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re: is solar viable for our new house?
16 feb 2001
pete prossen wrote:
>well, nick you got me there. i wouldn't quarrel with diffie and beckman.
hey, this is the internet. no need to actually read their book :-)
>i guess the engineers at neg were worried about this phenomenon too. that's
>probably why they used spectral selective glass and something exotic on the
>collector plate to make the emissivity only 0.12 while the absorbtion ratio
>is 0.91.
hard to get solar heat in through the walls of a thermos bottle, but an
inner selective surface sounds good. jim crater's owens illinois tubes
must have one too, since they can reach 1100 f inside with no coolant.
does neg mention the numerical emissivity or solar transmittance of this
"spectral selective glass" (low-e hardcoat?)
>...this is probably why they state the collector full of water will not
>freeze for a couple of weeks at 20 degrees f. i believe they mean 2 weeks
>of no sun, since they conducted the test in a freezer.
the freezer sounds like "no sun." it takes about 144x8x5 = 5760 btu to
freeze 5 gallons of water solid. with a 1' cube with 6 ft^2 of surface,
we need 2 weeks x 7 days x 24 hours x (32f-20f)6ft^2/rv, so rv 4.2, like
a cooler with 1" white beadboard walls.
nick
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