I have found out by just looking at the specifications of solar irradiation that any sort of artificial light that would mimic the sun would use up a lot of energy per m^2 which is simply not worth it since growing under the sun is cheap and easy.

The current growing LED modules you can find on Ebay that are rated 150W - 300W would probably be sufficient for any type of growing so there is no need for a development of such a solution I previously proposed.

I also can not see the point of skyscrapers growing food, where they use artificial lightning. They should rather build greenhouses I think. I'm open to any criticism.

EDIT: Maybe it is efficient because they use so few of the LEDs? I am not sure.