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Thread: Heater recommendations needed - Solar heaters?

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    Heater recommendations needed - Solar heaters?

    Hi all,

    I've seen on eBay a number of these solar heaters which are in effect a long length of black hose. I can understand the principal but living in the UK we don't a) get very hot days and b) have a tremendous amount of sunlight compared with other countries. Has anyone used these before and what is your feedback?

    My pool is an Intex 15' x 42" round above ground.

    Thanks
    Darren
    CERLAND OCTAGONAL ABOVE GROUND POOL

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    Re: Heater recommendations needed - Solar heaters?

    A single hose even coiled or zig-zagged isn't going to be particularly efficient. The best solar panels have around 80% efficiency meaning that they absorb and transfer 80% of the sun's energy into heating the water that flows through them. These solar panels have many thin tubes in parallel and close together. Some even have inside curve channels to create circular flow in the tubes for greater heating (though this only improves efficiency by about 5%). In the U.S., solar panels are independently rated by the Florida Solar Energy Center. The most efficient panels are the FAFCO Revolution at 1063 BTU/sq.ft. though most panels are in the 1000+ BTU/sq.ft. range which is reasonably efficient (these BTU/sq.ft. are heating amounts in Florida -- you won't get anywhere near this amount of heating where you live).

    The main problem you will have is that many of your days are cloudy and the air temperature is not that warm. This not only has the sun's energy hitting the panels be lower, but also makes the panel's less efficient since they will lose some heat if the water temperature is warmer than the air temperature. As shown in the chart in this post, on a cloudy day a water/air temperature difference of just 5ºC lowers panel efficiency from 80% to 46% on an already lower heating ability.

    Finally, there is wind. These black flat mat panels don't do well if there is a water/air temperature difference and there is any wind. The efficiency drops rapidly in that case.

    You can use this link to find out the amount of solar energy you get in your area. In southern England, for example, the peak solar is in June and July at around 4.8 kWh/m2/day for a horizontal surface. If you tilt your panels towards the sun (about 28 degrees), then you can increase this to 5.4 kWh/m2/day. Your 15' x 42" pool at around 618 cubic feet or about 4625 gallons (about 38,550 pounds of water) would need 38,550 BTU (11.3 kWh) to raise the water temperature by 1ºF. So assuming a generous 80% panel efficiency, you would need about 2 square meters of panel area for every 1ºF of temperature rise in one day. A typical 4'x12' panel is around 4.4 square meters.

    Your pool surface area itself is 177 square feet (16.4 square meters) so using a clear bubble-type solar cover is the least expensive approach to heating your pool and would be needed anyway even if you were to use solar panels so that you could retain heat at night. If your pool vinyl liner is dark, then you might get reasonably high efficiency of sunlight heating the pool, though probably not more than 80% efficiency at best between reflection from the vinyl color and the absorption in the solar cover. So just the solar cover alone could result in a temperature rise of up to 8ºF per day, at least initially (i.e. when the water is the same as average air temperature) though in practice you might see only half that. A good clear bubble-type insulating solar cover should be able to increase your water temperature to at least 15ºF higher than average day/night air temperature if not more. In June/July, the average day temperature in London is around 22.5ºC (72.5ºC) while at night it is 14ºC (57.2ºF) for a rough average with more day weighting of 66ºF so just a solar cover alone could get your pool water to 81ºF (27.2ºC) or more.

    Of course, if you live in the northern part of England, the achievable temps will be quite a bit lower.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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    Re: Heater recommendations needed - Solar heaters?

    Brilliant reply. Thanks. An Elecro 9KW electric heater is what I need then!
    CERLAND OCTAGONAL ABOVE GROUND POOL

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    solarboy's Avatar
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    Re: Heater recommendations needed - Solar heaters?

    What about a heat pump Darren?
    Self built 5500 gallon bare concrete (temporarily) pool with limestone coping, Pentair Swimmey 1/2 HP pump, Triton sand filter with DE, Simpool peristaltic muriatic acid pump with pH sensor and Monarch SWG. Home made solar heater with Pentair Compool control panel and 3 way valve. 1 skimmer, 1 main drain, 2 returns, 2" plumbing, Hayward auto fill valve.

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    Re: Heater recommendations needed - Solar heaters?

    (written while solarboy posted; so duplicate suggestion about a heat pump)

    Well, you should get a solar cover in any event, regardless of the supplemental heating method that you use. Also, an electric water heater is the least efficient way to heat pool water. If you have natural gas, that is far more efficient than electric direct heating. Now if by electric you meant a heat pump, that's a different story and the efficiency will be closer to gas and possibly less expensive to operate depending on your electricity vs. gas rates (your typical summer temps are OK for a heat pump). A heat pump with a Coefficient of Performance (COP) of 5 will cost 1/5th as much for the same heating compared to direct electric resistance heating.

