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Acuario 11-01-20 06:20 AM

Configuring hot water solar panels
I currently have 3 solar water panels connected in series to provide heating to my underfloor heating in the house.

As I write (a nice sunny Sunday at 13h) the water temperature in the floor is 32C and the exit temperature of the panels is 54C. I have a coil heat exchanger in a 100L water tank to transfer heat.

I have now obtained a 4th panel that I will add to the system.

The question is; do I connect the 4th panel in series with the 3 existing panels or do I split the panels into 2 banks of 2 panels.

Any thoughts? Is one configuration better than the other?

Daox 11-02-20 07:57 AM

Why put them in series at all? Lower panel and water temperatures generally mean higher efficiency.

Acuario 11-03-20 01:08 AM

I'm currently getting around 7C increase per panel. I can't increase the flow through the panels and the HX is quite small bore so there is a limit to what I can pass through it.

My thoughts are:
  • Add an extra panel in series so exit temperature is higher but flow rate is the same - would I get to 60C +?
  • Put 2 sets of 2 panels - flow rate through each panel is slower so exit temperature is higher - would I get 11C per panel increase?

Ultimately I will have a delta T of panel exit temperature - tank temperature, tank temperature is normally around 30C so the panel temperature is the important one.

Maybe, as the flow rate isn't going to change, it's pretty much the same one way or another.

Daox 11-03-20 09:38 AM

I imagine it won't matter a ton either way. I'd probably put them in whatever way is easier to mount.

jeff5may 11-05-20 06:43 PM

Since your hx and the flow through it is your limiting factor, put the panels all in series and force the highest dT across the hx. Make sure it is running counter flow as well to get the highest leaving water temperature. As long as there's no boiling risk in your panel loop, that is.

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