"Ian Stirling" wrote in message
...
Joe Strout wrote:
I'm getting tired of the widely-repeated claim that it is impractical to
grow crops under artificial light (particularly if your power source is
solar). It just doesn't make sense, for two reasons. First, if your
solar power plant is in orbit where it receives sunlight 24/7, you've
already got about seven times as much sunlight to start with as a field
on Earth. Second, though there are losses in converting the sunlight to
electricity and back to light, you can make the light you convert it to
be 100% pure clorophyll-absorbed prime wavelength, whereas the light
that falls on Earth is mostly wavelengths that plants can't use anyway.

There are a couple of caveats.
Current crop plants need more than one wavelength to thrive.
If you just feed them one then the plants do not perform as well as they
might as they use the spectrum of light to deduce the crowding of the
plant,
as obviously the solar spectrum can't change...


Put those factors together, and I suspect that a km^2 of solar cells (or
similar solar power collector area) could grow MORE than one km^2 of
crops.

Unless you really have to use solar cells, you probably don't want to.

Unless you need to beam the energy over long distances, the best way
seems to simply be to use mirrors.
The solar collector points at the sun, and bounces the light through
a small window in your rotating greenhouse.
Distribute the light internally.

This beats current solar cells/lights by a factor of several per unit
area.

If you have a multi-layered facility, it might be difficult to bounce light
to all floors.