[AngryData]

Unless you do pull out fusion, you will always have too huge loss between solar panels and LEDs. As efficient as LEDs are now, and I know because I just built 1200 watts of the latest and most efficient LEDs that are available, they are nowhere near cost effective in comparison tot he sun. Plants are not nearly as inefficient as people believe, especially when you consider the fact that solar panels themselves can also only absorb a small fraction of the light spectrum.

That 1200 watts is only really covering a 6 by 6 foot square worth of growth area at about 35 watts a square foot at 200 lumens per watts. It could be slightly larger but only if you want most plants to grow extremely slow or be really weak, and you can go up to 50 watts per square foot before requiring supplemental CO2 but not all plants like that amount of light.

Converting that to 1 acre worth of coverage, which is what is about what is needed to feed a single human for one year, you are looking at about 1,500,000 watts running 12-18 hours per day. That is a ridiculous amount of energy. Even assuming you can get away with 1/3 of that area by super careful and efficient growth year round that is still a half million watts in lighting costs alone. Not to mention all the other work and costs.

I don't see indoor farms being good for anything other than extreme specialty plants or extremely fragile plants until we can pull essentially limitless energy out for far cheaper than we can get even with fossil fuels.

[bjelkeman-again]

I am curious about the 36 sqft (3.34 square meter) and 1200 watt. As we end up with considerably less watt per area. We use about 100 watt per square meter. You have about 360 watt per square meter. So we use less than a third. Preliminary tests show very good growth rates. We will have better data in a few months.

This is for an indoor leafy green, mostly sallad, aquaponics growing facility.

[AngryData]

Technically I can still get growth down to 11-12 watts, closer to your levels, but it is definitely much slower growth and it won't be enough later on. Technically I run about 20 watts during the initial vegetative state, but once plants start flowering or fruiting there is a markedly different end result if I don't turn the lights up to around 35 watts a square foot, which is what most other people ive seen report. I mostly just run it at 35 all the time because I want them fruiting and producing as much as they can as fast as possible. But if you are growing leafy greens your plants are never even entering the flowering stage because you will be picking it by then.

Perhaps with a bigger more automated setup I could do slower growth, but there are other costs like ventilation or dehumidification or possibly heating or cooling too that don't really change a lot whether the plants are growing fast or slow, which makes faster growth possible optimal financially, even if I might be losing out a few percentage worth of light absorption.

[bjelkeman-again]

Ok, we don't have fruiting plants. So that can make a difference.