Design of a PV system with variations of hybrid system at Addis Ababa Institute of Technology

83 Pages·2015·30.75 MB·English

Design of a PV system with variations of hybrid
system at Addis Ababa Institute of Technology

Lovisa Bergman
Amanda Enocksson

Bachelor of Science Thesis 2015-06-15
KTH School of Industrial Engineering and Management
Energy Technology EGI-2015
SE-100 44 STOCKHOLM
Preface

This study has been carried out within the framework of the Minor Field Studies Scholarship
Programme, MFS, which is funded by the Swedish International Development Cooperation
Agency, Sida.

The MFS Scholarship Programme offers Swedish university students an opportunity to carry out
two months’ fieldwork, usually the student’s final degree project, in a country in Africa, Asia or
Latin America. The results of the work are presented in an MFS report which is also the student’s
Bachelor of Science Thesis. Minor Field Studies are primarily conducted within subject areas of
importance from a development perspective and in a country where Swedish international
cooperation is ongoing.

The main purpose of the MFS Programme is to enhance Swedish university students’ knowledge
and understanding of these countries and their problems and opportunities. MFS should provide
the student with initial experience of conditions in such a country. The overall goals are to widen
the Swedish human resources cadre for engagement in international development cooperation as
well as to promote scientific exchange between unversities, research institutes and similar
authorities as well as NGOs in developing countries and in Sweden.

The International Relations Office at KTH the Royal Institute of Technology, Stockholm,
Sweden, administers the MFS Programme within engineering and applied natural sciences.

Erika Svensson
Programme Officer
MFS Programme, KTH International Relations Office
Bachelor of Science Thesis EGI-2015

Design of a PV system with variations of hybrid system
at Addis Ababa Institute of Technology

