ACPV systems are the safest choice for generating solar rooftop power. With no DC wiring, AC modules powered by SolarBridge offer significant safety advantages over DC-based PV systems:
- Decreased shock hazard: Personal injury risk is greatest in a traditional DC-based system containing a string/central inverter where you have a high DC bus voltage (up to 600V dc in the US and up to 1000V dc in Europe). With an AC module system, installers and maintenance personnel are not exposed to high voltage DC. While installing or performing maintenance on a system, they must de-energize the AC distribution as part of normal protocol. This eliminates all live electricity from the output of the AC modules and therefore greatly reduces shock hazard.
- Fire prevention and arc faults: Arc faults are a major cause of PV fires, which are both dangerous and expensive. Unlike DC-based systems, AC systems are less likely to sustain arcs for two reasons. First, the current passes through zero twice per cycle. Second, the internal DC voltage is only that of a single PV module instead of multiple modules. An AC module system may also help prevent fires in the first place because the microinverter can detect an abnormality in the grid voltage and shut off the PV power automatically.
- Rescue worker safety: When firefighters first arrive on the scene, they shut off the power to protect workers and prevent the fire from spreading. However, in the case of a DC system, shutting off power at the circuit breaker only shuts off the central inverter, not the DC voltage still live on the roof. As a result, firefighters may hesitate to spray water, which can actually make a PV fire worse. Second, firefighters risk severing live wires when cutting through the walls or roof. Due to these concerns, they may let the building burn in a controlled manner rather than try to extinguish the fire. In AC modules, AC output automatically deactivates when disconnected from the utility (for example, by opening a circuit breaker), as mandated by codes and standards. This eliminates all live electricity from the output of the AC module and greatly reduces shock hazard during installation and maintenance. Unlike AC modules, conventional DC modules do not inherently have a shut-off switch.