How to Size a PV Array

Introduction

Solar Panels Sizing up a PV array  is an essential part of creating a solar power kit.

You now know what inverter you want.

But, how do we go about sizing your PV array needs?

Well, it’s quite simple.

Keep reading on to learn everything you need to know about sizing your PV array.

Fundamentals

Your inverter plays an important role in  sizing your array .

But, before we delve into the technical details of sizing your array, let’s go through some fundamentals first.

If you are electrically challenged (like I was), this might be beneficial before we get started.

 This section is for complete beginners. 

  • PV Array

    Photovoltaic Array refers to your  solar panel setup .


  • PV String

    A group of solar panels whose combined  voltage does not exceed the maximum MPPT range .


  • Watts

    Wattage is a  measurement of electricity .


  • Volts

    Voltage is the rate at which  electricity travels .


  • Series

    This way of connecting solar panels  increases the voltage .


  • Parallel

    This way of connecting solar panels  increases the amps .


  • MPPT

    An MPPT (Maximum Power Point Tracking) tracks the voltage coming from the PV array and  maximises the energy produced by the array .


  • Want to Learn More About Solar Inverters?

    Our inverter Guide will tell you everything you need to know about Solar inverters.

    Click Here

How to Size an Array

Calculate

Let’s take a closer look at  sizing up an array  according to your inverters solar charger data.

Find the inverter and the panel datasheet.

For the inverter, look for the Max PV Input and the Max MPPT Range value.

For the panel, look for the Max Power and the Open-circuit Voltage. (VOC).

Then follow the instructions below:

First, we will look at the  maximum PV array input . This value will differ from inverter to inverter.

In this instance, we’ll use 4500w.

Second,  we’ll look at the  power rating of the panel ; in this example, we are using 400W panels.

Third, we divide the  maximum PV array input  by the  panels power rating :

Max PV Array Input

4500W

/
Max Power

400W

=
Max No of Panels

11.25

We will round it down to 10 panels.

You do not want to exceed the maximum PV array input rating, and you need to be able to have the same number of panels on each string.

Lastly, we need to figure out how many panels you’ll need in a string.

You do this by checking what the maximum MPPT range is. Then take that number and divide it by the maximum power voltage. This will give you the number of panels per string:

Max MPPT Range

115V

/
Max Power Voltage

49V

=
Panels Per String

2.35

Again, we'll need to round this number down to 2 panels per string.

Most Off-Grid and Grid-Tied inverters have only one MPPT. If you have three or more strings, you will need a combiner box to connect your panels to the MPPT in your inverter. These can add an extra cost of around R 7,000.00+

Want to Learn More About Solar Panels?

Our Solar Panel Guide will tell you everything you need to know about Solar Panels.

Click Here

To help you better understand usage and sizing, take a look at the 3 case studies below:

Case Study 1:
5kW Low-Voltage Inverter with 400W Panels

Jim has decided that the 5kW Low-Voltage Off-Grid is his best inverter option. He now needs to size up his array. He will need to find out how many panels his inverter can handle and how many strings he will need to have to max out his array.

Firstly, he is going to find the key values on both his inverter and panels' datasheets.
Then he is going to use a simple equation to determine the number of panels he can use with his inverter:

Max PV Array Input

4500W

/
Max Power

400W

=
Max No of Panels

11.25

If the number you get is an odd number, it will need to be rounded down to the nearest even number.

In this case, the maximum number of panels Jim would need is 10.

Now Jim will need to know how many panels he can have in each string.

He uses another basic equation to work this out too:

Max MPPT Range

115V

/
Max Power Voltage

49V

=
Panels Per String

2.04

Again, we are going to round this number down to 2. This means you can have two panels per string.

Jim has decided to go with the maximum amount of panels. So this means he is going to have five strings of 2 panels.

He will need to make sure to purchase a combiner box so that he can connect all of the strings to his single MPPT inverter.

See Array Comparison Below

With A Combiner Box


Without A Combiner Box


The Bottom Line

Number of Strings

5

Panels Per String

2

Max Peak Power*

4kW

Daily Production*

18kW

Yearly Production*

6.57MW

*Power production are averages that are based on a 5.5 hour production time per day. Installation, weather, shading, and soiling all affect these figures.

