Nabin Khadka - ULisboa · Nabin Khadka Thesis to obtain Master of Science Degree in Electrical and...
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SOLAR MICROGRID CASE-STUDIES FOR TWO ELECTRIFICATION PROJECT SITES IN NEPAL Nabin Khadka Thesis to obtain Master of Science Degree in Electrical and Computer Engineering Supervisor(s): Prof. Paulo José da Costa Branco Prof. João Filipe Pereira Fernandes Examination Committee Chairperson: Prof. Rui Manuel Gameiro de Castro Supervisor(s): Prof. Paulo Jose da Costa Branco Members of Committee: Prof .Carlos Alberto Ferreira Fernandes December 2017
Transcript of Nabin Khadka - ULisboa · Nabin Khadka Thesis to obtain Master of Science Degree in Electrical and...
SOLAR MICROGRID CASE-STUDIES FOR TWO
ELECTRIFICATION PROJECT SITES IN NEPAL
Nabin Khadka
Thesis to obtain Master of Science Degree in Electrical and Computer Engineering
Supervisor(s): Prof. Paulo José da Costa Branco
Prof. João Filipe Pereira Fernandes
Examination Committee
Chairperson: Prof. Rui Manuel Gameiro de Castro
Supervisor(s): Prof. Paulo Jose da Costa Branco
Members of Committee: Prof .Carlos Alberto Ferreira Fernandes
December 2017
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ABSTRACT
As data recorded in 2016 only seventy-six percent of people have access to Electricity in Nepal.[1] Out
of which fifteen percent of the rural population gets electricity from the off-grid renewable energy source
as of National census 2011. Providing access to electricity to a large chunk of rural populace in Nepal has
traditionally been a daunting exercise, because of its huge capital investment, geographic difficulties, lack
of proper infrastructure in development of hydropower project, and where decentralization generation is
only way to electrify, where extension of national grid makes no sense because of need of long transmission
lines for less power consumption in a rural village, off-grid renewable energy is likely to be the key for
reaching rural population which still lacks access to electricity.
The average global solar radiation in Nepal varies from 3.6-6.2 kWh/m²/day, the sun shines for about
300 days a year, the number of sunshine hours amounts almost 2100 hours per year and average insolation
intensity about 4.7 kWh/m²/day (=16.92 MJ/m²/day).[2] Thus, Nepal lies in a favorable insolation zone in
the world even though the data in Nepal was based on one year and few sites.[3] Basically this thesis
research will make a case study on two sites from different places in Nepal named Site A & B. Detail
Feasibility Study(DFS) has already been conducted for both sites by Government organization of Nepal
and all the information has been adapted to perform further research in this report. Simulation results in
MATLAB of Site A suggested that there is possibility of reducing price of major component by nearly 20
percent while number of hours in a year when battery completely drains increases from thirteen to fifty-
five in normal operating conditions as compared to DFS (Detail Feasibility Study) design. And in Case B
this study concludes that If wind turbines are replaced by Solar PV of equivalent capacity approximately
15000 kWh of excess energy is produced in a year, while component cost remains the same. The number
of hours when batteries is drained also can be reduced from six hundred ten to sixty-six with the autonomy
days of 2 in comparison to DFS (Detail Feasibility Study) design.
Study suggests solar microgrid system can be incorporated for decentralized generation of electricity in
the rural areas.There are always both challanges and opportunity in any project. Optimum utilization of
resources, performance of the Solar PVs and cost of energy storage system in any solar off-grid system is
always a challenge.
Keywords: Solar Microgrid, Rural Electrification, Fault in Solar PVs, Nepal
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RESUMO
De acordo com dados de 2016, apenas 76% da população no Nepal tem acesso à energia elétrica, [1].
Destes, 15% da população rural tem energia elétrica a partir de fontes de energia renováveis em sistemas
não ligados à rede (off-grid, na designação anglo-saxónica), de acordo com dados de censos nacionais. O
fornecimento de energia elétrica à população rural tem sido sempre um trabalho árduo, tendo em conta o
enorme investimento de capital necessário, as dificuldades de acesso, a falta de infraestruturas adequadas
para o desenvolvimento de projetos de sistemas hídricos. A geração descentralizada de energia é a única
alternativa para essas populações rurais carentes de eletricidade, dado que não faz sentido recorrer a uma
extensão da rede nacional que necessitaria de longas linhas de transmissão para satisfazer as necessidades
de pequenos aglomerados.
A radiação solar global média no Nepal varia entre 3,6 e 6,2 kWh/m2/dia. O sol brilha em média 300
dias por ano, o que equivale a cerca de 2100 horas anuais e a uma intensidade média de 4,7 kW/m2/dia, ou
cerca de 16,92 MJ/m2/dia. Deste modo, o Nepal insere-se numa zona de elevada intensidade solar.
Basicamente o presente trabalho fará o estudo de duas regiões do Nepal, que serão designadas neste trabalho
por região A e região B. Um estudo pormenorizado de viabilidade (DFS) foi já realizado pelo Governo e
toda a informação foi adaptada para a investigação feita neste documento. A simulação realizada recorrendo
ao MATLAB para a região A sugere que existe a possibilidade de reduzir os custos associados à utilização
dos componentes principais em cerca de 20%, se o número de horas anuais em que a bateria está
descarregada aumentar de treze para cinquenta e cinco em condições normais de funcionamento, quando
se compara com os valores associados a DFS. No que toca ao caso B, o estudo presente permite concluir
que se as turbinas eólicas forem substituídas por geradores solares fotovoltaicos de capacidade equivalente,
ter-se-á um excesso de cerca de 15000 kWh de energia anual, para idêntico custo. Neste caso, o número de
horas em que as bateria se encontram descarregadas pode ser reduzido de seiscentos e dez para sessenta e
seis para dois dias de autonomia, quando se compara com o projeto DFS.
O presente estudo para um sistema solar de micro-rede pode ser incorporado num sistema descentralizado
de geração de eletricidade em zonas rurais. Uma utilização adequada dos recursos, uma otimização do
desempenho de sistemas solares fotovoltaicos e uma redução de custos de armazenamento de sistemas
off-grid representam desafios reais, para cuja solução procurámos contribuir com a realização deste
trabalho.
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ACKNOWLEDGEMENTS
I would like to express my gratitude and appreciation to the supervisor of this work, Professor Paulo
Branco and Professor João Fernandes for giving me this opportunity, his guidance, persistence and
encouragement. It would not be possible without their contributions.
I am eternally grateful to Erasmus Mundus for financially supporting my studies for past two years.
I would like to express my deep gratitude to my Lab mate Mr. Dinesh Rai, my friend Mr. Manish Adhikari
for their continuous support and encouragement through my study and thesis preparation.
Also most importantly like to thank all my family, especially my mother, father and brother, and sister
for all the patience and support and a very special thanks to my Girlfriend Miss Reshma Chettri who gave
me strength, unfailing support and a reminder about the thesis every time lost the track.
Finally, to all my colleagues and friends who listened, advised and made their questions as mine
contributing to a better research.
