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Last year I installed an electric pool heater in an attempt to extend our already short swimming season. It worked great... except that it resulted in $900 power bills (it's a 15kW heater). The big problem with heating my pool is that it is shaded most of the day, so it gets little heat from the sun. This year I decided to do a home made "redneck" pool heater using 300 feet of black rubber garden hose, some wood, some tinfoil, and some clear plastic "greenhouse" roof panels.  The beauty of a solar heater is that I can put it in a sunny area - much easier than moving the pool!

So today construction started. The heater is 4' X 8' with 300' of garden hose weaving back & forth, suspended 1.5" above the base, and has tinfoil glued to the base to reflect the sunshine that doesn't hit the hose directly back up to shine on the hose's underside. The top side of the solar panel will be plastic "greenhouse" panels to help keep the heat inside - I'm hoping to capture both radiant (infrared) and convective (like an oven) heat.

Here is today's progress:

The box (framework and base) is built and I've started weaving the hose through. There will be twice as many rows as shown here, an upper level and a lower level. You can see the holes for the lower level in the framework.



Here I've run a short piece of hose through the bottom level just to show how close the rows will be together once I'm finished. I would have liked to have made them closer together but am limited by how tightly I can bend the hose. I'm hoping the tinfoil on the bottom will turn the gaps between rows into an advantage by allowing reflected sunshine to strike the underside of the hoses

And here it is with the plastic panels temporarily sitting in place. I've got "finishing" pieces to seal up the ends.




The plan is to run the water through the bottom layer, then loop it back through the top layer, and finally into the pool. It's a continuous loop - both layers are in series. I'm trying to decide whether this is the best way, or whether it'd be better to have the two layers in parallel (two 150-foot loops instead of one 300 foot loop). Any thoughts?

buy a hot tub! lol looks like a good idea there

I think more ideal would be to have the whole thing black. At least everything other than the clear cover.
It may work, may not. I'd think it should at least make a dent in the temperature, certainly worth trying. I've always thought this would be a great idea. The scale of it might not be as easy as it sounds, but given enough land space, enough HOSE, it  well would heat a pool up...

i think thats a badass idea, would love to hear the end results!

I know in Vegas they do the same thing on a slightly larger scale with bigger pipe, built onto the roof of the house.  I think the biggest issue is going to be cycling enough water through the small hoses to get the temp up. Don't forget to use a solar blanket/cover to keep what heat you get, in.

  I say go with the two hoses in parallel and see what happens.

I thought about painting the interior black, but I think this would result in less heat. Sure, the plywood bottom would get hotter, but I'm not interested in heating plywood. I want to heat water in pipes, and I think the reflective bottom will create more hot water by heating the full pipe instead of just the top half.

As for flow rate, I think the small diameter pipe with water flowing relatively slowly through it will result in more heat than large pipe with lots of water. I live in a northern area with hazy sunshine (45 degrees latitude, right on the ocean) so sunlight is a rare commodity. When it does shine it is not nearly as intense as it would be in Nevada, so flowing the water too fast would result in it picking up little heat.

I'm going to set it up as a full series circuit at first and will monitor the temperatures with an infrared thermometer. If the temperature does not increase significantly between the end of the top row and the end of the bottom row I'll know the water has picked up as much heat as it can, so I'll switch to parallel so I have two circuits picking up that much heat. For example if I find the temp difference between the start and end of the top row is 50 degrees but there's only a difference of 10 degrees between the start and end of the second row, I'll know that the water is picking up as much heat as it can in the top row. I'll then switch to parallel, so I'll have two circuits each picking up 50 degrees, but there will be twice as much water. If I find it works as well as I hope I'll build another 4X8 panel next year.

It's all a big experiment, but one thing is certain: Every BTU of heat this thing generates is a BTU of heat that is free and not from the power company...

how are you going to pump it? Remember that the smaller the hose, the greater the pressure necessary to pump the water through it, meaning your pump will have to work harder, that being why a larger hose may work better for you.

...on the same basis, that may also be why running the two in parallel may work better for you, as it is then splitting the same volume of water along a technically larger pathway. think double-core radiator.....

