Going to build a solar pool heater system - need advice

[FantanaBandana]

I'm going to build a solar pool heater system. My pool is 16 x 32 feet and in ground. The surface area is about 330 sq ft. I'm shooting for a heater system that covers about 250 sq feet. I'm planning on getting 5 solar heater panels like this that are 4' x 12' each. The system will be completely independent from the rest of the pool system. The heater panels will be mounted at a 45 degree angle on a hill just feet behind my pool.

I already have 2x 100w solar panels, a 100aH battery, and a 40amp MPPT controller that I used last year for outdoor hydroponics. The 2 things I need help with are finding a DC pump for my needs and whether I should shoot to run my system continuously, or on a schedule. I read here that running continuously is more efficient, but I understand that could draw too much power in a system like this. Also from that link, I should shoot for a pump that pumps 4 gallons per minute per heater panel. At 5 heater panels, I'll need a pump that can do 20 gallons per minute. Based on the location of the panels, I'll need a pump that can do 20 feet lift max.

Does anyone have any suggestions for DC pumps for my needs? I found a few pumps online here and here, but it's hard to find exactly what I need. I'm willing to add up to 2 more 100w solar panels and 1 more 100aH battery for a total of 400w of power and 200aH of battery, if necessary. I also have a 600w continuous power inverter and a 1/3 hp sump pump already that I could do some experimentation with to see how it would work, but I assume with the power loss it wouldn't be as efficient as a pure DC pump.

So does anyone have any recommendations for DC pumps that can do 20GPM(1200GPH) with 20' of lift? And should I run my system on a schedule or continuously? I know on a schedule will be more complex as I'll have to add fittings that release the heater water back to the system on a timer. And the pump will need to be on a timer too. Sun light isn't a concern for this system as I'm in Southern California.

 

[yodamota]

Have you considered pv direct for pumping?

I imagine you only need to pump when the sun it out.

 

[FantanaBandana]

Have you considered pv direct for pumping?

I imagine you only need to pump when the sun it out.

I have and I'm open to it. With my panels, I figured if I wire them in series, I can get 24v out of them. But now that I'm looking up my panels again it looks like in series I can get 37.8 Volts and 5.29 amps under optimum conditions. Which opens up the possibility of running a 24v or 36v pump wired directly. If I get a 36v pump and conditions aren't optimum, will a pump just run slower? Or not run at all?

 

[yodamota]

yes, having a pv direct water pump for our garden. I always know when a cloud goes over the panels as it will slow down/stop. Hopefully your pump won't be loud enough to disturb your pool experience.

I am not sure if your small amount of panels/batteries can power a pump capable of 20GPM.

 

[FantanaBandana]

I found a few pumps that could work. Does anyone have any experience with this pump?

At 24v, 200 watts, 1584GPH(26.4 GPM) it looks like exactly what I'm looking for.

Or how about this pump? They have both 12v and 24v versions of that one. It doesn't put out as much but it's cheap enough that if I needed 2, I could buy 2. Granted I would need another 2 solar panels to run a second pump.

Maybe I should try doing this build in stages of 2 solar heater panels at a time instead of buying too many panels and not having enough power to pump the water.

 

[hwy17]

If you're using real pool panels why don't you just plumb the pool pump through them. You don't have to run these like those irrigation tube contraptions.

 

[FantanaBandana]

If you're using real pool panels why don't you just plumb the pool pump through them. You don't have to run these like those irrigation tube contraptions.

A few good reasons. The first is cost. I live in one of the most expensive places in the country for cost of electricity. So having a system where I don't need to pay to run it is very attractive to me. Another reason is I'm going to be installing this on a hill behind my pool. The pump is between my house and the pool, so I'd have to run pipes underground, all the way across the yard to do it. I can't install the system on my roof yet because I'm going to need a new roof pretty soon. And I already have a few solar panels I'd like to put to use. If I can find the right pump I should be able to set this system up in a day or two max.

 

[hwy17]

A few good reasons. The first is cost. I live in one of the most expensive places in the country for cost of electricity. So having a system where I don't need to pay to run it is very attractive to me. Another reason is I'm going to be installing this on a hill behind my pool. The pump is between my house and the pool, so I'd have to run pipes underground, all the way across the yard to do it. I can't install the system on my roof yet because I'm going to need a new roof pretty soon. And I already have a few solar panels I'd like to put to use. If I can find the right pump I should be able to set this system up in a day or two max.

Yeah it's $.40 for kwh for me. I only had to extend my runtime a couple hours to 6 for my pool solar. But the plumbing run does sound hard.

The panels lose efficiency as the flow rate goes down though, so I think you should be imagining a higher flow rate. Maybe .25-.5HP. I would look at pool pumps, whether that's the AC or DC ones.

 

[yodamota]

I found a few pumps that could work. Does anyone have any experience with this pump?

At 24v, 200 watts, 1584GPH(26.4 GPM) it looks like exactly what I'm looking for.

Or how about this pump? They have both 12v and 24v versions of that one. It doesn't put out as much but it's cheap enough that if I needed 2, I could buy 2. Granted I would need another 2 solar panels to run a second pump.

Maybe I should try doing this build in stages of 2 solar heater panels at a time instead of buying too many panels and not having enough power to pump the water.

I don't understand how that first pump can pump so much for 200w.
While the second link you give, those pumps hardly can put out 714GPH at 24v 550w seems fishy to me.

 

[FantanaBandana]

I don't understand how that first pump can pump so much for 200w.
While the second link you give, those pumps hardly can put out 714GPH at 24v 550w seems fishy to me.

I agree the numbers don't look right on those 2 which is why I was asking.

I found a vevor 48v pump that I did find a youtube video of someone actually testing. I'd have to get more solar panels, but it may be able to handle what I'm trying to do.