A vertical farm wouldn't be able to power itself with solar on its own roof. You can't convert from light to electricity to light again and end up with more light. Possibly it could if you're converting to specific wavelengths used by the plants, but given the sheer number of layers in even a single floor vertical farm, it's still unlikely to be able to power itself.

So if solar and wind is the answer, you have to have fields full of those two. But then, why not just grow food in those fields? There might be specific situations that have a good answer to that, like the land isn't suitable for agriculture, but otherwise, we have to look for solutions other than solar and wind.

Alternatively, if water use is a big deal, then we can seek ways to reduce water use in traditional agriculture.