Lighting Technologies For Space Farming

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.

Comments

Light sources and heat sinks.

[Christopher Thomas]

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.

Re:Light sources and heat sinks.

[Yazeran]

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.

Re:Real indoor lighting

[mmontour]

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.