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TABLE OF CONTENTS
Abstract ...................................................................................................................................................... i
Acknowledgements ................................................................................................................................... v
Table of Contents .................................................................................................................................... vii
List of Figures ........................................................................................................................................... ix
List of Tables ............................................................................................................................................. xi
List of Abbreviations ................................................................................................................................xiii
List of Symbols ......................................................................................................................................... xv
1. Introduction .................................................................................................................................. 1
1.1. Autonomous PV system- Actual Panorama –Global/Nepal .................................................. 3
1.2. Motivation and Problem definition ...................................................................................... 5
1.3. Objectives .............................................................................................................................. 6
1.4. Thesis Structure .................................................................................................................... 6
2. Solar Radiation, Angle Definition, and Measurement .................................................................. 9
2.1. Solar Radiation in Nepal ........................................................................................................ 9
2.2. Angle Description ................................................................................................................ 10
2.3. Solar Radiation Measurement in Nepal .............................................................................. 12
3. Autonomous Microgrids ............................................................................................................. 15
3.1. Microgrid System Constitutions .......................................................................................... 16
PV Panels ..................................................................................................................................... 16
Wind Generator (s) ...................................................................................................................... 18
Energy Storage System ................................................................................................................ 19
Inverter ........................................................................................................................................ 20
4. Case study of Nepal: Sites A and Site B ....................................................................................... 21
4.1. OFF-Grid System Site A – Chillikot (1.5 kWP) ..................................................................... 21
Electrical Consumption - Load Curve .......................................................................................... 22
Technical Configuration .............................................................................................................. 23
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Monthly Irradiance and Average Temperature in Chillikot ........................................................ 25
Simulation Results ....................................................................................................................... 26
Solar PV Generation .................................................................................................................... 26
The Battery State of Charge ........................................................................................................ 27
Solar PV Generation and battery state of charge during JULY .................................................... 29
Autonomy .................................................................................................................................... 31
Financial Analysis- Site A ............................................................................................................. 32
4.2. OFF-Grid System Site B – Bhorleni Solar-Wind Micro Grid (35.16kW) ............................... 34
Electrical Consumption - Load Curve .......................................................................................... 34
Technical Configuration .............................................................................................................. 35
Monthly Irradiation and Average Temperature in Bhorleni ....................................................... 37
Simulation Results ....................................................................................................................... 38
Generation from Solar/Wind ...................................................................................................... 38
The Battery State of Charge ........................................................................................................ 40
Solar PV Generation and battery state of charge during AUGUST ............................................. 41
Financial Analysis of Bhorleni – Case B ....................................................................................... 45
Original configuration: ................................................................................................................ 45
5. Non-Normal Operating Conditions ............................................................................................. 49
5.1. Effect of Partial Shading on Case Study B ........................................................................... 49
6. Conclusions and Future Work ..................................................................................................... 53
6.1. Conclusions ......................................................................................................................... 53
6.2. Future Works ...................................................................................................................... 53
7. References .................................................................................................................................. 55
8. Appendix ..................................................................................................................................... 59
8.1. PV Panel – Polycrystalline 250Wp – REC250 ...................................................................... 59
8.2. PV Panels- Mono Crystalline 280Wp – 280M .................................................................... 61
8.3. Solar Lead Acid Battery – Exide Industries 200 AH-12V,6LMS200L .................................. 63
8.4. Solar VRLA Gel Battery – Sacred Sun ,2V, 1000AH –GFMJ-1000AH ................................... 66
8.5. Wind Turbine - (5 KW) - Qingdao Anhua New Energy Equipment Co.Ltd. ......................... 68
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LIST OF FIGURES
Figure 1: Nepal and its surroundings [Source: Google map] 1
Figure 2: Nos. of autonomous PVs Systems installed (2006-2014)[11] 4
Figure 3: Price history of Silicon PV Cells[12] 5
Figure 4:Irradiation on a tilted surface [14] 9
Figure 5: Solar Radiation Map of Nepal[19] 11
Figure 6: Angles of the tilted surface [20] 11
Figure 7: Modern Pyranometer[21] 12
Figure 8: Pry heliometers [22] 12
Figure 9: Solar isolated Microgrid[25] 15
Figure 10: Hybrid Isolated Microgrid [26] 16
Figure 11: Polycrystalline Panel installed in a house of Nepal[13] 17
Figure 12: Wind Turbine farm[33] 18
Figure 13: Lithium ion Battery[34] 20
Figure 14: Lead Acid Battery[35] 20
Figure 15: Chillikot Village[36] 21
Figure 16: Daily Load profile 23
Figure17: Block diagram of Chillikot(Site-A) Solar Connection[23] 24
Figure 18: Energy produced per month by six panels under STC and NOCT 26
Figure 19: Energy produced per month by five panels under STC and NOCT 27
Figure 20: Battery state of charge during a typical year with six batteries 28
Figure 21: Battery state of charge during a typical year with four batteries 29
Figure 22: Battery state of charge in July (five panels & four Batteries) 30
Figure 23: Energy Production in July (five panels) 30
Figure 24: Energy, Load, SOC curve for three days 31
Figure 25: Bhorleni Village [38] 34
Figure 26: Daily Load profile 35
Figure 27: Block diagram of Site B Connection[23] 36
Figure 28: Solar and Wind Installed Capacity 37
Figure 29: Monthly Energy production from Solar PV and Wind Turbine 38
Figure 30: Monthly averaged production and Monthly average load. 39
Figure 31: Energy produced when wind turbines replaced by Solar PV 39
Figure 32: Battery State of charge with Solar and Wind turbines 40
Figure 33: Battery SOC when wind turbines replaced by Solar PVs. 41
Figure 34: Battery SOC during Aug with Solar and Wind 42
Figure 35: Battery SOC during Aug with wind turbines replaced by Solar PVs. 43
Figure 36: Energy from Solar and Wind during AUG. 44
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Figure 37: Energy from Solar replaced by Wind 45
Figure 38: Energy produced by Solar PVs at Normal operation conditions (DEC) 50
Figure 39: Energy produced by Solar PVs at Non-Normal operation conditions (DEC) 51
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LIST OF TABLES
Table 1: Site overview ............................................................................................................................... 2
Table 2: Load Appliances[36] .................................................................................................................. 22
Table 3: Load demand projection ........................................................................................................... 23
Table 4: Major Solar Microgrid component of Chillikot – Site A ............................................................. 24
Table 5: Monthly Metrological data- Site A ............................................................................................ 25
Table 6: Price quotation for original configuration ................................................................................. 32
Table 7: Price quotation for modified configuration .............................................................................. 33
Table 8: Major Solar Microgrid component of Bhorleni- Site B .............................................................. 36
Table 9: Monthly Metrological data- Site B ............................................................................................ 37
Table 10:Price quotation for original configuration ( Datasheet attached in Appendix 8.2) .................. 46
Table 11: Price quotation for modified configuration ............................................................................ 47
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LIST OF ABBREVIATIONS
AEPC – Alternative Energy Promotion Centre
AC – Alternating Current
AM1.5 –Air Mass 1.5
BMS – Battery Management System
CFL – Compact Fluorescent Lamps
CPV – Concentrated Photovoltaic’s
CRT – Cathode Ray Tube
CSP – Concentrated Solar Power
CV – Constant Voltage
DFS – Detail Feasibility Study
DC – Direct Current
D/G – Beam vs Diffuse Radiation Ratio
DIF – Diffuse Horizontal Irradiance/Irradiation
DOD – Depth of Discharge
DNI – Direct Normal Irradiance/Irradiation
EOT – Equation of Time
GoN – Government of Nepal
GHI – Global Horizontal Irradiance/Irradiation
IST – Instituto Superior Técnico
LED – Light-emitting Diodes
LFP - Lithium Iron Phosphate (LiFePO4)
LL – Local Longitude
MPPT – Maximum Power Point Tracking (or Tracker)
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NOCT – Normal Operating Cell Temperature
NRREP – National Rural and Renewable Energy Program
PV – Photovoltaic
PVGIS – Photovoltaic Geographical Information System
RERL– Renewable Energy for Rural Livelihood
SOC – State of Charge
STC – Standard Test Conditions
THD – Total Harmonic Distortion
UPS – Uninterruptible Power Supply
USD – Unites States Dollar
VRLA – Valve Regulated Lead Acid
Wp – Watt-peak
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LIST OF SYMBOLS
A – Amp
𝐴 – PV surface azimuth angle
𝐴𝑆 – Solar azimuth angle
𝐶 – Cell Capacity
𝐸𝐿𝑜𝑎𝑑𝑠 – Energy of the loads
𝐸𝑂𝑈𝑇 – Energy delivered (out)
𝐸𝑃𝑉 – Energy produced by the PV panels
𝐺 – Solar Irradiance
𝐺𝑏– Beam radiation
𝐺𝑏_ℎ𝑜𝑟𝑖𝑧 – Incident (beam) radiation component perpendicular to the ground horizontal plane
𝐺𝑏_𝑖𝑛𝑐𝑖𝑑𝑒𝑛𝑡– Maximum incident (beam) radiation
𝐺𝑏_𝑚𝑜𝑑𝑢𝑙𝑒– Module (beam) radiation or radiation incident on the tilted plane
𝐺𝑑 – Diffuse radiation
𝐺𝑔𝑙𝑜𝑏𝑎𝑙 – Global radiation
𝐺𝑟 – Reflected radiation
𝐻ℎ – Irradiation on horizontal plane
𝐻𝑖 – Solar Irradiation
LiFePO4 - Lithium Iron Phosphate
𝑚 – the diode ideality factor
𝑅 – Resistance
𝑆 – Incident radiation or sun ray vector
V – Volt
W – Watt
Wh – Watt-hour
𝑊𝐵𝑎𝑡,𝑇𝑜𝑡– Total energy of the batteries
𝛼 – Solar altitude or solar elevation angle
𝛽 – Surface inclination angle
𝛽𝑜𝑝𝑡 – Optimal inclination angle
𝜃𝑖 – Incidence angle
𝛿 – Declination angle
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𝜂𝐵𝐴𝑇 – Battery efficiency
𝜂𝐵𝑀𝑆 – BMS efficiency
𝜂𝑃𝑉 – PV panels efficiency
𝜂stc – PV panels efficiency at standard test conditions
𝜂𝑖𝑛𝑣 – Inverter efficiency
𝜂𝑙𝑜𝑠𝑠𝑒𝑠 – Cable losses factor
𝜂𝑠𝑦𝑠𝑡,𝑎𝑢𝑡– Autonomous/Off-grid system efficiency
𝜙 – latitude
𝜔 – hour angle
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1. INTRODUCTION
The Federal Democratic Republic of Nepal is a developing landlocked country in South East Asia. It is
bordered by China to the north and India to the south, east, and west. The Himalaya mountain range runs
across Nepal's northern and western parts and eight of the world's ten highest mountains, including Mount
Everest, are within its territory. The total area of Nepal is 147181 km² Nepal is located 27.33 degrees north
latitude & 85, 33 E longitude. The elevation of Nepal starts at 70m above sea level and ends with Mt.
Everest at 8848m. The map of Nepal and its surrounding is shown in figure 1.
Figure 1: Nepal and its surroundings [Source: Google map]
Nepal’s energy situation reflects its challenging terrain (over 75% mountainous) and very low-income
levels of the people. About 25% of Nepal’s 26.5 million people live below the poverty line, which varies
by region but averaged earning of 19,261 Nepali Rupee per year (or about € 0.71 per day) in the Fiscal year
2010/2011. The nation is among the poorest countries in the world, with per capita annual income of € 700
in Fiscal Year 2011/2012.[4]
Most of the energy in Nepal comes from fuelwood (68%), agricultural waste (15%), animal dung (8%),
and imported fossil fuels (8%). Except for some lignite deposits, Nepal has no known oil, gas or coal
deposits. All commercial fossil fuels (mainly oil and coal) are either imported from India or from
international markets routed through India and China. [5]
Most of the rural population that does have access to electricity, roughly a quarter get that power from
off-grid sources, while the other three quarters obtain access from the grid.[4]
Providing access to electricity to an outsized chunk of rural public in Nepal has historically been a
difficult exercise. This has been directly affected by geographical variations, poor transportability; low
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density settlements, poor energy development methods, lack of adequate capital and more on-going energy
crisis is also a major factor. Some study conducting objective assessment of the renewable energy based
off-grid energy sector in Nepal reveals despite visible progresses achieved, there still exist multiple
roadblocks to scale up particularly in remote areas where grid extension does not make sense because of
vast distance from transmission lines and low population in that particular areas.[6]
Alternative Energy Promotion Centre (AEPC) is the governmental institution promoting off-grid
renewable/alternative energy in Nepal under Ministry of Science, Technology, and Environment.
