Tuesday, July 28, 2009

First Full Scale Solar Pool Heater Cell!

Good heavens but it has been a long time since I have updated this blog! What will happen to my advertising revenues?

In this installment, I just wanted to run through the step-by-step of building the first cell of my solar pool heater project. Eventually, I will likely have three of these units and (assuming we ever get any sun this summer) they will bring the water temperature up from the current low 70s F (20s C) to something closer to 80 F (26 C). The construction turned out to be very easy, really, and just used common items from the hardware store. No fancy, high-tolerance machining - just rough & ready carpentry. I'll post a CAD drawing after I have built a couple of them.

So far I have not been able to get good performance data because of the weather, but a "bucket test" yesterday showed it could get around 20 liters of water up to around 50 C (122 F)! When I have a bit more performance data I will post it. This will just be the construction.

1. Assemble the base.

I Started off with an 8 foot by 2 foot sheet of plywood - basically half the standard sheet of 4 by 8. This was left over from some of the work we had done in the attic. I added a couple of 1 inch by 2 inch boards across to act as supports and cross bracing:

2. Layout the tubing.

I am using standard 1/2 inch CPVC tubing bought from the local home center. The elbows loop the tubes back to provide a complete circuit. There is about 140 feet of tubing in this box. Everything went together very smoothly, but the glue for the CPVC is foul stuff! Even working outdoors it was making me dizzy. Still, goes together super easily and is permanently bonded in <5 minutes. The brackets are just standard 1/2 brackets. They fit the tubing a bit loosely, but I figure that makes sense to handle thermal expansion.

3. Build a box.

Nothing hard here - just used 1 by 3 inch boards to build up the sides cut out holes for the intake & output.

4. Paint it black.

Astute observers will note that black absorbs heat better than white & wood color! This is just some matte black barbecue spray paint I got on sale. This shot shows the size of the unit a bit better. Eight feet is pretty tall actually!

5. Weather proof paint.

I put a thick coat of exterior alkyd on the back & sides so that it would be weather proof when eventually mounted on the roof of the garage. I also inadvertently put a pretty good coat on my patio stones!

6. Finally a 1.4 inch Plexiglas top.

This will weatherproof the tubes, but I am also assuming somewhat of a "greenhouse effect" to help increase the temperature.

And here you have it! This is it running it's first "bucket test" on 18 litres or so of water. As I said earlier, it did get the water over 50 degrees Celsius, but it wasn't a good run because of some leakage around the hose clamps.

I plan to try it with a couple of larger volumes of water just to assess its "performance envelope" and then hook it up to the pool. My guess is it would have a negligible impact on the pool and I will need to wait until its two brothers are built to have it really make a difference!

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