Re: New high end Solar Cell claims 42.8 % efficiency

On Fri, 27 Jul 2007 19:12:56 -0400, John Popelish <jpopelish@xxxxxxxx>
wrote:

Jon Slaughter wrote:

So what are the long term effects? If ~50%? of the solar energy that
normally be reflected back out into space is used to create electricity
which ultimately will end up as heat, doesn't this mean that global warming
will become a reality very quickly?
(snip)

So called global warming is caused by changes in the
composition of the atmosphere that slow the escape or
infrared radiation into space. Right now, 100% of the
radiation that reaches the surface is either bounced back as
visible or raises the temperature of the surface. that
energy must convect away, or radiate away as long wave IR
radiation. Swapping the natural surface for solar cells
bounces little back as visible radiation, because the cells
are generally pretty dark.

But about half of the radiation that penetrates their
surfaces is converted to electrical energy and half raises
the temperature of the cells, just like what happens to
dirt. The 50% converted to electricity actually lowers the
temperature rise of the cells, but that doesn't lower the
total IR radiation, because it is just transported elsewhere
and radiated away, there.

The net effect with or without solar cells is a wash, except
that people get to run appliances off the energy before it
leaves into space. If instead, those appliances are run off
fossil fuel, their heat is added to what the dirt in
sunlight produces, except that the burnt fuel gets added to
the atmosphere, getting in the way of the natural and waste
heat escaping into space. Either way, solar energy
overwhelms any addition from fuel consumption, as far as the
amount of heat to be radiated. The big difference is in the
composition of the atmosphere that heat has to pass through,
to escape.

For the last few decades, we have been pumping several
million barrels of oil out of the Earth, every day, and
setting fire to it. That is a lot of carbon added to the
atmosphere, and carbon dioxide in the atmosphere in the form
of carbon dioxide, is very absorbent in the long wave IR
part of the spectrum, where all that natural and wast heat
is being radiated. As the CO2 builds up it raises the
temperature of the atmosphere which raises the equilibrium
water vapor content in the atmosphere. Water vapor is
another IR absorbing gas, positive feedback takes over at
some point and the system swings rapidly to a very much
hotter equilibrium temperature, world wide. That is the so
called global warming process (originally called global
thermal run away, before the oil companies renamed it), in a
nut shell.

If water-vapor positive feedback were sufficient for the loop to run
away, it would have run away anyhow, CO2 or not. The water vapor loop
must be net *negative* feedback, probably because of clouds.

CO2 absorption is so small that the only way the GW enthusiasts can
get worked up is to apply a *lot* of conjectured "helper" positive
feedback mechanisms. And clearly (clearly to me, anyhow) if those
mechanisms existed 1000 years ago, they would have snapped then.

Earth is currently something like 20 degrees C below the temperature
of an equivalent spherical black body.

I read that, on average, water vapor absorbs as much reflected IR in
the first 30 feet as does all the CO2 from the ground to space.

John

.

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