Alternative Energy Promotion Centre ( AEPC) is supported by Renewable Energy for Rural Livelihood
(RERL) to remove barriers for scaling up less disseminated larger renewable energy systems such as mini
hydro, large micro hydro and large solar PV. Renewable Energy for Rural Livelihood (RERL) provides
incremental support to AEPC by providing technical assistance for developing conducive policy
environment, demonstration of financially attractive projects, implementation of sustainable modalities and
capacity development.[7] Recently National Rural and Renewable Energy Program (NRREP) is looking
forward to investing in the potential Solar/Wind off-grid system for the rural village where NEA
electrification is no-way near or it's not available. AEPC has appointed a private consultant to perform
detail feasibility study for two sites and based on that report handed over to AEPC; this thesis work will
begin the work. The two sites are the given in table 1.
Table 1: Site overview
S.N. Name Size Households Type
1 Site A- Chillikot Village 1.5 kWp 15 Solar microgrid
2 Site B-Bhorleni Village 35.16 kW 120 Solar-Wind microgrid
This Master thesis is focused on the design and analysis of low-cost solutions assuming overall efficiency
of eighty-five percent for autonomous solar microgrid system for two cases. For each case, it will be
pointing out its technical problems, if there is a better solution mainly concerning the system cost, and also
the viability of the system focusing on the storage systems and energy production.
For all the cases there are various challenges that must be faced, especially for the project sites where
people have low income and are not aware of development factor that is driven by a reliable energy source.
In the other hand, the battery storage of the off-grid system holds good amount of cost in it, also it can
increase for high autonomy days where the electricity must be supplied even without enough available solar
energy. Therefore, optimization of the battery energy storage system can help lower the total cost of the
system if batteries that have high number of cycle (charging and discharging cycle) are selected (their cost
and size must be considered at the same time).
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1.1. AUTONOMOUS PV SYSTEM- ACTUAL PANORAMA –GLOBAL/NEPAL
The Sun is the largest source of energy. The conversion of the solar radiation can be used in CSP
(Concentrated Solar Power), CPV (Concentrated Photovoltaic’s) and electricity production (electrical).In
1954 Bell Labs found that silicon doped with certain impurities was very sensitive to light which gave birth
to the first solar modules that allowed a practical application and with an energy conversion efficiency
around 6% in the laboratory. Photovoltaic (PV) technology is an active solar system type based on the
photoelectric effect, converting photons of light into electrical energy through photovoltaic cells that form
a photovoltaic panel. Today the most renounced solar PV technologies are crystalline silicon-based systems.
Silicon terrestrial module efficiencies cells can reach 22.9% at Standard Test Conditions1 (STC) in the
laboratory [8]. Each cell generates a Direct Current (DC) power of about 1.5W (0.5V and a 3A current) and
the number of cells depends on the panel technology [4]. Photovoltaic modules power is usually between
50W and 315W. Normally, the durability is higher than 20 years, making this a very reliable source of
renewable energy.
The global PV capacity grew 49% a year on average since 2003. Decentralised systems represent
approximately 60% of the global market, while centralized systems are close to 40%. The share of off-grid
installations is very small compared to grid-tied, once grid-tied systems expanded in large scale from 2000
to 2013. However, like PV technologies in general off-grid systems are expanding, especially in developing
countries with high solar exposure [9][10].
As compared to global context Nepal is way behind the picture. The study suggests energy consumption
in the country from Renewable sources (Solar, Wind, and Biomass. Micro/Pico hydropower) accounts only
1 percent of total consumption.[3] However, recent development has significantly increased. As data
recorded by Alternative Energy Promotion Centre (AEPC) in 2006 only 4464 numbers of the autonomous
solar system (20Wp-50kWp) were installed while in 2014 number rose to astounding 103271 as illustrated
in figure 2. There was significant increase in a number of solar systems in urban areas because of the huge
Load shedding almost up to 12 hours in winter and 3 hours in summer until 2016. [11]
1 Cell temperature, 𝜃𝑟=25°𝐶≡𝑇𝑟=298.16 K; Incident radiation, 𝐺𝑟=1000 𝑊/𝑚2
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Figure 2: Nos. of autonomous PVs Systems installed (2006-2014)[11]
Price of Solar Photovoltaic’s are following a downtrend as an investment in photovoltaic’s is expanding.
In a standalone system, batteries represent the largest share of investment usually greater than 40%. The
photovoltaic panels constitute about 15-20% of the investment and the inverter another 20%. The remaining
stands for the control system and other costs. As price depends upon the geographical location, size of the
system, specification of the major component as well as the needs of the consumer, the price is hard to
define. A survey in system (<1 kW) price of off-grid sector irrespective of the type of application done by
International Energy Agency in 2013 reporting Europeans countries2 showed that price ranged from 2.7 to
20 USD/W.[9]
Renewable energy favorable policy, investment in technology as well as market forces has resulted in
the decline of the installed price of solar energy has declined in recent years significantly. As seen in figure
3 there is a massive drop in the price of Silicon PV cells in recent years. In 1977 price was as high of
76$/watt which dropped as low up to 0.3$/ watt peak. With solar already achieving record-low prices, the
cost decline observed in 2015 indicates that the coming years will likely see utility-scale solar become cost
competitive with conventional forms of electricity generation.
2Austria, Denmark, France, Italy, Spain, Sweden and Switzerland
0
20000
40000
60000
80000
100000
120000
2006 2007 2008 2009 2010 2011 2012 2013 2014
No
s. o
f So
lar
Syst
ems
Years
Nos. of Solar Systems installed from 2006 to 2014 (20Wp-50kWp)
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Figure 3: Price history of Silicon PV Cells[12]
Likewise, Nepal follows the similar trend in terms of global price. According to leading Solar Company
price for European brand mono-crystalline cells imported in 2010 had an average selling price of 1.8 $/watts
while in 2017 price dropped more than 50 percent to 0.8$/watts. Similarly for Chinese brand panels price
has also dropped by more than 50 percent hitting as low as 0.50$/watts. [13]
1.2. MOTIVATION AND PROBLEM DEFINITION
The research on the potential of Renewable energy suggests that Nepal itself is capable of supplying its
demand. Annual renewable energy potential is 226,460 GWh (UNDP, 2012)[6]. but the generation from
renewable energy is 3,851 GWh(UNDP,2012)[6].
The average global solar radiation in Nepal varies from 3.6-6.2 kWh/m2/day, the sun shines for about
300 days a year, the number of sunshine hours amounts almost 2100 hours per year and average insolation
intensity about 4.7 kWh/m2/day (=16.92 MJ/ m2/day) [6].Off-grid renewable energy in Nepal has proven
its ability to play a significant role in the country’s overall power provision. Hence, Nepal lies in the
favorable zone in terms of solar fuel resource.
Electrical Energy is an essential need for any developing country individual as well as electricity plays a
significant role in the day-to-day life of human being. Nepal is a landlocked country located in South-East
Asia where around 76% of its population is only electrified. The challenge to meet one hundred percent
electricity access is not only possible by National Electrical Utility. Hence, it is important to develop an
alternative way that can provide and reliable and low-cost power source in those places where electrification
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is not a profitable option. As discussed earlier Nepal has sufficient solar resources in this case of grid
Renewable microgrid system can be the likely alternative way to power up those places [4]. In this case,
Wind/Solar microgrid systems can meet the demands and have its own salient features.
The Nepal power grid is still limited, supplying only the big cities and some villages. Another problem
is the lack of adequate income to invest in the energy infrastructure One can tell seeing the recent trends
[5], that PV panels’ cost is going down and it will further go down as there are many research and investment
going on for not only higher efficient cells but also better batteries. Despite this, the cost of the battery
storage system is still today around 30-45 percent of total system cost. The cheap lead-acid batteries have
an average number of lifetime 500 cycles. In other words, it can work up to maximum 5 years. Of course,
this depends on the load profile, the geography where the system is implemented. we can introduce Battery
Management System (BMS) system for the better performance of the system. This is very important
because the electrical needs in developing countries are constantly growing which sets new horizons for
energy isolated systems.
1.3. OBJECTIVES
This thesis will study the technical and financial part of two solar microgrids associated with two
electrification project sites in Nepal. The main objectives of this thesis are:
• For each project site: systematization and analysis of the technical problems; analysis and
characterization of the consumers and its load curves; elaboration of different operating scenarios
and its impact on the energy storage systems, etc;
• Design and characterization of an autonomous low-cost solar microgrid for each project site. ;
• Simulation of the system for each project site with different operating scenarios and validation of
the selected equipment.;
• Simulation of fault conditions that can occur in the systems
1.4. THESIS STRUCTURE
The dissertation consists of 6 chapters, as follows:
Chapter 1 provides an introduction about the work, conditions of solar PV in Nepal, including motivation
and objective
Chapter 2 describes solar radiation in Nepal, general theory of angles present in Solar Radiation,
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Measurement of Solar radiation and its application in Nepal
Chapter 3 present the introduction of Autonomous Solar-microgrid, description about major components
in the microgrids system, especially in Nepalese Market.
Chapter 4 summaries the results of MATLAB simulation of both the Case study named A and B, i.e.
Energy production, Load profile, Battery SOC, the comparison between original and modified
configuration, a price quotation for recommended options. etc
Chapter 5 provides a general introduction to non-normal operating conditions of PVs and its effect in
the Case study of Chillikot.
Chapter 6 summarizes the conclusions and recommendations for the future work.
