Resource Assessment and Optimal Sizing of Off-Grid Standalone
Photovoltaic (SPV) System for Rural Communities in Amhara Regional
State, Ethiopia
SHEGAW MELAK AKELE, WONDWOSSEN ASTATIKE HAILE
Department of Electrical and Computer Engineering,
Kombolcha Institute of Technology, Wollo University,
Kombolcha,
ETHIOPIA
*Corresponding Author
Abstract: - Ethiopia’s current population is more than 110 million people. Fifty six percent (56%) of whom live
in either the rural or less urbanized areas without access to grid electricity. The use of alternative energy sources
holds a promise in tackling this lack of grid electrical energy access. Standalone photovoltaic power systems, in
particular, can meet the daily electrical energy demand in rural communities yet unserved by the national power
grid. This paper aims to assess the solar energy potentials in the study area, and design off-grid standalone
photovoltaic power systems that can provide the communities with reliable off-grid power supply. The
assessment of the solar resource potential considers six widely separated areas in the Amhara Regional State of
Ethiopia. Solar resource assessment showed that the annual average solar irradiation of the region is 6.46
at normal tilt angle, 5.95
at a latitude tilt angle, and 6
at latitude
plus 15 degree tilt angle. An estimate of typical household annual energy requirement indicated a consumption
of 2,214.09 kWh. The design of the completed PV system includes sizing of system components and financial
analyses. The financial analysis showed, the total initial investment cost will be 97,941 ETB, and for operation,
maintenance and battery replacement requires of 61,770 ETB throughout the total life times of the system. The
study demonstrated that, the designed standalone photovoltaic system yields a payback period of 13 years
computed based on 3.7 ETB/kWh of energy cost. Moreover, this system will be financially feasible and, thus,
encourages the use of clean energy resource of PV systems in Ethiopia.
Key-Words: - Photovoltaic system, Off-grid, Resource assessment, Load estimation, System sizing, Unit energy
cost, Payback period.
Received: April 25, 2024. Revised: October 11, 2024. Accepted: November 15, 2024. Published: December 23, 2024.
1 Introduction
The extent to which a country develops and civilizes
is determined by the amount of energy its populace
utilize, [1]. In productive daily human activities,
energy plays a crucial, fundamental, and
indispensable role. Due to the rise of worldwide
industrialization and population, the scarcity of
energy has become a crosscutting issue. Ethiopia is
home to abundant renewable energy, particularly
hydropower, wind, geothermal, and solar; yet, due
to lack of energy technology and development, the
reality is, it is one of the energy deficient Sub-
Saharan countries.
The present population of Ethiopia of more than
110 million is the second largest in Africa, [2].
Around fifty-six percent (56%) of Ethiopians lack
access to electricity, and the same proportion holds
true in the Amhara Regional State. For their cooking
and other day-to-day activity needs, these people in
Amhara still depend on charcoal, wood, waste of
crops, and other solid fuels, the use of which leads
to many health-related issues that reduce their life
expectancies. In addition, the use of these materials
degrades the environment and contributes to carbon
emissions.
In 2020 G.C, Ethiopia has a total installed
power generation capacity of around 4,400 MW,
about 90% (3,965 MW) of which is generated by
hydroelectric power plants and 324 MW (7.65%),
7.3 MW (0.17%), and 99.17 MW (2.34%) are
produced by the wind, geothermal and diesel power
plants, respectively, [2]. Annual per capita
electricity consumption is 100 kWh, which is much
lower than the Sub-Saharan African average of 510
kWh, [3]. Roughly, the country needs to generate
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6000 MW on average to cover the shortage in
power.
Eighty-five percent (85%) of the people in the
country live in remote, rural, and less urban areas
that are geographically dispersed. Supplying them
with electricity via transmission lines presents a
number of problems - high capital investment, high
lead time, low load factor, poor voltage regulation,
and frequent power supply interruptions, among
others, [3]. On-site production of electricity via
generators is an alternative, but it also presents
challenges of its own when considering fuel
transportation - rough roads, long distances between
communities, and rising fuel cost. Therefore,
decentralized energy supply systems, such as
standalone solar photovoltaic systems, offer the best
option for rural electrification. The use of well-
suited technologies of good reliability can lead to
less transmission and distribution losses.
