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Iirc chlorophyll has 2 very distinct absorption peaks [1] so it should be possible to design lights that target those frequencies. But knowing how LEDs work an

Iirc chlorophyll has 2 very distinct absorption peaks [1] so it should be possible to design lights that target those frequencies. But knowing how LEDs work and the hacks with wavelength adjustment we use with phosphorus and others I’m sure it’s not easy. [1] https://upload.wikimedia.org/wikipedia/commons/f/f6/Chlorophyll_Absorption_Spectrum.svg https://upload.wikimedia.org/wikipedia/commons/f/f6/Chloroph...

tiagod 4y ago
Cree acknowledges this in the link, listing "Reduce complicated spectral analysis" as a feature, implying its just an easier way to achieve what is already done with multiple LEDs working together.
mytailorisrich 4y ago
I mix 6000K/6500K (daylight) LED strips with 2700K (warm white) ones and plants seem very happy about it and it is OK for humans, too. In fact I previously used only 6000K LED strips (in an insulated box so no other light at all) on cycad and other seeds and got very healthy plants. I think the key for commercial applications like vertical farms is to optimise energy use by trying not to waste electricity on wavelengths that won't do much to boost production.
- westurner 4y ago
  UV Ultraviolet light (UV-A, UV-B, and UV-C,) and near-UV "antimicrobial violet light" are sanitizing radiation. Natural sunlight sanitizes because the radiation from the sun includes UV-* band radiation that is sufficient to radiate organic cells at this distance. EM light/radiation intensity decreases as a function of the square of the distance from the light source (though what about superfluidic wave functions and accretion discs and microscopic black hole interiors (every 30km by one estimate) and Lagrangian points,). "Inverse-square law" https://en.wikipedia.org/wiki/Inverse-square_law https://en.wikipedia.org/wiki/Inverse-square_law Ultraviolet: https://en.m.wikipedia.org/wiki/Ultraviolet https://en.m.wikipedia.org/wiki/Ultraviolet > Short-wave ultraviolet light damages DNA and sterilizes surfaces with which it comes into contact. For humans, suntan and sunburn are familiar effects of exposure of the skin to UV light, along with an increased risk of skin cancer. The amount of UV light produced by the Sun means that the Earth would not be able to sustain life on dry land if most of that light were not filtered out by the atmosphere. [2] More energetic, shorter-wavelength "extreme" UV below 121 nm ionizes air so strongly that it is absorbed before it reaches the ground. [3] However, ultraviolet light (specifically, UVB) is also responsible for the formation of vitamin D in most land vertebrates, including humans. [4] The UV spectrum, thus, has effects both beneficial and harmful to life. Ultraviolet > Solar ultraviolet: https://en.wikipedia.org/wiki/Ultraviolet#Solar_ultraviolet https://en.wikipedia.org/wiki/Ultraviolet#Solar_ultraviolet > The atmosphere blocks about 77% of the Sun's UV, when the Sun is highest in the sky (at zenith), with absorption increasing at shorter UV wavelengths. At ground level with the sun at zenith, sunlight is 44% visible light, 3% ultraviolet, and the remainder infrared. [23][24] Of the ultraviolet radiation that reaches the Earth's surface, more than 95% is the longer wavelengths of UVA, with the small remainder UVB. Almost no UVC reaches the Earth's surface. [25] The fraction of UVB which remains in UV radiation after passing through the atmosphere is heavily dependent on cloud cover and atmospheric conditions. On "partly cloudy" days, [...] (Infrared light ~is heat. There's usually plenty of waste heat from mechanical friction, exothermic chemical processes with gravity, lossy AC-DC conversion, and electronic components that waste energy/electron_field_disturbance//thermions/heat like steaming water towers sans superconducting channels wide enough for electrons to not start tunneling out without a ground or a negative) Ultraviolet > Human health-related effects > harmful effects https://en.wikipedia.org/wiki/Ultraviolet#Harmful_effects https://en.wikipedia.org/wiki/Ultraviolet#Harmful_effects UV-A and UV-B protective eyewear (U6 polycarbonate) can be purchased in bulk. https://www.amazon.com/s?k=uvb+ansi+z87+glasses+20+pairs https://www.amazon.com/s?k=uvb+ansi+z87+glasses+20+pairs
kylehotchkiss 4y ago
Does each plant have it's own sweet spot of color balance?
- bavell 4y ago
  Just a layman here but I know plants use color temp as a signaling mechanism (e.g. to help determine time of year - warmer color temp in spring/fall) so I'd expect some variation between species in how that signal is interpreted and used.
  - latchkey 4y ago
    They also take advantage of different spectrum/color temp at different points in their lifecycle too. I was growing pre-led era and I'd swap bulbs for the weed growth phase and then flowering phase.
Centigonal 4y ago
It's really complicated, because plants also use other bands of color for decisionmaking (e.g.: am I being shaded out by another plant? Am I tall enough? What time of year is it? Should I make flowers? etc). Growers and light manufacturers have found that adding some infrared and other frequencies help, even though they don't contribute substantially to energy absorption. Also, there are multiple chlorophyll molecules, with slightly different spectra. Lots of fun stuff in this field.
- eitland 4y ago
  Brings back memories: when I went to farming school around 1998 - 2000 we once visited a local commercial greenhouse and one thing I remember is they told me they used to have chemicals (plant hormones possibly?) that they sprayed on the leaves of flower plants to stop them from stretching and develop a more compact form, but had stopped doing that and now just lowered the temperature in the room a couple of hours before sunrise to get the same effect.