8
9
2. SOLAR RADIATION, ANGLE DEFINITION, AND MEASUREMENT
2.1. SOLAR RADIATION IN NEPAL
Solar radiation is all of the light and energy that comes from the sun where sunlight is the part of the
electromagnetic radiation given off by the Sun. The incident solar power per unit area, 𝐺, is the solar
irradiance and is measured in 𝑊⁄𝑚2. Total irradiance on a tilted surface, Gglobal, is made up of three main
components. Direct or beam radiation, Gb, which is the radiation received directly from the sun. Diffuse
radiation, Gd, is the radiation that gets scattered throughout the atmosphere due to clouds and particles.
Reflected radiation, Gr, is the radiation reflected from the ground surface in front for the tilted surface.
These three radiations can be seen in figure 4
The sum of direct, diffused and reflected irradiance/irradiation is known as global irradiation as in
equation (2-1). Reflected irradiation is received only when the surface of PV is titled with respect to the
horizontal as illustrated in figure 4.
Figure 4:Irradiation on a tilted surface [14]
When the surface is tilted with reference to the horizontal plane there is a particular case of reflected
radiation 𝐺𝑟, which is the radiation, measured as ratio between the amount of reflected radiation and
received radiation. Global Insolation, Total Irradiance or Global Irradiance/Irradiation on a tilted surface is
the sum of direct and diffuse radiation that focus on a surface [15][16]
𝐺𝑔𝑙𝑜𝑏𝑎𝑙 = 𝐺𝑏 + 𝐺𝑑 + 𝐺𝑟 (2-1)
In this study, the Global irradiation is the most important parameter which will be used to simulate the
10
Solar Energy production at a particular place.
Nepal is situated in between latitude 26°22′–30°27′ and longitude 80°4′–88°12′ which is a favourable
position for Solar Radiation. It is estimated that the average Global Solar Radiation (GSR) to this latitude
ranges from 3.6 to 6.2 kWh/m2/day, with over 300 bright sunny days per year and, the whole nation has
6.8 h/day of bright sunshine, with the average solar intensity of 4.7 kWh/day. [17] As seen in the figure 5
country receives plenty amount of Solar Radiation per day while Western part of the country receives more
resources than the eastern part of the Country. The black and blue mark shows the location of two cases
that are under study in this Thesis. The A research paper suggested a yearly Global Solar Radiation of
around 4218 MJ/m2 and 3555 MJ/m2 in 2005 and 2007 respectively in Kathmandu. [17]
2.2. ANGLE DESCRIPTION
One of the important angles that affects the production of solar energy produced by the panel is the angle
of incidence, 𝜃i, This is the angle between the sun rays and the normal to the PV panel surface, as shown in
the Figure 5.The optimal angle 𝛽𝑜𝑝𝑡, refers to the fixed module inclination angle at which PV modules
should be oriented in order to maximize power (annual mean value). This angle depends mainly on the
installation geographical position (latitude) due to the variation of the sun altitude angle (𝛼) in the sky
across the year. The solar azimuth angle 𝐴𝑆 is the angle between the horizontal projection of the sun vector
𝑆 and the north direction. The panel azimuth angle 𝐴, is the angle between the horizontal projection of the
normal to the panel 𝑁 and the north direction. Various angles for titled surface are shown in figure 6.
Commonly, most of the metrological stations measure solar irradiance data on the horizontal plane as
global and diffused irradiance, since most of the time when the Panels are tilted and data on inclined
surfaces are not available [16].The direct and reflected radiation can be computed with good accuracy using
simple algorithms but the diffuse component is more complex and has to be estimated with different models
requiring the information of global and direct radiation incident on a horizontal surface. The Solar radiation
map of Nepal is shown in figure 5 which shows western mountains has a higher intensity of radiation as
compared to eastern mountains. [15][16][18].
11
Figure 5: Solar Radiation Map of Nepal[19]
Figure 6: Angles of the tilted surface [20]
𝑆 – Incident radiation or sun ray vector;
12
𝜃i – Angle of incidence between the Sun rays and the normal to PV surface;
𝛽 – Angle of inclination of the surface from the horizontal;
𝛼 – Solar altitude or solar elevation angle;
𝐴 – PV surface azimuth angle.
2.3. SOLAR RADIATION MEASUREMENT IN NEPAL
The accurate measurement of Solar Radiation is very important to determine the energy that Solar Panels
are capable of producing at a given place and given time. In this study, Global radiation data (hourly,
monthly) is used from the metrological site. Normally, there are two types of equipment for measuring the
irradiation data: Pyranometers and Pyrheliometers as shown in figure 7 and 8.
Figure 7: Modern Pyranometer[21] Figure 8: Pry heliometers [22]
A pyranometer is a type of actinometer used for measuring irradiance on a planar surface and it is
designed to measure the solar radiation flux density (W/m2) from the hemisphere above within a
suitable wavelength range It measures the total irradiance (beam and diffuse) from all the hemisphere
(180º field of view) on a planar surface by a thermopile sensor. The sensor may be coupled to a shade disk,
ring or sphere that follows the position of the sun in the sky “blocking” the beam radiation.[23]
13
Pyrheliometers are an instrument for measurement of direct beam solar irradiance.3 Sunlight enters the
instrument through a window and is directed onto a thermopile which converts heat to an electrical signal
that can be recorded. The signal voltage is converted via a formula to measure watts per square meter.[2] It
is used with a solar tracking system to keep the instrument aimed at the sun. Pyrheliometers are often used
in the same setup with a pyranometer. The aperture angle of the instrument is 5.7° so the detector receives
radiation from the sun and from an area of the circumsolar sky two orders of magnitude larger than that.[23]
In the context of Nepal, very few studies and experiments have been carried to measure Solar Radiations
and most of the time calculations of Solar PVs system are based on data obtained from the internet. This
thesis also intent to acquired required data from the internet since no any accurate measurement has not
been carried out in the exact location. Nevertheless, an experiment was carried out in a study by using
CMP6 Pyranometer in various place of Nepal and gave a discussion about the measured value and
calculated value. In the study, it was concluded that solar radiation was affected by varying seasons as well
as altitude. From the observation, the abundant solar irradiation in Nepal shows encouraging atmosphere
for the solar farming venture in near future relating to energy management for Nepal.[3]
3 http://www.kippzonen.com/?productgroup/881/Pyrheliometers.aspx
14
15
3. AUTONOMOUS MICROGRIDS
The US Department of Energy states that A microgrid is a group of interconnected load and distributed
energy resources (DERs) within clearly defined electrical boundaries that acts as a single entity with respect
to the grid. A Microgrid can connect and disconnect from the grid to enable it to operate in both grid-
connected or island-mode[24]. This kind of system can be operated in a non-autonomous way as well as
autonomous way. If the system is interconnected to the grid it is operated in a non-autonomous way and if
the system is not connected to grid it is an autonomous way. This kind of operation can be beneficial to the
overall system if managed efficiently. Microgrid can be both off-grid as well as on-grid based. In the off-
grid (figure 9) system are basically built in remote places with the load of houses ranging from (10-200)
households where there is no grid connection or electrification because of long transmission line distances,
economic issues or geographical factors. In this kind of system, the renewable source generate electricity
and supplies as well as store the energy for the autonomy. In island solar microgrid, every solar PV panel
connected in the array generates electricity by converting solar radiation into electrical energy. All PV
panels are connected in a particular order of parallel and series combinations to provide the required voltage.
Figure 9: Solar isolated Microgrid[25]
The electricity generated from the array of panels is transmitted to a central controller called the Power
Conditioning Unit (PCU), which is, in simple terms, a large power inverter. The PCU is connected to the
Distribution Box (DB) on one hand and the battery bank on the other. The PCU controls regulates and
directs the electrical energy transmitted from the array, and supplies electricity directly to homes, shops,
offices, street lights during the production from solar and stores the remaining energy in the battery. During
the day if the power generated is not used or surplus power is generated, the PCU directs this to the energy
storage system which stores power. This power can then be used at night (after the sun sets when there is
no production from the Solar). The microgrid and battery bank can also be connected to a computer for
local power usage monitoring. With the addition of a modem, this information can be accessed from a
remote location, eliminating the need for local manpower to monitor the system. In case of Solar-Wind
16
microgrid, Figure 10 system energy is produced by both the resources and feed to load as well store when
there is surplus. Basically, wind turbine can produce energy during the night and solar can generate during
the day.
Figure 10: Hybrid Isolated Microgrid [26]
3.1. MICROGRID SYSTEM CONSTITUTIONS
In this section, a brief review is done about the characteristics and components of a microgrid system
along with distributed sources such as PV panels and/wind generator(s) with energy storage and conversion
system.
PV PANELS
The PV system is a renewable and sustainable source of energy. Basically, PV is made up of Solar cells
arranged in parallel and series. Solar cells convert Sunlight into the Electrical energy (DC). A
typical photovoltaic system utilizes solar panels each comprising a number of solar cells. Which generate
electrical power. The initial step is the photoelectric effect followed by an electrochemical procedure where
crystallized atoms, ionized in a series, generate an electric current.[27]
There are several types of active (conversion of sunlight into other forms of thermic or electric energy)
and passive (heating buildings through constructive strategies) solar systems. PV panels are active solar
systems constituted by solar cells arranged in series and parallel to make a PV module with appreciating
power. The first generation technology is the crystalline silicon with a market share of 87% in three main
types: Monocrystalline, polycrystalline and silicon tapes. The polycrystalline cells are less efficient but
represent 49% of the market against 35% of Monocrystalline cells. They have also a lower manufacturing
cost (about 20%) being the correct decision to project the least expensive system possible .[28]
17
The working rule of solar cells is the photovoltaic impact found by Alexandre Edmond Becquerel in
1839. In a photovoltaic impact the electrons-hole sets created are exchanged between various groups
(valence groups to conduction groups) inside the material itself, bringing about the improvement of an
electrical voltage between two cathodes. Tilted Polycrystalline installed in a house is shown in the figure
below.
