailrace..................................................................................................90
Figure75MHPPowerhouseTailrace..................................................................................................91
Figure76TypicalMHPPowerhousewithimpulseturbine....................................................................91
Figure77TypicalMHPPowerhousewithreactionturbine...................................................................92
Figure78Powerhousefoundationforarrangementwithmechanicalgovernor...................................93
Figure79Powerhouseplandrawing......................................................................................................93
Figure80Trashrack..............................................................................................................................94
Figure81Trashrake..............................................................................................................................95
Figure82Slidegates.............................................................................................................................96
Figure83Slidegate...............................................................................................................................96
Figure84Valves....................................................................................................................................97
Figure85Airvent..................................................................................................................................98
Figure86Airvessel................................................................................................................................99
Figure
87
Typical
turbine
selection
diagram.......................................................................................100
7/30/2019 Lecturenote Micro hydropower development
8/120
Figure88Typicalturbinefoundationarrangements...........................................................................101
Figure89Nsvs.Hturbinediagram......................................................................................................101
Figure90Hvs.Nsturbinediagram(loglog).......................................................................................102
Figure91
Other
turbine
application
charts.........................................................................................102
Figure92Typicalturbineefficiencycurves..........................................................................................103
Figure93Centrifugalpumpinturbinemode......................................................................................105
Figure94Pumpasturbine..................................................................................................................105
Figure95T15crossflowturbine parts..............................................................................................106
Figure96T15crossflowturbine principle........................................................................................106
Figure97Generators...........................................................................................................................107
Figure98Transformersandswitchgears............................................................................................108
Figure99AutomatedcontrolofMHP.................................................................................................109
Figure100ExampleofGridconnection,electricaldistributionandsupervisionarchitectureofamicro
hydropowerplant..................................................................................................................................110
Figure101Powerhouselighting..........................................................................................................110
Figure102
Powerhouse
grounding.....................................................................................................111
Tables:
Table1SCScurvenumbers....................................................................................................................22
Table2Piperoughness..........................................................................................................................35
Table3Importantpipematerialproperties..........................................................................................36
Table4Canalflowcalculationsparameters.........................................................................................41
Table5ExampleofthecalculationforTyroleanintake........................................................................45
Table6Settlingvelocityoftheparticledependentonwatertemperature/viscosity...........................51
Table7ExampleofPowercomputationforarunofriverMHP...........................................................63
Table8ExampleofHydropowerclassification......................................................................................63
Table9Typicalenergyuses...................................................................................................................64
Table10Comparisonpenstockmaterials.............................................................................................77
Table11Weightcomparisonbythetypeofpipe(diameter500mm,by1m)......................................78
7/30/2019 Lecturenote Micro hydropower development
9/120
9
Coursecurriculum1. Datacollectionandacquisition
1.1. Basicgeodeticsurveyingrequirements.(Couldusehelphere)1.2. Basichydrologicaldatacollectionandanalysis(measurements,historical/witnessdata,
rainfallrunoffanalysesaveragedischarge,minimumandmaximumflowrates,flow
ratingcurve,flowdurationcurve.
1.3. Geologic/geomechanicprospection.
2. Basicsofhydraulics, conveyance systems (steady canalandpipe flow computation), friction
losses,spillwaysandoutlets,introductiontounsteadyflowandtransients/waterhammer.
3. Hydropowerbasics(withemphasisonmicrohydro),determinationofthewatercoursestream
potential (capacity), site selection, site development,possible schemes,design optimisation
and alternative arrangements, equipment selection, calculation of the main power
parameters.Differencesindemanddrivenandpowerdrivenapproachtohydropower.
4. HydraulicstructuresdescriptionofthemainhydraulicstructuresusedinMHPdevelopment:
river diversion (sill, weir), intake, sandtrap/settling basin, headrace (power canal or pipe),
penstock (and its supports and anchors),powerhouse, tailrace (canal)note:Merged with
Hydropower.
5. Hydromechanical equipment: gates, valves, trashracks, rakes, steel pipes (Pending
appropriateexpertise)
6. Electromechanical equipment: Turbine, generator (partly covered but still pending
appropriateexpertise)
7. Electrical equipment: transformers, alternators, switchgears, cabling (Pending
appropriate
expertise)
8. DrawingsTheminimumfortechnicaldrawingsanddetailsforeachMHP
9. MonitoringinstructiontocollectdatafornecessaryMonitoringoftheprogress.
10. Practicalexercise(s)
11. TrainingEvaluation
7/30/2019 Lecturenote Micro hydropower development
10/120
10
IntroductionThenorthwestpartofPakistan(KPK)isveryrichinhydropowerpotential,butitalsohassomeremote
areas with many villages that do not have access to electricity. In principle, these are areas with
considerabledegreeofpoverty.Withtheobjectivetoalleviatethepovertyandtohelpdevelopment
ofthoseareas,EUDhasdecidedtograntfundsfor(amongotherthings)developmentofanumberof
MHPsinthevillagesof7districtsoftheMalakandregion.
PeshawarseatedNGOSarhadRuralSupportProgrammeSRSP,hassubmittedtheProjectProposal
titledProgrammeforEconomicAdvancementandCommunityEmpowerment(PEACE).Alargepart
ofit,nearly50%isdealingwiththesetupandimplementationof297MHPschemesintheregionover
aperiodoffouryears.
Under the title:TechnicalAppraisalandMonitoringofaMicroHydelProgramme inPakistan,EUDissued the ToR for an FWC assignment for a consultantwhowouldprovide technical assistance in
relation to thesaidProposalandProject implementationwithin the first year.TheFWCassignment
envisaged3visitstoPakistanindifferentphasesoftheProposal/Projectdevelopment.TheConsultant
fortheFWCassignment isNijazLukovac(infarthertext:theConsultant),whomadethefirstvisitto
Pakistan(IslamabadandPeshawar)from1st27
thApril2012andpreparedtheReportforPhaseI.
Meanwhile,basedonfindingsofthevisitanddiscussionswithEUD,thedecisionwasmadetoslightly
adjusttheoriginalplanning inawaythat insteadof3thereshouldbe4visitsoftheConsultant,and
thatpartofthesecondvisitwouldbeusedtocarryonaTrainingcourseforSRSPengineers.Thetiming
oftheTrainingisoptimalatthebeginningoftheProjectimplementationphase.
TheConsultanthasproposedaCoursecurriculum (Chapter0),andhasenvisaged theTrainingasan
interactiveworkshop(s)withparticipationofcertainexternalinstructorsaswellasownSRSPsstaff.A
partofthetrainingworkshopwouldalsobeledbytheConsultant.Inordertohavemajorlinesalong
whichthetrainingshouldgo,thedraftofthecoursematerialhasbeenpreparedandpresentedfurther
on. There will be a number of handouts and free software packages distributed as well. The
workshopsaremeanttohaveadegreeofflexibilityandshouldadjust inaccordancewithneedsand
capabilitiesof theparticipants.At theendof theworkshop,aneffortwouldbemade toturn this
materialintoabaseforfutureSRSPMHPmanual.
7/30/2019 Lecturenote Micro hydropower development
11/120
11
1. Datacollectionandacquisition1.1. Survey
1.1.1. Overview
Whatisimportant?
1. Essential:
a. Determiningtheavailablehead
b. Determininglocationsofmajorstructures(intake,sandtrap,headracecanal,forebay,
penstock,powerhouse,tailrace)
c. Baseforpowercalculationsandcostestimate
2. Wouldbebeneficial:
a. Surveyinglocalmapsatstructures
b. longitudinalprofile
c. characteristiccrosssections
EssentialpartwouldbenecessaryforALLMHPsandtherestshouldberequiredatleastforMHPswith
P>100kW.
Each(future)MHPsiteshouldbesurveyedtoadegreethatwouldbesufficienttoprovidebasicdataandparametersforthedesign.Minimallyitshouldinclude:
Locationanddimensionsofmainstructures:o Intake
o Sandtrap(ifany)
o Canal(ifany)
o Forebay
o Powerhouse
Availablegrosshead
Moredetailedsurveydatashouldalsoprovide(ifpossible):
Moredetailedmapsaroundthestructures
Longitudinalprofile
Severalcrosssections
Thosedatawouldprovideabaseforbetterdesignoptimisationandmoreaccuratecostestimate(bill
ofquantities).
