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Solar Barn Version 2

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Posted by Gary on May 21, 2004, 3:21 am
 
Hi,

I reported earlier on the solar heater for my garage/barn when it was
built in February (with quite a bit of help from this group :-).  I have
added a short update based on the past few months of service that
suggest changing a couple things. The changes are listed at:
http://users.montanadsl.net/~reysa/   -- then choose the "Simple Solar
Barn Heater" link -- the update is all the way at the bottom.

I have been thinking about a different version of the
garage/barn/workshop heater that is quite a bit simplier yet, and have
built some test panels that use the new concept. It basically eliminates
the separate absorber, the collector framework, and the vents through
the garage wall.  The new concept is described in way too much detail
at: http://users.montanadsl.net/~reysa/ , then choose "Simpler Yet Solar
Barn Heater" link (its about a 280k pdf).

I would be very interested in any comments on the new concept (or the
old one).

Gary

Posted by Bert Menkveld on May 21, 2004, 3:15 pm
 
Hi Gary,

I have followed your solar space heating experiments with great interest.
It's great to see such simple technology work.

However, I wonder if your latest version isn't a little too simple.  Simply
putting glazing in front of a thin, dark, uninsulated wall obviously does
provide heat gain when the sun is shining, but the losses at other times
seem quite awful.  In terms of heat gain, I guess you've essentially found a
cheaper way of putting in a large area of double-glazed window.

It seems to me that the big advantage of a solar collecor over a window is
that you do NOT get the heat losses when the sun isn't shining.  Maybe this
trade-off makes sense for your barn, but it certainly does not make sense
for any building that's occupied both during the day and the night.

When you start to talk about moving insulation in and out of place behind
the panels, it starts to look simpler to revert to your original design that
leaves the insulation in place.

Still, I don't want to sound negative.  You're actually performing real live
experiments with useful results.  I think that's great, and hope you will
keep us apprised of your work.

Regards,

Bert

--
Bert Menkveld



Posted by nicksanspam on May 21, 2004, 4:31 pm
 Bert Menkveld <bertATreentronicsDOTcom> wrote:


That might be OK (as you say), if the barn is only used during the day.


It seems to me a double-glazed window would have more heat gain
(since the air near the glazing would be closer to 50 than 120 F.)
A single-glazed window (in place of siding) would be a more efficient
solar collector and also provide lots of light. A dark screen north of
the window would cut glare and warm air to heat ceiling mass.
 
I'm not sure max siding temp is a good figure of merit. Cooler solar heaters
are usually more efficient, ie they deliver more Btu/h. Higher radiant temps
are nice, but a human needs to be "fully enclosed" to fully feel their effects.
One warm wall may only contribute 1/6 to the MRT. Maybe it's best to have sun
shining on the human (with sunglasses.)


Insulation is nice, as well as hot thermal mass near the ceiling to store
heat for nights and cloudy days. David Delaney's flow organizer could
simplify the barn heater, with one layer of glazing and one layer of window
screen, some dark barn siding, and insulation behind that. No dampers...


Me too :-)

Nick


Posted by Gary on May 21, 2004, 7:42 pm
 nicksanspam@ece.villanova.edu wrote:

Hi Nick,


I have wondered about just siding the south wall with polycarbonate
glazing panels.  I think it might be kind of noisy in the wind, and
something else would have to provide the shear strength, but?


I had several of these 2ftX4ft test panels (with different types of
siding) all running at the same time (i.e. seeing the same solar input).
  My thought was that the one that produces the highest temperature on
the inside of the siding (the room side) must be transfering the most
heat to the room??  And, therefore was the most efficient?

Typically, the siding with the highest inside the room surface
temperature had the lowest outside surface temperature -- which means
less loss to the outside world?
I can understand Sunmans's facination with the IR surface temperature
measuring devices -- they are a wonder :-)


I have not actually (as yet) insulated the collector wall on the
existing collector.  It seemed like it might be almost a neutral thing
in that you get some gain through the wall during the day, but loose
some at night.  The night loss is not as much as for the Version 2
collector, since there are mulitiple layers of material to add to the R
value.

Sounds interesting -- is David's "flow organizer" work available?


Thanks -- Gary

Posted by Nick Pine on May 21, 2004, 9:35 pm
 

You might screw them into horizontal purlins. I'd use the 4' width
greenhouse roofing materials.


I guppose that's true for an opaque surface, but a transparent surface
would be more efficient.


Sure...


They used to cost about $0K. IIRC, Radio Shack's latest version is $5.


Sure. He's posted here, and has elaborate drawings on his web site.

Nick


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