Fuel cells and electric motors are vastly more efficient at turning propane into motion than a combustion engine. Its possible they found a dessicant that is particularly easy to reverse at stp. Theymention the absorbing dessicant is exothermic which is unusual I think? And they pump that heat over to regenerate the other dessicant under a slight vacuum. Sounds a bit like the oxygen generators people use for lung conditions, or to weld with.

My understanding is heat from first chamber + external vacuum is used to dry out a second chamber and then the system is reversed when the first chamber is saturated.

Energy is being put into the system but it is less than the AC unit cooling humid air on its own so is a net gain relatively speaking.