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TECHNO-ECONOMIC ANALYSIS OF HYBRID PHOTOVOLTAIC-
GENERATOR-BATTERY SYSTEM IN BARIO SARAWAK
TENG CHENG REEN
A project report submitted in partial fulfilment of the
requirements for the award of the degree of
Master of Engineering (Electrical Power)
School of Electrical Engineering
Faculty of Engineering
Universiti Teknologi Malaysia
JANUARY 2019
iv
ACKNOWLEDGEMENT
First, thank God for everything. I wish to thank my wife and family for
continuous support and encouragement during my project report preparation. I wish
to express my sincere appreciation to my supervisor, Dr. Ir. Tan Chee Wei, for
encouragement, guidance, critics and friendship.
My fellow postgraduate classmates should also be recognised for their
support. My sincere appreciation also extends to all my colleagues and others who
have provided assistance at various occasions. Their views and tips are useful indeed.
Unfortunately, it is not possible to list all of them in this limited space.
v
ABSTRACT
Solar energy is growing rapidly in recent years because of reduction of
capital cost and ease of installation compared to other renewable energy. However,
due to the intermittent characteristic, solar energy always combined with diesel
generator and energy storage to provide reliable supply. Even though, the hybrid
Photovoltaic (PV)-Diesel Generator-Lead Acid Battery system is having high
operation cost in term of high diesel fuel transportation cost because of difficult fuel
transportation and high replacement cost for lead acid battery. This study considered
the hybrid PV-Diesel Generator-Lead Acid Battery power station in Bario, Sarawak,
Malaysia. The Bario’s solar hybrid power station was built upon previous related site
surveys and it had been operational since January 2017. This study considered the
validation of the collected data from Bario’s solar hybrid power station, simulation of
actual system configuration, PV-Lead Acid Battery system and PV-Vanadium
Battery system. The comparison of actual system, PV-Lead Acid Battery system and
PV-Vanadium Battery system based on different load demand were performed. The
performance of different system were analyzed based on technical and economic
constraints, including net present cost, levelized cost of energy, and analysis taking
into account of operational aspects using Hybrid Optimization Model for Electric
Renewable (HOMER). Vanadium battery is proposed to replace the diesel generator
and lead acid battery because of the promising outcomes in long life cycle and lower
operation cost from previous researchers. Sensitivity analysis were also carried out to
analyze the effects of system performance and economic by changing main
parameters such as load demand, photovoltaic and battery prices. The findings show
that PV-Generator-Lead Acid Battery system has lower Cost of Electricity but higher
carbon emissions. PV-Vanadium Battery system is technically feasible and
financially competitive to used in Off-Grid Electrification.
vi
ABSTRAK
Tenaga solar telah berkembang dengan pesat sejak kebelakangan tahun ini
disebabkan pengurangan kos modal dan pemasangan jika dibandingkan dengan
tenaga boleh diperbaharui yang lain. Walaubagaimanapun, disebabkan
ketidakstabilan tenaga solar, ianya sering digabungkan bersama penjana kuasa diesel
dan bateri bagi tujuan penyimpanan kuasa. Walaupun begitu, sistem hibrid Solar PV-
Penjana Diesel-Bateri Asid Plumbum mempunyai kos operasi yang tinggi,
terutamanya dari aspek kos penghantaran bahan api yang disebabkan oleh
pengangkutan bahan api ke lokasi yang sukar serta kos pengantian bateri asid
plumbum yang tinggi. Kajian ini berdasarkan stesen janakuasa hibrid Solar PV-
Penjana Diesel-Bateri Asid Plumbum di Bario, Sarawak, Malaysia. Stesen jankuasa
Bario telah dibina berasaskan kaji selidik tapak yang telah dibuat sebelumnya dan
stesen tersebut telahpun beroperasi sejak Januari 2017. Kajian ini menganggap
pengesahan data yang dikumpulkan dari stesen janakuasa hibrid solar Bario, simulasi
konfigurasi sistem sebenar, sistem PV-Lead Acid Battery dan sistem Bateri PV-
Vanadium. Perbandingan sistem sebenar dibuat antara Sistem PV-Bateri Asid
Plumbum dan Sistem PV-Bateri Vanadium berdasarkan pemintaan beban yang
pelbagai. Prestasi sistem dinilai dan dianaliasis berdasarkan kekangan teknikal dan
ekonomi, termasuk nilai bersih semasa, kos tenaga bertingkat, dan analisis dengan
mengambil kira aspek operasi menggunakan Hybrid Optimization Model for Electric
Renewable (HOMER). Bateri Vanadium telah dicadang untuk menggantikan
penjanakuasa diesel dan bateri asid plumbum kerana jangka hayat yang lebih panjang
dan kos penyelenggaraan yang rendah berdasarkan pengkaji terdahulu. Analisis
sensitiviti juga dibuat untuk mengetahui kesan terhadap prestasi dan ekonomi sistem
dengan menukar paremeter utama seperti beban permintaan, harga photovoltaic dan
bateri. Penemuan menunjukkan bahawa sistem PV-Generator-Lead Acid Battery
mempunyai kos elektrik yang lebih rendah tetapi sitsem ini didapati melelepakan
karbon pada kadar yang lebih tinggi. secara teknikal, sistem Bateri PV-Vanadium
boleh dilaksanakan dan lebih berdaya saing dari segi kewangan untuk digunakan
dalam sistem elektrik luar talian.
