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re: dfw tx builder sought
19 may 2001
rex burkheimer wrote:
>i am contemplating building a home in the greater fort worth texas area.
that's an easy climate for solar house heating... 43.4 f in january, with
1260 btu/ft^2 of sun that falls on a south wall on an average day, and 910
on a horizontal surface... 600 btu/ft^2 falls on a west wall, with 560 on
an east wall and 250 on the north. nrel says an ew tracker can collect
3.2 kwh per m^2 per day (1014 btu/ft^2) in january. a fixed solar trough
might do as well.
an 48' square 2 story r25 6" sip house with 8% of the floorspace as r4
windows and 0.5 air changes per hour would have a thermal conductance of
2304ft^2/r25 = 92 for the ceiling plus 368ft^2/r4 = 92 for the windows
plus 2704ft^2/r25 = 108 for the walls. with a volume of 36864 f^3, 0.5
ach means 307 cfm of air leakage which adds about 307 to the conductance
for a total of 600, so the house would need about 24h(65-43.4)600 = 311k
btu of heat on an average january day. electrical energy use of 600 kwh/mo
could supply 68k of that, and 184 ft^2 of south windows with 50% solar
transmission would add 116k... 184 ft^2 of east and west windows would
add another 53k, leaving 311k-68k-116k-53k = 74k btu/day from some other
(solar :-) source.
>would like a specialist in passive solar, active solar, perhaps with
>geothermal cooling in the summer.
july's 24 hour average temp is 85.3 f, with an average daily min of 74.1
and humidity ratio w = 0.0149, which corresponds to a dew point of about
68.5. a "geothermal cooling" heat pump might have a cop of 3, ie it might
need 1 btu of electricity to move 3 btu of heat, vs an evaporative system
with a cop of 100 or 1000...
>interested in non-traditional styling etc.
you might build a parabolic reflective solar trough into an attic or shed.
heat water in wintertime and dessicate licl in the summer... a square foot
of 4:1 reflector aperture might collect 0.8x1014 = 811 btu/day in 180 f
water in january and lose about 6h(180-43.4)0.25ft^2/r1 = 205 btu, for a
net gain of 606. you might have 74k/606 = 122 ft^2 of aperture, eg an 8'
deep x 8' tall x 16' long reflector...
nick
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