Light pipes?

wowbagger

Tue Dec 02 14:12:31 -0800 2008

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Using artificial light seems to me to be a less-than-desirable way to go - couldn't you use light pipes of some form to bring sunlight into the system?

(a light pipe doesn't necessarily imply fibers - it could be anything from fibers to a shiny metal plenum - obviously fibers have a problem passing UV).

Light pipes?

zuzulo

Tue Dec 02 14:38:21 -0800 2008

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Well, one aspect of artificial lighting is that you can control the intensity and duration far more than is feasible with natural light. Also, the newer LED based full spectrum lights are actually quite cheap to operate, and in conjunction with a nice solar system can allow a 24x7 growing cycle with a similar amount of incident light.

Being able to separate the growing environment from the requirement for direct or indirect sunlight is quite an advantage.

Some sample consumption figures from the Omega site show that energy consumption with LEDs is not too bad - 171 KWH over 2 week operation:

CFL = compact flourescent

CFL (6 Kilowatts per Hour (KWH))
2 week total: 1646.4 KWH to produce 2160 units of Lettuce
Per Lettuce Unit = 0.76 KWH

LED (0.48 Kilowatt)
2 week total: 171 KWH to produce 2160 units of Lettuce
Per Lettuce Unit = 0.079 KWH

might be possible

zogger

Tue Dec 02 15:05:27 -0800 2008

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It seems OK if you can get cheap enough downtown/metro rents (cheap as in "dirt" cheap) and have enough for the initial upfront costs and have a ready and steady market. You have to move a lot of lettuce to pay thousands a month rent in some warehouse, plus your other expenses, like you might need heat,a lot of salad crops don't do well below 70 and below 50 they just stop, most crops anyway. Like at 50 tomatoes won't die..but they'll just sit there, do nothing. We have a lot of greens including lettuce outside now, but even here where it isn't that cold they aren't doing much, but the stuff in the greenhouse is doing a lot better, just that 20-30 degree difference is enough. So that's a cost you'll have to figure on, heating a big part of the year. As to why it isn't being done more..just isn't, same as why aren't the big car companies putting out better mileage and electric cars yet? The answer is more short term profits the other way. When gas was cheap, people wanted huge and powerful, not small and not so powerful. Cost of transport has not be a significant issue with bulk food until this past summer, another strike against local metro grown. I worked in a metro greenhouse/indoor electric lights operation, but they did rental ornamental and tropical plants, that pays well if you have a market. If they were doing food (and I built their greenhouse for them and did a lot of the indoor work with the halide lamps, etc), I don't think they could make anything at all.

might be possible

President4242

Tue Dec 02 15:13:38 -0800 2008

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An interesting thought based on this:

Why not a rooftop vertical farm for a supermarket?  You could even channel the refrigeration for the freezer & produce sections to heat the greenhouse levels, and shipping could be as cheap as dropping the harvest down a chute into the produce section. 

might be possible

zuzulo

Tue Dec 02 16:15:17 -0800 2008

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I was thinking more about crops like saffron and whatnot that have high market values. It is also interesting to note that organic 'essential oils' are extremely expensive even at wholesale prices.

Also there are really good LED based lighting systems currently in use in traditional hydroponics and greenhouses that are wavelength specific, so the idea of using solar panels to absorb all light then reemit at appropriate wavelengths is a good one.

in that case, yes

zogger

Tue Dec 02 17:40:12 -0800 2008

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If you have the market. I met one guy was doing a jamup business supplying fancy restaurants with fresh culinary crops/herbs/specialty items. He is/was a high end chef himself, with a country place, so he just drove into work with his surplus and sold it to more or less his competition, but he didn't care, he was booked solid all the time mostly catering, whereas his cooking herbs clientele worked for sit down restaurants, so they didn't compete as much. His contacts were just as important as his crop, and his crop was neat, you'd walk around his farm and he just had patches of this or that all over, it didn't even look like a farm unless you could identify the species readily, because they were in clearings on the edges of normal pasture (that got hayed, but no cows, he just sold the hay). Large scale edible landscaping. We've sold some like that but not much, just some surplus perennials we have, like once you have rosemary, you get a LOT of rosemary, etc. Yes, much better price per ounce instead of bulk cheap per lb.

Sun -> PV -> LED -> Food?

wowbagger

Tue Dec 02 15:05:42 -0800 2008

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If what you are suggesting it taking sunlight, driving a PV array, then an LED array, then the plants, it still seems to me a bit inefficient at this time. Perhaps when we get better efficiencies on PV arrays it would be better - perhaps even better than natural light (see below).

Now, if you are saying LED in addition to sunlight, then I can agree.

I'd also ask the question "Do you need 'full spectrum' LEDs?" Plants don't really do anything with green but reflect it, so I could see an illumination system that didn't put out green actually being more energy efficient than full spectrum LEDs. Given a high enough efficiency for the PV array, it might even be better than direct sunlight (let the panel soak up everything, including the wavelengths the plants don't use, then re-emit that as just the wavelengths they DO use.)

Sun -> PV -> LED -> Food?

Charles E Hill

Tue Dec 02 15:57:12 -0800 2008

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Something like these.  An additional benefit -- to my untrained eye -- would be the reduced heat generated by the LEDs, thus the reduced cooling needs.

Light pipes?

John Dalton

Tue Dec 02 21:03:13 -0800 2008

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At what point does solar energy flux become the limiting factor and not land area?  Going vertical without artificial lighting doesn't increase the amount of energy available for plants to grow.

Do plants use all incident wavelengths?  If not, would it be more efficient to illuminate them with narrowband sources?

Light pipes?

John Dalton

Tue Dec 02 21:10:04 -0800 2008

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To clarify my question and pose a few more: Obviously they are wavelength selective since they are green, but does that mean the growing mechanism is also wavelength selective?

This graph indicates that there are a number of peaks in the response of photosynthsis. Are LEDs available at these wavelengths? Surely someone has already done such experiments?

Light pipes?

anotherchance

Wed Dec 03 08:45:41 -0800 2008

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if we ens up with some kind of carbon trading sceme then this will likely do way better then the food system we have now.  farming is subsidized at an incredible $$$ amount, so it may look like its more at the start, but we are all realizing that the money really isnt worth anything, and what would you pay for food when its in short supply??? whatever it takes cause you cant eat money.

this is just a handful of hydroponics manufactures making this stuff for the medical crop wink wink so when and if it starts to hit for food growing then the scale will have a major effect on the pricing.

and this takes all the guess work out of farming, you will know how much of each you are able to produce at a fixed input rate.  this is the kind of thing that you can turn into a new trading medium, a currency backed by food insted of the current one which is......nothing