Thread: Plants in space
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Old August 28 2013, 03:47 PM   #5
gturner
Admiral
 
Location: Kentucky
Re: Plants in space

I don't have my calculations handy at the moment, but solar cells and LEDs aren't all that far from surpassing direct sunlight for photosynthesis. Plants mainly use a thin band of red and a little blue. Since so little of yellow, green, deep blue, and UV are useful to plants, using a solar cell to gather all the sunlight and then drive narrow band red and blue LEDs can up the overall efficiency of agriculture per square meter of collection area - once the LED's are a bit more efficient than present. As I recall off the top of my head, you're looking for about 30% efficiency when you multiply the solar cell and LED efficiencies for the break-over point. For space applications, once you factor in all the losses in a purely optical solution (windows, mirrors, etc), the breakover should happen a bit sooner.

From a design standpoint, this is a very good thing, because we need our plant habitats to have some artificial gravity, which of course means spinning. If you're trying to illuminate them with just windows and mirrors, this usually means they'll be spread out over a large surface area, which isn't a particularly efficient structure. It can also create very complicated topologies between the large, outboard collection mirrors and the required windows and light tubes to get the sunlight inside the station and shining on the plants.

With solar cells, you just put them in space without spinning and snake the power wires into your grow rooms, which can have plants stacked on racks, densely packed for maximum volumetric efficiency.

As for which plats to grow, grow just about everything you like to eat.
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