Firefighters and Solar

From the link:

The fears expressed in this article sound almost like a rerun of the fears some first responders had about hybrid and electric cars. The bulk of the fears stemmed from ignorance, and a few of them spread around a serious amount of FUD.

All of the potential dangers mentioned here are dealt with in the NEC (National Electric Code), produced and sold by the NFPA (National Fire Protection Association). So I agree that the next step should be to educate the front line firefighters. They need to know how to recognize and use the signage, equipment, disconnects, and other safety features that their own industry already requires to be installed on this solar equipment.

 

Please don't perpetuate the myth that PV solar requires batteries...they don't! Solar panels produce DC power, which is rectified (inverted to AC) and fed into the grid at proper voltage. The grid load acts as the "battery". A great misconception is that PV systems require (expensive) batteries.

Icarus

 

The whole thing is BS. It is not going to arc into you just by passing by or shooting water at it. Last I checked firefighters where big protective suits with rubber boots. Blasting water all over the area, if there are loose conductors on any of them, they will short and the panel will self destruct or at a minimum blow a breaker/fuse and shut off.

 

I wouldn't call the whole thing BS, just poorly informed.

In regular grid-tie systems, the AC lines will shut down (required by some regulatory body) when the firefighters pull the solar disconnects (required by NFPA) mounted right next to (as required by NFPA) the utility disconnects. In systems where the AC could remain live, a special backfeed warning label is required (by NFPA).

By having only individual microinverters under each individual PV module, with short low voltage DC lines not chained together, I was able to avoid having to understand and deal with the DC portion of the code. But that high voltage DC on multi-panel PV strings is a very real shock hazard. That is why the NFPA has many requirements for grounding, ground fault protection, metallic channels for DC cabling, and readily identifiable markings of these DC channels.

Those fire officials need some serious education about National Fire Protection Association protocols and codes.

 

I still don't buy it. Firefighters aren't standing out there without protection, and their boots are I thought by law or commonality electrically insulated. So even if standing in a charged pool of water, the people are safe.

Solar cells, the actual photoelectric diode, inherently has no protection. If you short input to output you will more than likely blow up one of the traces on one of the panels, break the circuit and now have 0 power generation from that panel. Microinverter panels should have short circuit protection, at least a fuse, so again if you short it before any bad happens, it is protected.

The only danger to a solar setup are batteries. And that is because generally short circuiting a battery with no protection will make it hot, it is already hot from the fire, and then a poison gas cloud and corrosive acid explosion could happen. But this has nothing to do with solar, this is battery backup. I don't hear people making a stink over server warehouses that contain millions of dollars of servers with probably hundreds of thousands of pounds of lead acid batteries sitting in racks and those have been around for a couple decades now.

This seems like another FUD against solar and wind, but the real reason has nothing to do with it. I have some spare solar cells, maybe next time it is sunny I will try to make fire with it. I am pretty certain it will spark, go pop and then just stop working.

 

if you use mini inverters on the back of the solar panels and running direct ac from the panels instead of high voltges DC then when the inverter detects a problem it will shutdown.
then you need to send a signal say wireless or using control wiring to every inverter ( network? ) you can reset them.
until then they will not start and if the box and cabling is connected water tight there wil be no risk
and even then every panel as a single panel only does around 40 volts or so.

also use melt breakers in the wires so when a short happens they stop working

 

If you short curcuit a panel, it will not blow out the traces, or anything else. It will simply not work. That said, multiple panels in paralel strings can and do provide an issue, hence the need to fuse paralell strings between panels.

I have never heard of a fire fighter being killed or injured from a PV installation. Not saying it hasn't happened, but I've never heard of it.

As I said before, grid tie PV does not need or use batteries, except for hybrid back up /UPS systems. Batteries are a much bigger source of danger than PV. Even a single, simple car battery can (and will) explode if shorted. There is also enough potential energy in a single car battery to create a huge fire hazzard in the event of a short in th DC wiring. Tie in a larger off grid batter bank and the potential is potentially catastrophic.

That said however, the danger of shock and or electrocution from a battery is slight, unless you get into large systems voltges, (48 vdc and higher). Very few off grid or UPS systems are wired higher than 48 vdc for this reason. It is critical that battery systems be properly wired,and fused.

Icarus

 

Oops, a serious typo. This should read:

"... the AC lines will shut down (required by some regulatory body) when the firefighters pull the solar disconnects ... "

These regular AC-interactive inverters shut down when disconnected from the grid, they can't operate in an island mode. Special inverters that can run independently require special labeling and safety equipment.

One of the first things the firefighters do is shut off power. So the regular PV shuts off either when the required PV disconnect is pulled, or when the main utility disconnect is pulled, or when the overhead line to the building is cut with a big set of shears.

 

The Unknown; Until we understand it, it's our nature to fear it - and our fear nature goes back a long long way.



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The cells are inherently current limited by the amount of light available, and can handle that full current, so will never melt a trace from their own power production.

Most large systems, such as in the OP fire, are multi-panel strings feeding one or a few large inverters, not like the individual microinverter-per-panel system I have. A dozen or so panels in series feed a DC line running hundreds of volts, well into the lethal range. Because of various code requirements, one side is very likely to be grounded. Should any sharp object cut through the insulation on the other side, a potential shock hazard develops. That is why the DC side is heavily regulated for physical protection, fault protection, marking and labeling, etc.

Agreed here, as the potential dangers are already well addressed by the fire industry. But the front line firefighters do need some training, not just cower in ignorant fear of the great unknown.

If it is just a few cells or ordinary size, I'm betting:
* No sparks whatsoever;
* No pop;
* It starts working again when you remove the short.

Remember that short circuit current is one of the tested points of PV cell specs. In high quality cells with a high fill factor, the normal operating current is not much below that.

 

Turnout gear (those "big suits and rubber boots") doesn't insulate you from electricity.

Some municipalities can purchase boots made to ASTM F2413-11 standards, which provide protection of up to 18,000 volts for up to one minute. Provided there are no defects to the boot. It must be discarded if there are any punctures etc, same as linemans gloves.

 

Ugh...

 

This NEVER happens. If there is a concern about power feeding a building, the local electric company is called out to properly sever the building from the grid. Nobody is pulling out "big shears" and cutting ANY wires. EVER.

 

Four months ago, when I asked one of my utility representatives about my PV disconnect, she said they (the utility) would never use it, emergency or otherwise. They'd just cut the service line to the building.

 

Grab the biggest pair of "shears" that you can find, and then go outside and cut the service line running to your house. Report back with the results.

 

I don't have the same equipment that the utility company has. Maybe they cut just one conductor at a time, next to the transformer, from their insulated basket truck, with fiberglass-handled shears.

 

YES this is how it is properly done. The building burns until the electric company shows up.

 

Will the building also burn until the gas company shows up to look around and tell them there is no gas service to the property?

 

They can shut off the gas valves or pull the electric meters, if they are accessible and as long as they are not cowering in fear. In industrial applications this sometimes is not the case. In which case the utilities will need to be brought out to shut off the utilities at the street.