Photovoltaic systems present some unique challenges of their own. Photovoltaic systems take the energy from the sun and convert it into electricity. The power that is created is alternating current and through an inverter is converted into direct current and used in the facility for specific circuits, or ties directly back into the utility power. Firefighters need to be aware of how buildings with these systems are tied into the electric system. In many instances, these systems are tied back into the buildings overall electrical system in a way that allows the solar power to provide power to a circuit and allow normal building power to power the circuit as well in times when the sun is not providing enough energy. This is where there is a large concern for firefighters.

As firefighters know, or should know, electricity flows through a conductor through the path of least resistance, so it can flow both ways. In many commercial fires one of the tasks for arriving companies is to secure the utilities. In the case of photovoltaic, even if the main power source for a facility is disconnected, power may flow from the inverter back though the system and energize what is thought to be a de-energized system. Therefore, when securing the utilities it is important that firefighters identify the source of the power from the photovoltaic system and disconnect that as well. This may be difficult if you are in a building for the first time and have no idea where it may be located. In some jurisdictions, however, the utility companies and code enforcement authorities have required the installation of a disconnect outside of the facility near the meter to disconnect the solar power from the buildings electrical system.

Another concern to firefighters is the solar panels themselves. Much like the solar thermal panels, these panels block access to the roof and are generally tied into the building structure or ballasted down and not easy to move, making vertical ventilation nearly impossible. As discussed with solar thermal panels, photovoltaic panels are also mounted on the exterior walls of building, making access to windows difficult and creating a significant falling-debris hazard.

source: firehouse