In article ,
Ian Stirling wrote:

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...

True, I was oversimplifying. Still, my basic point is that with
gas-discharge and solid-state lighting, we have great control over the
spectrum of the light we generate. We can generate light which is more
or less perfectly tuned to what our crops need. Compare this with
sunlight, which is about half unusable (most of it is infrared, which
plants simply don't use).

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.

Yes, I know, I'm not saying that artificial lighting is better than
natural lighting when natural lighting is available. My point is that,
when natural lighting is not available or practical for whatever reason,
you don't give up on the whole idea and conclude that crops can only be
grown on Mars or some such. Instead, you put in artificial lights, and
this is a perfectly reasonable thing to do.

Basically I'm trying to debunk claims I hear bandied about, from Zubrin
and others, that growing crops under artificial light is thoroughly
impractical due to energy requirements. I believe that's a
politically-motivated load of crap, and I'd like to demonstrate that.

Cheers,
- Joe

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