Instructables

Pool Solar Heater or Optical Illusion for Entertainment

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Picture of Pool Solar Heater or Optical Illusion for Entertainment
Commercial solar pool heaters are expensive, especially if you need multples.  Here's how you can cobble together a solar collector/heater for your pool and create interesting 3-D optical illusions to entertain (or frighten) your neighbours and friends.

It's not as hard as it looks.  If I can do it, anyone can do it.
 
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Step 1: Why Another?

Picture of Why Another?
There are a lot of pool heater instructions on the internets; this one culls together the best parts of each (sort of) and provides more specific advice for the pumping situation.

Step 2: Components

Picture of Components
The solar heater consists of three main components:
  1. Pool water
  2. A pump
  3. Solar heater
The action is:
  1. Water is pumped from the pool to the collector
  2. The collector transfers its heat to the water going through it
  3. The heated (sort of) water is returned to the pool

Step 3: Components, cont.

Picture of Components, cont.
For this 'able, we'll be using two collectors and two input/output streams.

Why?
I started out with just one collector and wanted to try more for more heat exchange.

Step 4: Tools and Materials

Picture of Tools and Materials
The hardest (uhm, next-to-the-hardest) part of the solar collector system is getting the right materials and getting them to all fit together without becoming a Rube Goldberg project.

As we go along the steps, I'll show you more details about what specific parts were used.
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dougmorency3 months ago

I have done this myself for the past couple of years.

get one of the utility pumps used for flooded basements, that have a garden hose attachments. buy the thinist, cheapest garden hoses you can find, 2 or 3 of them.

buy an outdoor timer with setting of 15 min or less off on cycles and plug the pump into it. water will almost boil coming out of the end of it.

http://www.rona.ca/images/2003351_L.jpg

dbuckley63 months ago
I intend building one of these. kinks seem to be a big hassle when winding. However if the coil is filled with water and sealed ( tied kink at each end) I think kinking will be greatly reduced. You can actually bend copper this way without in kinking - I have done it - as water is non compressable - unlike air. Great detailed job BTW ; good pic etc prob helped by wine!
mwatson167 months ago
bib is a TLA for " bit in between"
I built one very similar to yours except I used 1/2" garden hose inside an insulated box with glass over it. In my area(NE Ohio) ,we don't have enough sunny days to heat the water very much. A pump that circulated 1 gallon a min brought the water temp up the best maybe 20 degrees.
cobinrox (author)  bignail195411 months ago
Holy cow! How long was the hose?
iconrl1 year ago
Do you think it would be possible to use a small DC pump powered directly by a solar panel? It would only run when the sun is out and pump faster the more sun it received.
cobinrox (author)  iconrl1 year ago
That'd be a great idea-- it would depend on the horsepower/GPH of the motor. The A/C motor I'm using is 800GPH, for example.
joshem1 year ago
Thanks a lot, very useful!!!
zawy1 year ago
Here's a less expensive way: drape black plastic just beneath the surface of the pool (assuming you don't want to paint the bottom of the pool black. Now your heater collect is as big as your pool and more efficient than any other design (96% because the only loss is the reflection from the water surface). Split large black plastic garbage bags can be used, but I don't know how to easily connect them to make a large sheet. To make it up to twice as powerful, place 4x8 aluminum-sided insulation boards on each side of the pool where light can be reflected into the pool. $12 for each 3 m^2, 20 times cheaper per watt than this method.
cobinrox (author)  zawy1 year ago
Yah, I saw something like this in this 'able:
http://www.instructables.com/id/Pool-Heating-XL-Lily-Pads/

