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This is one of the most important steps you can take to ensure you donβt waste your money on an oversized system or end up with a system that isnβt able to meet your energy needs sufficiently.
Total energy needed: 39 kWh/day
1kWh=1000Wh
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After you have determined how much energy we need, we need to figure out the number of batteries needed.
So, how many batteries do we need for our off-grid solar system?
Calculations:
We will use:
200 Ah 48V Lithium Battery, 2 days of storage
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In this step, we must figure out how many solar panels we need. For this, we need to know the following:
The number of sun-hours in our location. Sun-hours is how many hours 1000 Watts worth of solar radiation strikes a square meter of surface area over the course of a day.
Calculations:
We suppose that:
1- The sun hour is 6 kWh per square meter for 6 hours.
2- PV panel: power rating 400 w, peak efficiency 19%, Impp 9,9 A, Vmpp 40 V, Isc 10.6 A, Voc 49 V.
We need to add the losses; we have to multiply our solar array by 1.3 to avoid the undersizing of the system.
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In this step, we need to make the power usable.
Note that an inverter is designed for a specific voltage battery bank (12V, 24V, or 48V). Keep in mind If you plan on having a higher voltage battery bank later, the lower voltage inverter wonβt work in the new bigger system. So go with the higher voltage.
Calculations:
To consider the surge power, every piece of equipment with a motor should be multiplied by 3, while the others should be multiplied by 1.5.
The inverter rating is 12 kW.
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In this step, we need to figure out what size solar charge controller
If the voltage of the solar panel array matches the voltage of the battery bank, we can use a PWM charge controller.
If your solar panel voltage differs from the battery bank, we need to use an MPPT charge controller.
In general, for our home system, the best is a 48V battery bank and an MPPT charge controller.
Calculations:
Sizing of charger control can be obtained by multiplying the short circuit current of the module connected in parallel by a safety factor. Let’s choose this factor equal to 1.3.
Very insightful Sir, I am currently reading the chapter 11 Solar PV of your book. I will soon enrol the online course you are offering.
Thank you. All the best.