vii
TABLE OF CONTENTS
TITLE PAGE
DECLARATION ii
DEDICATION iii
ACKNOWLEDGEMENT iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS vii
LIST OF TABLES ix
LIST OF FIGURES x
LIST OF ABBREVIATIONS xii
LIST OF APPENDICES xiii
CHAPTER 1 INTRODUCTION 1
1.1 Introduction 1
1.2 Problem Statement 3
1.3 Motivations 5
1.4 Project Objectives 5
1.5 Scope of Study 6
1.6 Report Outline 6
CHAPTER 2 LITERATURE REVIEW 7
2.1 Introduction 7
2.2 Hybrid PV System 8
2.2.1 Solar PV Panels 10
2.2.2 Energy Storage 12
2.2.3 Solar Charge Controller 14
2.2.4 Inverter 15
2.2.5 Diesel Generator 17
viii
2.3 Energy Storage Technology 17
CHAPTER 3 RESEARCH METHODOLOGY 23
3.1 Introduction 23
3.2 Bario Hybrid System 25
3.3 Load Profile 27
3.4 Software used for Analysis 28
3.4.1 HOMER 28
3.5 Techno-Economic Analysis 29
3.5.1 Net Present Cost (NPC) 29
3.5.2 Cost of Energy (COE) 30
CHAPTER 4 RESULT AND DISCUSSION 32
4.1 Introduction 32
4.2 Load Demand 32
4.3 Cost of Components 34
4.4 Economics Input 36
4.5 Part 1 – Simulation Results and Comparison of Lead
Acid Battery and VRFB as Storage 36
4.5.1 Part 1 – Load Demand of 1600 kWh/day 36
4.5.2 Part 1 – Load Demand of 3000 kWh/day 41
4.6 Part 2 – Simulation Results and Comparison of PV-
Generator-Battery, PV-Battery and PV-VRFB 44
4.7 Summary of Work 51
CHAPTER 5 CONCLUSION AND RECOMMENDATIONS 53
5.1 Research Outcomes 53
5.2 Future Works 54
REFERENCES 55
ix
LIST OF TABLES
TABLE NO. TITLE PAGE
Table 2.1 Datasheet of Cellcube 100kWh VRFB 20
Table 2.1 Components of PV Hybrid System in Bario 26
Table 4.1 Cost of Component for Hybrid System 35
Table 4.2 Storage Output Results for Part 1 – 1600 kWh/day 38
Table 4.3 Emissions Output Results for Part 1 – 1600 kWh/day 39
Table 4.4 Economics Output Results for Part 1 – 1600 kWh/day 40
Table 4.5 Storage Output Results for Part 1 – 3000 kWh/day 42
Table 4.6 Emissions Output Results for Part 1 – 3000 kWh/day 42
Table 4.7 Economics Output Results for Part 1 – 3000 kWh/day 43
Table 4.8 Simulation Results for Part 2 47
Table 4.9 Economics Output Results for Part 2 49
x
LIST OF FIGURES
FIGURE NO. TITLE PAGE
Figure 1.1 Sarawak Major Generation Plants and Transmission Grid
[4] 2
Figure 1.2 View of Bario 3
Figure 1.3 Journey to Bario 4
Figure 1.4 Transportation of Components to Rural Area 4
Figure 2.1 Average Annual Residential Load and PV Production [14] 9
Figure 2.2 PV-Wind-Battery Hybrid System 9
Figure 2.3 PV-Generator-Battery Hybrid System 10
Figure 2.4 AC Bus System 10
Figure 2.5 PV Working Principle [14] 11
Figure 2.6 I-V and Power Curves of PV Cell [14] 12
Figure 2.7 The Equivalent Circuit of the Boost Converter 14
Figure 2.8 Block Diagram of a Typical Bi-directional Inverter [20] 16
Figure 2.9 Block Diagram of a PV Hybrid System from Leonics 16
Figure 2.10 Working Principle of VRFB 18
Figure 2.11 VRFB Manufacturing Plant in China 19
Figure 2.12 Dimension of Cellcub VRFB [27] 20
Figure 2.13 Working Principle of VRFB [28] 21
Figure 2.14 VRFB System at SnoPUD Everett Substation, USA [29] 21
Figure 2.15 VRFB Installation Work at PUD’s Everett Substation 22
Figure 2.16 Life Time Capacity of VRFB vs Solid Batteries [29] 22
Figure 3.1 Methodology Flowchart 23
