Rooftop solar electricity
Solar-powered 12-volt off-grid house
One of the first jobs I took back in the 1980’s was in what is euphemistically called a developing country. I spent about half of my time in a provincial capital at the university. The rest of the time was spent in a very remote location beyond the fringe of most infrastructure. It was my home off and on for the next twenty years. I had a motorcycle for transportation. Kerosene was available for cooking and for a small refrigerator that I was able to have shipped in.
When my family joined me, I built an off-grid house that was a step above the surrounding bamboo and thatch structures. Local people did the framing and masonry, but they weren’t up to the tasks of plumbing and electricity that I wanted. I did that part myself—for better or for worse.
- Rainwater Plumbing: Designing, Building & Owning my House
Living far from public utilities, I designed and built my house to collect rain water, store it in a cistern and gravity-feed the few basic plumbing fixtures that we had. Click for story and photos.
My 12-volt electric system
I designed the electric system around 12-volts, cognizant that many automotive and RV products are available at that voltage. Solar panels charged heavy-duty marine batteries through a charge controller. The batteries operated laptop computers, fluorescent lights and fans—all 12-volt items that seem crude thirty years later!
I also tried a 120 VAC inverter, but that didn’t work out so well. The inverter supplied square-wave alternating current, while the computer printer I’d hoped to use required sine-wave current. This sort of compatibility problem is less likely today, but illustrates the need to carefully cross-check design specifications.
Complete kit; just add batteries
The solar panel array
The panels I used were approximately four feet long and one foot wide. I arranged three of these in a wooden frame that could rock back and forth to track the sun’s daily path. Then I rigged a rope and pulley system so that about three times a day I would go out and re-aim it to be more perpendicular to the sun’s rays.
I wired the solar panels in parallel and connected them through a charge controller that was custom-built, since nothing like it was available back then. It prevented the batteries from overcharging, a standard feature now with all modern charge controllers. It also kept them from discharging through the panels at night when the solar panels didn’t generate any current.
I had bought the batteries empty (of acid) and filled them on location, which made them even heavier. I built a small wheeled dolly so that it was easier to pull them out for periodic service. Every month I would check the fluid level and add distilled water if necessary. I vented the cabinet with screen to prevent build-up of explosive gases or heat.
The "utility room"
Deep-cycle marine batteries
I used two very heavy 12-volt batteries that were designed for marine use. Deep-cycle batteries have thicker lead plates that enable them to repeatedly withstand being cycled to a lower state of discharge than ordinary automotive batteries can tolerate.
My charge controller displayed voltage and current, but did not directly measure the state of charge. For that I had to rely on a couple of tables, depending on ambient temperature readings, which never varied much anyway near the equator.
The screened battery compartment
Batteries on a roll-out service cart
The batteries were wired in parallel, just as the solar panels were. Since 12-volt systems have a greater current loss than do systems at higher voltages, I tried to limit losses where possible. I ran relatively heavy 10-gauge solid copper wire down the centerline of the L-shaped house and located the batteries close to the mid-point.
I positioned my power outlets directly below the centerline of the house, rather than on exterior walls. They were also only halfway to the floor, since nothing I wanted to operate needed to connect any lower than that. Dropping down to the outlets, I used lamp cord--about 14-gauge-- which is stranded and was therefore flexible enough to make some of the bends more neatly.
Finally, I soldered all connections instead of using wire nuts. One advantage this had was that I had an uncut main conductor running the entire length of the house. Soldering in this environment, of course required a 12-volt soldering iron.
12-volt low-powered accessories
I installed naked 10-watt fluorescent lights on the ceiling in each room, except two that were large enough to warrant 20-watt (double length) lights. The first was the living room, where we would read, do home-schooling and correspondence. The second was a combination kitchen and dining area, where we carefully positioned the light between the two so that bugs falling from the lights (!) missed both the kitchen counter and the dining table. Our lighting was dim, but a lot brighter than the kerosene lamps used in the rest of the neighborhood.
Laptop computer in 1983
We had two 6-inch fans, a welcome luxury since we were close to the equator. They seem so puny, but they consumed precious power. One was portable and the other mounted in the office. When battery current was running low, these were the first place to conserve.
I used a 12-volt single-sideband (SSB) radio for communication with the outside world.
Finally, but most importantly, we had one or more laptop computers. That might seem like a no-brainer, but remember that thirty years ago, IBM hadn’t even come out yet with its PC! The first computer we had that actually worked in the village was a Sharp PC-5000 with an 8-line LCD screen and an internal thermal printer.
Roof-mounted solar panels
A couple of my solar panels developed leaks, permitting inside condensation and mold growth. In one case, the leak was caused by strain from a wire leading to the terminal post on the backside of the solar panel. I would recommend that be reinforced with an extra fillet of RTV sealant.
I think one of the corner joints leaked as well. The panels were constructed of extruded aluminum and glass, screwed together and sealed with RTV sealant. That should theoretically last forever, but practice doesn’t always follow theory.
I was remote enough that when something didn’t work, I just had to make it work. There was no such thing as sending something back.
When public electricity finally reached all the way to our village, we were 1,000 meters off the main road. There weren’t enough people down our path to warrant the expense of setting the power poles. I kept asking and finally, in a fit of disgust, offered to subsidize it by US$1,000. Stubborn they were! So a couple years later, they finally ran a line down my way and were trying to enroll subscribers. Me? No way. Stubborn I was!
Victoria Lynn from Arkansas, USA on February 18, 2013:
Wow, that's impressive. I'm always impressed by those who can do these things themselves. Good for you! I enjoyed reading your story. Very cool. Voted up, awesome, useful, and interesting.
Peg Cole from Northeast of Dallas, Texas on February 10, 2013:
Living off the grid is a great way to go green if you're willing to sacrifice time, space and money to implementing the structure necessary. A friend is living on some remote acreage in Oklahoma. He tells us there are certainly challenges and sacrifices to be made at this point in time, like your description of maintenance for the batteries and rotating the solar panels to optimize the sun. Still, it is a beginning and I believe it will ultimately be the way to go. Enjoyable read.
LongTimeMother from Australia on February 09, 2013:
Wow, Howard, I am impressed. I live off the grid with a solar system but I am not restricted to 12v appliances, I have a lot more battery storage and there's a solar expert living around the corner from me. To have achieved all of this so long ago working alone with no professional support is quite remarkable. Voting up!