a solar drum shack SOLAR.KnowledgePublications.com

a solar drum shack
22 jan 2002
recall d. c. beard's old book called "shelters, shanties and shacks"
written for boy scouts around 1910? it has lots of drawings for simple
inexpensive structures made with branches, twine, pine boughs, and so on.
it might be rewritten to use modern "found materials" like wood pallets
and packing peanuts and old engine blocks and plastic film :-) 

one drawing shows a frontier "railroad shack," a shoebox with walls made
from empty wooden (nail?) barrels, stacked vertically. we might make a
structure like that with water-filled plastic drums, large enough to
stand up in, and dismantleable...

it might have 8'x12' of clear space inside, 9' tall, surrounded by 24
vertical drums, with another 48 stacked up on them. the outside walls
might be 2"x4"x48" welded wire fencing attached to 4'x8' frames with
perimeter 2x4s. the ceiling panels might use 2x6s. these might support
p pounds per square foot of snow, with a total load w = 32p pounds per
4x8' panel and bending moment m = wl/8 = 32p8'x12"/8 = 384p in-lb and
modulus s = m/f = 384p/1000 in^4 (using wood with a 1000 psi max fiber
stress in bending), so s = 0.384p = bd^2/6 = 3(5.5^2)/6 and p = 39 psf.
the ceiling panels might have another 2x4 screwed flat underneath...

add an airtight vapor barrier, with more plastic film on the ground
under old carpeting. then 2' of insulation. strawbales, mulch, leaves,
packing peanuts in plastic bags, or dry horse manure and bedding, say r48.
the south side could have a 2' deep x 20' long x 12' tall plastic film
(or polycarbonate) sunspace, like this, in courier font: 

 -----------------------------------------          ---
|             insulation       f|    |    |             <- f are plastic
|     --------------------------|    | s  |   ---            film dampers
|    |    |                |    |    | u  |
|  i |    |  <--drums-->   |    | i  | n  |
|  n | -- |                | -- | n  | s  |         12'
|  s |    |                |    | s  | p  |   9'
|  u |    |                |    | u  | a  |
|  l | -- |                | -- | l  | c  |
|    |    |                |    |    | e  |
|    |    |                |    |    |f   |             <-
-------------------------------------------------------

| 2' | 2' |       8'       | 2' | 2' | 2' |  
 
|                18'                      |

 -----------------------------------------          ---
|             insulation             |    |   
|     --------------------------     |    |  
|    |           drums          |    | s  |
|    |     ----------------     |    |    |
|  i |    |                |    | i  | u  |                pond?
|  n |    |                |    | n  |    |
|  s |    |                |    | s  | n  |
|  u |  d |      view      | d  | u  |    |
|  l |  r |                | r  | l  | s  |
|  a |  u |      from      | u  | a  |    |         20'
|  t |  m |                | m  | t  | p  |
|  i |  s |      above     | s  | i  |    |
|  o |    |                |    | o  | a  |
|  n |    |                |    | n  |    |
|    |    |                |    |    | c  |
|    |    |                |    |    |    |
|    |     ----------------     |    | e  |
|    |           drums          |    |    |
|     --------------------------     |    |  
|             insulation             |    |   
 -----------------------------------------          ---

the flat roof could be a single 20'x22' piece of epdm rubber.

on an average 25.7 f december day in cloudy hornell, ny, between buffalo
and elmira, it would collect 0.9x600x12x20 = 129.6k btu (or 30% more with
a frozen reflecting pool) and lose 6h(t-25.7f)12x20/r1+18h(t-25.7)9x20/r48
+24h(t-25.7)16x20/r48[for the ceiling]+24h(t-25.7)((16+20+16)9)/r48[walls]
= 1902(t-25.7), so t = 25.7+129.6k/1902 = 93.8 f :-) 

with the sunspace closed off, g = (16x20+2(16+20)9)/r48 = 20.2 btu/h-f
and c = 72x450 = 32.4k btu/f, so rc = c/g = 1607 hours, or 67 days :-)
if the drums begin a cloudy 25.7 f week at 75 f, after 7 days, they might
cool to 25.7+(75-25.7)exp(-7/67) = 70.1...

nick