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Large hot water solar collector design questions

 
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Hi Everyone,

I'm in WV and winters can get below zero for a few days at a time and then cycle back to 40s and 50s the next week.

I'm building a pole barn style rabbit / duck coop 12 ' up hill behind my aquaponics greenhouse. Greenhouse is 48 x 24. Pole Barn is 38 x 16. Buildings run east to west. I want to build a huge solar hot water collector to keep my 4000 gallon aquaponics system warm through winter.

My south roof will be angled 45 deg to the south and have a surface area of 38 x 6. I'm thinking of installing black metal roofing sideways, building headers from wall to peak at both ends, running Pex lines horizontal on the metal roofing, and capping the metal roofing with duel wall solexx (left over from greenhouse) or poly (buy new)

Some of my questions:
1. What material and design should I build my headers from. I'm thinking I need 2" pipe for my headers with 3/4" Pex running the 38' length of the roof.
2. What type of connectors should I use.
3. Do I have to strap my pex tightly to the metal roof or can they just lay there? Should I place them under the metal on the plywood, or perhaps sandwich them between two sheets of metal for tighter contact and even heat.
4. Will pex stretch and not break if water is in the lines and freezes?
5. I hope to build the headers so they drain back to the system, but just in case, what header options do I have that can take freezing?

I look forward to hearing anyone's ideas or design options.

Thank you,
Jason


PoleBarn.jpg
[Thumbnail for PoleBarn.jpg]
 
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Posts: 2493
Location: Central Texas zone 8a
417
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Based on you not using a glass covering, you might look into solar pool heaters. Mainly cause they have the engineering built in or optional:

Drain back when off.

Dual thermostat. It only turns the pump on when the collector area is warmer than the storage area.

The only drawback is a pump is not included. It relies on the filter pump of the pool to move the water.
 
Jason Warren
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Thank you Wayne for responding. I'll check into it, thank you.
 
wayne fajkus
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Location: Central Texas zone 8a
417
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Here's an interesting tidbit when sizing the collector. This is swimming pool related but may apply for your situation. They generally don't care how many gallons, just how many Sq ft of surface area there is. I suspect this is critical cause this is where the heat is lost.

With swimming pools (in my locale) they say the collector should be 75 - 100% of the surface area of the pool. This generally extends swimming season one month earlier and one month later.

It's also stated that a pool cover (bubble wrap) is as effective as the solar collector. Once again, I'm speaking about my locale in central Texas.





 
Jason Warren
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Thank you.
 
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