Solar irradiance reaching the surface of the earth
varies with time of day, season, location, and
weather conditions. Among these factors, location is
a particularly major consideration in photovoltaic
power system design. A standalone PV system
designed for a given place may not be able to supply
the same amount of load at another. Thus, a single
standard will not apply as the system specification,
for the same load, will vary from place to place, [1],
[4].
Globally, many investigations were carried out
to study the design, optimize, implement, operate,
and cost-analyse off-grid SPV systems for remote
household electrification, [5], [6], [7], [8], [9], [10].
The reference in [5], for example, designed and
implemented a stand-alone photovoltaic system for
Egyptian rural communities. The designed system is
to meet the daily load demand of
2.936
.The 48-V PV system has a 712
(watt power), 20A charge controller, 395 Ah storage
capacity and 700 W inverter. The SPV system unit
cost, life cycle cost (LCC), and annualized life cycle
cost (ALCC) are
, $3029 and $215,
respectively. They conclude the designed PV
system has the smallest unit cost compared to those
in other recent studies. The reference in [6]
introduced a standalone PV system used for the
electrification of a conference hall in Bhopal, India.
The unit energy cost is Rs28.99/kWh with
9.5
energy demand. The reference in [7]
also carried out a techno-economic analysis of
stand-alone hybrid photovoltaic-diesel-battery
systems for rural electrification in the eastern part of
Iran.
The reference in [8] introduced the long-term
perspectives of off-grid PV system based on the
system’s ongoing technological improvements and
cost reductions. The stand-alone PV system should
cover the energy necessities for light, cooking, food
conservation and electronic appliances.
The financial viability and system feasibility of
stand-alone solar home systems in Bangladesh were
presented in reference, [9]. The study shows the
different evaluation parameters such as life cycle
and energy costs, cost effectiveness, and financial
indicators. The reference in [10] introduced an SPV
system driving a biscuit packaging machine that
requires 233.17 Ah/day. The system consisted of a
total PV area of 172.23 with 315 storage
batteries. Their analysis shows the system LCC is
Rs15.059/kWh.
The reference in [11] investigated off-grid PV
system for a typical modern house in Shewa Robit,
Ethiopia. The system requires 16 modules with
130 each, 58.176 kWh storage capacity, and 3
kWh inverter to meet the annual energy
consumption of 4240.936 kWh/year. The initial
investment cost of the SPV system is $12,960.36
and its unit energy cost $0.058/kWh. The Optimal
Sizing and Performance Evaluation of a Hybrid
Renewable Energy System for an Off-Grid Power
System was studied in [12].The reference in [13]
present off-grid PV system for electrification of a
single residential household in Pakistan. The peak
power, capacity of battery backup, and size of
charge controller and inverter were calculated to be
1928Wp, 9640.5Wh, 56.65A and 1020W,
respectively. The economic evaluation using LCC
analysis of the complete system has also been
carried out. The LCC is found to be PKR. 457,306.
The reference in [14] compared energy payback
and simple payback periods for an SPV system. The
author determined that the system simple payback
period ranges between 13.3 years and 14.6 years,
whereas the energy payback period is estimated to
be in between 1.9 years and 2.6 years. Estimates of
the costs induced by additional reserve capacities to
reduce the uncertainty of solar generation in the
Korean power system, and analyses of the
effectiveness of the Energy Storage System (ESS) in
reducing these costs, using the stochastic form of
multi-period security-constraint optimal power flow,
were carried out by reference, [15].
In this paper, the objectives are to assess the
potential of the solar power resource in the remote
areas of the Amhara Regional State, Ethiopia, and,
based on the resource, to design a standalone PV
system to electrify these areas. The resource
assessment takes into account 30 consecutive years
of data at different surface tilt angles. The design
and optimal sizing of SPV system components are
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based on the daily load demand in the area and the
site's solar resource potential. Based on components
available in the local market, the components are
specified and their cost provided. In addition, the
paper details the financial analyses of the SPV
system over the life cycles of mono-crystalline PV
arrays in terms of LCC, electric unit cost, and
payback period.
2 Standalone PV System Design
Methodology
The process of assessing the solar resource and
designing a standalone PV system is subdivided into
the following four main categories.
2.1 Data Collection
Data pertaining to six separate stations in Amhara
Regional State, Ethiopia were collected from
different sources.
