Why are the desert plants on the west side of the greenhouse?

The desert plants are always on the west side of the greenhouse. This is because

the sun sets in the west and light is more intense as the day goes on.

This is also similar to the light that desert plants are used to. This is the hottest part of the day and the plant is now in the optimal position to absorb most heat.

Sun rises in the East and sets in the West. The west side gets the most sun. It also gets the least moisture because the tropical easterly winds become dry by the time they reach the west. It brings no rainfall.