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US farmland occupies 895 million acres (3.6M km^2) [1]. Average solar irradiance on most US farmland is about 200 W/m^2 [2]. By being generous and assuming ver

US farmland occupies 895 million acres (3.6M km^2) [1]. Average solar irradiance on most US farmland is about 200 W/m^2 [2]. By being generous and assuming vertical farming is 100x more efficient than natural photosynthesis, the energy requirements come out to 7.2 terawatts of generating capacity. In contrast, the US currently has 1.1 terawatts of generating capacity. [3] Vertical farming isn't just uneconomical: it's completely absurd. [1] https://www.statista.com/statistics/196104/total-area-of-land-in-farms-in-the-us-since-2000/ https://www.statista.com/statistics/196104/total-area-of-lan... [2] https://en.wikipedia.org/wiki/Solar_irradiance https://en.wikipedia.org/wiki/Solar_irradiance [3] https://www.eia.gov/energyexplained/electricity/electricity-in-the-us-generation-capacity-and-sales.php https://www.eia.gov/energyexplained/electricity/electricity-...

mensetmanusman 4y ago
Thanks for doing the numbers, it’s interesting that in 50 years people are predicting annual TW installs of global solar capacity. So maybe a technology for the future if storage and distribution gets solved.
jaegerpicker 4y ago
Except none of that matters, Solar Irradiance has very little to do with actual photosynthesis. You are measuring Watt's as a pure energy source, that's useless in this case. Photosynthetic photon flux density (PPFD's) are what's important, that's the amount of light wavelengths that the plant needs to absorb to power photosynthesis. Here is a definition from another source, I'll post the link at the bottom: PPFD is a measure of photosynthetic active radiation, PAR for short. PAR is not a measure of anything itself but is more of a description. PAR light is all the visible wavelengths of light which cause photosynthesis, found within the 400-700 nanometer range. PPFD is a ‘spot’ measurement that tells you how many photons from the PAR range hit a specific area of your canopy over time. It is expressed as micro moles per square meter per second (μmol/m2/s). For this reason, PPFD is the most accurate measure of light power. First, unlike other measures, it considers the entire spectrum of light that plants see. PPFD also takes into account the amount of light that will actually reach the plant instead of focusing only on the point of origin. A light source can be very bright and powerful, but if it is too away from the plant, or obstructed in some way, the plant won’t be getting all the light it needs for photosynthesis. PPFD controls for this kind of inaccuracy. With LED's you can place the plants much closer to the light source and control the color spectrum along with the obstructions 24/7. It allows you to grow indoors at an extremely efficient rate. Your formula has almost nothing to do with indoor farming. https://www.freightfarms.com/blog/indoor-grow-lights#:~:text=LEDs%20(light%2Demitting%20diodes),same%20consistent%20and%20directional%20light https://www.freightfarms.com/blog/indoor-grow-lights#:~:text.... Here are some additional sources: https://archipel.uqam.ca/1619/1/1998_025_Gendron.pdf https://archipel.uqam.ca/1619/1/1998_025_Gendron.pdf https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1066711/pdf/plntphys00572-0025.pdf https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1066711/pdf/pln... https://www.researchgate.net/profile/Paul_Hanson7/publication/283601390_An_optimal_sampling_strategy_for_determining_CO2_exchange_rate_as_a_function_of_photosynthetic_photon_flux_density/links/566ae06608aea0892c4baafb/An-optimal-sampling-strategy-for-determining-CO2-exchange-rate-as-a-function-of-photosynthetic-photon-flux-density.pdf https://www.researchgate.net/profile/Paul_Hanson7/publicatio... https://www.horti-growlight.com/en-gb/par-ppf-ypf-ppfd-dli#:~:text=The%20Photosynthetic%20Photon%20Flux%20Density,a%20given%20surface%20each%20second https://www.horti-growlight.com/en-gb/par-ppf-ypf-ppfd-dli#:.... https://www.sciencedirect.com/topics/medicine-and-dentistry/photosynthetic-photon-flux-density https://www.sciencedirect.com/topics/medicine-and-dentistry/... Quick summary: PPFD measures the amount of light wavelengths that the plant captures that kicks off the chemical reaction of Chlorophyll. Red and Blue lights are the vast majority of wavelengths that interact with Chlorophyll. That's a major reason why the solar irradiance measure of pure Wattage is irrelevant.
- chroem- 4y ago
  Are you able to achieve a 10000x efficiency improvement vs natural photosynthesis by using those technologies? If not, the idea is still completely unfeasible.
  - jaegerpicker 4y ago
    IT'S COMPLETELY IRRELEVENT, the efficiency at generating electricity is not what powers photosynthesis. It's a chemical reaction to light wavelengths (ie the absorbing of Red and Blue light) that powers it. More watt's doesn't equal more growth, it equals more heat which allows longer growing seasons. LED's and Sunlight have EXACTLY the same level of photosynthesis, none of the math you did matters at all. For LED's you need to calculate coverage of the area not pure power. If you produce Red or Blue wavelength's that's all that matters, the Sun does that and a hell of a lot more but we don't need the power of the sun or even a tiny faction of it's power for photosynthesis, we need to heat and cool and creat weather which effect plant growth but Watt's is irrelevant.
    - throwaway9870 4y ago
      So do the math and show us the equivalent amount of electricity to equal current farming in America.
      - jaegerpicker 4y ago
        WHAT MATH?!?!? Electricity doesn't have any thing to do with it except in very tiny amounts. You need light coverage not heat wattage! There is no math to do! Photosynthesis doesn't work like that. It's a chemical reaction to light wavelengths. I posted numerous papers detailing this. The unit of measure is PPFD Photosynthesis Photon Flux Density, that's the coverage of the number of light wavelengths the plant can absorb. LED's provide plenty of PPFD's, exactly the same as the Sun. So all you need is the correct amount to cover your growing space with a minimum amount.
        4y ago

mensetmanusman 4y ago

Thanks for doing the numbers, it’s interesting that in 50 years people are predicting annual TW installs of global solar capacity. So maybe a technology for the future if storage and distribution gets solved.