(i) The data are collected from government
agencies. Such as; solar radiation data are
obtained from the National Meteorological
Service Agency (NMSA); electrification status
of the region and transmission line loss from the
Ethiopian Electric Power (EEP), cost of
electricity from the Ethiopia Electric Utility
(EEU), and the country’s future plans,energy
potential, per capita energy consumption, and
other relevant information from the Ministry of
Water, Irrigation and Energy (MoWIE).
Radiation data for a few sites not available from
NMSA are sourced from the National
Aeronautics and Space Administration (NASA)
website.
(ii) Community electric demand and existing daily
load requirement for basic, standard and
modern households are obtained from site
visits.
(iii) Off-grid solar PV system components rating,
specifications and technological options are
taken from numerous websites.
2.2 Resource Potential Assessment
Based on the solar radiation data collected, the
monthly lowest and highest average solar irradiation
in the region, at different surface tilt angles and
measured in
, are assessed.
2.3 SPV System Design
The process of designing a standalone PV system
involves determining the system capacity in terms of
power, voltage, and current with the view of
meeting the daily load requirements of a standard
house. The sizing process is carried out by using the
following steps, [16], [17]:
(i) Calculating the average daily solar energy
input
(ii) Estimating the residential power
consumption
(iii) Sizing the PV module/ array
(iv) Choosing the PV module orientation
(v) Sizing the storage batteries and specifying
their configuration
(vi) Sizing the solar charge controller
(vii) Sizing the DC-AC inverter
(viii) Sizing the system cable
2.4 Economic Analyses
The economic analyses demonstrate the
acceptability or feasibility of the designed SPV
system. The process requires the determination of
specific values: initial investment cost, storage
battery bank replacement cost, operation and
maintenance cost, life cycle cost (LCC), annual life
cycle cost (ALCC), system unit energy cost, present
values, future values, and payback period.
Appropriate inflation rate, discount rate, and
lifetimes are applied.
3 Result and Discussion
3.1 Resource Potential Assessment
Ethiopia is located near the equator and its solar
resource is obviously significant. The annual
average daily radiation in Ethiopia reaching the
ground is estimated to be at 5.5
[3].
For the purpose of this study, six widely separated
meteorological stations in the Amhara regional state
are selected for assessing solar irradiation potential.
These stations are in Gonder, Bahir Dar, Deber
Markos, Debre Berhan, Dessie, and Woldia. The
nearest and furthest distances between stations are
120 km and 883 km, respectively. Table 1 shows
the coordinates (latitude and longitude) and
elevation of each station as well as their distances
from Addis Ababa and Bahir Dar. Also, in order to
obtain values used in the design that closely reflect
conditions in the field, solar radiation data from a
30-consecutive-year period (January 1984 –
December 2013 G.C) were used.
The variation in solar irradiation monthly
average, measured in
, at different
tilt angles are shown for each station in Figure 1,
Figure 2, Figure 3, Figure 4, Figure 5 and Figure 6.
DNIR means solar irradiation at normal tilt angle,
SIRLT at latitude tilt angle, and SIRLP15T at
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latitude plus 15 degrees tilt angle. Notably, the
variation in tilt angles directly affects the amount of
solar power that can be captured.
Bahir Dar is a special zone and the capital city
of the Amhara Regional State. It is situated at the
north-northwest of the country capital Addis Ababa
and on the southern shore of Lake Tana, the source
of the Blue Nile or Abay. Gonder is a city and
separate administrative center of the Semien
Gonder. Debre Markos is a city and the
administrative center of the Misrak Gojjam Zone in
northwest Ethiopia. Debre Berhan is a city and
governmental center of the Semien Shewa Zone.
Dessie is a city north of Addis Ababa and
administrative center of Debub Wollo Zone. Woldia
is the capital and governance center of the Semien
Wollo Zone, [18].
The lowest and highest monthly averages solar
irradiation are 3.95
(August, Debre
Markos Station) and 8.76
(December, Gonder Station), respectively, at normal
tilt angle position. Correspondingly, at latitude plus
15-degree tilt angle, the values are 4.18
(July, Debre Markos Station) and
7.63
(January, Gonder station).
Similarly, at latitude tilt angle, the values registered
are 4.64
(July, Debre Markos
Station) and 7.02
at (January,
Gonder Station).
