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stephen

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Posts: 4
Reply with quote  #1 
And of course I mean:  in any useable volume. <g>

I would like to get a sauna to near those temperatures by collecting solar energy.  It would be in Florida at least. <g>

The active hydronic system I built in NJ won't do anything like that.  I have 120 square feet of collectors heating now only 80 gallons of storage and even in the summer I can barely get to 130ª F.  

Does anyone think that what I suggest is possible?

If so;  how? <g>




 

stmbtwle

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Reply with quote  #2 
160F, yes, 180, maybe. An all-metal collector can easily hit boiling when stagnated, but this may damage many homebuilt systems.

My hot water room heater could easily hit 160 on a good day, but I set it to shut off at that temperature to avoid damage. Even then, sometimes the metal collector would get hot enough to force steam into the plumbing. By morning the storage temperature had dropped to around 140, still usable for heating.

It's all a matter of energy in vs energy out. The water is actually a COOLANT, in that it cools the collector by transferring the heat somewhere else (think of your car engine). If you want a lot of heat, you need a BIG collector to capture it. If you want high temperatures, you restrict the coolant flow and use lots of insulation. With enough insulation, a smaller collector might do the job, given several days.

While it's theoretically possible, I doubt it would be cost effective. You'll need a really big collector, and you'll probably need a big, well-insulated hot water storage system. On days when you DON'T use the sauna, what are you going to do with all the heat (you can't turn off the sun).

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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
stephen

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Reply with quote  #3 
Thanks.

You mention 160 degree stored water - what ratio of collector square feet to storage gallon does your system have?

Can you describe your "hot water room heater" ?

This sauna-heating concept would of course require the opposite of stagnation - just maintaining the temperature would be a constant demand on the stored heat. <g>


stmbtwle

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Reply with quote  #4 
The room heater is here: 
http://simplysolar.supporttopics.com/post/willies-solar-hot-water-space-heater-7257880?highlight=willie&pid=1285917467

Bear in mind that the only way you're going to get those temperatures is with a: stagnation or b: recirculation.  IF you have enough input and IF you recirculate long enough and IF you have enough insulation, you'll get there.  The higher the temperature you try to achieve the more your losses will be, other things being equal, and of course once you start USING that heat the storage temperature will start to drop.

I had a 4x8 all copper collector, PEX lines run in insulated sleeves, and a 55 gallon drum with two layers of 3/4" poly iso.  I think the 12v pump could pump about 2 gal/minute.  I could get the drum up to 160 on a good day but it would lose nearly 20d by 6 in the morning when I turned it on.  I would get about 4 hours of heat but by then the sun was high enough to heat the room through the windows. 

IMO the system wasn't near big enough. I contemplated an 8x8 Aretha collector and a 275 gallon "tote" for storage, with at least 8" of insulation.   However after some thought I decided that for the 1-2 months a year I would use it, it wasn't worth the cost, work, and aggravation.   I disassembled it and scrapped most of the components, and today we use a portable electric space heater to heat that same room.  

I don't have any experience with saunas so I can't give you any suggestions on that.

To be honest, I'm not a big fan of solar thermal here in Florida.  In my experience we spend 6 months or more of the year trying to get rid of heat.  Here it is nearly Thanksgiving and we're still running the AC.  Therefore I feel that solar electric (PV) is the way to go here.  My grid-tied array has been running nearly trouble-free for 10 years now, and it runs year-round, cooking my food and COOLING my home.  What I can't produce I buy from TECO, which is also big on PV.

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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
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