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Scott Davis

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Yes, it is called thermal storage. Fortunately, water is clean, cheap, easily circulated and makes excellent thermal storage. Here is a link with great construction details:

http://www.builditsolar.com/Projects/SpaceHeating/SolarShed/Tank/Tank.htm

Here is the thermal storage system I'm using for both hot water and space heating at my house:



Here is a list of thermal mass material options, followed by their volumetric heat capacity, (KJ/m³.k):

Water - 4186

Concrete - 2060

Sandstone - 1800

Compressed earth blocks - 1740

Rammed earth - 1673

FC sheet (compressed) - 1530

Brick - 1360

Earth wall (adobe) - 1300

AAC - 550

Do you have other suggestions for thermal storage?  Please click reply and share your ideas!

Do you have questions about thermal storage?  Please click reply, this is the place to ask and we will do our best to help!


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Scott Davis

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Here is a spreadsheet that will give you the volume, weight, thermal storage capacity and other useful information for any given set of dimensions:

http://www.n3fjp.com/solar/tank.xls


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Kurtt

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Reply with quote  #3 
Heat can be stored in solutions of various chemicals, such as caustic soda (lye) calcium chloride and others.
If you dilute a concentrated solution with water, then heat is generated. Read the warnings on tins of caustic soda can re the danger of steam explosions if adding water to the dry chemical.

This effect was used by Honigman in Germany back in the 1800s to power various steam locomotives, running on lines of some 45 km or more, with reasonable gradients.

Basically his steam generators consisted of a tank of 85% caustic soda solution, with an embedded steam boiler. Spent steam from the engine was led back into the tank, where it condensed, diluting the solution and generating heat. At each end of the railway a stationary coal fueled evaporator brought the concentration back up to max.

This concept was printed in a Scientific American of the times. I've since lost my reference to it. See also <<http://www.google.com/patents/US381967?printsec=claims#v=onepage&q&f=false>> for a patent on an improvement of the concept.

Garage_Hermit

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Hi, regarding heat-storage, from an air collection system, I have been designing a "Modified Trombe Cabinet", based on the trombe wall principle, but using warm air routed in from a standard collector.
I carefully read the FAQ's, and understand that normally a gigantic collection area is required in order to stor solar air. However, my intent is to design this storage so that it would run on a minimal airflow bais...

I am considering using a pair of juxtaposed existing steel office cabinets, containing any or all of the following (in no particular order, but basically starting with cheapest, and working down to most expensive !)
  • pop/beer tins filled with water (free and efficient, like Scott says above...) (also gives a large wetted area of air to liquid...)
  • plastic milk bottles, idem,
  • jerrycans of brine (salt & water solution),
  • hollow metal drain pipes, laid horizontal, half-filled with sand or salt,
  • breeze blocks / bulk sand in trays / old scrap iron (builders stays etc...)
  • jerry cans of engine oil,
  • cans of cooking oil, new or salvaged
  • idem, but with metal sponge soaking in the oil
  • slabs of solid paraffin wax, in sealed tins

Efficiency-wise, paraffin (candle) wax sounds like the best, from my reading (search the web for "'phase-change materials").
Cooking fat might get smelly unless it is really sealed tight.
Engine oil idem.

Hopefully I will get round to experimenting with all of these, pretty soon !

The steel cabinet would probably be surrounded by jointed/semi-unpointed brick, and would require a plenum to entrap the incoming air, and perhaps a small fan to provide forced heating, via an offtake. Otherwise, the cabinet just radiates heat naturally -- it needs to be in the furthest dark corner of the basement !).

Would be interested in all or any feedback regarding this idea !

Regards to all,
Garage_Hermit

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(1)  "Heat goes from hot to cold, there is no directional bias"
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Garage_Hermit

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Reply with quote  #5 
There is a very good discussion on this subject here :-

http://www.extension.purdue.edu/extmedia/ae/ae-89.html

G_H

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farmerj11

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Reply with quote  #6 
Has anyone every used an old chest freezer for hot water storage. I have one that doesnt work and was thinking about turning it into my storage tank. Any ideas on how it would work???
Scott Davis

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Reply with quote  #7 
Hi Farmerj11,

As long as it would withstand the water pressure (which is very heavy) or you built a reinforcing frame around it, that should work.  Here is a spreadsheet that will give you an idea of the weight, volume and pressure:

http://www.n3fjp.com/solar/tank.xls

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Seatec

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Reply with quote  #8 
When my shop get up to temp for working, i store my extra heat in my cement floor . I ran 5 in ductwork in my cement floor when I had it built, about 40 ft, I just add 2 elbows to close the loop, takes a good day of heat to build it up, next time I would have 80ft for each panel, as there is no restriction and it takes time for the heat to get in the cement.
gbwillson

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Reply with quote  #9 
Quote:
Originally Posted by Seatec
When my shop get up to temp for working, i store my extra heat in my cement floor . I ran 5 in ductwork in my cement floor when I had it built, about 40 ft, I just add 2 elbows to close the loop, takes a good day of heat to build it up, next time I would have 80ft for each panel, as there is no restriction and it takes time for the heat to get in the cement.


I bet that feels real nice underfoot. When your feet are cold, the rest of you usually is also. Even my basement workshop floor is chilly when you aren't moving around much. Of course, where I live, we do have a frost line that's 48" down below the surface. I have a bunch of those cheap interlocking cushions/pads underfoot. They not only help block out some of the chill, but are much more comfortable than standing on concrete. I assume your garage floor slab has insulation underneath and on the sides? 

Greg in MN[wave]
Seatec

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Reply with quote  #10 
It's hard to get enough days of sunlight to warm it up any amount, it will be warm at the end of the day, and gives off its heat all night. If I could get about 5 days of sunshine then I would see a bib difference. I have the interlocking rubber pads over the heated area, at at the end of the day there is a big difference when you feel the floor under the pad. I have 2 in og insulation under the slab.
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