growing crops under artificial lighting

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.

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.

But suspicions aren't worth much; I really need some numbers. And here
my ignorance is getting in the way, and I'd like to correct that.
Can anyone point me to sources of data on absorption spectra for
important crop species, etc.?

I've started googling but have turned up surprisingly little so far.
(E.g., I know the difference between chlorophyll A and B, but I have no
info on what the relative balance between them is for any relevant
plant.)

Thanks,
- Joe

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| Joseph J. Strout Check out the Mac Web Directory: |
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`------------------------------------------------------------------'

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.

"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.

"Mike Rhino" wrote in message ...
"Ian Stirling" wrote in message
...
Joe Strout wrote:
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.

I don't think this is true unless you are in an extremely high orbit.
In LEO orbits, like the space station's, satellites go through a
sunrise and sunset about every 90 min. That seriously cuts the amount
of actual light you're getting. Of course as you go higher up, you're
getting less and less earth shaded night--but from about 250-1500 nm
you're in the thick of the Van Allen belts. Any plant growing station
is going to need significant rad protection in htis area.
Anyway the best place to do this would be GEO or lunar L-1, as you're
well above most Van Allen radiation and rarely blocked by the earth.

There are a couple of caveats.
Current crop plants need more than one wavelength to thrive.

Chloraphyll is not the only bit of cell machinery that requires
sunlight to work. Many other proteins are formed with help from the
sun, and not all at even visible wavelengths. This is true of nearly
all species on earth, even humans, as UV helps regulate folic acid and
Vitamin D, and is a cause of the existence of different skin colors.
Of course, the result of a frequency deprivation won't always be
death--but less overall crop health is likely.

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.

Not really. Fibre optics, light pipes, and solar diffusers can be used
quite effectively (and still many times more efficiently than solar
cells/lights). The Artemis Project and the Lunar Reclamation society
have done quite a bit of study and research in these areas, although
their focus is on lunar day/night cycles that require a mix of both
natural and artificial light.

Tom Merkle

In article ,
(Tom Merkle) wrote:

"Mike Rhino" wrote in message
...
"Ian Stirling" wrote in message
...
Joe Strout wrote:
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.

I don't think this is true unless you are in an extremely high orbit.

I'm assuming a high orbit (probably GEO or one of the langrange points).

Anyway the best place to do this would be GEO or lunar L-1, as you're
well above most Van Allen radiation and rarely blocked by the earth.

Right.

,------------------------------------------------------------------.
| Joseph J. Strout Check out the Mac Web Directory: |
| http://www.macwebdir.com |
`------------------------------------------------------------------'

"
Chloraphyll is not the only bit of cell machinery that requires
sunlight to work. Many other proteins are formed with help from the
sun, and not all at even visible wavelengths. This is true of nearly
all species on earth, even humans, as UV helps regulate folic acid and
Vitamin D, and is a cause of the existence of different skin colors.
Of course, the result of a frequency deprivation won't always be
death--but less overall crop health is likely.

UV destroys folic acid and that is not a good thing.
UV converts cholesterol into vitamin D3 at the skin.
Then it convert by the liver to another form and then
it convert to the active form in kidney. The amount of
the active form is fairly well regulated by internal
biocchemical mechanisms. Blacks likely do better
conserving their folic acid in the sunlight. But in the
higher latitudes get less than optimal levels of vitamin
D and therefore end up having higher cancer rate
especially of the prostate. Whites take less sunlight
to make their vitamin D and so are less prone to
rickets than darker skinned folks. They pay a price
of at times being somewhat depleted of folic acid
by sunlight exposure. I assume white/lighter
skinned folks have a slightly higher rates
of neural tube defects (NTD's) in neonates
and certain cancers



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.

Not really. Fibre optics, light pipes, and solar diffusers can be used
quite effectively (and still many times more efficiently than solar
cells/lights). The Artemis Project and the Lunar Reclamation society
have done quite a bit of study and research in these areas, although
their focus is on lunar day/night cycles that require a mix of both
natural and artificial light.

They might need a fluorescent tube manufacturing facility on the Moon.



Tom Merkle

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

,------------------------------------------------------------------.
| Joseph J. Strout Check out the Mac Web Directory: |
| http://www.macwebdir.com |
`------------------------------------------------------------------'

Joe Strout wrote:
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).
snip
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.

Perhaps.

How much does your garden weigh.
With silver pumps,
And Cabbage Heads,
......

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

Maybe also mass requirements too.
Solar cells can be quite heavy, as can lights, thermal radiators, hydroponic
systems, growing plants, pressure vessels, even atmospheres.

Considering only dried food, you can get down to under around 1Kg/day.

(recycling most water into water and O2, using metabolic water to makeup
losses)

A garden at the very least means that you need (over stuff yuu wouldn't
need) lights (meaning either extra solar panels, or mirrors) extra volume
so a larger pressure vessel, segmented enviromental system (plants and
humans don't want quite the same things), thermal radiators, ...

I don't think it's a clear win until you'r into 5 year missions.

In article ,
Ian Stirling wrote:

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

Maybe also mass requirements too.
Solar cells can be quite heavy, as can lights, thermal radiators, hydroponic
systems, growing plants, pressure vessels, even atmospheres.

True, but most of what's needed to make solar cells can be easily found
on the Moon or NEAs. No need to loft it up from Earth.

A garden at the very least means that you need (over stuff yuu wouldn't
need) lights (meaning either extra solar panels, or mirrors) extra volume
so a larger pressure vessel, segmented enviromental system (plants and
humans don't want quite the same things), thermal radiators, ...

I don't think it's a clear win until you'r into 5 year missions.

Missions?!? Goodness, I'm talking about space colonies here --
permanent habitation. I agree it certainly doesn't make sense for
shorter jaunts.

Cheers,
- Joe

,------------------------------------------------------------------.
| Joseph J. Strout Check out the Mac Web Directory: |
| http://www.macwebdir.com |
`------------------------------------------------------------------'

Joe Strout wrote:
In article ,
Ian Stirling wrote:

rearranged
I'm talking about space colonies here --
permanent habitation. I agree it certainly doesn't make sense for
shorter jaunts.
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


Maybe also mass requirements too.
Solar cells can be quite heavy, as can lights, thermal radiators, hydroponic
systems, growing plants, pressure vessels, even atmospheres.

True, but most of what's needed to make solar cells can be easily found
on the Moon or NEAs. No need to loft it up from Earth.

Depends somewhat on the cost of launch to where you are.
Japan seems to do OK.