Stripped Down Solar

One of the reasons the repair I tried for the 3′ x 7’ solar panels was a disaster is that the glass broke when I was moving it. The glass in the solar panels seems to be extremely fragile.
I decided to revisit the smaller panel that I had not broken yet just because it would be easier to carry. While I was doing that I looked more closely at the collector plate in the broken panel. I cut it out of the panel by slicing the bent copper with my multi tool and a metal blade. Now I had just the copper collector plate from the solar panel.

Copper Collector
Copper Collector

The panel is copper on the back side and has a black finish on the sun side.

Black panel side
Black panel side

The collector gets very hot in the sun. But I can’t run the salt water from the pool through it because it will corrode. So I bought the stainless steel heat exchanger to separate the heating fluid (plain water in this case) from the pool water being heated.

Shell and tube system
Shell and tube system

In most designs with a shell and tube heat exchanger the solar fluid is run by a pump. But it would be nice if I could use just a thermosiphon system for this function. The simplified example below uses liquid without a pump. The tank must be above the collector and the circulation of the fluid occurs naturally when the hot liquid rises and cooler liquid sinks back into the collector. A more complete thermosiphon system would be connected like the diagram on the right.

Simple thermosiphon closed loop
Simple thermosiphon closed loop
Thermosiphon System
Thermosiphon System

What if instead of a water tank, I placed the shell and tube exchanger above the collector? Would that create a natural thermosiphon? Imagine the lower tank is the pool. The pool pump would drive the water through the tank at the top to pick up the warmth from the solar heated water. Then it would return to the pool. Would the water in the solar panel and heat exchange tube circulate naturally? What would happen when the pool water is not being heated by the system?

I began to set up the system using a garden cart that has a slanting lid. I bought a few of these from a craigslist ad and they have been very useful as outside work tables.

Panel on garden cart frame
Panel on garden cart frame

I used the hose to fill the lower panel hose with water and had the upper hose running into a bucket of water. I was able to fill the system with water by eliminating bubbles while filling the hose attached to the bottom of the panel. I laid the hose vertically when it was full and there were no more bubbles in the bucket and eventually all the water emptied into the bucket. So it had to be siphoning.

Panel with high and low hoses
Panel with high and low hoses

The question is whether the circulation would continue if the loop was closed. I’ll have to experiment. When I get all the connections for the shell and tube heater, I’ll install it at the top of the panel and figure out how to get the natural convection started. That is the plan anyway.

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