Some of them took the time to send in pictures and descriptions — have a look here:
http://www.builditsolar.com/Projects/SpaceHeating/Space_Heating.htm

I’m happy to answer email questions if you run into a problem.

If you are looking for a warm up project that is a bit smaller, there are several listed at the link above — they are all fun and will get you hooked on solar

Gary

You could put solar electric panels on the roof and use them to charge batteries during the day, then run the space heater via an inverter at night. This is inefficient, expensive and heavy (batteries).

A better way might be to put a water heating collector on the roof (maybe better on the south side). Use it to heat a water tank in the trailer, and let the water tank radiate heat during the night to keep it above freezing. Solar heating collectors are about 4 times more efficient than solar electric panels, and (therefore) you only need 1/4 the area for the same amount of heat.

The best thing you could do would be to insulate the trailer, or at least the part you want to say above freezing) as well as you possibly can. This would allow a smaller solar collector or small space heater.

I think if it were me, I would try for the best insulation possible, add some thermal mass in the trailer, and use a simple solar air heating collector to heat the mass up during the day, and store enough heat to avoid freezing at night. A small space heater set to come on at (say) 35F could be the backup for cloudy days.

You can email me if you want to discuss some actual collector and tank sizes that would make sense.
gary AT BuildItSolar DOT com

Gary

I took a 4′x4′ piece of scrap plywood, spray painted it black. I screwed scrap 2×4’s around the perimeter to make a box about 3″ thick. I bought a $2.99 pack of window film and stapled it on the box. I put a 3 inch hole at the bottom and the top.

I laid the box up against a stone wall angling it towards the sun. Then I went to go get a thermometer (I had a digital one). So not to get direct sunlight on the thermometer probe, I put a piece of insulation over the probe. This was I was sure to read the true temperature of the air coming out of the top vent hole.

Well within a minute, the temperature of the air coming out had pegged the thermometer at it’s max of 130 degrees. So then I got my meat thermometer that I use for grilling, and the temperature read 160 degrees. There was a bit of an air flow coming out of the hole, so I know I was getting the hot air to rise, being replaced by cool air at the bottom.

So, the concept works. I haven’t done anything with it though.

- The collector has no fan, no controller. Its a thermosyphon collector — the lower density of the heated air makes it rise up out of the exit vent, which pulls cool air into the inlet vent. The $350 was all for the materials to build it — this is a large collector — about 160 sq ft, so this is just a bit over $2 per sq ft of collector — almost free compared to $30 a sq ft commercial panels.

- Solar thermal collectors are much more efficient that solar electric panels. Efficiency depends on the sun and out side temperature, but 60% efficiency might be a good average. Payback is very short for this kind of collector.

Gary