Simple Solar Heating for RVs

Having lived full-time in an RV for several years now, my "green" side tends to run wild at times yielding some interesting results. With the economy just totally sucking the way it does, and so many people ending up living in campers "not by choice", some of these quirky projects from my past may be invaluable. This will be the first of a series of posts where I share some of these projects.

For those of you living in a location that receives cold winters, this project might prove invaluable. It saved me hundreds of dollars in heating costs while living in central New Hampshire, and only cost less than $50 to set up!

Firstly, here's an animated gif that demonstrates simple passive solar heating. With just a basic understanding of how this works, you'll probably find yourself coming up with some pretty cool ideas on how to harness the power of the sun. Keep in mind that the amount of heat generated when sunlight hits black collector plates is substantial - up to 800 or even 1200 BTUs per square foot! That easily translated to air temperatures of 50 to 100 degrees warmer coming out of the heater than the air that goes in.

I tried various ideas, from what I called a "solar curtain" hung in my kitchen window to various simple window collectors made from old cardboard boxes spray painted black. They certainly worked, and worked well, but I knew I could do better. Plus, all the projects I had been trying would just recycle the stale indoor air. You see, I smoke cigarettes and absolutely refuse to "smoke outside" in the middle of a New Hampshire winter. I wanted a way to pipe in heated fresh air from outside.

The solution was to set up some solar collectors on the outside of my camper, one on each south-facing window. To ensure the temperature of the air coming in to the camper was good and hot, I used 12V computer fans (hooked into my RV's 12V system of course) to blow the air in through the window when a thermostat registers high enough temperatures.

The "collector plates" were simply thin sheets of wood, painted black and taped to the side of my camper. I used 1x2 lumber to create a simple frame for securing the clear plastic (.7 mil). The cold outside air entered through the bottom of the collector and heated up against the black collector plates. The heated air naturally rose to the top of the collector, where it was then blown inside by a computer fan.

Outside air temperatures were around 30 degrees on the day I took these photos. By 3:30pm, the temperatures inside the collector were over 110 degrees and the temperature of the air blowing into the camper was about 87 degrees.

Kitchen window collector
Fan is not in operation (note plastic flap)

Bedroom window collector
Fan in operation

Thermostat in operation
At 80* and above, the thermostat
sends 12V power to the fans
Air temperatures in operation
Numbers top to bottom:
temp of air blowing in, temp inside
the collector and humidity

A cheap programmable thermostat, set to the "cool" mode, monitored the air temperature inside the collector. When the temp was above my setting of 80 degrees, it sent power, as though it were turning on the AC, to the computer fans. When the air inside the collector cooled down, either because the sun was beginning to set or it had gone behind clouds, the thermostat stopped sending power and the fans shut off.

Like I said, this system saved me hundreds of dollars in heating costs over the course of that one winter, and the total cost to set it up was less than $50. There were problems with the system, of course: on windy nights, cold air would often sneak through creating drafts. Overall, though, this system was a huge success.

Watch for my post about a makeshift "sun room" made from plastic and electrical conduit that ended up saving me over a thousand dollars AND provided fresh greens all winter!