Do-It-Yourself Solar Swimming Pool Heater

I made this solar-powered swimming pool heater out of common materials anyone could get, with ordinary tools most average homeowners have (or can borrow from friends). A friend of mine named Ace gave me a sliding glass door that was going to be thrown out from a job site he was working on (he's a roofer, and the door had some minor cosmetic damages to the metal frame).

Step 1: Building the collector box

I decided to make it out of pressure treated 2�4s and 3/43 plywood - the glass had leaned against my studio for over a year and you can see weeds and the weather had them filthy (wow I need to pressure wash my siding):

Comments

[cm3stars]

Nice work! I was wondering if a modified version might have the water intake at the top of the panel, say upper left. And the outflow at the lower right. That way if you had (10) six foot pipes in your manifold the water would have a 60 foot run in the pipe instead of 10 pipes each only running six feet. I think your outflow temp would be substantially higher.

[GOOD OL BAD GUY]

The object is to cool the collector, the longer the water is in the pipe the hotter the water AND the collector will be hotter, i.e., not cooled as well.

Like any heat exchanger the greater the temperature differential the greater the efficiency.

[daveryder]

I agree.

[vistal]

Copper and chlorine dont mix your pool will start turning green and the copper will soon be eaten away. great Idea i build them myself with black PVC/

[useraaaaa]

who needs pool heater.
make pool cooler please.

[chspyder]

Just a thought but copper is a very bad thing to have with the pool chemicals and causes staining. I have to bypass my heater when not used to keep the staining to a minim, this may be low cost heater but the stain remover is about 60$ for my size pool, and two to three times per season it adds up.
I am building a dome shaped heater with black flex hose (vacuum line) like in the new leslies flier and will post results.

[dweston]

I added a new twist to this basic design - I installed a temperature switch under the glass (They sell at Lowes for around $17 and are for use atic vint fans) - the switch turns the pump on  when the air temp reaches 100 degrees inside the pannel, and off when the temp falls back below 100 so the it only runs when there is heat to transfer - seems to work well

[glubash]

Nice project.  I have a couple of coworkers looking at doing something similar.  You mentioned that you might be able to radiate some heat during the summer months at night, any luck with that?  A small exhaust fan might help in that situation.

[guynoble]

That looks like you did a really good job but a cheaper more effective option would probably be to place heat absorbers directly in the pool, such as a black thermal blanket floating on the pool surface. If you don't want to buy an expensive blanket, perhaps a couple of those large black plastic trays, intended for mixing concrete, floating on the surface. Cheap, easy to clean, stackable for storing and virtually indestructible. You could then use your solar panel for preheating water for the house instead. This way you'd be lowering your energy usage and making a difference to your fuel bills and the environment.

[daveryder]

It works. You can't use pool water for your house. You worry about your bills, I'll worry about mine. All I wanted is for my family to enjoy more swimming time, and in that regard I succeeded.

[leebarret]

Yeah I live in Houston Texas & I'm working on a pool cooler, since my 12,000 gallon gets too hot from july to sept! (like taking a bath) They sell pool covers for fairly cheap that will do the same thing in principle you are doing. They raise the water temp 5-10 degrees.

[daveryder]

It's called a solar cover - I use that in addition to the heater - we swim one month sooner than most people around here, and one month later with the combination.

Plus, after a cold snap or rain, it heats up way faster. The whole point is getting more swimming time than you would get without the heater, and last year was a total success in that regard.

If you built one without the glass, and ran it only at night, it would work as a radiator and cool your pool down.

[Utahtabby]

61 degrees still seems like FREEZING to be swimming in....In my opinion, ha! I need my pool temperature way hotter! also what is the point of using copper (other than it prevents algae) could you have used PVC or other metal, tin perhaps? I am clueless on this stuff so I am just asking, not criticizing.

[daveryder]

Oh for sure, 61 degrees feels like ice! I like it 75+ for swimming, but it's all about getting it to heat up more quickly.

[kaos211976]

This is a fantastic project. Thank you for sharing it. I have been planning something like this for my pool for some time now and this has given me a lot of good research. Mine will be 10' x 4' and be mounted on my garage roof. I will be forgoing the glass as I don't see the need in my application. I will also be using Aluminium sheeting instead of the costly copper. Copper would be better but it will be too expensive. Thanks again.