Lovisa Bergman
Amanda Enocksson
Approved Examiner Supervisor
Catharina Erlich Getachew Bekele
Commissioner Contact person
Abstract
This paper proposes a renewable power generation system for Addis Ababa Institute of
Technology (AAiT). The aim of hybridizing renewable energy sources is that the main load shall
be covered by the available solar energy source and other sources shall function as a complement
when there is a deficiency in the main source. The aim of the system is to cover outdoor lighting,
which is also designed in this report, at the campus of AAiT during night. Due to frequent power
outages in Addis Ababa, Ethiopia, the PV system has been designed to provide enough electricity
supply to cover most of the offices in the Administration Building at AAiT.
The solar potential of the site is based on monthly average data of solar irradiation provided by
NASA. The optimum angle to mount the PV modules is determined through simulations based
on irradiation on a horizontal surface. The design of outdoor lighting is based on giving a suitable
illumination dependent on what the area is used for after sunset. The PV system was
dimensioned to supply enough energy to light the campus.
Four backups to the PV system were examined to find the optimal solution: battery, diesel
generator and the two hybrid systems with battery and diesel generator or grid. The
configurations made to find the optimized system were modeled in The Hybrid Optimization
Model for Electric Renewables (HOMER) software.
The most cost-effective system was determined by finding the Net Present Cost (NPC) and the
Cost of Energy (COE) of each setup. A sensitivity analysis was carried out for the two most
suitable setups: battery and diesel generator as backup and battery and grid as backup. The
variables included in the sensitivity analysis were: PV capital cost, diesel- and conventional
electricity price.
Based on simulation results, it was found that a PV system with battery and grid as backup would
give the most profitable investment. 53% of the energy use required by the setup would come
from solar energy, and the remaining 47% from the national grid that produces electricity
through hydroelectric power. Thus, the renewable fraction would be 100%. It would also provide
the institute with a sustainable power system. The setup has a NPC of $ 32 548 and COE of
0.127 $/kWh.
The economic evaluation of the final setup included a study of forecasting the electricity kWh-
price in Ethiopia. It was determined that the tariff price would be more than twice as high
(233%) at the end of the PV system’s lifetime (25 years) to equal today’s export tariff which
resulted in an annual increase of 3.45%. For a more reliable sensitivity analysis the annual cost of
the investment was compared to the estimated costs based on an annual electricity increase of
6.90%. To find the payback time of the investment, simulations were performed in MATLAB.
The payback time for the system would be reached within the lifetime of the system if the
electricity tariff would increase by 6.90%. It was found that the payback time would occur after
22 years.
Sammanfattning
I detta kandidatexamensarbete har ett förslag tagits fram på en lösning för ett förnybart
energisystem på Addis Ababa Institute of Technology (AAiT). Syftet med ett förnybart system är
att huvudbelastningen ska täckas av solenergi och andra källor ska fungera som sekundära
energikällor då det råder brist på energi från huvudkällan. Systemets primära energianvändning är
dimensionerat för att täcka energianvändningen av utomhusbelysning på AAiTs campus under
natten. Då strömavbrott är regelbundet förekommande i Addis Ababa, Etiopien, är systemet
anpassat för att kunna förse de administrativa kontoren på AAiT med elektricitet vid den typen
av händelse.
Potentialen av solenergi i Addis Ababa bestämdes baserat på genomsnittlig månadsdata för
solstrålning tillhandahållen av NASA. Med hjälp av simuleringar baserade på strålningen mot en
horisontell yta har den optimala vinkeln för solpanelernas montering bestämts.
Dimensioneringen av utomhusbelysningen fastlades utifrån vilken belysningsstyrka området
kräver baserat på dess användningsområde under natten. Det gav det totala energibehovet som
solcellssystemet behövde täcka.
Fyra backup-lösningar till solcellssystemet undersöktes för att finna den optimala lösningen:
batteri, dieselgenerator, hybrid system med batteri och dieselgenerator samt batteri och
uppkoppling mot elnätverket. Den primära kraftkällan i de fyra systemen var solpanelerna.
Sammansättningen av komponenterna modellerades i mjukvaran The Hybrid Optimization
Model for Electric Renewables (HOMER). Det mest prisvärda systemet kunde hittas genom att
nuvärdet av investeringen och kostnaden av energi per kWh beräknades. En känslighetsanalys
utfördes på de två mest relevanta systemen: batteri och dieselgenerator som backup samt batteri
och elnätverket som backup. Känslighetsanalysen innefattade variationer i dieselpris, inköpspris
av solpaneler och landets nationella elnätspris.
Det mest effektiva systemet bedömdes utifrån dess investeringskostnad och dess möjlighet att
förse universitetet med nattbelysning. Ett önskemål var att täcka eventuella strömavbrott. Baserat
på resultaten visade det sig att ett solcellssystem med elnätverket som backup ger den mest
lönsamma investeringen. 53% av systemets energigenerering kom från solenergi, och de
resterande 47% från elnätet som är helt drivet av vattenkraft. Den slutliga förnybarhetsfaktorn
blev därför 100%. Investerings nuvärde är $ 32 548 och har en energikostnad på 0,127 $/kWh.
Systemet klarar även att täcka eventuella strömavbrott under dagtid för att sedan kunna köpa
ytterligare elektricitet under natten för att täcka den eventuella förlusten av solenergi som istället
gick åt till att förse kontoren med el under dagen.
En ekonomisk prognos togs fram för att kunna göra en rättvis bedömning av investeringens
återbetalningstid. Den ekonomiska utvärderingen inkluderade en prognostisering av
prisutvecklingen på elektricitet i Etiopien. Bedömningen var att tariffen kommer att bli mer än
dubbelt så hög (233%) som dagens tariff för inrikes bruk inom livstiden för solcellssystemet
vilken är 25 år. Detta för att motsvara den exporttariff som landet idag säljer för, vilket
resulterade i en årlig ökning på 3,45%. För en mer omfattande känslighetsanalys jämfördes den
årliga kostnaden för investeringen med en energianvändning från elnätet vars elpris ökas med
6,90% årligen. För att hitta återbetalningstiden för investeringen användes MATLAB som
program för simuleringarna. Återbetalningstiden skulle vara uppnådd inom solpanelernas livstid
om elkostnaden ökar med 6,90% årligen. Återbetalningstiden för det slutgiltiga systemet med
solpaneler, inverterare, batteri och elnätet som backup-lösning hamnade på 22 år.
Acknowledgements
A major thank to our supervisor Dr. Getachew Bekele who has guided us through this project
with his valuable advice both regarding our thesis and practical matters for our trip to Addis
Ababa. Both he and his family have supported us while in Ethiopia and we are very grateful for
all the kindness they have shared.
We would also like to take this opportunity to thank our examiner Prof. Catharina Erlich who
has supported us from the very beginning when we came up with the idea of conducting a Minor
Field Study. She has generously shared ideas and solutions of how to continue with our thesis.
Catharina has a talent in giving direct and constructive answers.
Our special thanks to Asst. Prof. Mekonnen Tadesse who has provided us with an office at the
Faculty of Science in Addis Ababa to make it possible for us to complete our thesis.
Finally thanks to Mr. Kiros Tesfay who guided us around the campus of AAiT. Our special
thoughts go to Mr. Dawit Habtu who has been a loyal friend and has helped us to integrate in the
Ethiopian culture.
Table of Contents
Nomenclature ................................................................................................................................................ 1
1 INTRODUCTION ............................................................................................................................. 4
1.1 Background .................................................................................................................................... 4
1.2 Theory ............................................................................................................................................. 5
1.3 Purpose ........................................................................................................................................... 6
1.4 Delimitations .................................................................................................................................. 7
1.5 Approach ........................................................................................................................................ 9
