Homemade solar heater

[Rumbleehockey03]

So I got bored today and went to lowes and spent about $30 on materials and made a solar heater. Specs are 4’x4’ ply sheet with 150’ of 1/2” irrigation tubing coiled and a heavy duty shower curtain to cover it.
Performance:
85 degree ambient air
136 degrees in the box
62 degree pool water
68 degree outlet temp
Approx 2gpm through the heater and 75’ of garden hose using my pool cover sump pump

I’m happy ?‍ But realize it won’t be extremely effective heating my pool by itself.

 

[mas985]

You may already be aware of this but given that panel is only about 6 sq-ft of hose (only the hose absorbs the sun's energy), at most you would get about 10000 BTU/day or about 0.1F temperature rise. BTW, the gain will be lower with the shower curtain covering the panels. It would only help in very windy and cold conditions.

 

[bobwatson]

Applause for the idea and fabrication.

 

[chayne]

this is the one i made 2 years ago.

this is what it puts out. i usually have to stop using it around the middle to late May. then i use it again at the end Sept. this temp here is the at the beginning of turning the pump on for the heater. it usually keeps a constant temp of about 102 for as long as i want to run it. you have to adjust the flow or it will not have time to heat the water running through the pipe.

 

[mas985]

this is what it puts out. i usually have to stop using it around the middle to late May. then i use it again at the end Sept. this temp here is the at the beginning of turning the pump on for the heater. it usually keeps a constant temp of about 102 for as long as i want to run it. you have to adjust the flow or it will not have time to heat the water running through the pipe.

BTUs delivered to the pool is related to the temperature rise in the panels in addition to the flow rate of the water. The amount of energy hitting the solar panels is fixed (under constant atmospheric conditions) so when you halve the flow rate, the temperature rise in the panels doubles but total heat remains the same. But the net heat gain delivered to the pool is actually slightly lower because of heat loss. Heat loss is proportion to the temperature difference between the water and the surrounding environment. So the higher the water temperature, the more heat is lost to the environment.

So the heat delivered to the pool is more than just the water temperature exiting the panels. It is also about how much of the water you are heating over the course of the day and how much of that heat actually makes it to the pool. Given the rise in the water temperature, your flow rate must be very small and so you are not heating much of the water over the course of the day.

 

[Rumbleehockey03]

View attachment 130869
this is the one i made 2 years ago.
View attachment 130870
this is what it puts out. i usually have to stop using it around the middle to late May. then i use it again at the end Sept. this temp here is the at the beginning of turning the pump on for the heater. it usually keeps a constant temp of about 102 for as long as i want to run it. you have to adjust the flow or it will not have time to heat the water running through the pipe.

Holy cow. How much tubing do you have? I used 150ft and got 6degrees but only at about 1.5gpm

 

[chayne]

i have 300ft of piping. i think if i remmeber the flow rate, it was about 1.25 gallons a minute.

 

[mas985]

300 ft of 1/2" poly is about 12.5 sq-ft of solar collection area. In your area, the maximum solar radiance on a flat plane is about 2634 BTU/sqft/day. At that flow rate, the panel should be about 80% efficient so the maximum BTU the panel could possible produce is about 26340 BTUs. Assuming the pool is about 5500 gallons, that would add only 0.57 degrees to the pool.

Exit temperature of the panel is not all that relevant without taking into account the flow rate and inlet temperature. What is important is the number of BTUs added to the pool each day and then the amount of those BTUs that is lost each day.

But I think your flow rate is much lower than what you think it is. The maximum heat gain at solar noon would be only 5F at that flow rate for that size panel. To get that high of an exit temperature, flow rate would need to be much lower.

Pool Parameters	Scenario1
Pool Volume (g)	5500​
Panel Size (sqft)	12.5​
Panel Flow Rate (GPM)	1.25​
Panel Efficiency	80%​
Solar Input
Solar Daily (BTU/sqft/day)	2634​
Solar Peak (BTU/sqft/Hr)	315​
Calculations
Total Pool Heat Gain (BTU)	26340​
Pool Temperature Rise (F) - Without Heat Loss	0.57​
Peak Hour Panel Output (BTU/min)	53​
Peak Hour Panel Inlet to Outlet Heat Gain (dF)	5​

 

[Brett S]

You may already be aware of this but given that panel is only about 6 sq-ft of hose (only the hose absorbs the sun's energy), at most you would get about 10000 BTU/day or about 0.1F temperature rise. BTW, the gain will be lower with the shower curtain covering the panels. It would only help in very windy and cold conditions.

How do you do this calculation? I have a 4x20 foot solar panel that I had used for my old 15’ round pool. I’m debating whether it’s worth getting it installed and connected to my new 16x32’ rectangle pool. I know it will be undersized for the pool, so I’m trying to decide if it will really make enough of a difference to go through the trouble of installing and connecting it to the new pool.

I’m a little north of Orlando and obviously I’m really just interested in the late fall/winter/early spring seasons as the pool stays warm enough on it’s own through the rest of the year.

Unfortunately the pool takes up a significant portion of my yard as it is, so I don’t really have an option to install additional panels. I’m trying to avoid using the roof because I would really like to get solar panels for electricity up there and I will need most of the roof area for that when and if I do.

 

[mas985]

I have a simple spreadsheet to do that calculation (Panel Gain). I also have a much more complicated version (Heat Txfr) that takes into account heat loss as well. See here Pump/Pool Spreadsheets.

 

[IsThisWhereIPutMyName?]

How do you do this calculation? I have a 4x20 foot solar panel that I had used for my old 15’ round pool. I’m debating whether it’s worth getting it installed and connected to my new 16x32’ rectangle pool. I know it will be undersized for the pool, so I’m trying to decide if it will really make enough of a difference to go through the trouble of installing and connecting it to the new pool.

I’m a little north of Orlando and obviously I’m really just interested in the late fall/winter/early spring seasons as the pool stays warm enough on it’s own through the rest of the year.

Unfortunately the pool takes up a significant portion of my yard as it is, so I don’t really have an option to install additional panels. I’m trying to avoid using the roof because I would really like to get solar panels for electricity up there and I will need most of the roof area for that when and if I do.

If you are getting solar power from the roof and don’t want to waste yard space, you can use the green power to run an electric heat pump. Even a moderate sized heat pump will give more BTUs than solar thermal panels considering how much size you have to work with.

 

[chayne]

all those calculations are great. each time i reply to something about my homemade solar heater, i get told this does not work. all i know, is that when that heater is running my pool temp goes up. usually i have to turn it off. so, i will not be commenting or posting anymore about my heater.

 

[mas985]

First, I don't think anyone said it does not work. Solar panels will usually always add heat to a pool. The real question is how much heat will it add and will it make a difference. That is the only aspect I was addressing.

Thermodynamics has been around for almost 200 years and is universally accepted as fact.