However, the book shows a picture of a wall lined with stainless steel passive solar heat tubes filled with "Glauber's Salt" or calcium chloride hexahydrate. To my dismay, no resources for this were listed. I have spent several days researching, and although this method has received incredibly high marks for passive solar heat retention (just hundreds and hundreds of research papers out there), I could find no suppliers except a company in India. I wrote to Ortho and the book publisher hoping for some more info.

Anyone ever heard of this or have any ideas where one might find these materials?

Thanks!

Glauber's salt is the chemical sodium sulfate decahydrate, sometimes used instead of sodium chloride in immersion dyeing, especially with wool and nylon. It is widely available from almost any company that supplies dyes at retail, such as Tie-dyed.com, PRO Chemical & Dye, Dharma Trading Company, etc.

In my freestanding GH, i don't want a wall of anything. I also was worried about using toxic materials and expense but looks like this stuff is considered non-toxic(?) and is cheap (saw one reference for $60 per ton - shipping may kill you though! lol). It has sources in Mexico and Canada so it may be available closer to home.

You might try contacting the fellow behind this page...

http://allanstime.com/SolarHome/index.html#5

There is a "contact" mailto link on the bottom left. looks like he built a home as least partially heated with the stuff in Utah.

Good luck and keep us posted!
Poppa

If you just doing heat storage, you may be better off filling your barrels with rocks and water. (rocks for mass and water to help pump the heat around if necessary) If you're concerned about freezing, add some rock salt (for a water softner) to the water. 10grams/liter will make it about the same as the ocean...and will get the freezing point down to 0C.

I looked at the link mentioned in the previous post, but again does not discuss if all you put in the PVC tubes is the salt or if there needs to be some kind of mixture.

No it won't react with PVC, but PVC itself is an evil material. Use ABS (sewer) pipe instead. Cheaper and a lot easier on the environment.

All salts that are highly soluble in water are very corrosive to metals.

If you work out the BTU's needed, you're better off having a wall of black PEX pipe, and a tiny pump that moves water between that wall and a bunch of barrels you have under your benches.

The Glauber's salt should be used in SOLID form, not as a solution. The salt itself is just sodium sulfate with 10 waters as part of the solid crystal structure. Upon heating, the crystal structure breaks down, liberating the water molecules to form a very concentrated solution of sodium sulfate. When the temperature drops, the salt tends to recrystallize, releasing heat.

I don't know about the practicability of scaling the process up to a greenhouse wall scale (I've got a simple PVC free-stander, so it's out for me...), but the salt is certainly not "toxic" in the usual sense (remember, ingesting too much water will kill you!) and it would not attack PVC pipes.

Just based on supposition and observation in my own greenhouse (which gets both too hot and too cold), I would be most concerned about the kinetics of the process, i.e., how quickly would unstirred salt be able to make the initial phase change to liquid. I would not expect this to have much of an effect on the high temps of the greenhouse.

The other process, that is the recrystallizing, has a tendency to occur rather quickly once it gets going, meaning all of the heat is going to be released over a short period of time, although admittedly it will take it time to radiate away from sizable samples of the salt as might be stored in PVC pipes.

The only other issue that might be a problem is the potential for the liquefied salt to remain in that state even when the temperature drops, barring some kind of agitation (forming a supersaturated solution). Probably this could be forestalled by not using pure-grade salt but rather a (cheaper) technical grade. Or, you could just add a little dirt to each pipe!

Edit: looks like there is some reasonably current research into the practical problems associated with use of Glauber's salt for thermal storage: http://intraweb.stockton.edu/eyos/energy_studies/content/docs/FINAL_PA PERS/4B-4.pdf