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The energy problem is mentioned almost in passing, but it could be a deal breaker for this type of farming. Ventilation, heating and delivering light for photos

The energy problem is mentioned almost in passing, but it could be a deal breaker for this type of farming. Ventilation, heating and delivering light for photosynthesis require vast amounts of electrical energy, which, according to the article, comes mainly from diesel. Averaged over a day, the sun provides > 12kWh per m^2 in farmable regions (estimated). It takes 70 days to grow cabbage, so for 1m^2 of cabbage that would amount to 168$ at 20cents/kWh.

patall 10y ago
It is expensive of course, else they would have been doing it for a long time. But 12kWh/m^2 is for direct sunlight which cabbage etc. probably do not need, as they will have had some thoughts into that, also other hydroponic farms like in Singapore have the same problem. Also the light is tinted more violet and thus more efficiently usable for the plants. And I would not count with 20ct/kWh, as they probably pay industrial rates (though I have no idea how much that is over there).
- donquichotte 10y ago
  You're right, industrial rates in Anchorage are around 11ct/kWh. Also, it's possible to use LEDs tuned to the absorbtion spectra of chlorophyll, as you say. If my back of the envelope calculations above are wrong by more than an order of magnitude, it might in fact be a commercially viable option for farming. Is this [1] the Singaporean project you were refering to? They probably don't need heating, but nonetheless their quoted energy needs of 3$/month/structure are astonishingly low. [1] http://permaculturenews.org/2014/07/25/vertical-farming-singapores-solution-feed-local-urban-population/ http://permaculturenews.org/2014/07/25/vertical-farming-sing...
- kw71 10y ago
  A 400W arc lamp plus losses (possibly bringing the total to 600W) was enough to grow 3x3ft. of plants in soil. Plenty of this light was in the green area so not absorbed by plants. I have never seen lima bean plants grow so big or be so productive (4th harvest of the year in december.) I don't want to plant anything outside anymore after this.
  - drieddust 10y ago
    Do you have a blog post or some pictures to share? I am trying to experiment with this on a small scale, but don't really know how small I can start.
    - keenerd 10y ago
      "Space buckets" are probably the smallest scale you can easily do. With the red/blue grow LEDs you can get more usable light from a solar panel than straight sunlight can provide. I've been looking for a change from outdoor gardening and a high density 1 m^2 indoor plot with 100W red/blue LED + 100W panel + automatic watering system sounds like a fun combination. Plus I can finally try growing tropical fruit and vegetables.
      - mmastrac 10y ago
        > With the red/blue grow LEDs you can get more usable light from a solar panel than straight sunlight can provide This is interesting - do you have more information on it?
        keenerd 10y ago
        I guess I messed up the math the first time around because I'm getting something different this time. * 45% of sunlight is in the photosynthetically active wavelength range * Solar cells are 20% efficient * Red LEDs are 39% efficient and blue LEDs are 35% efficient So no, I was kind of off base there. Straight sunlight is still 6x more energy for plants. But it is close! 40% efficient panels exist and my LEDs efficiency numbers were from 2012 so the gap might be smaller. If you do this calculation yourself, remember to ignore lumens. They are a human perceptual unit and are completely meaningless for plants. Now for human-visible light it is a little different. With the most efficient solar cells and white LEDs we can do better than the sun. (Straight sunlight is 93 lumens per watt. A 40% solar cell and 250 lumen/watt LED outperforms the sun.) Maybe this is what I was thinking of.
      - drieddust 10y ago
tom_mellior 10y ago
> The energy problem is mentioned almost in passing, but it could be a deal breaker for this type of farming. Indeed. Some harsh places do have lots of essentially free energy, though: 100% of Iceland's electricity comes from a combination of geothermal and hydropower; 99% of Norway's from hydro (source: Wikipedia). I've been wondering for a while if they could use that for this kind of agriculture. Looks like it might work.
- sdx23 10y ago
  It does. Look Hveragerði: http://www.waymarking.com/waymarks/WMPE5W_Tomato_Greenhouses_Hveragerdi_Iceland http://www.waymarking.com/waymarks/WMPE5W_Tomato_Greenhouses...
- ogrisel 10y ago
  More than electricity, heating can be very cheap when your farm is on top of an active volcano. In Iceland many greenhouses can grow tomatoes and bananas because they have direct access to hot water from the ground bellow.
SixSigma 10y ago
Doing it in a living space would make more sense. You already have to heat the place
lightedman 10y ago
"Ventilation, heating and delivering light for photosynthesis require vast amounts of electrical energy, which, according to the article, comes mainly from diesel." They must have forgotten about thermodynamics. Even with LED lighting, there's still a fair amount of generated heat to deal with. Also, with LED lighting, you reduce the amount of light actually required for growth as you focus on the more actively-utilized wavelengths of light. As long as they use the diesel for controlling atmospherics, the rest of the place could easily be done on solar + sufficient battery bank. Arctic and Antarctic insolation is actually much higher than a good portion of the globe. [1] [1]: https://en.wikipedia.org/wiki/Climate_of_the_Arctic#Solar_radiation https://en.wikipedia.org/wiki/Climate_of_the_Arctic#Solar_ra...

