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SOLAR SOLUTION FOR MOBILE CHARGING CENTERS IN NIGERIA

VIEWS: 86 PAGES: 9

									INTERNATIONAL JOURNAL Of ACADEMIC RESEARCH                                            Vol. 3. No.1. January, 2011, Part II


                     SOLAR SOLUTION FOR MOBILE CHARGING
                             CENTERS IN NIGERIA
                                Dr. F.K Opara, Ovuorie E. Efemena, Egbujo Felix

                               Federal University of Technology, Owerri (NIGERIA)
                E-mails: kefelop@yahoo.com, efemenaovuorie@yahoo.com, pheleix@yahoo.co.uk

         ABSTRACT

         Nigeria is one of the emerging markets for mobile operators who are increasingly looking towards the
developing world for future subscriber growth. This comes with great benefit to individuals, business activities and
access to information. The unreliable grid power in the country hinders the smooth spread of these operators
across the country, it equally affects subscribers to these mobile operators who find it difficult to charge their mobile
phones hence reducing the Average Revenue per User (ARPU) of the mobile operators. This paper presents a
solar solution for charging mobile phone batteries as against the fossil fuel generator system currently being used
by commercial vendors. The developed system consists of a 100 watt solar panel, 10 amps charge controller,
50AH deep cycle battery and a 400 watt inverter. It was designed to work continuously for 14 working hours with
the solar panel having a lifespan of 25 years, charge controller – 8 years and the batteries – 3 years. Apart from
being environmentally friendly without emission of CO2 and noise pollution, from the economic feasibility carried
out, though the system has a high installation cost, the system has a payback time of six months depending on the
location and the number of customers.

         Key words: solar, mobile charging, gsm, inverter, battery charger.


         1. INTRODUCTION

           Nigeria is currently ranked sixth amongst the oil producing nations in the world yet much of its citizens do
not have access to uninterrupted supply of electricity. Power outages are frequent and the power sector operates
well below its installed capacity of 6,861 megawatts (MW). A major reason given for the unreliable supply of power
is the low generating capacity of the power sector relative to installed capacity. As a result of this, constant power
shedding due to excess loads on the national grid lines are the order of the day and the result is that most people
have to look for alternative means of power (generators).
           With the introduction of GSM in 2001, this brought great opportunities not just revenue to the government,
it came along with business opportunities to organizations and individuals in the areas of call centers, recharge
card business, mobile phone charging centers etc. It has equally helped to increase access to information by
Nigerians even while on the move as against the era when only the privileged ones could afford a phone. These
mobile operators on the other hand have been faced with two major obstacles which are; solving the power issue
for their operation and providing security for their cell sites.
           As a result of the unavailability of electricity, most mobile subscribers are faced with the challenge of
charging their mobile phones which results in their batteries running out of power. When mobile phones are
switched off, it results in missed calls and reduced airtime revenues for mobile operators. According to the Global
System for Mobile Association (GSMA), the Average Revenue per User (ARPU) of mobile operators reduce in the
10 – 14% range when mobile subscribers are either out of network coverage area or when their batteries are out of
power [1].
           The mobile charging centers in Nigeria have been a source of joy to mobile subscribers especially in
areas where grid power is unreliable. They operate on a pay-per-charge basis i.e. the customer takes his phone to
the local charging center and leaves it (or just the battery) to charge whenever the phone power is low. In Nigeria,
the price of a mobile charge varies between N30 per hour charge to N50 for complete charge of the mobile battery.
A mobile phone requires an average of two hours to charge completely using the phone charger and three hours
with a desktop charger. The frequency of charges per customer ranges between one per day to twice per day
depending on the frequency of calls made by the customer and the state of the battery.




                                               Fig. 1. Desktop charger


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INTERNATIONAL JOURNAL Of ACADEMIC RESEARCH                                            Vol. 3. No. 1. January, 2011, Part II

         A typical mobile charging centre in Nigeria uses the following components;
              550 watt petrol generating set
              Socket outlets on a flat board (ranging between 15 – 35 outlets)
              Desktop chargers
              200 watt bulb (to stabilize the generator)




                                  Fig. 2. Typical mobile charging centre in Nigeria

           This paper takes a critical look at the current situation of energy supply in Nigeria, the abundance of solar
energy within the country, the developed solar charging system for mobile charging centers and the economic
feasibility of this developed system compared with the existing system used by these mobile charging centers.

