How To Connect Solar Panels Together to Increase Power?

Connecting Solar Panels Together

The trick here when connecting solar panels together is to choose a connection method that is going to give you the most energy efficient configuration for your particular requirements.

Connecting solar panels together is a simple and effective way of increasing your solar power capabilities. Going green is a great idea, and as the sun is our ultimate power source, it makes sense to utilize this energy to power our homes. As solar power becomes more accessible, there is need to know how best to connect the panels together to achieve more power.

There are three basic but very different ways of connecting solar panels together and each connection method is designed for a specific purpose. For example, to produce more output voltage or(and) to produce more current.

Solar photovoltaic panels can be electrically connected together in series to increase the voltage output, or they can be connected together in parallel to increase the output amperage. Solar PV panels can also be wired together in both series and parallel combinations to increase both the output voltage and current to produce a higher wattage array.

Whether you are connecting two or more solar panels, as long as you understand the basic principles of how connecting multiple solar panels together increases power and how each of these wiring methods works, you can easily decide on how to wire your own panels together. After all, connecting solar panels together correctly can greatly improve the efficiency of your solar system.

Connecting Solar Panels Together in Series

Sometimes the system voltage required for a power inverter is much higher than what a single PV module can produce. In such cases, N-number of PV modules is connected in series to deliver the required voltage level. This series connection of the PV modules is similar to that of the connections of N-number of cells in a module to obtain the required voltage level. Solar panels in series add up or sum the voltages produced by each individual panel, giving the total output voltage of the array as shown.

In this method ALL the solar panels are of the same type and power rating. The total voltage output becomes the sum of the voltage output of each panel. Using the same three 6-volt, 3.0-amp panels from above, we can see that when these PV panels are connected together in series, the array will produce an output voltage of 18 Volts (6 + 6 + 6) at 3.0 Amperes, giving 54 Watts (volts x amps) at full sun.

Now let’s look at connecting solar panels in series with different nominal voltages but with identical current ratings.

Solar Panels in Series of Different Voltages

In this method all the solar panels are of different types and power rating but have a common current rating. When they are connected together in series, the array produces 21 volts at 3.0 amps, or 63 watts. Again, the output amperage will remain the same as before at 3.0 amps but the voltage output jumps to 21 volts (5 + 7 + 9).

Finally, let’s look at connecting solar panels in series with completely different nominal voltages and different current ratings.

Solar Panels in Series of Different Currents

In this method all the solar panels are of different types and power rating. The individual panel voltages will add together as before, but this time the amperage will be limited to the value of the lowest panel in the series string, in this case 1 Ampere. Then the array will produce 19 Volts (3 + 7 + 9) at 1.0 Ampere only, or only 19 watts out of a possible 69 watts available reducing the arrays efficiency.

We can see that the solar panel rated at 9 volts, 5 amps, will only use one fifth or 20% of its maximum current potential reducing its efficiency and wasting money on the purchase of this solar panel. Connecting solar panels in series with different current ratings should only be used provisionally, as the solar panel with the lowest rated current determines the current output of the whole array.

Example:

Now to understand these steps in a more mathematical way. Let’s take an example of a power plant of 2 MW, in which a large number of PV modules are connected in series. (The 2 MW inverter can take input voltage from 600 V to 900 V).

Determine the number of modules be connected in series to obtain a maximum power point voltage of 800 V. Also determine the power delivered by this PV array.

The parameters of the single PV module are as follows;

• Open circuit voltage VOC = 35 V

• Voltage at maximum power point VM = 29 V

• Short circuit current ISC = 7.2 A

• Current at maximum power point IM = 6.4 A

Step 1: Note the voltage requirement of the PV array

• PV array open-circuit voltage VOCA = Not given

• PV array voltage at maximum power point VMA = 800 V

Step 2: Note the parameters of PV module that is to be connected in the series string

Open circuit voltage VOC = 35 V

Voltage at maximum power point VM = 29 V

Short circuit current ISC = 7.2 A

Current at maximum power point IM = 6.4 A

Maximum Power PM

PM = VM x IM

= 29 V x 6.4 A

PM = 185.6 W

Step 3: Calculate the number of modules to be connected in series

N = VMA / VM

N = 800 / 29

N = 27.58 (Higher integer value 28)

Take higher integer value 28 modules. Due to the higher integer value of N, the value of VMA and VOCA will also increase.

VMA = VM × N

= 29 × 28

= 812 V

Step 4: Calculating the total power of the PV array

PMA = N × PM

= 28 × 185.6

= 5196.8 W

Thus, we need 28 PV modules to be connected in series having a total power of 5196.8 W to obtain the desired maximum PV array voltage of 800 V.

Connecting Solar Panels Together in Parallel

Sometimes to increase the power of the solar PV system, instead of increasing the voltage by connecting modules in series the current is increased by connecting modules in parallel. The current in the parallel combination of the PV modules array is the sum of individual currents of the modules.

The parallel combination is achieved by connecting the positive terminal of one module to the positive terminal of the next module and negative terminal to the negative terminal of the next module as shown in the following figure.

When you connect solar panels together in parallel, the total voltage output remains the same as it would for a single panel, but the output current becomes the sum of the output of each panel as shown.

In this method ALL the solar panels are of the same type and power rating. Using the same three 6 Volt, 3.0 Amp panels as above, the total output of the panels, when connected together in parallel, the output voltage still remains at the same value of 6 volts, but the total amperage has now increased to 9.0 Amperes (3 + 3 + 3), producing 54 watts at full sun.