patall 10y ago

It is expensive of course, else they would have been doing it for a long time. But 12kWh/m^2 is for direct sunlight which cabbage etc. probably do not need, as they will have had some thoughts into that, also other hydroponic farms like in Singapore have the same problem. Also the light is tinted more violet and thus more efficiently usable for the plants. And I would not count with 20ct/kWh, as they probably pay industrial rates (though I have no idea how much that is over there).

donquichotte 10y ago
You're right, industrial rates in Anchorage are around 11ct/kWh. Also, it's possible to use LEDs tuned to the absorbtion spectra of chlorophyll, as you say. If my back of the envelope calculations above are wrong by more than an order of magnitude, it might in fact be a commercially viable option for farming. Is this [1] the Singaporean project you were refering to? They probably don't need heating, but nonetheless their quoted energy needs of 3$/month/structure are astonishingly low. [1] http://permaculturenews.org/2014/07/25/vertical-farming-singapores-solution-feed-local-urban-population/ http://permaculturenews.org/2014/07/25/vertical-farming-sing...
kw71 10y ago
A 400W arc lamp plus losses (possibly bringing the total to 600W) was enough to grow 3x3ft. of plants in soil. Plenty of this light was in the green area so not absorbed by plants. I have never seen lima bean plants grow so big or be so productive (4th harvest of the year in december.) I don't want to plant anything outside anymore after this.
- drieddust 10y ago
  Do you have a blog post or some pictures to share? I am trying to experiment with this on a small scale, but don't really know how small I can start.
  - keenerd 10y ago
    "Space buckets" are probably the smallest scale you can easily do. With the red/blue grow LEDs you can get more usable light from a solar panel than straight sunlight can provide. I've been looking for a change from outdoor gardening and a high density 1 m^2 indoor plot with 100W red/blue LED + 100W panel + automatic watering system sounds like a fun combination. Plus I can finally try growing tropical fruit and vegetables.
    - mmastrac 10y ago
      > With the red/blue grow LEDs you can get more usable light from a solar panel than straight sunlight can provide This is interesting - do you have more information on it?
      - keenerd 10y ago
        I guess I messed up the math the first time around because I'm getting something different this time. * 45% of sunlight is in the photosynthetically active wavelength range * Solar cells are 20% efficient * Red LEDs are 39% efficient and blue LEDs are 35% efficient So no, I was kind of off base there. Straight sunlight is still 6x more energy for plants. But it is close! 40% efficient panels exist and my LEDs efficiency numbers were from 2012 so the gap might be smaller. If you do this calculation yourself, remember to ignore lumens. They are a human perceptual unit and are completely meaningless for plants. Now for human-visible light it is a little different. With the most efficient solar cells and white LEDs we can do better than the sun. (Straight sunlight is 93 lumens per watt. A 40% solar cell and 250 lumen/watt LED outperforms the sun.) Maybe this is what I was thinking of.
    - drieddust 10y ago

tom_mellior 10y ago

> The energy problem is mentioned almost in passing, but it could be a deal breaker for this type of farming. Indeed. Some harsh places do have lots of essentially free energy, though: 100% of Iceland's electricity comes from a combination of geothermal and hydropower; 99% of Norway's from hydro (source: Wikipedia). I've been wondering for a while if they could use that for this kind of agriculture. Looks like it might work.

sdx23 10y ago
It does. Look Hveragerði: http://www.waymarking.com/waymarks/WMPE5W_Tomato_Greenhouses_Hveragerdi_Iceland http://www.waymarking.com/waymarks/WMPE5W_Tomato_Greenhouses...
ogrisel 10y ago
More than electricity, heating can be very cheap when your farm is on top of an active volcano. In Iceland many greenhouses can grow tomatoes and bananas because they have direct access to hot water from the ground bellow.

SixSigma 10y ago

Doing it in a living space would make more sense. You already have to heat the place

lightedman 10y ago

"Ventilation, heating and delivering light for photosynthesis require vast amounts of electrical energy, which, according to the article, comes mainly from diesel." They must have forgotten about thermodynamics. Even with LED lighting, there's still a fair amount of generated heat to deal with. Also, with LED lighting, you reduce the amount of light actually required for growth as you focus on the more actively-utilized wavelengths of light. As long as they use the diesel for controlling atmospherics, the rest of the place could easily be done on solar + sufficient battery bank. Arctic and Antarctic insolation is actually much higher than a good portion of the globe. [1] [1]: https://en.wikipedia.org/wiki/Climate_of_the_Arctic#Solar_radiation https://en.wikipedia.org/wiki/Climate_of_the_Arctic#Solar_ra...