Finally, once implemented scheme should ideally be recorded and filed in terms of the Asbuilt
documentation. In other words, once completed, the MHP scheme should be surveyed at actual
locationsofbuiltstructures.
7/30/2019 Lecturenote Micro hydropower development
12/120
12
1.1.2. MultiplefrequencyGPS
InSRSPsProject,ithasbeenforeseentoacquireacoupleofdouble/triplefrequencyGPSSystemsthat
canprovidequickandaccuratedatawhichcaneasilybeimportedintothesoftwareapplicationsused
fordesign(e.g.AutoCAD).Thiskindofprocedureshouldcertainlybeemployedat leastwithlarger
MHPs(say>100kW).DuetothelargenumberoftheMHPstobeconstructedwithin4yearsitmaybe
impossibletousethissophisticatedsurveyingequipmentateachandeverysite.Forveryremotesites
andverysmallMHPsitwouldstillbeacceptabletousemoretraditionalsitemethodsofmeasuring.
Figure1UsingGPSinthefield
1.1.3. TraditionalmethodsofquickSurvey
Severalmethodsexistformeasurementoftheavailablehead.Somemeasurementmethodsaremore
suitableon lowheadsites,butaretootediousand inaccurateonhighheads.Ifpossible,it iswiseto
takeseveralseparatemeasurementsoftheheadateachsite.Advice:Alwaysplanforenoughtimeto
allowonsitecomparisonofsurveyresults.Itisbestnottoleavethesitebeforeanalysingtheresults,
asanypossiblemistakeswillbeeasiertocheckonsite.
Afurtherveryimportantfactortobeawareofisthatthegrossheadisnotstrictlyaconstantbutvaries
withtheriverflow.Astheriverfillsup,thetailwaterleveloftenrisesfasterthantheheadwaterlevel,
thusreducingthetotalheadavailable.
Althoughthisheadvariationismuchlessthanthevariationinflow,itcansignificantlyaffectthepower
available,especially in lowheadschemeswhereeveryhalfmetre isessential.Toassesstheavailable
grossheadaccuratelyheadwaterandtailwaterlevelsneedtobemeasuredforthefullrangeofriver
flows.(SomeexamplesareillustratedinFigure2throughFigure5).
DumpylevelsandtheodoliteTheuseofadumpylevel(orbuilder'slevel)istheconventionalmethodformeasuringheadandshould
be used wherever time and funds allow. Such equipment should be used by experienced operators
whoarecapableofcheckingthecalibrationofthedevice.
7/30/2019 Lecturenote Micro hydropower development
13/120
13
Dumpy levelsareusedwith staffs tomeasurehead ina seriesof stages.Adumpy level isadevice
whichallowstheoperatortotakesightonastaffheldbyacolleague,knowingthatthelineofsightis
exactlyhorizontal.Stagesareusuallylimitedbythelengthofthestafftoaheightchangeofnomore
than3m.Aclearunobstructedviewisneeded,sowoodedsitescanbefrustratedwiththismethod.
Dumpy levelsonly allow ahorizontal sightbut theodolite can alsomeasure vertical andhorizontalangles,givinggreaterversatilityandallowingfasterwork.
Sightingmeters
Handheldsightingmetersmeasuresangleofinclinationofaslope(theyareoftencalledinclinometers
orAbneylevels).
Theycanbeaccurate ifusedbyanexperiencedperson,but it iseasy tomakemistakesanddouble
checking is recommended.Theyaresmallandcompact,andsometimes include range finderswhich
savethetroubleofmeasuring lineardistance.Theerrorwilldependontheskilloftheuserandwilltypicallybebetween2and10%.
Waterfilledtubeandpressuregauge
Itisprobablythebestofthesimplemethodsavailable,butitdoeshaveitspitfalls.Thetwosourcesor
errorwhichmustbeavoidedareoutofcalibrationgaugesandairbubbles inthehose.Toavoidthe
firsterror,youshouldrecalibratethegaugebothbeforeandaftereachmajorsitesurvey.Toavoidthe
second,youshoulduseaclearplastictubeallowingyoutoseebubbles.
Thismethodcanbeusedonhighheadsaswellaslowones,butthechoiceofpressuregaugedepends
ontheheadtobemeasured.
Waterfilledtubeandrod
Thismethod is recommended for lowhead sites. It is cheap, reasonablyaccurateandnotprone to
errors. Inthiscase, ifmorebubblesaretrapped inonerisingsectionofthetubesthan intheother,
thenthedifferenceinverticalheightofthesetsofbubbleswillcauseanequaldifferenceinthehead
beingmeasured,thoughthisisusuallyinsignificant.Twoorthreeseparateattemptsmustbemadeto
ensurethatyourfinalresultsareconsistentandreliable.Inadditiontheresultscanbecrosschecked
againstmeasurementsmadebyanothermethod,forinstancebywaterfilledhoseandpressuregauge.
Spiritlevelandplank
Thismethod is identical inprincipletothewaterfilledtubeandrodmethod.Thedifference isthata
horizontal sighting is established not by water levels but by a carpenter's spirit level placed on a
reliablystraightplankofwoodasdescribedabove.Ongentleslopesthemethod isveryslow,buton
steepslopes it isuseful.Markoneendofplankandturn itateachreadingtocanceltheerrors.The
errorisaround2%.
7/30/2019 Lecturenote Micro hydropower development
14/120
14
MapsLargescalemapsareveryusefulforapproximateheadvalues,butarenotalwaysavailableortotally
reliable.Forhighheadsites(>100m)1:50,000mapsbecomeusefulandarealmostalwaysavailable.
AltimetersThese can be useful for highhead prefeasibility studies. Surveying altimeters in experienced hands
will give errors of as little as 3% in 100 m. Atmospheric pressure variations need to be allowed for,
however,andthismethodcannotbegenerallyrecommendedexceptforapproximatereadings.
Figure2Measuringheadinsteps
Figure3Measuringheadinstepsusingspiritlevelmeter
7/30/2019 Lecturenote Micro hydropower development
15/120
15
Figure4Measuringheadinstepsusingpocketsightinglevel
Figure5Measuringheadinstepsusingclinometermethod
Awaterfilledhosewithpressuregauge(manometer)canalsobelowereddowntofindoutthehead
difference,assaidabove.
7/30/2019 Lecturenote Micro hydropower development
16/120
16
1.2. Hydrology
Figure6Hydrologic
cycle
1.2.1. Overview
Whatisimportant?
1. Essential:
a. Determiningthemeanflowrate(discharge)=availablewaterwhichisarowmaterialfor
Hydropowergeneration.
b. Estimatingflooddischargeinordertosafelyplacerequiredstructures
c. Baseforpowercalculationsandcostestimate
2. Wouldbebeneficial:
a. Establishingwatergaugingstation(s)
b. Determiningflowratingcurve(s)(FRC)
c. Determiningflowdurationcurve(FDC)
d. Determiningafloodhydrograph
e. Determiningthedutyflowandpoweravailableflow
EssentialpartwouldbenecessaryforALLMHPsandtherestshouldberequiredatleastforMHPswith
P>100kW.
7/30/2019 Lecturenote Micro hydropower development
17/120
17
Basichydrologicaldatacollectionandanalysisincludemeasurements,historical/witnessdata,rainfall
runoff analyses average discharge, minimum and maximum flow rates, flow rating curve, flow
durationcurve.
Normally, fora reliableHydrological studybasedonproper statisticalanalyses,onehas tocollect
longtermdata series (20,30,40,50ormoreyears).However,MHP sitesarealmostalways in theunexploredareas,andsome tradeoffsshouldbemade,keeping inmind that themarginoferror
mightbehigh.
ThemajorhydrologicalparametersneededforMHPinstallationinclude:
Meanflowestimation(QAV)
TimedistributionofflowsFlowDurationCurve(FDC)
DepthflowrelationshipFlowRatingCurve(FRC)
Floodwaterdischargesayhundredyearflood(Q1/100)
Floodhydrograph(e.g.SCSUnithydrograph)
1.2.2. Analyses
a) Availabledischarge
Mean flow canbeobtained fromdata series,but since theyarenormallynotavailable, itcouldbe
estimatedbasedonprecipitationdata (whicharemore readilyavailable) combinedwith catchment
characteristicsandgeometry.
