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?

Jim, I'll certainly be interested in hearing how that works for you -- it sounds like a great system to me!

I have already ordered the pump and solar panel. Tomorrow, I am going to order the tubing and bulk head fittings. I figured I would build this during the coming Summer for next Fall, but I have moved up my plans to have it finished by the end of February, so I can start my seeds earlier and have considerable growth by the time I set y plants out in May.

It sounds like a great project! Be sure to give us an update after it's in use.

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....

Got the first solar collector done this afternoon. The entire inside will be sprayed a flat black heat resistant paint and covered with a plexiglass top.

It's looking good, Jim. Let us know how well it works once you're using it.

I got the second solar collector built yesterday. I was hoping to get the two of them painted black today, but it is too cold to use the spray paint. I don't want to take a chance that it doesn't adhere properly. It is sunny and in the upper 30's. I think I will wash out the 4 drums. They held coconut oil before I bought them, and I need to get the residue out.

That is cold! I bet the drums will smell good!

I washed out the 4 drums today, but didn't smell the coconut oil. I was quite the site out there with my pink Playtex Gloves! They are drying off in my workshop now. Looks like I won't be able to paint the solar collectors for the foreseeable future, but I can cut the holes in the drums for the hose bulkheads, level the drums of in my greenhouse, and run all the hosing for the collectors. Once I can paint the collectors and attach the plexiglass, I can get the system up and running.

The drums are leveled and in place. I cut the holes for the bulkheads and have the 4 drums connected now with the tubing. Finally, this weekend it is supposed to be in the forties, so I may be able to get the solar collectors painted. If that happens, I should have the system up and running shortly.

I'm eagerly awaiting the finish and testing of your system, Jim.!

Here are a couple of pictures of the barrels with the hosing connected, and it was finally warm enough outside today that, with my little propane heater, I was able to get the two solar collectors painted.









I still have to cover the collectors with plexiglass and hand them. Then, I will just need to make the final attachments, fill everything with water, and give the system a test run!

I got the 2 collector boxes hung today. I did a "dry run" hanging without the plexiglas just so I wouldn't scratch or crack it. Now, I have to take them down, cut and attach the plexiglass and re-hang them; that's for tomorrow afternoon. I had to make the angle a bit higher than I wanted which should be 23 degrees, but at 23 degrees, I will hit my head on them. Even with the increased tilt, about 30 degrees, I was surprised at how warm the metal surface covering the tubing got. I think this just might work. I am excited.

This is exciting and I can't wait to hear your results!

I will also be waiting to hear your results, and sure hope they are wonderful.

Got the pics taken and the video made today. Right now, the temperature in the drums has risen from 50 early this morning to 67 as I write this on a mostly sunny day at 1:35 in the afternoon.

Enjoy the video!

Very nice! You've done a really nice job making it, and I'm betting it will add a lot of heat to your greenhouse!

Jim, Very nice job a pat on your back. I sure would like to know how this is working and heating in a few weeks from now.

I can't wait to hear results!