Return to the Renewable Energy Forum | Post a Follow-Up

Solar water heating

Posted by zick (My Page) on
Wed, Oct 8, 08 at 13:52

Went on the solar tour last weekend and saw a really neat design.
A guy had active water roof mounted solar panels that were run through PEX tubing into a bed of sand under the foundation slab. He had 2ft of sand that the PEX was turning it into a large thermal mass.

My question is this;
We are building a new home on a concrete slab that will already have PEX tubing in the concrete for radiate heat that will run off a Geothermal unit.
Will I be able to connect the solar unit into the same PEX tubing that will be used by the Geo unit so that the Geo unit only runs when the solar can't keep up?

I was also thinking about running PEX under the garage to use strictly w/ the solar unit to help warm the garage in the winter.
Which would work better, having the large 2ft sand bed or just running the PEX in the concrete like the rest of the house?


Follow-Up Postings:

RE: Solar water heating

yes, you will need a large water tank store the heat from the panels.

where did you see the sand bed?

RE: Solar water heating

Sorry greif, I'm confused by your answer. I never asked about a large water tank for storage. Not sure what your referring to.

I did not personally see the sand bed, I saw pictures of it and that is what the owner told me.

I'm just wondering if I would need to run two separate PEX tubing lines (one for the Geo unit and one for the Solar unit) or if both units can use the same lines together.

RE: Solar water heating

I would think if you are attempting to design a heat sink out of a sand bed, and once it's solar potential is recovered, you would want automated changeover valves to redirect flow and kick in the geo system. Thus the solar tubes and sand bed tubes are separate, much like a heat exchanger in a solar storage tank.

RE: Solar water heating

How did they recapture the heat from the heat sink? There are similar systems for greenhouses that circulate air through the mass (2 ft of soil) to warm the greenhouse in the winter.

What climate is this in?

RE: Solar water heating

Good thought zl700.

This guys particular setup did have a water tank to storage the excess heat. It was a insulated 600 gallon tank.
I was going to go with some kind of water tank heat storage but probably not to that extreme since his house is larger than what ours is going to be.
I'm just wondering if I need to keep the two systems independent of each other.
This is in Southern WI.

Here is the link to the guy place we looked at;

Here is a link that might be useful:

RE: Solar water heating

It sounds like he has a pretty complicated system. Anyhow, I would keep the systems separate.

"Which would work better, having the large 2ft sand bed or just running the PEX in the concrete like the rest of the house?"

The sand bed (heat sink) and the floor should be thermal insulated from each other. Your storing heat from the high solar months(summer) and recapturing it in the cooler months. You don't want to heat the slab in the summer, otherwise your fighting the AC. They also usually have a thermal break on the sides of a large soil heat sink. They are not usually needed on the bottom.

RE: Solar water heating

if you are talking about the pex in the slab, same pex for both. you will need a control to tell it which source to use.
the water tank is to storage the heat from the solar colectors as they only heat during the day, also they can generate heat in the 170-180 degree range on some nice winter days and that is way to hot to put into the floor.
if corectly design the system will pull only the heat from the tank as needed.

if you want to do this system, hire this guy as an consultant, I have learned a lot from him

Here is a link that might be useful: solar consultant

RE: Solar water heating

I think I may have confused you, I'm not trying to use the sand bed as a storage unit like a water tank. I'm trying to use it as a larger thermal mass like the concrete slab and use it to heat the house. Putting a thermal break between the two will defeat what I'm trying to accomplish.

That you for that info, I will definately consider contacting that solar consultant.

Thanks for the info guys!

RE: Solar water heating

gary, thanks for the solar today link, that's bob ramlow who is the consultant I said zick should hire if he is serious, he's got 30 years in solar hot water and air and now works for wisconsin's focus on energy and does consulting and teaching


 o Post a Follow-Up

Please Note: Only registered members are able to post messages to this forum.

    If you are a member, please log in.

    If you aren't yet a member, join now!

Return to the Renewable Energy Forum

Information about Posting

  • You must be logged in to post a message. Once you are logged in, a posting window will appear at the bottom of the messages. If you are not a member, please register for an account.
  • Please review our Rules of Play before posting.
  • Posting is a two-step process. Once you have composed your message, you will be taken to the preview page. You will then have a chance to review your post, make changes and upload photos.
  • After posting your message, you may need to refresh the forum page in order to see it.
  • Before posting copyrighted material, please read about Copyright and Fair Use.
  • We have a strict no-advertising policy!
  • If you would like to practice posting or uploading photos, please visit our Test forum.
  • If you need assistance, please Contact Us and we will be happy to help.

Learn more about in-text links on this page here