Solar panels vs coil/spiral collectors

[SoCal_Refugee]

This is my first post and thanks in advance to all of those so willing to share their knowledge and experience. I look forward to the day when I can contribute more to the forum. I couldn't find my specific question in my forum searches, so I hope I'm correct in starting a new topic rather than attaching to one of the earlier solar threads.

We just moved into a Tucson home with 9,000 gal inground pool, our first pool experience. The existing solar panels are deteriorated, leaking and poorly installed (roof leaks) so we are re-finishing our flat roof and installing new collectors. We're trying to evaluate collector panels (heliocol) vs the spiral/coil type like those manufactured by SolarTech. There's about a $1,500 price difference with heliocol panels more expensive. We've heard the spiral/coil collectors dismissed as "garden hose on the roof" but in my experience the simpler designs are often the best. Does anyone have experience with either collector type that can help our decision?

 

[JohnT]

Welcome to TFP!

The mats are the only way to go. Surface area where water and heat come together is what makes panels efficient. They don't even compare in heat capturing ability.

 

[jblizzle]

Welcome to TFP!!! Another Tucsonan

Solar heating is all about sqft of exposure to the sun and the flow rate through the tubes. You can usually get more sqft from the panels than from the coils in a given area of roof.

When I bought my current house there was 2500' of 1" black pipe thrown randomly around the roof (which is nearly flat, but it is pitched). It heated some, but I was always fighting with leaks ... likely because there was no way to easily get them fully drained. If they were properly coiled, I would have had about 200 sqft of exposure and they would have heated better, just not sure what to do about the leaks (granted maybe the true coils are better than the pipe that I had).

I did a DIY install of used Heliocol panels that I bought of craigslist in PHX. I have much more area and they are all sloped so they drain properly. With a flat rood, a DIY install is pretty easy. If your roof is completely flat, I thought I had heard that the coils may be a little more resistant to freeze damage (although not sure how to explain my experience with the black pipe).

While I can not completely recommend it, I will say that my panels are only attached to the roof with roofing cement on the header clamps with no roof penetrations. Being that the Heliocol panels are individual tubes, they catch less wind and require less anchoring than other panels. Now if the house takes a direct hit from a dust devil are the panels going to stay on my roof ... I think so ... but I could be wrong

 

[linen]

linen edit for clarity

Welcome to tfp, SoCal_Refugee

Just to add to what others have said above, even if a long coil of tubing gives you comparable surface area, the temp of the water will increase a lot as if flows through those coils, and this will decrease efficiency. Best solar heating designs are high flow with a small temp change in the water from inlet to outlet [s:1ellnx34]low temp change across the[/s:1ellnx34] of the collector. I would pass on those spiral coils and go with a mat style. In addition to the Helicol design (which as I understand is a mat style with separated tubes), there are a bunch of other mat style choices.

 

[Isaac-1]

Like the other's have said solar pool heating is primarily about 2 things, surface area and water flow, sure material selection, tube thickness, etc play a part, but it is a surprisingly small one. Conventional rectangular panels win both of those points. Sprial tubes waste space between each section, and tend to have a lot more flow resistance since all the water has to go through the whole spiral, where conventional panels have a header pipe on each end and only some of the water goes through each finger. My past experience with agricultural black tubing for a home built solar collector is also one of constant fight against leaks and patching, and the only way I would consider something like it again in the future would be if I could get the tubing for free, even then I might opt for a commercial panel.

Ike

 

[SoCal_Refugee]

Wow, I didn't expect so many very helpful responses within hours of my original post. Thanks to all, your posts were thoughtful and instructive, and I learned more about the question than I had in the previous week of endless web searching. Heading for Pool School to learn more and become a contributor. Thank you!