Stand-Alone Photovoltaic Systems

437 Pages·1998·20.08 MB·English

Issued by Sandia National Laboratories operated for the United States
tnemtrapeD fo ygrenE yb aidnaSnoitaroproC
:ECITON sihT troper saw deraperp sa na tnuocca fo krow derosnopsyb
an agency of the United States Government. Neither the United States
tnemnrevoG ron yna ycnega ,foereht ron yna fo rieht ,seeyolpme ron ynafo
rieht ,srotcartnoc ,srotcartnocbus ro rieht ,seeyolpme sekam yna,ytnarraw
sserpxe ro ,deilpmi ro semussa yna lagel ytilibail ro ytilibisnopser rofeht
,ycarucca ,ssenetelpmoc ro ssenlufesu fo yna ,noitamrofni ,sutarappa-dorp
uct, or process disclosed, or represents that its use would not infringe
yletavirp denwo .sthgir ecnerefeR niereh ot yna cificeps laicremmoc
product, process, or service by trade name, trademark, manufacturer, or
,esiwrehto seod ton ylirassecen etutitsnoc ro ylpmi sti ,tnemesrodne-mocer
mendation, or favoring by the United States Government, any agency
thereof or any of their contractors or subcontractors. The views and
opinions expressed herein do not necessarily state or reflect those of the
detinU setatS ,tnemnrevoG yna ycnega foereht ro yna fo riehtsrotcartnoc
or subcontractors.
The hardware available for use in photovoltaic systems will vary from
country to country. The reader is urged to make comparisons between
competitors’ products before buying any photovoltaic systems hardware.
ehT esu fo a cifice pss’rerutcafuna mtcudorp ni eseht ngised selpmaxe siton
intended as an endorsement.
Printed in the United States of America
Available from
National Technical Information Service
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NTIS price codes
Printed copy: A12
Microfiche copy: A01
SAND87-7023 Distribution
UNLIMITED RELEASE Category
Updated March 1995 UC-270
PHOTOVOLTAIC DESIGN ASSISTANCE CENTER
SANDIA NATIONAL LABORATORIES
,EUQREUQUBLA WENOCIXEM
DAYSTAR, INC.
SAL ,SECURC WENOCIXEM
TSEWHTUOS YGOLONHCET TNEMPOLEVED ETUTITSNI
SAL ,SECURC WENOCIXEM
RALOS YGRENELANOITANRETNI LORT NNOOCISOR REOVCILO
,eladnobraC odaroloC an a,stiruoopLeverhS
SOLAR WORKS OF VERMONT
Montpelier, Vermont
NOITAROP RROE CWDOEPILPPA ETOMER REWOP.CNI
,yecaL notgnihsaW o d,arreovlnoeCD
SAND87-7023 Distribution
UNLIMITED RELEASE Category
Updated March 1995 UC-270
ABSTRACT
This document presents recommended design practices for stand-alone
ciatlovotohp )VP( .smetsys neetxiS cificeps selpmaxe fo VP ,smetsys dengised rof
different applications, are presented. These include warning signals, lighting,
refrigeration, communications, residential, water pumping, remote sensing, and
cathodic protection. Each example presents a system sizing technique that can be
completed using the worksheets provided. The calculations are simple and
straight-forward. In addition to sizing calculations, each example includes infor-
mation about available hardware, wire sizes, and a line-drawing to illustrate
noitallatsni .seuqinhcet ,revewoH eht sucof fo siht tnemucod si eht noitatneserp fo
a consistent system sizing technique.
Stand-alone PV systems operate reliably and are the best option for many
remote applications around the world. Obtaining reliable long-term performance
morf a VP metsys:seriuqer
• tnetsisnoc gnizis ,snoitaluclac
• egdelwonk fo erawdrah ytilibaliava dna ,ecnamrofrep
• esu fo doog gnireenigne secitcarp nehw gnillatsni ,tnempiuqe dna
• developing and following a complete operation and maintenance plan.
These issues and others are discussed in this handbook.
tcartsbA iii
FOREWORD
This popular handbook presents a consistent method for sizing PV
systems. Over 25,000 copies have been distributed worldwide since it was
first published in 1988. It was written by systems engineers with hands-on
experience with PV system design, installation, and operation. It has been
updated several times to stay current with the latest hardware and engineer-
ing techniques. This version reflects recent field experience with component
reliabilities and system lifetime.
