# I am still having problem figuring solar panels operations.

Registered Users Posts: 7
I am still having problem in figuring the right formula for calculating the number of cells and wattage. I have 3 swing fans and I think each fan operates on 240v I think it is consumes 300 watt each, and I have 1000watt inverter. I used car battery one of them is 60 amps and other one is 100 amps. My solar panel total is 50 watt and plenty of sun shine. So how many cells I need to operate these fans for 10 hours continuous. How much battery I need to keep these fans running, I heard that car battery is not the proper way to be operated with solar panel for storing energy. Please pass some information regarding this dilemma.

• Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
Re: I am still having problem figuring solar panels operations.

Alsayyed,

Here are some rough calculations for your requirement:

(1) Net Energy Requirement: 3 fans x (300 W / fan) x 10 hours/day = 9 kWh/day.
(2) Allowing for 90% inverter efficiency, the battery bank will need to be able to supply 10 kWh/day
(3) Allowing for occasional (2 days?) poor weather and limiting battery discharge to 50%, the battery bank capacity will need to be ~40 kWh. That translates into a 48 V battery rank rated at 40 kWh / 48 V = 833 Ah.
(4) Net overall system efficiency in your fairly hot environment might be but ~55%. Accordingly, you’ll need a system rated to generate 9 kWh / day / 55% = 16.4 kWh/day.
(5) Tilt-corrected seasonal insolation in Doha, Qatar, seems to range between 5 hrs/day and 8 hrs/day. Using the smaller number, you’ll need a south-facing PV array tilted up at ~latitude (~25 degrees) rated at 16.4 kWh/day / 5 hrs/day = 3.3 kW (STC) minimum.

Hope this helps,
Jim / crewzer
Re: I am still having problem figuring solar panels operations.

Translation: VERY EXPENSIVE.
Re: I am still having problem figuring solar panels operations.

To finish up Jim's very fine work:

3.3 kWatt of solar panels in your terms of 50 watt panels:

3,300 watts/50 watts = 66 solar panels at 50 watts each...

For batteries, assuming each battery is 100 amp*hours at 12 volts and you need an 833 Amp*Hour bank at 48 volts:

(833AH/100AH) * (48V/12V) = ~ 32 or 36 batteries...

-Bill

And regarding batteries... Car batteries are made to start cars--be light weight, lots of current, for a very short time... So the plates are very thin.

A true storage battery has thicker plates and is made to supply lower current for a much longer period of time... So, a true deep cycle storage battery will last much longer.

There are two major useful types of lead acid deep cycle storage batteries. One is the Wet Cell (fill with acid and keep up with distilled water) and the other is AGM--This is a "sealed" battery. Very nice, but expensive, less messy, and easy to kill if overcharged.

Both work well in solar installations. Wet Cells are many times used as "training batteries" to learn how to run your system and AGMs are purchased once you have your system working well and have gotten tired of servicing/cleaning the wet cell type batteries.

Our host (Wind-Sun) sells several types of storage batteries and has a nice FAQ (frequently asked questions) about batteries... (you probably won't buy from the US, but it is still a good place to find some good brands and read about using them).

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
Re: I am still having problem figuring solar panels operations.

Yikes!! I missed the battery question.

Thx, Bill.
Jim / crewzer