Dependingonthecatchmentarea(AC),forgivenannualprecipitation(p),volumeofwaterthatfallson
it,canbecalculatedas:
V=pAC(m3)
Allunitsshouldbeconvertedtom.Precipitation isusuallyexpressed inmillimetreswhileCatchment
areaisexpressedinkm2,orsometimesinhectares(ha)oracres(a).
Ifall thewater could find itsway to the streamandbedrained through it, then the flow couldbe
calculated as ratio of the volume over the time in which that volume was discharged (annually it
meansca.T=31.5106seconds).However,duetoevapotranspiration,aportionofthefallenwater
neverendsup in the stream.The ratioofvolumeofwater that flows through the streamover the
volumeofwaterbroughtbyprecipitationiscommonlycalledrunoffcoefficient.Itisdimensionlessand
commonlymarkedas .Thus,averageflowcanroughlybeestimatedas:
QAV= V/T(m3/s)
Runoffcoefficientdependsontheshapeandslopeofthecatchment,typeofsoilandbedrock,extents
andtypeofvegetationandotherfactors. Itcanrange from0.2to0.8,butmorecommonlytheyfall
withinrangeof0.4to0.6.Ifonewantstobeonthesafetyside,thelowervaluesshouldbeadopted.
If the largercatchment is relativelyknown, thenby itsanalysisaspecificdischargeqSP (l/s/km2)
couldbedeterminedandbasedonit,theactualflowcouldbeestimated.Itusuallyhasaform:
qsp = a AC+ b (l/s/km2)
7/30/2019 Lecturenote Micro hydropower development
18/120
18
Withreciprocaltrendvs.Area:
Figure7Exampleofqsp AC (=Fsl)
TodetermineratedMHPflow,amoredetailedanalysisisneeded.FDCwillgivetheinsightinhowthe
availablevaryingflowscouldbestbeutilised.ForthatonewouldneedatleastonereliableFDCinthe
same or nearby catchment and to make a series of simultaneous flow measurements in order to
determine correlation relationship. In addition, to be able to use longer series from the correlating
gauging station, one would need to form one on the profile of interest (intake) and to make FRC in
ordertobeabletoconvertwaterstagesintoflows.
TypicallyratedflowoftherunofriverMHPisaroundthemeanflow.Therewillbesomefloodwater
during the year (all exceeding Qi) that would spill unutilised, and there should be some duty flow
releasedtosustainlifeinthestreambetweentheintakeandthepowerhouse.Allthisleadstocertain
lossof water for power generation. Typically the ratioof useful mean flow to available flow is 50
60%.
Figure8ExampletypicalMHPFDC
y =-0.0046x +13.515
R2
=0.6196
10.5
11
11.5
12
12.5
13
13.5
0 100 200 300 400 500 600
qsp (l/s/km 2)
Fsl
(km
2)
7/30/2019 Lecturenote Micro hydropower development
19/120
19
Figure9Catchmentareaboundaries
Inordertocarryonabovementionedanalysesoneshoulddeterminethecatchmentareafirst.Forthat
somesortofmapshouldbeavailable.Forsmallcatchmentsideallyitwouldbe1:25000or1:50000or
similar.
Figure10Catchmentareaboundaries(3D)
7/30/2019 Lecturenote Micro hydropower development
20/120
20
Figure11ExampleofMHPcatchmentshownon1:25000
b) Flooddischarge
Remember:Thebiggestenemyofallhydraulicstructuresiswateritselfthroughitsdestructiveforces
offloodorleakage. ofallhydraulicstructurefailureswastheactionofwater!
The best way of determining the flood peak flow and volume is to statistically analyse the historical
data.Forthatmethodtobereasonable,longmeasurementseriesneedtobeavailable.Theproblemis
thatinremotesmallcatchmentssuchmeasurementsareseldomavailable.However,ifinthevicinity
thereiswellknownstreamsforwhichsuchdataareexist,thenanattemptcouldbemadetomake
correlationoftheunknownstreamwiththeknownone.
This can be done through a series of simultaneous flow measurements in different hydrological
regimes. Even a series of 45 measurements could be used, but waiting for proper hydrological
conditionsusuallytakesuptoayear.
The known watercourse is analysed by taking the
highest flood hydrographs for each year (40 years or
moreareneededforreliabledata,butevenmuchlessis
betterthannothing).Observedfloodhydrographsareusually determined through water gauging pole or
limnighraph(automaticwaterlevelmeter).Priortothat,
many flow measurements had to be taken in order to
determine correlation between flowrate and the stage
/level. In such a way a flow rating curve (FRC) is
determined.
Analysed flood flows can then be determined through one of usually used statistical distributions
(mostcommonlyLogPiersonIIIorGumbel).Thisgivesfloodswithdifferentreturnperiodsthatcanbe
usedasDesignFloodDischarge(DFD),dependingontheimportanceofthestructureanddangertothesurroundingarea.
7/30/2019 Lecturenote Micro hydropower development
21/120
21
Theproblemhereisthatcorrelationbetweencatchmentsmaynotbereliableoreventhatdatafrom
the known catchment may be dubious since it is very difficult to take measurements in flood
conditions.ThusFRCisusuallyextrapolatedtowardshighflowsandthusnotreallyobserved.
Anyway, in small remote catchments such data availability is unlikely ant therefore other, less
accurate,methodsareemployed.
Empirical formulae
Forveryroughflood levelestimation,wheretherearenodataortheyareverypoorsomeempirical
formulaecouldbeused,keepinginmindthattheobtainedvaluescouldbewithlargemarginoferror.
Nevertheless,thatisstillbetterthannothing.
Inglisformula:
QMAX=124 AC/ (10.4+AC)
Dickensformulae:
QMAX=a AC0.75
Whereais:
11fordry/aridclimatetype
17fornormalclimate
23forwetclimate
AndACiscatchmentareainkm2,whilepeakflowQMAXisinm
3/s.
Both formulae areneglecting thegeology, shapeand slopeof the catchment andwhether there is
vegetationandtowhatextent.Bothformulae(andespeciallyInglis)giveratherhighflowpeaks,which
is understandable sine high safety factor is taken into account. The values obtained are roughly
corresponding to PMF (Probable Maximum Flood), which is too high for design of MHPs. The
reasonableapproachwouldbetotake tooftheobtainedvalue.
Rational method (RM)
Iftherearegoodrainfalldatathismethodcanbeusedtobetterdeterminethepeakflood.