Figure 11: Polycrystalline Panel installed in a house of Nepal[13]
In Nepalese market, as there are mainly two types of solar panels: Mono-crystalline, Poly-crystalline. In
solar microgrid system, we can use monocrystalline or polycrystalline. Energy production depends upon
various factors such as solar insulation in the particular geographic location, panel temperature.
We can determine the efficiency of the panel by the temperature of the cells; efficiency is decreasing
with increasing temperature due to the higher dark current. We can produce the better results with
simulation data using the following equation 3-1 and 3-2 to calculate energy produced.[29][30]
𝜂(𝑇) = 𝜂𝑆𝑇𝐶 ∗ [1 + 𝛾(𝑇𝑐 − 𝑇𝑠𝑡𝑐 ) ] (3-1)
𝐸𝑃𝑉 = 𝜂(𝑇) ∗ 𝐴 ∗ 𝐺 (3-2)
where 𝑇𝑐is the temperature of the cells, 𝑇𝑆𝑇𝐶= 25°C is the temperature of the cells at STC conditions, 𝜂stc
18
is the efficiency of the module at STC conditions and γ is the empirically estimated relative efficiency
temperature coefficient, approximately equal to -0.004/K for polycrystalline silicon cells. And A is area of
photovoltaic’s and G is the irradiance [31]
WIND GENERATOR (S)
The sudden increases in the price of oil in 1973 stimulated a number of research, development, and
demonstrations of wind turbines and other alternative energy technologies in different countries. The large
masses of air moving over the earth surface are in the form of kinetic energy which is converted to electrical
energy with the help of wind turbine. Wind turbine receives this kinetic energy which is further converted
into useful mechanical energy and again transformed into electrical energy depending on the end use. A
rotating wind turbine is shown in figure 12. [32]
Figure 12: Wind Turbine farm[33]
Wind turbines work by converting the kinetic energy in the wind, first to rotational kinetic energy in the
turbine and then the electrical energy that can be supplied to the battery, load, or to the national grid. A
German physicist Albert Betz has concluded that no wind turbine can convert more than 16/27 (59%) of
the kinetic energy of the wind into mechanical energy turning a rotor. The maximum power efficiency of
any design of wind turbine is 0.59. (i.e. no more than 59% of the energy carried by the wind can be extracted
by a wind turbine.) This is called “maximum power coefficient”: Cpmax = 0.59 and the Power by the Wind
turbine can be calculated by equation (3-3)
19
𝑃𝑤𝑖𝑛𝑑 = 0.5 ∗ 𝜌 ∗ 𝐶𝑝 ∗ 𝐴 ∗ V3 (3-3)
Where ρ is density (kg/m3), A is swept area (m2) , Cp is Power Coefficient, V is wind speed(m/s). [28]
The energy available for conversion always depends on the wind speed and swept area of the turbine.
Wind turbines are available in various sizes from a large number of wind turbine manufacturers, agents,
and developers. As compared to Solar PVs Wind Energy system is very new to Nepal and contributes very
less share for Renewable energy. V3 However, there are few companies working on Wind sector.
ENERGY STORAGE SYSTEM
An electric battery is an energy storage device that converts stored chemical energy into electrical energy
as required by the load in accordance with the chemical reactions – redox equations. Batteries that can be
recharged and discharge have largely replaced primary cells, as they save resource and reduce pollution.
The most commonly used batteries for storing applications are lead-acid batteries type as well as solar lead-
acid batteries in Nepal, but they are being substituted by Lithium-ion batteries over time due to several
advantages. Li-ion batteries have high capacity, high electrochemical potential, superior energy density,
durability, as well as the flexibility in design. All the above outstanding properties accelerate the
substitution of conventional secondary batteries.[23]
The batteries used in autonomous Microgrid systems should have the following characteristics for better
performance:
• Low maintenance necessity ;
• Long lasting durability ;
• Low self-discharge and high energy efficiency;
• High storage capacity and power density;
• Good performance/price relation;
• Protection against the occurrence of hazards to the environment and health.
The figure 13 & 14 are batteries that are generally used with the autonomous solar system in Nepal. The
voltage of the battery can be 2, 6 or 12 V depending on the need of electrical parameters. Most of the
batteries are imported from India; there is only one Battery manufacturer in Nepal.
20
Figure 13: Lithium ion Battery[34]
Figure 14: Lead Acid Battery[35]
INVERTER
For any isolated microgrid system, the off-grid inverter is the essential electronic device that converts
low voltage DC electricity from a battery or other power source to 100V-120V or 220V-240V AC signal
depending upon the need of the load. Off-grid Inverters produce a voltage wave, with an independent
frequency from the grid. If correctly dimensioned according to the battery voltage levels. Some
requirements are indispensable for an off-grid inverter.[23]
• Autostarting and adequate protection warning signs;
• Peak power capacity – it should support more than two times its nominal power; Low THD(Total
harmonic distortion);
• Low standby power; High efficiency; Voltage stability – between the range of 230V±10%;
• Possibility to connect other inverters in parallel.
• The waveform should be selected accordingly to the type of application.
21
4. CASE STUDY OF NEPAL: SITES A AND SITE B
In this section, two sites located in Nepal are analyzed for potential installation of a microgrid system.
For each site, the typical load curves is analysed, simulation for average energy production and its impact
on energy storage system is presented for a proper definition of the microgrid system configuration. To
verify the feasibility of these systems, economic assessment can be done in future for typical microgrid
systems.
4.1. OFF-GRID SYSTEM SITE A – CHILLIKOT (1.5 KWP)
Figure 15: Chillikot Village[36]
The project site Chillikot of Bijauri VDC is located on the top of the hill of western Nepal with 15
households. Households distribution pattern lie almost in a straight line as per as Detail Feasibility Study
(DFS) of Chillikot .The national utility grid, Nepal Electricity Authority (NEA) is not expected to reach
this site within five years. A survey was done to this site to observe the load demand and acceptability of a
microgrid implementation. Almost all respondent was interested in installing a solar microgrid system.
During the survey, it was found that most of the population depend on Agriculture as their source of income
and their monthly income various between $ 15- $ 40. Monthly income data given by the respondents are
low as compared to average living standard and demand for electricity for Nepal. Therefore, the system
costs and the remoteness of this site will be the major factors for this project. [36]
22
ELECTRICAL CONSUMPTION - LOAD CURVE
The daily electrical consumption profile for the year 2015 was estimated by taking into account different
typical electrical appliances at different periods of time in a day as shown in table 2. As per the survey, the
demand for electricity in the morning is for lighting and television whereas in evening for lighting,
television, and radio. Appliances usage hours are taken by discussing with the respondents which are
adapted in this case study directly from the details feasibility study of the chillikot microgrid project. These
typical appliances and its energy consumptions are from and those were estimated based on the demand
and activities of residents. [36]
Table 2: Load Appliances[36]
Appliance Power [W] No. of Household
LED bulbs 44 15
Television 60 5
Radio 5 13
Mobile Chargers 3 15
As shown in table 2, the main load is LED bulbs for lighting purpose and Televisions. The total household
demand for the base year 2015 is calculated to be nearly 3.890 KWh/day. As per the survey, energy demand
for appliances such as lighting (67%) and TV (24%) are the main energy consuming appliance, while the
mobile charging and radio energy demand are residual, as shown in table 2.
In, figure 16 daily demand curves match a cup shape profile in the morning and evening. Considering the
diversity and consumption pattern of various appliances, the peak demand is estimated to be 900 Watts.
The load is assumed to be nearly constant here because main loads are lights and a few televisions. [36]
23
Figure 16: Daily Load profile
The load demand has been projected for next five years. According to the Nepal Electricity Authority
(NEA) standard, the demand for household use is estimated to increase by 6-7% annually in the rural areas.
As per the discussion with respondents, household also tends to follow this increase for the next years. due
to the main economy as agriculture, the energy demand projection for next five year is taken at a rate of
5%as per as the Detail Feasibility Study (DFS). Therefore, based on the energy consumption of the year
2015, the estimated peak load in five years is 1150 watts the estimated energy consumption for the next
five years is listed in Table 3.
Table 3: Load demand projection
TECHNICAL CONFIGURATION
Based on the Detail Feasibility Study (DFS) for this site, this section deals with base technical outlines
of the Chillikot Solar microgrid which was originally designed. For the load profile and renewable resources
available at the site a total of six solar panels of 250 Wp and a nominal voltage of 24, each was required.
Total area required for installing 6 panels is around 10 square meters. Each panel would be connected in
parallel with each other to obtained system voltage of 24 V.[36]
A total of 6 Solar Tubular Lead Acid batteries with 12V and 200 Ah are used in series and parallel to
0 5 10 15 200
200
400
600
800
1000Load Curve
Time [hours]
Po
wer
Watt
s
Years 2016 2017 2018 2019 2020
Energy Demand
(Wh) 4085 4288 4503 4728 4964
24
generate a bus voltage of 24 V. This type of battery was chose due easy availability. during the calculation
of battery size, depth of discharge is considered to be 80%, battery efficiency as 85% and rated charging
time of 10 hours. The modeling of the battery bank was done for an autonomy period of 2 days. Taking all
into consideration, total battery in parallel required was 3 and 2 in series to generate system voltage of 24
V.[36]
In fig. 17 a schematic of the microgrid to be installed on this site is shown where PV panels feed the
battery as well as dc loads and inverter supplies the ac loads. And the major components considered for this
system listed in table 4.
Figure17: Block diagram of Chillikot(Site-A) Solar Connection[23]
Solar Photovoltaics’ manufactured by REC Norway group with the specification attached in annex 1.
Will be installed along with the Solar Tubular Lead acid battery manufactured by Exide company located
in India. To ensure the maximum extraction of power from Solar Panels the Maximum Power Point Tracker
(MPPT) solar regulator will be used instead of normal PWM charge controller. The normal inverter with
around 90 percent will be installed. The global system is assumed to be 85 percent. Major components are
shown in table 4 below.
