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Lighting Technologies For Space Farming

Posted by timothy on from the lumens-for-bloomins' dept.

dlkf writes: "Space.com has an excellent article discussing current technologies in light sources for growing plants in space. ".. .the high-tech lighting systems here have been used to grow potatoes, sweet potatoes, lettuce, spinach, radishes, wheat onion and a whole plethora of herbs such as marjoram and parsley." The main problems for the lighting sources were energy usage, lifetime of light source and heat generation. To address these issues researchers are using both LED and microwave technology." The electrical advantages of LED growlamps may soon become manifest here on Earth, too.

15 comments

  1. Don't forget marijuana. by SpanishInquisition · · Score: 0, Funny

    I can't wait for "Cheech & Chong in Space"

    --
    Je t'aime Stéphanie
    1. Re:Don't forget marijuana. by Anonymous Coward · · Score: 1, Interesting
      Only slightly off-topic.


      Marijuana [or hemp] is one of the fastest growing plants, and also one of the hardiest. A Marijuana plantation of a few hundred square meters provides a LOT of oxygen, and the biomass can then be converted back to fuel or fertilizer for the less hardy plants you grow for food. A self-sufficient spaceship has to be the way to go, and this is how to do it. Forget your expensive NASA-developed oxygen supply equipment, and go green!


      "Cheech & Chong in Space" might turn out to be the most appropriate analogy.

  2. Real indoor lighting by Verne · · Score: 2, Interesting

    cool, when this hits production, we can replace all our indoor lights and actually get some skin colouring while being stuck in these cubicles...

    --


    There are only two things in this world that smell like fish. And one of them's fish...
    1. Re:Real indoor lighting by mmontour · · Score: 5, Informative

      Several years ago I worked in a university lab that had a prototype of a 1 kW sulfur microwave lamp. It was very bright, but the light had a distinctive green tint. After a while your eyes would adapt, but then when you looked out the window (or at anything lit with a "conventional" light source) everything looked pink. Maybe the newer models have solved this problem, but if not I wouldn't want it as indoor lighting.

      As for getting your skin colouring, one of the advantages of the sulfur lamp was that it put out much less UV radiation than other light sources. Good for museums where the UV would damage old paintings and documents; bad for getting a tan in your cubicle.

  3. Light sources and heat sinks. by Christopher+Thomas · · Score: 3, Informative

    While I understand the convenience of compact light sources, I'm curious as to why we wouldn't just use mirrors and (on Mars) solar concentrators to light greenhouses. This is much more efficient than converting sunlight to electricity and then back to light again.

    Heat buildup is a problem in the craft itself, but you can just insulate the greenhouse and regulate the amount of light you give it to let it regulate its own temperature by radiation of heat back into space. It's no coincidence that the Earth is a comfortable temperature - At our distance from the sun and with the Earth's albedo (reflectivity), energy input from sunlight and output from radiative emission are exactly matched at Terrestrial temperatures. Rig your mirrors so that you have the same average amount of energy absorbed by the greenhouse plants as by the Earth's surface, and you should be fine for temperature.

    On the other hand, if you have a powerful, compact power source like a fission or fusion plant, you'd want to be able to pack your plants more densely, which means many layers and an artificial light source. However, I doubt we'll be lofting that large an amount of nuclear fuel into space any time soon.

    1. Re:Light sources and heat sinks. by Winged+Cat · · Score: 3, Interesting

      What if you get nuclear (or whatever) energy from resources on-site? Say, a Martian geothermal plant, with the output gasses vented to help build the atmosphere. Or a helium-3 fusion plant, where the helium-3 is mined from the Moon (inefficiency of lifting from Earth aside, there just plain isn't that much helium-3 down here).

      You're right, using sunlight directly makes sense if we are using sunlight to begin with. And that's a good option. But not the only one.

    2. Re:Light sources and heat sinks. by Yazeran · · Score: 4, Informative
      well on the Moon or on Mars you would use sunlight as far as ever possible, as it is cheap and renewable (a term which is as much relevant in space engineering as is is on earth). However, on the Moon (on the surface that is) the 'night' is 2 weeks long! Not that many plants can survive 2 weeks without sunlight.


      On a spaceship or space station other factors have to be considered. In order to use sunlight as light-source, you have to have large windows (if you plan to grow more than a fwe pretty plants that is). Space engineers usually dont like windows for two reasons: One: they are difficult to make so thay are durable and second, they are heavy! The last factor is the most important, as ewry kg of matter sent into space requires at least 100 kg of launch-vechicle (rocket + fuel).


      The last reason for not using sunlight for growing crops in a space station is that spacecraft usually rotate in order to maintain a constant bearing and in order to equalize the heat recieved from the sun. In order to maintain sunshine through the small window you would have to have an elaborate mirror-arrangement outside to direct the sunlight through the window. Such things are expensive to make, and second they also weight something and have to be sent up. Electricity is not so sparce in space, as solar pannels produce electricity. With the new lamps, the power-consumption by the growth lamps is lowered enough, so heat is nolonger a problem.

      All this makes the new lamps worth something.


      Yours Yazeran


      Plan: To go to Mars one day with a hammer.