Q = C i AC (m3
/s)
Where:
CRunoffcoefficient(rangingfrom0.25to0.75,say0.5)
iIntensityoftheprecipitationinmm/min
ACCatchmentareainkm2
However intensity drops with increase of rainfall duration and selection of the proper duration
would depend on the size and shape of the catchment. There are many rational formulae to
calculatethedurationT.Hereisonethatneglectstheshapeofthecatchment:
T = 0.27 AC0,612
7/30/2019 Lecturenote Micro hydropower development
22/120
22
Figure12ExampleofintensitycurvesforvariousreturnperiodsforSarajevo
Unit Hydrograph (UH)
However,forlargerMHPsitisalwaysadvisabletoperformatleastunithydrographcomputation,say
by using HECHMS free computer program. The program provides several methods to compute the
UH.PerhapsthemostpopularisSCSmethod(SoilConservationService)whichrequiresaminimumof:
Theprecipitationforadurationcorrespondingtocatchmentparameters
Catchmentarea
Catchmentshaperesultinginlagtime
SCS Curve number (see Table1SCScurvenumbers)
Table1SCScurvenumbers
Land Use
Description on
Input Screen
Description and Curve Numbers from TR-55
Cover Description
Curve
Number for
Hydrologic
Soil Group
Cover Type and Hydrologic Condition
%
Impervious
Areas
A B C D
AgriculturalRow Crops - Straight Rows + Crop Residue
Cover- Good Condition
(1)
64 75 82 85
Commercial Urban Districts: Commercial and Business 85 89 92 94 95
Forest Woods(2) - Good Condition 30 55 70 77
Grass/Pasture Pasture, Grassland, or Range(3) - Good
Condition39 61 74 80
High Density
Residential
Residential districts by average lot size: 1/8
acre or less65 77 85 90 92
Industrial Urban district: Industrial 72 81 88 91 93
Low Density
Residential
Residential districts by average lot size: 1/2
acre lot25 54 70 80 85
7/30/2019 Lecturenote Micro hydropower development
23/120
23
Land Use
Description on
Input Screen
Description and Curve Numbers from TR-55
Cover Description
Curve
Number for
Hydrologic
Soil Group
Cover Type and Hydrologic Condition%
Impervious
Areas
A B C D
Open Spaces
Open Space (lawns, parks, golfcourses,
cemeteries, etc.)(4) Fair Condition (grass
cover 50% to 70%)
49 69 79 84
Parking and
PavedSpaces
Impervious areas: Paved parking lots, roofs,
driveways, etc. (excluding right-of-way)100 98 98 98 98
Residential 1/8
acre
Residential districts by average lot size: 1/8
acre orless65 77 85 90 92
Residential 1/4
acre
Residential districts by average lot size: 1/4
acre38 61 75 83 87
Residential 1/3
acre
Residential districts by average lot size: 1/3
acre30 57 72 81 86
Residential 1/2
acre
Residential districts by average lot size: 1/2
acre25 54 70 80 85
Residential 1
acre
Residential districts by average lot size: 1
acre20 51 68 79 84
Residential 2
acres
Residential districts by average lot size: 2
acre12 46 65 77 82
Water/ Wetlands 0 0 0 0 0
Hydraulic condition isbasedon combination factors that affect infiltration and runoff, including (a)
densityandcanopyofvegetativeareas,(b)amountofyearroundcover,(c)amountofgrassorclose
seeded legumes, (d)percentof residueon the landsurface (good>=20%),and (e)degreeofsurface
roughness.
Majorcatchmentparameters,apartfromitsarea,are:
LG=unithydrographlagtime,inhours,
C=constant,(=26n,nisManningcoefficientrangingfrom0.03to0.07)
N=constant(usually0.33)
L=thelengthofthelongestwatercoursefromthepointofconcentrationtotheboundaryofthedrainagebasin,inmiles.Thepointofconcentrationisthelocationonthewatercoursewhereahydrographisdesired,
LCA=thelengthalongthelongestwatercoursefromthepointofconcentrationtoapointoppositethecentroidofthedrainagebasin,inmiles,and
S=theoverallslopeofthelongestwatercourse(alongL),infeetpermile.
Lagtimeiscalculatedfrom:
N
CA
GS
LLCL
5.0
TimeofconcentrationTC=5/3LG(seeFigure13Exampleofafloodhydrograph)
RelevantprecipitationdurationTP=TCx(1+TC)0.2
7/30/2019 Lecturenote Micro hydropower development
24/120
24
Since lagtimeisempiricallydeterminedthereareotherformulaeaswell.Somemetricformulaegive
theLagtimeas:
LG=1.864 AC0.39
S0.31
LG=0.4 Ls0.67
(L LCA/S)0.086
LG=2.3 (L/(S)0.5)0.66
Incaseofdoubtusethemeanvalueofallthreeorjusttwothatgivecloserresults.
After that, knowing precipitation, one can compute the flood hydrograph by using manual unit
hydrographprocedureorrunningtheHECHMSprogram.
Figure13Exampleofafloodhydrograph
1.2.3. Measurements
Thepurposeofahydrologystudyistopredictthevariationintheflowduringtheyear.Sincetheflow
variesfromdaytoday,aoneoffmeasurementisoflimiteduse.Inabsenceofanyhydrological
analysis,alongtermmeasuringsystemmaybesetup.Suchasystemisoftenusedtoreinforcethe
hydrologicalapproachandisalsothemostreliablewayofdeterminingactualflowatasite.Oneoff
measurementsareusefultogiveaspotcheckonhydrologicalpredictions.
Theflowmeasuringtechniquesdescribedhereare:
theweirmethod,
stagecontrolmethod,
thesaltgulpmethod,
thebucketmethod,
thefloatmethod,
currentmeters.
7/30/2019 Lecturenote Micro hydropower development
25/120
25
c) Measuringweirs
Aflowmeasurementweirisaweirwithanotchinitthroughwhichallthewaterinthestreamflows.
The flowrate can be determined from a single reading of the difference in height between the
upstreamwaterlevelandthebottomofthenotch(seeFigure14).Forreliableresults,thecrestofthe
weirmustbekeptsharp, theoverflowshouldnotbesubmergedbytailwater andsedimentmustbe
prevented from accumulating behind the weir. Sharp and durable crests are normally formed from
sheetmetal,preferablybrassorstainlesssteel,asthesedonotcorrode.
Figure14Flowmeasurementsusingweir
Weirscanbetimber,concreteormetalandmustalwaysbeorientedatrightanglestothestreamflow.
Sitingoftheweirshould beata pointwhere thestream isstraightandfreefromeddies.Upstream,
thedistancebetweenthepointofmeasurementandthecrestoftheweirshouldbeatleasttwicethe
maximumheadtobemeasured.Thereshouldbenoobstructionstoflownearthenotchandtheweir
mustbeperfectlysealedagainstleakage.
Temporary measuring weirs are used for shortterm or dryseasoned measurements and are usuallyconstructedfromwoodandstakedintothebankandstreambed.Sealingproblemsmaybesolvedby
attachingalargesheetofplasticandlayingitupstreamoftheweirhelddownwithgravelorrocks.Itis
necessarytoestimatetherangeofflowstobemeasuredbeforedesignedtheweir,toensurethatthe
chosensizeofnotchwillbecorrect.
The use of permanent weirs may be a useful approach for small streams, but larger streams might
betterbemeasuredbystaging(explainedbelow).
d) Stagedischargemethod
Oncesetup,thismethodprovidesan instantmeasurementoftheflowatanytime.Itdependsona
fixed relationship between the water level and the flow at a particular section of the stream. This
7/30/2019 Lecturenote Micro hydropower development
26/120
26
section (the contour section) is calibrated by taking readings of water levels and flow (stage and
discharge)forafewdifferentwaterlevels,coveringtherangeofflowsofinterest,soastobuildupa
stagedischarge curve. During calibration the flow does not have to be measured at the contour
sectionitself.Readingscanbetakeneitherupstreamordownstreamusing,forinstance,atemporary
weir,aslongasnowaterentersorleavesthestreaminbetween.Thestagedischargecurveshouldbe
updated each year. Calibrated staffs are then fixed in the stream and the water level indicated
correspondstoariverflowratewhichcanbereadoffthestagedischargecurve.
Figure15Flowmeasurementsusingfloat
e) 'Saltgulp'method
The `salt gulp' method of flow measurement is adapted from dilution gauging methods with
radioactivetracersusedforrivers.Ithasprovedeasytoaccomplish,reasonablyaccurate(error
7/30/2019 Lecturenote Micro hydropower development
27/120
27
Figure16Flowmeasurementsusingdilution
Theaboveargumentassumesthatthecloudpassestheprobeinthesametimeineachcase.Butthe
slowertheflow,thelongerthecloudtakestopasstheprobe.Thusflowisalsoinverselyproportional
to the cloudpassing time. Detailed mathematics will not be covered here because the conductivity
metreisusuallysuppliedwithdetailedinstructions.
