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RE: Solar hot water for pool

Post in 'The Green Room' started by firefighterjake, May 8, 2012.

  1. firefighterjake

    firefighterjake Minister of Fire

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    Thinking about buying one of those kits that you can hook up to your pool pump . . . something like the Sun Pirate . . . anyone here use one of these? Looking to warm things up a bit quicker so I can start swimming earlier and keep swimming later.

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  2. Delta-T

    Delta-T Minister of Fire

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    you might like building one for yourself. My brother and I built a solar heater for a pool out of a full sheet of plywood, some 2x4's, and a few sheets of lexan,black paint, and a garden hose.
    Did this for a gent we did landscaping for. Worked very well considering it took us just a few hours to build, and the cost was fairly low. We used a small water pump to move the water from the pool to the collector. In full sun the water came out well warmer than 120F, sometimes it was too hot to touch.
  3. btuser

    btuser Minister of Fire

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    In ground or above ground? I've got an 30k gallon in ground and looked into solar options, but the square footage required for the collectors was enough so I lost interest.
  4. fishingpol

    fishingpol Minister of Fire

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  5. firefighterjake

    firefighterjake Minister of Fire

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    24 foot above ground.
  6. btuser

    btuser Minister of Fire

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    If you've got Southern exposure on the side of the pool you could put in a pretty good size collector and up your temps quite a bit. I did notice that a lot of the sites that help with sizing them discount the use of a solar cover. When we bought the house there was a 400k propane heater and no solar cover. After running it for 8 hours once I decided I would rip it out to avoid temptation. We bought a solar cover and it helped but the pool was still cool till mid June.

    I used to run the filter at night (off-peak load etc) but I started noticing the top of the water was very warm during the day. The sun was warming the top 2' of the water 10-15 degrees warmer than the bottom. I started running the filter in shifts from 12pm-4pm and 12am-4pm and the temp of the pool went up by almost 5 degrees mid Summer and builds much faster earlier in the year. It helps a lot. I've got a long-range plan of a shed for outdoor furniture + pool stuff to hide the filter and whatnot. I will end up with a roof of about 140 sqft which may help a little.
  7. jimbom

    jimbom Combustion Analyzer

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    Jake, I know this is not intuitive, but I believe you can build a slanted surface and run the water down the surface without a cover and raise the temperature 20::F at a flow of 0.03 gpm/ft^2of surface. Collect it in a gutter and run or pump it into the pool.

    I have been running tests and get 20::F temperature rise from 60 to 80 degree slopes from horizontal on 8 foot panels. It is real easy to check this out yourself at your location.

    Just paint a surface flat black and set it up at the best angle for your latitude in May. I use my hose with a nozzle, a five gallon bucket, and bathroom scale to get the flow rate needed for the square foot used in the test. Then the IR thermometer and a cookie pan to catch the warm water at the bottom of the panel. I am testing an eight foot panel, because that is how high my collectors will be. I am testing 80 degree slopes because I want more heat in the winter and less heat in the summer. IR the water out of the hose and the water in the cookie pan.

    If the panel surface area is the same as your pool surface area, evaporation loss on the heat panel will be about half the gallons per day as daily loss from the pool itself when uncovered 24 hours. You could check this yourself by circulating the same water over the panel for an hour then weighing the loss.
  8. btuser

    btuser Minister of Fire

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    A lot of good solar collectors can be seen at builditsolar. You're still only getting <10k an hour and that ain't a lot. 60k/day is a far cry from 300k/hr, but it's free after the initial so I'm interested.

    I like the idea of the waterfall over the metal panels, but would like to add polycarbonate to the top to avoid the evaporation losses and to improve the efficiency in cooler months. Depending on the thickness of the water layer and slope I would worry about it buldging out at the bottom or cooking/warping when it was dry or the pool was too hot. The black coils look like they'd work when it's already hot outside, but they're ugly and I'd have to stare at them all year long. Maybe make the system modular so I can disassemble+store the coils when not needed (Winter and the hot season) You could do the glass door thing, work up some crazy stuff. It would be fun.
  9. btuser

    btuser Minister of Fire

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    Here's s a pretty straight-foward site. Well maybe not that straight forward but there's a lot of numbers to dig through to compare.

    http://www.solar-estimate.org/

    I came up needing a collector area of 808 square feet. Probably not going to happen, but I can get by with lower than 81 degrees May 1st. However, below 70f there is the danger of significant shrinkage.
  10. Jags

    Jags Moderate Moderator Staff Member

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    Reduced drag for faster swimming. Just say'in.
    Gary_602z likes this.
  11. GaryGary

    GaryGary Feeling the Heat

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    Hi,
    I think the small kits that include a collector and hook up to your regular pool pump are a good way to go -- quick return on investment.

    I did some work on just running water down a dark colored metal plate as mentioned above: http://www.builditsolar.com/Projects/PoolHeating/DIY/SimplePoolHeat.htm
    I think that for these its a good idea to use a plate that has descrete grooves for the water to follow. This reduces evaporation cooling because most of the surface is running dry with no evaporation. The grooves have to be close enough so that the metal can do a good job of conducting the heat through the metal and into the water flowing in the groove. The efficiency I measured for this kind of panel was very close to the commercial rubber mat collectors. I tried glazing with SunTuf polycarbonate and (at least for the conditions I tested under) there was no improvement in efficiency -- colder weather would be a different story.
    For any pool collector its good to get the flow rate up to where the temperature rise over the panel is small -- I'd say 5F or less if possible. The reason being that the warmer the collector runs, the more heat it loses to the ambient air.

    One idea that easy to overlook on the pool page at BuildItSolar is this very simple paint the south side of the pool black: http://www.builditsolar.com/Projects/PoolHeating/BlackSide.htm Deane (who sent this in) is a solar guru, so I believe that this really can result in a worthwhile improvement under the circumstances he listed. If you don't like black, any dark shade will do.

    But, the kits for above ground pools with a collector or two that just hook up to your current pump seem hard to beat -- I got a rough payback estimate of 67 days for the one that Costco was offering a while back: http://www.builditsolar.com/Projects/PoolHeating/Payback.htm

    GAry
  12. jimbom

    jimbom Combustion Analyzer

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    Gary has done it again. Excellent ideas and pages for pool heat. My hat is off to builditsolar.com and Gary. He is doing more to reduce carbon emissions than all the politicians in the world.

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