Aug 242017
 
mobile-tiny-house-truck_first-solar-panel-on-the-back

The prior mobile tiny house living update ended with dependent or autonomous? I clearly seek being autonomous. There are two basic needs to be autonomous in your dwelling, regardless whether it is mobile or stationary: energy and water.

When embarking on my mobile tiny house journey with Miguel, initially we had neither. Really, neither, for six months. Only the last 6 weeks of that, with the winter in full swing and freezing temperatures in the north of the country where the truck was for its yearly inspection, I finally accepted the offer of who have become friends to run a cable roll from their factory's mains into my tiny house "so that you have heating" (I had an oil radiator that runs on electricity, now sold on a flea market). Before that, I tried to keep Miguel warm as well, like this:

cold dog, warm blanketcold dog, warm blanket

cold dog, warm blanketcold dog, warm blanket

You see that both his thick Westpaw nap mat and the normal Westpaw blanket had to be underneath him because remember the house was off the truck, standing right on freezing ground with just its plywood basement floor. Hence to cover him from above I sacrificed a bedsheet.

To my surprise, other than having to live during winter at inside 3C / 37F in a yet UNinsulated house :roll: I neither much missed energy nor running water: Getting used to having no electricity is easy, 6l potable water bottles I buy for next to nothing, and places to shower are abound (municipal pools etc) and once we were back in the Algarve we went swimming in the ocean daily, and no, it wasn't too cold in the midst of winter.

But no energy also means no computer and no internet, no fridge etc. So I am overly happy to now have (first) energy autonomy.

Free Energy - thanks to our sun!

I still have moments where I am just amazed, where it feels like a miracle: the sun spending warmth and electricity. No wonder it seemed like everyone else already had solar panels! :mrgreen:

All tiny houses, motorhomes, RVs, caravans, and campers seem to have their solar panels on the roof. When I started to think about how to build my own tiny house, I knew that on the roof wouldn't work for me:

  • Being a mobile tiny house carried on a truck, the roof is high up: 3.50m or 11.5ft
  • I no longer can easily climb up that high onto the roof to keep the panels clean
  • In winter the sun is so low in the sky that flat roof panels have minimal solar yield
  • And you cannot tilt roof panels on a mobile house truck that is that high (bridges, trees)
  • Roof panels not only get rapidly dirty (dried rain drops are enough) but even collect debris (bird poop etc) that is hard to scratch off
  • Also, I am not the kind of person who blindly follows what others do. :mrgreen:

No seriously, you see there are plenty of reasons that speak against roof panels. In fact, the only reason I could think of that speaks in favor of roof panels is one particular kind of safety: it protects from vandalism. But currently being in Portugal - undoubtedly the safest country I have ever been to - vandalism is not on the top of my mind. Besides, the tiny house being on the truck and the solar panels hanging down from the top-most steel beam, they are still so high up that average height people can only reach the bottom of the panels.

And so, this is exactly how I was going to fit the panels. But first I had to plan the electrics too:

Solar panel connectivity design

I started out with one panel, Miguel watching me closely that I fit the panel properly. When I had the funds I added two more panels:

mobile tiny house solar panel positionmobile tiny house solar panel position
The panels are all of the same type, this is important for maximum solar yield. All around the panels I put aluminum beams:

  • to protect the panels from any shocks to any edge
  • and to allow the panels to be tilted to the sun easily.

solar panel flexible positioningTherefore I drilled a row of holes in the beams left and right of each panel, and fitted an alu strip left and right on the back of the panels. I got round alu rods that during travel I directly store in the alu strip holes behind the panels, and that I position in the right holes when I feel we need targeted sun exposure.

  • In the winter, when the sun is low in the sky, the panels hanging down vertically is perfect, and that's the time when we need every sun rays we can get: Fridge is using much less power, but heating will use most (we will get to both points later).
  • In the summer, when the sun is high in the sky and the fridge compressor has to turn on a lot to try to maintain the desirable fridge temperature (under 5C / 41F for food safety), I do tilt the panels often (with the alu rods) to quickly recharge the batteries. Because that's best for battery health, more on this later.
solar panel sufficient tilt
  • In fact, I recorded that in mid summer and around noon the extra solar yield from directing the panels towards the sun maxes out at 2.5 times the solar yield than when the panels hang down on the rear wall.
  • Conversely in mid winter, even around noon when the sun is highest, tilting the panels didn't improve the solar yield at all, so low the sun is in winter.
  • Hence why I usually have the panels just hanging down vertically from the wall, except in summer.
  • In late spring and early autumn I tilt the panels towards the sun only when I seek maximum solar yield.
  • However, I am not stretching out for this and not getting the ladder out: what you see on the photo is already the maximum angle I tilt the panels.

So there we've discussed solar panel angle, solar yield, and convenience. As for dirty panels: in the summer, even though I tilted the panels no more than you see above, I promptly got bird droppings on a panel twice (very acidic, I don't want to leave that on there for long), and generally the panels grew a dirt layer much quicker.

Keeping solar panels cleanSo yes, in every aspect I am very glad that from the start I had decided against roof panels. With my panels' vertical position, dirt washes off itself when it rains and every other month at most I take the (plant) spray bottle with a mix of half vinegar half water, douse the panels, and drag it all down with the squeegee. Easier is not possible. :grin:

Be aware that on a truck and a trailer alike, the rear tires aren't near the end, so there's nothing splashing back up like with a car. In fact I only had to thoroughly clean the panels after a 650km journey up north that included lots of unpaved roads through the mountains.

What if you have a tiny house, motorhome, RV, caravan, or camper, and no space on the rear wall, say because there's a rack with bicycles or whatever, could the panels then go on a side wall?

I'd strongly suggest NO. In that case accept the inconvenience and inefficiency of having the panels on the roof: Even if your overall vehicle width is within the legal limit, that's just the legal limit. Within just the first year I've already had plenty of situations where I was glad that my tiny house is not a centimeter wider than 250 (8.2ft), so close it got on a road!

So, rear is best, else roof is safe.

Lastly, here you see another benefit of the alu beams enclosing the solar panels: short alu scrap pieces clamp the panels against the wall so that no road bump makes them swing out. Also, I put a small compass in the cockpit to see even in the dark which orientation is best to park up:

Keeping solar panels safecompass for solar orientation

Next mobile tiny house living update is here

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