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Posts: 68
Reply with quote  #1 
Ok. I retired from teaching and was able to bring home the solar collectors I built last year.  I now have 8 collectors, 2 foot by 4 foot.  If I set them up for home heat what is the best way to run the air?  Hook all the top vents together and bottom vents together+ or try to make one long stream?


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Posts: 3,030
Reply with quote  #2 
Series will get you higher temperatures but less air so the end result would be about the same, and is less efficient. I would be inclined to go with parallel.

However considering the small size of the collectors, a combination (series-parallel) might be appropriate.

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

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Reply with quote  #3 

If you have 8 collectors, each with two screen layers, you have a total of 16 layers of screen to pass through before any air exits. Even if you were using 8" or 10" openings and ducting, it's far too much resistance, and that is before you consider all of the elbows and changes in direction. 

Try connecting a few together in different configurations to see how the airflow is at the exit. You may need to make more than one, or even several. I do like your idea of connecting the top and bottom vents together. In any case you will very likely need a more powerful fan to move enough air. Use the temperature differential between the intake and exhaust as a guide. A deltaT between 30˚F-50˚F will be about right. 

Being that you have so many collectors, why not try a few different configurations to see what works "best". After all, it's all in the name of science!

Greg in MN


Posts: 68
Reply with quote  #4 
Thanks Greg,   I only have 4 inch duct input/outputs on them. I have 2 set up in series now on my porch. They work ok, I wasnt sure if in parallel there would be airflow problems with the last few collectors not moving enough air.
Rick H Parker

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Posts: 809
Reply with quote  #5 
Hook together parallel collectors using Reverse Return Piping. That is the intake pipe is on the first collector and the return is on the last collector.  Reverse return piping will even out the air flow through across the collectors.

With Direct Return the length of the path from S to R is different for each unit. Different path lengths = Different Air flow resistance = Different rate of air flow.
With Reverse return the length of the path from S to R is the same for each unit. Equal path lengths = Equal Air flow resistance = Equal rate of air flow.

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Rick H Parker
Kansas, USA
Electronics Engineering Technologist

Posts: 21
Reply with quote  #6 
Panels in series would theoretically give you the highest temperature but in practice the air flow would be very restricted and the efficiency of the array would be way down because of heat losses from the higher temperature panels. A combination of series and parallel would be the way to go. Perhaps the first four panels discharging into a header that the second four panels drew from. That would average out temperatures (in case there were shadows) and produce a low resistance set up.
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