Re:Arctic farming: Town defies icy conditions with hydroponics
by keenerd on Monday November 07, 2016 @03:08PM
(#12894547)
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.
* 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.