A few scratches on the hands this weekend from spending a couple of days rewiring the “aisle 3” solar array. There’s some experimenting going on, some changes to system design, and a couple of useful hints to share.
Ham radio and drone-lifted ham antenna adventures are on hold this week as other, more pressing work of Life has come to the foreground. Oh, and the #22 AWG wire was mis-shipped, so maybe that will show up one of these days.
Solar Panel Aging
People don’t spend enough time on maintenance. I am as guilty as anyone, I suppose. But the best reason to do maintenance is time and money. Nowhere is this any more evident than in solar panels and related “balance of system” components.
The maintenance problem begins when you do your installation. Long-time readers will remember that when we went with our first rack of panels (2008_ we cobbled up a simple array mounting design out of readily available materials. On a tree farm, those are T-post (of the sort used for fencing) and rebar (reinforcing bar) used for all kinds of neat projects.
The basic rack around here consists of lower case “h” components. Two hunks of T-post “nailed into the dirt” with a post driver. Then a horizontal piece between them to maintain spacing. These lower case “h” units are then spaced out 2-3 feet apart and mounting rails are constructed of 5/8 rebar, which was the largest we could get (inexpensively) at the time. And honestly, it’s been a great design.
There is one problem which developed late last year on the first set of panels deployed. The “normal” top of T-post welds are supposed to be aging like this one:
However, for reasons unknown to me (though bad workmanship on my part and a poor weld is obvious now) one of the welds broke loose. As a result, the panel dropped onto the T-post, so an emergency repair – in the form of a small C-clamp – was employed to spread the weight of the panel a bit.
You can see, looking at the hinge on the left (this rebar rail allows panels to have a low winter angle and be propped up into a summer angle) the drop was significant. That’s one of the repairs finally coming off the checklist (List Of Things to Do or LOSTD).
Not to “lay no bummers on you” but it’s looking to us like the odds are rising that somewhere this year, nuclear weapons may “come out of the closet.” And when they do, the odds then quickly rise that America will experience the bitter results of an Electro-Magnetic Pulse (EMP) attack.
Like fire prevention, the time to “do something” is not when the house is burning, but to design more robust systems well in advance of needing them. Hence, in this article and more to come on hydroponics, our focus will be on making key changes to our personal infrastructure in the name of enhanced resilience.
Two major changes related to our “aisle 3” work this week were changing out the cheapo automotive battery switches used for the original panel disconnect while also updating our charge controller strategy. Let me show you the dual 100-amp panel disconnect switch that went in first.
Two reasons for putting this in, the first of which is metal enclosures are a good thing. The second is it gave me a ground bar to which additional RF system grounding can be added.
This is an especially vexing area – this matter of “grounding” because just “connecting to Earth” isn’t the point, in most cases. While in “earthing” (the Brits use the term) is what you are after for lightning protections, in EMP you are more concerned with the low-frequency radio pulse. Most EMP energy is under 10 MHz. The NEC (last time I looked) was very specific about single point system grounds for AC house wiring.
Theory seems to go that if you have two AC grounds, say one at either end of the house, then if you had a neutral (white wire) failure, and at the same time the green ground wire opened, THEN you could have a “hot ground” which would be dangerous. Only if the power was still on…but I don’t write the Code. I just try to see what they’re getting at.
RF (the radio frequency ground) is designed to dissipate radio noise pulses and the best way to do that is to tie multiple ground radials (each >70-feet) out every 10-degrees of the compass from a vertical antenna, for example. Or, in the case of a horizontal antenna, you would have parallel RF ground wires either buried, or above ground as an NVIS (near vertical incident skywave passive ground reflector) depending on the take-off angle planned for your antenna design.
Anyway, I previously had a small metal box and now I have this dual 100-amp disconnect marvel wired in.
Which gets us to the second design change. I decided to go with split load simple (analog) PWM controllers instead of less robust (to EMP by my reasoning) MPPT (maximum power point tracking) microprocessor-controlled charge controllers.
To effect this change, a pair of (from the Faraday garbage can) out came a couple of NIB Trace C-40 charge controllers. Since my “aisle 3” of panels are used and will “only” put out about 1,900-watts, being able to handle 80-amps at 28-volts will be just fine. Oh, and cheap.
This is not a formal engineering study, merely a “parts count calculation.” There are a lot fewer things to go wrong in one of the C40’s compared with the MPPT-type Isome call them MPTP). They are smaller and (to simple me) the lines of code are a risk. Because in the event of an actual EMP event, seems logical you’d be depending on the integrity of a flash-ROM part and, er, not too keen on that in a pulsed world. Cautious Luddite, that’s me.
A Useful Tip or Two
Working with the wire on this project has been a trip. It’s 3-strands of #4 plus a #6 ground wire. All in one plastic direct burial casing that’s a decade and a half old.
Which means? This stuff is a 24-karat bitch to work with. So here’s the two useful tips:
Tip #1 Old Hard Wire Cutting. I had purchased a pretty good slug of this wire and have been using it for all kinds of heavy wire projects around here. For example, a run from the ham radio tower over to the radio grounding field – 40-50 foot run my consigliere helped me dig in over Thanksgiving.
When I cut that (miserable old hard) wire then, I used a 3-foot bolt cutter. It worked, but it’s not easy and at 75, by-God easy counts for a lot.
The new and improved cutting? I put a hacksaw/metal-cutting blade in the battery powered portable zip saw (this one). You’ll expend a little effort holding the wire from moving, but compared to working overhead with heavy bolt cutters? Yep, this is my favorite trick.
Tip #2 Old Hard Wire Stripping
The main part of this tip is “Heat the wire before stripping.”
Done in the shop, at the bench, a simple hand-held plug-in heat gun on high for half a minute will turn the insulation extremely soft and cooperative.
Outside, where presumably you have less risk of fire, a small Bernz-o-matic type propane torch will work great.
With a little focus, you can do pretty good work if you just take your time.
Two for the Road
It is probably total overkill, at least when just turning up the revised and improved solar system, but I did take the time to put on good copper battery fittings and then soldered them.
Most people don’t know this, but annealed copper will continue to flow over long periods of time. I have heard from DC power electricians that you can pick up sometimes 10-percent, or more, from old panels by simply clearing up the wiring issues. Compression fittings are fine (and expedient as hell) but in the long run they need to be serviced.
I’m also a fan of having an electrician (if you aren’t comfortable doing the job yourself) go through your entire home’s electrical system every 10-years, or so. You’d be shocked (bad pun, sorry) at how many connections will give an eighth of a turn (and more) when properly snugged up to new specs.
The second thing to keep in mind is the use of heat shrink tubing in an assortment of colors. You can make some mighty professional looking wiring with a few tie-wraps to add some neatness to the job, along with bands to inform anyone who comes along later what the various wires are for. Red is for DC hot, black is DC ground. Green are system grounds, and blue is the battery plus in my system. Knowing this, next time I go through and do solar wiring maintenance (I will be 85 then, lol) having strict adherence to a color-coding scheme in life will be very useful.
In the military (and not many people know this) wire colors are very indicative of what is being carried.
This attention to detail is the kind of “little thing” that separates a serious maker from a kluger. And you don’t want to be one of those, now, do you?
Now, go bang something,