# EMP hardening of solar panels



## sideKahr (Oct 15, 2014)

I came across this report published recently (November 2016) by the Swiss Federal Government. It is a technical assessment of the vulnerability of solar panels to EMP, reports of real world testing of panels, and how to protect them.

http://ece-research.unm.edu/summa/notes/SDAN/SDAN0047.pdf

There is good news and bad news:

_"It was shown that photovoltaic cells and modules are much more robust against [EMP] threats than commonly expected..."

"...Extensive tests have shown that shielding of PV-modules is definitively not required. However, two things are important: to protect the bypass-diodes in the modules from reverse surge currents, and to protect the subsequent electronics, such as inverter, battery storage and control electronics..."

"...it is concluded that some protection against conducted disturbances in the cabling is required to avoid surge currents in reverse direction of the diodes."_

- edit - The bypass diodes used in the tests were all Schottky type diodes; new technology active bypass diodes with ultra low forward voltages weren't invented yet at the time of the tests. New PV panels may be even MORE resistant to EMP than represented here. -sideKahr


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## jim-henscheli (May 4, 2015)

I wonder if I could just turn my entire boat into a faraday cage?


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## sideKahr (Oct 15, 2014)

jim-henscheli said:


> I wonder if I could just turn my entire boat into a faraday cage?


Think bigger: how about the entire country. "Shields up," Capt Kirk had it going on.


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## paraquack (Mar 1, 2013)

Thanks for the info!
Jim, get 2 aluminum boats and put 1 upside down on the other and use aluminum or copper tape to seal the gap.


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## jim-henscheli (May 4, 2015)

Seriously though, if I laid screen then foam, could it work?


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## sideKahr (Oct 15, 2014)

jim-henscheli said:


> Seriously though, if I laid screen then foam, could it work?


It's a job for experts. Every tiny hole, wire grommet, or pipe chase is an entry point. In fact, a door crack would act as a slot antenna and intensify the pulse inside.


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## 8301 (Nov 29, 2014)

Good article, I may do some research about adding TVS diodes on the panel strings. 

I keep spare schlocky diodes but my panels have the diodes encased in silicone so it would be tricky to replace them without ruining the panel. I also have 4 Midnight Solar surge protectors inline, 2 on the DC side and 2 on the AC side (rated to 115,000 amps max surge) which the article says will help reduce reverse current.


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## azrancher (Dec 14, 2014)

Y'all know reverse current protection after EMP is a simple solution don't ya... we use diodes now because we're lazy, after the SHTF, you find the diodes in your panel, either check them or remove them and put a jumper in it's place.

Then every late afternoon, disconnect the panels, every morning reconnect the panels.

What you need to have on hand is a disconnect switch capable of switching in and out the panels, and that depends on how all your panels are interconnected. You will also need to know where the blocking diode is on the panel, probably in the connection box on the back of the panel.

You need to have spare converters/inverters stored away in your EMP garbage can.

*Rancher*


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## Redneck (Oct 6, 2016)

sideKahr said:


> "...Extensive tests have shown that shielding of PV-modules is definitively not required. However, two things are important: to protect the bypass-diodes in the modules from reverse surge currents, and to protect the subsequent electronics, such as inverter, battery storage and control electronics..."
> 
> "...it is concluded that some protection against conducted disturbances in the cabling is required to avoid surge currents in reverse direction of the diodes."[/I]


So does the surge in reverse direction only come from the cabling in an installed system? My panels are in storage, to be used to power a well pump & a couple of solar generators, and curious about this reverse current. The diagram showing protection, plus his discussion leads me to think stored panels would be safe.


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## sideKahr (Oct 15, 2014)

******* said:


> So does the surge in reverse direction only come from the cabling in an installed system? My panels are in storage...


That's the gist of what I get. It makes sense, the unshielded cable acting as an antenna to direct current through the diodes in reverse bias.

But I wouldn't unwrap your stored panels (I saw the pictures); the report may be wrong.


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## Redneck (Oct 6, 2016)

sideKahr said:


> But I wouldn't unwrap your stored panels (I saw the pictures); the report may be wrong.


Nope, won't do that but would be nice for all panels to survive an EMP.


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