What factors should I consider when sizing solar panel strings?

Determining System Voltage

To determine the optimal system voltage, calculate the total system voltage drop, including the losses due to wire resistance. For a typical off-grid solar system, 48V or 60V is a good starting point. As a rule of thumb, use a minimum of 12V per string, with a maximum of 24-30 strings per inverter. This allows for safe and efficient operation while minimizing voltage drop.

Sizing Solar Panel Strings

To size solar panel strings, consider the following factors: the total system power, panel wattage, and inverter efficiency. A good starting point is to use a minimum of 200-250W per string, depending on the inverter’s maximum power point tracking (MPPT) capabilities. For example, if you have a 24V, 300W inverter, you can use two 150W panels in series, resulting in a 24V string with a total power output of 300W.

Wire Sizing and String Configuration

When configuring wire sizing and string configuration, consider the distance between panels and the inverter, as well as any potential shading issues. Use a minimum of 2 AWG wire for strings up to 50 feet, increasing to 1 AWG for longer distances or multiple strings in parallel. For series-parallel configurations, ensure that the inverter can handle the combined string voltage and current. Typically, use a 1:1 ratio for series-parallel configurations, such as 2 strings in series and 2 strings in parallel.