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 cause partial shading at different times of the day. To mitigate the impact of this partial shading on system performance, which of the following design strategies is most effective?
- AIncreasing the voltage of the PV array to overpower shaded sections.
- BConnecting all modules in a single long series string.
- COrienting all modules to face true south regardless of shading.
- DUsing bypass diodes within each module or string segments.
Show answer & explanationAnswer & explanation
Correct answer: D. Using bypass diodes within each module or string segments.
Bypass diodes provide an alternate path for current to flow around shaded or underperforming cells/modules, preventing them from becoming reverse-biased and significantly reducing the output of the entire string.
Why the other options are wrong
- A. Increasing array voltage does not address the fundamental issue of current mismatch caused by shading; it could even exacerbate hot spots.
- B. A single long series string is highly susceptible to severe performance degradation from partial shading.
- C. Orienting modules to true south is for optimal sun exposure, but does not mitigate the effects of partial shading once it occurs.
Partial Shading Mitigation (Bypass Diodes)
Electronic components (diodes) integrated into PV modules or junction boxes that shunt current around shaded or faulty cells/modules, preventing hot spots and minimizing power loss in a string.
- Prevents reverse bias and hot spot formation.
- Improves system performance under non-uniform irradiance.
- Typically found in module junction boxes, often in groups of 2-3 per module.
Memory trick: Shading Solutions: Bypass, Optimize, Separate