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Solar Power Calculation
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EXAMPLE
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An LED lamp of 40W for 12 Hours per day
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A refrigerator of 80W for 8 Hours per day
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A DC Fan of 60W for 6 Hours per day.
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Finding the Total Load
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Total Load in Wh / Day
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S.NOWattstime in ( H)Remarks UnitsRequired wattage by Solar Panels SystemUnits
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14012480Wh/day
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2808640Wh/day
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3606360Wh/day
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Total1480Wh/day1924Wh/day
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Finding the Size and No. of Solar Panels
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WPeak Capacity of Solar PanelUnit
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WPeak Capacity of Solar Panel601.25Wpeak
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Required No of Solar Panels
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S.NoWPeak Capacity of Solar PanelRequired No of Solar PanelsNo of Modules
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1601.255.015
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Find the Rating and Size of Inverter
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wattwattwatt Total required wattage is:Unit
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408060180Watts
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Rating of inverter should be 25% greater than the total load due to losses in the inverter
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unit
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Inverter Rating & Size225Watts
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Find the Size, Rating & No of Batteries
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[(40W x 12 hours) + (80W x 8 hours) + (60W x 6 hours) / (0.85 x 0.6 x 12V)] x 2 days
Ah
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483.6601307Ah
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This way, we need a 12V 500Ah battery capacity for 2 days of autonomy
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In this case, we may use 4 number of batteries each of 12 V, 125 Ah connected in parallel.
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Required Number of batteries = Required capacity of batteries in Ampere-hour / Available battery Ah rating
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1Find the Rating and Size of Solar Charge Controller
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Size of solar charge controller in Amp = Short circuit current of PV × 1.25
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PV module specification
PM = 120 WPeak
VM = 15.9 VDC
IM = 7.5 A
VOC = 19.4 A
ISC = 8.8
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The required rating of solar charge controller is = (5 panels x 8.8 A) x 1.25 = 44 A
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Size of solar charge controller in AmpShort circuit current of PV X 1.25=
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So you can use the next nearest rated charge controller which is 45A.
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Charging Current for Batteries
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Now the Required Charging Current for these two batteries.
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(Charging current should be 1/10 of batteries Ah)
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200Ah x (1/10) = 20A
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20Ah
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Charging Time required for Battery
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Here is the formula of Charging Time of a Lead acid battery. Charging Time of battery = Battery Ah / Charging Current T = Ah / A
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For example, for a single 12V, 100Ah battery, the charging time would be:
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T = Ah / A = 100Ah / 10A = 10 Hrs. (Ideal Case)
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Charging Time
10H
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