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## Main Question or Discussion Point

Right now I am working on a small pump that is capable of running on solar power for 24 hours a day.

So far, I have solar panels with specs at typical irradiance/temp of 1000Wm^-2 and 25C:

Pmax = 135 W

Vpmax = 17.7 V

Ipmax = 7.63 A

Voc = 22.1 V

Isc = 8.37 A

Area = 1m^2

and batter(ies) with specs:

12V, 100 Ah

@20 hour rate to 1.75 VPC (No idea what this is useful for)

For my area I have found that during the worst month (December) we receive 2.52 kWh/m^2*day (I believe this is sun hours per day) so I am trying to model a pump around this scenario to be autonomous for 3 days with a safety factor of 1.2.

I am able to measure the Ah draw of the pump I am running through a meter and I am wondering how I can figure out the amount of solar panels / batteries I will need with this number. If needed I am also able to find out the Wh, A(peak), W(peak), V(max) of the pump during its operation.

Right now the formula I am using to calculate the amount of solar panels is:

[tex]\frac{[(Ah)*(24)*(1.2)]/(Sun Hours Per Day)}{8}[/tex]

The 24 is for a continuous runtime throughout the day and the 1.2 represents the safety factor I would like. The formula was suggested to me, but it doesn't seem to add up in units to me. I have no idea where the 8 came from in this equation so it is hard for me to trust. I think it may have to do with the Ipmax value of 7.63A.

I also have an equation for a smaller 85W solar panel which is

[tex]\frac{[(Ah)*(24)*(1.2)]/(Sun Hours Per Day)}{5}[/tex]

Which may somewhat help with understanding what the 8 is for in the first equation.

The battery equation I am using right now is:

[tex]\frac{(Ah)*(24)*(1.2)*(3)}{100}[/tex]

Where the 100 is the total Ah capacity of the battery, and the 3 is the days of autonomy. This seems to make more sense to me (although I think I should reduce the batteries Ah by ~30% to account for efficiency).

Throughout my time using these equations, the numbers for panels / batteries required has always seemed extremely high and I know next to nothing about energy / electricity / solar panels so I look forward to any feedback and criticism.

So far, I have solar panels with specs at typical irradiance/temp of 1000Wm^-2 and 25C:

Pmax = 135 W

Vpmax = 17.7 V

Ipmax = 7.63 A

Voc = 22.1 V

Isc = 8.37 A

Area = 1m^2

and batter(ies) with specs:

12V, 100 Ah

@20 hour rate to 1.75 VPC (No idea what this is useful for)

For my area I have found that during the worst month (December) we receive 2.52 kWh/m^2*day (I believe this is sun hours per day) so I am trying to model a pump around this scenario to be autonomous for 3 days with a safety factor of 1.2.

I am able to measure the Ah draw of the pump I am running through a meter and I am wondering how I can figure out the amount of solar panels / batteries I will need with this number. If needed I am also able to find out the Wh, A(peak), W(peak), V(max) of the pump during its operation.

Right now the formula I am using to calculate the amount of solar panels is:

[tex]\frac{[(Ah)*(24)*(1.2)]/(Sun Hours Per Day)}{8}[/tex]

The 24 is for a continuous runtime throughout the day and the 1.2 represents the safety factor I would like. The formula was suggested to me, but it doesn't seem to add up in units to me. I have no idea where the 8 came from in this equation so it is hard for me to trust. I think it may have to do with the Ipmax value of 7.63A.

I also have an equation for a smaller 85W solar panel which is

[tex]\frac{[(Ah)*(24)*(1.2)]/(Sun Hours Per Day)}{5}[/tex]

Which may somewhat help with understanding what the 8 is for in the first equation.

The battery equation I am using right now is:

[tex]\frac{(Ah)*(24)*(1.2)*(3)}{100}[/tex]

Where the 100 is the total Ah capacity of the battery, and the 3 is the days of autonomy. This seems to make more sense to me (although I think I should reduce the batteries Ah by ~30% to account for efficiency).

Throughout my time using these equations, the numbers for panels / batteries required has always seemed extremely high and I know next to nothing about energy / electricity / solar panels so I look forward to any feedback and criticism.

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