[extropy-chat] Greenhouse Power? (was A Grim Vision ...?)
spike66 at comcast.net
Thu Apr 26 05:12:13 UTC 2007
> bounces at lists.extropy.org] On Behalf Of Lee Corbin
> Keith writes
> > Think about how hot it gets inside a parked car in the summer
> > and you will get an idea of how hard it would be to seal up a
> > greenhouse. You could also look up the power bills for cooling
> > Biosphere II.
> Why doesn't this furnish a productive energy source? That is, the
> temperature difference generated between such an enclosure and
> the outside sounds as though it could be useful.
Lee this may have already been answered by others. I am way behind on my
email due to a business trip and vacation.
The reason greenhouse effect doesn't provide an energy source is that the
efficiency of running a heat engine in a greenhouse would be very low. To
estimate a maximum Carnot efficiency using greenhouse effect, take the
difference in temperature inside a typical greenhouse minus the temperature
outside, probably about 10 kelvin, and divide by the temperature outside, at
least high 200s, probably about 300. A Carnot cycle using a greenhouse as a
hot thermal energy reservoir (TER) and the outside as the cold TER could
produce power at around 3% efficiency at best, which is still probably on
the high end. You would do better with even low efficiency solar cells.
Let me know when you have some time, I will bring over to your house my
thermodynamics book and show you the equations.
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