Where are you placing these solar panels? Why can't those locations be rooftop hydroponic farms instead?

Because rooftop hydroponic farms have to be tended to almost daily, or at least for planting/harvesting. Solar panels don't need nearly as much maintenance and allow you to concentrate the actual growing operations for the economies of scale.

Do you mind if I ask why you're so against the idea?

> Do you mind if I ask why you're so against the idea?

Because it is clearly inefficient to convert sunlight -> electricity -> simulated sunlight.

But you're ignoring the inefficiency of building separate hydroponic operations on individual rooftops and driving around to all of them, etc. Also as SamBam mention above, you don't have to make a simulated sun. Instead it can work as sun -> electricity -> narrow-spectrum-light-that-plants-convert-at-higher-efficiency. You might even genetically modify plants to be more productive with the smallest spectrum possible.