Domestic pool turnover rates

[CarlD]

Thanks, Mark. Yes, it's correct that my solar panels are part of my deck and priming them is only an issue in the spring because they were drained for the winter. Other panels I've used have also not been elevated so I've no experience with the control valves needed.

[chem geek]

The recommended flow rate for my solar panels is 4 GPM per panel and I have 12 panels in parallel so that's 48 GPM. I could run slower with somewhat less efficiency. Even going from 4 GPM per panel to 3 GPM per panel (which is the "minimum recommended") only drops efficiency from 80% to 70% while energy usage would drop from 1500 Watts down to less than 900 Watts. Or I could split the difference and do 3.5 GPM per panel at less than 1200 Watts. I've considered doing that, but haven't changed to it yet. My wife often swims earlier in the day so needs the heating to occur more quickly, but it's a dance for how high to get the temperature the night before so that it is warm enough at the start of the next day.

The other reason my pump energy cost is pretty high when solar is running is that I have a long 75 foot pipe run to and then from the solar system on the single-story roof. I lose 1.2 PSI because my PB used 2" pipe instead of 2.5" (or 3") plus the 12 panels are spread over 3 different roof hips over the length of the house. Also, marginal electricity rates are high at 35 cents per kilowatt-hour (or more). My filter pressure with solar at 48 GPM is roughly 24 PSI which is high (55 feet of head) where the highest point of solar on the roof is perhaps 20 feet high so the rest is largely inefficiency in the piping and outlets. I'm sure I could operate at a slower flow rate without the VRV opening since 36 GPM with solar on is roughly 16 PSI in my pool system.

[CarlD]

Thanks for the explanation, Richard.
Do you use a solar cover at night, too, to hold in heat? I find it's critical to efficiency.
If you have an attic, have you thought of running additional plumbing through THAT to pick up more heat energy?

Luckily, since my panels are only about 3 1/2' above my pump and, at most 10' away, I don't have to deal with all those issues you do.

[chem geek]

I have an automatic electric safety cover that is on all the time except when the pool is in use. The pool is used almost every day for about an hour or two. And yes, having a solar system without a pool cover will have less benefit. Basically, with no cover then overnight in the non-peak of the swim season I can lose 6ºF but with the thin non-insulating but opaque cover I lose 3ºF. If I had an insulating bubble-type cover, I'd lose around 1.5ºF.

The solar panels on the roof pick up the sun's energy directly so our attic is cool when they are running and is a side benefit to keeping the house cooler as well (though the attic is fairly well insulated from the house interior). It's more efficient to have the panels on the roof than it would be having them in the attic. For maximum efficiency in the attic one would want very dark roof tiles thermally connected to the attic. The fact that our synthetic shingles are gray and not black has them not absorb as much heat as the black solar panels and they do not transfer the heat as efficiently to the attic through the roofing materials. Roof attic heating is not an efficient solution unless the roof was designed specifically for that purpose -- it's not that such systems don't work, but that they aren't as efficient as panels on the roof.

[CarlD]

Hm.....Can you find a way to velcro a solar cover to the underside of the auto safety cover?