Need help: Heating issue

Decided to post a little project I've been considering. A few months back I started tinkering with an idea I've had. Picked up a used camper last summer. Heater works great but I need other options as well. Propane will only last so long. When it warms up I'm also going to figure out how to use wood to heat it. I won't put a stove in it for many reasons. The stove will go outside. But that's later.

Solar is what I'm trying to figure out now. It needs to be as light as possible. Easily portable. Relitively easy to setup. Passive or a limited mechanical system.

Thermal mass as heat storage isn't an option unless the camper gets parked for an extended period of time. Then maybe a pile of rocks or small swimming pool insulated somehow.

Anyway, here's where I'm at so far.

I played around with a few sheets of plastic taped together. Stuck a 12 volt fan in one end and measured the heat output at the other end. Wasn't as good as I was hoping for but a 20 degree increase isn't bad. Obviously it doesn't have a baffle system in the collector. Not sure how I would accomplish that using thin plastic.

It would be fairly simple to either tie into the existing duct work or install some new ( I'm leaning toward new). I was surprised at how much restriction ducts cause. Having played around before with fans and flexible 4" vent pipe suspended above my outside firepit.

The air would need to be circulated through the system. Air from the camper. Through the collector, then back into the camper. That way it should keep increasing the inside temperature more effectively rather than using cooler outside air.

Some issues I see with this idea is locating UV resistant plastic. Well, black anyway. Greenhouse plastic is easy enough. Insulating the underside (large heat loss without). Bonding the plastic together and wind.

Simple thermostat should work OK. Power will come from the camper battery after I get the solar setup.

Wondering if I should scrap the plastic idea and go with something more ridged. Foam board?

I looked online for something already made. I just assumed somebody must have had this idea before and was selling them. Like a large air mattress. No luck.

So please have at it. I'm open to all ideas and suggestions on improving this concept.

 

Propane is one of the most expensive ways to heat.
How cold does it get there?

 

Shop BARRICADE 10-ft x 25-ft x 6-mil Black Plastic Sheeting at Lowes.com
or
HUSKY 10 ft. x 25 ft. Black 6 mil Plastic Sheeting-RSHK610-25B-U - The Home Depot
Might suit the task better than clear...fairly inexpensive, too.

For a portable setup, the plastic film may be better than a rigid structure, but if you experience windy conditions the rigid form may save you headaches in the long run.

 

I'm in Colorado. I've seen it around -15f at the bol. Thinking the solar would work for a good part of the year though. Wood is going to be my primary heat source long term however I don't see a reason to not augment with solar. Ideally I would like a large greenhouse type structure to park the camper in. Like the plastic sheeting greenhouses that nursery's use. Just not sure I'm willing to go to that much brain damage trying to figure it out. Well, even just laying plastic over the whole thing would help alot I bet.

 

That's what I'm using now. Plastic from home depot. It will not last long being exposed to the UV rays. My greenhouse is covered with UV plastic except the ends. I tried using cheaper plastic for the ends. Might get 6 months before it starts falling apart. Finally purchased clear corrugated sheeting just haven't installed it yet.

 

Photos don't show it but the bottom plastic is black. It was around 50f that day. The black plastic was almost to hot to touch

 

Great idea with the bags! Have you tried several in series to increase the temp? I may try your idea but my immediate thoughts were to put 2 or 3 in series for hotter air.

 

They make some really fine small wood stoves for boats, (for example: https://cubicminiwoodstoves.com/ ) that use small chucks of wood.

A solar heater without storage isn't much....you're totally dependent on sunshine.

 

No I haven't. I decided to only cut about 5 feet off the rolls of plastic just to play with. I could make the thing alot bigger, just not sure if that would be practical.

 

I've looked at reviews and videos on the small woodstoves. Heat output seems good. Burn time is fairly short. If I could figure out a way to install one in the camper without major modifications that would be OK. Even thought about installing one in one of the storage compartments underneath. Decided that was a very bad idea. Placing a stove outside wouldn't take up inside space and if I could build it right it would have a long burn time. Some of my thoughts are using a propane tank for the firebox with a sheet metal case around it. Then same concept with ducts and fan.
I'm only considering alternative heat sources as an emergency backup.

 

2 years ago a large snowstorm destroyed my plastic covered PVC framed greenhouse. The next spring I rebuilt it with 2 x 4's. The plastic covering is about 8 or 9 years old now. It has a one inch hole where a piece of broken PVC punctured it. The greenhouse plastic isn't cheap but well worth it. Just not sure where to get strong UV black plastic. That's one of the reasons why I am considering a more solid backing.

 

When I was in engineering school(mechanical) as an undergrad i work in the solar reaserch lab back in the 70's.

I built the first solar hot water testing rig in the state of AZ. I welded a 2x2 Steel tube frame with a slanted side that i roofed with plywood, felt and asphalt signals. It was 60 feet long and we had upto 10 systems running side by side at varying times.

Then ordered soloar hot water systems from around the world including OZ(Solarhart). Plumbed the system with copper and added thermocouples. Then the grad students stepped in and did their research.

The most efficent system (cant remember the name) but is was passive and had 4 inch dia copper tubes coat d with a special black coating that microscoply was very "ruff" running the lenght of the collector. It has probably 8 of these 4 inch tubes in each box. The ruff coating gave more surface area for heating according to the mfg,

The point of all of this is that the water sat on the roof and heated under the glass and when there was a demand, the water flowed out of the collectors into the hotwater tank then in the house.

It was the "thermal mass" of the water sitting on the roof ahd the black copper 4 inch pipes and black copper backing plate that made it efficient.

So you are on the right track but I would thing a ridgid system with mass insted of the black plastic that get hot but has no mass.

If you could get something cheap, from a thermal mass standpoint, like cement board used in showers(cheaper than a sheet of Alum), paint it black and insulate the backside, that would tend to be more efficient.

The downside of thermal mass is.........well the mass and toss in gravity...... now you have weight. So moving and deploying/setup can be an issue.

My 2¢

 

From another thread

Solar Air Heating for Mobile Homes and Metal Outbuildings

 

Concrete board is Hardi panel or Nichi ha boards. I like what you've said here. If you built that system, could it work to pump the warm water thru a radiator set in the house in the furnace system. Sounds viable to me.

 

A greenhouse of sorts.PVC pipe with plastic over it would be cheap. I used a shelter logic greenhouse for several years with good results.I still have it and it seems to be a good value for the money.

 

Dickerson oil or wood is what we have on a sail boat

 

/since your counting on solar or sun just go with a Fresnel lens from an old big screen TV and instead of a plastic weenie a steel box like a stainless steel fold up guide stove use the fan just as your doing to blow air through the stove in to your camper's duct work.
full sun that lens will produce 2,000 + degrees if you have a thermal pile that should hold you overnight or for a while.