Figure 3.2 Proposed PV-VRFB System 24
Figure 3.3 Photos of Hybrid PV System in Bario 25
Figure 3.4 Schematic Diagram of PV Hybrid System in Bario 26
xi
Figure 3.5 Load Profile in Bario 27
Figure 3.6 Daily Load Profile used in HOMER 28
Figure 4.1 Daily Load Profile Pattern 33
Figure 4.2 Data from Leonics monitoring system 34
Figure 4.3 System Schematic for Existing Configuration 37
Figure 4.4 Graphical view of results in Part 1 – 1600 kWh/day 41
Figure 4.5 Graphical view of results in Part 1 – 3000 kWh/day 44
Figure 4.6 Optimization Results from HOMER 45
Figure 4.7 Schematic for Optimized PV-Generator-Battery 46
Figure 4.8 Schematic for Optimized PV-Battery 46
Figure 4.9 Schematic for Optimized PV-VRFB 47
Figure 4.10 Total NPC by Components for PV-Generator-Battery 49
Figure 4.11 Total NPC by Components for PV-Battery 50
Figure 4.12 Total NPC by Components for PV-VRFB 50
xii
LIST OF ABBREVIATIONS
AC
COE
DC
-
-
-
Alternating Current
Cost of Energy
Direct Current
NPC - Net Present Cost
PV - Photovoltaics
VRFB - Vanadium Redox Flow Battery
1
CHAPTER 1
INTRODUCTION
1.1 Introduction
By the year of 2018, Malaysia, while moving rapidly towards a delveloped
nation, still consists of considerable number of rural areas which are under
developed. Most of these rural areas are small villages, scattered across large areas of
East Malysia (Sarawak and Sabah). In general, basic infrastructures are inadequate
including proper roads, electiricty supply and water supply [1]. Some 400 villlages in
the remote rural heartlands of Sarawak are difficult to connect to the main electricity
grid. The extremely rugged and challenging terrain, mostly include hilly terrain
means these communities are economically impossible to be supplied with electricity
by extending distribution poles and power lines. At the year of 2018, over 8,700
households in the 300 isolated villages in Sarawak area still without 24-hours supply,
but 2,000 households such as Batang Ai, Murum Resettlement in Belaga, Pelagus
and Katibas in Central Region, Baram, Bario and Bakelalan in the North are already
connected with 24-hour electricity through Off-Grid Solar Hybrid System funded
either by Malaysia’s federal government or local Sarawak government [2].
Sarawak’s major generation plants and transmission grid is exteremely far
from most of the remote rural areas such as Bario as shown in Figure 1.1. Bario is
located 180km from Miri, the second largest town in Sarawak. Bario, lying an
altitude of about 1,000 meters above sea level in the Northern region of Sarawak can
be reached either by 45 mins flight of Twin Otter from Miri or 10-14 hours of four
wheel drive on rugged and challenging logging road from Miri to Bario [3].
2
Figure 1.1 Sarawak Major Generation Plants and Transmission Grid [4]
Since year 2016, Bario community enjoys 24-hour electricity supply of a 887
kilowatt peak solar hybrid system. This solar hybrid system has the capital cost of
RM27 Million and is currently operaated and maintaned by Sarawak Energy, the
only electricity utility company in Sarawak [5]. The detail design of Bario Solar
Hybrid System will be discussed in Chapter 2. Figure 1.2 shows the view of Bario
highland.