The annual average solar irradiation of the
region is 6.46
at normal tilt angle,
5.95
at a latitude tilt angle, and 6
at latitude plus 15 degree tilt angle.
For this design, the highest value of average solar
irradiation (6.46
) is used for
satisfying the power demand throughout the year in
all stations with a latitude tilt angle orientation.
Table 1. Station coordinates and elevation above
sea level
Station
Coordinates
Elevation
(in
meters)
Distance
from
Addis
Ababa
(in km)
Distance
from
Bahir
Dar
(in km)
Bahir
Dar
11° 59' N,
37° 39' E
1,800
570
-
Gonder
12°6′
N, 37°46′E
2,133
758
188
Debre
Markos
10° 35' N,
37° 73' E
2,446
295
275
Debre
Berhan
9° 67' N,
39° 53' E
2,840
130
700
Dessie
11°13′N,
39°63′E
2,470
401
480
Woldia
11° 83' N,
9° 68' E
2,112
520
360
Fig. 1: Solar irradiation in Bahir Dar Station at
normal, latitude, and latitude plus 15 degrees tilt
angles
Fig. 2: Solar irradiation in Gonder Station at normal,
latitude, and latitude plus 15 degrees tilt angles
Fig. 3: Solar irradiation in Debre Markos Station at
normal, latitude, and latitude plus 15 degrees tilt
angles
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Fig. 4: Solar irradiation in Debre Berhan Station at
normal, latitude, and latitude plus 15 degrees tilt
angles
Fig. 5: Solar irradiation in Dessie at normal, latitude,
and latitude plus 15 degrees tilt angles
Fig. 6: Solar irradiation in Woldia Station at normal,
latitude, and latitude plus 15 degrees tilt angles
3.2 Household Daily Load Estimation
The entire solar PV system design is based on the
size of the load and the available solar irradiation
resource. Thus, the design of a solar PV system
begins with the calculation of the daily energy
consumed. Inaccurate load calculation may lead to a
system failure or a high loss of load probability,
[19]. If the bases of load calculation are inaccurate,
either the initial cost will be too high or the battery
and array/module sizes be too small so as to cause
the system to fail eventually.
Above 98% of the people who live in the
Amhara Regional State rural area are farmers. The
variation in land and water availability,
transportation access, weather condition, among
others, result in farmers having different standards
of living. In this study, the farmers are classified
based on certain levels of standard of living: 1)
Basic Level - represents poor farmers; 2) Standard,
or Middle, Level – contains average class farmers,
and 3) Modern, or High, Level - consist of farmers
who have very good economic capacities. The
present SPV design caters to households belonging
to farmers in the Standard and Modern Levels, they
being in a category of households that has the
capacity to invest in an undertaking of this
magnitude. The design of an SPV system for
households at the Basic Level will entail a different
set of requirements, and putting up the designed
system will need financial assistance from the
government. Most of the people who live in the
middle and high levels have three structures,
buildings, or shelters on their premises. The first
structure, which has an area of between 25 and
35, is used as enclosure for animals, kitchen, and
store. Its roof is covered with grass and hull and
circular or rectangular in shape. The second is used
for dining and sleeping, and its area, commonly
42, 56, or 72, depends on the number of
people who lives in it. The last consists of toilet and
bathroom. The household electric devices and their
corresponding daily energy requirements are listed
in Table 2 and Table 3, respectively. Based on these
tables, the following values are arrived at:
Total household power requirement per day
() =3.948 kW
Total household daily energy consumption =
6.066 kWh
Total household annual energy consumption =
2,214.09 kWh
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Table 2. Lighting loads
Lamp
placement
Qty
Power
rating
per lamp
(W)
Total
power
(kW)
Operating
hours per
day (h)
Energy
required
per day
(kWh/day)
Dining
(Salon)
room
2
11
0.022
3
0.066
Master
bedroom
1
11
0.011
1
0.011
Children’s
bedroom
1
9
0.009
5
0.045
Outdoor
2
9
0.018
3
0.054
Kitchen
1
7
0.007
2
0.014
Toilet and
bathroom
2
5
0.01
1
0.01
Animal
living room
1
11
0.011
1
0.011
Total
0.088
0.211
3.3 System Design
The design of standalone PV system is a process of
putting together all the different electrical
components sized correctly and economically to
generate electricity from sunlight and satisfy the
daily energy requirement without interruption even
during autonomy days, [1]. The components include
solar PV modules, charge controller, batteries, DC
to AC inverter, protective device and system wiring.
