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You are never going to beat the efficency of the sun shining down on plants for free, no matter what. I mean the entire idea is absurd, what are you going to have solar panels on the building that somehow collect light and re-emit it, and have that be more efficent than just the plants collecting the light directly?

So you take more land area for solar, why wouldnt you just plant crops on that land area instead...

If you grow things indoors close to where they will be consumed you can control the environment reducing risk of drought, flooding, pest, pollution, wildfires, storm damage, blight etc etc. You also reduce the supply chain complexities around collection, transport and storage (inert gas storage etc). There are many other considerations apart from energy and when energy becomes cheap enough the game will turn in favour of growing in urban areas.

None of those issues are actually serious problems for agriculture in most areas most of the time. And energy will never be cheap enough in our lifetimes to change the calculation significantly.

you can also enclose fields as they exist if those are somehow significant problems. There is still absolutely zero need to build vertical

The sun produces a full spectrum of light, like a blackbody of a certain temperature. The atmosphere then selectively absorbs, scatters, or reflects a portion of it. That produces the Earth daylight spectrum, which varies by season, latitude, and time of day. It doesn't ever match up precisely with the absorption spectrum of plant pigments.

A grow light can produce the exact wavelength of blue light most readily absorbed by chlorophyll, and the exact wavelength of red light most readily absorbed by phytochrome, and the exact wavelengths of other hormone/signaling photoreceptor pigments.

The grow light produces exactly the light that the plant needs, whereas the sun throws out a lot of energy that the plant cannot use effectively. If we had a material that could absorb two green photons and emit one blue photon, that would improve the photosynthetic efficiency of sunlight, but for now, it's still easier for us to turn green light into electricity and power a blue LED.

Not only that but with careful management you can squeeze 4 seasons into a year

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