Theequipmentneededfor`saltgulp'flowmeasurementis:
abucket, puretablesalt,
athermometer(range0 40C),
aconductivitymeter(range01000mS),
anelectricalintegrator(Optional).
f) Bucketmethod
Thebucketmethodisasimplewayofmeasuringflowin
very small streams. The entire flow is diverted into a
bucketorbarrelandthetimeforthecontainertofill isrecorded. The flow rate is obtained simply by dividing
thevolumeofthecontainerbythefillingtime.Flowsof
upto20l/scanbemeasuredusinga200litreoilbarrel.
g) Floatmethod
TheprincipleofallvelocityareamethodsisthatflowQequalsthemeanvelocityVmeantimescross
sectionalA:
Q=AVmean(m3/s)
7/30/2019 Lecturenote Micro hydropower development
28/120
28
Onewayofusingthisprincipleisforthecrosssectionalprofileofastreambedtobechartedandan
averagecrosssectionestablishedforaknownlengthofstream.Aseriesoffloats,perhapsconvenient
piecesofwood,arethentimedoverameasuredlengthofstream.Resultsareaveragedandaflow
velocityisobtained.Thisvelocitymustthenbereducedbyacorrectionfactorwhichestimatesthe
meanvelocityasopposedtothesurfacevelocity.Bymultiplyingaveragedandcorrectedflowvelocity,
thevolumeflowratecanbeestimated.
h) Currentmeters
Theseconsistofashaftwithapropellerorrevolvingcupsconnectedtotheend.Thepropellerisfree
to rotate and the speed of rotation is related to the stream velocity. A simple mechanical counter
records the number of revolutions of a propeller placed at a desired depth. By averaging readings
takenevenlythroughoutthecrosssection,anaveragespeedcanbeobtainedwhichismoreaccurate
thanwiththefloatmethod.
Figure17Flowmeasurementsusingcurrentmeters
i) Automatedmeasurements
Therearealsosomesophisticatedpiecesofequipmentthattakeautomaticflowrateandcrosssection
readings byjust pulling the device across the stream. These are used for larger rivers difficult to
measurebytraditionalmethods.OnesuchdeviceiscalledRiverCATandisratherexpensive(sayabout
$30000ormore,dependingonthytype).
Figure18RiverCATinaction
7/30/2019 Lecturenote Micro hydropower development
29/120
29
1.3. GeologyandGeomechanics
1.3.1. Overview
Whatis
important?
1. Essential:
a. Determiningthetypeofsoil
b. Determiningthetypeofthebedrock
c. Determiningthedepthofoverburden
d. Lookforactualorpotentiallandslidesandscrees(slidingdebris)
e. Roughestimationofgeotechnicalparameters(bad,poor,fair,good,excellent)
2. Wouldbebeneficial:
a. Makinggeologicalmapofthearea
b. Preparingcharacteristicgeologicalprofiles
c. Determiningactualgeotechnicalparameters(c, , ,etc.)
EssentialpartwouldbenecessaryforALLMHPsandtherestshouldberequiredatleastforMHPswith
P>100kW.
Geology(geologicalconditionsandformations)canbegenerallydeterminedfromregionalgeological
maps if available. However, for site specific conditions it is necessary to make site geological
assessmentinsitu.
Figure19ExampleoftheuseofGoogleEarthinanalysingthearea
7/30/2019 Lecturenote Micro hydropower development
30/120
30
Figure20Exampleofthegeologicalprofiletakenfromthegeologicalbasemap1:100000
Figure21Exampleofthegeologicalbasemap1:100000
Figure22Landslides
7/30/2019 Lecturenote Micro hydropower development
31/120
31
Figure23
Screes
Itisimportanttodeterminegeneralgeologicalsiteconditionstakingintoaccountengineeringgeology
andhydrogeology.Itisusedforproperassessmentofthesoil/rockparametersintermsoffoundation,
buildingmaterial,permeabilityetc.Thisgeologyislinkedto:
Geomechanics Hydrology Structuraldesign Hydraulicdesign
Tofindoutaboutgeotechnicalparametersandengineeronthesitecanuseapickhammer,excavatea
testpitortrenchandbasedonexperiencemakeengineeringjudgments.Formorerequiringstructures
(inlargerschemes),itwouldbeadvisabletousesomedrillingandtakesamplesthatwouldbeanalyses
in the geotechnical laboratory. Obtained parameters could be used to run a number of different
analyses.Oneofthecommonlyusedisslopestabilityanalysis:
Figure24Slopestabilityresults
One very good such computer program for geotechnical analyses is GEO5 by FINE, which has 22
differentmodules(fromslopestability,tofoundation,gabionwall,gravitywalltoFEM).Eachmodule
7/30/2019 Lecturenote Micro hydropower development
32/120
32
costsabout$400to$600,butdiscountscanbeobtainedforasetandmultipleusers.Theprogramhas
a free option with limited functionality. It will run only a few soil layers (and we usually dont need
manyforMHPs)anditwilluseonlydefaultparametersoftheselectedsoiltypeandwouldnotallow
youtochangethemtothoseobtainedfromthesite.Thisisstilluseful,sinceitgivespossibilitytouse
standardparameterswithouttakingsamples.Thentheonlystepneededistorecognizethesoiltype
andselectit.
Other similar programs are GeoStudio and Slope. Figure 24 shows an output from Geostudio
program.
Figure253Dsitegeologicalpresentation
7/30/2019 Lecturenote Micro hydropower development
33/120
33
2. Basicsofhydraulics2.1. Overview
Whatisimportant?
1. Essential:
a. Performingsteadystatecalculationsfor
i. Canals(headrace,tailrace)
ii. Pipelines,penstocks
b. Hydrauliccalculationatintakeifany
c. Hydraulicandsettlementcalculationatsandtrapifany
d. HydrauliccalculationatForebay
e. Hydrauliccalculationforspillways(atintake,sandtrapandforebay)
f. Hydrauliccalculationforoutlets(sandtrap,forebay)
g. Hydrauliccalculationofthestillingbasin(orapron)ifany
2. Wouldbebeneficial:
a. Performingunsteady(transient)computations
i. Channelunsteadyflow
ii. Penstockwaterhammer
EssentialpartwouldbenecessaryforALLMHPsandtherestshouldberequiredatleastforMHPswith
P>100kW.
2.2. PipelinesPipelinesareusedforwaterorsewerconveyanceusuallyunderpressure,butalsowithfreeflow.They
canbemadeofvariousmaterialssuchas:Steel,GRP,PE,castiron,concrete,wood(obsolete),vitrified
clay(obsolete),asbestoscement(consideredenvironmentallydangerous),plasticmaterials(PVC)and
othermaterialsforspecialpurposes(brass,copper,lead,glass,rubber,etc.).
Hydraulics
Mostoftheprincipleswillbegiveninthissubchapterofpipelines,andonlysomespecificissueswould
bementionedforcanalsandtunnelsintheirrespectivesubchapters.
Basic hydraulic problems for steady flow through pipelines can be solved by 2
formulae:
Continuity(massconservation):Aivi=Constant
Bernoulli(energyconservation): 21
2
222
2
111
22
H
g
v
g
pZ
g
v
g
pZ
7/30/2019 Lecturenote Micro hydropower development
34/120
34
H isthesumofhead lossesbetweensectionsof interest.They include linearfriction lossesalong
thepipeandlocalorminorlosses(inbends,elbows,joints,valves,contractions,expansions,etc.).
Numerousformulaeareavailabletocomputelinearfrictionlosses.Probablythemostuniversallyused
is DarcyWeisbach formula: g
v
D
L
fHf 2
2
(in USA practice HazenWilliams expression is more
commonlyused)
HerefisDarcysfrictioncoefficient.Differentresearchershavedetermineditsvalueinthepast.There
arevariousexperimentallyobtainedexpressionsusedtodeterminef.
Therearedifferentflowregimespossibleinthepipes,dependentonReynoldsnumber:
Re=vD/orReR=vR/R=D
/4isHydraulicradiusofthepipe.iskinematiccoefficientoffluids
viscosity(forwater:t=20o=1.01x106m2/s,andt=10o=1.3x106m2/s)
ForRe
7/30/2019 Lecturenote Micro hydropower development
35/120
35
Table2Piperoughness
Materialandthestateofpipe (103m)
Concreterough 13
Concretesmooth 0.30.8
Steel(welded)new 0.040.1
Steel(welded)used,stained,incrusted 0.151.5Castiron 0.251.5(4)
Moredetailedlistcanbeobtainedfromdifferenthandbooks(e.g.Davis).Asmostpracticalproblemsin
hydraulic(civil)engineeringoccurintheregionofquadraticresistance(fullturbulence),evenmanning
formula could be applied with reasonable accuracy. Then better known values for n can be used
and/orconvertedtof.EquatingenergyslopeinManningandDarcyWeisbachequations:
326.124 Dnf
However, this could be applied only in fully developed turbulent flow as in transitional regime
Manningnshould not be considered constant as it is there dependent on Re as well. (See following
graphthatclearlydemonstratesthisforasetofmeasurements).