3
Figure 1.2 View of Bario
1.2 Problem Statement
Solar hybrid system proven to be feasible and suitable solution for rural
electrification in Sarawak because of difficulty to construct transmission grid to rural
villages that is situated at interior of Sarawak. Previous researcher concluded that
hybrid PV-Lead Acid Battery-Diesel Generator system perform best technically
while also provide good economic and environmental performance [6]. Other
research also showed that PV-Battery-Diesel Generator system is more economical
[7] compared to PV-Wind-Battery-Diesel Generator system and Wind-Battery-Diesel
Generator system [8]. However, maintenance cost especially replacement cost for
lead-acid batteries was not realistically considered during desing stage. Lead Acid
Battery has design life cycle of about 3000 cycles but can only last less than 5 years
in practical considering temperature factor and also influenced by the depth of
4
discharge. The challenges also include the transportation of bulky Lead Acid Battery
to the rural villages that can be 10 of hours logging roads drive from nearest town.
Figure 1.3 Journey to Bario
Figure 1.4 Transportation of Components to Rural Area
5
1.3 Motivations
Due to technology advancement, Vanadium Redox Flow Battery (VRFB)
was commercialized and used in Photovoltaic (PV) power system application in
other country such as China. Compared to other storage technologies, VRFB has
advantages including longer lifecycle, lower operation and maintenance cost, higher
storage efficiency, faster response, and can operate over a wide range of power
outputs. Simulation results from previous researcher show that VRFB was better and
fitter as long term energy storage solution compared to lead acid battery in term of
physical characteristics and financial feasibility [9]. Other researcher salso proved
that VRFB can be promising energy storage for reliability, quality, secure, scalability
and deep discharge capacity for renewable energy system especially PV system [10].
VRFB is also believe to have competitive capital cost according to researcher in
paper [11], and claimed to be half of the lithium battery cost.
1.4 Project Objectives
The objectives of the project are :
(a) To evaluate the feasibility of Vanadium Redox Flow Battery (VRFB) as
energy storage system for actual medium scale hybrid PV system (887 kWp)
at rural villages in Bario, Sarawak, Malaysia
(b) To optimize the size of hybrid PV system using HOMER with minimum total
net present cost (NPC) and cost of energy (COE) by satisfying real load
demand in Bario, Sarawak
(c) To perform techno-economic analysis on simulation result of the (i) PV-
Generator-Battery, (ii) PV-Battery, and (iii) PV-VRFB system by using
HOMER
6
1.5 Scope of Study
1.6 Report Outline
Chapter 1 describes the introduction of Bario, Sarawak and Solar Hybrid
System initiatives in Sarawak. This chapter also includes the problem statement,
motivation, research objectives, and scope of this study.
Chapter 2 presents the previous literature and studies relevant to this project.
It also reviews the Solar Hybrid System of Bario and various type of energy storage
system used in Photovoltaic system.
In Chapter 3, the methodology of the project is described. The economical
analysis is described.
Chapter 4 discusses about the results and analysis for different configuration.
The technical performance and economical studies were presented and discussed.
Chapter 5 concludes the study and recommend future work to be performed.
55
REFERENCES
[1] A. M. Mahmud, "Evaluation of the Solar Hybrid System for Rural Schools in
Sabah, Malaysia," World Renewable Energy Congress, 2011.
[2] "Alternative Energy for Sarawak," Sarawak Energy, [Online]. Available:
http://www.sarawakenergy.com.my/index.php/about-us/what-we-
do/alternative-energy-for-sarawak. [Accessed 1 May 2018].
[3] "Bario, Land of a Hundred Handshakes, Visit Sarawak," Sarawak Tourism,
[Online]. Available: https://sarawaktourism.com/attraction/bario/. [Accessed 1
May 2018].
[4] "Distribution System and Tarriff in Malaysia," [Online]. Available:
https://slideplayer.com/slide/9237821/. [Accessed 20 July 2017].
[5] "Electrification of Bario Highlands Via Solar Hybrid Power System," Sarawak
Energy, 2016. [Online]. Available:
http://www.sarawakenergy.com.my/index.php/news-events-top/latest-news-
events/latest-media-release/2039-electrification-of-bario-highlands-via-solar-
hybrid-power-system. [Accessed 10 May 2018].
