Heating and Cooling as passive and with as low electric usage as possible.

Stampie said:

In reply to alfadriver :

Water was considered but at the cost of electricity to move it.

Thermosiphon.  Heat will cause convection to move the water natrually.

Roof thermospihon systems are a relatively easy solution, and I see suggestions here along those lines.

If designing your own house, use a roof overhang to get the winter/summer light split correct.  Direct sunlight is 1000w/m^2 at sea level.  It doesn't take much to dump a lot of heat into the house.  Let it hit something like stone or brick which will absorb and re-radiate it slowly over the course of the day/night.

wvumtnbkr said:

If there is airflow under the cabin, block that off in the winter!  Nothing worse than the floor being the cold area.

Good point.  Can't see that hurting in the summer either.  Because of CyberEric I'm currently melting down shortening to make a candle.  I think I'll blame him also for the prepper videos that are going to show up in my YouTube feed the next few months.  I got everything to build the heater he described.  Hopefully I'll finish that this afternoon.

In reply to TravisTheHuman :

You are correct.  I was on my happy medicine last night so I didn't think about thermosiphon with the water.

The thermosiphon works great in the day but not well at night. In winter, the nights are longer than the days (though less so in Florida).

You should also think about thermal mass inside the cabin. Keeps temperature stable throughout the day. Things like countertops, rock/brick floors and walls, etc. using water instead of air in a thermosiphon system increases the thermal mass a lot, but adds different complications.

Other passive ideas I love use natural sun angles for shade during the summer and sun in the winter. The sun can cool you in the summer if you use it to suck hot air out of the very top of the inside and bring cool air in from the bottom (or even better bring it in from underground).

finally, fluid pumps don't take much electricity, and could even be run by hand. Prepped correctly, a bunch of buried water tubes provides both heat in the winter and cool in the summer. (The earth is the largest thermal mass available to you).

In reply to Stampie :

Cool. Glad you like the idea. And yeah prepper videos are endless, ha. I hope it works, I'm curious to try it myself as option between fires in the stove, it's just so damn cold here in doubt it will be worth it, but who knows.

Ive also seen people use some sort of electrical conduit to heat up the sand using a small lead acid battery. Might be another option to try.

You might be able to do it in a Sun Oven. I've got them up to 350 F before in just a few hours. They might just have enough room for a metal bucket. Not sure how long the sand would maintain the heat though. I've been messing around with "sand batteries", it's a learning curve.

Go Sun also makes a nice option, but I don't think you can fit a bucket in it.

Well yesterday was interesting with some challenges.  The biggest challenge was how does one clean up 40oz of melted shortning off your kitchen floor.  From experience I can tell you to walk away for about 10 minutes and let it gel up again on the floor.  Then it's pretty easy to scrape up the majority of it.  Quick mop and you're good to go.  Do not, repeat, do not think that you can step over the spill to go get towels.  It is larger than you think and you will bust your butt.

Did some research and candles produce about 80 watts of heat.  Ok so that took all of about 10 seconds but I made it sound like it was hard didn't I?  I could see that helping in the cabin.  I ran it yesterday evening in my kitchen which I closed off with a sheet.  I ran it for a little over 5 hours and the sand went from 70.5 to 78 degrees F.  The sand I got was pretty moist so I don't know how much energy was used to drive off the water vs heating the sand.  I'm running it again today to try and dry it out totally.

Since everyone loves pictures here's what I made.  I tried to slit the top copper pipe and open it up to be able to capture more heat but it was kicking my behind so I said berk it.  I have some 4 inch wide copper plate here.  If I continued with the candle I'd put solder it right over the candle to capture more heat.  Forgive me for my soldering skills.

I'm thinking a solar oven is next.  I'm going to try and come up with plans to make one out of one sheet of plywood and see how that goes.

In reply to Stampie :

I would think the moist sand would hold more heat than dry at those temps. I'm not sure if you'd lose much heat to evaporation while in operation, but that would depend on the humidity. 

In reply to No Time :

I just know that a phase change requires energy so that's why I assumed some of the energy that could have heated up the sand went to evaporating the water off.  

In reply to Stampie :

You are probably right that you lost a bit of energy to phase change and evaporation, but the water in the sand has takes more energy to warm than the sand, so you are probably storing more energy (heat).  If you were working at higher temps then the evaporation and energy lost to phase change increases. 
 

Have you looked at homemade heat pipes as a way to transfer energy? I haven't thought it through, but it may be work a bit of reading or video watching. 

CyberEric said:

You could try a candle and copper strip in a metal bucket of sand for heat in the winter. I haven't tried it yet, but want to. Might be enough to take the edge off in Florida. A bunch of videos on YouTube if you haven't seen it.

In the summer, a battery powered fan works wonders.

I think shading that decreases light in the summer but allows more light in during the winter will be the ticket.

Ive lived off grid for a few years now and it's fire in the winter and shade/open windows/battery fans in the summer for me. But I live in a colder place than Florida.

Never heard of this so off to googles I went. Very interesting 

In reply to OHSCrifle :

I'm not sure the copper is doing much.  In running mine I have a circle around the candle jar that shows the moisture driven off.  No rings around the copper pipe.  Maybe I'm not grabbing enough heat for them.

Well this is interesting. Seems our body heat might be enough at least in milder weather. We got in around 1600 and as you can see I opened the door to let heat out. I closed it a little later and as you can see the temp stayed pretty level until I opened the door again around 1930 to dump more heat. After that it actually rose a little thru the night before slightly dropping in the morning. I found some leaks around the door so I'm wondering if our body heat is going to be enough. Just for reference, it was 58 this morning when I took the screenshot. 

Whats the intended workflow with the candle-in-a-sand-bucket?

A candle produces 80 watts of heat, which is just slightly less than a human body.  You are trying to run one all day, capture the heat, then bring the bucket inside and let heat out overnight?

If so, can you just paint the bucket black and put it in the sun all day?  The sun will dump a E36 M3load more heat into it than a candle will.  Heck, spread it out into smaller buckets to maximize the surface exposed to the sun, then dump them all in a big insulated bucket before the sun goes down.

Or use another heat source (campfire, stove, etc.)  Hundreds of years ago people used to let big-ass rocks heat up by the campfire, then bring them into their tents at night.  A "sand-battery" is just a large thermal mass with a relatively slow heat transfer rate on the surface.  There are lots of ways to accomplish this.

Alternatively, if you are going to try and capture heat from a candle as energy, you'd be better off burning it inside (forget the sand/bucket) in a miniature stove of some sort.

In reply to TravisTheHuman :

Oh yeah I should have been more clear, I was just playing with the candle. I intend to build a solar heater if I move forward with the sand idea.