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Active Solar Collector to Radiator?

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Posted by mbaguide2000-buy on December 9, 2007, 5:56 pm
We are wondering about the possibility of connecting an active solar
collector (panel with a pump to circulate the water) to a radiator
inside the house, strictly as a supplemental system to collect what
heat might be available when the sun shines on the collector.

We figure that any heat we get will reduce the need to burn propane to
make heat.

We are in a heavily shaded area and we do not get sunshine on the
walls of the house during the winter, so we can't do a trombe wall,
but we do get some sun up t the level of the roof, and a collector
there is a possibility.


Posted by Robert Scott on December 9, 2007, 7:14 pm
On Sun, 9 Dec 2007 09:56:12 -0800 (PST), mbaguide2000-buy@yahoo.com wrote:

The problem is that most radiators ("steam" type) are designed to use high-grade
heat (near 212 deg. F).  Flat panel solar collectors work best when supplying
low-grade heat (90-120 deg. F).  If you circulate that lukewarm water from the
collector through your radiator, it will transfer very little of its heat to the
room.  To do any good at all you would need a radiator with maybe ten times as
much surface area to effeciently transfer heat.

You could try to raise the temperature of the water from the solar collector,
but that will require things like multi-layer glazing or focusing techniques.  I
think increasing the surface area of your delivery system inside the house is
more cost-effective.  Or forget about using water and switch to an air type
system, if you can run some ductwork.  The collector will cost less and compared
to using a radiator, efficiency will be much higher.

Robert Scott
Ypsilanti, Michigan

Posted by J. Clarke on December 9, 2007, 8:34 pm
 Robert Scott wrote:

It depends on what he means by "radiator".  If he's talking about the
things designed for baseboard hot water hydronic systems they should
work fine at around 120F.

to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)

Posted by nicksanspam on December 9, 2007, 10:13 pm

With 1 gpm of average 200 F water and 65 F air, Argus fin-tubes make
690 Btu/h-ft with a 690/(200-65) = 5.1 Btu/h-F-ft conductance... 2 gpm
at 120 F only makes 690*2^0.04*(9.6865E-04*(120-65)^1.4172) = 201 Btu/h-ft,
ie 201/(120-65) = 3.7 Btu/h-F-ft, ie a 201/690 = 0.29 output fraction.


Posted by J. Clarke on December 9, 2007, 10:45 pm
 nicksanspam@ece.villanova.edu wrote:

And so the world comes to an end.  .29 output fraction is just a
number.  Doesn't mean that the system doesn't work it just means that
you size it accordingly.

to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)

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