I'll post a write-up sometime before the end of the summer, with pictures of our most recent stage of construction.

Very good; I'm looking forward to pictures and details. Where does that leave us in terms of Freebuild; you'll have time for it starting around September?

From the looks of it, Elf, you might want to make that 50 years. lol

If we have at least 3 days below 17F to refreeze our salt solution during the winter, we have enough insulation and thermal mass to withstand up to a week of 110F (which NEVER happens in VT). Given that we usually have a couple weeks in the negative teens, and never more than a day or two above 95F, we've got a lot of buffer space for climate change.

What's the maximum average temperature that it work at, then? IE, it sounds like for every day at (avg+N) degrees, you have to have had at least a day at (avg-N) degrees. Is that true, or am I oversimplifying it?

We don't look at a maximum average temperature, but rather a maximum average temperature gradient, the surface area of our room. and total R value of our insulation per unit of area (R >= 5/inch * 24 inches) for the BTU transfer per unit of time from the outside environment to the inside freezer space. Then we look at the freezing temperature for X% salt solution and choose X based on a reliably achievable freezing temperature and period and to set a baseline for our temperature gradient. We calculate the total BTU input over a year and choose a mass of salt solution required to balance that input against the latent heat of crystallization for the solution using approximations for the surface area and R value of a 2 liter bottle.

Right now, given our structure, we're looking at being able to maintain around 22F with 6000 liters of 10% salt solution.

Very impressive! 6000L is a heck of a lot, though; where do you store all of that? Around the room, or circulating between a tank and coils?

No tank or coils, the point is to be completely passive (no energy input/outputs other than environmental and manual opening/shutting of the hatches). We have 3000 * 2L bottles that will be stored ala wine cellar around the periphery of the room.

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Also, frozen things tend not to circulate well

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topic split.

Sorry for the double post, here are some pictures of the construction of the freezer part of the building. The upstairs isn't as critical for understanding the way it works, but it is designed to thermosiphon when the hatches are open.

It's worth noting there is a ground-level floor, a loft, and a roof above what you see pictured (these are about 3 week old pictures), plus space for a composting toilet, and an outdoor roof-overhang-thing for storing sheep feed.


Sealing the foundation against moisture:




We're essentially building a room within a room, as far as insulation is concerned. Here we are laying down LOTS of polystyrene insulation on top of the foundation, and then pouring a concrete slab on top of that. There's more insulation UNDER the foundation to prevent the ground freezing and heaving.







Outside, we have "drainage" pipes sloping uphill to conduct cold air down and around to help freeze the ground around the freezer. They will be plugged during the summer.







Framing up the basement wall. We now have some post-and-beam going inside to support the upstairs floor joists, double walls, and a false ceiling hanging down, all to be filled with insulation. More pictures to follow.



And a broader view of the project:





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Woot, got some pictures from today (I took all of this batch)

We worked on framing out the rafters for the roof for the sheep food side-shed.


Woot for climbing up 2 stories above the path with a nail gun. Also, that funky overhang on the left is where the composting toilet goes.



About 1/6th of our themal store. 512 bottles. Note the framing for the double walls, where the insulation goes.








Rick mans our salting station:


And a few hours later we are up to 624 (ran out of the bottle caps to complete the targeted 640 for the day):

Hey everyone! Here is a link to one of the write-ups we got in a local newspaper towards the end of the summer. It focuses more on the environmental implications of the project than the technical aspects, but if anyone wants to get down and dirty with the thermodynamics of the project, I'm happy to dish out.

Please do dish! I would also love to see further photos if you have them.

Small solar panel + microcontroller + thermometer + actuator = no human intervention for opening the hatches and whatnot.

EDIT: Or better yet, I bet you could devise an entirely kinetic system. If these types of thermometers (http://ecx.images-amazon.com/images/I/21KRVH6VGTL.jpg) can move around using just the temperature and physical properties, you can use the same principle to open some hatches based on temperature.

For some reason that strikes me as relatively inefficient...

But really really self-indulgently neat. Like my lego mindstorms bot that I made to clean up all of my legos that I dumped out. It takes about 5x longer than I would to personally clean them, but it's still cool...

Ooooh, does it really work? You should totally post picks in the Building with Blocks subforum!

Mechanical systems are a lot more prone to wear and tear than a system that requires human labor, though such systems ARE under construction elsewhere in the world. At least one tribal group in Alaska is building a climate-cooled freezer similar to ours, but with active pumping to circulate the coolant around the building.

Here are the pics. I'll post the tech specs when I have a little more time to type them up.

Wall Raising







Roofing










Smashing the chicken coop








Clambering around for some post&beam/floor joists

Epic! This looks like it was a ton of fun; I'm actually quite jealous of your summer outdoors working on this project.

I, for one, do not trust Courtney in a construction vehicle.

Heh, especially with such a maniacal look on her face at the prospect of destroying things.