Two Letters Re: Protection from EMP Effects for Photovoltaic Panels and Communication Gear

Tuesday, Jun 2, 2009

Jim,

I'm not very certain Solar Panels or photovoltaic (PV) Modules if you prefer) are up to surviving electromagnetic pulse (EMP). Solar Panel manufacture is akin to basically creating large scale photosensitive semiconductors and few manufacturers will quote even static electricity resistance, much less EMP resistance. Additionally, most PV modules have bypass diodes to protect cells. Some designs put these diodes in the junction boxes, while others incorporate them more integrally in the PV assembly.
Obviously the controllers are at great risk, but the modules themselves are not free from risk.

About the only references to PV and EMP you can find are discussions concerning space deployed PV Modules being at risk to solar flares, which have many characteristics of an EMP event.

I just made some queries with contacts at University of Manchester and Michigan Tech. They told me that there that almost no EMP test results have been released to public domain, but that their Aerospace departments feel that PV Arrays are vulnerable at the junction level as well as the wiring diode matrix and controller levels.

The [PV-powered] satellite literature repeats the observation that even a minor solar flare can wipe years to decades off of the life of a PV array and a full coronal mass ejection (CME) will take the array out. Though an EMP [cascade waveform] is not exactly the same radiation, the corollary is there.

Several of the Disaster Shelter Builders state that PV Panels are at risk in EMP and include shielded storage for "after the event panels." I wonder whether that is marketing hype or good science? For now, this is the best that I can find. - Steve W.

 

Mr. Rawles,
There is a very detailed 4-part article about EMP protection for Amateur Radio equipment. It's a study that was done by the ARRL in the mid 1980s. Product model numbers and such have changed, but the basic concepts haven't. If you want to just skip to the recommendations, go to "Part 4 of "Electromagnetic Pulse and the Radio Amateur".

In a nutshell, they make the following recommendations:
1. Your equipment will not survive a direct lightning hit no matter how well protected. EMP or near-misses can be protected against.
2. Install a high-quality surge protector on all AC power cords. You'll need to shop around to find one with the highest possible rating.
3. Install coax surge protectors (available from most ham radio suppliers) within 6 feet of the radio equipment to be protected.
4. Install a grounding antenna switch and keep the antennas grounded when not in use. (Note: antenna switches are often used when folks have multiple radios/antennas, such as a CB and ham radio or a 2 Meter VHF radio and a scanner. Make grounding the antennas part of your checklist when shutting down the station after use.
5. Get a piece of Copper plate or thick sheet metal, install it on the wall or workbench your equipment is on, and attach all equipment grounds and protection devices to this. Install a good Earth ground, per their guide. This basically consists of 2 or more standard electrical grounding rods connected with #6 solid Copper wire that is buried. I've found that the electrical panel bonding lugs sold in [building] contractor stores work great for this.

Finally, the book Nuclear War Survival Skills by Cresson H. Kearney [Available for free download] states that equipment such as hand held radios with short antennas (less than 14") should be okay against EMP. Grid connected electronics would be more vulnerable, and stuff with long antennas worse still.
Here are some quick links to EMP protection devices:

Solar Panel charge controller protection.

Coax lightning protection (manufacturer)

Cheers, - JN-EMT


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