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re: solar closet details...
16 aug 2000
news  wrote re
solar closets at http://www.ece.vill.edu/~nick:

>> then again, you could design a closet to operate without a fan.
>> it would be thermally less-efficient that way, and may need 
>> larger air passages, but solar heat is free, and some extra glazing
>> might be cheaper or quieter or more reliable than a fan, and the
>> "waste heat" usually ends up in sunspace air, which ends up heating
>> the house.
 
>nick, this waste heat that eventually gets into the house.  what if it is
>unwanted heat, as in summer?

not good... i'd close the dampers between the house and the sunspace
in summertime (they are also closed at night in wintertime) and cover
the sunspace glazing with greenhouse shadecloth (or overhangs, grapes,
runner beans, trumpet vines, etc.) and open vents to the outdoors at
the top and bottom. this leaves the solar closet in shade. its thermal
mass might still be useful for capturing nighttime coolth.

>...the problem then is that all that heat you could have had to heat
>hot water is not being used.  your web site shows that the dhw can be
>heated via finned tube - although this would have a slow response time
>and can only be regarded as "assisting" heating hot water.

there's a response time calc in the paper. we can have 100% dhw with
enough fin tube and water tank volume, but there's that summertime
problem, and a large sun angle difference (wintertime heat is better
captured with vertical surfaces), and making hot water with the closet
requires a lot more closet glazing and closet thermal mass surface.
a concentrating solar trough attic with a steep south roof and a
parabolic reflective north roof seems like a better alternative
for year-round water heating.
 
>i like the concept of the solar closet, which i would call a "remote
>passive system" - not sure of the true technical term...

the phrase "indirect gain" would apply. it's really two systems,
a sunspace with no memory that supplies all the heat the house needs
over an average day with an average amount of sun, and a closet with 
lots of memory and a low heat transfer rate that only supplies heat
on cloudy days.

>when is there to be a full size house version?

dunno. we gave that paper at the world renewable energy congress in
denver in 1996, and since then i've helped a few dozen people through
some initial designs, but i don't think anyone's followed through yet.

>...i was looking in the archives of geenbuilding and an engineer
>commented on your design in complimentary terms. he had checked
>all the figures and claimed it would work in a full sized house.

one un-obvious requirement is lots of thermal mass and thermal mass
surface inside the house to help it store overnight heat from the warm
sunspace air, eg a couple of concrete block walls to keep the day-night
room temperature swing below say, 10 f on an average day, with no help
from the closet. 

>let's see the full sized house then with operational data.

ok. let me know when you are finished! :-) 

nick




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