Trailer Hut Solar — Completo

Post by blogger | December 27, 2011      

Solar electricity is like powder snow: when it’s there, you smile; when it’s not, you just work on the gear and hope for the best. Thing is, in Colorado we’re blessed (or not, considering this winter’s lack of snow) with mass quantities of clear crisp blue sky that cooks solar panels like you’re smoking ribs at a pit barbeque. So you get those electron buckets facing the sun, hook up the copper, and that green tingle runs up and down your leg because you know you’re doing the right thing. The greenie vibe was strong for me a few days ago, when we finally hit the big red switch and enjoyed being off the grid but under the lights. Check it all out, our Christmas present to WildSnow Field HQ! (And right here up front, let me thank Steve at Sunsense for his help as a consultant. I think he’s afraid to check out the owner-built system in person as it might burn up his VOM, but I think I can lure him up there once the skiing gets good and I assure him I’ll provide eye protection.)

Solar PV power at the tiny house portahut cabin.

From the sun, to electric light! Sadly, I didn't experience the mythical green O when I flipped the switch, but I did get some tingles thinking of all the AA batteries we'd not be buying for our headlamps. Mainly, it is awesome having bright available light for cooking and that sort of thing. Most of our lighting uses basic Edison type fixtures, only we'll equip them with LED or CF bulbs to make sure we're well within our capacity for use several nights in a row.

Blue Sky charge controller and IPN Remote for backcountry skiing cabin.

Blue Sky charge controller and IPN Remote. The remote readout is optional but without it you'd be in constant mystery as to your system status. A charge controller of some sort is mandatory if you have much panel wattage. This Blue Sky model provides several modes (depending on setup) and turns off the system automatically if battery voltage gets too low to prevent battery damage.

Solar panels Kyocera KD 1356X-LPU

We installed our pair of Kyocera KD 1356X-LPU 135 watt panels on a temporary mast (attached to stump) and ran feed cable to trailer hut. We could mount the panels on the structure, but I was concerned about wind vibration and noise as due to orientation of the structure the panels would have to be on a mast and rack protruding from the roof. When we move the trailer, the panels are easy to take down and re-position -- and we could easily mount them on the trailer roof or walls.

At the rear of the portahut (front of trailer), battery vent and feed.

At the rear of the portahut (front of trailer), battery vent is the black stack, feed from panels heads up through conduit to breaker box where one 30 amp breaker provides panel disconnect, while another protects the whole interior system (we're small enough to only need one breaker for the residential load). The batteries also have a 30 amp blade fuse near the positive terminal connection, and I wired in a few 15 amp fuses near the interior accessory outlets. It wasn't intentional, but I already blew the battery fuse once, so at least I know it works. No, I am not an electrician.

Interior conduit for PV backcountry cabin.

To save money and time I was originally planning on wiring the system with #10 romex on the interior surface, no conduit. But once I got going that just seemed too trashy, not to mention a bit on the funky side in terms of safety. So I used flex conduit for nearly everything but a few low amperage branches that are well protected by fuses and still covered with automotive wire loom.

Solar PV 12v outlets for cabin.

I provided a few 12v accessory outlets made with automotive 'lighter' sockets from NAPA. These are wired through a nearby 15 amp blade fuse, and include a nice on-off switch and small LED so you know when they're powered up. The idea with how all this runs is that we're mostly using the same accessories and systems we'd use in our truck or RV camper. Thus, we save money by sharing accessories between our different locations, as well as using stuff we're used to hacking together, such as automotive computer chargers, E-reader chargers, and that sort of thing.

Interior, the day after Christmas.

Interior, the day after Christmas. Battery box is behind sheet metal to right. Cushion is usually not exposed to stove heat. Everything is carefully designed for wood stove 'mobile home' clearance distances. Battery box actually stays too cool. Christmas tree lights are hooked up to a battery pack because I didn't have an extension cord, but they'd work fine off our PV system (I used a small inverter we had kicking around).

Solar electricity for small  backcountry skiing cabin.

As pictured in our previous post about doing this PV work, here are the two Trojan L16H model batteries in the box, 125 lbs each, rated at 420 amp hours each. Battery box is ventilated to daylight, sealed from living space interior, and lined with non flamable materials.