         A. Electricity Scenerio in Nigeria

         Electricity is used in Nigeria for a number of purposes that include industrial, commercial and household
purposes. The Nigerian power sector is marked by low generating capacity relative to installed capacity and much
of the country’s citizens do not have access to uninterrupted supplies of electricity. At present electricity generation
ranges between 2,500 MW to about 3000 MW as shown in fig. 3 while estimated national consumption is in excess
of 10,000 MW. Potential demand in the next few years is estimated at about 15,000 MW




                                Fig. 3. Electricity generation in Nigeria, 1970 – 2005

           As seen in fig. 3, there is a wide gap between the installed capacity and total electricity generation
capacity and this started in 1978. Lack of planning has been the problem facing the power sector with the last
major electric generation installation in Nigeria being the Shiroro power station commissioned in 1990. Low water
levels at the hydro stations and lack of gas at the thermal stations are frequently claimed to be responsible, but in
actual sense poor maintenance has actually been responsible for the gap between installed capacity and
generated capacity. Lack of planning is also responsible for our inability to progress beyond the 6,861 MW
installation capacity as at 2005.




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INTERNATIONAL JOURNAL Of ACADEMIC RESEARCH                                          Vol. 3. No.1. January, 2011, Part II

            B. Solar Radiation in Nigeria

         Nigeria is endowed with an average daily sunshine of 6.25 hours, ranging between 3.5 – 4.0 peak sun
hours at minimum at the coastal areas and 5.0 – 5.5 peak sun hours at minimum at the northern region. The
northern region of Nigeria can have a maximum of 9.0 peak sun hours.




                                      Fig. 4. Yearly minimum peak sun hours
                                                                                                  2
        Similarly, it has an annual average daily solar radiation of about 5.25kWh/m /day, varying from
         2                                       2
3.5kWh/m /day at the coastal areas to 7.0kWh/m /day at the northern boundary. Nigeria receives about
        12
4.851x10 kWh of energy per day from the sun [2].

         C. Photovoltaic System Components

          Photovoltaic systems consist of solar panels, a battery, charge controller, and an inverter. The lifetime of
the panels is typically 20 to 25 years, which is considered the lifetime of the total system. The battery stores the
power from the sun and is used when the sun isn’t shining or during cloudy weather. Two types of batteries can be
used, deep-cycle and starter batteries. The deep-cycle batteries are more efficient and most commonly used, but
starter batteries are already available in Nigeria due to their use in cars. A deep-cycle battery lasts between three
and eight years. The charge controller regulates the current added to and drawn from the battery in order to
maximize the battery lifetime and for user safety. Because photovoltaic systems produce a direct current, the
inverter is necessary especially when the end-user requires an alternating current.




                                         Fig. 5. PV system components [3]

         3. SYSTEM DESIGN

        The Solar solution was designed to work continuously for 14 hours (8am – 10pm) which is the operating
hours of the mobile charging centers in Nigeria. Some factors were taken into consideration during the design
phase, which are as follows:
         Balance of the rate of solar energy deposition in an area with the power required by the load
         Daily peak sun hours, load power requirement, battery storage and discharge efficiencies were
considered to obtain the required capacity/number of panels
         Higher inverter rating to allow for expansion (more panels and batteries)


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INTERNATIONAL JOURNAL Of ACADEMIC RESEARCH                                          Vol. 3. No. 1. January, 2011, Part II


                                     Charge                           Inverter /
                                                                                                     AC Load
                                    controller                          fuses
          PV Panel