The designed SPV system is applicable for
implementation anywhere in Amhara Regional
State, Ethiopia. As shown in the solar resource
assessment, all the stations have closely similar
solar irradiation patterns throughout the year,
especially in the summer season, and slight
differences in the winter season. To reduce to the
lowest possible value the required number of PV
modules and storage batteries, the most efficient
available components are selected. 48 V DC is the
selected nominal system voltage ().
Table 3. Appliance loads
Appliance
Qty
Power
rating per
appliance
(W)
Total
power
(kW)
Operating
hours per
day (h)
Energy
required
per day
(kWh/day)
Stove
1
1000
1
2
2
Electric Mitad
1
2500
2.5
0.05
0.125
Refrigerator
1
100
0.1
24
2.4
Boiler
1
100
0.1
1
0.1
Radio
1
20
0.02
4
0.08
TV(21’’)
1
100
0.1
7
0.7
DVD /VCD
player
1
30
0.03
7
0.21
Telephone
2
10
0.01
24
0.24
Total
3.86
5.855
3.3.1 Sizing of PV Array
The PV array is one of the key components of off-
grid PV system. The power generated by the PV
array must be enough to meet not only the required
daily energy consumption as shown in Table 2 and
Table 3 but the system losses as well. To size the
array, there is basic information required: insolation
in the given location, module efficiency, module
temperature coefficient (), voltage loss in cables,
and battery, inverter, and charge controller
efficiencies, [4], [5], [11]. The PV module derating
factor () accounts for the dirt or dust that
accumulates on the PV module surface over time
and reduces its effectiveness to generate power. The
PV module surfaces will thus require periodic
cleanup as part of maintenance. In this paper the
following values are applied: 21% PV module
efficiency (), [20], 98% charge regulator
efficiency(), [21], 93% inverter efficiency (),
[22], 90% battery efficiency(), [23], 0.98 [11],
3% cable loses (, and unity temperature
coefficient factor (), [24], because at all stations
the temperature is above standard. From these
parameter values, the total power that the PV array
must generate is determined by using equation (1)
[19]. Peak sun hours () is the ratio of the
average solar irradiation at the site (6.46
/day) to standard power generated by the
PV module () as
at 25 , [25] . As
per equation (1), [26], the minimum required power
the PV array needs to generate is 5.74 kW per day.
where = the total power generated by SPV array,
= daily energy consumption, and = total
efficiency =
Mono-crystalline, polycrystalline and thin-film
solar cells are the most common type of solar cells
and they differ in the type of silicon used,
manufacturing process, and product quality. In this
work mono-crystalline KFM275M-20 PV modules
are used because they cost less and are available in
the local market. The technical specification for this
module is shown in Table 4.
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Table 4. KFM275M-20 PV module technical
specification, [20]
Parameters
Values
Module Type
KFM275M-20
Power rating
275 W
38.3 V
9.49 A
8.76 A
31.3 V
Module Efficiency
21.5 %
Mono solar cell
156x156mm (60 pics)
Power tolerance
0-5%
Maximum system
voltage
1000 V
Power temperature
coefficient
-0.3%/
Dimensions (lxwxh)
1640x992x35mm
Weight
19.5 kg
The total number of modules () required to
supply the daily energy need of a standard home is
20 modules per equation (2). represents the
selected module rated power.
Those modules must be so connected as to
obtain the specified system voltage. Thus, a number
of modules are connected in series to form a string
and a number of strings in parallel to obtain the
overall rated current and voltage of the array. The
number of modules connected in series () to
form a string and the number of strings in parallel
() are calculated using equation (3) and (4),
respectively.
Based on the calculation = 2 and = 10,
which mean two modules will form a string and ten
of these strings will connect in parallel to yield a
maximum charging current of 10 strings times
8.76A per string or 87.6 A.
