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Aluminum can solar heater or thermal mass storage? Solar klin

Started by Doug_D, May 10, 2010, 05:26:33 PM

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Doug_D

Anyone tried using the aluminum can style solar heater or using some type of thermal mass (bricks, water) for heat storage?  It just seems that there are better ways to skin this cat these days then what was tried several years ago. 

http://www.blackenergy.com/amandla/lowcost-solar-heater-soda-cans/

I am getting pretty serious about building a solar kiln soon and just want to make sure I don't over look some opportunities.

Thanks
Doug
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TimRB

That design is interesting, but given the labor involved in cutting and gluing 240 soda cans, each joint a potential leak, I have to wonder what problem they think they're solving over using thin-wall aluminum tubing.  In any event, water makes a fine heat-storage medium.  A thermosiphon (http://en.wikipedia.org/wiki/Thermosiphon) can be built easily, the catch being that the storage tank must be physically higher than the solar heater. 

Tim

ARKANSAWYER

For a solar heat sink to be used in a solar kiln, water is not a good choice.  One thing that solar kilns do well is cool off at night which allows the wood to relax and water to come to the surface.  The wood it's self is a heat sink for storage of energy.  Insulating the concrete from the ground and having a good collector will insure the energy is put into the kiln and not lost.  Some things are just best if kept simple.
ARKANSAWYER

pineywoods

Doug, I think you will find that allowing the kiln contents to cool down at night is a desireable feature. As arky says, a stack of wood will retain a lot of heat. Cooling off allows the wood to stabilize, much less chance of ruining good wood due to checking and case hardening. I have built 2 solar kilns, work well enough to make oak flooring, and dry cypress down to less than 10%.
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Doug_D

Back in the early 80's Pete Chen did a design while he was at SIU that had 260 SqFt of collector per 1000 BdFt.   He also used the aluminum can design and a complete opaque wall design.  Basically it was an external solar collector hooked to a sealed box .  I have not been able to track down the original writing, but from what little I could find (WW dryer #7) , the performance was very good.   He was able to dry green poplar (95%MC) to 15% MC in 8 days in the summer.  I cannot help but to think a design such as this would benefit from some type of thermal storage.   It appears he had a surplus of thermal energy, but nowhere to go but vent it. 

I personally think that if someone could improve a solar kilns winter performance, they would become more attractive. 

I do understand what you guys are saying about giving the wood a chance to cool off, but if it was possible to control humidity and air flow reasonably well why not take advantage of faster drying times? 

It would not be a kiln you load and forget, it would need attention.  Then again I have no idea what all is involved in running a real kiln...can you load and forget about them?   Maybe adding some PLC stuff to a solar kiln would do the trick? 

Just tossing out ideas and thinking out loud.
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low_48

I built a can collector in the 80's. I cut the cans in half, and had the open end face the sun. My theory was that the light would bounce around in the can as the sun moved. I glued them to foil faced insulation and painted it all flat black. My glazing was visqueen wrapped around a frame to make it double wall. I built 2 4'x8' units and used an old furnace squirrel cage blower in the basement, ducted out to the collectors. When it warmed up, a bonnet control turned on the blower. The air would loop around the two collectors. My wife was at home, so she would turn on the house furnace blower to distribute the heat coming from the collectors to the cold air return on the furnace. On a sunny day, with outside temps above 20 deg., the collectors would heat my 1000 sq.ft. house from 10am to 4pm by itself. The visqueen lasted the heating season, but I let it overheat on a warm spring day. The foil based warped, and ruined the panels. It was a cheap and effective experiment.

Den Socling

One thing to remember is the fact that one design can't be perfect. A kiln designed to dry pine or poplar could be disastrous with hickory or oak. You need to make adjustments in heat and venting.

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