Figure26n=f(R)relationshipintransitionalflowzone
HazenWilliamsformula:
7/30/2019 Lecturenote Micro hydropower development
36/120
36
Where:
A=Flowareaofthepipe,ft2orm2.
C=HazenWilliamsroughnesscoefficient.
D=Pipediameter,ft.orm.
g=gravitationalconstant=32.174ft/s
2
=9.807m/s2
.hf=Frictionlosses,ftorm.
hm=Minorlosses,ftorm.
k=conversionfactor=1.318(forimperialunits)=0.85(forSI)
Km=sumofminorlosscoefficients
P1=Upstreampressure,lb/ft2orN/m2.
P2=Downstreampressure,lb/ft2orN/m2.
Q=Discharge,ft3/sorm3/s.
S=Waterdensity =62.4lb/ft(forimperialunits)=9800N/m(forSI)
V=flowvelocityinpipe,ft/sorm/s.
V1=upstreamvelocity,ft/sorm/s.
V2=Downstreamvelocity,ft/sorm/s.
Z1=Upstreamlevel,ftorm.
Z2=Downstreamlevel,ftorm.
Table3Importantpipematerialproperties
Ductileiron Steel PVC PE/GRP AC
Manningn 0.12 0.013 0.01 0.011 0.011
HazenWilliamsC 130 100 150 140 140
Roughness(mm) (DarcyWeisbach) 0.2591 0.04572 0.00152 0.00152 0.00152
YoungModulusE(MPa) 100000 207000 3300 1300/73500 24000
Coefficientoflinearexpansion (x10
6) 11 12 54 140/5 8.1
Poissonratio 0.25 0.3 0.45 0.45 0.3
Minororlocallossesarecalculatedbasedonexperienceandexperiments.Somecoefficientsto
calculatelocallossesaregivenhere:
Entrance:sharp=0.5,rounded=0.2,bellmouth=0.05,pipestickingintoreservoir
=1
Suddenexpansion:
22
2
11
D
D inregardtoinflowingvelocity.Ifexpansionisgradual
then this coefficient would be diminished (by multiplier k
7/30/2019 Lecturenote Micro hydropower development
37/120
37
Elbow:
5.3
285.113.0
901.0
R
Dor
R
D
R
Lo
whereL isarc length,R isbend
radius,Dispipediameter,andisdeflectionangleofthecurve.
Valves and gates: ifopen0.05
7/30/2019 Lecturenote Micro hydropower development
38/120
38
stress=pD/eforunitlengthofpipe.Hereeispipeshell(wall)thickness(orequivalentthicknessoftensiontakingpart).Thicknesscouldbecalculatedfromhere if insteadoftensilestress,allowable
tensilestress (forgivenmaterial) isused.Usualprocedurewouldbe tocompute this thickness first,
taking into accountpressure transients. This procedure requires iterations since thepipe thickness
affectspressurewaveceleritya,whichisrelevantfordeterminationofpressureriseH.
Changeofheadforquickclosure/openingcanbeexpressedby:
g
avH 0 Zhkovskycasefullwaterhammer
Whereaiscelerityofthepressurewave:
e
Dk
eE
D
K
a
50
10
1
1 4
Forwater=1000kg/m3,bulkmodulusK20108N/m2,k=1011/E
ForsteelE201010N/m2,k=0.5;Dispipelinediameter,eispipewallthickness.
Forothermaterials:k=1(castiron),k=5(concrete,lead),k=10(wood,plastic)
Openingorclosureisconsideredtobequickifitsshorterthantimeneededforpressurewaveto
traveltotheupperreservoirandback(0T,=2L/a).
Iftheopeningorclosuretakeslongerthanpressurechangeisdiminished:gT
LvH 02 .Ifalongthe
pipelinecrosssectionchanges,eachchangegeneratestransmissionandreflectionpressurewavesthat
superimposewithoriginalonesandaffecttheresults.Forbranchingorloopingnetworksthesemust
betakenintoaccount,andcomputationbecomesrathermorecomplicated.Ifthepumpingstations
areplacedalongtheconveyanceitisoftendifficulttocontroltimesofopeningand(especially)
closure,thusdifferentmeasurescanbeappliedtocontrolthedrop/riseofhead:
Flywheelsifcoupledwiththepumptheyprovideadditionalinertiasothatpumprotatesawhile
afterpowercutoccurs.Suitableforsmallinstallations.
Bypassesandpressurereliefvalvesbypasswithnonreturnvalvesuckspartoftheoriginalflow
mitigating thenegative effectsof sudden stoppage.Pressure release valves and air inlet valves
couldbeprovidedinthepipelineasadditionoralternatively.
Surge tanksandairvesselshave tobeplacedasclose to thepump(s)aspossible.Therefore,
often it isnotpracticable touseopen surge tanks (for theywould require enormousheights).
Rather,closeairvesselswithaircompressorsaremorecommonlyused.Theyconvert(orlimitin
space)more severewaterhammereffects tomilder (and longer/slower) surge (massoscillation)
effects.
Airvesselsservebothforsuddenopeningandclosure.Acheckvalveshouldbeprovidedbetweenthe
pumpandairvessel.Predeterminedextremelevelsintheairvesseltriggerthecompressedair
delivery.
Neglectingheadlosses,simplifiedsolutionforsuddencompleteclosure(intermsofheadchange)is:
7/30/2019 Lecturenote Micro hydropower development
39/120
39
t
LV
gAH
gAV
LHQHH
0
0
0
0
00 sin
0
000min
gAV
LHQHH
FromhereVmaxcanbecomputed:
Vmax1.2Hmin=V0
1.2H0
Periodofoscillationis:
0
0
2
LV
gAHT
Including losses in the pipeline and (entrance into/exit from) the air vessel, computation gets
somewhatmore complicated and isusually solvedby finitedifference equationorbyusingdesigngraphs forgiven (orassumed)head losses.Forpipelineswithchangingdiametersequivalent length
(onediameter lengththatwouldhavesamehead lossesasoriginalpipe)canbeused insimplified
computations.
Ifthepipethickness(obtainedinthisway)islessthancertainstructuralminimum,thanthislatervalue
shouldbeadopted.Structuralminimumwoulddependonmaterialusedandpipediameter(forsteel
pipesthisshouldbe8mmormoreforlargerpipes,includingupto2mmprovisionforcorrosionand
abrasion lossesof themassduringoperation).Suchdimensions shouldbechecked ifcanwithstand
otherloads,andadjustedifnecessary.
Usually temperature induced loads should be alleviated using deformable coupling elements
(expansionjoints) that canaccommodate resultingdeformations.Due to temperature changespipe
wouldtendtoexpand(contract)betweentwofixedpoints(anchorblocks)dependingontemperature
differencebetweenparticularmomentandambienttemperatureduringpipeplacement.Temperature
linearexpansioncoefficient is(m/moC).Forsteel it isabout12x106.Withoutanchors,extensionof
thepipeslengthwouldbe:L=Ltt.Ifexpansionisdisabledbyanchorblocksreactingstresswoulddevelop:
= EL/L,E ismodulusofelasticityofmaterial (forsteel20x1010Pa).Thesestressesand resultingforcescanbeunacceptable,andtodiminishthemspecialpipelineconstructionarrangementscanbe
introducedeitherexpansionjointsorharpshapedpipelinedeformableparts.
For freesurface or lowpressure pipes, loads caused by burying, backfill and surcharge are more
important.Iftheyarenotburied,thenstructuralthicknessdependentonthematerialusedandpipes
diameter, shouldbe adopted. For concrete pipes t=1/12D,but not less than 15 cm (D innerpipe
diameter).
7/30/2019 Lecturenote Micro hydropower development
40/120
40
Theplatethicknessrequiredtoresistbucklingunderuniformexternalpressureisapproximately:
36
6.1 pE
De
Ownweightofthepipeandwaterinitmustbetakenintoaccountforcalculationoftheforcesacting
on supports and anchorblocks. Friction, inertial,deflection (centrifugal) andother effectsmust be
accountedfor.
