Original post made on Oct 8, 2007
Read the full story here Web Link posted Wednesday, July 4, 2007, 12:00 AM
on Oct 8, 2007 at 3:03 pm
The danger in solar photovoltaic modules comes from letting current flow through people (ouch!) or equipment not intended for such flow (such as into a nearby piece of metal structure, where it could arc and be a fire hazard or flow through people from there). The only people-protection in a PV system is the insulation... do not break the insulation if you want to be safe. PV power systems have an automatic shut-off inside the inverter that notices when current has "escaped" the wires it is intended to flow through, and stops that current flow to eliminate a possible ignition source. However, there is nothing that can make a PV module safe to touch once you have broken the insulation... no "rooftop switch" will help. Solution is: don't break the modules, and if you do, stay away from them unless you have electrical protective gear. Rooftop switches are a waste of money, and provide only an illusion of control over the safety of the system.
There is one borderline case where a rooftop switch might help... if a firefighter manages to cut both positive and negative leads and short them together (cut+cut+touch=three faults, which ought to be unlikely). However, the National Electric Code already requires these wires to be inside metal conduit if they are routed inside the house... are they planning to chop through conduits? Most of the wires on the roof are dispersed among the modules. If we have to be worried about such things, then having a switch at the edge of the array would still leave the individual wires on the modules unprotected from wanton axe-work. Fortunately, these days modules have pull-apart connectors, so using their axe to hook the wire and pull the connectors apart to stop the arcing will work right up next to the module, where a switch would be too far away to help. However, I suspect most firefighters would prefer to never touch a PV module... so requiring "access ways" between the panels is much more practical than adding switches that won't help anyway.
on Dec 24, 2007 at 12:37 pm
Being a firefighter, it is absolutely necessary in certain fire attack situations for vertical ventilation (venting through the roof area of a structure) to be performed. While I agree that these solar cells are crucial to reducing emmisions and economy, it is inherently dangerous for firefighter to vent through or around these P.V. cells for many reasons. It is entirely possible to invite an electrical shock or invoke and electrocution (nevermind the shattered glass and possible chemical release). By venting a fire in a different location can cause disasterous effects, redirecting the fire through unburned portions of the structure and potentially onto firefighters or victims. Vertical vent is also necessary to reduce superheated gasses and smoke from collecting, speeding fire attack and victim removal while performing the least amount of damage.
There needs to be a compromise between enviornmental friendlieness, economy, and safety.
on Mar 27, 2008 at 10:47 pm
"If they're spraying water on a (panel) that's compromised but still live,
the voltage comes back to the firefighters." (Woodside Fire Marshal Denise
through the water?
what a highlight in ignorance.
electricity does move faster than water can be pumped. I guess I see their point. (sarcasm)