Table 4: Major Solar Microgrid component of Chillikot – Site A
Components Quantity Unit Total
Solar PV,Polycrystalline, REC Norway 6 250 Wp 1500 Wp
Solar Tubular Lead Acid , Exide, Battery Bank 6 12V/200Ah 14,400 Wh
Solar regulator (MPPT) 1 24V,20 A 20A
DC/AC Inverter 1500VA 1 1500 VA 1500 VA
25
A MATLAB simulation was done to estimate the average energy production from the solar microgrid
and its storage system. Figures below show the production capacity from Solar Panels for all the months
during a year. The monthly irradiance data was taken from the Detail Feasibility Study (DFS). [25] and
hourly irradiance was obtained by making calculations from series of data available in [37]. The datasheet
for Solar Panels and Solar Batteries are attached in Appendix 8.1 and 8.3
MONTHLY IRRADIANCE AND AVERAGE TEMPERATURE IN CHILLIKOT
There are various sources to obtain irradiance and temperature data for the simulation. In this work
monthly average Irradiance, hourly irradiance value for one year, daily average irradiance and temperature
values is taken from for chillikot.[37] The table 5 below shows the average Global Horizontal Irradiance
(GHI) and average temperature each month. Module temperature is obtained from average ambient
temperature by converting to Normal Operating Cell Temperature (NOCT) using equation 4-1.
𝑇𝑐𝑒𝑙𝑙 = 𝑇𝑎𝑖𝑟 + 𝑁𝑜𝑐𝑡−20
80∗ 𝐺 4-1
Table 5: Monthly Metrological data- Site A
Month GHI Amb. Temp Module Temp
Jan 127 12 27
Feb 146 15.7 30.7
Mar 190 20.7 35.7
Apr 209 27 42
May 191 25.8 40.8
June 180 25.9 40.9
July 138 24.7 39.7
Aug 179 25.9 40.9
Sep 175 24.1 39.1
Oct 164 21.4 36.4
Nov 143 16.5 31.5
Dec 130 12.8 27.8
26
SIMULATION RESULTS
SOLAR PV GENERATION
The figure 18 and 19 below shows the production of electrical energy from solar panels monthly with six
and five Solar PVs connected in the system respectively. As per as the report, six panels shall be installed
to feed the daily load of 4085 Wh (2016) which is an average total of 122.55 kWh monthly. Assuming the
global system efficiency of eighty-five percent the production from panels is surplus as compared to the
total load to be feed. so further simulation work is performed to see the if system component can be reduced
without altering the basic load demand. from this bar diagram of fig 18 it is seen there is highest production
of 293.11 kWh during April and lowest production of 189.58 kWh during January, while net energy
produced in a year is 2344.25 kWh in average at Normal operating cell temperature (NOCT), at Standard
Test Conditions (STC) the production is slightly higher as shown in the bar diagram below.
However, there is the possibility of reduction of system size, on performing the simulation with only five
Solar PVs connected in the system the gross energy production during Jan also the lowest yielding month
is 157.98 kWh as shown in fig 19 below. It is nearly seventeen percent less than actual design yield from
Solar PVs. Total gross energy produced during a whole year is 2357.23 kWh. The global efficiency of the
system is eighty-five percent which gives the net energy of 2003.64 kWh in a year.
Figure 18: Energy produced per month by six panels under STC and NOCT
0
50
100
150
200
250
300
350
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Ener
gy [
kW
h]
Energy Production each month (STC,NOCT)
Energy produced per month @NOCT [kwh] Energy produced per month @STC [kwh]
27
Figure 19: Energy produced per month by five panels under STC and NOCT
THE BATTERY STATE OF CHARGE
Fig: 20 and 21 presented in the next page are the result of the Matlab simulation that's indicated the
condition of the battery through the year. Basically, battery is the device that stores electrical energy in the
form of chemical energy. It gets charged when there is surplus energy in the system and gets discharge
when generation is lower than demand, thus supplying the energy it has stored before. Higher the state of
charge higher is the amount of energy stored in it. Here in this graph, it can be seen the state of charge
remains mostly between eighty-five percent (full storage ) and sixty-five percent. Beside few hours when
the battery is completely discharged during the month of Feb and July, it's because of the faulty weather
conditions while measuring the data of Irradiance and temperature , which has been used in this simulation.
The nos. of hours during the year when the battery goes to its nominal level is thirteen.
0
50
100
150
200
250
300
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Ener
gy [
kWh
]Energy Production each month (STC,NOCT)
Energy produced per month @NOCT [kwh] Energy produced per month @STC [kwh]
28
Figure 20: Battery state of charge during a typical year with six batteries
Likewise, in Fig 21 it is seen that state of charge remains fairly between eighty-five percent (full storage
) and sixty percent. There are months like Jan, July, and Dec where the charge in the storage system goes
down to below twenty percent. The change is seen because there is decrease in the nos. of the battery thus
decreasing the storage capacity. The nos. of hours during the year when the battery goes to its nominal level
is fifty-five. During this hours the load is completely shut down or external charger should be introduced
which is not an option for this case. So, residents must rely on their alternative option. Since this is the
worst case scenario where the values of irradiance are very low during few days of July. The cost of the
battery is significantly reduced with this option.
0 744 1416 2160 2880 3600 4344 5064 5808 6528 7272 8016 87600
10
20
30
40
50
60
70
80
90
100Battery State of charge
Time [Hours]
Sta
te o
f C
harg
e [%
]
29
Figure 21: Battery state of charge during a typical year with four batteries
SOLAR PV GENERATION AND BATTERY STATE OF CHARGE DURING JULY
Fig 22 and 23 below are the results of battery state of charge during the July and net energy production
during July respectively. As shown in fig. 22 battery state of charge at the end of the previous month is
assumed to be fifty-five percent which then in July increases up to eighty-five percent and dips below to
less than nominal value. After the third week of July, batteries starts to discharge completely to its nominal
values and charges only up to forty percent of its capacity. Similarly, in figure 23 it is seen that production
from the Solar PVs also decreases by almost half during the start of the third week of July. The faulty
weather condition results in low irradiance and thus decreasing the yield of energy. The number of hours
when the load is completely shut down is thirty-one.
0 744 1416 2160 2880 3600 4344 5064 5808 6528 7272 8016 87600
10
20
30
40
50
60
70
80
90
100Battery State of charge
Time [Hours]
Sta
te o
f C
harg
e [%
]
30
Figure 22: Battery state of charge in July (five panels & four Batteries)
Figure 23: Energy Production in July (five panels)
0 168 336 504 672 7440
10
20
30
40
50
60
70
80
90
100Battery State of charge July
Time [Hours]
Sta
te o
f C
harg
e [%
]
0 168 336 504 672 7440
500
1000
1500Energy from PV in July
Time [Hours]
Energ
y [W
h]
31
AUTONOMY
The autonomy is defined as the time during which the load can be met with the battery alone, without
any solar inputs, this is accounted as the worst case. For this case, as the worst case is during July, figure
24 below is the simulation made for 3 consecutive days when there is very low irradiance for two
consecutive days. The dashed curve represents the energy produced. From this simulation, the no of hours
load can be met is Thirty-six(1.5 days). So, the autonomy of this system is 1.5 days.
Figure 24: Energy, Load, SOC curve for three days
0 24 48 720
100
200
300
400
500
600
700
800
900
1000
Time [Hours]
Energ
y [W
h],Load [w
],S
OC
[%]
Energy
Load
Battery SOC
32
FINANCIAL ANALYSIS- SITE A
In this section cost of the system will be discussed for both the original configuration as well as modified
configuration.
Original configuration:
As per as retail price for the product and service offered by Nepalese Solar Company sums around
4675.00 Euros for the original configuration as shown in table 6.
Table 6: Price quotation for original configuration
Components Quantity Unit Price
(Euros)
Solar PV, Poly Crystalline, REC Norway 6 250 Wp 1.205,00
Solar Tubular Lead acid , Exide, Battery Bank 6 12V/200AH 2.143,00
Solar regulator (MPPT) 1 24V,20 A 300,00
DC/AC Inverter 1500VA 1 1500 VA 357,00
Installation Materials and Installation with
Transportation
1 - 670,00
33
Modified Configuration:
As per as retail price for the product and service offered by Nepalese Solar Company sums around
3685.00 Euros for the original configuration as shown in the table 7. As compared to the table 7 modified
configuration can save up to 22 percent of total cost. Obviously have certain disadvantages during winter
months but this can be minimised by using low wattage energy efficient Luminaries .
