Simple Pressurized Storage questions

[Nofossil]

I've had an enormous amount of PM traffic with several people related to the Simple Pressurized Storage' sticky, perhaps because you can't reply to it. I've realized that some of these discussions might benefit others, and in any event might save me some typing ;-)

With that in mind, SteveJ has agreed to let me post the content of a PM discussion. Here goes:

nofossil,

For some reason, I cannot post a reply to your “Simplest Pressurized Storage Solution” thread.
Maybe that is why there is only one comment?

Questions about the thread:

1. Do you see anyway to incorporate a closed active solar system (flat plate or evac tubes) into the system?

2. If you had it to do all over, would you go with pressurized storage instead of unpressurized?

Thanks,
Steve

 

[Nofossil]

You can’t post to it because Craig closed it. He’s thinking of it as a read-only document, not a discussion. New threads that reference it would be fine. Would it be OK if a started a thread with this content? Don’t have to use your name....

Any solar system could be integrated. I didn’t discuss it, but I think my preferred approach for solar would be to build a largish sidearm heat exchanger and rely on thermosiphoning to transport heat from the exchanger into the storage. This could be a vertical piece of 4” PVC with several parallel copper pipes inside. The copper pipes would be connected to the top and bottom of the storage, and the inside of the PVC would be conencted to the solar system with heated water coming in the top and cooled water exiting the bottom. Hope that’s clear - I’ll have to draw it up some day. You could also use such a system for DHW preheat, or you could use a flat plate HX with additional small circulator for either or both. Finally, some folks have paid to have a larger flange welded to their tank allowing heat exchangers to be inserted into the tank itself.

If I had it to do over, I’d design my attached garage to have space for two 500 gallon propane tanks used as pressurized storage. Too late for that by about 20 years.......

 

[Nofossil]

Your side arm description is very clear - maybe a drawing for the thread would be nice.

What about a largish (> 200 sq ft) flat plat collector array - would you suggest scaling the side arm accordingly?

You can always add another garage - right?

Thanks,
Steve

 

[Nofossil]

I don't have any performance data on convection sidearm heat exchangers. Typically, flow rates from solar panels are very low, so the dwell time for hot water inside a piece of 4" PVC would be fairly long. A more sophisticated (and complicated) solution would be a flat plate HX with a small circulator that was controlled by looking at the difference between HX temperature and tank top temperature.

I think additional garages are our of the question - low WAF.

 

[Willman]

with a small circulator

Nofossil
I have been looking at small circs for flat plate and haven't had any luck finding any high head units. I want to mount my array on the roof which is approx. 20ish feet from basement. Any recommendations. or where to look ?

Will

 

[Nofossil]

with a small circulator

Nofossil
I have been looking at small circs for flat plate and haven't had any luck finding any high head units. I want to mount my array on the roof which is approx. 20ish feet from basement. Any recommendations. or where to look ?

Will

As long as the loop is pressurized and you have an air vent at the top, you don't need a high-head circulator. The water coming down balances the water coming up. You just need to make sure that there's positive pressure at the top - figure 1/2 psi per foot of height plus a safety margin of 5 or 10 psi. If the roof is 20 feet above the basement, then you'd want the loop pressurized to 15 or 20 psi measured in the basement.

Laing among others makes circulators in the under 2gpm range.

 

[Willman]

Thanks. Will check out the Laing.

Will