Solar powered hot water system for use as thermal mass storage

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MoonShadows

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#1
This is my plan. I would appreciate any feedback from anyone who has experience using heated water for thermal mass or has experience with solar hot water systems...or anyone that just has an opinion.


I am building a solar powered hot water system for use as thermal mass storage for night time heating in cold weather. My plan is to circulate water from the solar collector through 4 – 55 gallon steel drums, gradually increasing the water temperature throughout the day so it can be released back into the greenhouse during the night.

I am building the solar collector using ½" OD x .062 Wall Black LLDPE Tubing and 9 - 4" x 48" Solar Hot Water Heater Absorber Fins with 5/8" channel. The collector will measure 12' long x 1' high with a collection area of 12 square feet using 36 linear feet of tubing. The collector will be housed in an insulated box with the interior painted flat black and it will have a plexiglass cover. This collector will be situated inside my greenhouse approximately 7 feet off the ground and mounted in a horizontal position. The total run in tubing will be approximately 56 linear feet when I take into account the collector, up feed to collector, down feed to drums and piping between drums.

I plan to place the solar panel outside the greenhouse and the pump inside. I am doing the whole project this way to protect the system from freezing on cold winter nights, figuring the 210 gallons of thermal mass and an electric backup heater will keep the pump and tubing from freezing. I know I could use a closed glycol system and heat exchanger, thus allowing me to place the collector and pump outside, but I think this system will work.

Feedback? bigear.gif
tiphat.gif
 

MoonShadows

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#2
Before I posted this yesterday, I wrote an email to Heliatos Solar (http://www.heliatos.com/) in Eversen, WA asking for advice, since this is the company I plan to buy the pump and solar panel from; they had helped me earlier with another question a few months back. I heard back today. Looks like from their response, my plan is viable: thumbsup.gif

Hello,

While I have not built a system like this for a greenhouse it sounds entirely feasible. Putting the panel in the greenhouse will diminish the overall performance somewhat because you will be capturing heat that is already entering the greenhouse, but you will be moving that heat into the thermal mass instead of it simply ending up in the air and on the surface. Anyway we have two pumps, of which you would realistically only need the much less expensive one. So I recommend using the HS-17 pump ( http://shop.heliatos.com/Heliatos-HS-17-Solar-DC-Circulation-Pump-0130021.htm ) which is also waterproof. This would be handy in a greenhouse environment. For the larger tubing and because you have 220 gallons of water I would recommend using a 25W PV panel ( http://shop.heliatos.com/25W-Photovoltaic-Solar-Panel-with-Wire-and-Mounting-Kit-0720019.htm ) with the pump.

Thank You,

Aki Abtahi, Ph.D.
Heliatos Solar
www.heliatos.com
Phone: (661) 7SOLAR7
 

MoonShadows

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#3
Well the heat absorber fins arrived from eBay, the solar panel and pump have been ordered from Heliatos, and tubing and all the fittings have been ordered from US Plastic Corp. The only things I need to get now are the wood to build the collector and some black spray paint.

I got to thinking yesterday that a 12' x 1' collector box is probably going to be too heavy and difficult to maneuver and attach into position in my greenhouse, so now I am thinking of making 3 - 4' x 1 collectors and attaching them...might be easier that way, but I have some time to decide before all the parts arrive.
 

jordan

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I think the 3 smaller collectors might be easier to handle like putting them up and if you have to take them down for cleaning or repairs. This looks like an expensive project, Moon. Is it worth it? Maybe you should just buy a heater or get your winter vegetables from the growcery store...LOL
 

MoonShadows

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Ah...if it wasn't for money, things would be a lot easier. Check out this system I was reading about tonight. It is a GAHT System. GHAT stands for Ground to Air Heat Transfer System. It is a "climate battery", different from a geothermal system, and was developed by Ceres Greenhouse Solutions. The GHAT System cools the greenhouse when it is hot outside and warms the greenhouse when it is cold outside. These folks specialize in year-round solar greenhouses. I posted about this GHAT system in our Resources. Besides a short video, there is also a link to a Ceres webinar about the GHAT system. OK, this goes on my Wish List for my dream greenhouse.

NEW_GAHT_infographic.jpg
 
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MoonShadows

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#9
Really interesting stuff, isn't it Lori.

My pump, solar panel, tubing and all the fittings arrived yesterday. The tubing is stiffer than I thought it would be; I could have gotten more flexible tubing, but it wouldn't have been UV resistant. As a result, this stiff tubing will not be able to make a 180 degree turn from one collector plate to the next in a 4 inch loop, so instead of 3 collector boxes with 3 collector plates, I am going to have to build 2 collector boxes with 5 plates each and thread the tubing around to every other one in 8 inch loops. I also ordered the wrong fittings for the 3 way valve...no biggy...I'll order them today.
 

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All the parts have arrived. If it weren't so cold out, I would have already started building it, but my workshop is an old unheated, uninsulated shed, and even though I have a small propane heater, it's not raising the temperature out of the 30's. That's too cold to work out there.

The tubing that will carry the water is too stiff to make a 180 degree turn within 4 inches....the distance between each collector plate, but it is the only black tubing I could find that is UV resistant. I suppose I could have used a more flexible clear tubing, but I want any of the exposed tubing to be black to absorb as much radiation as possible. So, I had to make a design change. Instead of 3 collector boxes measuring 54" x 12", I will make 2 collector boxes measuring 54" x 20" and run the tubing like so....
solar-collector.jpg
 
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#11
Yes, kinking hoses is the big enemy. I made that booboo when I triedmto make a collector with coiled black pipe inside a large clear water bottle. Frustrating to say the least.

Think I might play around with this stuff come summer..
 
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