Testing a method for de-energizing solar panels for firefighting

Solar power installations present potential electrical hazards during firefighting operations. Even if a building is disconnected from the electrical grid during an emergency, live high DC voltage electrical lines may still be present between the panels and the inverter due to solar irradiance. While newer installations may feature disconnects, they may be located in difficult to access areas (e.g., on the roof). One strategy for eliminating potential electrical hazards is by blocking the panel's solar access using a tarp. However, this process poses a safety hazard. An alternate procedure was developed to test the ability of a common foam agent (fluoro-protein Foam) to de-energize a 2.8 kW solar array under sunny conditions. This agent is carried by almost all firefighting trucks and tankers and can be sprayed through a hose, eliminating the need for firefighters to access the roof of a burning building. The agent can be washed off using water, returning the panels to an operable state. During testing, the voltage and current on both the AC and DC sides of the inverter was recorded to evaluate the effect of the foam on the power output of the array. While the foam did create a dramatic reduction in power, it appears that the reduction was insufficient to eliminate the electrical hazard in the DC lines. Ongoing efforts include testing of the optical properties of the foam to determine whether possible improvements could be made, and testing of other foam agents and foaming strategies.