1.5.1 The NASA-data ..................................................................................................................... 9
1.5.2 Introduction to SketchUp .................................................................................................... 9
1.5.3 Introduction to HOMER ................................................................................................... 10
2 FRAME OF REFERENCES .......................................................................................................... 11
3 THE PROCESS ................................................................................................................................. 13
3.1 Calculation of Solar Irradiation ................................................................................................. 13
3.2 Investigation of Load .................................................................................................................. 14
3.2.1 Measurement of Campus Area .......................................................................................... 14
3.2.2 Design Specifications for Lighting ................................................................................... 14
3.2.3 Investigation of Offices ...................................................................................................... 15
3.3 Dimensioning of the PV System ............................................................................................... 15
3.3.1 Battery as Backup ................................................................................................................ 17
3.3.2 Diesel Generator as Backup .............................................................................................. 18
3.3.3 Battery and Diesel Generator as Hybrid Backup ........................................................... 19
3.3.4 Battery and Grid as Hybrid Backup ................................................................................. 20
3.4 Sensitivity Analysis of the Investment ..................................................................................... 20
4 DATA ANALYSIS AND LOAD ESTIMATION ..................................................................... 22
4.1 Calculation of Solar Irradiation ................................................................................................. 22
4.2 Investigation of Load .................................................................................................................. 24
4.2.1 Measurement of Campus Area .......................................................................................... 24
4.2.2 Design Specifications for Lighting ................................................................................... 27
4.2.3 Inventory of Offices ........................................................................................................... 28
4.3 Input to HOMER ....................................................................................................................... 28
5 RESULTS AND DISCUSSION ..................................................................................................... 31
5.1 Dimensioning of the PV system ............................................................................................... 31
5.1.1 Battery as Backup ................................................................................................................ 32
5.1.2 Diesel Generator as Backup .............................................................................................. 33
5.1.3 Battery and Diesel Generator as Hybrid Backup ........................................................... 34
5.1.4 Battery and Grid as Hybrid Backup ................................................................................. 36
5.2 Sensitivity Analysis of the Investment ..................................................................................... 38
5.3 Sustainability ................................................................................................................................. 42
5.3.1 Environmental ..................................................................................................................... 43
5.3.2 Social ...................................................................................................................................... 43
5.3.3 Economical ........................................................................................................................... 43
6 CONCLUSION ................................................................................................................................. 45
6.1 Recommendation ........................................................................................................................ 46
6.2 Future Work ................................................................................................................................. 46
REFERENCES .......................................................................................................................................... 47
APPENDIX I – Photo gallery of campus at AAiT .............................................................................. 49
APPENDIX II – Meteorological data from NASA ............................................................................. 50
APPENDIX III – Technical data for 250 W PV module ................................................................... 51
APPENDIX IV – Technical data for inverter ....................................................................................... 52
APPENDIX V – Technical data for charge controller ........................................................................ 53
APPENDIX VI – Technical data for battery ........................................................................................ 54
APPENDIX VII– Technical data for diesel generator ........................................................................ 55
APPENDIX VIII – Stiftung Solarenergie Assembly Factory ............................................................. 56
APPENDIX IX– Optimization result for PV system with no backup ............................................. 57
APPENDIX X– Optimization result for PV system with battery as backup .................................. 58
APPENDIX XI– Optimization result for PV system with diesel generator as backup ................. 63
APPENDIX XII – Optimization result for PV system with battery and
diesel generator as backup ......................................................................................................................... 66
APPENDIX XIII – Optimization result for PV system with battery and grid as backup ............. 70
List of Figures
Figure 1 The relationship between energy demand in society and
solar energy supply (Tesla Motors, 2015). __________________________________________ 5
Figure 2 General schemes for the PV system with 3 alternative backups. _________________ 6
Figure 3 Visualization model showing the sizing procedure of the PV system. _____________ 9
Figure 4 Tilting the solar array at an angle β to the incoming light increases the
module output (PV Education, 2013). ___________________________________________ 13
Figure 5 HOMER diagram for a PV system without backup. _________________________ 15
Figure 6 HOMER diagram for a PV system with battery as backup. ____________________ 18
Figure 7 HOMER diagram for a PV system with diesel generator as backup. _____________ 19
Figure 8 HOMER diagram for a PV system with battery and diesel generator as backup. ____ 20
Figure 9 HOMER diagram for a PV system with battery and grid as backup. _____________ 20
Figure 10 Optimum angle of tilt of all months are seen at the maximum of each curve. _____ 22
Figure 11 Monthly averaged insolation at optimum angle  β. __________________________ 23
Figure 12 Overview of Addis Ababa Institute of Technology. _________________________ 24
Figure 13 Mounting of PV modules. ____________________________________________ 25
Figure 14 LED path lighting placed in zigzag pattern on the ground. ___________________ 25
Figure 15 LED floodlight placed along the parking lots. _____________________________ 26
Figure 16 LED wall lighting mounted on the building frontage. _______________________ 26
Figure 17 LED mount lighting placed around the pole of the study-huts. ________________ 27
Figure 18 Placement of outdoor LED lighting at campus. ____________________________ 27
Figure 19 Contribution of power sources for option (b) displayed in Table 8. ____________ 36
Figure 20 Contribution of power sources for option (b) displayed in Table 9. ____________ 37
Figure 21 Sensitivity analysis of the setup with battery and diesel generator as backup. ______ 38
Figure 22 Net present cost sorted by component. __________________________________ 41
Figure 23 Breakeven of PV setup with grid as backup system. _________________________ 42