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DESIGN OF PHOTOVOLTAIC SYSTEM FOR A HOUSEHOLD IN A VILLAGE- KAGERA REGION
Table of Content
1.0 General Objective: ………………………………………………………………………………………………………………………………………….3
1.1 Specific objective: …………………………………………………………………………………………………………………………………………..3
2.0 Introduction………………………………………………………………………………………………………………………………. 3
3.0 Sketch of the floor plan of the household showing the PV system layout ………………………………………………………………….4
4.0 Determining the daily load energy demand of the system based on appliances to be used………………………………….... 4
4.1 Determination of Daily system Charge requirement (Ah)……………………………………………………………………….. 5
5.0 Selection of the components for accomplishing the system …………………………………………………………………………………..5
5.1 Sizing and choosing the solar module ……………………………………………………………………………………………………………….5
5.2 Determination of the system design charging current ………………………………………………………………………………………….5
5.3 Sizing of the modules …………………………………………………………………………………………………………………………………….5
5.4 Battery selection…………………………………………………………………………………………………………………….. 6
5.5 choosing charge controller………………………………………………………………………………………………………… 6
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5.6 selecting the Inverter……………………………………………………………………………………………………………….. 7
5.7 Selection of DC-DC converter…………………………………….……………………………………………………………….. 8
5.8 Choosing wiring cables……………………………………………….……………………………………………………………. 9
5.9 selections of fuses………………………………………………………………………………………………………………… 10
5.10 Selections of switches ……………………………………………………………………………………………………………………………….10
5.11 selections of sockets …………………………………………………………………………………………………………………………………10
5.12 Selections of sockets……………………………………………………………………………………………………………. 11
5.13 Earthing the system …………………………………………………………………………………………………………………………………..11
6.0 To determine the declination of the solar modules………………………………………………………………………………… 11
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DESIGN OF PHOTOVOLTAIC SYSTEM FOR A HOUSEHOLD DOMESTIC USE IN KAGERA REGION
1.0 General Objective:
To design the Photovoltaic system for a household domestic use in a village located in Kagera region.
1.1 Specific objective:
i)To sketch the floor plan of the household showing the PV system layout,
ii) To determine the daily Load energy demand of the system based on appliances to be used,
iii) To select the components for accomplishing the system, and
iv) To determine the declination of the fixed solar modules on a mast.
2.0 Introduction
Electricity supply in Tanzania consists of both interconnected and isolated systems. The isolated systems are ones
usually carter the rural areas where the grid connection is not available. The stand alone PV system is the isolated
electric system. It contributes a lot in rural electrification for enhancing the development in area in question. There
are huge merits of having the reliable source of energy in rural area as it helps in facilitation of the information
technology like charging phones and powering computers to mention a few. Also due the hike of sky rocketing
price of fuel especially kerosene for lighting in the rural areas, solar lamp prove low operating cost so that savings
can be earned. The solar PV system is the one of the system which can be used to realize the mission of rural
electrification as the Tanzania Energy Policy of 2003 stipulates. Based on the advantages of PV system in rural
areas brings to the justification of its design for one of the household of a village located in Kagera region. Kagera
region lies just below the Equator between latitudes 1° 00’ and 2° 45’south. In terms of longitude it lies between
30° 25’ and 32°40’ east of Greenwich. As a part of Tanzania, it is located in the extreme north-western corner of
the Mainland. The region includes a large portion of Lake Victoria. It has a common border with Uganda to the
north, Rwanda and Burundi to the west, Shinyanga and Kigoma regions to the south. The household where the
system will be installed is near to 1° 00’ South of Equator.
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3.0 Sketch of the floor plan of the household showing the PV system layout
According to the appliances to be used the system will be a combination of AC and DC storage system. Refer
appendix 1. Figure 1.
4.0 Determining the daily load energy demand of the system based on appliances to be used
Determination of daily load energy demand
Section of
appliance
Voltage(V)
Power(W)
Daily use(h)
residency
Daily energy
use(Wh)
Bed room 3
lamp
12
8
2
16
Radio
9*
10
4
40
Lamp
12
11
4
44
TV set
240AC**
80
3
240
Phone charger
240VAC**
5
0.6
3
Store
lamp
12
11
4
44
Bed room 2
lamp
12
8
0.5
4
Night dining
Lamp
12
11
4
44
Sitting room
room
Total daily Load energy demand 435
*require DC-DC converter
**require 12Vdc-240VAC inverter
Estimation of losses
•
New system loss=15% of Total daily load energy=66Wh (435 x 0.15=65.25 Wh, i.e. approx. 66 or 66.3)
•
Inverter Loss=15% of Daily energy of inverter(3+240)=37Wh (TV set and Phone charger)
fed into the
Total estimated system energy losses=66+37=103Wh
Total daily system energy demand= Total daily Load energy demand+ Total estimated system energy losses
=435+103=538Wh
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4.1 Determination of Daily system Charge requirement (Ah)
Selected system voltage is 12 Vdc.
