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Re: Deployable Doubt Dispellers - Page 4

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Posted by 3D Peruna on February 28, 2006, 3:30 pm


Do you have URLs, references, books?  Anything else?



Posted by Solar Flare on February 28, 2006, 10:49 pm
...and needs an expensive heat exchange system so it's occupants don't
die in their sleep, like many have, from CO poisoning.



Posted by Goedjn on February 27, 2006, 3:45 pm

There's one On Hayes Park Road in Barrington, RI.
Currently on sale for about $00,000 on account of
the owners decided to give up their jobs and become
starving artists.

Posted by nicksanspam on February 25, 2006, 11:27 pm

It's easy to see that won't work near Phila: if the thermal conductance
of 3 sides and the top is 4x4ft^2/R7.2 + 4ft^2/R28.8 = 1.8 Btu/h-F and
it's 80 F on a 30 F January day, it needs a 2'x2' window with (say) 50%
solar transmission, where 0.5x1000x4 = 2K Btu = 24h(80-30)G, so G = 1.7,
so the window's R-value is 4ft^2/(1.7-1.8) = minus 40 :-) R1 glazing with
90% transmission would make 0.9x1000x4 = 24h(T-30)(1.8+4), so T = 56 F...

That's a popular misunderstanding spread by the Sustainable Building
Industry Council's Guidelines for Passive Solar House Design (with USDOE
support and 239 customized regional editions) and the books by Mazria,
Chiras, and Kachadorian, among others. But PE Norman Saunders has been
engineering houses that are very close to 100% solar-heated in cold cloudy
New England since 1946. Some have long track records with digital data
loggers. Norman's writings are hard to read. His "Solar Basics" (6th edition,
1974) is inscrutable. A lot is handwritten, with illegible differential
equations. He says people will likely find his Notes for Professionals
Developing Solar Designs "remote and incomprehensible" :-)

Nonsense. With enough insulation, you don't even need the sun.

The math can be interesting. For instance, the smallest indirect gain D-cube
might be L' on a side with fL feet of R40 per inch vacuum aerogel insulation
around a (1-f)L water cube, with G = 6L^2/(480fL) Btu/h-F and C = 62((1-f)L)^3
Btu/F and RC = C/G = 538 hours = 4987(1-f)^3L^2, ie (1-f)^3fL^2 = 0.108. If
d(RC)/df = 0, 3(1-f)^2(-1)f+(1-f)^3 = 0, so -3f + 1-f = 0, ie f = 1/4, ie no
matter what the cube size or what kind of insulation or mass we use, making
the cube wall thickness 1/4 of the cube edge length maximizes RC. With f=1/4,
(1-1/4)^3(1/4)L^2 = 0.105L^2 = 0.108 makes L = 1.01 feet.

Sure. It works everywhere, altho some climates are easier.

I'd prefer something that unbolts and stacks in the back of a pickup truck,
with on-site water for thermal mass. A "house" would be nice, but that's not
a pure play. Lots of people know how to make beautiful houses. Let's make
heatflow concepts perfectly clear and invite those people to make larger
more comfortable and more attractive structures while preserving the high
solar heat fraction. Given conventional wisdom and many low-solar-fraction
houses (ie "engineering failures" :-), the first step seems to be reproving
that high solar fractions can be achieved at all :-)

It's like an existance proof in mathematics or physics or chemistry.
Once you prove that something can exist, people start looking for it.
f they believe it cannot exist, they don't look for it.

I'd like people to see that they can be warm even after a cloudy week.


Posted by RicodJour on February 26, 2006, 5:19 pm
 nicksanspam@ece.villanova.edu wrote:

A pure play?  That comment alone indicates that you're not in touch
with what drives innovation and markets.

To paraphrase that: To prove that you can heat a house with solar,
build a solar heated house.

If you want to play with truncated demonstrations, get little Timmy to
do his 7th grade science project on your scaled back experiment.


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