Just for fun, I hooked up the trailer tail lights for porch lights.

Just for fun I hooked up the trailer tail lights for porch lights with an interior switch. The actual trailer registration plate is under the skis to the left, license plate wall is decorative -- not sure what the County Mountie will think of those if we're hauling the portahut to a new location -- we'll probably have to cover them. And yes Virginia, that's a small deck that is totally NOT attached to the trailer.


16 Responses to “Trailer Hut Solar — Completo”

  1. Steve December 27th, 2011 8:35 am


    Have you thought of making these huts for others? Now that you have it down I think you should go for a mail order kit or “build and ship.” I could see you selling a few of these…

  2. Lou December 27th, 2011 8:45 am

    Jeez, now you want me to go for career #642 !? Mercy!

  3. chris blatter aka silvertonslim December 27th, 2011 9:32 am

    That system looks to be well thought out and well installed. It ought to last a long time….nice job Lou.

  4. Lou December 27th, 2011 10:04 am

    Slim, thanks, it seems to be working. Not much sun these days so it looks like we’d drain it down with continuous use instead of being away from the system for a few days at a time letting it catch up. But once we’re back to Late January sun arc we should be ok for as much use as we’d want. Amazing to watch the sun with some purpose and observe how the arc decreases so much during the winter solstice.

  5. RyanB December 27th, 2011 10:50 am

    I don’t think there is a commercially available option yet but a stirling engine based generator in the wood stove or chimney might supplement the solar panels nicely during times when there isn’t a lot of sun and you are spending a lot of time inside with the fire going.

  6. Forest December 27th, 2011 11:09 am

    Nice setup, Lou! Looks like you’ve got a fun and convenient winter to look forward to. I lug my little 16′ travel trailer around in the winter but it’s awfully fragile compared to your hut and no PV (yet).

  7. carl December 27th, 2011 1:01 pm


    I am very impressed by this project.

    Was wondering though what you would estimate the completed weight at?

    Is it within the load limits of the trailer or will you need to slim down to move the thing?


  8. Jeff December 27th, 2011 5:01 pm

    Lou – Nice to see you briefly last Thursday afternoon. Kim and I had a meeting to get to so we weren’t able to stop by the cabin after – we would have loved to! I’ll be back in town, or in Marble this Friday, and around for the week. Be fun to do some skiing if you’re around. We’d still like to check out the cabin! Hope your Christmas was great – Jeff (now from Durango)

  9. Lou December 27th, 2011 6:54 pm

    Hey Carl, I calced out the weight to be around 7,000 lbs which is easily within the capacity of the trailer, which is a double axle car hauler. I did this last summer and forgot what the trailer nameplate said, am just going from memory. Could easily trim weight, the whole thing is screwed together. For example, when I move it I’ll take out the stove and batteries — those things alone are around 400 lbs! I said in another comment that I didn’t design this rig for long distance hauls, keep that in mind. If long distance hauling was required the unit could be built more like a camper or camp trailer (thinner walls, less roof structure, etc.)

    Jeff, if you see us there please stop by. But wWe may be at another cabin for New Years days

  10. d. diggler December 28th, 2011 8:50 am

    Lou, have you ever considered fuel cell systems? Might work better if you are in a “darker” canyon in the wintertime. I guess these things are quite popular in Europe.

  11. steveo December 28th, 2011 10:27 am

    Excellent job Lou!

    I can’t wait to see your little cabin buried up to its eves in fresh snow fall! Wow, it is dry this winter in CO!!!

  12. Andrew Fox December 29th, 2011 10:19 am

    Neat story on the BBC about “tiny houses” which are pretty darn similar to the portahut:

  13. Lou December 29th, 2011 10:40 am

    Great minds think alike!

  14. DV January 6th, 2012 9:48 am

    OK so where do you guys sleep in that thing? Up in the rafters? Who has a fisheye lens that can shoot the interior? Great project by the way!

  15. borse April 9th, 2012 1:57 am

    It turns out to be a successful environmentally-friendly experiment. Nice work and keep trying sth else innovative!

  16. collezione borse April 12th, 2012 12:32 am

    Nice try for the better use of solar eletricity. Especially the setting on snowy mountains like that, pretty awesome!

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