But actually when doing research, I didn't find that to be a popular option. Have you actually tried this and found it to be effective? It would be a great alternative if so.
zawy cobinrox1 year ago
We have a 4x8 foot inflatable pool where I have split black trash bags and added the reflectors. But the physics are simple enough that calculations are more accurate than DIY comparisons. The lily pads you link to are better per square foot than any plastic pipe method because the heat transfer through the thin plastic is better and there is no loss in transfer to and from the pool. The lily pad method would be better if they were below the surface of the water by at least 6 inches. It is losing heat from its surface being hotter than it would be if it were sunk. The ideal method for winter would be to have painter's plastic sheets (clear polyethylene, very inexpensive) or the clearest greenhouse plastic you can find to lay on top of the water's surface., then have a sunken black plastic layer, or, less optimal because more heat into the soil, the bottom and sides black. Then add reflectors to the north side for midday and to the west side in morning and east side in afternoon. Amount of temperature increase is 6 kWh per m^2 per day for the yearly average of most U.S. locations, times the m^2 of the pool if it is summer which is still correct in winter if you use reflectors, times 96% for 4% loss from the top plastic (8% if it does not lay on the surface of the water), divided by heat capacity of pool which is 1 degree Celcius per calorie of heat per cm^3 water times m^3 volume of pool water times 1E6 cm^3/m^3 times 4.184 Joules/calorie times 1/3,600,000 kWh/Joule. If 18x30' pool averages 4.5 feet deep (meters: 6x10x1.5= 90 m^3) this gives:
6 kWh/m^2/day * 6x10 * .96 / ( 90*1E6*4.184*1/3.6E6)
or to simplify canceling the large numbers and the pool surface area:
6*0.96*3.6/1.5 depth/4.184 = 3.3 C increase during one day which is 6 F. Plus or minus any gains or losses from the hotter or cooler ground and air. If pool is kept same temperature into fall, then there will not be much ground heat loss compared to the surface. If aluminum-sided 4x8 insulation boards were used as the reflectors, then you flip them down to cover the pool when Sun is not shining (aluminum side UP, important). Heat loss in watts is ft^2 surface * F temp difference divided by R-factor divided by 3.4. For 6-hour sunshine day R-factor=0.5. When insulation R=4. These are underestimates if the water is still which is maybe R=2 from the water itself insulating. So watt-hour loss per day for 50 F day for 12 hours and 35 F night and 85 F pool is (30x18)/3.4*{6 hour*(85-50)/0.5+6 hour*(85-50)/4 + 12 hour*(85-35)/4} = 100 kWh per day. If the reflectors kept an effective pool-area exposed to the Sun, then the pool's 6x10 m surface gained 5 kWh per m^2 (winter) or 300 kWh per day for the pool, 3 times more than the heat loss. Even with 30% cloudy days and 30% shade from trees, 85 F pool throughout winter for 80% of U.S. should be "easy" by this method....with enough reflectors (20 4x8 insulation boards in this case, $11 each) aimed moderately well throughout the day which is a reason I did a heliostat instructable. Even without reflectors, a pool painted black and covered at night (to prevent evaporation which kills the heat gain) will get hotter than a shallow pond in a few days, over 100 F in the summer.
cobinrox (author)  zawy1 year ago
Well it's been about thirty years since my theromodynamics class but the main idea of the submersible pads would be much less deep than other rabbit holes I've been down. Might give this a try next year.
throwedoff1 year ago
I have thought about this method. Right now I have been using a solar blanket for several years. From mid June through mid September my pool temperature runs about five degrees below the outside air temperature when the cover is left on except when the pool is being used. In late July and August we have to uncover the pool in the afternoon or the water temperature will be close to 100 degrees!!! Not to refreshing when you've been mowing the yard!
cobinrox (author)  throwedoff1 year ago
Wow; I used a solar blanked too but never saw the temperature rise to more than 79, and that's with the solar collector pumping.
I live in the Texas panhandle. By ten o'clock in the morning from mid June through the end of August it is usually ninety degrees or better outside. I have full sun exposure on my pool during those months from 10:00 a.m. through 7:00 p.m. with the overnight temperature averaging just above eighty degrees. My pump is on a timer and doesn't run at night. I think a solar collector running at night would act as a heat exchanger pulling heat out of the pool if the ambient air temperature is lower than the water temp.
cobinrox (author)  throwedoff1 year ago
That's what I've heard (i.e. that the collector running at night would work in reverse).
klubow1 year ago
How much do you spend on electricity for the pump ? I assume less than for a heater?
cobinrox (author)  klubow1 year ago
Actually I don't know because by the time I had everything running the rains came in and the season was over. I looked into a heater (both electric and gas) but they were very expensive. The pump is a fountain/pond pump so running it 8 hours a day would not be any more of a hardship than having a water feature.
IDThoris1 year ago
Aw man, my dad and I built one of these in the 70's for the community pool! Bringing back some sweet father/daughter memories! Thanks!
woodpuppy1 year ago
One of the best instructables I have seen yet. My vote= 1. There is a lot that could be done better... But that is what instructables is all about!! I Hope to see more from you.
Sad, cold pool owner here- I always thought I'd want a coil system like this built into my existing pump/filter system. Any reason not to go that route and use a separate pump? I was also thinking a (copper?) coil around the hot part of the pump itself might make good use of some residual heat, as well as cool the pump down, which can overheat on really hot days.
I used a small submersible pond style pump for my rig. So the heat generated from the pump went directly into the pool... I would take the pump out when the kids were swimming, plus I also double check the GFCI ciruit to make sure its safe about every couple of weeks.
beefsupreme, if I used copper or aluminum tubing around the hot pump motor or pump(which I think is a great idea), I think that I would plumb it so that you could bypass the 'heater' in the case of really hot summer days when the water is already very warm and you'd really rather to cool it down a few degrees than heat it more. You could use a tee with a smaller diameter going to the heater and let most of your water do like it's been doing and go to the filter and then tie the heated water line back to the filter line by means of another tee. If you put a shutoff valve between the 'heater' and one of your tees, you would essentially turn the 'heater' off but the filter would still work like it did before the heater was installed.
Hope this helps!
cobinrox (author)  jack85591 year ago
Beef-- I originally started with one of the commercial collectors that DOES inter-connect with the pool's pump. The reasons that I did not attach the new home-made coils to the pools pump included the fact that a) I had no idea how to connect the 1/2" tubing to the big honking Intex pool pump tubes and did not want to have to disconnect the pool pump just to get the tube to take along to the hardware store; b) I incorrectly thought that it would be more effective to use a timer on the collector pump and have it turn on and off every 1/2 hour and did knew that the pool pump would throw a fuse if I did that so therefore I wanted to us a separate pump; c) I was experimenting and wanted to use a stand-alone pump again because the pool pump was too much of a hassle to connect and disconnect.
cobinrox (author)  cobinrox1 year ago
Sorry, boy I just re-read what I typed and it made no sense. I didn't want to use the pump pool because:
a) I wanted to experiment and attaching and un-attaching the pool's pump is a hassle (been there done that too many times)
b) I didn't want to waste time trying to find an adapter to fit my coil's 1/2 tubing to the pool pump hose (been there too many times too)
c) I incorrectly wanted to use a timer to turn the coil's pump on every 1/2 hour and I knew that the pool pump would crap out doing that
d) I wanted to experiment
igusdude1 year ago
Great Instructable. I have done this exact thing for my in-ground pool. It took 6 coils, a total of 600 feet of black drip irrigation tubing to produce enough warm water for a 15000 gallon pool. It works great. But two things I made a mistake on... 1. I used brass fittings as my connectors. They do not do well with chlorinated salt water!!! My interconnects were brass garden hose m/f, so I could pack the coil away during the off-season. 2. My second mistake was using the zip-ties. I used black zip ties that said they were UV resistant and OK for outdoor use... After the first year, all my zip ties broke during handling. The sun made them very brittle. I would suggest you use some other method of keeping your coils together.