Case Study 2:
5kW High-Voltage Inverter with 400W Panels

George has done his homework and has decided to buy a 5kW High-Voltage Off-Grid inverter. Now all he needs to do is work out the details of his array. George is not sure what size panel he should buy, so below, we have two different examples with the same inverter but different panels.

Scenario 1

Again, we are going to work out how many panels he needs:

Max PV Array Input

5500W

/
Max Power

400W

=
Max No of Panels

13.75

To work out the number of strings. This time, we will be able to fit more panels in a string, thanks to the higher voltage range of the inverter. That gives us a rounded down maximum total of 12 panels.

Max MPPT Range

430V

/
Max Power Voltage

49V

=
Panels Per String

8.77

Rounded down: 8 panels.

However, because your Maximum PV array is 5500W, you will only be able to have six panels per string.

See Diagram Below

The Bottom Line

Number of Strings

2

Panels Per String

6

Max Peak Power*

4.8kW

Daily Production*

26.4kW

Yearly Production*

9.6MW

*Power production are averages that are based on a 5.5 hour production time per day. Installation, weather, shading and soiling all affect these figures.

Scenario 2

The same exercise can be done using a smaller panel, like a 330W, and this is what your calculations would look like:

Max PV Array Input

5500W

/
Max Power

330W

=
Max No of Panels

16.66

Now let’s work out the strings: Round it down: 16 Panels.

Max MPPT Range

430V

/
Max Power Voltage

49V

=
Panels Per String

8.77

Round it down: 8 panels per string.

See Diagram Below

The Bottom Line

Number of Strings

2

Panels Per String

8

Max Peak Power*

5.3kW

Daily Production*

29kW

Yearly Production*

10.5MW

*Power production are averages that are based on a 5.5 hour production time per day. Installation, weather, shading and soiling all affect these figures.

Case Study 3:
8kW Hybrid Inverter with 400W Panels

Juan has bought a large hybrid inverter and wants to max out his PV array.
The equation to work out his PV array will be the same as the first two case studies. However, Juan has bought a hybrid which has 2 MPPT’s, instead of the usual 1 MPPT.

Not only will Juan be able to have up to 4 strings of panels without having to use a combiner box, but he will have a far more efficient array.

Here’s why:

If one of the arrays is unable to function correctly due to shading or soiling, Juan has another array that can still work at full capacity. This will ensure that Juan’s system is still generating solar power.

Let’s work out Juan’s array size.

Firstly, he is going to find the key values on both his inverter and panels' datasheets.
Then he is going do the maths to determine the number of panels he can use with his inverter:

Max PV Array Input

10400W

/
Max Power

400W

=
Max No of Panels

26

We don’t need to round it down this time so Juan can have a maximum of 26 panels in total.

Then we need to divide that by 2 (MPPT), and we have 13 panels per MPPT.

We will need to work out how many strings Juan can have on each MPPT so we do the sum:

Max MPPT Range

425V

/
Max Power Voltage

49V

=
Panels Per String

8.67

Juan can have a maximum of 8 panels per string.

However, because Jaun can only have a maximum of 26 x 400W panels, he won’t be able to put 8 panels on 4 strings as this will exceed the Max PV Input.

Remember that each string needs to have the same number of panels per MPPT. So, while we cannot divide 13 equally, we can put 14 panels on one MPPT, and we can put 12 on the other.

See Diagram Below

The Bottom Line

MPPT 1
Number of Strings

2

Panels Per String

7

MPPT 2
Number of Strings

2

Panels Per String

6

Max Peak Power*

10.4kW

Daily Production*

57.2kW

Yearly Production*

20.8MW

*Power production are averages that are based on a 5.5 hour production time per day. Installation, weather, shading and soiling all affect these figures.

Conclusion

Now that you know how to size an array, you'll be able to size up one for yourself. Remember to take both the Maximum PV Array Input and the MPPT Voltage Range into consideration when you are sizing up your array.

Contact Us

If you have any questions, please Contact Us.

Leave a Reply

Sign Up for Deals

Sign up to get notified of our deals

Thank you for subscribing.

Something went wrong.