What made people to build smelting plant in the middle of the desert.
energy it drinks. Hall-Heroult an electrolysis process which used to produce aluminium consumes a lot of energy. It is the king of the process since alternative methods are less viable economically and ecologically.
Even the most modern smelters require 12.8 kW.h to produce one Kilogram of Aluminium. Electric power represents 20% to 40% of the cost of producing aluminium. Off course this costs depends on location and when the location is in the middle of, deserts floating over oil and gas it will be much cheaper.