There are basically 3 ways to cool a coach
1: Power cooling (Air Conditioning)
2: Shade
3: Ventelation (NOTE 1 and 3 confilct in many cases)
Now, Southern engineering says you build nice THICK stone walls that soak up the heat in the day (keeping it from the house) and release it at night (Keepin said house warm cause nights get COLD in the dessert) However you are not in a built in place house,,,, You are in a RV, much thinner (But insulated, one hopes) walls.
So, it's either AC or Ventelation during the day, heat at night and SHADE if you can arrange it. Shade can be natural or artifical
Best shade: An array of SOLAR panels (Hooked to an inverter, powering the AC of course)