                                                      Battery


                                   Fig. 6. Block diagram of developed system

         4. LOAD POWER REQUIREMENT

         The power rating of most mobile phone chargers and desktop chargers fall within the range as presented
below:
              China phone*: 5.0Vdc x 550mA = 2.75 watts
              Nokia phones (small pin charger): 5.0Vdc x 350mA = 1.75 watts
              Desktop charger: 4.3Vdc x 150mA = 0.645 watts
         Note: (*) refers to the new mobile phones made in china which is widely used by Nigerians due to     its
cheap price.
         Due to the fact that most customers are unable to sit with their mobile phones while charging, they do
prefer to leave only their mobile batteries and go away with their phones hence, the power rating of the desktop
charger (0.645 watts) is used in this analysis.
             No. of socket outlets on a board = 30 sockets
             Total power consumption for one board consisting of 30 socket outlets @ 0.645 watts
             = 30 x 0.645 watts x 14 hours
             = 270.9 Wh

         5. PV SIZING

         With the total power consumption of the desktop chargers known, the number of solar panels was
obtained as shown below [4]:
         Step    PV Sizing                           Value
         1.      Daily PV output needed              270.9Wh
         2.      70% System Eff. Factor              270.9Wh ÷ 0.7 = 387 Wh
         3.      Average sun hours / day             6.25
         4.      Minimum system size                 387 Wh ÷ 6.25 = 61.92 W
         5.      Chosen system module                100 W
         6.      No. of modules required             61.92 W ÷ 100 W = 0.6192
                                                                        ≈ 1 module required
         Note: BP Solar panel rated at 100 watts, 17.6 volts @ 5.682 amps was chosen for this system. The PV
module was over-rated to give a faster charging current to the batteries.

         6. BATTERY SIZING

         The battery size and the number of batteries required for the developed system was obtained as shown
below:
         Step    Battery Sizing                     Value
         1.      System voltage                     12 volts
         2.      Total amp-hrs / day                270.9Wh ÷ 12 volts             = 22.575 AH
         3.      20% deep Discharge Reserve         40.635 AH
         4.      Optimum Temp. Multiplier           1.0
         5.      Optimum Battery Size               40.635 x 1.0                   = 40.635 AH
         6.      Chosen Amp-hrs per battery         50 AH
         7.      No. of batteries required          40.635AH ÷ 50AH            = 0.8127
                                                                               ≈ 1 battery required
         Note: The battery was over-rated to give room for tolerance having in mind that the PV module chosen is
higher than what is required. This simply means the PV module will charge the battery at a faster rate.

         7. CHARGE CONTROLLER SIZING

         A charge controller is used to regulate the current added to or drawn from the batteries. In this design,
sunlight-10 charge controller rated at 10 amps is used. The calculation is shown below;
         Where I = P / V
         Maximum power draw is 100 watts, and the system voltage is 12 volts, hence:
         I = 100 watts ÷ 12 volts
           = 8.33 amps


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INTERNATIONAL JOURNAL Of ACADEMIC RESEARCH                                          Vol. 3. No.1. January, 2011, Part II

           ≈ 10 amps charge controller required
          Note: As the system is upgraded to higher wattage for example 320 watts, a 30 amps charge controller
will be required. The amp rating of the charge controller must not be exceeded.

         Some of the features of this chosen charge controller (Sunlight-10) are as follows:
                PWM battery charging system
                Full automation operation
                Low voltage disconnect (when battery gets to 11.7 volts) and system reconnect (when battery
gets to 12.7 volts)
                Battery temperature compensation
                MPPT charging (reduces the charging voltage from 17.6 volts to 13.8 volts thereby increasing the
charging current from 5.68 amps to 7.24 amps)

         4. INVERTER SIZING

           A 400 watts inverter was built as against the rated minimum power of 61.92 watts which is expected to be
drawn from the system. This was done to give room for future expansion purposes. In the inverter circuit as shown
in fig. 7, a solid state oscillator which is a 16 pin integrated circuit was used.




