> you're never going to get more efficient use of an acre of sunlight (~4 MW at noon) than you will with photovoltaics (~75% loss ~= 1 MW at noon)
green plants don't use the middle, thus they are green, of the spectrum - i.e. they use only 10-20% of the sunlight. So, very efficient photovoltaics (or other type of solar powerplant) -> electricity -> only red and violet LEDs may even beat the Mother Nature in efficiency a bit. Add to that various optimizations - for example with the LEDs you aren't limited by the Sun singular position in the sky and can shine light from all the needed angles, like no more leaves being in the shadow of other leaves, thus increasing the photosynthesis throughput of a given plant.
green plants don't use the middle, thus they are green, of the spectrum - i.e. they use only 10-20% of the sunlight. So, very efficient photovoltaics (or other type of solar powerplant) -> electricity -> only red and violet LEDs may even beat the Mother Nature in efficiency a bit. Add to that various optimizations - for example with the LEDs you aren't limited by the Sun singular position in the sky and can shine light from all the needed angles, like no more leaves being in the shadow of other leaves, thus increasing the photosynthesis throughput of a given plant.