Has anyone here built solar hot water panels and storage set

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Has anyone here built solar hot water panels and storage set

Postby DigitalDreams » Mon Apr 06, 2009 10:07 pm

If anyone has built a hot water /liquid solar panel with storage I am interested in your design and performance specs as my two hot air thermal panels saved me so much this winter on heating I am looking to go 85 to 90 % solar if I can.

But to do that I need to be able to store heat, and even tho I've watched practically every utube video and surfed a zillion web sites on it no one seems to really get down to the nitty gritty of how much panel I need for each gallon of liquid storage I plan to have.

I am figuring about 500 gallons of storage so if anyone has a clue
how many square foot of panel it would take to heat that much to
140-170 degrees within 4-6 hours I'd be most grateful.
DigitalDreams
 

RE: Has anyone here built solar hot water panels and storage

Postby hawk909 » Mon Apr 13, 2009 9:04 am

The only link I know is this one.

http://www.builditsolar.com/Projects/Sp ... tm#Concept





Updated February 21, 2009:

Just as a check that the system is still working as well as it was when it was first installed, I did this little test.



Today was a sunny day. The storage tank was at 89F this morning at about sunrise. I set the house solar thermostat low enough so that the no solar heat would be used during the day to heat the house. So, all of the heat generated by the collectors today went into heating the storage tank. The tank went from 89F in the early morning to 135F at the end of the collection period. The storage tank now hold 420 gallons, so the heat gain was:



Heat Gain for day = (420 gal)(8.32 lb/gal)(135F - 89F)(1 BTU/lb-F) = 160,750 BTU



This is very close to the initial performance of the system listed above -- so, no appreciable degradation over the couple years.



The 161K BTU is equivalent to about 2.2 gallons of propane burned in an 80% efficient furnace.



The ambient temps for the day were: 15F @ 8am, 25F @ 10am, 31F @ 12 noon, 38F @ 2pm.
hawk909
 
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Postby DigitalDreams » Mon Apr 13, 2009 7:30 pm

Just out of curiosity what type of absorbers are you using closed loop - trickle down or the newer vacuum absorber tubes.

My plan was closed loop finned aluminum absorber pipe or else copper absorber with finned heat sink
design. And transfer to two linked 265 gallon super insulated steel tanks as thats what I have laying
around.

But am open to suggestion on the absorbers as I have equipment to create most anything metal.

Thanks for the formula, does this btu gain your showing keep the place warm most all night with out backup heat or do you supplement
existing heat source with that heat.
DigitalDreams
 

RE: Has anyone here built solar hot water panels and storage

Postby hawk909 » Mon Apr 13, 2009 8:33 pm

I am not involved with that at all. That update I found on his site.

I have been trying to find what absorbers he used but I think the website he bought from changed so they don't do a direct sale anymore.
hawk909
 
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Postby DigitalDreams » Mon Apr 13, 2009 9:09 pm

Well then I guess my best bet is build the first panel measure btu output , subtract that from btu output overnight from my furnace and times panels will equal needed panels to match btu desired or close.
DigitalDreams
 

Postby Gary Gary » Fri Apr 17, 2009 2:45 pm

DigitalDreams wrote:Just out of curiosity what type of absorbers are you using closed loop - trickle down or the newer vacuum absorber tubes.

My plan was closed loop finned aluminum absorber pipe or else copper absorber with finned heat sink
design. And transfer to two linked 265 gallon super insulated steel tanks as thats what I have laying
around.

But am open to suggestion on the absorbers as I have equipment to create most anything metal.

Thanks for the formula, does this btu gain your showing keep the place warm most all night with out backup heat or do you supplement
existing heat source with that heat.


Hi,
The Solar Shed system that is mentioned above is my system.

The collectors on the Solar Shed use premade absorber plates from a company that makes collectors. I did the glazed housing they fit into.

On my last system I did build the whole collector, and if I were doing the Solar Shed over, I'd use the new homebuilt collectors.
The new collector uses copper riser tubes with aluminum heat collection fins. The real key on this kind of system is getting a good thermal bond between the fin and the tube, and I spent a lot of time getting this right. The collectors and testing on them is described in gory detail here:
http://www.builditsolar.com/Experimenta ... lumCol.htm

Basically, the testing I did shows that the homemade collector at $5 per sqft delivers nearly the same thermal performance as a $30 per sqft commercial collector with a black painted (non-selective) absorber.

The actual solar water heating system I use (which uses the PEX version of the collector) is described here:
http://www.builditsolar.com/Experimenta ... erview.htm
At the current prices of copper, I think copper is the way to go, but the link does show how the rest of the system fits together. It has kind of a clever (cheap) heat exchanger for domestic hot water that allows the storage tank to be a simple (non-pressurized) EPDM lined box (like the Solar shed tank).


Another collector design that I think is good is this MTD design:
http://www.builditsolar.com/Experimental/MTD/MTD.htm


Gary
Gary Gary
 
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Location: Bozeman, MT

RE: Has anyone here built solar hot water panels and storage

Postby DigitalDreams » Fri Apr 17, 2009 11:12 pm

Gary thanks for the links have seen some before but found a few new ones and glass not a problem,I got people.
And copper/aluminum same story so my only big question, as I can build it cheap enough is storing higher temp liquid and using glycol closed loop gonna gain anything as I already have two super insulated 250 gallon storage tanks I was gonna use for storage so heat not an issue on storage tank.
DigitalDreams
 

RE: Has anyone here built solar hot water panels and storage

Postby Gary Gary » Sat Apr 18, 2009 8:42 am

Hi,
For most people in cold climates, about 1.5 to 2 gallons of storage per sqft of collector works out pretty well. This is enough storage to store about one full sunny days worth of output from the collector. Unless you have a whole lot of collector, or a very very well insulated home, you will use that stored heat overnight and maybe a bit into the next cloudy day.

If you do have lot of collector or a very very well insulated home (or both), then more storage can be helpful to store heat for multiple cloudy days.

If you have a drain back system, all of the collector and storage water can be just plain water (like my Solar Shed). If you have a closed loop system, you would (I think) want to run antifreeze in the collector loop and transfer the heat to the storage tank(s) with a heat exchanger so that you don't have to have 500 gallons of antifreeze protected water. The heat exchanger can be as simple a a big coil of copper pipe immersed in the storage tank.

Gary
Gary Gary
 
Posts: 16
Joined: Mon Mar 12, 2007 9:07 am
Location: Bozeman, MT

RE: Has anyone here built solar hot water panels and storage

Postby DigitalDreams » Sat Apr 18, 2009 10:24 am

Thanks for the info (guess i will need about 8 panels.
And as to collector type!
I like you copper design, but had a brain storm on concentrating collector design and am going to build a small test
panel within a couple of weeks will let you know if it works well.
It is a hybrid between your design and a hot air design which has showed massive promise and luckily I have access to benders in a machine shop for the heat sink bending.
If the design works I can double square footage of a panels heat sink
without making panel bigger.
DigitalDreams
 


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