Table 7: Price quotation for modified configuration
Components Quantity Unit Price
(Euros)
Solar PV, Poly-crystalline, REC Norway 5 250 Wp 1.000,00
Solar Tubular Lead acid ,Exide, Battery Bank, India 4 12V/200Ah 1.428,00
Solar regulator (MPPT) 1 24V,20 A 300,00
DC/AC Inverter 1500VA 1 1500 VA 357,00
Installation Materials and Installation with
Transportation
1 - 600,00
34
4.2. OFF-GRID SYSTEM SITE B – BHORLENI SOLAR-WIND MICRO GRID
(35.16KW)
Bhorleni Village is located in Farhadi VDC ward no 2 of Makwanpur district. Fig 25 shows the
photographic image of the village takes from a distance adapted from the Detail Feasibility Study
(DFS)report.[38]
Figure 25: Bhorleni Village [38]
According to the detail feasibility study, the initial design allocates 150Watts per household plus about
17 kW for productive end use activities among 120 households in the Bhorleni village including a lower
secondary school. The proportion of productive end use is about one half of the proposed installation to
facilitate commercial activities in the village.[38]
A wind solar hybrid system of total capacity 35.16 kW has been proposed to meet base year (2013) and
forecasted electricity demand of 120 households.[38]
ELECTRICAL CONSUMPTION - LOAD CURVE
With the help of MAT-Lab simulation and load demand survey, daily load profile is presented here. The
Load patters suggest there is peak load in the evening, moderate in the day and very low demand during
morning and night and is presented in fig 26. The peak load is 16 kW, productive end use alone accounts
for 30 percent of the demand. General loads are lights, refrigerators, televisions, photocopy machines,
furniture, chilling plants and cold stores. The total daily average load is 98707 kWh and the total monthly
35
average is 2961.21 kWh. For the purpose of simplicity load for one year is assumed to be constant and load
demand is subject to increase by 5 percent each year resulting daily average load of 125977.9 kWh after
five years as per as Nepal Electricity Authority.[38]
Figure 26: Daily Load profile
TECHNICAL CONFIGURATION
According to the detail feasibility study, the size of the autonomous system with Wind and Solar PV
plant is approximately 35.16 out of which 15 kW wind turbine and 20.16 kWp capacity of Solar PVs shall
be installed. As per as detail feasibility study a hybrid (solar and wind) electricity generation system has
been designed to utilize locally available renewable energy after analyzing the resource availability and the
electricity demand in the village. The simplified block diagram is shown in figure 27.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 240
2
4
6
8
10
12
14
16
18
20Daily Load Curve
Time [Hours]
Load [kW
H]
36
Figure 27: Block diagram of Site B Connection[23]
The hybrid system shall consist of (a)three wind turbines, each with a rated capacity of 5 kW (total 15
kW), (b) 72 solar PVs of 280 Wp each (total 20.16 kWp), and (c) an energy storage system to store
electricity. The storage system has been designed to match the load patterns and the wind-solar power
output, in order to achieve a balance between the demand and supply. A total of 330 batteries (in 3 strings,
and each with 2V, 1000 Ah at C/10; 330 KAH at 50% depth of discharge) are to be installed to store two
days of electricity output that can satisfy about four days’ of electricity demand (excluding productive end
use) in the base year 2013. Table 8 below presents the size of the key components of the proposed solar
wind hybrid system for the Bhorleni village.[38]
Table 8: Major Solar Microgrid component of Bhorleni- Site B
The hybrid system shall consist of three wind turbines, each with a rated capacity of 5 kW (total 15 kW),
72 solar PVs of 280 Wp each (total 20.16 kWp), as shown in figure 28. Size of Solar PVs is around 57
percent of total size while Wind turbines hold 43 percent of total size as shown in fig below.
Components Quantity Unit Total
Solar PV, Mono-crystalline cell ,Canadian
Solar
72 280 Wp 20.16 kWp
Wind Turbine, Pitch Controlled 3 5 kW 15 kW
Battery Bank, GEL VRLAs 330 2V/1000Ah 660 kWh
DC/AC Inverter 2 60 kVA 2*60 kVA
37
Figure 28: Solar and Wind Installed Capacity
MONTHLY IRRADIATION AND AVERAGE TEMPERATURE IN BHORLENI
There are various sources to obtain irradiance and temperature data for the simulation. In this work monthly
average Irradiance, hourly irradiance value for one year, daily average irradiance and temperature values is
taken from for Bhorleni.[37] The table 9 below shows the average Global Horizontal Irradiation (GHI) and
average temperature each month. Module temperature is obtained from average ambient temperature by
converting to Normal Operating Cell Temperature (NOCT) with equation below.
𝑇𝑐𝑒𝑙𝑙 = 𝑇𝑎𝑖𝑟 + 𝑁𝑜𝑐𝑡−20
80∗ 𝐺 4-2
Table 9: Monthly Metrological data- Site B
Month GHI Ambient Temp Module Temp
Jan 122 12.0 25.5
Feb 138 9.4 27.6
Mar 184 13.7 33.0
Apr 211 16.7 37.4
May 179 17.9 34.2
June 165 19.4 34.0
July 136 19.6 31.2
Aug 160 19.4 33.2
Sep 109 18.0 28.2
Oct 153 14.8 30.3
Nov 136 11.1 27.1
Dec 123 13.0 26.2
38
SIMULATION RESULTS
GENERATION FROM SOLAR/WIND
The MATLAB & Excel simulation was made to have an idea about the generation of energy from the
solar/wind microgrid for a period of one year / one month. Irradiance & Temperature data is adapted
from[37] Details of wind data are obtained from the local Wind energy company in Nepal. Further, input
parameter like a model of solar panels and battery (which are mostly used in Nepal) are adapted from the
internet and detailed feasibility study report respectively. The datasheet for Solar PV, Solar Battery and
Wind turbine is attached in appendix 8.2, 8.4 and 8.5 respectively. [38]
The Energy produced by Solar PVs and Wind Turbines for each month is shown in figure 29 below which
was simulated in MS-Excel. From the graph, it can be observed that highest production is during the month
of April accounting total production of net Energy of 4450 kWh and lowest production during Sep
accounting total production of only 2072.6 kWh less than half the yield in the month of April.
Figure 29: Monthly Energy production from Solar PV and Wind Turbine
Furthermore, from figure 30 it is observed during the month of Jan, Jul, Aug, Sep, Dec the production
doesn’t fully supply the load. In this situation, the load is prioritized manually resulting the shutdown of a
portion of productive end loads. This situation has arisen because of very less production from Wind
Turbines. Wind Turbines size is 43 percent of total size while it generates only 19 percent of total average
energy. Replacing Wind turbines and installing similar size of Solar PVs is more profitable in this specific
case study since Solar resources in higher as compared to wind speeds.as we can see in figure 31 ,15000
0.0
500.0
1000.0
1500.0
2000.0
2500.0
3000.0
3500.0
4000.0
4500.0
5000.0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Ener
gy [
kWh
]
Energy from Solar [kWh] Energy from Wind [kWh]
39
kWh of excess energy is produced in year if this option is implemented. The disadvantages of this
configuration would be energy production is totally depended upon only one source of energy i.e. Solar
Energy.
Figure 30: Monthly averaged production and Monthly average load.
Figure 31: Energy produced when wind turbines replaced by Solar PV
0.0
500.0
1000.0
1500.0
2000.0
2500.0
3000.0
3500.0
4000.0
4500.0
5000.0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Ener
gy [
kWh
]
Total Energy [kWh] Total load [kWh]
0
1000
2000
3000
4000
5000
6000
7000
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Ener
gy [
]kW
h
Energy produced per month with solar replaced by wind [kWh]
Excess energy per month compared to prior configuration[kWh]
40
THE BATTERY STATE OF CHARGE
The figure 32 presented below are obtained from MAT-LAB simulation for the time period of one year.
The input parameter is hourly irradiance data, hourly temperature hourly load and battery characteristics. It
is observed that batteries remain in very comfortable position from Jan to June fluctuate from 85 percent to
nearly 58 percent of SOC. As mention in the Detail feasibility Study (DFS )report, it is seen the battery is
drained for several hours during July-Oct mainly because of low production from Solar PVs and Wind
turbines. The number of hours in a year when battery shuts down is six hundred ten which equals around
twenty-six days. The way to solve this problem as recommended in Detail feasibility Study (DFS )report is
to disconnect the portion of productive end load and supply the residential load.
Figure 32: Battery State of charge with Solar and Wind turbines
However, this study suggests there is an option to solve the foreseen problem. As discussed earlier in
section 4.3 Wind Turbines size is 43 percent of total size while it generates only 19 percent of total average
energy. Replacing Wind turbines and installing similar size of Solar PVs is more profitable in this specific
0 744 1416 2160 2880 3600 4344 5064 5808 6528 7272 8016 87600
10
20
30
40
50
60
70
80
90
100
Battery State of charge [Solar and Wind]
Time [Hours]
Sta
te o
f C
harg
e [%
]
41
case study since Solar resources in higher as compared to wind speeds. The disadvantages of this
configuration would be energy production is totally depended upon only one source of energy i.e. Solar
Energy.
As in figure 33 represents the battery SOC while a portion of wind energy is replaced an equivalent
capacity of Solar PVs are connected. Upon installation of this configuration, no of hours, when battery hits
to its minimal level, is reduced to 66 hours in a year. A significant difference is seen during the month of
Sep-Nov as compared to a formal configuration where during this months battery is drained most of the
time as shown in Fig 32.
Figure 33: Battery SOC when wind turbines replaced by Solar PVs.
SOLAR PV GENERATION AND BATTERY STATE OF CHARGE DURING AUGUST
In addition, to have deep analysis on Battery SOC and in order to compare both the configuration
simulation for a month of Aug is carried out. Fig 34 & 35 represents the Battery SOC for the month of Aug
with an energy source as Solar PVS and Wind and with Solar PVs only respectively. It is observed that
Battery SOC drops from 85 percent to 50 percent in 120 hours if connected with the original configuration.
0 744 1416 2160 2880 3600 4344 5064 5808 6528 7272 8016 87600
10
20
30
40
50
60
70
80
90
100
Battery State of charge [Solar]
Time [Hours]
Sta
te o
f C
harg
e [%
]
42
On the Contrary, SOC of Battery drops from 85 percent to 50 percent in 480 hours i.e.20 days if connected
according to modified configuration i.e. Wind turbines completely replaced by Solar PVs. Correspondingly
no. of hours when the battery gets empty is 152 hours with original configuration (Solar PVs and Wind
Turbines and 66 hours when Wind turbines are completely replaced by Solar PVs.
Figure 34: Battery SOC during Aug with Solar and Wind
24 72 120 168 216 264 312 360 408 456 504 552 600 648 696 7440
10
20
30
40
50
60
70
80
90
100Battery State of charge
Time [Hours]
Sta
te o
f C
harg
e [%
]
43
Figure 35: Battery SOC during Aug with wind turbines replaced by Solar PVs.
