"Nick Pine" wrote in message
...
People still doubt that houses can be close to 100% solar heated outside
of
the Southwest, inexpensively. Here's another 8' D-cube that might be
deployed
to regional Infestations of Doubt, with 2" double-foil polyisocyanurate
walls
and ceiling and an 8'x8' layer of Thermaglas Plus twinwall polycarbonate
over
the south wall and 0.44 inches of water under the ceiling and 6.86" of
water
in a 6'x6' EPDM-rubber-lined cloudy day heat storage tank under the floor.

On an average day, thermosyphoning sunspace air would heat the ceiling
mass
to about 160 F, and it would cool to about 80 by dawn. A room temp
thermostat
with a 2-watt damper motor would rotate foil foamboard louvers below the
mass
to keep the room 70 F by radiation. On a cloudy day, a low-power pump
would
move hot water up from the floor tank through the ceiling.

20 TA=30'outdoor temp (F)
30 TI=70'indoor temp (F)
40 SS=1000'south sun (Btu/ft^2-day)
50 TAU=.8'south glazing solar transmission
60 UVG=.58'south glazing U-value
70 SUN=64*TAU*SS'sun in (Btu/day)
80 RVW=15.5'wall R-value
90 RVS=RVW+1/UVG'south wall R-value
100 HC=(TI-TA)*64*(1/RVS+3/RVW)'required ceiling heat (Btu/h)
110 GC=4*1.714E-09*(TI+5+460)^3'min ceiling rad conductance (Btu/h-F-ft^2)
120 TMIN=TI+HC/GC/64'min ceiling temp (F)
130 SWNL=18*(TI-TA)*64/RVS'south wall night loss (Btu)
140 OWL=24*(TI-TA)*3*64/RVW'other wall loss (Btu/day)
150 RC=15.5'ceiling R-value
160 NETSUN=SUN-SWNL-OWL+6*TA*64*UVG-(TMIN/2-TA)*64/RC'net sun (Btu/day)

Nick, I believe the last term in line 160 above should be,
"...-24*(TMIN/2-TA)*64/RC". If the RC is in the usual units of 'R-value'
(it seems so, considering its usage in line 220), then what you have in the
term above is only BTU/hr versus BTU/day in all the other terms. But this
only lowers performance slightly (TS comes out to 155.5F instead of 158.9F)

You don't seem to account for any heat to 'charge' the under-floor tank.
With it in/under the floor, you would have to run the pump on sunny days to
'charge' it, as well as on cloudy days to 'discharge' it. If it takes five
days to 'charge' it for five cloudy days, wouldn't that about double the
heat load on the sun space? Is the ratio of sunny/cloudy days in
Philadelphia about 50/50?

Heat losses through the floor? Granted, the ground is warmer, it isn't 70F.

Anyway, all well and good if you want to live in an 8' cube with no windows
or doors. A pair of St. Bernards' doghouse?? What about a 'practical'
house, say a very modest 1200 sq ft single story with only a few windows,
say 48 ft^2 of double glazed (that's about one double-hung window in each
wall). And a paltry 2 air-changes per day.

Would such a 'practical' house still perform in the 'regional infestations
of doubt'?? What you've posted here has very little to do with heating what
most people would call "a house". (even a dog house has a door)


daestrom