3.3.2 Sizing of Storage Capacity
The storage capacity should be enough to store
sufficient energy to power the household loads for
the specified period at night time and on cold days
and rainy seasons. The battery chosen for this design
is 3TT200, and its technical specification is shown
in Table 5. To determine the required number of the
specified battery, the days of autonomy (),
efficiencies of inverter and battery, and maximum
allowable depth of discharge (DOD) must be
considered carefully. The days of autonomy is the
number of days the standalone PV system can
operate without sunshine. Its value for a design
purpose is usually three to five days, [4], [11], [17],
[23]; 3 days is used in this design. The required
battery capacity () is determined as in equation
(5).
From this equation, it can be shown that the
storage capacity required for the given household
load and parameter values is 27.161 kWh.
Calculation of the ampere-hour storage capacity
() of the battery bank using equation (6) gives
us 556Ah.
Table 5. 3TT200 battery technical specification,
[23]
Parameters
Values
Type of battery
3TT200
Nominal voltage ( )
12V
Capacity @ C-10
200Ah
Depth of discharge (DOD)
80% for 1500 cycles
50% for 3000-5000cycles
Efficiency
90%
Dimension (lxwxh)
500x187x450mm
Self-discharge
Less than 3% per month
Weight
44.7kg
Service life under
6-10 years
A number of batteries () has to be connected
in series to meet the system voltage specification; a
number of this series connections () are then
connected in parallel to meet the current
specification. and are found using
equations (7) and (8), respectively, [26].
where, = nominal voltages of selected battery
= ampere-hour storage capacity of selected
battery. Hence, the total number of batteries needed
to store the energy for the given 3 days of autonomy
can be calculated as in equation (9).
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Thus, from Equations 7, 8, and 9, we find that 3
battery strings connected in parallel, with each
string having 4 batteries connected in series, are
needed to ensure the system bus voltage and current.
All in all, the storage battery bank will use twelve
3TT200 batteries.
3.3.3 Selection of Solar Charge Controller
The main role of charge controller in a standalone
PV system is to protect the batteries from over-
charging and over-discharging which can lead to
battery damage. The maximum load current ()
capacity is determined by using equation (10).
The maximum charging current capacity
() can be calculated from the
equation. The controller must
also be capable of carrying the PV array short-
circuit current (), which can be determined
from the equation .
and represents the maximum current at
maximum power and short-circuit current of the
selected PV module respectively. The design current
should be the larger of the two. Thus, the rating of
the selected charge controller must be equal or
greater than 87.6A/48V. The selected charge
regulator should fully meet not only the system
operating voltage and maximum charge current
capacity but also the maximum load current
capacity, reverse leakage current, high and low
voltage disconnect set point, and operating ambient
conditions as well, [19]. Consequently, the
maximum power point tracking charge regulator
whose technical specification is shown in Table 6 is
selected. The selected charge controller has a battery
charge indicator, storage level indicator, load
indicator, power reset point, and terminals for
connecting the storage battery bank, PV array, and
DC loads.
3.3.4 Sizing of DC- AC Inverter
The inverter is used to convert DC power stored in
the battery to AC power. Its sizing is based on surge
capability, continuous power output, efficiency,
waveform, input DC voltage, output AC voltage,
frequency and voltage regulation, [19]. From
equation (11), the inverter power rating () is
4.245 KVA at unity power factor (PF).
Table 6. Charge controller technical specification,
[21]
Parameters
Value
Type
MPPT
Operating Voltage
48V
Charging current
100A
Efficiency
98-99.5%
Enclosure protection class
IP43
Operating temperature
0- 55
Heat dissipation
Self-cooling
Dimension (lxwxh)
406x314x128 mm
Weight
7.1 kg
The power rating of the selected inverter should
be greater than 10%-25% than this calculated
power, [5], [11]. Thus, using a compensation of
20%, an inverter rated at about 5.094 KVA is
selected. The technical specification for the selected
5 kVA inverter is shown in Table 7.
Table 7. Inverter technical specification, [22]
Parameters
Values
Model
Sprit 5KVA+SCC
Rated output power
5KVA
Output voltage waveform
Pure sine wave
Output voltage
230Vac±5%
Output frequency
50 Hz
Efficiency
93%
Nominal DC input Voltage
48V
Overload capability
110-150 % load for 10s
>150% loaded for 5s
High DC cut off voltage
58 V
Low DC cut off voltage
40
3.3.5 System Cable Sizing
The design of a SPV system is incomplete until the
correct size and type of cable is selected for
interconnecting the system components together,
[1]. Different cable sizes are used in different parts
of the SPV system like PV array to charge the
controller, battery to charge controller, battery to
inverter, and AC distribution board to load.
