Build your own flat panel solar thermal collector

Step 6 Testing

If you have removed all the air and have a sealed system and there is enough sunlight hitting the panel, it should start thermo-siphoning almost instantly.

1. Turn the panel towards the sun and raise or lower the top end of the panel to better aim it towards the sun. One end of the panel must be raised higher than the other in order for thermo-siphoning to work. The storage tank must also be kept higher than the top end of the panel.

2. Feel the top hose where it exits the panel. It should be hot if your setup is thermo-siphoning. The bottom hose should still be cool. If this isn't the case, it probably means you have a vapor lock (air bubbles) somewhere preventing the water from circulating. Connect the bottom hose to your tap again and repeat the filling process, attempting to remove all the air bubbles.

3. Once thermo-siphoning starts, use a digital thermometer with probe to measure the water temperature. By sticking the temperature probe inside the ends of the hoses, you can measure the inlet and exit temperatures of the collector. It took me about a minute after filling before I had my thermometer set up. At that time the inlet temperature was 23 degrees C (basically the initial temperature of the water) and the exit temperature was 50.7 degrees C (123 degrees F).

4. Measure the inlet temperature over a period of an hour or so (or till the temperature stabilizes). The inlet temperature should always be the lowest temperature in the system. Measuring here will give conservative results when calculating the amount of energy transfered to the water.

Comments

[weldor]

I believe that what is being referred to as "thermal siphoning" is actually a natural type of circulation called convection. It is also called "ebullient cooling" when the process is used to transfer heat out and a way from (as a method of cooling a piece of machinery (typically an engine).

To avoid air bubbles it is a good idea to install your fill point at the lowest point of the system. This is because air always rises to the top. The expansion tank should also have a safety relief valve from a water heater installed. Better yet, use a water heater as the expansion tank.

[davey703]

I've been planing on doing this ideas myself with a car radiator, I'm just a bit confused about the thermo siphoning, or how it is judged, in your design once inplaced at its angle, is the cold water feed entering from the top or the bottom??

[iwilltry]

The cold water should exit from the bottom of the storage container and feed into the bottom of your collector (radiator in your case). The hot water should exit the top of your collector and feed into the top of the storage container. The collector should be lower than the storage container for effective thermo-syphoning.

[davey703]

I'm using a car radiator, a small copper cylinder and extension tank(if the water overheats) all connected by copper pipes, what would be the main causes if the system doesn't work, or the thermo-siphoning doesn't work....in diagram 1 to 10

[iwilltry]

Without seeing how you've set up your system, it's difficult to say, but the usual cause of thermo-siphoning issues are:

• air locks
• collector not low enough relative to storage tank
• connecting tubes not large enough in diameter
• connecting tubes not providing a continuously rising (for hot tube) or continuously falling (for cold tube) path for the water to follow
  

I don't know what diagrams you are referring to.

[onebitpixel]

I wonder if this could this be utilized within a pool system that would help keep it heated as well as filtering... while it is moving through the hose and through the filter assembly...

[AbelK89]

I'm been planning on trying this idea... and will post any ideas upon trying.