A better comparison would be an A/C condenser or tranny cooler. I'll be pumping it with the pool pump. I'm going to make a manifold up that has a branch feeding the heater and another branch for the returnin th with an adjustable restriction between them to create a pressure difference. I'm going to put solenoids in to control when the water flows - I figure between 8:00AM and 4:00PM - the sun is too low in the sky outside of those hours to get any heat out of it.

Now I think about it I will do parallel. The water might not get as hot, but there will be more of it. I figure there is only so much energy going to be absorbed into this panel regardless how fast the water flows through it (to a point, of course)

That must be something to do with your location... Down here we have (summertime at least) sun in the sky daylight from more like 8:00 to 7:00. Althogh I guess it also depends on your angle to the sun of course...

...in any case, if the scorching hot water that comes out when you first turn your water hose on after at the end of a long day is any indication, I think you will have a real winner here lol

Actually, believe it or not, we probably get more hours of sunshine than you do in the summer. The sun rises around 4:30AM and sets around 10PM around the solstice (conversely, at the winter solstice it rises at around 8 and sets around 4:30). This might seem counter-intuitive, but the further north you go the more sunshine you get in summer, to the point that it doesn't set at all above the arctic circle. The only problem is it doesn't spend all that time directly overhead - early morning and late evening I'd almost have to stand the solar heater vertical to capture any heat. While it'd be cool to make this thing follow the sun that's a little outside of the scope of this project. Since it will be stationary I have to optimize it for the most direct sun

Yeah I see what you mean

wish i had saw this earlier.

i did a controlled test on this already.
what the below chart says is that i had three conditions measured in one day during early march in zip code 24941.

there are three setups titled.
three measurments were taken of each setup from 12:30AM to 2pm.  same for 2pm to 5 pm.

the conclusion was that a small black tube with a black background and glass front wins.


What really wins the most is if you can run this black hose you have *UNDER" an existing metal roof.
IN my log home my metal roof is attached to my existing shingle system.  there is a 3/4'' gap between my shingles and the metal roof.
Under the tin roof during a 14 deg day in early feb, the temp under the roof at 10AM was 97degF, and at 1pm it was about 120degf.
In late may the temp under the roof was 156degF at 11am.

I see what you are doing,
the distance the hose sits above the foil matters because the shadow of the two tier hoses will be wider than the actual hose.  the suns angle may shade the foil and not offer the reflection your after.

so small black tubes in your situation wins and thats what your doing,, hopefully the foil isnt shaded out too much.  I am very interested in your results and other options you may try or revise.

one thing i was actually able to do for a short test was use the transmission duct chambers of a radiator to circulate old cooking oils that was given to me which i strained.  I put a radiator on my garage roof thus making it a brown(ish) background.  I placed plexi glass over the radiator.
next i pumped a 5 gal bucket of water sitting in the shade up through the radiator and measured  the return temps of over 154 deg F in early march at around high noon.

then someone told me to sit 5gal buckets in the sun with lids side by side and series them with hoses.  Paint them black but have them sit with a dark backgroud if possible.  the incoming water is "x" value in temperature but the output is much higher.  the first entry bucket is the lowest temp but since they are daisy chained they naturally aspire to have higher and higher temps the more buckets you have.
since they are lined up, they could be disguised as a "bench to sit on with a wooden top or a raised flower bed box above it.

my tests were driven by your same issues but mine directly related to my tankless water heater system which is 18kva.  Getting the incoming water temp *UP* in order to use less power was my objective.

even now with 54degF water coming in i use a lot of power to enjoy endless hot water, yet my electric bill dropped 20% without any mods.  I know there is a lot more money to be saved by employing the right system of pre-heating.,, and it all can be done cheaply.
I employed the "under the tin roof" with 200' of garden hose and was happy to see my amps draw drop from 42A down to 19 however, winter time came and i did not build in a provision to bypass or drain it,, I never thought in a million years that under the metal roof it could freeze but it did so i had to demo it out.

oh, and in your area, you have very little time to "use" sun for work due to the angle.  Solar jobs ive handled basically says NJ is the end of the line for any measureable means of using sun, however compensating with a perimeter cheap mirror arrangment for light concentration could be tried, never did it but your smart, you think things through.

curiosity is killing me man!
i keep checking on this one thread every day!

that sunshine stuff is complicated!!!!!!!!!!!!!!!!!!!!!!!

