My rough estimate would go like this

- 20% efficency of solarpanels

- 1000W/m² sun under good conditions (at the equator)

-> we get 200W/m² from solar panels

- 600 W/m² energy needed for the plants

- 60% efficency of the LEDs

(both from the paper linked in another comment)

600/0.6 = 1000 W elecricity needed per m²

1000/200=5

So for 1 acre LED farm, we need 5 acres solar panels, if I made no major misstake.

Add to that further losses from energy transformation and you see that solar panel powered, it makes even less sense.

If you want to grow grain indoors, because for example outside is a dessert, but sun, you just would use windows, (mainly to keep your water).

This project only makes sense in space or very remote areas with other good sources of energy.

Your desert idea tracks (many of the biggest greenhouses already are) but to keep the majority of the water, you would dehumidify it from the exhaust air. There are systems for this, I saw a couple in NW Mexico when I worked in greenhouse hydroponics in a past life