Rooftop Solar (and RFI?)

[Jay Francis]

Hi all,

I’m looking into rooftop solar for my house.  I’m wondering if any club members have rooftop solar and do/do not have ham radio RFI issues.  Years ago I heard horror stories about RFI from micro-inverters, not sure if this is still the case.

Thanks!

Jay, KA1PQK

 

 

[Jay Francis]

Some reference info:

http://ka7oei.blogspot.com/2016/03/the-solar-saga-part-1-avoiding.html

And, there’s a good article in the April 2016 issue of QST.

The big question is… are things better in 2021?

–Jay

 

[Burns FISHER]

I have rooftop solar, and it gives me no problems, but my situation may be different.  First, the panels are on my garage (faces south) which is on the far end of the house from my shack.  Second, the actual Enphase box and the breaker box where it is all tied in is on the opposite side near my shack.  Thus having a string inverter in the Enphase box seemed a bit risky.  The solar company had had experience with this sort of thing and so we DID use microinverters on the panels (longest distance from the shack) and they pre-installed ferrite chokes on each inverter.

I have no problem.  But the other thing to say is that I do mostly satellite work, so I am on the 2m and 70cm bands exclusively.  Not sure where the majority of the interference usually happens.

BTW, search around for Bob Bruninga on the web.  (The inventor of APRS.) He is also interested in solar and has a lot to say about it.

[Jay Francis]

Thanks Burns.  Can you say who you used for the install?  So far the folks who have come out to my house didn’t seem to have experience with RFI mitigation (or… didn’t recall doing an install at a ham radio operator’s QTH).

–Jay

[Burns FISHER]

Certainly Jay:  ReVision Energy.  They have offices and installations in at least Maine, NH, and Mass (https://www.revisionenergy.com/).  They are not the cheapest, but they were very helpful and not pushy.  We have a number of friends who have also been happy with them.

As I recall, I brought up the RFI question when we first talked to them, and the first person was not familiar ham radio.  However, he did some checking around and determined that they had at least one other installation at a ham’s QTH, and offered me a chance to talk to him.  In any case, their solution was as I said above, and that seemed to work well for both the other customer and me.  But again, my distances may be more the fix than the actual chokes.

73, Burns WB1FJ

[Jay Francis]

Great – Revision is one of the companies I’m talking with, and I had asked for a ham referral if they had one.  Let’s see if your name comes up 🙂

Was part of you decision to use the Enphase micro inverter on each panel solution instead of a single string inverter with optimizers on each panel due to potential RFI / mitigation strategies?  Or was it more due to the configuration of your system (i.e. lots of panels with various levels of shading)?

At first I thought the optimizers could be less of an RFI issue, but the more internet browsing I do has me going in the micro inverter direction.

Thanks for the info – besides making sure solar is cost effective for my situation, the next concern is that it doesn’t ruin my hobby.

–Jay

[Nashua Area Radio Society]

Jay,

Another option to consider for solar is self-installation.  I pulled the permits and set everything up on my roof with the help of this organization: https://www.harei.org

They are a local group of enthusiasts who enjoy working with solar and have a lot of experience with the ‘tricks of the trade’.  Bonus points are that their free labor drastically helped improved my ROI.

My hardware is Panasonic PV panels w/ Enphase micros.  I purchased them from: https://www.altestore.com which is located just South of us in Boxborough, MA. My configuration is similar to Burns (located on the opposite side of the house from my shack location), but from all accounts, there is no RFI from the PV panels/inverters.

I hope that this helps.

 

Ryan

 

[Burns FISHER]

Jay, as I recall ReVision tended to use single-string inverters in general.  That would have been fine on my roof which is unshaded and all pointing in the same direction.   However, apparently (per Bob Bruninga) *optimizers* are even worse for RFI than microinverters (I think they are DC-to-DC converters).  But essentially the change to microinverters was all for RFI–largely because it kept all the conversion at a distance and did not have optimizers.  (I probably would not have needed an optimizer since my panels are all so consistently pointed and not shaded, but they don’t do it that way anymore).

[Jay Francis]

Ryan:  Thanks for the pointer to harei and your setup info.  Do you operate HF?

Burns: Yes, ReVision still does lean towards the optimizers instead of micro inverters.  It will be interesting to see what they propose.  For string systems, optimizers (of some sort) are required now by code to provide a quick shutdown in the case of an emergency.

I’ve been poking around Bob Bruninga’s site and suspect some of what I’m reading is outdated (? I hope ?).  i.e. “My 10 kW array generates modest RFI every XX Khz across the HF spectrum which sounds like a 60 Hz buzz. Fortunatly, I do not currently operate HF, and fortunately, my AC disconnect is right outside my kitchen door so if I needed to , I can kill all the inverters at once for daytime operation, or I can simply operate at night.”

–Jay

[Burns FISHER]

Jay, you might send an email to Bob.  He is very interested in both solar and radio and will likely respond.  I think he also has a relatively recent ARRL book on power systems.

Re the optimizers and cutoff:  Oh, I see. interesting.  I was wondering why they did that.   I guess the micros perform the same function.

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