Ah=Wh/Vdc=538/12=44.8=approximately 45Ah
Thus the module should be able to supply Daily system charge of 45Ah.
5.0 Selection of the components for accomplishing the system
5.1 Sizing and choosing the solar module
Estimation of solar insolation value in Kagera region
The system to be designed is a stand alone one, therefore the monthly mean daily insolation will be used. Based
on lack of the immediate meteorological data of solar insolation, the estimation of the required value has been
made based on the literature available. From figure 1.7&1.8 page 8 of a Guide for Planning and Installing Solar
Electricity Systems in a Rural for Africa the monthly mean daily insolation of Mbarara will be used since Mbarara is
closest town to Kagera region. The design month (month with lowest daily insolation) is October in which 4.3 peak
sun hours (kWh/m2) is recorded (Hankins, 1995). The Solar panel will be fixed mounted on a post (no tracking).
Therefore the design solar insolation value is 4.3 peak sun hours.
5.2 Determination of the system design charging current
The system design charging current= daily system charge requirement/design solar insolation (peak sun hours)
=45Ah/4.3psh=10.46= approximately 11 A
5.3 Sizing of the modules
From the table 9.5 of solar electricity for Africa written by Hankins in 1995, one of type of module presented is
Solarex MSX-60 rated 60Wp with actual current output of 3.75.Number of modules required of the type mentioned
above is given as system design charging current divided by actual current output of a single module, i.e.
11A/3.75A=2.9333 approximately 3 modules. Therefore three modules of Solarex MSX-60 rated 60Wp will be
required for the designed system and will be connected in parallel.
Typical Electrical Characteristics of Solarex MSX-60
Maximum power (Pmax) 60W
Voltage @ Pmax (Vmp) 17.1V
Current @ Pmax (Imp) 3.5A
Guaranteed minimum Pmax 58W
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Short-circuit current (Isc) 3.8A
Open-circuit voltage (Voc) 21.1V
Temperature coefficient of
open-circuit voltage . . . . . –(80±10)mV/°C . . . .
Temperature coefficient of
short-circuit current . . . .(0.065±0.015)%/°C . .
Temperature coefficient of power . . . . . –(0.5±0.05)%/°C . . .
5.4 Battery selection
System charge = 45Ah
Number of storage days=3
Maximum depth of discharge =50%=0.5
The required system battery capacity=(Daily system charge requirement * Number of storage days)/Maximum
allowable depth of discharge of a battery
=45*3/0.5=270Ah
The required system battery capacity is 270Ah (minimum battery size required). With availability of Deka Solar
Gelled-Electrolyte Battery 12VDC 108AH @100 Hr Rate from ENSOL (T) Ltd, number of batteries of the same
rating to carter the system battery requirement is 270Ah/108Ah=2.5. i.e.3. The batteries will be connected in
parallel.
Specifications of selected battery
Voltage …………… 12 volts nominal (8GGC2 is 6 volts)
Plate alloy ……… Lead calcium
Element, post …… Threaded stud or “flag” terminal, forged bushing
Container/cover … Polypropylene
Electrolyte ……… Sulfuric acid thixotropic gel
Vent ……………… Self sealing
5.5 choosing charge controller
Sizing of the charge controller depend on the input current from solar PV panel and load current as well as the
system voltage. The system voltage is 12Vdc, and the module has Short-circuit current (Isc) 3.8A.
Solar charge controller rating = Total short circuit current of PV array x 1.3
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Therefore, charge controller rating will be given as 3.8X3X1.3=14.82A(minimum value) at 12 Vdc.
Selected charge controller is SUNSAVER with the following specifications:
Electrical Specifications
12 Volt
Rated Solar Input 6.5 /10/20 A
Rated Load 6/10/20 A
25% Current Overload 5 min.
Regulation Voltage:
Sealed Battery 14.1 V
Flooded Battery 14.4 V
Load Disconnect 11.5 V
LVD Reconnect 12.6 V
Self-consumption 6 to 10 mA
Operating Temp. -40 to +85oC
5.6 selecting the Inverter
Inverter sizing depends on the type of device being powered. Device start-up or surge, efficiency (60%-80%) of
inverter and, should always be considered. For example, motors and compressors have start-up surges. It's
generally a good idea to oversize an inverter. The rating of the TV set is 80 W and 240VAC,hence by including the
losses the inverter selected is Selectronic 200Watt 12volt True Sinewave Inverter.
