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Mud Dawg

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Hi everyone, just joined and intend on sticking around and contributing for the long haul.  I live in Ontario, Canada where the energy policies over the last 7 years have been so badly mismanaged, you'd swear there was a criminal element involved.  And going forward, the policies are so out to lunch, that even other ministers within the party are calling the energy minister nuts.  Guaranteed there's a business class out there discussing the failure and lunacy of our energy policies.   



Solar stuff intrigues and tickles my fancy to no end, and now there's a serious economic benefit to slowly start cutting the cord.  Not to mention that joy of not letting the government ruin things any further.   I have spent many hours reading different threads on here, so thank you.  To start, I had some stuff laying around the garage and built a small window solar heat collector.  I used a sheet of galvanized metal lath in a VVVV pattern inside the box.  I'm letting the paint cure for now and will report back.

Onto my question.  My wife wants the pool heated, and I flat out refuse to put in an expensive heater of any kind relying on any fuel.  So the plan is to run some hoses on the roof.  The roof is fairly new, very large area and south facing with 0 shading of any kind. 


Option 1: I can just build a diverter into the current pump plumbing and run water through the hoses on the roof.  But running the pump during daytime hours is very expensive.

Option 2: I can get PV panels, run a small bilge pump off the panels to feed the hoses on the roof.  This will be the cheapest option by far, but I can't see the little pump being happy.  If it'll work and I have to replace the pump every year, then I'm OK with that.

Option 3: Get more PV panels and run the current pool pump (1 HP, AC) to both filter and feed water to the heating hoses.  I'll probably need batteries, a good controller and inverter, but I like this option as it'll make the pool 100% off grid, but I can always use grid power if I needed.  This is also nice as I can run the filter and heater at once, and during the day when it's needed the most.

Option 4: Get PV panels and buy a more efficient DC pump.  However, more efficient pumps are 4 - 5 times the price of the regular pump I have.

Any thoughts?

Thank you in advance.

SolarInterested

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Welcome Mud Dawg. Be sure to spec out your pump to handle the head. There's lots of info on pool heating at Build-It-Solar (a sister site, sorta)

http://www.builditsolar.com/Projects/PoolHeating/pool_heating.htm

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Mud Dawg

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Quote:
Originally Posted by SolarInterested
Welcome Mud Dawg. Be sure to spec out your pump to handle the head. There's lots of info on pool heating at Build-It-Solar (a sister site, sorta)

http://www.builditsolar.com/Projects/PoolHeating/pool_heating.htm



Thank you Solar Interested, and thanks for the link.  I went through them and didn't find quiet what I was looking for.

For my needs, as you said, the pump specs are the biggie, and I'm doubtful a bilge pump will handle about a 25 foot head, and push water through 500 feet of 1/2 or 3/4 inch tubing.  I don't mind giving up flow rate, but I know a small pump will struggle.  There are heavier duty agricultural pumps, like ShurFlo, that might work, but I haven't seen anyone try it yet.

I see little info on using 2 or 3 PV panels and just running your existing pump.  I found a video bellow that has done that, but he doesn't appear to have any batteries in the system.  So my question is how long will the pump last the constantly varying amount of power coming out of the PV panels? 


SolarInterested

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Did you see the section on Solar PV Powered Pumps -- DC pumps made specifically to be directly driven by a PV panel.

http://www.builditsolar.com/Projects/SpaceHeating/Components.htm#Pumps

While these are typically used to circulate water to hydronic panels for space heating or domestic hit water (DHW), properly sized they should work for a pool heater. DC pumps driven off a PV panel can be run without a controller as they self regulate only running when there's sunlight.

Why a PV Driven Pump
http://www.builditsolar.com/Projects/WaterHeating/DougPV.htm

http://www.builditsolar.com/Projects/WaterHeating/DougsSolarWater.htm

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Mud Dawg

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Reply with quote  #5 
Thanks again SI, I totally missed that section on DC pumps, I'm glad those options are available.  Would I be correct to assume the possibility of running 2 pumps to increase the head? If that's not the case, then I could always build something lower and closer to the pool than the roof.
FloridaSolarDesignGroup

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You are right that a bilge pump will probably not have enough head to run water to the roof and back. There isn't as much extra head as you might think because you have the siphon effect of the water returning off the roof, but there is still restriction in the plumbing to and from and in solar panels themselves. That's why for our professional solar pool heating panels, we use only 2 inch plumbing for the solar collector loop and the iSwim Solar Pool Heating Panel has the lowest restriction in the industry among panels offered by solar contractors in Florida. Whether these would work in Ontario is another question, as freeze protection does become a concern.

Typically we see no problems running a system with a 3/4 HP pump around here as long as the initial pressure at the filter is under 20 PSI to start. Smaller pumps are rare for Florida in-ground pools, so I am not familiar with your situation, but your concerns are well founded.

You do need a lot of surface area to make a solar pool heater work in a satisfying way. Another option would be ground-mounted panels. Just a thought...
SolarInterested

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Quote:
Originally Posted by Mud Dawg
... Would I be correct to assume the possibility of running 2 pumps to increase the head?
I believe pumps hooked up in series would work but it would be best to check with the pump manufacturer.

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Both temperature rise and airflow are integral to comparing hot air collectors
sundug

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Reply with quote  #8 
Quote:
Originally Posted by SolarInterested
Welcome Mud Dawg. Be sure to spec out your pump to handle the head. There's lots of info on pool heating at Build-It-Solar (a sister site, sorta)

http://www.builditsolar.com/Projects/PoolHeating/pool_heating.htm


Making a loop from the pool to the roof that is not open to the air anywhere will only have internal pipe friction to pump against, as the water on the downside of the loop will offset the weight of the water on the up side, so no concern about vertical lift head. Doug

 
 My YouTube videos-

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FloridaSolarDesignGroup

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Quote:
Originally Posted by sundug

Making a loop from the pool to the roof that is not open to the air anywhere will only have internal pipe friction to pump against, as the water on the downside of the loop will offset the weight of the water on the up side, so no concern about vertical lift head. Doug


Technically a solar pool heater is not a closed loop system. There should be a vacuum relief valve installed to keep the pipe from collapsing. That said, the water coming down does offset the water going up to an extent. If the pressure becomes negative at the location of the relief valve, air will get into the system. 

On that note, vertical lift is definitely a low addition of head in a well designed solar pool heater - it is more about the friction in the system (plumbing, valves, and panels). Using panels with ultra-low restriction also helps a lot, as some panels have almost 10 times the restriction as others at the recommended flow rate.
sundug

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Quote:
Originally Posted by FloridaSolarDesignGroup


Technically a solar pool heater is not a closed loop system. There should be a vacuum relief valve installed to keep the pipe from collapsing. That said, the water coming down does offset the water going up to an extent. If the pressure becomes negative at the location of the relief valve, air will get into the system. 

On that note, vertical lift is definitely a low addition of head in a well designed solar pool heater - it is more about the friction in the system (plumbing, valves, and panels). Using panels with ultra-low restriction also helps a lot, as some panels have almost 10 times the restriction as others at the recommended flow rate.


 The simple solution would be to not use a vacuum relief valve, and just use hoses that won't collapse. Doug

 
 My YouTube videos-

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