[VAC] Re: Solar Heat?

["Dr. Gerald N. Johnson, electrical engineer" <geraldj@xxxxxxxx>]

A solar heater depending on heat siphoning will work, but not very well.
The air temperature has to rise too high to get an efficient air flow,
so the collecting surface is too hot and looses the majority of its heat
by radiation. The performance of such a collector is improved immensely
by adding a mechanical fan to speed up the air flow which improves the
heat transfer to the moving air and makes the collecting surface run
cooler and thus to loose less heat by radiation.

In my last active solar experiments, I found that Krylon ultra flat
black paint gave me a greater temperature rise than any other paint
including a special solar collector coating I bought from Edmund
Scientific for 5 or 6 times the price.

After a few years of experiment, I concluded that the same effort
applied to house insulation and gap filling would have saved more fuel
and provided greater comfort without the eyesore of the solar collector
(and mine was 8' x 24', it provided about 100,000 BTU per sunny day
before its frame rotted. It used a furnace blower to move air through
it).

Gerald J.