3.3.5.1 PV Array to Charge Controller Cable
The wire joining the PV array to the charge
controller should be able to resist sunlight and water
as well as mechanical damage, [19]. The size of the
wire depends upon the allowable voltage drop, the
current flow, and the wiring length between the PV
array and the charge controller. Most of the time,
PV arrays are installed on the roof of the house.
Here, the cable length is assumed to be ten meters.
The percent voltage drop along the length of the
wire must be reasonably less than 10% of the system
voltage (), [4], [11], [19]. Accordingly, with a
wire length () of 10 m, voltage drop () of 4%,
and array current () of approximately 88A, the
WSEAS TRANSACTIONS on POWER SYSTEMS
DOI: 10.37394/232016.2024.19.40
Shegaw Melak Akele, Wondwossen Astatike Haile
E-ISSN: 2224-350X
482
Volume 19, 2024
minimum cross sectional area of the wire () is
50 as computed from equation (12).
3.3.5.2 Battery to Charge Controller Cable
The size of the wire connecting the charge controller
and the battery is also calculated by using equation
(12). However, ∆V, LC, should be taken as 1% and
5m, respectively, while the current should be the
largest value that can flow through the wire. During
the charging process, the current flowing through
the wire is similar to the current received from the
PV arrays while during the discharging process the
current is equal to the total load current. The largest
current flow through the wire during charging and
that is 87.6A. Calculating, the minimum cross-
sectional area of the wire would then be 50.
The same wire size is used for connecting the
storage battery bank to the inverter.
A similar calculation is carried out for the size
of the cable connecting the AC distribution board to
the loads. The wire must be no less than 4 in
cross sectional area, considering wiring length of 50
meters and a voltage drop of five percent.
3.4 Financial Analyses
Unit energy cost and payback period are the two
basic indicators of the project feasibility, and life
cycle cost (LCC) analysis is the most valuable
statistical tool for evaluating the economic behavior
of renewable energy systems, [5]. The LCC analysis
cover all the system’s life stages: initialization stage,
operation and maintenance stage, and replacement
stage, [27], [28], [29], [30]. In the initial stage, the
initial investment cost required to setup the system
is incurred and includes the expenses for purchasing
the PV array, charge controller, storage batteries,
inverters, switch, lamp, breaker, distribution board,
and cable and installation costs as shown in Table 8.
Operation and maintenance stage expenses are
periodical expenditures for the regular maintenance,
operation, and management of the system.
Replacement stage expenses are those incurred for
replacing storage batteries, which may not regularly
happen, to ensure continuous, proper, and efficient
operation of the system. Depending on the battery
type and operating condition of the storage batteries
in the PV system, batteries may be replaced every
six to ten years, [4], [5], [23]. The expected
lifetimes of PV modules are estimated to be
between twenty and thirty years, [31], [32]. For the
current design, the lifetimes of the PV module and
battery are twenty-four and eight years, respectively.
The storage batteries will thus need to be replaced
two times, on the eighth and sixteenth year, during
the 24-year life of the system.
Table 8. Initial investment cost
No.
Items
Qty
Unit
price
(ETB)
Total
(ETB)
Remark
1
PV module
20
1,800
36,000
As per
Table 4
2
Battery
12
2,500
30,000
As per
Table 5
3
Charge
controller
1
8,000
8,000
As per
Table 6
4
Inverter
1
13,968
13,968
As per
Table 7
5
Cable
SPV to
charge
controller
10
m
45/m
450
Battery to
charge
controller
5m
30/m
150
Battery to
inverter
5m
30/m
150
AC
distribution
board to
load
50
m
15/m
750
6
Switch
7
30
210
7
Installation
cost
3,600
10%PV
cost
8
Other
equipment’s
4,663
5% total
cost
Total
investment
cost
97,941
Inflation and discount or interest rates should be
considered when making future estimations of costs
associated with off-grid PV systems. The inflation
rate represents the decrease in the value of money
over time, while the discount rate represents the
increase in the value of money with time due to
interest, [19]. Currently, the Commercial Bank of
Ethiopia interest rate (r) is seven percent. The
inflation rate (f) of the country is taken as five
percent. In this study, it is taken that operation and
maintenance () and installation () costs are
two and ten percent, respectively, of the PV
investment cost (). The first battery replacement
cost () is 25,731 Ethiopian birr (ETB) by
equation (13), and second replacement cost ()
is 22,071 ETB as per equation (14), [5].
