alt.energy.renewable

nicksanspam@ece.villanova.edu wrote:
>
> Morris Dovey wrote:
>
> >... overcast doesn't prevent a good panel from producing real heat.
>
> Au contraire. This is simple physics. On a cold enough day, the glazing
> loss can cool 70 F room air more than an overcast sun can warm it. For
> instance, in 10% sun (25 Btu/h-ft^2), a collector with R2 glazing with
> 80% solar transmission (eg twinwall polycarbonate) will lose heat if
> (70-T)1ft^2/R2 > 0.8x25, ie T < 30 F.

The day I burned myself with my water-heating panel, it was about
52F outside but I had no insolation measurements.

Instrumentation is in the works to track performance of the
current (and future) panel designs, and I'm really looking
foreward to seeing how well actual performance matches calculated
values.

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/