Time It Takes For DIY Solar Heater To Raise Water Temp

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coollx
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Posts: 7
Joined: Thu 23 Jul, 2009 17:42
My Pool: 16X32 inground w/ hayward earth filter
Location: Upstate NY

Time It Takes For DIY Solar Heater To Raise Water Temp

Postby coollx » Sun 26 Jul, 2009 10:19

I'm a new member with a couple of questions about DIY solar pool heaters.

I've read as many threads as I could find on building your own solar heaters and one conclusion seems to be to use 1/2" black poly pipe not something larger. I believe it will collect more heat and is easier to work with than the larger tubing. I have a 16 X 32 inground pool with an average depth of 4'. This summer in Upstate NY has been the "summer that wasn't" which is my motivation for trying to build a solar heater at this time rather than wait.

One question I have for anyone who has built and used their own solar heater is how long will it take to bring the water temperature up from say 75-78 degrees to 85 or so? Most threads talk about DIY solar heaters, if they are large enough, being able to raise the water temperature 10+ degrees but fail to indicate how long it takes to do it. Is it 2 days or 1 week or some other number of days. I'm just looking for a ballpark idea so I know what to expect.

BTW, my plan is to initially mount about 400' of 1/2" black poly tubing on 2 pieces of 4' x 8' plywood facing south which should receive direct sunlight for about 7 hours a day.

Any input will be greatly appreciated.

Thanks

Dom


chem geek
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Time It Takes For DIY Solar Heater To Raise Water Temp

Postby chem geek » Sun 26 Jul, 2009 11:10

Dom,

In a pool with an average depth of 4.5 feet, the rate of temperature rise will be a maximum of 0.9ºF per hour in direct noontime sun on a clear day under ideal conditions using an 80% efficiency for black mat solar panels that have an area equal to the size of the pool. This is best case and your solar panels are probably not that efficient. Also, there is additional heating of 0.7ºF per hour from sunlight hitting the pool itself (in a white plaster pool; a somewhat higher rise in a pool with a dark bottom), but this is at least partially offset from heat loss via evaporation. Use of a fairly transparent pool cover (ideally opaque to UV so that chlorine usage is minimized from breakdown in sunlight) will eliminate the evaporation while letting some sunlight heat the pool.

This post can give you an idea of the heating rate per day in my own pool when using Fafco solar panels that are around 75% of the pool surface area in solar panels, though some of it isn't in sun, and I have an opaque electric safety cover so get minimal heating from sunlight hitting the pool itself. I live in the San Francisco Bay Area.

Richard
JohnRoss

Time It Takes For DIY Solar Heater To Raise Water Temp

Postby JohnRoss » Sun 23 Aug, 2009 13:49

I don't know if this is of any help but on my own DIY pool heater I get the following figures. Flow rate through the solar heated pipes 54 litres/minute 5 degrees rise (Celsius) on the return to the pool, 36 litres/minute 7 degrees rise, 21 litres/minute 9 degree rise. Pool is 75 000 litres and solar heated pipes are some 260 metres of 100mm plastic pipe painted black with non-reflective blackboard paint................JR.
JohnRoss

Time It Takes For DIY Solar Heater To Raise Water Temp

Postby JohnRoss » Sun 23 Aug, 2009 14:40

Sorry forgot you use imperial. 54 litres = 14.04 US gallons, 36 litres 9.36 gallons, 21 litres 5.46 gallons, 9 degrees Celsius rise = 16.2 rise Farenheit, 7 degrees Celsius = 12.6 degrees F rise and 5 degrees Celsius = 9 degrees F rise. 75000 litres = 19500 US gallons...........................................JR

PS I am a retired Brit living in France and my pool is at 32 degrees Celsius (89.6 Fahrenheit) today and that is too hot for the plastic liner so will have to run the solar pipes tonight to cool it down a bit!
JohnRoss

Time It Takes For DIY Solar Heater To Raise Water Temp

Postby JohnRoss » Sun 23 Aug, 2009 16:10

And 260 metres is 853 feet. 100mm is 4 inches as near as makes no odds. I am about halfway down France on the left hand side near the City of Niort in the department of Deux Sevres (79).................JR

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