    Also note that a clear solar cover will unfortunately also allow the UV from sunlight into the water which will break down chlorine. So your chlorine usage will be higher than if you used a more opaque cover, but with an opaque cover you only retain heat but do not gain any from solar heating through the cover. That's the tradeoff, but in your case with heating probably more important, a clear cover would likely make more sense. You'll just need to add chlorinating liquid (Javel) or bleach every day or two to the pool, or perhaps you can get away with using Trichlor pucks/tabs in a floating feeder since your season will probably be relatively short and you may drain/refill between seasons (?).
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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    Re: Heater recommendations needed - Solar heaters?

    Quote Originally Posted by solarboy
    What about a heat pump Darren?
    Way too expensive for me I'm afraid.
    CERLAND OCTAGONAL ABOVE GROUND POOL

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    Re: Heater recommendations needed - Solar heaters?

    Quote Originally Posted by chem geek
    (written while solarboy posted; so duplicate suggestion about a heat pump)

    Well, you should get a solar cover in any event, regardless of the supplemental heating method that you use. Also, an electric water heater is the least efficient way to heat pool water. If you have natural gas, that is far more efficient than electric direct heating. Now if by electric you meant a heat pump, that's a different story and the efficiency will be closer to gas and possibly less expensive to operate depending on your electricity vs. gas rates (your typical summer temps are OK for a heat pump).

    Also note that a clear solar cover will unfortunately also allow the UV from sunlight into the water which will break down chlorine. So your chlorine usage will be higher than if you used a more opaque cover, but with an opaque cover you only retain heat but do not gain any from solar heating through the cover. That's the tradeoff, but in your case with heating probably more important, a clear cover would likely make more sense. You'll just need to add chlorinating liquid (Javel) or bleach every day or two to the pool, or perhaps you can get away with using Trichlor pucks/tabs in a floating feeder since your season will probably be relatively short and you may drain/refill between seasons (?).
    I do have a solar cover. It's blue, and like bubble wrap. Whether it's good or not I have no idea.
    CERLAND OCTAGONAL ABOVE GROUND POOL

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    JasonLion's Avatar
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    Re: Heater recommendations needed - Solar heaters?

    Any solar cover is way better than no solar cover.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    solarboy's Avatar
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    Re: Heater recommendations needed - Solar heaters?

    Quote Originally Posted by darrenkarp
    Quote Originally Posted by solarboy
    What about a heat pump Darren?
    Way too expensive for me I'm afraid.
    I think you'll find your first electric bill after installation even more shocking. It takes a truly monumental amount of energy to heat up a pool and keep it warm. Some of my clients here estimate it around 100€ to initially heat it up, and then 100€ per month to keep it there. And this is in Portugal.
    I've never seen and electric heater fitted here and only 2 gas heaters. The rest is heat pumps which cost from 3k€ upwards. Do you have space for a gigantic solar heater or have you looked into a glazed panel system?
    Self built 5500 gallon bare concrete (temporarily) pool with limestone coping, Pentair Swimmey 1/2 HP pump, Triton sand filter with DE, Simpool peristaltic muriatic acid pump with pH sensor and Monarch SWG. Home made solar heater with Pentair Compool control panel and 3 way valve. 1 skimmer, 1 main drain, 2 returns, 2" plumbing, Hayward auto fill valve.

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    Re: Heater recommendations needed - Solar heaters?

    Quote Originally Posted by solarboy
    Quote Originally Posted by darrenkarp
    Quote Originally Posted by solarboy
    What about a heat pump Darren?
    Way too expensive for me I'm afraid.
    I think you'll find your first electric bill after installation even more shocking. It takes a truly monumental amount of energy to heat up a pool and keep it warm. Some of my clients here estimate it around 100€ to initially heat it up, and then 100€ per month to keep it there. And this is in Portugal.
    I've never seen and electric heater fitted here and only 2 gas heaters. The rest is heat pumps which cost from 3k€ upwards. Do you have space for a gigantic solar heater or have you looked into a glazed panel system?
    As the British seasons is short (roughly June - August) at £100 per month is okay with me. Keep in mind that my pool comes down when the season is over.
    CERLAND OCTAGONAL ABOVE GROUND POOL

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    solarboy's Avatar
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    Re: Heater recommendations needed - Solar heaters?

    True enough ! Nice and simple too.
    Self built 5500 gallon bare concrete (temporarily) pool with limestone coping, Pentair Swimmey 1/2 HP pump, Triton sand filter with DE, Simpool peristaltic muriatic acid pump with pH sensor and Monarch SWG. Home made solar heater with Pentair Compool control panel and 3 way valve. 1 skimmer, 1 main drain, 2 returns, 2" plumbing, Hayward auto fill valve.

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