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Increase in collector temps due to snow relection?

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Posted by schooner on December 10, 2005, 4:30 pm
 
Just wondering if anyone has noticed any increase in their air collector
temps due to sun reflection from snow.  Does this have any impact on the
collector or is the reflected sun of no advantage?



Posted by daestrom on December 10, 2005, 7:49 pm
 


It's a very real thing.  In some areas that get a lot of snow, you can get
more energy if you mount the collecter vertical on a south wall than if you
mount it at latitude minus 23 degrees.  The loss in direct radiation because
non perpendicular angle can be made up for in the gain in ground reflected
radiation.

The only 'hitch' is you need a nice open area to the south from the
collector that is covered with snow.

http://rredc.nrel.gov/solar/pubs/bluebook/appendix.html
Under 'Global solar radiation', the radiation reflected from the ground is
discussed.  They suggest that an albedo of 0.2 is typical for green
vegetation.  I think snow can be as high as 0.9.

daestrom



Posted by SolarFlare on December 10, 2005, 8:16 pm
 This is a thermal group. I doubt there would be much
"thermal" radiation off snow. PV?...definitely.

message

in their air collector

have any impact on the

of snow, you can get

south wall than if you

direct radiation because

gain in ground reflected

south from the

http://rredc.nrel.gov/solar/pubs/bluebook/appendix.html

reflected from the ground is

typical for green


Posted by daestrom on December 10, 2005, 9:53 pm
 

Or you might want to read the whole manual
http://rredc.nrel.gov/solar/pubs/bluebook/bluebook_index.html

The albedo correction is used to correct the total solar radiation received
(btu/ft^2) for windows to determine heat gain from solar radiation.

daestrom



Posted by Robert Scott on December 10, 2005, 9:56 pm
 On Sat, 10 Dec 2005 15:16:00 -0500, "SolarFlare"


Why would you think that?  The snow is not heating up and
re-radiating, if that what you're thinking.  The snow is acting like a
mirror, passively reflecting the energy together with all its
potential for thermal use.  A mirror does not need to get hot to be
effective in a concentrating solar collector.  The only disadvantage
of snow reflection is that it reflects in all directions.  So to be
effective in enhancing a solar collector, you need to have snow spread
out over a wide area, as viewed from the collector.


-Robert Scott
 Ypsilanti, Michigan

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