Solar heat question

[Gomez9356]

I have a 18' roundx54" deep AG pool, before spring we are going to put a fence around it. My plan is to put a narrow 'roof' on the east fence so that I can put a solar heater on it. That side of the fence will be in the sun from early morning to about 4pm. The fence will be 32 feet long and I can make the roof as wide as needed but prefer to not be over 48". I plan to use 1/2" poly tubing for the heater. Assuming I'll need to leave about a foot in the center so as not to kink the tubing, I can still get 36" x 30', giving me some 13,000 linear feet of tubing (or about 90 square feet) for gathering heat. I already have a manifold built to connect in between the pump and pool.
Is this a reasonable plan?
TIA

 

[gwegan]

Probably not.

For a variety of reasons homebrew solar collection is not nearly as efficient as purchasing panels. With solar heat its volume of water with slow gain that is most efficient. Narrow tubes on the purpose built panels are much more efficient at transferring solar energy to the water. Stick around and watch this thread and some folks will come on and suggest some panels. Many of which don't cost that much. Or watch craigslist and ebay and you can get them used. If you do a search for DYI solar panels on here you will also get a lot of ideas.



We would also recommend a solar controller like suntouch but that is not vital.

 

[needsajet]

60% to 100% of the pool surface area is a good target to shoot for. Sounds like you have long daily exposure, which is great. Spend a bit of money on the panels, do the rest DIY, and you'll have a good system.

I'm in the camp that strongly recommends a controller. You can turn it on and off manually, but for many people, it's easy to miss a day (or part of a day) and/or leave it running after the sun is off the panels.

The greatest temperature gain you can get for the money is a pool cover. There's some methods here that are inexpensive. I'm using one just to get us swimming earlier in the spring, and now the cover is put away for the summer.

Make sure everything can handle a windstorm. Sounds like a fun project

 

[xyz]

I'm familiar with HotSun (hopefully I'll be able to finish by the weekend), so I'll tell you why I like them and how you can do DIY using this approach. Also, like most, since I went with this company, I'm obviously biased! But just because I parnoid doesn't mean they are not out to get me!



Why I chose H2otSun:

- PVC. More robust material, more heat resistant, and higher pressure capability (less chance of blowout if valve is open and pump is at full bore, etc.

- Flexibility. You can make arrays 2' or 200' long, route around obstacles, and/or turn corners.

- Simpler plumbing (usually).

- Good for DIY. The plumbing design is far trickier than I thought. In fact, had I plumbed my (simple!) setup like I initially thought, I'd have not known that 1/2 my array eff ctiveness wouldmhave been lost.

- Terrific advice, support review. I sent my approach to Ken and he showed me the places where I could fix, improve, and optimize.

- I think normally this would be somewhat higher than the more standard arrays, but for me, slightly less array cost since the install flexibility allowed me to put in 2 large arrays vs 12 smaller (and less effective) arrays. Or, said another way, because of the flexibility, I didn't need as large an array, plus significant pot fewer headers and subsequent plumbing.

- Easily repairable. Or more like extremely repairable.

In summary, if the standard arrays are an easy install, I'd think these would be a better deal (e.g., helicoil). But if you want an easy install with plenty of tech support, and the standard array sizes don't work well for you, H2otSun may be a better choice.


So, you have 254 sq ft surface area. So you want between 70 and 100% (rule of thumb). More if you want very warm and don't cover, less if you don't need as much temp increase and you have a cover.

254 x 0.7= 177 sqft

With Ho2Sun, the rolls are ~90' long, so for a no waste system, a 180 sqft system would be 6' wide. Since a roll is 4" wide (three strips per foot per header), just add another roll and 2 more headers, and you have 7' or 210, another roll and 2 headers yields 8' or 240 sqft etc.

in fact, you could leave space and plumbing for 9', but start at 5' and then add 2 headers and a row if it is not enough.


we can help more with more info:

1) direction the fence roof faces (directly south is very good)
2) is the fence completely unobstructed from the sun?
3) How windy do you think it normally is?
4) how high is the bottom of the array from the pool pump in elevation?
5) what angle is the array (is it angled toward the sun?

 

[Gomez9356]

A little more info and some answers:
We do keep the pool covered when not in use, just a cheap vinyl cover but it helps, and the pump is on a timer.
xyz: I have not built the fence yet but it will run north and south. That area will be shaded after 5pm during DST.
It's Kansas. Most days the wind is less than 15mph but gusts in the 30mph are not unheard of and we can get 70mpg+ during thunderstorms.
the fence will be 6' tall although I have contemplated making the north end higher for a little south facing angle. I also have a garage next to the pool with a south facing roof, I'd have to measure again to see how many square feet it would have available. the lower edge of the roof would be about 7' above the pump and around 15' at its highest.
My wife and I have both had back surgery so we like to float and splash around in warmer water than most people prefer.

 

[xyz]

Ah, bummer about the non-optimal fence direction.

Tell us more about this south facing roof. This may be a better solution, and may be better suited to standard array sizes.

A few more questions:

1) So can I assume the Fence will look like a "T" with the array sitting on top of it? Do you plan to make it high enough so that one could walk under the Array?
2) What is the approximate size of the roof? How much of an array could you fit on it?


And some comments. 7-15' of head would work just fine, so the roof is looking very good.

So I think you would optimally want very roughly a 30 degree declination optimally, given April-Oct. If your fence ran east/west, you could have leaned the panel(s) 30 degrees into the Sun. But even a flat roof (or a flat fence) will still work, it won't work quite as well. In fact, by the cosine of the desired depression angle.

So your 254 sqft [if you are going fro 1:1 ration] would yield a desire for 293 sqft [254/cos(30)] to achieve the equivalent cooling of a 1:1 array. Contrast that with your garage roof, which is already is likely angled at or near 30 degrees, so another reason why this would be a good idea. I'd also guess that the garage roof may have less shading, providing even more capability [or a need for a smaller array].

 

[Gomez9356]

Any east-west fences I have will not get as much sun.
The roof is about 14' wide and 17' peak to gutter. The upper 8 feet is around a 8/12 pitch and the lower section is more like a 4/12 pitch.
The roof is probably in the sun a little longer by virtue of being higher, but it probably won't be more than 30 minutes extra.

 

[xyz]

Hmm. If you could figure out how to cover most of that roof, I think you might have a better time of it all. I'd think it would be more efficient, and be less obtrusive. If you do the whole thing, you can get pretty close to a 1:1, and that will work really well.

Id say if you can find 14' wide arrays that can be run sideways [you have to think about he air relief], that would be ideal, otherwise, the hotsun "build your own array size" flexibility would let you do a top to bottom, or left to right array.