tiagod 4y ago

Cree acknowledges this in the link, listing "Reduce complicated spectral analysis" as a feature, implying its just an easier way to achieve what is already done with multiple LEDs working together.

mytailorisrich 4y ago

I mix 6000K/6500K (daylight) LED strips with 2700K (warm white) ones and plants seem very happy about it and it is OK for humans, too. In fact I previously used only 6000K LED strips (in an insulated box so no other light at all) on cycad and other seeds and got very healthy plants. I think the key for commercial applications like vertical farms is to optimise energy use by trying not to waste electricity on wavelengths that won't do much to boost production.

westurner 4y ago
UV Ultraviolet light (UV-A, UV-B, and UV-C,) and near-UV "antimicrobial violet light" are sanitizing radiation. Natural sunlight sanitizes because the radiation from the sun includes UV-* band radiation that is sufficient to radiate organic cells at this distance. EM light/radiation intensity decreases as a function of the square of the distance from the light source (though what about superfluidic wave functions and accretion discs and microscopic black hole interiors (every 30km by one estimate) and Lagrangian points,). "Inverse-square law" https://en.wikipedia.org/wiki/Inverse-square_law https://en.wikipedia.org/wiki/Inverse-square_law Ultraviolet: https://en.m.wikipedia.org/wiki/Ultraviolet https://en.m.wikipedia.org/wiki/Ultraviolet > Short-wave ultraviolet light damages DNA and sterilizes surfaces with which it comes into contact. For humans, suntan and sunburn are familiar effects of exposure of the skin to UV light, along with an increased risk of skin cancer. The amount of UV light produced by the Sun means that the Earth would not be able to sustain life on dry land if most of that light were not filtered out by the atmosphere. [2] More energetic, shorter-wavelength "extreme" UV below 121 nm ionizes air so strongly that it is absorbed before it reaches the ground. [3] However, ultraviolet light (specifically, UVB) is also responsible for the formation of vitamin D in most land vertebrates, including humans. [4] The UV spectrum, thus, has effects both beneficial and harmful to life. Ultraviolet > Solar ultraviolet: https://en.wikipedia.org/wiki/Ultraviolet#Solar_ultraviolet https://en.wikipedia.org/wiki/Ultraviolet#Solar_ultraviolet > The atmosphere blocks about 77% of the Sun's UV, when the Sun is highest in the sky (at zenith), with absorption increasing at shorter UV wavelengths. At ground level with the sun at zenith, sunlight is 44% visible light, 3% ultraviolet, and the remainder infrared. [23][24] Of the ultraviolet radiation that reaches the Earth's surface, more than 95% is the longer wavelengths of UVA, with the small remainder UVB. Almost no UVC reaches the Earth's surface. [25] The fraction of UVB which remains in UV radiation after passing through the atmosphere is heavily dependent on cloud cover and atmospheric conditions. On "partly cloudy" days, [...] (Infrared light ~is heat. There's usually plenty of waste heat from mechanical friction, exothermic chemical processes with gravity, lossy AC-DC conversion, and electronic components that waste energy/electron_field_disturbance//thermions/heat like steaming water towers sans superconducting channels wide enough for electrons to not start tunneling out without a ground or a negative) Ultraviolet > Human health-related effects > harmful effects https://en.wikipedia.org/wiki/Ultraviolet#Harmful_effects https://en.wikipedia.org/wiki/Ultraviolet#Harmful_effects UV-A and UV-B protective eyewear (U6 polycarbonate) can be purchased in bulk. https://www.amazon.com/s?k=uvb+ansi+z87+glasses+20+pairs https://www.amazon.com/s?k=uvb+ansi+z87+glasses+20+pairs

kylehotchkiss 4y ago

Does each plant have it's own sweet spot of color balance?

bavell 4y ago
Just a layman here but I know plants use color temp as a signaling mechanism (e.g. to help determine time of year - warmer color temp in spring/fall) so I'd expect some variation between species in how that signal is interpreted and used.
- latchkey 4y ago
  They also take advantage of different spectrum/color temp at different points in their lifecycle too. I was growing pre-led era and I'd swap bulbs for the weed growth phase and then flowering phase.

Centigonal 4y ago

It's really complicated, because plants also use other bands of color for decisionmaking (e.g.: am I being shaded out by another plant? Am I tall enough? What time of year is it? Should I make flowers? etc). Growers and light manufacturers have found that adding some infrared and other frequencies help, even though they don't contribute substantially to energy absorption. Also, there are multiple chlorophyll molecules, with slightly different spectra. Lots of fun stuff in this field.

eitland 4y ago
Brings back memories: when I went to farming school around 1998 - 2000 we once visited a local commercial greenhouse and one thing I remember is they told me they used to have chemicals (plant hormones possibly?) that they sprayed on the leaves of flower plants to stop them from stretching and develop a more compact form, but had stopped doing that and now just lowered the temperature in the room a couple of hours before sunrise to get the same effect.