The efficacy of fire-fighting foams for disrupting power generation from silicon solar panels

The use of fire-fighting foams for disrupting the electrical output of a solar array has been evaluated. A diffusion model was employed to calculate the light transmitted through foam as a function of its physical properties (thickness, density, and mean bubble diameter). From the transmitted light spectrum, the power generated from a c-Si solar cell was simulated. The individual cell results were extrapolated to a 5 kW solar array. It was determined that a foam ranging from 0.5 to 10 cm thick could significantly reduce the open-circuit voltage of the array, yet maximum voltages under load still represented an electrocution hazard to humans, capable of generating currents in excess of 20 mA through human skin. The risk was substantially reduced with the addition of light absorbing particle suspensions to the foam. It was found that 0.1 wt% carbon black or 0.5 wt% iron black (Fe3O4) added to the foam liquid medium decreased the maximum system voltage to a safe range (>10 V).