Today we will learn the simplest calculations required to install a solar power system in our home. The calculations are kept simple so that student is able to design a solar power system at home.

For example, take my own home and calculate my required power, this Is my home requirements.

Four (4) DC power 12 volt fans and three (3) twenty (20) watt bulbs then I will use the simplest equation that is

P= V.I

Where

P = Power

V = voltage

I = current

We know that current consumption of a medium 12 volt DC fan is about 5 amperes therefore power consumption of one fan is

P_{f1} = V.I = 12 x 5 = 60 Watt

And power consumption of four fans is

P_{f} = 4 x 60 = 240 Watt

Also consumption of three 20 Watt bulbs is

P_{b} = 3 x 20 = 60 Watt

Therefore, my total power requirement is

P_{r} = 240 + 60 = 300 Watts

The above 300 Watts is the total required power, remember that every system is composed of three types of powers that is,

(1) The Required Power (P_{r})

(2) The Available Power (P_{a}) and

(3) The Excess Power (P_{e}).

For our home systems the available power is the solar panels. Now the important thing to note is that the available power must be greater than the required power that is P_{a }> P_{r}. And because the batteries act as a power storage unit between the availability (p_{a}) and the requirement (P_{r}) therefore the right sequence for the home solar power system is

P_{a} > P_{b }> P_{r} where (P_{b} = Battery Power)

The equation defining the three powers is

P_{a} = P_{r} + P_{e}

Therefore, for our 300 Watt home requirement if we arrange 400 Watt batteries and about 600 Watt availability of solar panels then our system will work satisfactorily, but remember that increasing the battery power will increase the system running time but the solar availability i.e. the solar panels must also be increased.

For example for our 300 Watt unit if we increase the storage unit i.e. the batteries to 500 Watt then the availability of solar panels must also be increased to about 700 Watts for better performance. That is because the greater the available solar power the more easily and quickly the batteries will charge and the greater the battery power than the home required power the longer the time the batteries will give us power.

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