[daveryder]

I thought about putting mine on the roof, but didn't know if the pump had the pressure to raise it that high without putting a big strain on it. Plus, I didn't want to mess up my shingles with a mounting system. Plus I hate heights.

[guynoble]

Your pool will adopt the mean ambient temperature. If you want to raise the temperature you must put in more heat than it is losing to the surroundings. Perhaps you should therefore think about insulating the pool sides before you expend too much effort on heating methods. Its not a difficult calculation for any first year engineering student.

[daveryder]

Maybe, but the whole point is getting more swimming time, and last year proved to be a big success - see my comment above reply to leebarret.

[domestic_engineer]

nice instructable, but that's a lot of copper, and a lot of $. we're thinking of doing something similiar, but with flexible tubing and tin foil.

[gwest77]

domestic_engineer, you can use pex tubing and make your own aluminum fins to fit around the tubing. You can use a 5/8's metal rod to make the grooves for the pex, a very very thin bead of silicone to adhere the pex to the fins. Make the fins wide enough to touch each other inside what ever size collector you build. Running the pex tubing in a serpentine fashion will allow you more mass in the collector. This is a good place to start
http://www.builditsolar.com/Experimental/PEXCollector/PEXCollector.htm
 This website is a wealth of info for any DIY'er  Have fun

[annekaelber]

I'm aware of the better conductivity of metal over plastic/rubber. I'm curious if the "black garden hose in the sun" multiplied by how much more could be purchased for so much cheaper can overwhelm the benefits of using a metal like copper?

The original author states s/he spent $250 in *just* the copper tubing for a 76" x 46" solar heater.

I've seen, on HomeDepot.com, 500 ft of 1/2 tubing (designed for drip-type watering solutions I believe) for between $30 and $35. I used this page: http://deepfriedneon.com/tesla_f_calcspiral.html
to do a rough calculation of how many feet of tubing I would use in a 4x4 box, which is approximately 300 ft of tubing -- well within my 500 ft mentioned above.

I'm still searching for ways to determine how much I might reasonably hope to gain in temperature via 300+ ft of black tubing. I welcome any suggestions or data input here.

As for the instructions, if we do decide to use copper tubing, we're definitely going to be referencing this Instructable! Thanks for sharing!

Anne.

[jonralph]

copper is the right material to use for this application. As has been said before plastic is an insulator and won't absorb any heat from the sun.

It does look like the flow of water is going to just run through the pipe nearest the inlet, it will always take the path of least resistance. There are 2 things you can do to improve this though, and they are both reasonably easy.

Flow should always be controlled on the outlet, not on the inlet. This has the effect of slowing everything down and not giving the flow an easy route through the pipes. This should help spread the flow over all the pipes.

Turn the panel so that it is vertical, with the valve at the top becoming the outlet and the inlet at the bottom. The valve on the outlet will keep the flow across all the tubes and also thermal convection will help move the water through the outermost pipes. As the water is heated it will rise naturally.

If you go for this please let us all know how you get on.

If you want to work out the volume, first go and look on the manufacturers website, it will likely say so.

if not, measure across your pool in meters(diameter), half of that is your radius. The area of a circle is radius x radius x 3.14. I am guessing that the radius of your pool is about the same as the panel is wide (76" so near as dammit 2 Meters) 2 x 2 x 3.14 = 12.56 Sq M is the area of your pool. For the volume of a cylinder in cubic meters you just multiply the area of the circle by the depth. So I am guessing the pool is about a meter deep? So

12.56 sq Meters x 1 meter = 12.56 cubic meters.

1 cubic meter = 264 gallons
so..
12.56 cubic meters x 264 = 3315 gallons

measure your pool and work it out with your son for the fun of it. or measure it and pass the measurements on, happy to work it out for you

Nice piece of kit already though and any gain is a benefit.

[davefredrich]

jonralph hows it .
my name is dave, joined today after reading your comments on pool solar. i live in a small town pennington south coast natal south africa. two things i would like to ask. one would ambient temp govern the size of a panel area.
2 working out your btu ratings for area water to be heated, not also depend on ambient temp. eg 20 square meters pool area, ambient temp 15 deg c
20 30 deg c
why i ask is our temp is similar 2 south coast america winter max 19 deg c summer +- 32 deg c would you design be worked on winter conditions.
shot
dave richards.