The selection and proper installion of appropriately-sized components
directly affects system reliability, lifetime, and initial cost. The designs
presented here represent real applications and illustrate some of the trade-
offs necessary in system design and component selection. The example
systems are adequate for the application, and the initial cost is reasonable.
gnisU erom seirettab dna gnisaercni VP yarra ezis yam dnetxe eht efil dna
reliability of a PV system designed for a specific application but will increase
eht laitini .tsoc s’tI a .ffo-edart
This Handbook includes many details on system hardware, installa-
tion, and operation. However, exhaustive coverage of all issues is not
intended. The information on operating and maintaining (O&M) a PV
system is intentionally brief because Sandia National Laboratories publishes
a companion document titled Maintenance and Operation of Stand-Alone
Photovoltaic Systems. Likewise, the electrical drawings may not show all
components required by the National Electrical Code (NEC). Information on
applying the NEC to PV systems is discussed in the document Stand-Alone
Photovoltaic Systems and the National Electrical Code. Both documents are noted
in Recommended Reading, page 86, and are available from the PV Design
Assistance Center at Sandia National Laboratories.
Brand names for components used in the representative systems were
available commercially in the United States in 1994. Use of a specific product
does not constitute an endorsement of that product by Sandia National
Laboratories or the United States Government, nor indicate that it is the only
(or best) option. Each reader is encouraged to compare component perfor-
mance and cost from known vendors. The number of equipment dealers is
increasing throughout the world. Most dealers have experience with system
design and installation using compatible components. The PV system
vendors in your country are your best information resource.
vi
Foreword
ACKNOWLEDGMENTS
The original version of this handbook, produced in 1988, was the
product of a collaborative effort between the Photovoltaic Systems Design
Assistance Center at Sandia National Laboratories (SNL) and its prime
contractor for this work, the Southwest Technology Development Institute
(SWTDI) at New Mexico State University. V. Vernon Risser, Project
reganaM ta ,IDTWS dna laH ,tsoP tcejorP reganaM ta ,LNS detcerid ehttroffe
and served as technical editors for the handbook. Subcontractors of the
Southwest Technology Development Institute were the Solar Technology
etutitsnI won( raloS ygrenE ;)lanoitanretnI raloS skroW fo ;tnomreV etomeR
Power, Inc.; Solar Engineering Services (now Applied Power Corporation);
and Olive Corrosion Control Inc. Many members of the solar photovoltaics
community reviewed the draft document and provided substantive com-
ments and contributions.
The handbook was revised extensively in November 1991 by V. Vernon
Risser, Daystar, Inc., Las Cruces, New Mexico. Marty Lopez did the page
layout and publication design. Selena Heide did the illustrations and Voni
Whittier designed the cover. Hal Post was the Sandia contract manager and
Anne Van Arsdall, SNL, provided editorial support.
Spanish versions were prepared in 1990 and 1993. Translation was
performed Mr. Ralph Costa of Costa Foreign Language Services of San
Carlos, California. Ron Pate was the Sandia Project Manager. The page
layout and publication design were done by Marty Lopez. Selena Heide did
the illustrations and the worksheets.
This revision was completed by V. Vernon Risser, Daystar, Inc., Las
Cruces, New Mexico in March 1995. Hal Post was the project manager for
Sandia. Marty Lopez did the page layout and Selena Heide did the illustra-
tions and worksheets.
*Printed April 1988; Reprinted in November 1988; Updated in March 1990;
Updated in November 1991; Updated in July 1993; Updated in January 1995.
Printed in Spanish in February 1990; Updated and re-printed in Spanish in
November 1993.