                        IC SG3524



                                          Fig. 7. 400 watts inverter circuit

          The MOSFETS used in the design of the inverter are IRF 150N, while a preset resistance is connected to
pin 6 of the IC so as to set the output frequency to 50Hz. The 50Hz signal generated by the IC reaches the flip flop
inside the IC and converts into two different polarity signals at pins 11 and 14 which are known as the MOS drive
signals. This drive signals are used to fire the gate of the MOSFETS at the output section.
          Some of the parameters used in actualizing the inverter design are as follows [5]:

         Inverter Calculation:

         i. Winding calculation:
            The voltage per turn VT = C√KVA                                                         (1)
            where C is a constant (0.56)
            Note: Papparent = Pinst / Power factor                                                  (2)
 where Pinst = 400W
 Power factor = 0.8
         Hence Papparent = 400 / 0.8
                    = 500 VA
                    = 0.500 KVA
         Substituting the value of Papp into equation 1, the value of VT is obtained as shown below:
         VT = C√KVA
   = 0.56 √0.500
   = 0.396 volts / turn
         No. of turns in the primary side:
                  No. of turns in the primary side:
                   N1 = V1 / VT                                                               (3)
where V1 = 12 volts, VT = 0.396
N1 = 12 / 0.396 = 30.3 turns


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INTERNATIONAL JOURNAL Of ACADEMIC RESEARCH                                                Vol. 3. No. 1. January, 2011, Part II

        No. of turns in the secondary side:
                 No. of turns in the secondary side:
                  N2 = V2 / VT                                                                    (4)
where V2 = 220 volts, VT = 0.396
N2 = 220 / 0.396 = 555 turns
        ii. Current rating of inverter:
                  Given that P = IV                                                                (5)
        Where P = Power in watts
                  I = Current in amps
                  V = Voltage in volts
                  Current rating for the primary side of the Inverter is given by:
                  I=P/V                                                                           (6)
                  I = 400 / 12 = 33.33 amps
                  Current rating for the secondary side of the Inverter is given by:
                  I=P/V
                  I = 400 / 220 = 1.82 amps
                                                                                    220V
                            +12V
                                                                         555T
                                        31T

                                   0                                   (SWG) = 20

                                 (SWG) = 16

                               -12V
                                                                                     0V
                                      Fig. 8. Inverter transformer turns / gauge rating

         The standard wire guage (SWG) used in the design can be found in wiring datasheet and is capable of
withstanding the calculated currents. In this design, enamel led copper wire is used.
         iii. Fuse rating:
              The fuse rating for the inverter which is the full load current that can be drawn from the inverter is
obtained as shown below:
                   Ifl = KVA rating / Output voltage                                           (7)
             = 500 / 220
             = 2.27 amps
         iv. Frequency calculation:
              The output frequency of 50Hz was achieved using the formula obtained from the SG3524 datasheet;
                   F = 1.18 / (RTCT)                                                  (8)
                   where f = frequency,         C = capacitor,      R = Resistor
                   Hence, 50Hz = 1.18 / (RT x 0.104µF)
        1.18 = 50 x RT x 0.104µF
        RT = 1.18 / (50 x 0.104µF)
        RT = 220 KΩ
         Hence, to achieve a frequency of 50Hz, a variable resistor of 220KΩ was used.




                                                                             Fig. 9. (a) 100 watts BP Solar module
                                                                                    (b) Sunlight-10 charge controller
                                                                                    (c) The developed system
                                                                          Note: A stabilizer casing was used to package
                                                                           the inverter since it was locally constructed




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INTERNATIONAL JOURNAL Of ACADEMIC RESEARCH                                                       Vol. 3. No.1. January, 2011, Part II

                5. ECONOMIC FEASIBILITY

         The current system of charging mobile phones by vendors has a low installation cost compared with using
a solar system but in this economic feasibility, it will be seen that using solar in the long run is much more
economical.
           Some parameters which are currently being used by these mobile charging centers were taken into
consideration in our analysis, they are as follows:
         - No. of sockets outlets on a board = 30
         - Total power consumption of a board consisting of 30 socket outlets = 61.92 watts
         - Power rating of generating set (TIGER) = 550 watts
         - Power rating of stabilizing bulb = 200 watts
         - Fuel tank maximum capacity = 4 litres
         - No. of working hours / litre of fuel = 3 hours
         - Cost of petrol / litre = N65
         - Charging of mobile battery per hour = N30
         - Charging until battery is full = N50
         - No. of charging hours = 3 hours
         - Cost of procuring a desktop charger = N200