[6] Laith M. Halabi, Saad Mekhilef, Lanre Olatomiwa and James Hazelton,
"Performance analysis of hybrid PV/diesel/battery system using HOMER: A
case study Sabah, Malaysia," Energy Conversion and Management , vol. 144,
pp. 322-339, 2017.
[7] M.S. Ismail, M. Moghavvemi and T.M.I. Mahlia, "Techno-economic analysis
of an optimized photovoltaic and diesel generator hybrid power system for
remote houses in a tropical climate," Energy Conversion and Management, vol.
69, 2013.
[8] Jagriti Kumari, P. Subathra, J. Edwin Moses and Shruthi D., "Economic
Analysis of Hybrid Energy System for Rural Electrification using Homer,"
IEEE International Conference on Innovations in Electrical, Electronics,
Instrumentation and Media Technology (ICIEEIMT 17), 2017.
[9] Guozhen Hu, Shanxu Duan, Cai tao and Changsong Chen, "Techno-economical
Analysis of Vanadium redox and Lead-acid batteries in Stand-alone
56
Photovoltaic systems," 2nd IEEE International Symposium on Power
Electronics for Distributed Generation Systems, 2010.
[10] Ankur Bhattacharjee, Dipak Kumar Mandal and Hiranmay saha, "Design of an
Optimized Battery Energy Storage Enabled Solar PV Pump for Rural
Irrigation," 1st IEEE International COnference on Power Electronics,
Intelligent Control and Energy Systems (ICPEICES-2016), 2016.
[11] Jongwoo Choi, Wan-Ki Park and Il-Woo Lee, "Application of Vanadium
Redox Flow Battery to Grid Connected Microgrid Energy Management,"
International Conference on Renewable Energy Research and Applications,
2016.
[12] R.K Akikur, R. Saidur, H.W Ping and K.R Ullah, "Comparative study of stand-
alone and hybrid solar energy systems suitable for off-grid rural electrification:
A review," Renewable and Sustainable Energy Review, vol. 27, pp. 738-752,
2013.
[13] Martin Uhrig, Sebastian Koenig, Michael R. Suriyah and Thomas Leibfried,
"Lithium-based vs Vanadium Redow Flow Batteries - A Comparison for Home
Storage Systems," 10th International Renewable Energy Storage Conference,
2016.
[14] K. Brian, "How Hawaii Has Empowered Energy Storage and Forever Changed
the US Solar Industry," [Online]. Available:
https://www.renewableenergyworld.com/articles/2015/12/how-hawaii-has-
empowered-energy-storage-and-forever-changed-the-u-s-solar-industry.html.
[Accessed 1 June 2018].
[15] "Solarworld SW240 Datasheet," [Online]. Available:
http://www.solarelectricsupply.com/fileuploader/download/download/?d=0&fil
e=custom%2Fupload%2Fsw-240-mono.pdf. [Accessed 2 Feb 2018].
[16] "Frequently Asked Questions about Solar Power," [Online]. Available:
http://www.mitsubishielectric.com/bu/solar/faq/index.html. [Accessed 1 Feb
2018].
[17] J. Lim, "Optimal Combination and Sizing of a New and Renewable Hybrid
Generation System," International Journal of Future Generation
Communication and Networking , vol. 5, 2012.
57
[18] "Leonics Website," 1 July 2018. [Online]. Available:
https://www.leonics.com/system/solar_photovoltaic/customized/MW-scale-
stand-alone-pv-hybrid_en.php.
[19] "GEESYS Solar PCU," [Online]. Available:
http://www.geesysindia.com/solar_pcu.php. [Accessed 11 July 2018].
[20] "Cummins Diesel Generator D175 D5e Datasheet," [Online]. Available:
http://www.cummins.cz/pdf/motory/C175_C220D5_QSB7G5.pdf. [Accessed 1
May 2018].
[21] "Cummins Diesel Generator C300 D5 Datasheet," [Online]. Available:
https://www.generatorwarehouse.co.uk/media/blfa_files/C300_D5_1.pdf.
[Accessed 1 May 2018].
[22] K. Belmokhtar, H. Ibrahim, Z. Feger and M. Ghandour, "Charge Equalization
Systems for Serial Valve Regulated Lead-Acid (VRLA) Connected Batteries in
Hybrid Power Systems Applications," 10th International Renewable Energy
Storage Conference (IRES 2016), 2016.
