Polyisocyanurate or extruded polystyrene for in ground use?

[strider3700]

I just came across this link
solar Photo Gallery by Eric at pbase.com

He dug a hole lined it with extruded polystyrene (pink) added a liner to make the inside water tight and covered it over.

I haven't mentioned that my tank will be just outside of my house. I can place the tank on a gravel bed that can drain directly down into my perimeter drain to help remove standing water. If I wrap the polyiso with some thick poly and am careful when back filling not to rip it it would be water tight except for whatever comes from above which is relatively easy to deal with. I'd be more worried about trapping vapor leaking from the tank at that point. Also I can back fill completely with gravel to create quick and easy channels for water to drain down to the perimeter drains.

[AC_Hacker]

Originally Posted by strider3700

inside the tank, depends on what I limit the collectors to. Probably closer to 60 C would be my max. My test collector hit's 115 C when stagnant so steam is all that comes out initially.

Have you considered phase change materials?

I can point you toward some info.

The biggest advantage is that you can store energy without raising the temperature of your storage media much.

I spent months searching out information on PCM.

This link was the most valuable one I came across:

Reversible phase change compositions of calcium chloride hexahydrate with potassium chloride

Regards,

-AC_Hacker

[strider3700]

phase change would be cool, but water is pretty effective, is proven tech for these type of systems and has passed building code requirements in a single wall heat exchanger in my province before. If I was to add antifreeze or go to anything more exotic I'll almost certainly need to go double wall which would add a bunch to the cost.

THat was a very detailed and interesting read though. I wonder how difficult the base chemicals are to get.

[AC_Hacker]

Originally Posted by strider3700

I wonder how difficult the base chemicals are to get.

Calcium chloride is the active chemical in DowFlake driveway salt.

Sodium chloride is common table salt.

Strontium chloride is a bit tough, but I have found it here.

Here is a page about the stuff.

Food for thought.

By the way, I was commenting on another thread where a guy was contemplating using a 210 gallon fish tank for heat storage... I suggested PCM, check out the numbers.


Regards,

-AC_Hacker

[Daox]

Do you know how the phase change medium reacts with common plumbing materials (copper, steel, pex)?

[AC_Hacker]

Originally Posted by Daox

Do you know how the phase change medium reacts with common plumbing materials (copper, steel, pex)?

The PCM materials that have interested me the most, Eutectic Salts are very corrosive to common plumbing metals, like iron and copper. To my knowledge, stainless is ok. Plastics and glass, no problem. PEX ok, PEX fittings not good.

There is another type of PCM, paraffin, which also has PCM qualities and has no reversibility problems, which, to my knowledge, has no problems with metals or plastics.

Paraffin, as found in the grocery store, is a mix of many different kinds of paraffins.

Link to paper cited

To be useful for PCM you need a paraffin that has a narrow phase change range (AKA: technical grade paraffin). I know this can be obtained, but I haven't found it domestically yet...



-AC_Hacker

[mrd]

EPS vs. XEPS

Extruded is referred to as XEPS or XPS.. Expanded is EPS. Colored stuff is XPS. This thread is going to confuse people

[strider3700]

I've edited all of my posts to remove any acronyms.

[AC_Hacker]

Originally Posted by mrd

EPS vs. XEPS

Extruded is referred to as XEPS or XPS.. Expanded is EPS. Colored stuff is XPS. This thread is going to confuse people

I read over my posts in this thread, when I refered to EPS, Expanded Poly Styrene is what I intended.

[strider3700]

yep and when I was incorrectly referring to EPS I was meaning extruded polystyrene. My Bad