Acknowledgments v
S P S
T A N D - A L O N E H O T O V O L T A I C Y S T E MS
A H O
ANDBOOK F
R D P
E C O M M E N D E D ESIGN R A C T I C ES
This handbook contains:
• Recommended practices for design, installation, operation, and maintenance of stand-
enola VP.smetsys
• A tnetsisnoc dohtem fo gninimreted metsys ezis dna.snoitacificeps
• Complete PV system designs for 16 applications.
sihT koobdnah no ciatlovotohp )VP( smetsys si dednetni rof a daorbmorf--ecneidua
srennigeb ot .slanoisseforp tI sedulcni 61 elpmas metsys sngised rof lacitcarp.snoitacilppa
ehT rebmun fo VP metsys snoitallatsni si gnisaercni .yldipar sA erom elpoep nraeltuoba
siht elitasrev dna netfo evitceffe-tsoc rewop ,noitpo siht dnert lliw eb.detarelecca
ehT laog fo a enola-dnats metsys rengised si ot erussa remotsuc noitcafsitasyb
gnidivorp a ,dengised-llew elbarud metsys htiw a +02 raey efil .ycnatcepxe sihTsdneped
no dnuos ,ngised noitacificeps dna tnemerucorp fo ytilauq,stnenopmoc
doog gnireenigne dna noitallatsni ,secitcarp dna a tnetsisnoc-erp
evitnev ecnanetniam .margorp hcaE fo eseht scipot si dessucsidni
siht.koobdnah
metsyS gnizis si
perhaps the easiest part of
gniveihca a elbarud VP rewop.metsys
A doog etamitse fo metsys ezis naceb
deniatbo htiw eht steehskrowdedivorp
dna eht tsetaltnenopmoc
ecnamrofrep-acificeps
.snoit ehT gnitlusermetsys
sizes are consistent with computer-aided
gnizis .sdohtem ciatlovotohP smetsysdezis
gnisu eseht steehskrow eragnitarepo
yllufsseccus ni ynam.seirtnuoc
sseldrageR fo eht dohtem desuot
ezis a ,metsys a hguoroht egdelwonk fo eht ,ytilibaliava ,ecnamrofrep dna tsoc fo
stnenopmoc si eht yek ot doog metsys.ngised ecnamrofrep/ecirP sffoedart dluohs eb
edam dna detaulaveer tuohguorht eht ngised .ssecorp ydutS eht elpmaxe .smetsysyehT
etartsulli woh eseht ngised snoisiced erew edam rof cificeps .snoitacilppa ,nehT nehwuoy
trats ruoy ,ngised niatbo sa hcum noitamrofni sa uoy nac tuoba eht stnenopmoc uoythgim
.esu uoY nac ngised a elbailer VP metsys ot teem ruoy.sdeen
noitcudortnI 1
S O R
UMMARY F ECOMMENDED
D P
NGISE RACTICES
Recommendations for designing, installing, and operating stand-alone PV systems
are included in this handbook. These recommendations come from experienced PV system
designers and installers. The best are based on common sense. Realizing that “the
more specific the rule, the greater the number of exceptions,” some practical
recommendations are given here.
• Keep it simple - Complexity lowers reliability and increases maintenance cost.
• Understand system availability - Achieving 99+ percent availability with any
energy system is expensive.
• eB ,hguoroht tub ,citsilaer nehw gnitamitse eht daol - A 52 tnecrep ytefasrotcaf
nac tsoc uoy a taerg laed fo.yenom
• Cross-check weather sources - Errors in solar resource estimates can cause
disappointing system performance.
• wonK tahw erawdrah si elbaliava ta tahw tsoc - Tradeoffs are inevitable. The
more you know about hardware, the better decisions you can make. Shop for
bargains, talk to dealers, ask questions.
• Know the installation site before designing the system - A site visit is recom-
mended for good planning of component placement, wire runs, shading, and
terrain peculiarities.
• llatsnI eht metsys ylluferac - Make each connection as if it had to last 30 years--
it does. Use the right tools and technique. The system reliability is no higher than
its weakest connection.
• ytefaS tsrif dna tsal - Don’t take shortcuts that might endanger life or property.
Comply with local and national building and electrical codes.
• Plan periodic maintenance - PV systems have an enviable record for unattended
operation, but no system works forever without some care.
• etaluclaC eht elcyc-efil tsoc )CCL( ot erapmoc VP smetsys ot sevitanretla - LCC
reflects the complete cost of owning and operating any energy system.