I haven't got it installed yet. Hope to have that done this weekend, then I'll keep y'all posted

Too late to change design, but an optimum design would look similar to a radiator - header to parallel lines to header on the other side. Also, smallest tubes possible. Something like this - http://www.builditsolar.com/Projects/WaterHeating/Woodsy1K/Woodsy1K.htm However, I'd imagine you're spending WELL under $1k! :)

Looking forward to seeing how many BTU it pumps out!

Way, WAY under $1k. Counting the wooden frame I've built to stand this thing on I think I might have $200 into it.

I thought about radiator style, but the cost of the T's that would be required would be prohibitive. This tubing is flexible enough that I can just loop it back and forth with no kinking.

Also, I'm not sure I like the copper pipe with aluminum fins mentioned in your link. Copper and aluminum react with each other. The galvanic reaction could result in leaks in a short time...

I can't seem to write a reply that doesn't make me sound like douche engineer, but anything is better than just paying your utility for power when there's free energy lying about!

That's the key. Every BTU of heat I get out of this is a BTU of heat that doesn't have to come from the power company...

Got the unit finished and mounted today. Had to build a stand to elevate it above the ground (and pool - it's about 10 feet off the ground, 6 above the pool). Where it's mounted sees full sun from 10AM to 3PM, so it should generate heat. Except that we're in for a run of shiznitty weather and won't see the sun for a week or more...

Cool I like it. You could turn the stand into an enclosure of some type or maybe like a little flower garden or something.

Cool I like it. You could turn the stand into an enclosure of some type or maybe like a little flower garden or something.

on another note, its halfway through May... where are all the leaves on your trees??

The leaves are a few weeks late this year. Been a really shiznitty winter and spring. We were still getting snowstorms well into April (the pool was still frozen until then, too). If you look closely you can see the leaves are just starting to come out. In a week or two everything will be green (in fact I really should have mowed my lawn for the first time of the year today but was busy working on this)

So we finally had some sun. The verdict is in: The water at the inlet was 55 degrees. The water coming out was 80 degrees. Free heat :hick: Also, when I first turned it on, after the sun had been shining on it but water was not circulating, the water coming out was over 120 degrees (my thermometer only goes up to 120, and it pegged that). Now I'm wondering whether I should let the water circulate freely, or put a timer in it that lets the water sit in it for 15 minutes or so, then open up a solenoid to let the water flow for 5 minutes, then close it to let the water absorb heat again, and so on...

One thing is certain: I'll be building another one next to it next year

Do you know the flow-rate of the system?

yeah,, Id recommend you wash, rinse and repeat the design modular like along the railing till you have about 10 of them in series.
it would be really nice if this was on a hinge, that way they fold down in the winter.
the inlet and outlet would have to be outboard though so when you fold them down, the lines can drain.

nice work.

its all about volume ,, and for the price point and delay timer, you could build another.

nice angle by the way,, i think you nailed it

Neat! im curious to see  what it does this winter lol might not freeze the pool lol

I don't know the flow rate, but imagine a garden hose flowing with the valve turned about half way on. I've purposely restricted the flow because I don't want the water to go through so fast that it doesn't have a chance to heat.

Scott: That angle serves two purposes: A) It angles the heater a bit south, facing the sun and B) It allows water to run off. I will be building another next year, but this year I've got too many other projects on the boil.

87thunderbirdBlackJack: It won't be running in the winter. It uses the pool's pump to move the water, and that will be put away. I'll pump some plumbing antifreeze into it before winter, since draining it would be difficult (although the piping is flexible enough freezing probably wouldn't hurt it, but I'm not gonna find out)

Now that I know this thing can heat water over 120, I'd love to be able to build a larger one and put it on the roof of the house for domestic hot water. I'd have to run antifreeze through it and use a heat exchanger inside to transfer the heat out of the antifreeze and into the water, but I think it would work well. Unfortunately my fear of heights, while it can be overcome for modest height such as building my garage with 12' walls (although my heart rate was quite elevated the entire time I spent on a ladder), would paralyse me on this two-story house with a roof a good 20 feet off the ground...

Well the solar pool heater is looking good, for the first time I see a pool heater (http://"http://www.thepoolfactory.com/pool-supplies/pool-equipment/pool-heaters") from inside. But are you sure that it will work like a normal heater? Anyhow please update us with the results.