CSLB C-46 Solar ContractorPhotovoltaic System InstallationMedium
A solar designer is planning a PV system for a residential building with a complex roof layout, featuring multiple small shading obstructions (e.g., chimneys, vents, dormers) at different times of the day. Which type of power electronics would be most effective at maximizing energy harvest in this scenario?
- ACentral inverter with a single Maximum Power Point Tracker (MPPT).
- BTransformer-based string inverter.
- CString inverter with two MPPTs.
- DMicroinverters or power optimizers.
Show answer & explanationAnswer & explanation
Correct answer: D. Microinverters or power optimizers.
Microinverters and power optimizers (Module-Level Power Electronics, MLPE) perform MPPT at the individual module level. This allows each module to operate at its maximum power point independently, significantly mitigating the impact of partial shading on the overall system output. Central and string inverters with fewer MPPTs would be less effective as shading on one module would reduce the output of an entire string or array.
Why the other options are wrong
- A. A single MPPT central inverter would be severely impacted by partial shading, as the entire array's output would be pulled down by the shaded modules.
- B. Transformer-based vs. transformerless design primarily relates to grounding and efficiency, not shading mitigation effectiveness.
- C. While better than a single MPPT, two MPPTs would still mean that shading on a module within one of the two strings would affect all modules in that string.
Module-Level Power Electronics (MLPE)
Electronic devices (microinverters or power optimizers) that perform Maximum Power Point Tracking (MPPT) at the individual solar module level.
- Maximizes energy harvest in shaded or complex arrays.
- Provides granular monitoring and rapid shutdown capabilities.
- More expensive per watt than string inverters but offers performance benefits.
Memory trick: Shade's a problem, but MLPE's the solution, avoiding power dilution!