The rest of your instructable was spot on!!! Great work.
cobinrox (author)  igusdude1 year ago
Igus-- did you have your coils in parallel or series? And can I ask what area of the earth you're in? I have a total of 400 feet of the tubing (actually a little more since I have the crappy commercial coil too) and almost a third of your pool size (5000 gallons) yet still had trouble getting the water temperature up (notwithstanding some of the obvious problems like no insulation for the coil frames and not running the pump continuously of course).
Cobinrox, I live in southern california, so the sun and weather help keep things warm. My coils were in series. I measured about 10 degree increase in temperature between inlet and outlet. The Pond pump was rated at 300gph, but with all the tubing friction, the water poured out at a much lower rate. I think it was the slow flow rate that gives the water time to get warm. My best pool water temp was about 92 degrees, a little too warm for comfort, but I thought that was awesome!!! The coils were not insulated either, they just sat on top of the concrete deck which is a medium grey color. Not sure the deck helped or not, but it did get warm also. The biggest loss of heat is due to evaporation, so covering your pool with a bubble sheet cover will help.
Maybe take a strand of copper wire and wrap it around each pipe then back to the previous one, like sewing it to the board might work well for you. Aluminum wire might work well too since neither will rust, but remember that copper will oxidize and may leave a green line where rain rinses it off over time and aluminum oxidizes into a white color.
My neighbor preheats water going to his water heater and we used black well pump line (1" ID) and put 500 feet on his roof in a huge coil with 2 x 4s spaced every 8 feet and we fastened the pipe down to the 2 x 4s with plumber's tape and deck screws.
Plumber's tape goes by many names such as carpenter's tape, etc, but it's nothing more than a thin strip of metal either galvanized or zinc coated with holes about 1/2 inch or so apart. It's usually sold in 50 or 100 foot long rolls and doesn't oxidize easily.
cobinrox (author)  jack85591 year ago
That's an interesting idea, I also would wonder if you could actually even use thin rope to "weave" the piping.
If I were to do that, I would make certain that the rope could withstand rain and sunlight first, but remember that rope won't conduct heat well but copper and aluminum will which might make a little difference in how much heat is transferred into the pipe but it will be very little. Look at youtube.com under solar heat exchangers, solar heaters and the like and you will get some pretty good ideas. If you have heat sources that are vented to the outside in the summer that may also be a good source for heating your water (exhaust from the air conditioner, clothes dryer etc.).
Hi Cobinrox,

