Solar Water Heating

[mannytheseacow]

About time I posted my passive solar hot water heating system up here.

The core of the system is the tank. I framed up the sides just like standard 2x4 rough construction. The interior dimensions come out to be 3'x4'x4'. It's all marine treated lumber, built for the long haul. Inside the construction is 1" foil faced foam sheeting, then an EPDM pond liner. The lumber side of things is insulated with fiberglass insulation, just like a home. (excuse the mess)

The tank is filled with water just for heating purposes. I don't drink it or bathe with it- I filled the tank years ago and there it sits. The top is covered with a piece of plywood, a layer of 2" foam and wrapped in more rubber pond liner. That water gets pumped up through some panels on my roof:

There are 4 panels, 8'x4' each, for a total of 128 sq.ft. A small pump circulates the water up through the panels through 1" PEX. Here's the control system:

There's a sensor mounted to the panels on the roof and when the panels are warmer than the water in the tank the pump will turn on. The whole system is sloped at 1/2" per foot so that when it is not pumping the whole thing will drain back into the tank (important feature in cold winter climates). I have never had any freezing issues; the PEX lines to the roof are wrapped with that foam pipe wrap and it seems to work just fine.

So, that's the core of the system. From there I have a 100' roll of 1" pex that sits in the tank and that is what my well water goes to in order to get hot. By the time it passes through that 100' roll it will be the same temp as the tank water. This works amazingly well. Most of the year my pumps shut down when the tank hits 120*. It can heat hotter, but this seems to be the right balance for my system. If my tank hits 120, I can still depend on comfortably hot water for several days without sunlight, still in the 110* range. If all else fails , or if there is a long period of no sun, the output from the 100' pex heat exchanger passes through a tankless water heater.

The beauty of this is that the tankless heater is programmed for 107.5* and only turns on if the water temp is below that. If the water is 106* it will heat the water to 107.5*. If the water is 108*, it doesn't run.

I have the option to circulate my tank water through my floors, but I don't do it very often. It takes a lot of heat out of my tank by trying to heat my floors. I originally installed this system to heat my floors but once I discovered the beauty of the domestic water heating I pretty much just use it for that now. The newest addition is RMH option, but we'll see where that goes.

I can't take any credit for this system, Gary Reyes is the mastermind behind it. He outlines his build explicitly on his site:

[matt walker]

I'm so glad you posted this Manny, thank you. Gary does good stuff man, he should be a millionaire for all the info he shares everywhere, and so nicely.

So, did you build the collectors yourself? Would you mind linking to the build info on those, I always get lost over at Gary's site, there's so much to learn.

This looks like it was a huge project, and seems completely overwhelming to me, even though I can grasp all of it in parts. Did you find it really daunting? One step at a time and no big deal? I dream of doing this here, but I'm not sure I have enough sun and I'm not sure I can handle the build. I'm really, really inspired though. May be my winter research project, along with the home brew.

[DevilsBrew]

Wow, Manny. Nice set up.

[mannytheseacow]

Yes, Gary is super cool, very helpful, and has a site full of information (like someone else I know ). I really like all the testing and monitoring he does on his completed projects to document the performance. I know what you mean about getting lost on his site. It is so packed with information and projects, and I'm sure the way the site is mapped makes perfect sense to him, but I struggle with it too sometimes.

I didn't find the project too daunting. After reading Gary's project and reading through the details it seemed simple. I just had to modify it for my home. His build has the tanks and collectors located in an outbuilding and then he pumps the water into his house. There are tradeoffs with my setup, as his. I have to pump my water 30' to the roof, so I'm paying more for pumping, but then I don't need the underground run and heat loss like he has in the outbuilding- anyway... Once I had my basic radiant heat system in place then the tinkering begins. "What if I add this other part to heat my domestic water?" "What if I add another pump and circulate water through my wood stove". etc.

No, I didn't build my collectors. Gary has a bunch of good info there on building it. When I was doing the math on building vs. buying I found a solar installer 5 hours away from me that was going out of business and that guy just happened to have my four panels laying around. One was damaged on the back but it was only cosmetic and has held up for years now. It just worked out cheaper for me to buy in this instance.

One other thing, I'm not sure how the system would work in the PNW. It works for me and I live in the woods. I get a substantial amount of sun on the collectors in the morning but not so much by the afternoon. They heat up all winter long when there is no foliage on the trees and all summer just because the ambient air temperature is so hot. I do have declines in performance in spring and fall when there are still leaves on the trees but air temps stay cold. You'd have to experiment with your climate and rainfall. By the way, tankless water heaters are the best, in my opinion. If you were to start there, then you are only adding efficiency with the solar heating working as a booster, even if it didn't heat it all the way.
Oh, and here's some links to Gary's Projects:

This one is new but looks very good, too:


I should also mention, because of state and federal rebates I only paid for 1/3 of this system. I don't think this is true for every state.

[matt walker]

Thanks Manny, I'll tear into it when I get back from D.C. I can't really put anything else in my brain right now, but I am very interested.

Your comment about my location is why I asked specifically about the collector plans. I'd like to mock up a cheap one and put it out in my barn (sunniest winter building) and see how it does during my low angle months. I have about 6 weeks of very, very little direct sun.

Yep on the tankless heaters, my neighbor has been praising them to me for years and when I need to replace my standard 220v heater that's the direction I'm going for sure.

[DrewInToledo]

[matt walker]

Dang, badass Drew! Thank you. Have I mentioned how glad I am to have you here? 'Cause I am!

[rjdudley]

Manny, I may have just witnessed my future!
Nice setup. Is that a Titan tankless? It looks similar to the one I have in my home. I have been dying to figure out and implement a way to preheat the well water before it hits my tankless. I was really hesitant to put anything into my RMH after hearing all the noise about the "Boom/Squish" if it's not done correctly.
Now I wish I had done a little more research and figured out how to put some copper tubing into it.
I love the idea of the water mass preheating. Maybe I could figure out how to wrap my vertical exhaust tube with some copper and still pipe something like you've created.
Man, the wheels are turning!!! There are two things I hate: 1)losing any heat that could be captured and reused, 2) thinking about my well water coming in at 50˚ and needing to be heated by my tankless. Marrying those two thing would make me VERY happy, and you're system may be just the thing.
Thanks again for posting it.
Drew, seriously? That looks like something NASA would try to put into orbit
I LOVE, LOVE, LOVE that. Solar kinda spooks me. Attaching things to the roof, plumbing, possible boom/squish. I need a swift kick is what I really need.
Great work guys, great work.
Ray

[mannytheseacow]