WSEAS TRANSACTIONS on POWER SYSTEMS
DOI: 10.37394/232016.2024.19.40
Shegaw Melak Akele, Wondwossen Astatike Haile
E-ISSN: 2224-350X
483
Volume 19, 2024
Hence, the total battery replacement cost
required over 24 years is 47,802 ETB and the
operation and maintenance cost is 13,968 ETB as
per equations (15) and (16), respectively[4]. In
equation (16), Y represents replacement years.
The system life cycle cost can be calculated by
adding the initial investment, operation and
maintenance, and battery replacement costs as in
equation (17).
The annual life cycle cost (ALCC) is estimated
from equation (18) [28].
As calculated from equations (17) and (18), the
system LCC is 159,711 ETB and the ALCC is 8,225
ETB. The unit electrical cost () is 3.7 ETB/kWh
as per equation (19), [28].
For calculating the payback period, total
investment cost, annual income and annual
expenditure must be considered [16], [19], [27].
Based on this, the investment recovery period is
12.8 years. Figure 7 shows the designed system
component percent cost distribution over a 24-year
life cycle.
Fig. 7: The designed system component percent cost
distribution over a 24-year life cycle
This implies the power system will return its
investment cost within 12 years and 8 months at a
unit energy cost of 3.7 ETB/kWh. The results of the
economic analysis shows, this project is feasible.
4 Conclusions
This study focuses on assessing the solar energy
resource potential and designing a standalone solar
photovoltaic system that matches the given solar
resource and the specified load so as to provide
electricity for rural, remote areas where access to the
utility grid is nonexistent. The solar energy resource
potential of the Amhara Regional State is
investigated using 30-year data from the region’s six
geographically and widely separated stations
considering different tilt angles. Based on the
irradiance data, Gonder Station has relatively higher
solar irradiance while Debre Markos and Debre
Behan Stations have relatively lower irradiance.
The study has shown that a standard and modern
household with a daily load of 6.066 kWh/days and
an annual average solar irradiance of
6.46
can be served by an SPV
system having twenty KFM275M-20 modules with
a total power generation capacity of 5.74 kW,
twelve 3TT200 batteries each rated at 12V and
200Ah, a 100-A/48-V MPPT charge controller, and
a 5-kW inverter.
The economic analyses of the off-grid
photovoltaic system shows that the system needs
97,941 ETB initial investment, 47,802 ETB for
battery replacement, and 13,968 ETB for operation
and maintenance, on the basis of 24 years of PV
array and 8 years of battery lives, 5% inflation rate,
and 7 % interest rate. The analyses also show that
the system life cycle cost is 159,711 ETB, the
annual life cycle cost is 8,225 the unit energy cost is
3.7 ETB/kWh, and the payback period is 12.8 years.
The analyses thus indicate that the system is
feasible. Though the initial investment cost of the
SPV system is high, the amount can be recovered
within approximately thirteen years and the system
is usable for more than 24 years without power
interruption and bills. Finally, the standalone
photovoltaic power system can provide access to
electrical energy that hasn’t access to grid electricity
approximated around 56% of the Ethiopian people.
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DOI: 10.37394/232016.2024.19.40
Shegaw Melak Akele, Wondwossen Astatike Haile
E-ISSN: 2224-350X
484
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Contribution of Individual Authors to the
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Policy)
The authors equally contributed in the present
research, at all stages from the formulation of the
problem to the final findings and solution.
Sources of Funding for Research Presented in a
Scientific Article or Scientific Article Itself
No funding was received for conducting this study.
Conflict of Interest
The authors have no conflicts of interest to declare.
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WSEAS TRANSACTIONS on POWER SYSTEMS
DOI: 10.37394/232016.2024.19.40
Shegaw Melak Akele, Wondwossen Astatike Haile
E-ISSN: 2224-350X
486
Volume 19, 2024