[Lynxspring]

Can you tell us what the pickup is on your heater? Like what the inlet VS outlet temp is compared to the outside air temp in a perfectly sunny day? (Delta T) thanks

[hackinblack]

improvements to this design I see:- 1.run the copper pipes vertically NOT full length horizontally they are toooo long to support water weight and expansion,using more,but shorter pipes, gives a greater surface area (more heat!) and more strength (no leaks!) 2.put the inlet diagonally opposite the outlet for more efficiency

[SurferGeek]

Wouldn't it be better to use plastic piping? Wouldn't using copper put metals into the water?

[kaos211976]

You have a point about the copper. I would say that an occassional metals treatment would fix this up.

[thetech101]

Plus most types of thick plastic piping are very good insulators. Metals transfer more heat than plastics. A good rule of thumb is "if it conducts electricity, then it'll conduct heat. If it doesn't conduct electricity, it won't conduct heat."

[daveryder]

No. The plastic would put more toxins in. I drink from copper pipes everyday, and remember, the temp never gets above 80 degrees.

[SurferGeek]

PVC piping is, and has been used for years in household for water pipes and as you state, the water never get's above 80 degrees there wouldn't be any leeching.

Copper is a good choice as it does have better thermal conductivity but PVC is a much cheaper choice of materials that will have no chemical reactions to other materials used in the pool or with other metals used like in the pump.

[l8nite]

Any updates on the new design? You could modify what you have by cutting every other connector pipe and capping the stub to make a repeating "s". An added benefit of using copper is it helps control algae growth, copper wires are strung on a roof to prevent algae and moss growth, copper nails inserted around the base of a tree will kill it etc. Nice instruc!

[kaos211976]

I will be using the continuous "S" coil and forgoing the "T" connectors. My only fear is that the water will be too hot! LOL

[TheCowStir]

Copper/metal is a better conductor of heat. So there will be more transfer of sun heat through the black copper pipe than there would be through pvc pipe. Plastic is more of an insulator.

[kaos211976]

Copper is the best, most cost effective, metal used to conduct heat into water. As a frame of reference, Copper rates 380.0 in conductivity whereas Aluminium is 180.0 (not bad for a common alloy) and PVC is only 0.12-0.16 (Polyvinyl). Painting the copper flat/matte black allows for more absorption as the shiny copper surface does not reflect the light energy away but rather draws it in.

[strmrnnr]

I think you need to have the feed in the bottom and the exit at the top, so that a unit of water has to travel through all the pipe before exiting to the pool. As I look at it I can't help but see the water comming in and going straight across to the exit, leaving the water in the top and bottom pipes almost unmoved. It may help to turn it 90 degrees if you didn't want to change the piping. Tip on th esoldering to. If you have it all planned out, you can slit the flashing and solder it to the pipe through the slit from the back. Takes a lot more planning though.

[daveryder]

I think you're right. It should enter at the bottom, and make a series of s-turns all the way to the top and exit. I talked to a lot of people about this who have told me the way I did it is technically correct, and I STILL think you're right and they are wrong. I'm going to change it, and take temp measurements both ways, and I'd be willing to bet a large sum YOUR method gets the water hotter faster. I'll post updates.

[strmrnnr]

Don't mean to tell you what to do but, you might try the 90 degree turn before rebuilding - this looks pretty expensive. I also noticed your pool was not insulated. The bubble wrap they use under radiant heat floors in garages would work great on that. I believe the stuff is rated for R10, is 3/8" thick, and the animals don't steal it for nesting.

[SeamusDubh]

Try slowing down the water flow through the panel. I've worked with heat exchangers in the past and if the flow is too great you're not going to be transferring heat efficiently enough.

[wobblestar]

If you reduce the flow rate, you get a smaller volume of hotter water. A high flow rate gives you a larger volume of water at a lower temperature. You can't buck thermodynamics: you're limited by the solar energy hitting the panel. I think a high flow rate is better in this application. You don't want the panel to get too hot to minimize loss of captured energy by re-radiation to te environment (and convection?). Of course, a set-up designed to provide domestic hot water works differently. In that application you need the water to get HOT-HOT-HOT not just warm, and a slower flow rate feeding an insulated storage tank might be better.