But what if our newly acquired solar panels are non-identical, how will this affect the other panels. We have seen that the currents add together, so no real problem there, just as long as the panel voltages are the same and the output voltage remains constant. Let’s look at connecting solar panels in parallel with different nominal voltages and different current ratings.

Solar Panels in Parallel with Different Voltages and Currents

Here the parallel currents add up as before but the voltage adjusts to the lowest value, in this case 3 volts. Solar panels must have the same output voltage to be useful in parallel. If one panel has a higher voltage it will supply the load current to the degree that its output voltage drops to that of the lower voltage panel.

We can see that the solar panel rated at 9 volts, 5 amps, will only operate at a maximum voltage of 3 volts as its operation is being influenced by the smaller panel, reducing its efficiency and wasting money on the purchase of this higher power solar panel. Connecting solar panels in parallel with different voltage ratings is not recommended as the solar panel with the lowest rated voltage determines the voltage output of the whole array.

Then when connecting solar panels together in parallel it is important that they ALL have the same nominal voltage value, but it is not necessary that they have the same ampere value.

Example:

Let’s take an example, calculate the number of modules required in parallel to obtain maximum power point current IMA of 40 A. The system voltage requirement is 14 V.

The parameters of the single PV module are as follows;

• Open circuit voltage VOC = 18 V

• Voltage at maximum power point VM = 14 V

• Short circuit current ISC = 6.5 A

• Current at maximum power point IM = 6 A

Step 1: Note the current requirement of the PV array

• PV array short-circuit current ISCA = Not given

• PV array current at maximum power point IMA = 40 A

Step 2: Note the parameters of PV module that is to be connected in parallel

Open circuit voltage VOC = 18 V

Voltage at maximum power point VM = 14 V

Short circuit current ISC = 6.5 A

Current at maximum power point IM = 6 A

Step 3: Calculate the number of modules to be connected in parallel

N = IMA / IM

= 40 / 6

N = 6.66 (Higher integer value 7)

Take higher integer value 7 modules. Due to the higher integer value of N, the value of IMA and ISCA will also increase.

IMA = IM × N

= 6 × 7

IMA = 42 A

Step 4: Calculating the total power of the PV array

PMA = N × PM

= 7 × 84

PMA = 588 W

Thus, we need 7 PV modules to be connected in parallel having a total power of 588 W to obtain the desired maximum PV array current of 40 A.

Series – Parallel Connection of Modules – Mixed Combination

When we need to generate large power in a range of bigger-watts for large PV system plants we need to connect modules in series and parallel. In large PV plants first, the modules are connected in series known as “PV module string” to obtain the required voltage level.

Then many such strings are connected in parallel to obtain the required current level for the system. The following figures shows the connection of modules in series and parallel. To simplify this, take a look at right in the following figure.

Module 1 and module 2 are connected in series let’s call it the string 1. The open-circuit voltage of the string 1 is added. Whereas the short-circuit current of string 1 is the same.

Similar to string 1, the modules 3 and 4 make up the string 2. The open-circuit voltage of the string 2 is added. Whereas the short-circuit current of string 2 is the same.

Now string 1 and string 2 are connected in parallel, nowhere the voltage remains the same but the current is added.

Example:

Now let’s take an example for the mix – combination. We have to determine the number of modules required for a PV array having the following parameters;

• Array power PMA = 40 KW

• Voltage at maximum power point of array VMA = 400 V

• Current at maximum power point of array IMA = 100 A

The module for the design of the array has the following parameters;

• Voltage at maximum power point of module VM = 70 V

• Current at maximum power point of module IM = 17 A

Step 1: Note the current, voltage, and power requirement of the PV array

• PV array power PMA = 40 KW

• PV array voltage at maximum power point VMA = 400 V

• PV array current at maximum power point IMA = 100 A

Step 2: Note the PV module parameters

• Voltage at maximum power point of module VM = 70 V

• Current at maximum power point of module IM = 17 A

Maximum power PM:

PM = VM x IM

PM = 70V x 17A

PM = 1190 W

Step 3: Calculate the number of modules to be connected in series and parallel

NS = VMA / VM

NS = 400 / 70

NS = 5.71 (Higher integer value 6)

Take higher integer value 6 modules. Due to the higher integer value of NS, the value of VMA and VOCA will also increase.

VMA = VM × NS

= 70 × 6

VMA = 420 V

Now,

NP = IMA / IM

NP = 100 / 17

NP = 5.88 (Higher integer value 6)

Take higher integer value 6 modules. Due to the higher integer value of NP, the value of IMA and ISCA will also increase.

IMA = IM × NP

IMA = 17 × 6

IMA = 102 A

Step 4: Calculating the total power of the PV array

PMA = NS × NP × PM

= 6 × 6 × 1190

PMA = 42840 W

Thus, we need 36 PV modules. A string of six modules connected in series and six such strings connected in parallel, having a total power of 42840 W to obtain the desired maximum PV array current of 100 A and voltage of 400 V.

Note that due to higher integer value of 6 the maximum PV array current and voltage is 102 A and 420 V respectively.

Conclusion

Connecting solar panels together to form bigger arrays is not all that complicated. How many series or parallel strings of panels you make up per array depends on what amount of voltage and current you are aiming for. If you are designing a 12-volt battery charging system than parallel wiring is perfect. If you are looking at a higher voltage grid connected system, than you’re probably going to want to go with a series or series-parallel combination depending on the number of solar panels you have.

But for a simple reference in regards to how to connect solar panels together in either parallel or series wiring configurations, just remember that parallel wiring = more amperes, and series wiring = more voltage, and with the right type and combination of solar panels you can power just about any electrical device you may have in your home.