Placement considerations
Pipescanbeburiedoropen.Botharrangementshaveadvantagesanddisadvantages.Decisionistobe
madebasedonprojectneeds,localconditionsandthelike.
Buriedpipes:
Advantages Keepwater temperaturepretty constant andprotect from freezing;Ambienttemperaturesdonot imposeextra loads (savingsonexpansionjoints);Onceplaced theydo
notconsumeextraspace;Frequentanticorrosionpaintingnotneeded
Disadvantages difficult accessibility for maintenance; Backfill pressures; Expensive trench
excavation,beddingmaterial,carefulbackfilling;difficultplacementlimitedspaceforwork;
Painfuldetectionofleakageandotherproblems.
Openpipes:
Advantagessimpleaccessibilityformaintenance;Nobackfillpressures;Noexpensivetrench
excavation,beddingmaterial,carefulbackfilling;Simplifiedplacementplentyof space for
work;Easydetectionofleakageandotherproblems
Disadvantageswater temperature affected by ambient and no protection from freezing;
Ambienttemperaturesimposesevereextraloads(expensiveexpansionjoints);theyoccupya
lotofvaluablespace;Frequentanticorrosionpaintingneeded;Anchorblocksandnumerous
supports.
Economic considerations
Importanceofoptimizedlayout.Severalalternativesshouldbecompared.Savinginlengthand
diameter/wallthickness(aswellaspumpingfacilities)
Selectionofeconomicconduitsize(Pumpingstations,HPP,etc.).Incasewhenplentyofheadis
available (nopumpingneeded,ornoHPP foreseen/feasible) then considerationofminimum
diametermax.allowablevelocityandavailableenergyhead.
Comparisonorcombinationwithothertypesofconveyancesifapplicable.
Intermsofmaterialsforthepipesinhydraulicconstruction(largerscale)mostcommonaresteeland
concrete. Asbestoscement introduced after the other two, seemed to be promising due to its
favorableproperties(durability,easeofplacement,etc.),butlatelyitissuspectedtoberesponsiblefor
potentiallycausingcancer,andisnolongerconsideredenvironmentfriendlymaterial.
Steelpipesaremostlyweldednowadays,thoughothertypesofjointsarestillused.Theyarerelatively
expensive and require protection (and maintenance) against corrosion. Otherwise, they are
7/30/2019 Lecturenote Micro hydropower development
41/120
41
comparatively easy to handle, they can stand extreme pressure and tension stresses, easy to make
fittings,joints,branches,expansions,contractions,bends,andwhateverelseneeded.
2.3. Canals
Inasimilarmanner,theopencanalscouldbeanalyzedinordertoobtainparametersforpreliminary
design.ForhydrauliccomputationsManningformulawasused:
SARn
Q 32
1
Fromherecrosssectionisoptimizedforvariouslateralcanalslopes.Overalloptimumwithsidesat60o
is in most cases not technically feasible from the construction viewpoint. Therefore, as earlier
mentionedfollowing,morecommon slopes wereused V: H=1: m(form=0, 1,1.5and 2). (Here mi =
1/Si)
Figure27 Typicalcanalsection
Inordertofitthecanalintothegroundafreeboardshouldbedeterminedaswell.Traditionallythisis
between30and120cmandusuallytakenas30cm+0.25.h(wherehisthewaterdepthinthecanalin
cm).Alsoinamoregeneralformalateralslopeoftheterrainshouldbeconsideredinordertofitthe
canalandcalculatethebillofquantities:
Figure28 Typicalcanalsectionwithlateralgroundslope
The quantities will generally increase for increased lateral terrain slope for the HJK value. In the
present model this has been ignored and taken into account as contingencies or the lump sum for
unforeseenworksintheformofpercentagebasedongeneralengineeringjudgmentfortheparticularsiteconditions.
The same type of the conveyance formula, as the one for pipes, is derived for those types of
trapezoidal canals. Instead of filling coefficient as in pipes, optimal ratio of h/B would determine a
coefficientintheformula:
8
3
S
QnD
Table4Canalflowcalculationsparameters
m OPT.B/h Applicable
0 2 1.834 m=0
7/30/2019 Lecturenote Micro hydropower development
42/120
42
m OPT.B/h Applicable
1 0.84 1.81.e (0.833.m) m1
1.5 0.62 0.592.Log(m)+0.7854 1
7/30/2019 Lecturenote Micro hydropower development
43/120
43
Figure30Typicalchangesofflowregimes
2.4. Tyroleanintake
7/30/2019 Lecturenote Micro hydropower development
44/120
44
Figure31Tyroleanintake
2.4.1. Intake
7/30/2019 Lecturenote Micro hydropower development
45/120
45
AfterP.NovakAppliedHydraulics,IHEDelft,1981.
E
hh
E
hh
crx 11
1 11
Distancefromthebeginningoftheintake
Where
r=0.57ratiooftheintakebreadthtoriverbreadth
c=0.45coefficient(0.40.5afterMostkov)forlongitudinaltrashrackbars.
h1=hCRwaterdepthatthebeginning(forx=0)
hDepthforwhichdistancefromthebeginningisdetermined
EEnergyoftheflow
Forallwatertobetakeninthedepthattheendwouldbeh=0,thus:
E
hh
crbz
11 1
1
Forexampleofthedischarge:
Qz=0.21m3/s
Onethird oftheareaisblockedbybarsandbytheleavesanddebris:
Table
5
Example
of
the
calculation
for
Tyrolean
intake
Q L q hc b
B
(increased) Bpot
0.21 2.00 0.105 0.10 0.25 0.38 0.75
0.21 2.50 0.084 0.09 0.22 0.32 0.65
0.21 3.00 0.070 0.08 0.19 0.29 0.57
0.21 4.00 0.053 0.065 0.16 0.24 0.47
0.21 5.00 0.042 0.06 0.14 0.20 0.41
Figure32Waterprofileontheintake
h
0.000
0.010
0.020
0.030
0.040
0.050
0.060
0.070
0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18
7/30/2019 Lecturenote Micro hydropower development
46/120
46
Otherapproach:
Bz= Breadthofthecanal
Lz= Lengthofthecanal
br= Heightoftherackc= Coefficient
q= Unitdischarge
hkr= Criticaldepth
h= Depthofwaterontherack
Dh= Freeboardofnonspillwaysection
bpot= Neededwidth
AfterHajdin,Sarajevo1966.
AndafterI.Valant,Ljubljana1986.
Data:
Bz= 0,914xQ0,4
Lz= 7xBz
br= Bz/cosb
c= 0,6x(a/d)xcos1,5b
q= Q/Lz
hkr= 0,476xq0,6667
h= kxhkr
Dh= 1,5xhkr
bpot= 0,3386*(q/(cxmxh0,5
)
Qinst= 0.21 m3/s
Slopeoftherack= 10 %
a= 20 mm
d= 30 mm
m= 0.65 (forflatiron)
k= 0.91 (forb=10o)
Q Bz Lz b beta c qs hc h h Bpot k mu ar d0.21 0.490 3.43 0.492 0.100 0.357 0.061 0.073 0.066 0.091 0.348 0.91 0.65 15 25
2.4.2. CollectioncanalLengthofcollectioncanalundertherackisdonebyempiricalformula:
AfterP.NovakAppliedHydraulicsIHEDelftand1981,HydraulicStructures,London1990:
Computationofthewatersurface
Q 0.21
B 0.6
n 0.02
7/30/2019 Lecturenote Micro hydropower development
47/120
47
So 0.025
hc 0.232
L 4
Rackheight 0.04
Elevationoftherack 254.4
Elevationofthecanalbeginning 253.66Elevationofthecanalend 253.56
Scr 0.013704
xSSQ
Qvv
QQg
vvQh
f
0
1
2
21
211
WhereS0bedslope, Sfenergyslope
Figure33Waterprofileonthecollectioncanal
2.4.3. Spillwayonthesill(Q1/100)Discharge:Q1/100=35m
3/s
233
232 2 HBCHBgCQ
Dischargecoefficient:C2=0.40,orC3=1.77
BSpillwaybreadth
HSpillwaydepth
Elevationofthesill254.50mASL.
