If that were possible then all these vertical farms deserve to fail because they didn't take such a basic strategy into account.

I'm not sure I understand what you mean. What I'm driving at is the ratio of m² used to grow plants the old fashioned way / m² used for solar panels + vertical hydroponics to grow an equivalent yield. It's unclear to me what this ratio is with current photovoltaic (PV) and LED efficiencies. Vertical farm owners may not know or care unless they're also involved in power generation.

Photosynthesis only uses a subset of the visible spectrum. PV panels make power using a different (larger? certainly non-identical) subset of the visible spectrum, albeit at a maximum of maybe 30% efficiency in practice. At first glance, if solar panels convert enough unused parts of the spectrum into LED output that can drive photosynthesis, there might be a net gain on crop yield per m² versus traditional farming. I'm sure someone's run this experiment by now. If so, I'd be curious to see the results.

Incidentally, PV panels discard IR light which makes up 55% of all received solar energy. Concentrated solar power systems seem theoretically more efficient per m² since they capture all light as heat, but I imagine maintenance, energy storage, and heat engine/dynamo inefficiencies combine to bring their total efficiency down.

In short, back of the napkin calculations for this stuff are harder than they may seem! I'd love to see the results of some real-world experiments.

Red and blue mostly I think, hence purple lights, and why plants look green and not black.

As I understand the variation in green light and it’s intensity mucks up photosynthesis, now if photosynthesis could be tuned to use green light too that would be handy, it’s just that evolution has a head start of billions of years.

Of course though eukaryotic cells run on mitochondria, if energy could be sourced to the cell to replace the chloroplasts directly that could be one way around. But denaturing food like that could have unforeseen consequences.

There was a Tommorow’s World item about making food from petrochemicals, I’m still aghast.

> There was a Tommorow’s World item about making food from petrochemicals, I’m still aghast.

You make that sound so bad.

https://en.wikipedia.org/wiki/Single-cell_protein

Imagine the potential... ;->

You can save some energy by choosing specific spectrum LEDs but you can't go overboard as that is tricky, since in addition to photosynthesis a bunch of other processes in plants are activated by light, and if you just put in one frequency then you may get weird results as some processes in the plant "think" that it's nighttime and screw up its growth.

I can think of one plant that will never flower under fluorescent bulbs, because they lack enough red wavelengths to trigger the hormones that shift its biochemistry from vegetative to reproductive growth.