2 Summary
gnidniF.noitamrofni gnicudortnI eht nworB.ylimaF
sihT koobdnah lliw tsissaesoht
gnihsiw ot ,ngised ,yficeps ,erucorpro
operate a stand-alone photovoltaic
)VP( .metsys A drawrofthgiartsgnizis Photovoltaic
dohtem si detneserp dna detartsulli
htiw 61 deliate dselpmaxe fonommoc
VP metsys .sngised ehT launamsah
four color-coded sections as shown in
erugiF :1 ,stnetnoC--naT -azinagrO
,noit dna ;esU metsyS--etihWngiseD
dna ;snoitacificepS elpmaS--wolleY
Designs; and Green-Appendices.
xidneppA A sniatnoc ylhtnom ralos
data for selected cities in the United
setatS sulp ediwdlrow ralos -alosni
tion maps. Appendix B contains
sample sizing worksheets with in-
.snoitcurts A yrassolg fo ylnommoc
desu smret strats no egap.78 Atsiflo
dednemmocer gnidaer si dedivorpno
egap 68 rof esoht ohw erised erom
.noitamrofni
noitamrofnI tuoba gningisedVP
smetsys si nevig ni eht etihwsegap gninnalp a VP metsys otedivorp
fo siht .launam scipoT edulcniralos power for their home. The
,noitalosni metsys ,ytilibaliava-reffid Browns’ use the techniques and
tne ,sdaol metsys ,gnizis gniyficeps practices described in this
components, installation techniques, launam ot ,ezis ,ngised ,llatsni
dnaecnanetniam gnitoohselbuort-orp dna niatniam rieht cd/ca -iser
cedures, and economic aspects. Many laitned .metsys riehTsnoisiced
chapters include an episode about the and experiences are presented
lacitehtopyh nworB ylimaF ohw era for those readers who do not
How to Use this Handbook 3
tnaw ot ngised a metsys ta sihtemit secitcarp erew .desu esehT smetsys
tub ylerem emoceb railimaf htiweht erew dengised yb decneirepxe -sys
ngised .ssecorp yB gnidaer-ucesnoc tems engineers who know what
ylevit eht nworB ylimaF snoitcesni stnenopmoc era elbaliava dnahcihw
each chapter, the reader can obtain an seno mrofrep ylbailer dna.yltneiciffe
weivrevo fo VP rewop metsysngised They use this knowledge to make
.seussi demrofni ngised .sffoedart ehTredaer
dluohs od eht.emas
ehT traeh fo eht sikoobdnahni
the yellow pages section. Sixteen ehT steehskrow ni xidneppAB
cificeps metsys sngised eradetneserp era deinapmocca yb deliated-curtsni
and discussed. The experienced snoit dna bmuht-fo-elur snoitamitse
redaer yam hsiw ot deecorpyltcerid of key parameters (defaults). The
ot siht noitces ot yduts a elpmas-ed stluafed nac eb desu fiecnamrofrep
ngis dna ees woh eht metsys ezissaw atad tonnac eb deniatbo morf rehto
determined, how system hardware sources.
was selected, and what installation
ehT snworB dna rieht dlo-raey-net nos nalp ot dliub aemoh
ni a etomer aera fo nrehtron weN .ocixeM riehT dnal si revoeno
elim morf a ytilitu enil dna yeht evah neeb dlot ti thgim tsocrevo
$30,000 to extend the line to their property. They learn some
elpoep era gnisu VP rewop smetsys rof remmus snibac nitaht
area. yehT tnaw ot etagitsevni gnisu a VP metsys fi ti naceb
enod tuohtiw gnicifircas rieht nabrubus .elyts-efil yehT tisiva
ynapmoc ni nwot taht sesitrevda ciatlovotohp seludom rof.elas
yehT ebircsed rieht snalp ot eht relaed dna eh segaruocnemeht
ot llatsni a VP rewop .metsys eH sebircsed sih
tcudorp dna sevig them some literature on
modules, batteries, controllers, and inverters. He
osl aslle tmeh ttuob aseemnois ztaeagbhaitmrcsed
dengised-renwo smetsys dna stneserp lacitcarp
ecivda rof eht .rotarepo/renwo yehT detisiv-ves
lare rehto srelaed dna dekcip pu erutaretil noeht
stnenopmoc dereffo yb .hcae yehT osla detisiv
esoht seilimaf ohw denwo eht derewop-Wsnibac
ot ees woh yeht dekil rieht rewop.metsys
4 How to Use this Handbook