DIY Solar heater

Jump to latest Follow Reply
A

APrime

0
Jul 1, 2010
13
I'm looking at a Sungrabber type system for my pool, but my main questions are 1) isnt plastic a insulator and not a very good conductor of heat. 2) Why not just "coil" or parallel a few 100" lenghts of black garden hose on a pool deck. I would think the black rubber would absorb/transfer heat better than any plastic pipe and on a concrete pool deck.
 
1) Plastic is a good electrical insulator but if it is black, it is also a very good thermal conductor.

2) Solar panels are all about area. By the time you make a panel large enough, the cost of all that pipe is likely to be nearly the same as the solar panel and the solar panel will be a lot easier to install. The material used matters less than the color. There are panels made of both plastic and EPDM, a rubber material, and they both work well.
 
I really like our solar bear panels...that said +1 to what Mark said. One 4x20 panel easily has 30+ tubes that the water passes through x 20ft each = alot of tubing if you were to DIY and would not be able to fit it in a 4x20 area.

Ever touch a black trash bag that's been sitting out in the sun? When the water is running through the panel it's cool to the touch, but feels hot just like the trash bag when the pump is off and the panel is in full sun :goodjob:
 
Yeah, I was lookin to be lazy and see if anybody had built a solar heater with garden hoses. The real question I have about the plastic mat styles are about durability. Is 2-3 seasons is what you would get? If you get a leak then what? Is there a mil thickness? Where is the best place to buy, I'm looking for 2 - 4X20 panels for a 20,000 gal 16X32 rectangle
 
I'm about to build one with 4kg/cm2 pressure rated irrigation pipe. Because I'm in an agricultural area and in the trade building a spiral panel myself works out about the third the cost for the same area and I think mine will be a lot tougher but possibly slightly less efficient in use of space. The cheapest panels I can get here are around 200$ for a 2' x 20 ' panel. I'll be starting the panel itself in about a month, I've already fitted the 3 way valve etc. I'll let you know how I get on.
 
Spirals are generally much less efficient in terms of heat gathering. You want as many parallel runs of pipe as possible, while spirals are typically done with a single length of pipe. Optimal efficiency occurs when the flow rate is as high as possible and the heat gain in minimal. Single long runs of pipe dramatically increase the flow resistance, lowering the flow rate. They also allow the water to heat up more in a single trip through the system, lowering efficiency.
 
You don't want the panels to "retain" heat, you want them to transfer heat to the water as quickly as possible. The reason panels are more efficient with higher flow rates is because the water temperature in the panels is kept as low as possible and thus the heat loss from the panels will be minimized. The higher the water temp in the panels, the faster they lose heat to the surroundings.

As for flow rates, most panels will peak in efficiency around 0.1 GPM/sq-ft.
 
APrime said:
Yeah, I was lookin to be lazy and see if anybody had built a solar heater with garden hoses. The real question I have about the plastic mat styles are about durability. Is 2-3 seasons is what you would get? If you get a leak then what? Is there a mil thickness? Where is the best place to buy, I'm looking for 2 - 4X20 panels for a 20,000 gal 16X32 rectangle
Click to expand...

The rule of thumb around here is to have equivalent solar panel covetage for about 80% of your pools surface area. Two 4X20 panels aren't going to be enough for your pool.
 
carlscan26 said:
APrime said:
Yeah, I was lookin to be lazy and see if anybody had built a solar heater with garden hoses. The real question I have about the plastic mat styles are about durability. Is 2-3 seasons is what you would get? If you get a leak then what? Is there a mil thickness? Where is the best place to buy, I'm looking for 2 - 4X20 panels for a 20,000 gal 16X32 rectangle
Click to expand...

The rule of thumb around here is to have equivalent solar panel covetage for about 80% of your pools surface area. Two 4X20 panels aren't going to be enough for your pool.
Click to expand...

Ditto...anything will help, but you are looking at 3-4 panels on a 20K gal pool. And using a solar cover to retain the heat generated during they day is essential.
 

Enjoying this content?

Support TFP with a donation.

Give Support
I am planning on 8 parallel 5/8" pipes running around together with a total area of around 160 square feet. I totally understand the premise that it's better to have a large quantity of moderately heated water than a small quantity of highly heated water, as this would lose more to and from the panels as the temperature differential is so high. I was more thinking it would be less efficient due to the shape not fully occupying the rectangular shade it will be on.
I plan to take some very detailed measurements which I will post here.
 
mas985 said:
As for flow rates, most panels will peak in efficiency around 0.1 GPM/sq-ft.
Click to expand...

:-D That works out the same as the Australian standard which recommends between 1.8LPM and 4.8LPM per m2.

This is one guys home made panels. I don't know enough math to tell if his calculations are correct, but I found it an interesting read.

My gut feeling is that unless you have access to very cheap black tubing, it's better to get some premade panels.

If going the homemade route, is polyethelene the best plastic to use? As opposed to polyurethane, nylon or something else?
 
For the life of me, I can't imagine how that would be cheaper than a premade panel. Plus, spirals are not very space efficient. Nearly 1/4th of the area is wasted instead of generating heat.
 
Well a 40 sq ft panel here is 264$ (189€). I can get 38 x 20 foot lengths of 5/8 " (760 foot) for 129 $ (92€) leaving me 135$ for 16 clamp brackets to go on about 1 metre of 2" "manifold" at either end. As these brackets cost me about 50c each and the pipe about 2 dollars I save 125$ just on the one panel. In that I intend to have a panel about 3 times this size I hope to save around 375$ for an afternoons work. And the panels I saw for sale looked liked they'd only last a season or two while the irrigation pipe and fittings lasts decades.
 
Jimmy_from_NZ said:
mas985 said:
As for flow rates, most panels will peak in efficiency around 0.1 GPM/sq-ft.
Click to expand...

:-D That works out the same as the Australian standard which recommends between 1.8LPM and 4.8LPM per m2.

This is one guys home made panels. I don't know enough math to tell if his calculations are correct, but I found it an interesting read.

My gut feeling is that unless you have access to very cheap black tubing, it's better to get some premade panels.

If going the homemade route, is polyethelene the best plastic to use? As opposed to polyurethane, nylon or something else?
Click to expand...

Now figure does help me, so I will probably need to have 32 runs of shorter pipe to fall in the middle of that spec. The pipe I'll be using is polyetheylene by the way.
 
You must log in or register to reply here.
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Top Bottom
Back
Jump to latest Follow Reply