          Revenue:
          The revenue which is expected to be obtained from operating a mobile charging center is as shown in
table 1. To obtain this we considered the following:
          - Revenue = No. of customers x Charge rate
          - Charge rate = N50
          - No. of business hours = 14 hours (8am – 10pm)
          - No. of working days per month (excluding Sundays) = 6 x 4 = 24
          - No. of customers vary on daily basis

                                        Table 1. Revenue generated from mobile phone charging centers

     Duration             Unit No. of            Total No. of          Revenue/Day                     No. of working       Revenue /
                          Customers              Customers                 (N)                          days/month            month
                                                                                                                               (N)
      3 hours                 30                      30               30 x 50 = 1,500                      24               36,000
                              25                      25               25 x 50 = 1,200                      24               30,000
                              20                      20               20 x 50 = 1,000                      24               24,000
                              15                      15                15 x 50 = 750                       24               18,000
                              10                      10                10 x 50 = 500                       24               12,000
                              5                       5                  5 x 50 = 250                       24                6,000
                              1                       1                  1 x 50 = 50                        24                1,200
     12 hours                 30                     120             4 x 30 x 50 = 6,000                    24               144,000
                              25                     100             4 x 25 x 50 = 5,000                    24               120,000
                              20                      80             4 x 20 x 50 = 4,000                    24               96,000
                              15                      60             4 x 15 x 50 = 3,000                    24               72,000
                              10                      40             4 x 10 x 50 = 2,000                    24               48,000
                              5                       20             4 x 5 x 50 = 1,000                     24               24,000
                              1                       4                4 x 1 x 50 = 200                     24                4,800

        Expenditure using Generator Option:
        The amount spent in the first month of operation differs from subsequent months; hence in determining
the expenditure for using generator to charge mobile phones, table 2 is broken into two parts.
                                            Table 2. Expenditure using Generator as Power Source
     S/                                   ITEM                            QTY              UNIT COST (N)                AMOUNT (N)
     N
           st
          1 Month of Operation:
 1          Cost of 550 watts petrol engine                                 1                 13,000                      13,000
 2.         Socket Outlets                                                 30                  100                        3,000
 3.         Cost of board (plywood)                                       Lot                                             1,000
                                   2
 4.         Cable (3 core, 1.5 mm )                                      10m                   100                        1,000
 5.         Labour & Transportation                                       Lot                                             1,500
 6.         Desktop chargers                                               30                  200                        6,000
 7.         Servicing of generator every 3 days within a month          8 times                300                        2,400
 8.           Fuelling of generator for a month @ 4 litres per day         96                   65                        6,240
 9.          Oil for generator for a month                                24                   50                        1,200
10.          Spareparts & other miscellaneous costs                       Lot                                            2,000
             Total Expenditure                                                                                           37,340
           nd
          2 and subsequent months of operation
1.           Servicing of Generator                                     8 times                300                       2,400
2.           Fuelling of generator for a month @ 4 litres per day          96                   65                       6,240
3.           Oil for generator for a month                                 24                   50                       1,200
4.           Spareparts & other miscellaneous costs                       Lot                                            2,000
             Total expenditure                                                                                           11,840



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INTERNATIONAL JOURNAL Of ACADEMIC RESEARCH                                                              Vol. 3. No. 1. January, 2011, Part II

