COMPLETE SOLAR PANEL INSTALLATION DESIGN & CALCULATIONS

COMPLETE SOLAR PANEL INSTALLATION DESIGN & CALCULATIONS

Table of Contents

A.    Inverter / UPS Rating:

B.     Required No of Batteries

C.   Backup Hours of Batteries

D.   Series or Parallel Connection for Batteries

a)    Why Batteries in Parallel, not in Series?

E.    Charging Current for Batteries

F.    Charging Time required for Battery

G.   Required No of Solar Panel

H.   Rating of Charge Controller

Below is a Complete Note on Solar Panel design installation, calculation about No of solar panels, batteries rating / backup time, inverter/UPS rating, load and required power in Watts. With Circuit, wiring diagrams and solved examples.

If you pick this article related to solar panel installation, you will be able to;

a.     To calculate the no of solar panel (with rating).

b.     To calculate the rating of Solar panel.

c.      To calculate the rating of batteries for Solar panel system.

d.     To calculate the backup time of batteries.

e.      To calculate the charging current for batteries.

f.       To calculate Charging time for batteries.

g.     To calculate the rating of charge controller.

h.     How much watt solar panel we need.

i.       How to select the proper solar panel for home.

j.       UPS / Inverter Rating for load requirement and much more…

Solar Panel Installation: Step by Step Procedure with calculation and examples,

Suppose, we are going to install a solar power system in our home for a total load of 800W where the required backup time of battery is 3 hours (You may use it your own as it is just for sample calculation)

Load = 800 Watts

Required Backup time for batteries = 3 Hours

What we need to know?

1. Inverter / UPS Rating =?

2. No of batteries for backup power =?

3. Backup Hours of batteries =?

4. Series or Parallel Connection of Batteries =?

5. Charging Current for Batteries =?

6. Charging Time for batteries =?

7. Required No of Solar Panel =?

8. Rating of Charge Controller =?

Solution:

Inverter / UPS Rating:

Inverter / UPS rating should be greater than 25% of the total load (for the future load as well as taking losses in consideration)

800W x (25/100) = 200W

Our Load + 25% Extra Power = 800+200 = 1000 Watts

This is the rating of the UPS (Inverter) i.e. we need 1000W UPS / Inverter for solar panel installation according to our need (based on calculations)

Required No of Batteries

Now the required Back up Time of batteries in Hours = 3 Hours

Suppose we are going to install 200Ah, 12 V batteries,

12V x 200Ah = 2400Wh

Now for One Battery (i.e. the Backup time of one battery)

2400Wh / 800 W = 3 Hours

But our required Backup time is 3 Hours.

Therefore, 3/3 = 1 → i.e. we will have to connect one batteries of 200Ah, 12V.

Backup Hours of Batteries

If the number of batteries is given, and you want to know the Backup Time for these given batteries, then use this formula to calculate the backup hours of batteries.

2400Wh x 1 Battery = 2400Wh

2400Wh / 800 W = 3 hours.

In the first scenario, we will use 12V inverter system; therefore, we will have to connect one battery (of 12V, 200Ah) in Parallel. But a question raised below:

Battery Charging Time

Series or Parallel Connection for Batteries

Why Batteries in Parallel, not in Series?

Because this is a 12V inverter System, so if we connect these batteries in series instead of parallel, then the rating of batteries become V₁ + V₂ = 12V + 12V = 24V while the current rating would be same i.e.200Ah.

That’s why we will connect the batteries in parallel, because the Voltage of batteries (12V) remains same, while its Ah (Ampere Hour) rating will be increased. I.e. the system would become = 12V and 100Ah + 100Ah = 200Ah.

We will now connect 2 batteries in parallel (each of 200Ah, 12V)

i.e. 2, 12V, 100Ah batteries will be connected in Parallel to have 12V,200Ah

= 12V, 100Ah + 100Ah = 12V, 200 Ah (parallel)

Charging Current for Batteries

Now the Required Charging Current for these two batteries.

(Charging current should be 1/10 of batteries Ah)

200Ah x (1/10) = 20A

Charging Time required for Battery

Here is the formula of Charging Time of a Lead acid battery.

Charging Time of battery = Battery Ah / Charging Current

T = Ah / A

For example, for a single 12V, 200Ah battery, The charging time would be:

T = Ah / A = 200Ah / 20A = 10 Hrs  (Ideal Case)

due to some losses, (it has been noted that 40% of losses occurred during the battery charging), this way, we take 10-12 A charging current instead of 10 A, this way, the charging time required for a 12V, 200Ah battery would be:

200Ah x (40/100) = 80A (200Ah x 40% of losses)

The battery rating would be 200Ah + 80 Ah = 280 Ah (200Ah + losses)

Now the required charging current for the battery would be:

280Ah / 82A = 4Hours.

Required No of Solar Panel

Now the required No of Solar Panels we need for the above system as below.

Scenario 1: DC Load is Not Connected = Only Battery Charging

We know the famous power formula (DC)

P = VI ………… (Power = Voltage x Current)

Putting the values of batteries and charging current.

P = 12V x 20 A

P = 240 Watts

These are the required wattage of solar panel (only for battery charging, and then battery will supply power to the load i.e. direct load is not connected to the solar panels)

Now

240W/60W = 4 Solar panels

Therefore, we will connect 4 Solar Panels (each of 60W, 12V, 5A) in parallel.

Fig: Circuit Diagram for the above Calculation for Solar Panel Installation (Solar Panels only for battery charging)

The above calculations and system was only for battery charging (and then battery will supply power to the desired Load) to AC electrical appliances, which will get power through inverter and DC loads via Charge controller (via charged batteries)

Scenario 2: DC Load is connected as well as Battery Charging

Now suppose there is a 10A directly connected load to the panels through inverter (or may be DC load via Charge Controller). During the sunshine, the solar panels provide 10A to the directly connected load + 20A to the battery charging i.e. solar panels charge the battery as well as provide 10A to the load as well.

In this case, the total required current (20A for Batteries Charging and 10A for directly connected load)

In this case above, total required current in Amperes,

20A + 10 A = 30A

Now, I = 30A, then required Power

P = V x I = 12V x 30A = 360Watts

I.e. we need 360W system for the above explained system (This is for both Direct Load and Batteries Charging)

NOW, THE NUMBER OF SOLAR PANELS WE NEED

360W/60W = 6

Therefore, we will Connect 6 No of Solar panels (each of 60W, 12V, 5A)

 

fig: Circuit Diagram for the above Calculation for Solar Panel Installation (Solar Panels only for battery charging + Direct connected load)

Rating of Charge Controller

As we have calculated above that the charging current for 200Ah battery is 20-22 Amperes (22A For Battery Charging+10A for direct DC Load), therefore we can use a charge controller about 30-32 Amp.

Note: The above calculation is based on ideal case, so it is recommended to always choose a solar panel some bigger then we need, because, there are some losses occurs during battery charging via solar panel as well as the sunshine is not always in ideal mood.