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Passive Solar Panel Design - Food for Thought

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Posted by Morris Dovey on November 14, 2006, 10:02 am
 
At: http://www.iedu.com/DeSoto/SC_Types.html

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



Posted by Gary on November 14, 2006, 4:53 pm
 
Morris Dovey wrote:

Hi Morris,

Interesting ideas.

"Type 1 Panels

The Type 1 panel has a bottom intake and a top discharge, with a straight path
connecting the openings. The trap/exchanger occupies most of this pathway. The
simplicity of construction and minimum material content makes the Type 1 panel
the most popular choice for amateur builders. The advantage of Type 1 panels is
that it is designed to heat the coolest air (near the floor). Its disadvantages
are it insulates only as well as its glazing; and that, without some mechanism
to prevent airflow during periods of darkness, it can operate in reverse. The
most frequently used mechanism used to prevent airflow closes the top opening,
which still allows cooled air to spill out the intake opening - better than
nothing at all; but definitely not the best solution."



I think that another advantage of this one is that it has the shortest and least
obstructed air path through the collector.  It seems that this is a key
advantage when you only have buoyancy forces moving the air.
You can add a poly film back flow damper on the bottom vent, its just a bit more
awkward to build than the top vent ones -- for that matter, you could put them
on both upper and lower vents.
You could also add insulation to the back wall.

One disadvantage (to me) is that the when you discharge the hot air at the
ceiling, it tends to stratify the air in the room.  This could be good if you
placed thermal mass just under the ceiling, but if you want the heat quickly
distributed tot he room, some kind of fan (like a ceiling fan) to keep the room
air mixed up is needed.

Overall, I think this design has a lot going for -- I'd have to see test data on
the other two to be convinced that they perform as well.


My 2 cents :)

Small test on David Delaney's flow organizer collector:
http://www.builditsolar.com/Experimental/FlowOrganizer/FlowOrg.htm


Gary




--


Gary

www.BuildItSolar.com
gary@BuildItSolar.com
"Build It Yourself" Solar Projects









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Posted by Morris Dovey on November 15, 2006, 1:22 pm
 Gary (in 1163523289_6361@sp6iad.superfeed.net) said:

| One disadvantage (to me) is that the when you discharge the hot air
| at the ceiling, it tends to stratify the air in the room.  This
| could be good if you placed thermal mass just under the ceiling,
| but if you want the heat quickly distributed tot he room, some kind
| of fan (like a ceiling fan) to keep the room air mixed up is needed.

Agreed. In a reasonably "snug" structure, locating the collector
intake as close to the floor as possible does seem to help reduce the
difference between the air temperatures at ceiling and floor. Ceiling
fans seem to be almost always helpful, regardless of heat source.

| Overall, I think this design has a lot going for -- I'd have to see
| test data on the other two to be convinced that they perform as
| well.

All three have a lot going for 'em - and each type offers its own set
of advantages and disadvantages. There doesn't appear to be any single
best solution for all applications; and AFAICT most choices involve
identifying and locating the balance points so that trade-offs can be
made intelligently.

I've built and tested the three types shown on the web page - using
(in each instance) a limited assortment of glazing materials and
methods, a limited number of trap/exchanger strategies and materials,
a limited set of construction materials and dimensions, and a limited
set of plenum designs (round vs square corners, etc). I found more
significant variables than I'd expected and there are more
permutations than I think I'd care to build, measure, and tabulate.

As a commercial producer, it'd probably be foolish of me to publish
anything that'd provide a significant assist to competitors; but I
think I can safely provide some measure of assistance to the broader
community - but probably never as much as you might like. :-)

I think I understand why you particularly like the Type 1 panel - and
I recognize that it has a lot to do with context. IMO within that
context the Type 1 is not a bad choice.

Anyway, it seemed worthwhile to provide a bit of "food for thought" to
the wider community (beyond DIYers and cost minimizers) to stimulate a
bit more thought about when and how different panel configurations
might be appropriate - since it's difficult to make trade-off
decisions without some awareness that there /are/ choices.

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



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