         Expenditure using Solar Solution Option:
                                                               st
         In carrying out this analysis, cost incurred for the 1 month of operation and subsequent months are
equally taken into consideration as shown in table 3.
                                  Table 3. Expenditure using Solar Solution as Power Source
 S/N       ITEM                                                            QTY                   UNIT COST (N)               AMOUNT (N)
  st
 1 Month of Operation:
 1         Cost of 100 watt BP Solar panel                                  1                           90,000                   90,000
 2.        Cost of 10 amps Sunlight-10 charge controller                    1                           15,000                   15,000
 3.        Cost of 50AH deep cycle battery                                  2                           15,000                   30,000
 4.        Cost of 400 watts inverter                                       1                           4,000                     4,000
                                  2
 5.        Cable (3 core, 2.5mm ) for panel                                10m                           100                      1,000
 6.        Socket outlets                                                   30                           100                      3,000
 7.        Socket board base (plywood)                                     Lot                                                    1,000
                                             2
 8.        Socket instal. cable (3core, 1.5mm )                            10m                           100                      1,000
 9.        Solar stand (using aluminium)                                    1                           5,000                     5,000
 10.       Desktop chargers                                                 30                           200                      6,000
 11.       Miscellaneous                                                   Lot                                                    2,000
           Total Expenditure                                                                                                     158,000
  nd
 2 and Subsequent months of operation
 1.       nil                                                                  -         -                                            -
          Total Expenditure                                                                                                          nil
          Note:        i. Battery has to be changed once every 3 years
                       ii. Panel has a lifespan of 25 years
                       iii. Charge controller has a lifespan of 8 years

         Profit Margin for both Options:
         To determine the best out of the two options of using generator and solar solution, a profit table based on
the analysis earlier done is presented in table 4.
                                   Table 4. Profit Margin for both Generator & Solar Solution
       Month          No. of        Revenue         Revenue         Expenditure          Expenditure                Profit     Profit for Solar
                  Customers per     per day         per month       using Gen.           using Solar              for Gen.            (N)
                       day            (N)              (N)              (N)                  (N)                     (N)
       Jan*            120           6,000           144,000                                                      106,660         - 14,000
                       100           5,000           120,000                                                       82,660         - 38,000
                        80           4,000           96,000                                                        58,660         - 62,000
                        60           3,000           72,000           37,340*                158,000*              34,660          -86,000
                        40           2,000           48,000                                                        10,660         -110,000


                        20           1,000          24,000                                                        - 13,340        -134,000
                        4             200            4,800                                                        - 32,540        -153,200
  Feb. to              120           6,000          144,000                                                       132,160          144,000
   Dec.                100           5,000          120,000                                                       108,160          120,000
                       80            4,000          96,000                                                         84,160          96,000
                       60            3,000          72,000             11,840                   nil                60,160          72,000
                       40            2,000          48,000                                                         36,160          48,000
                       20            1,000          24,000                                                         12,160          24,000
                        4             200            4,800                                                         - 7,040          4,800
          Note:
          i.   Profit = Revenue – Expenditure
         ii.   Same applies for months of February to December, there will only be a difference in the third year when the solar
               battery is to be replaced
                            st
        iii.   (*) means 1 month of operation
        iv.    The generator if ran continuously for 14 hours will be due for replacement after 5000 hours of operation

               6. RESULTS AND DISCUSSION
        Based on the data in table 4, it should be noted that the number of customers will vary on monthly basis,
hence to obtain the actual payback time and years to positive cash flow for both systems, a random sampling of
number of customers for each month is used as shown in tables 5 & 6.
                                  Table 5. Random Sampling of Customers for different months
        Month           No. of          Revenue            Expenditure using       Expenditure using               Profit       Profit for
                      Customers         per month               Gen.                    Solar                    for Gen.         Solar
                                           (N)                   (N)                     (N)                        (N)            (N)
          Jan*            4               4,800                37,340                  158,000                   - 32,540       -153,200
          Feb             20             24,000                11,840                     nil                     12,160         24,000
         March            40             48,000                11,840                     nil                     36,160         48,000
          April           20             24,000                11,840                     nil                     12,160         24,000
          May             40             48,000                11,840                     nil                     36,160         48,000
          June            60             72,000                11,840                     nil                     60,160         72,000
          July            40             48,000                11,840                     nil                     36,160         48,000
         August           60             72,000                11,840                     nil                     60,160         72,000
          Sept.           40             48,000                11,840                     nil                     36,160         48,000
          Oct.            80             96,000                11,840                     nil                     84,160         96,000



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       Nov.           60                72,000                11,840                      nil              60,160            72,000
       Dec.           40                48,000                11,840                      nil              36,160            48,000
              TOTAL                     604,800               167,580                   158,000            437,220           446,800

