5 ms·

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 no

by 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
    Thanks, this look interesting.
- kw71 10y ago
  I think the most remarkable part of my basement garden was that I did not put all that much effort into it. I got a Lithonia "high bay" 400 HPS fixture, reasoning that the reflector on a lamp made to be mounted high would focus the light in a smaller area. I just put a cord on it and hung it from a chain. Except for the lamp, it is just like growing plants in pots outside, except there are 90% less insects and no hungry critters to snack on your crops. I did some experiments with adjusting the lamp timer and long days didn't keep my beans from producing. Some plants want "seasons" but mine didn't seem to mind. Now I have a wife, and a basement again, and we are both interested in starting a small "farm." LEDs are viable now and I want to look into this.
lightedman 10y ago
"Plenty of this light was in the green area so not absorbed by plants." This isn't true. The majority of light from an HPS light is green, yet huge crops are grown using that light all the time. Plants utilize almost every visible wavelength (and some invisible wavelengths) to some extent. LEDs generally just focus on the wavelengths that have been determined to be efficiently utilized. It is all however still 100% crop-dependent. Some plants simply hate LED lighting because of the missing spectrum (like my orchids.)
- kw71 10y ago
  Thank you for your insight. I thought that whatever makes chlorophyll green, filters the green light rendering it extraneous.
  - lightedman 10y ago
    Gotta remember photon physics - a photon gets absorbed and then another photon is re-emitted at a lower wavelength. That is just the nature of thermodynamics, second law specifically.

by kw71 10y ago

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
  Thanks, this look interesting.
kw71 10y ago
I think the most remarkable part of my basement garden was that I did not put all that much effort into it. I got a Lithonia "high bay" 400 HPS fixture, reasoning that the reflector on a lamp made to be mounted high would focus the light in a smaller area. I just put a cord on it and hung it from a chain. Except for the lamp, it is just like growing plants in pots outside, except there are 90% less insects and no hungry critters to snack on your crops. I did some experiments with adjusting the lamp timer and long days didn't keep my beans from producing. Some plants want "seasons" but mine didn't seem to mind. Now I have a wife, and a basement again, and we are both interested in starting a small "farm." LEDs are viable now and I want to look into this.

lightedman 10y ago

"Plenty of this light was in the green area so not absorbed by plants." This isn't true. The majority of light from an HPS light is green, yet huge crops are grown using that light all the time. Plants utilize almost every visible wavelength (and some invisible wavelengths) to some extent. LEDs generally just focus on the wavelengths that have been determined to be efficiently utilized. It is all however still 100% crop-dependent. Some plants simply hate LED lighting because of the missing spectrum (like my orchids.)

kw71 10y ago
Thank you for your insight. I thought that whatever makes chlorophyll green, filters the green light rendering it extraneous.
- lightedman 10y ago
  Gotta remember photon physics - a photon gets absorbed and then another photon is re-emitted at a lower wavelength. That is just the nature of thermodynamics, second law specifically.