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a solar shed for a youth hostel
18 aug 1996
youth hostels now have educational goals, ie "programming," including posters
and demonstrations. a nearby hostel has a "sustainable living" theme, and
its keepers beverly and arnold would like to redo a 10x12' shed on a concrete
pad in the backyard into a 100% solar-heated structure, a room for two people
to stay in, with no other means of heat. this could be a way for some people
to try out a sunspace/solar closet house, and say to themselves "hey, it's
warm in here and cold outside, and there's been no sun for a week, and this
is a simple system!" (with one voice :-) and a place to put our lambert data
logger and modem this winter. the shed has electricity now, and there's a
pnone line nearby. 

the hostel runs on a shoestring, with some 600 yearly visitors, even though
they can put up 24 people. (how many hotels charge $12/night and have a 7%
occupancy rate? :-) they would like to be able to house a classroom or
schoolbus full of people, now that they are in the education business.

right now the shed is just 2x4 studs with clapboard on the sides, on a
concrete pad, with slightly rotting sills, and 2 2x6' single pane skylights
and 2 6'x6' single pane windows recently installed by young architect eric.
the south side is a blank 12' wall, facing a state park road. 

    main building     |                                ^
 ---------------------                               s |
                                     |                    |
         view from above             |        pond        | 16'
                                     |                    | 
                                     |                    |
                                          |   sunspace    | 4'
                           solar closet-->| dd|     .     |
                                          | dd| sky . sky | 10' 
                                          | dd|     .     |
                                           --- -----------
                                            4'      12'

                                         campfire/picnic area

                -----     (gable roof)              .
                -----                     .....           .
             . |     |                    | dd|  window/  | 8' window
     pond   .ss| sc  |                    | dd|    door   |
  ---------------------------       --------------------------------

        view from the east                view from the north

the sunspace might look like this from the east, larger:

    sun                 |                 10'                   |
                        |                                       |
                      .  ---------------------------------------
                    .   |  data logger                          |
                        |                                       |
                  .     |                                       |
                        |  drum  drum  drum  drum      sauna?   | ~8'
                 .      |                                       |
                        |                                       |
                        |                                       |
     pond       .  4'   |  drum  drum  drum  drum               |

the sunspace might be $1/ft^2 0.020" very clear flat replex (800) 726-5151
polycarbonate plastic from a 49" wide x 50' roll, with a 10 year guarantee,
attached to curved beams on 4' centers, made from 2 8' 1x3s screwed to some
spacers between them. it might have a railroad tie "foundation" spiked to
the ground with 4' of rebar, and a layer of dark green shadecloth hooked to
the inside of the 1x3s in winter, and hanging over the outside in summer. 

some tyvek on the inside of the shed might stop the wind from blowing through
the clapboards (long-haired hostel friend george, from west virginia, who
added the skylights and reshingled the roof, recently treated the outside of
the clapboards with his secret formula of old crankcase oil and kerosene.)
insulating it and adding on a 4' wide x 8' tall x 8' deep solar closet,
perhaps with no inner glazing, might allow the the shallow sunspace, eg some
"solar siding" or a plastic film lean-to greenhouse, about 8' tall x 16' long,
to gather about 118k btu/day of sun. an epdm-rubber-lined 16' wide x 20' long
x 1' deep pond along the south wall might increase this to 157k btu/day when
it's frozen, making a skating rink, reducing lawn mowing, and keeping weeds
and lawnmowers away from the glazing. with a sunspace glazing loss of 6 hr
x (80-36)6x16/r1 = 34k btu, it might gain 123k btu/day (36 kwh/day, like
$50k worth of pvs :-), net. 

if the insulation inside were us r20 (5 1/2" of compressed fiberglass, with
some horizontal 1x3s over that, and a vapor barrier and drywall, (visiting
green german architect claudia suggests a straw/clay mixture instead), and we
could somehow board up all those architecturally-interesting windows and
skylights with r10 shutters on december nights, the shed would have a total
thermal conductance of about 96 ft^2/r10 = 9.6 btu/hr-f for the glazing and
another 584 ft^2/r20 = 29.2 for the walls and roof, ie 38.8 btu/hr-f, so
it would need 24(68-36)38.8 = 30 k btu to stay warm inside on an average
36 f phila december day, with no sun, and over 5 days it would need 150k btu.
if the solar closet had 16 55 gallon drums in it, the water would need to
lose 150k/16x500 = 19 f to provide that heat, so it might have a steady-state
temperature of 100 f, after a long string of average december days, with some
sun, if an 80 f solar closet could keep the room at 68 f. the room needs
1250 btu/hr on an average day, and c cfm of airflow 12 f warmer than the
house would move about 12c btu/hr, ie c = 104. 

maybe this could this work by natural convection. an h foot chimney with warm
air inside and vent areas a ft^2 at top and bottom has an airflow of about
16.6 a x sqrt(h dt), ie 163 a = 104, so a = 1.6 ft^2. we might want a small
low-power fan that seldom turns on, as well as a motorized damper, eg a
1' x 2' piece of foil-faced foamboard attached to a $50 honeywell ml6161a1001
direct-coupled damper motor about the size of a cigarette pack with a 24 vac
motor the size of a ping-pong ball that uses 2 watts when it is moving and
0 watts when it is not.

if 157k btu flowed into the sunspace on an average december day, and 30k of
that heated the house (altho the south wall will be warm), 127k might flow
out of the 128 ft^2 of sunspace glazing, so 1000 btu = 6 hours x (t-36)/r1,
and the average sunspace temperature might be 36 + 1000/6 = 203 f. probably
not, but it looks like the sunspace-house heating airpath can definitely work
by natural convection, and maybe the sunspace-solar closet airpath (although
a pv-powered fan would be useful). we might need to leave some of the shed
windows open during the day...

the ases solar house tour is october 18 :-)

anyone else want to help with this project? 

I got ALL of these 85 Solar Panels for FREE and so can you.  Its in our Ebook

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