CSLB C-46 Solar ContractorPlanning and EstimatingHard
A C-46 contractor is designing a grid-tied PV system for a residential client. The client has a limited budget but wants to ensure the system is as resilient as possible to minor grid fluctuations and momentary outages, without the full cost of a battery backup system. Which design choice offers a cost-effective compromise for this specific need?
- AOversizing the PV array significantly beyond consumption.
- BInstalling a secure power supply (SPS) inverter.
- CUsing a standard string inverter with rapid shutdown.
- DImplementing a microinverter system for module-level resilience.
Show answer & explanationAnswer & explanation
Correct answer: B. Installing a secure power supply (SPS) inverter.
A Secure Power Supply (SPS) inverter (also known as 'daylight backup' or 'grid-forming' inverter without a battery) can provide a limited amount of AC power directly from the PV array to a dedicated outlet during a grid outage, as long as the sun is shining. This offers a basic level of resilience for critical loads without the significant cost of a full battery storage system, making it a cost-effective compromise.
Why the other options are wrong
- A. Oversizing the array increases grid export but does not provide power during an outage without storage or an SPS feature.
- C. Rapid shutdown is a safety feature for emergency responders and does not provide backup power during an outage.
- D. Microinverters offer module-level optimization but do not inherently provide backup power during a grid outage.
Secure Power Supply (SPS)
A Secure Power Supply (SPS) inverter allows direct power from the PV array to a dedicated outlet during grid outages, providing limited daylight-only backup without a battery.
- Provides power only when sun is shining and grid is down.
- Typically limited to a single dedicated outlet and specific loads.
- More cost-effective than full battery backup.
Memory trick: SPS: Sun Power Saver for outages.