> Artificial lighting is a very expensive way to drive photosynthesis compared to natural sunlight No, that's not necessarily true. Sunlight is actually fairl

> Artificial lighting is a very expensive way to drive photosynthesis compared to natural sunlight No, that's not necessarily true. Sunlight is actually fairly wasteful when landing on a leaf. It goes across a wide band of frequencies, most of which aren't used by the plant. And lots of it scatters on the earth near the plant, also unused. Finally, the solar irradiation is almost always larger than the total energy a plant could absorb, even if it were the perfect frequencies. Solar panels turn a much higher percentage of that falling energy into electricity. By re-emitting only the frequencies best absorbed by the plants, and having a much denser planting than would be possible outdoors, and, most importantly, only providing each plant with the light it needs, you can take that huge volume of "wasted" solar energy and use it to grow many more plants. So if you take all the sunlight that is falling on the roof of the farm, even after you account for all the conversion losses you can still come out ahead because you're using the remaining energy in a much more efficient manner for plant growth. Plants only need in the order of 10-100 W/m^2 in order to grow. A solar panel, however, easily generates 200 W/m^2 and more. Therefore, a 1m^2 solar panel can support the needs of > 1m^2 of plants, even before taking into account the spectrum efficiencies.