                              Table 6. Cumulative Profit for both Generator & Solar Solution
         Month        Profit for Gen.     Cumulative Profit for Gen     Profit for Solar Solution     Cumulative Profit for Solar
                            (N)                     (N)                             (N)                       Solution
                                                                                                                 (N)
         Jan*            - 32,540                 - 32,540                     -153,200                      -153,200
         Feb              12,160                  - 20,380                      24,000                       -129,200
        March             36,160                   15,780                       48,000                        - 81,200
         April            12,160                   27,940                       24,000                        - 57,200
         May              36,160                   64,100                       48,000                         - 9,200
         June             60,160                  124,260                       72,000                         62,800
         July             36,160                  160,420                       48,000                        110,800
        August            60,160                  220,580                       72,000                        182,800
         Sept.            36,160                  256,740                       48,000                        230,800
         Oct.             84,160                  340,900                       96,000                        326,800
         Nov.             60,160                  401,060                       72,000                        398,800
         Dec.             36,160                  437,220                       48,000                        446,800

          From the results obtained in tables 5 and 6, it’s observed that the generator solution has a smaller start-up
cost of N37,340 compared to the solar solution with an initial cost of N158,000. For subsequent months, the
generator solution has a fixed monthly maintenance expenditure of N11,840 whereas the solar solution has no
monthly maintenance costs except in the third year of its operation where the deep cycle battery has to be replaced
with a new one.
          It can equally be observed from table 6 that the payback time for the generator solution is shorter i.e. after
three months of operation, the system will payback the cost of startup and a positive cash flow starts. Whereas, in
the case of the solar solution, it takes a longer time i.e. six months for the system to payback for its initial startup
cost after which positive cash flows into the system. In the long run i.e. after a year, it’s observed that more profit is
made from the solar solution as seen in table 6 compared to the generator solution. This high profit margin will
become obvious if the second year profit margin for both solutions is carried out using the same procedure as
presented in tables 5 & 6 taking into consideration the need for replacement of the generator after 5000 hours of
operation.
          Continous usage of the petrol engine generator for 14 hours for a year will have adverse effects on the
engine except if properly maintained. After 5000 hours of operation, the generator should be replaced for better
efficiency, but in the case of the solar solution, the only maintenance required will be to wipe off dust from the face
of the solar panel so as to increase its efficiency. All components of the solar solution are durable and reliable and
can stand the test of time.
          It should be noted that in the event of cloudy weather for more than a day, an alternative power source
can be used to charge up the battery, that is why a spare 50AH battery was provided for in our calculation.

         7. CONCLUSION

          This paper has successfully presented a functional solar solution for mobile charging centers in Nigeria.
Though the system has a high initial cost, it has a higher yield on the long-run. The energy from this system is
environmentally friendly devoid of noise pollution and toxic gas emission. This system saves these mobile charging
vendors from problems such as maintenance of generators, loss of time due to maintenance and system
breakdown due to generator failure. The price of petrol used in this paper was fixed at N65 per litre, but in real
context, the price actually fluctuates. This system will equally save these vendors the problems of price fluctuations
and fuel scarcity as is common with Nigeria. Most of the materials used in the construction of this system are
readily available in the market.

         REFERENCES

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                 pp 563 – 575
              3. G.A. Torshizi, M. Niknam (2007), “Solar Energy in Telecommunications,” Bechtel
                 Telecommunications Technical Journal, pp 65 – 74
              4. T.C. Chineke, E.C. Igwiro (2008), ”Urban and Rural Electrification: Enhancing the Energy Sector in
                 Nigeria Using Photovoltaic Technology”, AJST, Vol. 9, No. 1, pp 102 - 108
              5. M.J.E. Evbogbai, G.I Ighalo (2007), “Realization of a 3KVA, Single Phase, Electric ARC Welding
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              6. S. Akoma, A. Nnanna, U. Adindu (2010), “Design and construction of Inverter using available
                 accessories in the Nigerian Market”, International Conference on Renewable & Alternative Energy
                 (FUTO Alternative Energy, 2010), May 16 – May 20, 2010




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