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re: solar heat project ineffective.
14 dec 2005
yourname wrote:
>>>>>where i live near phila, 40 ft^2 of r2 south windows with 80% solar
>>>>>trasmission might admit 32k btu and lose 6h(70-30)40ft^2/r2 = 4.8k on
>>>>>an average 30 f january day, for a net gain of 27.2k btu, enough to keep
>>>>>336 ft^2 with 1000 ft^2 of exterior walls and ceiling 70 f for 24
>>>>>hours if 27.2k = 24h(70-30)1000/rv with rv = 35 walls and ceiling, given
>>>>>night insulation for the window/collectors and enough thermal mass.
>>>>
>>>in the north east, clear day radiation is worth ~64 btu per square foot
>>>of south facing glass.
>>
>> what does that mean??? nrel says 1880 btu/ft^2 falls on a south wall on
>> an clear january day in phila.
>
>i am not arguing with you, just the numbers from the book 'from the
>ground up' from some years ago.
nice book. i can't find my copy, altho i've still got some copies of "from
the walls in," having given away lots of them. if that's an accurage quote,
what did charlie wing mean by "64 btu per square foot"? full sun (am2) is
about 250 btu/h-ft^2. i've heard wing's books and lectures and tv show and
cornerstones school did such a good job teaching people how to save energy
that exxon bought him out after a couple of years, and now he spends most
of his time sailing around the world on his large yacht :-)
>also fits my seat of the pants for my barn built then. 50 sq ft of south
>facing glass did not come close to what 200 gallons of heating oil did
>in a season.
where i live near phila, each $1 square foot of polycarbonate solar siding
might collect the heat equivalent of 1 gallon of oil per year...
mon temp sun gain loss net
oct 56.4 1150 1035 142 893 temp is the 24 hour vs daytime average.
nov 46.4 990 891 202 689 sun is average btu/ft^2-day on a south wall
dec 35.8 900 810 265 545 gain is 0.9xsun
jan 30.4 1000 900 298 602 loss is 6h(80-temp)1ft^2/r1
feb 33.0 1080 972 282 690 net is gain - loss
mar 42.4 1070 963 226 737
apr 52.4 950 855 166 689
----
4224 btu/day x 30 days = 126720 btu/year.
>>>now, figure my well insulated 1000sq ft great room runs 40000 btus on
>>>a cold night, you do the math.
>>
>> btdt. the ops room was 336 ft^2. i assumed 1000 ft^2 of exterior surface.
>
>again, i am not arguing with you, merely stating what my room needs, and
>how unreasonable it is you expect that amount of heat from a small window.
it would be unreasonable to expect that.
nick
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