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Understanding the series and parallel connection of solar panels

18 November 2022
Figure 1: The wiring and arrangement of solar panels impact the performance of the system and dictate the type of inverters that can be used for an application. Source: bilanol/Adobe Stock

Solar panel systems are essential technologies helping engineers to harness solar energy. However, given that solar panel systems are quite easy to assemble, one might assume that the wiring of solar panels isn’t really important. But that assumption would be wrong.

The wiring and arrangement of solar panels impact the system's performance and dictate the type of inverters to be used for an application. As a rule, engineers want their panels wired using the series, parallel or series-parallel configurations. The ideal choice will depend on several factors, including the application’s amperage and voltage requirements.

Series connection

To understand how series connections work, consider Figure 1, which shows solar panels (having the same specifications) connected in series.

Figure 1: Solar panels connected in series. Source: Alternative Energy TutorialsFigure 1: Solar panels connected in series. Source: Alternative Energy Tutorials

Notice how the positive terminal of each panel is connected to the negative terminal of the next panel. As a result, the voltage in the panels adds together while the amperage remains the same. So suppose each of these solar panels has a rated voltage of 24 V and amperage of 4 A. In such a scenario, the total voltage of the series connection would be 96 V, while the amperage would remain at 4 A.

Solar panels connected in series are ideal in applications with low-amperage and high voltage and power requirements. The total power of solar panels connected in series is the summation of the maximum power of the individual panels connected in series. However, because every panel in a series connection is important in the circuit, this type of connection might not be ideal in applications where there is a possibility of shade covering some of the panels.

Nevertheless, it is essential to use the MPPT (Maximum Point Power Tracking) charge controllers when connecting solar panels in series. These controllers regulate the high voltage levels from the solar panels and match it with the battery bank’s voltage.

[Learn more about solar charge controllers on GlobalSpec.com]

Parallel connection

To understand how parallel connections work, consider Figure 2, which shows four solar panels (having the same specifications) connected in parallel.

Figure 2: Solar panels connected in parallel. Source: Alternative Energy TutorialsFigure 2: Solar panels connected in parallel. Source: Alternative Energy Tutorials

In this type of connection, all the panels' positive terminals are connected, and the negative terminals are also connected. The resulting effect is to produce a solar panel system with an increased amperage rating (the sum of the individual amperages in the parallel array) while the total voltage remains the same. So, for instance, by connecting four solar panels (each rated at 12 V, 4 A) in parallel, the total voltage of the system remains 12 V, and the output current will be obtained as 16 A, as shown below.

Unlike the series connection, solar panels connected in parallel operate independently of one another, making them ideal in applications with mixed light conditions. For instance, if shade covers some of the panels connected in parallel, engineers can still expect the remaining panels to continue generating power.

Solar panels connected in parallel are generally used with pulse width modulation (PWM) charge controllers.

Series-parallel connection

Engineers also connect solar panels in a series-parallel configuration. Several panels are first wired together in series to form strings of panels (for instance, three strings of solar panels featuring two panels connected in series would make up a total of six solar panels). To form a series-parallel connection, these strings of panels are then wired in parallel, as shown below:

Figure 3: Three strings of solar panels in a series-parallel configuration. Source: MPPTSolarFigure 3: Three strings of solar panels in a series-parallel configuration. Source: MPPTSolar

This method increases the voltage of each panel connected in series and the amperage of the string of panels wired in parallel. Engineers will find them useful in applications with high voltage and amperage requirements.

Conclusion

Solar panels can be wired to meet different voltage and amperage requirements. However, that’s one of the many factors engineers must consider when designing a solar photovoltaic (PV) system. For instance, there is still a need to size and choose the ideal solar charge collectors and battery bank and the ideal environment where this solar PV system will be mounted.

Therefore, engineers are advised to reach out to solar PV system manufacturers to discuss their application needs.



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