Elevationofthespillway254.70mASL.
Bp 4.0 BreadthofTyroleanpart
0.000
0.050
0.100
0.150
0.200
0.250
0.300
0.350
0.400
0.450
0.500
0 0.5 1 1.5 2 2.5 3 3.5 4
h
h+v2/2g
7/30/2019 Lecturenote Micro hydropower development
48/120
48
B 7.0 Breadthofthesill total
Qsr 0.24
DischargesQ1/100 35
Qi 0.37
Qmin 0.0125
Pu 0.95 SillheightupstreamPn 1.7 Sillheightdownstream
Hp 1.88 Heightofspillingpart
Ht 2.08 HeightofTyroleanpart
m 0.4 SpillwayCoefficient
hc 1.37 Criticaldepth
Eo 3.78 Availableenergy
Floodwaterelevation=254.50+2.08=256.58mASL.
Orroughly256.60mASL.
2.4.4. Stillingbasin(Q1/100)2
1
2
2
12 yg
qyE
,availableenergy
3
1
2
1
2 8112 gy
qyy ,conjugatedepths(y1iy2)
Stillingbasin(SB)length:
Lb=K(y2y1)Where4.5
7/30/2019 Lecturenote Micro hydropower development
49/120
49
DepthattheSBend:
S 1.20% Bedslopedownstream
n 0.02 Roughness(Manning)
h 0.94 DownstreamdepthendofSB
Fr 1.87 Froude number
Checkup
Manningsformula:
SARn
Q 32
1
Where:
QDischarge
nRoughnesscoefficient
ACrosssectionalarea
RHydraulicradius
SRiverbedslope
Graduallyvariedflow:
2
0
2
0
11 rF
SS
x
y
Fr
SS
dx
dy ff
Where:
SoRiverbedslope
SfEnergyslopeFrFroudenumber
EndofSBdepth:
S 1.20% Downstreamslope
n 0.028 Roughness
h 1.37 DownstreamdepthendofSB
Fr 1.06 Froudenumber
Figure34
Water
profile
along
SB
252.6
252.8
253
253.2
253.4
253.6
253.8
0 1 2 3 4 5 6 7 8
kota dna
kota vode
7/30/2019 Lecturenote Micro hydropower development
50/120
50
Figure35WaterprofilealongSBanddownstream
Waterdepthdownstream:
bk 4.5 Riverbedbreadth
S 1.20% Downstreamslope
n 0.033 Roughness
m 1.25 Sideslopes
A 10.9 Area
Bw 10.9 Watersurfacebreadth
h 1.42 DepthattheendofSB
Fr 1.02 Froudenumber
2.4.5. Settlingbasin(Qi)
H1= Waterdepthatthebeginning H1= k1xh0
k1= Coefficientoftransitionv0tovT k1= 1,6xQ0,1
BT= Settlingbasinbreadth BT= ST/H1
LTC.= Lengthofthesettlingbasin(theoretical) LTra.= H1x(vT/u)
LT= Lengthofthesettlingbasin(adopted) LT= 1,6xLTra.
Exampledata:
Discharge Qinst= 0.21 m3/s
Depthatthebeginningoftransition h0= 0.85 m
Breadthofthecollectioncanal b0= 0.60 m
Adoptedflowvelocity vT= 0.3 m/s
Adoptedsedimentfallvelocity u= 0.025 m/s
Adoptedbedslope I= 2 %
252.4
252.6
252.8
253
253.2
253.4
253.6
253.8
254
0 2 4 6 8 10 12 14 16
kota dna
kota vode
7/30/2019 Lecturenote Micro hydropower development
51/120
51
Q h0 b0 v0 vT ST H1pot BT BTusv u L LT LTusv
(m3/s) (m) (m) (m/s) (m/s) (m
2) (m) (m) (m) (m/s) (m) (m) (m)
0.210 0.85 0.80 0.31 0.15 1.45 1.16 1.24 1.70 0.03 6.76 10.82 11.20
CheckupbyStokesLaw:
Table6Settlingvelocityoftheparticledependentonwatertemperature/viscosityoC
t 20 12 10 8 6
A m2 1.25 1.25 1.25 1.25 1.25
Q m3/s 0.37 0.37 0.37 0.37 0.37
VAV m/s 0.30 0.30 0.30 0.30 0.30
d mm 0.20 0.20 0.20 0.20 0.20
vSET m/s 0.033 0.026 0.025 0.024 0.022
hAV m 0.85 0.85 0.85 0.85 0.85
L m 11.20 11.20 11.20 11.20 11.20
TSET s 25.99 32.20 34.00 36.17 38.29
t flow s 37.84 37.84 37.84 37.84 37.84
7/30/2019 Lecturenote Micro hydropower development
52/120
52
Otherapproachcanusethefollowingformulae:
Basinlength:h/vD
7/30/2019 Lecturenote Micro hydropower development
53/120
53
HpHbottom 0.93
b 0.4
h 0.4
A 0.16
H 0.73
m 0.7
Q 0.424
Qout=424l/s
Timetoempty=?
Volumeca.
V 15.90 m3
hmax 0.73 mD 0.4 m
A 0.16 m2
m 0.7
Q 0.42 m3/s
Timetoempty 75 s = 1.25 min
Forpartiallyclosedgate:
10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
0.05 0.10 0.15 0.20 0.24 0.28 0.32 0.36 0.39 0.42
Q=f(opening)
Propusna mo ispusta
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Otvor zatvaraa
Q(m3/s)
y
ydy
c
A
ga
HT
a
a
H
Hy
H
Hy
a
12
2
22
11
7/30/2019 Lecturenote Micro hydropower development
54/120
54
2.4.2. Spillwayfromsettlingbasin(Qmax)
After G.A.Simonjan(1960.):
gvvLSShh f
29,0 21012
27,023,008,02
2
2
2
2
B
LhL
B
Lhm
23
22 HLgmQ
So 0.02
B 1.7
n 0.02
m 0.113
L 3
Hp2 0.832
v1 0.614
v2 0
P 0.87
h2 1.702
A 2.894
R 0.567m(Hp2) 0.113
m= 0.08*(h2*L/B2)^20.23*((h2*L/B
2)
2)+0.27
Sf2 0.013%
h2h1=(SoSf)*L+0.9(v12v2
2)/2g
h1 1.635
A 2.783
R 0.560
Hp1 0.765
Sf1 0.015%
2.4.3. Dutyflowoutlet(Qmin)Firstapproach:
gHACQ 2
D
Lf
c1
7/30/2019 Lecturenote Micro hydropower development
55/120
55
Where:
fCoefficientDarcyWeisbachg
v
D
LfHf
2
2
.
32
6.124 Dnf =0,029
sumofminorlosses(1.5)
LPipelength
DDiameter
C=0.762
Secondapproach:
Re=vD/orReR=vR/R=D/4=157000
ColebrookC=0.762
Thirdapproach:
For 3
7/30/2019 Lecturenote Micro hydropower development
56/120
56
3. HydropowerbasicsandHydraulicstructures3.1. General
Thebasicprincipleofhydropower isthat ifwatercanbepiped fromacertain leveltoa lower level,
thentheresultingwaterpressurecanbeusedtodowork.Ifthewaterpressureisallowedtomovea
mechanical component then thatmovement involves the conversionof thepotentialenergyof the
water intomechanicalenergy.Hydro turbines convertwaterpressure intomechanical shaftpower,
whichcanbeusedtodriveanelectricitygenerator,agrindingmillorsomeotherusefuldevice.
3.2. HistoryThe use of falling water as a source of energy is known for a long time. In the ancient times
waterwheels were used already, but only at the beginning of the nineteenth century with the
inventionofthehydroturbinetheuseofhydropowergotanewimpulse.
Smallscalehydropowerwasthemostcommonwayofelectricitygeneratingintheearly20thcentury.
In 1924 for example in Switzerland nearly 7000 small scale hydropower stationswere in use. The
improvement of distribution possibilities of electricity by means of high voltage transmission lines
causedfaintedinterestinsmallscalehydropower.
Renewed interest in the technologyof small scalehydropower started inChina.Estimates say t