Pool Solar Heating - Help orienting the roof-top solar collector please

In summary: Today's collectors have tubing webs made of either single or multiple layers of plastic.The first layer is the insulation, and wind can easily penetrate the plastic and cause the tubing to freeze.The second layer is the transparent plastic, and the wind can easily blow the frost off the top of the transparent plastic and onto the underlying insulation, which then causes the insulation to freeze.In summary, Sean's advice is that homes with south-facing slopes are the best orientation for pool solar.
  • #1
Hello there, Physics forum. I live in Alamo, California and I'm planning to install pool solar. All of the installers have completely different POVs on which face of the roof I should put them, and hoping to get some physics-based advice. Here's the home with the 3 face options (front already has actual solar, so can't use).

Sat view .png

Two installers really like using both faces #1/2 (individually the system might not be large enough), and two others like face #3.

  • Face #1 gets the most direct afternoon sunlight with the best angle of attack
  • Face #2 is about equivalent to face #1 for total sun, but afternoon angle of attached worse
  • Face #3 probably gets the most TOTAL SUNLIGHT for the day, but afternoon sun is less direct. Morning sun is stronger.
I'm getting very different answers on if with pool solar, the angle of the sun relative to the panel matters or doesn't matter like it does with electrical solar. One installer says, all you're doing is heating the collectors so better to optimize for total light. Another says shoot for the most perpendicular afternoon angle of sun to panels.

Any guidance or thoughts on how to approach this problem? Things I need to come up with a point of view on:
  • What are the optimal thermodynamics here and time of day considerations?
    • The pool water itself will be colder in the AM, as will the ambient temp and panel temp? What set up at the end of the day transfers the most heat to the pool water -- e.g. a.) running slightly colder AM water through panels that may heat up a little more quickly on face #3 given the AM light? b.) running slightly warmer afternoon water through warmer afternoon panels (might argue for face #1).
  • Does the angle of attack matter for pool solar (i know it does for electrical) relative to how how the panels get?
  • For the installers that are eyeing using both faces #1/2 does that create a problems / inefficiencies that the panels would be different temperatures throughout the day?
Thanks so much if you're open to spending a minute to help me think through this!

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  • #2
What is the prevailing direction of winds?

Here in Florida, South is the preferred orientation.
As we are located on the North hemisphere, the Sun comes out from the ESE and goes down at the WSW.
Therefore, 20 some degrees of slope, facing South, gets the most Sun exposure intensity and time.

That being said, many customers complain about the low effectiveness of new plastic solar collectors.
The reason is wind exposure of the naked plastic tubing webs.
Old stile collectors had an insulated enclosure with a single or double glass, which greatly reduced heat loss due to wind.
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Likes berkeman

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