    3. Re:Light sources and heat sinks. by Christopher+Thomas · · Score: 2

      However, on the Moon (on the surface that is) the 'night' is 2 weeks long! Not that many plants can survive 2 weeks without sunlight.

      Good point.

      The last reason for not using sunlight for growing crops in a space station is that spacecraft usually rotate in order to maintain a constant bearing and in order to equalize the heat recieved from the sun. In order to maintain sunshine through the small window you would have to have an elaborate mirror-arrangement outside to direct the sunlight through the window. Such things are expensive to make, and second they also weight something and have to be sent up. Electricity is not so sparce in space, as solar pannels produce electricity.

      You could reduce the window size needed by using a curved mirror and focusing sunlight through a slit or an aperture. This should still be reasonably cheap, as a mirror doesn't have to be very strong in space.

      Rotation is a trickier problem. If I was designing the station, I'd either make the greenhouse portions not rotate, or I'd put a nonrotating mirror above the axis of the craft and focus light through an aperture on the axis.

      That, or use a nonrotating craft. Attitude control isn't a problem with modern spacecraft guidance systems, and the heating problem is manageable, albeit with a small amount of extra mass.

      Academic, of course, since I'm not in a position to design spacecraft :).

  4. Why not GM plants to grow without light? by Cy+Guy · · Score: 2

    There are some saprophytic, true (ie non-fungal) plants that don't rely on photosynthesis (and therefore light) to grow. It seems that GM technology could be used to modify existing food plants to grow without light, recycling the 'compost' created by the passengers into food. The same could be done with fungi without any GM, but I expect it result in a rather boring (and probably nutritionally poor) diet if this was their only food supply (wasn't there a some SciFi movie where they lived off mushrooms?).

    A drawback is that the other major product of photosynthesis is the breaking down of CO2 to free up oxygen for the crew to breath. But current spacecraft and stations instead rely on CO2 'scrubbers' (ala Apollo 13 & duct tape fame) to do this. So for deep space exploration, where light is either not available, or requires too much energy, I think GM'd saprophytic plants would be a good alternative.

    --
    Work for Change & GET PAID!
    1. Re:Why not GM plants to grow without light? by gorilla · · Score: 2
      A drawback is that the other major product of photosynthesis is the breaking down of CO2 to free up oxygen for the crew to breath. But current spacecraft and stations instead rely on CO2 'scrubbers' (ala Apollo 13 [amazon.com] & duct tape fame) to do this. So for deep space exploration, where light is either not available, or requires too much energy, I think GM'd saprophytic plants would be a good alternative

      Unfortunatly only 2 things wrong with your theory:

      1) Saprophytic plants live by ingesting other organic material. Therefore they must always have a decrease in the net organic mass. Your plan is equivilant to finding that your ship can't carry enough corn, so you decide to bring along some cows to eat the corn, and you'll eat the corn. The cows will grow, but you'll end up with less calories than if you ate the corn yourself.

      2) The reason that they use scrubbers because the trip is either very short, or it's easy to resupply from Earth. For deep space, neither would apply, and it would require huge amounts of supplies to carry enough scrubbers and fresh oxygen to last.

      Thus photosynthesising plants would have a huge advantage for both problems.

  5. Nice, but not required on Mars.... by Fenris2001 · · Score: 2, Interesting

    It's nice to see research in this area go forward, but it's really not needed. A quick look at some numbers tells us why:

    A Martian greenhouse gets only half as much light as one on sunny Earth. Does this mean we get half as much yield per acre? Not quite

    On Earth, carbon dioxide levels are typically well below 1% (usually around 350 parts per million). Raising the level of CO2 in a closed greenhouse is possible, but not economical. On Mars, however, the atmosphere is hardly anything but CO2 - and any greenhouse there must be tightly sealed already, so we can alter the CO2 level without additional construction.

    What this means is that, although plants on Mars would get less light, they would actually produce higher yields per acre than plants on Earth, by virtue of the fact that they are growing in an atmosphere containg about 3% carbon dioxide! Now, this means astronauts would have to wear scuba masks to work in the greenhouse, but not spacesuits, since the greenhouse would be pressurized.

    The point is, we can go to Mars with technology that exists today, right now, with no investment in R&D, and, more importantly, without waiting years for new technology. Yes, we should vigoursly pursue new technologies that lower the cost of space missions, but we don't have to.

    --
    ---------------
    Vpered na Mars!
    1. Re:Nice, but not required on Mars.... by Anonymous Coward · · Score: 0

      The "greenhouse effect" is about raising the temperature using infrared radiation, not raising the amount of visible radiation (used for photosynthesis). The best greenhouse won't help you if you lack visible light for photosynthesis.

  6. Hmmmm..... by Anonymous Coward · · Score: 1, Insightful

    LED...low heat, low power usage, grows plants well....yeah, that could be pretty useful for certain kinds of people....

  7. salad machines by Anonymous Coward · · Score: 0

    I just wonder how long it takes until those "salad machines" appear in Japanese cities.

  8. I hear nichia blue LEDs aren't really efficient. by ahfoo · · Score: 1

    Perhaps I got it wrong, I can't remember the URL, it was one of those Google searches, you can look up LED and check for yourselves if you're interested, but I seem to recall that the blue LEDs are less efficient in terms of lumen output than compact flourescents althoug the latter give off a lot more heat.