Chosen inverter has following specification
Electrical Characteristics
30 mins Output Power "TRUE POWER"
250 W
Continuous Output Power "TRUE POWER"
200 W
Surge Power
600 W
Battery Voltage
12V DC
Output
220 - 240V AC
Peak Efficiency
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91 %
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Thermal Share Technology
Standard
High Battery Voltage Protection
17V DC
Low Battery Voltage Protection
10V DC
Overload Protection
Standard
Auto Recover From Overload
Standard
Operating Temperature Range
-10 ºC to + 50ºC
Isolated Output
Standard
Power Point
Standard
Mechanical Characteristics
No of LED indicators
3
Dimensions
215W x 80H x 190D mm
This inverter (200W, efficiency 91) was chosen because the Total system daily load (538 Wh in a location with 4.3 peak sun hours) is handled
by the inverter sufficiently based on the following analysis.
538 / 0.91 = 591 Wh. Calculated Wattage of inverter = 591 /4.3 = 138 W. Given wattage by manufacturer is 200 W greater than calculated.
Current supply safety: 200 W / system voltage (12 V) = 16.67 A. Calculated current (16.667A) is lower than max. allowable (100 A). Hence,
safe.
5.7 Selection of DC-DC converter
The required converter has the following the specification. To be used to run various low voltage devices.
Technical Specifications
Model Number
PST-DC292 DC/DC Converter
Input Voltage Range
6 VDC to 30 VDC (see chart below)
Peak Output Power
24 Watts
Peak Output Current
2-3 Amps output
Output Voltage Nominal
No-Load Overhead
1.5, 3, 4.5, 5.0, 6.0, 7.5, 9.0, 12.0 Volts
10 to 30 mA is drawn from the battery when no load is connected
Line Regulation
1 to 2%
Load Regulation
2 to 5%
Efficiency
54 to 78%
Automotive surge protection
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Withstands the standard 80 volt load dump test.
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Agency Approvals
ROHS, CE
Dimensions
100 x 70 x 32 mm
Weight
200 g,
Figure 1: House floor plan with locations of the appliances
5.8 Choosing wiring cables
Referring Table 8.4 page 73 solar electric systems for Africa written by Hankins of 1995, the resistance factor for
copper cable and equivalent sizes of America wire gauge are available. Cable runs are depicted from floor plan
shown in appendix 1. Figure 1
Cable run
Yusto Yustas
Distance
of
cable(m)
Voltage Drop table
Maximum
K-value of
current(A)
intended
wire(Ohms/m)-
DAELP-SUA (2013)
Total
resistance
Voltage
drop
High voltage
drop?(Yes/No)
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Module-Charge
Control
Charge
Controller-Battery
Charge
Controller- TV
Charger/inverter
ChargeControllerstore&sitt.room
Charge
controller- bed
room2
Charge
controller- bed
room2+Converter
Charge
controller-rear
dining room
Voltage drop
/system voltage
3
11
on two way
run
4mmsq-0.010
1.5
11
2.5mmsq-0.016
0.024
0.264
2.2%
8
8
2.5mmsq-0.016
0.128
1.024
8.5%***
8
2
2.5mmsq-0.016
0.128
0.256
2.13%
4.5
1
2.5mmsq-0.016
0.072
0.072
0.6%
6
1.5
2.5mmsq-0.016
0.096
0.144
1.2%
7.8
1
2.5mmsq-0.016
0.1248
0.1248
1.04%
0.030
0.33
2.75%
*** High voltage drop. Therefore, wiring cable proposed before should be changed to 4mmsq-0.010 ohm/mm.
Which will results to 0.010X8=0.08V i.e. 0.6% voltage drop which is satisfactory.
5.9 selections of fuses
The fuse should always be rated less than the wire/run it is protecting; the fuse must always be the weakest link.
For the case in hand on Fuse is required for protecting the TV set and charger/inverter. As the maximum current in
the run in question is 8A, then fuse rate 7.8A is appropriate.
5.10 Selections of switches
Five switches are required. Since the DC-type switches are not readily available in the market, then the standard
switches rated at 240VAC and 3A for lamp in 5 locations as shown in the plan are to be used.
5.11 selections of sockets
Two sockets are required. Since the DC-type sockets are not readily available in the market, then the standard
sockets rated at 240VAC and 13A can be used. One being used for TV set and phones charger the other socket
for radio in bed room 3.
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5.12 Selections of sockets Connectors
Three connectors are required. The connectors will be used at junction of sitting room and store, node for the bed
room 3 and converter as well as for node of lamp to dinning room, bedroom 2 and bed room 3. The recommended
connectors are connector strips.
5.13 Earthing the system
lightening
Since the system is rated higher than 50Wp, then should be earthen (grounded) to protect it from lighting and
protecting people from electric shocks. Hence the earthing rod is required.
6.0 To determine the declination of the solar modules.
Mounting the PV Array
The array will be fixed on the mast. Since the household is near to 1oS, then array will be fixed facing north
hemisphere at an inclination angle of 1o+10o=11o i.e. the array will be inclined at 11o.
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