CSLB C-46 Solar ContractorPhotovoltaic System InstallationMedium
A solar designer is laying out a rooftop PV system. The building has several vents and chimneys that will cast shadows on the array at various times of the day. To mitigate the impact of partial shading, which of the following system configurations is generally MOST effective?
- AA microinverter system where each module has its own inverter.
- BA central inverter system with bypass diodes enabled in all modules.
- CA single string inverter with all modules connected in one long string.
- DA string inverter system with modules connected in parallel strings without optimizers.
Show answer & explanationAnswer & explanation
Correct answer: A. A microinverter system where each module has its own inverter.
Microinverters operate independently for each module. This means that if one module is shaded, only that module's output is affected, while the other unshaded modules continue to produce at their maximum potential. This significantly reduces the impact of partial shading compared to string inverter systems where shading on one module can reduce the output of the entire string.
Why the other options are wrong
- B. While bypass diodes help a shaded module from completely blocking current, they don't optimize the output of the shaded module itself and still lead to significant losses compared to module-level power electronics.
- C. A single string inverter with one long string is highly susceptible to shading; one shaded module significantly reduces the entire string's output.
- D. Parallel strings can help reduce the impact slightly compared to a single string, but without optimizers, the overall string voltage/current is still affected by the weakest link, making it less effective than microinverters.
Partial Shading Mitigation
Strategies and technologies used in PV systems to minimize energy losses caused by shadows on a portion of the solar array.
- Shading can drastically reduce PV system output.
- Microinverters and power optimizers are effective solutions.
- Physical layout adjustments are the first step.
Memory trick: Shading's a snag, but smart tech brings power back!