System Design and Configuration of a Stand-Alone PV-Biomass Micro Grid

154 Pages·2014·14.15 MB·English

by  Marte Wiig Løtveit

System Design and Configuration of a
Stand-Alone PV-Biomass Micro Grid
An Application for Wawashang, Nicaragua
Marte Wiig Løtveit
Master of Energy and Environmental Engineering
Submission date: July 2014
Supervisor: Marta Molinas, ELKRAFT
Norwegian University of Science and Technology
Department of Electric Power Engineering

Problem Description
ThefocusofthisthesiswillbeondevelopinganalternativemicrogridintheWawashang
Agroforestal Complex, Nicaragua, that can satisfy the specific needs of the community
also in the long term when expansion is considered. During a specialization project in
thefallof2013, thebestmixofenergysourceswasevaluatedusingthesimulationtools
PVsystandHOMER.
The objectives of the thesis will be to find the optimal configuration of the micro grid
includingadistributionsystemdesign.Thespecifictaskwillbeonevaluatingtwodifferent
scenariostoidentifythemostefficientoperationofthesystem. Afieldtriptothecomplex
in Wawashang may be carried out in order to maximize the outcome of the project by
collecting data from the field and to feed in the simulation model. This will possibly be
partiallysponsoredbyEngineerswithoutBordersNORWAY.
StartDate: 6thofFebruary,2014
Supervisor: MartaMolinas
i
ii
Preface
Thismaster’sthesishasbeenwrittenattheDepartmentofElectricPowerEngineeringat
theNorwegianUniversityofScienceandTechnology(NTNU),spring2014. Thetitleis
System Designand Configuration ofa Stand-AlonePV-Biomass Micro Grid- an Appli-
cationforWawashang,Nicaragua.
First, I would like to thank my supervisor, Professor Marta Molinas at NTNU and my
advisers Post.Doc. Jon Are Suul and Professor Elisabetta Tedeschi at NTNU for their
support and guidance during the last year. My travel companion during the field trip to
Wawashang,ThomasVictorFernandes,IUGNorway,deservesabigthanksforgivingme
anewperspectiveonthetaskinhand,foraskingthequestionsIcouldn’tthinkofmyself
andforbeinganinvaluablesourceofknowledge.Awouldalsoliketoextendmygratitude
toSusanneThienhaus,althoughweregrettablynevermet,forherhelpinplanningthefield
trip.AheartfeltthankstothewonderfulpeoplewemetattheWawashangComplex,Silver
Borge Guitie´rrez, Luiz Guille´n Luna and Pascal Herrera are mentioned amongst many
others,andinKahkaCreek. Theenthusiasmwithwhichtheydotheirwork,whetheritis
educatingyoungstudentsincarpentry,agricultureorpreservingtheforest,isinspirational.
Theinteresttheyshowedintheprojectandtheirdesiretohelpandtomakeusfeelwelcome
wastrulyamazing.RemiMaupasandGillesCharlierfromblueEnergy,deservemysincere
thanks for their time, invaluable advice and experience. I would also like to thank Inger
Johanne Rasmussen, IUG NTNU for her efforts in making the field trip happen and for
helpandadviceintheplanningstage.ToIUGIwanttogiveamyappreciationforallowing
metheopportunityofworkingonthisprojectthatIhavebeensopassionateabout,andfor
financiallysupportingthefieldtriptoWawashang.
IwouldalsoliketothankallofmyfriendsfrommyyearsinTrondheimforallthegood
memories. Finally,myparentsdeservemydeepestappreciationforalwayssupportingand
encouragingme.
MarteWiigLøtveit
Trondheim,24thofJuly,2014
iii
iv
Abstract
Inthisthesis,anevaluationofastand-alonehybridmicrogridfortheWawashangComplex
in rural Nicaragua is presented. A solution for a new electricity supply and distribution
systemforthecomplexisproposedwithafocusonoptimalconfigurationofthesystem.
AfieldtriptoWawashangwasconductedinApril2014inordertocollectdataregarding
biomass potential for electricity production and information for a possible distribution
system design. The demand to be covered is divided into two systems; the micro grid,
whichdenotesallbuildingsexcludingthecarpentryworkshopandisthesystemforwhich
thedistributionsystemisdesigned,andthecarpentryworkshop.Asingle-phase/three-wire
(split-phase)solutionissuggestedforthedistributionsystemconfiguration,presentingthe
advantageofconsiderablysmallerconductorsizerequirementsthansingle-phase/two-wire
systemsforthesamevoltagedropandpowerloss. Thetotalpowerlossofthedistribution
systemis896kWh/yearor2.4%ofthedemand.
TheproductionsystemforthemicrogridconsistsofaPVarrayandabatterybank, and
for the carpentry workshop a diesel generator. Additionally, a biomass based generator
is available for both systems according to a defined schedule. The simulation software
HOMERisusedtorunsimulationsforthetwosystemssimultaneously,withtheintention
ofobtainingoptimaloperationofthebiomassgenerator. Twocasesareevaluatedonboth