[23] Shinichi Sano, Yoshiaki Ito, Yoshikazu Hirose, Hisaki Takeuchi and Shigeo
Aone, "Development of long cycle life valve-regulated lead-acid battery for
large-scale battery energy storage system to utilize renewable energy,"
Telecomunications Energy Conference (INTELEC), 2015.
[24] Ruben Lopez-Vizcaino, Esperanza Mena, Maria Millan and Manual A.
Rodrigo, "Performance of a vanadium redox flow battery for the storage
electricity produced in photovoltaic solar panels," Renewable Energy 114
(2017) 1123-1133, 2017.
[25] Mark Moore, Robert Counce, Jack Watson and Thomas Zawodzinski, "A
Comparison of the Capital Costs of a Vanadium Redox-Flow Battery and a
Regenerative Hydrogen-Vanadium Fuel Cell," Journal of Advanced Chemical
Engineering, 2015.
[26] "200MW/800MWh Vanadium Flow Battery," [Online]. Available:
https://electrek.co/2017/12/21/worlds-largest-battery-200mw-800mwh-
vanadium-flow-battery-rongke-power/. [Accessed 20 May 2018].
[27] "Cellcube Vanadium Redox Flow Technology," 1 August 2018. [Online].
Available: https://www.cellcube.com/.
58
[28] "User Manual of Cellcub Vanadium Redox Flow Battery," 2 August 2018.
[Online]. Available: https://www.vsunenergy.com.au/wp-
content/uploads/2017/02/Environmental-Controls.pdf.
[29] HOMER Energy, "HOMER," [Online]. Available:
https://www.homerenergy.com/.
[30] Himadry Shekhar Das, Chee Wei Tan, A.H.M. Yatim and Kwan Yiew Lau,
"Feasibility analysis of hybrid photovoltaic/battery/fuel cell energy system for
an indigenous residence in East Malaysia," Renewable and Sustainable Energy
Reviews 76 (2017) 1332-1347, 2017.
[31] Sunanda Sinha and S.S. Chandel, "Review of software tools for hybrid
renewable energy systems," Renewable and Sustainable Energy Reviews Rev
2014:32:192-205, 2014.
[32] Andrew Stiel and Maria Skyllas-Kazacos, "Feasibility Study of Energy Storage
Systems in Wind/Diesel Applications Using the HOMER Model," Applied
Sciences, 2012.
[33] Nader Barsoum and Pearl Dianne Petrus, "Cost Optimization of Hybrid Solar,
Micro-Hydro and Hydrogen Fuel Cell Using Homer Software," Energy and
Power Engineering, pp. 337-347, 2015.
[34] A. M. Mahmud, "Evaluation of the Solar Hybrid System for Rural Schools in
Sabah, Malaysia," World Renewable Energy Congress 2011, 2011.
[35] Official Sarawak Tourism, "Bario, 'Land of a hundred handshakes' Visit
Sarawak," Sarawak Tourism, [Online]. Available:
https://sarawaktourism.com/attraction/bario/. [Accessed 1 May 2018].
[36] "Hoppecke OPzS Solar Battery Datasheet," [Online]. Available:
http://www.off-grid-europe.com/downloads/dl/file/id/125/opzs_datasheet.pdf.
[Accessed 1 May 2018].
[37] M.S. Ismail, M. Moghavvemi and T.M.I. Mahlia, "Techno-economic analysis
of an optimized photovoltaic and diesel generator hybrid power system for
remote houses in a tropical climate," Energy Conversion and Management 69,
2013.
[38] National Renewable Energy Laboratory, "System Advisor Model (SAM),"
[Online]. Available: https://sam.nrel.gov/. [Accessed 1 March 2018].
59
[39] Universidad Zaragoza, "iHOGA," [Online]. Available:
https://ihoga.unizar.es/en/.
[40] University of Massachusetts, "Hybrid2," [Online]. Available:
http://www.umass.edu/windenergy/research/topics/tools/software/hybrid2.
[41] Natural Resources Canada, "RETScreen," [Online]. Available:
http://www.nrcan.gc.ca/energy/software-tools/7465. [Accessed 1 May 2018].
[42] Hafeez Olasunkanmi Tijani, Chee Wei Tan and Nouruddeen Bashir, "Techno-
economic analysis of hybrid photovoltaic/diesel/battery off-grid system in
northern Nigeria," Renewable and Sustainable Energy , vol. 6, 2014.