solar power sytem design - all confused need help

while designing solar pwer system
total load 1200 watts
inverter designed at 1.3kva approx with 400v dc input 230v rms ac output @5A
now about the battery and panel selection :
battery : if 2-3 hr backup is needed then what should be the Ah rating of battery bank ?
as the needed output is 400v approx dc so which would be better battery bank with 12v battery as individual component or 24 or 48v? which one is better with optimum efficieny and economical too.
as the volatge of individual battery decreases no of battery increases in the battery bank

Solar panel : if going for direct on line system i.e as only day time use what should be the panel total wattage required ?? and what should be the panel voltage (individual unit rating)?

which system should be better going with a battery bank or direct online eliminating battery bank completly . in terms of system efficiency and economicality.

im all confused plaese help me.

Your output energy requirement is 5*230*3=3450 Ah. Your input requirement will be a function of your inverter efficiency: 3450/Efficiency.

You already know what your wattage requirement is: 5*230. Again, you have to take your efficiency into consideration.

Which is more economical, buying a whole bunch of batteries or not buying any batteries? Further, charging and discharging batteries is less efficient than going direct, assuming you will always have the power you need. Like during solar eclipses and alien spaceships blocking out the sun.

can you plese suggest a book for this kind of design (solar system design)

Hi,

Your output energy requirement is 5*230*3=3450 Ah.

Click to expand...

This is Wh, not Ah.
It is calculated as 5A x 230V x 3h ..... but this is the absolute worst case energy that you need at full load.

You should calculate what is your realistic load.
Let's say 350W.
Then the energy is 350W x 3h = 1050Wh (output energy)
Then your inverter will need "no load power". Just as an example let's say this is 20W.
And your inverter maybe has an efficiency of 85%.

Then the total input energy is 1050Wh / 0.85 + 20W x 3h = 1235Wh + 60Wh = 1295 Wh.

Then let's assume you have a 24V battery system..
Divide the energy by the battery voltage: 1295Wh / 12V = 108Ah
This again isno realistic value, becauae that means you use 100% of the charge of new batteries.
Maybe you can use 80% of the charge ....and your batteries afetr some time can only deliver 75% of the specified charge..
Then the needed Ah is: 108Ah / ( 0.80 × 0.75) = 180Ah.

****
12V, 24V, 48V..
From the electrical efficiency one tends to use the higher voltage: 48V
--> the current is lower abd thus the power loss is lower.
The drawback is...that you may need an additional charge balancing circuit.
If you connect batteries in series, then the weakest battery is resposible for the system lifetime.
The weakest battery gets stressed the most and therfore will fail first.

Solar panel:
The worst case are a couple of cloudy days...in ttimes wher you need al lot of energy.
How much this is depends on your region and your power consumption.

Klaus

Hi


In terms of economy, direct on-line or grid connected converter is cheaper. There are many application notes available from micro-chip, TI regarding solar inverter. You can check them out for a start.