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MaxR

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Reply with quote  #1 
Hi All,
I'm quite new to all things solar, thus I'm hoping someone can offer a bit of advice on what to do next on a hobbyshop project of mine:

I've built a couple of well working solar heat exchangers, which I plan to heat my pool with. I had a 12V/3A DC pump sitting around and recently got my grubby little hands on a cheap solar 250W panel, which should be way more than enough to drive that pump. The panel gives out about 32V, thus I'll obviously need something in between. However, I'm not planning on adding a battery as there's no need for the pump to run, if there's no sun.

So my question to the panel is; does anyone know of a charge controller or some other gadget which can handle the power from that big panel and give me 12V out without having a battery involved - or am I going about this the wrong way?

Any advice or recommendation on what I need here would be appreciated!
Thanks,
Max

stmbtwle

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Reply with quote  #2 
Go on Amazon or ebay and get a 12v (output) "buck converter". It will take the high voltage from the panel and drop it to 12v for the pump. Easy to connect and no battery required. You can get waterproof models too. For a little more power to the pump you can get an adjustable model and set it at about 14v.

This one may work for you: https://www.amazon.com/Regulator-DROK-Waterproof-Synchronous-Adjustable/dp/B00CNXLDCQ/ref=sr_1_22?crid=3TWOZMBVDMRM8&keywords=adjustable+buck+converter&qid=1562171683&s=gateway&sprefix=Adjustable+Buck+converte%2Caps%2C191&sr=8-22

You can get them for up to 48v input and 20 amps if needed.

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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
MaxR

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Reply with quote  #3 
Willie, thanks a bunch for the advice! A buck converter sounds like the ticket.
As per your suggestion, I'll probably need a 10 amp unit, as 250W/32V = about 7.8 Amps, although the panel has a couple of years on it, it might be putting out less.
This is probably the droid I'm looking for: https://www.amazon.com/Converter-DROK-Voltage-Regulator-10V-75V/dp/B071LGTTRN/

Thanks again!
/Max
stmbtwle

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Reply with quote  #4 
That would work, and it has a built-in display. You would need to keep it out of the weather though.

I like the waterproof models (no enclosure required), but I give up the display.

It all depends on your installation.

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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
MaxR

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Reply with quote  #5 
Nice! just ordered one. Let's see how it works. I've got a nice little outdoor conduit box ready for it. I usually drill a few holes in the bottom for ventilation, gluing a strip of gauze and mosqutonet over, to keep the bugs out.
stmbtwle

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Reply with quote  #6 
Hm, never thought of the bug screen! Great idea, thanks!

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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
sundug

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Reply with quote  #7 
Quote:
Originally Posted by MaxR
Hi All,
I'm quite new to all things solar, thus I'm hoping someone can offer a bit of advice on what to do next on a hobbyshop project of mine:

I've built a couple of well working solar heat exchangers, which I plan to heat my pool with. I had a 12V/3A DC pump sitting around and recently got my grubby little hands on a cheap solar 250W panel, which should be way more than enough to drive that pump. The panel gives out about 32V, thus I'll obviously need something in between. However, I'm not planning on adding a battery as there's no need for the pump to run, if there's no sun.

So my question to the panel is; does anyone know of a charge controller or some other gadget which can handle the power from that big panel and give me 12V out without having a battery involved - or am I going about this the wrong way?

Any advice or recommendation on what I need here would be appreciated!
Thanks,
Max


Hi Max, 
 I'm curious about the heat exchangers you built for the pool. Most common metals are not compatible with most pool chemicals. Doug

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MaxR

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Reply with quote  #8 
Hi Sundug, pardon the late reply - you're right about the metals, which is why I opted for plastic :-)
I built two wood boxes 36x36" (mostly dictated by the standard 72x36" plexiglass sheet which Lowes carries - besides anything larger would become hard to handle. Speaking of which, I added a shelf-handle on the top, making it easy to carry both units at the same time.

For the plumbing I use regular half-inch sprinkler tubing. It's black already and only costs like 12 bucks for 100' the ends. The ends go into two of those pressure fittings which ind in a gardenhose male thread, making it easy to hook them up with things. It's a good idea to give them a gob of epoxy to make sure they keep tight. The tubes are held in place with zipties run through holes in the back of the box. To keep them nice and tight I dont strap down more than 4 loops of tubing at a time.

Btw, as an intake before the pump I had one of these bubbler attachments lying around the shop https://www.amazon.com/Orbit-SunMate-Hose-End-58049N-Irrigator/dp/B0002YUESC - turns out to be an effective debris filter

One word of warning: since the tubing is really thin, DO NOT put them out in the sun, or at least cover them with a blanket or something until you're ready to hook up the pump. Here in the Vegas sun they get so friggin hot inside that the plastic tubing melts without water running through them!

Numbers: The pump is humming along at 14V/3A, which the buck converter and the 250W panel  delivers without breaking a sweat. Important, the buck converter I bought (see thread above) needs to be programmed to turn on automatically, but that's covered in the manual. Acrylic glass, wood and tubing probably ran about 50 bucks per exchanger give or take.

I timed filling a milk jug and it looks my two redneck exchangers in series, 10 hours a day are spitting out about 70GpH of water heated 16F from intake to output. Planning on adding two more soon.

Here's a picture of one of them in the shop before the acrylic cover was mounted







Attached Images
jpeg solarheater.jpg (124.82 KB, 12 views)

sundug

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Reply with quote  #9 
I built an unglazed collector with 300' of irrigation tubing, it would air lock and not get up to temp. So I built a 4 x 8' collector and put the 300' in it, with twinwall glazing. It melted the several times it stagnated. I replaced with PEX and it has been doing well since. Doug

https://simplysolar.supporttopics.com/post/new-evacuated-tube-spa-swh-7477891?highlight=spa+hot+tub&pid=1304990455

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stmbtwle

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Reply with quote  #10 
Sundug

What did you paint the PEX with? Not much will stick to polyethylene.

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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
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