In the same way, fig 36 and 37 supports the analysis of this study where it is concluded that energy
production is higher with Solar PVs as compared to the configuration with Solar PVs and Wind Turbines.
The average net energy production during Aug with Solar PVs and Wind turbines is 2.37 Megawatts while
on the other hand production soars up to 3.26 Megawatts with the installation of Solar PVs only. There is
around 37 percent increase in energy production.
24 72 120 168 216 264 312 360 408 456 504 552 600 648 696 7440
10
20
30
40
50
60
70
80
90
100Battery State of charge
Time [Hours]
Sta
te o
f C
harg
e [%
]
44
Figure 36: Energy from Solar and Wind during AUG.
24 72 120 168 216 264 312 360 408 456 504 552 600 648 696 7440
5
10
15
20
25
30Energy from PV and Wind [kWh]
Time [Hours]
Energ
y [kW
h]
Energy from Solar PV
Energy from Wind
45
Figure 37: Energy from Solar replaced by Wind
FINANCIAL ANALYSIS OF BHORLENI – CASE B
In this section cost of the major systems components will be discussed in brief for both the original
configuration as well as modified configuration. As, since their no deduction in any components as
compared to case A, There is no any significant price drop in modified configuration. However, the main
advantage of this modified configuration is energy production is increased. [38]
ORIGINAL CONFIGURATION:
For this system the price including tax and duties has been outline here as per as Detail Feasibility Study
(DFS) report. The total price for the major component for the original configuration is approx 184,516
Euros and the breakdown cost is shown in Table 10.[38]
24 72 120 168 216 264 312 360 408 456 504 552 600 648 696 7440
5
10
15
20
25
30Energy from PV replaced by Wind [kWh]
Time [Hours]
Energ
y [kW
h]
46
Table 10:Price quotation for original configuration ( Datasheet attached in Appendix 8.2)
S.N. Components Origin Quantity Price (Euros)
1 Solar PVs, 280Wp Canadian Solar China 72 17,793
2 Wind Turbines 15KW China 3 10,322
3 VRLA Gel Battery 2V,1000AH , China 330 113,542
4 Charge Controller 5kW Wind(3) &
30kW PV(1)
NA 4 2647
5 DC/AC Inverter, 60 kVA-3 NA 2 17652
6 Installation Materials Installation
,Transportation and Testing
Nepal 1 22,560
Modified Configuration:
From the results of the simulation shown in detail in the previous chapter, the wind turbines are replaced
by the equivalent capacity of Solar PVs. Hence, the cost of Wind turbine, Wind turbine tower, and Wind
charge controller is deducted and cost of extra-Solar PVs and accessories is added.
For this system, the price including tax and duties has been outlined here as per as Detail Feasibility Study
(DFS) report. The total price for the major component for the original configuration is approx. 187,144
Euros and the breakdown cost is shown in Table 11.[38]
47
Table 11: Price quotation for modified configuration
S.N. Components Origin Quantity Price (Euros)
1 Solar PVs, 280Wp Canadian Solar China 125 30,890
2 VRLA Gel Battery 2V,1000AH , China 330ss 113,542
3 Charge Controller 70kW NA 1 2500
4 DC/AC Inverter, 60 kVA-3 NA 2 17652
5 Installation Materials Installation
,Transportation and Testing
Nepal 1 22,560
48
49
5. NON-NORMAL OPERATING CONDITIONS
Fault analysis in PV system is a fundamental task to ensure the reliability, efficiency of the system.
Operating characteristics of PV system in the case of the non-normal operation conditions is important to
study for the design of Microgrid System. Physical damages, shading, aging, bypass diode damages are
some examples of the non-normal operating conditions. The installed PV system has to operate in these
abnormal environmental conditions which lead to adverse effects on the performance of the PV system, so
there is need of systematic study of those conditions. The systematic study includes the detailed study of
the variation in the output parameters i.e. current voltage and the power. The waveform of current and
voltage of the PV cell, module, and the panel is measured and IV curve is recorded. The waveforms are
recorded for the normal operating condition as well as the abnormal conditions. The obtained curves are
then compared and figure out the problem associated with the PV system. By comparing those two
waveforms the faults are detected.
Partial shading is one of the most frequent situations that can induce abnormal conditions, occurring
when some module of the PV array is shaded. This is a regular phenomenon mainly caused by clouds and/or
nearby obstacles. Due to the nature of shading, it will show its influence on the IV characteristics. The study
of the nature of defects and its influences in the IV curves (either in a single solar cell and in a module), has
found that module was broken, degradation, cracking, sand and snow effects, corrosion, and shading, all
have in common will result in the variation of its fill factor. There can be also heating of the cells due to
some defects, hotspots may occur due to the rise in cell’s temperature.[39]ssssss There may be degradation
of the interconnection between the modules, corrosion in the inter-cell bonds; all this will give rise to the
variation of series resistance
Till date, in Nepal systematic study of the faults, &maintenance has not been carried out so it is not
possible to say the exactly the conditions of the PV system in Nepal. This thesis work tries to identify the
frequent faults& cause of degradation and finally tries to recommend the solution of the problems which
they are facing
5.1. EFFECT OF PARTIAL SHADING ON CASE STUDY B
Figure 38 & 39 are the simulation result of energy produced by Solar PVs at normal conditions and
nonnormal conditions respectively. To obtain the effect of partial shading one month (DEC) global
irradiance data in change by diffused irradiance skipping a day. i.e. in general assumption of total cloudy
days of fifty percent of the time in a month. In figure 38 each curve represents energy production during a
day with the normal operating condition. The total average energy yield during of month equal to
50
Figure 38: Energy produced by Solar PVs at Normal operation conditions (DEC)
Similarly, as a result of partial shading, the energy yield from Solar Panels gets reduced as shown in the
curve of figure 39. Each small curve in the graph represents energy generated by Solar PVs during a cloudy
day (partial shading, hence some energy is being produced). The total average energy produced during this
condition in a month of Dec is equal to. , which is 36 percent less than the energy that is produced during
normal operating conditions of the same period.
These types of operating conditions are unpredictable and have effects on Battery SOC and feeding of
the load. To overcome and protect batteries to drain, the only most critical load should be run during this
kind of period. Upgrading the system size is costlier and difficult to integrate into the existing system.
However, this kind of conditions should be taken into account while desiring Solar Autonomous Systems.
24 72 120 168 216 264 312 360 408 456 504 552 600 648 696 7440
5
10
15
20
25
30Energy from PV at normal conditions [kWh]
Time [Hours]
Energ
y [kW
h]
51
Figure 39: Energy produced by Solar PVs at Non-Normal operation conditions (DEC)
24 72 120 168 216 264 312 360 408 456 504 552 600 648 696 7440
5
10
15
20
25
30Energy from PV during cloudy month [kWh]
Time [Hours]
Energ
y [kW
h]
52
53
6. CONCLUSIONS AND FUTURE WORK
6.1. CONCLUSIONS
In Nepal, Renewable Energy based off-grid electrification has huge potential to be an alternative solution
to cross-ridden grid-based electrification system, especially in rural areas. In this decade considerable
progress has been made on this front due to the presence of strong and dedicated engagement of various
key institutions and government bodies like Alternative Energy Promotion Centre, (AEPC) donor agencies
and moreover by a presence of a strong market supported by private entrepreneurs.
This thesis study approached autonomous solar microgrids case study of two villages in Rural Nepal.
The simulation of both of the cases was done in MATLAB; Irradiation and temperature data of the sites
was obtained from PVGIS website. [37] Wind speed data is provided by one of the local company who
measured at the specific site4. Regarding the average load which was obtained from Detail Feasibility Study
(DFS) report is assumed to be constant throughout the year, but subject to increase by 5 percent yearly. The
overall efficiency of 85 percent is assumed in both the cases.
In Site A (1.5kWp) the simulation results indicated that, total nos. of installed capacity can be reduced
from 1.5kWp to 1.25kWp. In a year average total net energy at the consumers end is 2003.64 kWh while
average demand is 1470.6 kWh at normal conditions. Each hour simulation for one whole year to analyse
battery state of charge was performed which resulted nos. of battery could be decreased from 6 to 4. Nos.
of hours in a year when batteries are emptied is thirty-five with autonomy days of 1.5. These conditions
further concluded that price of major equipments was reduced by nearly 20 percent.
In Site B, the simulation result indicated that the choice of Solar-wind microgrid has not good impact on
the load. Certain Loads should be turned off during month of (Jan, Jul, Aug, and Sep) because of low
production. If Wind turbines are replaced by Solar PV of equivalent capacity kWh of excess energy is
produced. The nos. of hours when batteries is drained was reduced from 610 to 66 with the autonomy days
of 2. The price of major components nearly remained the same.
6.2. FUTURE WORKS
This thesis only includes the simulation results of the case study, in the future further study can be
conducted by experimental validations of the systems which interns give the precise results, also this thesis
includes a very short description of the economic aspects of the project including only the cost of major
4www.windpowernepal.com
54
equipment. Further study may include the details economic assessment of both of the system. Also in
future, the major study could be the detail fault and maintenance study of both the projects.
55
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59
8. APPENDIX
8.1. PV PANEL – POLYCRYSTALLINE 250WP – REC250
60
61
8.2. PV PANELS- MONO CRYSTALLINE 280WP – 280M
62
63
8.3. SOLAR LEAD ACID BATTERY – EXIDE INDUSTRIES 200 AH-12V,6LMS200L
64
65
66
8.4. SOLAR VRLA GEL BATTERY – SACRED SUN ,2V, 1000AH –GFMJ-1000AH
67
68
8.5. WIND TURBINE - (5 KW) - QINGDAO ANHUA NEW ENERGY EQUIPMENT
CO.LTD.
69
