CSLB C-46 Solar ContractorPlanning and EstimatingMedium
A C-46 contractor is performing a site analysis for a residential PV system. The client's roof has multiple dormers and vents, creating numerous small, shaded areas throughout the day. To maximize energy harvest from each module independently and mitigate the effects of partial shading, which component combination is most appropriate for the system design?
- ADC optimizers paired with a central string inverter.
- BCentral string inverter with a single MPPT.
- CCentral string inverter with multiple MPPTs.
- DMicroinverters for each module.
Show answer & explanationAnswer & explanation
Correct answer: D. Microinverters for each module.
Microinverters optimize power at the individual module level, meaning each module operates independently. This is ideal for situations with complex shading patterns, as it prevents a shaded module from reducing the output of other unshaded modules in the array, maximizing overall energy harvest.
Why the other options are wrong
- A. DC optimizers also provide module-level optimization, but they still require a central string inverter. Microinverters offer a fully distributed solution without a central string inverter, simplifying design in complex layouts.
- B. A single MPPT inverter would be highly inefficient with multiple shaded areas, as the entire string's output would be reduced to that of the lowest performing module.
- C. While better than a single MPPT, multiple MPPTs can only optimize for large sections (strings) of modules, not individual modules, so small, scattered shading would still cause losses.
Module-Level Power Electronics (MLPE)
Electronic devices (microinverters or DC optimizers) that perform maximum power point tracking (MPPT) at the individual solar module level.
- Mitigate shading and mismatch losses.
- Enable module-level monitoring.
- Enhance safety with rapid shutdown capabilities.
Memory trick: Shade's Impact: Use MLPEs.