jaegerpicker 4y ago

Except none of that matters, Solar Irradiance has very little to do with actual photosynthesis. You are measuring Watt's as a pure energy source, that's useless in this case. Photosynthetic photon flux density (PPFD's) are what's important, that's the amount of light wavelengths that the plant needs to absorb to power photosynthesis. Here is a definition from another source, I'll post the link at the bottom: PPFD is a measure of photosynthetic active radiation, PAR for short. PAR is not a measure of anything itself but is more of a description. PAR light is all the visible wavelengths of light which cause photosynthesis, found within the 400-700 nanometer range. PPFD is a ‘spot’ measurement that tells you how many photons from the PAR range hit a specific area of your canopy over time. It is expressed as micro moles per square meter per second (μmol/m2/s). For this reason, PPFD is the most accurate measure of light power. First, unlike other measures, it considers the entire spectrum of light that plants see. PPFD also takes into account the amount of light that will actually reach the plant instead of focusing only on the point of origin. A light source can be very bright and powerful, but if it is too away from the plant, or obstructed in some way, the plant won’t be getting all the light it needs for photosynthesis. PPFD controls for this kind of inaccuracy. With LED's you can place the plants much closer to the light source and control the color spectrum along with the obstructions 24/7. It allows you to grow indoors at an extremely efficient rate. Your formula has almost nothing to do with indoor farming. https://www.freightfarms.com/blog/indoor-grow-lights#:~:text=LEDs%20(light%2Demitting%20diodes),same%20consistent%20and%20directional%20light https://www.freightfarms.com/blog/indoor-grow-lights#:~:text.... Here are some additional sources: https://archipel.uqam.ca/1619/1/1998_025_Gendron.pdf https://archipel.uqam.ca/1619/1/1998_025_Gendron.pdf https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1066711/pdf/plntphys00572-0025.pdf https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1066711/pdf/pln... https://www.researchgate.net/profile/Paul_Hanson7/publication/283601390_An_optimal_sampling_strategy_for_determining_CO2_exchange_rate_as_a_function_of_photosynthetic_photon_flux_density/links/566ae06608aea0892c4baafb/An-optimal-sampling-strategy-for-determining-CO2-exchange-rate-as-a-function-of-photosynthetic-photon-flux-density.pdf https://www.researchgate.net/profile/Paul_Hanson7/publicatio... https://www.horti-growlight.com/en-gb/par-ppf-ypf-ppfd-dli#:~:text=The%20Photosynthetic%20Photon%20Flux%20Density,a%20given%20surface%20each%20second https://www.horti-growlight.com/en-gb/par-ppf-ypf-ppfd-dli#:.... https://www.sciencedirect.com/topics/medicine-and-dentistry/photosynthetic-photon-flux-density https://www.sciencedirect.com/topics/medicine-and-dentistry/... Quick summary: PPFD measures the amount of light wavelengths that the plant captures that kicks off the chemical reaction of Chlorophyll. Red and Blue lights are the vast majority of wavelengths that interact with Chlorophyll. That's a major reason why the solar irradiance measure of pure Wattage is irrelevant.

chroem- 4y ago
Are you able to achieve a 10000x efficiency improvement vs natural photosynthesis by using those technologies? If not, the idea is still completely unfeasible.
- jaegerpicker 4y ago
  IT'S COMPLETELY IRRELEVENT, the efficiency at generating electricity is not what powers photosynthesis. It's a chemical reaction to light wavelengths (ie the absorbing of Red and Blue light) that powers it. More watt's doesn't equal more growth, it equals more heat which allows longer growing seasons. LED's and Sunlight have EXACTLY the same level of photosynthesis, none of the math you did matters at all. For LED's you need to calculate coverage of the area not pure power. If you produce Red or Blue wavelength's that's all that matters, the Sun does that and a hell of a lot more but we don't need the power of the sun or even a tiny faction of it's power for photosynthesis, we need to heat and cool and creat weather which effect plant growth but Watt's is irrelevant.
  - throwaway9870 4y ago
    So do the math and show us the equivalent amount of electricity to equal current farming in America.
    - jaegerpicker 4y ago
      WHAT MATH?!?!? Electricity doesn't have any thing to do with it except in very tiny amounts. You need light coverage not heat wattage! There is no math to do! Photosynthesis doesn't work like that. It's a chemical reaction to light wavelengths. I posted numerous papers detailing this. The unit of measure is PPFD Photosynthesis Photon Flux Density, that's the coverage of the number of light wavelengths the plant can absorb. LED's provide plenty of PPFD's, exactly the same as the Sun. So all you need is the correct amount to cover your growing space with a minimum amount.
      - 4y ago