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From: cu-arpa.dietz@Cornell.ARPA
Newsgroups: net.space
Subject: Up on the farm
Message-ID: <1077@sri-arpa.UUCP>
Date: Tue, 22-May-84 12:28:00 EDT
Article-I.D.: sri-arpa.1077
Posted: Tue May 22 12:28:00 1984
Date-Received: Sat, 26-May-84 12:00:49 EDT
Lines: 21

Photosynthesis is very inefficient in converting light to
usable chemical energy (efficiency ~ 1%).  One problem is the
thermal nature of sunlight.  Much of the energy arrives at wavelengths
where chlorophyll absorbs inefficiently.

The massive part of a space farm is likely to be the pressure vessel
and soil in which the plants are grown -- reflectors for sunlight have
low mass.  Too much sunlight focused on the plants causes heat
dissipation problems.  One can differentially reflect different
wavelengths of sunlight with plastic diffraction grating mirrors.
Focusing only those wavelengths where chlorophyll absorbs efficiently
could greatly increase crop yields,  without too much waste heat frying
the plants.  Ultimately, one would want to breed plants of algae to
efficiently absrob light in a narrow frequency range, then illuminate
with a laser beam of that frequency.  If the laser was chosen to
radiate at a frequency where the human body was fairly transparent,
perhaps the algae could be encouraged to grow in the human body,
eliminating the need for breathing.

So: how efficient is chlorophyll at various wavelengths?  Has anyone
ever tried growing algae by laser light?