technical and economical aspects. In Case I, the high frequency AC power output from
the biomass generator is rectified to DC power and then connected to the single-phase
ACbusofthemicrogridthroughaDC-ACconverterandsimilarlytothethree-phaseAC
loads of the carpentry workshop. In Case II, the output from the biomass generator is
connectedtotheDCbusofthemicrogridafterrectification. Thesimulationresultsshow
thattheoptimalsolutionforthecarpentryworkshopinbothcasesistooperatethebiomass
generatorasmuchaspossible,withthedieselgeneratoravailabletocoverpeakloads. In
themicrogridinCaseI,thebiomassgeneratorisoperatedwithaloadfollowingstrategy,
whileinCaseIIacyclechargingstrategyisapplied,resultinginahigherexploitationofthe
availablebiomassresourceinthelatter. Bothcasespresentadvantagesanddisadvantages
andaresimilarinreliabilityandcost. CaseIIisevaluatedastheoptimalsolutionforthe
WawashangComplex,asitistheoverallleastexpensiveandmostreliablesystem,andthe
least unbalanced system when it comes to seasonal variations. The system consists of a
9kWconverter, aPVarraywithaglobalpowerof30kWp, producingatotalof37254
kWh/year and a battery bank with a nominal capacity of 294 kWh (for the micro grid),
a 15 kW biomass generator producing a total of 38 477 kWh/year divided between the
micro grid (19.4 %) and the carpentry workshop (80.6 %) and a 15 kW diesel generator
producing 5 400 kWh/year for the carpentry workshop. Total excess electricity is 6.3 %
and unmet load is 0.21 %. Total net present cost is US$ 311 224 and levelized cost of
electricityisUS$0.285/kWh.
v
vi
Sammendrag
I denne avhandlingen evalueres et frittsta˚ende microgrid for det avsidesliggende Wawa-
shang-komplekset pa˚ øst-kysten av Nicaragua. En løsning for et nytt energiforsynings-
ogdistribusjonssystemforkomplekseterforesla˚ttmedfokuspa˚optimalkonfigurasjonav
systemet. EtfeltarbeidiWawashangbleutførtiApril2014meddenhensikta˚ samleinn
dataompotensialetfora˚ utnyttebiomassetilproduksjonavelektrisitetitilleggtilinfor-
masjonanga˚endeetmuligdesignavetdistribusjonssystemforkomplekset.Etterspørselen
somskaldekkeserdeltinnitosystemer;microgridet,sombetegnerallebygningerutenom
verkstedet og som distribusjonssystemet er utformet for, og verkstedet. Et enfasesystem
medtreledereerforesla˚ttforkonfigurasjonenavdistribusjonssystemet,dadettesetterbe-
traktelig lavere krav til størrelse pa˚ lederene for a˚ oppna˚ samme spenningsfall og tap i
linjenennetenfasesystemmedtoledere. Distribusjonstapeneilinjenutgjør896kWh/a˚r
eller2.4%avdentotaleetterspørselen.
Produksjonssystemet for microgridet besta˚r av solcellepanel og en batteribank, og for
verkstedet en dieselgenerator. I tillegg er en generator basert pa˚ biomasse tilgjengelig
forbeggesystemeneihenholdtilendefinerttimeplan. SimuleringsprogrammetHOMER
erbrukttil kjøresimuleringeravdetosystemenesamtidig,meddenhensikt oppna˚ opti-
maldriftavbiomassegeneratoren. Toalternativekonfigurasjoneravmicrogridsystemeter
vurdertmedhensynpa˚ ba˚detekniskeogøkonomiskefaktorer. Biomassegeneratoreneren
dampdreventurbogenerator,ogdenhøyfrekventeACkraftensomproduseresma˚ førstom-
formestilDCførdenkanentenomformestilbaketilACogkoblesdirektetilAC-buseni
microgridsystemet(AlternativI),ellerkoblestildenfellesDC-busenmedsolcellepanelene
og batteriet (Alternativ II). I begge alternativene kobles produksjonen fra generatoren til
trefaselasteneiverkstedetetterAC-DC/DC-AComforming. Simuleringsresultateneviser
at optimal løsning for verkstedet for begge alternativene er a˚ kjøre biomassegeneratoren
sa˚ mye som mulig med dieselgeneratoren tilgjengelig for a˚ dekke topplast. I Alternativ
Iblirbiomasseproduksjonenimicrogridetkunbrukttila˚ dekkelasten, mensialternativ
IIkjøresgeneratorenalltidvedsa˚ høyeffektsommuligfora˚ ladebatterienedersomden
ma˚ settesigangfora˚ dekkelasten. ResultateteratmerbiomasseutnyttesialternativII.
Beggealternativeneharfordelerogulempervedsegogerrelativtlikeiba˚depa˚litelighetog
kostnad. Alternativ II vurderes som den optimale løsningen for Wawashang-komplekset
ettersomdeterdetminstkostbareogmestpa˚liteligesystemet,ogdetmestbalansertesys-
temetna˚rdetgjeldervariasjonmeda˚rstidene. Systemetbesta˚raven9kWomformer,30
kWp solcellepanel som produserer 37 254 kWh/a˚r og en batteribank med nominell kap-
asitetpa˚ 294kWh(formikrogridet), en15kWbiomassegeneratorsomproduserertotalt
38477kWh/a˚rfordeltmellommicrogridet(19.4%)ogverkstedet(80.6%)ogen15kW
dieselgeneratorsomproduserer5400kWh/a˚rforverkstedet. Overflødigelektrisitetspro-
duksjoner6.3%ogudekketlaster0.21%. Totalkostnad(na˚verdi)erUS$311224,eller
US$0.285/kWh.
vii
viii