Unquestionably Confused wrote:
| Morris Dovey wrote:

|| My current aim is to lower that 140F to 120F for a 6'-tall panel
|| without major cost increase. The Madison County installation won't
|| quite make it but I'm getting closer with every design iteration.
|| Interestingly, I'm not sure that achieving that goal will
|| necessarily produce a more efficient /system/.
|
| How about a hybrid system? Would not adding, say, a low-cost
| (operation) axial/muffin fan with a rheostat allow you to tweak the
| internal temperature?
|
| In your scheme of things that'd be cheating, I know, but... I'm
| just thinking aloud here. Even from a testing/design aspect you'd
| at least be able to see if the 120F would be more efficient, no?

I don't consider fans cheating - but insist that they not actually
/impede/ operation of the panel.

At this point, the best of the axial/muffin fans (I have a small
collection of not-so-cheap fans of a variety of types brought in by
well-meaning friends) and all except the very largest (1/2 HP and up)
act more as obstructions than enhancements to the airflow - even when
running full-bore.

Although it's not an issue involving "cheating", I really do prefer
the absolutely silent operation of the purely convectional operation.

I can boost the natural convection (lower temperature) by
"streamlining" the interior plenums - rounding all the interior angles
in the plenums, providing still smoother internal surfaces, etc. - but
from where the design is today, all of these represent significant
increases in labor and/or material costs.

The system question is: "What is the optimal discharge temperature
that provides a comfortable environment for humans yet allows maximum
_coincidental_ heat storage in a typical installation?"

The question contains a hidden twist in that excess heat can be
discarded without impacting operational costs in any way - with an
additional consideration that the discard mechanism can be used to
control humidity.

It's the "typical installation" that's the unknown here. I don't need
fans - what I really need is a variety of solar-heatable /structures/
to test. :-)

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/