Are there advantages to using smaller strings for solar panels?

Benefits of Smaller Strings

Smaller strings reduce the impact of shading on system performance. When a single string is affected by shading, the entire string’s output is reduced, but if the system is divided into smaller strings, the unaffected strings can continue to produce power, maintaining overall system efficiency. For example, a 12-string system with 3 panels per string can continue to produce power even if 2 strings are shaded, whereas a single-string system would be heavily impacted.

Design Considerations

To effectively use smaller strings, the system designer must consider the maximum system voltage and the number of strings required to achieve it. Typically, a maximum system voltage of 600 volts is recommended for residential solar systems. Smaller strings can be connected in series to achieve this voltage, with each string consisting of 12-20 panels. For instance, a 600-volt system with 12 strings of 15 panels each can provide a more robust and flexible system design.

Wiring Techniques

In a series-parallel configuration, the goal is to maintain a balance between the number of strings and the number of panels per string. A common technique is to use a “series-parallel” wiring scheme, where multiple strings are connected in series to achieve the required system voltage, and then these series strings are connected in parallel to increase the overall system power output. This approach allows for a more efficient use of space and reduces the impact of shading and other electrical losses.