Just an thought, can you not use copper tubing instead of rubber one for your collector ? Copper tubing would heat up faster and once it is heat up even cold water gushing in would become hot.

I know copper tube is bit expensive but if you would use copper tube then you dont need that much long coil to wind in a collector. this way you can reduce the cost but increase the heating effect in less time.

I also know bending copper tube is bit tricky but there are lots of instructables available some by putting salt inside or some put water or some put something else. Google it and you would find tons of it.

Best regards,
Rohit
cobinrox (author)  Rohit.Agrawal1 year ago
Hi Rohit- copper's always an option, but I knew that I'd have a hard enough time just getting the poly tubing to fit together. For copper I'd probably need a lot more equipment than I'd be willing to buy. Thanks for the info though, good to know for anyone else pursuing this quest.
adamjoe861 year ago
As far as point 5 above, why don't you try taking the outlet from the collectors down toward the bottom of the pool. The outlets could be spread further apart and pointing the same direction around the pool to mix the water as well.
LobosSolos1 year ago
I'm guessing that this is for during colder winter months? Because otherwise what's the point? As far as I know the purpose of a pool or other swimming area is to cool down. I grew up swimming in a spring fed creek that's the same temperature year round (pretty cold).
I Like your tubing panels but a couple ideas that will not only reduce the cost of construction. Instead of using a seperate pump, use the outlet side of the pool pump filter. I put my pool pump/filter on a timer to run only during daylight hours and hooked the tubing after the filter using a simple PVC T with the half inch hose fitting. One could put in a valve if they did not run system on a timer but they would have to remember to turn off the heater at night. But eliminating the pump saves money and time and the stream can power the flow through several heater assemblies then simply run the other end of the tubing over the edge of the pool and afix in place. I placed my tubing to run around the pool railing using a heavy aluminum wire (8 gauge) to make brakets to afix to railing. I figure about 2 degrees increase in warmth of a 25000 gallon pool per 50 foot length of tubing.
ravenjams1 year ago
Well worth doing. Nice idea, My pool generally is at 95 F every day when the sun is shining then it drops drastically with no sun. Sometimes the darn thing is just to hot. My pool pump runs 7 hours a day which I think really bad for my electric bill. So next solar panels for my pump to reduce the cost of operating this beast. But I like your Idea!
dbradford1 year ago
Great effort! Very detailed and informative too. I hope you don't get sniped at for your methods (there are lot of different ways ways to make the fitting connections, fasten the coils to the back plate and even run the solar heaters in series). The simple fact is YOU did it and I have not...great job!!! The other aspect is that while others like myself are great Monday morning quarterbacks, YOU LEARNED first hand. This is great and you have given me some ideas for an outdoor solar shower. Thanks for taking the time to document YOUR work!!!
cobinrox (author)  dbradford1 year ago
Hee hee, that's exactly why I had never tried this before: too many conflicting (and missing) details floating around out there. One thing I have not found out how to do is efficiently empty the coils at the end of the season. I about burned my hands off this weekend trying to unravel the coils in an effort to get the remaining water out. It was about 93 degrees outside and the pipes were pretty hot!
An easy way to clear out the coils would be with an air compressor and using a air nozzle attachement to blow compressed air into the line to remove the water. I use this method to blow out the copper pipes on a cabin I have to get it ready for the winter and it works well. I would say a small pancake tank compresser would be all you need for this.
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