glazed copper tube solar panels for pool heating

bobyoeMarch 11, 2005

We have a number of good quality copper tube, glazed solar panels that we would like to use for heating our pool. We would use a heat exchanger, of course, so pool water would not pass through the copper tubes. I have tried to find comparisons on heat output of plastic (unglazed) panels vs glazed copper systems. All the info I find talks about glazed panel systems not being cost effective for pool-heating, which would be a factor if we were paying full price for the panels, but we already own them. What I'd like is a BTU output per square foot comparison, or something like that, without factoring in the cost. I am thinking that we would not need the 75 to 90% ratio with the glazed panels to get the same pool heat....right? I posted this on the pool and spa forum, but I am not sure they knew what I was referring to in the glazed panels, and replied that "BTU out put is the same for all brands." That can't be right when comparing black plastic unglazed to the glazed panels. Any help would be appreciated!

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The point of glazing solar panels is to reduce their heat loss. When heating domestic hot water (DHW) this is important as you need water that is about 150 degrees F whereas a pool solar panel can quite easily handle water at 90F and be adequate. I don't know why you would not circulate pool water through the panels so long as their throughput capacity is matched to the pool pump. Pool heating is about circulating a lot of water for a relatively modest heat gain as compared to a DHW system which circulates 40 gallons for a required heat increase of 100F plus! The heat exchanger seems an unnecesary complication unless you plan to use solar pool heating in winter and need freeze protection. (Why?)

The rule of thumb relating pool size to panel size is very rough as a lot depends on local climate and the temperature rise needed. Is your roof facing south or southwest?

You should be able to find a link for solar insolation (the amount of energy coming in from the sun) and then guesstimating that your panels capture a fraction of that. I would be surprised if you did not end up needing at least half the pool surface area for solar panels, but then you have the panels already, right?

    Bookmark   March 14, 2005 at 2:31PM
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We cannot circulate thru the panels because of the copper pipes (in the panels). It would react with the chlorine and salt in our sanitation system. I have heard that older pools that had copper plumbing faced a lot of staining issues as well as chemical imbalance. We realize these panels are overkill for pool heat, but we have them and thought we should put them to use.

    Bookmark   March 14, 2005 at 3:06PM
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Pool area is about 550 square feet. Panels are 4x12 so we were thinking that 6 panels ought to do the job. Sound about right? Our property faces almost due south, and the panels will be placed on a slope, not on the roof. There will be plantings further down the slope to hide the panels from the road and neighbors, but not to block the sun.

    Bookmark   March 14, 2005 at 3:57PM
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My simple black plastic panels allegedly put out 80,000 btu per day and they are 80 square feet for each panel. Your glazed panels will be more efficient but not by much but any sort of heat exchanger will reduce that efficiency.

So your 6 panels are 288 square feet which will put out at least 288,000 and maybe (guessing) 320,000 Btu per day. 1 Btu raises 1 pound of water by 1 degree fahrenheit (assuming no losses) so work out the weight of water in your pool and see what heat gain that will provide. I don't know the U.S. gallon formula, but an imperial gallon weighs 10 lbs and the U.S. gallon is about 20% smaller.

You will get additional heat gain from direct sun falling on the pool which would be helped by a solar blanket.

Good luck

    Bookmark   March 16, 2005 at 5:41PM
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