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We saw a piece today about a fire on a distribution warehouse in New Jersey that was gutted in part because the local fire department was afraid to interact with the solar power system on the warehouse roof. As solar makes greater inroads on commercial buildings, what can we as an industry do to address this concern? (H/T SolarWakeup.com)
The distribution center, owned by Dietz & Watson, was a refrigerated warehouse that supported over 7,000 solar modules according to news reports. From Google we get this image of the center in happier days:
This is a very large commercial array by any measure - even if those are 200 Watt modules you are looking at a 1.4 MW install on the roof, to say nothing of the additional capacity installed in the carports to the west.
It is also a very nicely designed array with clear access paths throughout the roof and plenty of potential areas that could be broken open to allow for venting (although I’m sure from a fire fighter’s perspective, they would always want more).
Sadly, this is how it looked during the fire:
Here is the view of the blaze taken from the raw video recorded by local TV station NBC10:
This image makes clear that the NE quadrant of the building has been extensively damaged - the black area is where the solar panels have been completely destroyed.
The image also makes clear that the fire department chose to fight this fire from the ground, spraying water and foam onto the roof as opposed to going on to the roof itself. (There was no explanation given as to the cause of the fire.)
The local reporting indicated that the fire crews were concerned about possible collapse of the roof due to the amount of water being poured onto the fire. But they also mentioned the concern over possible electrocution:
Firefighters had to pull back at some points because the fully-charged solar panels posed the risk of electrocution.
“With all that power and energy up there, I can’t jeopardize a guy’s life for that,” said [Delanco Fire Chief Ron] Holt.
So what to make of all of this?
There can be no doubt that solar installations have the potential to make the already dangerous business of fighting a fire more hazardous. Strings of solar panels can produce as much as 600 Volts DC and as a general rule, there is no way to shut them off from the ground. While a DC disconnect on the ground could isolate the array from a ground mounted inverter, there is still potential in the conductors leading from the roof to the inverter. If those conductors are shorted together - due to either a fireman’s actions or the fire itself - there is the potential for significant arcing and possibly even electrocution.
Of course, one way to reduce that risk is through the use of microinverters or AC modules. With a microinverter, the only conductor runs are AC which can be safely switched off from the ground meaning that any conductors coming from the roof to the ground will be safe. The individual solar modules can still produce power, but there are no strings to slice into or suddenly short to create a dangerous condition on the roof. While microinverter systems are not generally considered on systems of this size, Enphase recently announced the use of their products on a 2.3 MW commercial array - possibly larger than this one.
Which begs the question - would that have mattered here? Maybe, maybe not. The question really is a function of how well would the local fire department understand the difference? When we talk with local fire inspectors, they are always appreciative of the added safety to be found with microinverter systems but how well does the inspector’s understanding extend to the fire crews reporting to that fire? Would they have trusted that the claimed safety was real and moved more aggressively to fight the fire on the roof? Or would they have elected to play it safe?
The solar industry can work to develop safer products - which microinverters surely are - but that won’t matter if local fire crews aren’t educated as to how best to fight these fires. Interestingly, while local codes require solar installers to provide all sorts of largely useless signage on our arrays - for example, specifying the nominal AC voltage and current as if that would make the least difference to anyone - there is no requirement to indicate whether the type of inverter being used. Absent such signage, how would a local fire crew know what they were facing?
Maybe our friends at Enphase can design a placard to attach to our AC disconnect switches that advises the local fire department that throwing that one switch renders the conductors coming down from the roof safe.
So much of what we must do in the solar industry is education - this is perhaps one area where we need to improve our efforts.
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